JP2003244519A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera that can conduct accurate AF operation at a higher speed. <P>SOLUTION: This digital camera 1 calculates a first lens position, based on the detected result of an auxiliary AF means 2 composed of a phase difference AF, etc., by means of a first lens position calculating means 6 and makes the first movement of an AF lens 11, aimed at the calculated first lens position by means of a lens control means 16. In the midst of moving the AF lens 11 to the first lens position, the camera 1 performs the calculation the contrast evaluation value of an image by means of a contrast evaluation value calculating means 10 and the detection of the position of the lens 11, by means of a lens position detecting means 12 several times and calculates a second lens position, at which the contrast evaluation value reaches a peak, based on the calculated and detected results of the calculating means 10 and detecting means 12 by means of a contrast peak position calculating means 13. Then the camera 1 makes the second movement of the AF lens 11 aimed at the second lens position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a digital camera,
More specifically, the present invention relates to a digital camera that captures a subject image, digitizes it, and processes it.

[0002]

2. Description of the Related Art In a digital camera in which a subject image is picked up by an image pickup element, the obtained image signal is digitized, image processing is performed, and then recorded in a recording medium or the like, a subject formed on the image pickup element Various methods have been used to focus the image.

Japanese Patent Laid-Open No. 6-
In Japanese Patent Laid-Open No. 62304, there is provided an extracting means for extracting a sharp signal from a video signal and a lens position detecting means for detecting a lens position, and a focus lens position, a sharpness signal, and delay information of the sharp signal, A technique for controlling the focus lens driving means based on the above is described. The one described in this publication stores the past focus lens position in consideration of the delay time until the sharpness signal is input to the control device, and by using the stored lens position,
This is so-called hill-climbing AF in which the motor is rotated in reverse after the peak of the contrast amount is exceeded to focus.

[0004]

However, in the device described in Japanese Patent Laid-Open No. 6-62304, the delay time is taken into consideration to prevent the deviation between the lens position and the sharp signal. However, after all the mountain climbing A
Since it is F, it goes back and forth until it reaches the in-focus position, which is the peak of the contrast amount, and it takes time to perform forward / reverse rotation of the motor and correct the backlash. After all, it takes time to stop the lens at the in-focus position.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a digital camera capable of performing accurate AF operation at a higher speed.

[0006]

In order to achieve the above object, a digital camera according to the first aspect of the present invention uses auxiliary AF means for detecting a subject distance and photoelectric conversion of a subject image to integrate for a predetermined integration period. After that, an image pickup means for outputting as an image signal, an AF lens for focusing the subject image formed on the image pickup means, and an image formed on the image pickup means based on the image signal outputted from the image pickup means. Contrast evaluation value calculation means for calculating the contrast evaluation value of the subject image, lens position detection means for detecting the lens position of the AF lens, and the AF lens based on the lens position detected by the lens position detection means. A lens control means for controlling and moving, and a lens position detecting means for moving the AF lens by the lens control means. Contrast of the subject image formed on the image pickup means based on the plurality of lens positions detected by the image pickup means and the plurality of contrast evaluation values calculated by the contrast evaluation value calculation means corresponding to the plurality of lens positions. Contrast peak position calculating means for calculating a lens position at which the evaluation value reaches a peak, and calculating a first lens position corresponding to the subject distance detected by the auxiliary AF means, and calculating the first lens position. The first lens extension is performed on the AF lens with the aim of, and while the first lens extension is being performed, the contrast evaluation value of the image is calculated, and the lens position is detected when the contrast evaluation value is calculated. , Multiple times and based on these calculation results and detection results, the contrast peak position calculation means performs contrast evaluation. There calculating a second lens position where the peak, the second lens position as a target is performed a second lens extension for the AF lens.

The digital camera according to a second aspect of the present invention is the digital camera according to the first aspect of the present invention, wherein lens speed detecting means for detecting the moving speed of the AF lens and moving speed detected by the lens speed detecting means are used. From the stop position predicting means for predicting the stop position of the AF lens, the lens control means controls the AF lens based on the difference between the target feeding position and the predicted stop position. is there.

Further, a digital camera according to a third aspect of the present invention is the same as the digital camera according to the first aspect, wherein the auxiliary AF means detects the subject distance by phase difference AF and detects two images. The detecting means, the first focusing distance calculating means for obtaining the first focusing distance based on the phases of the two images detected by the detecting means, and the undulation of the two images detected by the detecting means. A distance measuring error calculating means for calculating a distance measuring error based on the second focusing and a second focusing with a small amount of extension within a range where focusing may occur based on the first focusing distance and the distance measuring error. Second focusing distance calculating means for obtaining a distance,
The lens position of is obtained based on the second focusing distance.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 26 show an embodiment of the present invention, and FIG. 1 is a block diagram showing a conceptual configuration of a digital camera.

This digital camera 1 has a phase difference A, for example.
Auxiliary AF means 2 for detecting the object distance by F, and first in-focus distance calculation means 3 for obtaining a first in-focus distance based on the phases of the two images detected by this auxiliary AF means 2.
And a distance measuring error calculating means 4 for calculating a distance measuring error based on the undulations of the two images, and there is a possibility of focusing on the basis of the first focusing distance and the distance measuring error, and the distance is extended. Second focusing distance calculating means 5 for obtaining a second focusing distance having a small amount
And a first lens position calculating means 6 for calculating a first lens position for extending a lens, which will be described later, based on the second focusing distance obtained by the second focusing distance calculating means 5, and a subject. An image pickup unit 8 that photoelectrically converts an image and outputs an image signal, and a periodic flicker is detected from a change in the subject luminance detected by the image pickup unit 8 to stabilize the subject luminance without being affected by the flicker. A flicker timing detecting means 9 which also functions as a flicker detecting means and a stable timing detecting means for detecting a stable timing which can be detected by an image forming means, and an image is formed on the image capturing means 8 based on an image signal output from the image capturing means The contrast evaluation value calculation means 10 for calculating the contrast evaluation value (specifically, the contrast amount) of the subject image to be formed, and the subject image are connected to the image pickup means 8. The AF lens 11 for focusing in the photographing optical system, the lens position detection means 12 for detecting the lens position of the AF lens 11, and the lens control means 16 described later move the AF lens 11 according to The image pickup means 8 based on the plurality of lens positions detected by the lever lens position detection means 12 and the plurality of contrast evaluation values calculated by the contrast evaluation value calculation means 10 corresponding to the plurality of lens positions. Contrast peak position calculating means 13 for calculating the lens position where the contrast amount of the subject image formed on the lens reaches a peak, lens speed detecting means 14 for detecting the moving speed of the AF lens 11, and this lens speed detecting means 14 Stop position for predicting the stop position of the AF lens 11 from the moving speed detected by The AF lens 11 is determined based on the difference between the stop position predicted by the stop position predicting unit 15 and the amount of extension from the lens position detected by the lens position detection unit 12 to the target extension position. It is configured to have a lens control means 16 for controlling and moving, and a control means 7 for comprehensively controlling the digital camera 1 including each element as described above.

The operation of the digital camera 1 thus constructed is as follows.

First, the auxiliary AF means 2 obtains the first lens position, and the first lens extension is carried out with this first lens position as a target.

While the first lens is being extended, the contrast evaluation value calculating means 10 detects the contrast amount of the image and the lens position detecting means 12
The detection of the lens position at that time is performed multiple times.

Then, based on these detection results, the second lens position that maximizes the contrast amount is calculated,
The second lens extension is carried out with this second lens position as the target.

The control for moving the AF lens 11 is performed by the stop position predicting means 15 based on the lens speed detected by the lens speed detecting means 14 to calculate an expected stop position, and by the lens control means 16 as a target. The operation is performed based on the difference between the feeding position and the expected stop position.

More specifically, the first lens position is obtained as follows.

The auxiliary AF means 2 is constructed so as to be able to perform distance measurement for a plurality of distance measurement areas, and performs distance measurement for these plurality of distance measurement areas to be the closest distance. The distance measurement error is calculated for the distance measurement area in which the first focus distance is obtained, and the second distance is the distance with a small amount of extension among the distances in which focus may occur in consideration of the distance measurement error. Find the focus distance. Then, the first lens position for performing the first extension is calculated based on the second focusing distance.

The extension of the AF lens 11 is carried out with the first lens position as a target. While the AF lens 11 is being extended to the first lens position, contrast AF is performed on the distance measuring area that has been closest by the auxiliary AF means 2, and the second lens is a more accurate focus position. The position is calculated, and thereafter, the second lens position is set as the target to perform the extension.

The image pickup means 8 is also the auxiliary AF means 2
It is configured such that the plurality of distance measuring areas corresponding to the plurality of distance measuring areas can be imaged.

In general, there is some play in the lens feeding mechanism, and when the lens is fed in after being fed, it is necessary to move the lens by more than that amount to remove the play. Furthermore, when changing the moving direction of the lens, both braking time and returning time are required because it is necessary to brake and stop the lens securely and then change the direction for control. It takes a long time to reach the point of burning.

On the other hand, since the first lens position is calculated on the basis of the distance with a small amount of extension within the focusable range as described above, there is no excessive extension of the lens from the true focus position. It becomes possible to control the lens position without changing the direction, and it is possible to focus at high speed without the need for backlash removal.

The auxiliary AF means 2 may be provided with a dedicated element, but it is also possible to use an area other than the image pickup area of the image pickup means 8. In addition, the AF of the auxiliary AF means
As a method, as will be described later, phase difference AF or active AF can be used, and not limited to these, various other means can also be used.

The position where the contrast amount of the subject image formed on the image pickup means 8 reaches a peak (that is, the in-focus position)
As will be described in detail later, the calculation of is calculated by approximating the relationship between the contrast amount and the lens position by a normal distribution or the like.

The peak position of the contrast amount is a position where the amount of change in the contrast becomes zero, and therefore is calculated by extrapolation by performing a plurality of operations for detecting the contrast amount while the AF lens 11 is extended.

Further, when performing contrast AF, when performing integration by the image pickup means 8 with respect to the selected distance measuring area, the intermediate timing of the integration period is controlled so that the flicker changes little. At the same time, the lens position of the AF lens 11 is also detected at an intermediate timing. This allows
It is possible to suppress fluctuations in brightness due to flicker.

Next, FIG. 2 is a perspective view showing the appearance of the digital camera 1 from the lens side, and FIG.
It is a perspective view showing the appearance when used as A (Personal Digital (Data) Assistants). Note that in FIG. 3, the lens side is oriented downward.

In this digital camera 1, a lens barrel 22 containing a lens which is a zoom optical system is arranged on the front side of a main body 21, and a barrier 23 is opened in the lens barrel 22. With the main body 21,
It is designed to be driven up to the wide-angle end where shooting is possible.
When the barrier 23 is opened / closed, a barrier switch (not shown) is turned on / off accordingly, that is, by opening the barrier 23, the digital camera 1 operates as a camera.

On the upper surface of the digital camera 1, a release switch 24 for instructing and inputting a photographing operation and a power source for making the digital camera 1 function as a PDA with the barrier 23 closed are turned on. Do P
A DA power switch 25 is provided.

Further, the main body 21 of the digital camera 1
A finder 26 for confirming a subject at the time of shooting, a zoom switch 27 for changing the focal length of the lens, and a brightness setting volume 31 for adjusting the brightness of a sheet light source 33 described later are provided on the back side of the. And each member used when the digital camera 1 operates as a PDA as described later, that is, the image reversing switch 29.
An image display mode switch 30 and a magnet 28 are provided.

The digital camera 1 is provided with a display section 89 which can be opened and closed by a hinge 32a on the back side of the main body 21. The display unit 89 is formed in a thin plate shape having a size that exposes the viewfinder 26 and the zoom switch 27 when the display unit 89 is in the closed position substantially along the back surface of the main body 21, and is transparent for displaying an image. LCD 35 in the form of a mold, a sheet-shaped light source 33 for illuminating the LCD 35 with illumination light from the back side, and a diffusion plate 34 for uniformly diffusing the light emitted from the sheet-shaped light source 33 to the LCD 35. And are stacked and held in a rectangular frame-shaped support frame 32.

The display unit 89 constitutes an image display member 86 (see FIG. 4) described later by the LCD 35, the diffusion plate 34, and the sheet-shaped light source 33, and further has a touch panel 88 (see FIG. 4). Has become
Information can be input through the touch panel 88.

Although the diffusing plate 34 and the sheet-shaped light source 33 are used in the above description, instead of these, for example, organic E
An L sheet or the like may be used.

As described above, since the support frame 32 has a rectangular frame shape, the image display member 86 is used.
By adopting a translucent member as each member constituting the touch panel 88, it becomes possible to use external light from the back side as a light source. As a result, when the outside light is bright, the brightness setting volume 31 is operated to make the brightness low (Low) or off (OFF).
By doing so, it becomes possible to observe the image clearly while suppressing the battery consumption.

A magnet 36 is fitted in, for example, the upper left corner of the support frame 32, and when the display portion 89 is closed, the magnet 2 disposed on the back side of the main body 21 is inserted.
It is configured so that it can be easily opened when a rotating force is applied by a hand or the like while preventing the display section 89 from being opened carelessly by adhering to each other.

A memory card 39 for storing photographed image data can be removably attached to the digital camera 1.

FIG. 4 is a block diagram showing mainly the electrical configuration of the digital camera 1.

This digital camera 1 has a zoom lens 4
4, a shutter 45, a diaphragm 46, and an AF lens 47, the lens barrel 22, a zoom lens control unit 48 for controlling and moving the zoom lens 44, and a shutter control for controlling and driving the shutter 45. Means 49
And a diaphragm control means 50 for controlling and driving the diaphragm 46.
An LD motor 54, which serves as a drive source for moving the AF lens 47, a focus motor drive circuit 52 for controlling and driving the LD motor 54, and the AF lens 47.
Focus lens control means 51 including a focus lens position detection circuit 53 for detecting the lens position of
A phase difference based on an output from a sensor unit 55 including lenses 56R and 56L that form a plurality of images and a sensor 57 that is a detection unit that converts the plurality of images formed by the lenses 56R and 56L into electric signals. Phase-difference AF means 58 for performing AF, a strobe light emitting section 59 for illuminating an object with illumination light, a strobe main condenser 60 for supplying light emission power to the strobe light emitting section 59, and charging of the strobe main condenser 60. And the discharge to the strobe light emitting section 59, which will be described later, in the sub CPU 42 and the phase difference AF.
A strobe charging light emission control means 61 for controlling light emission by controlling based on the output of the means 58, the zoom lens control means 48, the shutter control means 49, the aperture control means 50, the focus lens control means 51, and the phase difference AF means 58. , A sub-CPU 42 for controlling these while acquiring information and the like from the strobe charging light emission control means 61 as necessary.
An image pickup element 65 for photoelectrically converting a subject image formed by the zoom lens 44 and the AF lens 47 to output an image signal; and an image pickup area designating means 66 for designating an image pickup area in the image pickup element 65. An A / D circuit 67 for converting an analog image signal output from the image pickup device 65 into digital image data, and a signal level for adjusting the gain of the image pickup device 65 based on the output of the A / D circuit 67. Control means 68, memory 71 for storing the image data output from the A / D circuit 67, image processing circuit 72 for image-processing the image data stored in this memory 71, and processing by this image processing circuit 72. Image compression means 73 for compressing the compressed image data and the image data compressed by the image compression means 73 are recorded in the memory card 39. Memory I / F 74, the memory card 39 for storing the image data under the control of the memory I / F 74, and the subject brightness detecting means for reading the image data stored in the memory 71 to detect the brightness of the subject. The brightness detecting means 76, the flicker timing detecting means 77 for detecting flicker based on the brightness detected by the brightness detecting means 76, and the timing not affected by the flicker, and the flicker timing detecting means 77. Depending on the timing detected by the A / D circuit 6
Timing generation circuit 69 for performing digitization by 7
And a contrast evaluation value calculation means 78 that reads out the image data stored in the memory 71 and calculates a contrast evaluation value (for example, a contrast amount), and differentiates the contrast evaluation value based on the output of the contrast evaluation value calculation means 78. Contrast evaluation value differentiating means 79 for calculating
Then, the focus position predicting means 80 for predicting the focus position based on the output of the contrast evaluation value differentiating means 79, and the focus detection by performing, for example, hill-climbing AF based on the output of the contrast evaluation value calculating means 78. The focus detection means 81, the image display control means 85 for controlling the image display member 86 for displaying the image data output via the image compression means 73, and the image display control means 85 Display unit 89 including an image display member 86 for displaying images and characters and a touch panel 88 arranged along the display surface of the image display member 86.
The touch panel input means 87 for generating and outputting an input signal based on the output from the touch panel 88, and the digital camera 1 in conjunction with the operation of opening and closing the barrier 23.
Barrier switch for turning on / off the power source, the release switch 24, the zoom switch 27, the P
An operation unit 91 including a DA power switch 25, a mode switch, a USB (Universal Serial Bus) terminal 92, and a USB for controlling the USB terminal 92.
The control means 93 and IEEE802. b circuit 94 and this IEEE
802. b for controlling the b circuit 94.
b B for connecting the control means 95 and the devices wirelessly
Bluetooth circuit 96 and this Bluetooth
A Bluetooth control means 97 for controlling the circuit 96, an EEPROM 98 for storing a processing program for operating a main CPU 41, which will be described later, and various data relating to the digital camera 1, and a battery for supplying power to the digital camera 1. 99 and the sub CPU 42
A main CPU 4 that communicates with the sub CPU 42 to control each circuit connected to the sub CPU 42 and controls the entire digital camera 1 including each circuit connected to itself.
1 is included.

An image pickup circuit 64 is constituted by the image pickup element 65, the image pickup area designating means 66, the A / D circuit 67, the signal level control means 68, the timing generating circuit 69 and the like.

The memory card 39 is removable from the digital camera 1, and the battery 99 is also removable, for example.

In the structure shown in FIG. 4,
In comparison with the configuration of FIG. 1 described above, the sensor unit 55 and the phase difference AF
The means 58 is the auxiliary AF means 2, and the main CPU 41 is the first.
The imaging element 65 captures an image on the focusing distance calculation means 3, the distance measurement error calculation means 4, the second focusing distance calculation means 5, the first lens position calculation means 6, the control means 7, and the stop position prediction means 15. Means 8, flicker timing detection means 77, flicker timing detection means 9, contrast evaluation value calculation means 78, contrast evaluation value calculation means 10, AF lens 47, AF lens 11, focus lens position detection circuit 53; Focusing position predicting means 80 in contrast detecting means 12 and lens speed detecting means 14, contrast peak position calculating means 13, focus motor drive circuit 52
Correspond to the lens control means 16, respectively.

FIG. 5 is a diagram showing a region of an image pickup device used for contrast AF, and FIG. 6 is a diagram showing a region of a line sensor used for phase difference AF.

First, when performing the phase difference AF, FIG.
An elongated line sensor 103 as shown in FIG.
Areas A to 103A to 103g shown in (B)
By dividing into G, distance measurement is performed for a plurality of distance measurement areas, and the distance measurement value related to the distance measurement area showing the shortest distance among these distance measurement areas and the distance measurement error of the distance measurement values are considered. Then, the distance measurement result by the phase difference AF is calculated.

In this way, the second lens position, which is an accurate in-focus position, is detected by moving out to the first lens position based on the distance measurement value obtained by the phase difference AF and further performing the contrast AF. The lens is extended to the second lens position. At this time, as shown in FIG.
The image pickup area 101 of the image pickup element 65 is set to the line sensor 1
03 is divided into a plurality of areas A to G (reference numerals 102a to 102g) so as to correspond to the divided areas A to G, respectively, and a distance measurement result (that is, the closest distance) by the phase difference AF among these is given. Contrast AF is performed on the distance measurement area.

The image pickup device 65 is configured as a CMOS type sensor, for example, which can read out any pixel by designating a horizontal line and a vertical line, and is shown in FIG. Area A ~
It is possible to read only one of G.

FIG. 7 is a diagram showing the basic structure of the phase difference AF, and FIG. 8 is a diagram for explaining the procedure for obtaining the first lens position based on the output of the phase difference AF.

The sensor section 55, as shown in FIG.
Lenses 104L and 104R arranged in a pair on the left and right (see FIG.
(Corresponding to the lenses 56L and 56R), the left and right line sensors 103L and 103R, which are detecting means corresponding to the sensor 57, are arranged. The base line length, which is the distance between the pair of lenses 104L and 104R, is D, the distance from the lenses 104L and 104R to the line sensors 103L and 103R in the optical axis direction is f, and the distance from the lenses 104L and 104R to the subject 107 is When the offset amount of the subject image on the right line sensor 103R with respect to the subject image on the L and left line sensors 103L is W, L: D
= F: W holds, the subject distance L is calculated as L = D × f / W.

Further, the phase difference AF means 58 is converted by the A / D means 105L and 105R for converting the outputs of the line sensors 103L and 103R into digital signals, and the A / D means 105L and 105R. And a calculating means 106 for obtaining the subject distance L using the above-mentioned mathematical expression based on the digital signal.

FIGS. 8A and 8B show an example of a high-contrast subject, and outputs (A / D) at the left (L) side line sensor 103L and the right (R) side line sensor 103R. It is a diagram showing a state of the output (digitalized by means 105L, 105R). As shown,
It can be seen that the high-contrast subjects, which are presumed to be the same subject, have shifts at the positions formed by the left and right line sensors 103L and 103R.

FIG. 8C shows the right (R) side line sensor 1 with respect to the output of the left (L) side line sensor 103L.
It shows that the output of 03R is sequentially shifted and the left and right approximation degree F (S) is obtained for each shift.

Here, the left and right approximation degree F (S) is, as shown in the following expression 1, the left (L) side line sensor 103L.
From the output of the right side (R) side line sensor 1
The output of 03R is subtracted, and the absolute value is summed to obtain the sum.

[0051]

## EQU1 ## F (S) = Σ | (LR shift) |

The degree of approximation F (S) thus obtained is, for example, as shown in FIG. 8 (D). In the illustrated example, the value of the degree of approximation F (S) is smallest when the shift amount is +3. In this example, it is "1" (see FIG. 8C).

Here, the point where the degree of approximation is the minimum (the point where the shift amount is +3 and the degree of approximation is 1) and the third point where the degree of approximation is smaller (the shift amount is +4 and the degree of approximation is 12). Point) is connected by a first straight line, and the slope of this straight line is inverted (that is, the sign is inverted), and the second point from the smallest approximation degree (shift amount +2 and approximation degree 11 The second straight line with a slope that is the opposite of this sign,
When the intersection of the first straight line and the second straight line is obtained, the shift amount of this intersection is the shift amount S0 that does not consider the variation, and corresponds to the first focusing distance.

Further, the average value of the approximation F (S) is calculated,
0.3 times between this average value and the degree of approximation at the shift amount S0 is set as the range of variation related to the degree of approximation. The intersection of the horizontal dotted line indicating the range of the variation and the second straight line is the shift amount S considering the variation.
The subject distance corresponding to this shift amount S1 becomes the second focusing distance. Therefore, by obtaining the lens position of the AF lens 47 corresponding to this second focusing distance, it becomes the first lens position.

However, when the difference between S0 and S1 is smaller than the predetermined amount Scnt, that is, | S1−S0 | <Scnt, instead of adopting the above S1, S1 =
S0-Scnt is newly adopted as S1, a minimum limit is set for the variation, and the first lens position is obtained.

FIG. 9 is a diagram showing the basic structure of the active AF, and FIG. 10 is a diagram for explaining the procedure for obtaining the first lens position based on the output of the active AF.

Although the first lens position is obtained by the phase difference AF in the above, it is also possible to obtain the first lens position by active AF instead.

First, with reference to FIG. 9, an outline of the configuration of the auxiliary AF means by active AF will be described.

When performing distance measurement by active AF,
The infrared LED 110 emits light under the control of the light emission control unit 111. The emitted infrared light is the first
The image is projected onto the subject 107 via the lens 112.

The infrared light reflected by the irradiated subject 107 is transmitted to the PSD 114 via the second lens 113 which is arranged so as to be separated from the first lens 112 by a predetermined base line length D. Collected.

On the PSD 114, by detecting the condensing position of the reflected infrared light, that is, the shift amount (offset amount) W from the image forming position of the object at infinity.
The object distance can be calculated by detecting the. PSD 11 including information related to this offset amount W
The output signal from No. 4 is input to the light receiving position detecting means 115 and processed such as being converted into a digital signal, and then the calculating means 116 calculates the subject distance.

At this time, the baseline length, which is the distance between the pair of lenses 112 and 113, is D, and the lens 113 to PSD1
14 is f, the distance from the lens 112 to the subject 107 is L, and the offset amount of the actual subject image with respect to the subject image at infinity is W, the subject distance L is the phase difference AF described above. Just as in the case of, L = D × f / W is obtained (triangular AF).

Further, in this active AF,
By detecting the amount of infrared light received by the PSD 114, the subject distance corresponding to the amount of light is also obtained (light amount AF).

FIG. 10A shows a triangular AF and a light amount AF.
FIG. 7 is a diagram showing a state when a normal result is obtained by performing

In this diagram, the relationship between the output value and the distance (the reciprocal of the distance) when performing the triangular AF is shown by the solid line f0, and the range of the distance measurement error is the range surrounded by the dotted lines f1 and f2. Has become. Further, the error range due to the light amount AF is the range surrounded by the one-dot chain lines f3 and f4. As shown in the figure, the error of the triangular AF tends to increase slightly on the long distance side, while the error of the light amount AF tends to increase on the short distance side.

In the diagram, scaling is performed so that the output value of the triangular AF and the output value of the light amount AF are the same when the distance measurement values are the same.

FIG. 10A shows an example of a normal case in which most of the projected infrared light is irradiated to the subject 107 and reflected, and then returns to the PSD 114.

As shown in the figure, the distance range DR1 including the error obtained by the triangular AF and the distance range DR2 including the error obtained by the light amount AF overlap with each other.

At this time, in the present embodiment, the triangular AF
To the infinity side of the subject distance range DR1 predicted by (the first distance at the intersection of the dotted line f1 and the triangular AF output value at which the amount of extension is small) and the infinity of the subject distance range DR2 predicted by the light amount AF. Side (one-dot chain line f3 and light intensity A
The third distance DT2 is obtained by taking the average of the second distance at which the amount of feeding is small at the intersection with the F output value), and this is made to correspond to the first lens position. There is.

As described above, when the AF lens 47 is driven from the far side, in order to approach the AF lens 47 gradually without passing the focus position, the first lens position is set within the focusable area. It is necessary to select the long distance side.

At this time, the error of the triangular AF is large at the long distance as shown by the dotted line, and the error of the light amount AF is large at the short distance as shown by the one-dot chain line. If the one on the infinity side is simply selected, the third distance will be on the infinity side, and the third distance will result from the in-focus position. Therefore, here, by taking the average of these, a reasonable distance that is on the infinite side within the range close to the in-focus position is obtained.

On the other hand, FIG. 10B is a diagram showing a state where the results of the triangular AF and the light amount AF do not overlap.

In this example, the light amount AF is larger than the distance range DR1 in which focusing is possible estimated by the triangular AF.
The distance range DR2 that has the possibility of focusing estimated by is farther away, and there are no overlapping portions.

Such a result is obtained, for example, when the projected infrared light is only partially irradiated on the subject, or the reflectance of the subject is greater than the expected average reflectance. It is considered to be obtained when it is too small.

Even in such a case, similarly to the above, the object distance range DR1 expected by the triangular AF is obtained.
On the infinite side (the first distance at the intersection of the dotted line f1 and the triangular AF output value at which the extension amount is small) and the infinite side of the subject distance range DR2 predicted by the light amount AF (the one-dot chain line f3 and the light amount). The third distance DT2 is obtained by taking the average of the intersection with the AF output value and the second distance at which the feeding amount is small).
By calculating, it is possible to calculate a reasonable distance.

FIG. 11 is a timing chart showing the integration timing and the like of the image pickup device for performing the contrast AF so as to minimize the influence of flicker.

As shown in FIG. 11A, some commercial power supplies such as fluorescent lamps have a brightness that changes every half cycle due to the commercial power supply being an alternating current. The cycle of the commercial power source is often either 50 Hz or 60 Hz, and the cycle in which the brightness fluctuates in these cases is as follows. Cycle at 50 Hz: 1000/50/2 = 1
Cycle in the case of 0.0 mS · 60 Hz: 1000/60/2 = 8.
333 ms

Therefore, the timing t at which the brightness peaks
It is considered that the time interval between p is often one of these cycles.

Luminance detecting means 76 which is the subject luminance detecting means
As a result, when the luminance of the subject affected by the flicker is detected, for example, it becomes as shown in FIG. 11 (A).

On the basis of the change in the subject brightness detected by the brightness detecting means 76, the flicker timing detecting means 77, which also serves as the flicker detecting means and the stable timing detecting means, detects the periodic flicker and detects the flicker. The stable timing is detected so that the subject brightness can be detected stably without being affected.

That is, as shown in FIG. 11 (A), since the change in the brightness is the most gradual in the vicinity of the timing tp at the peak, the integration period when the contrast AF is performed by the image pickup device 65 is It is desirable to perform it so that it coincides with the portion where the luminance changes gently. FIG. 11B shows the timing for this.

FIG. 11B shows the integration period of each pixel in any one of the selected distance measurement areas of the areas A to G shown in FIG. 5 in the image pickup device 65.

The integration start timing of each pixel in the selected distance measuring area is slightly shifted for each pixel as shown in the figure. After performing integration for each pixel for the same period, integration is performed at different timings. It is designed to be read after finishing.

At this time, the peak timing of the flicker luminance is midway between the integration start timing of the pixel in which the integration is started earliest in the selected area and the integration end timing of the pixel in which the integration is ended latest in the selected area. By controlling the integration so that tp is located,
The influence of brightness change due to flicker is suppressed to a minimum.

Further, the count value of the LDPI (lens drive photo interrupter), which is provided in the focus lens position detection circuit 53 and outputs a pulse in response to the extension of the AF lens 47, is shown in FIG.
As shown in (C), it is determined at this peak timing tp.

FIG. 12 is a timing chart showing the timing of distance measurement calculation and lens extension based on the output of the image pickup device 65 read in response to flicker.

Although the scale in the time axis direction is slightly different, FIG. 12 (A) is different from FIG. 11 (A) and FIG. 12 (B).
11 (B) above and FIG. 12 (C) above FIG.
(C) shows almost the same output and the like.

Further, distance measurement calculation is performed at the timing shown in FIG. 12D based on the signal of the distance measurement area read from the image sensor 65, and the distance measurement result and the read LDPI count value are obtained. By updating the number of pulses that the AF lens 47 is extended from, the focus motor drive circuit 52 controls the LD motor 54 at the timing as shown in FIG. 12E based on the updated number of pulses.
The lens is extended.

FIG. 12 (F) shows an example of the amount of extension of the AF lens 47 when such control is performed.

In the example shown in the drawing, the lens is first extended at a constant speed toward the first lens position detected by the phase difference AF, but the speed is temporarily reduced when the position approaches the first lens position. ing. Since the second lens position is detected by the contrast AF while performing such an operation, the second lens position is slightly accelerated and extended again, and decelerated again when the second lens position is approached.

Although the distance measurement calculation by contrast AF is performed for each flicker cycle here, if the number of pixels in the distance measurement area of the image sensor 65 is large, a time longer than the flicker cycle is measured. It may be necessary for distance calculation. In such a case, the contrast AF may be performed with a cycle of an appropriate integral multiple of the flicker cycle.

FIG. 13 shows A with respect to the number of pulses of LDPI.
6 is a timing chart showing the relationship of the amount of extension of the F lens 47 and the change timing of the AF switch.

When the driving pulse is started to be supplied to the LD motor 54 when the AF lens 47 is at the most retracted position, as shown in FIG. Can actually start feeding.

When the AF lens 47 is extended to a certain extent, as shown in FIG. 13B, an AF switch (AF) provided in the focus lens position detection circuit 53 is provided.
SW) changes from low (L) to high (H). AF
This position where the switch is changed becomes the reference position when the AF lens 47 is extended.

The position where the predetermined number of reset pulses RST_PLS is extended from the reference position is the infinite position, and the position where the target pulse number M_PLS is further extended from the infinite position is the target position.

Further, when the feeding is further performed after passing the target position, the AF is mechanically continued beyond the closest position.
When you reach a position where you cannot extend the lens 47,
After passing through some play, the LD motor 54 cannot be driven any more.

As described above, the infinite position is determined with reference to the position where the AF switch changes, and the target position is reached by giving the target pulse number from this infinite position.

FIG. 14 is a diagram showing the relationship between the amount of extension of the AF lens 47 and the contrast amount (AF evaluation value) near the in-focus position.

The contrast amount takes a smaller value as it goes away from the in-focus position toward the infinite side and the close-up side, and forms a peak (maximum) at the in-focus position. When you follow the curve like this by extending the lens,
Circles indicate the integration timing of the image sensor 65 that matches the peak timing tp that gives the flicker luminance peak described above.

As shown in the figure, in the region R1 along the curve, the AF lens 47 is initially extended at a high predetermined extension speed, but at the first lens position calculated based on the phase difference AF. When approaching, the feeding speed becomes slightly slower and the intervals between the circles become slightly narrower.

In the subsequent region R2 along the curve, the feeding speed becomes slower and stops as it approaches the first lens position.

When the second lens position is calculated by the contrast AF performed at the timing marked with a circle, the target is updated, so that the area R along the curve is updated.
As shown in 3, the driving of the AF lens 47 is stopped when the second lens position is accelerated again and decelerated again toward the second lens position to reach the peak of the contrast amount. There is.

The second lens position is updated every time the contrast AF is performed as indicated by the circle, and the focus position is set with higher accuracy.

FIG. 15 shows the amount of extension of the AF lens 47 at the lens speed indicated by the LDPI pulse width.
FIG. 16 is a diagram showing how the lens speed changes until the target position is reached, and FIG. 17 is a diagram showing the lens speed from the start of lens extension until the target position is reached. It is a diagram which shows the mode of change.

Since the LD motor 54 rotates at a high speed when the number of pulses applied per unit time is large, and conversely at a low speed when the number of pulses is small, the pulse width and the lens speed are opposite to each other. There is a proportional relationship.

Therefore, in FIG. 15, the lens speed is slower as the coordinate in the vertical axis direction is larger (that is, the pulse width is larger), and the lens speed is faster as the coordinate in the vertical axis direction is smaller (that is, the pulse width is smaller). Is shown.

At this time, the target feed amount when the predicted pulse control is performed is in a range such that it is sandwiched between two curves shown by dotted lines with the curve shown by solid lines as the center. As a matter of course, this curve is a curve in which the amount of extension is small when the lens speed is low (the number of LDPI pulses is small), and is large when the lens speed is high (the number of LDPI pulses is large), and the kinetic energy is Reflecting the fact that it is proportional to the square of the speed, the curve is as shown in the figure.

The area under the curve shown by the dotted line on the lower side is the area related to the amount of extension until the LD motor 54 is stopped when the LD motor 54 is controlled only by the motor brake.
The area above the curve indicated by the upper dotted line is the LD motor 54.
This is an area related to the amount of feeding until the motor stops when the motor is open controlled.

FIG. 16 shows a control example when the AF lens 47 having such a relationship between the lens speed and the amount of extension is actually stopped. In FIG. 16,
The number of pulses until the stop with respect to the lens speed is shown on the left side, and the relationship between the number of moving pulses and the lens speed is shown on the right side.

In order to stop at the target position, it is ideal to perform the control shown by the solid line on the right side. While comparing the lens speed, the motor stop control is performed by adjusting the motor open control and motor brake control.

Taking the point A shown on the actual control curve shown by the dotted line as an example, the control is performed as follows.

First, let CT_PLS be the number of pulses emitted from the reference position of point A, and let vA be the lens speed at point A.

The remaining number of pulses to the target position at this point A is the number of pulses from the reference position to the target position shown in FIG.
As shown in 3 (A), M_PLS + RST_PLS
Therefore, M_PLS + RST_PLS-CT_
It becomes PLS.

On the other hand, when the ideal control is performed at the lens speed vA, the expected number of pulses until the stop is shown in FIG.
As can be seen by referring to the left side of 6, it is Y_PLS, and in the case of open control, in addition to this, OPN_
The number of pulses for PLS only increases.

Therefore, by comparing these, that is, by evaluating the next quantity, Y_PLS- (M_PLS + RST_PLS-CT_PLS) + OPN_PLS, either stop at the target position at the current lens position and lens speed, or It is possible to predict whether to stop before the position or to stop beyond the target position.

In the example shown in FIG. 16, Y_PLS- (M_PLS + RST_PLS-CT_PLS) + OPN_PLS <0 (that is, the point A has a lens speed higher than that when the ideal control shown by the solid line is performed. It is expected that the vehicle will stop before the target position. Therefore, the LD motor 54 is rotated in the normal direction and adjustment is performed so as to follow the ideal control.

FIG. 17 shows an example of how the lens speed changes with respect to the amount of extension when the AF lens 47 is extended from the most extended position to stop at the target position. In FIG. 17, the ideal control is shown by a dotted line and the actual control is shown by a solid line, and the actual control is performed with a certain width with respect to the desired ideal control curve. There is.

18 and 19 show the digital camera 1
6 is a flowchart showing the main operation of FIG.

As described above, this digital camera 1
Is configured to function as a camera when the barrier 23 is open, and to function as a PDA when the PDA power switch 25 is turned on when the barrier 23 is closed. The flow of is explained.

That is, when this operation is started, it is first determined whether or not the barrier 23 is opened (step S1).

Here, if the barrier 23 is closed, it is judged whether or not the lens barrel 22 is collapsed (step S2). If not, the lens barrel 22 is zoomed. A process for driving the lens barrel to retract it to the stored state is performed (step S3), and the display of the LCD 35 is turned off (step S4). The operation of the digital camera 1 is stopped when the step S4 ends or when the lens barrel 22 is retracted in the step S2.

When the barrier 23 is opened in step S1, the zoom is widened to enable the photographing (step S5), and the 4-minute timer is started (step S6).

Then, it is judged whether the barrier 23 is still open (step S7), and if it is closed, the process goes to step S3.

If the barrier 23 remains open, it is determined whether or not the release switch 24 has been operated (step S8).

Here, when the release switch 24 is operated, a series of processing for taking an image is performed.

That is, first, the image pickup circuit 64 is turned on (step S9), an external light distance measurement (that is, distance measurement by phase difference AF in the above example) request is output to the sub CPU 42 (step S10), and the signal is sent. Level control means 68
The gain adjustment (photometry) of the image sensor 65 is performed (step S11).

Next, the flicker timing detection means 7
The brightness change of the commercial frequency is measured by 7 to determine the distance measurement timing (step S12).

The main CPU 41 is a sub CPU.
Obtain the external light distance measurement information from 42 (step S13),
Sub-routine "LDR for focusing while measuring distance
"IV_M" is executed (step S14). Details of this subroutine will be described later.

Then, an image is picked up by the image pickup device 65 (step S15), defective pixels are corrected in the image data obtained by the image processing circuit 72 (step S16), and white balance is corrected (step S16). In step S17), image data compression is performed by the image compression means 73 (step S18).

Then, the image display is turned on to display the image on the display section 89 (step S19), and the compressed image file is stored in the memory card 39 via the memory I / F 74 (step S20).

Thereafter, the number of image pickup frames is counted up (step S21), the 4-minute timer is started (step S22), and the 10-second timer for image display is restarted (step S23).

In step S8, if the release switch 24 is not operated, then the zoom up (ZU) switch or the zoom down (ZU) switch is pressed.
D) It is judged whether or not the switch is operated (step S
24) If any of them is operated, zoom control is performed according to the operation (step S25), and the process goes to step S22.

If neither the zoom up switch nor the zoom down switch has been operated, it is next determined whether or not the mode switch has been operated (step S2).
6) If it is operated, the mode is changed according to the operation (step S27), and the step S22 is performed.
Go to

If the mode switch has not been operated, it is next determined whether or not the image display switch has been operated (step S28), and if it has been operated, image display is performed. (Step S29), go to step S22.

If the image display switch has not been operated, it is next determined whether or not the image up / down switch has been operated (step S30). Then, the photographed image immediately before or after is displayed (step S31), and the process goes to step S22.

On the other hand, if the image up / down switch is not operated, or if step S23 is finished, it is judged whether 10 seconds of the image display time has elapsed (step S32), and If the image display is turned off (step S33), the image display 10-second timer is stopped (step S34), and if the image display time of 10 seconds has not elapsed, the image display is stopped as it is.
It is determined whether minutes have passed (step S35).

Here, if it is less than 4 minutes, the process goes to the step S7, while if 4 minutes have elapsed, a process for widening the zoom is performed (step S3).
6) The display of the display unit 89 is turned off (step S3
7) The operation of the digital camera 1 is stopped. To stop the operation here, the clock (original oscillation) is also stopped so that the current consumption becomes almost zero. Further, from this stopped state, the barrier 23 is restored when the barrier 23 is operated or the battery 99 is detached.

Next, FIG. 20 and FIG. 21 show a subroutine "LDRIV" when performing focusing while measuring the distance.
7 is a flowchart showing details of "_M".

This subroutine is roughly performed to perform gain adjustment for flicker detection (steps S41 to S46), detect a timing at which the flicker luminance vibration is small (steps S47 to S63), and perform AF.
Control until the switch is changed (measurement of AF contrast) is performed (steps S64 to S71), and then feedback control (curve control) by contrast detection is performed (steps S72 to S8).
5) The AF lens is stopped at a desired position, and the actual lens control is performed by the sub CPU 42.

That is, when the operation is started, first, A
It is determined whether or not the exposure time (integration period) of the F region is smaller than 1 ms (step S41). If it is larger, the gain of the image sensor 65 is increased by the signal level control means to increase the exposure time (integration period). It is set within 1 ms (step S42).

Next, a timing adjustment timer (AF timer) is started (step S43), and an image of the AF area designated by the image pickup area designating means 66 is imaged (step S44).

Then, the brightnesses of the AF areas are summed to obtain the AF
Substitute in _SUM (n) (step S45), n is 25
Is reached, that is, whether or not imaging has been repeated 25 times is determined (step S46).

If the number of times is less than 25, the process proceeds to step S44 to repeat the imaging of the AF area as described above, and when the number of times reaches 25, the sub CPU 42
A lens control start request is transmitted to (step S4).
7).

Then, the rate of change in luminance is calculated by the following mathematical formula 2.
It is calculated as shown in and is substituted into AF_HENKA (step S48).

[0145]

[Equation 2] AF_HENKA = Σ | {AF_SUM (n) -AF_SUM (n) average} | /
ΣAF_SUM (n) Here, the sum (Σ) is taken for the variable n.

Then, it is judged whether or not the calculated AF_HENKA is larger than a predetermined value (step S49). If the calculated value is less than the predetermined value, the AF timer is set to 9.167 ms.
The pulse output is set in step S63 (step S63).

If it is larger than the predetermined value, AF
The brightness change rate of the area is calculated as shown in the following Equation 3,
Substitute into AF_SUM_D (n) (step S5)
0).

[0148]

[Equation 3] AF_SUM_D (n) = {AF_SUM (n + 1) -AF_SUM (n)} / AF_SUM (n)

Next, it is judged whether or not n has reached 24 (step S51), and if it has not yet reached 24, the processing of step S50 is repeated.

Thus, when n reaches 24, the variable m is set to 1 (step S52), and AF_S
UM_D (n) ≧ 0 and AF_SUM_D (n + 1) ≦
It is determined whether 0 is satisfied (step S5).
3).

Here, if it is satisfied, the brightness peak timing is calculated as shown in the following formula 4,
It is substituted into T_AF_PK (m) (step S54).

[0152]

[Equation 4] T_AF_PK (m) = n + AF_SUM_D (n) / {AF_SUM_D (n + 1) -AF
_SUM_D (n)}

Then, m is incremented (step S55).

When this step S55 ends or when the above step S53 is not satisfied, it is judged whether or not n has reached 24 (step S56), and if it has not yet reached 24, Then, the procedure goes to step S52, and the above-mentioned processing is repeated.

Thus, when n reaches 24, T
_AF_PK (n + 1) -T_AF_PK (n) is 1
Whether it is almost equal to 0.0 ms, that is, frequency 50 Hz
(Step S)
57), if they are almost equal, wait until the AF timer count value becomes (a multiple of 10.0 ms−half the AF imaging time (integration period)) (step S5).
8), the AF timer is set to output a pulse at 10.0 ms (step S59).

In step S57, 1
If different from 0.0 ms, then T_AF_PK
It is determined whether or not (n + 1) -T_AF_PK (n) is approximately equal to 8.333 ms, that is, approximately half the cycle of the frequency 60 Hz (step S60).

Here, if they are almost equal, the AF timer count value is waited until it becomes (a multiple of 8.333 ms-half of the AF image pickup time (integration period)) (step S61), and then the AF timer is reached. Is set to output a pulse at 8.333 ms (step S62).

On the other hand, in step S60, 8.
If it is different from 333 ms, the process goes to step S63, and as described above, the AF timer is set to output a pulse at 9.167 ms. In addition, this 9.167
ms is an average value of 10.0 ms and 8.333 ms.

Thus, when the AF timer is set in any of the steps S59, S62, and S63, the variable n is set to 0 (step S64), and then the imaging (integration) of the AF area is started. Yes (step S65).

Then, it is judged whether or not it is an intermediate timing of image pickup (integration) (step S66), and if so, CT_PLS (the number of pulses extended from the infinite position) is received from the sub CPU 42. And CT_
Substitute in PLS (n) (step S67).

If step S67 is completed or if it is judged in step S66 that it is not the intermediate timing of image pickup (integration), it is judged whether the image pickup of the AF area is finished (step S68). Until the end, the process goes to the step S65 to continuously capture the AF area.

In this way, when it is determined that the imaging of the AF area is completed, the contrast evaluation value is set to AF_CO
It is substituted for N (n) (step S69), and it is determined whether the AF timer output is inverted (step S70).

If it is reversed here, the above step S
65, the above-described processing is repeated, and if not reversed, it is determined whether CT_PLS is positive, that is, whether the AF switch has changed (step S71).

Until it changes, the process goes to the step S70, and when it changes, next, it waits until the AF timer output is reversed (step S72).

In this way, when it is confirmed that the timer output is inverted, n is incremented (step S73), and then the image pickup (integration) of the AF area is started (step S74).

Then, it is judged whether or not the intermediate timing of the image pickup (integration) is reached (step S75), and when the intermediate timing is reached, the sub CPU 42 sends CT.
_PLS is received and substituted into CT_PLS (n) (step S76).

If this step S76 ends or if it is not the intermediate timing of the image pickup (integration) in the step S75, it is judged whether or not the image pickup of the AF area is finished (step S77), and the process ends. Up to step S74, the above-described processing is repeated.

In this way, when the imaging of the AF area is completed, the contrast evaluation value calculation means 78 calculates the contrast evaluation value and substitutes it into AF_CON (n) (step S78), and the expected result is obtained. The number of focal pulses is calculated and is substituted into M2_PLS (n) (step S79).

Then, M2_PLS (n) becomes M1_PL
It is judged whether it is larger than S (step S80),
If it is not larger, it waits until the AF timer output is inverted (step S84), and when it is inverted, the process goes to step S73 to perform the above-described processing.

Further, M2_PLS (n) is M1_PLS.
If it is larger than the above, ZZ is calculated by the following formula 5 (step S81).

[0171]

[Equation 5] ZZ = M2_PLS (n)-(RST_PLS + CT_PLS + OPN_PLS)

Then, it is judged whether the calculated ZZ is 0 or less (step S82), and if it is larger than 0,
After transmitting M2_PLS (n) to the sub CPU 42 (step S83), go to the above step S84 to perform AF.
Wait for the timer output to reverse.

As described above, distance measurement by contrast AF is performed in accordance with the AF timer which is a timer for measuring the stable timing of flicker, and the newly calculated expected focusing pulse number M2_PLS (n) is sent to the sub CPU 42. Feedback control is performed.

In step S82, ZZ
If is less than or equal to 0, the LD control end code is transmitted to the sub CPU 42 (step S85), then this subroutine is exited and the above-described main routine is returned to.

Here, the principle of calculating the expected focusing pulse in step S79 will be described with reference to FIGS. 23 and 24. FIG. 23 is a diagram showing a curve in which the contrast amount is approximated by a normal distribution in the vicinity of the focus position, and FIG. 24 is a diagram showing a straight line g (x) for calculating the focus position using a plurality of contrast AF results. is there.

First, how the contrast amount of the subject image formed on the image pickup device 65 changes with respect to the driving amount x of the AF lens 47 is expressed by the following mathematical expression 6, which is a function F (x) of normal distribution. It is assumed (approx.) That
reference).

[0177]

[Equation 6]

In this coordinate system, the point where x = 0 is set to the peak of the contrast amount, that is, the in-focus position.

Next, the function obtained by differentiating this F (x) is f
Let (x) be given by the following Equation 7 (FIG. 23).
reference).

[0180]

[Equation 7]

This f (x) divided by F (x) is g
Assuming that (x), the focusing position x =
It is a linear function that passes through 0 (see FIG. 23).

[0182]

[Equation 8]

Therefore, this g (x) can be determined by obtaining two points passing through this g (x), and the in-focus position can be calculated by using the determined g (x). Become.

However, F (x) which is the denominator of g (x)
Is rapidly decreased as the absolute value of x becomes large, and it is considered that the error increases. So F
After passing x = a0 which is an inflection point of (x) (that is, a peak (maximum) position of f (x)), two points a1 and a2 for determining g (x) are obtained. , I try to suppress the error. That is, g with the required accuracy
In order to calculate (x), F related to the contrast evaluation value
It is desirable to calculate in the vicinity of x = 0 where (x) becomes a peak, and the range between the maximum value and the minimum value of g (x) is adopted as the range of such a vicinity.

Further, the drive amount x specifically corresponds to, for example, the number of pulses when pulse driving is performed.

FIG. 22 is a flow chart showing the processing for calculating the predicted focusing pulse in step S79 of FIG.

When this operation is started, an array P (m) of feed pulses and an array F (m) of contrast are created (step S91). That is, the variable m is incremented, and the obtained feed pulse CT_PLS (n) is set to P.
Substituted in (m) and acquired contrast AF
Substitute _CON (n) into F (m). Since this operation is repeated each time this subroutine is called, P
(M) and F (m) will be created as an array.

Similarly, the contrast differential array f
(M) is created as shown in the following Expression 9 (step S92).

[0189]

[Equation 9]

Further, as shown in the following expression 10, f
An array of g (m) is created by dividing (m) by F (m) (step S93).

[0191]

## EQU10 ## g (m) = f (m) / F (m)

Then, it is determined whether or not f (m) has already exceeded its own peak depending on whether or not the peak flag is 1 (step S94). If it has not yet exceeded the peak, f (m) m) is the previous array element f
By determining whether it is smaller than (m-1),
Based on f (m) calculated this time, it is determined whether the peak is exceeded (step S95).

Here, if f (m) is still f (m-1) or more, it is determined that the peak has not been exceeded yet, and the process returns as it is, and f (m) is smaller than f (m-1). In this case, the peak flag is set to 1 (step S96) and the process returns.

On the other hand, in step S94, f
When it is determined that (m) exceeds the peak, linear approximation is performed by the following formula 11 (see FIG. 24) to calculate the in-focus position M2_PLS (n) (step S
97) and then return.

[0195]

[Equation 11]

By thus approximating the contrast amount by a normal distribution and utilizing the fact that the ratio between the contrast amount and the derivative of the contrast amount becomes a straight line, the in-focus position can be calculated accurately.

Further, since the linear approximation is performed after passing the peak position of the differential, it is possible to obtain the in-focus position with high accuracy.

25 and 26 show a subroutine "LDRIV_S" for focusing in the sub CPU 42.
It is a flow chart which shows operation of "B".

In this subroutine, after setting the initial value and so on, the number of pulses from the AFSW to the first lens position (RST
_PLS + M1_PLS) to perform constant velocity control of the stop speed (steps S106 to S118), and AFS
After W becomes high (H), curve control is performed until the second lens position is reached (step S120 to step S1).
33).

At this time, when the second lens position is updated by communication from the main CPU 41, the control is performed so as to stop at the updated lens position.

That is, when this operation is started, the LDPI pulse number from the time when the AF switch is changed to the infinite position is read from the EEPROM 98, and RS
Substitute for T_PLS (step S101).

Further, the number of pulses for open control is read out from the EEPROM 98 and substituted into OPN_PLS (step S102).

After that, as the target pulse number M_PLS from the infinite position to the stop, the pulse number M1_PLS from the infinite position to the focus position obtained by the external light distance measurement is substituted (step S103), and further extended from the infinite position. The number of pulses CT_PLS is set to 0 (step S
104).

After that, the LD motor 54 is normally rotated (step S105), and it is detected whether the LDPI has changed (step S106).

If a change in LDPI is detected, the LDPI pulse width is measured and the result is W_P.
Substitute for LS (step S110), and
The number of pulses from PLS to stop is predicted, and the result is substituted into Y_PLS (step S111).

Then, Z is calculated by the following formula 12 (step S112).

[0207]

[Equation 12] Z = Y_PLS- (RST_PLS + M_PLS)

In this way, the calculated value of Z is judged (step S113), and if Z is positive, M1_PL
Assuming that the LD motor 54 is extended further than S, the LD motor 54 is braked (step S114).

In step S113, Z
Is less than or equal to 0 and greater than -OPN_PLS, L
A process for controlling the opening of the D motor 54 is performed (step S115).

Furthermore, in the above step S113,
If Z is less than or equal to -OPN_PLS, M1_PL
If you stop too far before S, (RST_PLS
After setting the motor voltage according to + M_PLS) (step S116), the process of rotating the LD motor 54 forward is performed (step S117).

On the other hand, in step S106, L
When it is determined that the DPI has not changed, it is determined whether the LDPI has not changed for a predetermined time (step S1).
07), when the predetermined time has been reached, the motor voltage is increased by a predetermined voltage and set (step S108), and the LD
The motor 54 is normally rotated (step S109). In this way, when the LDPI does not change, the motor voltage is increased stepwise by a predetermined voltage and the motor is restarted.

When the LDPI is changed within the predetermined time in step S107, the step S109 is completed, or the steps S114 and S are executed.
When either of 115 and step S117 is completed, it is determined whether or not the AF switch is changed from low (L) to high (H) (step S118). The above-described processing is repeated.

In the loop of steps S106 to S118, when a CT_PLS request is interrupted, C_PLS (= 0) is set as the main CP.
An interrupt process for transmitting to U41 is performed (step S141).

If it is detected in step S118 that the AF switch has changed from low (L) to high (H), the CT_PLS counting counter is started (step S119) to determine whether LDPI has changed. Is detected (step S120).

When a change in LDPI is detected, the count value of the counter is substituted into CT_PLS (step S124), the LDPI pulse width is measured, and the result is substituted into W_PLS (step S1).
25) Further, the number of pulses from W_PLS to the stop is predicted, and the result is substituted into Y_PLS (step S126).

Then, Z is calculated by the following expression 13 (step S127).

[0217]

[Expression 13] Z = Y_PLS- (RST_PLS + M_P
LS-C_PLS)

In this way, the calculated value of Z is judged (step S128), and if Z is positive, M_PLS
If the LD motor 54 is excessively extended, the LD motor 54 is braked (step S129).

In step S128, Z
Is less than or equal to 0 and greater than -OPN_PLS, L
A process for controlling the opening of the D motor 54 is performed (step S130).

Furthermore, in step S128,
If Z is less than or equal to -OPN_PLS, M_PLS
If you stop too far in front of (RST_PLS +
After setting the motor voltage according to (M_PLS-CT_PLS) (step S131), the process of rotating the LD motor 54 in the forward direction is performed (step S132).

On the other hand, in step S120, L
When it is determined that the DPI has not changed, it is determined whether the LDPI has not changed for a predetermined time (step S1).
21) If the predetermined time has been reached, increase the motor voltage by a predetermined voltage and set it (step S122).
The motor 54 is normally rotated (step S123). Similar to the above, here, the motor voltage is increased step by step by a predetermined voltage and restarted.

When the LDPI is changed within the predetermined time in the step S121, the step S123 is completed, or the steps S129 and S are executed.
If either 130 or step S132 is completed, it is judged whether or not the LD control end code is received (step S133), and the above step S12 is executed until it is received.
0, and the above-described processing is repeated.

In the loop of steps S120 to S133, when there is a CT_PLS request interrupt, an interrupt process for transmitting C_PLS to the main CPU 41 is performed (step S142), and M
If there is a 2_PLS request interrupt, M2_P
Upon receiving the LS (step S143), this M2_PLS
Is substituted into M_PLS (step S14
4) If there is an LD end request interrupt, LD
A process of receiving the control end code is performed (step S14).
5) It looks like this.

When the LD control end code is received in step S133, the LD motor 54 is braked (step S134), waits for 30 ms (step S135), and the LD motor 54 is opened (step S134). (S136), and returns.

According to such an embodiment, since the focusing can be performed by moving the lens in one direction only to climb toward the peak of the contrast amount without going up and down, accurate AF operation can be performed. It can be performed at high speed.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications and applications can be made without departing from the spirit of the invention.

[Additional Notes] According to the above-described embodiment of the present invention as described in detail above, the following configuration can be obtained.

(1) Auxiliary AF means for detecting the subject distance, image pickup means for photoelectrically converting the subject image and integrating it for a predetermined integration period, and then outputting it as an image signal, and subject image formed on this image pickup means. A for focusing
An F lens, a contrast evaluation value calculation means for calculating a contrast evaluation value of a subject image formed on the image pickup means based on an image signal output from the image pickup means, and a lens for detecting the lens position of the AF lens. Position detecting means, lens control means for controlling and moving the AF lens based on the lens position detected by the lens position detecting means, and the lens position according to moving the AF lens by the lens controlling means. Based on a plurality of lens positions detected by the detecting means, and a plurality of contrast evaluation values calculated by the contrast evaluation value calculating means corresponding to the plurality of lens positions, respectively,
And a contrast peak position calculating means for calculating a lens position where the contrast evaluation value of the subject image formed on the image pickup means reaches a peak, the first lens corresponding to the subject distance detected by the auxiliary AF means. The position is calculated, the first lens extension is performed for the AF lens with the first lens position as a target, and the contrast evaluation value of the image is calculated while the first lens extension is performed. The detection of the lens position at the time of calculating the contrast evaluation value is performed a plurality of times, and the second lens position at which the contrast evaluation value reaches a peak is calculated by the contrast peak position calculation means based on the calculation result and the detection result. , The AF targeting the second lens position
A digital camera characterized by performing a second lens extension for a lens.

(2) Lens speed detecting means for detecting the moving speed of the AF lens, and stop position predicting means for predicting the stop position of the AF lens from the moving speed detected by the lens speed detecting means are further provided. The digital camera as set forth in appendix (1), characterized in that the lens control means controls the AF lens based on a difference between a target feeding position and an expected stop position.

(3) The lens position detecting means sets the AF at the intermediate timing of the integration period of the image pickup means for a plurality of pixels relating to the contrast evaluation value.
The digital camera according to appendix (1), which detects a lens position of a lens.

(4) The auxiliary AF means is a phase difference AF
The object distance is detected by means of a detecting means for detecting two images, and a detecting means for detecting two images.
A first focusing distance is calculated based on the phases of the two images.
Focusing distance calculating means, distance measuring error calculating means for calculating a distance measuring error based on the undulations of the two images detected by the detecting means, the first focusing distance and the distance measuring error. Based on the second focusing distance calculating means for obtaining a second focusing distance with a small amount of extension within a range in which focusing may occur, the first lens position is The digital camera described in appendix (1), which is obtained based on the second focusing distance.

(5) Subject brightness detecting means for detecting subject brightness, flicker detecting means for detecting periodic flicker from changes in subject brightness detected by this subject brightness detecting means, and being affected by flicker Without
A stable timing detecting means for detecting a stable timing capable of stably detecting the subject brightness; and the contrast evaluation by the imaging means in synchronization with the stable timing detected by the stable timing detecting means. The digital camera according to appendix (1), wherein integration is performed for a plurality of pixels related to the value and detection of the lens position by the lens position detection means is performed.

(6) The auxiliary AF means is capable of performing distance measurement for a plurality of distance measuring areas, and the image pickup means is also a plurality of distance measuring areas corresponding to the plurality of distance measuring areas by the auxiliary AF means. As a result of performing the distance measurement for the plurality of distance measuring areas by the auxiliary AF means, the distance measuring area becomes the closest distance measuring area. The digital camera according to appendix (1), wherein integration is performed by the image pickup device for a plurality of pixels relating to the contrast evaluation value with respect to the distance measurement region of the image pickup device corresponding to the distance region.

(7) The contrast peak position calculating means calculates the contrast evaluation value calculated or detected a plurality of times during the first lens extension and the lens position at the time of calculating the contrast evaluation value. The digital camera according to appendix (1), wherein the second lens position, which is the lens position where the contrast evaluation value reaches a peak, is calculated based on at least two or more sets of

(8) The contrast peak position calculating means further approximates the change in the contrast evaluation value with respect to the lens position by a normal distribution in the vicinity of the lens position where the contrast evaluation value reaches a peak, and the normal distribution is used to calculate the normal distribution. Based on the result of dividing the distribution differentiation,
The digital camera described in appendix (7), which is for calculating a second lens position that is a lens position where the contrast evaluation value has a peak.

(9) The digital value as set forth in appendix (8), characterized in that the vicinity of the lens position where the contrast evaluation value reaches a peak is between a maximum value and a minimum value obtained by differentiating the normal distribution. camera.

[0237]

As described above, according to the digital camera of the present invention, an accurate AF operation can be performed at a higher speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conceptual configuration of a digital camera according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the outer appearance of the digital camera in the above embodiment from the lens side.

FIG. 3 illustrates the digital camera in the above embodiment as a PDA.
FIG.

FIG. 4 is a block diagram mainly showing an electrical configuration of the digital camera of the above embodiment.

FIG. 5 is a diagram showing a region of an image sensor used for contrast AF in the embodiment.

FIG. 6 is a diagram showing a region of a line sensor used for phase difference AF in the above embodiment.

FIG. 7 is a diagram showing a basic configuration of phase difference AF in the embodiment.

FIG. 8 is a diagram for explaining a procedure for obtaining the first lens position based on the output of the phase difference AF in the above embodiment.

FIG. 9 is a diagram showing a basic configuration of active AF in the embodiment.

FIG. 10 is a diagram for explaining a procedure for obtaining the first lens position based on the output of active AF in the embodiment.

FIG. 11 is a timing chart showing the integration timing of the image sensor for performing contrast AF so as to minimize the influence of flicker in the above embodiment.

FIG. 12 is a timing chart showing the timing of distance measurement calculation and lens extension based on the output of the image sensor read in response to flicker in the above embodiment.

FIG. 13 is a timing chart showing the relationship between the number of LDPI pulses and the amount of extension of the AF lens and the change timing of the AF switch in the above embodiment.

FIG. 14 is a diagram showing the relationship between the amount of extension of the AF lens and the contrast amount (AF evaluation value) near the in-focus position in the above embodiment.

FIG. 15 is a graph showing the extension amount A at the lens speed indicated by the pulse width of LDPI in the above embodiment.
The line diagram which shows whether F lens stops.

FIG. 16 is a diagram showing how the lens speed changes until the target position is reached in the above embodiment.

FIG. 17 is a diagram showing how the lens speed changes from the start of lens extension to the arrival of a target position in the embodiment.

FIG. 18 is a flowchart showing a part of a main operation of the digital camera of the above embodiment.

FIG. 19 is a flowchart showing another part of the main operation of the digital camera in the above embodiment.

FIG. 20 is a flowchart showing a part of the details of a subroutine “LDRIV_M” when focusing is performed while measuring a distance in the above embodiment.

FIG. 21 is a flowchart showing another part of details of the subroutine “LDRIV_M” when focusing is performed while measuring the distance in the above embodiment.

22 is a flowchart showing a process of calculating an expected focusing pulse in step S79 of FIG. 21.

FIG. 23 is a diagram showing a curve or the like in which the contrast amount is approximated by a normal distribution in the vicinity of the in-focus position in the above embodiment.

FIG. 24 is a straight line g for calculating a focus position using a plurality of contrast AF results in the above embodiment.
The figure which shows (x).

FIG. 25 is a flowchart showing a part of the operation of the focusing sub-routine “LDRIV_SB” in the sub CPU in the above embodiment.

FIG. 26 is a flowchart showing another part of the operation of the focus adjustment subroutine “LDRIV_SB” in the sub CPU in the above embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Auxiliary AF means 3 ... 1st focusing distance calculation means 4 ... Distance measurement error calculation means 5 ... 2nd focusing distance calculation means 6 ... 1st lens position calculation means 7 ... Control means 8 Image pickup means 9 Flicker timing detection means (flicker detection means,
Stable timing detecting means) 10 ... Contrast evaluation value calculating means 11 ... AF lens 12 ... Lens position detecting means 13 ... Contrast peak position calculating means 14 ... Lens speed detecting means 15 ... Stop position predicting means 16 ... Lens control means 41 ... Main CPU (First focusing distance calculating means, distance measuring error calculating means, second focusing distance calculating means, first lens position calculating means, control means, stop position predicting means) 42 ... Sub CPU 47 ... AF lens 51 Focus lens control means 52 Focus motor drive circuit (lens control means) 53 Focus lens position detection circuit (lens position detection means, lens speed detection means) 54 LD motor 55 Sensor parts (auxiliary AF means) 56R, 56L ... Lens 57 ... Sensor (detection means) 58 ... Phase difference AF means (auxiliary AF means) 64 ... Shooting Circuit 65 ... Imaging element (imaging means) 66 ... Imaging area designating means 67 ... A / D circuit 68 ... Signal level control means 69 ... Timing generating circuit 76 ... Luminance detecting means (subject luminance detecting means) 77 ... Flicker timing detecting means ( Flicker detection means, stable timing detection means) 78 ... Contrast evaluation value calculation means 79 ... Contrast evaluation value differentiation means 80 ... Focus position prediction means (contrast peak position calculation means) 81 ... Focus detection means 103L, 103R ... Line sensor ( Detection means) 104L, 104R ... Lenses 105L, 105R ... A / D means 106 ... Calculation means 110 ... Infrared LED 111 ... Emission control means 112, 113 ... Lens 114 ... PSD 115 ... Light receiving position detection means 116 ... Calculation means

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // H04N 101: 00 G03B 3/00 A

Claims (3)

[Claims] 1. An auxiliary AF unit for detecting a subject distance, an image pickup unit for photoelectrically converting a subject image and integrating it for a predetermined integration period, and then outputting it as an image signal, and an object image formed on the image pickup unit. An AF lens for focusing, a contrast evaluation value calculation means for calculating a contrast evaluation value of a subject image formed on the image pickup means based on an image signal output from the image pickup means, and a lens of the AF lens A lens position detecting means for detecting a position, a lens controlling means for controlling and moving the AF lens based on the lens position detected by the lens position detecting means, and a lens controlling means for moving the AF lens. Accordingly, the plurality of lens positions detected by the lens position detecting means and the above-mentioned coordinates corresponding to the plurality of lens positions are respectively provided. Contrast peak position calculation means for calculating a lens position at which the contrast evaluation value of the subject image formed on the image pickup means has a peak based on a plurality of contrast evaluation values calculated by the trust evaluation value calculation means, And calculating a first lens position corresponding to the subject distance detected by the auxiliary AF means, and performing a first lens extension with respect to the AF lens with the first lens position as a target. While the lens extension is being performed, the calculation of the contrast evaluation value of the image and the detection of the lens position at the time of calculating the contrast evaluation value are performed a plurality of times, and based on these calculation results and detection results, the contrast The second lens position at which the contrast evaluation value reaches a peak is calculated by the peak position calculating means, and the second lens position is determined by the eye. Digital camera, characterized in that performing the second lens extension for the AF lens as. 2. A lens speed detecting means for detecting a moving speed of the AF lens, and a stop position predicting means for predicting a stop position of the AF lens from the moving speed detected by the lens speed detecting means. The digital camera according to claim 1, wherein the lens control means controls the AF lens based on a difference between a target feeding position and an expected stop position. 3. The auxiliary AF means detects a subject distance by phase difference AF, and based on the detecting means for detecting two images and the phases of the two images detected by the detecting means. A first focusing distance calculating means for obtaining a first focusing distance; a distance measuring error calculating means for calculating a distance measuring error based on the undulations of the two images detected by the detecting means; Second focusing distance calculation means for obtaining a second focusing distance with a small extension amount within a range where focusing may occur, based on the focusing distance of 1 and the distance measurement error. The digital camera according to claim 1, wherein the first lens position is obtained based on the second focusing distance.