JP3564050B2 - Camera, focus adjustment device, focus adjustment method, medium for providing focus adjustment program - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a video device such as a video camera having a focus adjustment function, a focus adjustment device applied to the video device, a focus adjustment method, and a medium for supplying a focus adjustment program.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an automatic focusing method used in video equipment such as a video camera, a high-frequency component in a video signal obtained from an image pickup device such as a CCD is extracted and a focusing lens is used so that the high-frequency component is maximized. A so-called hill-climbing method is known in which the focus is adjusted by driving the light. In such an automatic focus adjustment method, focus is detected based on the sharpness of a subject image, so that the subject is accurately focused regardless of the distance, whether the subject is far or close. It has advantages such as being able to.
[0003]
Conventional hill-climbing auto focus (hereinafter, referred to as “AF”) is an integration used for focusing control by integrating a signal that has been subjected to a high-pass filter processing for extracting a high-frequency component from a video signal within a distance measurement frame on a screen. The type AF method is the mainstream. Since the integrated AF method integrates and uses the extracted high-frequency components in the distance measurement frame, there is an advantage that the stability of the AF operation is excellent and an optimum focusing point is easily obtained.
[0004]
FIG. 14 is a block diagram showing a configuration of a video camera system that employs a conventional integral AF method.
[0005]
In the figure, reference numeral 101 denotes a fixed first group lens, 102 denotes a variable power lens for performing zooming, 103 denotes an aperture, and 104 denotes a fixed second group lens. Reference numeral 105 denotes a focus compensation lens (hereinafter, referred to as a “focus lens”), which has both a function of correcting movement of a focal plane due to zooming and a function of focusing.
[0006]
Reference numeral 106 denotes a CCD which is an image sensor. Reference numeral 107 denotes a CDS / AGC which samples and holds the output of the CCD 106 and amplifies the output. The amplification factor is adjusted by a signal from a camera control unit (microcomputer) 114 described later. An A / D converter 108 converts an analog signal from the CDS / AGC 107 into a digital signal, and 109 denotes a camera signal processing circuit. An output signal from the camera signal processing circuit 109 is recorded on a recording medium (not shown) such as a magnetic tape or a memory.
[0007]
Reference numeral 110 denotes a timing generator that supplies various drive pulses and timing pulses to the CCD 106, CDS / AGC 107, and other parts of the camera.
[0008]
Reference numeral 111 denotes a variable power lens driver for driving the variable power lens 102, 112, an iris driver for driving the aperture 103, 113, a focus driver for driving the focus lens 105, and each of the drivers 111 to 113. The included motor is driven by a signal from a camera control unit 114 described later.
[0009]
Reference numeral 120 denotes an AF evaluation value processing unit, which is a high-pass filter 121 for extracting a predetermined high-frequency component from the luminance signal output from the A / D conversion unit 108, and only a signal within a predetermined distance measurement frame from the screen. The distance measurement frame gate 122 for performing the extraction process, the line peak hold 123 for peak-holding the signal peak extracted by the distance measurement frame gate 122 for each horizontal scanning line, and the peak value of each peak-held scan line And an integrator 124 for integrating. This integrated value is called “integrated AF evaluation value”.
[0010]
The integrator 124 is configured to reset the value for each screen, and can calculate the integrated AF evaluation value for each screen. The integrated AF evaluation value is input to the camera control unit 114, and drives the focus lens 105 via the focus driver 113 so that the integrated AF evaluation value becomes maximum.
[0011]
Note that, in the above-described conventional example, the configuration is such that the peak value of each scanning line that has been peak-held is integrated as described above. However, the configuration is such that integration is performed without performing peak holding, or for each of a plurality of horizontal scanning lines. It is needless to say that the peak value can be peak-held and the value can be integrated.
[0012]
The output luminance signal of the A / D conversion unit 108 is also input to the AE evaluation value processing unit 130, where an evaluation value for controlling exposure is generated from a screen signal, and is input to the camera control unit 114. The camera control unit 114 drives the aperture 103 based on the AE evaluation value so as to obtain an optimal exposure amount. A key unit 115 is connected to the camera control unit 114, and various key operation information of the camera unit such as a zoom key for operating the zoom lens 102 is output to the camera control unit 114. . For example, when the zoom key is pressed, the camera control unit 114 drives the variable power lens 102 via the variable power lens driver 111 so that a desired zoom magnification (focal length) is obtained.
[0013]
However, the above-mentioned integral AF method is controlled so that the average contrast in the screen becomes the highest, so that there is no problem with a normal subject, but an image in which the subject has a high brightness or a night view point light source (hereinafter, referred to as an image). , "Peak image"), there is a problem that the focusing performance is reduced.
[0014]
FIG. 15 is a diagram illustrating an example of an integrated AF evaluation value in a normal subject, and FIG. 16 is a diagram illustrating an example of an integrated AF evaluation value in a peak image. For a normal subject, the focal point and the peak value of the integrated AF evaluation value can be in the same portion P0 as shown in FIG. 15, but there is no problem. The peak cannot be located at the same portion, and the peak of the integrated AF evaluation value appears at a slightly shifted focus position PB.
[0015]
This is because, in the case of a point light source of a night view, which is a representative of a peak image, the integrated AF evaluation value is larger in the case of blur as shown in FIG. 18 than in the case of perfect focusing as shown in FIG. It is because it becomes. FIGS. 17 and 18 are diagrams illustrating an example of a video that appears on a screen when a peak image is captured. As described above, the peak of the integrated AF evaluation value appears at a portion deviating from the original focal point. However, since the camera control unit 114 operates to control the focus lens 105 to a position where the integrated AF evaluation value becomes a peak, the focus control is performed. The lens 105 is controlled to the portion PB shown in FIG. As a result, the obtained video is out of focus.
[0016]
In addition, there is a peak AF method in which the maximum peak value within a distance measurement frame is used for focusing control from among signals subjected to high-pass filtering for extracting a high-frequency component from a screen luminance signal instead of the integral AF method. . FIG. 19 is a block diagram showing the configuration of a video camera system employing the conventional peak AF method.
[0017]
The video camera shown in the figure changes the configuration of the AF evaluation value processing unit 120 in the configuration of the video camera shown in FIG. 14 so that the maximum value of the high-frequency component of the luminance signal in the ranging frame can be obtained. It is what was constituted. In FIG. 19, the maximum value of the high-frequency component of the luminance signal in the distance measurement frame output from the AF evaluation value processing unit 120 is referred to as “peak AF evaluation value”.
[0018]
FIG. 20 is a diagram illustrating a peak AF evaluation value in a peak image that is difficult to focus with the integration type AF. It should be noted that the integrated AF evaluation value is also shown in the figure for comparison with the integral AF. As can be seen from FIG. 20, there is a characteristic that the peak AF evaluation value is maximized at the correct focal point even in the peak image. FIG. 21 is a diagram illustrating a focused point light source, which shows a luminance signal for one horizontal line of a portion indicated by LA in FIG. 17 and an output of a high-pass filter. FIG. FIG. 19 is a diagram showing a luminance signal for one horizontal line in a portion indicated by LB in FIG. 18 and an output of a high-pass filter.
[0019]
In this way, even in a peak image where saturation occurs in the luminance signal, the rise of the luminance signal is different between the case of focusing and the case of blurring, so a difference appears in the output of the high-pass filter, and it is necessary to determine the focal point. Can be done. As described above, in the peak AF method, it is possible to determine a correct focus point on the peak image.
[0020]
However, the peak AF evaluation value has a smaller AF evaluation value than the integrated AF evaluation value, so that the stability of a general subject is lower than that of the integral AF method, and the AF operation is affected by panning and the like. There was a problem of becoming unstable.
[0021]
[Problems to be solved by the invention]
However, the above-mentioned integral AF method is controlled so that the average contrast in the screen becomes the highest, so that there is no problem with a normal subject. The AF method has a problem of lack of stability.
[0022]
An object of the present invention is to provide a camera, a focus adjustment device, a focus adjustment method, and a focus adjustment program that can accurately focus not only on a normal subject but also on a subject that partially includes a high-brightness part. It is intended to provide a medium to perform.
[0024]
[Means for Solving the Problems]
The imaging device of the present invention includes:Claims1The present invention described in the above, a lens, an imaging element that photoelectrically converts the light condensed by the lens, an imaging unit including a diaphragm provided between the lens and the imaging element, the imaging unit, Filter means for extracting a focus signal including a predetermined frequency component that changes according to a focus state from a video signal output from the imaging means; and a focus signal corresponding to a focus detection area from the focus signal extracted by the filter means. Gate means for extracting, area peak hold means for extracting the maximum value of the focus signal corresponding to the focus detection area extracted by the gate means, and output of the focus signal extracted by the gate means for each horizontal scanning line Line peak holding means for peak holding at a line, and the output of the line peak holding means is integrated in the vertical direction of the screen. In-peak integrating means, subject discriminating means for discriminating whether the subject is a peak image containing high brightness or a normal image, and when the subject image is discriminated as the peak image by a subject discriminating signal from the subject discriminating means. A signal selecting means for selecting an output signal of the area peak holding means and selecting an output of the line peak integrating means when it is determined that the image is the normal image, and a focus based on an output signal of the signal selecting means. The focus adjusting device includes a focus adjusting unit that performs an adjusting process.
[0026]
Claims7The present invention described in above, photoelectrically converts the light condensed by the lens in the image sensor, from the video signal output from the imaging means composed of a stop provided between the lens and the image sensor A focus signal including a predetermined frequency component that changes according to the focus state is extracted, a focus signal corresponding to a focus detection area is extracted from the extracted focus signal, and a focus corresponding to the extracted focus detection area is extracted. The maximum value of the signal is extracted, the output of the extracted focus signal is line-peak-held for each horizontal scanning line, and the line-peak-held output is integrated in the vertical direction of the screen, so that the object has a peak including high brightness. Determine whether the image is an image or a normal image, if the determination is determined to be the peak image, select the maximum value of the focus signal, Serial in which usually selects the output signals integrated in the vertical direction when it is determined that the image, the focus adjustment method of performing focusing operation based on the selected output signal.
[0028]
ClaimsThirteenThe present invention described above has a focus including a lens, an imaging device that photoelectrically converts light condensed by the lens, and an imaging unit that includes a diaphragm provided between the lens and the imaging device. A recording medium recording a focus adjustment program in a format readable by a computer of an adjustment device, wherein the focus adjustment program converts a predetermined frequency component that changes according to a focus state from a video signal output from the imaging unit. A filter step of extracting a focus signal including the focus signal, a gate step of extracting a focus signal corresponding to a focus detection area from the focus signal extracted in the filter step, and a focus corresponding to the focus detection area extracted in the gate step. An area peak hold step of extracting a maximum value of a signal, and an output of the focus signal extracted in the gate step A line peak hold step of holding a peak for each horizontal scanning line, a line peak integration step of integrating the output of the line peak hold step in the vertical direction of the screen, and a peak image or a normal image of the subject with high brightness A subject discriminating step of discriminating whether or not the output signal in the area peak hold step is selected when it is determined that the image is the peak image in the subject discriminating step, and the line is selected when the image is determined to be the normal image. The method includes a signal selection step of selecting an output signal in the peak integration step, and a focus adjustment step of performing focus adjustment processing based on the output signal in the signal selection step.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0038]
(1st Embodiment)
First, a first embodiment of the present invention will be described with reference to FIGS.
[0039]
FIG. 1 is a block diagram illustrating a configuration of a video camera system that employs the focus adjustment method according to the present embodiment. In the figure, the same components as those in the configuration of the conventional video camera system shown in FIG. 14 described above are denoted by the same reference numerals, and description thereof will be omitted. The features of the video camera system according to the present embodiment include an AF evaluation value processing unit 220 capable of outputting an integrated AF evaluation value and a peak AF evaluation value, and an AE evaluation value processing capable of outputting a screen average luminance value and a luminance peak value. Unit 230 and the operation of the camera control unit 240 that inputs those values.
[0040]
The luminance signal output from the A / D conversion unit 108 input to the AF evaluation value processing unit 220 is subjected to a process of extracting a predetermined high-frequency component from the luminance signal by the high-pass filter 221. Then, a process is performed by the ranging frame gate 222 to extract only signals within a predetermined ranging frame from the screen. The line peak hold unit 223 holds the peak of the extracted signal for each horizontal scanning line. The integrator 224 integrates the peak value of each scanning line within the ranging frame, and outputs an integrated AF evaluation value. Further, the output from the distance measuring gate 222 is input to the peak hold 225, and a high-frequency component which is maximum in the distance measuring frame can be extracted. This value is called a peak AF evaluation value. These integration circuits and peak hold circuits are configured such that the values are reset for each screen as in the conventional example, and the integrated AF evaluation value and the peak AF evaluation value for each screen are transmitted to the camera control unit 240. It is configured to be able to output.
[0041]
The AE evaluation value processing unit 230 performs a process of extracting only a signal inside a predetermined photometry frame from the screen by the photometry frame gate 231 with respect to the input luminance signal from the A / D conversion unit 108. The luminance signal extracted by the photometric frame gate 231 is input to the integrator 232, and outputs the average luminance signal integrated in the photometric frame to the camera control unit 240. The luminance signal extracted by the light metering frame gate 231 is also input to the peak hold circuit 233, and outputs the value of the maximum luminance signal in the light metering frame to the camera control 240.
[0042]
FIG. 2 is a flowchart illustrating an AF focusing control procedure executed by the camera control unit 240 using these input signals.
[0043]
First, luminance data (luminance average value Yavr and luminance peak value Ypeak) is read (step S200), and it is determined whether the luminance peak value Ypeak is higher than a predetermined value Yth1 (step S201). If the luminance peak value Ypeak is lower than the predetermined value Yth1 in this determination, it is unlikely that the image is a high-luminance object or a point light source, and it is determined that the image is a normal image. Therefore, the integrated AF evaluation value output from the integrator 224 is determined. A reading process is performed (step S210).
[0044]
When the luminance peak value Ypeak is higher than the predetermined value Yth1 in the determination in step S201, it is determined whether the luminance average value Yavr output from the integrator 232 is very low, that is, the luminance average value Yave is higher than the predetermined value Yth2. It is determined whether it is low (step S202). In this determination, when the average luminance value Yavr is lower than the predetermined value Yth2, the subject can be regarded as a peak image (night view or the like), and therefore, a process of reading the peak AF evaluation value output from the peak hold unit 225. Is performed (step S220). FIG. 3 is an explanatory diagram showing an example of a peak image discrimination method based on the average luminance value Yavr and the luminance peak value Ypeak. The condition that the luminance peak value Ypeak is not low in step S201 and the luminance average value Yavr is very low in step S202 corresponds to the region 1 shown in FIG.
[0045]
If it is determined in step S202 that the average luminance value Yavr is not lower than the predetermined value Yth2, it is determined whether the luminance peak value Ypeak is very high, that is, whether the luminance peak value Ypeak is higher than the predetermined value Yth3 (Yth3> Yth1). (Step S203) If the luminance peak value Ypeak is higher than the predetermined value Yth3, it is determined whether the average luminance value Yavr is lower than the predetermined value Yth4 (Step S204).
[0046]
If it is determined in step S204 that the average luminance value Yavr is lower than the predetermined value Yth4 (Yth4> Yth2), that is, if the luminance peak value Ypeak is very high and the average luminance value Yavr is somewhat low, it is possible to use, for example, a tree leakage day. It is determined that the image is a peak image, and the process of reading the peak AF evaluation value is performed in step S220. This condition corresponds to the area 2 shown in FIG.
[0047]
If the subject does not satisfy the condition of the region 1 or the region 2, that is, if the peak luminance value Ypeak is low, or if both the average luminance value Yavr and the luminance peak value Ypeak are high, it is regarded as a normal image, and in step S210 A process of reading the integrated AF evaluation value is performed. The condition of the normal image corresponds to the area 3 in FIG.
[0048]
By such a procedure, it is determined whether the subject is a peak image or a normal image based on the average luminance value Yavr and the luminance peak value Ypeak, and when the subject is determined to be a normal image, the integrated AF evaluation value is used. AF focusing process is performed, and when it is determined that the image is a peak image, the AF focusing process is performed using the peak AF evaluation value (step S230).
[0049]
Thus, in the case of an image of a subject (peak image) such as a night scene or a point light source, which is a problem in the conventional integral AF method, correct focusing control can be performed using the peak AF evaluation value. Further, in the case of another normal image, the integrated AF evaluation value is used for the AF calculation, so that a stable focusing process can be performed.
[0050]
In addition, by performing the subject AF and performing the optimal AF control for the subject in this manner, it is possible to realize a system having both advantages of the integral AF system and the peak AF system. That is, according to the present embodiment, an effect is obtained that an accurate focusing operation can be performed not only for a normal image but also for a peak image.
[0051]
(2nd Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The present embodiment is characterized in that a peak image is determined based on a luminance signal by a method different from the first embodiment.
[0052]
FIG. 4 is a flowchart illustrating a focusing control procedure according to the present embodiment, and FIG. 5 is an explanatory diagram illustrating a method of determining the peak image. 4, the procedure of step S200 and steps S210 to S230 is similar to the procedure of step S200 and steps 210 to S230 in the procedure of FIG. 2 described above.
[0053]
In step S200, the luminance data (the average luminance value Yavr and the luminance peak value Ypeak) are read, and it is determined whether the luminance peak value Ypeak and the luminance average value Yavr satisfy the following expression (1) (step S201B).
[0054]
Ypeak> K1 × Yavr + Yth5 (1)
[0055]
Here, the coefficient K1 is a ratio between the luminance peak value Ypeak and the average luminance value Yavr, and corresponds to the slope of the straight line L1 in FIG. Further, the predetermined value Yth5 is an offset of the straight line L1 and is Yth5 in FIG. In the present embodiment, since the maximum level when the luminance peak value is 8-bit data is 255, the slope K1 is:
K1 = (255−Yth5) / Yth6 (2)
It becomes. The relationship satisfying this condition corresponds to the peak image area shown in FIG. The subject in this area is subjected to AF focusing processing using the peak AF evaluation value in step S230 in FIG. If this condition is not satisfied, the image is determined to be a normal image, and AF focusing processing is performed using the integrated AF evaluation value.
[0056]
As described above, according to the present embodiment, a peak AF evaluation value is used for AF calculation for a subject (peak image) such as a night scene or a point light source, which has been a problem in the conventional integral AF method. Therefore, accurate focusing processing can be performed even on the peak image. In addition, since the integrated AF evaluation value is used for AF calculation for other general normal images, a stable focusing process can be performed.
[0057]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.
[0058]
In the present embodiment, as in the second embodiment, the ratio between the average luminance value Yavr and the luminance peak value Ypeak and the offset are used as conditions, but the second embodiment differs in that a plurality of ratios are used. This is different from the method described above.
[0059]
FIG. 6 is a flowchart showing a focusing control procedure according to the present embodiment, and FIG. 7 is an explanatory diagram showing a method of determining the peak image. Steps S200 and S210 to S230 in FIG. 6 are the same as steps S200 and S210 to S230 shown in FIG. 2 of the first embodiment.
[0060]
When the luminance data is read, the luminance data is stored in the first condition.
Ypeak> K2 × Yavr + Yth7 (3)
, That is, whether the luminance data is in the peak image area shown in FIG. 7 (step S201C). In the equation (3), the coefficient K2 is a ratio between the average luminance value Yavr and the luminance peak value Ypeak, and corresponds to the slope of the straight line L2 in FIG. Further, the predetermined value Yth7 corresponds to the offset of the straight line L2 shown in FIG. In the present embodiment, if the luminance peak value Ypeak is 8-bit data, the maximum level is 255, so the slope K2 is
K2 = (255−Yth7) / Yth8 (4)
It becomes. If it is determined in step S201C that the image is located in the peak image area satisfying the above expression (3), the peak AF evaluation value is read in step S220, and AF focusing processing is performed in step S230.
[0061]
On the other hand, if it is determined in step S201C that the above expression (3) is not satisfied, the luminance data is set in the second condition.
Ypeak> K3 × Yavr + Yth9 (5)
Is determined (step S201C). In the equation (5), the coefficient K3 is a ratio between the average luminance value Yavr and the luminance peak value Ypeak, and corresponds to the slope of the straight line L3 in FIG. Further, the predetermined value Yth9 corresponds to the offset of the straight line L3 shown in FIG. In the present embodiment, if the luminance peak value Ypeak is 8-bit data, the maximum level is 255, so the slope K3 is
K3 = (255−Yth9) / Yth10 (6)
It becomes. Also when the second condition is satisfied, it is determined that the image is a peak image, and the AF focusing process using the peak AF evaluation value is performed in step S230. If the second condition is not satisfied, the image is determined to be a normal image, and AF focusing processing using the integrated AF evaluation value is performed.
[0062]
As described above, according to the present embodiment, a peak AF evaluation value is used for AF calculation for a subject (peak image) such as a night scene or a point light source, which has been a problem in the conventional integral AF method. Therefore, accurate focusing processing can be performed even on the peak image. In addition, since the integrated AF evaluation value is used for AF calculation for other general normal images, a stable focusing process can be performed.
[0063]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
[0064]
FIG. 8 is a block diagram illustrating a configuration of the video camera system according to the present embodiment. In the figure, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0065]
The present embodiment is characterized in that the output of the aperture position detector 250 for detecting the aperture amount of the aperture and the zoom position information (focal length information) are employed for peak image discrimination. The zoom position information can be determined based on a signal such as the address of a variable power lens driving stepping motor output from the camera control unit 240 to the variable power lens driver 111. Further, the aperture position detector 250 includes a Hall element or the like, and is configured to output a voltage corresponding to the opening amount of the aperture to the camera control unit 240.
[0066]
Here, the reason why information on the aperture and the focal length is added to the peak image determination will be described.
[0067]
Generally, as the focal length increases, the depth of field decreases, and as the focal length decreases, the depth of field increases. When the aperture is opened, the depth of field becomes shallow, and when the aperture is closed, the depth of field becomes deep. Also, when the subject is shifted from the in-focus position by the same amount, the blur amount is large when the depth of field is shallow, and the blur amount is small when the depth of field is deep.
[0068]
FIG. 9 is a diagram illustrating the relationship between the depth of field and the integrated AF evaluation value in the peak image. As shown in the figure, when the depth of field is deep even in the peak image, the peak of the integrated AF evaluation value may appear at the correct focus position P0.
[0069]
In other words, even when the image is determined to be a peak image based on the luminance peak value and the average luminance value, if the depth of field is deep in the state of the focal length or the aperture, focusing is performed using the integrated AF evaluation value. In other words, there is no problem in performing the processing.
[0070]
In the present embodiment, for the above reason, the output of the aperture position detector 250 and the zoom position information (focal length information) are added to the peak image determination.
[0071]
FIG. 10 is a flowchart illustrating a focusing processing procedure according to the present embodiment.
[0072]
First, luminance data (luminance peak value Ypeak and average luminance value Yavr), zoom position data, and iris position data are read (step S300). Then, it is determined whether or not the luminance peak value Ypeak is higher than a predetermined value Yth11 (step S301).
[0073]
In this determination, when the luminance peak value Ypeak is lower than the predetermined value Yth11, it is unlikely that the image is a high-luminance object or a point light source. Therefore, the image is determined to be a normal image regardless of the iris or zoom state, and the integrated AF evaluation value is read. A focusing process is performed (step S310), and a focusing process using the integrated AF evaluation value is performed (step S330). The reason that the state of iris and zoom is not considered in the result of step S301 is that such a subject having a low luminance peak value Ypeak is unlikely to be a peak image regardless of the state of zoom or iris.
[0074]
When the luminance peak value Ypeak is higher than the predetermined value Yth11 in the determination in step S301, it is determined whether the average luminance value Yavr is a very low value, that is, whether the average luminance value is lower than the predetermined value Yth12. It is determined (step S302). If the average luminance value Yavr is lower than the predetermined value Yth12, it is determined that the image is a peak image irrespective of the iris or zoom state, the peak AF evaluation value is read (step 320), and the peak AF evaluation value is used. A focusing process is performed (step S330). The reason why the state of zoom or iris is not considered here is that the probability of a peak image is high regardless of the state of zoom or iris.
[0075]
If it is determined in step S302 that the average luminance value Yavr is higher than the predetermined value Yth12, it is determined whether the luminance peak value Ypeak is higher than a predetermined value Yth13 higher than the predetermined value Yth11 (step S303), and the average luminance value Yavr is higher than the predetermined value Yth13. It is determined whether or not it is lower than a predetermined value Yth14 which is larger than the predetermined value Yth12 (step S304). When the luminance peak value Ypeak is lower than the predetermined value Yth13, or when the average luminance value Yavr is higher than the predetermined value Yth14, the image is determined to be a normal image. Then, in step S310, a process of reading the integrated AF evaluation value is performed, and a focusing process using the integrated AF evaluation value is performed.
[0076]
When the luminance peak value Ypeak is higher than the predetermined value Yth13 and the average luminance value Yavr is lower than the predetermined value Yth14, the zoom position corresponding to the focal length is further compared with a predetermined threshold value Zth1, and the zoom position is set to the telephoto position having the longer focal length. It is determined whether it is on the side (step S305). If the zoom position is smaller than the predetermined value Zth1 and is not on the telephoto side, a process of reading an integrated AF evaluation value is performed in step S310, and a focusing process using the integrated AF evaluation value is performed in step S330.
[0077]
If the zoom position is on the telephoto side, it is determined whether or not the iris is larger than a predetermined threshold value Ith1 (step S306). If it is determined that the iris is closed smaller than the predetermined threshold value Ith1, a process of reading the integrated AF evaluation value is performed in step S310, and a focusing process using the integrated AF evaluation value is performed in step S330. Done. On the other hand, if it is determined in step S306 that the iris is larger than the predetermined threshold value Ith1, it is considered that the image is a peak image and the depth of field is shallow, so that the peak AF evaluation value is determined in step S320. The reading process is performed, and in step S330, a focusing process using the peak AF evaluation value is performed.
[0078]
FIG. 11 is an explanatory diagram showing a peak image discrimination method according to the above procedure. In the figure, a region with a shallow depth of field that satisfies the conditions of steps S305 and S306 corresponds to region B.
[0079]
As described above, according to the present embodiment, a peak AF evaluation value is used for AF calculation for a subject (peak image) such as a night scene or a point light source, which has been a problem in the conventional integral AF method. Therefore, accurate focusing processing can be performed even on the peak image. In addition, since the integrated AF evaluation value is used for AF calculation for other general normal images, a stable focusing process can be performed. Further, in the present embodiment, since the position information of the zoom and the iris is also referred to, it is possible to more accurately determine the subject of the peak image which is not good with the integrated AF evaluation value.
[0080]
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
[0081]
FIG. 12 is a flowchart showing a focusing control procedure according to the present embodiment, and FIG. 13 is an explanatory diagram for explaining the peak image discriminating method. The processing procedure of steps S300 to S304 and steps S310 to S330 in FIG. 12 is the same as the processing procedure of steps S300 to S304 and steps S310 to S330 shown in FIG. 10 of the above-described fourth embodiment.
[0082]
If it is determined in step S304 that the average luminance value Yavr is lower than the predetermined value Yth14, it is determined whether or not the region is a region with a small depth of field, that is, whether the iris position data Iris and the zoom position data Zoom satisfy Expression (7). It is determined whether or not it is (step S307).
[0083]
Iris> K4 × Zoom + Ith3 (7)
[0084]
Here, the coefficient K4 is a ratio between the zoom position data Zoom and the iris position data Iris, and corresponds to the inclination of the straight line L4 shown in FIG. 13A, and Ith3 corresponds to the offset of the straight line L4. In the present embodiment, the maximum level of the slope K4 is 255 when the zoom position data and the iris data are 8-bit data.
K4 = − (255−Ith2) / (255−Zth2) (8)
It becomes.
[0085]
When the condition of Expression (13) is satisfied, it is determined that the depth of field is shallow. This state corresponds to the area B in FIG.
[0086]
If the conditions from step S301 to step S304 are satisfied and it is determined in step S307 that the depth of field is shallow, it is considered that the image is a peak image, and therefore, processing for reading the peak AF evaluation value is performed in step S320. Then, in step S330, a focusing process using the peak AF evaluation value is performed.
[0087]
Further, even if the conditions from step S301 to step S304 are satisfied and a peak image candidate is obtained, if the condition of step S307 is not satisfied, the image is considered to be a normal image. Therefore, the integrated AF evaluation value is read in step S310. The process is performed, and in step S330, the AF focusing process is performed using the integrated AF evaluation value.
[0088]
As described above, according to the present embodiment, accurate focusing processing can be performed on an image (peak image) of a subject such as a night scene or a point light source, which has been a problem in the conventional integral AF method. . Further, since the zoom and iris position information are also referred to, it is possible to more accurately determine the subject of the peak image which is not good with the integrated AF evaluation value.
[0089]
The method of determining the depth of field is not limited to the method using FIG. 13A described above. For example, as shown in FIG. 13B, two conditions (using straight lines L5 and L6) are used. (Determination of the peak image area).
[0090]
(Other embodiments)
Note that the present invention may be applied to a camera system including a plurality of devices, or may be applied to an apparatus including a single device. Further, it is needless to say that the present invention can be applied to a case where the present invention is implemented by supplying a program to a camera system or an apparatus. In this case, a medium such as a storage medium storing the program according to the present invention constitutes the present invention. Then, by reading the program from a medium such as a storage medium into a system or an apparatus, the system or the apparatus operates in a predetermined manner.
[0091]
Further, a program code of software for realizing the functions of the above-described embodiments is supplied to a system or an apparatus via a medium such as a storage medium, and a computer (or CPU or MPU) of the system or the apparatus reads and executes the program code. It is needless to say that the object of the present invention is also achieved by doing so.
[0092]
In this case, the program code itself read from the medium of the storage medium realizes the novel function of the present invention, and a medium such as a storage medium that supplies the program code constitutes the present invention.
[0093]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.
[0094]
In addition, the functions of the above-described embodiments are implemented when the computer executes the readout program codes, and the OS or the like running on the computer performs the actual processing based on the instructions of the program codes. It goes without saying that a case where some or all of the functions are performed and the functions of the above-described embodiments are realized by the processing is also included.
[0095]
Furthermore, after the program code read from a medium such as a storage medium is written to a memory provided in a function expansion board or a function expansion unit connected to the computer, based on an instruction of the program code, It goes without saying that a CPU or the like provided in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0096]
Further, in the above-described embodiment, the focus adjustment signal is formed by two focus adjustment signal forming methods from the high frequency components in the same range of the image signal. The focus adjustment signal may be formed by a focus adjustment signal forming method.
[0097]
Further, in the above-described embodiment, only one of the signals obtained by the two focus adjustment signal forming methods is selectively used. However, the present invention employs both types of signals by predetermined weighting or the like. , Or signals obtained by three or more focus adjustment signal forming methods.
[0098]
In the above embodiment, the method of forming the focus adjustment signal is changed according to the photometry result. However, the present invention changes other operations for focus adjustment such as the driving speed of the focus adjustment lens. You may make it.
[0099]
Further, the present invention may use an evaluation photometry method other than the above-described embodiment, or may use a focus adjustment signal forming method or a focus adjustment method other than the above-described embodiment.
[0100]
Further, in the above-described embodiment, both the focal length and the aperture are taken into account when determining the peak image, but only one of them may be used.
[0101]
Further, the software configuration and the hardware configuration of the above embodiments can be appropriately replaced.
[0102]
In addition, the present invention may combine the above-described embodiments or the technical elements as needed.
[0103]
In addition, the present invention may be applied to a case where all or a part of the configuration of the claims or the embodiment forms one device or is combined with another device. , Which may be a constituent element of the device.
[0104]
In addition, the present invention provides various types of cameras such as an electronic camera that captures a still image or a moving image with an image sensor, a camera that uses a silver halide film, a single-lens reflex camera, a lens shutter camera, and a surveillance camera. Imaging devices, optical devices, and other devices, as well as cameras, imaging devices, optical devices, and devices and methods applied to other devices, and media such as computer-readable storage media, and the like. It can be applied to elements that do.
[0105]
【The invention's effect】
As described above, according to the embodiments of the present invention, a camera, a focus adjustment device, and a focus adjustment method that can accurately focus not only on a normal subject but also on a subject partially including a high-brightness part And a medium for supplying a focus adjustment program.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a video camera system employing a focus adjustment method according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a focusing control procedure also executed by the camera control unit 240.
FIG. 3 is an explanatory diagram showing an example of a peak image discriminating method based on an average luminance value Yavr and a luminance peak value Ypeak.
FIG. 4 is a flowchart showing a focusing control procedure according to a second embodiment of the present invention.
FIG. 5 is an explanatory diagram showing a method of determining a peak image.
FIG. 6 is a flowchart illustrating a focus control procedure according to a third embodiment of the present invention.
FIG. 7 is an explanatory diagram showing a method of determining a peak image.
FIG. 8 is a block diagram showing a configuration of a video camera system employing a focus adjustment method according to a fourth embodiment of the present invention.
FIG. 9 is a diagram showing the relationship between the depth of field and the integrated AF evaluation value in the peak image.
FIG. 10 is a flowchart showing a focusing control procedure.
FIG. 11 is an explanatory diagram showing a method of determining a peak image.
FIG. 12 is a flowchart illustrating a focus control procedure according to a fifth embodiment of the present invention.
FIG. 13 is an explanatory diagram showing a method of determining a peak image.
FIG. 14 is a block diagram illustrating a configuration of a video camera system that employs a conventional integral AF method.
FIG. 15 is a diagram illustrating an example of an integral AF evaluation value of a normal subject.
FIG. 16 is a diagram illustrating an example of an integral AF evaluation value in a peak image.
FIG. 17 is a diagram illustrating an example of a video that appears on a screen when a peak image is captured.
FIG. 18 is a diagram illustrating an example of a video that appears on a screen when a peak image is captured.
FIG. 19 is a block diagram showing a configuration of a video camera system employing a conventional peak AF method.
FIG. 20 is a diagram illustrating a peak AF evaluation value in a peak image.
FIG. 21 is a diagram illustrating a luminance signal for one horizontal line and an output of a high-pass filter.
FIG. 22 is a diagram illustrating a luminance signal for one horizontal line and an output of a high-pass filter.
[Explanation of symbols]
106 CCD
112 Iris driver
221 High-pass filter
222 Ranging frame gate
223 line peak hold
225, 233 Peak hold
224, 232 Integrator
240 Camera control unit
250 Aperture position detector

Claims (18)

A lens, an image sensor that photoelectrically converts light collected by the lens,
An image pickup unit including an aperture provided between the lens and the image pickup element; and a focus signal including a predetermined frequency component that changes according to a focus state is extracted from a video signal output from the image pickup unit. Filter means, and gate means for extracting a focus signal corresponding to a focus detection area from the focus signal extracted by the filter means,
Area peak hold means for extracting the maximum value of the focus signal corresponding to the focus detection area extracted by the gate means,
Line peak hold means for peak holding the output of the focus signal extracted by the gate means for each horizontal scanning line, line peak integration means for integrating the output of the line peak hold means in the vertical direction of the screen,
Subject determining means for determining whether the subject is a peak image or a normal image including high brightness,
The output signal of the area peak hold unit is selected when it is determined that the image is the peak image by the subject determination signal from the subject determination unit, and the output signal of the line peak integration unit is determined when the output image is determined to be the normal image. A focus adjustment device comprising: a signal selection unit that selects an output; and a focus adjustment unit that performs focus adjustment processing based on an output signal of the signal selection unit. Maximum value detection means for detecting the maximum value of the luminance signal in the focus detection area set at least at a predetermined position in the screen,
Average value detection means for detecting the average value of the luminance signal in the peripheral region including the focus detection region,
Maximum value comparing means for comparing the maximum value of the luminance signal and a plurality of thresholds,
Having an average value comparing means for comparing the average value of the luminance signal and a plurality of thresholds,
2. The object determination unit according to claim 1, wherein the determination unit determines whether the subject is the peak image or the normal image based on a comparison result by the maximum value comparison unit and the average value comparison unit. Focus adjustment device. Maximum value detecting means for detecting a maximum value of a luminance signal in a focus detection area set at least at a predetermined position in a screen, and detecting an average value of the luminance signal in a peripheral area including the focus detection area Average value detecting means, and calculating means for calculating information on a ratio between the maximum value of the luminance signal and the average value of the luminance signal, wherein the subject discriminating means determines that the calculated information is greater than or equal to a predetermined value. 2. The focus adjusting device according to claim 1, wherein the subject is determined to be a peak image in a certain case. The object determination unit, when the depth of field based on the aperture value of the diaphragm of the imaging means is determined to shallow, claim 2 or 3 wherein the subject is characterized by determining that the peak image The focus adjustment device according to claim 1. The object determination unit, when the depth of field based on the focal length of the lens of the imaging means is determined to shallow, claim 2 or 3 wherein the subject is characterized by determining that the peak image The focus adjustment device according to claim 1. The focus detection area is focusing device according to claim 1, characterized in that it consists of a region including a part or all of the imaging screen. The light condensed by the lens is photoelectrically converted by the image sensor,
A focus signal including a predetermined frequency component that changes according to a focus state is extracted from a video signal output from an imaging unit including the lens and an aperture provided between the imaging element,
A focus signal corresponding to a focus detection area is extracted from the extracted focus signal,
Extract the maximum value of the focus signal corresponding to the extracted focus detection area,
Line peak hold of the output of the extracted focus signal for each horizontal scanning line,
Integrating the line peak held output in the vertical direction of the screen,
Determine whether the subject is a peak image containing high brightness or a normal image,
Select the maximum value of the focus signal when it is determined that the peak image by the determination,
Select the output signal integrated in the vertical direction when it is determined that the normal image,
A focus adjustment method comprising: performing focus adjustment processing based on the selected output signal. Detecting the maximum value of the luminance signal in the focus detection area set at least at a predetermined position in the screen, detecting the average value of the luminance signal in the peripheral area including the focus detection area, Comparing a maximum value and a plurality of threshold values, comparing the average value of the luminance signal and a plurality of threshold values, and determining whether the subject is the peak image or the normal image based on a result of the comparison. The focus adjustment method according to claim 7, wherein the determination is performed. Detecting the maximum value of the luminance signal in the focus detection area set at least at a predetermined position in the screen, detecting the average value of the luminance signal in the peripheral area including the focus detection area, 8. The method according to claim 7 , wherein information relating to a ratio between a maximum value and an average value of the luminance signal is calculated, and when the calculated information is equal to or more than a predetermined value, the subject is determined to be a peak image. Focus adjustment method. If the depth of field based on the aperture value of the diaphragm of the imaging means is determined to shallow, focusing method according to claim 8 or 9, wherein said subject is characterized by determining that the peak image. If the depth of field based on the focal length of the lens of the imaging means is determined to shallow, focusing method according to claim 8 or 9, wherein said subject is characterized by determining that the peak image. The focus adjustment method according to claim 7 , wherein the focus detection area is an area including a part or the whole of an imaging screen. A computer of a focusing device having a lens, an image pickup device that photoelectrically converts light condensed by the lens, and an image pickup unit including a stop provided between the lens and the image pickup device is read by a computer of a focus adjustment device. A recording medium recording a focus adjustment program in a possible format,
A filtering step of extracting a focus signal including a predetermined frequency component that changes according to a focus state from a video signal output from the imaging unit;
A gate step of extracting a focus signal corresponding to a focus detection area from the focus signal extracted in the filter step;
An area peak hold step of extracting a maximum value of a focus signal corresponding to the focus detection area extracted in the gate step,
A line peak holding step of peak holding the output of the focus signal extracted in the gate step for each horizontal scanning line,
A line peak integration step of integrating the output of the line peak hold step in the vertical direction of the screen,
A subject discriminating step of discriminating whether the subject is a peak image containing high luminance or a normal image;
The output signal in the area peak hold step is selected when it is determined that the image is the peak image in the subject determination step, and the output signal in the line peak integration step is selected when the image is determined to be the normal image. A signal selection step;
A focus adjustment step of performing focus adjustment processing based on an output signal in the signal selection step. The focus adjustment program includes: a maximum value detection step of detecting a maximum value of a luminance signal in a focus detection area set at least at a predetermined position in a screen; and a luminance signal in a peripheral area including the focus detection area. An average value detecting step of detecting an average value of the luminance signal; a maximum value comparing step of comparing the maximum value of the luminance signal with a plurality of threshold values; and an average value comparing step of comparing the average value of the luminance signal with a plurality of threshold values. In the subject determination step, it is determined whether the subject is the peak image or the normal image based on the comparison result in the maximum value comparison step and the average value comparison step. The recording medium according to claim 12, wherein The focus adjustment program includes: a maximum value detection step of detecting a maximum value of a luminance signal in a focus detection area set at least at a predetermined position in a screen; and a luminance signal in a peripheral area including the focus detection area. An average value detection step of detecting an average value of the luminance signal, and an operation step of calculating information on a ratio between a maximum value of the luminance signal and an average value of the luminance signal. 13. The recording medium according to claim 12 , wherein when the information is equal to or more than a predetermined value, the subject is determined to be a peak image. 15. The method according to claim 14, wherein in the subject determining step, the subject is determined to be a peak image when it is determined that the depth of field is shallow based on the aperture amount of the aperture of the imaging unit. 16. The recording medium according to 15 . 15. The method according to claim 14, wherein, in the subject determining step, when the depth of field is determined to be shallow based on a focal length of a lens of the imaging unit, the subject is determined to be a peak image. 16. The recording medium according to 15 . 14. The recording medium according to claim 13, wherein the focus detection area includes an area including a part or the entirety of an imaging screen.

Images