JPH10336508A - Automatic focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize final focusing which with less afocus in the case that plural contrast peaks are obtained due to the coexistence of remote and near objects in the scanning type imager AF. SOLUTION: This device is provided with a discrimination means 1d that makes scanning by changing a relative position between a focusing lens 2 and an image-pickup element 3 and discriminates a focal position, based on contrast information in image information which is an output of the image-pickup element obtained at each scanning position. The discrimination means recognizes a position corresponding to a prescribed peak of the contrast information, at least as a local focal position and selects a median focal point in the scanning order among plural focal points as a final focal point for the final focal adjustment, when plural local focal points obtained as the scanning executed over a prescribed scanning range exist within a prescribed scanning range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing apparatus, and more particularly, to a camera for photographing continuous images and discontinuous still images, for example, a camera for both movie / still and a still / still mode type still camera. And an automatic focusing device mounted on a movie camera with a one-shot function.

[0002]

2. Description of the Related Art In recent years, video cameras for movies that have been widely used for general home use, photographing lenses and imaging devices used in electronic still cameras and the like sold by various manufacturers have been developed. Some of the video signal processing circuits have the same function.
Therefore, by sharing them, it is possible to realize a movie / still dual-purpose electronic camera that is compactly integrated and advantageous in cost. Therefore, the above-mentioned dual-purpose camera disclosed in Japanese Patent Application Laid-Open No. 55-165077 has a structure in which a photographic lens, an imaging device, a video signal processing circuit, and the like are shared.

[0003] In the above-mentioned dual-purpose camera, the focusing device becomes a problem. Automatic focusing of a conventional camera (hereinafter A
Some devices use a detection element dedicated to AF, and others use image data of an image sensor (hereinafter, referred to as an imager) as an AF signal. The imager AF using the imager signal has the AF
The focusing lens is driven while detecting the degree of focusing by the signal, a hill-climbing imager AF that determines the peak point of the degree of focusing as the focal point, and the lens is scanned over the entire range to compare and measure the degree of focusing. There is a scanning-type imager AF that drives the lens to a predetermined point determined based on comprehensive judgment to perform photographing.

[0004]

At least in the case of the scanning type imager AF described in the prior art,
When the objects coexist at a distance, a plurality of contrast peaks corresponding to the respective objects are often obtained with the scanning. In such a case, it is not obvious how to perform the final focusing.

First, it is known that final focusing is performed at a point where the obtained contrast value is the maximum. This method has an advantage that a focusing point is uniquely determined regardless of the number of peaks. Since the focusing is always performed at the maximum contrast, for example, when there is a background having a high contrast, the main subject is not focused.

Therefore, it is conceivable to perform the final focusing on a peak point (the latest peak point) corresponding to the shortest distance among a plurality of peaks. However, this method is suitable for photographing a person against a distant background. Although a result is obtained, in the case of a plurality of distant and coexistent subjects in which a specific main subject does not exist, there is a disadvantage that the focus of a distant subject tends to be poor.

In order to cover the entire subject on average, it is conceivable to perform focusing at an intermediate position between the latest peak point and the farthest peak point. However, this method can expect good results on average. Normally, since the focusing position is different from the peak point, a state where “no subject comes into focus” is obtained. Therefore, there is a very high possibility that a result in which the whole subject is not well focused will be obtained.

An object of the present invention is to provide an imager AF such as the above-mentioned scanning type imager AF, in which a plurality of contrast peaks are obtained due to the coexistence of a subject at a distance, etc. Is to make it happen.

[0009]

An automatic focusing apparatus according to the present invention scans by moving a relative position between a focusing lens and an image sensor, and outputs an image which is an output of the image sensor obtained at each scanning position. Determining a focus position based on contrast information in the information, wherein the determination means recognizes a position corresponding to a predetermined peak of the contrast information as at least a local focus and performs predetermined scan; When a plurality of the local focusing points obtained as a result of the scanning performed over the range are present in the predetermined scanning range, a center order in the scanning order among the plurality of local focusing points is determined. The automatic focusing device according to the present invention is characterized in that a certain focusing lens is selected as a final focusing point where final focusing adjustment is to be performed. Scanning means for moving the relative position of the image sensor and the image sensor, and determining a focus position based on contrast information in image information output from the image sensor obtained at each scan position. The determining means recognizes a position corresponding to a predetermined peak of the contrast information as at least a local focal point, and determines the local focus obtained as a result of the scanning performed over a predetermined scanning range. When there are a plurality of focal points in the predetermined scanning range, a focal point closest to an intermediate position of the predetermined scanning range among the plurality of local focusing points is a final focusing point to be subjected to final focusing adjustment. Is selected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to illustrated examples. FIG. 1 is a block diagram of an automatic focusing apparatus according to an embodiment of the present invention. The automatic focusing device is mounted on a movie / still electronic camera. When the camera is used in a movie shooting mode (hereinafter, referred to as an M mode) in which continuous moving image shooting is performed, the camera performs a tracking type focusing operation as a first focusing adjustment mode, that is, a so-called hill-climbing operation. The first focus adjustment means of the imager AF is further provided with a still photography mode (hereinafter, referred to as an S mode) in which discontinuous photography is performed.
In the case of using the second focusing adjustment mode, the second focusing adjustment means, which is the scanning type imager AF, is used as a second focusing adjustment mode.
The function is selected and operated by the mode changeover switch 8.

The configuration of the automatic focusing apparatus is composed of an AF data processing circuit 1a for AF processing, an AF data storage section 1b,
The comparison circuit 1c, the judgment circuit 1d, and A in the M and S modes
System controller 1 with built-in F processing program
A lens group 2 including a focusing lens 2a; a motor driver 4 of a motor for driving the focusing lens 2a; an imager 3 for outputting an imaging signal based on a photographic light beam from the lens group 2; An S / H circuit 5 as a circuit, a video circuit 6 for processing the sampling output and outputting a video signal to each recording device in accordance with the M and S modes selected by the selection means described later; A / D converter for converting the output of the / H circuit 5 into an A / D converter whose digital image output is input to the AF data processing circuit 1a. It is constituted by a certain mode changeover switch 8.

Then, the AF data processing circuit 1a
Contrast information (hereinafter referred to as a contrast value) which is a value obtained by separating high frequency components of digital image data output from the / D conversion circuit 7 and which indicates a degree of focusing.
Is calculated. The AF data storage unit 1b stores the processing circuit 1a
Is stored. The comparison circuit 1c compares the contrast value calculated by the AF data processing circuit 1a with the contrast value of the AF data storage unit 1b in accordance with an instruction of an AF processing routine in each mode described later. Further, the determination circuit 1d similarly determines the drive of the focus lens 2a or the end of focusing based on the comparison result of the contrast value of the comparison circuit 1c according to the instruction of the AF processing routine in each mode.

The operation of the focusing apparatus of the present embodiment constructed as described above will be described with reference to the flowcharts of the AF routine shown in FIGS. Will be described with reference to FIG. The driving position of the focusing lens 2a is obtained by dividing the lens positions corresponding to the close distance and the ∞ distance by a predetermined number of steps, and expressing the number of steps by the number n of lens driving steps. The closest position is the number of steps n = 0, and the position ∞ is the number of steps n = nmax. The setting of the step number position does not change the gist of the present invention even if the closest position is controlled to n = nmax and the ∞ position is controlled to n = 0.

First, when the M mode, ie, the movie shooting mode, is selected by the mode selection switch 8, the M mode A shown in FIG.
The F processing routine is called. At any position, the focusing lens 2a is driven in either direction relative to the imager 3, and the contrast value of the image data calculated by the AF data processing circuit 1a is compared with the contrast value at the immediately preceding lens driving position. It is determined whether or not the number has increased (step S101). Note that the contrast value at the immediately preceding lens position is stored in the AF data storage unit 1b. Then, when the contrast value increases, driving is further performed in the same direction (step S10).
2) It is determined again whether the contrast value has increased. If the value further increases, step S1 is performed again.
02, the process is repeated until the contrast value does not increase. Then, when the contrast value does not increase, it is determined that the peak point has been reached, the lens driving is stopped, the completion of focusing is displayed, and the routine processing ends.

For example, assuming that point E in FIG. 4 is a driving start point of the focus lens 2a, the processing is performed according to the above-described routine, and the contrast value diagram is traced in the direction of the arrow from the point E to reach the peak value C of the contrast value. Then, it is determined that focusing has been completed.

On the other hand, if the contrast value has not increased in step S101 in the AF routine, the process jumps to step S103. Then, the lens is driven in the reverse direction to check whether the contrast value has increased or decreased. If the value increases, the process returns to step S102. If the value does not increase, the process returns to step S103, and the driving in the reverse direction is performed. Then, when the drive circuit reaches a predetermined number of times, the lens driving is stopped, a display indicating that focusing is impossible is performed, and the process is terminated.

In addition, for example, under low illuminance or the like, the S /
In the case where H is bad or the contrast value is abnormally large due to large blur of the lens or the like, the process returns to step S103 due to a turbulent state in this processing, and the focusing may not be performed. When setting the sensitivity and the focusing speed, it is necessary to determine the sensitivity and the focusing operation sufficiently in consideration of the influence of the disturbance of the subject and the stability of the response operation.
When the main AF processing routine is terminated and the process returns to the main routine photographing processing, the present AF processing routine always monitors the contrast value for restart except in the so-called focus lock state in the main routine. The standby state is kept.

As described above, the M mode AF process has a feedback control element, and can follow a moving subject from an arbitrary position to focus. Therefore, it can be said that this is suitable for continuous tracking shooting of a subject, such as shooting with a movie.

On the other hand, the mode selection switch 8
When the mode, that is, the still shooting mode is selected, the S mode AF processing routine shown in FIG. 3 is called by the AF operation command of the shooting sequence. First, the focusing lens 2a is driven to the initial position, that is, the closest position where the number of driving steps n is 0, and the number of steps n is reset to 0 at the same time. Then, the contrast value of the image data at that time is calculated by the AF data processing circuit 1a and stored as data d (n) in the AF data storage unit 1b (step S2).
01). Then, the focusing lens 2a is driven one step forward relative to the imager 3, and the number of steps n is incremented. As long as the value of the step number n does not exceed the final step number nmax (∞ position), the process returns to step S201, and the contrast value for each scanning position of each lens is sequentially stored in the AF data storage unit 1b.

When the focusing lens is scanned over the entire area and the number of stages becomes n> nmax, the lens driving is stopped. Then, the stored data d
(N) is searched, the number of steps corresponding to the maximum value of the data d (n) is set to M, and the focusing lens 2a is driven to the above-mentioned step number position M to complete focusing, and the routine ends. Then, control is returned to the photographing sequence, and photographing is performed. In the above routine, the case where the contrast value is stored in the storage unit 1b as an array variable has been described. However, the contrast value is compared at the time of storage, and only the larger one of the contrast value and the number of steps are stored. Needless to say, this may be done.

The above process will be described with reference to the example of the contrast value diagram of FIG. 4. The process starts from a point E on the diagram corresponding to the number of steps n = 0, and changes the contrast value in the middle to d (n).
And reaches the number of steps nmax at the ∞ position. Then, the maximum point D of d (n) is searched, and the number M of steps corresponding to the maximum point D, which indicates the focal point, is determined.

As described above, the AF processing by the S mode processing routine has the form of open control and searches for the highest focal point in substantially the entire scanning range, so that there is no operationally unstable element. . Also, since the lens is driven again to the above-mentioned focal point and the AF operation is completed, A which is more suitable for still shooting which is one shot than for movie shooting is used.
You can say F. In the hill-climbing AF, the focusing time changes depending on conditions such as the state of a subject and a large blur of a lens. In some cases, a considerable time is required and the operation becomes unstable. In this case, high-speed focusing for a certain period of time is always obtained, which is optimal for still photography.

In the S-mode processing in the above embodiment, the final focus is set when the state of maximum contrast is reached. However, the method of determining the final focus by comprehensively judging the contrast information in the scanning area is not limited to this. There can be various things. For example, as a process when there are a plurality of peaks of the contrast value in the scanning area, when the number n of lens drive stages corresponding to each peak is P1, P2, P3,. Select the above P1 as the number of steps of the final focal point, select the above PK, and select PINT ((k + 1) / 2), where INT (x) indicates an integer part of x . Alternatively, in the above P1 to Pk, (Pi -nmax
/ 2) The number of stages when the value of / 2) becomes minimum, that is, a peak point located closest to the intermediate position of all the number of drive stages is selected, and various other methods can be considered.

Next, the details of the mode changeover switch 8 for the M and S modes of the camera equipped with the automatic focusing device of the above embodiment will be described with reference to FIG. The configuration of the mode change switch 8 is such that the two switches 8a and 8b are arranged so as to operate in the order of the switches 8a to 8b by pressing the actuator. The output terminal of the switch 8a is connected to a monomultivibrator (MM
V) The switch SW8b is connected to one input terminal of the NOR circuit 8d via the 8c, while the switch SW8b is connected to the other input terminal of the NOR circuit 8d. The output terminal of the NOR circuit 8d is connected to the mode detection terminal 8g. The output terminal of the switch 8b branches off and is connected to the recording trigger terminal 8h. Each of the resistors 8e and 8f is a pull-up resistor.

The mode detection terminal 8g and the recording trigger terminal 8h are connected to the system controller 1, respectively. When the mode detection terminal 8g changes to the H level by the switch operation and a falling trigger is output to the recording trigger terminal 8h, the S mode photographing is selected, and the mode detection terminal 8g does not change and the L mode is not changed. When the falling trigger is output to the recording trigger terminal 8h in the state of the level, the M mode shooting is selected, and a recording start command is given to the controller 1.

The operation of the mode changeover switch S configured as described above will be described. The mode is selected by selecting the S mode or the M mode depending on whether the actuators of the switches 8a and 8b are quickly pressed and when the actuator is slowly pressed. It is assumed that the switch is pressed, and the switch is slowly pressed to select the M mode in which the image is continuously taken for a certain period of time. When the S mode is designated, the actuators of the switches 8a and 8b are quickly pressed as described above. First, switch 8a is set to O
In the N state, the MMV 8c outputs a pulse having a constant width of L level.
The switch 8b is also turned on during the time within the pulse width. Accordingly, the mode detection terminal 8g becomes H level, at the same time, a trigger signal is output to the recording trigger terminal 8h by turning on the switch 8b, and a recording start command for S mode imaging is given to the system controller 1.

On the other hand, when selecting the M mode, the actuator of the switches 8a and 8b is slowly pressed.
First, the switch 8a is turned on, and the MMV 8c outputs a pulse having a constant width of L level. However, when the switch 8b is turned on because the actuator is depressed slowly, the L level pulse of the MMV 8c is already at H level. The level has returned to the level, and no signal is output from the NOR circuit 8d. Accordingly, the S mode detection terminal 8g remains at the H level and does not change, only the trigger is output from the recording trigger terminal 8h, and the system controller 1 is given an M mode shooting / recording start command. Note that when a shooting start command in each mode described above is input to the system controller 1, shooting control is started, and the AF routine of the automatic focusing apparatus according to the present embodiment is called in accordance with the focusing command.

Next, a circuit of a mode changeover switch as a modification of the mode changeover switch 8 will be described with reference to FIG. The mode change switch of this modified example has switches 9a, 9a,
9b, the terminal of the switch 9a is connected to the input terminal of the T-type flip-flop 9c, and the switch 9a is turned on.
Flip-flop 9 that changes to H or L level each time it is operated
The output terminal of c is connected to the mode detection terminal 9f. The terminal of the switch 9b is connected to the recording trigger output terminal 9g. The terminals 9f and 9g are respectively connected to the system controller 1, and the mode detection terminal 9f is
When the trigger is output to the recording trigger terminal 9g in the level state, the system controller 1 starts recording in the S mode shooting, and the trigger is output to the recording trigger terminal 9g when the terminal 9f is at the L level. And the recording of the M mode shooting is started. When the power is turned on, the mode detection terminal 9f connected to the output terminal of the T-type flip-flop 9c is reset to L level.

The operation of the mode changeover switch of the modified example configured as described above will be described. First, the mode detection terminal 9f is set to the H level by the first pressing of the switches 9a and 9b, and the recording trigger terminal 9g is triggered. Is output, the S mode is designated, and shooting and recording are started. Further, when the switches 9a and 9b are pressed for the second time, the mode detection terminal 9f returns to the L level, a trigger is similarly output to the recording trigger terminal 9g, and the M mode is designated, and shooting and recording are started. Become. Thereafter, the switches 9a, 9
When b is operated, the above operation is repeated.

As an image recording medium of a movie / still camera to which the automatic focusing apparatus of the above embodiment is applied, a combination of a magnetic tape / magnetic disk, a magnetic disk, a magneto-optical disk, and the like are used. As the recording device, there is a recording device having a built-in structure or a recording device having an external structure. In addition to the movie / still camera, the automatic focusing device of the present invention can be applied to an electronic still camera having a continuous / still shooting mode, a movie camera with a one-shot shooting function, and the like.

Further, it is not always necessary to associate the camera with the photographing mode. For example, even in a camera dedicated to still photography, a changeover switch is set according to the preference of a focusing sensation when the photographer looks into the viewfinder. In this case, both the M and S modes may be switched.

[0032]

As described above, according to the automatic focusing apparatus according to the first aspect of the present invention, among the plurality of local focal points, the one at the intermediate order in the scanning order is used for final focusing adjustment. Since it is selected as the final focal point to be performed, focusing is always performed at any peak position. That is, a state where “no subject comes into focus” does not occur. In addition, a relatively average focusing can be realized with a very simple calculation for a large number of coexisting subjects.

According to the automatic focusing apparatus of the second aspect of the present invention, of the plurality of local focal points, the one closest to the intermediate position of the predetermined scanning range is subjected to final focusing adjustment. Since it is selected as the final focal point to be focused, focusing is always performed at any peak position. That is, a state where “no subject comes into focus” does not occur. In addition, relatively average focusing similar to so-called pan-focus shooting is realized for a large number of co-existing subjects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an automatic focusing position according to an embodiment of the present invention;

FIG. 2 is a flowchart of an M mode AF processing routine for an automatic focusing position in FIG. 2;

FIG. 3 is a flowchart of an S-mode AF processing routine of the automatic focusing position in FIG. 1;

FIG. 4 is a diagram of a contrast value of a subject, which is used for describing the automatic focusing position in FIG. 1;

FIG. 5 is a circuit diagram of a mode switch of the automatic focusing apparatus of FIG. 1;

FIG. 6 is a circuit diagram showing a modification of the mode changeover switch of the automatic focusing apparatus of FIG. 1;

[Explanation of symbols]

 1a AF data processing circuit 1b AF data storage section 1c Comparison circuit 1d Judgment circuit 2a Focusing lens 3 Imager (imaging element) 8 Mode switch

Claims (2)

[Claims] A scanning is performed by moving a relative position between a focusing lens and an image sensor, and a focus position is determined based on contrast information in image information output from the image sensor at each scanning position. Determining means for recognizing a position corresponding to a predetermined peak of the contrast information as at least a local focal point, and obtaining the position as a result of the scanning performed over a predetermined scanning range. When a plurality of the obtained local focal points are present in the predetermined scanning range, a final focusing adjustment should be performed on the local focal points which are located at the center in the scanning order among the plural local focusing points. An automatic focusing device, which is selected as a final focusing point. 2. Scanning is performed by moving a relative position between a focusing lens and an image sensor, and a focus position is determined based on contrast information in image information output from the image sensor obtained at each scanning position. Determining means for recognizing a position corresponding to a predetermined peak of the contrast information as at least a local focal point, and obtaining the position as a result of the scanning performed over a predetermined scanning range. If a plurality of the obtained local focal points are present in the predetermined scanning range, the local focusing point closest to the intermediate position of the predetermined scanning range among the plurality of local focusing points is finally focused. An automatic focusing device which is selected as a final focusing point to be adjusted.