JP2001116980A - Automatic focusing camera and photographing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for automatic focusing which can obtain an image put in focus on subjects by measuring the distances to the subjects present in a subject image and varying the depth of field of an image pickup optical system. SOLUTION: This camera is provided with a focusing position information measuring means which can measure movement position on the image pickup plane of a lens group 12 or CCD 14 for focusing on the subjects present in a photographic range and is equipped with a photographing means which moves the image pickup plane of the lens group 12 or CCD 14 by an AF motor 24 to nearly the center position among the focusing positions, controls a stop by a stop motor 26 so that the subjects are put in the depth of field, and takes pictures, so even when the subjects differing in distance are present together, an image put in focus on a subject that a user intends can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-focus camera and a photographing method, and more particularly to an auto-focus camera and a photographing method for photographing a plurality of objects by focusing.

[0002]

2. Description of the Related Art As a method of reliably focusing on a main subject, a multi-point distance measuring camera in which a plurality of small distance measuring areas are provided, and a camera determines the best point and focuses on the object is disclosed in Japanese Patent Laid-Open Publication No. Hei.
No. 3,138,39. In addition, Japanese Unexamined Patent Publication
In the publication of -289279, the gaze of the photographer is detected,
2. Description of the Related Art A camera that provides a distance measurement area near a line of sight is known.

[0003]

However, the method disclosed in Japanese Patent Application Laid-Open No. 6-313839 has a disadvantage that the object does not always match the object intended by the photographer.

Further, according to the method disclosed in Japanese Patent Application Laid-Open No. 6-289279, it is difficult for the camera to detect the user's line of sight when the user is wearing spectacles. There was a problem of not being scorched.

As described above, in the conventional autofocus camera,
In many cases, the focus position determined by the camera is different from the focus position desired by the user. This is likely to occur when the subject at the focus position desired by the user is small and there is a subject with a large area before and after the desired focus position. For example, this is a problem that frequently occurs when a person in front of a mountain is focused on the background.

The present invention has been made in view of such circumstances, and even if a plurality of subjects at different distances are mixed,
It is an object of the present invention to provide an automatic focusing camera and an imaging method capable of obtaining an image focused on a subject intended by a user.

[0007]

In order to achieve the above object, the present invention measures a plurality of moving positions of a focus lens or an imaging surface for separately focusing a plurality of objects existing in a photographing range. Possible measurement means, and when a plurality of movement positions are measured by the measurement means, focus adjustment means for moving the focus lens or the imaging surface to a position substantially at the center of the movement positions at both ends of the plurality of movement positions, An aperture adjusting unit configured to control an aperture so that the plurality of subjects enter the depth of field when the plurality of subjects are imaged by the focus lens or the imaging surface adjusted by the focus adjusting unit; and A focus lens or an imaging surface adjusted by the adjustment means and the aperture adjustment means, and an imaging means for taking an image with the aperture. It is set to.

According to the present invention, a measuring means capable of measuring a plurality of moving positions of a focus lens or an imaging surface for separately focusing a plurality of objects present in a photographing range, and the measuring means When a plurality of movement positions are measured, focus adjustment means for moving the focus lens or the imaging surface to a position substantially at the center of the movement positions at both ends of the plurality of movement positions, and a focus lens adjusted by the focus adjustment means or When the plurality of subjects are imaged by the imaging surface, the plurality of subjects are adjusted by an aperture adjustment unit that controls an aperture so that the plurality of subjects fall within a depth of field, and the focus adjustment unit and the aperture adjustment unit are respectively adjusted. Since it is provided with a focus lens or an imaging surface and an imaging means for imaging with an aperture, a plurality of subjects having different distances are mixed. Even, it is possible to obtain an image focused on the subject to the user's intention.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an autofocus camera and a photographing method according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an electronic camera to which an automatic focus (hereinafter abbreviated as AF) camera and a photographing method according to the present invention are applied.

The optical system of the electronic camera 10 includes a photographing lens group 12 capable of adjusting the focus, and an aperture 13 for adjusting the amount of incident light and adjusting the depth of field of the optical system.
And a CCD (solid-state imaging device) 14 for converting a subject image into an electric signal. The image signal obtained by the CCD 14 is transmitted to the AF evaluation value detecting means 16. AF
The evaluation value detecting means 16 converts the image pickup signal into a digital R,
After conversion into G and B signals, a process of extracting a component having a large contrast is performed. Further, the subject image is divided into each area, the contrasts in each area are summed and averaged, and output to the CPU 18.

The CPU 18 is provided with a RAM which is a readable and writable storage means, and a ROM which is a read-only storage means which stores programs, constants, and the like for controlling the operation of the CPU 18.

The CPU 18 is connected to a display means 20 for displaying photographing data and a storage means 22 for recording or reading out photographing data. Further, the CPU 18 is connected with an AF motor 24 as a means for adjusting the focus (focus) of the lens group 12 and an aperture motor 26 as a means for adjusting the opening of the aperture 13.
Focus adjustment and aperture adjustment can be performed by a command from 18. The lens group 12 and the CCD 1
The distance information from the imaging surface 4 and the opening degree information of the aperture 13 can be measured, and the distance information is input to the CPU 18.

The CPU 18 extracts a luminance component in the image from the digital signal value of the obtained image, acquires the luminance level of the subject by integrating the luminance component in a predetermined area, and obtains the luminance level of the subject. To determine the exposure power (shooting aperture and shutter speed) required for shooting from the brightness level of
Equipped with LAE function. In addition, AF and AE (automatic exposure) are commanded to the electronic camera 10 at the first stage,
A release switch (not shown) for instructing shooting at the second stage is provided. In the above-described configuration of the means for adjusting the focus, an example in which the focus is adjusted by moving the lens group 12 has been described. However, the present invention is not limited to this, and the focus is adjusted by moving the imaging surface. Even so, the object of the present invention can be achieved.

An AF method for the electronic camera 10 configured as described above will be described.

First, the focus of the lens group 12 is waiting at the position of the longest shooting. An image to be photographed is formed on a light receiving surface of a solid-state imaging device (CCD) 14 via a photographing lens group 12. The subject image is converted into signal charges of an amount corresponding to the amount of incident light by each sensor in the CCD 14. The charge signal thus accumulated is transmitted to the AF evaluation value detecting means 16, where R, R,
The G and B signals are converted into digital R, G, and B signals, and an AF evaluation value for determining a focus (focus position) when autofocusing is performed by a high-frequency component extraction circuit is calculated.

In the AF evaluation value detecting means 16, for example, 8
The high-frequency component of the data of the subject image divided into the × 8 AF integrated area is calculated as the contrast of the luminance difference between adjacent pixels. The contrast in each region is obtained, and the contrast in each region is summed and averaged, and A
The value is output to the CPU 18 as the F evaluation value. When performing AE, the CPU 18 obtains the luminance level of the subject in the image from the digital signal value of the obtained image,
Is determined, and the depth of field of the optical system according to the aperture is stored. When the opening of the aperture 13 is directly designated by the photographer, the CPU 18 reads the aperture opening information from the aperture motor 26 and reads the aperture of the aperture 13 and the object field of the optical system corresponding to the opening. Remember depth.

As described above, the focus position is moved from infinity to the closest position, and the AF evaluation value at each focus position is obtained. That is, when the AF evaluation value of ΣA1 at the first point at infinity is measured, the CPU 1
Numeral 8 outputs an instruction to the AF motor 24 to move the lens group 12 by one step to the “near” side of focus along the optical axis. If one step at this time is set to a width of the depth of field that fluctuates according to the degree of narrowing of the aperture 13, the number of measurement points of the AF evaluation value can be reduced, and the speed of AF can be increased.

The AF evaluation value ΔA2,
ΣA3, ΣA4... Are sequentially obtained, and an AF search is performed. Then, AF among the AF evaluation values of ΣA1 to ΣA13
The focus position at which the evaluation value indicates the maximum value is calculated, and the position is determined as the focus position. Then, shooting is performed while focusing on the focus position thus obtained. Also,
If a curve connecting the AF evaluation values of adjacent focus positions has a plurality of inflection points, an inflection point that is convex upward may be determined as the focus position.

When a plurality of in-focus positions are calculated in this way, the difference between the maximum value and the minimum value of the plurality of in-focus positions is determined, and the difference between the maximum value and the minimum value of the plurality of in-focus positions at the time of shooting is stored. Compare with the depth of field of the optical system. If the depth of field is deeper than the difference between the maximum value and the minimum value of the plurality of focus positions, a focus position intermediate between each focus position is calculated and set as a new focus position, Photographing is performed at this new focus position.

If the depth of field is smaller than the focus position as a result of the comparison, it is determined whether or not an aperture value corresponding to the depth of field covering each focus position can be obtained. Do.
If it is determined that an aperture value corresponding to the depth of field covering each focusing position can be obtained, the CPU 18 calculates a new aperture value and instructs the aperture motor 26 to that aperture value. Then, an intermediate focus position between the plurality of focus positions is calculated, and this is set as a new focus position, and photographing is performed at this new focus position.

If the CPU 18 determines that the aperture amount corresponding to the depth of field covering each in-focus position is too small to be obtained, the CPU 18 determines whether or not the depth of field corresponding to the aperture value can fall within the depth of field. Select the focus position. Then, an intermediate focus position between the plurality of focus positions is calculated, and this is set as a new focus position. Photographing is performed at this new focus position, and the focus position that does not fall within the depth of field is again focused. A new focus position is obtained by comparison with the depth of field.

If the aperture 13 is excessively narrowed to increase the depth of field, the shutter speed (or the charge accumulation time) becomes longer, and the possibility of blurring during photographing increases. A threshold value of the aperture value is provided according to the focal length of the photographing lens, and programming is performed so that the aperture value is not reduced beyond the threshold value except when special photographing is performed.

Also, when the background exists at a position far from the subject, other main subjects are concentrated at a close position, and all the in-focus positions are not within the depth of field corresponding to the aperture value. May be set so that the in-focus position of the background is deleted and no image is taken at the in-focus position of the background. In general, when contrast AF is performed on a low contrast background such as the sky, the sea, and a wall, the obtained AF evaluation value indicates a low value.

When the present invention is applied to an electronic camera 10 capable of rewriting photographing data, data photographed at each in-focus position is temporarily stored, and the image data required for later display is stored. Only one of them may be selected and stored in the storage unit 22.

FIG. 2 shows an example of measurement results of the AF search.

FIG. 2 shows the result of an AF search for a subject image in which a main subject exists concentrated at the distance of the focus position "7". This is the AF evaluation value in FIG.
An (n = 1, 2, 3,..., 13) shows the maximum value at the focus distance of ΣA7, and its peak is clear. Here, the CPU 18 determines that ΣA6 near ΣA7
From the AF evaluation values such as ΣA8 and the like, ΣA7 is a convex inflection point, ΣA7 is the maximum value, and so on.
It is determined that the focus position of A7 is the focus position.

Further, the CPU 18 digitizes the shape near the maximum value of the curve connecting the AF evaluation values of the adjacent focus positions, and if it is determined that the shape is gentle, issues a command to stop the aperture 13 to the aperture motor. May be output. By automatically controlling the opening degree of the aperture 13 in this manner, when the depth of the subject is deep, the focusing range can be automatically increased. When it is determined that the shape is steep, shooting is performed with the aperture amount of the aperture 13 obtained by AE.

FIG. 3 shows a photographing range in which a subject image is mixed at a plurality of distance positions.

As shown in FIG. 3, a photographing range 30 includes a person 32 located closest to the electronic camera 10 and a person 32.
An automobile 34 located farther away and a background 36 located farther are mixed. When an AF search is performed on the subject image shown in FIG. 3 to calculate an AF evaluation value at each focus position, an AF search result shown in FIG. 4 is obtained.

According to FIG. 4, the AF evaluation value ΣB4 at the focus position of the background 36, the AF evaluation value ΣB8 at the focus position of the car 34, and the AF evaluation value 近 傍 B12 at the focus position of the person 32 are shown. Form an inflection point convex upward. Therefore, CP
U18 indicates that the focus positions are "4", "8" and "12".
Is determined to be the in-focus position, and the difference between the maximum value and the minimum value of these focus positions is compared with the stored depth of field of the optical system corresponding to the aperture value at the time of shooting. I do. As a result of the comparison, if the depth of field of the optical system is deeper than the difference between the maximum value and the minimum value of the focus position, a focus position intermediate between the respective focus positions is calculated and this is set as a new focus position. Then, shooting is performed at this new focus position.

FIG. 5 shows a flowchart of the in-focus position calculation according to the present invention.

When the AF evaluation value at each focus position is calculated, the process jumps to a subroutine of step S100 "calculation of focus position" (hereinafter, step S100 is abbreviated as S100) shown in FIG. Then, the process goes to S102.
The process proceeds to the determination of “has one peak in the evaluation value?”.

In S102, it is determined whether or not the curve connecting the AF evaluation values of the adjacent focus positions has one peak (whether or not the curve has a plurality of upwardly convex inflection points). If the number of peaks is one, the process branches to S104 “focus and focus on peak”, and shooting is performed with the peak position of the AF evaluation value as the focus position. If the number of AF evaluation value peaks is not one, the process proceeds to S106 “confirm distance between both ends of peak”.

In step S106, the difference between the maximum distance and the minimum distance among the distances from the plurality of measured subjects to the image pickup unit is calculated. In the example shown in FIG. 4, it corresponds to the distance from the focus position “4” to “12”.

In the next step S108 "Calculate the lens extension amount corresponding to the middle of the distance between both ends", an intermediate point of the depth of field between the maximum distance and the minimum distance of a plurality of focusing positions is calculated to achieve focusing. And position. In the example shown in FIG. 4, the position of the FZ which is an intermediate point between the focus positions “4” and “12” is calculated. At this time, in the depth of field corresponding to the aperture value obtained by AE (for example, in the case of Fd shown in FIG. 4), A
If all the peaks (focus positions) of the F evaluation values are included, the program branches to S110 “move the lens to the calculated lens extension position”.

In S110, the calculated intermediate point FZ is set as a new focus position, and the AF motor 24 is controlled to control the FZ.
Adjust the focus to the position. Then, in S112 “set to the calculated aperture value”, the aperture motor 26 is driven to set the aperture so that the aperture value obtained by AE is obtained.

When the setting is completed, a photograph is taken in "Shooting" in S114, and the photographing data is stored in the storage means 22.

Further, all the peaks (in-focus positions) of the AF evaluation values are included in the depth of field corresponding to the aperture value obtained by AE in S108 (for example, in the case of Fa, Fb, Fc shown in FIG. 4). If not, the program proceeds to S116 “Calculate FNo. Encompassing both end distances”.

In step S116, an aperture value (corresponding to Fd in the example shown in FIG. 4) is calculated so that all the peaks of the AF evaluation value are included in the depth of field, and the flow advances to step S112 to execute photographing. I do.

FIG. 6 is a timing chart of photographing when the automatic focusing camera and the photographing method according to the present invention are applied. Note that, in the following example, a plurality of focus positions cannot be included within the depth of field of the optical system, and thus, a case where shooting is performed at three types of focus positions is shown.

According to the figure, at time t1, the electronic camera 1
When the first step of the release switch provided at 0 is pressed, the AF search is started, the focus position is step-moved from "1" to "13", and the AF evaluation value at each focus position is calculated. Then, the focus position is calculated between t10 and t11, and the focus position is set to “1” at t12.
It moves to the position "2" again and enters the shooting standby state.
Here, when the lens group is stopped at the focus position “12”, if the focus position is stopped from the (near) side, it is the stop direction executed during the AF search (far).
Since the direction differs from the stop direction from the side, when the lens system is affected by friction or backlash of the drive system of the lens group, a hysteresis phenomenon occurs in which the lens group stops at a position different from the position "12" stopped during the AF search. In order to solve this problem, when stopping at the focus position "12", as shown at the time from t11 to t12 in FIG. 6, the focus position is once moved to the (far) side from the position "12" and then again. The focus position is moved toward the (near) side and stopped at the position "12". If the AF drive system has a structure that does not cause hysteresis, no problem occurs even if the AF drive system is stopped from either (near) or (far) side.

When the second step of the release switch provided on the electronic camera 10 is pressed, an image is taken at the focus position "12", then at the position "8", and then at the position "4". Then, the focus position is similarly moved to execute the continuous shooting. One of the release buttons of the electronic camera 10
When the first and second steps are continuously pressed, the processing from t1 to t17 is continuously executed.

In the continuous photographing method from t11 to t17 shown in FIG. 6, it takes a long time to reciprocate in order to eliminate the hysteresis at the focus stop position. Therefore, in the case of the “bracket mode” in which shooting is continuously performed at a plurality of focus positions, as shown at times t31 to t35 in FIG. If the camera is moved to the side and continuous shooting is performed, the shooting time can be reduced.

In the above description, an example of the automatic focusing camera using the distance measuring means of the contrast AF for calculating the in-focus position from the image data output from the CCD 14 has been described. However, the present invention is not limited to this. Instead, the object of the present invention can be achieved by using other distance measuring means such as a triangulation type, an external light passive type, an optical active type, and an ultrasonic type. Further, the present invention is not limited to an electronic camera, and can be applied to an automatic focusing camera and a photographing method of a silver halide camera.

[0046]

As described above, according to the autofocus camera and the photographing method according to the present invention, a plurality of focus lenses or a plurality of image pickup surfaces for individually focusing a plurality of objects existing in a photographing range are provided. A measuring unit capable of measuring a moving position, and a focus for moving the focus lens or the imaging surface to a position substantially at the center of the moving positions at both ends of the plurality of moving positions when the plurality of moving positions are measured by the measuring unit. Adjusting means, and aperture adjusting means for controlling the aperture so that the plurality of objects are within the depth of field when the plurality of objects are imaged by the focus lens or the imaging surface adjusted by the focus adjusting means. A focus lens or an imaging surface adjusted by the focus adjustment means and the aperture adjustment means, and a photographing hand for imaging with the aperture. Since with the door, the distance of different subjects be mixed, it is possible to obtain an image focused on the subject to the user's intention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic camera to which an autofocus camera and a photographing method according to the present invention are applied.

FIG. 2 is a diagram showing an example of a measurement result of an AF search.

FIG. 3 is a diagram showing a shooting range in which subject images are mixed at a plurality of positions.

FIG. 4 is a diagram illustrating an A of a photographing range in which a subject image is mixed at a plurality of positions.
The figure which shows the measurement result of F search

FIG. 5 is a flowchart of a focus position calculation according to the present invention.

FIG. 6 is a timing chart of photographing using the autofocus camera and the photographing method according to the present invention.

FIG. 7 is a timing chart of photographing using the autofocus camera and the photographing method according to the present invention.

[Explanation of symbols]

10 electronic camera, 12 lens group, 13 aperture, 14
... CCD (solid-state imaging device), 16 ... AF evaluation value detecting means, 18 ... CPU, 20 ... Display means, 22 ... Storage means,
24 ... AF motor, 26 ... Aperture motor, 30 ... Shooting range

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihisa Yamazaki 3-11-46 Izumi, Asaka-shi, Saitama F-term in Fujisha Shin Film Co., Ltd. (Reference) 2H011 AA03 BA31 CA21 2H051 AA00 BA47 CE14 DA03 DA07 DD10 EB04 GB12 5C022 AA13 AB02 AB12 AB28 AB29 AB30 AC01 AC42 AC52 AC54

Claims (8)

[Claims] 1. A measuring means capable of measuring a plurality of moving positions of a focus lens or an image pickup surface for separately focusing a plurality of objects present in an imaging range, and a plurality of moving positions by the measuring means. Is measured, focus adjustment means for moving the focus lens or the imaging surface to a position substantially at the center of the movement positions at both ends of the plurality of movement positions, and the focus lens or the imaging surface adjusted by the focus adjustment means, An aperture adjusting unit that controls an aperture so that the plurality of objects are within the depth of field when forming a plurality of objects; a focus lens or an imaging device adjusted by the focus adjusting unit and the aperture adjusting unit, respectively. An autofocus camera comprising: a photographing means for photographing with a surface and an aperture. 2. The method according to claim 1, wherein the aperture adjusting unit is configured to determine the plurality of subjects based on a moving distance of both ends of the plurality of moving positions of the focus lens or the imaging surface measured by the measuring unit or a subject distance corresponding to the moving positions of both ends. 2. The automatic focusing camera according to claim 1, wherein an aperture value for obtaining the aperture value within the depth of field is obtained, and the aperture is adjusted so as to have the obtained aperture value. 3. The measuring means moves the focus lens or the imaging surface in the optical axis direction, and extracts and integrates a high-frequency component from an output signal of the imaging means for each moving position of the focus lens or the imaging surface. The autofocus camera according to claim 1, wherein an evaluation value is calculated by using the autofocus camera, and a movement position of one or more of the focus lens or the imaging surface at which the evaluation value reaches a peak is measured. 4. The focus lens or the image pickup surface having a plurality of distance measuring areas, measuring a subject distance for each of the distance measuring areas, and separately focusing the subject at each of the subject distances. The autofocus camera according to claim 1, wherein a movement position of the camera is measured. 5. A plurality of moving positions of a focus lens or an imaging surface for separately focusing on a plurality of objects present in a photographing range are measured, and a plurality of moving positions of the plurality of moving objects are measured at a substantially central position of the plurality of moving positions. Moving the focus lens or the imaging surface, when imaging the plurality of objects by the moved focus lens or the imaging surface, controlling the aperture so that the plurality of objects fall within the depth of field; A photographing method characterized by photographing with the moved focus lens or imaging surface and the controlled aperture. 6. The method of controlling the aperture, comprising: moving the plurality of subjects based on the measured moving distances of both ends of the plurality of moving positions of the focus lens or the imaging surface or subject distances corresponding to the moving positions of the both ends. 6. The photographing method according to claim 5, wherein an aperture value for setting the aperture value within the depth of field is obtained, and the aperture is controlled so as to be the obtained aperture value. 7. The measurement of the movement position includes moving the focus lens or the imaging surface in the optical axis direction and extracting a high-frequency component from an output signal of the imaging unit for each movement position of the focus lens or the imaging surface. 7. The imaging method according to claim 5, wherein the evaluation value is calculated by integrating, and the measurement is performed based on a movement position of the focus lens or the imaging surface at which the evaluation value reaches a peak. 8. The moving position measurement includes a plurality of distance measuring areas, a subject distance is measured for each of the distance measuring areas, and a moving position of the focus lens or the imaging surface is determined based on each of the subject distances. 7. The method according to claim 5, wherein the measurement is performed.