JP2010072284A - Focusing unit for camera - Google Patents

Abstract

A focus adjustment response performance and a subject tracking performance in a dynamic AF mode are improved.
In a camera focus adjustment device that performs focus adjustment of a photographing lens based on a focus detection result detected in a focus detection area within a preset region among a plurality of focus detection areas in a photographing screen. The movement of the camera is detected, and when the movement of the camera is detected, the area is enlarged, and the focus of the photographing lens is adjusted based on the focus detection result detected in the focus detection area in the enlarged area.
[Selection] Figure 9

Description

  The present invention relates to a camera focus adjustment apparatus.

  When multiple focus detection areas are set in the shooting screen and the focus of the photographic lens is adjusted based on the focus detection results of the selected area, even if the main subject to be focused is outside the selected area, the other areas There is known a camera focus adjustment apparatus having a so-called dynamic AF (automatic focus adjustment) mode in which a main subject is continuously focused using the focus detection result (see, for example, Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 09-318865 A

By the way, in the focus adjustment device of a camera, the number of focus detection areas is increasing, and a camera in which several tens or more focus detection areas are set up in a shooting screen has appeared. In such a camera having many focus detection areas, if the focus adjustment control of the conventional camera described above is performed, focus detection is performed in all focus detection areas other than the selected area, and therefore, focus detection calculation time is required. Therefore, there is a high possibility that another subject approximated to the main subject is mistaken for the main subject.
Therefore, the area of the focus detection area that refers to the focus detection result in the dynamic AF is limited to the peripheral area of the selected area, and the dynamic AF is performed using the focus detection result of the focus detection area in the area. However, if the area is enlarged, the above-described problem of focus detection time and main subject misidentification occurs.

(1) According to the first aspect of the present invention, the focus detection unit detects the focus adjustment state of the photographing lens in a plurality of focus detection areas in the photographing screen, and the focus adjustment of the photographing lens is performed based on the focus detection result by the focus detection unit. A focus adjusting unit that performs the focus adjustment of the photographic lens by the focus adjusting unit based on a focus detection result detected in a focus detection area within a preset region of the plurality of focus detection areas. The camera focus adjustment apparatus includes motion detection means for detecting camera motion, and the control means enlarges the area when the motion detection means detects the camera movement, and the focus detection area in the enlarged area. Based on the focus detection result detected in step 1, the focus adjustment unit adjusts the focus of the photographing lens.
(2) According to a second aspect of the present invention, in the camera focus adjustment apparatus according to the first aspect, the motion detecting means detects the moving direction of the camera, and the control means detects the moving direction of the camera detected by the motion detecting means. The area is enlarged according to the above.
(3) According to a third aspect of the present invention, in the camera focus adjustment apparatus according to the second aspect, the region is enlarged only in the moving direction of the camera by the control means.
(4) According to a fourth aspect of the present invention, in the camera focus adjustment apparatus according to the second aspect, the control means expands the area by the same amount in the direction in which the camera moves and in the opposite direction.
(5) A fifth aspect of the present invention is the camera focus adjustment apparatus according to any one of the first to fourth aspects, wherein the motion detection means detects the moving speed of the camera, and the control means moves the camera. The faster the speed, the larger the amount of enlargement of the area.

  According to the present invention, it is possible to reduce the possibility of misidentifying other subjects approximate to the main subject as the main subject while shortening the focus detection calculation time and improving the responsiveness in the focus adjustment control. You can keep focusing.

  An embodiment in which the focusing device of the present invention is mounted on a single-lens reflex digital camera will be described. The focus adjustment device of the present invention is not limited to a single-lens reflex digital camera, and can be applied to all types of cameras such as a compact camera and a video camera.

  FIG. 1 shows the configuration of a single-lens reflex digital camera according to one embodiment, and FIG. 2 shows a cross-sectional view of the camera according to one embodiment. In FIGS. 1 and 2, illustration of camera devices and circuits not directly related to the present invention is omitted. The microcomputer 1 includes peripheral components such as a CPU and a memory, performs various calculations and various sequence controls of the camera, and executes a control program described later to execute focus adjustment control. The camera of one embodiment shows an example of an interchangeable lens type, and the microcomputer 1 inputs lens information such as an open aperture value, a focal length, and an exit pupil from a lens control device (not shown) built in the interchangeable lens.

  The photometry circuit 2 measures the subject luminance by dividing the subject luminance into a plurality of regions by the photometry sensor 3. The exposure control circuit 4 calculates the shutter speed and the aperture value based on the subject brightness detected by the photometry circuit 2 and the preset imaging sensitivity, and controls the shutter control unit 5 and the aperture control unit 6. The shutter control unit 5 controls the shutter 7 so that the shutter speed of the calculation result is obtained, and the aperture control unit 6 controls the aperture 8 so that the aperture value of the calculation result is obtained.

  The focus detection circuit 9 receives a signal indicating the focus adjustment state of the interchangeable lens 11 from the focus detection sensor 10 disposed at the bottom of the camera body, and detects the defocus amount of the interchangeable lens 11 by a phase difference detection method. The lens driving circuit 12 drives a focusing lens (not shown) of the interchangeable lens 11 according to the defocus amount of the detection result, and performs focus adjustment. In this embodiment, an example in which a motor for driving the focusing lens is built in the interchangeable lens 11 is shown, but it may be installed in the camera body. The mode setting circuit 13 sets various shooting modes such as exposure, autofocus, and image. The setting operation member 14 is an operation member for performing a setting operation of the camera. The half-push switch SW1 is closed by a first stroke of a release button (not shown), and is closed by a second stroke deeper than the first stroke of the release button. And a fully-pressing switch SW2 is included.

  The image pickup device 15 is configured by a CCD, a CMOS, or the like, picks up a subject image formed by the interchangeable lens 11 and outputs a subject image signal. The A / D conversion circuit 16 A / D converts the subject image signal output from the image sensor 15. The timing circuit 17 controls the imaging timing of the imaging device 15 and the A / D conversion timing of the A / D conversion circuit 16. The image processing control circuit 18 performs image processing such as white balance adjustment, sharpness adjustment, gamma correction, and gradation adjustment on the subject image data, and performs interpolation processing on the subject image data of each color. Note that the image pickup device 15, the A / D conversion circuit 16, the timing circuit 17, and the image processing control circuit 18 are mounted on an image pickup substrate 19 disposed behind the image pickup device 15.

  The SDRAM 20 temporarily stores the corrected subject image data, and the image recording medium 21 records the subject image data and shooting data together in various file formats. The image recording medium 21 can be a compact flash (registered trademark), an SD card, smart media, or the like. The rear liquid crystal control circuit 22 controls the rear liquid crystal monitor 23 provided on the rear surface of the camera body to display images and various information. The in-finder display control circuit 24 controls the in-viewfinder transmissive liquid crystal display 25 and its backlight 26, and the shooting mode, the number of shots, the shutter speed, and the aperture are displayed below the viewfinder screen viewed from the viewfinder eyepiece window (not shown). Various shooting information such as values are displayed.

  Dichroic prisms 31 and 32 are arranged between the penta roof prism 27 of the finder optical system and the eyepiece lenses 28, 29 and 30. The penta roof prism 27 and the dichroic prisms 31 and 32 are bonded to each other, and the bonding surface of the penta roof prism 27 and the dichroic prism 31 and the bonding surface of the dichroic prisms 31 and 32 are 2 with different angles with respect to the optical axis of the interchangeable lens 11. Two optical surfaces are formed. Above the dichroic prisms 31 and 32, a projection lens 33, a folding mirror 34, a superimposing transmissive liquid crystal display 35, an illumination lens 36, and an illumination LED light source 37 are arranged. Note that a prism 38 and a photometric lens 39 are disposed above the exit surface of the dichroic prism 32, and thereby subject light is guided to the photometric sensor 3.

  The superimpose display control circuit 40 controls a superimpose transmissive liquid crystal display 35 and an illumination LED light source 37 disposed above the dichroic prisms 31 and 32, and forms an image on the screen 41 by the interchangeable lens 11. The 51 focus area (focus detection area) marks shown in FIG. 4 are superimposed on the subject image to be displayed, that is, superimposed display. The superimpose transmission type liquid crystal display 35 has a shutter function, and the red light from the LED light source 37 passes through the display portion and is enlarged by the projection lens 33, and further, two optical elements of the dichroic prisms 31 and 32. Reflected by the surface and superimposed on the subject image from the penta roof prism 27. That is, the focus area mark is displayed superimposed on the subject image. The focus area mark displayed by the superimposing transmission type liquid crystal display 35 is displayed in the color of the illumination LED light source 37 (red in this embodiment).

  In FIG. 2, a part of the subject light transmitted through the lens group of the interchangeable lens 11 is reflected by the main mirror 42 and guided to the finder optical system, and is imaged on the screen 41. The subject image formed on the screen 41 passes through the penta roof prism 27, the dichroic prisms 31 and 32, and the eyepiece lenses 28 to 30 and is guided to the viewfinder eyepiece window, and is visually recognized by the photographer. At this time, the superimpose transmission type liquid crystal display 35 superimposes the focus area mark on the subject image.

  In FIG. 2, a part of the subject light transmitted through the lens group of the interchangeable lens 11 is transmitted through the main mirror 42, reflected by the sub mirror 43, and guided to the focus detection sensor 10. The focus detection sensor 10 detects the focus adjustment state of the interchangeable lens 11, that is, the defocus amount at each position of the focus area mark in the shooting screen by a known phase difference detection method. Then, a focus area to be finally subjected to focus detection is selected from the 51 focus areas by a predetermined algorithm, and the selected focus area is displayed on the finder image by superimposition. If the photographer arbitrarily selects a focus area, the selected area is displayed superimposed on the viewfinder image.

  Further, in FIG. 2, at the time of photographing, the main mirror 42 and the sub mirror 43 are retracted from the photographing optical path of the imaging lens 11, and the subject light is guided to the image sensor 17 through the shutter 7 and the low-pass filter 44, and on the image sensor 17. An image is formed and imaged.

  The acceleration sensor 45 is installed on the substrate 19 as shown in FIGS. 2 and 3, and detects acceleration in the X-axis direction, that is, the left-right direction of the camera, and the Y-axis direction, that is, the vertical direction of the camera. When the camera is held at the normal position and a stationary subject is captured, the acceleration in the X-axis direction is 0G and the acceleration in the Y-axis direction is 1G. When the camera is turned over and the camera is turned over while capturing a subject moving in the horizontal direction in the field, the acceleration in the X-axis direction is detected. Further, when the camera is turned over while the camera is turned over while the subject is moving in the vertical direction with the camera in the normal position, acceleration in the Y-axis direction is detected. When the camera is turned over in the direction of the ground of the object scene, an acceleration exceeding 1 G is detected in the Y-axis direction. Further, the left direction and the right direction in the X-axis direction and the upper direction and the lower direction in the Y-axis direction can be identified by the polarity of the acceleration detection value of the acceleration sensor 45, respectively.

  FIG. 3 is a rear view of the single-lens reflex digital camera according to the embodiment. A setting operation member 14 and a rear liquid crystal monitor 23 are provided on the back of the camera. Here, only the switches directly related to the focus adjustment control among the various switches of the setting operation member 14 will be described. The AF mode switch 14a is an operation member for switching an automatic focus adjustment (AF) mode, and is a switch for selecting any one of three AF modes of a single AF mode, a dynamic AF mode, and an auto area AF mode.

  The single AF mode is a mode in which automatic focus adjustment (AF) is performed only in a selected focus area. The dynamic AF mode is a mode in which the main subject is continuously focused using the defocus amount detected in another focus area even when the main subject to be focused temporarily deviates from the selected focus area. . The auto area AF mode is a mode in which the camera selects a focus area and focuses.

  FIG. 5 shows a viewfinder screen according to an embodiment. In this embodiment, focus areas (indicated by rectangular frames in the figure) are set at 51 locations on the shooting screen. When the photographer selects any focus area, only the selected focus area is lit. Note that FIG. 5 shows a state in which all the focus areas are turned on for easy understanding, but usually all the focus areas are not turned on in this way. Below the finder screen outside the shooting screen, various types of shooting information such as the shooting mode, the number of shots, the shutter speed, and the aperture value are displayed by the above-described transmissive liquid crystal display 25 in the viewfinder.

  FIG. 6 shows a viewfinder screen when a person on a sports car is captured in the dynamic AF mode. The selection area is a focus area at the center of the shooting screen. When a person in a sports car that is the main subject moves out of the focus area at the center of the screen, the conventional focus adjustment device described above uses the defocus amount detected in the focus area other than the selected area to focus on the main subject. Try to keep focusing. For example, the focus detection is performed in 50 focus areas other than the selection area at the center of the screen to detect the defocus amount, and the defocus amount close to the defocus amount detected last time in the focus area at the center of the screen is selected. Extract and adjust the focus according to the defocus amount, and continue to focus on the main subject.

  However, when the focus adjustment method in the conventional dynamic AF mode is carried out with a camera having a large number of focus areas, it takes a long time for focus detection calculation, and there is a high possibility that another subject approximated to the main subject is mistaken as the main subject. Become. Therefore, in this embodiment, the main subject is continuously focused based on the defocus amounts detected in, for example, a total of nine focus areas around the selected area. Although the focus area referred to in the dynamic AF around the selected area, that is, the effective area in the dynamic AF is an area including nine focus areas, the area is not necessarily limited to this size.

  As a result, the focus detection calculation time can be shortened compared to the case where all the focus areas other than the selected area are effective areas in the dynamic AF mode, and the responsiveness in the focus adjustment control is improved. The possibility that the subject is mistaken as the main subject can be reduced, and the main subject can be kept in focus.

  However, when capturing a fast moving main subject such as a person riding in a sports car, it may not be captured in only nine focus areas around the selected area, and may deviate from these focus areas. However, when the area of the effective area in the dynamic AF is enlarged, the above-described problems of the focus detection time and the main subject misidentification occur.

  Therefore, in this embodiment, the direction in which the direction of the camera is to be changed by the acceleration sensor 45, that is, the direction in which the camera is turned over is detected, and the effective area area in the dynamic AF is set in both the detection direction and the opposite direction. Expanding. For example, as shown in FIG. 7, when acceleration in the X-axis direction is detected by the acceleration sensor 45, the area of the effective area in dynamic AF is expanded in both the X-axis direction and the opposite direction, and a total of 15 points of focus The area is set as an effective area in the dynamic AF, and the main subject is continuously focused based on the defocus amounts detected in these 15 focus areas.

  Accordingly, it is possible to continue focusing on the main subject that moves faster than in the case where the nine focus areas around the selected area are effective areas in the dynamic AF mode.

  Further, in the embodiment shown in FIG. 7, since the dynamic AF effective area is expanded both in the direction in which the camera is turned over and in the opposite direction, when the camera is turned over while capturing the moving subject in the selected area. Even if the camera is turned over too quickly or late with respect to the movement of the moving subject, the main subject can be reliably captured within the area expanded in the detection direction and the opposite direction. This focus area can be used as an effective area for dynamic AF and the main subject can be kept in focus.

  In the embodiment shown in FIG. 7, an example in which the effective area of the dynamic AF is enlarged by the same amount both in the direction in which the camera is turned over and in the opposite direction is shown. You may change the amount of enlargement with.

  Here, since the acceleration sensor 45 can distinguish the positive direction and the negative direction of the X-axis and the Y-axis, the effective area area in the dynamic AF can be expanded only in the direction with acceleration. For example, as shown in FIG. 8, when the acceleration sensor 45 detects acceleration in the negative direction of the X axis (here, the left direction of the shooting screen), the dynamic AF area is expanded only in the negative direction of the X axis, A total of 12 focus areas are set as effective areas in dynamic AF, and the main subject is continuously focused based on the defocus amounts detected in these 12 focus areas.

  This makes it possible to shorten the focus detection calculation time and further improve the responsiveness in the focus adjustment control compared to the case where the effective area area in the dynamic AF is expanded to both the plus side and the minus side in the direction in which the acceleration is detected. However, it is possible to continue focusing on the main subject that moves quickly.

  When acceleration is detected in both the X-axis direction and the Y-axis direction by the acceleration sensor 45, for example, as shown in FIG. 9, when the main subject moves in the diagonally downward left direction of the shooting screen, the X-axis direction and the Y-axis The moving direction of the main subject is determined based on the direction sensor output, and the effective area in the dynamic AF is expanded in the moving direction and the opposite direction. Thereby, the effect similar to the Example shown in FIG. 7 can be acquired.

  Also, as shown in FIG. 10, the same effect as in the embodiment shown in FIG. 8 can be obtained by expanding the area of the effective area in the dynamic AF only in the moving direction of the main subject, that is, the lower left direction.

  FIG. 11 is a flowchart illustrating a control program according to an embodiment. When the release button is pressed halfway in step 1 and the switch SW1 is turned on, the microcomputer 1 starts executing this control program. In step 2, it is determined whether or not the dynamic AF mode is selected by the AF mode switch 14a. If the dynamic AF mode is selected, the process proceeds to step 3, and the single AF mode and the auto area AF mode are selected. If so, go to Step 5.

  If the dynamic AF mode is selected, whether or not the acceleration of the acceleration sensor 45 in the X-axis direction (camera left-right direction) and Y-axis direction (camera up-down direction) exceeds a predetermined value in step 3 Is determined. When acceleration greater than or equal to a predetermined value is detected in the X-axis direction, if the sensor output is positive, it is determined that the moving subject is captured and the camera is turned over to the left, and if the sensor output is negative, it moves It is determined that the subject is captured and the camera is turned over to the right.

  On the other hand, if acceleration of a predetermined value or more is detected in the Y-axis direction, if the sensor output is positive, it is determined that the moving subject is captured and the camera is turned over, and the sensor output is minus 1G or more. If so, it is determined that the moving subject is captured and the camera is turned downward. Further, when acceleration of a predetermined value or more is detected in the X-axis direction and the Y-axis direction, the direction in which the camera is turned over is determined based on the detected acceleration value and its polarity as described above.

  If an acceleration greater than or equal to a predetermined value is detected in at least one of the X-axis direction and the Y-axis direction, the process proceeds to step 4, and if both the directions are less than the predetermined value, the process proceeds to step 5. In step 4, dynamic AF is performed from the area of the effective area in the normal dynamic AF mode around the selected area to the direction in which the camera is turned over (and the opposite direction), that is, the moving direction of the moving subject (and the opposite direction). Enlarge the area of the effective area. Note that when the dynamic AF mode is not selected, or when the accelerations in the X-axis direction and the Y-axis direction are both less than a predetermined value, the effective area is not enlarged in the dynamic AF.

  When enlarging the effective area, the enlargement area may be a predetermined range, but the larger the acceleration, the faster the movement of the moving subject. You can keep focusing.

  In step 5, focus detection is performed in the selected area. If the dynamic AF mode is selected at this time, if the current defocus amount detection value in the selection area changes by a predetermined value or more compared to the previous detection value, the main subject that has been captured in the selection area until then is displayed. Judge that it has been removed from the selected area. Then, the defocus amount is detected in the focus area in the effective area area in the dynamic AF described above, and the defocus amount detected in the focus area in the effective area area excluding the selected area is detected in the selected area last time. The defocus amount, that is, the defocus amount close to the defocus amount detected when the main subject is captured in the selected area is extracted, the focusing lens of the interchangeable lens 11 is driven according to the defocus amount, and the focus is Make adjustments.

  In the next step 6, photometry of the object scene is performed by the photometry circuit 2, and exposure calculation is performed based on the subject luminance of the photometry result. In step 7, it is determined whether or not the release button has been fully pressed and the full press switch SW2 is turned on. If not, the process returns to step 1, and if it is turned on, the process proceeds to step 8. In step 8, a well-known image capturing operation is performed. In subsequent step 9, various processes are performed on the captured image, and then the image is recorded.

  Note that the number and arrangement of focus areas in the shooting screen are not limited to this embodiment. In the above-described embodiment, an example in which the area of the effective area in the dynamic AF is determined with the focus area arbitrarily selected by the photographer as the center has been described. However, the camera selects the main subject using, for example, a face recognition algorithm. Then, the effective area area of the dynamic AF may be determined using the focus area corresponding to the main subject as the selection area.

  The dynamic AF control algorithm is not limited to the algorithm of the above-described embodiment, and it is possible to continue focusing on a main subject that is out of the selected area using a known dynamic AF algorithm.

  In the above-described embodiment, the acceleration sensor 45 is used to detect the camera movement, that is, the turnover direction and the speed thereof. However, the motion detection unit detects the camera turnover direction and the speed thereof. Is not limited to an acceleration sensor.

  In the above-described embodiments and their modifications, all combinations of the embodiments or the embodiments and the modifications are possible.

  According to the above-described embodiment and its modifications, the following operational effects can be achieved. First, in a camera having a dynamic AF mode for performing focus adjustment of a photographing lens based on a focus detection result detected in a focus area within a preset area among a plurality of focus areas in a photographing screen, When the movement is detected and the camera movement is detected, the above area is enlarged and the focus of the photographic lens is adjusted based on the focus detection result detected in the focus detection area within the enlarged area. While shortening detection calculation time and improving responsiveness in focus adjustment control, it is possible to reduce the possibility of misidentifying other subjects close to the main subject as the main subject, and to keep focusing on the main subject . That is, the responsiveness of the focus adjustment control and the tracking performance of the main subject can be improved.

  In addition, according to the embodiment and its modification, the camera moving direction is detected, and the area is expanded according to the camera moving direction, so that the focus adjustment control is performed by the minimum necessary area expansion. And the tracking performance of the main subject can be further improved.

The figure which shows the structure of one embodiment Cross-sectional view of camera of one embodiment The figure which shows the acceleration sensor installed in the camera Rear view of camera of one embodiment Figure showing a viewfinder image with the focus area superimposed The figure which shows the normal area | region of the effective area in dynamic AF mode The figure which shows the area | region expansion example of the effective area in dynamic AF mode when a to-be-photographed object moves to the left direction of the camera The figure which shows the area | region expansion example of the effective area in dynamic AF mode when a to-be-photographed object moves to the left direction of the camera The figure which shows the area | region expansion example of the effective area in dynamic AF mode when a to-be-photographed object moves to the lower left direction of a camera The figure which shows the area | region expansion example of the effective area in dynamic AF mode when a to-be-photographed object moves to the lower left direction of a camera The flowchart which shows the control program of the camera of one embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Microcomputer, 9; Focus detection circuit, 10; Focus detection sensor, 11: Interchangeable lens, 12: Lens drive circuit, 45; Acceleration sensor

Claims (5)

Focus detection means for detecting the focus adjustment state of the taking lens in a plurality of focus detection areas in the shooting screen;
Focus adjusting means for adjusting the focus of the photographing lens based on a focus detection result by the focus detecting means;
Control means for adjusting the focus of the photographic lens by the focus adjustment means based on the focus detection result detected in a focus detection area within a preset area of the plurality of focus detection areas. In the camera focus adjustment device,
A motion detection means for detecting the motion of the camera;
The control means enlarges the area when camera motion is detected by the motion detection means, and the imaging by the focus adjustment means based on the focus detection result detected in a focus detection area within the enlarged area. A focus adjustment device for a camera, wherein the focus adjustment of the lens is performed. The camera focus adjustment apparatus according to claim 1.
The movement detecting means detects a moving direction of the camera;
The camera focus adjustment apparatus characterized in that the control means enlarges the area in accordance with the moving direction of the camera detected by the motion detection means. The camera focus adjustment apparatus according to claim 2.
The camera focus adjustment apparatus, wherein the control means enlarges the area only in a moving direction of the camera. The camera focus adjustment apparatus according to claim 2.
The camera focusing apparatus according to claim 1, wherein the control means enlarges the area by the same amount in a direction opposite to the moving direction of the camera. In the focus adjustment apparatus of the camera as described in any one of Claims 1-4,
The motion detection means detects the speed of movement of the camera;
The focus adjustment apparatus for a camera, wherein the control means increases the enlargement amount of the region as the moving speed of the camera increases.

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