JP5098746B2 - Electronic camera - Google Patents

Description

The present invention relates to electronic cameras.

  2. Description of the Related Art Conventionally, an automatic focus control device that keeps focusing while automatically following a moving subject (moving object) is known.

As an example, Patent Document 1 discloses an automatic focus control device that continues to focus on a moving object based on information on a defocus amount of a distance measurement result for the moving object and the speed of the moving object.
JP-A-6-102450

  However, in the prior art, since tracking is performed by focus detection based only on simple information on the defocus amount and the speed of the moving object, for example, for a moving object moving at a high speed in the distance, When the following focusing state cannot be maintained, it is difficult to return to the state again. As a result, a delay occurs in the focus control operation, and the photographer has lost the shutter chance in an electronic camera or the like.

  Further, in the prior art, it has been impossible to reliably follow and focus on various moving objects having different states such as different moving speeds and different distances to moving objects.

The present invention is to solve the above-mentioned problems of the prior art. The present invention aims to provide a can Ru electronic camera that state performs focus surely follow if against a variety of different elements.

In the electronic camera of the present invention, the optical system capable of focus adjustment, the focal length information of the optical system, the information of the distance to the subject, the color of the subject, the brightness of the subject, and the visual field of the subject of the optical system. Used for focus adjustment of the optical system based on a plurality of scene discrimination information including the moving speed and moving direction of the subject and information in the field of view of the optical system that is at least one of these temporal changes. A focus control algorithm is selected from among a plurality of focus control algorithms, and the selected focus control algorithm is executed to adjust the focus of the optical system so as to track the subject, and the focus adjustment is performed by the control means. A photographing unit that obtains a photographed image by photographing an optical image of the subject imaged through a system, and the control unit cannot track the subject. It is obtained to perform the tracking within a certain distance range depending on the selected the focus control algorithm.

If the subject cannot be tracked when it is determined that the subject is a shooting scene where a subject moving fast at a distance is being shot, the control means can track the subject within a certain distance range away from the electronic camera. You may comprise so that the focus control algorithm for the far-distance moving body tracking which controls a focus adjustment may be selected.

In addition, as a control means, when it is determined that the subject is a shooting scene that is about to shoot a subject moving at a low speed, if the subject cannot be tracked, the control means is in a certain range near the far distance. A focus control algorithm for tracking a moving object that controls focus adjustment so as to track the subject may be selected.

Further, as a control means, when it is determined that it is a shooting scene that is shooting a subject moving near at a low speed, it is compared with a case where it is determined that it is a shooting scene that is shooting a subject moving fast at a distance. Thus, the focus adjustment of the optical system in which the focus adjustment is performed may be finely performed.

  In the present invention, a focus control algorithm is selected from a plurality of scene discrimination information based on a plurality of scene discrimination information, and the optical system is continuously focused on the optical image of the subject formed through the optical system according to the focus control algorithm. Adjust the focus.

  Therefore, if the present invention is used, it is possible to reliably follow and focus on various moving objects having different states.

  Embodiments of the present invention will be described below. This embodiment is an embodiment of a single-lens reflex electronic camera.

  FIG. 1 is a configuration diagram of the electronic camera of the present embodiment. The electronic camera has a camera body 1 and a lens unit 2 that houses a photographing optical system.

  The camera body 1 and the lens unit 2 are each provided with a pair of mounts 9 and 10 having a male-female relationship. The lens unit 2 is attached to the camera body 1 in a replaceable manner by coupling the mount 9 on the lens unit 2 side to the mount 10 on the camera body 1 side by a bayonet mechanism or the like. The mounts 9 and 10 are each provided with an electrical contact 11. When the camera body 1 and the lens unit 2 are coupled, the electrical connection between the electrical contacts 11 is established.

  First, the configuration of the lens unit 2 will be described. The lens unit 2 includes a photographic lens 3, a lens driving unit 4, a distance detection unit 5, a diaphragm control unit 6, a diaphragm 7, and a lens side microcomputer 8. The lens driving unit 4, the distance detection unit 5, and the aperture control unit 6 are each connected to the lens side microcomputer 8.

  The photographing lens 3 is composed of a plurality of lens groups including a focus lens and a zoom lens. For simplicity, the photographing lens 3 is illustrated as a single lens in FIG.

  The lens driving unit 4 generates a lens driving signal in accordance with an instruction from the lens-side microcomputer 8, moves the photographing lens 3 in the optical axis direction to perform focus adjustment and zoom adjustment, and moves the position of the moved photographing lens 3. Is output to the lens-side microcomputer 8 and the distance detector 5.

  The distance detection unit 5 detects the distance to the subject based on information on the position of the photographing lens 3 in the optical axis direction, and outputs the detected information to the lens-side microcomputer 8.

  The diaphragm 7 adjusts the amount of light incident on the camera body 1 by opening and closing the diaphragm blades. The aperture controller 6 controls the aperture of the aperture 7 in accordance with an instruction from the lens side microcomputer 8.

  The lens side microcomputer 8 communicates with the camera side microcomputer 21 of the camera body 1 through the electrical contact 11 of the mount 9 and executes various controls in the lens unit 2. The lens-side microcomputer 8 transmits lens information (information such as the focal length and brightness (open F value) of the lens) recorded in the ROM (not shown) of the lens unit 2 to the camera body 1.

  Next, the configuration of the camera body 1 will be described. The camera body 1 includes a quick return mirror 12, a finder optical system (13 to 15), a photometric re-imaging lens 16, an evaluation image acquisition unit 17, an imaging unit 18, a mechanical shutter 19, and a sub mirror 20. And camera circuits (21 to 31).

  The quick return mirror 12, the mechanical shutter 19, and the imaging unit 18 are arranged along the optical axis of the photographing optical system. The sub mirror 20 is disposed behind the quick return mirror 12. Further, the finder optical system (13 to 15), the photometric re-imaging lens 16, and the evaluation image acquisition unit 17 are arranged on the upper part of the camera body 1.

  The quick return mirror 12 is pivotally supported by a rotation shaft (not shown) and can be switched between an observation state and a retracted state. The quick return mirror 12 in the observation state is inclined and disposed in front of the mechanical shutter 19 and the imaging unit 18. The quick return mirror 12 in the observation state reflects the light beam that has passed through the photographing optical system upward and guides it to the finder optical system. The central portion of the quick return mirror 12 is a half mirror.

  A part of the light beam transmitted through the quick return mirror 12 is refracted downward by the sub mirror 20 and guided to the lower part of the camera body 1 for focus detection.

  On the other hand, the retracted quick return mirror 12 is flipped upward together with the sub mirror 20 and is at a position off the photographing optical path. When the quick return mirror 12 is in the retracted state, the light beam that has passed through the photographing optical system is guided to the mechanical shutter 19 and the imaging unit 18.

  The finder optical system (13 to 15) includes a diffusion screen (focus plate) 13, a condenser lens (not shown), a pentaprism 14, and an eyepiece lens 15. Among these, the pentaprism 14 is housed in a protruding portion position on the upper part of the camera body 1.

  The diffusing screen 13 is positioned above the quick return mirror 12, and the light beam reflected by the quick return mirror 12 in the observation state once forms an image. The light beam formed on the diffusing screen 13 passes through a condenser lens (not shown), is reflected inside the pentaprism 14, and is guided to an exit surface having an angle of 90 degrees with respect to the incident surface of the pentaprism 14. . The light flux from the exit surface of the pentaprism 14 reaches the eyes of the photographer through the eyepiece 15.

  The photometric re-imaging lens 16 and the evaluation image acquisition unit 17 are arranged in the vicinity of the pentaprism 14. The photometric re-imaging lens 16 re-images part of the light beam imaged on the diffusing screen 13, and the evaluation image acquisition unit 17 photoelectrically converts the finder image formed on the light receiving surface by the re-imaging. An analog image signal of the evaluation image is generated. The evaluation image acquisition unit 17 includes a color image sensor including a CCD area sensor and a CMOS area sensor.

  The imaging unit 18 is an imaging element such as a CCD area sensor or a CMOS area sensor, and generates a main captured image that is a recording image. The imaging unit 18 photoelectrically converts the subject image formed on the imaging surface when the quick return mirror 12 is in the retracted state, and generates an analog image signal of the actual captured image.

  The mechanical shutter 19 adjusts the exposure time of the imaging unit 18 by controlling the opening and closing thereof.

  The camera circuit (21 to 31) includes a camera-side microcomputer 21, a focus detection unit 22, a shutter control unit 23, a ROM 24, a RAM 25, an external storage device 26, an A / D conversion unit 27, and an image sensor drive. The unit 28, the image processing unit 29, the A / D conversion unit 30, and the image sensor driving unit 31 are connected to each other via a system bus 32. The A / D conversion unit 27 and the image sensor driving unit 28 are connected to the evaluation image acquisition unit 17, and the A / D conversion unit 30 and the image sensor driving unit 31 are connected to the imaging unit 18, respectively.

  The focus detection unit 22 is disposed below the camera body 1, generates two subject images from a light beam guided by the sub mirror 20 by a separator lens (not shown), and measures the image interval with a line sensor (not shown). Then, the amount of focus shift is detected for each AF area (so-called phase difference detection method). Then, the focus detection unit 22 outputs information on the detected focus shift amount (defocus amount) to the camera-side microcomputer 21.

  The shutter control unit 23 performs opening / closing control of the mechanical shutter 19 at the time of shooting in accordance with an instruction from the camera-side microcomputer 21.

  The image sensor drive unit 28 drives the evaluation image acquisition unit 17 based on an instruction from the camera-side microcomputer 21 to generate an analog image signal of the evaluation image.

  The A / D conversion unit 27 performs CDS (correlated double sampling), gain adjustment, A / D on the analog image signal of the evaluation image generated by the evaluation image acquisition unit 17 based on an instruction from the camera-side microcomputer 21. Analog signal processing such as conversion is performed, and data of the evaluation image after the processing is output to the RAM 25.

  The imaging element driving unit 31 drives the imaging unit 18 based on an instruction from the camera-side microcomputer 21 to generate an analog image signal of the actual captured image.

  The A / D conversion unit 30 performs CDS (correlated double sampling), gain adjustment, A / D conversion, and the like on the analog image signal of the actual captured image generated by the imaging unit 18 based on an instruction from the camera-side microcomputer 21. The analog signal processing is performed, and the data of the captured image after the processing is output to the RAM 25. In addition, the A / D conversion unit 30 sets an adjustment amount for gain adjustment based on an instruction from the camera-side microcomputer 21, and thereby adjusts photographing sensitivity corresponding to ISO sensitivity.

  The image processing unit 29 performs image processing such as white balance adjustment, color separation (interpolation), edge enhancement, and gamma correction on the actual captured image in the RAM 25 in accordance with an instruction from the camera-side microcomputer 21. The image processing unit 29 is configured as an ASIC or the like.

  The RAM 25 is used and used by the evaluation image data output from the A / D conversion unit 27, the actual captured image data output from the A / D conversion unit 30, and various processes executed by the camera-side microcomputer 21. Temporarily store generated data and the like.

  The external storage device 26 is a memory card with a built-in semiconductor memory, a small hard disk, or the like, and stores data of the captured image that has been compressed by the camera-side microcomputer 21 or a compression / decoding unit (not shown). The compression process is performed in JPEG (Joint Photographic Experts Group) format or the like.

  The ROM 24 stores various programs executed by the camera-side microcomputer 21 and various data necessary for the execution. The ROM 24 stores a plurality of types of algorithms used for automatic focus adjustment (AF) of the photographing lens 3. This algorithm will be described later.

  The camera-side microcomputer 21 performs overall control of each part of the electronic camera in accordance with the content of the photographer operating an operation member (not shown). For example, when the photographer presses the release button halfway, the camera-side microcomputer 21 communicates with the lens-side microcomputer 8 so as to drive the lens drive unit 4, the distance detection unit 5, and the aperture control unit 6 of the lens unit 2. At the same time, the focus detection unit 22, the image sensor drive unit 28, and the A / D conversion unit 27 are driven via the system bus 32 to start focus detection and photometry.

  At this time, the light beam from the object field that has passed through the lens unit 2 is reflected upward by the quick return mirror 12 and is passed through the diffusion screen 13, the pentaprism 14, and the photometric re-imaging lens 16 to obtain an evaluation image acquisition unit. Then, a finder image that is an image of the subject is formed on the light receiving surface. Further, when a part of the light beam from the object field that has passed through the lens unit 2 is transmitted through the central portion of the quick return mirror 12 that is a half mirror, it is refracted downward by the sub mirror 20 and is focused on the lower part of the camera body 1. Guided to the detector 22.

  The focus detection unit 22 detects the defocus amount for each AF area based on the light flux from the object field guided by the sub mirror, and outputs the detected information to the camera side microcomputer 21 via the system bus 32. To do. The camera-side microcomputer 21 performs automatic focus adjustment (AF) of the photographing lens 3 in cooperation with the lens driving unit 4 until it is determined that the AF area is in focus based on the information on the defocus amount.

  The evaluation image acquisition unit 17 driven via the image sensor driving unit 28 photoelectrically converts the finder image formed on the light receiving surface to generate an analog image signal of the evaluation image. Then, the A / D converter 27 performs analog signal processing on the image signal, and outputs the processed evaluation image data to the RAM 25. The camera-side microcomputer 21 determines shooting conditions (whether or not strobe light is emitted, aperture value, shutter speed, etc.) based on the evaluation value calculated based on the evaluation image data in the RAM 25. The evaluation value is a value indicating the brightness of the subject or the entire shooting scene and the brightness distribution of the shooting scene. The evaluation value is calculated by a known photometry method such as multi-division photometry (multi-pattern photometry), center-weighted photometry, spot photometry.

  When the photographer fully presses the release button, the camera-side microcomputer 21 performs the actual shooting under the previously determined shooting conditions. The camera-side microcomputer 21 drives the aperture control unit 6 through the lens-side microcomputer 8 and also flips up the quick return mirror 12 in the observation state. Then, the shutter control unit 23, the image sensor driving unit 31, the image capturing unit 18, and the A / D The converter 30 is driven to capture the actual captured image. The captured actual image is output to the RAM 25 by the A / D converter 30. Next, the camera-side microcomputer 21 drives the image processing unit 29 to perform image processing on the actual captured image in the RAM 25. Then, the camera-side microcomputer 21 compresses the actual captured image after the image processing and records the compressed image in the external storage device 26.

  Hereinafter, the operation of automatic focus adjustment (autofocus: AF) of the electronic camera of this embodiment will be described with reference to the flowchart of FIG. The flow of FIG. 2 is executed when the photographer presses the release button halfway when the autofocus operation mode is set to continuous AF. Note that continuous AF is an autofocus function that keeps the subject in focus (moving object) in focus continuously.

  Step 101: When the release button is half-pressed by the photographer, the camera-side microcomputer 21 that has detected this operation communicates with the lens-side microcomputer 8 of the lens unit 2 to acquire information on the focal length of the lens.

  Step 102: The camera side microcomputer 21 communicates with the lens side microcomputer 8, and acquires information on the distance to the moving body (moving subject) detected by the distance detection unit 5 of the lens unit 2.

  Step 103: The camera-side microcomputer 21 starts continuous driving of the evaluation image acquisition unit 17 via the image sensor driving unit 28. Thereby, an analog signal of the evaluation image starts to be output from the evaluation image acquisition unit 17, and data of the evaluation image after analog signal processing by the A / D conversion unit 27 is sequentially output to the RAM 25.

  The camera-side microcomputer 21 acquires information in the field of view (field of view) of the lens based on the evaluation image stored in the RAM 25. Here, the information in the field of view of the lens includes, for example, (1) the color of the moving object, (2) the luminance of the moving object, (3) the ratio of the moving object in the field of view, (4) the moving speed and moving direction of the moving object, (5) Information on changes in time of each of (1) to (4).

  Step 104: The camera-side microcomputer 21 selects an algorithm (focus control algorithm) to be used for automatic focus adjustment from a plurality of information based on various information acquired at steps 101 to 103, that is, a plurality of scene discrimination information.

Specifically, the camera-side microcomputer 21 selects a focus control algorithm by the following method.
(1) A method for selecting a focus control algorithm based on information on the focal length of a lens and information on a distance to a moving object.

  The camera-side microcomputer 21 selects one of the focus control algorithms for the far-distance moving object tracking or the close-distance moving object tracking based on the information on the focal length of the lens and the information on the distance to the moving object.

  For example, when the information on the focal length of the lens indicates “200 mm” and the information on the distance to the moving object indicates “10 m or more”, the camera-side microcomputer 21 uses the telephoto lens. Then, it is determined that a distant moving object is to be photographed (scene determination), and a focus control algorithm for tracking a distant moving object corresponding to the scene (distance: distant) is selected.

  For example, when the information on the focal length of the lens indicates “50 mm” and the information on the distance to the moving object indicates “3 m or less”, the camera-side microcomputer 21 uses the standard lens. Then, it is determined that a nearby moving object is to be photographed (scene determination), and a focus control algorithm for tracking a moving object corresponding to the scene (distance: proximity) is selected.

  It should be noted that the focus control algorithm for tracking the moving object is far away from the electronic camera, for example, from the electronic camera to the moving object when a situation in which the moving object cannot be tracked occurs, such as when the brightness of the object field changes suddenly. The auto focus adjustment operation is performed so that tracking of the moving object is restarted within the range of 10 m to infinity.

On the other hand, the focus control algorithm for tracking a moving object is similar to the conventional general AF operation, and when a situation in which the moving object cannot be tracked occurs, the moving object is detected from a position close to the electronic camera. The auto focus adjustment operation is performed so as to start tracking again.
(2) A method for selecting a focus control algorithm in consideration of information in the field of view of the lens.

  The camera-side microcomputer 21 selects a focus control algorithm based on at least one piece of information in the field of view of the lens, in addition to the information on the focal length of the lens and the information on the distance to the moving object.

  For example, the information on the focal length of the lens is “200 mm: telephoto lens”, the information on the distance to the moving object is “10 m or more: far away”, and the information on the color and brightness of the moving object among the information in the field of view of the lens. Is “artificial and bright red” and the moving speed information of the moving object indicates “high speed”, the camera-side microcomputer 21 estimates that the moving object is a “red car”. Then, the camera-side microcomputer 21 determines that the photographer is shooting a red car that moves at a high speed in the distance using a telephoto lens (scene discrimination), and the scene (distance: far, movement speed: Select a focus control algorithm that supports (fast).

  Here, the selection may be performed using a table or the like in which the correspondence between the scene and the focus control algorithm is predetermined as shown in FIG. 3, for example.

  In this scene (distance: far, movement speed: high), the camera-side microcomputer 21 selects, for example, the focus control algorithm F1 in the table of FIG. The focus control algorithm F1 is a process applied to a scene that tracks a moving object that moves at a high speed in the distance, such as a race car or an airplane. The processing content of the focus control algorithm F1 is the same as that of the focus control algorithm for tracking the far-distance moving object described above.

  Also, in the case of a scene (distance: proximity, movement speed: low speed) that tracks a moving object that moves near the electronic camera at a low speed, such as a pedestrian (distance: proximity, movement speed: low speed), the camera-side microcomputer 21 performs focus control of the table in FIG. Select algorithm L2. As the moving object is closer to the camera, the photographing lens 3 needs to be moved back and forth more finely for focusing the AF area in the focus detection unit 22 as compared with the case where the moving object is farther away. The tracking sensitivity is improved.

  Furthermore, in the case of a scene that tracks a moving object with an irregular moving speed, if the distance from the electronic camera is long (distance: far, moving speed: irregular), the camera-side microcomputer 21 may, for example, use the table in FIG. Focus control algorithm R1 is selected. On the other hand, if the distance from the electronic camera is short (distance: proximity, moving speed: irregular), the camera-side microcomputer 21 selects, for example, the focus control algorithm R2 in the table of FIG.

  The camera-side microcomputer 21 discriminates a scene based on a plurality of acquired scene discrimination information by the method as described above, and selects one corresponding to each scene from a plurality of focus control algorithms.

  Step 105: The camera-side microcomputer 21 performs an automatic focus adjustment operation so as to keep the optical image of the moving object in the focus detection unit 22 in focus according to the selected focus control algorithm.

  Specifically, the camera-side microcomputer 21 acquires information on the defocus amount detected by the focus detection unit 22, and determines the defocus amount of the AF area (selected AF area) selected by the photographer from the acquired information. Extract information. Next, the camera-side microcomputer 21 determines the focus of the selected AF area based on the extracted defocus amount. If the in-focus state is not determined, the camera-side microcomputer 21 transmits the extracted defocus amount information to the lens-side microcomputer 8. Here, the lens-side microcomputer 8 that has received this information drives the lens driving unit 4 to move the photographing lens 3 in accordance with the defocus amount. When the photographing lens 3 moves, the camera-side microcomputer 21 acquires information on the defocus amount detected by the focus detection unit 22 again. Then, the camera-side microcomputer 21 repeats the above automatic focus adjustment operation until it is determined that the selected AF area is in focus from the defocus amount information.

  Step 106: The camera-side microcomputer 21 determines shooting conditions (whether or not strobe light is emitted, aperture value, shutter speed, etc.) based on the evaluation image data stored in the RAM 25.

  Step 107: The camera side microcomputer 21 determines whether or not the release button is fully pressed by the photographer. If it is fully pressed (Yes side), the camera-side microcomputer 21 proceeds to Step 109 to perform the main photographing. On the other hand, if it is not fully pressed (No side), the camera side microcomputer 21 proceeds to Step 108.

  Step 108: The camera side microcomputer 21 determines whether or not the half-press of the release button has been released. When the half-press is released (Yes side), the camera-side microcomputer 21 stops the operation of the evaluation image acquisition unit 17 via the image sensor driving unit 28 and then ends the processing of this flow. On the other hand, if the release button is pressed halfway (No side), the camera side microcomputer 21 proceeds to Step 102 and repeats the above processing.

  Step 109: The camera-side microcomputer 21 performs the main photographing under the photographing condition determined in Step 106. Note that the actual captured image is output to the RAM 25.

  Step 110: The camera-side microcomputer 21 drives the image processing unit 29 to perform image processing such as white balance adjustment and gamma correction on the actual captured image in the RAM 25.

  Step 111: The camera-side microcomputer 21 performs compression processing on the actual captured image in the RAM 25 after image processing, and records the compressed image in the external storage device 26.

(Supplementary items of this embodiment)
It should be noted that the scene discrimination and the estimation of moving objects (moving subjects) performed by the camera-side microcomputer 21 in step 104 are performed using a database in which information on feature quantities used for scene discrimination and motion estimation is stored in advance. You may do it.

  Further, after the image processing in step 110, the actual captured image after the image processing may be displayed on an LCD monitor (not shown) provided in the electronic camera housing. Then, the photographer can confirm the performance of the actual captured image.

  In addition, when the actual captured image is recorded in the external storage device 26 in step 111, the photographer may be instructed whether to record the actual captured image. The instruction may be given to the photographer through a GUI screen displayed on an LCD monitor (not shown) or the like.

  In addition, after the actual captured image is recorded in the external storage device 26 in step 111, the actual captured image is transferred to an image server or the like outside the electronic camera via an interface (not shown) for a wireless communication line such as a wireless LAN. You may do it. In this case, the photographer may be instructed whether to transfer the actual captured image. The instruction may be given to the photographer through a GUI screen displayed on an LCD monitor (not shown) or the like.

(Operational effect of this embodiment)
As described above, in the electronic camera according to the present embodiment, the scene that the photographer intends to shoot is determined based on the information on the focal length of the lens and the information on the distance to the moving object included in the acquired plurality of scene determination information. Is selected from a plurality of focus control algorithms.

  For example, when it is determined that the scene is about to photograph a distant moving object using a telephoto lens, a focus control algorithm for tracking a distant moving object is selected. When it is determined that the scene is about to capture a nearby moving object using a standard lens, a focus control algorithm for tracking a moving object is selected.

  Then, in accordance with the selected focus control algorithm, automatic focus adjustment (AF) of the photographing lens 3 is performed so as to keep the optical image of the moving body in the focus detection unit 22 in focus.

  In a conventional general continuous AF, when a situation in which a moving object cannot be tracked occurs, an automatic focus adjustment operation is performed so that tracking of the moving object starts again from a position close to the electronic camera. For this reason, in the case of a scene in which the photographer is going to photograph a moving object that is far away, it takes a very long time to return to the follow-up focus state again, and the focus control operation is delayed.

  However, in the electronic camera of the present embodiment, as described above, an appropriate focus control algorithm is selected for the scene that the photographer intends to photograph.

  For example, in the case of a scene where the photographer is going to photograph a moving object far away, a focus control algorithm for tracking a distant moving object is selected. As described above, the focus control algorithm for tracking a moving object automatically detects that the moving object cannot be tracked automatically so that tracking of the moving object is started again within a certain distance range far from the electronic camera. A focus adjustment operation is performed.

  Therefore, even if a situation in which the moving object cannot be tracked occurs, the tracking operation is quickly restarted regardless of the state of the moving object such as far away or close, so that the photographer does not lose the shutter chance in shooting the moving object.

  In the electronic camera of this embodiment, in addition to the information on the focal length of the lens and the information on the distance to the moving object included in the acquired plurality of scene determination information, at least one of the information in the field of view of the lens Based on the information, the scene that the photographer intends to photograph is determined. Then, a focus control algorithm corresponding to the scene is selected from a plurality.

  For example, the scene is based on information on the focal length of the lens, information on the distance to the moving object, and information on the color of the moving object, information on the luminance, information on the moving speed of the moving object, etc. Shall be determined. Then, based on the information, when it is determined that the scene is about to shoot a distant, fast moving race car using a telephoto lens, the focus control algorithm F1 is selected. Also, when it is determined that the scene is about to capture a pedestrian moving at a low speed nearby using a standard lens, the focus control algorithm L2 is selected. Also, when it is determined that the scene is about to photograph a nearby white-tailed butterfly using a standard lens, the focus control algorithm R2 is selected.

  Thereafter, in accordance with the selected focus control algorithm, automatic focus adjustment of the taking lens 3 is performed so as to keep the optical image of the moving object in the focus detection unit 22 in focus.

  As described above, in the electronic camera according to the present embodiment, tracking of a moving object is performed by an automatic focus adjustment operation using a focus control algorithm that is appropriately selected for a scene that the photographer intends to capture.

  Therefore, in the electronic camera according to the present embodiment, it is possible to reliably follow and focus on various moving objects having different states.

(Other)
In the above-described scene determination, the distance has been described as two types, that is, far and close. However, the present invention is not limited to these two types, and any number of types may be determined. In addition, the moving speed has been described as being discriminated into three types of high speed, low speed, and irregularity, but the present invention is not limited to this, and any number of types may be discriminated.

  Further, the present invention can be applied not only to the single-lens reflex type electronic camera described above but also to a single-lens reflex type silver salt camera and a compact type electronic camera. When the present invention is applied to a compact electronic camera, a through image (decimated readout image) output from an imaging device (corresponding to the imaging unit 18 of the electronic camera of the present embodiment) for capturing the actual captured image is used. It is good to use for the image for evaluation.

  The present invention can also be applied to optical devices other than cameras, such as binoculars.

It is a block diagram of a single-lens reflex type electronic camera to which the present invention is applied. It is a flowchart which shows the operation | movement of the automatic focus adjustment of the electronic camera to which this invention is applied. It is a figure of the table which shows a response | compatibility with a scene and a focus control algorithm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Camera body, 2 ... Lens unit, 3 ... Shooting lens, 4 ... Lens drive part, 5 ... Distance detection part, 6 ... Aperture control part, 7 ... Aperture, 8 ... Lens side microcomputer, 9 ... Mount, 10 ... Mount 11 ... Electric contact, 12 ... Quick return mirror, 13 ... Diffusion screen (focal plate), 14 ... Pental prism, 15 ... Eyepiece lens, 16 ... Photometric re-imaging lens, 17 ... Evaluation image acquisition unit, 18 ... Imaging unit, 19 ... mechanical shutter, 20 ... sub-mirror, 21 ... camera side microcomputer, 22 ... focus detection unit, 23 ... shutter control unit, 24 ... ROM, 25 ... RAM, 26 ... external storage device, 27 ... A / D conversion , 28... Image sensor drive unit, 29... Image processing unit, 30... A / D conversion unit, 31.

Claims (4)

An optical system with adjustable focus,
Information on the focal length of the optical system, information on the distance to the subject, color of the subject, luminance of the subject, ratio of the subject in the field of view of the optical system, movement speed and direction of the subject, And a plurality of scene discriminating information including information in the field of view of the optical system that is at least one of these time changes, and a plurality of focus control algorithms used for focus adjustment of the optical system Control means for performing focus adjustment of the optical system to select and execute the selected focus control algorithm to track the subject ;
Photographing means for photographing an optical image of the subject imaged through the optical system in which focus adjustment is performed by the control means, and obtaining a photographed image;
The control means performs tracking within a certain distance range according to the selected focus control algorithm when the subject cannot be tracked;
An electronic camera characterized by that. In the electronic camera according to claim 1,
When the control means determines that the subject is a shooting scene that is about to shoot a subject moving at a high speed in the distance, and if the subject cannot be tracked, the control means tracks the subject within a certain distance range from the electronic camera. Select a focus control algorithm for far-field tracking that controls the focus adjustment to do
An electronic camera characterized by that. The electronic camera according to claim 2 ,
When it is determined that the control unit cannot track the subject when it is determined that it is a shooting scene that is about to shoot a subject moving at a low speed in the vicinity, the control unit is within a certain range near the far distance range. Select a focus control algorithm for tracking a moving object that controls focus adjustment to track the subject.
An electronic camera characterized by that. The electronic camera according to claim 3.
The control means, when it is determined that it is a shooting scene that is shooting a subject moving at a low speed in the vicinity, compared to when it is determined that it is a shooting scene that is shooting a subject moving at a high speed in the distance, Finely adjust the focus of the optical system to be focused,
An electronic camera characterized by that.

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