JP4591120B2 - Imaging apparatus, autofocus control method, and autofocus control program - Google Patents

Description

  The present invention relates to an imaging apparatus provided with an autofocus function, an autofocus control method for the same, and an autofocus control program.

  Conventionally, in an imaging apparatus such as an electronic camera provided with an autofocus function, a method of adjusting a focus area to a subject position desired by a user can be achieved by pinpoint AF for narrowing the focus area or a plurality of focus areas, not only in the center. A multi-point AF or the like that is set at a suitable position in the focus area is used.

For example, Patent Document 1 describes a lateral distance device that can prevent a void from being caused by a spot light deviation and prevent a void from being detected even with respect to a subject that is not located at the center of a shooting screen.
JP 2002-48970 A

  By adjusting the focus area to the subject position desired by the user, it is possible to prevent a so-called hollow image that focuses on a specific part of the subject or focuses on the inner center of the subject. .

  However, for example, when taking an image of an animal in a cage at a zoo or taking an image of a subject (player) over the net at a baseball stadium or the like, the bag or the net will be in focus and the subject An image could not be taken.

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus and an autofocus capable of capturing an image with a good focus on the subject even if there is an object that is not an imaging target, such as a bag or a net, between the subject and the subject. A control method and an autofocus control program are provided.

According to the first aspect of the present invention, an imaging unit that captures an image of a subject incident through the focus lens, and the focus lens is scanned from the closest side to the infinity side to focus on the first subject. A contrast-type first auto-focusing means for moving to a position, and an edge is detected from the image when the focus lens is focused on the first object by the first auto-focusing means, and this edge Mask means for masking the detected image portion, and a second autofocus of a contrast method for moving the focus lens to a position for focusing the second object on the image masked by the mask means. Means.

According to a second aspect of the present invention, an imaging step for capturing an image of a subject incident through a focus lens, and the focus lens is scanned from the closest side to the infinity side to focus on the first subject. A contrast-type first autofocus step for moving to a position, and an edge is detected from the image when the focus lens is focused on the first subject by the first autofocus step, and as the edge A mask step for masking the detected image portion, and a second autofocus of a contrast method for moving the focus lens to a position for focusing the second object on the image masked by the mask step And a step.

According to a third aspect of the present invention, a computer mounted on an imaging apparatus scans an imaging unit that captures an image of a subject incident through a focus lens and the focus lens from the closest side to the infinity side. a first auto focusing means of the contrast method of moving to a position where focusing to a first object Te, images in when the focus lens by said first auto focusing means was focused on the first object A mask means for detecting an edge from the mask and masking an image portion detected as the edge, and moving the focus lens to a position for focusing the second object on the image masked by the mask means. It is made to function as a contrast type second autofocus means.

According to the first, second, and third aspects of the invention, for example, when taking an image of an animal in a cage at a zoo or taking a subject (player) over the internet at a baseball field or the like, After focusing as a first subject, mask this first subject part and focus on the subject again, so that the animals in the cage and players over the net can focus well. You can also take images.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a detailed configuration of a camera device 1 (imaging device) according to an embodiment of the present invention.

  In the camera apparatus 1 shown in FIG. 1, in the photographing mode that is the basic mode, the focus lens 8, the zoom lens 9, and the diaphragm 10 included in the lens optical system are controlled by the control unit 25. Is moved to the lens position corresponding to the aperture position and photographing.

  A CCD (Charge Coupled Device) 12, which is an image sensor disposed behind the photographing optical axis of the lens optical system, is scanned and driven by a timing generator (TG) 13 and a vertical driver 14, and is imaged at regular intervals. The photoelectric conversion output corresponding to is output for one screen.

  The photoelectric conversion output is appropriately gain-adjusted for each primary color component of RGB in the state of an analog value signal, sampled and held by a sample hold (S / H) circuit 15, and digital data by an A / D converter 16. The color process circuit 17 further performs color process processing including pixel interpolation processing and gamma correction processing to generate a digital luminance signal Y and color difference signals Cb, Cr, and a DMA (Direct Memory Access) controller. 18 is output.

  The DMA controller 18 once uses the luminance signal Y and the color difference signals Cb and Cr output from the color process circuit 17 by using the composite synchronization signal, the memory write enable signal, and the clock signal from the color process circuit 17 once. And the DMA transfer to the DRAM 21 used as a buffer memory through the DRAM interface (I / F) 20.

  The control unit 25 includes a CPU, a ROM in which various operation programs and data executed by the CPU are fixedly recorded, a RAM used as a work memory, and the like. Control. The operation program includes an autofocus control program for controlling autofocus (AF), an automatic exposure control program for controlling automatic exposure control (AE), and the like.

  After completing the DMA transfer of the luminance and color difference signals to the DRAM 21, the control unit 25 reads the luminance and color difference signals from the DRAM 21 via the DRAM interface 20 and writes them to the VRAM 27 via the VRAM controller 26.

  The digital video encoder 28 periodically reads luminance and color difference signals from the VRAM 27 via the VRAM controller 26, generates a video signal based on these data, and outputs the video signal to the display unit 29.

  The display unit 29 functions as a monitor display unit (electronic finder) in the shooting mode, and performs display based on the video signal from the digital video encoder 28 to display image information captured from the VRAM controller 26 at that time. The base image (through image) is displayed in real time.

  When a through image is displayed in real time on the display unit 29, a trigger signal is generated when the shutter key of the key input unit 37 is operated at the timing of capturing a still image.

  In response to this trigger signal, the control unit 25 stops driving the CCD 12 at that time, and then performs an automatic exposure process to obtain an appropriate exposure value, and controls the aperture of the lens optical system and the exposure time of the CCD 12. Re-capture the image.

  After the newly obtained image data for one frame is DMA-transferred and written in the DRAM 21 in this way, the control unit 25 reads out the image data for one frame written in the DRAM 21 to the image processing unit 30. Write. The image processing unit 30 encodes image data by JPEG (Joint Photographic Experts Group) with respect to the image data.

  The encoded image data is a non-volatile memory card 32 that is detachably mounted as a recording medium of the camera device 1, or a non-volatile memory that is fixedly built in the case where the memory card 32 is not mounted. It is written in the built-in memory 33.

  Then, with the completion of the writing of the image data to the memory card 32 or the built-in memory 33 for one frame, the control unit 25 resumes the drive for displaying the through image from the CCD 12 via the DRAM 21 on the display unit 29. .

  In addition, a key input unit 37, an audio processing unit 40, and a strobe driving unit 41 are connected to the control unit 25.

  The key input unit 37 includes a power key, a shutter key, a mode switching key, a menu key, a selection key, a cross key (cursor key), and the like, and signals associated with these key operations are directly sent to the control unit 25. Is done.

  The audio processing unit 40 includes a sound source circuit such as a PCM sound source, digitizes the audio signal input from the microphone unit (MIC) 42 when recording audio, and performs a predetermined data file format such as MP3 (MPEG-1 Audio Layer-). 3) According to the standard, the data is compressed and an audio data file is created and sent to the memory card 32 or the built-in memory 33, while the audio data file sent from the memory card 32 or the built-in memory 33 is uncompressed at the time of playing the sound. Then, it is converted into an analog signal and the speaker unit (SP) 43 is driven to emit loud sounds.

  Furthermore, the sound processing unit 40 generates various operation sounds, for example, a pseudo shutter sound associated with the operation of the shutter key, a beep sound associated with the operation of other keys, and the like based on the control from the control unit 25. The sound is emitted from 43.

  The strobe drive unit 41 charges a large-capacitance capacitor for strobe (not shown) at the time of still image shooting, and then drives the strobe light emitting unit 45 to flash based on the control from the control unit 25.

(First embodiment)
Next, the operation in the first embodiment will be described.
FIG. 2 is a flowchart showing an image shooting processing procedure by the control unit 25 when the user sets the cage shooting mode by operating the shooting mode switching key in the first embodiment. The cage shooting mode is designed to prevent the focus on the kite or the net when taking an image of an animal in the cage at a zoo or shooting a subject (player) over the net at a baseball stadium, for example. It is a shooting mode that can focus on animals and players located farther away than the net.

  In the first embodiment, it is assumed that the AF operation is executed by, for example, contrast autofocus (AF).

  First, when the user operates the shooting mode switching key of the key input unit 37 to set the cage shooting mode, periodic shooting by the CCD 12 is started and a through image of the subject is displayed on the display unit 29 ( Step A1). Thereby, the user can identify the subject to be photographed by visually recognizing the through image.

  The control unit 25 determines whether or not the shutter button is half-pressed, and when the shutter button is half-pressed (Step A2, Yes), starts the first contrast AF process according to the AF sequence (Step A3). The first contrast AF process is a process for focusing on a subject located near the camera device 1, that is, a bag or a net (first subject).

  First, the control unit 25 acquires the current position of the focus lens 8 (step A4), and starts moving in a predetermined direction from the current position (step A5). In the contrast AF process, the contrast value (AF evaluation value) of a predetermined focus area provided in a part of the subject image is calculated while moving the focus lens 8 (step A6). For example, the focus lens 8 is moved by moving the focus lens 8 to the lens end closer to the lens position from the current lens position, and then moving the focus lens 8 one by one toward the opposite lens end. The contrast value for each is calculated.

  As the predetermined focus area, for example, an area provided at the center of the screen, a part of the screen selected by the user, or a part of the area automatically selected on the screen is set as the focus area. Shall. The contrast value may be calculated using the entire screen output from the CCD 12.

  The control unit 25 determines whether the contrast value calculated while moving the focus lens 8 is a peak until the position of the focus lens 8 reaches the lens end (step A8) (step A7). . For example, the control unit 25 represents a change in which the contrast value sequentially calculated with the movement of the focus lens 8 is detected, and after detecting a contrast value that is equal to or higher than a predetermined value, it is detected that the contrast value continuously decreases. It is determined that the peak position has been detected.

  Thus, when the peak of the contrast value in the focus area is detected (step A7, Yes), the control unit 25 moves the focus lens 8 to the lens position at the peak and stores the lens position (step S7). A9).

  Here, the control unit 25 detects the edge of the image in the focus area where the contrast value is picked (step A10), and masks the image portion in the focus area detected as the edge (step A10). A11).

  FIG. 3A shows an example of a state in which a mask is applied to the focused image in the first contrast AF process. FIG. 3A shows an example in which a landscape with a “tiger” in a cage is photographed. In this case, the focus is on the eyelid (first subject) positioned closer to the camera device 1 than the “tiger” of the subject to be photographed. Here, by detecting the edge portion in the image, the image portion corresponding to the eyelid is masked.

  Next, the control unit 25 excludes the masked image portion and starts the second contrast AF process similar to the first contrast AF process described above (step A12).

  That is, the control unit 25 acquires the current position of the focus lens 8 (step A13), and starts moving in a predetermined direction from the current position (step A14). In the contrast AF process, as in the first contrast AF process, the contrast value (AF evaluation value) of a predetermined focus area provided in a part of the subject image is calculated while moving the focus lens 8 (step A15). ). For example, the focus lens 8 is moved by moving the focus lens 8 to the lens end closer to the lens position from the current lens position, and then moving the focus lens 8 one by one toward the opposite lens end. The contrast value for each is calculated.

  FIG. 3B shows an example of an image during the second contrast AF process. As shown in FIG. 3B, since the heel portion is masked by the first contrast AF process, the focus lens 8 is moved to a position where the “tiger” existing at a position far from the heel is in focus. The contrast value reaches a peak.

  The control unit 25 determines whether the contrast value calculated while moving the focus lens 8 is a peak until the position of the focus lens 8 reaches the lens end (step A17) (step A16). .

  When the peak of the contrast value in the focus area is detected (step A16, Yes), the control unit 25 compares the lens position at the peak with the lens position detected by the first contrast AF process, and the second It is determined whether the distance to the subject corresponding to the lens position detected by the contrast AF processing is farther than the subject corresponding to the lens position detected by the first contrast AF processing (step A18).

  Here, the position of the subject corresponding to the lens position detected by the second contrast AF process is substantially the same as or closer to the position of the subject corresponding to the lens position detected by the first contrast AF process. Is determined, for example, the focus lens 8 is moved to the lens position detected by the first contrast AF process to complete the autofocus process (steps A19 and A20).

  On the other hand, when the position of the subject corresponding to the lens position detected by the second contrast AF process is farther than the position of the subject corresponding to the lens position detected by the first contrast AF process, the second The focus lens 8 is moved to the lens position detected by the contrast AF process to complete the autofocus process (steps A19 and A20). That is, it is possible to focus on a “tiger” (second subject) located farther than the heel.

  Here, the control unit 25 determines whether or not the half-press of the shutter button is continued. If the half-press is continued, the control unit 25 waits until the shutter button is fully pressed (step A22, Yes). ).

  When the shutter button is fully pressed (step A21, Yes), the control unit 25 executes the image capturing process (step A23). That is, the pixel signal for one screen output from the CCD 12 is converted into digital data by the A / D converter 16, further subjected to each image processing by the color process circuit 17 and taken into the DRAM 21, and the captured image data is subjected to image processing. The process of compressing in the unit 30 is started. When the compression process is completed, the control unit 25 generates a still image file (file in JPEG format or the like) based on the compressed image data, and records it in the memory card 32, for example.

  As described above, the camera device 1 according to the first embodiment uses the first method when, for example, an animal in a cage is imaged at a zoo or a subject (player) is imaged over the net at a baseball field or the like. After focusing the eyelids and net as the first subject by the contrast AF process, the first subject portion is masked, and the subject is again focused by the second contrast Af process. You can take images with good focus on animals in the cage or players over the net.

(Second Embodiment)
Next, a second embodiment will be described. In the second embodiment, after focusing on the subject by the initial autofocus process, the focus lens is moved by a predetermined amount so that the focus is on a position farther than the subject, for example, in a cage Focus on animals and players over the net so that they can take images.

  FIG. 4 is a flowchart showing an image shooting processing procedure by the control unit 25 when the user sets the cage shooting mode by operating the shooting mode switching key in the second embodiment.

  Also in the second embodiment, it is assumed that the AF operation is executed by, for example, contrast autofocus (AF).

  First, when the user operates the shooting mode switching key of the key input unit 37 to set the cage shooting mode, periodic shooting by the CCD 12 is started and a through image of the subject is displayed on the display unit 29 ( Step B1). Thereby, the user can identify the subject to be photographed by visually recognizing the through image.

  The control unit 25 determines whether or not the shutter button has been half-pressed. If the shutter button has been half-pressed (step B2, Yes), the contrast AF process according to the AF sequence is started (step B3). The contrast AF process is a process for focusing on a subject located near the camera device 1, that is, a eyelid or a net.

  First, similarly to the first embodiment, the control unit 25 acquires the current position of the focus lens 8 (step B4), and starts moving in a predetermined direction from the current position (step B5). In the contrast AF process, the contrast value (AF evaluation value) of a predetermined focus area provided in a part of the subject image is calculated while moving the focus lens 8 (step B6).

  In the same manner as in the first embodiment, the control unit 25 peaks the contrast value calculated while moving the focus lens 8 until the position of the focus lens 8 reaches the lens end (step B8). (Step B7).

  Thus, when the peak of the contrast value in the focus area is detected (step B7, Yes), the control unit 25 moves the focus lens 8 so that the focus is on the far side from the lens position where the contrast value is the peak. A lens position moving process for moving a predetermined amount is executed (step B9).

  In other words, by performing contrast AF processing, it is possible to focus on the eyelids and the net, and focus on a subject located farther than the focused lens position, that is, farther than eyelids. Thus, the focus lens 8 is moved. Details of the lens position movement process will be described later.

  In this way, the autofocus process is completed by moving the focus lens 8 by a predetermined amount so that the focus is farther than the lens position detected by the contrast AF process (step B10).

  Here, the control unit 25 determines whether or not the half-press of the shutter button is continued. If the half-press is continued, the control unit 25 waits until the shutter button is fully pressed (step B12, Yes). ).

  If the shutter button is fully pressed (step B11, Yes), the control unit 25 executes image shooting processing (step B13), generates a still image file of the shot image, and stores it in the memory card 32, for example. Record.

  Next, the lens position movement process in step B9 will be described. In the second embodiment, the first or second lens position movement process shown in the flowcharts of FIGS. 5A and 5B can be used.

  First, the first lens position movement process shown in the flowchart of FIG. In this case, when the position of the focus lens 8 is obtained so that the subject (the eyelid or the net) is focused by the contrast AF process, the distance to the subject at this time is calculated based on the lens position (step C1).

  Then, a lens movement amount at which the position of the subject is outside the depth of field is calculated (step C2), and the focus lens 8 is moved in accordance with the calculated lens movement amount (step C3).

  FIGS. 6A and 6B show how the lens position is moved so that the position of the subject is outside the depth of field. FIG. 6A shows a state in which the eyelid is focused as a subject by contrast AF processing. Here, the lens position of the focus lens 8 is moved so that the in-focus position is out of the depth of field so that the in-focus position is outside the depth of field. As a result, as shown in FIG. 6B, it is possible to focus on a subject (“tiger”) located farther than the heel.

  In the above description, the position of the focus lens 8 is moved so that the position of the subject focused by the initial autofocus processing is outside the depth of field. It can also be controlled to be outside the depth of field in combination with the control for.

  Next, the second lens position movement process shown in the flowchart of FIG. In this case, when the position of the focus lens 8 is obtained so that the subject (the eyelid or the net) is focused by the contrast AF process, the distance to the subject at this time is calculated based on the lens position (step D1).

  Then, a lens movement amount for focusing on a subject located at a predetermined multiple of the distance to the subject, for example, 1.5 times the distance is calculated (step D2), and the focus lens 8 is calculated according to the calculated lens movement amount. Is moved (step D3).

  In the second lens position movement process, the focus lens 8 is fixedly moved so that the distance is a predetermined multiple of a predetermined distance in accordance with the distance from the camera device 1 to the subject (eg, eyelid). First, it is possible to focus on a subject (such as an animal in a cage) that is originally intended to be photographed, which is located farther than a subject (such as a kite) that is initially focused by autofocus processing.

  In the second lens position movement process described above, the focus is adjusted to a distance that is 1.5 times the distance of the subject. It may be arbitrarily specified. For example, 1.5 times, 2 times, 3 times, etc. are prepared as multiples prepared in advance, and are selected by operating the key input unit 37 (cursor key) by the user. This makes it possible to focus more favorably by setting the optimal magnification according to the positional relationship between the position of the kite or net and the subject to be photographed (such as an animal in the kite or a player over the net). Can be matched.

  In this way, in the camera device 1 of the second embodiment, for example, when taking an image of an animal in a cage at a zoo or when imaging a subject (player) over the net at a baseball field or the like, After focusing on the net as the subject, place the focus lens so that the focus lens is in a position farther away than the subject on which the focus lens is focused, i.e., where there are animals in the cage or players over the net. By moving the fixed amount, it is possible to take an image with a good focus on animals in the cage or players over the net.

  In the second embodiment described above, the contrast AF method is used, but other AF methods such as a phase shift AF method and an active side distance AF method can be used. In this case, the lens position moving process can be executed using the distance to the subject obtained by the AF process.

(Third embodiment)
Next, a third embodiment will be described. In the third embodiment, the first embodiment and the second embodiment are combined, and a subject (a subject located farther than the eyelids or the net) is subjected to the second contrast AF process in the first embodiment. When focus cannot be achieved, the autofocus method according to the second embodiment is used.

  FIG. 7 is a flowchart showing an image shooting processing procedure by the control unit 25 when the user sets the cage shooting mode by operating the shooting mode switching key in the third embodiment. In FIG. 7, step E1 to step E17 are not described because they are the same as steps A1 to A17 in the first embodiment.

  In step E17, when the peak of the contrast value equal to or greater than the predetermined value is not detected while moving the focus lens 8 to the lens end, the control unit 25 determines that the contrast value detected by the first contrast AF process is the peak. The autofocus process is completed by executing a lens position moving process for moving the focus lens 8 by a predetermined amount so that the focus is on the far side from the lens position (steps E18 and E20). The lens position movement process is executed in the same manner as in the second embodiment described above.

  On the other hand, when the lens position where the contrast value reaches a peak is detected by the second contrast AF process (step E16, Yes), the control unit 25 moves the focus lens 8 to the lens position detected by the second contrast AF process. To complete the autofocus process (steps E19 and E20).

  Here, the control unit 25 determines whether or not the half-press of the shutter button is continued. If the half-press is continued, the control unit 25 waits until the shutter button is fully pressed (step E22, Yes). ).

  If the shutter button is fully pressed (step E21, Yes), the control unit 25 executes image shooting processing (step E23), generates a still image file of the shot image, and stores it in the memory card 32, for example. Record.

  In this way, with the camera device 1 of the third embodiment, for example, when taking an image of an animal in a cage at a zoo or when imaging a subject (player) over the net at a baseball field or the like, Even if the focus position cannot be specified when trying to focus on the subject again after masking the portion of the first subject after focusing the net as the first subject, the focus By moving the focus lens by a predetermined amount so that the focus is in the direction of the far side of the subject where the lens is focused, i.e., the position of the animal in the cage or the player over the net, You can take images with good focus on animals and players over the net.

  Note that the imaging apparatus of the present invention is not limited to the camera apparatus 1 described in each of the above-described embodiments, but includes a mobile phone having a photographing function, a watch, a PDA (personal digital assistant), and a still image imaging function. The present invention can be applied to a device equipped with an imaging device with an AF function, such as a video camera or a personal computer with a camera.

The block diagram which shows the detailed structure of the camera apparatus 1 (imaging apparatus) in embodiment of this invention. The flowchart which shows the image imaging processing procedure by the control part 25 when the cage imaging | photography mode in 1st Embodiment is set. The figure which shows an example of the section image for demonstrating 1st Embodiment. The flowchart which shows the image imaging processing procedure by the control part 25 when the cage imaging mode in 2nd Embodiment is set. 9 is a flowchart for explaining lens position movement processing in the second embodiment. The figure for demonstrating the movement of the lens position in 2nd Embodiment. The flowchart which shows the image imaging processing procedure by the control part 25 when the cage imaging | photography mode in 3rd Embodiment is set.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Camera device, 8 ... Focus lens, 9 ... Zoom lens, 10 ... Diaphragm, 11 ... Motor drive part, 12 ... CCD, 13 ... Timing generator (TG), 14 ... Vertical driver, 15 ... Sample hold circuit (S / H), 16 ... A / D converter, 17 ... color process circuit, 18 ... DMA controller, 20 ... DRAM interface (I / F), 21 ... DRAM, 25 ... control unit, 26 ... VRAM controller, 27 ... VRAM 28 ... Digital video encoder, 29 ... Display unit, 30 ... Image processing unit, 32 ... Memory card, 33 ... Built-in memory, 37 ... Key input unit, 40 ... Audio processing unit, 41 ... Strobe drive unit, 42 ... Microphone unit (MIC), 43 ... Speaker unit (SP), 45 ... Strobe light emitting unit.

Claims (3)

An image pickup means for picking up an image of a subject incident through the focus lens;
A first autofocus means of a contrast system that moves the focus lens from a closest side to an infinitely far side and moves the focus lens to a position for focusing on the first subject;
Mask means for detecting an edge from an image when the focus lens is focused on the first object by the first autofocus means and masking an image portion detected as the edge;
An image pickup apparatus comprising: a contrast-type second autofocus unit that moves an image masked by the mask unit to a position where the focus lens is focused on a second subject. . An imaging step of capturing an image of a subject incident through the focus lens;
A first autofocus step of a contrast method for moving the focus lens from the closest side to the infinity side and moving the focus lens to a position for focusing on the first subject;
A mask step of detecting an edge from an image when the focus lens is focused on the first object by the first autofocus step and masking an image portion detected as the edge;
And a contrast-type second autofocus step for moving the focus lens to a position for focusing the second subject on the image masked by the mask step. Method. The computer installed in the imaging device
An image pickup means for picking up an image of a subject incident through the focus lens;
A first autofocus means of a contrast system that moves the focus lens from a closest side to an infinitely far side and moves the focus lens to a position for focusing on the first subject;
Mask means for detecting an edge from an image when the focus lens is focused on the first object by the first autofocus means and masking an image portion detected as the edge;
An autofocus control functioning as a second autofocus means of a contrast type for moving the focus lens to a position for focusing on a second subject for an image masked by the mask means. program.

Images