JP2006349908A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus and an imaging method by which AF focusing operation is widely performed without trouble from high luminance to low luminance when changing a driving method for a CCD in accordance with photographing environment. <P>SOLUTION: The imaging apparatus has: an imaging device 101 to receive a subject image by light from a subject passing through a focus lens 72a; a filter selection means 104 to select a filter which transmits the frequency component of the subject image through; an automatic focus detection means 104 to detect a focus from image data based on a signal from the imaging device 101 obtained by moving the focus lens 72a; and a pixel addition means 104 to perform driving for pixel addition of the imaging device 101, and uses the pixel addition means 104 in accordance with a photographing condition. The filter of the filter selection means 104 is changed in accordance with the pixel addition state of the pixel addition means 104. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus that performs automatic focus detection, in particular, automatic focus detection according to the luminance of a subject, and an image pickup method thereof, and relates to an improvement of an electronic image pickup apparatus such as a digital still camera.

  2. Description of the Related Art An electronic imaging device such as a digital camera is known that includes an autofocus (hereinafter referred to as “AF”) device that automatically focuses on a subject. As an AF control method of this AF apparatus, hill-climbing AF control is widely used. In this hill-climbing AF control, an integrated value of a luminance difference between high-frequency components or adjacent pixels is obtained from a video signal obtained for each field or frame, and the integrated value of the luminance difference is regarded as an AF evaluation value indicating the degree of focus. Yes.

  When the subject is in focus, the AF evaluation value increases because the edge portion of the subject is clear, and when the subject is out of focus, the AF evaluation value decreases.

  Therefore, when the AF operation is performed, the AF evaluation values are sequentially acquired while moving the autofocus lens, and the lens position at which the AF evaluation value is maximized, that is, the peak position is used as a focal point to stop the movement of the lens (for example, , See Patent Document 1).

  In particular, an imaging apparatus that captures a still image, such as a digital still camera, generally requires strict focusing as compared to an apparatus that captures a moving image of a video camera. Or, the focusing operation is always repeated in the recording mode.

  Also, luminance data corresponding to the digital image data is output as an automatic exposure evaluation value (“AE evaluation value”), and an AF evaluation value is acquired when the AE evaluation value is smaller than a predetermined value or the subject is dark. There is also known a method of increasing AF and performing AF control (see, for example, Patent Document 2).

Furthermore, when the subject brightness in the AF area is low, a method is also known in which AF control is performed by performing vertical pixel addition processing to make it one or two steps brighter than usual (for example, And Patent Document 3).
Japanese Examined Patent Publication No. 39-5265 Japanese Patent Laid-Open No. 2003-230039 JP-A-5-344398

  However, the one disclosed in Patent Document 1 has a low peak of AF evaluation values when shooting a low-luminance or low-contrast object, or noise occurs in AF evaluation data due to low contrast, resulting in a peak. A plurality of (mountains) may appear, and there is a problem that the subject cannot be accurately focused.

  On the other hand, the one disclosed in Patent Document 2 can solve the above problem, but if the AF area is unintentionally enlarged, the photographer focuses on the background without focusing on the subject intended for photographing. There is an inconvenience of being burnt.

  Moreover, although the thing currently disclosed in patent document 3 can eliminate the problem which the technique disclosed in patent document 1 and patent document 2 has, since the resolution deteriorates based on pixel addition, the low frequency component becomes large. There is a problem that it is difficult to detect the peak of the AF evaluation value.

  The present invention has been made in view of the above circumstances. When the CCD driving method is changed according to the shooting environment, a wide range of AF focusing operations can be performed from high brightness to low brightness without any trouble. It is an object of the present invention to provide an imaging apparatus and an imaging method that can perform the above-described process.

  The imaging apparatus according to claim 1, an imaging element that receives a subject image by light from a subject that has passed through a focus lens, a filter selection unit that selects a filter that transmits a frequency component of the subject image, and the focus lens An automatic focus detection unit that detects a focus from image data based on a signal from an image sensor obtained by moving the image sensor, and a pixel addition unit that enables pixel addition drive of the image sensor. Accordingly, the filter using the pixel adder is changed according to the pixel addition state of the pixel adder.

The imaging apparatus according to claim 2, an imaging element that receives a subject image by light from a subject that has passed through a focus lens, a filter selection unit that selects a filter that transmits a frequency component of the subject image, and the focus lens Automatic focus detection means for detecting a focus from image data based on a signal from an imaging signal obtained by moving the image sensor, pixel addition means for enabling pixel addition driving of the imaging element, and photometry for measuring subject luminance And an image pickup apparatus using the pixel addition unit according to a photometric result obtained by the photometric unit,
The filter of the filter selection unit is changed according to the pixel addition state of the pixel addition unit.

  The imaging apparatus according to claim 3, further comprising: a detection result determination unit that determines whether focus detection is possible as a result of performing focus detection by the automatic focus detection unit, according to a pixel addition state of the pixel addition unit. The threshold value of the detection result judging means is changed.

  The image pickup apparatus according to claim 4, wherein when the pixel addition is performed by the pixel addition unit, a filter selected by the filter selection unit is used as a filter that transmits only a higher frequency through the filter of the filter selection unit. It is characterized by changing.

  6. The imaging apparatus according to claim 5, wherein when pixel addition is not performed by the pixel addition unit, the filter selected by the filter selection unit is changed to a filter that allows the filter of the filter selection unit to pass through the low frequency side. It is characterized by doing.

  According to a sixth aspect of the present invention, when pixel addition is performed by the pixel addition unit, a threshold value of the detection result determination unit is lowered.

  The imaging apparatus according to claim 7 is characterized in that, when pixel addition is not executed by the pixel addition driving unit, a threshold value of the detection result determining unit is increased.

  The imaging method according to claim 8, wherein the imaging device receives a subject image by light from a subject that has passed through a focus lens, a filter selection step that selects a filter that transmits a frequency component of the subject image, and An automatic focus detection step for detecting a focus from image data based on a signal from an image pickup device obtained by moving a focus lens, a pixel addition step for enabling pixel addition drive of the image pickup device, and according to a shooting condition A step of executing the pixel addition step, and a step of changing a filter of the filter selection step according to a pixel addition state of the pixel addition step.

  The imaging method according to claim 9, wherein the imaging device receives an image of a subject by light from the subject that has passed through a focus lens, a filter selection step of selecting a filter that transmits a frequency component of the subject image, and An automatic focus detection step for detecting a focus from image data based on a signal from an image sensor obtained by moving a focus lens, a pixel addition step for enabling pixel addition drive of the image sensor, and a luminance of the subject A step of measuring the pixel, a step of executing the pixel addition step in accordance with the photometric result obtained in the photometry step, and a step of changing the filter in the filter selection step in accordance with the pixel addition state of the pixel addition means It is characterized by having.

  The imaging method according to claim 10, further comprising a detection result determination step for determining whether or not focus detection is possible as a result of performing focus detection by the automatic focus detection means, and the pixel addition state of the pixel addition step The threshold value of the detection result judging means is changed according to the above.

  The imaging method according to claim 11, wherein when pixel addition is performed by the pixel addition unit, a filter selected by the filter selection unit is used as a filter that transmits only a higher frequency through the filter of the filter selection unit. It is characterized by changing.

  13. The imaging method according to claim 12, wherein when the pixel addition is not performed by the pixel addition unit, the filter selected by the filter selection unit is changed to a filter that allows the filter of the filter selection unit to pass through the low frequency side. It is characterized by doing.

  The imaging method according to a thirteenth aspect is characterized in that, when pixel addition is executed in the pixel addition step, a threshold value of the detection result determination unit is lowered.

  The imaging method according to claim 14 is characterized in that, when pixel addition is not performed by the pixel addition unit, a threshold value of the detection result determination unit is increased.

  According to the present invention, when the CCD driving method is changed according to the photographing environment, it is possible to perform AF focusing operation widely from high luminance to low luminance without any trouble.

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

  1 is a front view showing an example of a digital still camera (hereinafter also referred to as a camera) as an imaging apparatus according to the present invention, FIG. 2 is a rear view thereof, FIG. 3 is a top view thereof, and FIG. 4 is an internal view of the digital camera. It is a block circuit diagram which shows the outline | summary of a system configuration | structure.

  In FIG. 1, a release switch (release shutter) SW1, a mode dial SW2, and a sub liquid crystal display (hereinafter also referred to as a sub LCD) 1 shown in FIG.

  In front of the camera, a lens barrel unit 7 including a photographing lens, an optical finder 4, a strobe light emitting unit 3, a distance measuring unit 5, a remote control light receiving unit 6, and a lid 2 for a memory card / battery loading chamber are provided.

  On the back of the camera, as shown in FIG. 2, a power switch 13, an LCD monitor 10, an AF LED 8, a strobe LED 9, an optical viewfinder 4, a wide angle direction zoom switch SW3, a telephoto direction zoom switch SW4, a self-timer setting / release switch SW5, A menu switch SW6, an upward movement / strobe set switch SW7, a rightward movement switch SW8, a display switch SW9, a downward movement / macro switch SW10, a leftward movement / image confirmation switch SW11, an OK switch SW12, and a quick access switch SW13 are provided.

  Since the functions and operations of these members are well known, the description thereof will be omitted, and the system configuration inside the camera will be described next.

  In FIG. 4, reference numeral 104 denotes a digital still camera processor (hereinafter also referred to as a processor).

  The processor 104 includes a CCD1 signal processing block 1041, a CCD2 signal processing block 1042, a CPU block 1043, a local SRAM 1044, a USB block 1045, a serial block 1046, a JPEG / CODEC block 1047, a RESIZE block 1048, a TV signal display block 1049, a memory card controller. Block 10410 is included. Each of these blocks is connected to each other via a bus line.

  An SDRAM 103 for storing RAW-RGB image data, YUV image data, and JPEG image data is arranged outside the processor 104. The SDRAM 103 is connected to the processor 104 via a memory controller (not shown) and a bus line. .

  Further, a RAM 107, a built-in memory 120, and a ROM 108 storing a control program are provided outside the processor 104, and these are also connected to the processor 104 by a bus line.

  The lens barrel unit 7 includes a zoom optical system 71 having a zoom lens 71a, a focus optical system 72 having a focus lens 72a, a diaphragm unit 73 having a diaphragm 73a, and a mechanical shutter unit 74 having a mechanical shutter 74a.

  The zoom optical system 71, the focus optical system 72, the aperture unit 73, and the mechanical shutter unit 74 are driven by a zoom motor 71b, a focus motor 72b, an aperture motor 73b, and a mechanical shutter motor 74b, respectively.

  Each of these motors is driven by a motor driver 75, and the motor driver 75 is controlled by a CPU block 1043 of the processor 104.

  A subject image is formed on the CCD 101 by each lens system of the lens barrel unit 7, and the CCD 101 converts the subject image into an image signal and outputs the image signal to the F / E-IC 102. As is well known, the F / E-IC 102 includes a CDS 1021, an AGC 1022, and an A / D conversion unit 1023.

  The F / E-IC 102 performs predetermined processing on the image signal, converts the image signal into a digital signal, and outputs the digital signal to the CCD 1 signal processing block 1041 of the processor 104.

  These signal control processes are performed via the TG 1024 by the VD / HD signal output from the CCD1 signal processing block 1041 of the processor 104.

  The CPU block 1043 of the processor 104 controls the sound recording operation by the sound recording circuit 1151. The voice recording circuit 1151 records the amplified signal by the microphone amplifier 1152 of the voice recording signal converted by the microphone 1153 according to the command. The CPU block 1043 also controls the operation of the audio reproduction circuit 1161. The audio reproduction circuit 1161 is configured to reproduce an audio signal stored in the memory as appropriate according to a command, output the audio signal to the audio amplifier 1162, and output the audio from the speaker 1163.

  The CPU block 1043 further controls the strobe circuit 114 to emit illumination light from the strobe light emitting unit 3. In addition to this, the CPU block 1043 also controls the distance measuring unit 5.

  The CPU block 1043 is connected to the sub CPU 109 of the processor 104, and the sub CPU 109 performs display control by the sub LCD 1 via the CCD driver 111. The sub CPU 109 is further connected to the buzzer 113, an operation key unit including the AF LED 8, the strobe LED 9, the remote control light receiving unit 6, and the operation switches SW1 to SW13.

  The USB block 1045 is connected to the USB connector 122, and the serial block 1046 is connected to the RS-232C connector via the serial driver circuit 1231. The TV display block 1049 is connected to the LCD monitor 10 via the LCD driver 117 and also connected to the video jack 119 via the video amplifier 118. The memory card controller block 10410 is connected to a contact with the card contact of the memory card slot 121.

  Next, a general operation outline of the camera according to the present invention will be described.

  When the mode dial SW2 is set to the recording mode, the camera is activated in the recording mode. The mode dial SW2 is set by the processor 104 detecting whether or not the mode switch shown in FIG. 3 is turned on in the recording mode.

  The processor 104 controls the motor driver 75 to move the lens barrel unit 7 to a position where photographing can be performed. Further, the processor 104 turns on power to each circuit such as the CCD 101, the F / E-IC 102, the LCD display 10 and the like to start operation. When the power of each circuit is turned on, the operation in the finder mode is started.

  In the finder mode, light incident on the image sensor (CCD) 101 through each lens system is photoelectrically converted and transmitted to the CDS circuit 1021 and the A / D converter 1023 as R, G, and B analog signals. The A / D converter 1023 converts the analog signal into a digital signal, and the digital signal is converted into a YUV signal by a YUV conversion unit in the digital signal processing IC (SDRAM 103) and written into the frame memory by a memory controller (not shown).

  The YUV signal is read by the memory controller and transmitted to the TV (not shown) and the LCD monitor 10 via the TV display signal block 1049, thereby displaying the captured image. This process is performed at 1/30 second intervals, and the viewfinder mode is updated every 1/30 seconds.

  The CCD 101 can perform pixel addition processing depending on the reading mode. In this pixel addition, as shown in FIG. 5A, the read vertical two pixels are added, or the read vertical two pixels and horizontal two pixels as shown in FIG. 5B. It is known that an electric signal having an output twice as high as that of vertical only pixel addition can be transmitted by adding a total of four pixels.

  Normally, nothing is set in the finder mode, and by default, the CCD 101 is driven by the vertical pixel addition driving method as pixel addition, and vertical addition processing is executed.

  An AF evaluation value indicating the degree of focus of the image and an AE evaluation value indicating the exposure state are calculated based on the digital RGB signal captured in the CCD I / F block (not shown) of the digital signal processing IC (SDRAM 103). .

  The AF evaluation value data is read to the CPU block 1043 as a characteristic data of a predetermined area section of the CCD 101 and used for AF processing. The AF evaluation value is created by the output integrated value of the frequency component extraction filter and the integrated value of the luminance difference between adjacent pixels.

  There are two types of frequency component extraction filters, a high frequency filter (A) shown in FIG. 6B and a low frequency filter (B) shown in FIG. 6A. These high frequency filters (A), The low frequency filter (b) is a filter for image processing. In addition, a filter (C) configured by multiplying these filters (A) and (B) is also known.

  The high-frequency filter (A) is a high-pass filter that emphasizes the luminance difference between pixels, and is configured to multiply the luminance data of adjacent pixels by, for example, coefficients of “−1”, “2”, and “−1”. .

  The low-frequency filter (b) is a low-pass filter that smoothes the correlation between adjacent pixels and removes noise components, and multiplies the luminance data of adjacent pixels by coefficients of “1”, “2”, and “1”, respectively. It is configured.

  The filter (c) is used to remove noise by transmitting the luminance data emphasized by the high frequency filter (b) to the low frequency filter (b).

  Usually, the filter used when outputting the AF evaluation value data is a high frequency filter (A) or a filter (C) formed by multiplying a high frequency filter (A) and a low frequency filter (B). Use.

  Since the edge portion of the subject is clear when in focus, the integral value of adjacent pixels has a high frequency component. Therefore, during the focus detection operation by AF, the AF evaluation value at each focus lens position is acquired, and the maximum point (peak position) is detected. Also, considering that there are multiple local maxima, if there are multiple local maxima, compare the size of the evaluation value at the position of the local maximum point with the evaluation value of the surrounding area, and descend the mountain. The degree of ascent is determined, and the AF point is executed by regarding the local maximum point that seems to have the most reliability as the in-focus position.

  The AE evaluation value is obtained by dividing a digital RGB signal into several areas and using luminance data in the areas. A pixel that exceeds a predetermined threshold with respect to the pixels in each area is determined as a target pixel, and the luminance value is added and divided by the number of target pixels. An appropriate exposure amount is calculated from the luminance distribution of each area, and correction is performed for the capture of the next frame.

  When the release shutter button (release shutter SW1) is pressed, a still image shooting start signal is taken into the processor 104 via the F / E-IC 102 from the CCD 101 shown in FIG. Subsequently, the CPU block 1043 drives the drive motor 72b of the focus lens 72a via the motor driver 75 in synchronization with the frame rate, whereby hill-climbing AF is executed.

  When the in-focus range of the camera is the entire range from infinity to close, the focus lens moves from close to infinity or from infinity to close to each frame at each focus position created by the digital signal processing IC. The AF evaluation value is read to the CPU block 1043. The maximum point of the AF evaluation value at each focus position is regarded as the focus position, and the focus lens 72a is moved to the focus position.

  After the AF is completed, the analog RGB signal taken out from the CCD 101 is converted into a digital RGB signal and stored in a RAM 107 as a frame memory via a memory controller. The digital RGB signal is read again by the processor 104, converted into YUV data, and written back to the RAM 107 as a frame memory.

  At the time of still image shooting, YUV converted image data is transmitted to a JPEG CODEC block 1047 as an image compression / decompression circuit of the processor 104. The YUV data transmitted to the image compression / decompression circuit is compressed and written back to the RAM 107 as a frame memory. The RAM 107 as a frame memory reads compressed data via a memory controller (not shown) and stores it in, for example, a memory card 121 'as a data storage memory.

  Next, an embodiment relating to the main part of the present invention will be described with reference to the drawings.

  FIG. 7 is a flowchart for explaining the operation of the imaging apparatus according to the first embodiment of the present invention. First, when the release shutter button SW1 shown in FIG. 1 is operated, a shooting mode (shooting condition) immediately before the release shutter button SW1 is pressed is detected (S.1). There are two shooting modes, a normal shooting mode and a dark shooting mode, which can be switched by the mode dial SW2 shown in FIG. The mode dial SW2 functions as a photographing condition changing unit.

  The setting for pixel addition reading of the CCD 101 is determined in accordance with the photographing mode (S.2). The pixel addition selection process is performed based on the flowchart shown in FIG. First, the processor 104 determines whether or not the shooting mode is the normal shooting mode (S.21). If the shooting mode is the normal shooting mode, the pixel addition state is set to the vertical pixel addition process (S.22), and S in FIG. . The process proceeds to 3. When the shooting mode is the dark shooting mode, it is often used in the dark and it is necessary to increase the image output. Therefore, the pixel addition state is set to the vertical / horizontal addition execution process, and the image output is doubled ( S.23), the following S.23. The process proceeds to 3. That is, the processor 104 also functions as a pixel addition unit.

  Next, the processor 104 performs filter selection processing (see S.3 in FIG. 7). That is, the processor 104 functions as a filter selection unit, and this filter selection process determines whether or not the pixel addition state is the default vertical pixel addition process as shown in FIG. When the addition state is the default vertical pixel addition process, a filter (C) obtained by multiplying the high frequency filter (A) by the low frequency filter (B) is selected as a filter (S.32). When the pixel addition state is vertical / horizontal addition execution, the high frequency filter (A) is selected as a filter (S.33). And S. Move to 4.

  When the vertical / horizontal pixel addition is executed, the resolution is lowered by adding the horizontal pixel, but the high frequency side can be emphasized by using the filter accordingly.

  Next, the processor 104 moves the focus lens 72a to the focus start position (see S.4 in FIG. 7), and acquires the AF evaluation value (S.5). That is, the processor 104 also functions as an automatic focus detection unit, and the processor 104 executes a peak determination process (S.6) after obtaining the AF evaluation value, and determines whether or not the AF evaluation value is a peak. "Peak detection NG?" Is judged (S.7). The processor 104 functions as a detection result determination unit, and determines whether or not it is a peak based on a threshold value.

  An appropriate threshold is used for the peak determination process, and when a peak is detected, the process proceeds to a peak position determination process (S.10). If no peak is detected, the process proceeds to determination (S.8) of whether or not the scan is completed to the final end of the focus position. If the scan is not completed, the focus position is sequentially moved (S.9). Returning to the evaluation value acquisition process (S.5), the same process is repeated again. When the scan is completed, the process proceeds to the peak position determination process (S.10).

  Next, the processor 104 determines a more reliable peak position from the scanned AF evaluation value, moves the focus lens to the determined peak position, and ends the operation.

  If no reliable peak position is found, the focus lens 72a is moved to a predetermined focus position, for example, a focus position corresponding to about 2.5 m, as the AF scan NG, and the operation ends (S. 10).

  Here, it is preferable to use a CCD 101 that can change the number of pixels that can be added. In the embodiment of the present invention, the number of pixels that can be added is two vertical pixels and two horizontal pixels. However, for example, addition of four vertical pixels and four horizontal pixels may be possible. In this case, image output data (brightness) )) Becomes larger, which is effective for AF processing at lower luminance.

  Further, in the first embodiment of the present invention, a simple three-factor high-frequency filter (A) and a low-frequency filter (B) are used, but a five-factor and seven-factor filter can be used. The use of a 5-coefficient and 7-coefficient filter can improve the extraction accuracy of high-frequency components and low-frequency components, and is more desirable for performing AF processing.

  In the first embodiment of the present invention, the filter is varied according to the pixel addition state. However, if the filter can be changed according to the luminance or according to the subject, the high frequency component, the low frequency An improvement in component extraction accuracy can be expected, which is more desirable in performing AF processing.

  That is, when pixel addition is executed by the pixel addition means, it is desirable to change the filter to a filter that allows only higher frequencies to pass through, so that the high frequency side can be emphasized by the amount of resolution reduction. On the other hand, when the pixel addition is not performed by the pixel addition means, it is desirable to change the filter to a filter that also transmits the low frequency side because normal AF processing can be performed.

  Further, considering that the output of the peak of the AF evaluation value peak varies depending on the pixel addition state and the filter selection, the threshold used for peak determination in the peak determination process (S.6) is set to the output state of the image data. Even more preferably, it can be varied accordingly.

  In other words, when pixel addition is performed by the pixel addition means, if the threshold value of the detection result determination means is lowered, detection of the peak is facilitated. On the other hand, detection is performed when pixel addition is not performed by the pixel addition means. It is desirable to increase the threshold value of the result judging means because normal AF processing can be executed.

  In the first embodiment, the pixel addition is selected for the two shooting modes. However, the present invention is not limited to this. For example, in the macro mode, the camera itself may become a shadow when shooting a macro subject. As a result, there may be a low brightness state on the screen, so in consideration of this, it is possible to increase the brightness by setting the pixel addition state to the vertical / horizontal addition state in the macro shooting mode. it can.

  FIG. 10 is a flowchart for explaining the operation of the imaging apparatus according to the second embodiment of the present invention.

  When the release shutter button SW1 shown in FIG. 1 is operated, the luminance of the subject is determined based on the photometric result immediately before the release shutter button SW1 is pressed (S.41). The subject brightness is measured based on the output of the CCD 101. In accordance with the luminance (LV value) obtained from the photometric result, the pixel addition readout setting of the CCD 101 is determined (S.42).

  The pixel addition selection process is performed according to the flowchart shown in FIG. First, the processor 104 determines whether or not the subject brightness is LV6 or more (S.91). When the subject brightness is LV6 or higher, the pixel addition state is set to vertical pixel addition (S.92). The process proceeds to 43. If it is less than LV6, the processor 104 sets the pixel addition to the vertical / horizontal addition execution process (S.93). The process proceeds to 43. As a result, the image output (brightness) can be doubled when the image is darker than LV6.

  Step S. The luminance threshold value (LV value) set in 91 is limited to that in the second embodiment, and can be appropriately changed according to the lens aperture value (F value), the performance of the CCD 101, and the like. desirable.

  Next, the processor 104 performs filter selection processing (see S.43 in FIG. 10). In this filter selection process, as in the first embodiment, it is determined whether or not the pixel addition state is the default vertical pixel addition process (see S · 31 in FIG. 9), and the pixel addition state is the default vertical pixel addition. In the case of processing, a filter (C) obtained by multiplying a high frequency filter and a low frequency filter is selected as a filter (see S.32 in FIG. 9). When the pixel addition state is vertical / horizontal addition execution, the high frequency filter (A) is selected as a filter (see S.33 in FIG. 9). And S. 44.

  When the vertical / horizontal pixel addition is executed, the resolution is lowered by adding the horizontal pixel, but the high frequency side can be emphasized by using the filter accordingly.

  Next, the processor 104 moves the focus lens 72a to the focus start position (S.44), and acquires the AF evaluation value (S.45). After acquiring the AF evaluation value, the processor 104 executes a peak determination process (S.46), and determines whether or not the evaluation value is a peak position, that is, “peak detection NG?” (S.47). ). An appropriate threshold value is used for the peak determination process, and when a peak is detected, the process proceeds to a peak position determination process (S.50).

  If no peak is detected, the process proceeds to determination of whether or not the scan has been completed to the final end of the focus position (S.48). If the scan has not been completed, the focus position is sequentially moved (S.49). Returning to the evaluation value acquisition processing step (S.45), the same processing is repeated again. When the scan is completed, the process proceeds to the peak position determination process (S.50).

  Next, the processor 104 determines a more reliable peak position based on the scanned AF evaluation value, moves the focus lens 72a to the determined peak position, and ends the operation. If a reliable peak position is not found, the focus lens 72a is moved to a predetermined focus position, for example, a focus position corresponding to about 2.5 m, as the AF scan NG, and the operation ends (S.50). ).

  Here, it is preferable to use a CCD 101 that can change the number of pixels that can be added. In the second embodiment of the present invention, the number of pixels that can be added is two vertical pixels and two horizontal pixels. However, for example, addition of four vertical pixels and four horizontal pixels may be possible. In this case, image output data ( (Brightness) becomes larger, which is effective for AF processing at a much lower luminance.

  In the second embodiment of the present invention, a simple three-factor high-frequency filter (A) and a low-frequency filter (B) are used, but by improving the processing capability of the microcomputer (CPU block 1043), 5 and 7 coefficient filters can be used. When such 5 and 7 coefficient filters are used, the extraction accuracy of high frequency components and low frequency components can be improved, and AF processing is executed. More desirable.

  In the second embodiment of the present invention, the filter is variable according to the pixel addition state. However, if the filter can be changed according to the luminance or according to the subject, the high frequency component, the low frequency An improvement in component extraction accuracy can be expected, which is more desirable in performing AF processing.

  Further, in consideration of the fact that the output of the peak of the AF evaluation value varies depending on the pixel addition state and filter selection, the threshold used for peak determination in the peak determination process (S.46) is the output state of the image data. It is even more preferable that it can be varied depending on

  As described above in the first and second embodiments, in order to appropriately perform shooting according to the luminance of various subjects, when the luminance is low, when shooting a dark subject such as the dark shooting mode. Since vertical and horizontal pixel addition is performed and a decrease in resolution at that time is compensated for by selecting a filter, appropriate photographing can be performed corresponding to subjects having various luminances.

1 is a front view of a digital camera as an imaging apparatus according to an embodiment of the present invention. It is a rear view of the digital camera as an imaging device concerning the Example of this invention. 1 is a top view of a digital camera as an imaging apparatus according to an embodiment of the present invention. 1 is a block circuit diagram illustrating an outline of an internal system configuration of a digital camera as an imaging apparatus according to an embodiment of the present invention. 2A and 2B are explanatory diagrams illustrating an example of pixel addition of a digital camera according to an embodiment of the present invention, where FIG. 1A is an explanatory diagram illustrating an example of vertical pixel addition, and FIG. 2B is an explanatory diagram illustrating an example of vertical / horizontal pixel addition; FIG. An example of the filter concerning the Example of this invention is shown, (a) shows an example of the filter for high frequencies, (b) shows an example of the filter for low frequencies. 3 is a flowchart for explaining an operation of the imaging apparatus according to the first embodiment of the present invention. It is a flowchart which shows an example of the pixel addition setting process shown in FIG. It is a flowchart which shows an example of the filter selection process shown in FIG. It is a flowchart for demonstrating operation | movement of the imaging device concerning Example 2 of this invention. It is a flowchart which shows an example of the pixel addition setting process shown in FIG.

Explanation of symbols

72a ... focus lens 101 ... imaging element 104 ... processor (filter selection means, automatic focus detection means, pixel addition means, filter selection means)

Claims (14)

An image sensor that receives a subject image by light from a subject that has passed through a focus lens, a filter selection unit that selects a filter that transmits a frequency component of the subject image, and an image sensor obtained by moving the focus lens An image pickup apparatus, comprising: an automatic focus detection unit that detects a focus from image data based on a signal from a signal; and a pixel addition unit that enables pixel addition driving of the image sensor, and uses the pixel addition unit according to a shooting condition In
An image pickup apparatus, wherein the filter of the filter selection unit is changed according to a pixel addition state of the pixel addition unit. An image sensor that receives a subject image by light from the subject that has passed through the focus lens, a filter selection unit that selects a filter that transmits the frequency component of the subject image, and an imaging signal obtained by moving the focus lens Automatic focus detection means for detecting a focus from image data based on a signal from the image sensor, pixel addition means for enabling pixel addition drive of the image sensor, and photometry means for measuring subject luminance. In the imaging device using the pixel addition means according to the obtained photometric result,
An image pickup apparatus, wherein the filter of the filter selection unit is changed according to a pixel addition state of the pixel addition unit.   As a result of focus detection by the automatic focus detection means, there is a detection result judgment means for judging whether or not focus detection is possible, and the threshold value of the detection result judgment means is changed according to the pixel addition state of the pixel addition means The imaging apparatus according to claim 1 or 2, wherein   2. When performing pixel addition by the pixel addition means, the filter selected by the filter selection means is changed to a filter that allows only a higher frequency to pass through the filter of the filter selection means. The imaging device according to any one of claims 3 to 4.   The filter selected by the filter selection means is changed to a filter that allows the filter of the filter selection means to pass through even a low frequency side when pixel addition is not performed by the pixel addition means. The imaging device according to claim 3.   The imaging apparatus according to claim 3, wherein when pixel addition is performed by the pixel addition unit, a threshold value of the detection result determination unit is lowered.   The imaging apparatus according to claim 3, wherein when the pixel addition is not performed by the pixel addition driving unit, a threshold value of the detection result determination unit is increased. Receiving an image of a subject by light from a subject that has passed through the focus lens by an image sensor;
A filter selection step for selecting a filter that transmits the frequency component of the subject image;
An automatic focus detection step of detecting a focus from image data based on a signal from an image sensor obtained by moving the focus lens;
A pixel addition step that enables pixel addition driving of the image sensor;
Executing the pixel addition step according to the shooting conditions;
And a step of changing a filter of the filter selection step according to a pixel addition state of the pixel addition step. Receiving an image of a subject by light from a subject that has passed through the focus lens by an image sensor;
A filter selection step for selecting a filter that transmits the frequency component of the subject image;
An automatic focus detection step of detecting a focus from image data based on a signal from an image sensor obtained by moving the focus lens;
A pixel addition step that enables pixel addition driving of the image sensor;
A photometric step of measuring the brightness of the subject;
Executing the pixel addition step according to the photometric result obtained in the photometric step;
And a step of changing a filter of the filter selection step in accordance with a pixel addition state of the pixel addition means.   A detection result determination step for determining whether or not focus detection is possible as a result of focus detection by the automatic focus detection unit, and a threshold value of the detection result determination unit according to the pixel addition state of the pixel addition step; The imaging method according to claim 8, wherein the imaging method is changed.   9. When performing pixel addition by the pixel addition means, the filter selected by the filter selection means is changed to a filter that allows only a higher frequency to pass through the filter of the filter selection means. The imaging method according to claim 10.   9. The filter selected by the filter selection unit is changed to a filter that transmits a low-pass filter through the filter of the filter selection unit when pixel addition is not performed by the pixel addition unit. The imaging method according to claim 10.   The imaging method according to claim 10, wherein when pixel addition is performed in the pixel addition step, a threshold value of the detection result determination unit is lowered.   The imaging method according to claim 10, wherein when the pixel addition is not performed by the pixel addition unit, a threshold value of the detection result determination unit is increased.

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