JP2011019024A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device which exhibits excellent image quality by using pixels for focus detection.SOLUTION: The image pickup device has: an image sensor 107 having a plurality of pixels for photography each receiving the light passing through the exit pupils of photographic lenses (101, 103, 105) and creating the image of an object, and a plurality of pixels for focus detection each receiving the light passing through a partial area of the exit pupils of the photographic lenses; a first focus detection means 135 for detecting the shift of a pair of images of the object formed on the pixels for focus detection; and a CPU 121 which controls the photographic lenses to move based on the detection results from the first focus detection means, when an addition/decimation/read mode is set so that the signals from the pixels for photography which acquire the brightness information as a major component are added, and the signals from the pixels for photography which acquire the color information as the major component are decimated and outputted.

Description

  The present invention relates to an imaging apparatus.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses an imaging apparatus in which focus detection pixels are provided in an imaging element to realize focus detection (phase difference AF) by a phase difference detection method, and a focus detection pixel is included in a thinning readout target pixel. Disclosure. Patent Document 2 discloses an imaging apparatus that outputs by switching between a thinning readout mode and an addition readout mode.

JP 2009-60597 A JP 2003-189183 A

  The imaging device of Patent Document 1 has two types of readout modes, an all-pixel readout mode and a thinning readout mode. On the other hand, the image sensor of Patent Document 2 does not use a focus detection pixel. For this reason, in an imaging apparatus that realizes phase difference AF by providing focus detection pixels in the imaging device, there has been no proposal for a reading mode that leads to an improvement in image quality and efficient focus detection at that time compared to Patent Document 1. .

  It is an exemplary object of the present invention to provide an image pickup apparatus having excellent image quality using focus detection pixels.

  An imaging apparatus according to an aspect of the present invention includes a plurality of shooting pixels that each receive light passing through an exit pupil of a shooting lens to generate an image of a subject, and each of which is a part of the exit pupil of the shooting lens An image sensor having a plurality of focus detection pixels that receive light passing through the region, and a first focus detection unit that detects a shift amount of the pair of images of the subject formed on the focus detection pixels. Addition thinning readout mode is set in which the signals of the photographing pixels for obtaining luminance information as a main component are added and the signals of the photographing pixels for obtaining color information as a main component are thinned out and output. And a control means for controlling the photographic lens to move based on the detection result of the first focus detection means.

  The present invention can provide an imaging device with excellent image quality using focus detection pixels.

It is a block diagram of the camera (imaging device) of the present embodiment. It is a block diagram of the image pick-up element of the camera shown in FIG. It is a figure explaining operation | movement in the all-pixel reading mode of the image pick-up element shown in FIG. It is a figure explaining the operation | movement of the addition thinning-out reading mode and addition mode of an image pick-up element shown in FIG. It is a figure explaining the operation | movement of the addition thinning-out reading mode and addition mode of an image pick-up element shown in FIG. It is a figure explaining the operation | movement of the addition thinning-out reading mode and addition mode of an image pick-up element shown in FIG. It is a figure explaining addition reading and addition thinning-out reading. 6 is a timing chart in a mode in which an addition reading mode and an addition thinning-out reading mode are mixed. It is a timing chart of all pixel readout mode. It is a timing chart of addition thinning-out reading mode.

  FIG. 1 is a block diagram of the electronic camera (imaging device) of this embodiment. In an electronic camera, a camera body having an image sensor and a photographing lens are integrated.

  In FIG. 1, reference numeral 101 denotes a first lens group disposed at the tip of a photographing lens or photographing optical system (imaging optical system) that forms an image of a subject, and is held so as to be able to advance and retreat in the optical axis direction OA.

  An aperture / shutter 102 adjusts the aperture diameter and adjusts the amount of light during shooting, and also functions as an exposure time adjustment shutter when shooting a still image. Reference numeral 103 denotes a second lens group. The diaphragm / shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction OA, and perform a zooming function (zoom function) in conjunction with the forward and backward movement of the first lens group 101.

  Reference numeral 105 denotes a third lens group (focus lens group) that performs focus adjustment by advancing and retreating in the optical axis direction OA.

  The first lens group 101, the second lens group 103, and the third lens group 105 constitute a photographing lens. The photographing lens includes a focus lens group and forms an image of a subject.

  An optical low-pass filter 106 is an optical element that reduces false colors and moire in the captured image.

  Reference numeral 107 denotes an image sensor composed of a C-MOS sensor and its peripheral circuit. A photoelectric conversion element is arranged on light receiving pixels arranged in m pixels in the horizontal direction and n pixels in the vertical direction. The image sensor 107 uses a two-dimensional single-plate color sensor on which a Bayer array primary color mosaic filter is formed on-chip. The image sensor 107 is configured to be able to output all pixels independently. In addition, some pixels of the image sensor 107 are focus detection pixels, and focus detection (imaging surface phase difference AF) using a phase difference detection method is possible on the imaging surface.

  For this reason, the image sensor 107 receives and photoelectrically converts a light beam that passes through the entire exit pupil of the photographing lens that forms the image of the subject, converts the light into a plurality of pixels for photographing (photographing signals). Pixel group).

  The image sensor 107 further includes a plurality of focus detection pixels (focus detection pixel groups) that each receive light passing through a partial region of the exit pupil of the photographing lens. The plurality of focus detection pixels as a whole can receive light passing through the entire exit pupil of the photographing lens. The focus detection pixels are discretely arranged in the imaging region. The focus detection pixel is a functional pixel configured to give an output other than imaging a part of a plurality of pixels having color information. The imaging device 107 replaces the R pixel and the B pixel with focus detection pixels while leaving a pair of G pixels arranged diagonally among the pixels in 2 rows × 2 columns as photographing pixels.

  This is because when an imaging signal is obtained, the G pixel is the main component of the luminance information, and human image recognition characteristics are sensitive to the luminance information. On the other hand, the R pixel and the B pixel are pixels that acquire color information, but since humans are insensitive to color information, pixels that acquire color information are less likely to notice deterioration in image quality even if some loss occurs. It is.

  Reference numeral 111 denotes a zoom actuator that rotates a cam cylinder (not shown) to drive the first lens group 101 to the third lens group 103 forward and backward in the optical axis direction OA to perform a zooming operation. Reference numeral 112 denotes an aperture shutter actuator, which controls the aperture diameter of the aperture / shutter 102 to adjust the amount of imaged light and to control the exposure time during still image shooting. Reference numeral 114 denotes a focus actuator, which performs focus adjustment by driving the third lens group 105 back and forth in the optical axis direction OA. The focus actuator 114 has a function as a position detection unit that detects the current position of the third lens group 105.

  Reference numeral 115 denotes an electronic flash for illuminating a subject at the time of photographing, which uses a flash illumination device using a xenon tube or an illumination device including LEDs that emit light continuously. Reference numeral 116 denotes an AF auxiliary light unit that projects an image of a mask having a predetermined aperture pattern onto a subject field via a light projecting lens, and improves focus detection capability for a dark subject or a low-contrast subject.

  Reference numeral 121 denotes a CPU (control unit, processor) that controls various controls of the imaging apparatus. The CPU 121 includes, for example, a calculation unit, ROM, RAM, A / D converter, D / A converter, communication interface circuit, and the like. The CPU 121 drives various circuits included in the imaging device based on a predetermined program stored in the ROM, and executes a series of operations such as AF, shooting, image processing, and recording.

  Reference numeral 122 denotes an electronic flash control circuit that controls the lighting of the flash illumination device 115 in synchronization with the photographing operation. Reference numeral 123 denotes an auxiliary light driving circuit, which controls the lighting of the AF auxiliary light unit 116 in synchronization with the focus detection operation.

  Reference numeral 124 denotes an image sensor driving circuit that controls the imaging operation of the image sensor 107 and A / D-converts the acquired image signal and transmits it to the CPU 121. An image processing circuit 125 processes an image output from the image sensor 107. Image processing includes gamma conversion, color interpolation, JPEG compression, and the like.

  Reference numeral 126 denotes a focus drive circuit that controls the focus actuator 114 based on the focus detection result, and performs focus adjustment by driving the third lens group 105 back and forth in the optical axis direction OA. A shutter drive circuit 128 controls the aperture shutter actuator 112 to control the aperture of the aperture / shutter 102. Reference numeral 129 denotes a zoom drive circuit that drives the zoom actuator 111 in accordance with the zoom operation of the photographer.

  Reference numeral 131 denotes a display such as an LCD, which displays information related to the shooting mode of the image pickup apparatus, a preview image before shooting and a confirmation image after shooting, a focus state display image when focus is detected, and the like.

  Reference numeral 132 denotes a group of operation switches including a power switch, a release (shooting trigger) switch, a zoom operation switch, and a shooting mode selection switch (moving image shooting mode and still image shooting mode). The operation switch group 132 also includes an electronic viewfinder mode (live view mode) selection switch and an enlarged display mode setting dial of the display 131.

  Reference numeral 133 denotes a detachable flash memory that records a photographed image.

  Reference numeral 134 denotes a readout mode setting unit, which sets three types of readout modes, that is, an all-pixel readout mode, an addition readout mode, and an addition thinning readout mode in this embodiment. However, it is sufficient for the read mode setting unit 134 to set at least the addition thinning read mode. The read mode setting unit 134 may also serve as the CPU 121.

  The all-pixel reading mode is a mode in which image signals of all the pixels of the image sensor 107 are read out without addition. The addition readout mode is a mode in which a plurality of pixel outputs in the image sensor 107 are added and read out. In addition thinning-out readout mode, a plurality of G pixel image signals acquired with luminance information of the image sensor 107 as a main component are added, and a plurality of B pixel and R pixel image signals acquired with color information as a main component are thinned out. This is the output mode. Based on the mode set by the read mode setting unit 134, levels such as an ADD1 signal, an ADD2 signal, and a SKIP signal described later are set.

  The CPU 121 sets various modes in the read mode setting unit 134 based on the information input from the operation switch group 132 and the contrast component of the image information obtained by the image processing circuit 125.

  In this embodiment, when the electronic viewfinder mode is set by the operation switch (group) 132, the CPU 121 sets the addition reading mode as described with reference to FIG. Insert read mode. As a result, the readout mode setting unit 134 sets a mode in which the addition readout mode and the addition thinning readout mode are mixed. Insertion may be performed at regular intervals or based on contrast components. This is because the imaging surface phase difference AF cannot be performed in the addition readout mode, and therefore, the addition decimation readout mode is inserted to extract information on the imaging surface phase difference AF, thereby improving the focus detection response.

  As will be described with reference to FIG. 8 to be described later, the CPU 121 may replace all the addition reading modes with the addition thinning readout mode. In the addition thinning readout mode, contrast, AF, and imaging plane phase difference AF, which will be described later, can be performed, so that high-speed and highly accurate focus detection can be provided.

  In addition, when the enlarged display mode is set by the operation switch (group) 132, the CPU 121 sets the all-pixel readout mode as will be described later with reference to FIG. In the all-pixel readout mode, contrast, AF, and imaging plane phase difference AF, which will be described later, can be performed, so that high-speed and high-precision focus detection can be provided.

  Reference numeral 135 denotes an imaging surface phase difference focus detection unit (first focus detection means), which is a pair formed on focus detection pixels embedded in the image sensor 107 by a light beam passing through a pair of pupil regions of the imaging optical system. The imaging plane phase difference AF is performed based on the amount of image deviation. The principle of the imaging surface phase difference AF is the same as that described in FIGS.

  The arrangement for detecting vertical lines of focus detection pixels is the same as that described in FIG. 7 of Patent Document 1, and the arrangement for detecting horizontal lines is the same as that described in FIG. 8 of Patent Document 1. It is. The arrangement that enables vertical line detection and horizontal line detection within the same focus detection field is the same as that described in FIG. The arrangement of focus detection pixels for vertical line detection corresponding to a case where a part of a shooting screen is cut out and read out as in the case where the enlargement mode of the electronic viewfinder and the digital zoom for moving images are designated is shown in FIG. This is similar to that described in FIG.

  That is, the focus detection pixels are discretely arranged in a pixel group read out at the time of thinning-out reading, and are arranged so that any of a pair of pupil-divided pixels exists in the signal read out by thinning-out. As a result, focus detection accuracy can be ensured.

  Reference numeral 136 denotes a contrast focus detection unit (second focus detection means) using a contrast detection method, which performs focus detection (TVAF) using the contrast method of the image information obtained by the image processing circuit 125. The TVAF detects the position of the third lens group 105 at which the contrast reaches a peak by moving the third lens group 105 using a focus detection frame that defines a focus detection area and a hill-climbing method. That is, the contrast focus detection unit detects the peak position of the contrast of the image of the subject formed by the plurality of shooting pixels as the focus position. Here, the contrast of the image of the subject is also referred to as a focus signal because it indicates the in-focus state of the third lens group 105.

  FIG. 2 is a block diagram of the image sensor 107. FIG. 2 shows a minimum configuration for explaining the reading operation, and a pixel reset signal and the like are omitted.

In FIG. 2, reference numeral 201 denotes a photoelectric conversion unit, which includes a photodiode, a pixel amplifier, a reset switch, and the like. Hereinafter, the photoelectric conversion unit 201 is also referred to as PD _mn . m is an X-direction address, m = 0, 1,... m−1, n is a Y-direction address, and n = 0, 1,. In the image sensor 107, m × n PD _mn is two-dimensionally arranged. For the sake of simplicity, the subscript (mn) is attached only to some PD _mn . R, G, and B attached to PD _mn are color filters, and the color filters are arranged so as to form a Bayer array. The same applies to FIG. 3 and subsequent figures.

_{Reference numeral} 202 denotes a switch for selecting the output of PD _mn , which is selected for each row by the vertical scanning circuit 213.

_{Reference numeral} 203 denotes a constant current source serving as a load for a pixel amplifier (not shown) of the PD _mn , which is disposed on each vertical output line.

204 is a line memory for temporarily storing the output of the PD _mn, and stores the output of the selected one row of the PD _mn by the vertical scanning circuit 213, usually, the capacitor is used.

  205 and 206 are switches for shorting the vertical output lines, and are used for adding pixels in the horizontal direction during addition reading. The switches 205 and 206 add and output three pixels, that is, an R pixel and an odd-numbered G pixel.

  207 and 208 are switches for short-circuiting the vertical output lines in the same manner as the switches 205 and 206, and are used for adding pixels in the horizontal direction during addition reading. The switches 207 and 208 add and output three pixels of B pixels and G pixels in even rows.

  In the pixel addition, the capacitors of the line memory 204 are connected in parallel, so that the addition average output of three pixels can be obtained by short-circuiting the switch. The switches 205 and 206 are turned on when the signal ADD1 becomes H level. The switches 207 and 208 become conductive when the signal ADD2 becomes H level. In FIG. 2, the switches in the eighth and subsequent columns are omitted, but the switches are arranged so that the same color addition can be performed every three pixels.

Reference numeral 209 denotes a switch for sequentially outputting the output of PD _mn stored in the line memory 204 to the horizontal output line. The horizontal scanning circuit 211 sequentially scans m switches 209 from H ₀ to H _m−1. The output of photoelectric conversion for one row is read out.

  A switch 210 is connected to the horizontal output line and resets the horizontal output line to a predetermined potential VHRST, and is controlled by a signal HRST.

The horizontal scanning circuit 211 sequentially scans the m switches 209 and outputs the output of PD _mn stored in the line memory 204 to the horizontal output line. PHST is a data input signal of the horizontal scanning circuit 211, PH1 and PH2 are shift clock inputs, data is set when PH1 = H, and data is latched by PH2. When a shift clock is input to PH1 and PH2, the PHST signal can be sequentially shifted and m switches 209 can be sequentially turned on. SKIP is a control signal input for setting during thinning readout. When SKIP is set to H level, the horizontal scanning circuit 211 can be skipped at predetermined intervals. Details of the read operation will be described later.

  Reference numeral 212 denotes a buffer amplifier for pixel signals sequentially output from the horizontal output line.

The vertical scanning circuit 213 can select the PD _mn switch 202 by sequentially scanning and outputting V ₀ to V _n−1 . The control signal is controlled by PVST, PV1, PV2, and SKIP as in the horizontal scanning circuit 211. Since the operation is the same as that of the horizontal scanning circuit 211, details are omitted.

  Hereinafter, the operation in the all-pixel reading mode for reading out all the pixels of the image sensor 107 will be described with reference to FIG.

FIG. 3A is a diagram showing an arrangement of PD _mn of m columns and n rows, and the numbers appended on the upper side and the left side are the numbers of X (horizontal) and Y (vertical). All pixels with hatched lines are to be read. Normally, a light-shielded OB (optical black) pixel that detects a black level is also arranged and read out on the image sensor 107, but it is omitted for the sake of simplicity.

  FIG. 3B is a timing chart for reading data of all pixels of the image sensor 107, and is controlled by the CPU 121 controlling the image sensor drive circuit 124 and sending pulses to the image sensor 107.

First, the vertical scanning circuit 213 is driven to activate V _0, and the outputs of the pixels in the 0th row are output to the vertical output lines, respectively. In this state, the MEM signal of the line memory 204 is activated and the data of each pixel is sampled and held in the line memory 204.

Then enter the shift clock activated to PH1, PH2 and PHST signal, and the sequence _{H 0} Activate _{H m-1} outputs the pixel output to the horizontal output line. The output pixel output is output as VOUT through the buffer amplifier 212, converted into digital data by an AD converter (not shown), and subjected to predetermined image processing by the image processing circuit 125.

The vertical scanning circuit 213 is driven to activate V _1, and outputs the pixels in the first row to the vertical output lines. In this state, similarly, the MEM signal is activated and the data of each pixel is temporarily stored in the line memory 204.

Then enter the shift clock activated to PH1, PH2 and PHST signal, and the sequence _{H 0} Activate _{H m-1} outputs the pixel output to the horizontal output line. As described above, reading up to the (n-1) th row is sequentially performed.

  At the time of all pixel readout, the ADD1, ADD2 signal, and SKIP signal are set to L level.

  Hereinafter, an example of reading in the electronic viewfinder mode of the image sensor 107 will be described with reference to FIGS. 4A to 4C.

FIG. 4A is a diagram showing an arrangement of PD _mn of m columns and n rows, and is the same image sensor 107 as FIG. The hatched pixel is a pixel to be read (center of gravity) at the time of electronic viewfinder mode reading. In this embodiment, both X and Y are compressed to an image size of 1/3 and read.

  4B and 4C are timing charts at the time of reading the electronic viewfinder mode. Setting of thinning-out reading is performed by activating the shift register control signal and SKIP signal. By making the SKIP signal active, the operation of the horizontal scanning circuit 211 and the vertical scanning circuit 213 is changed from sequential scanning for each pixel to sequential scanning for every three pixels. At this time, if the ADD1 and 2 signals are set to the L level, a simple decimation output without addition is obtained, and if the ADD1 and 2 signals are set to the H level and the horizontal scanning circuit 211 is driven, the pixel output obtained by adding the pixels is obtained. can get.

FIG. 4B is a timing chart at the time of addition thinning readout. First, the vertical scanning circuit 213 is driven to activate V _0, and the outputs of the pixels in the 0th row are output to the vertical output lines, respectively. In this state, the MEM signal is activated and the data of each pixel is sampled and held in the line memory 204.

Next, the PHST signal is activated, shift clocks are input to PH1 and PH2, and the SKIP signal is set to active to change the path of the shift register, so that H ₂ , H ₅ , H _8. Controlled to be active. In addition, when outputting even-numbered rows, the ADD1 signal is set to L level and pixel addition is not performed. The ADD2 signal is set to the H level so that pixel addition is performed.

As a result, the switches 205 and 206 are non-conductive and the R pixel is read out by thinning out. That is, by H ₂ becomes active, PD ₂₀ is output to the horizontal output line by itself. Further, the switches 207 and 208 are turned on, and pixel addition is performed on the G pixel. That is, _{by H 5} becomes _active, averaging the output of the _{PD 30,} PD 50, PD ₇₀ is output to the horizontal output line.

  Similarly, the R pixel is output independently, and the G pixel is averaged every three pixels, and the pixel output is output to the horizontal output line. The output pixel output is output as VOUT via the buffer amplifier 212, converted into digital data by an AD converter (not shown), and image processed by the image processing circuit 125.

Next, similarly to the horizontal scanning circuit 211, the vertical scanning circuit 213 skips V ₁ and V ₂ to activate V ₃ and outputs the pixel output of the third row to the vertical output line. Thereafter, the pixel output is temporarily stored in the line memory 204 by the MEM signal.

Next, the PHST signal is activated, a shift clock is input to PH1 and PH2, and H ₂ , H ₅ , H ₈ ... Are sequentially activated, and a pixel output is output to the horizontal output line. At this time, when an odd row is selected, the ADD1 signal is set to H level and the ADD2 signal is set to L level. Thereby, the addition output of 3 pixels is output for the G pixel, and the B pixel is output independently.

As described above, reading is performed while performing vertical scanning sequentially every three rows as in V ₆ , V ₉ . As a result, while the number of read pixels is compressed to 1/3 both horizontally and vertically, the G pixel is output as an average output, and the R pixel and B pixel are output independently.

FIG. 4C is a timing chart at the time of addition reading. First, the vertical scanning circuit 213 is driven to activate V _0, and the output of the pixel in the 0th row is output to the vertical output line. In this state, the MEM signal is activated and the data of each pixel is sampled and held in the line memory 204.

Next, the PHST signal is activated and a shift clock is input to PH1 and PH2. At this time, the path of the shift register is changed by setting the SKIP signal to active, and control is performed so that H ₂ , H ₅ , H ₈ . Further, the ADD1 and ADD2 signals are set to H level to perform pixel addition. As a result, the switches 205 to 208 are turned on, and pixel addition is performed. That is, when H ₂ becomes active, the addition average output of PD ₀₀ , PD ₂₀ , PD ₄₀ is output to the horizontal output line.

When H ₅ is active, the addition average output of PD ₃₀ , PD ₅₀ , and PD ₇₀ is output to the horizontal output line, and is averaged every three pixels, and the pixel output is output to the horizontal output line. The output pixel output is output as VOUT via the buffer amplifier 212, converted into digital data by an AD converter (not shown), and image processed by the image processing circuit 125.

Next, similarly to the horizontal scanning circuit 211, the vertical scanning circuit 213 skips V ₁ and V ₂ to activate V ₃ and outputs the pixel output of the third row to the vertical output line. Thereafter, the pixel output is temporarily stored in the line memory 204 by the MEM signal. Next, the PHST signal is activated, a shift clock is input to PH1 and PH2, and H ₂ , H ₅ , H ₈ ... Are sequentially activated, and a pixel output is output to the horizontal output line.

As described above, reading is performed while sequentially performing vertical scanning every three rows, such as V ₆ , V ₉ ... Thereby, addition thinning-out readout of 1/3 is performed both horizontally and vertically.

  FIG. 5A is a diagram illustrating addition reading of the GR rows (even rows) and GB rows (odd rows). The upper row shows the pixel arrangement for reading all pixels, and the lower row shows the pixel arrangement after addition. More specifically, the output values (pixel values) of the R pixels in the 0th, 0th, 2nd, and 4th rows of the 0th row are added and averaged to generate the pixel value of the first R pixel. The output values (pixel values) of the G pixels in the third, fifth, and seventh columns of the 0th row are added and averaged to generate a pixel value of the G pixel. Further, the output values (pixel values) of the R pixels in the 6th, 8th, and 10th columns of the 0th row are added and averaged to generate the pixel value of the second R pixel. Further, the output values (pixel values) of the G pixels in the third row, the 0th column, the 2nd column, and the 4th column are added and averaged to generate the pixel value of the first G pixel. The output values (pixel values) of the B pixels in the third column, the fifth column, and the seventh column of the third row are added and averaged to generate a pixel value of the B pixel. Further, the output values (pixel values) of the G pixels in the 6th, 8th, and 10th columns of the third row are added and averaged to generate the pixel value of the second G pixel.

  FIG. 5B is a diagram illustrating G pixel addition readout and RB thinning readout. The upper part shows the pixel arrangement for reading all pixels, and the lower part shows the pixel arrangement after G addition and RB thinning. More specifically, the output value (pixel value) of the R pixel in the second column of the 0th row is thinned to generate the pixel value of the first R pixel. The output values (pixel values) of the G pixels in the third, fifth, and seventh columns of the 0th row are added and averaged to generate a pixel value of the G pixel. Further, the output value (pixel value) of the R pixel in the eighth row of the 0th row is thinned to generate the pixel value of the second R pixel. Further, the output values (pixel values) of the G pixels in the third row, the 0th column, the 2nd column, and the 4th column are added and averaged to generate the pixel value of the first G pixel. The output value (pixel value) of the B pixel in the third row and the fifth column is thinned to generate a pixel value of the B pixel. Further, the output values (pixel values) of the G pixels in the 6th, 8th, and 10th columns of the third row are added and averaged to generate the pixel value of the second G pixel.

  6A and 6B are timing charts for explaining an imaging operation sequence in the electronic viewfinder (described as “live view” in FIG. 6). FIG. 6A shows a standby state and FIG. 6B shows a group of operation switches. The state when a release switch, which is one of 132, is activated is shown.

  As shown in FIG. 6, after the exposure operation is performed, the image sensor 107 reads out the accumulated charge of each internal pixel as an image signal. The read operation is performed in synchronization with a control pulse vertical synchronization signal VD and a horizontal synchronization signal HD (not shown).

  VD is a signal representing one frame of imaging. For example, the VD receives a command from the CPU 121 every 1/60 seconds (that is, performs moving image shooting of 60 frames per second) and receives an image from the image sensor driving circuit 124. 107. Reading during moving image shooting such as in the electronic viewfinder mode is normally performed by addition reading that reduces the number of read pixels and reduces moire and the like. HD is a horizontal synchronization signal of the image sensor 107, and the number of pulses corresponding to the number of horizontal lines is sent out at a predetermined interval during one frame period to control the horizontal lines.

  When accumulation reading is executed by the VD and HD signals, the VD signal is sent out and the accumulation operation of the next frame is started. Further, the read image signal is transferred to the image processing circuit 125 to perform defective pixel correction and the like, and thereafter image processing (described as “image processing 1” in FIG. 6) is performed. In FIG. 6, image processing 1 represents image processing at the time of addition reading.

  The defective pixel corrected signal is transferred to the contrast focus detection unit 136 to detect the focus state, detects the sharpness of the image, and calculates the contrast AF evaluation value. When the focus detection pixels of the image sensor 107 are included in the pixels to be added in addition reading, they are regarded as defective pixels and defect correction is performed. Based on the peak value (contrast AF evaluation value) detected by the contrast focus detection unit 136, the CPU 121 controls the focus drive circuit 126 to operate the focus actuator 114 to adjust the focus of the photographing lens. In addition, the image processed image is updated on the display 131 in the next frame.

  Reading other than the frame 9 in FIG. 6A is performed by addition reading. In frame 9, G pixel addition RB thinning readout is executed. The read image signal is transferred to the image processing circuit 125 to perform defective pixel correction and the like, and image processing (described as “image processing 2” in FIG. 6) is executed. In FIG. 6, image processing 2 represents image processing at the time of thinning readout.

  At this time, the focus detection pixel data included in the image data of the R pixel and the B pixel is transferred to the imaging surface phase difference focus detection unit 135, and the correlation calculation of the pixel group obtained by pupil division is performed, and the phase difference AF evaluation value is obtained. calculate. Thereby, the CPU 121 controls the focus driving circuit 126 to operate the focus actuator 114 to adjust the focus of the photographing lens.

  In the imaging standby mode shown in FIG. 6A, the phase difference AF detection means by RB pixel thinning readout is performed every 10 frames. In addition, since the focus detection pixel group is discretely arranged on the image sensor 107, a detection error due to a folding error occurs in a subject having a spatial frequency equal to or higher than the sampling frequency of the focus detection pixel group. For this reason, it is desirable to use a contrast AF evaluation value in combination.

  In the addition readout mode and the G addition RB thinning readout mode, it is necessary to switch between contrast AF and phase difference AF according to the readout mode. In addition readout, pixel information of phase difference AF cannot be extracted, and in G addition RB decimation readout inserted appropriately in addition readout, the low-pass effect due to addition cannot be obtained for R and B pixels. May lose continuity.

  In the image read out by RB, G pixels are added. Therefore, although the frequency of occurrence is less than that of an image read out by thinning out all the RGB pixels, moire tends to occur. For this reason, in addition reading and G addition RB decimation readout, it is necessary to shift the characteristics of the low-pass filter applied by the image processing circuit 125 to the low frequency side so that image degradation is not noticeable.

  FIG. 6B shows a sequence when the switch SW1 that is turned on when the release switch is half-pressed by the photographer from the photographing standby is operated. When the read mode setting unit 134 sets a mode in which the addition read mode and the addition decimation read mode are mixed, and the release switch is pressed in the addition read mode, the mode shifts to the addition decimation read mode in the next frame. . By switching the mode in this way, the phase difference AF can be performed in the next frame. Since the photographing trigger is applied by the photographer, the focus detection response can be improved.

  FIG. 7 is a timing chart of the electronic viewfinder when enlargement of the display 131 is designated. When enlargement display is designated, a part of the enlargement designated area is cut out and read out. Although one area of the image sensor 107 is partially read, the pixel itself is read without thinning out (described as “all pixel reading” in FIG. 7), so that contrast AF and phase difference AF can be calculated. Both can be executed.

  FIG. 8 is a timing chart of the electronic viewfinder which is all read out by G addition RB thinning readout. Focus detection can be performed for both contrast AF and phase difference AF.

  7 and 8 are based on the premise that the phase difference AF calculation is performed at a predetermined interval during shooting standby, and both are executed when the release switch is activated. Of course, both calculations may be performed for each frame, and the lens may be driven appropriately.

  As shown in FIG. 8, if all readings are thinned out by G addition RB, the image quality is continuous between frames, so that a series of moving images can be more relaxed than mixing reading modes. Accordingly, either an electronic viewfinder mode in which no recording is left or a shooting mode such as a moving image recording mode in which a moving image is recorded may be used properly. Further, the readout of FIG. 8 may be selected when moving images of moving objects are desired, and the readout of FIG. 6 may be selected when photographing a subject with relatively little movement.

  As described above, in order to read out the focus detection pixel in the electronic viewfinder mode or the moving image recording mode, the G pixel addition RB thinning out reading mode function is added to the image sensor, so that the desired timing can be efficiently achieved without significantly degrading the moving image. It becomes possible to read by.

  It should be noted that inserting thinning-out readings at regular intervals during addition reading is merely an example, and the present invention is not limited to this. For example, focus detection by phase difference detection may be performed by inserting thinning readout as appropriate in consideration of conditions such as a sudden change in contrast value. Further, the thinning-out at the time of thinning-out reading of the image sensor 107 is not limited to 1/3 thinning-out.

  The imaging device is not limited to a camcorder (movie camera) that performs moving image shooting, various inspection cameras, a surveillance camera, an endoscopic camera, a robot camera, and the like.

  The imaging device can be applied to imaging a subject.

105 Third lens group (focus lens group)
107 Image sensor 121 CPU (control unit, processor)
134 Reading mode setting unit 135 Imaging surface phase difference focus detection unit 136 Contrast focus detection unit

Claims (6)

A plurality of imaging pixels each receiving light passing through the exit pupil of the photographic lens to generate an image of the subject, and a plurality of focal points each receiving light passing through a partial area of the exit pupil of the photographic lens An image sensor having a detection pixel;
First focus detection means for detecting a shift amount of a pair of images of the subject formed on the focus detection pixels;
When the addition decimation readout mode is set in which the signals of the imaging pixels for acquiring luminance information as a main component are added and the signals of the imaging pixels for acquiring color information as a main component are output by decimation Control means for controlling the photographic lens to move based on a detection result of the first focus detection means;
An imaging device comprising: A second focus detection means for detecting a focus signal of the subject based on a signal of the photographing pixel;
When the addition reading mode for adding and reading out the signals of the imaging pixels different from the addition thinning-out readout mode is set, the control unit is configured to use the imaging lens based on the detection result of the second focus detection unit. The imaging apparatus according to claim 1, wherein the imaging apparatus is moved. A second focus detection means for detecting a focus signal of the subject based on a signal of the photographing pixel;
The control means moves the photographic lens based on a detection result of the first focus detection means and a detection result of the second focus detection means when the addition thinning readout mode is set. The imaging apparatus according to claim 1 or 2. A second focus detection means for detecting a focus signal of the subject based on a signal of the photographing pixel;
The control means switches between the addition readout mode for adding and reading out the signals of the imaging pixels and the addition thinning readout mode, and the detection result of the second focus detection means in the addition readout mode. 4. The photographing lens according to claim 1, wherein the photographing lens is moved based on the detection result of the first focus detection means in the addition thinning readout mode. The imaging device described in 1.   The imaging apparatus according to claim 4, wherein when the release switch is pressed in the addition readout mode, the imaging frame is switched to the addition thinning readout mode in the next frame. 2. A still image is picked up when an all-pixel reading mode is set in which a moving image is picked up when the addition thinning-out reading mode is set and all the pixel groups of the image pickup device are set. The imaging device according to any one of 5.