JP2011091492A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which provides a more accurate luminance signal by performing proper OB clamping by photosensitivity of pixels of a photometric sensor. <P>SOLUTION: When outputting an effective pixel 802 existing in a first region and having a vertical structure of PN junction, a photometric sensor 208 performs black level correction using a signal output of a vertical structure light shielding pixel region 803 having the vertical structure of PN junction. When outputting the effective pixel 802 existing in a second region in a periphery of the effective pixel 802 and not having the vertical structure of PN junction, the photometric sensor 208 performs black level correction using an output signal of a non-vertical structure light shielding pixel region 804 having no vertical structure of PN junction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus including a photometric sensor having a plurality of pixels having different light receiving sensitivities.

  Conventionally, an image pickup device that picks up images with a first sensitivity and a second sensitivity lower than the first sensitivity is provided, and an image picked up with the first sensitivity and the second sensitivity is synthesized to adjust a dynamic range of the image pickup device. The technique to do is proposed (patent document 1).

  In this proposal, the luminance level of the subject is detected based on one of the first image and the second image, and the histogram of the first image is calculated. Then, an evaluation value representing the degree of high contrast is calculated from data on a predetermined highlight side in the calculated histogram and the detected luminance level. Then, an adjustment gain for adjusting the dynamic range of the image sensor is calculated based on the calculated evaluation value, and the first image and the second image are synthesized based on the calculated adjustment gain, Expand.

  Further, there is proposed an imaging apparatus that performs focus detection using a TTL phase difference detection method, in which a photometric sensor has a light measurement function and a light source detection function for use in correcting a focus detection result (Patent Document 2). .

  In this proposal, a method of detecting the spectral intensity of visible light and near-infrared light is exemplified as a method of detecting the light source, and the light source is detected based on the ratio of the spectral intensity of visible light and near-infrared light. In order to perform this light source detection, among the pixels of the photometric sensor, the pixel corresponding to the position where the focus is detected on the imaging screen is configured by a vertical structure pixel, and the vertical structure pixel has a near infrared spectral characteristic together with visible light. Make it. With such a configuration, it is possible to perform light source detection used for correcting the focus detection result together with photometry at the focus detection position on the imaging screen without increasing the sensor size.

  In addition, an imaging apparatus that performs subject tracking using the output of a photometric sensor has been proposed (Patent Document 3).

  In this proposal, photometry and colorimetry are performed in each divided area where the entire photometry area of the photometry sensor is divided into multiple areas, and the main subject and its size are repeatedly detected, so that the photometry area where the main subject exists is determined. Identify and track the subject.

JP 2004-186876 A JP 2009-37139 A JP-A-7-92248

  In Patent Document 1, when correcting the black level of the image sensor, the data of the light shielding area of the image sensor in which the first sensitivity and the second sensitivity are mixed is subtracted from the signal output of the non-light shield area of the image sensor. (OB clamp). Therefore, the black level of the first image is affected by the data of the light-shielding area having the second sensitivity, and the black level of the second image is affected by the data of the light-shielding area having the first sensitivity. For this reason, there is a possibility that a correct black level signal cannot be obtained in both the first image and the second image, and the correct luminance cannot be obtained. In particular, when the subject has a low luminance, the luminance level of the subject and the black level of the light-shielding area are closer than when the subject has a high luminance, so that the influence of the light-shielding area appears more prominently.

  On the other hand, in Patent Document 2, since the photocurrent flowing through each pixel of the photometric sensor is logarithmically compressed and converted into a voltage before being output, there is no need to correct the black level using a light-shielded pixel.

  However, when the photocurrent of each pixel is used for subject tracking as in Patent Document 3, it is necessary to accurately detect, for example, the signal ratio of each color of RGB in order to perform correct color measurement. In order to accurately detect the signal ratio of each color, it is desirable that the photocurrent is not logarithmically compressed as in Patent Document 2 and is output in a linear state. When the photocurrent is output from the photometric sensor while maintaining the linearity, it is necessary to correct the black level with respect to the luminance level of each pixel in order to obtain the signal ratio of each color more accurately.

  Therefore, an object of the present invention is to provide an imaging apparatus capable of obtaining a more accurate luminance signal by performing appropriate OB clamping for each light receiving sensitivity of a pixel of a photometric sensor.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a photometric sensor having a plurality of pixels having a first sensitivity characteristic and a plurality of pixels having a second sensitivity characteristic different from the first sensitivity characteristic. The photometric sensor has an effective pixel region and a light-shielded pixel region for each of the plurality of pixels having the first sensitivity characteristic and the plurality of pixels having the second sensitivity characteristic. The signal of the effective pixel having the first sensitivity characteristic is corrected based on the signal output of the light-shielding pixel having the sensitivity characteristic, and the effective pixel having the second sensitivity characteristic is corrected based on the signal output of the light-shielding pixel having the second sensitivity characteristic. It is characterized by comprising a correction means for correcting the above signal.

  According to the present invention, a more accurate luminance signal can be obtained by performing an appropriate OB clamp according to the light receiving sensitivity of the pixel of the photometric sensor.

1 is a block diagram illustrating a configuration example of a digital camera that is a first embodiment of an imaging apparatus of the present invention. It is a schematic diagram which shows the example of arrangement | positioning of the focus detection area | region within an imaging screen. It is a schematic diagram which shows the example of arrangement | positioning of the photometry area | region within an imaging screen. It is a schematic diagram which shows the positional relationship of a focus detection area | region and a photometry area | region. It is a schematic diagram for demonstrating the longitudinal cross-section of the pixel contained in a 1st area | region. It is a schematic diagram for demonstrating the planar structure of the pixel contained in a 1st area | region. It is a schematic diagram for demonstrating the longitudinal cross-section structure of the pixel contained in a 2nd area | region. It is a schematic diagram for demonstrating the planar structure of the pixel contained in a 2nd area | region. It is a graph which shows the spectral sensitivity characteristic of the pixel which has a vertical structure contained in the 1st field. It is a graph which shows the spectral sensitivity characteristic of the pixel which is contained in a 2nd area | region and does not have a vertical structure. It is a graph which shows the spectral transmittance characteristic of a visibility correction filter and IR cut filter. It is a graph which shows the spectral sensitivity characteristic at the time of combining a visibility correction filter or an IR cut filter with a photometric sensor. It is a schematic diagram for demonstrating the example of arrangement | positioning of the OB pixel of a photometry sensor. It is a flowchart for demonstrating a focus detection operation | movement. FIG. 10 is a flowchart for explaining subject tracking operation. In the digital camera which is 2nd Embodiment of the imaging device of this invention, it is a schematic diagram which shows the example of arrangement | positioning of the focus detection area within an imaging screen. It is a schematic diagram which shows the example of arrangement | positioning of the photometry area | region within an imaging screen. It is a schematic diagram which shows the positional relationship of a focus detection area | region and a photometry area | region. It is a schematic diagram for demonstrating the example of arrangement | positioning of the OB pixel of a photometry sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration example of a digital camera which is a first embodiment of an imaging apparatus of the present invention.

  In the digital camera of this embodiment, as shown in FIG. 1, an interchangeable imaging lens 100 is detachably attached to a camera body 200 via a mount portion (not shown) having an electrical contact unit 107. The electrical contact unit 107 is provided with a terminal for a communication bus line including a communication clock line, a data transmission line, a data reception line, and the like, so that the camera body 200 and the imaging lens 100 can communicate with each other. .

  The camera body 200 communicates via the imaging lens 100 and the electrical contact unit 107 to control the driving of the focus lens 101 in the imaging lens 100 and the diaphragm 102 that adjusts the amount of light. In FIG. 1, only the focus lens 101 is shown as a lens in the imaging lens 100, but a variable magnification lens and a fixed lens (not shown) are provided in addition thereto, and these constitute a lens unit. In addition to the communication bus line, the electrical contact unit 107 is also provided with a synchronization signal line for transmitting the image accumulation timing from the camera body 200 side to the imaging lens 100 side.

  The light flux from the subject is guided to the quick return mirror 203 in the camera body 200 via the lens unit including the focus lens 101 in the imaging lens 100 and the diaphragm 102. The quick return mirror 203 is disposed obliquely with respect to the optical axis in the photographing optical path, and retracts to the first position (illustrated position) for guiding the light beam from the subject to the upper viewfinder optical system and out of the photographing optical path. It can be moved to the second position.

  The central portion of the quick return mirror 203 is a half mirror, and when the quick return mirror 203 is down to the first position, a part of the light beam from the subject passes through the half mirror portion. The transmitted light beam is reflected by a sub mirror 204 provided on the back side of the quick return mirror 203 and guided to a phase difference AF sensor 205 that constitutes an automatic focus adjustment unit together with a focus detection circuit 206. The focus detection circuit 206 detects the focus state of the imaging lens 100 using the phase difference AF sensor 205.

  On the other hand, the light beam reflected by the quick return mirror 203 reaches the eyes of the photographer through a finder optical system including a finder screen 202, a pentaprism 201, and an eyepiece lens 207 existing on the focus surface.

  When the quick return mirror 203 is moved up to the second position (withdrawn from the imaging optical path), the light flux from the imaging lens 100 passes through the focal plane shutter 210, which is a mechanical shutter, and the optical filter 211 to the imaging device 212. Reach. The optical filter 211 has a function of cutting infrared rays and guiding only visible light to the image sensor 212 and a function as an optical low-pass filter. The focal plane shutter 210 includes a front curtain and a rear curtain, and controls transmission and blocking of the light flux from the imaging lens 100.

  When the quick return mirror 203 is raised to the second position, the sub mirror 204 is also folded with respect to the quick return mirror 203 and retracts out of the photographing optical path. The quick return mirror 203 is raised to the second position not only during still image shooting but also during live view.

  The camera body 200 includes a system controller 230 that controls the entire digital camera. The system controller 230 is configured by a CPU, an MPU, and the like, and controls operations of respective circuits described later. The system controller 230 communicates with the lens controller 108 in the imaging lens 100 via the electrical contact unit 107 via a communication bus line. Similarly to the system controller 230, the lens controller 108 is also configured by a CPU, MPU, and the like, and controls the operation of each circuit in the imaging lens 100.

  In communication between the system controller 230 and the lens controller 108, a drive command, a stop command, a drive amount, a required drive speed, a drive amount of the aperture 102, and a transmission request for various data on the lens side are transmitted from the system controller 230. Is done. From the lens controller 108, status information indicating whether or not the focus lens 101 and the diaphragm 102 are being driven, and various parameters on the lens side such as an open F value, a focal length, and a settable driving speed are transmitted.

  At the time of focus control, the system controller 230 instructs the lens controller 108 about the lens driving direction, the driving amount, and the driving speed by communication. When the lens controller 108 receives a lens driving command from the system controller 230, the lens controller 108 controls the lens driving mechanism 103 that performs focusing by driving the focus lens 101 in the optical axis direction via the lens driving control circuit 104. The lens driving mechanism 103 has a stepping motor or a DC motor as a driving source.

  When the lens controller 108 receives the aperture drive command from the system controller 230, the lens controller 108 controls the aperture drive mechanism 105 that drives the aperture 102 via the aperture drive control circuit 106, and drives the aperture 102 to the commanded value.

  The system controller 230 is also connected to the shutter control circuit 215 and the photometry circuit 209. The shutter control circuit 215 controls the driving of the front and rear curtains of the focal plane shutter 210 in accordance with a signal from the system controller 230. Further, the system controller 230 transmits a lens driving command to the lens controller 108 to control the lens driving mechanism 103 via the lens driving control circuit 104. As a result, a subject image is formed on the image sensor 212.

  Further, the system controller 230 transmits an aperture drive command to the lens controller 108 based on the set Av value, and the lens controller 108 controls the aperture drive mechanism 105 via the aperture drive control circuit 106. Further, the system controller 230 outputs a control signal to the shutter control circuit 215 based on the set Tv value.

  The drive source of the front curtain and rear curtain of the focal plane shutter 210 is constituted by a spring, and after the shutter travels, a spring charge is required for the next operation. The shutter charge mechanism 214 controls this spring charge. Further, the mirror drive mechanism 213 drives the quick return mirror 203 up and down.

  In addition, a camera DSP 227 is connected to the system controller 230. The camera DSP 227 is a correction data sample circuit and a correction circuit configured by a DSP (digital signal processor). The camera DSP 227 executes control of the image sensor 212 and correction and processing of image data input from the image sensor 212 based on commands from the system controller 230. Auto white balance is also included in the items of image data correction / processing.

  The auto white balance is a function for correcting the maximum luminance portion in the photographed image to a predetermined color (white). For auto white balance, the correction amount can be changed by a command from the system controller 230.

  An A / D converter 217, a video memory 221 and a work memory 226 are connected to the camera DSP 227 via a timing generator 219 and a selector 222, respectively.

  The electrical signal output from the image pickup device 212 has reset noise or the like removed by a known correlated double sampling method or the like, and also sequentially for each pixel via a CDS / AGC circuit 216 that amplifies the output to a predetermined signal level. The digital signal is converted by the A / D converter 217.

  Here, the image sensor 212 is driven by an output from a driver 218 that controls horizontal driving and vertical driving for each pixel based on a signal from a timing generator 219 that determines the overall driving timing. Thus, the subject image is photoelectrically converted, and an image signal is generated and output.

  The CDS / AGC circuit 216 that analogly processes the image signal output from the image sensor 212 and converts it to a predetermined signal level, and the A / D converter 217 also operate based on the timing signal from the timing generator 219. The output from the A / D converter 217 is input to the memory controller 228 via the selector 222 that selects a signal based on the signal from the system controller 230, and is all transferred to the DRAM 229 that is a frame memory.

  After the shooting operation is completed, the contents of the DRAM 229 storing the shooting data are transferred to the camera DSP 227 via the selector 222 under the control of the memory controller 228. The camera DSP 227 generates each color signal of RGB based on each pixel data of each shooting data stored in the DRAM 229.

  In a digital video camera or a compact digital camera, each color signal generated by the camera DSP 227 is periodically (every frame) transferred to the video memory 221 in a pre-shooting state, so that the monitor display unit 220 displays a finder (live view). Etc.

  On the other hand, in a single-lens reflex digital camera, since the image pickup device 212 is usually shielded from light by the quick return mirror 203 and the focal plane shutter 210 before shooting, live view display cannot be performed. In this regard, the live view operation can be performed by raising the quick return mirror 203 and retracting it from the photographing optical path and then opening the focal plane shutter 210. Further, when the image signal from the image sensor 212 is processed by the camera DSP 227 or the system controller 230 during live view, a contrast evaluation value corresponding to the sharpness of the image can be obtained. Then, it is possible to perform contrast AF using the contrast evaluation value.

  Further, during live view, the light beam does not reach the photometric sensor 208 for photometry, and therefore the imaging surface AE that performs photometric calculation based on the luminance information of the image data from the image sensor 212 is performed. The average brightness value for each photometric area in the screen necessary for the imaging surface AE is also obtained by processing by the camera DSP 227 or the system controller 230.

  At the time of shooting, each pixel data for one frame is read from the DRAM 229 according to a control signal from the system controller 230, subjected to image processing by the camera DSP 227, and temporarily stored in the work memory 226. Then, the data in the work memory 226 is compressed by the compression / decompression circuit 225 based on a predetermined compression format, and the result is stored in an external nonvolatile memory (external memory) 224. Examples of the nonvolatile memory 224 include a flash memory, a hard disk, and a magnetic disk.

  The display unit 231 connected to the system controller 230 displays the operation state of the camera set or selected by each switch described later using a display element such as a liquid crystal element, LED (light emitting diode), or organic EL. The operation switch 232 is an operation member that performs operation input for various setting items of the camera body 200. The release switch (SW1) 233 is a switch for starting a photographing preparation operation such as a photometry / focus detection area. The release switch (SW2) 234 is a switch for starting a photographing operation (charge accumulation and charge read operation for acquiring a still image). The live view mode switch 235 is a switch for controlling on / off of the live view display.

  The system controller 230 is also connected to the subject tracking circuit 236. The subject tracking circuit 236 is a circuit that tracks the position of the subject of interest based on the output of each pixel included in the photometric sensor 208. Details of the operation of the subject tracking circuit 236 will be described later.

  On the other hand, in the imaging lens 100 as a lens unit, a memory 109 is connected to the lens controller 108. The memory 109 stores performance information such as a focal length and an aperture value of the imaging lens 100, lens ID (identification) information that is unique information for identifying the imaging lens 100, and a distance from the lens end corresponding to the focus position. Information is stored. The memory 109 stores information received from the system controller 230 through communication.

  The performance information and lens ID information stored in the memory 109 are transmitted to the system controller 230 via the lens controller 108 by initial communication when the imaging lens 100 is attached to the camera body 200. The system controller 230 stores the received performance information and lens ID information in the EEPROM 223.

  Further, the imaging lens 100 is provided with a lens position information detection circuit 110 for detecting position information of the focus lens 101. The lens position information detected by the lens position information detection circuit 110 is read by the lens controller 108. The plurality of lens position information is used for driving control of the focus lens 101 by the lens driving mechanism 103, or transmitted as lens position information to the system controller 230 via the electrical contact unit 107.

  The lens position information detection circuit 110 includes, for example, a pulse encoder that detects the number of rotation pulses of a motor that constitutes the lens driving mechanism 103. The output from the lens position information detection circuit 110 is counted by a hardware counter (not shown) in the lens controller 108. When the focus lens 101 is driven, the lens position information is counted by hardware. When the lens controller 108 reads the lens position information, it accesses the internal hardware counter register and reads the stored counter value.

  FIG. 2 is a schematic diagram illustrating an arrangement example of focus detection areas in the imaging screen. In FIG. 2, a plurality of (21 in the figure, A1 to A21) focus detection areas 251 are arranged on the imaging screen 250.

  FIG. 3 is a schematic diagram showing an example of the arrangement of the photometric areas in the imaging screen. In FIG. 3, a plurality (63 Bmn (63 integers where m = 0 to 6 and n = 0 to 8)) photometry areas 252 are arranged on the imaging screen 250. Here, m represents a row number, and n represents a column number.

  FIG. 4 is a schematic diagram showing the positional relationship between the focus detection area and the photometry area. In FIG. 4, 21 focus detection areas 251 and 21 photometry areas 252 are arranged so as to overlap each other in a substantially circular first area including the center of the imaging screen 250. In addition, 48 photometric areas 252 are arranged in the second area around the first area. Note that the focus detection area 251 and the photometry area 252 do not have to completely coincide with each other, and at least a part thereof may overlap.

  Here, the pixel structure in the photometric sensor 208 includes a pixel included in the first region and a pixel included in the second region due to the necessity of light source detection used for correcting the focus detection result together with the above-described photometry. Different.

  Next, the difference in pixel structure will be described.

  FIG. 5 is a schematic diagram for explaining a vertical cross-sectional structure of a pixel included in the first region. In FIG. 5, a p-substrate 301 is a p-type semiconductor substrate. The cn regions 302 and 303 are p-type regions formed for electrical connection with the p substrate 301 and for separating adjacent pixels. Electrodes are drawn from the cn regions 302 and 303, and the p substrate 301 is grounded to electrically separate the pixels.

  nEpi 304 is an n-type epitaxial layer formed on the p substrate 301. The p-well 305 is a p-type well formed inside the nEpi 304. The n region 306 is an n-type region formed inside the p-well 305. Ir307 is a photocurrent flowing through the PN junction of the photoelectric conversion unit configured by nEpi304 and p-well305. The photoelectric conversion unit according to Ir307 has a spectral sensitivity peak in the red region to the near infrared region. Iw 308 is a photocurrent flowing through the PN junction of the photoelectric conversion unit configured by the p-well 305 and the n region 306. The photoelectric conversion unit according to Iw308 has a spectral sensitivity peak in the visible light region.

  Note that the pixel structure shown in FIG. 5 is an example, and each photoelectric conversion unit having a plurality of mutually different spectral sensitivity characteristics may have a vertical structure that is at least partially different in the incident direction of the subject image.

  FIG. 6 is a schematic diagram for explaining a planar structure of pixels included in the first region. In FIG. 6, the photocurrent Ir307 generated at the PN junction of nEpi304 and p-well 305 is integrated by the gate capacitance of the source follower amplifier transistor B and temporarily stored as photocharge. Similarly, the photocurrent Iw308 generated at the PN junction between the p-well 305 and the n region 306 is also temporarily stored.

  In order to sequentially read out the integrated photocharge as a voltage, a read pixel is selected in units of rows by the pixel selection transistor S, and the photocharge of the selected pixel is connected to the column output line by the selection transistor S. To the column output line. The reset transistor Re is connected to the reset potential Vn or Vp (Vn> Vp), and is used for resetting the capacitance in the PN junction and the source follower amplifier transistor B.

  FIG. 7 is a schematic diagram for explaining a vertical cross-sectional structure of pixels included in the second region. In FIG. 7, parts having the same structure as in FIG.

  The pixel structure shown in FIG. 7 is different from the pixel structure shown in FIG. 5 in that the n region 306 is not formed inside the p-well 305. Iwr 501 is a photocurrent that flows in the PN junction of the photoelectric conversion unit configured by nEpi 304 and p-well 305. Since the n region 306 in FIG. 5 is not formed, the photocurrent Iwr501 is obtained by adding the photocurrents Ir307 and Iw308 in FIG.

  FIG. 8 is a schematic diagram for explaining a planar structure of pixels included in the second region. In FIG. 8, the photocurrent Iwr501 generated at the PN junction of nEpi304 and p-well 305 is integrated by the gate capacitance of the source follower amplifier transistor B and temporarily stored as photocharge.

  In order to sequentially read out the integrated photocharge as a voltage, a read pixel is selected in units of rows by the pixel selection transistor S, and the photocharge of the selected pixel is connected to the column output line by the selection transistor S. To the column output line. The reset transistor Re is connected to the reset potential Vn or Vp and is used for resetting the capacitance in the PN junction and the source follower amplifier transistor B.

  Next, the spectral sensitivity of the pixels included in the first area and the pixels included in the second area will be described.

  The pixels in the photometric sensor 208 are different from each other in the pixels included in the first region and the pixels included in the second region due to the necessity of light source detection used for correcting the focus detection result together with the above-described photometry. Has sensitivity.

  FIG. 9 is a graph showing the spectral sensitivity characteristics of the pixels included in the first region, that is, the pixels having a vertical structure. In FIG. 9, reference numeral 701 indicates the spectral sensitivity characteristic of the first photoelectric conversion unit that is configured by a PN junction between the p-well 305 and the n region 306 of the pixel and outputs the photocurrent Iw. The first photoelectric conversion unit has a peak sensitivity with respect to a wavelength near 500 nm. Here, the spectral sensitivity characteristic of the pixel having the vertical structure corresponds to an example of the first sensitivity characteristic of the present invention.

  Reference numeral 702 denotes a spectral sensitivity characteristic of a second photoelectric conversion unit configured by a PN junction of the pixel nEpi 304 and the p-well 305 and outputting the photocurrent Ir. The second photoelectric conversion unit has a peak sensitivity with respect to a wavelength near 750 nm.

  Note that the peak sensitivities of the spectral sensitivity distributions of the first photoelectric conversion unit and the second photoelectric conversion unit may be shifted to the short wavelength side or the long wavelength side, respectively.

  FIG. 10 is a graph showing the spectral sensitivity characteristics of the pixels included in the second region, that is, the pixels not having the vertical structure. In FIG. 10, reference numeral 703 indicates the spectral sensitivity characteristic of a conventional photometric sensor having a spectral sensitivity peak sensitivity of 650 nm. Here, the spectral sensitivity characteristic of the pixel not having the vertical structure corresponds to an example of the second sensitivity characteristic of the present invention.

  FIG. 11 is a graph showing the spectral transmittance characteristics of the visibility correction filter and the IR cut filter.

  In FIG. 11, reference numeral 704 denotes a spectral transmittance characteristic of the visibility correction filter. Although not shown, the visibility correction filter is disposed in front of the photometric sensor 208, and the spectral sensitivity characteristic of the photometric sensor 208 is represented by a human. Used to approximate the eye's specific luminous sensitivity characteristics. Reference numeral 705 denotes a spectral transmittance characteristic of the IR cut filter. Although not shown, the IR cut filter is disposed on the front surface of the phase difference AF sensor 205 and used to cut excess infrared rays. .

  12 is a graph showing spectral sensitivity characteristics when the photometric sensor 208 is combined with the visibility correction filter or IR cut filter described in FIG.

  In FIG. 12, reference numeral 706 is a combination of the spectral transmittance characteristic 704 of the visibility correction filter and the spectral sensitivity characteristic 703 of the photoelectric conversion unit in the pixel in the second region constituted by pixels having no vertical structure of the PN junction. The spectral sensitivity characteristics (hereinafter referred to as conventional characteristics) are shown. The spectral sensitivity characteristic 703 of the photoelectric conversion unit in the pixel in the second region is corrected so as to have a peak sensitivity near 555 nm by the spectral transmittance characteristic 704 of the visibility correction filter.

  Reference numeral 707 denotes a spectrum obtained when a spectral sensitivity characteristic 701 of the IR cut filter is combined with the spectral sensitivity characteristic 701 of the first photoelectric conversion unit in the pixel in the first region composed of pixels having a vertical structure of a PN junction. Shows sensitivity characteristics. In this spectral sensitivity characteristic, the sensitivity of the blue and red components is relatively increased with respect to the conventional characteristic 706.

  Reference numeral 708 indicates the spectral sensitivity characteristic when the spectral transmittance characteristic 705 of the IR cut filter is combined with the spectral sensitivity characteristic of the second photoelectric conversion unit in the pixel in the first region. This spectral sensitivity characteristic has a peak sensitivity around 700 nm.

  Next, an arrangement example of OB pixels in the photometric sensor 208 will be described.

  FIG. 13 is a schematic diagram for explaining an arrangement example of OB pixels of the photometric sensor 208.

  In FIG. 13, a photometric area group 801 is an area group that is not shielded in order to perform photometry upon receiving subject light. The photometric area group 801 includes the photometric areas B00 to B68 described with reference to FIG. A photometric area 802 surrounded by a broken line in FIG. 13 is a photometric area included in the first area, and the PN described with reference to FIG. 2 is used to perform light source detection used for correcting the focus detection result. It is composed of effective pixels having a vertical structure of junction.

  In addition, since OB clamping is performed on the pixels in the first area and the pixels in the second area included in the photometry area group 801, the photometry sensor 208 has the pixel structure described in FIG. For example, a vertical structure light-shielded pixel region 803 whose side is shielded by an aluminum layer is provided. Further, the photometric sensor 208 includes a non-vertical structure light-shielded pixel region 804 that similarly shields light from the incident light incident side in the pixel structure described with reference to FIG.

  When the photometric sensor 208 outputs a signal of the effective pixel 802 having the vertical structure of the PN junction in the first region, the photometry sensor 208 uses the signal output of the vertical structure light-shielding pixel region 803 having the vertical structure of the PN junction to output black. Perform level correction. On the other hand, when the photometric sensor 208 outputs a signal of an effective pixel that is in the second region and does not have the vertical structure of the PN junction, the signal output of the non-vertical structure light-shielding pixel region 804 that also has no vertical structure of the PN junction. To correct the black level.

  Since the light receiving sensitivity differs between vertical and non-vertical pixels, when performing black level correction using light-shielded pixels, it is necessary to detect both black and light structures by arranging both the vertical and non-vertical structures. There is. For this reason, the photometric sensor 208 of this embodiment includes both the vertical structure light-shielding pixel region 803 and the non-vertical structure light-shielding pixel region 804.

  With such a configuration, it is possible to obtain a more accurate luminance signal because appropriate OB clamping is performed for each light receiving sensitivity.

  Next, with reference to FIG. 14, a focus detection operation for performing light source detection and correcting a focus detection result in the digital camera of the present embodiment will be described. Each process in FIG. 14 is executed by the CPU or the like of the system controller 230 by loading a program stored in a predetermined storage area of the digital camera into the RAM.

  In step S901, the system controller 230 determines whether the release switch (SW1) 233 has been pressed to perform a focus detection request operation. If the release switch (SW1) 233 has been pressed, the process proceeds to step S902. .

  In step S902, the system controller 230 communicates with the lens controller 108, and information related to the imaging lens 100, such as the focal length of the lens, the maximum aperture value, the minimum aperture value, and chromatic aberration data necessary for focus detection and photometry. To get. Then, the system controller 230 outputs the acquired information regarding the imaging lens 100 to the photometric circuit 209, and the process proceeds to step S903.

  In step S903, the system controller 230 starts a timer (not shown) built in the photometry circuit 209, and proceeds to step S904.

  In step S904, the system controller 230 performs focus detection on the focus detection area selected by the system controller 230 or the user among the 21 focus detection areas 251 in FIG.

  Then, the system controller 230 calculates the defocus amount of the focus lens 101 based on the focus detection result, calculates the drive amount of the focus lens 101 from the calculated defocus amount, and proceeds to step S905.

  In step S905, the system controller 230 sequentially outputs the output voltages Vwr and Vw, which are photometric outputs including the visible light region, from the photometric sensor 208, and A / D converts them into digital data by the photometric circuit 209.

  The system controller 230 stores the digital data A / D converted by the photometry circuit 209 in a built-in memory (not shown), and the process proceeds to step S906. Here, the output voltage Vwr is specifically the output voltage of the pixels B00 to B12, B16 to B21, B27 to B31, B37 to B41, B47 to B52, and B56 to B68 in FIG. The output voltage Vw is an output voltage of the pixels B13 to B15, B22 to B26, B32 to B36, B42 to B46, and B53 to B55 in FIG.

  In step S906, the system controller 230 sequentially outputs a photometric output in the near-infrared region from the photometric sensor 208, that is, an output voltage Vr from the second photoelectric conversion unit, and A / D converts the digital voltage by the photometric circuit 209. Convert to data.

  The system controller 230 stores the digital data A / D converted by the photometric circuit 209 in a built-in memory (not shown), and the process proceeds to step S907. Here, the output voltage Vr is specifically the output voltage of the pixels B13 to B15, B22 to B26, B32 to B36, B42 to B46, and B53 to B55 in FIG.

  In step S907, the system controller 230 performs photometric calculation of each pixel from each output voltage Vw and Vwr acquired in step S605, calculates an EV value that is exposure amount information of each pixel, and proceeds to step S908.

  In step S908, the system controller 230 obtains an exposure correction value ΔEV corresponding to the ratio (colorimetric information) of the visible light photometric output Vw data and the near infrared photometric output Vr data of each pixel. The exposure correction value ΔEV is a value for correcting the value of Vw data in which an error occurs due to the color of the subject and the color temperature of the light source that illuminates the subject.

  Then, the system controller 230 calculates the EV value after light source correction of each pixel by adding the exposure correction value ΔEV to the exposure amount information EV calculated in step S907. Further, the system controller 230 performs a predetermined weighting operation on the EV values after light source correction of all the pixels, calculates a shutter speed and an aperture value for performing exposure control according to the calculation result, and proceeds to step S909. .

  In step S909, the system controller 230 corrects the defocus amount calculated in step S904 according to the ratio (colorimetric information) of the visible light metering output Vw data and the near infrared metering output Vr data of each pixel. The focus correction value ΔBP is calculated.

  In the present embodiment, as described with reference to FIG. 13, the photometric area (pixels of the photometric sensor 208) has a one-to-one correspondence with the focus detection area in the central area of the imaging screen. Therefore, the focus correction value ΔBP is calculated using the ratio of the Vw data and the Vr data of the pixel of the photometric sensor 208 corresponding to the focus detection area. Specifically, the focus correction value ΔBP is calculated using the ratio between the Vw data and the Vr data and the chromatic aberration information of the imaging lens 100.

  Then, the system controller 230 adds the focus correction value ΔBP to the defocus amount calculated in step S904, calculates the final drive amount of the focus lens 101, and proceeds to step S910.

  In step S910, the system controller 230 transmits information on the driving amount of the focus lens 101 calculated in step S909 to the lens controller 108, drives the focus lens 101, and proceeds to step S911.

  In step S911, the system controller 230 determines whether the release switch (SW2) 234 has been pressed. If it has been pressed, the process proceeds to step S912. If not, the process proceeds to step S913.

  In step S912, the system controller 230 performs exposure control based on the shutter speed and aperture value calculated in step S908, executes shooting, and ends the process.

  In step S913, the system controller 230 determines whether or not a predetermined time has elapsed and timed out. If timed out, the focus detection and photometry operation are terminated. If not timed out, the process returns to step S901. Repeat focus detection and photometry.

  Next, a subject tracking operation for performing subject tracking and updating the focus detection area in the digital camera of the present embodiment will be described.

  Digital data of the photometric output voltages Vw and Vwr including a visible light region stored in a memory (not shown) of the system controller 230 is output to the subject tracking circuit 236 and used for tracking the subject of interest.

  FIG. 15 is a flowchart for explaining the subject tracking operation by the subject tracking circuit 236. Each process in FIG. 15 is executed by a CPU or the like of the system controller 230 by loading a program stored in a predetermined storage area of the digital camera into the RAM.

  In step S1001, the system controller 230 determines whether or not the photometric operation by the photometric sensor 208 is started by pressing the release switch (SW1) 233. If the photometric operation is started, the process proceeds to step S1002.

  In step S1002, the system controller 230 starts a timer (not shown) built in the subject tracking circuit 236, and proceeds to step S1003.

  In step S1003, the system controller 230 sets a tracking counter (not shown) built in the subject tracking circuit 236 to an initial value n = 1, and the process proceeds to step S1004.

  In step S1004, the system controller 230 acquires the digital data of the output voltages Vw and Vwr A / D converted by the photometric circuit 209, and the process proceeds to step S1005.

  In step S1005, the system controller 230 determines whether or not the initial value n of the tracking counter built in the subject tracking circuit 236 is 1, and if the initial value n is 1, the process proceeds to step S1006. If n is not 1, the process proceeds to step S1007.

  In step S1006, the system controller 230 calculates digital data corresponding to the selected focus detection area and its adjacent digital data range from the digital data (hereinafter referred to as input information) of the output voltages Vw and Vwr of the photometry circuit 209. Set as tracking frame. Then, the system controller 230 stores digital data set as a tracking frame (hereinafter referred to as tracking information) in a memory (not shown), and proceeds to step S1011.

  In step S1007, since the initial value is n ≧ 2, the system controller 230 determines where the tracking information stored in the memory in step S1006 is moving with the input information acquired in the latest step S1004 by a known correlation calculation. Calculated as a movement vector. After the calculation, the process proceeds to step S1008.

  In step S1008, the system controller 230 determines whether the size of the movement vector calculated in step S1007 exceeds a predetermined movement amount and the tracking frame needs to be updated. The predetermined movement amount is an amount determined based on the vertical and horizontal intervals of each pixel in the photometric areas B00 to B68 described with reference to FIG. The system controller 230 proceeds to step S1009 if the tracking frame needs to be updated, and proceeds to step S1011 if the tracking frame needs not be updated.

  In step S1009, the system controller 230 updates the tracking frame setting position based on the movement vector calculated in step S1007, and the process proceeds to step S1010.

  In step S1010, the system controller 230 updates the focus detection area in the same manner as the tracking frame is updated in step S1009, and the process proceeds to step S1011. If the focus detection area does not exist at the movement vector pointing destination, the system controller 230 bypasses the update of the focus detection area and proceeds to step S1011.

  In step S1011, the system controller 230 determines whether or not the release switch (SW2) 234 has been pressed. If the release switch (SW2) 234 is pressed, the system controller 230 ends the subject tracking operation in order to perform the imaging operation in step S912 in FIG. 14, and proceeds to step S1012 if not pressed.

  In step S1012, the system controller 230 determines whether a predetermined time has elapsed from the start of the timer in step S1002 and timed out. If the system controller 230 has timed out, the subject tracking operation ends. If not, the system controller 230 proceeds to step S1013.

  In step S1013, the system controller 230 sets an initial value n of a tracking counter (not shown) built in the subject tracking circuit 236 to n + 1, returns to step S1004, and repeats the subject tracking operation.

  As described above, in the present embodiment, in a digital camera having a photometric sensor 208 in which a plurality of pixels having different light receiving sensitivities are mixed and the amount of incident light is proportional to the output, appropriate OB clamping is performed for each light receiving sensitivity. An accurate luminance signal can be obtained. In addition, since an accurate luminance signal can be obtained, it is possible to improve the accuracy of operations such as photometry, light source detection, and subject tracking described above.

(Second Embodiment)
A digital camera which is a second embodiment of the imaging apparatus of the present invention will be described with reference to FIGS.

  In the first embodiment, the vertical structure OB pixel and the non-vertical structure OB pixel of the photometric sensor 208 are arranged in the entire area in the vertical direction and the horizontal direction. On the other hand, in the present embodiment, either one of the photometric sensor 208 and the non-vertical structured light-shielding pixel are selectively arranged according to the necessity of the light-shielding pixel region and thus the photometric sensor 208. Plan Note that this embodiment is different from the first embodiment only in the internal configuration of the photometric sensor 208, and only the differences will be described.

  FIG. 16 is a schematic diagram showing an example of the arrangement of focus detection areas in the imaging screen. In FIG. 16, a plurality of (21 in the figure, C1 to C21) focus detection areas 1101 are arranged on the imaging screen 1100.

  FIG. 17 is a schematic diagram illustrating an example of the arrangement of the photometric areas in the imaging screen. In the imaging screen 1100, photometric areas R00 to R68 with the R filter attached to the front surface, photometric areas Gr00 to Gr68 and Gb00 to Gb68 with the G filter attached to the front surface, and photometric area B00 with the B filter attached to the front surface. To B68 are arranged.

  A column (hatched area in the figure) composed of Gr00 to Gr68 and B00 to B68 is a photometric area composed of the PN junction vertical structure pixels described in FIGS. 5 and 6 of the first embodiment. Represents that. The columns (non-hatched areas in the figure) composed of R00 to R68 and Gb00 to Gb68 are photometric areas composed of the non-vertical structure pixels described in FIGS. 7 and 8 of the first embodiment. Represents.

  FIG. 18 is a schematic diagram showing the positional relationship between the focus detection area and the photometry area. Near the center of the imaging screen 1100, 21 photometry areas are arranged so as to overlap (coincide with) each other, as well as the 21 focus detection areas 1101. In FIG. 18, pixels in a part of the photometry area (Gr13 to Gr15, Gr22 to Gr26, Gr32 to Gr36, Gr42 to Gr46, Gr53 to Gr55 21 pixels) in which the Gr filter is arranged in front are mutually connected to the focus detection area 1101. They are overlapping. Note that the focus detection area and the photometry area do not have to coincide completely, and at least a part of them may overlap.

  Next, an arrangement example of the OB pixels of the photometric sensor 208 will be described.

  FIG. 19 is a schematic diagram for explaining an arrangement example of OB pixels of the photometric sensor 208. In the figure, the region composed of R00 to R68, Gr00 to Gr68, Gb00 to Gb68, and B00 to B68 is a photometric region group that is not shielded in order to receive subject light and perform photometry.

  As described with reference to FIG. 18, the photometric region column 1205 composed of Gr00 to Gr68 and B00 to B68 is composed of effective pixels having a vertical structure of PN junction, and the photometric region column 1206 composed of R00 to R68 is non-displayed. It is composed of vertical effective pixels.

  A region 1203 indicated by a diagonally downward slanting line (broken line) is a vertical structure light-shielded pixel region which is composed of PN-junction vertical structure pixels and whose object light incident side is shielded by an aluminum layer, for example. A region 1204 indicated by a diagonal line rising to the right (broken line) is a non-vertical structure light-shielded pixel region that is configured by pixels that are not PN-junction vertical structures and the incident light incident side is shielded by, for example, an aluminum layer.

  The vertical structure light-shielding pixels 1203 are arranged on the upper end of the column 1205 of PN junction vertical structure pixels in the photometry region group and on the left side of the photometry region group, and are arranged with respect to the PN junction vertical structure pixels. It is an arrangement that can perform OB clamping in the direction (vertical direction) and the row direction (lateral direction). The non-vertical structure pixel 1204 is disposed on the upper end of the column 1206 of pixels that are not vertical in the photometry area group and on the left side of the photometry area group, and is arranged in the column direction and the row direction with respect to the non-vertical structure pixel. The OB clamp can be arranged.

  As described above, in this embodiment, the vertical structure light-shielded pixel 1203 is arranged at the upper end of the column 1205 of PN junction vertical structure pixels, and the non-vertical is arranged at the upper end of the column 1206 of non-vertical pixels. The structural light-shielding pixels 1204 are arranged, and the light-shielding pixels are alternately arranged in the row direction. As a result, the photometric sensor 208 can be reduced in size only in the region 1207 surrounded by the broken lines above the vertical structure light-shielding pixels 1203 and the non-vertical structure light-shielding pixels 1204. Further, the readout time can be shortened by reducing the number of pixels to be read out. Other configurations and operational effects are the same as those of the first embodiment.

  In addition, this invention is not limited to what was illustrated by said each embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

  For example, in the second embodiment, the vertical structure light-shielding pixel 1203 is arranged at the end of the column 1205 of PN junction vertical structure pixels, and the non-vertical structure light-shielded pixel 1204 is arranged at the end of the column 1206 of non-vertical pixels. However, the present invention is not limited to this. For example, the vertical structure light-shielding pixel 1203 is arranged at the end in the row direction of the vertical structure pixel of the PN junction, and the non-vertical structure light-shielding pixel 1204 is arranged at the end in the row direction of the non-vertical structure pixel. Alternatively, they may be arranged alternately in the column direction.

100 Imaging Lens 208 Photometric Sensor 209 Photometric Circuit 200 Camera Body 230 System Controller 236 Subject Tracking Circuit

Claims (4)

An imaging apparatus comprising a photometric sensor having a plurality of pixels having a first sensitivity characteristic and a plurality of pixels having a second sensitivity characteristic different from the first sensitivity characteristic,
The photometric sensor has an effective pixel region and a light-shielded pixel region for each of the plurality of pixels having the first sensitivity characteristic and the plurality of pixels having the second sensitivity characteristic,
The signal of the effective pixel of the first sensitivity characteristic is corrected based on the signal output of the light-shielded pixel having the first sensitivity characteristic, and the second sensitivity is corrected based on the signal output of the light-shielded pixel having the second sensitivity characteristic. An image pickup apparatus comprising correction means for correcting a signal of a characteristic effective pixel. The plurality of pixels having the first sensitivity characteristic are vertical structure pixels having a PN junction vertical structure in the thickness direction of the semiconductor substrate, and the plurality of pixels having the second sensitivity characteristic have the PN junction vertical structure. There are no non-vertical structure pixels,
The imaging apparatus according to claim 1. The light shielding pixel of the vertical structure is arranged at the end of the column or row of the effective pixels of the vertical structure of the PN junction, and the light shielding pixel of the non-vertical structure is arranged at the end of the column or row of the effective pixels of the non-vertical structure Then, the light shielding pixels of the vertical structure and the non-vertical structure are alternately arranged in the row direction or the column direction.
The imaging apparatus according to claim 2. The focus detection area and the photometry area of the imaging screen are arranged to overlap each other in the plurality of pixel areas having the first sensitivity characteristic, and the photometry of the imaging screen is arranged in the plurality of pixel areas having the second sensitivity characteristic. Area is placed,
The imaging apparatus according to any one of claims 1 to 3, wherein