JP2011022458A - Focus detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform focus detection of an object with sufficient precision without overflowing a line sensor. <P>SOLUTION: A focus detector arranges monitor sensors juxtaposing a minute sensor part 140m on the side of the line sensor juxtaposing a plurality of photodiode pairs 120Aj, 120Bj respectively. Each minute sensor part 140m includes a photoelectric conversion part 142 composed of a photodiode, and a pixel signal readout circuit 144 for the monitor sensor for outputting pixel signals generated in the photoelectric conversion part 142 by photoelectric conversion. The focus detector forms a center part 142X along a longitudinal direction of the photoelectric conversion part 142 in the form of a notch, and stores the signal readout circuit 144 in the notch part 142X. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a focus detection apparatus mounted on a photographing apparatus such as a single-lens reflex camera.

  A single-lens reflex camera is equipped with a phase difference type focus detection device as an automatic focus adjustment (AF) mechanism. The focus detection apparatus includes an imaging optical system including a condenser lens and a separator lens. In an area where a subject image is projected by the imaging optical system, a plurality of line sensor groups each having line sensors arranged in parallel are two. A set is arranged two-dimensionally (see, for example, Patent Document 1). Each line sensor has a configuration in which a plurality of photodiodes are arranged in parallel (for example, see Patent Document 2), and signal charges generated in each photodiode are read out as pixel signals.

  Usually, the line sensor is a charge accumulation type sensor, and the charge accumulation time is adjusted by a monitor sensor arranged beside the line sensor (see Patent Document 3). Further, since the amount of light received by each photodiode of the line sensor varies depending on the brightness distribution of the subject, the charge accumulation time of the line sensor is controlled independently for each photodiode.

  Monitor sensors equipped with photoelectric conversion elements (photodiodes, etc.) are designed to prevent the photodiodes in the line sensor from receiving light that exceeds the dynamic range and overflowing. ) In real time, and a monitor signal is output by the pixel signal readout circuit.

  When the monitor signal exceeds a predetermined threshold value, the charge accumulation (integration) of the corresponding line sensor ends, and the accumulated charge is temporarily stored in a memory or the like. When the charge accumulation of all the line sensors is completed, a series of pixel signals are output as the image signal of the subject image, and calculation processing for obtaining the defocus amount is performed.

JP 11-205694 A JP-A-2005-300844 JP 2006-145792 A

  The photoelectric conversion unit of the monitor sensor needs to receive light having the same intensity as that of the line sensor to be monitored, and needs to be equal to the amount of light received by the line sensor. Therefore, it is necessary to secure the length of the photoelectric conversion unit of the monitor sensor so as to cover the entire longitudinal direction of the line sensor to be monitored.

  However, if the photoelectric conversion unit of the monitor sensor is lengthened, the distance between the light receiving position and the signal readout circuit becomes long, and it takes time until light is received and output from the signal readout circuit. Therefore, if the light from the subject changes abruptly, the change cannot be monitored instantaneously. For example, if strong light suddenly hits only the vicinity of both ends of the photoelectric conversion unit of the monitor sensor, the line sensor receiving the same light before the monitor signal is output overflows due to charge accumulation. As a result, an accurate image signal of the subject image cannot be output.

  The focus detection apparatus of the present invention is a focus detection apparatus in which the monitor sensor can instantaneously and accurately detect the brightness of the subject regardless of the luminance distribution, and the plurality of lines arranged in the projection area of the subject image. A sensor, a plurality of monitor sensors arranged on the side (side) of the plurality of line sensors, respectively, for monitoring the amount of light received by the corresponding line sensor, and an image of the subject image based on the charges accumulated in the plurality of line sensors Image signal output means for outputting a signal. When used in a photographing apparatus such as a camera, for example, a plurality of line sensor groups are arranged in a cross shape.

  For example, the line sensor is configured by a plurality of photoelectric conversion elements (CMOS sensors or the like), and the line sensor photoelectric conversion units may be paired and arranged in parallel along the longitudinal direction. On the other hand, each monitor sensor includes at least one monitor photoelectric conversion unit (such as a photodiode) and at least one pixel signal readout circuit that outputs charges generated in the monitor photoelectric conversion unit as pixel signals. The monitor sensor may be on either side of the line sensor. The pixel signal readout circuit may perform signal output by converting signal charge into a voltage signal, amplification processing, and the like.

  In order to detect the brightness distribution of the subject in detail, it is preferable to monitor a predetermined number of photoelectric conversion units of the line sensor collectively, and each monitor sensor faces a predetermined number of line sensor photoelectric conversion units. It is preferable to provide a plurality of minute sensor units arranged in parallel along the longitudinal direction of the line sensor. In this case, each minute sensor unit includes a monitor photoelectric conversion unit and a pixel signal readout circuit.

  In the present invention, the monitor photoelectric conversion unit has a length facing the entire monitoring target area of the corresponding line sensor, and is configured to cover the entire area of the target line sensor along the longitudinal direction. The pixel signal readout circuit is disposed at a position where the distances from both ends of the monitor photoelectric conversion unit are substantially equal. That is, the pixel signal readout circuit is arranged along a transverse line passing through the central portion of the monitor photoelectric conversion unit. For example, the size is smaller than the monitor photoelectric conversion unit, and is shorter than the monitor photoelectric conversion unit along the longitudinal direction of the line sensor.

  Since the monitor sensor photoelectric conversion unit faces the entire area of the target line sensor, the monitor sensor receives light having the same luminance distribution regardless of the luminance distribution of light incident on the target area. On the other hand, the distance between the light receiving position and the pixel signal readout circuit on the left and right sides of the monitor photoelectric conversion unit is symmetrical and balanced. Therefore, even if the monitor photoelectric conversion unit becomes long or receives light at the end of the photoelectric conversion unit, the monitor signal readout time is shortened, and a monitor sensor with good response is realized.

  In order to provide a large number of ranging areas, it is desirable to arrange the line sensors in the projection area as much as possible and shorten the pitch between the line sensors. For this reason, it is desirable to form a notch in the center of the monitor photoelectric conversion unit of the monitor sensor and accommodate the pixel signal readout circuit of the monitor sensor in the notch of the monitor photoelectric conversion unit. The size of the monitor sensor is determined by the width of the monitor photoelectric conversion unit. That is, the size of the monitor sensor is determined regardless of the size of the pixel signal readout circuit, and the pitch between the line sensors can be made as short as possible.

  A focus detection apparatus according to another aspect of the present invention outputs, as a pixel signal, a plurality of monitor photoelectric conversion units arranged in parallel on each side of a plurality of line sensors arranged in a projection area of a subject image, and charges generated in the monitor photoelectric conversion units. A plurality of pixel signal readout circuits, the monitor photoelectric conversion unit has a length facing the entire monitoring target area of the corresponding line sensor, the pixel signal readout circuit is smaller in size than the monitor photoelectric conversion unit, and the monitor It is characterized in that the distance from both ends of the photoelectric conversion unit is approximately equal.

  Thus, according to the present invention, it is possible to accurately detect the focus of a subject without causing the line sensor to overflow.

It is a typical internal block diagram of the single-lens reflex digital camera which is 1st Embodiment. It is a block diagram of a focus detection part. FIG. 4 is an enlarged layout view of one line sensor and a monitor sensor corresponding thereto. It is an electric circuit diagram of a pixel signal readout circuit for line sensors. It is an electric circuit diagram of a pixel signal readout circuit for a monitor sensor. It is a wiring diagram of a pixel signal readout circuit for line sensors. It is a layout diagram of a line sensor and a monitor sensor in the second embodiment.

  Below, the digital camera which is this embodiment is demonstrated with reference to drawings.

  FIG. 1 is a schematic internal configuration diagram of a single-lens reflex digital camera according to the first embodiment.

  The single-lens reflex digital camera 10 includes a main body 12 and an interchangeable lens 14 that can be attached to and detached from the main body 12. Inside the main body 12, a pentagonal roof prism (hereinafter referred to as a pentaprism) 16, a quick return mirror 18, a focal plane. An image sensor 22 such as a shutter 20 and a CCD is provided.

  The photometry IC 23 arranged near the pentaprism 16 detects the brightness of the subject image formed by the focusing plate 17 arranged above the quick return mirror 18 in accordance with the TTL photometry method. Further, the AF module 24 disposed below the quick return mirror 18 detects the in-focus state according to the phase difference method.

  A system control circuit 30 including a ROM 36, a RAM 37, and a CPU 38 controls camera operations and outputs control signals to the peripheral control circuit 32, the display unit 33, the AF module 24, the photometric IC 23, the EEPROM 39, and the like. The peripheral control circuit 32 controls the exposure mechanism such as the focal plane shutter 20, the diaphragm (not shown), the image sensor 22, and acquires lens information from the lens memory 13.

  When the camera 10 is turned on, the photographing mode is set. The light passing through the photographic optical system 15 is guided to the pentaprism 16 by the quick return mirror 18, and the user visually recognizes the subject through a finder (not shown). When a release button (not shown) is pressed halfway for shooting, the photometry IC 23 detects the brightness of the subject, and the AF module 24 detects the in-focus state.

  A part of the light passing through the photographing optical system 15 passes through the quick return mirror 18 and is guided to the AF module 24 by the sub mirror 19. The AF module 24 includes a condenser lens 26, a separator mask 29, a separator lens 27, and a focus detection unit 40, and a separator mask 29 disposed at a position (conjugate surface) equivalent to the imaging surface (light receiving surface of the image sensor 22). The divided subject image is re-imaged on the focus detection unit 40 by the separator lens 27. The focus detection unit 40 outputs an image signal of a subject image projected as a pair.

  The system control circuit 30 performs defocus amount and focus adjustment based on the image signal sent from the AF module 24. That is, a control signal is output to the AF motor driver 34 according to the defocus amount detected by the AF module 24 and the direction of the focus shift. The AF motor 35 shifts the focusing lens in the photographing optical system 15 based on the drive signal from the AF motor driver 34. A series of focus detection and lens driving are performed until the in-focus state is reached.

  When focus adjustment is performed in the state where the release button is half-pressed and the brightness of the subject is detected, the system control circuit 30 calculates and determines an exposure value, that is, a shutter speed and an aperture value. When the release button is fully pressed, a series of recording operation processing is executed. That is, the subject image is formed on the image sensor 22 by the operations of the quick return mirror 18, the diaphragm, and the shutter 20, and an image signal for one frame is output from the image sensor 22 to the signal processing circuit 25. The signal processing circuit 25 generates digital image data and stores the image data in a recording medium such as a memory card (not shown).

  FIG. 2 is a block diagram of the focus detection unit.

  The focus detection unit 40 is configured by an integrated substrate on which a plurality of CMOS type line sensors are arranged. On the surface of the focus detection device 40, line sensor groups EA1 and EA2 are installed in the vertical direction of the substrate along the vertical direction of the subject image, and the line sensor groups EB1 and EB2 are set in the horizontal direction of the substrate along the horizontal direction of the subject image. is set up. The line sensor groups EA1, EA2, and EB1, EB2 face each other across the center of the substrate.

  The imaging optical system including the condenser lens 26, the separator mask 29, and the separator lens 27 forms subject images in two sets of subject images by pupil division, a projection area in which the line sensor groups EA1 and EA2 are arranged, and a line A pair of subject images are formed on the projection areas where the sensor groups EB1 and EB2 are arranged.

  Each line sensor group is composed of a plurality of line sensors arranged in the left-right or up-down direction at predetermined intervals, and the line sensors in the line sensor groups EA1, EA2 are arranged in parallel in the left-right direction, and the line sensors in the line sensor groups EB1, EB2 Are in parallel along the vertical direction. Each line sensor is composed of a plurality of photoelectric conversion elements (here, photodiodes) arranged one-dimensionally.

  The line sensor group EA1 includes nine line sensors LSA1 to LSA9, and functions as a reference line sensor. On the other hand, the line sensors LSA11 to LSA19 constituting the line sensor group EA2 function as reference line sensors. Similarly, the line sensors LSB1 to LSB5 constituting the line sensor group EB1 function as reference sensors, and the line sensors LSB6 to LSB10 constituting the line sensor group EB2 function as reference line sensors.

  In the line sensor groups EA1 and EB1, a series of monitor sensors LMA1 to LMA9 and LMB1 to LMB5 are arranged on the corresponding line sensor side. The monitor sensors LMA1 to LMA9 and LMB1 to LMB5 have a configuration in which a plurality of sensor units are arranged in parallel along the line sensor, and the corresponding line sensor region is divided into a plurality of areas for monitoring.

  The monitor sensors LMA1 to LMA9 are arranged in a line along the side surfaces and the longitudinal direction of the line sensors LSA1 to LSA9, respectively, and output the amount of received light (light intensity) as a monitor signal. Monitor sensors LMB1 to LMB5 also output monitor signals to monitor the amount of light received by line sensors LSB1 to LSB5.

  Further, vertical shift registers VSR1 to VSR9 and VSS1 to VSS5 for reading pixel signals are provided on the side of the line sensors LSA1 to LSA9 of the line sensor group EA1 and the line sensors LSB1 to LSB5 of the line sensor group EB1. The vertical shift registers VSR11 to VSR19 and VSS6 to VSS10 are similarly arranged for the line sensors EA2 and EB2. Further, a monitor sensor (not shown) for detecting the black level is arranged beside each monitor sensor of the line sensor groups EA1 and EB1.

  The AGC circuits 42A to 42C compare the monitor signal value sequentially output from each monitor sensor with a threshold value. The threshold value is an index value for determining whether or not the amount of light necessary for focus detection is incident on the target line sensor, and is set to prevent the dynamic range of the line sensor from being exceeded.

  When the monitor signal value exceeds the threshold, the amount of light necessary for focus detection is incident on the line sensor, so the control signal that terminates the charge accumulation (integration) of the corresponding line sensor, that is, the line sensor being monitored Is output. When the control signal is transmitted to the line sensor, the charge accumulation ends and the charge is temporarily stored in the line sensor.

  The charge accumulation time of the line sensor is independently controlled for each monitoring target area of the licensor, and the charge accumulation time of each line sensor is adjusted according to the light intensity distribution of the subject. When the charge accumulation of all the line sensors is completed, the accumulated charge is subjected to voltage conversion and amplification processing in a pixel signal readout circuit (not shown here) of each line sensor, and a pixel signal is generated.

  The focus detection unit 40 outputs a series of pixel signals generated by each line sensor. That is, a series of pixel signals generated by the vertical shift registers VSR1 to VSR9, VSR11 to VSR19, VSS1 to VSS5, VSS6 to VSS10 and the horizontal shift registers 45 and 46 arranged beside each line sensor are output to the output circuit 40A. Transferred.

  A series of pixel signals sent to the output circuit is sent to the system control circuit 30 as an image signal of the subject image. In the system control circuit 30, the phase difference is detected based on the image signal of the pair of line sensor groups, and the defocus amount is obtained.

  The logic circuit 44 controls the AGC circuits 42A to 42C, the vertical shift registers VSR1 to VSR9, VSR11 to VSR19, VSS1 to VSS5, VSS6 to VSS10, and the horizontal shift registers 45 and 46, sets a threshold for the monitor signal, and monitors Set an offset value based on the black level of the sensor.

  FIG. 3 is an enlarged layout view of one line sensor and a monitor sensor corresponding thereto. The configuration of the line sensor and the monitor sensor will be described with reference to FIG.

  FIG. 3 shows in detail a partial configuration of the line sensor LSB3 and the monitor sensor LMB3 shown in FIG. The line sensor LSB3 is a sensor in which a plurality of photodiodes are arranged in parallel, and the pair of photodiodes 120Aj (j = 1, 2,...) And 120Bj are staggered along the longitudinal direction of the line sensor LSB3. It is lined up like a child.

  The monitor sensor LMB3 is disposed at a predetermined distance on the upper side of the line sensor LSB3, and wiring portions 170 and 180 are provided on both sides of the monitor sensor LMB3. On the other hand, a vertical shift register 190 is provided on the lower side of the line sensor LSB3 with the wiring portion 185 interposed therebetween.

  The photodiodes 120Aj and 120Bj arranged in parallel with each other are arranged with the longitudinal direction thereof directed toward the line sensor array direction JK of the line sensor group EB1, and the upper photodiode 120Aj and the lower photodiode 120Bj are The wiring circuit unit 150 including the signal output line, the control line, and the like is opposed to each other with the wiring circuit unit 150 interposed therebetween.

  The wiring circuit unit 150 includes a line sensor pixel signal output circuit 130j that reads out signal charges from the photodiode pairs 120Aj and 120Bj and outputs pixel signals. The line sensor pixel signal output circuit 130 j is disposed along the longitudinal direction of the line sensor, and the pixel signals of the entire line sensor are output via the wiring circuit unit 150.

  The monitor sensor LMB3 is divided into a plurality of sensor portions 140m (m = 1, 2,..., Hereinafter, each divided portion is referred to as a fine sensor portion), and the longitudinal direction thereof is parallel to the longitudinal direction of the line sensor LSB3. They are lined up. Each micro sensor unit 140m is configured to monitor a predetermined number of photodiode pairs. Here, eight pairs of photodiodes are set as monitoring target areas.

  The micro sensor unit 140m includes a photoelectric conversion unit 142 configured by a photodiode and the like, and a monitor sensor pixel signal readout circuit 144 that outputs a signal charge generated in the photoelectric conversion unit 142 as a pixel signal. The photoelectric conversion unit 142 has an end 142S formed in a cutout shape, and the pixel signal readout circuit 144 is housed in the cutout portion 142S.

  Here, the shape of the notch portion 142S is determined in accordance with the size of the monitor sensor pixel signal readout circuit 144 so that the minute sensor portion 140m is formed in a rectangular shape. Thereby, the micro sensor unit 140m is arranged in parallel to the bar-shaped monitor sensor arrangement area MD that is defined in accordance with the width 140Z of the micro sensor unit 140m.

  The photoelectric conversion unit 142 of each micro sensor unit 140m has an area to be monitored, that is, a side part 142T that covers the entire eight pairs of photodiodes, and the side part 142T has a length facing the eight pairs of photodiodes. W. That is, a wide portion of the photoelectric conversion unit 142 is formed between the monitor sensor pixel signal readout circuit 144 and the line sensor LSB3 disposed in the notch portion 142S, and the monitor sensor pixel signal readout circuit 144 is a line sensor. Located on the opposite side of LSB3.

  For this reason, the micro sensor unit 140m receives substantially the same light as that incident on the area of the eight pairs of photodiodes to be processed, and the light amount distribution in the area is received by the photoelectric conversion unit 142 of the micro sensor unit 140m. It becomes almost equal to the light intensity distribution.

  As described above, the focus detection unit 40 is an integrated IC board, and the circuit board is configured with the monitor sensor and the vertical shift register provided on both sides of the MOS type line sensor. A separation unit in which a logic unit LS in which a vertical shift register is arranged and a pixel unit PS in which a photodiode and a minute sensor unit are arranged are alternately formed, and a wiring is provided between the logic unit LS and the pixel unit PS. DS intervenes.

  FIG. 4 is an electric circuit diagram of the line sensor pixel signal readout circuit. FIG. 5 is an electric circuit diagram of the monitor sensor pixel signal readout circuit. FIG. 6 is a wiring diagram of the pixel signal readout circuit for line sensors. The pixel signal readout circuit configurations of the line sensor and the monitor sensor will be described with reference to FIGS.

  FIG. 4 shows a circuit configuration related to a pair of photodiode pairs 120Aj and 120Bj of the line sensor LSB3 and a line sensor pixel signal readout circuit 130j connected thereto. The photodiode pairs 120Aj and 120Bj are both connected to the line sensor pixel signal readout circuit 130j.

  The line sensor pixel signal readout circuit 130j includes anti-blooming gates (ABG) 121A and 121B, transfer gates (TG) 122A and 122B, and floating diffusion gates (FD) 123A and 123B, which are transistors.

  Further, the line sensor pixel signal readout circuit 130j includes temporary charge storage capacitors (MEM) 124A and 124B, a floating diffusion capacitor (CFD) 125 that performs charge-voltage conversion, a reset gate (RG) 26, and a source follower amplifier. 127, a shared circuit portion 133 provided with a selection gate 128 is provided.

  The shared circuit portion 133 is a circuit shared in the pixel signal output of the photodiodes 120Aj and 120Bj, and signal charges generated in the photodiodes 120Aj and 120Bj are shared through the first circuit portion 131 and the second circuit portion 132, respectively. To the circuit portion 133. FIG. 6 schematically shows a wiring pattern of the pixel signal readout circuit 130.

  On the other hand, in the small sensor portion 140m of the monitor sensor shown in FIG. 5, the photoelectric conversion portion 142 that is a photodiode is connected to the monitor sensor pixel signal readout circuit 144. The pixel signal readout circuit 144 includes an anti-blooming gate (ABG) 151, a transfer gate (TG) 152, a reset gate (RG) 154, and further includes a capacitor (MEM) 153 and a source follower amplifier 155.

  When light from the subject reaches the line sensor, a signal charge (pixel signal) is generated by photoelectric conversion of the photodiodes 120Aj and 120Bj, and the charge is accumulated according to the amount of light. On the other hand, the signal charge generated in the photoelectric conversion unit 142 of the monitor sensor 140m is converted into a charge voltage by the capacitor 153, and is output to the AGC circuit shown in FIG. 2 through the source follower amplifier 155 as needed.

  In order to prevent light exceeding the dynamic range from entering the eight pairs of photodiodes to be monitored, the AGC circuit compares the pixel signal (monitor signal) of the micro sensor unit 140m with a threshold value. The signal charge is accumulated until the monitor signal exceeds the threshold value.

  When the pixel signal (monitor signal) exceeds the threshold value, the charge accumulation in the eight pairs of photodiodes to be monitored is terminated, and the accumulated charge is transferred to the capacitors 124A and 124B through the transfer gates 122A and 122B. The accumulated charges are temporarily stored in the capacitors 124A and 124B, respectively, until the charge accumulation of the other photodiode pairs is completed.

  When the charge accumulation of all the photodiode pairs is completed, the accumulated charges generated in the photodiodes 120Aj and 120Bj and stored separately are transferred to the capacitor 125, that is, the floating diffusion separately or simultaneously. Thereby, the signal charge is converted into a voltage signal. Then, after being amplified by the source follower amplifier 127, a pixel signal (voltage signal) is output.

  As described above, according to the present embodiment, the line sensor group in which the plurality of photodiode pairs 120Aj and 120Bj are arranged in parallel is arranged in a cross shape, and the monitor sensor is arranged on the side of the line sensor in one line sensor group. . Each monitor sensor is composed of a plurality of minute sensor units 140m to divide and monitor the line sensor, and the minute sensor unit 140m outputs pixel signals (monitor signals) with eight photodiode pairs as monitoring targets. Thus, by dividing one line sensor into areas and monitoring with a plurality of sensors, it is possible to receive substantially the same light as the line sensor. In addition, the brightness of the subject can be detected finely without averaging.

  The micro sensor unit 140m includes a photoelectric conversion unit 142 and a monitor sensor pixel signal readout circuit 144 that generates and outputs a pixel signal. The side unit 142T of the photoelectric conversion unit 142 includes eight photodiode pairs to be monitored. Is entirely covered, that is, has a length W that is entirely opposed to the eight photodiode pairs. On the other hand, the end 142S of the photoelectric conversion unit 142 is formed in a cutout shape, and the monitor sensor pixel signal readout circuit 144 is housed in the cutout portion.

  Since the minute sensor unit 140m is configured in a rectangular shape, the width Z of the minute sensor unit 140m is determined by the width of the photoelectric conversion unit 142. That is, the width Z of the minute sensor unit 140m is defined without being affected by the monitor sensor pixel signal readout circuit 144. Thereby, each micro sensor part 140m can be arranged in the bar-shaped monitor sensor area MD whose width Z is the same as the width of the photoelectric conversion part 142.

  In the separation unit DS between the logic unit LS and the pixel unit PS, neither a logic circuit nor a photodiode can be arranged, and a pixel signal readout circuit cannot be arranged. Therefore, if the pixel signal readout circuit is disposed outside the width Z of the photoelectric conversion unit, the area MD in which the monitor sensor is disposed needs to be widened accordingly. Such a monitor sensor configuration enlarges the pitch between line sensors and limits the number of line sensors arranged.

  However, in this embodiment, since the pixel signal readout circuit is housed in the area of the minute sensor unit, the width of the monitor sensor area can be set to the minimum, and the width of the pixel unit PS (see FIG. 4) is reduced. It can be suppressed. Therefore, the pitch between the line sensors can be shortened, and as many line sensors as possible can be arranged in the projection area defined by the imaging optical system.

  On the other hand, according to the present embodiment, the line sensor pixel signal readout circuit 130j that generates and outputs the pixel signals of the photodiode pairs 120Aj and 120Bj of the line sensor is disposed between the photodiode pairs 120Aj and 120Bj. . The line sensor pixel signal readout circuit 130j converts the charges stored in the photodiodes 120Aj and 120Bj into voltages in the shared circuit portion 133, and outputs the voltages as pixel signals. Alternatively, the accumulated charges are mixed and output as a mixed pixel signal of two photodiodes.

  Instead of separately arranging the pixel signal readout circuits on both sides of the line sensor, it is arranged in the opposing space of the photodiode pairs arranged in two rows, so that the wiring space such as the control signal line and the pixel signal output line can be gathered, The pitch between line sensors can be shortened. In addition, since pixel signals of a pair of photodiodes can be mixed and output, sensitivity can be increased even when the luminance of the subject image is low, and focus detection can be performed with high accuracy.

  Next, a second embodiment will be described with reference to FIG. In the second embodiment, the monitor sensor pixel signal readout circuit is arranged at the center of the photoelectric conversion unit. About another structure, it is the same as 1st Embodiment.

  FIG. 7 is a layout diagram of the line sensor and the monitor sensor in the second embodiment.

  Each micro sensor unit 140 includes a photoelectric conversion unit 142 configured by a photodiode, and a monitor sensor pixel signal readout circuit 144 that outputs a pixel signal generated in the photoelectric conversion unit 142 by photoelectric conversion. The photoelectric conversion unit 142 has a central part 142X along the longitudinal direction thereof formed in a cutout shape, and the signal readout circuit 144 is housed in the cutout part 142X. Therefore, the pixel signal readout circuit 144 is disposed at an equal distance from both ends of the photoelectric conversion unit 142.

  As described above, according to the present embodiment, the pixel signal readout circuit 144 is disposed along the line X that crosses the central portion 142X of the photoelectric conversion unit 142. Since the distance from the both ends of the photoelectric conversion unit 142 to the pixel signal readout circuit 144 is equal and the photoelectric conversion unit 142 is symmetric with the pixel signal readout circuit 144 as the center, the pixel signal depends on the incident light position of the photoelectric conversion unit 142. There is no bias in output time.

  Therefore, even under shooting conditions where light is incident on the end of the monitor sensor, the pixel signal and the monitor signal are output quickly, so that the photodiode of the line sensor where almost the same light is incident will overflow. prevent.

  In the first embodiment, the monitor sensor may be configured only by a cut-out minute sensor unit, and the line sensor pixel signal readout circuit is not disposed between the photodiode pair, but is disposed on both sides of the line sensor. May be. In this case, a CCD line sensor can be arranged instead of the MOS type line sensor. Further, the pixel signal readout circuit may be simply arranged between the photodiode pair.

  In the second embodiment, the photoelectric conversion unit 142 may be formed in a rectangular shape without providing the notch portion 142X, and the pixel signal readout circuit may be disposed at a position facing the central portion of the rectangular shape. That is, the pixel signal readout circuit may be disposed at a position that is substantially equidistant from both ends of the photoelectric conversion unit 142.

  The distance measurement may be configured to measure multiple points or only the center of the screen, and the number of line sensors, the number of line sensor groups, and the arrangement direction of the line sensors are arbitrary. Further, the present invention may be applied to a camera other than a single-lens reflex camera, or may be applied to a photographing apparatus having a camera function such as a mobile phone.

10 SLR digital camera 24 AF module (focus detection device)
40 Focus detection unit (image signal output means)
120Aj, 120Bj Photodiode pair (photoelectric conversion element pair)
130j Pixel signal readout circuit for line sensor (pixel signal readout circuit)
131 1st circuit part 132 2nd circuit part 133 Shared circuit part 140m Minute sensor part (monitor sensor)
140S End of photoelectric conversion unit 142 Photoelectric conversion unit (monitor photoelectric conversion unit)
142T Side part of photoelectric conversion part 142S End part of photoelectric conversion part 142X Center part (notch part) of photoelectric conversion part
144 Pixel signal readout circuit for monitor sensor (pixel signal readout circuit)
LMA1 to LMA9 monitor sensor LMB1 to LMB5 monitor sensor

Claims (4)

A plurality of line sensors arranged in the projection area of the subject image;
A plurality of monitor sensors arranged on the side (side) of the plurality of line sensors, respectively, for monitoring the received light amount of the corresponding line sensors;
Image signal output means for outputting an image signal of a subject image based on charges accumulated in the plurality of line sensors,
Each monitor sensor includes at least one monitor photoelectric conversion unit and at least one pixel signal readout circuit that outputs charges generated in the photoelectric conversion unit as a pixel signal,
The monitor photoelectric conversion unit has a length facing the entire monitoring target area of the corresponding line sensor,
The focus detection device, wherein the pixel signal readout circuit is disposed at a position where distances from both ends of the monitor photoelectric conversion unit are substantially equal.   The focus detection apparatus according to claim 1, wherein a central portion of the monitor photoelectric conversion unit is formed in a cutout shape, and the pixel signal readout circuit is accommodated in the cutout portion. Each line sensor has a plurality of line sensor photoelectric conversion units in parallel,
Each monitor sensor has a plurality of minute sensor units arranged in parallel along the longitudinal direction of the line sensor so as to face a predetermined number of line sensor photoelectric conversion units,
The focus detection apparatus according to claim 1, wherein each minute sensor unit includes the monitor photoelectric conversion unit and the pixel signal readout circuit. An imaging device comprising the focus detection device according to claim 1.