JP2014165778A - Solid state image sensor, imaging device and focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a focus appropriately in both low brightness and high brightness, and to detect a focus at the same position in low brightness and high brightness.SOLUTION: A solid state image sensor 4 performs photoelectric conversion of a subject image captured by an optical system. The solid state image sensor 4 includes a plurality of imaging pixels 20A having a photoelectric conversion part 41 for receiving and converting incident light photoelectrically, and a plurality of focal detection pixels 20L, 20R having a first photoelectric conversion part 45 and a second photoelectric conversion part 46 existing in a region on one side and a region on the other side, respectively in plan view, and from which the signals are read independently from each other with different sensitivities.

Description

  The present invention relates to a solid-state imaging device, an imaging device, and a focus detection device.

  Conventionally, there has been known a solid-state imaging device that can appropriately perform focus detection at both low luminance and high luminance by using two types of focus detection pixels having different pixel sizes (for example, Patent Document 1).

JP 2007-103590 A

  However, in the invention of Patent Document 1, since the pixels used for focus detection differ between low brightness and high brightness, focus detection at the same position cannot be performed at low brightness and high brightness.

  The present invention has been made in view of such circumstances, and can appropriately perform focus detection at both low luminance and high luminance, and substantially at both low luminance and high luminance. It is an object of the present invention to provide a solid-state imaging device and a focus detection device capable of detecting a focus at the same position, and an imaging device using the solid-state imaging device.

  The following aspects are presented as means for solving the problems. The solid-state imaging device according to the first aspect is a solid-state imaging device that photoelectrically converts a subject image formed by an optical system, and includes a plurality of imaging pixels having a photoelectric conversion unit that receives and photoelectrically converts incident light. , A plurality of focus detections having a first photoelectric conversion unit and a second photoelectric conversion unit which are present in one region and the other region in plan view, respectively, read signals independently of each other, and have different sensitivities. Pixels.

  The solid-state imaging device according to the second aspect is different from the first aspect in that an effective light receiving area of the first photoelectric conversion unit is different from an effective light receiving area of the second photoelectric conversion unit.

  In the solid-state imaging device according to the third aspect, in the second aspect, the effective light receiving area of the first photoelectric conversion unit is at least a part of an outer edge of the first photoelectric conversion unit and / or the first photoelectric conversion unit. The effective light receiving area of the second photoelectric conversion unit is determined by at least one of the outer edges of the second photoelectric conversion unit, and is determined by at least a part of the opening of the light shielding unit disposed on the light incident side of the one photoelectric conversion unit. Part and / or at least part of the opening of the light-shielding part arranged on the light incident side of the second photoelectric conversion part.

  In the present specification, “and / or” means both or any one of them.

  The solid-state imaging device according to a fourth aspect is the light incidence of at least one of the first photoelectric conversion unit and the second photoelectric conversion unit in any of the first to third aspects. On the side, a light attenuating portion is provided.

  The solid-state imaging device according to a fifth aspect is the optical system according to any one of the first to fourth aspects, wherein the first photoelectric conversion unit and the second photoelectric conversion unit of each focus detection pixel are the optical system. The light beams from the exit pupil regions decentered in the opposite directions from the center of the exit pupil are selectively received and photoelectrically converted.

  The solid-state imaging device according to a sixth aspect is the solid-state imaging device according to any one of the first to fifth aspects, wherein each of the focus detection pixels is provided on a one-to-one basis with respect to the pixel. A microlens that guides incident light to the conversion unit and the second photoelectric conversion unit is provided.

  An image pickup apparatus according to a seventh aspect receives a detection signal indicating a focus adjustment state of the optical system based on a signal from the solid-state image pickup element according to any one of the first to sixth aspects and the focus detection pixel. A detection processing unit for outputting is provided.

  According to an eighth aspect of the present invention, in the seventh aspect, the detection processing unit is configured to detect the first and second photoelectric elements when the luminance is relatively high according to photometric information related to luminance of a subject. The detection signal is output based on a signal from a photoelectric conversion unit having a lower sensitivity among the conversion units, and when the luminance is relatively low, the detection signal is output from the first and second photoelectric conversion units. The detection signal is output based on a signal from the photoelectric conversion unit with higher sensitivity.

  In the seventh or eighth aspect, an imaging apparatus according to a ninth aspect includes an adjustment unit that performs focus adjustment of the optical system based on a detection signal from the detection processing unit.

  The focus detection apparatus according to the tenth aspect includes a first photoelectric conversion unit and a second photoelectric conversion unit that are present in one region and the other region in plan view, read signals independently of each other, and have different sensitivities. A plurality of focus detection pixels each having a photoelectric conversion unit, wherein the first photoelectric conversion unit and the second photoelectric conversion unit of each focus detection pixel have a center of an exit pupil of an optical system as a focus detection target. To selectively receive light beams from the exit pupil regions decentered in opposite directions from each other, and perform photoelectric conversion.

  According to the present invention, it is possible to appropriately perform focus detection at both low luminance and high luminance, and it is possible to detect focus at substantially the same position at low luminance and high luminance. An imaging device, a focus detection device, and an imaging device using the solid-state imaging device can be provided.

It is a schematic block diagram which shows the electronic camera as an imaging device by the 1st Embodiment of this invention. It is a circuit diagram which shows schematic structure of the solid-state image sensor in FIG. It is a schematic plan view which shows typically the solid-state image sensor in FIG. It is the schematic enlarged view which expanded a part in FIG. It is a figure which shows typically the principal part of the pixel for imaging in FIG. It is a figure which shows typically the principal part of the predetermined AF pixel in FIG. It is a figure which shows typically the principal part of the other predetermined AF pixel in FIG. It is a circuit diagram which shows the pixel for an imaging of the solid-state image sensor in FIG. It is a circuit diagram which shows the pixel for AF of the solid-state image sensor in FIG. 3 is a schematic flowchart illustrating an example of an operation of the electronic camera illustrated in FIG. 1. It is a partial expansion schematic plan view of the solid-state image sensor by the 2nd Embodiment of this invention. It is a figure which shows typically the principal part of the pixel for predetermined | prescribed AF in FIG. It is a figure which shows typically the principal part of the other predetermined AF pixel in FIG. It is a partially expanded schematic plan view of the focus detection apparatus by the 3rd Embodiment of this invention. It is a schematic block diagram which shows typically the electronic camera as an imaging device carrying the focus detection apparatus shown in FIG.

  Hereinafter, a solid-state imaging device, an imaging apparatus, and a focus detection apparatus according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic block diagram showing an electronic camera 1 as an imaging device according to the first embodiment of the present invention.

  The electronic camera 1 according to the present embodiment is configured as, for example, a single-lens reflex digital camera. However, the imaging apparatus according to the present invention is not limited to this, and is mounted on another electronic camera such as a compact camera or a mobile phone. The present invention can be applied to various imaging devices such as an electronic camera and an electronic camera such as a video camera that captures moving images.

  The electronic camera 1 is equipped with a photographing lens 2 as an optical system for forming a subject image. The photographing lens 2 is driven by a lens control unit 3 for focus and diaphragm. In the image space of the photographic lens 2, the imaging surface of the solid-state imaging device 4 is arranged.

  The solid-state imaging device 4 is driven by a command from the imaging control unit 5 and outputs a digital signal. The digital signal output from the solid-state imaging device 4 is either an imaging signal for forming an image signal indicating a subject image or a focus detection signal for detecting the focus adjustment state of the photographing lens 2. . In the present embodiment, each signal is temporarily stored in the memory 7 after being subjected to digital amplification and other processing by the digital signal processing unit 6. The memory 7 is connected to the bus 8. The bus 8 is also connected with a lens control unit 3, an imaging control unit 5, a CPU 9, a focus calculation unit (detection processing unit) 10, a recording unit 11, an image compression unit 12, an image processing unit 13, and the like. An operation unit 14 such as a release button is connected to the CPU 9. A recording medium 11a is detachably attached to the recording unit 11.

  FIG. 2 is a circuit diagram showing a schematic configuration of the solid-state imaging device 4 in FIG. The solid-state imaging device 4 has a plurality of pixels 20 arranged in a two-dimensional matrix and a peripheral circuit for outputting a signal from the pixels 20. An effective pixel region (imaging region) in which the pixels 20 are arranged in a matrix in n rows and m columns is denoted by reference numeral 21. The number of pixels is not particularly limited.

  In the present embodiment, the solid-state imaging device 4 has three types of pixels 20A, 20L, and 20R, which will be described later, as pixels, but in FIG. Show. These pixels 20 output either imaging signals or focus detection signals in accordance with peripheral circuit drive signals. In addition, all the pixels 20 can be reset so that the photoelectric conversion unit is simultaneously reset to have the same exposure time and timing, or can be a so-called rolling shutter that reads out one row at a time.

  The peripheral circuit includes a vertical scanning circuit 22, a control line 23 provided for each row of the pixels 20, and a plurality (m) of signals received from the pixels 20 in the corresponding column provided for each column of the pixels 20. A vertical signal line 27, a constant current source 28 provided in each vertical signal line 27, a CDS circuit (correlated double sampling circuit) 29 and an A / D converter 30 provided corresponding to each vertical signal line 27 And a horizontal readout circuit 31.

  The vertical scanning circuit 22 and the horizontal readout circuit 31 output drive signals based on commands from the imaging control unit 5 of the electronic camera 1. Each pixel 20 is driven by receiving a drive signal output from the vertical scanning circuit 22 from a predetermined control line 23, and outputs an imaging signal or a focus detection signal to the vertical signal line 27. There are a plurality of drive signals output from the vertical scanning circuit 22 and a plurality of control lines 23 accordingly. These will be described later.

  The signal read from the pixel 20 to the vertical signal line 27 is subjected to a predetermined noise removal process by the CDS circuit 29 for each column, and then converted to a digital signal by the A / D converter 30. The digital signal is held in the A / D converter 30. The digital image signal held in each A / D converter 30 is horizontally scanned by a horizontal readout circuit 31 and converted into a predetermined signal format as necessary, and externally (digital signal processing unit 6 in FIG. 1). ). The solid-state imaging device 4 does not necessarily include the A / D converter 30 and may be configured so that an analog image signal is output from the horizontal readout circuit 31.

  FIG. 3 is a schematic plan view schematically showing the solid-state imaging device 4 (particularly, its effective pixel region 21) in FIG. In the present embodiment, as shown in FIG. 3, the effective pixel region 21 of the solid-state imaging device 4 is provided with three focus detection regions 32 to 35 that extend linearly in the X-axis direction so as to be aligned vertically. It has been.

  As shown in FIG. 3, an X axis, a Y axis, and a Z axis that are orthogonal to each other are defined. The direction of the arrow in the X-axis direction is called the + X direction or + X side, and the opposite direction is called the -X direction or -X side, and the same applies to the Y-axis direction. A plane parallel to the XY plane coincides with the imaging surface (light receiving surface) of the solid-state imaging device 4. The arrangement in the X-axis direction is a row, and the arrangement in the Y-axis direction is a column. Incident light is incident from the front side of the drawing in FIG. These points are the same for the drawings described later.

  FIG. 4 is a schematic enlarged view in which the vicinity of the focus detection region 32 in FIG. 3 is enlarged. As described above, the solid-state imaging device 4 includes the three types of pixels 20A, 20L, and 20R as the pixels 20.

  The pixel 20 </ b> A is an imaging pixel that outputs an imaging signal for forming an image signal indicating a subject image formed by the photographing lens 2. FIG. 5A is a schematic plan view schematically showing the main part of the imaging pixel 20A, and FIG. 5B is a schematic cross-sectional view taken along line X1-X2 in FIG. 5A.

  The imaging pixel 20A includes a photodiode 41 as a photoelectric conversion unit, a microlens 42 formed on-chip on the photodiode 41, and R (red) and G (provided on the light incident side of the photodiode 41). A color filter 60 of either green) or B (blue). Although not shown in the drawing, the color of the color filter 60 is set in accordance with a Bayer array or the like. As shown in FIG. 5, a light shielding layer 43 such as a metal layer as a light shielding portion is formed on a substantially focal plane of the microlens 42. The light shielding layer 43 also serves as a wiring layer as necessary. In the light shielding layer 43, a square opening 43a concentric with the optical axis O of the microlens 42 of the imaging pixel 20A is formed in the imaging pixel 20A. The photodiode 41 of the pixel 20A has a size capable of effectively receiving all the light that has passed through the opening 43a. An interlayer insulating film or the like is formed between the light shielding layer 43 and the microlens 42 or between the substrate 44 and the light shielding layer 43.

  In the present embodiment, in the imaging pixel 20 </ b> A, the opening 43 a is formed in the light shielding layer 43 disposed substantially at the focal plane of the microlens 42, so that the photodiode 41 of the pixel 20 </ b> A can be A light beam from the exit pupil region (corresponding to a projection image by the microlens 42 of the opening 43a) that is not substantially decentered from the center of the exit pupil is received and photoelectrically converted.

  The pixels 20L and 20R are focus detection pixels (hereinafter referred to as “AF pixels”) that output a focus detection signal for detecting the focus adjustment state of the photographic lens 2. FIG. 6A is a schematic plan view schematically showing the main part of the AF pixel 20L, and FIG. 6B is a schematic cross-sectional view taken along line X3-X4 in FIG. 6A. FIG. 7A is a schematic plan view schematically showing the main part of the AF pixel 20R, and FIG. 7B is a schematic cross-sectional view taken along line X5-X6 in FIG. 7A. 6 and 7, the same or corresponding elements as those in FIG. 5 are denoted by the same reference numerals, and redundant description thereof is omitted.

  In the AF pixel 20L, instead of one photodiode 41 as one photoelectric conversion unit, two photoelectric conversion units that are divided into two and only one (photodiode 45 only) has a reduced area. The two photodiodes 45 and 46 are included. The two photodiodes 45 and 46 are divided into a region on the −X side and a region on the + X side, which are divided by the dividing line Y3-Y4 in the Y axis direction in a plan view as viewed from the normal direction (Z axis direction) of the substrate 44. , Each is arranged. The microlens 42 is arranged so that the optical axis O passes through the intersection of the dividing line Y3-Y4 and the center line of the photodiodes 45 and 46 in the Y-axis direction. In the AF pixel 20L, the light shielding layer 43 includes a square opening 43a concentric with the optical axis O of the microlens 42 of the AF pixel 20L (a square having the same size as the opening 43a of the imaging pixel 20A). The opening 43a) is formed. Therefore, the incident light guided from the microlens 42 is divided into pupils, one light beam thereof is selectively incident on the photodiode 45 having a relatively small area, and the other light beam is a photodiode 46 having a relatively large area. Is selectively incident. That is, in the pixel 20L, the photodiode 45 having a relatively small area (relatively low sensitivity in the present embodiment) is an area of the exit pupil that is decentered from the center of the exit pupil of the photographing lens 2 to the + X side. The photodiode 46 that selectively receives the light flux from the light source and has a relatively large area (relatively high sensitivity in this embodiment) from the center of the exit pupil of the photographing lens 2 to the −X side. The light beam from the eccentric exit pupil region is selectively received effectively. For example, in the pixel at the center of the effective pixel region, the microlens 42 is arranged so that the optical axis O passes through the intersection point, while in the pixel at the peripheral portion of the effective pixel region, the microlens 42 is positioned at the optical axis. You may arrange | position so that O may pass through the position which shifted | deviated from the said intersection.

  In the present embodiment, the entire area of the photodiode 45 is the effective light receiving area of the photodiode 45, and the effective light receiving area of the photodiode 45 is determined by the entire outer edge of the photodiode 45. The entire area of the photodiode 46 is the effective light receiving area of the photodiode 46, and the effective light receiving area of the photodiode 46 is determined by the entire outer edge of the photodiode 46. In this embodiment, the area of the photodiode 45 is made smaller than the area of the photodiode 46, so that the effective light receiving area of the photodiode 45 is made smaller than the area of the photodiode 46. The sensitivity of 45 is set lower than the sensitivity of the photodiode 46. Here, the sensitivity of the photodiode is the ratio of the output (charge amount) of the photodiode to the luminance of the subject (in this embodiment, the amount of light incident on the microlens 42 of the pixel).

  However, the effective light receiving area of the photodiode 45 can be obtained by appropriately combining the shape / size of the photodiode 45 and the shape / size of the opening 43a, so that at least a part of the outer edge of the photodiode 45 and / or the photodiode 45 It may be determined by at least a part of the opening 43a of the light shielding part 43 disposed on the light incident side. In addition, the effective light receiving area of the photodiode 46 is obtained by appropriately combining the shape / size of the photodiode 46 and the shape / size of the opening 43a, so that at least a part of the outer edge of the photodiode 45 and / or the photodiode 45 It may be determined by at least a part of the opening 43a of the light shielding part 43 disposed on the light incident side.

  In order to make the sensitivity of the photodiode 45 lower than the sensitivity of the photodiode 46, it is not always necessary to make the effective light receiving area of the photodiode 45 smaller than the effective light receiving area of the photodiode 46.

  Further, the color filter 60 is not provided in the AF pixel 20L. In order to increase the amount of incident light on the photodiodes 45 and 46 of the AF pixel 20L and increase the focus detection accuracy, it is preferable not to provide the color filter 60 in the pixel 20L. However, the present invention is not limited to this. is not.

The difference between the AF pixel 20R and the AF pixel 20L is that in the AF pixel 20R,
This is only the point where the photodiodes 45 and 46 are arranged opposite to each other in FIGS. 6 and 7. Therefore, in the AF pixel 20R, the photodiode 45 having a relatively small area (relatively low sensitivity in the present embodiment) is emitted from the center of the exit pupil of the photographing lens 2 toward the −X side. The photodiode 46 that selectively and effectively receives a light beam from the pupil region and has a relatively large area (relatively high sensitivity in this embodiment) is + X from the center of the exit pupil of the photographing lens 2. The light beam from the exit pupil region decentered to the side is selectively received effectively.

  In the present embodiment, as shown in FIG. 4, the AF pixels 20 </ b> L and 20 </ b> R are alternately arranged in the X-axis direction in the focus detection region 32. The focus detection areas 33 and 34 are the same as the focus detection area 32. An imaging pixel 20 </ b> A is arranged in an area other than the focus detection areas 32 to 34 in the effective pixel area 21. Note that the number and arrangement of the focus detection areas 32 to 34 are not limited to the above-described example, and the arrangement of the AF pixels 20L and 20R is not necessarily limited to a straight alternate arrangement.

  FIG. 8 is a circuit diagram showing the imaging pixel 20A of the solid-state imaging device 4 in FIG. Each imaging pixel 20A includes a photodiode 41 as a photoelectric conversion unit that generates and accumulates charges according to incident light, and a floating capacitance unit 47 as a charge-voltage conversion unit that receives the charges and converts the charges into voltages. A transfer transistor 48 for transferring charge from the photodiode 41 to the floating capacitor 47, an amplifier transistor 49 as an amplifier for outputting a signal corresponding to the voltage of the floating capacitor 47, and resetting the voltage of the floating capacitor 47 A reset transistor 50 as a reset unit to be selected, and a selection transistor 51 as a selection unit for selecting the pixel 20A. In FIG. 8, VDD is a power supply, and 235 is a power supply wiring for connecting to the power supply VDD.

  FIG. 9 is a circuit diagram showing the AF pixels 20L and 20R of the solid-state imaging device 4 in FIG. These pixels 20L and 20R have the same circuit configuration. 9, elements that are the same as or correspond to those in FIG. 8 are given the same reference numerals, and redundant descriptions thereof are omitted. The AF pixels 20L and 20R are different from the imaging pixel 20A in terms of circuit configuration in place of one photodiode 41 as one photoelectric conversion unit and divided into two (only the photodiode 45). And having two photodiodes 45 and 46 as two photoelectric conversion units with a reduced area, and accordingly, two transfer transistors that can operate independently of each other instead of one transfer transistor 48 It is only the point which has 52,53. The transfer transistor 52 transfers charge from the photodiode 45 to the floating capacitor 47, and the transfer transistor 53 transfers charge from the photodiode 46 to the floating capacitor 47. Thereby, the signals of the photodiodes 45 and 46 are read out independently of each other.

  The transfer transistor 48 of the imaging pixel 20A and the gate electrode of one of the transfer transistors 52 of the AF pixels 20L and 20R are connected in common to each pixel row, and the wiring 231 among the control lines 23 is connected from the vertical scanning circuit 22. The drive signal φTGA is supplied through the via. The gate electrodes of the other transfer transistors 53 of the AF pixels 20L and 20R are connected in common to each pixel row, and the drive signal φTGB is supplied from the vertical scanning circuit 22 via the wiring 232 of the control line 23. .

  The gate electrodes of the selection transistors 51 of the pixels 20 </ b> A, 20 </ b> L, and 20 </ b> R are commonly connected to each pixel row, and the drive signal φS is supplied from the vertical scanning circuit 22 through the wiring 233 of the control line 23. The gate electrodes of the reset transistors 50 of the pixels 20 </ b> A, 20 </ b> L, and 20 </ b> R are commonly connected to each pixel row, and the drive signal φR is supplied from the vertical scanning circuit 22 through the wiring 234 of the control line 23.

  The vertical scanning circuit 22 receives the control signal from the imaging control unit 5 in FIG. 1 and controls the control signals φS, φR, φTGA for each row of the pixels 20 in accordance with the operation of a general CMOS type solid-state imaging device. , ΦTGB, respectively, and controlling the pixel 20 of the pixel unit 21, the imaging signal is read out from the imaging pixel 20 </ b> A, and the high-sensitivity photodiode 45 from the low sensitivity photodiode 45 of the AF pixels 20 </ b> L, 20 </ b> R The focus detection signal is read out, and the low-luminance focus detection signal is read out from the high-sensitivity photodiode 46 of the AF pixels 20L and 20R. In any of the operation modes, all of the imaging signal, the high-intensity focus detection signal, and the low-intensity focus detection signal may be read out. However, only the high-intensity focus detection signal needs to be read when the subject is in the high-intensity focus detection mode, and only low-intensity focus detection signals can be read out when the subject is in the low-intensity focus detection mode. In the imaging mode, it is only necessary to read out the imaging signal. Therefore, in each mode, speeding up may be achieved by avoiding unnecessary signal reading as much as possible.

  FIG. 10 is a schematic flowchart showing an example of the operation of the electronic camera 1 shown in FIG.

  First, after the main power is turned on, the power of each unit is turned on (step S1). Thereafter, the CPU 9 opens the aperture of the taking lens 2 via the lens control unit 3 in order to control the exposure amount. The output from the solid-state imaging device 4 is stored in the memory 7 after passing through the digital signal processing unit.

  When the focus adjustment (steps S2 to S6) is started, first, the CPU 9 determines the subject based on the output of the photometric sensor (not shown) provided in the electronic camera 1 (photometric information relating to the luminance of the subject). It is determined whether or not the luminance is less than a predetermined value (step S2). As the photometric information relating to the luminance of the subject, data corresponding to the output of the imaging pixel 20A among the data stored in the memory 7 may be used instead of the output of the photometric sensor.

  If it is determined in step S2 that the luminance is smaller than the predetermined value, the CPU 9 causes the focus calculation unit 10 to use the focus detection signal from the high-sensitivity photodiode 46 of the AF pixels 20L and 20R, and the pupil division phase difference. By causing the focus calculation unit 10 to perform calculation (focus adjustment state detection processing) according to the detection method, the focus calculation unit 10 calculates the defocus amount of the photographing lens 2 (step S3), and the process proceeds to step S5. .

  On the other hand, when it is determined in step S2 that the luminance is equal to or higher than the predetermined value, the CPU 9 causes the focus calculation unit 10 to use a focus detection signal from the low-sensitivity photodiode 45 of the AF pixels 20L and 20R. By causing the focus calculation unit 10 to perform calculation (focus adjustment state detection processing) according to the divided phase difference detection method, the focus calculation unit 10 calculates the defocus amount of the photographing lens 2 (step S4), and step S5. Migrate to

  In step S5, the CPU 9 determines whether or not the taking lens 2 is in an in-focus state based on the defocus amount calculated in step S3 or S4. If it is determined in step S5 that the focus state is achieved, the process proceeds to step S7.

  On the other hand, if it is determined in step S5 that the in-focus state is not achieved, the CPU 9 selects a focusing lens among the photographing lenses 2 via the lens control unit 3 based on the defocus amount calculated in step S3 or S4. Driven and moved toward the in-focus position (step S6). Thereafter, the CPU 9 takes in the output (photometric information relating to the luminance of the subject) of the photometric sensor (not shown), and focuses from the AF pixels 20L and 20R by the control of the solid-state imaging device 4 via the imaging control unit 5. After the detection signal is stored in the memory 7, the process returns to step S2, and the focus adjustment (steps S2 to S5) is repeated until the defocus amount becomes zero.

  If it is determined in step S5 that the in-focus state is obtained, the CPU 9 proceeds to the process of step S7. When the CPU 9 detects that the release button of the operation unit 14 is pressed, the image is taken via the imaging control unit 5. The operation is executed (step S8). That is, the output from the solid-state imaging device 4 is stored in the memory 7 via the digital signal processing unit 6. If it is not detected that the release button has been pressed even after waiting for a predetermined time after moving to step S7, the CPU 9 captures the output of the photometric sensor (not shown) (photometric information relating to the luminance of the subject). After the focus detection signals from the AF pixels 20L and 20R are stored in the memory 7 by the control of the solid-state imaging device 4 via the imaging control unit 5, the process returns to step S2.

  After step S8, the CPU 9 generates an image signal using data corresponding to the output of the captured image pixel 20A among the data stored in the memory 7 by the photographing operation of step S8 (step S9). The image signal at the position of the imaging pixel 20A of the solid-state imaging device 4 is generated based on the data of the imaging pixel 20A. The image signals at the positions of the AF pixels 20L and 20R are generated by a known interpolation process based on the data of the imaging pixels 20A around the pixels 20L and 20R. Thereafter, the CPU 9 takes in the output (photometric information relating to the luminance of the subject) of the photometric sensor (not shown), and focuses from the AF pixels 20L and 20R by the control of the solid-state imaging device 4 via the imaging control unit 5. After the detection signal is stored in the memory 7, the process returns to step S2.

  It should be noted that an image signal is generated by data corresponding to the output of the imaging pixel 20A stored in the memory 7 before determining YES in step S7, and this image signal is displayed on a liquid crystal display element such as a liquid crystal viewfinder (not shown). May also be displayed. At this time, it is preferable to perform the same interpolation processing as described above to generate and display image signals at the positions of the focus detection pixels 20L and 20R.

  The CPU 9 performs desired processing on the image signal generated in step S9 based on a command from the operation unit 14 in the image processing unit 13 or the image compression unit 12 as necessary, and stores it in the recording unit 11. The processed signal is output and recorded on the recording medium 11a.

  According to the present embodiment, since the focus detection pixels 20L and 20R have both the low-sensitivity photodiode 45 and the high-sensitivity photodiode 46, the high-sensitivity photodiode even when the luminance of the subject is low. 46, the focus detection signal can be appropriately obtained without being buried in noise or the like, and the focus detection signal can be obtained without saturation from the low-sensitivity photodiode 45 even if the luminance of the subject is high. You can get it properly. As described above, according to the present embodiment, the dynamic range for obtaining the focus detection signal is wide even when the change in the luminance of the subject is large. Therefore, the focus detection is appropriately performed at both low luminance and high luminance. It can be carried out.

  In this embodiment, since both the low-sensitivity photodiode 45 and the high-sensitivity photodiode 46 are provided in the same focus detection pixel, the positions are substantially the same at low luminance and high luminance. It is possible to detect the focus.

[Second Embodiment]
FIG. 11 is a partially enlarged schematic plan view of a solid-state imaging device 74 according to the second embodiment of the present invention, and corresponds to FIG. 12A is a schematic plan view schematically showing the main part of the AF pixel 20L, and FIG. 12B is a schematic cross-sectional view taken along line X7-X8 in FIG. This corresponds to 6 (a) and FIG. 6 (b). 13A is a schematic plan view schematically showing the main part of the AF pixel 20R, and FIG. 13B is a schematic cross-sectional view taken along line X9-X10 in FIG. 13A. This corresponds to 7 (a) and FIG. 7 (b). 11 to 13, elements that are the same as or correspond to those in FIGS. 4, 6, and 7 are assigned the same reference numerals, and redundant descriptions thereof are omitted.

  In FIG. 12A and FIG. 13A, the photodiode 45 is given the same hatching as the light attenuating portion 61 in FIG. 12B and FIG. It shows that the light attenuation part 61 is provided on the side.

  The solid-state imaging device 74 according to the present embodiment differs from the solid-state imaging device 4 according to the first embodiment only in the configuration relating to the low-sensitivity photodiode 45 of the AF pixels 20L and 20R. The solid-state image sensor 74 according to the present embodiment can be used in place of the solid-state image sensor 4 in the first embodiment.

  The sensitivity of the low-sensitivity photodiode 45 of the solid-state imaging device 4 is lower than that of the photodiode 46 by making the area smaller than the high-sensitivity photodiode 46 and reducing the effective light receiving area. In contrast, the low-sensitivity photodiode 45 of the solid-state imaging device 74 of the present embodiment has the same area as the high-sensitivity photodiode 46 and the same effective light receiving area, but the low-sensitivity photo diode 45 has the same area. While the light attenuating unit 61 is disposed on the light incident side of the diode 45, the light attenuating unit 61 is not disposed on the light incident side of the high sensitivity photodiode 46, so that the sensitivity is higher than that of the high sensitivity photodiode 46. It is low.

  In the present embodiment, the height position of the light attenuating unit 61 is the same as the height position of the color filter 60 of the imaging pixel 20A. Examples of the material of the light attenuating unit 61 include a gray filter and a color filter 60 that are made by combining red, blue, and green dyes in accordance with the spectral characteristics of the image sensor. But the height position and material of the light attenuation part 61 are not specifically limited.

  Also in this embodiment, the same advantages as those in the first embodiment can be obtained.

  Note that the sensitivity of the photodiodes 45 and 46 may be varied by disposing two types of light attenuating portions having different light attenuation factors on the light incident side of the photodiodes 45 and 46, respectively. Further, after making the effective light receiving areas of the photodiodes 45 and 46 different, a light attenuating portion is arranged on one or both light incident sides of the photodiodes 45 and 46, and the photodiodes 45 and 46 as a total of them. You may vary the sensitivity.

[Third Embodiment]
FIG. 14 is a partially enlarged schematic plan view of the focus detection apparatus 104 according to the third embodiment of the present invention, and corresponds to FIG. 14, elements that are the same as or correspond to those in FIG. 4 are given the same reference numerals, and redundant descriptions thereof are omitted.

  The focus detection apparatus 104 according to the present embodiment is obtained by replacing the imaging pixels 20A with AF pixels 20L and 20R in the solid-state imaging device 4 according to the first embodiment. That is, in the focus detection apparatus 104 according to the present embodiment, the AF pixels 20L and 20R are alternately arranged in the X-axis direction in any region. However, the AF pixels 20L and 20R may be formed only in a region necessary for detecting a desired focus, and the pixels 20L, 20R, and 20A may not be formed in other regions. Note that the focus detection apparatus according to the present invention may be, for example, one in which the imaging pixel 20A is replaced with the AF pixels 20L and 20R in the solid-state imaging device 74 according to the second embodiment.

  FIG. 15 is a schematic configuration diagram schematically showing an electronic camera 111 as an imaging device equipped with the focus detection device 104 shown in FIG. The electronic camera 111 is configured as a single-lens reflex electronic camera, but the focus detection device 104 is not limited to a digital single-lens reflex camera, and may be used in, for example, an electronic camera other than a single-lens reflex camera, a video camera, or the like. it can.

  In the electronic camera 111, a photographing lens 113 as an optical system to be a focus detection target is attached in front of the camera body 112. On the optical axis of the photographing lens 113, a main mirror 114 and a sub mirror 115 are arranged in order. A mat surface 116 and a pentaprism 117 are arranged along the reflection direction of the main mirror 114. On the rear surface side of the pentaprism 117, an eyepiece lens 118 and a photometry unit 119 as an AE detection unit are arranged. In the reflection direction of the sub mirror 115, an optical system 105 for arranging the focus detection device 104 at a position optically corresponding to the solid-state imaging device 110, and a focus detection device 104 as an AF sensor chip are sequentially arranged. Yes. On the rear side in the camera body 112, a solid-state image sensor 110 that images a subject image formed by the photographing lens 113 when the mirrors 114 and 115 are retracted is disposed. As the solid-state image sensor 110, for example, a general CMOS type or CCD type solid-state image sensor can be used.

  An operation unit (not shown), a photometry unit 119, and a focus detection device 104 provided in the camera body 112 are connected to a CPU 113 disposed in the camera body 112. In the first embodiment, the same elements as those in which the imaging control unit 5, the digital signal processing unit 6, the memory 7, and the focus calculation unit 10 are provided for the solid-state imaging device 4 are focus detections. Although it is similarly provided for the device 104, the illustration thereof is omitted in FIG. The CPU 113 is connected to a motor 120 that extends the photographing lens 113 back and forth.

  In this camera 111, an AF operation can be realized based on a focus detection signal from the focus detection device 104.

  In the focus detection device 104 according to the present embodiment, as in the solid-state imaging device 4 in the first embodiment, the dynamic range obtained by the focus detection signal is wide even when the luminance of the subject is large. Thus, it is possible to appropriately perform focus detection at both low luminance and high luminance. In the focus detection device 104 according to the present embodiment, as in the solid-state imaging device 4 in the first embodiment, both the low sensitivity photodiode 45 and the high sensitivity photodiode 46 have the same focus detection pixel. Therefore, it is possible to detect the focus at substantially the same position when the brightness is low and when the brightness is high.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

  For example, the configuration of the pixel 20 is not limited to the configuration illustrated in FIGS. 8 and 9 described above. For example, for each of a plurality of pixels 20 adjacent in the column direction, the plurality of pixels 20 may share one set of the floating capacitor 47, the amplification transistor 49, the reset transistor 50, and the selection transistor 51.

  Further, for example, in each of the above embodiments, in the effective pixel region 21, in addition to the focus detection region extending in the X-axis direction, a focus detection region extending in the Y-axis direction may be added, or the X-axis Instead of providing the focus detection area extending in the direction, a focus detection area extending in the Y-axis direction may be provided. In these cases, for example, in the focus detection region extending in the Y-axis direction, the AF pixel 20L is rotated 90 ° clockwise around the Z axis, and the AF pixel 20R is rotated 90 ° around the Z axis. The AF pixels rotated to the right may be alternately arranged in the Y-axis direction.

  In the present invention, it may be configured for black and white, and in that case, a color filter may not be provided in the imaging pixel 20A. Further, even when configured for color, it is not limited to the Bayer arrangement as described above.

DESCRIPTION OF SYMBOLS 1 Electronic camera 4,74 Solid-state image sensor 20A Imaging pixel 20L, 20R AF pixel Photodiode 41, 45, 46
104 Focus detection device

Claims (10)

A solid-state imaging device that photoelectrically converts a subject image formed by an optical system,
A plurality of imaging pixels having a photoelectric conversion unit that receives and photoelectrically converts incident light;
A plurality of focus detection units each having a first photoelectric conversion unit and a second photoelectric conversion unit that are present in one region and the other region in plan view, read signals independently of each other, and have different sensitivities. Pixels,
A solid-state imaging device comprising:   The solid-state imaging device according to claim 1, wherein an effective light receiving area of the first photoelectric conversion unit is different from an effective light receiving area of the second photoelectric conversion unit. The effective light receiving area of the first photoelectric conversion unit is at least a part of the outer edge of the first photoelectric conversion unit and / or the opening of the light shielding unit disposed on the light incident side of the first photoelectric conversion unit. Determined by at least part of
The effective light receiving area of the second photoelectric conversion unit is at least a part of the outer edge of the second photoelectric conversion unit and / or the opening of the light shielding unit disposed on the light incident side of the second photoelectric conversion unit. Determined by at least part of
The solid-state imaging device according to claim 2.   4. The light attenuating unit is provided on a light incident side of at least one of the first photoelectric conversion unit and the second photoelectric conversion unit. 5. The solid-state image sensor described in 1. The first photoelectric conversion unit and the second photoelectric conversion unit of each focus detection pixel emit light beams from the exit pupil regions that are decentered in the opposite directions from the center of the exit pupil of the optical system, respectively. Each receives light selectively and performs photoelectric conversion.
The solid-state imaging device according to claim 1, wherein the solid-state imaging device is provided.   Each of the focus detection pixels includes a micro lens that is provided on a one-to-one basis with respect to the pixel and guides incident light to the first photoelectric conversion unit and the second photoelectric conversion unit of the pixel. The solid-state image sensor according to any one of claims 1 to 5.   7. A solid-state imaging device according to claim 1, and a detection processing unit that outputs a detection signal indicating a focus adjustment state of the optical system based on a signal from the focus detection pixel. An imaging apparatus characterized by the above.   When the luminance is relatively high, the detection processing unit receives a signal from the photoelectric conversion unit having the lower sensitivity of the first and second photoelectric conversion units when the luminance is relatively high. The detection signal is output based on the signal, and when the luminance is relatively low, the detection is performed based on a signal from the photoelectric conversion unit having the higher sensitivity of the first and second photoelectric conversion units. 8. The imaging apparatus according to claim 7, wherein a signal is output.   The imaging apparatus according to claim 7, further comprising an adjustment unit that performs focus adjustment of the optical system based on a detection signal from the detection processing unit. A plurality of focus detection units each having a first photoelectric conversion unit and a second photoelectric conversion unit that are present in one region and the other region in plan view, read signals independently of each other, and have different sensitivities. With pixels,
The first photoelectric conversion unit and the second photoelectric conversion unit of each focus detection pixel are from the exit pupil regions that are decentered in opposite directions from the center of the exit pupil of the focus detection target optical system. Each of the light fluxes is selectively received and photoelectrically converted,
A focus detection apparatus.

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