Image sensor and imaging device

Abstract

To perform focus detection of a phase difference detection method for division directions by using signals output from a plurality of pixels different in the division direction with respect to microlenses, and bring phase difference detection performances between the division directions closer to each other.SOLUTION: An image pickup device includes a plurality of pixels arranged in a matrix state and reads signals from the pixels row by row. The plurality of pixels have a plurality of microlenses, and for each of the microlenses, a pair of first semiconductor areas, a pair of second semiconductor areas, and a plurality of connection areas connecting the first semiconductor areas and the second semiconductor areas. The arrangement direction of the first and second semiconductor areas of pixels having first arrangement is a first direction being a row direction. The arrangement direction of the first semiconductor areas of pixels having second arrangement is a second direction orthogonal to the first direction, and the arrangement direction of the second semiconductor areas of the pixels is the first direction. The crosstalk ratio between the first semiconductor areas in the second arrangement is reduced compared with the first arrangement.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an imaging device in which pixel portions each having a plurality of photoelectric conversion portions are two-dimensionally arranged, and an imaging apparatus equipped with the imaging device.

Background Art

[0002] As one of the focus detection methods performed in an imaging device, there is known a so-called imaging surface phase difference method in which a pair of pupil division signals are acquired using focus detection pixels formed in an imaging device, and phase difference focus detection is performed.

[0003] As an example of such an imaging surface phase difference method, Patent Document 1 discloses an imaging device using a two-dimensional imaging device in which one microlens and a plurality of divided photoelectric conversion portions are formed for one pixel. The plurality of photoelectric conversion portions are configured to receive light transmitted through different regions of the exit pupil of the imaging lens via one microlens, and perform pupil division. By calculating the amount of image shift from the phase difference signals which are the signals of the individual photoelectric conversion portions, phase difference focus detection can be performed. Further, an image can be acquired from an imaging signal obtained by adding together the signals of the individual photoelectric conversion portions for each pixel.

[0004] In such an image sensor, in a configuration in which a plurality of photoelectric conversion portions are arranged horizontally within a pixel and the pupil division direction is horizontal, for example, when the subject has a horizontal stripe pattern or the like, parallax is unlikely to appear and the focus detection accuracy may decrease.

[0005] To address this problem, Patent Document 2 discloses a technique for improving focus detection accuracy by using two different pixel arrangement directions for each microlens and two different pupil division directions. Patent Document 2 discloses a structure that separates adjacent pixels in the vertical direction and a structure that separates adjacent pixels in the horizontal direction, and the intensity of charge leakage to adjacent pixels is made different. With this structure, supersaturated charge received in an amount exceeding the charge that a single pixel can store is leaked and accumulated to different pixels arranged in predetermined directions, making it possible to perform phase-difference focus detection in the horizontal or vertical direction even when one pixel becomes saturated. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 58-24105 [Patent Document 2] Japanese Patent Publication No. 2014-107835 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the image sensor described in Patent Document 2 does not disclose the phenomenon of charge leakage to adjacent pixels (hereinafter referred to as "charge crosstalk") when a pixel is not saturated.

[0008] Furthermore, if the separation direction for multiple pixels corresponding to each microlens is a mix of horizontal and vertical directions, the simultaneity between signals read from pixels separated vertically (orthogonal to the row direction) is lost in an image sensor that reads signals sequentially row by row. Therefore, the focus detection performance of the phase-difference detection method may be lower than when using signals read from pixels separated horizontally (the row direction).

[0009] This invention has been made in view of the above problems, and aims to bring the phase difference detection performance between division directions closer together when performing focus detection using a phase difference detection method for each division direction using signals output from multiple pixels with different division directions for each microlens. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides an image sensor that includes a plurality of pixels arranged in a matrix and reads out the signals of the pixels row by row, wherein the plurality of pixels include a plurality of microlenses, a pair of first semiconductor regions formed at a first depth from the surface into which light is incident relative to each of the plurality of microlenses, a pair of second semiconductor regions formed at a second depth deeper than the first depth, and a plurality of connection regions connecting the pair of first semiconductor regions and the pair of second semiconductor regions respectively, wherein, for the plurality of pixels having a first arrangement, the direction of arrangement of the pair of first semiconductor regions and the pair of second semiconductor regions is the direction of the row, and for the plurality of pixels having a second arrangement, the direction of arrangement of the pair of first semiconductor regions is the second direction orthogonal to the first direction, and the direction of arrangement of the pair of second semiconductor regions is The aforementioned An image sensor characterized in that, in a first direction, the crosstalk rate between the pair of first semiconductor regions of a pixel having the second arrangement is lower than the crosstalk rate between the pair of first semiconductor regions of a pixel having the first arrangement. [Effects of the Invention]

[0011] According to the present invention, when performing focus detection using a phase difference detection method for each division direction using signals output from multiple pixels with different division directions for each microlens, the phase difference detection performance between division directions can be made more uniform. [Brief explanation of the drawing]

[0012] [Figure 1] A block diagram showing the schematic configuration of the imaging device according to the first embodiment. [Figure 2]A diagram schematically showing an example of the overall configuration of an image pickup device according to the first embodiment. [Figure 3] An equivalent circuit diagram of a pixel according to the first embodiment. [Figure 4] A schematic diagram showing the configuration of a pixel having the first arrangement according to the first embodiment. [Figure 5] A schematic diagram showing the configuration of a pixel having the second arrangement according to the first embodiment. [Figure 6] A diagram showing the relationship between a pixel having the first arrangement according to the first embodiment and a partial pupil region. [Figure 7] A conceptual diagram showing an example of the pupil intensity distribution of a partial pupil region corresponding to a pixel having the first arrangement according to the first embodiment. [Figure 8] A diagram schematically explaining the sensor entrance pupil of an image pickup device according to the first embodiment. [Figure 9] A diagram showing a schematic relationship between the amount of image shift and the amount of defocus between parallax images according to the first embodiment. [Figure 10] A diagram showing the relationship between a pixel having the second arrangement according to the first embodiment and a partial pupil region. [Figure 11] A conceptual diagram showing an example of the pupil intensity distribution of a partial pupil region corresponding to a pixel having the second arrangement according to the first embodiment. [Figure 12] A schematic diagram showing the configuration of a pixel having the third arrangement according to the second embodiment. [Figure 13] A schematic diagram showing the configuration of a pixel having the fourth arrangement according to the second embodiment. [Figure 14] A diagram showing the relationship between a pixel having the third arrangement according to the second embodiment and a partial pupil region. [Figure 15] A conceptual diagram showing an example of the pupil intensity distribution of a partial pupil region corresponding to a pixel having the third arrangement according to the second embodiment. [Figure 16] A diagram showing the relationship between a pixel having the fourth arrangement according to the second embodiment and a partial pupil region. [Figure 17] A conceptual diagram showing an example of the pupil intensity distribution of a partial pupil region corresponding to a pixel having the fourth arrangement according to the second embodiment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] <First Embodiment> [Overall Configuration] FIG. 1 is a block diagram showing a schematic configuration of an imaging device according to a first embodiment of the present invention. The imaging device of the present embodiment includes an image sensor 1, an overall control / arithmetic unit 2, an instruction unit 3, a timing generation unit 4, a photographing lens unit 5, a lens driving unit 6, a signal processing unit 7, a display unit 8, and a recording unit 9.

[0015] The photographing lens unit 5 forms an optical image of a subject on the image sensor 1. Although it is represented by a single lens in the figure, the photographing lens unit 5 may include a plurality of lenses including a focus lens, a zoom lens, etc., and an aperture, and may be detachable from the main body of the imaging device or may be integrally configured with the main body.

[0016] The image sensor 1 converts the light incident through the photographing lens unit 5 into an electrical signal and outputs it. From each pixel of the image sensor 1, a pupil-divided pupil-divided signal (hereinafter referred to as a "phase difference signal") that can be used for phase difference type focus detection and an image signal that is a signal for each pixel are read out as signals so as to be acquired.

[0017] The signal processing unit 7 performs predetermined signal processing such as correction processing on the signal output from the image sensor 1, and outputs a phase difference signal used for focus detection and an image signal used for recording.

[0018] The overall control and calculation unit 2 performs the overall drive and control of the entire imaging device. It also performs calculations for focus detection using the phase difference signal processed by the signal processing unit 7, and performs predetermined signal processing on the image signal, such as calculation processing for exposure control, development, and compression to generate images for recording and playback.

[0019] The lens drive unit 6 drives the shooting lens unit 5 and performs focus control, zoom control, aperture control, etc., on the shooting lens unit 5 according to the control signals from the overall control and calculation unit 2.

[0020] The instruction unit 3 receives inputs from the outside, such as instructions to execute shooting, settings for the drive mode of the imaging device, and various other settings and selections, via user operations, and transmits them to the overall control and calculation unit 2.

[0021] The timing generation unit 4 generates timing signals to drive the image sensor 1 and the signal processing unit 7 according to the control signals from the overall control and calculation unit 2. The display unit 8 displays information such as preview images, playback images, and the drive mode settings of the imaging device.

[0022] The recording unit 9 is equipped with a recording medium (not shown) on which recording image signals are recorded. Examples of recording media include semiconductor memory such as flash memory. The recording medium may be detachable from the recording unit 9 or may be built into it.

[0023] [Image sensor] Figure 2 is a schematic diagram showing an example of the overall configuration of the image sensor 1 shown in Figure 1. The image sensor 1 includes a pixel array section 201, a vertical selection circuit 202, a column circuit 203, and a horizontal selection circuit 204.

[0024] Multiple pixels 205 are arranged in a matrix in the pixel array section 201. The output of the vertical selection circuit 202 is input to the pixels 205 via the pixel drive wiring group 207, and the pixel signals of the pixels 205 in the row selected by the vertical selection circuit 202 are read out row by row via the output signal line 206 to the column circuit 203. One output signal line 206 can be provided for each pixel column, or for multiple pixel columns, or multiple output signal lines 206 can be provided for each pixel column. Signals read out in parallel via multiple output signal lines 206 are input to the column circuit 203, where processing such as signal amplification, noise reduction, and A / D conversion is performed, and the processed signals are held. The horizontal selection circuit 204 sequentially, randomly, or simultaneously selects the signals held in the column circuit 203, and the selected signals are output outside the image sensor 1 via a horizontal output line and output section (not shown).

[0025] By sequentially performing the operation of outputting the pixel signals of the rows selected by the vertical selection circuit 202 to the outside of the image sensor 1, while changing the rows selected by the vertical selection circuit 202, it is possible to read out a two-dimensional imaging signal or a phase difference signal from the image sensor 1.

[0026] [Pixel circuit / signal readout] Figure 3 is an equivalent circuit diagram of pixel 205 in this embodiment. Each pixel 205 has two photodiodes 301 (PDA) and 302 (PDB), which are photoelectric conversion units. Depending on the amount of incident light, the signal charge is photoelectrically converted by the PDA 301 and stored, and then transferred via the transfer switch (TXA) 303 to the floating diffusion unit (FD) 305, which constitutes the charge storage unit. The signal charge is photoelectrically converted by the PDB 302 and stored, and then transferred via the transfer switch (TXB) 304 to the FD 305. When the reset switch (RES) 306 is turned on, it resets the FD 305 to the voltage of the constant voltage source VDD. Also, by turning on RES 306, TXA 303 and TXB 304 simultaneously, the PDA 301 and PDB 302 can be reset.

[0027] When the selection switch (SEL) 307 for selecting pixels is turned ON, the amplification transistor (SF) 308 converts the signal charge stored in FD305 into a voltage, and the converted signal voltage is then used to select pixels. 205 The signal is output to output signal line 206. In addition, the gates of TXA303, TXB304, RES306, and SEL307 are connected to the pixel drive wiring group 207 and controlled by the vertical selection circuit 202.

[0028] In this embodiment, the signal charge accumulated in the photoelectric conversion unit is assumed to be electrons, the photoelectric conversion unit is formed from an N-type semiconductor, and the separation is performed using a P-type semiconductor. However, the signal charge may be assumed to be holes, the photoelectric conversion unit may be formed from a P-type semiconductor, and the separation may be performed using an N-type semiconductor.

[0029] Next, we will describe the operation of reading the signal charge from PDA301 and PDB302 after resetting PDA301 and PDB302 and after a predetermined charge accumulation time has elapsed, in a pixel having the above-described configuration. First, when the SEL307 of the row selected by the vertical selection circuit 202 is turned on and the source of SF308 and the output signal line 206 are connected, the output signal line 206 enters a state where a voltage corresponding to the voltage of FD305 is read. Subsequently, RES306 is turned on / off and the potential of FD305 is reset. After that, the circuit waits until the output signal line 206, which has been affected by the voltage fluctuation of FD305, stabilizes, and the voltage of the stabilized output signal line 206 is acquired as the signal voltage N by the column circuit 203, and the signal is processed and held.

[0030] Subsequently, TXA303 is switched on / off, and the signal charge stored in PDA301 is transferred to FD305. The voltage of FD305 decreases by an amount corresponding to the amount of signal charge stored in PDA301. Then, the system waits until the output signal line 206, which has been affected by the voltage fluctuation of FD305, stabilizes. The voltage of the stabilized output signal line 206 is then taken as signal voltage A by the column circuit 203, processed, and held.

[0031] Subsequently, TXB304 is switched on / off, and the signal charge stored in PDB302 is transferred to FD305. The voltage of FD305 decreases by an amount corresponding to the amount of signal charge stored in PDB302. Then, the circuit waits until the output signal line 206, which has been affected by the voltage fluctuation of FD305, stabilizes. The voltage of the stabilized output signal line 206 is then taken as the signal voltage (A+B) by the column circuit 203, processed, and held.

[0032] In this way, the difference between the acquired signal voltage N and signal voltage A allows us to obtain signal A corresponding to the amount of signal charge stored in PDA301. Furthermore, the difference between signal voltage A and signal voltage (A+B) allows us to obtain signal B corresponding to the amount of signal charge stored in PDB302. This difference calculation may be performed in the column circuit 203 or after output from the image sensor 1. A phase difference signal can be obtained using signals A and B respectively, and the imaging signal can be obtained by adding signals A and B together. Alternatively, if the difference calculation is performed after output from the image sensor 1, the imaging signal may be obtained by taking the difference between signal voltage N and signal voltage (A+B).

[0033] [Configuration of the photoelectric conversion area] • Lateral phase difference detection pixel structure Figure 4 is a schematic diagram showing the first arrangement of semiconductor regions constituting the pixel 205 according to this embodiment, where Figure 4(a) is an oblique schematic diagram and Figure 4(b) is a planar schematic diagram showing the positional relationship in a planar view. Note that "planar view" refers to viewing from the z direction or -z direction with respect to a plane (xy plane) that is roughly parallel to the side of the semiconductor substrate where the transistor gate is located. Also, the "horizontal" direction refers to the x direction, the "vertical" direction refers to the y direction, and the "depth" direction refers to the z direction.

[0034] As shown in Figure 4(a), the pixel 205 having the first arrangement includes a microlens (ML) 401, storage regions 411, 412, sensitivity regions 413, 414, connection regions 415, 416, TXA303, TXB304, and FD305. Furthermore, the sensitivity regions 413 and 414 are formed to a first depth from the surface into which light is incident. Storage areas 411 and 412 areIt is formed at a second depth, which is deeper than the first depth. Also, for the sake of clarity, the region where charge is mainly generated in response to incident light is called the "sensitivity region," and the region where the generated charge is mainly accumulated is called the "accumulation region," however, there is no clear distinction between the charge generation region and the accumulation region. Charge is also generated in the accumulation regions 411 and 412 in response to the arriving light, and some of the generated charge is retained in the sensitivity regions 413 and 414. It is assumed that a color filter (not shown) is placed between ML401 and the sensitivity regions 413 and 414.

[0035] In the first configuration, PDA301 includes a storage area 411, a sensitivity area 413, and a connection area 415, while PDB302 includes a storage area 412, a sensitivity area 414, and a connection area 416. In the first configuration, storage areas 411 and 412 and sensitivity areas 413 and 414 all extend in the y-direction, i.e., in the same direction. That is, the division direction of the sensitivity area and the division direction of the storage area in the first configuration are both in the x-direction. Because the division direction of the sensitivity area is in the x-direction, phase difference AF can be performed using phase difference signals obtained at the same timing from the same row selected by the vertical selection circuit 202.

[0036] Most of the light incident through ML401 is photoelectrically converted in sensitivity regions 413 and 414. The charge generated in sensitivity region 413 moves to storage region 411 via connection region 415 and is stored there. Similarly, the charge generated in sensitivity region 414 moves to storage region 412 via connection region 416 and is stored there. Here, a potential gradient is formed within sensitivity regions 413 and 414 such that the potential experienced by electrons decreases in the depth direction, so that charge moves from sensitivity regions 413 and 414 to storage regions 411 and 412. In addition, the region between sensitivity region 413 and sensitivity region 414 has a higher p-type impurity concentration than within the sensitivity region so that a potential barrier is formed. In the following explanation, the regions between sensitivity regions and between storage regions will be referred to as partitioned regions.

[0037] • Charge crosstalk rate distribution Most of the charge generated within the sensitivity region 413 is stored in the storage region 411 via the connection region 415 as described above. However, it may also move from the sensitivity region 413 to the sensitivity region 414, and then to the storage region 412 via the connection region 416, where it may be stored. This phenomenon of charge moving from PDA 301 to PDB 302, or from PDB 302 to PDA 301, is called "charge crosstalk." The rate at which charge crosstalk occurs (hereinafter referred to as the "charge crosstalk rate") is higher the closer it is to the division region between the sensitivity regions in a plan view. That is, in a plan view, the charge crosstalk rate of a charge generated in the center of the sensitivity region 413 is lower than the charge crosstalk rate of a charge generated in the sensitivity region 413 closer to the sensitivity region 414. Also, the shorter the path to the storage region, the lower the charge crosstalk rate. That is, within the sensitivity region, for the same x and y coordinates, the charge crosstalk rate is lower at locations closer to the storage region than at locations closer to ML 401. In the following explanation, the distribution of crosstalk rate within the sensitivity region will be referred to as the "charge crosstalk rate distribution."

[0038] This charge crosstalk rate distribution is smaller as the potential barrier between sensitivity region 413 and sensitivity region 414 is higher, and also as the potential gradient in the depth direction within the sensitivity region is steeper. In this embodiment, since the sensitivity region and the storage region are formed separately in the depth direction, the charge crosstalk rate distribution can be adjusted by changing the structure between the sensitivity regions without changing the structure between the storage regions, which is one of the factors that determine the transport characteristics of supersaturated charge.

[0039] Charge crosstalk can also occur between adjacent pixels. Charge crosstalk between adjacent pixels is a factor that reduces the resolution of the imaging signal. Therefore, it is desirable to keep the charge crosstalk rate between adjacent pixels lower than the charge crosstalk rate from PDA301 to PDB302 or from PDB302 to PDA301. Specifically, for example, the charge crosstalk rate can be kept low by separating adjacent pixels with an insulator or by increasing the height of the potential barrier.

[0040] • Vertical phase difference detection pixel structure Figure 5 is a schematic diagram showing the second arrangement of semiconductor regions constituting the pixel 205 according to this embodiment, where Figure 5(a) is an oblique schematic diagram and Figure 5(b) is a plan schematic diagram showing the positional relationship in a plan view. The definitions of "plan view" and x, y, and z are the same as in Figure 4, so their explanation is omitted.

[0041] As shown in Figure 5(a), the pixel 205 having the second arrangement includes ML401, storage regions 411 and 412 formed at a second depth, sensitivity regions 513 and 514 formed at a first depth, connection regions 415 and 416, TXA303, TXB304, and FD305. In the second arrangement, PDA301 includes storage region 411, sensitivity region 513, and connection region 415, and PDB302 includes storage region 412, sensitivity region 514, and connection region 416. Also in the second arrangement, storage regions 411 and 412 are y It extends in the direction, and the sensitive regions 513 and 514 are x It extends in the direction and in a plan view in a direction that is orthogonal, i.e., in a different direction. Furthermore, in the second arrangement, the division direction of the sensitivity region is the y direction, and the division direction of the accumulation region is the x direction. Note that a color filter (not shown) is placed between ML401 and the sensitivity regions 513 and 514.

[0042] In the second configuration, the potential gradient in the depth direction within the sensitive regions 513 and 514 is formed to be steeper than the potential gradient in the depth direction within the sensitive regions 413 and 414 in the first configuration. Furthermore, the potential barrier between sensitive region 513 and sensitive region 514 is higher than the potential barrier between sensitive region 413 and sensitive region 414, so that the p-type impurity concentration in the region between sensitive regions 513 and 514 is higher than that in the region between sensitive regions 413 and 414. By forming it in this way, the charge crosstalk rate distribution between sensitive regions 513 and 514 becomes smaller than the charge crosstalk rate distribution between sensitive regions 413 and 414.

[0043] • Method for detecting lateral phase difference Next, we will explain the calculation performed in the overall control and calculation unit 2 to calculate the defocus amount from the phase difference signal.

[0044] First, with reference to Figures 6 to 9, the focus detection method using the x-direction phase difference detection method in this embodiment will be described. In the focus detection method using the x-direction phase difference detection method in this embodiment, the amount of image displacement in the x-direction is calculated from the phase difference signal of the pixel 205 having the first arrangement, and converted into a defocus amount using a conversion coefficient.

[0045] Figure 6 shows a cross-sectional view of pixel 205 having the first arrangement, shown along the line A-A' in Figure 4, and the pupil plane at a distance Ds in the negative z-axis direction from the imaging surface 600 of the image sensor 1. Note that x, y, and z represent the coordinate axes on the imaging surface 600, and xp, yp, and zp represent the coordinate axes on the pupil plane.

[0046] Through ML401, the pupil surface and the light-receiving surface of the image sensor 1 are in a substantially conjugate relationship. Therefore, the light beam passing through the partial pupil region 601 is received in the sensitivity region 413 or the accumulation region 411. Similarly, the light beam passing through the partial pupil region 602 is received in the sensitivity region 414 or the accumulation region 412. Thus, when the pupil surface is divided in the x direction, the pupil division direction is the x direction. Therefore, the position dependence of the pupil intensity distribution on the division direction takes the shape illustrated in Figure 7.

[0047] In Figure 7, the first pupil intensity distribution corresponding to the sensitivity region 413 and the storage region 411 is 701, and the second pupil intensity distribution corresponding to the sensitivity region 414 and the storage region 412 is 702. Since the signal charge received in the sensitivity region 413 and the storage region 411 is stored in the storage region 411, the signal read out from the pixel is a combined signal as shown in the first pupil intensity distribution 701. Looking at each region individually, the pupil intensity distribution corresponding to the sensitivity region 413 is 703, and the pupil intensity distribution corresponding to the storage region 411 is 705. Similarly, the pupil intensity distribution corresponding to the sensitivity region 414 is 704, and the pupil intensity distribution corresponding to the storage region 412 is 706.

[0048] Next, with reference to Figure 8, the sensor entrance pupil of the image sensor 1 will be described. In the image sensor 1 of this embodiment, the ML401 of each pixel 205 is continuously shifted toward the center of the image sensor 1 according to the image height coordinate on a two-dimensional plane. That is, each ML401 is arranged to be eccentric toward the center as the image height increases. The center of the image sensor 1 and the optical axis of the imaging optical system change due to the mechanism that reduces the effects of blur caused by camera shake, etc., by driving the imaging optical system or the image sensor 1, but they are approximately the same. As a result, the first pupil intensity distribution 701 and the second pupil intensity distribution 702 of each pixel 205 positioned at each image height coordinate of the image sensor 1 are configured to be approximately the same at the pupil plane at a distance Ds from the image sensor 1. In other words, the first pupil intensity distribution 701 and the second pupil intensity distribution 702 of all pixels of the image sensor 1 are configured to be approximately the same at the pupil plane at a distance Ds from the image sensor 1.

[0049] Hereinafter, the first pupil intensity distribution 701 and the second pupil intensity distribution 702 will be referred to as the "sensor entrance pupil" of the image sensor 1, and the distance Ds will be referred to as the "sensor pupil distance" of the image sensor 1. It is not necessary for all pixels to have a single entrance pupil distance; for example, the entrance pupil distances of pixels up to 80% of the image height may be made approximately the same, or pixels may be configured to have different entrance pupil distances for each row or detection area.

[0050] Figure 9 shows a schematic relationship between the amount of image shift and the amount of defocus between disparity images. The image sensor 1 (not shown) of this embodiment is placed on the imaging surface 600, and, as in Figure 6, the exit pupil of the imaging optical system is divided into two parts: a partial pupil region 601 and a partial pupil region 602.

[0051] The amount of defocus d is defined as the distance from the imaging plane to the subject's imaging position, with magnitude |d| being negative (d<0) for a front-focus state where the subject's imaging position is on the subject side of the imaging plane, and positive (d>0) for a back-focus state where the subject's imaging position is on the opposite side of the imaging plane. The in-focus state where the subject's imaging position is on the imaging plane is d=0. Figure 9 shows an example where the subject on object plane 901 is in focus (d=0) and the subject on object plane 902 is front-focused (d<0). The front-focused state (d<0) and the back-focused state (d>0) together are considered a defocused state (|d|>0).

[0052] In the front-focused state (d<0), the light beam from the subject on the object surface 902 that passes through the partial pupil region 601 (602) converges once, then spreads out with a width Γ1 (Γ2) centered on the centroid position G1 (G2) of the light beam, resulting in a blurred image on the imaging surface 600. The blurred image is received by the sensitivity region 413 and the accumulation region 411, and the sensitivity region 414 and the accumulation region 412, and a disparity image is generated. Therefore, the generated disparity image will have the image of the subject on the object surface 902 blurred with a width Γ1 (Γ2) at the centroid position G1 (G2).

[0053] The blur width Γ1 (Γ2) of the subject image increases roughly proportionally with increasing defocus amount d |d|. Similarly, the amount of image displacement p (=G2-G1) of the subject image between the parallax images |p| also increases roughly proportionally with increasing defocus amount d |d|. The same applies in the back-focused state (d>0), although the direction of image displacement of the subject image between the parallax images is opposite to that of the front-focused state. In the in-focus state (d=0), the centroid positions of the subject images between the parallax images coincide (p=0), and no image displacement occurs.

[0054] Therefore, in the two phase difference signals obtained using the signals from sensitivity region 413 and storage region 411, and sensitivity region 414 and storage region 412, the magnitude of the x-direction image shift between the two phase difference signals increases as the magnitude of the defocus amount of the disparity image increases. Based on this relationship, the phase difference detection method performs focus detection by converting the image shift amount calculated by correlation calculation of the x-direction image shift amount between disparity images into a defocus amount. The coefficient multiplied when converting from image shift amount to defocus amount is called the conversion coefficient. If this conversion coefficient is large, compared to the case where the conversion coefficient is small, a large defocus amount is calculated from a small image shift amount, making it more susceptible to noise in the phase difference signal and potentially degrading the phase difference detection performance.

[0055] • Method for detecting vertical phase difference Next, referring to Figures 10 and 11, we will explain the focus detection method using phase difference detection where the pupil division direction is in the y-direction. We will omit the explanation of parts that are the same as the focus detection method using phase difference detection where the pupil division direction is in the x-direction, and explain the differences. In the focus detection method using phase difference detection in the y-direction, the amount of image displacement in the y-direction is calculated from the phase difference signal of pixel 205 having a second arrangement where the pupil division direction is in the y-direction, and the amount of image displacement is converted into a defocus amount using the conversion coefficient Ky.

[0056] Figure 10 shows a cross-sectional view of pixel 205 having the second arrangement, taken along the line B-B' shown in Figure 5(b), and the pupil plane located at a distance Ds in the negative z-axis direction from the imaging surface 600 of the image sensor 1.

[0057] Through ML401, the pupil surface and the light-receiving surface of the image sensor 1 are in a roughly conjugate relationship. Therefore, the light received in sensitivity region 513 is the light beam that has passed through partial pupil region 1001, and the light received in sensitivity region 514 is the light beam that has passed through partial pupil region 1002. Similarly, the light received in storage region 411 is the light beam that has passed through partial pupil region 1003, and the light received in storage region 412 is the light beam that has passed through partial pupil region 1004. The proportion of light received in sensitivity regions 513 and 514 and the proportion received in storage regions 411 and 412 are roughly determined by the wavelength of the received light, but the majority of the light is received in sensitivity regions 513 and 514. Therefore, the pupil division direction is basically the y-direction, and the position dependence of the pupil intensity distribution on the division direction is as shown by the solid line in Figure 11.

[0058] The charge crosstalk rate distribution in sensitivity region 513 and sensitivity region 514 is smaller than that of sensitivity region 413 and sensitivity region 414. Therefore, the corresponding pupil intensity distributions are 1103 and 1104, and compared to pupil intensity distributions 703 and 704, the slope of the portion where the signal intensity matches (signal crossover point) is steeper. Also, since the storage regions 411 and 412 are not divided in the y direction, the corresponding pupil intensity distributions have shapes like 1105 and 1106. The signal charge received in sensitivity region 513 and storage region 411 is stored in storage region 411, so the signal read out from the pixel is a combined signal of pupil intensity distributions 1103 and 1105, as shown in the first pupil intensity distribution 1101. Similarly, the signal charge received in sensitivity region 514 and storage region 412 has a shape like the second pupil intensity distribution 1102. By making the charge crosstalk rate distribution between sensitivity region 513 and sensitivity region 514 smaller than the charge crosstalk rate distribution between sensitivity region 413 and sensitivity region 414, the accumulation region that is not divided in the pupil division direction is made smaller. Tsu stroke The slope of the phase difference signal read out from the source can be made approximately equal near the signal crossover point.

[0059] The method for calculating the defocus amount from the phase difference signal differs in that the direction of image shift calculation changes from the x-direction to the y-direction, but the calculation procedure is the same as for calculating the defocus amount in the x-direction. In this case, since the slopes near the signal crossover point of the first pupil intensity distribution 1101 and the second pupil intensity distribution 1102 are approximately equal, the defocus amount can be calculated from the image shift amount using approximately equal conversion coefficients. In other words, approximately equal phase difference detection performance can be obtained.

[0060] As described above, according to the first embodiment, the potential barrier of the separation region between sensitivity regions of pixels with different division directions for the sensitivity region and the storage region is made higher than the potential barrier of the separation region between sensitivity regions of pixels with the same division direction for the sensitivity region and the storage region. As a result, even if the division directions for the sensitivity region and the storage region are different, phase difference detection performance that is approximately the same as when the division directions for the sensitivity region and the storage region are the same can be obtained.

[0061] <Second Embodiment> Next, a second embodiment of the present invention will be described. The configuration of the imaging device in the second embodiment is the same as that described with reference to Figures 1 to 3, so its description will be omitted. As described with reference to Figure 2, signals are read out from the pixels 205 at different timings for each row by the selection of the vertical selection circuit 202. Therefore, the phase difference signals obtained from pixels 205 having the first arrangement are read out at the same timing, whereas the phase difference signals obtained from pixels 205 having the second arrangement are read out at different timings for each row, resulting in reduced simultaneity. In the second embodiment, charge crosstalk is used to bring the quality of the phase difference signals separated in the x direction and the phase difference signals separated in the y direction closer together. The pixel configuration and phase difference detection method in the second embodiment will be described below.

[0062] [Configuration of the photoelectric conversion area] • Vertical phase difference detection pixel structure Figure 12 is a schematic diagram showing a third arrangement of semiconductor regions constituting the pixel 205 according to the second embodiment, where Figure 12(a) is an oblique schematic diagram and Figure 12(b) is a plan schematic diagram showing the positional relationship in a plan view. The definitions of "plan view" and x, y, and z are the same as in Figure 4, so their explanation is omitted.

[0063] As shown in Figure 12(a), the pixel 205 having the third arrangement includes ML401, storage regions 1211 and 1212 formed at a second depth, sensitivity regions 1213 and 1214 formed at a first depth, connection regions 1215 and 1216, TXA303, TXB304, and FD305. In the third arrangement, PDA301 includes storage region 1211, sensitivity region 1213, and connection region 1215, and PDB302 includes storage region 1212, sensitivity region 1214, and connection region 1216. In addition, TXA303, TXB304, and FD305 are arranged next to PDA301 and PDB302. Therefore, in the third arrangement, storage regions 1211 and 1212 and sensitivity regions 1213 and 1214 all extend in the x direction, i.e., in the same direction. Furthermore, in the third configuration, the division direction of the sensitivity region and the accumulation region is the y-direction. In this case, since the division direction of the sensitivity region is the y-direction, phase difference AF is performed using phase difference signals obtained from different rows at different timings by the selection of the vertical selection circuit 202. It is assumed that a color filter (not shown) is placed between ML401 and sensitivity regions 1213 and 1214.

[0064] • Lateral phase difference detection pixel structure Figure 13 is a schematic diagram showing the fourth arrangement of semiconductor regions constituting the pixel 205 according to this embodiment. Figure 13(a) is an oblique schematic diagram, and Figure 13(b) is a planar schematic diagram showing the positional relationship in a planar view. The definitions of "planar view" and x, y, and z are the same as in Figure 4, so their explanation is omitted.

[0065] As shown in Figure 13(a), the pixel 205 having the fourth arrangement includes ML401, storage areas 1211 and 1212, sensitivity areas 1313 and 1314, connection areas 1215 and 1216, TXA303, TXB304, and FD305. In the fourth arrangement, PDA301 includes storage area 1211, sensitivity area 1313, and connection area 1215, and PDB302 includes storage area 1212, sensitivity area 1314, and connection area 1216. In the fourth arrangement, storage areas 1211 and 1212 extend in the x direction, and sensitivity areas 1313 and 1314 extend in the y direction, extending in orthogonal directions, i.e., different directions, in a plan view. In addition, the division direction of the sensitivity area in the fourth arrangement is the x direction, and the division direction of the storage area is the y direction. In this case, since the division direction of the sensitivity region is the x-direction, phase-difference AF can be performed using signals obtained at the same timing from the same row selected by the vertical selection circuit 202. Therefore, it has higher simultaneity compared to pixels 205 having a third arrangement. Note that ML401 and sensitivity region 13 13, 13 A color filter (not shown) is assumed to be placed between 14 and 14.

[0066] In the second embodiment, the potential barrier between sensitivity region 1213 and sensitivity region 1214 and the potential barrier between sensitivity region 1313 and sensitivity region 1314 have approximately the same structure. 1213、1214、1313、1314 The structure also has approximately equal potential gradients in the depth direction within the region. Therefore, the charge crosstalk rate distribution between sensitivity region 1213 and sensitivity region 1214 is approximately equal to the charge crosstalk rate distribution between sensitivity region 1313 and sensitivity region 1314.

[0067] • Vertical pupil intensity distribution Referring to Figures 14 and 15, the pupil intensity distribution of the phase difference detection method where the pupil division direction is in the y-direction will be explained.

[0068] Figure 14 shows a cross-sectional view of pixel 205 having the third arrangement, shown in Figure 12 along the line C-C', and the pupil plane of the image sensor 1 at a distance Ds in the negative z-axis direction from the imaging surface 600. Note that x, y, and z represent the coordinate axes on the imaging surface 600, and xp, yp, and zp represent the coordinate axes on the pupil plane.

[0069] Through ML401, the pupil surface and the light-receiving surface of the image sensor 1 are in a substantially conjugate relationship. Therefore, the light received in the sensitivity region 1213 and the storage region 1211 is the light beam that has passed through the partial pupil region 1401, and the light received in the sensitivity region 1214 and the storage region 1212 is the light beam that has passed through the partial pupil region 1402. As a result, the pupil division direction is the y-direction, and the position dependence of the pupil intensity distribution on the division direction is as shown in Figure 15.

[0070] In Figure 15, the first pupil intensity distribution corresponding to the sensitivity region 1213 and the storage region 1211 is 1501, and the second pupil intensity distribution corresponding to the sensitivity region 1214 and the storage region 1212 is 1502. Since the signal charge received in the sensitivity region 1213 and the storage region 1211 is stored in the storage region 1211, the signal read from the pixel becomes a combined signal as shown in the first pupil intensity distribution 1501. Looking at each region individually, the pupil intensity distribution corresponding to the sensitivity region 1213 is 1503, and the pupil intensity distribution corresponding to the storage region 1211 is 1505. Similarly, the sensitivity region 12 The pupil intensity distribution corresponding to 14 is 1504, and the pupil intensity distribution corresponding to the accumulation region 1212 is 1506.

[0071] • Lateral pupil intensity distribution Next, with reference to Figures 16 and 17, we will explain the pupil intensity distribution using a phase difference detection method where the pupil division direction is in the x-direction.

[0072] Figure 16 shows a D-D' cross-sectional view of pixel 205 having the fourth arrangement, as shown in Figure 13(b), and the pupil plane at a distance Ds in the negative z-axis direction from the imaging surface 600 of the image sensor 1.

[0073] Through the ML401, the pupil surface and the light-receiving surface of the image sensor 1 are in a substantially conjugate relationship. Therefore, the light received in the sensitivity region 1313 is the light beam that has passed through the partial pupil region 1601, and the light received in the sensitivity region 1314 is the light beam that has passed through the partial pupil region 1602. Similarly, the light received in the storage region 1211 is the light beam that has passed through the partial pupil region 1603, and the light received in the storage region 1212 is the light beam that has passed through the partial pupil region 1604. The proportion of light received in the sensitivity regions 1313 and 1314 and the proportion of light received in the storage regions 1211 and 1212 are similar to those in Embodiment 1, with the majority of the light being received in the sensitivity regions 1313 and 1314. Therefore, the pupil division direction is basically the x-direction, and the position dependence of the pupil intensity distribution on the division direction is as shown by the solid line in Figure 17.

[0074] The charge crosstalk rate distribution in sensitivity region 1313 and sensitivity region 1314 is equivalent to that of sensitivity region 1213 and sensitivity region 1214. Therefore, the corresponding pupil intensity distributions are 1703 and 1704, which have the same shape as pupil intensity distributions 1503 and 1504. Also, since the storage regions 1211 and 1212 are not divided in the x direction, the corresponding first and second pupil intensity distributions are 1705 and 1706. The signal charge received in sensitivity region 1313 and storage region 1211 is stored in storage region 1211, so the signal read out from the pixel is a combined signal of pupil intensity distributions 1703 and 1705, as shown in the first pupil intensity distribution 1701. Similarly, the signal charge received in sensitivity region 1314 and storage region 1212 has a shape like the second pupil intensity distribution 1702. In this way, by making the charge crosstalk rate distribution between sensitivity regions 1313 and 1314 equivalent to the charge crosstalk rate distribution between sensitivity regions 1213 and 1214, the slope near the signal crossover point in a vertical phase difference signal with an accumulation region that is not divided in the pupil division direction can be made steeper than the slope near the signal crossover point in a horizontal phase difference signal.

[0075] As described above, while the horizontal phase difference signal is obtained from a group of pixel signals driven simultaneously by the vertical selection circuit 202, the vertical phase difference signal is obtained from a group of pixel signals read out at different times, thus reducing the simultaneity of the phase difference signals. Therefore, by making the slope of the vertical signal crossover point steeper, as in the third and fourth pixels, the vertical conversion coefficient can be made smaller than the horizontal conversion coefficient. This improves the noise immunity of vertical phase difference detection and makes it less susceptible to the disruption of the simultaneity of the phase difference signals mentioned above. Consequently, approximately the same phase difference detection performance can be obtained for pixels with different division directions for the sensitivity region and the storage region, and for pixels with the same division direction for the sensitivity region and the storage region.

[0076] As described above, according to the second embodiment, by setting the division direction of the storage region to the row selection direction, it becomes possible to obtain approximately equal phase difference detection performance in the x and y directions without differentiating the potential gradient of the sensitivity region or the potential barrier between sensitivity regions.

[0077] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0078] 1: Image sensor, 202: Vertical selection circuit, 205: Pixel, 301: Photodiode (PDA), 302: Photodiode (PDB), 303: Transfer switch (TXA), 304: Transfer switch (TXB), 305: Floating diffusion section (FD), 401: Microlens (ML), 411, 412, 1211, 1212: Accumulation area, 41 3,414,513,514,1213,1214,1313,1314: Sensitivity area, 415,416,1215,1216: Connection area, 601,602,1001,1002 ,1401,1402,1601,1602: Partial pupil area, 701,1101,1501,1701: First pupil intensity distribution, 702,1102,1502,1702: Second pupil intensity distribution

Claims

1. An image sensor that includes a plurality of pixels arranged in a matrix and reads out the signals of the pixels row by row, wherein the plurality of pixels are Multiple microlenses, For each of the aforementioned multiple microlenses, A pair of first semiconductor regions formed to a first depth from the surface into which light is incident, A pair of second semiconductor regions formed at a second depth deeper than the first depth, It has a plurality of connecting regions that connect the pair of first semiconductor regions and the pair of second semiconductor regions, Among the plurality of pixels, the first direction in which the pair of first semiconductor regions and the pair of second semiconductor regions of the pixel having the first arrangement are aligned is the direction of the row, Among the plurality of pixels, the pixel having the second arrangement has a second direction in which the alignment direction of the pair of first semiconductor regions is orthogonal to the first direction, and the alignment direction of the pair of second semiconductor regions is the first direction. An image sensor characterized in that the crosstalk rate between the pair of first semiconductor regions of a pixel having the second arrangement is lower than the crosstalk rate between the pair of first semiconductor regions of a pixel having the first arrangement.

2. The image sensor according to claim 1, characterized in that the potential barrier of the region separating the pair of first semiconductor regions in the second arrangement is higher than the potential barrier of the region separating the pair of first semiconductor regions in the first arrangement.

3. The image sensor according to claim 1 or 2, characterized in that a potential gradient is applied in the second direction such that electrons or holes generated in the pair of first semiconductor regions of the second arrangement move away from the region separating the pair of first semiconductor regions.

4. The image sensor according to any one of claims 1 to 3, characterized in that a potential gradient is provided such that electrons or holes generated in the pair of first semiconductor regions of the second arrangement move toward the pair of second semiconductor regions, and the potential gradient is steeper than the potential gradient in the pair of first semiconductor regions of the first arrangement.

5. The image sensor according to any one of claims 1 to 4, characterized in that the potential barrier of the region separating the plurality of pixels from each other is higher than the potential barrier of the region separating the pair of first semiconductor regions in the second arrangement.

6. Among the plurality of pixels, the direction in which the pair of first semiconductor regions and the pair of second semiconductor regions of the pixel having the third arrangement are aligned is the second direction, Among the plurality of pixels, the orientation of the pair of first semiconductor regions of the pixel having the fourth arrangement is the first direction, and the orientation of the pair of second semiconductor regions is the second direction. The image sensor according to any one of claims 1 to 5.

7. The image sensor according to any one of claims 1 to 6, characterized in that the first semiconductor region generates an electric charge by photoelectric conversion of incident light, and the second semiconductor region stores the charge generated by the first semiconductor region via the connecting region.

8. The image sensor according to any one of claims 1 to 7, further comprising a selection means for sequentially selecting the plurality of pixels arranged in the matrix in the second direction on a row-by-row basis.

9. An image sensor according to any one of claims 1 to 8, Processing means for processing the signal output from the image sensor An imaging device characterized by having the following features.

Images