Image pick-up device and imaging apparatus

Abstract

To ensure the amount of incident on each of a pair of photoelectric conversion parts provided for one microlens.SOLUTION: An image pick-up device comprises a plurality of pixels arranged in a two-dimensional state and each having a plurality of microlenses and a pair of photoelectric conversion parts receiving light from a pair of pupil areas of an optical system. The plurality of pixels include a first photoelectric conversion part photoelectrically converting light passing through one of the pair of pupil areas of the optical system and a first microlens, a second photoelectric conversion part photoelectrically converting light passing through one of the pupil areas and a second microlens and different in the light receiving area from the first photoelectric conversion part, and a third photoelectric conversion part photoelectrically converting light passing through one of the pupil areas and a third microlens and different in the light receiving area from the first and second photoelectric conversion parts. The first to third photoelectric conversion parts are provided in a row direction. The first to third photoelectric conversion parts have a larger light receiving area as the distance from an optical axis of the optical system in the row direction increases, or have a smaller light receiving area as the distance from the optical axis of the optical system in the row direction increases.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an imaging device. [Background technology]

[0002] Conventionally, image sensors have been known in which a pair of light receiving elements is provided for one microlens, and focus detection pixels are arranged so that the pair of light receiving elements is symmetrical with respect to the optical axis of the microlens, and focus detection pixels are arranged so that the pair of light receiving elements is asymmetrical with respect to the optical axis of the microlens (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-221253 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the amount of light incident on each of a pair of light receiving elements arranged for the same microlens is different, the output of one of the light receiving elements becomes saturated and cannot be used for focus detection calculations, resulting in the problem that focus detection accuracy cannot be maintained. [Means for solving the problem]

[0005] According to a first aspect, an image sensor includes a plurality of microlenses and a pair of photoelectric conversion units provided for each of the plurality of microlenses, each of which receives a pair of light beams that have passed through a pair of pupil regions of an optical system, and the image sensor includes a plurality of pixels arranged two-dimensionally, the plurality of pixels including a first photoelectric conversion unit that photoelectrically converts light that has passed through one of the pair of pupil regions of the optical system and a first microlens, a second photoelectric conversion unit that photoelectrically converts light that has passed through the one pupil region of the optical system and a second microlens, and has a light receiving area different from that of the first photoelectric conversion unit, and a third photoelectric conversion unit that photoelectrically converts light that has passed through the one pupil region of the optical system and a third microlens, and has different light receiving areas for the first photoelectric conversion unit and the second photoelectric conversion unit, wherein the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit are arranged in a row direction, and the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit are configured so that the light receiving area becomes larger as the distance from the optical axis of the optical system in the row direction increases, or the light receiving area becomes smaller as the distance from the optical axis of the optical system in the row direction increases. [Effects of the Invention]

[0006] According to the present invention, it is possible to prevent the output of one of a pair of photoelectric conversion units from becoming saturated, even in pixels located near the periphery among a plurality of pixels, and to suppress a decrease in focus detection accuracy. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view illustrating a configuration of an imaging device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a block diagram illustrating a configuration of a main part of an imaging device according to an embodiment. [Figure 3] FIG. 1 is a diagram showing an example of an arrangement of imaging pixels according to an embodiment; [Figure 4] FIG. 1 is a diagram schematically illustrating the area of ​​a first photoelectric conversion unit and a second photoelectric conversion unit of an imaging pixel and the projection relationship with the exit pupil region of a photographing lens system according to an embodiment; [Figure 5] FIG. 10 is a diagram showing an example of an arrangement of imaging pixels in a modified example. [Figure 6] FIG. 10 is a diagram showing an example of an arrangement of imaging pixels in a modified example. [Figure 7] FIG. 10 is a diagram showing an example of an arrangement of imaging pixels in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] An image sensor according to an embodiment of the present invention, and a focus detection device and an image capturing apparatus including the image sensor will be described with reference to the drawings. Figure 1 is a cross-sectional view illustrating the configuration of a digital camera 100, which is an image capturing apparatus according to the embodiment. For convenience of explanation, a coordinate system consisting of x-, y-, and z-axes is set as shown in the figure.

[0009] Digital camera 100 is a so-called mirrorless camera that is made up of a camera body 200 and a photographing lens body 300, with photographing lens body 300 attached via a mount unit (not shown). Photographing lens bodies 300 having various photographing optical systems can be attached to camera body 200 via the mount unit. Electrical contacts 201 and 202 are provided on the mount unit, and when camera body 200 and photographing lens body 300 are coupled together, an electrical connection is established via electrical contacts 201 and 202.

[0010] The photographic lens body 300 comprises a photographic lens system 1, an aperture 2, a drive mechanism 3, and a lens data unit 4. The photographic lens system 1 is an optical system for forming a subject image on a predetermined planned focal plane, and is composed of multiple lenses including a focus adjustment lens. The aperture 2 forms an aperture with a variable diameter centered on the optical axis L to limit the light flux passing through the photographic lens system 1, i.e., the amount of incident light. The drive mechanism 3 calculates the lens drive amount using the defocus amount input from the camera body 200 side via electrical contacts 201, and drives the focus adjustment lens that constitutes the photographic lens system 1 along the optical axis L (z-axis direction) to a focus position according to the lens drive amount. The drive mechanism 3 also outputs an aperture drive signal in response to a command from the camera body 200 side to control the drive of the aperture 2.

[0011] The lens data section 4 is configured, for example, by a non-volatile recording medium, and stores various lens information related to the photographic lens body 300, such as the focal length and brightness (maximum F-number) of the lens. The lens data section 4 transmits the above lens information and the like to and from the camera body 200 via the electrical contacts 202.

[0012] The camera body 200 includes an arithmetic processing control unit 5, an image sensor control circuit 6, a mechanical shutter 7, an image sensor 8, an electronic viewfinder (EVF) 9, and an eyepiece 10. The camera body 200 also includes an operation unit 11. The image sensor 8 has imaging pixels, such as CCDs or CMOSs, arranged two-dimensionally (in rows and columns) on the xy plane. Each imaging pixel of the image sensor 8 is provided with an R (red), G (green), or B (blue) color filter. The image sensor 8 receives a light beam incident through the photographing lens system 1 and the mechanical shutter 7 to capture a subject image and outputs an imaging signal to the image sensor control unit 6. The imaging signal is used as a signal for generating image data (image signal) and as a signal for focus detection (focus detection signal). Because the image sensor 8 captures a subject image through a color filter, the imaging signal output from the imaging pixels of the image sensor 8 contains color information in the RGB color system. The image sensor 8 will be described in detail below.

[0013] The mechanical shutter 7 is provided immediately in front of the image sensor 8 and is composed of a front curtain and a rear curtain made up of multiple light-shielding blades. The mechanical shutter 7 moves by being driven by a drive mechanism (not shown) made up of a drive motor (for example, an electric motor such as a DC motor or a stepping motor), shielding the image sensor 8 from subject light. The electronic viewfinder 9 displays an image corresponding to the display image data generated by the arithmetic processing control unit 5. The electronic viewfinder 9 also displays various information related to the shooting conditions (shutter speed, aperture value, ISO sensitivity, etc.). The image and various information displayed on the electronic viewfinder 9 are observed by the user through an eyepiece 10.

[0014] The operation unit 11 includes various switches provided in correspondence with various operation members operated by the user, and outputs operation signals corresponding to the operation of the operation members to the arithmetic processing control unit 5. The operation members include, for example, a release button, a menu button for displaying a menu screen on a rear monitor (not shown) provided on the rear of the camera body 200, a cross key operated when selecting various settings, etc., a confirmation button for confirming settings selected by the cross key, an operation mode switching button for switching the operation of the digital camera 100 between a shooting mode and a playback mode, an exposure mode switching button for setting the exposure mode, etc.

[0015] Furthermore, the control system of the digital camera 100 will be described using the block diagram shown in FIG. 2. As shown in FIG. 2, the digital camera 100 has an A / D conversion unit 12, an image processing circuit 13, a focus detection calculation circuit 14, and a body-lens communication unit 15. The arithmetic processing control unit 5 is an arithmetic circuit that has a CPU, ROM, RAM, etc., and controls the components of the digital camera 100 and executes various data processing operations based on a control program. The control program is stored in a non-volatile memory (not shown) within the arithmetic processing control unit 5. The image sensor drive circuit 6 is controlled by the arithmetic processing control unit 5 and controls the drive of the image sensor 8 and the A / D conversion unit 12, causing the image sensor 8 to accumulate charge and read out an image signal. The A / D conversion unit 12 converts the analog image signal output from the image sensor 8 into a digital signal.

[0016] The image processing circuit 13 uses the imaging signal output from the imaging element 8 as an image signal, performs various image processes on the image signal to generate image data, and then adds additional information, etc. to generate an image file. The image processing circuit 13 records the generated image file on a recording medium (not shown) such as a memory card. The image processing circuit 13 generates display image data to be displayed on the electronic viewfinder 9 or a rear monitor (not shown) based on the generated image data and image data recorded on the recording medium.

[0017] The focus detection calculation circuit 14 uses the image signal output from the image sensor 8 as a focus detection signal and calculates the defocus amount using a known phase difference detection method. The body-lens communication unit 15 is controlled by the calculation processing control unit 5 and communicates with the drive mechanism 3 and lens data unit 4 within the photographic lens body 300 via electrical contacts 201 and 202, sending camera information (defocus amount, aperture value, etc.) and receiving lens information.

[0018] Next, the imaging element 8 in this embodiment will be described in detail. FIG. 3(a) is a plan view schematically illustrating a portion of the image sensor 8, including the central portion thereof; FIG. 3(b) is a diagram schematically illustrating a cross section of one image sensor pixel 80 located near the center of the image sensor 8; and FIG. 3(c) is a diagram schematically illustrating a cross section of one image sensor pixel 80 located in the peripheral portion of the image sensor 8. In FIG. 3, a coordinate system consisting of x, y, and z axes is set in the same manner as in the example shown in FIG. 1. The image sensor 8 has a plurality of image sensors 80 two-dimensionally arranged in rows (x direction) and columns (y direction). The above-described color filters (R: red filter, G: green filter, B: blue filter) are arranged at each pixel position of the image sensors 80, for example, according to the Bayer array rules. In FIG. 3(a), the colors of the color filters arranged in the image sensors 80 are schematically represented as "R," "G," or "B."

[0019] An imaging pixel 80 is composed of a microlens 81, and a first photoelectric conversion unit 82 and a second photoelectric conversion unit 83 provided below each microlens 81. The first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 are arranged side by side in the x direction. In the example shown in FIG. 3, the first photoelectric conversion unit 82 is provided on the positive side of the x direction, and the second photoelectric conversion unit 83 is provided on the negative side of the x direction. Light incident through different regions of the photographing lens system 1 is incident on the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83. That is, a pair of subject light beams that are used by the focus detection calculation circuit 14 for phase difference detection calculation are incident on the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83.

[0020] In this embodiment, in each row, the boundary 84 between the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 is offset from the center of the microlens 81 depending on the position where the imaging pixel 80 is arranged (see FIG. 3(c)). In all imaging pixels 80, the sum of the area of ​​the first photoelectric conversion unit 82 and the area of ​​the second photoelectric conversion unit 83 is substantially the same. In other words, the size (area) of the first photoelectric conversion unit 82 and the size (area) of the second photoelectric conversion unit 83 are different. On the positive x-direction side of the center column C of the imaging element 8, the boundary 84 is offset toward the negative x-direction side with respect to the center of the microlens 81, and on the negative x-direction side of the center column C, the boundary 84 is offset toward the positive x-direction side with respect to the center of the microlens 81. In other words, the area of ​​the first photoelectric conversion section 82 is larger than the area of ​​the second photoelectric conversion section 83, and the difference between the area of ​​the first photoelectric conversion section 82 and the area of ​​the second photoelectric conversion section 83 increases depending on the distance from the center row C. On the negative side in the x direction, the area of ​​the second photoelectric conversion section 83 is larger than the area of ​​the first photoelectric conversion section 82, and the difference between the area of ​​the second photoelectric conversion section 83 and the area of ​​the first photoelectric conversion section 82 increases depending on the distance from the center row C.

[0021] The amount of deviation of the boundary 84 from the microlens 81, i.e., the difference between the area of ​​the second photoelectric conversion unit 83 and the area of ​​the first photoelectric conversion unit 82, may vary linearly with the distance from the center column C, or may vary stepwise for each predetermined number of imaging pixels 80. In each row, in the imaging pixels 80 arranged in the center column C of the image sensor 8, the center of the microlens 81 and the boundary 84 substantially coincide with each other, i.e., the area of ​​the first photoelectric conversion unit 82 is equal to the area of ​​the second photoelectric conversion unit 83. As described above, in all imaging pixels 80, the sum of the area of ​​the first photoelectric conversion unit 82 and the area of ​​the second photoelectric conversion unit 83 is substantially the same. Therefore, the area ratio of the first photoelectric conversion unit 82 to the area of ​​the second photoelectric conversion unit 83 varies among the imaging pixels 80 depending on the distance in the x direction from the center column C of the image sensor 8.

[0022] As shown in FIG. 3A, a boundary 84a between the first photoelectric conversion unit 82a and the second photoelectric conversion unit 83a provided in each of the imaging pixels 80a arranged in the central row C of the image sensor 8 is substantially aligned with the center of the microlens 81a. That is, the first photoelectric conversion unit 82a and the second photoelectric conversion unit 83a have the same area. In the imaging pixel 80b arranged on the positive side of the x-direction relative to the imaging pixel 80a, the boundary 84b is shifted toward the negative side of the x-direction relative to the center of the microlens 81b. That is, the area of ​​the first photoelectric conversion unit 82b is larger than the area of ​​the second photoelectric conversion unit 83b. As described above, the sum of the areas of the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 is the same in all of the imaging pixels 80. Therefore, the area of ​​the first photoelectric conversion unit 82b of imaging pixel 80b is larger than the area of ​​the first photoelectric conversion unit 82a of imaging pixel 80a, and the area of ​​the second photoelectric conversion unit 83b of imaging pixel 80b is smaller than the area of ​​the second photoelectric conversion unit 83a of imaging pixel 80a.

[0023] In the imaging pixel 80c, which is arranged further to the positive side in the x-direction than the imaging pixel 80b, the deviation of the boundary 84c from the center of the microlens 81c is greater than the deviation of the boundary 84b from the center of the microlens 81b. That is, the further the imaging pixel 80 is arranged on the positive side in the x-direction, the greater the deviation of the boundary 84 from the center of the microlens 81 toward the negative side in the x-direction. The area of ​​the first photoelectric conversion unit 82c of the imaging pixel 80c is greater than the area of ​​the first photoelectric conversion unit 82b of the imaging pixel 80b, and the area of ​​the second photoelectric conversion unit 83c of the imaging pixel 80c is smaller than the area of ​​the second photoelectric conversion unit 83b of the imaging pixel 80b.

[0024] In the imaging pixel 80d, which is arranged further to the negative side in the x-direction than the imaging pixel 80a, the boundary 84d is shifted toward the positive side in the x-direction with respect to the center of the microlens 81d. That is, the area of ​​the second photoelectric conversion unit 83d is larger than the area of ​​the first photoelectric conversion unit 82d. Therefore, the area of ​​the first photoelectric conversion unit 82d of the imaging pixel 80d is smaller than the area of ​​the first photoelectric conversion unit 82a of the imaging pixel 80a, and the area of ​​the second photoelectric conversion unit 83d of the imaging pixel 80d is larger than the area of ​​the second photoelectric conversion unit 83a of the imaging pixel 80a. In the imaging pixel 80e, which is arranged further to the negative side in the x-direction than the imaging pixel 80d, the amount of shift of the boundary 84e toward the positive side in the x-direction with respect to the center of the microlens 81e is larger than the amount of shift of the boundary 84d toward the positive side in the x-direction with respect to the center of the microlens 81d. That is, the area of ​​the second photoelectric conversion unit 83e of the imaging pixel 80e is larger than the area of ​​the second photoelectric conversion unit 83d of the imaging pixel 80d, and the area of ​​the first photoelectric conversion unit 82e of the imaging pixel 80e is smaller than the area of ​​the first photoelectric conversion unit 82d of the imaging pixel 80d. The relationship between the boundary portion 84 and the center of the microlens 81 and the relationship between the area of ​​the first photoelectric conversion portion 82 and the area of ​​the second photoelectric conversion portion 83 will be described in detail later.

[0025] The length of each of the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 of the imaging pixel 80 is not changed in the y direction, but is changed in the x direction, thereby changing the area ratio between the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83. That is, for imaging pixels 80 arranged on the +x direction side, the length of the first photoelectric conversion unit 82 in the x direction increases and the length of the second photoelectric conversion unit 83 in the x direction decreases as the distance from the center column C of the imaging element 8 increases. For imaging pixels 80 arranged on the -x direction side, the length of the first photoelectric conversion unit 82 in the x direction decreases and the length of the second photoelectric conversion unit 83 in the x direction increases as the distance from the center column C of the imaging element 8 increases.

[0026] In the imaging pixels 80 arranged in the column direction (y direction) of the image sensor 8, the first photoelectric conversion units 82 and the second photoelectric conversion units 83 have the same area. That is, for example, an imaging pixel 80 arranged in the same column as imaging pixel 80c is provided with a first photoelectric conversion unit 82 having the same area as the first photoelectric conversion unit 82c and a second photoelectric conversion unit 83 having the same area as the second photoelectric conversion unit 83c.

[0027] In this embodiment, the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 of the imaging pixel 80 are formed in the above-described shapes to reduce the effect of vignetting in the peripheral region of the imaging element 8. The principle behind this will be described below. 4A and 4B schematically show the projection relationship between the areas of the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 of the imaging pixel 80 and the exit pupil region of the photographing lens system 1. FIG. 4A shows a case where the exit pupil distance PO1 of the photographing lens system 1 and the exit pupil distance PO2 of the imaging pixel 80 are substantially equal, i.e., the photographing lens system 1 is a dedicated interchangeable lens designed to fit the mirrorless digital camera 100. FIG. 4B shows a case where the exit pupil distance PO1 of the photographing lens system 1 is longer than the exit pupil distance PO2 of the imaging pixel 80, i.e., the photographing lens system 1 is, for example, an interchangeable lens designed for a single-lens reflex camera or a dedicated interchangeable lens designed to fit the mirrorless digital camera 100, but has a long exit pupil distance PO1. Note that, for ease of understanding, FIG. 4B uses dashed lines to show the photographing lens system 1 when the exit pupil distances PO1 and PO2 are equal. In this embodiment, the exit pupil distance PO2 of the imaging pixel 80 is set to be shorter than the median value of the exit pupil distances PO1, which vary for various dedicated interchangeable lenses. In the following explanation, the imaging pixel 80c arranged in the peripheral region on the positive side in the x direction in Figure 3 will be used as an example.

[0028] 4(a), the first photoelectric conversion unit 82c receives, via the microlens 81c, a light beam 851 that has passed through the exit pupil region 841 of a pair of exit pupil regions 841 and 842 of the photographing lens system 1, out of the light beams from the subject, and the second photoelectric conversion unit 83c receives, via the microlens 81c, a light beam 852 that has passed through the exit pupil region 842. As described above, FIG. 4(a) shows the case where the exit pupil distances PO1 and PO2 are substantially equal, and therefore the light beams 851 and 852 are incident on the first photoelectric conversion unit 82c and the second photoelectric conversion unit 83c, respectively, with no or little vignetting due to the structure of the photographing lens body 300, etc.

[0029] 4(b), light beam 852 from the subject passes through exit pupil region 842 of photographing lens system 1 and enters second photoelectric conversion unit 83c via microlens 81c of imaging pixel 80c. Because exit pupil distance PO1 of photographing lens system 1 is longer than exit pupil distance PO2 of imaging pixel 80, light beam 851 from the subject is partially vignetted. That is, of light beam 851, light beam 851a passes through exit pupil region 841 of photographing lens system 1 and enters first photoelectric conversion unit 82c via microlens 81c, while light beam 851b is vignetted and does not enter first photoelectric conversion unit 82c.

[0030] FIG. 4(c) is a schematic plan view of imaging pixel 80c, showing the positional relationship between light beam 852 and light beam 851 affected by vignetting as described above, and the first and second photoelectric conversion units 82c and 83c of imaging pixel 80c. Note that in FIG. 4(c), the region into which light beam 851b would have entered the first photoelectric conversion unit 82c if vignetting had not occurred is indicated by a dashed line. In this embodiment, the first photoelectric conversion unit 82c has a region 82c1 onto which light beam 851a is incident and a region 821c2 into which light beam 851b would have entered if vignetting had not occurred. In imaging pixel 80c, the amount of shift of boundary 84c toward the negative x-direction is determined so that region 82c1 of the first photoelectric conversion unit 82c and the second photoelectric conversion unit 83c onto which light beam 852 is incident have the same area. Therefore, by displacing the boundary 84c toward the negative x-direction with respect to the center of the microlens 81c, the incident light beams 852 and 851a are received by the first photoelectric conversion portion 82c and the second photoelectric conversion portion 83c, respectively, in substantially the same area.

[0031] Similarly to imaging pixel 80c, the amount of deviation of boundary 84b, i.e., the area between the first photoelectric conversion unit 82b and the second photoelectric conversion unit 83b, is determined for imaging pixel 80b. However, as described above, because imaging pixel 80b is arranged closer to the negative side in the x-direction than imaging pixel 80c, the amount of deviation of boundary 84b is smaller than the amount of deviation of boundary 84c. That is, the area of ​​the first photoelectric conversion unit 82b of imaging pixel 80b is smaller than the area of ​​the first photoelectric conversion unit 82c of imaging pixel 80c. Furthermore, for imaging pixels 8 arranged closer to the negative side in the x-direction from center row C of the image sensor 8, the direction in which the boundary 84 is deviation from the center of microlens 81, i.e., the size relationship between the areas of the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83, is reversed.

[0032] FIG. 4(d) is a plan view schematically illustrating light beams 851 and 852 incident on the first and second photoelectric conversion units 82a and 83a, respectively, when the imaging pixel 80a is arranged at the position where the imaging pixel 80c is arranged, i.e., when the boundary 84 substantially coincides with the center of the microlens 81 and the exit pupil distance PO1 is greater than the exit pupil distance PO2. In this case, the light beam 851 is vignetted, causing the light beam 851a to be received by the first photoelectric conversion unit 82a in the shaded area in the figure. The light beam 852 is received by the entire area of ​​the second photoelectric conversion unit 83a. Therefore, the output of the imaging signal from the first photoelectric conversion unit 82a is lower than the output of the imaging signal from the second photoelectric conversion unit 83a. That is, the output of the imaging signal from the second photoelectric conversion unit 83c saturates before the imaging signal from the first photoelectric conversion unit 82c reaches a sufficient output.

[0033] In contrast to this, the present embodiment has the structure shown in Fig. 4(c), which prevents the output of the imaging signal from the first photoelectric conversion unit 82c from decreasing compared to the output of the imaging signal from the second photoelectric conversion unit 83c, and prevents the output of the imaging signal from the second photoelectric conversion unit 83c from becoming saturated before the imaging signal from the first photoelectric conversion unit 82c reaches a sufficient output.

[0034] The focus detection calculation circuit 14 calculates the defocus amount using a known phase difference detection method, using the image pickup signals output from the image pickup pixels 80 having the above-described structure as focus detection signals. The focus detection calculation circuit 14 detects the relative deviation between the first signal sequence {an}, which is a sequential arrangement of focus detection signals from the first photoelectric conversion unit 82, and the second signal sequence {bn}, which is a sequential arrangement of focus detection signals from the second photoelectric conversion unit 83, and detects the focus adjustment state of the photographing lens system 1, i.e., the defocus amount.

[0035] When generating image data, the image processing circuit 13 uses the imaging signals output from the imaging pixels 80 as image signals. For each imaging pixel 80, the image processing circuit 13 adds the imaging signal output from the first photoelectric conversion unit 82 and the imaging signal output from the second photoelectric conversion unit 83, and processes the result as an image signal. Therefore, there is no effect due to the difference in area between the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83. Because the imaging pixel 80 is provided with a color filter of either R, G, or B, the added image signal has color information corresponding to the color filter provided in the imaging pixel 80. The image processing circuit 13 performs various image processes on the image signal generated by the addition to generate image data, and adds additional information, etc. to generate an image file.

[0036] The above-described embodiment provides the following advantageous effects. In all of the imaging pixels 80, the total area of ​​the pair of first and second photoelectric conversion units 82 and 83 is substantially equal, and the areas of the pair of first and second photoelectric conversion units 82 and 83 vary depending on the arrangement position of the imaging pixels 80, i.e., the distance from the vicinity of the center of the image sensor 8. That is, the difference in area between the pair of first and second photoelectric conversion units 82 and 83 increases with increasing distance from the vicinity of the center of the image sensor 8. Therefore, even in cases where incident light flux is affected by vignetting at the periphery of the image sensor 8, such as when a photographing lens system 1 is attached whose exit pupil distance PO1 is longer than the exit pupil distance PO2 of the image sensor 8, the amount of light incident on the first or second photoelectric conversion unit 82 or 83 can be ensured. Therefore, by the time the first photoelectric conversion unit 82 receives the amount of light that allows it to calculate the amount of light from the light beam 851 that has been affected by vignetting, the output of the second photoelectric conversion unit 83 that has received the light beam 852 that has not been affected by vignetting can be prevented from saturating, thereby suppressing a decrease in focus detection accuracy.

[0037] The following modifications are also within the scope of the present invention, and one or more of the modifications may be combined with the above-described embodiment. (1) In the embodiment, as shown in FIG. 4, the case where the exit pupil distance PO1 of the photographing lens system 1 is longer than the exit pupil distance PO2 of the imaging pixel 80 is described. However, the case where a photographing lens system 1 with a short exit pupil distance PO1 is attached will be described. In this case, vignetting does not occur in the light beam 851, but vignetting does occur in the light beam 852. Therefore, the light beam 851 from the subject passes through the exit pupil region 841 of the photographing lens system 1 and enters the first photoelectric conversion unit 82c via the microlens 81c of the imaging pixel 80c. Furthermore, as the light beam 852 is vignetted, a portion of the light beam 852 passes through the exit pupil region 842 of the photographing lens system 1 and enters the second photoelectric conversion unit 83c via the microlens 81c. In this case, to reduce the effect of vignetting in the peripheral region of the image sensor 8, the area of ​​the first photoelectric conversion unit 82c of the image sensor 80c may be configured to be larger than the area of ​​the second photoelectric conversion unit 83c. That is, the imaging pixels 80e may be arranged in place of the imaging pixels 80c shown in FIG. 3(a).

[0038] 5 shows an example of an arrangement of imaging pixels 80 in an image sensor 8 when the imaging pixels 80 are arranged in correspondence with a photographing lens system 1 in which the exit pupil distance PO1 is shorter than the exit pupil distance PO2. As shown in FIG. 5, on the positive side in the x-direction from the center column C of the image sensor 8, the area of ​​the first photoelectric conversion unit 82 is smaller than the area of ​​the second photoelectric conversion unit 83, and the difference between the area of ​​the first photoelectric conversion unit 82 and the area of ​​the second photoelectric conversion unit 83 increases depending on the distance from the center column C. On the negative side in the x-direction, the area of ​​the second photoelectric conversion unit 83 is smaller than the area of ​​the first photoelectric conversion unit 82, and the difference between the area of ​​the second photoelectric conversion unit 83 and the area of ​​the first photoelectric conversion unit 82 increases depending on the distance from the center column C. In this case, too, in each row, the area of ​​the first photoelectric conversion unit 82 and the area of ​​the second photoelectric conversion unit 83 are equal in the imaging pixels 80 arranged in the center column C of the image sensor 8.

[0039] (2) Fig. 6 shows an example of an arrangement of imaging pixels 80 of an image sensor 8 when used with both a photographing lens system 1 in which the exit pupil distance PO1 is longer than the exit pupil distance PO2 and a photographing lens system 1 in which the exit pupil distance PO1 is shorter than the exit pupil distance PO2. In this case, rows in which imaging pixels 80 having the structure shown in Fig. 3(a) are arranged (rows D2, D4, D6 in Fig. 6) and rows in which imaging pixels 80 having the structure shown in Fig. 5 are arranged alternately in the y direction (rows D1, D3, D5 in Fig. 6). Therefore, in the case of a photographing lens system 1 in which the exit pupil distance PO1 is longer than the exit pupil distance PO2, the imaging signals output from the imaging pixels 80 arranged in rows D2, D4, and D6 are used, and in the case of a photographing lens system 1 in which the exit pupil distance PO1 is shorter than the exit pupil distance PO2, the imaging signals output from the imaging pixels 80 arranged in rows D1, D3, and D5 are used, thereby making it possible to perform focus detection with reduced effects from vignetting.

[0040] (3) An embodiment of the present invention also includes an imaging pixel 80 in which the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 are arranged side by side in the y direction, instead of an imaging pixel 80 in which the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 are arranged side by side in the x direction. Also, an embodiment of the present invention also includes an imaging element 8 in which imaging pixels 80 in which the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 are arranged side by side in the x direction and imaging pixels 80 in which the first photoelectric conversion unit 82 and the second photoelectric conversion unit 83 are arranged side by side in the y direction are arranged.

[0041] (4) As shown in FIG. 7 , an image sensor 8 in which a first photoelectric conversion unit 82 is arranged in one of a pair of imaging pixels 80 and a second photoelectric conversion unit 83 is arranged in the other imaging pixel 80 is also included in one aspect of the present invention. In this case, in a pair of imaging pixels 80a1 and 80a2 arranged in a central column C of the image sensor 8, the second photoelectric conversion unit 83a of the imaging pixel 80a1 and the first photoelectric conversion unit 82a of the imaging pixel 80a2 have substantially the same area. In a pair of imaging pixels 80c1 and 80c2 arranged in the peripheral portion of the image sensor 8 (the positive side in the x direction in FIG. 7 ), the area of ​​the second photoelectric conversion unit 83c of the imaging pixel 80c1 is larger than the area of ​​the first photoelectric conversion unit 82c of the imaging pixel 80c2. The difference in area is determined according to the distance from the central column C of the image sensor 8, as in the embodiment. Therefore, even if the image sensor 8 is configured with image sensor pixels 80 having the configuration shown in FIG. 7, the effect of vignetting of the light beam at the periphery of the image sensor 8 can be reduced and the amount of incident light can be maintained, thereby suppressing a decrease in focus detection accuracy.

[0042] The present invention is not limited to the above-described embodiments, and other forms that can be considered within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention, as long as the features of the present invention are not impaired. [Explanation of symbols]

[0043] 8...imaging element, 13...image processing circuit, 14...focus detection calculation circuit, 80...imaging pixel, 81...microlens, 82...first photoelectric conversion unit, 83...second photoelectric conversion unit, 100...digital camera

Claims

[Claim 1] a plurality of pixels including a plurality of microlenses and a pair of photoelectric conversion units provided for each of the plurality of microlenses, the photoelectric conversion units receiving a pair of light beams that have passed through a pair of pupil regions of an optical system, the photoelectric conversion units being arranged two-dimensionally; The plurality of pixels are a first photoelectric conversion unit that photoelectrically converts light that has passed through one of the pair of pupil regions of the optical system and a first microlens; a second photoelectric conversion unit that photoelectrically converts light that has passed through the one pupil region of the optical system and a second microlens, and has a light receiving area different from that of the first photoelectric conversion unit; a third photoelectric conversion unit that photoelectrically converts light that has passed through the one pupil region of the optical system and a third microlens, and has a light receiving area different from that of the first photoelectric conversion unit and the second photoelectric conversion unit; Equipped with the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit are provided in a row direction, The imaging element is configured such that the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit have a larger light receiving area as the distance from the optical axis of the optical system in the row direction increases, or the light receiving area decreases as the distance from the optical axis of the optical system in the row direction increases.

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