Imaging device

Abstract

To improve a detection accuracy under a low light intensity of an image surface phase difference focal point detection.SOLUTION: An imaging apparatus comprises: an imaging element that includes a focused state detection part containing a plurality of image surface phase difference detection parts which are respectively arranged at different positions along a second direction crossing a first direction, the first direction being a detection direction, and are respectively different in design pupil distance; and an addition part that generates an addition signal by adding a detection signal output by two or more imaging surface phase difference detection parts containing each imaging surface phase difference detection part of the design pupil distance that is nearest to an ejection eye distance of an imaging optical system to be mounted from a plurality of detection signals detected by the plurality of imaging surface phase difference detection parts contained in the focused state detection part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] There is known an image sensor that includes focus detection pixels that receive light beams that have passed through a partial area of ​​the exit pupil of an imaging optical system (see, for example, Patent Document 1). There has long been a demand for improved accuracy in focus detection. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-66051 Summary of the Invention

[0004] According to a first aspect, an imaging device includes an imaging element having a focus state detection unit that detects a first direction and includes a plurality of image plane phase difference detection units with different design pupil distances, the image plane phase difference detection units being arranged at different positions in a second direction that intersects with the first direction, and an adder that generates a sum signal by adding together detection signals output by two or more image plane phase difference detection units, including an image plane phase difference detection unit with a design pupil distance closest to the exit pupil distance of an attached imaging optical system, from among a plurality of detection signals detected by the plurality of image plane phase difference detection units included in the focus state detection unit. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an imaging apparatus according to an embodiment. [Figure 2] FIG. 4 is a diagram showing an example of a bundle of rays incident on an image plane phase difference detection unit from an imaging optical system. [Figure 3] FIG. 2 is a plan view of the imaging element according to the embodiment, viewed from the imaging surface side. [Figure 4] FIG. 2 is a diagram showing an electric circuit included in a pixel. [Figure 5] FIG. [Figure 6] FIG. 4 is a diagram showing a state in which a bundle of rays that has passed through an exit pupil is incident on an image surface phase difference detection unit. [Figure 7] FIG. 4 is a diagram showing an example of the arrangement of an image plane phase difference detection unit in a focus state detection unit. [Figure 8] 5A and 5B are diagrams showing examples of positions of focus state detection units on an image sensor. [Figure 9] 10A and 10B are diagrams showing modified examples of the arrangement of the image plane phase difference detection unit in the focus state detection unit. DETAILED DESCRIPTION OF THE INVENTION

[0006] (First embodiment) FIG. 1 is a cross-sectional view that schematically shows the configuration of an imaging device 1 according to the first embodiment and an imaging optical system 2 that is attached to the imaging device 1 when used.

[0007] The X, Y, and Z directions indicated by arrows in Figure 1 are mutually orthogonal. Note that the X, Y, and Z directions shown in the following figures are the same as the X, Y, and Z directions shown in Figure 1. The directions of the arrows are the +X, +Y, and +Z directions, respectively. Hereinafter, a position in the X direction will also be referred to as an X position, a position in the Y direction as a Y position, and a position in the Z direction as a Z position.

[0008] FIG. 1 is a cross-sectional view of an imaging device 1 and an imaging optical system 2 as viewed from the +X direction. The imaging device 1 includes an imaging element 3, an imaging control unit 4, a lens driving unit 6, a display unit 7, an operation unit 8, and a first communication unit 9. The imaging optical system 2 forms a subject image on an imaging surface 3s of the imaging element 3. The imaging optical system 2 includes an aperture 21 having an aperture 22, a front lens group 20a arranged closer to the subject than the aperture 21, a rear lens group 20b arranged closer to the imaging element 3 than the aperture 21, and a second communication unit 23. Both the front lens group 20a and the rear lens group 20b may be composed of multiple lenses.

[0009] The diaphragm 21 may be an iris diaphragm, a light-blocking member having an opening with a predetermined diameter, or a lens whose effective diameter limits the effective diameter of the light beam passing through the imaging optical system 2. One of the front lens group 20a or the rear lens group 20b does not have to be provided.

[0010] The front lens group 20a or the rear lens group 20b, or at least one of the lenses that make them up, may be a focus adjustment lens that can move in the direction of the optical axis AX (Z direction) to adjust the focus of the imaging optical system 2. In addition, the front lens group 20a or the front lens group 20a, or at least one of the lenses that make them up, may be a variable magnification (zoom) lens that can be moved in the optical axis AX direction (Z direction) to change the focal length of the imaging optical system 2.

[0011] At least part of the focal length, aperture value (F-number) and current position information of the lens movable in the optical axis AX direction of the imaging optical system 2 is transmitted from the second communication unit 23 of the imaging optical system 2 to the first communication unit 9 of the imaging device 1, and then transmitted to the imaging control unit 4.

[0012] The imaging element 3 captures an image of a subject and outputs a signal. The imaging control unit 4 controls each unit, including the imaging element 3. The imaging control unit 4 performs image processing and the like on the image signal output by the imaging element 3 to generate image data. The imaging control unit 4 records the image data on a recording medium (not shown) and performs processing such as displaying an image based on the image data on the display unit 7. The display unit 7 is a display device having a display member such as a liquid crystal panel.

[0013] The imaging control unit 4 further performs focus detection processing, which is necessary for automatic focusing (AF), of the imaging optical system 2 by using a known image plane phase difference detection method. Specifically, the imaging control unit 4 detects a phase difference, which is the amount of phase shift between at least a pair of focus detection signals output from the imaging element 3, as will be described later.

[0014] Based on the detected phase difference, the imaging control unit 4 calculates the amount of deviation (defocus amount) between the imaging position of the subject in the imaging optical system 2 and the imaging surface 3s of the imaging element 3. Then, according to the defocus amount, it calculates the amount of drive in the direction of the optical axis AX for focusing the focus adjustment lens in the imaging optical system 2. A signal according to this drive amount is sent from the lens drive unit 6 via the first communication unit 9 and the second communication unit 23 to an actuator (not shown) in the imaging optical system 2, and the focus adjustment lens is moved in the direction of the optical axis AX, thereby automatically performing focus adjustment.

[0015] Figure 2 is a cross-sectional view of the imaging device 1 and the imaging optical system 2 viewed from the -Y direction, and shows an example of a bundle of rays LRB passing through the imaging optical system 2 and incident on one focus state detection unit FA on the imaging element 3.

[0016] The bundle of rays LRB shown in FIG. 2 is refracted by the front lens group 20a, and then its diameter is restricted by the aperture 21. The bundle of rays LRB passes through an aperture 22, is refracted again by the rear lens group 20b, and is incident on an image-side focal point FP near the focus state detection unit FA of the image sensor 3. Here, the incident side (+Z side) of the image sensor 3 is disposed so as to substantially coincide with the focal point of the bundle of rays LRB, i.e., the image-side focal point FP of the image sensor 3. In FIG. 2, the focus state detection unit FA of the image sensor 3 is disposed, as an example, at a position spaced a distance X1 in the +X direction from the optical axis AX of the image sensor 2.

[0017] The exit pupil EP is a virtual image of the aperture 22 of the diaphragm 21 formed by the rear lens group 20b as seen from the image-side focus FP. In other words, the exit pupil EP coincides with the XY plane that includes the intersection PCI between the optical axis AX and a line segment PRI, which is a linear extension of the optical path between the rear lens group 20b and the image sensor, of the chief ray LPR of the bundle of rays LRB that passes through the intersection PC between the XY plane on which the diaphragm 21 is located and the optical axis AX. The intersection PCI can be said to be the center (center PCI) of the exit pupil EP.

[0018] In this specification, the distance in the Z direction from the exit pupil EP to the image-side focus FP is also referred to as the exit pupil distance LPD. Furthermore, as mentioned above, the exit pupil EP is a virtual image of the aperture 22 of the aperture 21 and is optically equivalent, so the bundle of rays LRB passing through the aperture 22 is also referred to as the bundle of rays LRB passing through the exit pupil EP.

[0019] The exit pupil distance LPD of the imaging optical system 2 is transmitted from the second communication unit 23 of the imaging optical system 2 to the first communication unit 9 of the imaging device 1, similar to information such as the focal length of the imaging optical system 2 described above, and is further transmitted to the imaging control unit 4.

[0020] (image sensor) 3 is a view of the image sensor 3 as viewed from the imaging surface 3s side, i.e., from the +Z side. The image sensor 3 has a semiconductor substrate 30 and a plurality of pixels 40 arranged in the X and Y directions on the semiconductor substrate 30. The arrangement of the pixels 40 in the X direction is also called a "row," and the arrangement of the pixels 40 in the Y direction is also called a "column." Although some of the pixels 40 are omitted in FIG. 2, a large number of pixels 40 may be arranged in each of the X and Y directions, for example, 1,000 or more.

[0021] Each of the multiple pixels 40 has a higher spectral sensitivity to one of three different wavelengths of light than to the other wavelengths. Pixels 40 labeled R (hereinafter also referred to as "R pixels") have a high spectral sensitivity to red light, pixels 40 labeled G (hereinafter also referred to as "G pixels") have a high spectral sensitivity to green light, and pixels 40 labeled B (hereinafter also referred to as "B pixels") have a high spectral sensitivity to blue light. These RGB pixels 40 are arranged in the imaging area in, for example, a Bayer array. The above-mentioned spectral sensitivities of the R, G, and B pixels are set by color filters, which will be described later, provided in each pixel 40, for example.

[0022] 3, a horizontal control unit 31H is provided at the left end of the effective imaging area IA, which is an area in which a plurality of pixels 40 are arranged, and a vertical control unit 31V is provided at the top end of the effective imaging area IA. The horizontal control unit 31H and the vertical control unit 31V are collectively or individually referred to as a control unit 31.

[0023] A plurality of control lines 32 extend from the horizontal control unit 31H in the X direction, and each control line 32 is connected to a plurality of pixels 40 arranged in a row in the X direction among the plurality of pixels 40. A signal line 33 is connected to each of a plurality of pixels 40 arranged in a column in the Y direction among the plurality of pixels 40 in the image sensor 3.

[0024] Each pixel 40 generates a signal based on the amount of light incident thereon within a predetermined imaging period. The signal generated by the pixel 40 connected to one or more control lines 32 to which a predetermined control voltage is applied from the horizontal control unit 31H is read out by a predetermined readout unit 34 via a signal line 33 connected to the pixel 40. As an example, the signal output from each pixel 40 is an analog signal, and the readout unit 34 is an analog / digital converter that converts the analog signal into a digital signal (A / D conversion). The signals from the pixels 40 that have been subjected to A / D conversion and the like by the readout unit 34 are output as output signals Sg from the output unit 36 ​​of the imaging element 3 via the data lane 35 to the imaging control unit 4.

[0025] Some of the pixels 40 are designated as a first AF pixel P and a second AF pixel M for detecting a pair of detection signals used in the focus detection process required for AF of the imaging optical system 2 in the phase difference detection method described above. The first AF pixel P is a pixel 40 designated with the symbol P, and the second AF pixel M is a pixel 40 designated with the symbol M.

[0026] A plurality of first AF pixels P are arranged side by side in the X direction at predetermined positions in the Y direction. The plurality of first AF pixels P arranged side by side in the X direction at the same Y position are also referred to as first detection units F1. The signal output from the first detection unit F1 is the first detection signal, which is one of the pair of detection signals described above.

[0027] The second AF pixels M are also arranged side by side in the X direction at a predetermined position in the Y direction different from the first detection unit F1. The second AF pixels M arranged side by side in the X direction at the same Y position are also referred to as second detection units F2. The signal output from the second detection unit F2 is the second detection signal, which is the other of the pair of detection signals described above.

[0028] In addition, Fig. 3 In the figure, for convenience of illustration, a G pixel G is included within the dashed frame indicating the first detection unit F1 and the second detection unit F2, but the first detection unit F1 and the second detection unit F2 do not have to include the G pixel G. Also, Fig. 3 In the above, the first detection unit F1 and the second detection unit F2 are arranged from approximately the end on the -X side of the effective imaging area IA to approximately the end on the +X side, but the first detection unit F1 and the second detection unit F2 may be arranged in a part of the effective imaging area IA in the X direction. Also, the first detection unit F1 and the second detection unit F2 may be arranged in a plurality of discrete positions in the X direction of the effective imaging area IA.

[0029] A pair of one first detection unit F1 and one second detection unit F2 is also referred to as an image plane phase difference detection unit FS. The image plane phase difference detection unit FS generates a pair of detection signals for detecting the phase difference between the phase of the intensity distribution in the X direction of the image of the imaging optical system 2 formed on the first detection unit F1 and the phase of the intensity distribution in the X direction of the image of the imaging optical system 2 formed on the second detection unit F2.

[0030] The X direction in which the first AF pixel P and the second AF pixel M are arranged side by side can be referred to as the detection direction or the first direction, and the Y direction can be referred to as the second direction. The first AF pixel P and the second AF pixel M are also referred to as AF pixels, either together or individually. On the other hand, among the plurality of pixels 40, the pixels other than the AF pixels (R pixels, G pixels, B pixels) are collectively or individually referred to as imaging pixels.

[0031] As an example, the first AF pixel P and the second AF pixel M are both arranged in positions where B pixels would be arranged in the original Bayer array. However, the first AF pixel P and the second AF pixel M may also be arranged in positions where R pixels would be arranged in the original Bayer array.

[0032] In Figure 3, the distance in the Y direction between the first detection unit F1 and the second detection unit F2 is such that five pixels 40 are arranged therebetween, but it may also be such that any odd number of pixels 40, such as three or seven, are arranged therebetween.

[0033] 4 is a diagram showing an electric circuit included in a pixel 40. The pixel 40 includes a photoelectric conversion unit 41 and an amplifier circuit 42. The structure of the pixel 40 will be described later. The photoelectric conversion unit 41 is made up of a photodiode or the like and performs photoelectric conversion on incident light. When a transfer signal is input to the transfer unit TX, the charge generated by photoelectric conversion in the photoelectric conversion unit 41 is transferred to the storage unit FD by the transfer unit TX. A predetermined voltage VDD is supplied from the power supply to the amplification unit TA, and a signal corresponding to the charge transferred to the storage unit FD is amplified and output to the selection unit TS.

[0034] A control line 32 is connected to the selection unit TS, and when a predetermined signal is input from the horizontal control unit 31H to the control line 32, the signal output from the selection unit TS is output to a signal line 33. A predetermined voltage VDD is supplied to the reset unit TR from a power supply, and when a reset signal is input to the reset unit at a predetermined timing, the reset unit becomes conductive and the storage unit FD is reset to the voltage VDD.

[0035] The transfer unit TX, the amplifier unit TA, the selection unit TS, and the reset unit TR may be MOS transistors, and the electrical circuit that constitutes the pixel 40 may be the same as the electrical circuit included in the pixel of a conventional so-called four-transistor CMOS image sensor, for example. The transfer signal and reset signal described above may be supplied from the horizontal control unit 31H via a control line extending in the X direction similar to the control line 32.

[0036] The configuration of the pixel 40 including the first AF pixel P and the second AF pixel M will be described below with reference to FIGS. FIG. 5 is a diagram showing an enlarged view of the image plane phase difference detection unit FS (see FIG. 3) included in the focus state detection unit FA shown in FIG. FIG. 5(a) is a diagram showing an XZ cross section of the pixels 40 (the G pixel G and the first AF pixel P) in the first detection unit F1 (see FIG. 3) included in the image plane phase difference detection unit FS. FIG. 5(b) is a diagram showing an XZ cross section of the pixels 40 (the G pixel G and the second AF pixel M) in the second detection unit F2 (see FIG. 3) included in the image plane phase difference detection unit FS.

[0037] 5(a) and 5(b), the semiconductor substrate 30 is formed by laminating an upper layer substrate 30a on which a photoelectric conversion unit 41 such as a photodiode and an amplifier circuit 42 are formed, and a lower layer substrate 30b on which a wiring layer is formed. The upper layer substrate 30a and the lower layer substrate 30b may be electrically connected via bumps.

[0038] A transparent protective film 43 is formed on the upper substrate 30a (in the +Z direction), and the above-described color filter 44 is formed above the protective film 43. A microlens 45 that focuses light to be captured on the photoelectric conversion unit 41 is formed above the color filter 44. Light irradiated onto the pixel 40 from above (+Z direction) is refracted by the microlens 45, and the wavelength range of the transmitted light is roughly selected by the color filter 44, after which the light enters the photoelectric conversion unit 41.

[0039] The color filter 44 arranged in the first AF pixel P and the second AF pixel M may be a color filter that preferentially transmits any one of the above-mentioned blue light, green light, or red light, or may be a color filter that preferentially transmits any two of the above-mentioned blue light, green light, and red light, or may be a filter that transmits the entire range of visible light or a filter that transmits infrared light.

[0040] The photoelectric conversion section 41 may be a photodiode formed in the upper substrate 30a, or may be a photoelectric conversion section made of an organic film formed above (on the +z side of) the upper substrate 30a. If the spectral sensitivity of the photoelectric conversion unit 41 differs for each of the plurality of pixels 40, the color filter 44 may be omitted.

[0041] 5(a), the first AF pixel P has a first light-shielding portion 46P on the upper end (+Z side end) side of the photoelectric conversion unit 41 that blocks light that is incident on the +X side of the photoelectric conversion unit 41. Also, as shown in FIG. 5(b), the second AF pixel M has a second light-shielding portion 46M on the upper end (+Z side end) side of the photoelectric conversion unit 41 that blocks light that is incident on the -X side of the photoelectric conversion unit 41.

[0042] Figure 6 is a diagram showing the state in which a bundle of rays LRB that has passed through the exit pupil EP of the imaging optical system 2 is incident on the first AF pixel P and the second AF pixel M included in the image plane phase difference detection unit FS within the focus state detection unit FA of the imaging element 3, and shows an XZ cross section of the imaging element 3 viewed from the -Y direction. In FIG. 6, the first AF pixel P and the second AF pixel M are shown overlapping each other and are arranged at the same X position within the image plane phase difference detection unit FS, i.e., are arranged overlapping in the depth direction of the paper.

[0043] The distance in the Z direction between the vertex 45c of the microlens 45 and the first light-shielding portion 46P or the second light-shielding portion 46M is defined as a distance DML. The first light-shielding portion 46P and the second light-shielding portion 46M are disposed at Z position Z1 that is approximately conjugate (in imaging relationship) with the exit pupil EP of the above-described imaging optical system 2 via the microlens 45. In other words, the first light-shielding portion 46P and the second light-shielding portion 46M are disposed at Z position Z1 that is approximately conjugate with the diaphragm 21 of the above-described imaging optical system 2 via the microlens 45 and the rear lens group 20b (see FIG. 4).

[0044] For this reason, a large amount of light that has passed through the exit pupil EP on the +X side of the optical axis AX is incident on the photoelectric conversion unit 41 of the first AF pixel P. Also, a large amount of light that has passed through the exit pupil EP on the -X side of the optical axis AX is incident on the photoelectric conversion unit 41 of the second AF pixel M. The photoelectric conversion unit 41 of the first AF pixel P can also be said to be a first light receiving unit that detects more light that has passed through the + side (one side) in the X direction of the exit pupil EP of the imaging optical system 2 than light that has passed through the - side (the other side) in the X direction of the exit pupil. The photoelectric conversion unit 41 of the second AF pixel M can also be said to be a second light receiving unit that detects more light that has passed through the negative side in the X direction of the exit pupil EP of the imaging optical system 2 (the other side mentioned above) than light that has passed through the positive side in the X direction of the exit pupil (the one side mentioned above).

[0045] 2 and 6 is disposed, for example, at a position a distance X1 in the +X direction from the center of the image sensor 3 in the X direction and from the optical axis AX of the imaging optical system 2. For this reason, the bundle of rays LRB enters the focus state detection unit FA from a direction centered on a direction slightly tilted in the -X direction from the +Z direction.

[0046] Accordingly, in order to increase the light receiving efficiency of the photoelectric conversion unit 41, in each pixel 40 of the focus state detection unit FA, the center position in the X direction of the microlens 45 is shifted in the −X direction with respect to the center position in the X direction of the photoelectric conversion unit 41. Conversely, the center position in the X direction of the photoelectric conversion unit 41 is shifted in the +X direction with respect to the center position in the X direction of the microlens 45.

[0047] 5(a), the position of -X side edge 46PE of first light-shielding portion 46P in first AF pixel P is disposed at a position shifted by distance XP to the +X side from vertex 45c (the point closest to the +Z side) of microlens 45. Furthermore, as shown in FIG. 5(b), the position of +X side edge 46ME of second light-shielding portion 46M in second AF pixel M is also disposed at a position shifted by distance XM to the +X side from vertex 45c of microlens 45.

[0048] The vertex 45c of the microlens 45 is disposed a distance X1 away from the optical axis AX in the +X direction. The distance in the Z direction between the exit pupil EP and the vertex 45c of the microlens 45 is the exit pupil distance LPD. Therefore, the chief ray LPR of the bundle of rays LRB that passes through the center PCI of the exit pupil EP and is incident on the vertex 45c of the microlens 45 of the first AF pixel P and the second AF pixel M travels in a direction tilted from the -Z direction toward the +X direction by an angle θ determined by the following equation (1): tan(θ) = X1 / LPD (1)

[0049] That is, the chief ray LPR travels in a direction inclined by an angle θ with respect to both the optical axis AX parallel to the Z direction and the normal NL to the imaging surface 3s of the imaging element 3. The principal ray LPR is refracted near the vertex 45c of the microlens 45, passes through the microlens 45, the color filter 44, and the protective film 43, and is either shielded by the first light-shielding portion 46P or the second light-shielding portion 46M, or enters the photoelectric conversion portion 41.

[0050] The distance in the X direction from the vertex 45c of the microlens 45 to the chief ray LPR at the Z position Z1 where the first light-shielding portion 46P or the second light-shielding portion 46M is located is defined as a distance XC. From a geometrical optical perspective, the distance XC can be approximately calculated by the following equation (2). XC = tan(θ)×DML / n (2)

[0051] Here, the distance DML is the distance in the Z direction between the vertex 45c of the microlens 45 and the first light-shielding portion 46P or the second light-shielding portion 46M, as described above, and n is the refractive index of the lens material that makes up the microlens 45. Furthermore, the following equation (3) can be derived from equations (1) and (2). XC = X1×DML / (n×LPD) ···(3)

[0052] In this case, if the distance XC is equal to the average of the above-described distances XP and XM, the amount of light incident on the photoelectric conversion unit 41 of the first AF pixel P can be made approximately equal to the amount of light incident on the photoelectric conversion unit 41 of the second AF pixel M. In other words, the amount of light that passes through the +X side of the exit pupil EP and enters the photoelectric conversion unit 41 without being blocked by the first light-shielding portion 46P of the first AF pixel P can be made approximately equal to the amount of light that passes through the -X side of the exit pupil EP and enters the photoelectric conversion unit 41 without being blocked by the second light-shielding portion 46M of the second AF pixel M. Therefore, the accuracy of focus position detection by the image plane phase difference detection unit FS can be improved.

[0053] Conversely, once the distances X1, DML, XP, and XM, which are quantities related to the configuration of the image plane phase difference detection unit FS, and the refractive index n, are determined, it is possible to determine the value of the exit pupil distance LPD that is appropriate for the focus state detection unit FA. Hereinafter, the exit pupil distance LPD that is appropriate for a given image plane phase difference detection unit FS will also be referred to as the designed pupil distance DPD of the image plane phase difference detection unit FS.

[0054] As an example, the designed pupil distance DPD can be obtained by the following equation (4) obtained by substituting the above-mentioned condition XC=(XP+XM) / 2 into equation (3) and transforming it, and replacing the exit pupil distance LPD with the designed pupil distance DPD. DPD = X1×DML / {n×(XP+XM) / 2} (4)

[0055] To improve the accuracy of focus position detection by the image plane phase difference detection unit FS, it is desirable to match its designed pupil distance DPD with the exit pupil distance LPD of the imaging optical system 2. However, the exit pupil distance LPD differs depending on the imaging optical system 2, and if the imaging optical system 2 is a zoom lens, the exit pupil distance LPD also varies with zooming. For this reason, it is difficult to always match the designed pupil distance DPD of one image plane phase difference detection unit FS with the exit pupil distance LPD of the imaging optical system 2.

[0056] Therefore, in the image sensor 3 of the first embodiment, a plurality of image plane phase difference detection units FS (FSA to FSE) each having a different design pupil distance DPD are provided within one focus state detection unit FA, as shown in Fig. 7. Each of the image plane phase difference detection units FSA to FSE includes a first detection unit F1 (F1A to F1E) and a second detection unit F2 (F2A to F2E).

[0057] The first AF pixels P included in each of these first detection units F1A to F1E have mutually different distances XP, as an example. The second AF pixels M included in each of these second detection units F2A to F2E have mutually different distances XM, as an example. This results in the image plane phase difference detection units FSA to FSE having different designed pupil distances DPD.

[0058] In the imaging device 1 of the first embodiment, the imaging control unit 4 selects from the image plane phase difference detection units FSA to FSE an image plane phase difference detection unit FS having a designed pupil distance DPD close to the exit pupil distance LPD of the imaging optical system 2, and detects the focal position using a detection signal from the selected image plane phase difference detection unit FS. This makes it possible to detect the focal position with high accuracy even when the attached imaging optical system 2 is replaced or when the imaging optical system 2 is zoomed.

[0059] The number of image plane phase difference detection units FSA to FSE provided in one focus state detection unit FA is not limited to five as described above, and may be any m (m is a natural number greater than or equal to 2). The exit pupil distance LPD of each of the image plane phase difference detection units FSA to FSE may be any length between approximately 10 mm and 150 mm, for example. As a further example, the length may be any length between approximately 0.6 and 5 times the diagonal length of the effective imaging area IA of the image sensor 3.

[0060] The exit pupil distances LPD of the multiple image plane phase difference detection units FSA to FSE may be set so that they increase at approximately equal intervals between their minimum and maximum values. Alternatively, the tilt angles θ of the chief rays LPR incident on the first AF pixel P and the second AF pixel M from the exit pupil EP at each exit pupil distance LPD with respect to the normal line NL shown in FIG. 6 may be set so that they increase at approximately equal intervals between their minimum and maximum values.

[0061] The first AF pixels P included in each of the first detection units F1A to F1E may have mutually different values ​​of the distance DML, instead of or in addition to the distance XP.Furthermore, the second AF pixels M included in each of the second detection units F2A to F2E may have mutually different values ​​of the distance DML, instead of or in addition to the distance XM.

[0062] The exit pupil distance LPD of each of the multiple image plane phase difference detection units FSA to FSE may monotonically increase or decrease according to the respective Y positions, or may change randomly regardless of the respective Y positions.

[0063] 7, to avoid complication of the drawing, the imaging pixels (G pixels G, B pixels B, and R pixels R) arranged between the first detection units F1A to F1E and the second detection units F2A to F2E in the Y direction are not shown. However, within one focus state detection unit FA, for example, three or more imaging pixels may be arranged between the first detection units F1A to F1E and the second detection units F2A to F2E in the Y direction.

[0064] The distance in the Y direction between the first detection units F1A-F1E and the second detection units F2A-F2E in one image plane phase difference detection unit FSA-FSE can be referred to as a first distance P1. The distance in the Y direction between each of the multiple image plane phase difference detection units FSA-FSE can be referred to as a second distance P2. The second distance P2 may be longer than the first distance P1. Conversely, the second distance P2 may be shorter than the first distance P1.

[0065] Incidentally, when imaging is performed under low illumination using the imaging device 1, the amount of light of the light beam LRB from the subject decreases, which reduces the S / N ratio of the detection signal obtained from one of the image plane phase difference detection units FSA to FSE. In this case, there is a risk that the accuracy of the focus position detection by the image plane phase difference detection units FSA to FSE will decrease.

[0066] In the imaging device 1 and imaging element 3 of the embodiment, some of the detection signals detected by multiple focus state detection units FA arranged at different positions in the Y direction are added together to generate a sum signal, and this sum signal is used as the detection signal to improve the accuracy of focus position detection.

[0067] Specifically, signals generated by a plurality of first AF pixels P at the same X position but different Y positions within a plurality of image plane phase difference detection units FSA to FSE within one focus state detection unit FA are added together. Similarly, signals generated by a plurality of second AF pixels M at the same X position but different Y positions within a plurality of image plane phase difference detection units FSA to FSE within one focus state detection unit FA are added together.

[0068] As one example, the addition of the multiple detection signals is performed by so-called source follower addition. That is, signals generated by multiple first AF pixels P included in different focus state detection units FA and located at the same X position are output approximately simultaneously to signal lines 33 connected to those first AF pixels P. Similarly, signals generated by multiple second AF pixels M included in different focus state detection units FA and located at the same X position are output approximately simultaneously to signal lines 33 connected to those second AF pixels M. These added signals on signal lines 33 are then read out by readout unit 34.

[0069] The horizontal control unit 31H sends a control signal via a control line 32 to the first AF pixel P or the second AF pixel M, whose signals are added together, and causes the signals from these pixels to be output to a signal line 33 substantially simultaneously. In this case, the signal line 33 and the readout unit 34 constitute an adder that adds at least two of the plurality of detection signals to generate an added signal.

[0070] The addition of multiple detection signals may be performed using other configurations. For example, the output section 36 of the image sensor 3 may be provided with a memory that temporarily stores digital signals output from predetermined AF pixels (P, M) via the data lane 35, and an adder circuit that adds signals from a predetermined number of AF pixels, and the adder circuit may be used to add the multiple detection signals. In this case, the adder circuit provided in the output section 36 of the image sensor 3 constitutes an adder section that adds at least two of the plurality of detection signals to generate a sum signal.

[0071] It should be noted that these memories and adder circuits may be provided as an adder circuit unit 5 in the imaging control unit 4, rather than in the imaging element 3. In this case, the adder unit that generates a sum signal by adding at least two of the multiple detection signals is included in the imaging control unit 4.

[0072] As an example, the sum signal is generated by adding detection signals from image plane phase difference detection units FS whose designed pupil distances DPD are closest to the exit pupil distance LPD of the imaging optical system 2 (k is a natural number equal to or less than m). As an example, assume that the exit pupil distance LPD of the imaging optical system 2 is 100 mm, and the designed pupil distances DPD of the multiple image plane phase difference detection units FSA to FSE are 50 mm, 70 mm, 90 mm, 110 mm, and 130 mm, respectively. In this case, as an example, the adder adds detection signals from two (k=2) image plane phase difference detection units FS whose designed pupil distances DPD are 90 mm and 110 mm.

[0073] As described above, in order to improve the accuracy of focus position detection by the image plane phase difference detection unit FS, it is desirable to match the designed pupil distance DPD with the exit pupil distance LPD of the imaging optical system 2. For this reason, if a sum signal is generated by adding together detection signals from image plane phase difference detection units FSs having designed pupil distances DPD that are significantly different from the exit pupil distance LPD of the imaging optical system 2, the accuracy of focus position detection may decrease.

[0074] Therefore, when generating the sum signal, the number of detection signals to be summed may be changed based on the light amount of the light beam LRB, i.e., the magnitude of the detection signal from the image plane phase difference detection unit FS. In other words, when the amount of light incident on the image sensor 3 is small and the intensity of the image signal output from the image sensor 3 is low, the summation unit may sum more detection signals than when the intensity of the image signal is high. Here, the image signal output from the image sensor 3 may be a detection signal output by an AF pixel, or may be an image formation signal output by an image pixel (G pixel G, B pixel B, R pixel R).

[0075] The impact on the accuracy of focus position detection caused by the mismatch between the exit pupil distance LPD of the imaging optical system 2 and the designed pupil distance DPD of the image plane phase difference detection unit FS becomes greater as the aperture value (F-number) of the imaging optical system 2 increases. Therefore, when generating the addition signal, the addition unit may add more detection signals when the aperture value of the imaging optical system 2 is small than when the aperture value of the imaging optical system 2 is large.

[0076] Incidentally, the impact on the accuracy of focus position detection due to a mismatch between the exit pupil distance LPD of the imaging optical system 2 and the designed pupil distance DPD of the image plane phase difference detection unit FS also depends on the position of the focus state detection unit FA on the image sensor 3. That is, the impact is small when the focus state detection unit FA is located near the center of the detection direction (X direction) of the effective imaging area IA, that is, close to the optical axis AX of the imaging optical system 2 in the detection direction, but the impact is large when the focus state detection unit FA is far from the optical axis AX in the detection direction.

[0077] Therefore, when generating the sum signal, the adder may add more detection signals when the position of the focus state detection unit FA in the detection direction (X direction) is close to the center of the image sensor 3 than when the position of the focus state detection unit FA in the first direction is far from the center of the image sensor 3.

[0078] 8 is a diagram showing some example positions of focus state detection units FA (FA1 to FA6) on the image sensor 3. For example, in focus state detection units FA1 and FA2 whose distance in the X direction from the center CL in the X direction of the effective imaging area IA on the imaging surface 3s of the image sensor 3 is less than distance D1, all of the detection signals from the m image surface phase difference detection units FS may be added together.

[0079] On the other hand, the adder may add k1 detection signals for the focus state detectors FA5 and FA6 whose distance in the X direction from the center CL is equal to or greater than D2, and may add k2 detection signals for the focus state detectors FA3 and FA4 whose distance in the X direction from the center CL is equal to or greater than D1 but less than D2, where k1 and K2 are both natural numbers and 1≦k1 <k2<mである。

[0080] Note that, when there are multiple focus state detection units FA (FA1 to FA6) within the effective imaging area IA, the adder may determine a method for adding detection signals from all focus state detection units FA according to the position of the selected focus state detection unit FA in the detection direction (X direction). That is, when the position of the selected focus state detection unit FA in the X direction is close to the center of the image sensor 3, the adder may add more detection signals from the image plane phase difference detection units FS in the multiple focus state detection units FA compared to when the position is farther from the center of the image sensor 3.

[0081] Which focus state detection unit FA to select from the plurality of focus state detection units FA may be input by the user through the operation unit 8, or may be determined by the imaging control unit 4 based on the image output from the imaging element 3.

[0082] In the above, one focus state detection unit FA is described as including multiple image plane phase difference detection units FS each having a different designed pupil distance DPD, but one focus state detection unit FA may also include image plane phase difference detection units FS having the same designed pupil distance DPD. In this case, the adder may add detection signals from the image plane phase difference detection units FS having the same designed pupil distance DPD.

[0083] As an example of such a focus state detection section FA, a plurality of focus state detection sections FA shown in FIG. 7 may be arranged close to each other in the Y direction at the same X position. Alternatively, a group of image plane phase difference detection units FS having the same designed pupil distance DPD may be arranged close to each other in the Y direction, and a group of image plane phase difference detection units FS having a different designed pupil distance DPD may be arranged at a position relatively far away from the group in the Y direction.

[0084] Note that, depending on the imaging device 1, the size of the effective imaging area IA on the imaging element 3 may be changeable. For example, the size of the effective imaging area IA may be switchable between a so-called 35 mm full frame size and a smaller size. Changing the effective imaging area IA may change the optimal detection conditions of the image plane phase difference detection unit FS. Therefore, the adder may change the number of detection signals to be added depending on the size of the effective imaging area IA of the imaging element 3.

[0085] (Modification of the arrangement of the image plane phase difference detection unit) FIG. 9 is a diagram showing a modified example of the arrangement of the image plane phase difference detection unit FS in the focus state detection unit FA. In the first embodiment described above, in the focus state detection unit FA, the first AF pixel P and the second AF pixel M, which are AF pixels, are both arranged at positions where the B pixel B (or the R pixel R) should be arranged in the original Bayer array. Therefore, the X positions of the AF pixels are arranged at intervals of two pixels 40.

[0086] 9, the AF pixels are arranged at the positions of B pixels B in the original Bayer array in image plane phase difference detection units FSA, FSC, and FSE that are odd-numbered in the Y direction, and are arranged at the positions of R pixels R in image plane phase difference detection units FSBs and FSDs that are even-numbered in the Y direction. Therefore, within focus state detection unit FA, the X positions of the AF pixels are arranged at intervals of one pixel 40.

[0087] Therefore, in the arrangement of this modified example, the sampling density by the first AF pixel P and the second AF pixel M, which are AF pixels, for the image formed by the imaging optical system 2 is improved, making it possible to perform image plane phase difference detection with higher accuracy.

[0088] Note that the example in Figure 9 is just one example, and the AF pixel may be arranged at the position of the R pixel R in the original Bayer array in the image plane phase difference detection units FSA, FSC, and FSE that are odd-numbered in the Y direction, and may be arranged at the position of the B pixel B in the image plane phase difference detection units FSBs and FSDs that are even-numbered in the Y direction.

[0089] In the above embodiments and modifications, for example, as described above, when the adder section is configured by the signal line 33 and the readout section 34, or when it is configured by an adder circuit provided in the output section 36 of the image sensor 3, the image sensor 3 can also be said to be an imaging device. The adder circuit may be provided by being stacked on the imaging section of the image sensor 3.

[0090] (Effects of the embodiment and modifications) According to the above-described embodiment, the following effects can be obtained. (1) The imaging device 1 of each of the above embodiments has an imaging element 3 having a focus state detection unit FA with a first direction (X direction) as the detection direction and including multiple image plane phase difference detection units FS with different design pupil distances DPD, each of which is arranged at different positions in a second direction (Y direction) that intersects with the first direction, and an adder (such as the readout unit 34, or the imaging control unit 4) that adds at least two of the multiple detection signals detected by the multiple image plane phase difference detection units FS included in the focus state detection unit FA to generate a sum signal. This configuration can improve the accuracy of detecting the focus position even for a subject under low illumination.

[0091] (2) The image plane phase difference detection unit FS may include: a first detection unit F1 including a plurality of first light receiving units (photoelectric conversion units 41 of first AF pixels P) arranged in the first direction (X direction) that detect more light that has passed through one side of the exit pupil EP of the imaging optical system 2 in the first direction (X direction) than light that has passed through the other side opposite to the one side of the exit pupil EP; and a second detection unit F2 including a plurality of second light receiving units (photoelectric conversion units 41 of second AF pixels M) arranged in the first direction that detect more light that has passed through the other side of the exit pupil EP in the first direction than light that has passed through the one side of the exit pupil EP. The adder may add at least two of the plurality of detection signals from the first detection units F1 included in the plurality of image plane phase difference detection units FS, and may add at least two of the plurality of detection signals from the second detection units F2 included in the plurality of image plane phase difference detection units FS. This configuration can further improve the accuracy of detecting the focus position even for a subject under low illumination.

[0092] (3) When the amount of light incident on the image sensor 3 is small and the intensity of the image signal output from the image sensor 3 is low, the adder may add more detection signals than when the intensity of the image signal is high. In this case, when the amount of light incident on the image sensor 3 is small and the intensity of the image signal output from the image sensor 3 is low, the S / N ratio of the detection signal can be improved by adding more detection signals, thereby enabling highly accurate focus position detection. On the other hand, when the amount of light incident on the image sensor 3 is large and the intensity of the image signal output from the image sensor 3 is high, the detection signal with the highest detection accuracy, i.e., the detection signal from the image plane phase difference detection unit FS whose designed pupil distance DPD is closest to the exit pupil distance LPD of the imaging optical system 2, is used preferentially, enabling highly accurate focus position detection.

[0093] (4) When the aperture value (F-number) of the imaging optical system 2 is small, the adder may add more detection signals than when the aperture value of the imaging optical system 2 is large. When the aperture value (F-number) of the imaging optical system 2 is small, the impact on the accuracy of focus position detection caused by a mismatch between the exit pupil distance LPD of the imaging optical system 2 and the designed pupil distance DPD of the image plane phase difference detection unit FS is small. Therefore, when the aperture value of the imaging optical system 2 is small, the improvement in focus position detection accuracy due to the improvement in the detection signal S / N by adding more detection signals is greater than the decrease in focus position detection accuracy caused by a mismatch between the exit pupil distance LPD and the designed pupil distance DPD. This enables high-precision focus position detection.

[0094] (5) The image sensor 3 may have multiple focus state detectors FA, and the adder may add more detection signals when the focus state detector FA is located near the center of the image sensor 3 in the first direction than when the focus state detector FA is located farther from the center of the image sensor 3. When the focus state detector FA is located near the center of the image sensor 3 in the first direction, the impact on the accuracy of focus position detection caused by a mismatch between the exit pupil distance LPD of the imaging optical system 2 and the designed pupil distance DPD of the image plane phase difference detector FS is small. When the focus state detector FA is located near the center of the image sensor 3 in the first direction, the improvement in focus position detection accuracy due to the improvement in the detection signal S / N ratio achieved by adding more detection signals outweighs the decrease in focus position detection accuracy caused by a mismatch between the exit pupil distance LPD and the designed pupil distance DPD. This enables highly accurate focus position detection.

[0095] Although various embodiments and modifications have been described above, the present invention is not limited to these. Furthermore, each embodiment and modification may be applied independently or in combination. Other aspects conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0096] 1: imaging device, 2: imaging optical system, 3: imaging element, 4: imaging control unit, 6: lens driving unit, 7: display unit, 8: operation unit, 30: semiconductor substrate, 31: control unit, 40: pixel, P: first AF pixel, M: second AF pixel, F1: first detection unit, F2: second detection unit, FS: image plane phase difference detection unit, 32: control line, 33: signal line, 34: readout unit, 36: output unit, 41: photoelectric conversion unit, 42: amplifier circuit, 44: color filter, 45: microlens, 46P: first light-shielding unit, 46M: second light-shielding unit

Claims

1. an image sensor having a focus state detection unit including a plurality of image plane phase difference detection units each having a different design pupil distance, the image plane phase difference detection units being arranged at different positions in a second direction intersecting with a first direction as a detection direction; an adder that generates a sum signal by adding together detection signals output from two or more of the image plane phase difference detection units, including the image plane phase difference detection unit with a design pupil distance closest to the exit pupil distance of the attached imaging optical system, among a plurality of detection signals detected by the plurality of image plane phase difference detection units included in the focus state detection unit; and An imaging device comprising:

2. 2. The imaging device according to claim 1, The image plane phase difference detection unit a first detection unit including a plurality of first light receiving units arranged in the first direction, the first light receiving units detecting a larger amount of light that has passed through one side of an exit pupil of the imaging optical system in the first direction than light that has passed through the other side of the exit pupil opposite to the one side; a second detection unit including a plurality of second light receiving units arranged in the first direction, the second light receiving units detecting a larger amount of light that has passed through the other side of the exit pupil in the first direction than light that has passed through the one side of the exit pupil; an imaging device comprising:

3. 3. The imaging device according to claim 2, The adding unit adding together the detection signals output by two or more of the image plane phase difference detection units, including the image plane phase difference detection unit with a design pupil distance closest to an exit pupil distance of the imaging optical system, among the plurality of detection signals from the first detection units included in the plurality of image plane phase difference detection units; adding together the detection signals output by two or more of the image plane phase difference detection units, including the image plane phase difference detection unit with a design pupil distance closest to the exit pupil distance of the imaging optical system, among the plurality of detection signals from the second detection units included in the plurality of image plane phase difference detection units; Imaging device.

4. 4. The imaging device according to claim 2, wherein: the second detection unit is disposed at a first distance in the second direction from the first detection unit, the plurality of image plane phase difference detection units are arranged in the second direction, spaced apart by a second distance that is longer than the first distance, Imaging device.

5. 5. The imaging device according to claim 1, an imaging device, wherein when the amount of light incident on the imaging element is small and the intensity of the imaging signal output by the imaging element is small, the adder adds more of the detection signals than when the intensity of the imaging signal is large.

6. 6. The imaging device according to claim 1, The adder adds more of the detection signals when the aperture value of the imaging optical system is small than when the aperture value of the imaging optical system is large.

7. 7. The imaging device according to claim 1, The imaging element includes a plurality of focus state detection units, An imaging device wherein the adder adds more of the detection signals when the position of the focus state detection unit in the first direction is close to the center of the imaging element than when the position of the focus state detection unit in the first direction is far from the center of the imaging element.

8. 8. The imaging device according to claim 1, The imaging element includes a plurality of focus state detection units, an image pickup device, wherein the adder adds more of the detection signals from the image plane phase difference detection unit in the plurality of focus state detection units when the position in the first direction of the selected focus state detection unit from the plurality of focus state detection units is close to the center of the image pickup element, compared to when the position in the first direction of the selected focus state detection unit is far from the center of the image pickup element.

9. 9. The imaging device according to claim 1, The adder selects the plurality of detection signals to be added in accordance with an exit pupil distance of the imaging optical system.

10. 10. The imaging device according to claim 1, The adder changes the number of the detection signals to be added in accordance with the size of an effective imaging area of ​​the imaging element.

11. 11. The imaging device according to claim 1, An imaging device comprising: a communication unit that receives information about an exit pupil distance from the attached imaging optical system.

Images