JP2013157442A - Image pickup element and focal point detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a pixel size smaller than that of a conventional image pickup element.SOLUTION: Each of plural pixels of an image pickup element comprises: an optical waveguide; a photoelectric conversion part; a microlens; and at least three light-shielding layers arranged between the photoelectric conversion part and the microlens at different positions in an optical axis direction of the microlens. Each of at least three light-shielding layers is provided with an opening for limiting light transmitted from the microlens and making the photoelectric conversion part receive the light. Among at least three light-shielding layers, a main light-shielding layer except for the light-shielding layer nearest the photoelectric conversion part and the light-shielding layer nearest the microlens is arranged at a position optically conjugate with a pupil surface. At least one part of the light of a light flux passing through a predetermined region of the pupil surface is incident on the opening of the main light-shielding layer. The optical waveguide is provided between the main light-shielding layer and the photoelectric conversion part, and at least one part of the light incident on the opening of the main light-shielding layer is guided to the photoelectric conversion part.

Description

  The present invention relates to an imaging device having pixels that generate pixel signals for pupil division type phase difference detection and a focus detection device including the imaging device.

  An imaging element having a focus detection pixel composed of a microlens and a photoelectric conversion unit disposed behind the microlens is disposed on a planned focal plane of the photographing lens, and a pair of images formed by a pair of focus detection light beams passing through the optical system. Focus detection using a so-called pupil division type phase difference detection system that generates a pair of corresponding image signals and detects the focus adjustment state of the optical system by detecting an image shift amount (phase difference) between the pair of image signals. The device is known.

  In the focus detection pixel of this type of focus detection device, a light shielding layer having an opening between the microlens and the photoelectric conversion unit in order to selectively guide a pair of focus detection light beams passing through the optical system to the photoelectric conversion unit. Is placed. As the light shielding layer, a metal wiring layer closest to the photoelectric conversion unit among a plurality of metal wiring layers for controlling accumulation and reading of signal charges stored in the photoelectric conversion unit is used (for example, Patent Document 1). reference).

JP 2010-213253 A

  In recent years, with the increase in the number of pixels of an image sensor, the demand for pixel size reduction has increased, but in order to reduce the pixel size, it is necessary to reduce the area of the light receiving portion of the photoelectric conversion portion, and accordingly the above-described light shielding. It is also necessary to reduce the area of the opening of the layer.

  In order for a bright light beam having a small F number to enter an opening having a small area, it is necessary to reduce the distance between the microlens and the light shielding layer having the opening. This is because if the distance is not reduced, the photoelectric conversion unit may receive a light beam that has passed through the microlens adjacent to the microlens instead of the microlens directly above the photoelectric conversion unit.

  However, in the focus detection pixel, it is necessary to ensure a distance greater than the focal length of the microlens between the microlens and the light shielding layer. Also in the imaging pixel, the thickness of the plurality of metal wiring layers described above cannot be reduced excessively because the electrical resistance increases. Further, the distance between the metal wiring layers and the distance between the metal wiring layer and the photoelectric conversion unit may cause a noise malfunction caused by the capacitive coupling effect, and thus cannot be made thin.

  That is, the conventional image sensor has a problem that the pixel size cannot be reduced.

  The image pickup device according to claim 1 includes a plurality of pixels, and each of the plurality of pixels includes an optical waveguide, a photoelectric conversion unit that converts the light guided by the optical waveguide into a signal charge and stores the incident light, and an incident A microlens that collects the luminous flux to be emitted and emits the transmitted light toward the photoelectric conversion unit, and at least different positions along the optical axis direction of the microlens between the photoelectric conversion unit and the microlens. Each of the at least three light shielding layers is provided with an opening for limiting the transmitted light to be received by the photoelectric conversion unit, and of the at least three light shielding layers, the closest to the photoelectric conversion unit. The main light-shielding layer other than the light-shielding layer and the light-shielding layer closest to the microlens is optically conjugate with the pupil plane set at a predetermined distance away from the photoelectric conversion unit in the optical axis direction from the microlens. Placed in position At least a part of the light beam passing through a predetermined region of the pupil plane enters the opening of the main light shielding layer, and the optical waveguide is provided between the main light shielding layer and the photoelectric conversion unit. At least a part of light incident on the opening is guided to the photoelectric conversion unit.

  According to the image sensor of the present invention, the pixel size can be reduced as compared with the conventional image sensor.

It is a cross-sectional view showing the configuration of the digital camera of the first embodiment. It is a figure which shows a focus detection position. It is a figure which shows the detailed structure of an image pick-up element. It is sectional drawing of an imaging pixel. It is the figure which showed the shape of the opening part at the time of seeing an imaging pixel from the front, and a photoelectric conversion part. It is sectional drawing of a focus detection pixel. It is the figure which showed the shape of the opening part at the time of seeing a focus detection pixel from the front, and the shape of a photoelectric conversion part. It is a figure for demonstrating the mode of the imaging light beam which an imaging pixel receives. It is a figure for demonstrating the mode of the focus detection light beam which a focus detection pixel receives. It is a conceptual diagram which shows the circuit structure of an image pick-up element. It is a detailed circuit diagram of an imaging pixel. It is a figure which simplifies and shows the cross-section of an imaging pixel. It is an operation | movement timing chart of an image pick-up element. It is a flowchart which shows operation | movement of a digital camera. It is sectional drawing which shows the modification of a focus detection pixel. It is the elements on larger scale of an image sensor. It is sectional drawing of a focus detection pixel.

--- First embodiment ---
As an imaging apparatus according to the first embodiment, a lens interchangeable digital camera will be described as an example. FIG. 1 is a cross-sectional view illustrating a configuration of a digital camera 201 according to the first embodiment. A digital camera 201 according to the present embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204. An interchangeable lens 202 having various photographing optical systems can be attached to the camera body 203 via a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, a diaphragm 211, a lens drive control device 206, and the like. The lens drive control device 206 includes a microcomputer (not shown), a memory, a drive control circuit, and the like. The lens drive control device 206 performs drive control for adjusting the focus of the focusing lens 210 and adjusting the aperture diameter of the aperture 211, and detecting the states of the zooming lens 208, the focusing lens 210, and the aperture 211, and the like. In addition, transmission of lens information and reception of camera information (defocus amount, aperture value, etc.) are performed by communication with a body drive control device 214 described later. The aperture 211 forms an aperture having a variable aperture diameter at the center of the optical axis in order to adjust the amount of light and the amount of blur.

  The camera body 203 includes an imaging element 212, a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, and the like. In the imaging element 212, imaging pixels are arranged according to a two-dimensional array defined by rows and columns, and focus detection pixels are arranged at portions corresponding to the focus detection positions. Details of the image sensor 212 will be described later.

  The body drive control device 214 includes a microcomputer, a memory, a drive control circuit, and the like. The body drive control device 214 repeatedly performs drive control of the image sensor 212, readout of the pixel signal from the image sensor 212, focus detection calculation based on the pixel signal of the focus detection pixel, and focus adjustment of the interchangeable lens 202, and Processing and recording of image signals, camera operation control, etc. The body drive control device 214 communicates with the lens drive control device 206 via the electrical contact 213 to receive lens information and send camera information.

  The liquid crystal display element 216 functions as an electric view finder (EVF). The liquid crystal display element driving circuit 215 displays a through image on the liquid crystal display element 216 based on the image signal read from the image sensor 212, and the photographer can observe the through image through the eyepiece 217. The memory card 219 is an image storage that records image data generated based on an image signal captured by the image sensor 212.

  A subject image is formed on the light receiving surface of the image sensor 212 by the light beam that has passed through the interchangeable lens 202. This subject image is photoelectrically converted by the image sensor 212, and the pixel signals of the imaging pixels and focus detection pixels are sent to the body drive control device 214.

  The body drive control device 214 calculates the defocus amount based on the pixel signal from the focus detection pixel of the image sensor 212, and outputs this defocus amount to the lens drive control device 206. In addition, the body drive control device 214 processes the image signal of the imaging pixel of the imaging element 212 to generate image data, stores the image data in the memory card 219, and displays the through image signal read from the imaging element 212 on the liquid crystal display. The image is output to the element driving circuit 215 and the through image is displayed on the liquid crystal display element 216. Further, the body drive control device 214 outputs aperture control information to the lens drive control device 206 to perform aperture control of the aperture 211.

  The lens drive controller 206 updates the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the lens drive control device 206 detects the positions of the zooming lens 208 and the focusing lens 210 and the aperture value of the aperture 211, and calculates lens information according to these lens positions and aperture value. Or lens information corresponding to the lens position and the aperture value is selected from a lookup table prepared in advance.

  The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to the in-focus position according to the lens drive amount. Further, the lens drive control device 206 drives the diaphragm 211 in accordance with the received diaphragm value.

  FIG. 2 is a diagram showing a focus detection position (focus detection area) 101 on the imaging screen 100 set on the planned imaging plane of the interchangeable lens 202, that is, the imaging plane, and a focus detection pixel array on the imaging element 212 described later. Shows an example of a region (focus detection area, focus detection position) where an image is sampled on the photographing screen during focus detection. In this example, focus detection pixels are arranged in the horizontal direction in the focus detection area 101 arranged at the center (on the optical axis) on the rectangular shooting screen 100.

  3 is a diagram showing a detailed configuration of the image sensor 212, and FIG. 3 shows details of a pixel array in which the vicinity of the focus detection area 101 in FIG. 2 is enlarged. Imaging pixels 310 are densely arranged on the imaging element 212 in a two-dimensional square lattice pattern. The imaging pixel 310 includes a red pixel (R), a green pixel (G), and a blue pixel (B), and is arranged according to a Bayer arrangement rule. In FIG. 3, focus detection pixels 313 and 314 for horizontal focus detection having the same pixel size as that of the imaging pixel 310 for horizontal focus detection are alternately arranged, and originally green pixels and blue pixels are continuously arranged. Arranged continuously on a horizontal line to be done.

  The shape of the microlens 10 is a shape that is originally cut out from a circular microlens larger than the pixel size into a square shape corresponding to the pixel size. The imaging pixel 310 includes a rectangular microlens 10, a photoelectric conversion unit 11 whose light receiving area is limited to a square by a light shielding mask, and a color filter (not shown). There are three types of color filters: red (R), green (G), and blue (B). In the image sensor 21, image pickup pixels 310 having respective color filters are arranged in a Bayer array.

  The focus detection pixels 313 and 314 are provided with a white filter that transmits all visible light in order to perform focus detection for all colors. Accordingly, the focus detection pixels 313 and 314 have a spectral sensitivity characteristic that is obtained by adding the spectral sensitivity characteristics of the green pixel, the red pixel, and the blue pixel, and the light wavelength region exhibiting high sensitivity is the green pixel, the red pixel, and the blue pixel. In each pixel, each color filter includes a light wavelength region in which high sensitivity is exhibited.

  The focus detection pixel 313 includes a rectangular microlens 10, a photoelectric conversion unit 13 in which a light receiving region is limited to the left half of the light receiving region of the imaging pixel 310 by a metal wiring layer having a light shielding function described later, and a color filter (not illustrated). ). The focus detection pixel 314 includes a rectangular microlens 10, a photoelectric conversion unit 14 in which a light receiving region is limited to the right half of the light receiving region of the imaging pixel 310 by a metal wiring layer having a light shielding function described later, and a color filter ( (Not shown). When the focus detection pixel 313 and the focus detection pixel 314 are represented by superimposing the microlenses 10, the photoelectric conversion units 13 and 14 in which the light receiving area is limited by a metal wiring layer having a light shielding function are arranged in the horizontal direction. In FIG. 3, the microlens 10 and the photoelectric conversion unit 11 constituting the imaging pixel 310 and the microlens 10 and the photoelectric conversion units 13 and 14 constituting the focus detection pixels 313 and 314 are illustrated in a simplified manner. The configuration will be described later.

  FIG. 4 is a cross-sectional view of the imaging pixel 310. In the imaging pixel 310, a color filter 38 and three layers of metal wiring layers 40, 41, and 42 having a light shielding function are disposed between the microlens 10 and the photoelectric conversion unit 11. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29 (the surface on the microlens 10 side). A planarization layer 30 is formed on the photoelectric conversion unit 11 (on the microlens 10 side), and a metal wiring layer 40 having an opening 40a is formed on the planarization layer 30 (on the microlens 10 side). The planarization layer 31 is formed on the metal wiring layer 40 (microlens 10 side), and the metal wiring layer 41 having the opening 41a is formed thereon (microlens 10 side). A planarizing layer 32 is formed on the metal wiring layer 41 (microlens 10 side), and a metal wiring layer 42 having an opening 42a is formed thereon (microlens 10 side). A planarizing layer 33 is formed on the metal wiring layer 42 (on the microlens 10 side), and a color filter 38 is formed thereon (on the microlens 10 side). A planarizing layer 34 is formed on the color filter 38 (on the microlens 10 side), and the microlens 10 is formed thereon.

  The planarization layers 30 to 34 are made of the same material, and also have an electrical insulating function between the metal wiring layers 40 to 42 and between the metal wiring layer 40 and the semiconductor substrate 29 and the photoelectric conversion unit 11. Yes. An optical waveguide 50 made of a material having a higher refractive index than that of the planarization layers 30 and 31 is formed between the opening 41 a of the metal wiring layer 41 and the photoelectric conversion unit 11. The size of the light incident portion of the optical waveguide 50 (the upper end of the optical waveguide 50 in FIG. 4) is larger than the size of the opening 41a, so that the light incident on the opening 41a passes directly to the planarization layer 31. To prevent that. The size of the light emitting portion of the optical waveguide 50 (the lower end of the optical waveguide 50 in FIG. 4) is smaller than the size of the photoelectric conversion portion 11, and the light emitted from the light emitting portion of the optical waveguide 50 is other than the photoelectric conversion portion 11. The direct incidence to the area on the surface of the semiconductor circuit board 29 is prevented.

  A boundary surface 51 is formed at the boundary between the optical waveguide 50 and the planarization layers 30 and 31. The light beam 55 incident on the boundary surface 51 through the optical waveguide 50 has an incident angle (an angle between the normal line of the boundary surface 51 and the light beam 55) of the refractive index difference between the optical waveguide 50 and the planarizing layers 30 and 31. When the angle is larger than the critical angle determined by the equation (1), the light is totally reflected at the boundary surface 51 and travels toward the photoelectric conversion unit 11. Therefore, when the boundary surface 51 does not exist, light that does not enter the photoelectric conversion unit 11 can be efficiently received by the photoelectric conversion unit 11. When the incident angle of the light beam 55 incident on the boundary surface 51 through the optical waveguide 50 is smaller than the aforementioned critical angle, a part of the light beam 56 of the light beam 55 passes through the boundary surface 51, but the metal wiring layer 40 The light beam 56 is shielded. Therefore, it can be prevented that the light beam 56 is directly incident on the photoelectric conversion unit 11 of the semiconductor substrate 29 or the adjacent image pickup pixel 310 to generate a noise charge. The size of the opening 40 a of the metal wiring layer 40 is set as small as possible within a range that does not enter the optical waveguide 50.

  The surface 41b on which the second metal wiring layer 41 is disposed and the exit pupil plane set in front of the microlens 10 (upward in FIG. 4), that is, on the optical system side, are optically coupled to each other by the microlens 10. It is a conjugate relationship. As a result, the light passing through the region where the shape of the opening 41a is projected onto the exit pupil plane by the microlens 10 enters the opening 41a. Note that the surface of the average exit pupil position of various interchangeable lens groups that can be attached to the camera body 203 is set as the exit pupil surface described above. The region where the shape of the opening 41a is projected onto the exit pupil plane by the microlens 10 is configured to include a region where the brightest open F-number light beam in the interchangeable lens group passes through the exit pupil plane. Yes. In order to realize the above conjugate relationship, it is necessary to ensure a distance approximately equal to the focal length of the microlens 10 between the microlens 10 and the metal wiring layer 41 (main light shielding layer). However, if the distance between the microlens 10 and the metal wiring layer 41 is large, a light beam 57 emitted from the microlens 10 of an adjacent pixel and traveling toward the opening 41a of the metal wiring layer 41 may be incident as crosstalk light. There is. The metal wiring layer 42 blocks the light beam 57 in order to prevent the occurrence of such crosstalk light between adjacent pixels. The size of the opening 42a of the metal wiring layer 42 is set to be as small as possible without blocking the normal light 58 that passes through the outermost side and enters the opening 41a from the microlens 10.

  FIG. 4 shows a cross section of the image pickup pixel 310 disposed near the intersection between the image pickup element 212 and the optical axis of the interchangeable lens 202 on the image pickup element 212 corresponding to the vicinity of the center on the photographing screen 100. In addition, the optical axis 19 of the microlens 10 and the centers of the openings 40 a to 42 a of the metal wiring layers 40 to 42 and the centers of the photoelectric conversion units 11 coincide. In the imaging pixels 310 arranged in the periphery of the imaging screen 100, in order to prevent so-called shading of the imaging light flux, the imaging pixels 310 and the position on the imaging device 212 corresponding to the center on the imaging screen 100 are used. Thus, with respect to the optical axis 19 of the microlens 10, the centers of the openings 40 a to 42 a of the metal wiring layers 40 to 42 and the center of the photoelectric conversion unit 11 are on the image sensor 212 corresponding to the center on the imaging screen 100. It is decentered in the direction from the position toward the imaging pixel 310.

FIG. 4 is a diagram showing the basic structure of the imaging pixel 310, and other components such as an intra-layer lens and a passivation layer can be added as necessary. For example, the semiconductor substrate 29 is silicon (Si), the planarization layers 30 to 34 are silicon oxide (SiO ₂ , refractive index 1.46), and the optical waveguide is silicon nitride (SiN, refractive index 2.02) or titanium oxide (TiO ₂ , refractive index). 2.35) The metal wiring layer is made of aluminum (Al) or copper (Cu). The structure can be manufactured using a semiconductor manufacturing technique such as photolithography or etching, for example.

  FIG. 5 is a diagram illustrating the shapes of the openings 40 a to 42 a and the photoelectric conversion unit 11 when the imaging pixel 310 illustrated in FIG. 4 is viewed from the front. There is a regular octagonal opening 40a on the square photoelectric conversion part 11, a regular octagonal opening 41a smaller than the opening 40a on it, and a regular octagonal opening 42a larger than the opening 41a on it. is there. Note that the front-view shape (not shown) of the light incident portion of the optical waveguide 50 shown in FIG. 4 is a shape in which the opening 41a is made slightly larger.

  The shape of the photoelectric conversion unit 11 is not limited to a square, and may be, for example, a regular octagon or a circle. The shapes of the openings 40a to 42a are not limited to regular octagons, and may be squares or circles, for example. The shape of the openings 40a to 42a is preferably a circular shape capable of maximizing the opening area, but here is a regular octagon as an example based on the viewpoint of ease of manufacture. Further, when the interchangeable lens 202 is attached to the camera body 203, the light beam limited by the aperture opening of the interchangeable lens 202 enters a range smaller than the opening 41a. Therefore, the shape of the opening 41a is not a perfect regular octagon. Alternatively, the shape may be partially cut or distorted due to the convenience of wiring. Further, the shape of the openings 40a and 42a may not be a perfect regular octagon in order to satisfy the purpose of light shielding, and may be a shape that is partially missing or distorted due to the convenience of wiring.

  FIG. 6 is a cross-sectional view of the focus detection pixels 313 and 314. The same components as those of the imaging pixel shown in FIG. The configuration of the focus detection pixels 313 and 314 differs from the configuration of the imaging pixel 310 at least in the shape of the opening provided in the metal wiring layers 40 to 42, the spectral characteristics of the filter, and the configuration of the optical waveguide.

  In the focus detection pixels 313 and 314, a white filter 39 and three layers of metal wiring layers 40, 41, and 42 having a light shielding function are disposed between the microlens 10 and the photoelectric conversion units 13 and 14. The photoelectric conversion units 13 and 14 are formed on the semiconductor circuit substrate 29 (surface on the microlens 10 side).

  In the focus detection pixel 313, the planarization layers 30, 31 and 32 are sandwiched on the photoelectric conversion unit 13 (on the microlens 10 side), the metal wiring layer 40 having the opening 40c, the metal wiring layer 41 having the opening 41c, And the metal wiring layer 42 which has the opening part 42c is formed. A planarizing layer 33 is formed on the metal wiring layer 42 (on the microlens 10 side), and a white filter 39 is formed thereon (on the microlens 10 side). A planarizing layer 34 is formed on the white filter 39 (on the microlens 10 side), and the microlens 10 is formed thereon.

  In the opening 41c provided in the metal wiring layer 41, the right half from the optical axis 19 of the microlens 10 is substantially shielded as compared to the opening 41a in FIG.

  Between the opening 41c of the metal wiring layer 41 and the photoelectric conversion unit 13, an optical waveguide 50c made of a material having a refractive index higher than that of the planarization layers 30 and 31 is formed. The size of the light incident portion of the optical waveguide 50c is larger than the size of the opening 41c, thereby preventing light incident on the opening 41c from directly passing through the planarizing layer 31. The size of the light emitting portion of the optical waveguide 50 c is smaller than the size of the photoelectric conversion portion 13, and the light emitted from the light emitting portion of the optical waveguide 50 c is in a region on the surface of the semiconductor circuit substrate 29 other than the photoelectric conversion portion 13. Preventing direct incidence.

  A boundary surface 51 c is formed at the boundary between the optical waveguide 50 c and the planarization layers 30 and 31. When the incident angle of the light beam 55c passing through the optical waveguide 50c and entering the boundary surface 51c is larger than the critical angle, the light beam 55c is totally reflected by the boundary surface 51c and travels toward the photoelectric conversion unit 13. Therefore, when the boundary surface 51 c does not exist, light that does not enter the photoelectric conversion unit 13 can be efficiently received by the photoelectric conversion unit 13. When the incident angle of the light beam 55c passing through the optical waveguide 50c and entering the boundary surface 51c is smaller than the critical angle, a part of the light beam 56c of the light beam 55c passes through the boundary surface 51c, but the metal wiring layer 40 has this light beam. 56c is shielded from light. Therefore, it can be prevented that the light ray 56c is directly incident on the photoelectric conversion unit 14 of the semiconductor substrate 29 or the adjacent focus detection pixel 314 to generate a noise charge. The size of the opening 40c of the metal wiring layer 40 is set as small as possible within a range not entering the optical waveguide 50c.

  The surface 41b on which the second metal wiring layer 41 (main light shielding layer) is disposed and the exit pupil plane set in front of the microlens 10 (upward in FIG. 6), that is, on the optical system side are the microlens 10. Therefore, they are optically conjugate with each other. Note that the surface of the average exit pupil position of various interchangeable lens groups that can be attached to the camera body 203 is set as the exit pupil surface described above.

  In the focus detection pixel 314, as shown in FIG. 6, the configuration of the focus detection pixel 313 described above is reversed left and right with the optical axis 19 of the microlens 10 as the symmetry axis. That is, the planarization layers 30, 31 and 32 are sandwiched on the photoelectric conversion unit 14 (on the microlens 10 side), and the metal wiring layer 40 having the opening 40d, the metal wiring layer 41 having the opening 41d, and the opening 42d are formed. A metal wiring layer 42 is formed. Between the opening 41d of the metal wiring layer 41 and the photoelectric conversion unit 14, an optical waveguide 50d made of a material having a refractive index higher than that of the planarization layers 30 and 31 is formed.

  As described above, the surface 41b on which the second metal wiring layer 41 (main light shielding layer) is disposed and the exit pupil surface set in front of the microlens 10 (upward in FIG. 6), that is, on the optical system side. The microlenses 10 are optically conjugate with each other.

  The metal wiring layer 42 blocks a light beam 57 c that can be crosstalk light between focus detection pixels passing between the microlens 10 and the metal wiring layer 41. For example, a light beam 57 c from the microlens 10 of the adjacent focus detection pixel 313 toward the opening 41 d of the metal wiring layer 41 of the focus detection pixel 314 is blocked by the metal wiring layer 42. The size of the opening 42d of the metal wiring layer 42 is set to be as small as possible without blocking the normal light 58d that passes through the outermost side and enters the opening 41d from the microlens 10.

  6 shows a cross section of the focus detection pixels 313 and 314 arranged at a position on the image sensor 212 corresponding to the vicinity of the center on the photographing screen 100, that is, in the vicinity of the intersection of the image sensor 212 and the optical axis of the interchangeable lens 202. The optical axis 19 of the microlens 10, the centers of the openings 40 c to 42 c and 40 d to 42 d of the metal wiring layers 40 to 42, and the centers of the photoelectric conversion units 13 and 14 coincide with each other. In the focus detection pixels 313 and 314 arranged in the periphery of the shooting screen 100, the microlens 10 is selected according to the distance between the focus detection pixels 313 and 314 and the position on the image sensor 212 corresponding to the center on the shooting screen 100. The centers of the openings 40c to 42c and 40d to 42d of the metal wiring layers 40 to 42 and the centers of the photoelectric conversion units 13 and 14 with respect to the optical axis 19 are on the image sensor 212 corresponding to the center on the imaging screen 100. Is decentered in the direction from the position toward the focus detection pixels 313 and 314.

  FIG. 7 is a diagram illustrating the shapes of the openings 40c to 42c and 40d to 42d and the shapes of the photoelectric conversion units 13 and 14 when the focus detection pixels 313 and 314 illustrated in FIG. 6 are viewed from the front. is there.

  The square photoelectric conversion units 13 and 14 have the same shape as the photoelectric conversion unit 11 of the imaging pixel 310. The openings 41 c and 41 d are obtained when the regular octagonal shape of the opening 41 a of the imaging pixel 310 is divided symmetrically by a straight line that passes through the optical axis 19 of the microlens 10 and is orthogonal to the arrangement direction of the photoelectric conversion units 13 and 14. The left half and the right half of the shape. The straight portions 43c and 43d of the openings 41c and 41d are formed along the straight lines described above. The shapes of the openings 42c and 42d are larger than the shapes of the openings 41c and 41d. The regular octagonal shape of the opening 42a of the imaging pixel 310 is changed to the alignment direction of the photoelectric conversion units 13 and 14. This corresponds to the shape when divided by a straight line perpendicular to the line.

  The shapes of the openings 40c and 40d are larger than the shapes of the openings 41c and 41d. The regular octagonal shape of the opening 40a of the imaging pixel 310 is changed to the alignment direction of the photoelectric conversion units 13 and 14. This corresponds to the shape when divided by a straight line perpendicular to the line.

  Further, the front view shape (not shown) of the light incident portions of the optical waveguides 50c and 50d shown in FIG. 6 is a shape obtained by enlarging the openings 41c and 41d.

  The shape of the photoelectric conversion units 13 and 14 is not limited to a square like the shape of the photoelectric conversion unit 11, and may be, for example, a regular octagon or a circle. The shapes of the openings 40c, 42c, 40d, and 42d are not limited to the shapes shown in FIG. 7, and may be partially cut or distorted due to the convenience of wiring, for example.

  The shape of the openings 41c and 41d may not be a shape obtained by dividing a regular octagon into two equal parts, and may be a shape that is partially cut or distorted due to the convenience of wiring. However, in order to maintain the pupil division performance of the focus detection pixels, it is preferable that the straight portions 43c and 43d are not chipped or distorted.

  The configuration of the focus detection pixels 313 and 314 has been described above, but since the configuration is the same as the configuration of the imaging pixel 310, the imaging pixel 310 and the focus detection pixels 313 and 314 can be manufactured in substantially the same process. .

  In the conventional focus detection pixel configuration, the surface on which the metal wiring layer 40 closest to the photoelectric conversion unit is disposed and the exit pupil plane set in front of the microlens are optically conjugate by the microlens. It was. For this reason, when the pixel size is reduced, it is impossible to dispose a planarization layer and a metal wiring layer having the same configuration as the conventional one between the microlens and the photoelectric conversion unit. However, in the configuration of the focus detection pixels 313 and 314 shown in FIG. 6, the surface 41 b on which the second metal wiring layer 41 (main light shielding layer) is disposed and the exit pupil plane set in front of the microlens 10. Is in an optically conjugate relationship by the microlens 10. Light incident on the openings 41c and 41d of the metal wiring layer 41 is guided to the photoelectric conversion units 13 and 14 by the optical waveguides 50c and 50d, respectively. Therefore, even when the pixel size is reduced, it is possible to maintain a sufficient distance between the microlens 10 and the photoelectric conversion units 13 and 14 so as to arrange the planarization layer and the metal wiring layer having the same configuration as the conventional one, Light incident on the openings 41c and 41d of the metal wiring layer 41 can be efficiently condensed on the photoelectric conversion units 13 and 14.

  Further, in the configuration of the focus detection pixels 313 and 314 shown in FIG. 6, the metal wiring layer 42 is disposed between the microlens 10 and the openings 41 c and 41 d of the metal wiring layer 41, and the opening of the metal wiring layer 41 is provided. A metal wiring layer 40 is disposed between the portions 41 c and 41 d and the photoelectric conversion portions 13 and 14. Therefore, the crosstalk light between the focus detection pixels and the crosstalk light from the imaging pixel to the focus detection pixel can be efficiently prevented by the metal wiring layer 42, and stray light transmitted through the optical waveguides 50 c and 50 d is also prevented by the metal wiring layer 40. It can be shielded efficiently.

  In the configuration of the focus detection pixels 313 and 314 shown in FIG. 6, optical waveguides 50c and 50d are arranged between the surface 41b on which the second metal wiring layer 41 is arranged and the photoelectric conversion units 13 and 14. Thus, the optical waveguides 50c and 50d guide the light incident on the openings 41c and 41d to the photoelectric conversion units 13 and 14. Therefore, the height of the optical waveguides 50c and 50d (the dimension of the microlens 10 in the direction of the optical axis 19) can be minimized, and the light passing from the optical waveguide 50c through the boundary surface 51c to the planarizing layer 30 or 31 can be transmitted. It can be reduced to a minimum.

  FIG. 8 is a diagram for explaining the state of the imaging light beam received by the imaging pixel 310, and shows a cross section of the imaging element 212 in which the configuration of the imaging pixel array is simplified. The photoelectric conversion units 11 of all the imaging pixels 310 arranged on the image sensor 212 receive the light flux that has passed through the opening 41 a (not shown) of the metal wiring layer 41 disposed in the vicinity of the photoelectric conversion unit 11. . The shape of the opening 41a is common to all the imaging pixels 310 on the exit pupil 90 that is defined by the microlens 10 of each imaging pixel 310 at a distance from the microlens 10 toward the optical system by the distance measuring pupil distance d. Is projected onto a large area 95. As described above, since the shape of the opening 41a is a regular octagon or other shape, the region 95 has a shape similar to the shape of the opening 41a. However, in FIG. As shown.

  Therefore, the photoelectric conversion unit 11 of each imaging pixel 310 receives the light beam 71 that passes through the region 95 and the microlens 10 of each imaging pixel 310. Then, the photoelectric conversion unit 11 of each imaging element 310 outputs a signal corresponding to the intensity of the image formed on each microlens 10 by the light flux 71 that passes through the region 95 and travels toward the microlens 10 of each imaging pixel 310. To do.

  FIG. 9 is a diagram for explaining the state of the focus detection light beam received by the focus detection pixels 313 and 314 in comparison with FIG. 4, and shows a cross section of the image sensor 212 in which the configuration of the focus detection pixel array is simplified. Show. The photoelectric conversion units 13 and 14 of all the focus detection pixels 313 and 314 arranged on the image sensor 212 have openings 41c and 41d (non-existing portions) of the metal wiring layer 41 arranged in proximity to the photoelectric conversion units 13 and 14. The light beam that has passed through is received. The shape of the opening 41c is such that all the focus detection pixels on the exit pupil 90 defined by the microlens 10 of each focus detection pixel 313 are spaced from the microlens 10 toward the optical system by the distance measurement pupil distance d. It is projected onto a region 93 common to 313. Similarly, the shape of the opening 41d is such that all the focus detections on the exit pupil 90 defined by the microlens 10 of each focus detection pixel 314 are spaced from the microlens 10 toward the optical system by the distance measurement pupil distance d. It is projected onto a region 94 common to the pixels 314. As described above, since the shapes of the openings 41c and 41d are regular octagons or other shapes, the regions 93 and 94 are similar to the shapes of the openings 41c and 41d, but in FIG. It is shown as a rectangle for simplicity. The pair of regions 93 and 94 is called a distance measuring pupil.

  Therefore, the photoelectric conversion unit 13 of each focus detection pixel 313 receives the light flux 73 that passes through the distance measuring pupil 93 and the microlens 10 of each focus detection pixel 313. The photoelectric conversion unit 13 of each focus detection pixel 313 corresponds to the intensity of the image formed on the microlens 10 by the light flux 73 that passes through the distance measuring pupil 93 and travels toward the microlens 10 of each focus detection pixel 313. Output a signal. Further, the photoelectric conversion unit 14 of each focus detection pixel 314 receives the light flux 74 that passes through the distance measuring pupil 94 and the microlens 10 of each focus detection pixel 314. The photoelectric conversion unit 14 of each focus detection pixel 314 corresponds to the intensity of the image formed on the microlens 10 by the light flux 74 that passes through the distance measuring pupil 94 and travels toward the microlens 10 of each focus detection pixel 314. Output a signal.

  A region where the distance measuring pupils 93 and 94 on the exit pupil 90 through which the light beams 73 and 74 received by the pair of focus detection pixels 313 and 314 pass is integrated on the exit pupil 90 through which the light beam 71 received by the imaging pixel 310 passes. The region 95 of FIG. That is, on the exit pupil 90, the light beams 73 and 74 have a complementary relationship with the light beam 71.

  By arranging a large number of the pair of focus detection pixels 313 and 314 alternately and linearly, and collecting the outputs of the photoelectric conversion units of the focus detection pixels into a pair of output groups corresponding to the distance measuring pupils 93 and 94, Information on the intensity distribution of the pair of images formed on the focus detection pixel array by the pair of light fluxes passing through the distance measuring pupils 93 and 94 is obtained. This information is subjected to, for example, image shift detection calculation processing (correlation calculation processing, phase difference detection processing) disclosed in Japanese Patent Application Laid-Open No. 2007-333720 and Japanese Patent Application Laid-Open No. 2010-139624, so-called pupil division. An image shift amount of the pair of images by the mold phase difference detection method is detected. Further, by performing a conversion calculation according to the proportional relationship between the distance between the center of gravity of the pair of distance measurement pupils and the distance measurement pupil distance with respect to the image shift amount, the deviation between the planned image formation surface and the image formation surface at the focus detection position ( Defocus amount) is calculated.

  Next, details of the image sensor 212 included in the digital camera 201 in this embodiment will be described. FIG. 10 is a conceptual diagram showing a circuit configuration of the image sensor 212. The image sensor 212 is configured as a CMOS image sensor. For convenience of explanation, in FIG. 10, the circuit configuration of the image sensor 212 is simply shown as a layout of 8 pixels in the horizontal direction × 4 pixels in the vertical direction. FIG. 10 is drawn corresponding to the focus detection area 101 in the horizontal direction of FIG. 2, and shows how the focus detection pixels 313 and 314 are arranged in the same row in the horizontal direction.

  In FIG. 10, the second row in the vertical direction is a row in which the focus detection pixels 313 and 314 are arranged. The four focus detection pixels 313 and 314 in the center represent a plurality of focus detection pixels. A plurality of pixels in which the respective imaging pixels 310 are arranged on the left and right of the focus detection pixels 313 and 314 are shown as representatives. In FIG. 10, the first, third, and fourth rows in the vertical direction are rows in which only the imaging pixels 310 are arranged, and a plurality of rows above and below the row in which the focus detection pixels 313 and 314 are arranged. A row including only imaging pixels is shown as a representative.

  The imaging pixel 310 and the focus detection pixels 313 and 314 include a photoelectric conversion unit (photodiode: PD) that generates charges according to the amount of received light, and a floating diffusion unit (FD) that accumulates charges generated by the photoelectric conversion unit. And an amplifier (AMP) that outputs a pixel signal corresponding to the amount of charge accumulated in the FD as a basic configuration. In FIG. 10, a line memory 320 is a buffer that samples and holds pixel signals of pixels for one row and temporarily holds them, and a vertical scanning circuit emits pixel signals of the same row output to the vertical signal line 501. Sample and hold based on the control signal φH1. Note that the pixel signals held in the line memory 320 are reset in synchronization with the rise of the control signals φS1 to φS4.

  Output of pixel signals from the imaging pixel 310 and the focus detection pixels 313 and 314 is independently controlled for each row by a control signal (φS1 to φS4) generated by the vertical scanning circuit. Pixel signals of pixels in the row selected by the control signals (φS1 to φS4) are output to the vertical signal line 501. The pixel signals held in the line memory 320 are sequentially transferred to the output circuit 330 by the control signals (φV1 to φV8) generated by the horizontal scanning circuit, amplified by the amplification set by the output circuit 330, and output to the outside. The

  The image pickup pixel 310 and the focus detection pixels 313 and 314 are reset by the control signals (φR1 to φR4) generated by the vertical scanning circuit after the pixel signal is sampled and held, and the next pixel at the fall of the control signals φR1 to φR4. Start charge accumulation for signal. Control signals φT1 to φT4 generated by the vertical scanning circuit are signals for controlling gates between the photodiodes of the imaging pixel 310 and the focus detection pixels 313 and 314 and the floating diffusion portion. Whether or not charges generated by the photodiodes are transferred to the floating diffusion portion is controlled for each row by the control signals φR1 to φR4.

  The control signal φSync is a vertical synchronization signal, and is output to the outside (body drive control device 214) for each frame.

  FIG. 11 is a detailed circuit diagram of the imaging pixel 310 of the imaging device 212 shown in FIG. As shown in FIG. 11, the photoelectric conversion unit 11 includes a photodiode (PD). The PD and the floating diffusion layer (floating diffusion: FD) are connected via a MOS transistor 511 controlled by a control signal φTn (φT1 to φT4). Then, the charge generated by the PD is transferred to the FD during the period when the MOS transistor 511 is turned on by the control signal φTn (φT1 to φT4). The FD is connected to the gate of the amplification MOS transistor (AMP), and the AMP generates a signal corresponding to the amount of charge accumulated in the FD.

  FD is connected to the power supply voltage Vdd via the reset MOS transistor 510. When the reset MOS transistor 510 is turned on by the control signal φRn (φR1 to φR4), the charge accumulated in the FD is cleared and the FD is reset. The output of AMP is connected to a vertical output line 501 through a row selection MOS transistor 512. The row selection MOS transistor 512 is turned on by the control signal φSn (φS1 to φS4), so that the output of the AMP is output to the vertical output line 501. PD is connected to the power supply voltage Vdd through the MOS transistor 513. When the MOS transistor 513 is turned on by the control signal φU, the charge generated by the PD is cleared.

  FIG. 12 is a diagram illustrating a simplified cross-sectional structure of the imaging pixel 310 of the imaging element 212. FIG. 12 is a diagram corresponding to the detailed circuit diagram of the imaging pixel 310 shown in FIG. As shown in FIG. 12, in the imaging pixel 310, a buried photodiode (PD) composed of a P layer and an N + layer is formed on a P-type semiconductor substrate, and a floating diffusion (FD) composed of an N + layer is formed next thereto. Is done. An N + layer is further formed adjacent to PD and FD, and is connected to the power supply voltage Vdd. The FD is connected to the gate of the AMP. A gate 521 of a MOS transistor 511 is arranged between FD and PD, and a control signal φTn is connected. A gate 520 of MOS transistor 510 is arranged between FD and the N + layer adjacent to FD, and control signal φRn is connected.

  FIG. 13 is an operation timing chart of the image sensor 212 shown in FIG. When the image sensor 212 is a CMOS image sensor, pixel reset, exposure, and signal readout are performed by a so-called rolling shutter operation (line exposure) that overlaps the charge accumulation period of the photoelectric conversion element for each row by a predetermined period. As described above, the process is sequentially performed for each row.

  A vertical synchronization signal φSync (ON) is generated at time t0 in synchronization with the start of signal output of all pixels (output of image signals for one frame) from the image sensor 212. The vertical scanning circuit issues a control signal φS1 (ON) and a control signal φT1 (OFF) at time t0 in synchronization with the vertical synchronization signal φSync. The imaging pixel 310 in the first row is selected by the control signal φS1 (ON), and the pixel signal of the selected imaging pixel 310 in the first row is output to the vertical signal line 501. Further, the FD is disconnected from the PD when the pixel signal is output by the control signal φT1 (OFF). At this time, a pixel signal corresponding to the charge accumulated in the FD portion of the imaging pixel 310 is output to the vertical signal line 501.

  The pixel signal of the first row output to the vertical signal line 501 by the control signal φH1 generated from the vertical scanning circuit at time t1 is temporarily held in the line memory 320. The pixel signals of the imaging pixels 310 in the first row held in the line memory 320 are transferred to the output circuit according to the control signals φV1 to φV8 sequentially issued from the horizontal scanning circuit, and are amplified with the amplification degree set by the output circuit 330. Output to the outside.

  When transfer of the pixel signals of the imaging pixels 310 in the first row to the line memory 320 is completed (time t2), the reset circuit has the control signal φR1 (ON), the vertical scanning circuit has the control signal φS1 (ON), and the control signal Issue φT1 (ON). The imaging pixel 310 in the first row is reset by the control signal φR1 (ON). At this time, charges accumulated in the PD and FD of the imaging pixel 310 are sucked into the power supply voltage Vdd, and the FD is reset to the power supply voltage.

  At time t3, the reset circuit issues a control signal φR1 (OFF), and the next charge accumulation of the imaging pixels in the first row is started at the falling edge of the control signal φR1, and the charge generated by the PD after time t3 becomes FD. Accumulate. When the output of the pixel signal of the imaging pixel 310 in the first row from the output circuit 330 is finished, the imaging pixel 310 and the focus detection pixels 313 and 314 in the second row are selected by the control signals φS2 and φT2 generated by the vertical scanning circuit. The pixel signals of the selected imaging pixel 310 and focus detection pixels 313 and 314 are output to the vertical signal line 501.

  Hereinafter, similarly, holding of the pixel signals of the imaging pixels 310 and the focus detection pixels 313 and 314 in the second row, resetting of the imaging pixels 310 and the focus detection pixels 313 and 314, output of the pixel signals and start of the next charge accumulation are performed. Done. Subsequently, the pixel signals of the imaging pixels 310 in the third row and the fourth row are held, the imaging pixels 310 are reset, the pixel signals of the imaging pixels 310 are output, and the next charge accumulation is started. When the output of the pixel signals of all the pixels is completed, the operation returns to the first row again and the above operation is repeated periodically (frame 2).

  The reset operation of the imaging pixels 310 and the focus detection pixels 313 and 314 in the n-th row is performed during the time from the rise to the fall of the control signal φRn. The exposure operation of the imaging pixels 310 and the focus detection pixels 313 and 314 in the n-th row is performed during the time (exposure time, charge accumulation period) from the falling edge of the control signal φRn to the rising edge of the control signal φSn. The pixel signal readout operation of the n-th imaging pixel 310 and the focus detection pixels 313 and 314 is performed during the time from the rise of the control signal φSn to the rise of the control signal φSn + 1.

  Although the circuit configuration and operation of the image sensor 212 have been described above, various control signal lines, output lines, and the like in the circuit configuration are mounted as the metal wiring layers 40, 41, and 42 described with reference to FIGS.

  FIG. 14 is a flowchart showing the operation of the digital camera 201 shown in FIG. Each processing step shown in FIG. 14 is executed by the body drive control device 214. When the power of the digital camera 201 is turned on in step S100, the body drive control device 214 starts the operation after step S110. In step S <b> 110, the image pickup pixel data is read out and displayed on the liquid crystal display element 216. In subsequent step S120, a pair of image data corresponding to the pair of images is read from the focus detection pixel array.

  In step S130, an image shift detection calculation process (difference type correlation calculation process) is performed on the read pair of image data, and an image shift amount is calculated.

  In step S135, the image shift amount is multiplied by a conversion coefficient to be converted into a defocus amount. In step S140, it is checked whether or not the focus is close, that is, whether or not the calculated absolute value of the defocus amount is within a predetermined value. If it is determined that the lens is not in focus, the process proceeds to step S150, the defocus amount is transmitted to the lens drive control device 206, the focusing lens 210 of the interchangeable lens 202 is driven to the focus position, and the process returns to step S110. The above operation is repeated. Even when focus detection is impossible, the process branches to this step, a scan drive command is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is driven to scan from infinity to the nearest. Then, it returns to step S110 and repeats the operation | movement mentioned above.

  On the other hand, if it is determined in step S140 that the focus is close to the in-focus state, the process proceeds to step S160, and it is determined whether or not a shutter release has been performed by operating a shutter button (not shown). If it is determined that the shutter release has not been performed, the process returns to step S110 and the above-described operation is repeated. If the shutter has been released, the process proceeds to step S170, where an aperture adjustment command is transmitted to the lens drive control device 206, and the aperture value of the interchangeable lens 202 is controlled to an F value (an F value set by the photographer or an automatically set F value). Value).

  When the aperture control is finished, the image sensor 212 is caused to perform an imaging operation, and image data is read from the imaging pixels of the image sensor 212 and all focus detection pixels. In step S180, pixel data at each pixel position in the focus detection pixel column is generated by pixel interpolation based on pixel data of imaging pixels around the focus detection pixel. In subsequent step S190, the image data including the pixel data of the imaging pixel and the pixel data generated by the pixel interpolation is stored in the memory card 219, and the process returns to step S110 to repeat the above-described operation.

  The details of the calculation of the defocus amount in step S130 of FIG. 14 and the general image shift detection calculation process (difference type correlation calculation process) used for the calculation are described in JP2010-139624A and JP2007-333720A. The defocus amount is calculated by multiplying the image shift amount by a conversion coefficient. Note that the conversion coefficient changes according to the aperture diameter (F value) because the center-of-gravity interval of the distance measuring pupil changes according to the aperture diameter.

---- Modified example ---
In the first embodiment described above, the image sensor 212 is configured as a CMOS image sensor. In the CMOS image sensor, the number of metal wiring layers is generally three, and the structure of the imaging pixel shown in FIGS. 4 and 6 has been described as having three metal wiring layers. The number of wiring layers is not limited to three, and may be four or more, or may be two.

  When four or more metal wiring layers are used, one metal wiring layer of the metal wiring layers excluding the metal wiring layer closest to the photoelectric conversion portion and the metal wiring layer closest to the microlens is shown in FIG. These are used as the metal wiring layer 41 (main light shielding layer) shown in FIG. 6 and are arranged in the vicinity of the focal point of the micro lens. Thereby, the metal wiring layer is optically conjugate with the exit pupil plane by the microlens, and the focus detection light beam is defined by the opening provided in the metal wiring layer. An optical waveguide is provided between the opening and the photoelectric conversion unit so that light incident on the opening is efficiently received by the photoelectric conversion unit. Metal wiring layers other than the metal wiring layer function as a light shielding layer for preventing crosstalk light and stray light between focus detection pixels.

  When two metal wiring layers are used, the metal wiring layer close to the microlens is used as the metal wiring layer 41 (main light-shielding layer) shown in FIGS. 4 and 6, and in the vicinity of the focus position of the microlens. Placed in. Thereby, the metal wiring layer is optically conjugate with the exit pupil plane by the microlens, and the focus detection light beam is defined by the opening provided in the metal wiring layer. An optical waveguide is provided between the opening and the photoelectric conversion unit so that light incident on the opening is efficiently received by the photoelectric conversion unit. 4 and 6, a dedicated light shielding layer for preventing crosstalk light between adjacent pixels is provided instead of the metal wiring layer 42 shown in FIGS. 4 and 6, and the light shielding layer is composed of two metal wiring layers and a microlens. By arranging them in between, a total of three light-shielding layers are provided.

  In the first embodiment described above, the focus of the pupil division type phase difference detection method that can prevent crosstalk with a small number of structural requirements even when the pixel size is reduced by using the metal wiring layer also as a light shielding layer. A detection pixel can be configured. If the light shielding by the metal wiring layer alone is insufficient, the light shielding by a light shielding layer (black filter or the like) dedicated to the light shielding may be added as necessary. For example, in FIG. 6, a dedicated light shielding layer can be provided between the metal wiring layer 42 and the microlens 10. In addition, when an opening cannot be formed in the metal wiring layer and cannot be used as a light shielding layer, a part or all of the above-described embodiment may be replaced with a dedicated light shielding layer.

  For example, when a metal wiring layer closest to the microlens is used as the metal wiring layer 41 shown in FIGS. 4 and 6 in a CMOS image sensor structure having three metal wiring layers, the metal wiring layer is connected to the exit pupil plane by the microlens. Optically conjugate, and the focus detection light beam is defined by the opening provided in the metal wiring layer. An optical waveguide is provided between the opening and the photoelectric conversion unit so that light incident on the opening is efficiently received by the photoelectric conversion unit. In addition, a dedicated light shielding layer for preventing crosstalk light between adjacent pixels is provided in place of the metal wiring layer 42 shown in FIGS. 4 and 6, and the light shielding layer is disposed between the metal wiring layer and the microlens. It is good to do.

  In the configuration of the focus detection pixels 313 and 314 shown in FIG. 6, the shapes of the optical waveguides 51 c and 51 d arranged from the metal wiring layer 41 to the photoelectric conversion units 13 and 14 and the openings 40 c and 40 d of the metal wiring layer 40. Is different from the shape of the optical waveguide 51a of the imaging pixel 310 and the shape of the opening 40a of the metal wiring layer 40, but the shape of the optical waveguide 51a of the imaging pixel 310 and the opening 40a of the metal wiring layer 40 are different. It may be substantially the same as the shape.

  FIG. 15 is a cross-sectional view showing a modified example of the focus detection pixels 313 and 314 shown in FIG. 6. The same components as those in FIG.

  15 differs from FIG. 6 in that the material of the planarization layers 32a, 33a, and 34a is the same as the material of the optical waveguides 50c and 50d. In the configuration of the focus detection pixels 313 and 314 shown in FIG. 6, the material of the optical waveguides 50c and 50d and the material of the planarization layers 32, 33 and 34 are different, and the optical waveguides 50c and 50d are different depending on the refractive index difference. A part of the light rays incident on the openings 41c and 41d are reflected at the interface between the flattening layer 32 and the flattening layer 32, so that a light amount loss occurs. On the other hand, in the configuration of the focus detection pixels 313 and 314 shown in FIG. 15, the material of the optical waveguides 50c and 50d and the material of the planarization layer 32 are the same and there is no difference in refractive index. Reflection of light incident on the opening 41c does not occur at the interface with the layer 32, and there is no light loss. Also in the imaging pixel 310, by making the structure of the imaging pixel 310 the same as that in FIG. 15, it is possible to prevent light loss due to interface reflection at the incident portion of the optical waveguide.

  In the partial enlarged view of the image sensor 212 illustrated in FIG. 3, an example in which each pixel has a pair of focus detection pixels 313 and 314 having one photoelectric conversion unit is shown, but a pair of photoelectric conversions in one focus detection pixel. You may make it have a part. FIG. 16 is a partially enlarged view of the image sensor 212 corresponding to FIG. 3, and the focus detection pixel 311 has a pair of photoelectric conversion units 23 and 24.

  The focus detection pixel 311 performs a function corresponding to a pair of focus detection pixels 313 and 314. The focus detection pixel 311 includes the microlens 10 and a pair of photoelectric conversion units 23 and 24. The pair of photoelectric conversion units 23 and 24 receive a pair of light beams passing through the distance measuring pupils 93 and 94 on the exit pupil 90 of FIG.

  The focus detection pixel 311 is provided with a white filter, and its spectral sensitivity characteristic is a spectral sensitivity characteristic that combines the spectral sensitivity characteristic of a photodiode that performs photoelectric conversion and the spectral sensitivity characteristic of an infrared cut filter (not shown). It becomes. That is, the focus detection pixel 311 has a spectral sensitivity characteristic that is obtained by adding the spectral sensitivity characteristics of the green pixel, the red pixel, and the blue pixel. It covers the light wavelength region where each color filter exhibits high sensitivity.

  17 is a cross-sectional view of the focus detection pixel 311 shown in FIG. 16. The same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be partially omitted.

  15 differs from FIG. 6 in that one focus detection pixel 311 has a pair of photoelectric conversion units 23 and 24, and separate optical waveguides 50e and 50f are provided corresponding to the photoelectric conversion units 23 and 24, respectively. This is the point. The pair of photoelectric conversion units 23 and 24 are arranged with the element isolation region 17 therebetween with the optical axis 19 of the microlens 10 as a boundary.

  The light incident portions of the optical waveguides 50e and 50f (the interface between the planarizing layer 32 limited by the opening 41c and the optical waveguides 50e and 50f) are divided into portions with the optical axis 19 of the microlens 10 as a boundary. Yes. A partition wall 35 is provided so as to separate the optical waveguides 50e and 50f. The refractive index of the material of the partition wall 35 is set to be smaller than the refractive index of the optical waveguides 50e and 50f, and most of the light rays trying to pass from one of the optical waveguides 50e and 50f to the other are the optical waveguides 50e and 50f and the partition wall 35. Total reflection at the interface. Therefore, crosstalk light that enters the optical waveguide 50e and is received by the photoelectric conversion unit 24 can be prevented. By making the material of the partition 35 the same as that of the planarization layers 30 and 31, the manufacturing process can be simplified. It is possible to improve the prevention efficiency of crosstalk light by including a black pigment in the material of the partition wall 35 and absorbing the light beam that is about to escape from one of the optical waveguides 50e and 50f to the other.

  In the description of FIGS. 4, 6, and 15, the description has been made on the assumption that the planarization layers 30 and 31 disposed between the metal wiring layer 41 and the photoelectric conversion units 11, 13, and 14 are optically transparent. However, when the optical waveguides 50, 50c, and 50d are disposed between the metal wiring layer 41 and the photoelectric conversion units 11, 13, and 14 as in the present invention, the planarization layers 30 and 31 are not necessarily transparent. There is no need. For example, the material of the flattening layers 30 and 31 includes a black pigment, and the blackening of the flattening layers 30 and 31 causes crosstalk between adjacent pixels due to leakage light of the optical waveguides 50, 50c, and 50d. It can prevent more effectively.

  FIGS. 15 and 17 show the configuration of a front-illuminated focus detection pixel, and the metal wiring layer is disposed between the microlens and the photoelectric conversion unit. However, the present invention is not limited to this. It can also be applied to a back-illuminated pixel configuration. In that case, a dedicated light shielding layer (such as a metal layer or a black filter) can be used as the light shielding layer. Further, since it is not necessary to divert the metal wiring layer, the shape of the opening shown in FIGS. 5 and 7 can be realized accurately (with high accuracy), and crosstalk light and stray light can be reliably prevented. it can. In particular, when the configuration of the front-illuminated focus detection pixel in FIG. 17 is applied to a back-illuminated pixel configuration, optical waveguides 50e and 50f are formed between the opening 41c and the photoelectric conversion units 13 and 14. The necessary distance can be secured. Therefore, there is an advantage that the pair of light beams divided by the opening 41c can be reliably guided to the pair of photoelectric conversion units 13 and 14 across the element isolation region by the pair of optical waveguides 50e and 50f.

   In FIG. 2, the focus detection pixel column is arranged at the center of the screen, but the present invention is not limited to this, and the focus detection pixel column may be arranged around the screen.

  Although FIG. 10 shows the circuit configuration of a CMOS type image sensor, the image sensor is not limited to this, and the present invention can be applied to a circuit configuration of a CCD type image sensor, for example.

  In the imaging device 212 illustrated in FIG. 3, an example in which the imaging pixel 310 includes a color filter with a Bayer arrangement is shown, but the configuration and arrangement of the color filter are not limited to this. For example, an array of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) may be employed.

  In the image sensor 212 shown in FIG. 3, the focus detection pixels 312 and 313 are not provided with a color filter, but have one filter (for example, a green filter) among the color filters of the image pickup pixel 310. Even in this case, the present invention can be applied.

  In the imaging device 212 shown in FIG. 3, the example in which the imaging pixels 310 and the focus detection pixels 312 and 313 are arranged according to the dense square lattice arrangement is shown, but a so-called honeycomb arrangement or dense hexagonal lattice in which the dense square lattice arrangement is inclined 45 degrees is shown. You may arrange | position according to arrangement | sequence.

  The imaging device is not limited to a digital camera having a configuration in which an interchangeable lens is attached to the camera body as described above. For example, the present invention can be applied to a lens-integrated digital camera or digital video camera. Furthermore, the present invention can be applied to a small camera module built in a mobile phone, a vehicle-mounted camera, a surveillance camera, a robot vision recognition device, and the like. The present invention can also be applied to a focus detection device other than a camera, a distance measuring device, and a stereo distance measuring device.

10 microlens, 11, 13, 14 photoelectric conversion unit,
29 semiconductor circuit board, 71, 73, 74 luminous flux,
100 shooting screen, 101 focus detection area,
201 digital camera, 202 interchangeable lens, 203 camera body,
204 mount unit, 206 lens drive control device,
208 zooming lens, 209 lens, 210 focusing lens,
211 Aperture, 212 Image sensor, 213 Electrical contact,
214 body drive control device, 215 liquid crystal display element drive circuit, 216 liquid crystal display element,
217 eyepiece, 219 memory card,
310 Imaging pixels, 311, 313, 314 Focus detection pixels

Claims (10)

With multiple pixels,
Each of the plurality of pixels is
An optical waveguide;
A photoelectric conversion unit that converts the light guided by the optical waveguide into a signal charge and stores the signal charge;
A microlens that collects the incident light flux and emits it as transmitted light toward the photoelectric conversion unit;
Including at least three light shielding layers disposed at different positions along the optical axis direction of the microlens between the photoelectric conversion unit and the microlens,
Each of the at least three light shielding layers is provided with an opening for limiting the transmitted light to be received by the photoelectric conversion unit,
Of the at least three light shielding layers, the main light shielding layer other than the light shielding layer closest to the photoelectric conversion unit and the light shielding layer closest to the microlens is opposite to the photoelectric conversion unit in the optical axis direction from the microlens. It is arranged at a position optically conjugate with the pupil plane set at a position a predetermined distance on the side,
At least part of the light beam passing through a predetermined region of the pupil plane is incident on the opening of the main light-shielding layer;
The optical waveguide is provided between the main light-shielding layer and the photoelectric conversion unit, and guides the at least part of light incident on the opening of the main light-shielding layer to the photoelectric conversion unit. An image sensor. The imaging device according to claim 1,
The plurality of pixels includes a first pixel and a second pixel;
At least a part of one of the pair of light beams passing through the pair of regions on the pupil plane is incident on the opening of the main light shielding layer of the first pixel;
At least a part of the other light beam of the pair of light beams is incident on the opening of the main light shielding layer of the second pixel. The image sensor according to claim 1 or 2,
The light shielding layer disposed on the microlens side of the main light shielding layer is emitted from the microlens of a pixel adjacent to the pixel including the at least three light shielding layers and proceeds toward the opening of the main light shielding layer. An imaging device, wherein light traveling toward the opening of the main light shielding layer is shielded so that light does not enter the opening. The imaging device according to any one of claims 1 to 3,
The light shielding layer disposed closer to the photoelectric conversion unit than the main light shielding layer proceeds from the opening of the main light shielding layer toward a region other than the photoelectric conversion unit on the surface where the photoelectric conversion unit is disposed. An imaging device, wherein the light traveling toward the region is shielded so that the light does not enter the region. The imaging device according to any one of claims 1 to 4,
The at least three light shielding layers are three metal wiring layers;
The image pickup device, wherein the three metal wiring layers control the signal charges accumulated in the photoelectric conversion unit. The imaging device according to claim 5,
Each of the plurality of pixels further includes a light shielding layer dedicated to light shielding disposed between the at least three metal wiring layers and the microlens. The imaging device according to claim 5,
Each of the plurality of pixels further includes a metal wiring layer disposed between the at least three metal wiring layers and the microlens. An optical waveguide;
A photoelectric conversion unit that converts the light guided by the optical waveguide into a signal charge and stores the signal charge;
A microlens that collects the incident light flux and emits it as transmitted light toward the photoelectric conversion unit;
Including at least three light shielding layers disposed at different positions along the optical axis direction of the microlens between the photoelectric conversion unit and the microlens,
Each of the at least three light shielding layers is provided with an opening for limiting the transmitted light to be received by the photoelectric conversion unit,
Of the at least three light-shielding layers, the main light-shielding layer other than the light-shielding layer closest to the photoelectric conversion unit and the light-shielding layer closest to the microlens is disposed at a distance substantially equal to the focal length of the microlens from the microlens. And
At least part of the transmitted light is incident on the opening of the main light shielding layer,
The optical waveguide is provided between the main light-shielding layer and the photoelectric conversion unit, and guides the at least part of light incident on the opening of the main light-shielding layer to the photoelectric conversion unit. An image sensor. The imaging device according to any one of claims 1 to 8,
The imaging device, wherein a refractive index of the optical waveguide is higher than a refractive index of a planarizing layer other than the optical waveguide between the main light shielding layer and the photoelectric conversion unit. The imaging device according to any one of claims 1 to 9,
Focus adjustment of the optical system when an image is formed on the imaging element by the light transmitted through the optical system and guided by the optical waveguide based on the plurality of pixel signals output from the plurality of pixels. A focus detection apparatus comprising: focus detection means for detecting a state.

Images