Photodetector, optical element, and electronic apparatus

Abstract

A photodetector includes: a first layer including a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure; a second layer including a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure, the second layer being stacked on the first layer; and a photoelectric conversion element that photoelectrically converts light incident via the second layer and the first layer. The second structures are configured using a same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure.

Description

PHOTODETECTOR, OPTICAL ELEMENT, AND ELECTRONIC APPARATUSCross Reference to Related Applications

[0001] This application claims the benefit of Japanese Priority Patent Application JP 2023-143526 filed on September 5, 2023, the entire contents of each which are incorporated herein by reference.

[0002] The present disclosure relates to a photodetector, an optical element, and an electronic apparatus.

[0003] An image sensor has been proposed that includes a first lens layer including a plurality of nanoposts, a second lens layer including a plurality of nanoposts, and an etch prevention layer provided between the first lens layer and the second lens layer (PTL 1).

[0004] Japanese Unexamined Patent Application Publication No. 2022-074062Summary

[0005] It is desired, for a device that detects light, to improve characteristics for incident light.

[0006] It is desirable to provide a photodetector that makes it possible to improve characteristics for incident light.

[0007] A photodetector according to an embodiment of the present disclosure includes a first layer, a second layer that is stacked on the first layer, and a photoelectric conversion element. The first layer includes a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The photoelectric conversion element photoelectrically converts light incident via the second layer and the first layer. The second structures are configured using a same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure. An optical element according to an embodiment of the present disclosure includes a first layer and a second layer that is stacked on the first layer. The first layer includes a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The second structures are configured using a same material as a material of the first structures. The plurality of second structures including the second structure in contact with the first structure. An electronic apparatus according to an embodiment of the present disclosure includes an optical system, and a photodetector that receives light transmitted through the optical system. The photodetector includes a first layer, a second layer that is stacked on the first layer, and a photoelectric conversion element. The first layer includes a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The photoelectric conversion element photoelectrically converts light incident via the second layer and the first layer. The second structures are configured using a same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure.

[0008] Fig. 1 is a block diagram illustrating an example of a schematic configuration of an imaging device as an example of a photodetector according to a first embodiment of the present disclosure.Fig. 2 is a diagram illustrating an example of a pixel section of the imaging device according to the first embodiment of the present disclosure.Fig. 3 is an explanatory diagram of an example of a circuit configuration of a pixel of the imaging device according to the first embodiment of the present disclosure.Fig. 4 is a diagram illustrating an example of a planar configuration of the imaging device according to the first embodiment of the present disclosure.Fig. 5 is a diagram illustrating an example of a cross-sectional configuration of the imaging device according to the first embodiment of the present disclosure.Fig. 6A is a diagram illustrating an example of a planar configuration of a light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 6B is a diagram illustrating an example of a planar configuration of the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 7 is an explanatory diagram of another configuration example of the imaging device according to the first embodiment of the present disclosure.Fig. 8 is an explanatory diagram of another configuration example of the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 9A is an explanatory diagram of another configuration example of the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 9B is an explanatory diagram of another configuration example of the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 10 is an explanatory diagram of another configuration example of the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 11A is an explanatory diagram of an example of a method of manufacturing the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 11B is an explanatory diagram of an example of the method of manufacturing the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 11C is an explanatory diagram of an example of the method of manufacturing the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 11D is an explanatory diagram of an example of the method of manufacturing the light-guiding section of the imaging device according to the first embodiment of the present disclosure.Fig. 12 is an explanatory diagram of a configuration example of an imaging device according to a modification example of the present disclosure.Fig. 13 is an explanatory diagram of a configuration example of an optical element according to a second embodiment of the present disclosure.Fig. 14 is an explanatory diagram of a configuration example of the optical element according to the second embodiment of the present disclosure.Fig. 15 is a block diagram illustrating a configuration example of an electronic apparatus including the imaging device.Fig. 16 is a block diagram depicting an example of schematic configuration of a vehicle control system.Fig. 17 is a diagram of assistance in explaining an example of installation positions of an outside-vehicle information detecting section and an imaging section.Fig. 18 is a view depicting an example of a schematic configuration of an endoscopic surgery system.Fig. 19 is a block diagram depicting an example of a functional configuration of a camera head and a camera control unit (CCU).

[0009] Hereinafter, a description is given in detail of embodiments of the present disclosure with reference to the drawings. It is to be noted that the description is given in the following order. 1. First Embodiment 2. Second Embodiment 3. Application Example 4. Practical Application Examples <1. First Embodiment>

[0010] Fig. 1 is a block diagram illustrating an example of a schematic configuration of an imaging device that is an example of a photodetector according to a first embodiment of the present disclosure. Fig. 2 is a diagram illustrating an example of a pixel section of the imaging device according to the first embodiment. The photodetector is a device that is configured to detect incoming light. An imaging device 1, which is the photodetector, includes a plurality of pixels P each including a photoelectric conversion section (a photoelectric conversion element), and is configured to photoelectrically convert incident light to generate a signal.

[0011] The imaging device 1 can receive light transmitted through an optical system (unillustrated) including an optical lens and generate a signal. The imaging device 1 is configured using, for example, a semiconductor substrate (e.g., a silicon substrate) provided with the plurality of pixels P. The photoelectric conversion section of each of the pixels P of the imaging device 1 is, for example, a photodiode (PD), and is configured to photoelectrically convert light.

[0012] As illustrated in Figs. 1 and 2, as one example, the imaging device 1 includes, as an imaging area, a region (a pixel section 100) in which the plurality of pixels P is two-dimensionally arranged in a matrix. The pixel section 100 of the imaging device 1 is a pixel array in which the plurality of pixels P is arranged, and can also be referred to as a light-receiving region. The photoelectric conversion section of each of the pixels P can also be referred to as a photoelectric conversion region.

[0013] The imaging device 1 takes in incident light (image light) from a subject that is a measurement target via an optical system including an optical lens. The imaging device 1 captures an image of the subject formed by the optical lens. The imaging device 1 can photoelectrically convert received light to generate a pixel signal. The imaging device 1 that is the photodetector is a device that is configured to receive incident light and generate a signal, and can also be referred to as a light reception device.

[0014] The imaging device 1 (the photodetector) can be configured as an image sensor as one example. The imaging device 1 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging device 1 can include a structure (a stacked structure) configured by stacking a plurality of semiconductor layers. The imaging device 1 is usable for various electronic apparatuses such as a digital still camera, a video camera, and a mobile phone.

[0015] It is to be noted that, as illustrated in Fig. 2, a direction in which light from the subject is incident is defined as a Z-axis direction; a right-left direction on the sheet orthogonal to the Z-axis direction is defined as an X-axis direction; and an up-down direction on the sheet orthogonal to the Z-axis direction and the X-axis direction is defined as a Y-axis direction. In the following drawings, the arrow directions in Fig. 2 may be used, in some cases, as a standard to express a direction.Schematic Configuration of Imaging Device

[0016] As in the example illustrated in Fig. 1, as one example, the imaging device 1 includes a pixel section 100, a pixel control section 111, a signal processing section 112, a control section 113, and a processing section 114. In addition, the imaging device 1 is provided with a plurality of control lines Lread and a plurality of signal lines VSL. The control line Lread is a signal line that is configured to transmit a signal to control the pixel P, and is coupled to the pixel control section 111 and the pixels P of the pixel section 100.

[0017] In the example illustrated in Fig. 1, in the pixel section 100, the plurality of control lines Lread is wired for respective pixel rows each including a plurality of pixels P arranged side by side in a horizontal direction (a row direction). The control line Lread is configured to transmit a control signal to read a signal from the pixel P. The control line Lread can also be referred to as a drive line (a pixel drive line) that transmits a signal to drive the pixel P.

[0018] The signal line VSL is a signal line that is configured to transmit a signal from the pixel P, and is coupled to the pixels P of the pixel section 100 and the signal processing section 112. In the pixel section 100, for example, one or more signal lines VSL are wired for each pixel column including a plurality of pixels P arranged side by side in a vertical direction (a column direction). The signal line VSL is configured to transmit a signal outputted from the pixel P. In the imaging device 1, a plurality of signal lines VSL may be provided for one pixel column. The imaging device 1 can include a plurality of signal lines VSL for each pixel column.

[0019] The pixel control section 111 is configured to control each of the pixels P of the pixel section 100. The pixel control section 111 is a control circuit, and includes a plurality of circuits including a buffer, a shift register, an address decoder, and the like. The pixel control section 111 generates a signal to control the pixel P, and outputs the signal to each of the pixels P of the pixel section 100 via the control line Lread. The pixel control section 111 is controlled by the control section 113, and controls the pixels P of the pixel section 100.

[0020] For example, the pixel control section 111 generates signals to control the pixel P such as a signal to control a transfer transistor of the pixel P, a signal to control a selection transistor, and a signal to control a reset transistor, and supplies the signals to each of the pixels P by the control line Lread. The pixel control section 111 can perform control to read a pixel signal from each of the pixels P. The pixel control section 111 may also be referred to as a pixel drive section configured to drive each of the pixels P. It is to be noted that the pixel control section 111 and the control section 113 can also be collectively referred to as a pixel control section.

[0021] The signal processing section 112 is configured to execute signal processing on an inputted pixel signal. The signal processing section 112 is a signal processing circuit, and includes, for example, a load circuit, an AD (Analog-to-Digital) conversion circuit, a horizontal selection switch, and the like. As one example, the load circuit includes a current source that is configured to supply a current to an amplification transistor of the pixel P. The load circuit configures a source-follower circuit together with the amplification transistor of the pixel P.

[0022] The signal processing section 112 may include an amplification circuit that is configured to amplify a signal read from the pixel P via the signal line VSL. The load circuit, the amplification circuit, the AD conversion circuit, and the like are provided for each of the plurality of signal lines VSL. The load circuit, the amplification circuit, the AD conversion circuit, and the like can be provided for each pixel column of the pixel section 100.

[0023] The signal outputted from each of the pixels P selected and scanned by the pixel control section 111 is inputted to the signal processing section 112 via the signal line VSL. The signal processing section 112 can perform, for example, signal processing such as AD conversion and CDS (Correlated Double Sampling: correlated double sampling) on the signal of the pixel P. The signal of each of the pixels P transmitted through each of the signal lines VSL is subjected to signal processing by the signal processing section 112, and outputted to the processing section 114.

[0024] The processing section 114 is configured to execute signal processing on an inputted signal. The processing section 114 is a processing circuit, and includes, for example, a circuit that performs various types of signal processing on a pixel signal. The processing section 114 may include a processor and a memory. The processing section 114 performs signal processing on the pixel signal inputted from the signal processing section 112, and outputs the processed pixel signal. The processing section 114 can perform, for example, various types of signal processing such as noise reduction processing and gradation correction processing.

[0025] The control section 113 is configured to control each component of the imaging device 1. The control section 113 can receive a clock supplied from the outside, data ordering an operation mode, or the like, and output data such as internal information about the imaging device 1. The control section 113 is a control circuit, and includes, for example, a timing generator that is configured to generate various timing signals. The control section 113 controls driving of the pixel control section 111, the signal processing section 112, and the like on the basis of the various timing signals (a pulse signal, a clock signal, and the like) generated by the timing generator.

[0026] The pixel section 100 described above, the pixel control section 111, the signal processing section 112, and the like may be provided in one substrate. The pixel control section 111, the signal processing section 112, the control section 113, the processing section 114, and the like may be provided in one semiconductor substrate, or may be provided separately in a plurality of semiconductor substrates. The imaging device 1 may have a stacked structure configured by stacking a plurality of substrates. It is to be noted that some or all of the signal processing section 112, the control section 113, and the processing section 114 may be integrally configured.Configuration of Pixel

[0027] Fig. 3 is an explanatory diagram of an example of a circuit configuration of a pixel of the imaging device according to the first embodiment. The pixel P includes a photoelectric conversion section 12 (a photoelectric conversion element), and a readout circuit 20. The photoelectric conversion section 12 is configured to receive light and generate a signal. The readout circuit 20 is configured to output a signal based on electric charge generated by photoelectric conversion. The readout circuit 20 can read a pixel signal based on electric charge generated by photelectric conversion by the photoelectric conversion section 12.

[0028] The photoelectric conversion section 12 is a light-receiving section (a light-receiving element), and is configured to generate electric charge by photoelectric conversion. In the example illustrated in Fig. 3, the photoelectric conversion section 12 is a photodiode (PD), and converts incoming light into electric charge. The photoelectric conversion section 12 can perform photoelectric conversion to generate electric charge corresponding to a received light amount.

[0029] As one example, the readout circuit 20 includes a transistor TRG, a floating diffusion FD, a transistor AMP, a transistor SEL, and a transistor RST. Each of the transistor TRG, the transistor AMP, the transistor SEL, and the transistor RST is a MOS transistor (MOSFET) having terminals of a gate, a source, and a drain.

[0030] In the example illustrated in Fig. 3, each of the transistor TRG, the transistor AMP, the transistor SEL, and the transistor RST includes a NMOS transistor. It is to be noted that the transistor of the pixel P may include a PMOS transistor.

[0031] The transistor TRG is a transfer transistor, and is configured to transfer electric charge generated by photoelectric conversion by the photoelectric conversion section 12 to the floating diffusion FD. The transistor TRG is controlled by a signal STRG to electrically couple or decouple the photoelectric conversion section 12 and the floating diffusion FD to or from each other. The transistor TRG can transfer electric charge generated by photoelectric conversion and accumulated by the photoelectric conversion section 12 to the floating diffusion FD.

[0032] The floating diffusion FD is an accumulation section, and is configured to accumulate the transferred electric charge. The floating diffusion FD can accumulate electric charge generated by photoelectric conversion by the photoelectric conversion section 12. The floating diffusion FD can also be referred to as a holding section that is configured to hold the transferred electric charge. The floating diffusion FD accumulates the transferred electric charge and converts the transferred electric charge into a voltage corresponding to a capacitance of the floating diffusion FD.

[0033] The transistor AMP is configured to generate and output a signal based on the electric charge accumulated in the floating diffusion FD. The transistor AMP is an amplification transistor, and can generate and output a signal based on the electric charge generated by conversion by the photoelectric conversion section 12.

[0034] The gate of the transistor AMP is electrically coupled to the floating diffusion FD, and the voltage generated by conversion by the floating diffusion FD is inputted to the gate of the transistor AMP. In the example illustrated in Fig. 3, the drain of the transistor AMP is coupled to a power supply line to be supplied with a power supply voltage VDD.

[0035] The source of the transistor AMP is coupled to the signal line VSL via the transistor SEL. The transistor AMP is configured to generate a signal based on the electric charge accumulated in the floating diffusion FD, i.e., a signal based on the voltage of the floating diffusion FD, and output the generated signal to the signal line VSL.

[0036] The transistor SEL is configured to control the output of a pixel signal. For example, as in the example illustrated in Fig.3, the transistor SEL is electrically coupled in series to the transistor AMP. The transistor SEL is controlled by a signal SSEL, and is configured to output the signal from the transistor AMP to the signal line VSL. The transistor SEL is a selection transistor, and can control an output timing of the pixel signal.

[0037] The transistor SEL is configured to output a signal based on the electric charge generated by conversion by the photoelectric conversion section 12. The transistor SEL can output the pixel signal of the pixel P to the signal line VSL. It is to be noted that the transistor SEL may be electrically coupled in series between the power supply line to be supplied with the power supply voltage VDD and the transistor AMP. In addition, the transistor SEL may be omitted, as needed.

[0038] The transistor RST is configured to reset the voltage of the floating diffusion FD. In the example illustrated in Fig. 3, the transistor RST is electrically coupled to the power supply line to be supplied with the power supply voltage VDD, and is configured to reset electric charge of the pixel P. The transistor RST is a reset transistor.

[0039] The transistor RST can be controlled by a signal SRST to reset the electric charge accumulated in the floating diffusion FD and to reset the voltage of the floating diffusion FD. In the example illustrated in Fig. 3, the transistor RST can electrically couple the power supply line and the floating diffusion FD to each other, and discharge the electric charge accumulated in the floating diffusion FD. It is to be noted that the transistor RST can discharge the electric charge accumulated in the photoelectric conversion section 12 via the transistor TRG.

[0040] The pixel control section 111 (see Fig. 1) of the imaging device 1 supplies a control signal to the gates of the transistor TRG, the transistor SEL, the transistor RST, and the like of each of the pixels P via the control line Lread described above, to bring the transistors into an ON state (an electrically-conductive state) or an OFF state (a non-electrically-conductive state).

[0041] As one example, the plurality of control lines Lread for respective pixel rows of the imaging device 1 includes a wiring that transmits the signal STRG to control the transistor TRG, a wiring that transmits the signal SSEL to control the transistor SEL, a wiring that transmits the signal SRST to control the transistor RST, and the like.

[0042] It is to be noted that the readout circuit 20 may be configured to change a conversion efficiency (a gain) when converting electric charge into a voltage. For example, the readout circuit 20 can include a switching transistor used for setting of the conversion efficiency. As one example, the switching transistor is electrically coupled between the floating diffusion FD and the transistor RST.

[0043] In the readout circuit 20, a capacitance added to the floating diffusion FD of the pixel P is increased by turning on the switching transistor to switch the conversion efficiency. The switching transistor can switch a capacitance coupled to the gate of the transistor AMP to change the conversion efficiency.

[0044] The transistor TRG, the transistor SEL, the transistor RST, the switching transistor, and the like are controlled to be turned ON or OFF by the pixel control section 111. The pixel control section 111 controls the readout circuit 20 of each of the pixels P to thereby cause each of the pixels P to output a pixel signal to the signal line VSL. The pixel control section 111 can perform control to read the pixel signal of each of the pixels P to the signal line VSL.Configuration of Imaging Device

[0045] Fig. 4 is a diagram illustrating an example of a planar configuration of the imaging device according to the first embodiment. Fig. 4 illustrates an example of an arrangement of the pixels P of the pixel section 100 of the imaging device 1. The pixel P of the imaging device 1 includes a light-guiding section 60 and a filter 25. The light-guiding section 60 is configured with use of a plurality of layers (a plurality of stages) of structures (e.g., a first structure 51 and a second structure 52). It is to be noted that Fig. 4 illustrates only the first structure 51 out of the first structure 51 and the second structure 52.

[0046] The light-guiding section 60 (a light-guiding member) includes the first structure 51 and the second structure 52 that are nanostructures, and is configured to guide incoming light to side of the photoelectric conversion section 12. The light-guiding section 60 is a light-guiding element (a light-guiding member) utilizing a metamaterial (metasurface) technology. In the imaging device 1, for example, as in the example illustrated in Fig. 4, the light-guiding section 60 is provided for each pixel P or for each plurality of pixels P.

[0047] The filter 25 is configured to selectively transmit light of a specific wavelength region of the incoming light. The filter 25 is a color filter of RGB, a filter that transmits infrared light, or the like. The filter 25 is provided above the photoelectric conversion section 12 for each pixel P or for each plurality of pixels P (that is, each predetermined number of pixels P) (also see Fig. 5).

[0048] The plurality of pixels P provided in the pixel section 100 of the imaging device 1 includes a pixel Pr (an R pixel) provided with the filter 25 that transmits red (R) light, a pixel Pg (a G pixel) provided with the filter 25 that transmits green (G) light, and a pixel Pb (a B pixel) provided with the filter 25 that transmits blue (B) light. In the pixel section 100, a plurality of pixels Pr, a plurality of pixels Pg, and a plurality of pixels Pb are repeatedly arranged.

[0049] The pixels Pr, the pixels Pg, and the pixels Pb are arranged in accordance with Bayer arrangement, for example. In the pixel section 100, 2 ´ 2 pixels including one pixel Pr, two pixels Pg, and one pixel Pb are repeatedly provided. The pixel section 100 includes, for example, a pixel row in which the pixels Pg and the pixels Pr are alternately provided and a pixel row in which the pixels Pb and the pixels Pg are alternately provided.

[0050] The pixel Pr, the pixel Pg, and the pixel Pb in the pixel section 100 can respectively generate a pixel signal of an R component, a pixel signal of a G component, and a pixel signal of a B component. The imaging device 1 is able to obtain pixel signals of RGB. It is to be noted that the arrangement of the pixels P is not limited to the example described above, and is optionally settable.

[0051] For example, the pixels Pr may be arranged in units of 2 ´ 2 pixels, the pixels Pg may be arranged in units of 2 ´ 2 pixels, and the pixels Pb may be arranged in units of 2 ´ 2 pixels. In the pixel section 100, as one example, four adjacent pixels Pr, four adjacent pixels Pg, and four adjacent pixels Pb can be repeatedly arranged. It can be said that the pixels Pr in two rows and two columns, the pixels Pg in two rows and two columns, and the pixels Pb in two rows and two columns are periodically arranged.

[0052] The filter 25 provided for the pixels P of the pixel section 100 is not limited to a color filter of a primary color system (RGB), and may be a color filter of a complementary color system such as Cy (cyan), Mg (magenta), or Ye (yellow), for example. A filter corresponding to W (white), i.e., a filter that transmits light beams of all wavelength regions of incident light may be provided. The filter 25 may be a filter that transmits infrared light.

[0053] It is to be noted that the filter 25 may be omitted, as needed, in the imaging device 1. For example, depending on characteristics of the light-guiding section 60, the filter 25 may not be provided for some or all of the pixels P of the imaging device 1. In addition, for example, in a pixel that receives white (W) light to perform photoelectric conversion (which is referred to as a white pixel, a clear pixel, or the like), the filter 25 may not be provided.

[0054] Fig. 5 is a diagram illustrating an example of a cross-sectional configuration of the imaging device according to the first embodiment. As illustrated in Fig. 5, the imaging device 1 includes, for example, an optical layer 80, an insulating layer 90, the filter 25, a semiconductor layer 10, and a multilayer wiring layer 95. The imaging device 1 has a configuration in which the optical layer 80, the insulating layer 90, the filter 25, the semiconductor layer 10, and the multilayer wiring layer 95 are stacked in the Z-axis direction. The optical layer 80, the insulating layer 90, and a layer provided with the filter 25, the semiconductor layer 10, and the multilayer wiring layer 95 are provided from side on which light is incident.

[0055] The optical layer 80 includes a plurality of layers (a plurality of stages) of structures, and is configured to guide incoming light to side of the photoelectric conversion section 12. The optical layer 80 includes a plurality of structures (the first structure 51 and the second structure 52 in Fig. 5) that are provided to be stacked on each other. The optical layer 80 includes, for example, a first layer 71 (a first layer) provided with the first structure 51 and a second layer 72 (a second layer) provided with the second structure 52. The optical layer 80 including the first layer 71 and the second layer 72 is provided to be stacked on the insulating layer 90.

[0056] The optical layer 80 is an optical element (an optical member) utilizing a metamaterial (metasurface) technology. The first structure 51 and the second structure 52 each have, for example, a columnar (pillar) shape. The first structure 51 and the second structure 52 can also be referred to as a first metasurface element and a second metasurface element, respectively. The optical layer 80 can also be referred to as a metasurface layer (or a metamaterial layer).

[0057] The first layer 71 of the optical layer 80 includes a plurality of first structures 51 and a medium (a first member or material 61) provided around the first structures 51. The second layer 72 includes a plurality of second structures 52 and a medium (a second member or material 62) provided around the second structures 52. The second layer 72 is provided to be stacked on the first layer 71. Each of the first structures 51 and the second structures 52 is, for example, a pillar (a columnar member), and can be referred to as a nanopillar.

[0058] The first structures 51 and the first member 61 include materials having refractive indices different from each other. In addition, the second structures 52 and the second member 62 include materials having refractive indices different from each other. As in the example illustrated in Fig. 5, the optical layer 80 can include, for each pixel P or for each plurality of pixels P, the light-guiding section 60 including the first structures 51 and the first member 61, the second structures 52, and the second member 62.

[0059] As illustrated in Fig. 5, the semiconductor layer 10 has a surface 11S1 and a surface 11S2 opposed to each other. The surface 11S2 is a surface on side opposite to the surface 11S1. The surface 11S1 of the semiconductor layer 10 is a light-receiving surface (a light incident surface). The surface 11S2 of the semiconductor layer 10 is an element formation surface on which an element such as a transistor is formed. The surface 11S2 of the semiconductor layer 10 is provided with a gate electrode, a gate insulating film (e.g., a gate oxide film), and the like.

[0060] The semiconductor layer 10 includes a semiconductor substrate, e.g., an Si (silicon) substrate. The semiconductor layer 10 may be an SOI (Silicon On Insulator) substrate, an SiGe (silicon germanium) substrate, an SiC (silicon carbide) substrate, or the like. The semiconductor layer 10 may include a Group III-V compound semiconductor material, or may be formed using any other semiconductor material.

[0061] In the example illustrated in Fig.5, the filter 25, the insulating layer 90, and the like are provided on side of the surface 11S1 of the semiconductor layer 10. The optical layer 80, the insulating layer 90, and the filter 25 are provided to be stacked on the semiconductor layer 10 in a thickness direction orthogonal to the surface 11S1 of the semiconductor layer 10. The multilayer wiring layer 95 is provided on side of the surface 11S2 of the semiconductor layer 10. The optical layer 80 is provided on side on which light from an optical system is incident, and the multilayer wiring layer 95 is provided on side opposite to the side on which the light is incident. The imaging device 1 is a so-called back-illuminated imaging device.

[0062] In the semiconductor layer 10, a plurality of photoelectric conversion sections 12 (photoelectric conversion elements) is provided along the surface 11S1 and the surface 11S2 of the semiconductor layer 10. For example, the plurality of photoelectric conversion sections 12 is formed to be embedded in the semiconductor layer 10. The photoelectric conversion sections 12 are provided between the surface 11S1 and the surface 11S2 of the semiconductor layer 10. The photoelectric conversion sections 12 photoelectrically convert light incident via the optical layer 80, the insulating layer 90, and the filter 25. The photoelectric conversion sections 12 can each also be referred to as a photoelectric conversion layer.

[0063] The multilayer wiring layer 95 is provided to be stacked on the semiconductor layer 10. The multilayer wiring layer 95 includes, for example, a conductor film and an insulating film, and includes a plurality of wirings, vias (VIA), and the like. The multilayer wiring layer 95 has a configuration in which a plurality of wirings is stacked with an insulating film as an interlayer insulating film (an interlayer insulating layer) interposed therebetween. The multilayer wiring layer 95 includes, for example, two or more layers or three or more layers of wirings.

[0064] The wirings of the multilayer wiring layer 95 are formed using a metal material such as aluminum (Al), copper (Cu), or tungsten (W). It is to be noted that the wirings of the multilayer wiring layer 95 may be configured using polysilicon (Poly-Si) or any other electrically-conductive material. The interlayer insulating film is formed using, for example, silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), or the like.

[0065] The semiconductor layer 10 and the multilayer wiring layer 95 are provided with, for example, the readout circuit 20 described above (see Fig. 3) for each pixel P or for each plurality of pixels P. In addition, the pixel control section 111, the signal processing section 112, the control section 113, the processing section 114, and the like described above (see Fig. 1) can be formed in a substrate different from the semiconductor layer 10, or in the semiconductor layer 10 and the multilayer wiring layer 95.

[0066] The insulating layer 90 is provided between the optical layer 80 provided with the light-guiding section 60, and the semiconductor layer 10. In the example illustrated in Fig. 5, the insulating layer 90 is formed to be stacked on a layer provided with the filter 25. As one example, the insulating layer 90 is configured using an insulating film such as an oxide film, a nitride film, or an oxynitride film. The insulating layer 90 is formed using, for example, an insulating material such as silicon oxide (SiO), silicon nitride (SiN), or silicon oxynitride (SiON).

[0067] The insulating layer 90 may include a material having a low refractive index such as silicon oxide, or may include any other material that transmits light of a wavelength region to be measured. The insulating layer 90 can also be referred to a transparent layer that transmits light or a spacer layer. It is to be noted that the optical layer 80 may include the insulating layer 90.

[0068] As illustrated in Fig. 5, the imaging device 1 includes a separation section 30. The separation section 30 is provided between the plurality of photoelectric conversion sections 12 adjacent to each other to separate the photoelectric conversion sections 12 from each other. At least a portion of the separation section 30 is provided at a boundary between the pixels P (or the photoelectric conversion sections 12) adjacent to each other. The separation section 30 is configured using, for example, a trench.

[0069] The separation section 30 is provided to surround the photoelectric conversion section 12 of each pixel P in the semiconductor layer 10. The separation section 30 may be provided to penetrate the semiconductor layer 10. In other words, the separation section 30 may be formed to reach the surface 11S2 of the semiconductor layer 10. The separation section 30 can also be referred to as a pixel separation section or a pixel separation wall.

[0070] An insulating film, e.g., a silicon oxide film, a silicon nitride film, an aluminum oxide film, or the like is provided inside the trench of the separation section 30. The trench of the separation section 30 may be filled with polysilicon, a metal material, any other insulating material, or the like. The separation section 30 may be configured using a semiconductor region (a p-type semiconductor region or an n-type semiconductor region) formed by ion implantation.

[0071] The separation section 30 may be formed using any other insulating material having a low refractive index. For example, an air gap (a cavity) may be provided inside the trench of the separation section 30. In the imaging device 1, providing the separation section 30 suppresses leakage of electric charge generated by photoelectric conversion by the photoelectric conversion section 12 of the pixel P into surrounding pixels P (or photoelectric conversion sections 12). In addition, it is possible to suppress leakage of unnecessary light into surrounding pixels P, thus suppressing, for example, occurrence of color mixture.

[0072] The imaging device 1 may include at least one of a fixed charge film or an antireflection film on side of the surface 11S1 of the semiconductor layer 10. As one example, the fixed charge film and the antireflection film each include a metal compound (such as a metal oxide or a metal nitride), and each can also be referred to as a metal compound layer.

[0073] The fixed charge film and the antireflection film are provided between the semiconductor layer 10 and the filter 25, for example. The fixed charge film is a film having fixed electric charge, and can be formed using a high-dielectric constant material. As one example, the fixed charge film includes a metal oxide such as hafnium oxide or aluminum oxide. The fixed charge film is, for example, a film having negative fixed electric charge.

[0074] In the imaging device 1, providing the fixed charge film suppresses generation of a dark current at an interface of the semiconductor layer 10. It is to be noted that the fixed charge film may be configured using any other metal oxide film, or may be configured using a metal nitride film or a metal oxynitride film. As the fixed charge film, a film having positive fixed electric charge may be provided.

[0075] As one example, the antireflection film includes a metal oxide such as hafnium oxide or tantalum oxide. The antireflection film is provided on side of the surface 11S1 of the semiconductor layer 10, and reduces (suppresses) reflection. The antireflection film is provided to be stacked on the fixed charge film, for example. It is to be noted that the antireflection film may be configured using an insulating material such as silicon nitride (SiN), silicon oxide (SiO), or aluminum oxide (AlO), or may be configured using any other material.

[0076] As in the example illustrated in Fig. 5, the optical layer 80 of the imaging device 1 is provided above the photoelectric conversion sections 12. The optical layer 80 includes the first layer 71 provided with the first structures 51 and the second layer 72 provided with the second structures 52. The second layer 72 is stacked on the first layer 71. The light-guiding section 60 of the optical layer 80 includes the first structure 51 in a first stage and the second structure 52 in a second stage.

[0077] Light from a subject to be measured enters the light-guiding section 60. For example, light transmitted through an optical system such as an imaging lens enters the first structure 51 and the second structure 52 of the light-guiding section 60. Each of the first structure 51 and the second structure 52 is, for example, a structure having a size less than or equal to a predetermined wavelength of incoming light.

[0078] The optical layer 80 (or the light-guiding section 60) includes the first structure 51 and the second structure 52 that are nanostructures, and is configured to guide light incident from above to side of the photoelectric conversion section 12 in Fig. 5. Each of the first structure 51 and the second structure 52 has a size less than or equal to a wavelength region of light to be measured, e.g., a size less than or equal to a wavelength region of visible light. It is to be noted that each of the first structure 51 and the second structure 52 may have a size less than or equal to a wavelength region of infrared light.

[0079] Each of the first structure 51 and the second structure 52 is, for example, a columnar (pillar-shaped) structure. As one example, each of the first structure 51 and the second structure 52 has a cylindrical shape. The plurality of first structures 51 is arranged side by side in the X-axis direction (or the Y-axis direction) with a portion of the first member 61 interposed therebetween.

[0080] In addition, the plurality of second structures 52 is arranged side by side in the X-axis direction (or the Y-axis direction) with a portion of the second member 62 interposed therebetween. It is to be noted that the shape of each of the first structure 51 and the second structure 52 is appropriately modifiable, and may be a circular shape or a rectangular shape in a plan view. The shape of each of the first structure 51 and the second structure 52 may be an elliptical shape, a polygonal shape, a cross shape, or any other shape.

[0081] The first member 61 is provided to fill surroundings of the first structures 51. The first member 61 is formed to fill between the plurality of first structures 51 adjacent to each other in the first layer 71, for example. The second member 62 is provided to fill surroundings of the second structures 52. The second member 62 is formed to fill between the plurality of second structures adjacent to each other in the second layer 72, for example.

[0082] The first structures 51 are provided in the first member 61, and it can be said that the first structures 51 are provided to replace portions of the first member 61. The second structures 52 are provided in the second member 62, and it can be said that the second structures 52 are provided to replace portions of the second member 62. It is to be noted that the first member 61 and the second member 62 can each also be referred to as a medium layer or a protection layer (a protection member).

[0083] The light-guiding section 60 uses the first structure 51 and the second structure 52 that are nanostructures to propagate light to side of the photoelectric conversion section 12. Each of the first structure 51 and the second structure 52 can also be referred to as a metaatom, a nanoatom, a nanopost, a metasurface structure, a fine structure, or the like. The light-guiding section 60 is an optical element (an optical member) that guides (propagates) light.

[0084] The light-guiding section 60 is configured, for example, as a light-guiding element that causes a phase delay in incoming light and is configured to guide light. In the optical layer 80, as one example, the plurality of first structures 51 and the plurality of second structures 52 are arranged to provide a desired phase profile to incident light. For example, the sizes, the arrangement numbers, arrangement intervals (pitches), and the like of the first structures 51 and the second structures 52 are determined so as to condense light of a wavelength band to be detected onto the photoelectric conversion section 12.

[0085] Fig. 6A and Fig. 6B are diagrams illustrating an example of a planar configuration of the light-guiding section of the imaging device according to the first embodiment. Fig. 6A illustrates a configuration example of the second layer 72 of the light-guiding section 60, and Fig. 6B illustrates a configuration example of the first layer 71 of the light-guiding section 60. As one example, as in the example illustrated in Figs. 6A and 6B, the plurality of first structures 51 and the plurality of second structures 52 are two-dimensionally arranged in the X-axis direction and the Y-axis direction in a plan view.

[0086] A width in the X-axis direction (or the Y-axis direction) of the first structure 51 and a width in the X-axis direction (or the Y-axis direction) of the second structure 52 each may be less than or equal to a wavelength region of visible light. As illustrated in Fig. 6A, a width (a diameter) W2 of the second structure 52 may be from 80 nm to 800 nm as one example. In addition, as illustrated in Fig. 6B, a width W1 of the first structure 51 may be from 80 nm to 800 nm as one example.

[0087] In the first layer 71 of the imaging device 1, for example, the plurality of first structures 51 is arranged at an interval less than or equal to a predetermined wavelength of incident light. In addition, in the second layer 72, the plurality of second structures 52 can be arranged at an interval less than or equal to a predetermined wavelength of incident light. As one example, the plurality of first structures 51 (or the plurality of second structures 52) is provided at an interval less than or equal to a wavelength region of infrared light in the X-axis direction and the Y-axis direction.

[0088] In the imaging device 1, at least some second structures 52 out of the plurality of second structures 52 are provided in contact with the first structures 51. For example, as in the example illustrated in Fig. 5, some second structures 52 out of the plurality of second structures 52 of the second layer 72 are provided in contact with the first structures 51. In the example illustrated in Fig. 5, some second structures 52 are provided on the first structures 51, and are in contact with the first structures 51.

[0089] It is to be noted that, as used herein, the phrase "in contact" includes a case of being in direct contact as well as a case of being in contact with a natural oxide film or the like interposed therebetween. The phrase "the second structure 52 is in contact with the first structure 51" includes a case where the natural oxide film is interposed therebetween as well as a case where the second structure 52 is in contact with the first structure 51 with a thin natural oxide film interposed therebetween. The phases "in contact" indicates that no etching stopper film is provided between structures.

[0090] The first structure 51 and the second structure 52 are provided so as to be in contact with each other. In the example illustrated in Fig. 5, upper ends (tops) of some first structures 51 are in contact with lower ends (bottoms) of the second structures 52. The imaging device 1 has a stacked structure in which the first structure 51 and the second structure 52 are stacked. The light-guiding section 60 can have a structure in which the second structure 52 as a second metasurface element is directly stacked on the first structure 51 as a first metasurface element.

[0091] In addition, in the imaging device 1, the first member 61 and the second member 62 are provided so as to be in contact with each other. For example, as in the example illustrated in Fig. 5, the second member 62 is provided in contact with the first member 61. The second member 62 is directly stacked on the first member 61, and is provided in contact with the first member 61.

[0092] The first structure 51 has a refractive index different from a refractive index of an adjacent medium. In the example illustrated in Fig. 5 and the like, the first structure 51 has a refractive index different from a refractive index of the first member 61. The first structure 51 has a refractive index different from a refractive index of a medium around the first structure 51, that is, the first member 61. It is to be noted that the first member 61 can also be referred to as a first material layer having a refractive index different from the refractive index of the first structure 51.

[0093] The second structure 52 has a refractive index different from a refractive index of an adjacent medium. In the example illustrated in Fig. 5 and the like, the second structure 52 has a refractive index different from a refractive index of the second member 62. The second structure 52 has a refractive index different from a refractive index of a medium around the second structure 52, that is, the second member 62. The second member 62 can also be referred to as a second material layer having a refractive index different from the refractive index of the second structure 52.

[0094] The first structure 51 has, for example, a refractive index higher than the refractive index of the first member 61. The first structure 51 can include a material having a refractive index higher than the refractive index of the first member 61. In addition, the second structure 52 has, for example, a refractive index higher than the refractive index of the second member 62. The second structure 52 can include a material having a refractive index higher than the refractive index of the second member 62.

[0095] The first structure 51 and the second structure 52 can be configured using the same material. The second structure 52 includes, for example, the same material as that of the first structure 51, and is formed on the first structure 51. The first structure 51 and the second structure 52 may each be configured using, for example, an inorganic material, e.g., an oxide film. In addition, each of the first structure 51 and the second structure 52 may include an oxide film including titanium (Ti).

[0096] As one example, the first structure 51 and the second structure 52 are configured using titanium oxide (TiO). As another example, the first structure 51 and the second structure 52 are configured using a nitride film of silicon nitride (SiN), silicon oxynitride (SiON), or the like. The first structure 51 and the second structure 52 may be formed using silicon, polysilicon (Poly-Si), amorphous silicon (a-Si), germanium( Ge), or the like.

[0097] The first structure 51 and the second structure 52 may include a simple substance, an oxide, a nitride, or an oxynitride of titanium (Ti), hafnium (Hf), zirconium (Zr), aluminum (Al), tantalum (Ta), indium (In), niobium (Nb), or the like, or a composite thereof. The first structure 51 and the second structure 52 may include any other metal compound (such as a metal oxide or a metal nitride).

[0098] In addition, the first structure 51 and the second structure 52 may be configured using GaP, GaN, GaAs, or the like. The first structure 51 and the second structure 52 may be formed using silicon carbide (SiC) or any other silicon compound. The first structure 51 and the second structure 52 may be configured using air. For example, at least one of the first structure 51 or the second structure 52 may have air (an air gap).

[0099] The first member 61 and the second member 62 are configured using the same material. As one example, the first member 61 and the second member 62 are configured using an inorganic material such as an oxide, a nitride, or an oxynitride. The first member 61 and the second member 62 may be formed using, for example, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, or any other silicon compound. The first member 61 and the second member 62 may be configured using TEOS.

[0100] The first member 61 and the second member 62 may be configured using the same organic material. The first member 61 and the second member 62 may be configured using a siloxane-based resin, a styrene-based resin, an acrylic-based resin, or the like. The first member 61 and the second member 62 may include a material containing fluorine in any of these resins. The first member 61 and the second member 62 may be formed using a material in which any of these resins is filled with beads (filler) having a refractive index higher (or lower) than the refractive index of the resin.

[0101] Materials of the first structure 51, the second structure 52, the first member 61, and the second member 62 can be selected depending on a refractive index difference from a surrounding medium, a wavelength region of incident light to be measured, and the like. It is to be noted that the first structure 51, the second structure 52, the first member 61, and the second member 62 may be partially configured using air.

[0102] The light-guiding section 60 of the optical layer 80 causes a phase delay in incoming light due to a refractive index difference between the first and second structures 51 and 52 and a medium surrounding the first and second structures 51 and 52, thus making it possible to control a wave front. The light-guiding section 60 provides a phase delay to incoming light by, for example, the second structure 52 and the second member 62, and the first structure 51 and the first member 61, which makes it possible to adjust a direction in which light propagates.

[0103] The materials (optical constants of respective materials) of the first structure 51, the second structure 52, the first member 61, and the second member 62, sizes (such as widths (diameters) and heights), pitches (arrangement intervals), and the like of the first structure 51 and the second structure 52 are determined so as to allow light of any wavelength region included in incident light from a measurement target to travel in a desired direction. For example, the materials (refractive indices), dimensions, and pitches of the first structure 51 and the second structure 52, the materials (refractive indices) of the first member 61 and the second member 62, and the like can be set.

[0104] As one example, in the imaging device 1, materials, sizes, the arrangement numbers, and the like of the first structures 51 and the second structures 52 of each pixel P are determined so as to allow light of a specific wavelength band to be detected to propagate to the photoelectric conversion section 12 of the desired pixel P. For example, the first structures 51 and the second structures 52 of the light-guiding sections 60 of the pixel Pr, the pixel Pg, and the pixel Pb can be formed to have respective different sizes (e.g., widths and heights), respective different arrangement positions, and the like.

[0105] The optical layer 80 (or the light-guiding section 60) may be configured as a light-dispersing section (a light-dispersing element) that is configured to disperse incoming light. The optical layer 80 (or the light-guiding section 60) is configured as a splitter (a color splitter), and can also be referred to as a color splitter layer or a wavelength separation layer. The optical layer 80 (or the light-guiding section 60) can also be referred to as an optical element that is configured to redirect light.

[0106] As in the example illustrated in Fig. 5, the imaging device 1 includes an antireflection film 45 and a stopper film 46. The light-guiding section 60 of each pixel P can include the antireflection film 45 and the stopper film 46. The antireflection film 45 (a reflection suppression film) is provided on side on which light of the second structure 52 is incident, and is positioned on the second structures 52. For example, as illustrated in Fig. 5, the antireflection film 45 is provided to cover the plurality of second structures 52, and reduces (suppresses) reflection.

[0107] The antireflection film 45 is configured using, for example, a silicon compound such as silicon nitride (SiN) or silicon oxide (SiO). It is to be noted that the antireflection film 45 may be configured using a metal compound, or may be configured using any other material. The antireflection film 45 may be configured by stacking a plurality of films.

[0108] The stopper film 46 is provided, for example, between the first structures 51 and the insulating layer 90. When the imaging device 1 is manufactured, the stopper film 46 serves as an etching stopper film (a stopper layer). Providing the stopper film 46 makes it possible to improve processing controllability of the first structures 51. The stoper film 46 can also be referred to as an etching prevention film (an etching suppression film).

[0109] The stopper film 46 includes, for example, a single-layer film including one of silicon nitride (SiN), silicon oxynitride (SiON), hafnium oxide (HfO), aluminum oxide (AlO), and the like, or a multilayer film including two or more of them. The stopper film 46 may be formed using any other material. It is to be noted that the insulating layer 90 may include the stopper film 46.

[0110] As described above, light from a subject to be measured enters each pixel P of the imaging device 1 via the optical layer 80. Each pixel P can receive light incident via the second structure 52 and the first structure 51 of the light-guiding section 60 and generate a pixel signal. The imaging device 1 can generate image data representing a subject image with use of the pixel signal obtained by photoelectric conversion in each pixel P.

[0111] In addition, for example, the imaging device 1 can generate image data (distance image data) related to a distance to an object with use of the pixel signal of each pixel. In the present embodiment, the light-guiding section 60 including the first structure 51 and the second structure 52 makes it possible to appropriately guide light to the photoelectric conversion section 12. A plurality of stages of metasurface elements makes it possible to efficiently guide light of any wavelength region to photoelectric conversion section 12.

[0112] In the imaging device 1, as described above, the first structure 51 is provided in contact with the second structure 52. This makes it possible to suppress generation of unnecessary reflected light and improve quantum efficiency (QE). It is possible to reduce the number of interfaces and prevent an increase in reflectance, as compared with a case where an etching stopper film is provided between the first structure 51 and the second structure 52.

[0113] In the imaging device 1, the second structure 52 is provided in contact with the first structure 51, which makes it possible to suppress a decrease in light use efficiency. It is possible to improve sensitivity to incident light. In addition, it is possible to suppress occurrence of flare and prevent a decrease in image quality of an image. It is possible to implement a photodetector having superior optical characteristics.

[0114] In addition, in the present embodiment, the first structure 51 and the second structure 52 are configured using the same material. The first structure 51 and the second structure 52 including the same material makes it possible to suppress, for example, generation of unnecessary reflected light. In addition, it is possible to improve adhesion between the first layer 71 and the second layer 72.

[0115] Fig. 7 is an explanatory diagram of another configuration example of the imaging device according to the first embodiment. In addition, Fig. 8 is an explanatory diagram of another configuration example of the light-guiding section of the imaging device. The optical layer 80, the light-guiding section 60, and the like of the imaging device 1 may have a configuration illustrated in Fig. 7 and Fig. 8.

[0116] In the imaging device 1, at least some of the first structures 51 of the light-guiding section 60 may have shapes that are different from each other. In addition, at least some of the second structures 52 may have shapes that are different from each other. Moreover, some or all of the first structures 51 may have shapes that are different from the shape or shapes of the second structures 52. The light-guiding section 60 is configured using the first structure 51 and the second structure 52 having different shapes, which makes it possible to improve design flexibility. It is possible to improve light controllability.

[0117] The first structure 51 and the second structure 52 may have lengths different from each other in a direction in which the first layer 71 and the second layer 72 are stacked (in the Z-axis direction in Figs. 7 and 8). As one example, the first structure 51 and the second structure 52 may be formed so as to cause the length (height) in the Z-axis direction of the first structure 51 to be larger than the length of the second structure 52. In addition, the lengths in the Z-axis direction of at least some second structures 52 out of the plurality of second structures 52 may be larger than the length of the first structure 51.

[0118] In the example illustrated in Fig. 8, lower ends A2 of some second structures 52 out of the plurality of second structures 52 are each positioned lower than an upper end A1 of the first structure 51. The lower ends A2 (bottoms) of the second structures 52 are each positioned lower than the upper end A1 (a top) of the first structure 51. The second structures 52 can each be formed toward a region deeper than the upper end A1 of the first structure 51. The imaging device 1 configured in such a manner makes it possible to improve adhesion between the first layer 71 and the second layer 72. It is possible to improve reliability of the imaging device 1.

[0119] As in the example illustrated in Fig. 7 or Fig. 8, the first structure 51 may be provided so as to cause the width (the length) of the first structure 51 on side of the second structure 52 to be larger than the width of the first structure 51 on side opposite to the side of the second structure 52. The first structure 51 can be formed so as to cause a width of the upper end (the top) of the first structure 51 to be larger (thicker) than a width of a lower end (a bottom) of the first structure 51.

[0120] For example, the width in the X-axis direction (or the Y-axis direction) of the first structure 51 increases with decreasing distance to the second structure 52. It can be said that the width (the thickness) in the X-axis direction (or the Y-axis direction) of the first structure 51 decreases with decreasing distance to the stopper film 46 (or the insulating layer 90).

[0121] The width (the length) in the X-axis direction (or the Y-axis direction) of the first structure 51 may monotonically increase in accordance with a distance from the stopper film 46 in a predetermined segment (range). In the example illustrated in Fig. 7, the width of the first structure 51 gradually increases (becomes thicker) from the bottom to the top of the first structure 51. It can be said that the first structure 51 has a portion having a width gradually increasing (becoming thicker) with decreasing distance to the second structure 52.

[0122] As in the example illustrated in Fig. 7 or Fig. 8, the first structure 51 may have a recess section B1. The first structure 51 can have the recess section B1 (a groove or concave section) provided on side of the second structure 52. It is possible to form the first structure 51 having the recess section B1 with use of, for example, lithography and etching. The recess section B1 can also be referred to as a recess (a groove).

[0123] As schematically illustrated in Fig. 7 or Fig. 8, the recess section B1 can be provided at the top of the first structure 51. The recess section B1 is, for example, a portion that is formed to be relatively shallow, and can also be referred to as a recess portion. A depth (a height) of the recess section B1 may be, for example, less than or equal to several nm. A depth d1 of the recess section B1 illustrated in Fig. 8 may be about 5 nm as one example.

[0124] The second structure 52 may be provided in contact with the recess section B1 of the first structure 51. In the examples illustrated in Fig. 7 and Fig. 8, a portion of the second structure 52 is provided in the recess section B1 of the first structure 51. For example, the portion of the second structure 52 is provided to be embedded in the recess section B1.

[0125] Providing the portion of the second structure 52 in the recess section B1 of the first structure 51 makes it possible to prevent an increase in reflectance of the optical layer 80. It is possible to reduce reflection on the light-guiding section 60, and it is possible to improve quantum efficiency. It is possible to suppress occurrence of flare and prevent a decrease in image quality of an image.

[0126] In addition, the second structure 52 may have a recess section B2. The second structure 52 can have the recess section B2 (a groove section) provided on side opposite to the side of the first structure 51. The recess section B2 can also be referred to as a recess (a groove). It is possible to form the second structure 52 having the recess section B2 with use of, for example, lithography and etching.

[0127] The recess section B2 may be provided at the top of the second structure 52. The recess section B2 is, for example, a portion that is formed to be relatively shallow, and can also be referred to as a recess portion. A depth (a height) of the recess section B2 may be, for example, less than or equal to several nm. A depth d2 of the recess section B2 illustrated in Fig. 8 may be about 5 nm as one example.

[0128] The antireflection film 45 may be provided in contact with the recess section B2 of the second structure 52. In the examples illustrated in Fig. 7 and Fig. 8, a portion of the antireflection film 45 is provided in the recess section B2 of the second structure 52. For example, the portion of the antireflection film 45 is provided to be embedded in the recess section B2.

[0129] Providing the portion of the antireflection film 45 in the recess section B2 of the second structure 52 makes it possible to prevent an increase in reflectance and makes it possible to improve quantum efficiency. It is possible to suppress occurrence of flare and prevent a decrease in image quality of an image.

[0130] The shape of the recess section B1 of the first structure 51 and the shape of the recess section B2 of the second structure 52 are not limited to the example illustrated in Fig. 8. As in an example illustrated in Fig. 9A or Fig. 9B, the recess section B1 and the recess section B2 may each have a rounded shape. The recess section B1 of the first structure 51 and the recess section B2 of the second structure 52 can each have a rounded portion.

[0131] In addition, as in an example illustrated in Fig. 10, the second structure 52 may have a projected section C2. The second structure 52 can have the projected section C2 (a projection or bulbous portion) provided on a side surface of the second structure 52 on the side of the first structure 51. It is possible to form the projected section C2 of the second structure 52 with use of side etching, and the projected section C2 can also be referred to as a side etched portion. The projected section C2 can be provided along an interface between the first layer 71 and the second layer 72.

[0132] The projected section C2 of the second structure 52 is formed, for example, along a boundary between the first layer 71 and the second layer 72, and is projected in a direction orthogonal to a direction in which the first layer 71 and the second layer 72 are stacked. The projected section C2 is a projected structure portion, and can also be referred to as a projected portion. In the imaging device 1, providing the projected section C2 makes it possible to improve adhesion between the first layer 71 and the second layer 72. It is possible to improve reliability of the imaging device 1.

[0133] In the imaging device 1, the first structure 51 may have a seam. The first structure 51 having the seam makes it possible to prevent removal of the first structure 51 caused by stress concentration. It is possible to prevent deterioration in characteristics of the light-guiding section 60. It is to be noted that the second structure 52 may have a seam. This makes it possible to suppress removal of the second structures 52 and deterioration in characteristics of the light-guiding section 60.

[0134] As one example, a thickness d11 (a length) in the Z-axis direction of the first structure 51 illustrated in Fig. 8 and the like may be from 10 nm to 2000 nm. In addition, a thickness d12 in the Z-axis direction of the second structure 52 may be from 10 nm to 2000 nm. The thickness d11 of the first structure 51 and the thickness d12 of the second structure 52 may each be, for example, less than or equal to several hundreds of nm, or less than or equal to several tens of nm.

[0135] The thickness (height) of the first structure 51 may be different from the thickness of the second structure 52, or may be substantially the same as the thickness of the second structure 52. A film thickness (a thickness) d13 of the antireflection film 45 may be, for example, within a range from 10 nm to 3000 nm. In addition, a film thickness d14 of the stopper film 46 may be, for example, from 1 nm to 1000 nm.

[0136] Figs. 11A to 11D are each an explanatory diagram of an example of a method of manufacturing the light-guiding section of the imaging device according to the first embodiment. First, as illustrated in Fig. 11A, a hard mask 103, e.g., an a-Si film (an amorphous silicon film) is formed on the first structures 51 and the first member 61. Thereafter, as illustrated in Fig. 11B, the hard mask 103 is processed by etching.

[0137] Next, as illustrated in Fig. 11C, the second member 62 is formed on the first layer 71, and thereafter, the hard mask 103 is removed. Thereafter, as illustrated in Fig. 11D, the second structures 52 are formed to be embedded in the second member 62, and thereafter the antireflection film 45 is formed on the second structures 52 and the second member 62. The manufacturing method as described above makes it possible to manufacture the light-guiding section 60 illustrated in Fig. 7 and the like. It is to be noted that the manufacturing method described above is merely exemplary, and another manufacturing method may be employed.Workings and Effects

[0138] The photodetector according to the present embodiment includes a first layer (the first layer 71), a second layer (the second layer 72) that is stacked on the first layer, and a photoelectric conversion element (the photoelectric conversion section 12). The first layer includes a plurality of first structures (e.g., the first structures 51) that is provided side by side in a first direction (e.g., the X-axis direction), and a first medium (the first member 61) that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures (the second structures 52) provided side by side in the first direction, and a second medium (the second member 62) that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The photoelectric conversion element photoelectrically converts light incident via the second layer and the first layer. The second structures are configured using the same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure.

[0139] In the photodetector (the imaging device 1) according to the present embodiment, the first layer 71 including the plurality of first structures 51 and the second layer 72 including the plurality of second structures 52 are provided. The plurality of second structures 52 includes the second structure 52 in contact with the first structure 51. This makes it possible to suppress generation of unnecessary reflected light. It is possible to implement a photodetector that allows for an improvement in characteristics for incident light. (Modification Examples)

[0140] In the embodiment described above, the configuration example of the photodetector has been described; however, the configuration of the photodetector (the imaging device) is not limited to the example described above. For example, the optical layer 80 may have a stacked structure of three layers, or four or more layers. The light-guiding section 60 may include, for example, three stages or more, or four stages or more of nanostructures.

[0141] Fig. 12 is an explanatory diagram of a configuration example of an imaging device according to a modification example of the present disclosure. As in the example illustrated in Fig. 12, the optical layer 80 may have the first layer 71 (a first layer) provided with the first structures 51, the second layer 72 (a second layer) provided with the second structures 52, a third layer 73 (a third layer) provided with a third structure 53, and a fourth layer 74 (a fourth layer) provided with a fourth structure 54. The first to fourth structures 51 to 54 can be configured using, for example, the same material.

[0142] For example, the fourth layer 74, the third layer 73, the second layer 72, and the first layer 71 are provided from side on which light is incident. The first to fourth layers 71 to 74 are provided to be stacked with no etching stopper film interposed therebetween. This makes it possible to reduce the number of interfaces, and makes it possible to reduce reflection on the light-guiding section 60. It is possible to implement a photodetector having superior performance. Also in the present modification example, it is possible to achieve effects similar to those in the embodiment described above. <2. Second Embodiment>

[0143] Next, description is given of a second embodiment of the present disclosure. The technology according to the present disclosure is applicable to various electronic apparatuses, optical devices, and the like. The light-guiding section 60 (or the optical layer 80) configured using the nanostructures described above is applicable to various optical elements (optical members). Hereinafter, components similar to those of the embodiment described above are denoted by the same reference numerals, and descriptions thereof are omitted as appropriate.

[0144] Fig. 13 and Fig. 14 are each an explanatory diagram of a configuration example of an optical element according to the second embodiment of the present disclosure. An optical element 200 includes a substrate 120 and the optical layer 80. As one example, the optical layer 80 includes the first layer 71 including a plurality of first structures 51 and the second layer 72 including a plurality of second structures 52. The optical element 200 is an optical element (an optical member) configured using the first structures 51 and the second structures 52 that are nanostructures, and can be configured as a metalens (a metamaterial lens).

[0145] The substrate 120 is a substrate (a transparent substrate) that transmits light, and includes, for example, a glass substrate. As one example, the substrate 120 (a base) can include a material having a refractive index lower than the refractive index of the first structure 51 (or the second structure 52). The substrate 120 may include, for example, quartz glass, borosilicate glass, or the like, or may include a resin substrate. The substrate 120 (the base) may include any other material that transmits light to be measured.

[0146] As illustrated in Fig. 13, the substrate 120 has a surface 12S1 and a surface 12S2 opposed to each other. The surface 12S2 is a surface on side opposite to the surface 12S1. The optical layer 80 is provided on the substrate 120 on side on which light is incident. In the example illustrated in Fig. 13 or Fig. 14, the optical layer 80 including the plurality of first structures 51 and the plurality of second structures 52 is formed on the surface 12S1 of the substrate 120.

[0147] The optical layer 80 including the first structures 51 and the second structures 52 may be provided on side opposite to side on which light of the substrate 120 is incident (that is, on side from which light is outputted). The optical layer 80 may be stacked on the substrate 120 with an insulating layer interposed therebetween on light incident side or on light output side of the substrate 120. It is to be noted that the shape of the substrate 120 is not particularly limited, and may be a circular shape, a rectangular shape, or any other shape.

[0148] The second structure 52 may have a size or a shape different from that of the first structure 51. The first structure 51 may have the recess section B1. A portion of the second structure 52 can be provided in contact with the recess section B1 of the first structure 51. In addition, the second structure 52 may have the recess section B2. A portion of the antireflection film 45 can be provided in contact with the recess section B2 of the second structure 52. It is to be noted that the shapes, the numbers, arrangements, and the like of the first structures 51 and the second structures 52 are not limited to the illustrated example, and are appropriately modifiable.

[0149] The optical element 200 can be configured, for example, as a lens such as a lens that condenses light or a lens that disperses light. The optical element 200 may be configured as a splitter that disperses incident light, a filter that transmits light of a specific wavelength region, a deflector that changes a traveling direction of light, or the like. The optical element 200 may be configured, for example, as a part of an optical system of any of various apparatuses. Workings and Effects

[0150] The optical element according to the present embodiment includes a first layer (the first layer 71), and a second layer (the second layer 72) that is stacked on the first layer. The first layer includes a plurality of first structures (e.g., the first structures 51) provided side by side in a first direction (e.g., the X-axis direction), and a first medium (the first member 61) that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures (the second structures 52) provided side by side in the first direction, and a second medium (the second member 62) that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The second structures are configured using the same material as a material of the first structures. The plurality of second structures includes a second structure in contact with the first structure.

[0151] In the optical element (the optical element 200) according to the present embodiment, the first layer 71 including the plurality of first structures 51 and the second layer 72 including the plurality of second structures 52 are provided. The plurality of second structures 52 includes the second structure 52 in contact with the first structure 51. This makes it possible to improve characteristics for incident light. It is possible to implement an optical element having superior optical characteristics. <3. Application Example>

[0152] The imaging device 1 described above or the like is applicable, for example, to any type of electronic apparatus with an imaging function including a camera system such as a digital still camera or a video camera, a mobile phone having an imaging function, and the like. Fig. 15 illustrates a schematic configuration of an electronic apparatus 1000.

[0153] The electronic apparatus 1000 includes, for example, a lens group 1001, the imaging device 1, a DSP (Digital Signal Processor) circuit 1002, a frame memory 1003, a display unit 1004, a recording unit 1005, an operation unit 1006, and a power supply unit 1007. They are coupled to each other via a bus line 1008.

[0154] The lens group 1001 takes in incident light (image light) from a subject, and forms an image on an imaging surface of the imaging device 1. The imaging device 1 converts the amount of incident light formed as an image on the imaging surface by the lens group 1001 into electric signals on a pixel-by-pixel basis, and supplies the DSP circuit 1002 with the electric signals as pixel signals.

[0155] The DSP circuit 1002 is a signal processing circuit that processes signals supplied from the imaging device 1. The DSP circuit 1002 outputs image data obtained by processing the signals from the imaging device 1. The frame memory 1003 temporarily holds the image data processed by the DSP circuit 1002 on a frame-by-frame basis.

[0156] The display unit 1004 includes, for example, a panel-type display device such as a liquid crystal panel or an organic EL (Electro Luminescence) panel, and records image data of a moving image or a still image captured by the imaging device 1 in a recording medium such as a semiconductor memory or a hard disk.

[0157] The operation unit 1006 outputs an operation signal for a variety of functions of the electronic apparatus 1000 in accordance with an operation by a user. The power supply unit 1007 appropriately supplies the DSP circuit 1002, the frame memory 1003, the display unit 1004, the recording unit 1005, and the operation unit 1006 with various kinds of power for operations of these supply targets. <4. Practical Application Examples>

[0158] The technology according to the present disclosure (the present technology) is applicable to various products. For example, the technology according to the present disclosure may be achieved in the form of an apparatus to be mounted to a mobile body of any kind such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a vessel, or a robot.

[0159] Fig. 16 is a block diagram depicting an example of schematic configuration of a vehicle control system as an example of a mobile body control system to which the technology according to an embodiment of the present disclosure can be applied.

[0160] The vehicle control system 12000 includes a plurality of electronic control units connected to each other via a communication network 12001. In the example depicted in Fig. 16, the vehicle control system 12000 includes a driving system control unit 12010, a body system control unit 12020, an outside-vehicle information detecting unit 12030, an in-vehicle information detecting unit 12040, and an integrated control unit 12050. In addition, a microcomputer 12051, a sound / image output section 12052, and a vehicle-mounted network interface (I / F) 12053 are illustrated as a functional configuration of the integrated control unit 12050.

[0161] The driving system control unit 12010 controls the operation of devices related to the driving system of the vehicle in accordance with various kinds of programs. For example, the driving system control unit 12010 functions as a control device for a driving force generating device for generating the driving force of the vehicle, such as an internal combustion engine, a driving motor, or the like, a driving force transmitting mechanism for transmitting the driving force to wheels, a steering mechanism for adjusting the steering angle of the vehicle, a braking device for generating the braking force of the vehicle, and the like.

[0162] The body system control unit 12020 controls the operation of various kinds of devices provided to a vehicle body in accordance with various kinds of programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various kinds of lamps such as a headlamp, a backup lamp, a brake lamp, a turn signal, a fog lamp, or the like. In this case, radio waves transmitted from a mobile device as an alternative to a key or signals of various kinds of switches can be input to the body system control unit 12020. The body system control unit 12020 receives these input radio waves or signals, and controls a door lock device, the power window device, the lamps, or the like of the vehicle.

[0163] The outside-vehicle information detecting unit 12030 detects information about the outside of the vehicle including the vehicle control system 12000. For example, the outside-vehicle information detecting unit 12030 is connected with an imaging section 12031. The outside-vehicle information detecting unit 12030 makes the imaging section 12031 image an image of the outside of the vehicle, and receives the imaged image. On the basis of the received image, the outside-vehicle information detecting unit 12030 may perform processing of detecting an object such as a human, a vehicle, an obstacle, a sign, a character on a road surface, or the like, or processing of detecting a distance thereto.

[0164] The imaging section 12031 is an optical sensor that receives light, and which outputs an electric signal corresponding to a received light amount of the light. The imaging section 12031 can output the electric signal as an image, or can output the electric signal as information about a measured distance. In addition, the light received by the imaging section 12031 may be visible light, or may be invisible light such as infrared rays or the like.

[0165] The in-vehicle information detecting unit 12040 detects information about the inside of the vehicle. The in-vehicle information detecting unit 12040 is, for example, connected with a driver state detecting section 12041 that detects the state of a driver. The driver state detecting section 12041, for example, includes a camera that images the driver. On the basis of detection information input from the driver state detecting section 12041, the in-vehicle information detecting unit 12040 may calculate a degree of fatigue of the driver or a degree of concentration of the driver, or may determine whether the driver is dozing.

[0166] The microcomputer 12051 can calculate a control target value for the driving force generating device, the steering mechanism, or the braking device on the basis of the information about the inside or outside of the vehicle which information is obtained by the outside-vehicle information detecting unit 12030 or the in-vehicle information detecting unit 12040, and output a control command to the driving system control unit 12010. For example, the microcomputer 12051 can perform cooperative control intended to implement functions of an advanced driver assistance system (ADAS) which functions include collision avoidance or shock mitigation for the vehicle, following driving based on a following distance, vehicle speed maintaining driving, a warning of collision of the vehicle, a warning of deviation of the vehicle from a lane, or the like.

[0167] In addition, the microcomputer 12051 can perform cooperative control intended for automated driving, which makes the vehicle to travel automatedly without depending on the operation of the driver, or the like, by controlling the driving force generating device, the steering mechanism, the braking device, or the like on the basis of the information about the outside or inside of the vehicle which information is obtained by the outside-vehicle information detecting unit 12030 or the in-vehicle information detecting unit 12040.

[0168] In addition, the microcomputer 12051 can output a control command to the body system control unit 12020 on the basis of the information about the outside of the vehicle which information is obtained by the outside-vehicle information detecting unit 12030. For example, the microcomputer 12051 can perform cooperative control intended to prevent a glare by controlling the headlamp so as to change from a high beam to a low beam, for example, in accordance with the position of a preceding vehicle or an oncoming vehicle detected by the outside-vehicle information detecting unit 12030.

[0169] The sound / image output section 12052 transmits an output signal of at least one of a sound and an image to an output device capable of visually or auditorily notifying information to an occupant of the vehicle or the outside of the vehicle. In the example of Fig. 16, an audio speaker 12061, a display section 12062, and an instrument panel 12063 are illustrated as the output device. The display section 12062 may, for example, include at least one of an on-board display and a head-up display.

[0170] Fig. 17 is a diagram depicting an example of the installation position of the imaging section 12031.

[0171] In Fig. 17, the imaging section 12031 includes imaging sections 12101, 12102, 12103, 12104, and 12105.

[0172] The imaging sections 12101, 12102, 12103, 12104, and 12105 are, for example, disposed at positions on a front nose, sideview mirrors, a rear bumper, and a back door of the vehicle 12100 as well as a position on an upper portion of a windshield within the interior of the vehicle. The imaging section 12101 provided to the front nose and the imaging section 12105 provided to the upper portion of the windshield within the interior of the vehicle obtain mainly an image of the front of the vehicle 12100. The imaging sections 12102 and 12103 provided to the sideview mirrors obtain mainly an image of the sides of the vehicle 12100. The imaging section 12104 provided to the rear bumper or the back door obtains mainly an image of the rear of the vehicle 12100. The imaging section 12105 provided to the upper portion of the windshield within the interior of the vehicle is used mainly to detect a preceding vehicle, a pedestrian, an obstacle, a signal, a traffic sign, a lane, or the like.

[0173] Incidentally, Fig. 17 depicts an example of photographing ranges of the imaging sections 12101 to 12104. An imaging range 12111 represents the imaging range of the imaging section 12101 provided to the front nose. Imaging ranges 12112 and 12113 respectively represent the imaging ranges of the imaging sections 12102 and 12103 provided to the sideview mirrors. An imaging range 12114 represents the imaging range of the imaging section 12104 provided to the rear bumper or the back door. A bird’s-eye image of the vehicle 12100 as viewed from above is obtained by superimposing image data imaged by the imaging sections 12101 to 12104, for example.

[0174] At least one of the imaging sections 12101 to 12104 may have a function of obtaining distance information. For example, at least one of the imaging sections 12101 to 12104 may be a stereo camera constituted of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

[0175] For example, the microcomputer 12051 can determine a distance to each three-dimensional object within the imaging ranges 12111 to 12114 and a temporal change in the distance (relative speed with respect to the vehicle 12100) on the basis of the distance information obtained from the imaging sections 12101 to 12104, and thereby extract, as a preceding vehicle, a nearest three-dimensional object in particular that is present on a traveling path of the vehicle 12100 and which travels in substantially the same direction as the vehicle 12100 at a predetermined speed (for example, equal to or more than 0 km / hour). Further, the microcomputer 12051 can set a following distance to be maintained in front of a preceding vehicle in advance, and perform automatic brake control (including following stop control), automatic acceleration control (including following start control), or the like. It is thus possible to perform cooperative control intended for automated driving that makes the vehicle travel automatedly without depending on the operation of the driver or the like.

[0176] For example, the microcomputer 12051 can classify three-dimensional object data on three-dimensional objects into three-dimensional object data of a two-wheeled vehicle, a standard-sized vehicle, a large-sized vehicle, a pedestrian, a utility pole, and other three-dimensional objects on the basis of the distance information obtained from the imaging sections 12101 to 12104, extract the classified three-dimensional object data, and use the extracted three-dimensional object data for automatic avoidance of an obstacle. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 as obstacles that the driver of the vehicle 12100 can recognize visually and obstacles that are difficult for the driver of the vehicle 12100 to recognize visually. Then, the microcomputer 12051 determines a collision risk indicating a risk of collision with each obstacle. In a situation in which the collision risk is equal to or higher than a set value and there is thus a possibility of collision, the microcomputer 12051 outputs a warning to the driver via the audio speaker 12061 or the display section 12062, and performs forced deceleration or avoidance steering via the driving system control unit 12010. The microcomputer 12051 can thereby assist in driving to avoid collision.

[0177] At least one of the imaging sections 12101 to 12104 may be an infrared camera that detects infrared rays. The microcomputer 12051 can, for example, recognize a pedestrian by determining whether or not there is a pedestrian in imaged images of the imaging sections 12101 to 12104. Such recognition of a pedestrian is, for example, performed by a procedure of extracting characteristic points in the imaged images of the imaging sections 12101 to 12104 as infrared cameras and a procedure of determining whether or not it is the pedestrian by performing pattern matching processing on a series of characteristic points representing the contour of the object. When the microcomputer 12051 determines that there is a pedestrian in the imaged images of the imaging sections 12101 to 12104, and thus recognizes the pedestrian, the sound / image output section 12052 controls the display section 12062 so that a square contour line for emphasis is displayed so as to be superimposed on the recognized pedestrian. The sound / image output section 12052 may also control the display section 12062 so that an icon or the like representing the pedestrian is displayed at a desired position.

[0178] One example of the vehicle control system to which the technology according to an embodiment of the present disclosure is applicable has been described above. The technology according to an embodiment of the present disclosure is applicable to the imaging section 12031, for example, of the configurations described above. Specifically, for example, the imaging device 1 or the like is applicable to the imaging section 12031. Applying the technology according to an embodiment of the present disclosure to the imaging section 12031 makes it possible to obtain a photographed image having high definition. It is possible to perform highly accurate control utilizing the photographed image in the mobile body control system. (Example of Practical Application to Endoscopic Surgery System)

[0179] The technology according to an embodiment of the present disclosure (present technology) is applicable to various products. For example, the technology according to an embodiment of the present disclosure may be applied to an endoscopic surgery system.

[0180] Fig. 18 is a view depicting an example of a schematic configuration of an endoscopic surgery system to which the technology according to an embodiment of the present disclosure (present technology) can be applied.

[0181] In Fig. 18, a state is illustrated in which a surgeon (medical doctor) 11131 is using an endoscopic surgery system 11000 to perform surgery for a patient 11132 on a patient bed 11133. As depicted, the endoscopic surgery system 11000 includes an endoscope 11100, other surgical tools 11110 such as a pneumoperitoneum tube 11111 and an energy device 11112, a supporting arm apparatus 11120 which supports the endoscope 11100 thereon, and a cart 11200 on which various apparatus for endoscopic surgery are mounted.

[0182] The endoscope 11100 includes a lens barrel 11101 having a region of a predetermined length from a distal end thereof to be inserted into a body cavity of the patient 11132, and a camera head 11102 connected to a proximal end of the lens barrel 11101. In the example depicted, the endoscope 11100 is depicted which includes as a rigid endoscope having the lens barrel 11101 of the hard type. However, the endoscope 11100 may otherwise be included as a flexible endoscope having the lens barrel 11101 of the flexible type.

[0183] The lens barrel 11101 has, at a distal end thereof, an opening in which an objective lens is fitted. A light source apparatus 11203 is connected to the endoscope 11100 such that light generated by the light source apparatus 11203 is introduced to a distal end of the lens barrel 11101 by a light guide extending in the inside of the lens barrel 11101 and is irradiated toward an observation target in a body cavity of the patient 11132 through the objective lens. It is to be noted that the endoscope 11100 may be a forward-viewing endoscope or may be an oblique-viewing endoscope or a side-viewing endoscope.

[0184] An optical system and an image pickup element are provided in the inside of the camera head 11102 such that reflected light (observation light) from the observation target is condensed on the image pickup element by the optical system. The observation light is photo-electrically converted by the image pickup element to generate an electric signal corresponding to the observation light, namely, an image signal corresponding to an observation image. The image signal is transmitted as RAW data to a CCU 11201.

[0185] The CCU 11201 includes a central processing unit (CPU), a graphics processing unit (GPU) or the like and integrally controls operation of the endoscope 11100 and a display apparatus 11202. Further, the CCU 11201 receives an image signal from the camera head 11102 and performs, for the image signal, various image processes for displaying an image based on the image signal such as, for example, a development process (demosaic process).

[0186] The display apparatus 11202 displays thereon an image based on an image signal, for which the image processes have been performed by the CCU 11201, under the control of the CCU 11201.

[0187] The light source apparatus 11203 includes a light source such as, for example, a light emitting diode (LED) and supplies irradiation light upon imaging of a surgical region to the endoscope 11100.

[0188] An inputting apparatus 11204 is an input interface for the endoscopic surgery system 11000. A user can perform inputting of various kinds of information or instruction inputting to the endoscopic surgery system 11000 through the inputting apparatus 11204. For example, the user would input an instruction or a like to change an image pickup condition (type of irradiation light, magnification, focal distance or the like) by the endoscope 11100.

[0189] A treatment tool controlling apparatus 11205 controls driving of the energy device 11112 for cautery or incision of a tissue, sealing of a blood vessel or the like. A pneumoperitoneum apparatus 11206 feeds gas into a body cavity of the patient 11132 through the pneumoperitoneum tube 11111 to inflate the body cavity in order to secure the field of view of the endoscope 11100 and secure the working space for the surgeon. A recorder 11207 is an apparatus capable of recording various kinds of information relating to surgery. A printer 11208 is an apparatus capable of printing various kinds of information relating to surgery in various forms such as a text, an image or a graph.

[0190] It is to be noted that the light source apparatus 11203 which supplies irradiation light when a surgical region is to be imaged to the endoscope 11100 may include a white light source which includes, for example, an LED, a laser light source or a combination of them. Where a white light source includes a combination of red, green, and blue (RGB) laser light sources, since the output intensity and the output timing can be controlled with a high degree of accuracy for each color (each wavelength), adjustment of the white balance of a picked up image can be performed by the light source apparatus 11203. Further, in this case, if laser beams from the respective RGB laser light sources are irradiated time-divisionally on an observation target and driving of the image pickup elements of the camera head 11102 are controlled in synchronism with the irradiation timings. Then images individually corresponding to the R, G and B colors can be also picked up time-divisionally. According to this method, a color image can be obtained even if color filters are not provided for the image pickup element.

[0191] Further, the light source apparatus 11203 may be controlled such that the intensity of light to be outputted is changed for each predetermined time. By controlling driving of the image pickup element of the camera head 11102 in synchronism with the timing of the change of the intensity of light to acquire images time-divisionally and synthesizing the images, an image of a high dynamic range free from underexposed blocked up shadows and overexposed highlights can be created.

[0192] Further, the light source apparatus 11203 may be configured to supply light of a predetermined wavelength band ready for special light observation. In special light observation, for example, by utilizing the wavelength dependency of absorption of light in a body tissue to irradiate light of a narrow band in comparison with irradiation light upon ordinary observation (namely, white light), narrow band observation (narrow band imaging) of imaging a predetermined tissue such as a blood vessel of a superficial portion of the mucous membrane or the like in a high contrast is performed. Alternatively, in special light observation, fluorescent observation for obtaining an image from fluorescent light generated by irradiation of excitation light may be performed. In fluorescent observation, it is possible to perform observation of fluorescent light from a body tissue by irradiating excitation light on the body tissue (autofluorescence observation) or to obtain a fluorescent light image by locally injecting a reagent such as indocyanine green (ICG) into a body tissue and irradiating excitation light corresponding to a fluorescent light wavelength of the reagent upon the body tissue. The light source apparatus 11203 can be configured to supply such narrow-band light and / or excitation light suitable for special light observation as described above.

[0193] Fig. 19 is a block diagram depicting an example of a functional configuration of the camera head 11102 and the CCU 11201 depicted in Fig. 18.

[0194] The camera head 11102 includes a lens unit 11401, an image pickup unit 11402, a driving unit 11403, a communication unit 11404 and a camera head controlling unit 11405. The CCU 11201 includes a communication unit 11411, an image processing unit 11412 and a control unit 11413. The camera head 11102 and the CCU 11201 are connected for communication to each other by a transmission cable 11400.

[0195] The lens unit 11401 is an optical system, provided at a connecting location to the lens barrel 11101. Observation light taken in from a distal end of the lens barrel 11101 is guided to the camera head 11102 and introduced into the lens unit 11401. The lens unit 11401 includes a combination of a plurality of lenses including a zoom lens and a focusing lens.

[0196] The number of image pickup elements which is included by the image pickup unit 11402 may be one (single-plate type) or a plural number (multi-plate type). Where the image pickup unit 11402 is configured as that of the multi-plate type, for example, image signals corresponding to respective R, G and B are generated by the image pickup elements, and the image signals may be synthesized to obtain a color image. The image pickup unit 11402 may also be configured so as to have a pair of image pickup elements for acquiring respective image signals for the right eye and the left eye ready for three dimensional (3D) display. If 3D display is performed, then the depth of a living body tissue in a surgical region can be comprehended more accurately by the surgeon 11131. It is to be noted that, where the image pickup unit 11402 is configured as that of stereoscopic type, a plurality of systems of lens units 11401 are provided corresponding to the individual image pickup elements.

[0197] Further, the image pickup unit 11402 may not necessarily be provided on the camera head 11102. For example, the image pickup unit 11402 may be provided immediately behind the objective lens in the inside of the lens barrel 11101.

[0198] The driving unit 11403 includes an actuator and moves the zoom lens and the focusing lens of the lens unit 11401 by a predetermined distance along an optical axis under the control of the camera head controlling unit 11405. Consequently, the magnification and the focal point of a picked up image by the image pickup unit 11402 can be adjusted suitably.

[0199] The communication unit 11404 includes a communication apparatus for transmitting and receiving various kinds of information to and from the CCU 11201. The communication unit 11404 transmits an image signal acquired from the image pickup unit 11402 as RAW data to the CCU 11201 through the transmission cable 11400.

[0200] In addition, the communication unit 11404 receives a control signal for controlling driving of the camera head 11102 from the CCU 11201 and supplies the control signal to the camera head controlling unit 11405. The control signal includes information relating to image pickup conditions such as, for example, information that a frame rate of a picked up image is designated, information that an exposure value upon image picking up is designated and / or information that a magnification and a focal point of a picked up image are designated.

[0201] It is to be noted that the image pickup conditions such as the frame rate, exposure value, magnification or focal point may be designated by the user or may be set automatically by the control unit 11413 of the CCU 11201 on the basis of an acquired image signal. In the latter case, an auto exposure (AE) function, an auto focus (AF) function and an auto white balance (AWB) function are incorporated in the endoscope 11100.

[0202] The camera head controlling unit 11405 controls driving of the camera head 11102 on the basis of a control signal from the CCU 11201 received through the communication unit 11404.

[0203] The communication unit 11411 includes a communication apparatus for transmitting and receiving various kinds of information to and from the camera head 11102. The communication unit 11411 receives an image signal transmitted thereto from the camera head 11102 through the transmission cable 11400.

[0204] Further, the communication unit 11411 transmits a control signal for controlling driving of the camera head 11102 to the camera head 11102. The image signal and the control signal can be transmitted by electrical communication, optical communication or the like.

[0205] The image processing unit 11412 performs various image processes for an image signal in the form of RAW data transmitted thereto from the camera head 11102.

[0206] The control unit 11413 performs various kinds of control relating to image picking up of a surgical region or the like by the endoscope 11100 and display of a picked up image obtained by image picking up of the surgical region or the like. For example, the control unit 11413 creates a control signal for controlling driving of the camera head 11102.

[0207] Further, the control unit 11413 controls, on the basis of an image signal for which image processes have been performed by the image processing unit 11412, the display apparatus 11202 to display a picked up image in which the surgical region or the like is imaged. Thereupon, the control unit 11413 may recognize various objects in the picked up image using various image recognition technologies. For example, the control unit 11413 can recognize a surgical tool such as forceps, a particular living body region, bleeding, mist when the energy device 11112 is used and so forth by detecting the shape, color and so forth of edges of objects included in a picked up image. The control unit 11413 may cause, when it controls the display apparatus 11202 to display a picked up image, various kinds of surgery supporting information to be displayed in an overlapping manner with an image of the surgical region using a result of the recognition. Where surgery supporting information is displayed in an overlapping manner and presented to the surgeon 11131, the burden on the surgeon 11131 can be reduced and the surgeon 11131 can proceed with the surgery with certainty.

[0208] The transmission cable 11400 which connects the camera head 11102 and the CCU 11201 to each other is an electric signal cable ready for communication of an electric signal, an optical fiber ready for optical communication or a composite cable ready for both of electrical and optical communications.

[0209] Here, while, in the example depicted, communication is performed by wired communication using the transmission cable 11400, the communication between the camera head 11102 and the CCU 11201 may be performed by wireless communication.

[0210] One example of the endoscopic surgery system to which the technology according to an embodiment of the present disclosure is applicable has been described above. The technology according to an embodiment of the present disclosure is suitably applicable to, for example, the image pickup unit 11402 provided in the camera head 11102 of the endoscope 11100 of the configurations described above. Applying the technology according to an embodiment of the present disclosure to the image pickup unit 11402 makes it possible to provide the endoscope 11100 having high definition.

[0211] Although the description has been given hereinabove of the present disclosure with reference to the embodiments, the modification examples, the application example, and the practical application examples, the present technology is not limited to the embodiments described above and the like, and may be modified in a wide variety of ways. For example, although the modification examples described above have been described as modification examples of the embodiments described above, the configurations of the respective modification examples may be combined as appropriate.

[0212] In the embodiment described above, the imaging device is exemplified and described; however, it is sufficient for the photodetector of the present disclosure, for example, to receive incident light and convert the light into electric charge. The signal to be outputted may be a signal of image information or a signal of ranging information. The photodetector (the imaging device) is applicable to an image sensor, a distance measurement sensor, or the like. It is to be noted that the present disclosure is not limited to a back-illuminated image sensor, and is also applicable to a front-illuminated image sensor.

[0213] The photodetector according to the present disclosure is applicable also as a distance measurement sensor enabling distance measurement of a TOF (Time Of Flight) method. The light-receiving element (the photoelectric conversion section) of each pixel may be an APD (Avalanche Photo Diode). The light-receiving element may include, for example, a SPAD (Single Photon Avalanche Diode). The photodetector (the imaging device) is applicable also as a sensor enabling detection of an event, e.g., an event-driven sensor (referred to as an EVS (Event Vision Sensor), an EDS (Event Driven Sensor), a DVS (Dynamic Vision Sensor), etc.).

[0214] A photodetector according to an embodiment of the present disclosure includes a first layer, a second layer that is stacked on the first layer, and a photoelectric conversion element. The first layer includes a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The photoelectric conversion element photoelectrically converts light incident via the second layer and the first layer. The second structures are configured using the same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure. This makes it possible to implement a photodetector that allows for an improvement in characteristics for incident light.

[0215] An optical element according to an embodiment of the present disclosure includes a first layer, and a second layer that is stacked on the first layer. The first layer includes a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure. The second layer includes a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure. The second structures are configured using the same material as a material of the first structures. The plurality of second structures includes the second structure in contact with the first structure. This makes it possible to implement an optical element having superior optical characteristics.

[0216] It is to be noted that the effects described herein are merely exemplary and are not limited to the description, and may include other effects. In addition, the present disclosure may also have the following configurations. (1) A light detection device, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different than the second refractive index; a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index, and wherein the second surface of the first layer is in contact with the first surface of the second layer; and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer, wherein the second structures include a same material as a material of the first structures, and wherein at least some of the second structures are at least partially in contact with corresponding ones of the first structures. (2) The light detection device according to (1), wherein at least portions of the first medium corresponding to the second surface of the first layer are in contact with at least portions of the second medium corresponding to the first surface of the second layer. (3) The light detection device according to (1) or (2), wherein the second medium includes a same material as a material of the first medium. (4) The light detection device according to any of (1) to (3), wherein at least some of the second structures have shapes that are different from other of the second structures. (5) The light detection device according to any of (1) to (4), wherein at least one of the first structures and at least one of the second structures have lengths different from each other in a direction from the first medium to the second mediums. (6) The light detection device according to any of (1) to (5), wherein ends of some second structures closest to the second surface of the first layer are positioned closer to the first surface of the first layer than ends of the first structures that are closest to the second surface of the first layer. (7) The light detection device according to any of (1) to (6), wherein at least one of the first structures has a recess section on an end closest to the second surface of the first layer. (8) The light detection device according to (7), wherein some second structures out of the plurality of second structures are in contact with the recess section of a corresponding one of the first structures. (9) The light detection device according to any of (1) to (8), wherein the second structures have a recess section on an end closest to the second surface of the second layer. (10) The light detection device according to (9), further comprising an antireflection film disposed on the second surface of the second layer, wherein a portion of the antireflection film is provided in recess sections of the second structures. (11) The light detection device according to any of (1) to (10), wherein the second structures have a projected section on an end closest to the first surface of the second layer. (12) The light detection device according to any of (1) to (11), wherein at least one of the first structures or the second structures has an air gap. (13) The light detection device according to any of (1) to (12), wherein the refractive index of the first structures is higher than the refractive index of the first medium, and the refractive index of the second structures is higher than the refractive index of the second medium. (14) The light detection device according to any of (1) to (13), wherein the first structures and the second structures each have a width less than or equal to a wavelength region of visible light. (15) An optical element, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein each of the first structures extends from at least first surface of the first layer to a second surface of the first layer that is opposite the first surface, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different that the second refractive index; and a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index,, wherein the second surface of the first layer is in contact with the first surface of the first layer layer being stacked on the first layer, wherein the second structures include a same material as a material of the first structures, and wherein the at least some of the second structures are in contact with corresponding ones of the first structures. (16) The optical element according to (15), wherein the first surface of the second layer is in contact with the second surface of the first layer. (17) The optical element according to (15) or (16), wherein the second medium includes a same material as a material of the first medium. (18) The optical element according to any of (15) to (17), wherein at least some of the second structures have shapes that are different from other of the second structures. (19) The optical element according to any of (15) to (18), wherein at least some of the first structures and at least some of the second structures have lengths different from each other in a direction extending between the first and second surfaces of the first and second layers. (20) The optical element according to any of (15) to (19), wherein each of the first structures extends from at least a first surface of the first layer to a second surface of the first layer that is opposite the first surface, and wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface. (21) An electronic apparatus, comprising: an optical system; and a photodetector that receives light transmitted through the optical system, the photodetector including: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein each of the first structures extends from at least first surface of the first layer to a second surface of the first layer that is opposite the first surface, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different than the second refractive index, a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index,, and wherein the second surface of the first layer is in contact with the first surface of the first layer, and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer, wherein the second structures include a same material as a material of the first structures, and wherein at least some of the second structures are in contact with corresponding ones of the first structures. (22) A light detection device, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures,; a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein at least some of the second structures have shapes that are different from other of the second structures, wherein at least one of the first structures and at least one of the second structures have lengths different from each other in a direction from the first medium to the second mediums, wherein ends of some second structures closest to the second surface of the first layer are positioned closer to the first surface of the first layer than ends of the first structures that are closest to the second surface of the first layer, and wherein the second surface of the first layer is in contact with the first surface of the second layer; and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer. (23) A photodetector including: a first layer including a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure; a second layer including a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure, the second layer being stacked on the first layer; and a photoelectric conversion element that photoelectrically converts light incident via the second layer and the first layer, in which the second structures are configured using a same material as a material of the first structures, and the plurality of second structures includes the second structure in contact with the first structure. (24) The photodetector according to (23), in which the plurality of second structures includes the second structure that is provided to be stacked on the first structure, and the second medium is provided to be stacked on the first medium. (25) The photodetector according to (23) or (24), in which the second medium is configured using a same material as a material of the first medium. (26) The photodetector according to any one of (23) to (25), in which the first structures and some second structures out of the plurality of second structures have shapes different from each other. (27) The photodetector according to any one of (23) to (26), in which the first structures and some second structures out of the plurality of second structures have lengths different from each other in a direction in which the first layer and the second layer are stacked. (28) The photodetector according to any one of (23) to (27), in which lower ends of some second structures out of the plurality of second structures are each positioned lower than an upper end of the first structure. (29) The photodetector according to any one of (23) to (28), in which the first structure has a recess section provided on side of the second structure. (30) The photodetector according to (29), in which some second structures out of the plurality of second structures each have a portion provided in the recess section of the first structure. (31) The photodetector according to any one of (23) to (30), in which the second structure has a recess section provided on side opposite to side of the first structure. (32) The photodetector according to (31), further including an antireflection film provided on the second structure, in which a portion of the antireflection film is provided in the recess section of the second structure. (33) The photodetector according to any one of (23) to (32), in which the second structure has a projected section provided on a side surface of the second structure on side of the first structure. (34) The photodetector according to any one of (23) to (33), in which at least one of the first structure or the second structure has an air gap. (35) The photodetector according to any one of (23) to (34), in which the refractive index of the first structure is higher than the refractive index of the first medium, and the refractive index of the second structure is higher than the refractive index of the second medium. (36) The photodetector according to any one of (23) to (35), in which the first structure and the second structure each have a size less than or equal to a wavelength region of visible light. (37) An optical element including: a first layer including a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure; and a second layer including a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure, the second layer being stacked on the first layer, in which the second structures are configured using a same material as a material of the first structures, and the plurality of second structures including the second structure in contact with the first structure. (38) The optical element according to (37), in which the plurality of second structures includes the second structure that is provided to be stacked on the first structure, and the second medium is provided to be stacked on the first medium. (39) The optical element according to (37) or (38), in which the second medium is configured using a same material as a material of the first medium. (40) The optical element according to any one of (37) to (39), in which the first structures and some second structures out of the plurality of second structures have shapes different from each other. (41) The optical element according to any one of (37) to (40), in which the first structures and some second structures out of the plurality of second structures have lengths different from each other in a direction in which the first layer and the second layer are stacked. (42) An electronic apparatus including: an optical system; and a photodetector that receives light transmitted through the optical system, the photodetector including a first layer including a plurality of first structures that is provided side by side in a first direction, and a first medium that is provided around the first structures and has a refractive index different from a refractive index of the first structure, a second layer including a plurality of second structures that is provided side by side in the first direction, and a second medium that is provided around the second structures and has a refractive index different from a refractive index of the second structure, the second layer being stacked on the first layer, and a photoelectric conversion element that photoelectrically converts light incident via the second layer and the first layer, in which the second structures are configured using a same material as a material of the first structures, and the plurality of second structures includes the second structure in contact with the first structure.

[0217] It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

[0218] 1 imaging device 10 semiconductor layer 12 photoelectric conversion section 51 first structure 52 second structure 60 light-guiding section 61 first member 62 second member 71 first layer 72 second layer 80 optical layer

Claims

1. A light detection device, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different than the second refractive index; a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index, and wherein the second surface of the first layer is in contact with the first surface of the second layer; and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer, wherein the second structures include a same material as a material of the first structures, and wherein at least some of the second structures are at least partially in contact with corresponding ones of the first structures.

2. The light detection device according to claim 1, wherein at least portions of the first medium corresponding to the second surface of the first layer are in contact with at least portions of the second medium corresponding to the first surface of the second layer.

3. The light detection device according to claim 1, wherein the second medium includes a same material as a material of the first medium.

4. The light detection device according to claim 1, wherein at least some of the second structures have shapes that are different from other of the second structures.

5. The light detection device according to claim 1, wherein at least one of the first structures and at least one of the second structures have lengths different from each other in a direction from the first medium to the second mediums.

6. The light detection device according to claim 1, wherein ends of some second structures closest to the second surface of the first layer are positioned closer to the first surface of the first layer than ends of the first structures that are closest to the second surface of the first layer.

7. The light detection device according to claim 1, wherein at least one of the first structures has a recess section on an end closest to the second surface of the first layer.

8. The light detection device according to claim 7, wherein some second structures out of the plurality of second structures are in contact with the recess section of a corresponding one of the first structures.

9. The light detection device according to claim 1, wherein the second structures have a recess section on an end closest to the second surface of the second layer.

10. The light detection device according to claim 9, further comprising an antireflection film disposed on the second surface of the second layer, wherein a portion of the antireflection film is provided in recess sections of the second structures.

11. The light detection device according to claim 1, wherein the second structures have a projected section on an end closest to the first surface of the second layer.

12. The light detection device according to claim 1, wherein at least one of the first structures or the second structures has an air gap.

13. The light detection device according to claim 1, wherein the refractive index of the first structures is higher than the refractive index of the first medium, and the refractive index of the second structures is higher than the refractive index of the second medium.

14. The light detection device according to claim 1, wherein the first structures and the second structures each have a width less than or equal to a wavelength region of visible light.

15. An optical element, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein each of the first structures extends from at least first surface of the first layer to a second surface of the first layer that is opposite the first surface, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different that the second refractive index; and a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index,, wherein the second surface of the first layer is in contact with the first surface of the first layer layer being stacked on the first layer, wherein the second structures include a same material as a material of the first structures, and wherein the at least some of the second structures are in contact with corresponding ones of the first structures.

16. The optical element according to claim 15, wherein the first surface of the second layer is in contact with the second surface of the first layer.

17. The optical element according to claim 15, wherein the second medium includes a same material as a material of the first medium.

18. The optical element according to claim 15, wherein at least some of the second structures have shapes that are different from other of the second structures.

19. The optical element according to claim 15, wherein at least some of the first structures and at least some of the second structures have lengths different from each other in a direction extending between the first and second surfaces of the first and second layers.

20. The optical element according to claim 15, wherein each of the first structures extends from at least a first surface of the first layer to a second surface of the first layer that is opposite the first surface, and wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface.

21. An electronic apparatus, comprising: an optical system; and a photodetector that receives light transmitted through the optical system, the photodetector including: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures, wherein each of the first structures extends from at least first surface of the first layer to a second surface of the first layer that is opposite the first surface, wherein the first medium has a first refractive index, wherein the first structures have a second refractive index, and wherein the first refractive index is different than the second refractive index, a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein the second medium has the first refractive index, wherein the second structures have the second refractive index,, and wherein the second surface of the first layer is in contact with the first surface of the first layer, and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer, wherein the second structures include a same material as a material of the first structures, and wherein at least some of the second structures are in contact with corresponding ones of the first structures.

22. A light detection device, comprising: a first layer, including: a plurality of first structures, and a first medium that is disposed around portions of the first structures,; a second layer, including: a plurality of second structures, and a second medium that is disposed around portions of the second structures, wherein each of the second structures extends from at least a first surface of the second layer to at least a second surface of the second layer that is opposite the first surface, wherein at least some of the second structures have shapes that are different from other of the second structures, wherein at least one of the first structures and at least one of the second structures have lengths different from each other in a direction from the first medium to the second mediums, wherein ends of some second structures closest to the second surface of the first layer are positioned closer to the first surface of the first layer than ends of the first structures that are closest to the second surface of the first layer and wherein the second surface of the first layer is in contact with the first surface of the second layer; and a photoelectric conversion element, wherein a light incident surface of the photoelectric conversion element faces the first surface of the first layer.

Images