Patent Publication Number: US-11387272-B2

Title: Semiconductor device and electronic apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase of International Patent Application No. PCT/JP2019/000130 filed on Jan. 8, 2019, which claims priority benefit of Japanese Patent Application No. JP 2018-008111 filed in the Japan Patent Office on Jan. 22, 2018. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The technology according to the present disclosure (the technology will be hereinafter also referred to as the present technology) relates to a semiconductor device and an electronic apparatus, and more particularly, to a semiconductor device and an electronic apparatus that include a pixel having a metallic filter and a pixel not having the metallic filter. 
     BACKGROUND ART 
     There is a suggested imaging device in which the imaging region to be used for acquiring an image and the spectral region to be used for acquiring a color spectrum are formed in the same pixel region (see Patent Document 1, for example). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2012-59865 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the imaging device disclosed in Patent Document 1, color filters of a non-metallic organic material are used for the pixels in the imaging region, and plasmon filters made of a metal such as aluminum are used for the pixels in the spectral region, for example. Therefore, at a boundary portion between the imaging region and the spectral region, light reflected irregularly by a sidewall of a plasmon filter enters the imaging region, and as a result, the characteristics of the imaging device are degraded. 
     The present technology has been made in view of such circumstances, and is to improve the characteristics of a semiconductor device or an electronic apparatus that includes a pixel having a metallic filter and a pixel not having the metallic filter. 
     Solutions to Problems 
     A semiconductor device according to a first aspect of the present technology includes: a pixel unit in which a first pixel including a metallic filter and a second pixel not including the metallic filter are disposed adjacent to each other; and a reflected light reduction unit that reduces reflected light on a sidewall of the metallic filter at a boundary portion between the first pixel and the second pixel. 
     An electronic apparatus according to a second aspect of the present technology includes: a semiconductor device; and a signal processing unit that processes a signal output from the semiconductor device. In the electronic apparatus, the semiconductor device includes: a pixel unit in which a first pixel including a metallic filter and a second pixel not including the metallic filter are disposed adjacent to each other; and a reflected light reduction unit that reduces reflected light on a sidewall of the metallic filter at a boundary portion between the first pixel and the second pixel. 
     In the first aspect or the second aspect of the present technology, reflected light on the sidewall of the metallic filter at the boundary portion between the first pixel including the metallic filter and the second pixel not including the metallic filter is reduced. 
     Effects of the Invention 
     According to the first aspect of the present technology, it is possible to improve the characteristics of a semiconductor device that includes a pixel having a metallic filter and a pixel not having the metallic filter. 
     According to the second aspect of the present technology, it is possible to improve the characteristics of an electronic apparatus that includes a pixel having a metallic filter and a pixel not having the metallic filter. 
     Note that effects of the present technology are not limited to the effects described herein, and may include any of the effects described in the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing an embodiment of an imaging apparatus to which the present technology is applied. 
         FIG. 2  is a block diagram showing an example circuit configuration of an imaging device. 
         FIG. 3  is a diagram showing an example configuration of the pixel array of the imaging device. 
         FIG. 4  is a schematic cross-sectional view of an example configuration of the imaging device. 
         FIG. 5  is a diagram showing an example configuration of a plasmon filter having a hole array structure. 
         FIG. 6  is a graph showing the dispersion relationship of surface plasmons. 
         FIG. 7  is a graph showing a first example of the spectral characteristics of a plasmon filter having a hole array structure. 
         FIG. 8  is a graph showing a second example of the spectral characteristics of a plasmon filter having a hole array structure. 
         FIG. 9  is a graph showing a plasmon mode and a waveguide mode. 
         FIG. 10  is a graph showing an example of the propagation characteristics of surface plasmons. 
         FIGS. 11A and 11B  are diagrams showing other example configurations of plasmon filters having a hole array structure. 
         FIG. 12  is a view showing an example configuration of a plasmon filter having a two-layer structure. 
         FIGS. 13A and 13B  are diagrams showing example configurations of plasmon filters having a dot array structure. 
         FIG. 14  is a graph showing an example of the spectral characteristics of a plasmon filter having a dot array structure. 
         FIG. 15  is a diagram showing an example configuration of a plasmon filter having a square array structure. 
         FIG. 16  is a diagram showing an example configuration of a plasmon filter using GMR. 
         FIG. 17  is a graph showing an example of the spectral characteristics of a plasmon filter using GMR. 
         FIGS. 18A and 18B  are diagrams showing an example configuration of a plasmon filter using a bull&#39;s-eye structure. 
         FIG. 19  is a cross-sectional view schematically showing a first embodiment of the filter layer of an imaging device. 
         FIGS. 20A and 20B  are diagrams schematically showing the first embodiment of a reflected light reduction unit for the filter layer shown in  FIG. 19 . 
         FIG. 21  is a cross-sectional view schematically showing a second embodiment of the filter layer of an imaging device. 
         FIGS. 22A and 22B  are diagrams schematically showing the first embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 21 . 
         FIG. 23  is a cross-sectional view schematically showing a third embodiment of the filter layer of an imaging device. 
         FIGS. 24A and 24B  is a are diagrams schematically showing the first embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 23 . 
         FIG. 25  is a diagram showing an example width of a black filter. 
         FIG. 26  is a diagram for explaining the conditions for the amount of protrusion of the black filter. 
         FIG. 27  is a diagram showing a first modification of the black filter. 
         FIG. 28  is a diagram showing a second modification of the black filter. 
         FIG. 29  is a diagram showing a modification of the first embodiment of the reflected light reduction unit. 
         FIG. 30  is a diagram schematically showing a second embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 19 . 
         FIG. 31  is a diagram schematically showing the second embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 21 . 
         FIG. 32  is a diagram schematically showing the second embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 23 . 
         FIG. 33  is a diagram schematically showing a third embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 19 . 
         FIG. 34  is a diagram schematically showing the third embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 21 . 
         FIG. 35  is a diagram schematically showing the third embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 23 . 
         FIG. 36  is a diagram schematically showing a fourth embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 19 . 
         FIG. 37  is a diagram schematically showing the fourth embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 21 . 
         FIG. 38  is a diagram schematically showing the fourth embodiment of the reflected light reduction unit for the filter layer shown in  FIG. 23 . 
         FIG. 39  is a diagram for explaining the conditions for the inclination angle of a narrowband filter. 
         FIGS. 40A, 40B, 40C, and 40D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 41A, 41B, 41C, and 41D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 42A, 42B, 42C, and 42D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 43A, 43B, 43C, and 43D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIG. 44  is a diagram showing an example layout in the pixel array of an imaging device. 
         FIGS. 45A, 45B, 45C, and 45D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 46A, 46B, 46C, and 46D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 47A, 47B, 47C, and 47D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 48A, 48B, 48C, and 48D  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 49A, 49B, and 49C  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIGS. 50A, 50B, and 50C  are diagrams showing example layouts in the pixel array of an imaging device. 
         FIG. 51  is a diagram schematically showing how flare is generated in an imaging apparatus. 
         FIG. 52  is a diagram for explaining a fifth embodiment of the present technology. 
         FIG. 53  is a diagram showing an example layout of an antireflective film. 
         FIG. 54  is a diagram showing an example layout of an antireflective film. 
         FIGS. 55A and 55B  are diagrams showing example layouts of antireflective films. 
         FIGS. 56A and 56B  are diagrams showing example layouts of antireflective films. 
         FIGS. 57A and 57B  are diagrams showing example layouts of antireflective films. 
         FIG. 58  is a diagram showing an example in which a Fabry-Perot is used as the reflected light reduction unit. 
         FIG. 59  is a diagram showing example applications of the present technology. 
         FIG. 60  is a table showing examples of the detection band in a case where the flavor and the degree of freshness of food are detected. 
         FIG. 61  is a table showing examples of the detection band in a case where the sugar content and the water content of a fruit are detected. 
         FIG. 62  is a table showing examples of the detection band in a case where plastics are separated. 
         FIG. 63  is a block diagram showing an example configuration of an electronic apparatus. 
         FIG. 64  is a diagram schematically showing an example configuration of an endoscopic surgery system. 
         FIG. 65  is a block diagram showing an example of the functional configurations of a camera head and a CCU. 
         FIG. 66  is a block diagram schematically showing an example configuration of a vehicle control system. 
         FIG. 67  is an explanatory diagram showing an example of installation positions of external information detectors and imaging units. 
         FIG. 68  is a cross-sectional view of an example configuration of a solid-state imaging device to which the technology according to the present disclosure can be applied, and a first example configuration of the pixel separation unit of the solid-state imaging device. 
         FIG. 69  is a cross-sectional view of a second example configuration of the pixel separation unit of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
         FIG. 70  is a cross-sectional view of a third example configuration of the pixel separation unit of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
         FIGS. 71A, 71B, and 71C  are diagrams showing outlines of example configurations of stacked solid-state imaging devices to which the technology according to the present disclosure can be applied. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     The following is a detailed description of modes for carrying out the invention (these modes will be hereinafter referred to as “embodiments”), with reference to the accompanying drawings. Note that explanation will be made in the following order. 
     1. Example configuration of an imaging apparatus 
     2. First embodiment (an example in which a light absorber is disposed at a higher location than narrowband filters) 
     3. Second embodiment (an example in which a sidewall of a narrowband filter is covered with a light absorber) 
     4. Third embodiment (an example in which a sidewall of a narrowband filter is covered with a low-reflection film) 
     5. Fourth embodiment (an example in which a sidewall of a narrowband filter is inclined) 
     6. Example positions of a reflected light reduction unit in a pixel array 
     7. Fifth embodiment (an example in which an antireflective film is provided on the light incident surface of each narrowband filter) 
     8. Modifications of the filters of normal pixels and narrowband pixels 
     9. Image processing in an imaging apparatus 
     10. Example applications 
     11. Modifications 
     1. Example Configuration of an Imaging Apparatus 
     First, an example configuration of an imaging apparatus to which the present technology is applied is described, with reference to  FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 10, 11A, 11B, 12, 13A, 13B, 14, 15, 16, 17, 18A, and 18B . 
     &lt;Example Configuration of an Imaging Apparatus  10 &gt; 
       FIG. 1  is a block diagram showing an example configuration of an imaging apparatus  10  that is an electronic apparatus to which the present technology is applied. 
     The imaging apparatus  10  is formed with a digital camera that is capable of capturing both still images and moving images, for example. The imaging apparatus  10  is capable of detecting (multispectral) light of four or more wavelength bands (at least four bands) that are more than the conventional three wavelength bands (three bands) of R (red), G (green), and B (blue), or Y (yellow), M (magenta), and C (cyan) based on the three primary colors or the color-matching functions. 
     The imaging apparatus  10  includes an optical system  11 , an imaging device  12 , a memory  13 , a signal processing unit  14 , an output unit  15 , and a control unit  16 . 
     The optical system  11  includes a zoom lens, a focus lens, a diaphragm, and the like (not shown), for example, and causes light from outside to enter the imaging device  12 . The optical system  11  also includes various kinds of filters such as a polarization filter as needed. 
     The imaging device  12  is formed with a complementary metal oxide semiconductor (CMOS) image sensor, for example. The imaging device  12  receives the incident light from the optical system  11 , performs photoelectric conversion, and outputs the image data corresponding to the incident light. 
     The memory  13  temporarily stores the image data the imaging device  12  has output. 
     The signal processing unit  14  performs signal processing (processing such as denoising and white balance adjustment, for example) using the image data stored in the memory  13 , and supplies the resultant image data to the output unit  15 . 
     The output unit  15  outputs the image data supplied from the signal processing unit  14 . For example, the output unit  15  includes a display (not shown) formed with liquid crystal or the like, and displays the spectrum (image) corresponding to the image data supplied from the signal processing unit  14  as a so-called through-lens image. The output unit  15  includes a driver (not shown) for driving a recording medium such as a semiconductor memory, a magnetic disk, or an optical disk, for example, and records the image data supplied from the signal processing unit  14  on the recording medium. For example, the output unit  15  functions as a communication interface that communicates with an external device (not shown), and transmits the image data from the signal processing unit  14  to the external device in a wireless or wired manner. 
     The control unit  16  controls the respective components of the imaging apparatus  10 , in accordance with a user operation or the like. 
     Note that image data will be hereinafter also referred to simply as an image. 
     &lt;Example Circuit Configuration of the Imaging Device&gt; 
       FIG. 2  is a block diagram showing an example circuit configuration of the imaging device  12  shown in  FIG. 1 . 
     The imaging device  12  includes a pixel array  31 , a row scanning circuit  32 , a phase locked loop (PLL)  33 , a digital-analog converter (DAC)  34 , a column analog-digital converter (ADC) circuit  35 , a column scanning circuit  36 , and a sense amplifier  37 . 
     The pixel array  31  is a pixel unit in which a plurality of pixels  51  is two-dimensionally arranged. 
     Each pixel  51  is disposed at a point where a horizontal signal line H connected to the row scanning circuit  32  and a vertical signal line V connected to the column ADC circuit  35  intersect, and includes a photodiode  61  that performs photoelectric conversion, and several kinds of transistors for reading stored signals. That is, each pixel  51  includes a photodiode  61 , a transfer transistor  62 , a floating diffusion  63 , an amplification transistor  64 , a selection transistor  65 , and a reset transistor  66 , as shown in an enlarged view on the right side in  FIG. 2 . 
     The electric charges stored in the photodiode  61  are transferred to the floating diffusion  63  via the transfer transistor  62 . The floating diffusion  63  is connected to the gate of the amplification transistor  64 . When a pixel  51  becomes the target from which a signal is to be read out, the selection transistor  65  is turned on by the row scanning circuit  32  via the horizontal signal line H, and the amplification transistor  64  is driven by source follower driving, so that the signal of the selected pixel  51  is read out as the pixel signal corresponding to the amount of the electric charges stored in the photodiode  61  into the vertical signal line V. Further, the reset transistor  66  is turned on, to reset the pixel signal. 
     The row scanning circuit  32  sequentially outputs drive signals for driving (transferring, selecting, resetting, and the like, for example) the pixels  51  of the pixel array  31  row by row. 
     The PLL  33  generates and outputs a clock signal of a predetermined frequency required for driving the respective components of the imaging device  12 , on the basis of a clock signal supplied from the outside. 
     The DAC  34  generates and outputs a ramp signal having a shape (almost a sawtooth shape) that returns to a predetermined voltage value after the voltage drops at a predetermined gradient from a predetermined voltage value. 
     The column ADC circuit  35  includes comparators  71  and counters  72  that correspond in number to the columns of the pixels  51  of the pixel array  31 . The column ADC circuit  35  extracts signal levels from pixel signals output from the pixels  51  by performing a correlated double sampling (CDS) operation, and then outputs pixel data. That is, the comparators  71  compare the ramp signal supplied from the DAC  34  with the pixel signals (luminance values) output from the pixels  51 , and supply the resultant comparison result signals to the counters  72 . In accordance with the comparison result signals output from the comparators  71 , the counters  72  then count the counter clock signals of a predetermined frequency, so that the pixel signals are subjected to A/D conversion. 
     The column scanning circuit  36  supplies the counters  72  of the column ADC circuit  35  sequentially with signals for outputting the pixel data at predetermined timings. 
     The sense amplifier  37  amplifies the pixel data supplied from the column ADC circuit  35 , and outputs the amplified pixel data to the outside of the imaging device  12 . 
     &lt;Example Configuration of the Imaging Device&gt; 
       FIG. 3  shows an example configuration of the pixel array  31  of the imaging device  12  shown in  FIG. 2 . 
     In this example, the periphery of a normal pixel region  31 A is surrounded by a narrowband pixel region  31 B. 
     The normal pixel region  31 A is used primarily for imaging an object. For example, pixels  51  each including a color filter that is a filter made of a non-metallic material (a non-metallic filter) are disposed in the normal pixel region  31 A. 
     Note that a color filter may be either of an organic material type or of an inorganic material type. For example, organic color filters include dyed/colored filters using a synthetic resin or a natural protein, and dye-containing filters using pigment dyestuff or coloring dyestuff. Further, a material such as TiO2, ZnS, SiN, MgF2, SiO2, or a Low-k material is used for inorganic color filters, for example. Furthermore, a technique such as vapor deposition, sputtering, or chemical vapor deposition (CVD) film formation is used to form inorganic color filters, for example. 
     A color filter transmission band (color) is set for each pixel  51 , and the types and the layout of the colors are selected as appropriate. For example, the color filters include filters of three colors: R (red), G (green), and B (blue), or Y (yellow), M (magenta), and C (cyan). 
     Note that color filters are not necessarily used in the normal pixel region  31 A. In this case, the normal pixel region  31 A is used for capturing monochrome images. 
     The narrowband pixel region  31 B is used primarily for measuring the spectral characteristics of the object. In the narrowband pixel region  31 B, for example, pixels  51  each including a narrowband filter that is an optical filter that transmits narrowband light in a predetermined narrow wavelength band (narrow band) are disposed. For example, a plasmon filter that is a kind of metallic filter using a thin film made of a metal such as aluminum, and uses surface plasmons is used as the narrowband filter. 
     The transmission band of the narrowband filter is set for each pixel  51 . The types (the number of bands) of the transmission band of the narrowband filter are set as appropriate, and may be four or more, for example. 
     Here, a narrow band is a wavelength band that is narrower than the transmission bands of conventional color filters of R (red), G (green), and B (blue), or Y (yellow), M (magenta), and C (cyan) based on the three primary colors or the color-matching functions, for example. 
     A reflected light reduction unit  31 C that reduces light reflected by the sidewalls of the narrowband filters is disposed at the boundary portion between the normal pixel region  31 A and the narrowband pixel region  31 B. The reflected light reduction unit  31 C will be described later in detail. 
     Note that, in a case where the pixels  51  in the normal pixel region  31 A are distinguished from the pixels  51  in the narrowband pixel region  31 B in the description below, the former will be referred to as the normal pixels  51 A, and the latter will be referred to as the narrowband pixels  51 B. Further, in the description below, an image obtained with the normal pixels  51 A in the normal pixel region  31 A will be referred to as a normal image, and an image obtained with the narrowband pixels  51 B in the narrowband pixel region  31 B will be referred to as a multispectral image. 
       FIG. 4  schematically shows an example configuration of a cross-section of the imaging device  12  shown in  FIG. 1 .  FIG. 4  shows a cross-section of the four pixels: a normal pixel  51 A- 1 , a normal pixel  51 A- 2 , a narrowband pixel  51 B- 1 , and a narrowband pixel  51 B- 2  in the vicinity of a boundary portion B 1  between the normal pixel region  31 A and the narrowband pixel region  31 B (a boundary portion B 1  between a normal pixel  51 A and a narrowband pixel  51 B that are adjacent to each other) of the imaging device  12 . 
     Note that, in a case where there is no need to distinguish the normal pixel  51 A- 1  and the normal pixel  51 A- 2  from each other in the description below, the normal pixel  51 A- 1  and the normal pixel  51 A- 2  will be referred to simply as the normal pixels  51 A. In a case where there is no need to distinguish the narrowband pixel  51 B- 1  and the narrowband pixel  51 B- 2  from each other, the narrowband pixel  51 B- 1  and the narrowband pixel  51 B- 2  will be referred to simply as the narrowband pixels  51 B. 
     In each pixel  51 , an on-chip microlens  101 , an interlayer film  102 , a filter layer  103 , an interlayer film  104 , a photoelectric conversion element layer  105 , and a signal wiring layer  106  are stacked in this order from the top. That is, the imaging device  12  is a back-illuminated CMOS image sensor in which the photoelectric conversion element layer  105  is disposed closer to the light incident side than the signal wiring layer  106 . 
     The on-chip microlenses  101  are optical elements for gathering light onto the photoelectric conversion element layer  105  of each pixel  51 . 
     The interlayer film  102  and the interlayer film  104  include a dielectric material such as SiO2. As described later, the dielectric constant of the interlayer film  102  and the interlayer film  104  is preferably as low as possible. 
     In the filter layer  103 , color filters CF are provided for the respective normal pixel  51 A, and narrowband filters NB are provided for the respective narrowband pixels  51 B. 
     Note that, in the filter layer  103 , any color filter CF may not be provided for some or all of the normal pixels  51 A, for example. Also, in the filter layer  103 , any narrowband filter NB may not be provided for some of the narrowband pixels  51 B, for example. 
     The photoelectric conversion element layer  105  includes the photodiode  61  shown in  FIG. 2  (hereinafter, also referred to as the photodiode PD) and the like, for example, receives light that has passed through the filter layer  103 , and converts the received light into electric charges. The photoelectric conversion element layer  105  is also designed such that the pixels  51  are electrically separated from each other by a device separation layer. 
     The signal wiring layer  106  includes wiring lines and the like for reading the electric charges stored in the photoelectric conversion element layer  105 . 
     &lt;Plasmon Filter&gt; 
     Next, a plasmon filter that can be used as a narrowband filter NB is described, with reference to  FIGS. 5, 6, 7, 8, 10, 11A, 11B, 12, 13A, 13B, 14, 15, 16, 17, 18A, and 18B . 
       FIG. 5  shows an example configuration of a plasmon filter  121 A having a hole array structure. 
     The plasmon filter  121 A is formed with a plasmon resonator in which holes  132 A are arranged in a honeycomb fashion in a metallic thin film (hereinafter, referred to as the conductive thin film)  131 A. 
     Each hole  132 A penetrates the conductive thin film  131 A, and functions as a waveguide. Generally, a waveguide has a cutoff frequency and a cutoff wavelength determined by the length of a side, the shape of the diameter, or the like, and characteristically does not allow light of frequencies equal to or lower than that (and wavelengths equal to or longer than that) to pass therethrough. The cutoff wavelength of the holes  132 A depends primarily on the aperture diameter D 1 . The smaller the aperture diameter D 1 , the shorter the cutoff wavelength. Note that the aperture diameter D 1  is set to a smaller value than the wavelength of the light to be transmitted. 
     On the other hand, when light enters the conductive thin film  131 A in which the holes  132 A are arranged at intervals equal to or shorter than the wavelength of the light, light having longer wavelengths than the cutoff wavelength of the holes  132 A passes therethrough. This phenomenon is called an abnormal plasmon transmission phenomenon. This phenomenon occurs when surface plasmons are excited at the boundary between the conductive thin film  131 A and the interlayer film  102  thereon. 
     Referring now to  FIG. 6 , the conditions for an abnormal plasmon transmission phenomenon (surface plasmon resonance) to occur are described. 
       FIG. 6  is a graph showing the dispersion relationship of surface plasmons. In the graph, the abscissa axis indicates angular wave number vector k, and the ordinate axis indicates angular frequency ω. In the graph, ω p  represents the plasma frequency of the conductive thin film  131 A. Also, in the graph, ω sp  represents the surface plasma frequency at the interface between the interlayer film  102  and the conductive thin film  131 A, and is expressed by Equation (1) shown below. 
     
       
         
           
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     In the equation, ε d  represents the dielectric constant of the dielectric material forming the interlayer film  102 . 
     According to Equation (1), the surface plasma frequency W sp  becomes higher as the plasma frequency ω p  becomes higher. The surface plasma frequency ω sp  also becomes higher as the dielectric constant ε d  becomes lower. 
     A line L 1  indicates the light dispersion relationship (the light line), and is expressed by Equation (2) shown below. 
     
       
         
           
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     In the equation, c represents the speed of light. 
     A line L 2  indicates the dispersion relationship of surface plasmons, and is expressed by Equation (3) shown below. 
     
       
         
           
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     In the equation, ε m  represents the dielectric constant of the conductive thin film  131 A. 
     The surface plasmon dispersion relationship indicated by the line L 2  asymptotically approaches the light line indicated by the line L 1  in the range in which the angular wave number vector k is small, and asymptotically approaches the surface plasma frequency ω sp  as the angular wave number vector k becomes greater. 
     When Equation (4) shown below is satisfied, an abnormal plasmon transmission phenomenon then occurs. 
     
       
         
           
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     In the equation, λ represents the wavelength of the incident light. Further, θ represents the incident angle of the incident light. G x  and G y  are expressed by Equation (5) shown below.
 
| G   x   |=|G   y =2 π/a   0   (5)
 
     In the equation, a 0  represents the lattice constant of the hole array structure formed with the holes  132 A of the conductive thin film  131 A. 
     The left-hand side of Equation (4) indicates an angular wave number vector of the surface plasmons, and the right-hand side indicates the angular wave number vector of the hole array intervals in the conductive thin film  131 A. Therefore, when the angular wave number vector of the surface plasmons is equal to the angular wave number vector of the hole array intervals in the conductive thin film  131 A, an abnormal plasmon transmission phenomenon occurs. Further, the value of A at this point of time is the plasmon resonant wavelength (the transmission wavelength of the plasmon filter  121 A). 
     Note that the angular wave number vector of the surface plasmons on the left-hand side of Equation (4) is determined by the dielectric constant ε m  of the conductive thin film  131 A and the dielectric constant ε d  of the interlayer film  102 . Meanwhile, the angular wave number vector of the hole array intervals on the right-hand side is determined by the incident angle θ of light and the pitch (hole pitch) P 1  between adjacent holes  132 A of the conductive thin film  131 A. Accordingly, the resonant wavelength and the resonant frequency of the plasmons are determined by the dielectric constant ε m  of the conductive thin film  131 A, the dielectric constant ε d  of the interlayer film  102 , the incident angle θ of light, and the hole pitch P 1 . Note that, in a case where the incident angle of light is 0°, the resonant wavelength and the resonant frequency of the plasmons are determined by the dielectric constant ε m  of the conductive thin film  131 A, the dielectric constant ε d  of the interlayer film  102 , and the hole pitch P 1 . 
     Accordingly, the transmission band of the plasmon filter  121 A (the plasmon resonant wavelength) varies depending on the material and the thickness of the conductive thin film  131 A, the material and the thickness of the interlayer film  102 , the pattern intervals of the hole array (the aperture diameter D 1  and the hole pitch P 1  of the holes  132 A, for example), and the like. In particular, in a case the materials and the thicknesses of the conductive thin film  131 A and the interlayer film  102  have been determined, the transmission band of the plasmon filter  121 A varies depending on the pattern intervals of the hole array, or more particularly, on the hole pitch P 1 . That is, as the hole pitch P 1  becomes narrower, the transmission band of the plasmon filter  121 A shifts to the shorter wavelength side. As the hole pitch P 1  becomes wider, the transmission band of the plasmon filter  121 A shifts to the longer wavelength side. 
       FIG. 7  is a graph showing an example of the spectral characteristics of the plasmon filter  121 A in a case where the hole pitch P 1  is varied. In the graph, the abscissa axis indicates wavelength (unit: nm), and the ordinate axis indicates sensitivity (unit being selected as appropriate). A line L 11  indicates the spectral characteristics in a case where the hole pitch P 1  is set at 250 nm, a line L 12  indicates the spectral characteristics in a case where the hole pitch P 1  is set at 325 nm, and a line L 13  indicates the spectral characteristics in a case where the hole pitch P 1  is set at 500 nm. 
     In the case where the hole pitch P 1  is set at 250 nm, the plasmon filter  121 A primarily transmits light in the blue-color wavelength band. In the case where the hole pitch P 1  is set at 325 nm, the plasmon filter  121 A primarily transmits light in the green-color wavelength band. In the case where the hole pitch P 1  is set at 500 nm, the plasmon filter  121 A primarily transmits light in the red-color wavelength band. However, in the case where the hole pitch P 1  is set at 500 nm, the plasmon filter  121 A also transmits a large amount of light in lower wavelength bands than the red color, with the waveguide mode described later. 
       FIG. 8  is a graph showing another example of the spectral characteristics of the plasmon filter  121 A in a case where the hole pitch P 1  is varied. In the graph, the abscissa axis indicates wavelength (unit: nm), and the ordinate axis indicates sensitivity (unit being selected as appropriate). This example is an example of 16 kinds of spectral characteristics of the plasmon filter  121 A in a case where the hole pitch P 1  is varied from 250 nm to 625 nm, at intervals of 25 nm. 
     Note that the transmittance of the plasmon filter  121 A is determined primarily by the aperture diameter D 1  of the holes  132 A. Where the aperture diameter D 1  is greater, the transmittance is greater, but color mixing is more likely to occur. It is normally preferable to set the aperture diameter D 1  so that the aperture ratio becomes 50% to 60% of the hole pitch P 1 . 
     Further, each hole  132 A of the plasmon filter  121 A functions as a waveguide, as described above. Therefore, depending on the pattern of the hole array of the plasmon filter  121 A, not only the wavelength component to be transmitted by surface plasmon resonance (the wavelength component in the plasmon mode), but also the wavelength component to pass through the holes  132 A (waveguides) (the wavelength component in the waveguide mode) might become large in the spectral characteristics. 
       FIG. 9  shows the spectral characteristics of the plasmon filter  121 A in a case where the hole pitch P 1  is set at 500 nm, like the spectral characteristics represented by the line L 13  in  FIG. 7 . In this example, the longer wavelength side than the cutoff wavelength in the neighborhood of 630 nm is the wavelength component in the plasmon mode, and the shorter wavelength side than the cutoff wavelength is the wavelength component in the waveguide mode. 
     As described above, the cutoff wavelength depends primarily on the aperture diameter D 1  of the holes  132 A. The shorter the cutoff wavelength, the smaller the aperture diameter D 1 . Further, as the difference between the cutoff wavelength and the peak wavelength in the plasmon mode is made larger, the wavelength resolution characteristics of the plasmon filter  121 A improve. 
     Also, as described above, the higher the plasma frequency ω p  of the conductive thin film  131 A, the higher the surface plasma frequency ω sp  of the conductive thin film  131 A. Also, the lower the dielectric constant ε d  of the interlayer film  102 , the higher the surface plasma frequency ω sp . Further, as the surface plasma frequency ω sp  becomes higher, a higher plasmon resonant frequency can be set, and the transmission band of the plasmon filter  121 A (the plasmon resonant wavelength) can be set in a shorter wavelength band. 
     Accordingly, where a metal having a lower plasma frequency ω p  is used for the conductive thin film  131 A, the transmission band of the plasmon filter  121 A can be set in a shorter wavelength band. For example, aluminum, silver, gold, or the like is preferable. However, in a case where a long wavelength band such as the wavelength band of infrared light is set as the transmission band, copper or the like can be used. 
     Also, where a dielectric material having a lower dielectric constant ε d  is used for the interlayer film  102 , the transmission band of the plasmon filter  121 A can be set in a shorter-wavelength band. For example, SiO2, a Low-k material, or the like is preferable. 
       FIG. 10  is a graph showing the propagation characteristics of the surface plasmons at the interface between the conductive thin film  131 A and the interlayer film  102  in a case where aluminum is used for the conductive thin film  131 A, and SiO2 is used for the interlayer film  102 . In the graph, the abscissa axis indicates the wavelength of light (unit: nm), and the ordinate axis indicates the propagation distance (unit: μm). Further, a line L 21  indicates the propagation characteristics in the interfacial direction, a line L 22  indicates the propagation characteristics in the depth direction of the interlayer film  102  (a direction perpendicular to the interface), and a line L 23  indicates the depth direction of the conductive thin film  131 A (a direction perpendicular to the interface). 
     The propagation distance Λ SPP (λ) of the surface plasmons in the depth direction is expressed by Equation (6) shown below. 
     
       
         
           
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     In the equation, k SPP  represents the absorption coefficient of a substance through which the surface plasmons propagate. In the equation, ε m (λ) represents the dielectric constant of the conductive thin film  131 A with respect to light having the wavelength λ. Further, ε d (λ) represents the dielectric constant of the interlayer film  102  with respect to light having the wavelength λ. 
     Accordingly, the surface plasmons for light having a wavelength of 400 nm propagate from the surface of the interlayer film  102  including SiO2 to a depth of about 100 nm, as shown in  FIG. 10 . Thus, as the thickness of the interlayer film  102  is set at 100 nm or greater, the substance stacked on the surface on the opposite side of the interlayer film  102  from the conductive thin film  131 A is prevented from affecting the surface plasmons at the interface between the interlayer film  102  and the conductive thin film  131 A. 
     Also, the surface plasmons for light having a wavelength of 400 nm propagate from the surface of the conductive thin film  131 A including aluminum to a depth of about 10 nm. Thus, as the thickness of the conductive thin film  131 A is set at 10 nm or greater, the interlayer film  104  is prevented from affecting the surface plasmons at the interface between the interlayer film  102  and the conductive thin film  131 A. 
     &lt;Other Examples of Plasmon Filters&gt; 
     Next, other examples of plasmon filters are described, with reference to  FIGS. 11, 11B, 12, 13A, 13B, 14, 15, 16, 17, 18A, and 18B . 
     A plasmon filter  121 B in  FIG. 11A  is formed with a plasmon resonator in which holes  132 B are formed in an orthogonal matrix in a conductive thin film  131 B. In the plasmon filter  121 B, the transmission band varies depending on a pitch P 2  between adjacent holes  132 B, for example. 
     Meanwhile, in a plasmon resonator, not all the holes need to penetrate the conductive thin film. Even if some holes are formed with non-through holes that do not penetrate the conductive thin film, the plasmon resonator functions as a filter. 
     For example,  FIG. 11B  shows a plan view and a cross-sectional view (taken along the line A-A′ defined in the plan view) of a plasmon filter  121 C formed with a plasmon resonator in which holes  132 C formed with through holes and holes  132 C′ formed with non-through holes are arranged in a honeycomb fashion in a conductive thin film  131 C. That is, the holes  132 C formed with through holes and holes  132 C′ formed with non-through holes are arranged at intervals in the plasmon filter  121 C. 
     Further, a single-layer plasmon resonator is normally used as a plasmon filter, but a plasmon filter may be formed with a two-layer plasmon resonator, for example. 
     For example, a plasmon filter  121 D shown in  FIG. 12  includes two layers: a plasmon filter  121 D- 1  and a plasmon filter  121 D- 2 . Like the plasmon resonator forming the plasmon filter  121 A shown in  FIG. 5 , the plasmon filter  121 D- 1  and the plasmon filter  121 D- 2  each have a structure in which holes are arranged in a honeycomb fashion. 
     Also, the distance D 2  between the plasmon filter  121 D- 1  and the plasmon filter  121 D- 2  is preferably about ¼ of the peak wavelength of the transmission band. Further, with the degree of freedom of design being taken into account, the distance D 2  is preferably equal to or shorter than ½ of the peak wavelength of the transmission band. 
     Note that, like the plasmon filter  121 D, the holes may be arranged in the same pattern in the plasmon filter  121 D- 1  and the plasmon filter  121 D- 2 , but the holes may be arranged in patterns similar to each other in a two-layer plasmon resonator structure, for example. Also, in a two-layer plasmon resonator structure, holes and dots may be arranged in such patterns that the hole array structure and the dot array structure (described later) are reversed structures. Further, the plasmon filter  121 D has a two-layer structure, but a three or more layers may be adopted. 
     Also, in the above description, example configurations of plasmon filters using plasmon resonators each having a hole array structure have been described. However, a plasmon resonator having a dot array structure may be adopted as a plasmon filter. 
     Referring now to  FIGS. 13A and 13B , a plasmon filter having a dot array structure is described. 
     A plasmon filter  121 A′ in  FIG. 13A  is formed with a negative-positive reversed structure of the plasmon resonator of the plasmon filter  121 A in  FIG. 5 , or is formed with a plasmon resonator in which dots  133 A are formed in a honeycomb fashion in a dielectric layer  134 A. Spaces between the respective dots  133 A are filled with the dielectric layer  134 A. 
     The plasmon filter  121 A′ absorbs light in a predetermined wavelength band, and therefore, is used as a complementary color filter. The wavelength band of light to be absorbed by the plasmon filter  121 A′ (this wavelength band will be hereinafter referred to as the absorption band) varies depending on the pitch P 3  between adjacent dots  133 A (this pitch will be hereinafter referred to as the dot pitch) and the like. Further, the diameter D 3  of the dots  133 A is adjusted in accordance with the dot pitch P 3 . 
     A plasmon filter  121 B′ in  FIG. 13B  is formed with a negative-positive reversed structure of the plasmon resonator of the plasmon filter  121 B of  FIG. 11A , or is formed with a plasmon resonator structure in which dots  133 B are formed in an orthogonal matrix in a dielectric layer  134 B. Spaces between the respective dots  133 B are filled with the dielectric layer  134 B. 
     The absorption band of the plasmon filter  121 B′ varies depending on a dot pitch P 4  between adjacent dots  133 B or the like. Further, the diameter D 3  of the dots  133 B is adjusted in accordance with the dot pitch P 4 . 
       FIG. 14  is a graph showing an example of the spectral characteristics in a case where the dot pitch P 3  of the plasmon filter  121 A′ in  FIG. 13A  is varied. In the graph, the abscissa axis indicates wavelength (unit: nm), and the ordinate axis indicates transmittance. A line L 31  indicates the spectral characteristics in a case where the dot pitch P 3  is set at 300 nm, a line L 32  indicates the spectral characteristics in a case where the dot pitch P 3  is set at 400 nm, and a line L 33  indicates the spectral characteristics in a case where the dot pitch P 3  is set at 500 nm. 
     As shown in this drawing, as the dot pitch P 3  becomes narrower, the absorption band of the plasmon filter  121 A′ shifts to the shorter wavelength side. As the dot pitch P 3  becomes wider, the absorption band of the plasmon filter  121 A′ shifts to the longer wavelength side. 
     Further, in a plasmon filter having an array structure, rectangular squares can be used in place of circular dots. 
       FIG. 15  shows a plasmon filter  121 E having a square array structure using rectangular squares  135 . That is, the plasmon filter  121 E has the rectangular squares  135  in place of the circular dots  133 B of the plasmon filter  121 B′ in  FIG. 13B . Spaces between the respective squares  135  are filled with a dielectric layer  136 . 
     Likewise, the circular dots  133 A of the plasmon filter  121 A′ in  FIG. 13A  can be replaced with rectangular squares. 
     Note that, in any of plasmon filters having a hole array structure, a dot array structure, or a square array structure, it is possible to adjust the transmission band or the absorption band simply by adjusting the pitch in the planar direction of the holes, the dots, or the squares. Accordingly, the pitch of the holes, the dots, or the squares is simply adjusted in the lithography process, for example, so that the transmission band or the absorption band can be set individually for each pixel, and the filters are turned into multiple colors in a fewer number of steps. 
     Further, the thickness of a plasmon filter is about 100 to 500 nm, which is almost similar to that of an organic color filter, and its affinity to the process is high. 
     Furthermore, a plasmon filter  151  using guided-mode resonant (GMR) shown in  FIG. 16  can be used as a narrowband filter NB. 
     In the plasmon filter  151 , a conductor layer  161 , a SiO2 film  162 , a SiN film  163 , and a SiO2 substrate  164  are stacked in this order from the top. The conductor layer  161  is included in the filter layer  103  in  FIG. 4 , for example, and the SiO2 film  162 , the SiN film  163 , and the SiO2 substrate  164  are included in the interlayer film  104  in  FIG. 4 , for example. 
     In the conductor layer  161 , rectangular conductive thin films  161 A including aluminum, for example, are arranged at a predetermined pitch P 5 , so that the long sides of the conductive thin films  161 A are adjacent to one another. The transmission band of the plasmon filter  151  then varies depending on the pitch P 5  or the like. 
       FIG. 17  is a graph showing an example of the spectral characteristics of the plasmon filter  151  in a case where the pitch P 5  is varied. In the graph, the abscissa axis indicates wavelength (unit: nm), and the ordinate axis indicates transmittance. This example shows an example of the spectral characteristics in a case where the pitch P 5  is varied from 280 nm to 480 nm in six kinds at intervals of 40 nm, and the width of the slits between the adjacent conductive thin films  161 A is set at ¼ of the pitch P 5 . Further, the waveform having the shortest peak wavelength in the transmission band indicates the spectral characteristics in a case where the pitch P 5  is set at 280 nm. As the pitch P 5  becomes wider, the peak wavelength becomes longer. That is, as the pitch P 5  becomes narrower, the transmission band of the plasmon filter  151  shifts to the shorter wavelength side. As the pitch P 5  becomes wider, the transmission band of the plasmon filter  151  shifts to the longer wavelength side. 
     Like plasmon filters having the hole array structure and the dot array structure described above, this plasmon filter  151  using GMR also has a high affinity to organic color filters. 
     Further, a plasmon filter  171  using a bull&#39;s-eye structure shown in  FIGS. 18A and 18B  can be used as a narrowband filter NB. A bull&#39;s-eye structure has this name, because of its resemblance to a dart target or a bow and arrow target. 
     As shown in  FIG. 18A , the plasmon filter  171  having a bull&#39;s-eye structure has a through hole  181  at its center, and includes a plurality of protruding portions  182  formed concentrically around the through hole  181 . That is, the plasmon filter  171  having a bull&#39;s-eye structure has a shape to which a metallic diffraction grating structure that causes plasmon resonance is applied. 
     The plasmon filter  171  having a bull&#39;s-eye structure has characteristics similar to those of the plasmon filter  151  using GMR. That is, in a case where the pitch between the protruding portions  182  is a pitch P 6 , the plasmon filter  171  has the following characteristics: the transmission band shifts to the shorter wavelength side as the pitch P 6  becomes narrower, and the transmission band shifts to the longer wavelength side as the pitch P 6  becomes wider. 
     2. First Embodiment of the Present Technology 
     Next, a first embodiment of the present technology is described, with reference to  FIGS. 19, 20A, 20B, 21, 22A, 22B, 23, 24A, 24B, 25, 26, 27, 28 , and  29 . 
       FIG. 19  schematically shows an example configuration of an imaging device  12 A including a filter layer  103 A that is the first embodiment of the filter layer  103  in  FIG. 4 .  FIG. 19  shows a cross-section of the ten pixels: normal pixels  51 A- 1  through  51 A- 5 , and narrowband pixels  51 B- 1  through  51 B- 5  in the vicinity of the boundary portion B 1  between the normal pixel region  31 A and the narrowband pixel region  31 B of the imaging device  12 A. 
     In the filter layer  103 A, the color filters CF in the normal pixel region  31 A are disposed in a different layer from that of the narrowband filters NB in the narrowband pixel region  31 B. Specifically, the color filters CF are disposed at higher locations than the narrowband filters NB, or are disposed closer to the light incident surface of the imaging device  12 A. 
     Although not shown in the drawing, a reflected light reduction unit  31 C is disposed in the interlayer film  102  or the filter layer  103 A, as described later with reference to  FIG. 20B . 
       FIG. 20A  is an enlarged view of the region around the filter layer  103 A in the vicinity of the boundary portion B 1  of the imaging device  12 A shown in  FIG. 19 , and schematically shows the condition of incident light in a case where the reflected light reduction unit  31 C is not adopted. 
     As shown in this drawing, part of the incident light that has passed through the color filters CF enters the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and is irregularly reflected by the sidewall SW 1 . The light reflected irregularly by the sidewall SW 1  then enters the photodiodes PD of the normal pixels  51 A in the vicinity of the boundary portion B 1 . As a result, noise due to the reflected light is generated in the normal pixels  51 A in the vicinity of the boundary portion B 1 , and the characteristics of the imaging device  12 A (particularly, the normal pixels  51 A in the vicinity of the boundary portion B 1 ) are degraded. 
     On the other hand, a black filter  201 A that is a light absorber is provided as the reflected light reduction unit  31 C, for example, as shown in  FIG. 20B . 
     The black filter  201 A is formed with a black resist, carbon black, or the like, for example. The black filter  201 A is disposed at a higher location than the color filters CF and the narrowband filters NB (or is disposed closer to the light incident surface of the imaging device  12 A than the color filters CF and the narrowband filters NB) at the boundary portion B 1 . The black filter  201 A also overlaps at least part of the normal pixel  51 A- 1  and the narrowband pixel  51 B- 1  adjacent to the boundary portion B 1 , and covers at least part of the light incident surface of the color filter CF of the normal pixel  51 A- 1  and the light incident surface of the narrowband filter NB of the narrowband pixel  51 B- 1 . 
     This black filter  201 A absorbs incident light traveling toward the sidewall SW 1 , and reduces entrance of the incident light to the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Like  FIG. 19 ,  FIG. 21  schematically shows an example configuration of an imaging device  12 B including a filter layer  103 B that is a second embodiment of the filter layer  103  in  FIG. 4 . 
     In the filter layer  103 B, the color filters CF in the normal pixel region  31 A are disposed in the same layer as the narrowband filters NB in the narrowband pixel region  31 B. 
     Although not shown in the drawing, a reflected light reduction unit  31 C is disposed in the interlayer film  102  or the filter layer  103 B, as described later with reference to  FIG. 22B . 
     Like  FIG. 20A ,  FIG. 22A  schematically shows the condition of incident light in a case where the reflected light reduction unit  31 C is not adopted. 
     As shown in this drawing, part of the incident light that has entered the color filters CF enters the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and is irregularly reflected by the sidewall SW 1 . The light reflected irregularly by the sidewall SW 1  then enters the photodiodes PD of the normal pixels  51 A in the vicinity of the boundary portion B 1 . As a result, noise due to the reflected light is generated in the normal pixels  51 A in the vicinity of the boundary portion B 1 , and the characteristics of the imaging device  12 B (particularly, the normal pixels  51 A in the vicinity of the boundary portion B 1 ) are degraded. 
     On the other hand, as shown in  FIG. 22B , a black filter  201 B similar to the black filter  201 A in  FIG. 20B  is provided as the reflected light reduction unit  31 C. 
     The black filter  201 B is disposed at a higher location than the color filters CF and the narrowband filters NB (or is disposed closer to the light incident surface of the imaging device  12 B than the color filters CF and the narrowband filters NB) at the boundary portion B 1 . The black filter  201 B also overlaps at least part of the normal pixel  51 A- 1  and the narrowband pixel  51 B- 1  adjacent to the boundary portion B 1 , and covers at least part of the light incident surface of the color filter CF of the normal pixel  51 A- 1  and the light incident surface of the narrowband filter NB of the narrowband pixel  51 B- 1 . 
     This black filter  201 B absorbs incident light traveling toward the sidewall SW 1 , and reduces entrance of the incident light to the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Like  FIG. 19  and  FIG. 21 ,  FIG. 23  schematically shows an example configuration of an imaging device  12 C including a filter layer  103 C that is a third embodiment of the filter layer  103  in  FIG. 4 . 
     In the filter layer  103 C, while the narrowband filters NB are disposed in the narrowband pixel region  31 B, any color filter CF is not provided in the normal pixel region  31 A. 
     Although not shown in the drawing, a reflected light reduction unit  31 C is disposed in the interlayer film  102  or the filter layer  103 C, as described later with reference to  FIG. 24B . 
     Like  FIGS. 20A  and  FIG. 22A ,  FIG. 24A  schematically shows the condition of incident light in a case where the reflected light reduction unit  31 C is not adopted. 
     As shown in this drawing, light that has entered the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1  is irregularly reflected by the sidewall SW 1 . The light reflected irregularly by the sidewall SW 1  then enters the photodiodes PD of the normal pixels  51 A in the normal pixel region  31 A in the vicinity of the boundary portion B 1 . As a result, noise due to the reflected light is generated in the normal pixels  51 A in the vicinity of the boundary portion, and the characteristics of the imaging device  12 C (particularly, the normal pixels  51 A in the vicinity of the boundary portion B 1 ) are degraded. 
     On the other hand, as shown in  FIG. 24B , a black filter  201 C similar to the black filter  201 A in  FIG. 20B  and the black filter  201 B in  FIG. 22B  is provided as the reflected light reduction unit  31 C. 
     The black filter  201 C is disposed at a higher location than the narrowband filters NB (or is disposed closer to the light incident surface of the imaging device  12 C than the narrowband filters NB) at the boundary portion B 1 . The black filter  201 C also overlaps at least part of the normal pixel  51 A- 1  and the narrowband pixel  51 B- 1  adjacent to the boundary portion B 1 , and covers at least part of the light incident surface of the color filter CF of the normal pixel  51 A- 1  and the light incident surface of the narrowband filter NB of the narrowband pixel  51 B- 1 . 
     This black filter  201 C absorbs incident light traveling toward the sidewall SW 1 , and reduces entrance of the incident light to the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Note that the width of the black filters  201 A through  201 C in a direction perpendicular to the boundary portion B 1  can be changed as appropriate. However, if the width of the black filters  201 A through  201 C is too great, the invalid pixel region that no incident light enters becomes larger. On the other hand, if the width of the black filters  201 A through  201 C is too small, the reflected light reduction effect becomes smaller. 
     Therefore, the width of the black filters  201 A through  201 C is preferably adjusted as appropriate in accordance with the reflectance of the metallic thin films of the narrowband filters NB or the like. For example, the width of the black filters  201 A through  201 C is preferably set within a range of two to four pixels around the boundary portion B 1 . 
     For example,  FIG. 25  shows an example in which the black filter  201 A covers the four pixels  51  of two normal pixels  51 A and two narrowband pixels  51 B around the boundary portion B 1 . 
     Referring now to  FIG. 26 , the conditions for the amount of protrusion L 1  of the black filter  201 A from the boundary portion B 1  into the normal pixel region  31 A (the width of the black filter  201 A in the normal pixel region  31 A) are described. 
     Note that a distance d 1  indicates the distance between the bottom surface of the black filter  201 A on the opposite side from the light incident surface and the bottom surface of the narrowband filter NB on the opposite side from the light incident surface. An angle θ 1  indicates the angle between the sidewall SW 1  and the plane extending through the side of the bottom surface of the black filter  201 A on the side of the normal pixel region  31 A and the side of the bottom surface of the sidewall SW 1 . 
     Further, where the assumed value of the maximum incident angle of incident light on the sidewall SW 1  is represented by θmax, the amount of protrusion L 1  is preferably set so that θ 1 ≥θmax is satisfied. That is, the amount of protrusion L 1  is preferably set so as to satisfy Equation (7) shown below.
 
 L 1≥ d ×tan(θ max)  (7)
 
     Note that the maximum incident angle θmax is expressed by Equation (8) shown below.
 
θ max=( CRA+f -number maximum incident angle of light)×α  (8)
 
     CRA represents the principal ray angle of light incident on the normal pixel  51 A- 1  adjacent to the boundary portion B 1 . The f-number maximum incident angle of light is the maximum value of the angles of respective light rays incident on the normal pixel  51 A- 1  to the principal ray in a case where the f-number of the optical system  11  is the minimum. In the equation, α is a coefficient equal to or greater than 1, and is a coefficient obtained by adding 1 to a margin that is set with the production variations of the optical systems  11 , the on-chip microlenses  101 , and the like taken into account. 
     Note that CRA in Equation (8) varies with the image height, and therefore, the maximum incident angle θmax also varies with the image height. In view of this, a maximum incident angle θmax may be determined for each image height, and the amount of protrusion L 1  may be varied with the image height on the basis of the determined maximum incident angle θmax, for example. Alternatively, the maximum incident angle θmax may be fixed at the minimum value in the imaging device  12 , for example, and the amount of protrusion L 1  may be fixed, regardless of the image height. 
     For the black filter  201 B in  FIG. 22B  and the black filter  201 C in  FIG. 24B , the conditions for the amount of protrusion L 1  are determined by a similar calculation process. 
     Alternatively, the black filter  201 A may cover only the normal pixel region  31 A, as shown in  FIG. 27 , for example. 
     Further, as shown in  FIG. 28 , the black filter  201 A may cover only the narrowband pixel region  31 B, for example. 
     The contents of  FIGS. 27 and 28  can be similarly applied to the black filter  201 B in  FIG. 22B  and the black filter  201 C in  FIG. 24B . 
     Further, as shown in  FIG. 29 , an optical filter  211  in which two kinds of color filters, which are a red filter  211 R and a blue filter  211 B, are stacked may be used in place of the black filter  201 A, for example. 
     The red filter  211 R does not transmit light having a wavelength near blue, and the blue filter  21 B does not transmit light having a wavelength near red. Accordingly, as the red filter  211 R and the blue filter  211 B are stacked, an effect equal to that of the black filter  201 A can be expected. 
     Note that the optical filter  211  can also be used in place of the black filter  201 B in  FIG. 22B  and the black filter  201 C in  FIG. 24B . 
     3. Second Embodiment of the Present Technology 
     Next, a second embodiment of the present technology is described, with reference to  FIGS. 30 through 32 . 
       FIG. 30  shows the second embodiment of the reflected light reduction unit  31 C in the imaging device  12 A shown in  FIG. 19 . The embodiment in  FIG. 30  differs from the embodiment in  FIG. 20B  in that a black filter  221 A is adopted in place of the black filter  201 A. 
     The black filter  221 A covers the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and absorbs light incident on the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 31  shows the second embodiment of the reflected light reduction unit  31 C in the imaging device  12 B shown in  FIG. 21 . The embodiment in  FIG. 31  differs from the embodiment in  FIG. 22B  in that a black filter  221 B is adopted in place of the black filter  201 B. 
     The black filter  221 B covers the sidewall SW 1  of the narrowband filter NB between the color filter CF of the normal pixel  51 A- 1  and the narrowband filter NB of the narrowband pixel  51 B- 1  adjacent to the boundary portion B 1 , and absorbs light incident on the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 32  shows the second embodiment of the reflected light reduction unit  31 C in the imaging device  12 C shown in  FIG. 23 . The embodiment in  FIG. 32  differs from the embodiment in  FIG. 24B  in that a black filter  221 C is adopted in place of the black filter  201 C. 
     The black filter  221 C covers the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and absorbs light incident on the sidewall SW 1 . As a result, the light reflected by the sidewall SW 1  is reduced, and thus, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Note that an optical filter in which a red filter and a blue filter are stacked as in the optical filter  211  in  FIG. 29  may be used in place of the black filters  221 A through  221 C in  FIGS. 30 through 32 . 
     Further, a black filter, or a light absorption filter formed with an optical filter in which a red filter and a blue filter are stacked does not need to cover the entire sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and may cover only part of the sidewall SW 1 . 
     Alternatively, a light absorption filter may cover not only the sidewall SW 1  of the narrowband filter NB, but also the incident surface and/or the bottom surface of the narrowband filter NB. In this case, the light absorption filter may cover part of the incident surface and/or the bottom surface of the narrowband filter NB, or may cover the entire surface within a range of one to several pixels. 
     4. Third Embodiment of the Present Technology 
     Next, a third embodiment of the present technology is described, with reference to  FIGS. 33 through 35 . 
       FIG. 33  shows the third embodiment of the reflected light reduction unit  31 C in the imaging device  12 A shown in  FIG. 19 . The embodiment in  FIG. 33  differs from the embodiment in  FIG. 30  in that the black filter  221 A is replaced with a low-reflection film  231 A. 
     Like the black filter  221 A, the low-reflection film  231 A covers the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 . The low-reflection film  231 A is formed with a material having a lower reflectance than at least the metal forming the narrowband filters NB, such as titanium nitride, tungsten, or titanium, for example. 
     With this arrangement, reflection of light incident on the sidewall SW 1  is reduced by the low-reflection film  231 A. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 34  shows the third embodiment of the reflected light reduction unit  31 C in the imaging device  12 B shown in  FIG. 21 . The embodiment in  FIG. 34  differs from the embodiment in  FIG. 31  in that a low-reflection film  231 B is adopted in place of the black filter  221 B. 
     Like the black filter  221 B, the low-reflection film  231 B covers the sidewall SW 1  of the narrowband filter NB between the color filter CF of the normal pixel  51 A- 1  and the narrowband filter NB of the narrowband pixel  51 B- 1  adjacent to the boundary portion B 1 . With this arrangement, reflection of light incident on the sidewall SW 1  is reduced by the low-reflection film  231 B. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 35  shows the third embodiment of the reflected light reduction unit  31 C in the imaging device  12 C shown in  FIG. 23 . The embodiment in  FIG. 35  differs from the embodiment in  FIG. 32  in that a low-reflection film  231 C is adopted in place of the black filter  221 C. 
     Like the black filter  221 C, the low-reflection film  231 C covers the sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 . With this arrangement, reflection of light incident on the sidewall SW 1  is reduced by the low-reflection film  231 C. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Note that the low-reflection films  231 A through  231 C do not need to cover the entire sidewall SW 1  of the narrowband filter NB at the boundary portion B 1 , and may cover only part of the sidewall SW 1 . 
     Alternatively, the low-reflection films  231 A through  231 C may cover not only the sidewall SW 1  of the narrowband filter NB, but also the incident surface and/or the bottom surface of the narrowband filter NB. In this case, the low-reflection films  231 A through  231 C may cover part of the incident surface and/or the bottom surface of the narrowband filter NB, or may cover the entire surface within a range of one to several pixels. 
     5. Fourth Embodiment of the Present Technology 
     Next, a fourth embodiment of the present technology is described, with reference to  FIGS. 36 through 39 . 
       FIG. 36  shows the fourth embodiment of the reflected light reduction unit  31 C in the imaging device  12 A shown in  FIG. 19 . 
     In this embodiment, the sidewall SW 2  of the narrowband filter NB at the boundary portion B 1  is inclined with respect to the boundary portion B 1 . The sidewall SW 2  is inclined so as to move away from the boundary portion B 1  toward the narrowband pixel region  31 B (the narrowband pixel  51 B- 1 ) as the distance from the light incident surface of the narrowband filter NB becomes longer. 
     With this arrangement, light directly incident on the sidewall SW 2  decreases, and reflection of the incident light by the sidewall SW 2  is reduced. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 37  shows the fourth embodiment of the reflected light reduction unit  31 C in the imaging device  12 B shown in  FIG. 21 . 
     In this embodiment, the sidewall SW 2  of the narrowband filter NB at the boundary portion B 1  is inclined with respect to the boundary portion B 1 , as in the embodiment shown in  FIG. 36 . With this arrangement, light directly incident on the sidewall SW 2  decreases, and reflection of the incident light by the sidewall SW 2  is reduced. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
       FIG. 38  shows the fourth embodiment of the reflected light reduction unit  31 C in the imaging device  12 C shown in  FIG. 23 . 
     In this embodiment, the sidewall SW 2  of the narrowband filter NB at the boundary portion B 1  is inclined with respect to the boundary portion B 1 , as in the embodiments shown in  FIGS. 36 and 37 . With this arrangement, light directly incident on the sidewall SW 2  decreases, and reflection of the incident light by the sidewall SW 2  is reduced. As a result, entrance of the reflected light to the photodiodes PD in the normal pixel region  31 A and degradation of the characteristics of the normal pixels  51 A are reduced. 
     Referring now to  FIG. 39 , the conditions for the inclination angle θ 2  of the sidewall SW 2  with respect to the light incident surface of the narrowband filter NB are described. 
     The inclination angle θ 2  is preferably set so as to satisfy Equation (9) shown below.
 
θ2≤90°−θ max  (9)
 
     Note that the maximum incident angle θmax is determined according to Equation (8) shown above. 
     Where the thickness of the narrowband filter NB is represented by d 2 , and the length of the sidewall SW 2  (an inclined surface) in the depth direction is represented by L 2 , Equation (10) shown below is satisfied.
 
tan θ2= d 2/ L 2  (10)
 
     According to Equations (9) and (10), the length L 2  of the sidewall SW 2  in the depth direction is preferably set so as to satisfy Equation (11) shown below.
 
 L 2 ≥d 2/tan(90°−θ max)  (11)
 
     Note that the maximum incident angle θmax in Equation (8) varies depending on the image height, as described above. In view of this, a maximum incident angle θmax may be determined for each image height, and the length L 2  may be varied with the image height on the basis of the determined maximum incident angle θmax, for example. Alternatively, the maximum incident angle θmax may be fixed at the minimum value in the imaging device  12 C, for example, and the length L 2  may be fixed, regardless of the image height. 
     6. Example Positions of the Reflected Light Reduction Unit  31 C in the Pixel Array  31   
     Next, example positions of the reflected light reduction unit  31 C in the pixel array  31  are described with reference to  FIGS. 40A, 40B, 40C, 40D, 41A, 41B, 41C, 41D, 42A, 42B, 42C, 42D, 43A, 43B, 43C, 43D, 44A, 44B, 44C, 44D, 45A ,  45 B,  45 C,  45 D,  46 A,  46 B,  46 C,  46 D,  47 A,  47 B,  47 C,  47 D,  48 A,  48 B,  48 C,  48 D,  49 A,  49 B,  49 C,  50 A,  50 B, and  50 C. 
       FIGS. 40A, 40B, 40C, 40D, 41A, 41B, 41C, 41D, 42A, 42B, 42C, 42D, 43A, 43B, 43C, and 43D  show examples in which part of an invalid pixel region  31 D around the normal pixel region  31 A (the effective pixel region) of the pixel array  31  is replaced with the narrowband pixel region  31 B. Note that optical black pixels are disposed in the invalid pixel region  31 D in some cases. 
     In each example shown in  FIGS. 40A, 40B, 40C, and 40D , three of the four portions (the upper, lower, right, and left portions) of the invalid pixel region  31 D around the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portions between the narrowband pixel region  31 B, and the normal pixel region  31 A and the invalid pixel region  31 D. On the other hand, the reflected light reduction unit  31 C is not formed at the boundary portion between the normal pixel region  31 A and the invalid pixel region  31 D. 
     In each example shown in  FIGS. 41A, 41B, 41C, and 41D , two of the four portions, which are the upper, lower, right, and left portions, of the invalid pixel region  31 D around the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portions between the narrowband pixel region  31 B, and the normal pixel region  31 A and the invalid pixel region  31 D. On the other hand, the reflected light reduction unit  31 C is not formed at the boundary portion between the normal pixel region  31 A and the invalid pixel region  31 D. 
     In each example shown in  FIGS. 42A, 42B, 42C, and 42D , one of the four portions, which are the upper, lower, right, and left portions, of the invalid pixel region  31 D around the normal pixel region  31 A is replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portions between the narrowband pixel region  31 B, and the normal pixel region  31 A and the invalid pixel region  31 D. On the other hand, the reflected light reduction unit  31 C is not formed at the boundary portion between the normal pixel region  31 A and the invalid pixel region  31 D. 
     In each example shown in  FIGS. 43A, 43B, 43C, and 43D , the narrowband pixel region  31 B is formed in an image circle  301 . 
     In the example shown in  FIG. 43A , in the image circle  301 , the four sides of the normal pixel region  31 A are surrounded by the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portions between the narrowband pixel region  31 B, and the normal pixel region  31 A and the invalid pixel region  31 D. Further, the horizontal portions of the reflected light reduction unit  31 C extend to both the right and left ends of the pixel array  31  beyond the ends of the narrowband pixel region  31 B. 
     The example in  FIG. 43B  differs from the example in  FIG. 43A  in that the portions of the narrowband pixel region  31 B on the right and left sides of the normal pixel region  31 A, and the vertical portions of the reflected light reduction unit  31 C are removed. 
     The example in  FIG. 43C  differs from the example in  FIG. 43A  in that the portions of the narrowband pixel region  31 B on the upper and lower sides of the normal pixel region  31 A, and the horizontal portions of the reflected light reduction unit  31 C are removed. 
     The example in  FIG. 43D  differs from the example in  FIG. 43A  in that the portions of the narrowband pixel region  31 B on the right and lower sides of the normal pixel region  31 A, and the portions of the reflected light reduction unit  31 C on the right and lower sides of the normal pixel region  31 A are removed. 
     Note that, since the narrowband pixel region  31 B is formed in the image circle  301 , any unnecessary structure (such as a narrowband filter NB, for example) is not formed in any unnecessary portion, and thus, irregular reflection of light can be reduced or prevented. 
       FIGS. 44, 45A, 45B, 45C, 45D, 46A, 46B, 46C, 46D, 47A, 47B, 47C, and 47D  show examples in which part of the normal pixel region  31 A (the effective pixel region) of the pixel array  31  is replaced with the narrowband pixel region  31 B. 
     In the example shown in  FIG. 44 , the outer peripheral portion of the normal pixel region  31 A is replaced with the narrowband pixel region  31 B. Accordingly, the periphery of the normal pixel region  31 A is surrounded by the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. 
     In each example shown in  FIGS. 45A, 45B, 45C, and 45D , three of the four portions, which are the upper, lower, right, and left portions, of the outer peripheral portion of the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. Accordingly, three of the four portions of the periphery of the normal pixel region  31 A are surrounded by the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B and the invalid pixel region  31 D. 
     In each example shown in  FIGS. 46A, 46B, 46C, and 46D , two of the four portions, which are the upper, lower, right, and left portions, of the outer peripheral portion of the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. Accordingly, two of the four portions of the periphery of the normal pixel region  31 A are surrounded by the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B and the invalid pixel region  31 D. 
     In each example shown in  FIGS. 47A, 47B, 47C, and 47D , one of the four portions, which are the upper, lower, right, and left portions, of the outer peripheral portion of the normal pixel region  31 A is replaced with the narrowband pixel region  31 B. Accordingly, one of the four portions of the periphery of the normal pixel region  31 A is surrounded by the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the invalid pixel region  31 D. 
       FIGS. 48A, 48B, 48C, and 48D  show examples in which both the normal pixel region  31 A and the invalid pixel region  31 D are partially replaced with the narrowband pixel region  31 B. Note that the dotted lines in  FIGS. 48A   48 B,  48 C, and  48 D indicate the boundaries between the normal pixel region  31 A and the invalid pixel region  31 D before the replacement. 
     In the example in  FIG. 48A , the narrowband pixel region  31 B is disposed at the left end and the lower end of the pixel array  31 . The reflected light reduction unit  31 C is then disposed at the boundary portions between the narrowband pixel region  31 B, and the normal pixel region  31 A and the invalid pixel region  31 D. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B. 
     In the example in  FIG. 48B , the upper end portion and the left end portion of the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. The narrowband pixel region  31 B also extends to the upper and lower ends or the right and left ends of the pixel array  31 , and part of the invalid pixel region  31 D is replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B and the invalid pixel region  31 D. 
     In the example in  FIG. 48C , the upper end portion, the lower end portion, and the right end portion of the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. The lower end portion and the right end portion of the invalid pixel region  31 D are also replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B and the invalid pixel region  31 D. 
     In the example in  FIG. 48D , the upper end portion, the lower end portion, and the left end portion of the normal pixel region  31 A are replaced with the narrowband pixel region  31 B. The left end portion of the invalid pixel region  31 D is also replaced with the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. Further, each portion of the reflected light reduction unit  31 C extends to the upper and lower ends, or the right and left ends of the pixel array  31 . Therefore, the reflected light reduction unit  31 C is also disposed in the narrowband pixel region  31 B and the invalid pixel region  31 D. 
       FIGS. 49A, 49B, and 49C  show examples in which the pixel array  31  is divided into the normal pixel region  31 A and the narrowband pixel region  31 B. 
     Specifically, in the example in  FIG. 49A , the pixel array  31  is horizontally divided into the normal pixel region  31 A and the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. 
     In the example in  FIG. 49B , the pixel array  31  is vertically divided into the normal pixel region  31 A and the narrowband pixel region  31 B. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. 
     In the example in  FIG. 49C , the pixel array  31  is divided into four regions, the normal pixel region  31 A is located at the upper right portion and the lower left portion, and the narrowband pixel region  31 B is located at the upper left portion and the lower right portion. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. 
       FIGS. 50A, 50B, and 50C  show examples in which the narrowband pixel region  31 B is formed in part of the normal pixel region  31 A. 
     Specifically, in the example in  FIG. 50A , the narrowband pixel region  31 B is disposed at the lower left corner of the normal pixel region  31 A. The reflected light reduction unit  31 C is then disposed at the boundary portion between the narrowband pixel region  31 B and the normal pixel region  31 A. 
     In the example ink  FIG. 50B , the narrowband pixel region  31 B is disposed in the normal pixel region  31 A. The reflected light reduction unit  31 C is then disposed so as to surround the narrowband pixel region  31 B. 
     In the example in  FIG. 50C , a plurality of narrowband pixel regions  31 B is disposed in the normal pixel region  31 A. The reflected light reduction unit  31 C is then disposed so as to surround each narrowband pixel region  31 B. 
     As the reflected light reduction unit  31 C is disposed at least at the boundary portion between the normal pixel region  31 A and the narrowband pixel region  31 B in the above manner, the reflected light on the sidewall of the narrowband filter NB at the boundary portion can be reduced as described above. 
     Note that, if the narrowband pixel region  31 B is disposed in the invalid pixel region  31 D, it is possible to avoid a decrease in the number of pixels in the normal pixel region  31 A (the effective pixel region), a change in the angle of view, a change in the aspect ratio, and the like. Meanwhile, the image height of the narrowband pixel region  31 B becomes greater. Therefore, the lens aberration and the CRA become greater, and the characteristics of the narrowband pixels  51 B are degraded. Further, the oblique light component entering the narrowband pixels  51 B increases, and the irregular reflection component on the sidewall of the narrowband filter NB becomes larger. Therefore, to improve the characteristics of the imaging device (particularly, the characteristics of the narrowband pixels  51 B), the load of signal processing might increase. 
     On the other hand, if the narrowband pixel region  31 B is disposed in the normal pixel region  31 A, the lens aberration, the CRA, and the oblique light component become smaller, and degradation of the characteristics of the imaging device  12  can be reduced. Meanwhile, a decrease in the number of pixels in the normal pixel region  31 A, a change in the angle of view, a change in the aspect ratio, and the like are caused. 
     Therefore, it is preferable to position the narrowband pixel region  31 B, while taking into consideration the above advantages and disadvantages. 
     7. Fifth Embodiment of the Present Technology 
     Next, a fifth embodiment of the present technology is described, with reference to  FIGS. 51, 52, 53, 54, 55A, 55B, 56A, 56B, 57A, and 57B . In the fifth embodiment, to reduce generation of flare, an antireflective film that reduces light reflection is provided on the light incident surface of each narrowband filter NB. 
     Referring first to  FIG. 51 , a cause of generation of flare in the imaging apparatus  10  using the imaging device  12  shown in  FIG. 2  is described. 
     In the example shown in  FIG. 51 , the imaging device  12  is disposed in a semiconductor chip  402 . Specifically, the semiconductor chip  402  is mounted on a substrate  413 , and its periphery is covered with sealing glass  411  and resin  412 . Light that has passed through a lens  401  provided in the optical system  11  shown in  FIG. 1  and the sealing glass  411  then enters the imaging device  12 . 
     Here, in a case where the narrowband filters NB of the filter layer  103  of the imaging device  12  are formed with plasmon filters, a conductive thin film made of a metal is formed on each plasmon filter, as described above. This conductive thin film has a high reflectance, and easily reflects light having a wavelength outside the transmission band. Part of the light reflected by the conductive thin film is then reflected by the sealing glass  411  or the lens  401 , for example, and re-enters the imaging device  12 . Although not shown in  FIG. 51 , part of the light reflected by the conductive thin film is also reflected by an optical filter such as an infrared cutoff filter, bonding wires, or the like, and re-enters the imaging device  12 . Flare is then generated by these rays of re-entering light. In particular, a plasmon filter using a hole array structure has a low aperture ratio, and therefore, flare is easily generated. 
     On the other hand, as shown in  FIG. 52 , an antireflective film  421  is provided on the light incident surface of each narrowband filter NB. The antireflective film  421  is formed with a black filter, for example. 
     This antireflective film  421  absorbs the light reflected by the conductive thin film of the narrowband filter NB. As a result, the reflected light is reflected by the sealing glass  411 , the lens  401 , or the like, and is prevented from re-entering the imaging device  12 . As a result, generation of flare is reduced or prevented. 
     Next, example layouts of the antireflective film  421  are described, with reference to  FIGS. 53, 54, 55A, 55B, 56A, 56B, 57A, and 57B . 
       FIG. 53  and  FIG. 54  show a first example layout of the antireflective film  421 .  FIG. 53  shows an example layout of the antireflective film  421  in the entire pixel array  31 .  FIG. 54  shows an example layout of the antireflective film  421  in each narrowband pixel  51 B. 
     In this example, the antireflective film  421  is formed in a grid pattern in the narrowband pixel region  31 B, and the periphery of each narrowband pixel  51 B is surrounded by the antireflective film  421 . 
     The antireflective film  421  absorbs the light reflected by the conductive thin film of the narrowband filter NB of each narrowband pixel  51 B, and prevents generation of flare. 
     Further, the antireflective film  421  is not formed on the portions of the light incident surface of the narrowband filter NB through which incident light is to be transmitted. Thus, a preferred transmittance is maintained in the narrowband filter NB, and excellent characteristics are maintained in each narrowband pixel  51 B. 
     Note that, as the width of the antireflective film  421  (the width of the grids) becomes smaller, the sensitivity of each narrowband pixel  51 B becomes higher, but the effect to reduce reflected light becomes smaller. On the other hand, as the width of the antireflective film  421  (the width of the grids) becomes greater, the effect to reduce reflected light becomes larger, but the sensitivity of each narrowband pixel  51 B becomes lower. Therefore, it is preferable to adjust the width of the antireflective film  421  as appropriate, in accordance with the required specifications, performance, and the like. 
       FIGS. 55A, 55B, 56A, 56B, 57A, and 57B  show other example layouts of the antireflective film  421  in each narrowband pixel  51 B. 
     In the example layout in  FIG. 55A , a square portion of the antireflective film  421  is disposed at the portion where four narrowband pixels  51 B are adjacent to one another. Each vertex of the square portion of the antireflective film  421  is located on a side of each narrowband pixel  51 B. Further, the antireflective film  421  is not formed at the boundary portions other than the four corner portions of each narrowband pixel  51 B. 
     The example layout in  FIG. 55B  is a combination of the example layout in  FIG. 54  and the example layout in  FIG. 55A . That is, this example differs from the example layout in  FIG. 55A  in that the antireflective film  421  is also disposed at the boundary portions other than the four corner portions of each narrowband pixel  51 B, and the periphery of each narrowband pixel  51 B is surrounded by the antireflective film  421 . 
     Therefore, in the example layout in  FIG. 55A , the sensitivity of each narrowband pixel  51 B becomes higher, but the effect to reduce reflected light becomes smaller than in the example layout in  FIG. 55B . Conversely, in the example layout in  FIG. 55B , the effect to reduce reflected light becomes greater, but the sensitivity of each narrowband pixel  51 B becomes lower than in the example layout in  FIG. 55A . 
     In the example layout in  FIG. 56A , a four-vertex star-shaped portion of the antireflective film  421  is disposed at the portion where four narrowband pixels  51 B are adjacent to one another. Each vertex of the star-shaped portion of the antireflective film  421  is located on a side of each narrowband pixel  51 B. Further, the antireflective film  421  is not formed at the boundary portions other than the four corner portions of each narrowband pixel  51 B. 
     The example layout in  FIG. 56B  is a combination of the example layout in  FIG. 54  and the example layout in  FIG. 56A . That is, this example differs from the example layout in  FIG. 56A  in that the antireflective film  421  is also disposed at the boundary portions other than the four corner portions of each narrowband pixel  51 B, and the periphery of each narrowband pixel  51 B is surrounded by the antireflective film  421 . 
     Therefore, in the example layout in  FIG. 56A , the sensitivity of each narrowband pixel  51 B becomes higher, but the effect to reduce reflected light becomes smaller than in the example layout in  FIG. 56B . Conversely, in the example layout in  FIG. 56B , the effect to reduce reflected light becomes greater, but the sensitivity of each narrowband pixel  51 B becomes lower than in the example layout in  FIG. 56A . 
     In the example layout in  FIG. 57A , a four-vertex star-shaped portion of the antireflective film  421  is disposed at the portion where four narrowband pixels  51 B are adjacent to one another, as in the example layout in  FIG. 56A . However, this example differs from the example layout in  FIG. 56A  in that each vertex of the star-shaped portion is connected by a side on a circular arc. Further, the antireflective film  421  is not formed at the boundary portions other than the four corner portions of each narrowband pixel  51 B. 
     The example layout in  FIG. 57B  is a combination of the example layout in  FIG. 54  and the example layout in  FIG. 57A . That is, this example differs from the example layout in  FIG. 57A  in that the antireflective film  421  is also disposed at the boundary portions other than the four corner portions of each narrowband pixel  51 B, and the periphery of each narrowband pixel  51 B is surrounded by the antireflective film  421 . 
     Therefore, in the example layout in  FIG. 57A , the sensitivity of each narrowband pixel  51 B becomes higher, but the effect to reduce reflected light becomes smaller than in the example layout in  FIG. 57B . Conversely, in the example layout in  FIG. 57B , the effect to reduce reflected light becomes greater, but the sensitivity of each narrowband pixel  51 B becomes lower than in the example layout in  FIG. 57A . 
     Note that the antireflective film  421  may be formed for each set of plural narrowband pixels  51 B, such as each two pixels in the vertical direction and each one pixel in the horizontal direction, each one pixel in the vertical direction and each two pixels in the horizontal direction, each two pixels in the vertical direction and each two pixels in the horizontal direction, or each three pixels in the vertical direction and each three pixels in the horizontal direction. In this case, the antireflective film  421  is not necessarily formed on all the narrowband pixels  51 B. 
     8. Modifications of the Filters of Normal Pixels  51 A and Narrowband Pixels  51 B 
     Next, modifications of the filters of normal pixels  51 A and narrowband pixels  51 B are described. 
     A combination of the non-metallic filter included in a normal pixel  51 A and the narrowband filter NB (a metallic filter) included in a narrowband pixel  51 B is not limited to the example described above, but may be changed as appropriate. For example, metallic filters other than the plasmon filters described above can be used as the narrowband filters NB. 
     For example,  FIG. 58  shows an example in which a Fabry-Perot  501  is used as the narrowband filter NB shown in  FIG. 20B . 
     The Fabry-Perot  501  is also called a Fabry-Perot interferometer or an etalon, and a semitransparent film  511 A and a semitransparent film  511 B that are parallel to the light incident surface are disposed at a predetermined interval therein. When light is reflected multiple times between the semitransparent film  511 A and the semitransparent film  511 B, waves having the same phase then reinforce each other, and waves having different phases cancel each other. As a result, of the incident light, light of a particular wavelength is intensified, light of the other wavelengths is weakened, and the light of the particular wavelength is output. 
     Further, any non-metallic filter is not necessarily provided in the normal pixels  51 A, as described above. 
     9. Image Processing in the Imaging Apparatus  10   
     Next, image processing in the imaging apparatus  10  is described. 
     For example, imaging modes may be set in the imaging apparatus  10 , so that types of images to be output by the imaging device  12  can be switched. For example, in a case where a mode A is set, the imaging device  12  outputs only normal images. In a case where a mode B is set, the imaging device  12  outputs only multispectral images. In a case where a mode C is set, the imaging device  12  outputs both normal images and multispectral images. 
     For example, the user then selects an appropriate imaging mode in accordance with the scene, or the imaging apparatus  10  automatically selects an appropriate imaging mode in accordance with the scene. 
     For example, an imaging mode is selected in accordance with the object distance. In a case where the object distance is several meters, for example, the mode A is set, and normal images are captured and output. Also, in a case where the object distance is several centimeters to several tens of centimeters, for example, the mode B is set, and multispectral images are captured and output. Further, in a case where the mode C is set, for example, both normal images and multispectral images are captured and output for objects at the same object distance. 
     Meanwhile, in a multispectral image, wavelength resolution and spatial resolution are in a trade-off relationship. This is because the number of pixels per wavelength or the pixel area decreases when the spatial resolution is increased. 
     Therefore, a two-dimensional multispectral image, a one-dimensional multispectral image, or a zero-dimensional multispectral image may be selectively used depending on the purpose of use. 
     Here, a two-dimensional multispectral image is an image that expresses an object with two-dimensionally arranged pixels. A one-dimensional multispectral image is an image that expresses an object with one-dimensionally arranged pixels. A zero-dimensional multispectral image is an image that shows the spectral characteristics (spectroscopic spectrum, for example) of an object. 
     A two-dimensional multispectral image has a high spatial resolution and allows an object to be visually recognized, but has a low wavelength resolution. On the other hand, a zero-dimensional multispectral image has a low spatial resolution and does not allow an object to be visually recognized, but has a high wavelength resolution. 
     Here, an example of a method for calculating the spectral characteristics of an object is described. 
     Where the matrix indicating observation data (the pixel value of each narrowband pixel  51 B) is represented by b, the matrix indicating the spectral characteristics of each narrowband pixel  51 B is represented by A, and the matrix indicating the spectral characteristics of the object (hereinafter, referred to as the object spectrum) is represented by x, the relationship among the observation data b, the spectral characteristics A, and the object spectrum x is expressed by Equation (12) shown below.
 
 b=Ax   (12)
 
     The inverse problem of Equation (12) is then solved according to Equation (13), to determine the object spectrum x.
 
 x=A   −1   b   (13)
 
     Here, the least absolute shrinkage and selection operators n(LASSO) estimation technique using a first-order norm may be used as a useful technique for solving the inverse problem of Equation (13), for example. 
     For example, where the LASSO estimation technique is used, Equation (14) shown below is established on the basis of Equation (12) described above.
 
[Mathematical Formula 6]
 
 Â   LASSO   =argmin   x   {∥Ax−b∥   2   +λ∥Lx∥}   (14)
 
     Here, the second term on the right-hand side is called a regularization term or a penalty term, λ represents the regularization parameter, and L represents the regularization matrix. 
     Equation (15) shown below is then derived from Equation (14), so that the object spectrum x can be determined.
 
[Mathematical Formula 7]
 
 {circumflex over (x)}=Â   LASSO   b   (15)
 
     Note that, on the right-hand side of Equation (14), regularization terms may be increased, like the third term, the fourth term, . . . , and the nth term, for example. 
     Further, another useful technique for solving the inverse problem of Equation (13) is ridge regression using a second-order norm, for example. 
     Where ridge regression is used, for example, Equation (16) shown below is established on the basis of Equation (12) described above.
 
[Mathematical Formula 9]
 
 Â   ridge   =argmin   x   {∥Ax−b∥   2 +λ 2   ∥Lx∥   2 }  (16)
 
     Here, the second term on the right-hand side is called a regularization term or a penalty term, λ represents the regularization parameter, and L represents the regularization matrix. 
     Equation (17) shown below is then derived from Equation (16), so that the object spectrum x can be determined.
 
[Mathematical Formula 9]
 
 x=Â   ridge   b   (17)
 
     Note that, on the right-hand side of Equation (16), regularization terms may be increased, like the third term, the fourth term, . . . , and the nth term, for example. 
     10. Example Applications 
     Next, example applications of the present technology are described. 
     &lt;Example Applications of the Present Technology&gt; 
     For example, the present technology can be applied in various cases where light such as visible light, infrared light, ultraviolet light, or an X-ray is sensed, as shown in  FIG. 59 . 
     Devices that take images for appreciation activities, such as digital cameras and portable devices with camera functions. 
     Devices for transportation use, such as vehicle-mounted sensors that take images of the front, the back, the surroundings, the inside, and the like of an automobile to perform safe driving such as an automatic stop or recognize a driver&#39;s condition and the like, surveillance cameras for monitoring running vehicles and roads, and ranging sensors for measuring distances between vehicles or the like. 
     Devices to be used in conjunction with home electric appliances, such as television sets, refrigerators, and air conditioners, to take images of gestures of users and operate the appliances in accordance with the gestures. 
     Devices for medical care use and health care use, such as endoscopes and devices for receiving infrared light for angiography. 
     Devices for security use, such as surveillance cameras for crime prevention and cameras for personal authentication. 
     Devices for beauty care use, such as skin measurement devices that image the skin, and microscopes that image the scalp. 
     Devices for sporting use, such as action cameras and wearable cameras for sports and the like. 
     Devices for agricultural use, such as cameras for monitoring conditions of fields and crops. 
     In the description below, more specific example applications are described. 
     For example, the transmission band of the narrowband filter NB of each narrowband pixel  51 B of the imaging apparatus  10  shown in  FIG. 1  is adjusted, so that the wavelength band of light to be detected by each narrowband pixel  51 B of the imaging apparatus  10  (this wavelength band will be hereinafter referred to as the detection band) can be adjusted. The detection band of each narrowband pixel  51 B is then set as appropriate, or a plurality of multispectral images is then used, so that the imaging apparatus  10  can be used for various purposes. 
     For example, the imaging apparatus  10  can be used for detecting a particular index. Typical examples of such indices include the normalized difference vegetation index (NDVI), SPAD values, the photochemical reflectance index (PRI), the palmer drought severity index (SDVI), the normalized difference soil moisture index (NDSMI), the leaf-color verified index (LVI), DDVI, and the like. Such examples also include simple ratios (SR), the global environment monitoring index (GEMI), the soil adjusted vegetation index (SAVI), the enhanced vegetation index (EVI), the perpendicular vegetation index (PVI), the structure insensitive pigment index (SIPI), the plant senescing reflectance index (PSRI), the chlorophyll index (CI), modified simple ratios (mSR), modified normalized differences (mND), the canopy chlorophyll index (CCI), the water index (WI), the normalized difference water index (NDWI), the cellulose absorption index (CAI), and the like. 
     For example, it is possible to determine the NDVI according to Equation (18) shown below, using a near-infrared (NIR) image and a red (RED) image.
 
NDVI=( NIR - RED )/( NIR+RED )  (18)
 
     Further,  FIG. 60  shows examples of the detection band in a case where the flavor and the degree of freshness of food are detected, for example. 
     For example, in a case where myoglobin indicating the flavor component of tuna, beef, or the like is detected, the peak wavelength of the detection band is in the range of 580 to 630 nm, and the half width is in the range of 30 to 50 nm. In a case where oleic acid indicating the degree of freshness of tuna, beef, or the like is detected, the peak wavelength of the detection band is 980 nm, and the half width is in the range of 50 to 100 nm. In a case where chlorophyll indicating the degree of freshness of a leafy vegetable such as “komatsuna” is detected, the peak wavelength of the detection band is in the range of 650 to 700 nm, and the half width is in the range of 50 to 100 nm. 
       FIG. 61  shows examples of the detection band in a case where the sugar content and the water content of a fruit are detected. 
     For example, in a case where a flesh light path length indicating the sugar content of “raiden”, which is a kind of melon, is detected, the peak wavelength of the detection band is 880 nm, and the half width is in the range of 20 to 30 nm. In a case where sucrose indicating the sugar content of “raiden” is detected, the peak wavelength of the detection band is 910 nm, and the half width is in the range of 40 to 50 nm. In a case where sucrose indicating the sugar content of “raiden red”, which is another kind of melon, is detected, the peak wavelength of the detection band is 915 nm, and the half width is in the range of 40 to 50 nm. In a case where water content indicating the sugar content of “raiden red” is detected, the peak wavelength of the detection band is 955 nm, and the half width is in the range of 20 to 30 nm. 
     In a case where sucrose indicating the sugar content of an apple is detected, the peak wavelength of the detection band is 912 nm, and the half width is in the range of 40 to 50 nm. In a case where water indicating the water content of an orange is detected, the peak wavelength of the detection band is 844 nm, and the half width is 30 nm. In a case where sucrose indicating the sugar content of an orange is detected, the peak wavelength of the detection band is 914 nm, and the half width is in the range of 40 to 50 nm. 
       FIG. 62  shows examples of the detection band in a case where plastics are separated. 
     For example, in a case where polyethylene terephthalate (PET) is detected, the peak wavelength of the detection band is 1669 nm, and the half width is in the range of 30 to 50 nm. In a case where polystyrene (PS) is detected, the peak wavelength of the detection band is 1688 nm, and the half width is in the range of 30 to 50 nm. In a case where polyethylene (PE) is detected, the peak wavelength of the detection band is 1735 nm, and the half width is in the range of 30 to 50 nm. In a case where polyvinyl chloride (PVC) is detected, the peak wavelength of the detection band is in the range of 1716 to 1726 nm, and the half width is in the range of 30 to 50 nm. In a case where polypropylene (PP) is detected, the peak wavelength of the detection band is in the range of 1716 to 1735 nm, and the half width is in the range of 30 to 50 nm. 
     The present technology can also be applied to freshness management for cut flowers, for example. 
     Further, the present technology can be applied to checking for foreign substances in foods, for example. For example, the present technology can be applied to detection of foreign substances such as skins, shells, stones, leaves, branches, and wood chips mixed in nuts and fruits such as almonds, blueberries, and walnuts. The present technology can also be applied to detection of foreign substances such as plastic pieces mixed in processed foods, beverages, and the like, for example. 
     Further, the present technology can be applied to detection of the normalized difference vegetation index (NDVI), which is a vegetation index, for example. 
     The present technology can also be applied to human detection, on the basis of a spectral shape in the neighborhood of a wavelength of 580 nm derived from hemoglobin of human skin, and/or a spectral shape in the neighborhood of a wavelength of 960 nm derived from melanin pigment contained in human skin, for example. 
     Further, the present technology can be applied to biometric detection (biometric authentication), user interfaces, prevention and monitoring of forgery of signatures and the like, and the like, for example. 
     &lt;Example Application to an Electronic Apparatus&gt; 
       FIG. 63  is a diagram showing an example configuration of an electronic apparatus to which the present technology is applied. 
     An electronic apparatus  600  includes an optical system configuration unit  601 , a drive unit  602 , an imaging device  603 , and a signal processing unit  604 . 
     The optical system configuration unit  601  includes an optical lens and the like, and causes an optical image of an object to enter the imaging device  603 . The drive unit  602  controls the driving of the imaging device  603  by generating and outputting various kinds of timing signals related to the driving inside the imaging device  603 . The signal processing unit  604  performs predetermined signal processing on an image signal output from the imaging device  603 , and performs a process in accordance with the signal processing result. The signal processing unit  604  also outputs an image signal as the signal processing result to a subsequent stage, to record the image signal on a recording medium such as a solid-state memory, or transfer the image signal to a predetermined server via a predetermined network, for example. 
     Here, the imaging device  12  described above is used as the imaging device  603 . Thus, it is possible to capture an image with a higher image quality, and increase the accuracy in detecting spectral characteristics. 
     &lt;Example Application to an Imaging Module&gt; 
     The present technology can also be applied to an imaging module that is used for various kinds of electronic apparatuses such as an imaging apparatus, for example. An imaging module includes the imaging device  12 , an optical system (a lens or the like, for example) that causes the imaging device  12  to form an image of an object, and a signal processing unit (a DSP, for example) that processes a signal output from the imaging device  12 , for example. 
     &lt;Example Application to an Endoscopic Surgery System&gt; 
     The technology according to the present disclosure may also be applied to an endoscopic surgery system, for example. 
       FIG. 64  is a diagram schematically showing an example configuration of an endoscopic surgery system to which the technology (the present technology) according to the present disclosure may be applied. 
       FIG. 64  shows a situation where a surgeon (a physician)  11131  is performing surgery on a patient  11132  on a patient bed  11133 , using an endoscopic surgery system  11000 . As shown in the drawing, the endoscopic surgery system  11000  includes an endoscope  11100 , other surgical tools  11110  such as a pneumoperitoneum tube  11111  and an energy treatment tool  11112 , a support arm device  11120  that supports the endoscope  11100 , and a cart  11200  on which various kinds of devices for endoscopic surgery are mounted. 
     The endoscope  11100  includes a lens barrel  11101  that has a region of a predetermined length from the top end to be inserted into a body cavity of the patient  11132 , and a camera head  11102  connected to the base end of the lens barrel  11101 . In the example shown in the drawing, the endoscope  11100  is designed as a so-called rigid scope having a rigid lens barrel  11101 . However, the endoscope  11100  may be designed as a so-called flexible scope having a flexible lens barrel. 
     At the top end of the lens barrel  11101 , an opening into which an objective lens is inserted is provided. A light source device  11203  is connected to the endoscope  11100 , and the light generated by the light source device  11203  is guided to the top end of the lens barrel by a light guide extending inside the lens barrel  11101 , and is emitted toward the current observation target in the body cavity of the patient  11132  via the objective lens. Note that the endoscope  11100  may be a forward-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope. 
     An optical system and an imaging device are provided inside the camera head  11102 , and reflected light (observation light) from the current observation target is converged on the imaging device by the optical system. The observation light is photoelectrically converted by the imaging device, and an electrical signal corresponding to the observation light, or an image signal corresponding to the observation image, is generated. The image signal is transmitted as RAW data to a camera control unit (CCU)  11201 . 
     The CCU  11201  is formed with a central processing unit (CPU), a graphics processing unit (GPU), or the like, and collectively controls operations of the endoscope  11100  and a display device  11202 . Further, the CCU  11201  receives an image signal from the camera head  11102 , and subjects the image signal to various kinds of image processing, such as a development process (a demosaicing process), for example, to display an image based on the image signal. 
     Under the control of the CCU  11201 , the display device  11202  displays an image based on the image signal subjected to the image processing by the CCU  11201 . 
     The light source device  11203  is formed with a light source such as a light emitting diode (LED), for example, and supplies the endoscope  11100  with illuminating light for imaging the surgical site or the like. 
     An input device  11204  is an input interface to the endoscopic surgery system  11000 . The user can input various kinds of information and instructions to the endoscopic surgery system  11000  via the input device  11204 . For example, the user inputs an instruction or the like to change imaging conditions (such as the type of illuminating light, the magnification, and the focal length) for the endoscope  11100 . 
     A treatment tool control device  11205  controls driving of the energy treatment tool  11112  for tissue cauterization, incision, blood vessel sealing, or the like. A pneumoperitoneum device  11206  injects a gas into a body cavity of the patient  11132  via the pneumoperitoneum tube  11111  to inflate the body cavity, for the purpose of securing the field of view of the endoscope  11100  and the working space of the surgeon. A recorder  11207  is a device capable of recording various kinds of information about the surgery. A printer  11208  is a device capable of printing various kinds of information relating to the surgery in various formats such as text, images, graphics, and the like. 
     Note that the light source device  11203  that supplies the endoscope  11100  with the illuminating light for imaging the surgical site can be formed with an LED, a laser light source, or a white light source that is a combination of an LED and a laser light source, for example. In a case where a white light source is formed with a combination of RGB laser light sources, the output intensity and the output timing of each color (each wavelength) can be controlled with high precision. Accordingly, the white balance of an image captured by the light source device  11203  can be adjusted. Alternatively, in this case, laser light from each of the RGB laser light sources may be emitted onto the current observation target in a time-division manner, and driving of the imaging device of the camera head  11102  may be controlled in synchronization with the timing of the light emission. Thus, images corresponding to the respective RGB colors can be captured in a time-division manner. According to the method, a color image can be obtained without any color filter provided in the imaging device. 
     Further, the driving of the light source device  11203  may also be controlled so that the intensity of light to be output is changed at predetermined time intervals. The driving of the imaging device of the camera head  11102  is controlled in synchronism with the timing of the change in the intensity of the light, and images are acquired in a time-division manner and are then combined. Thus, a high dynamic range image with no black portions and no white spots can be generated. 
     Further, the light source device  11203  may also be designed to be capable of supplying light of a predetermined wavelength band compatible with special light observation. In special light observation, light of a narrower band than the illuminating light (or white light) at the time of normal observation is emitted, with the wavelength dependence of light absorption in body tissue being taken advantage of, for example. As a result, so-called narrowband light observation (narrowband imaging) is performed to image predetermined tissue such as a blood vessel in a mucosal surface layer or the like, with high contrast. Alternatively, in the special light observation, fluorescence observation for obtaining an image with fluorescence generated through emission of excitation light may be performed. In fluorescence observation, excitation light is emitted to body tissue so that the fluorescence from the body tissue can be observed (autofluorescence observation). Alternatively, a reagent such as indocyanine green (ICG) is locally injected into body tissue, and excitation light corresponding to the fluorescence wavelength of the reagent is emitted to the body tissue so that a fluorescent image can be obtained, for example. The light source device  11203  can be designed to be capable of suppling narrowband light and/or excitation light compatible with such special light observation. 
       FIG. 65  is a block diagram showing an example of the functional configurations of the camera head  11102  and the CCU  11201  shown in  FIG. 64 . 
     The camera head  11102  includes a lens unit  11401 , an imaging unit  11402 , a drive unit  11403 , a communication unit  11404 , and a camera head control 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 communicably connected to each other by a transmission cable  11400 . 
     The lens unit  11401  is an optical system provided at the portion connecting to the lens barrel  11101 . Observation light captured from the top end of the lens barrel  11101  is guided to the camera head  11102 , and enters the lens unit  11401 . The lens unit  11401  is formed with a combination of a plurality of lenses including a zoom lens and a focus lens. 
     The imaging unit  11402  is formed with an imaging device. The imaging unit  11402  may be formed with one imaging device (a so-called single-plate type), or may be formed with a plurality of imaging devices (a so-called multiple-plate type). In a case where the imaging unit  11402  is of a multiple-plate type, for example, image signals corresponding to the respective RGB colors may be generated by the respective imaging devices, and be then combined to obtain a color image. Alternatively, the imaging unit  11402  may be designed to include a pair of imaging devices for acquiring right-eye and left-eye image signals compatible with three-dimensional (3D) display. As the 3D display is conducted, the surgeon  11131  can grasp more accurately the depth of the body tissue at the surgical site. Note that, in a case where the imaging unit  11402  is of a multiple-plate type, a plurality of lens units  11401  is provided for the respective imaging devices. 
     Further, the imaging unit  11402  is not necessarily provided in the camera head  11102 . For example, the imaging unit  11402  may be provided immediately behind the objective lens in the lens barrel  11101 . 
     The drive unit  11403  is formed with an actuator, and, under the control of the camera head control unit  11405 , moves the zoom lens and the focus lens of the lens unit  11401  by a predetermined distance along the optical axis. With this arrangement, the magnification and the focal point of the image captured by the imaging unit  11402  can be adjusted as appropriate. 
     The communication unit  11404  is formed with a communication device for transmitting and receiving various kinds of information to and from the CCU  11201 . The communication unit  11404  transmits the image signal obtained as RAW data from the imaging unit  11402  to the CCU  11201  via the transmission cable  11400 . 
     The communication unit  11404  also receives a control signal for controlling the driving of the camera head  11102  from the CCU  11201 , and supplies the control signal to the camera head control unit  11405 . The control signal includes information about imaging conditions, such as information for specifying the frame rate of captured images, information for specifying the exposure value at the time of imaging, and/or information for specifying the magnification and the focal point of captured images, for example. 
     Note that the above imaging conditions such as the frame rate, the exposure value, the magnification, and the focal point may be appropriately specified by the user, or may be automatically set by the control unit  11413  of the CCU  11201  on the basis of an acquired image signal. In the latter case, the endoscope  11100  has a so-called auto-exposure (AE) function, an auto-focus (AF) function, and an auto-white-balance (AWB) function. 
     The camera head control unit  11405  controls the driving of the camera head  11102 , on the basis of a control signal received from the CCU  11201  via the communication unit  11404 . 
     The communication unit  11411  is formed with a communication device for transmitting and receiving various kinds of information to and from the camera head  11102 . The communication unit  11411  receives an image signal transmitted from the camera head  11102  via the transmission cable  11400 . 
     The communication unit  11411  also transmits a control signal for controlling the driving of the camera head  11102 , to the camera head  11102 . The image signal and the control signal can be transmitted through electrical communication, optical communication, or the like. 
     The image processing unit  11412  performs various kinds of image processing on an image signal that is RAW data transmitted from the camera head  11102 . 
     The control unit  11413  performs various kinds of control relating to display of an image of the surgical portion or the like captured by the endoscope  11100 , and a captured image obtained through imaging of the surgical site or the like. For example, the control unit  11413  generates a control signal for controlling the driving of the camera head  11102 . 
     The control unit  11413  also causes the display device  11202  to display a captured image showing the surgical site or the like, on the basis of the image signal subjected to the image processing by the image processing unit  11412 . In doing so, the control unit  11413  may recognize the respective objects shown in the captured image, using various image recognition techniques. For example, the control unit  11413  can detect the shape, the color, and the like of the edges of an object shown in the captured image, to recognize the surgical tool such as forceps, a specific body site, bleeding, the mist at the time of use of the energy treatment tool  11112 , and the like. When causing the display device  11202  to display the captured image, the control unit  11413  may cause the display device  11202  to superimpose various kinds of surgery aid information on the image of the surgical site on the display, using the recognition result. As the surgery aid information is superimposed and displayed, and thus, is presented to the surgeon  11131 , it becomes possible to reduce the burden on the surgeon  11131 , and enable the surgeon  11131  to proceed with the surgery in a reliable manner. 
     The transmission cable  11400  connecting the camera head  11102  and the CCU  11201  is an electrical signal cable compatible with electric signal communication, an optical fiber compatible with optical communication, or a composite cable thereof. 
     Here, in the example shown in the drawing, communication is performed in a wired manner using the transmission cable  11400 . However, communication between the camera head  11102  and the CCU  11201  may be performed in a wireless manner. 
     An example of an endoscopic surgery system to which the technique according to the present disclosure can be applied has been described above. The technology according to the present disclosure may be applied to the imaging unit  11402  of the camera head  11102  among the components described above, for example. Specifically, the imaging device  12  described above can be applied to the imaging unit  10402 , for example. This makes it possible to obtain an image of the surgical site with better image quality, and detect various kinds of indications, for example. Thus, the surgeon can check the surgical site in a more reliable manner. 
     Although an endoscopic surgery system has been described as an example herein, the technology according to the present disclosure may also be applied to a microscopic surgery system or the like, for example. 
     &lt;Example Applications to Mobile Structures&gt; 
     Further, the technology according to the present disclosure may be embodied as an apparatus mounted on any type of mobile structure, such as an automobile, an electrical vehicle, a hybrid electrical vehicle, a motorcycle, a bicycle, a personal mobility device, an airplane, a drone, a vessel, or a robot, for example. 
       FIG. 66  is a block diagram schematically showing an example configuration of a vehicle control system that is an example of a mobile structure control system to which the technology according to the present disclosure may be applied. 
     A vehicle control system  12000  includes a plurality of electronic control units connected via a communication network  12001 . In the example shown in  FIG. 66 , the vehicle control system  12000  includes a drive system control unit  12010 , a body system control unit  12020 , an external information detection unit  12030 , an in-vehicle information detection unit  12040 , and an overall control unit  12050 . Further, a microcomputer  12051 , a sound/image output unit  12052 , and an in-vehicle network interface (I/F)  12053  are shown as the functional components of the overall control unit  12050 . 
     The drive system control unit  12010  controls operations of the devices related to the drive system of the vehicle according to various programs. For example, the drive system control unit  12010  functions as control devices such as a driving force generation device for generating a driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle. 
     The body system control unit  12020  controls operations of the various devices mounted on the vehicle body according to various programs. For example, the body system control unit  12020  functions as a keyless entry system, a smart key system, a power window device, or a control device for various lamps such as a headlamp, a backup lamp, a brake lamp, a turn signal lamp, a fog lamp, or the like. In this case, the body system control unit  12020  can receive radio waves transmitted from a portable device that substitutes for a key, or signals from various switches. The body system control unit  12020  receives inputs of these radio waves or signals, and controls the door lock device, the power window device, the lamps, and the like of the vehicle. 
     The external information detection unit  12030  detects information about the outside of the vehicle equipped with the vehicle control system  12000 . For example, an imaging unit  12031  is connected to the external information detection unit  12030 . The external information detection unit  12030  causes the imaging unit  12031  to capture an image of the outside of the vehicle, and receives the captured image. On the basis of the received image, the external information detection unit  12030  may perform an object detection process for detecting a person, a vehicle, an obstacle, a sign, characters on the road surface, or the like, or perform a distance detection process. 
     The imaging unit  12031  is an optical sensor that receives light, and outputs an electrical signal corresponding to the amount of received light. The imaging unit  12031  can output an electrical signal as an image, or output an electrical signal as distance measurement information. Further, the light to be received by the imaging unit  12031  may be visible light, or may be invisible light such as infrared rays. 
     The in-vehicle information detection unit  12040  detects information about the inside of the vehicle. For example, a driver state detector  12041  that detects the state of the driver is connected to the in-vehicle information detection unit  12040 . The driver state detector  12041  includes a camera that captures an image of the driver, for example, and, on the basis of detected information input from the driver state detector  12041 , the in-vehicle information detection unit  12040  may calculate the degree of fatigue or the degree of concentration of the driver, or determine whether or not the driver is dozing off. 
     On the basis of the external/internal information acquired by the external information detection unit  12030  or the in-vehicle information detection unit  12040 , the microcomputer  12051  can calculate the control target value of the driving force generation device, the steering mechanism, or the braking device, and output a control command to the drive system control unit  12010 . For example, the microcomputer  12051  can perform cooperative control to achieve the functions of an advanced driver assistance system (ADAS), including vehicle collision avoidance or impact mitigation, follow-up running based on the distance between vehicles, vehicle speed maintenance running, vehicle collision warning, vehicle lane deviation warning, or the like. 
     The microcomputer  12051  can also perform cooperative control to conduct automatic driving or the like for autonomously running not depending on the operation of the driver, by controlling the driving force generation device, the steering mechanism, the braking device, or the like on the basis of information about the surroundings of the vehicle, the information having being acquired by the external information detection unit  12030  or the in-vehicle information detection unit  12040 . 
     The microcomputer  12051  can also output a control command to the body system control unit  12020 , on the basis of the external information acquired by the external information detection unit  12030 . For example, the microcomputer  12051  controls the headlamp in accordance with the position of the leading vehicle or the oncoming vehicle detected by the external information detection unit  12030 , and performs cooperative control to achieve an anti-glare effect by switching from a high beam to a low beam, or the like. 
     The sound/image output unit  12052  transmits an audio output signal and/or an image output signal to an output device that is capable of visually or audibly notifying the passenger(s) of the vehicle or the outside of the vehicle of information. In the example shown in  FIG. 66 , an audio speaker  12061 , a display unit  12062 , and an instrument panel  12063  are shown as output devices. The display unit  12062  may include an on-board display and/or a head-up display, for example. 
       FIG. 67  is a diagram showing an example of installation positions of imaging units  12031 . 
     In  FIG. 67 , a vehicle  12100  includes imaging units  12101 ,  12102 ,  12103 ,  12104 , and  12105  as the imaging units  12031 . 
     The imaging units  12101 ,  12102 ,  12103 ,  12104 , and  12105  are provided at the following positions: the front end edge of a vehicle  12100 , a side mirror, the rear bumper, a rear door, an upper portion of the front windshield inside the vehicle, and the like, for example. The imaging unit  12101  provided on the front end edge and the imaging unit  12105  provided on the upper portion of the front windshield inside the vehicle mainly capture images ahead of the vehicle  12100 . The imaging units  12102  and  12103  provided on the side mirrors mainly capture images on the sides of the vehicle  12100 . The imaging unit  12104  provided on the rear bumper or a rear door mainly captures images behind the vehicle  12100 . The front images acquired by the imaging units  12101  and  12105  are mainly used for detection of a vehicle running in front of the vehicle  12100 , a pedestrian, an obstacle, a traffic signal, a traffic sign, a lane, or the like. 
     Note that  FIG. 67  shows an example of the imaging ranges of the imaging units  12101  through  12104 . An imaging range  12111  indicates the imaging range of the imaging unit  12101  provided on the front end edge, imaging ranges  12112  and  12113  indicate the imaging ranges of the imaging units  12102  and  12103  provided on the respective side mirrors, and an imaging range  12114  indicates the imaging range of the imaging unit  12104  provided on the rear bumper or a rear door. For example, image data captured by the imaging units  12101  through  12104  are superimposed on one another, so that an overhead image of the vehicle  12100  viewed from above is obtained. 
     At least one of the imaging units  12101  through  12104  may have a function of acquiring distance information. For example, at least one of the imaging units  12101  through  12104  may be a stereo camera including a plurality of imaging devices, or may be an imaging device having pixels for phase difference detection. 
     For example, in accordance with distance information obtained from the imaging units  12101  through  12104 , the microcomputer  12051  calculates the distances to the respective three-dimensional objects within the imaging ranges  12111  through  12114 , and temporal changes in the distances (the speeds relative to the vehicle  12100 ). In this manner, the three-dimensional object that is the closest three-dimensional object on the traveling path of the vehicle  12100  and is traveling at a predetermined speed (0 km/h or higher, for example) in substantially the same direction as the vehicle  12100  can be extracted as the vehicle running in front of the vehicle  12100 . Further, the microcomputer  12051  can set beforehand an inter-vehicle distance to be maintained in front of the vehicle running in front of the vehicle  12100 , and can perform automatic brake control (including follow-up stop control), automatic acceleration control (including follow-up start control), and the like. In this manner, it is possible to perform cooperative control to conduct automatic driving or the like to autonomously travel not depending on the operation of the driver. 
     For example, in accordance with the distance information obtained from the imaging units  12101  through  12104 , the microcomputer  12051  can extract three-dimensional object data concerning three-dimensional objects under the categories of two-wheeled vehicles, regular vehicles, large vehicles, pedestrians, utility poles, and the like, and use the three-dimensional object data in automatically avoiding obstacles. For example, the microcomputer  12051  classifies the obstacles in the vicinity of the vehicle  12100  into obstacles visible to the driver of the vehicle  12100  and obstacles difficult to visually recognize. Then, the microcomputer  12051  then determines collision risks indicating the risks of collision with the respective obstacles. If a collision risk is equal to or higher than a set value, and there is a possibility of collision, the microcomputer  12051  can output a warning to the driver via the audio speaker  12061  and the display unit  12062 , or can perform driving support for avoiding collision by performing forced deceleration or avoiding steering via the drive system control unit  12010 . 
     At least one of the imaging units  12101  through  12104  may be an infrared camera that detects infrared rays. For example, the microcomputer  12051  can recognize a pedestrian by determining whether or not a pedestrian exists in images captured by the imaging units  12101  through  12104 . Such pedestrian recognition is carried out through a process of extracting feature points from the images captured by the imaging units  12101  through  12104  serving as infrared cameras, and a process of performing a pattern matching on the series of feature points indicating the outlines of objects and determining whether or not there is a pedestrian, for example. If the microcomputer  12051  determines that a pedestrian exists in the images captured by the imaging units  12101  through  12104 , and recognizes a pedestrian, the sound/image output unit  12052  controls the display unit  12062  to display a rectangular contour line for emphasizing the recognized pedestrian in a superimposed manner. Further, the sound/image output unit  12052  may also control the display unit  12062  to display an icon or the like indicating the pedestrian at a desired position. 
     An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the imaging units  12031  among the components described above, for example. Specifically, the imaging device  12  described above can be applied to the imaging units  12031 , for example. This makes it possible to obtain a captured image with better image quality, and detect various kinds of indications, for example. Thus, the accuracy of detection of the situations outside the vehicle, and the like become higher. Further, the imaging units  12031  can be made smaller in size, for example. 
     11. Modifications 
     The following is a description of modifications of the above described embodiments of the present technology. 
     For example, in the imaging device  12 A shown in  FIG. 19 , the narrowband filters NB may be disposed at higher locations than the color filters CF. In this case, the color filters CF are manufactured before the narrowband filters NB, but the color filters CF have a lower heat resistance than that of the narrowband filters NB. Therefore, the limitations on the manufacturing process, particularly the limitations on the temperature, need to be taken into consideration in conducting the design and manufacture. 
     The above described embodiments of the present technology can also be combined as appropriate. It is also possible to combine three or more embodiments. 
     Further, in the first embodiment and the second embodiment, for example, a light absorber that is neither a black filter nor an optical filter in which a red filter and a blue filter are stacked may be used. Such a light absorber preferably absorbs at least light in the wavelength band to be detected by the photodiodes PD, and more preferably absorbs not only visible light but also ultraviolet light and infrared light. 
     The present technology can also be applied to a semiconductor device in which a pixel including a metallic filter and a pixel not including any metallic filter are adjacent to each other, and to all electronic apparatuses including the semiconductor device. For example, the present technology can be applied not only to the back-illuminated CMOS image sensor described above, but also to a front-illuminated CMOS image sensor, a charge coupled device (CCD) image sensor, an image sensor having a photoconductor structure including an organic photoelectric conversion film and a quantum dot structure, and the like. 
     The present technology can also be applied to solid-state imaging devices (imaging devices) described below as examples. 
     &lt;Example Configuration of a Cross-Section of a Solid-State Imaging Device to Which the Technology According to the Present Disclosure Can Be Applied&gt; 
       FIG. 68  is a cross-sectional view of an example configuration of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
     In the solid-state imaging device, a photodiode (PD)  20019  receives incident light  20001  that enters from the back surface (the upper surface in the drawing) side of a semiconductor substrate  20018 . Above the PD  20019 , a planarizing film  20013 , a filter layer  20012 , and a microlens  20011  are disposed. The incident light  20001  that has entered and sequentially passed through the respective components is received by a light receiving surface  20017 , so that photoelectric conversion is performed. 
     For example, in the PD  20019 , an n-type semiconductor region  20020  is formed as the charge storage region that stores electric charges (electrons). In the PD  20019 , the n-type semiconductor region  20020  is formed in p-type semiconductor regions  20016  and  20041  of the semiconductor substrate  20018 . On a side of the n-type semiconductor region  20020 , which is the front surface (the lower surface) side of the semiconductor substrate  20018 , a p-type semiconductor region  20041  having a higher impurity concentration than the back surface (the upper surface) side is disposed. That is, the PD  20019  has a hole-accumulation diode (HAD) structure, and the p-type semiconductor regions  20016  and  20041  are formed so as to reduce generation of dark current in the respective interfaces with the upper surface side and the lower surface side of the n-type semiconductor region  20020 . 
     In the semiconductor substrate  20018 , a pixel separation unit  20030  that electrically separates a plurality of pixels  20010  from one another is provided, and the PD  20019  is disposed in a region partitioned by the pixel separation unit  20030 . In a case where the solid-state imaging device is viewed from the upper surface side in the drawing, the pixel separation unit  20030  is formed in a grid-like form so as to be interposed between the plurality of pixels  20010 , for example, and the PD  20019  is formed in a region partitioned by this pixel separation unit  20030 . 
     In each PD 20019 , the anode is grounded. In the solid-state imaging device, signal charges (electrons, for example) stored by the PD  20019  are read out via a transfer Tr (MOSFET) (not shown) or the like, and are output as an electrical signal to a vertical signal line (VSL) (not shown). 
     A wiring layer  20050  is provided in the front surface (the lower surface) of the semiconductor substrate  20018  on the opposite side from the back surface (the upper surface) in which the respective components such as a light-blocking film  20014 , the filter layer  20012 , the microlens  20011 , and the like are provided. 
     The wiring layer  20050  includes wiring lines  20051  and an insulating layer  20052 , and is designed so that the wiring lines  20051  are electrically connected to each component in the insulating layer  20052 . The wiring layer  20050  is a so-called multilayer wiring layer, and is formed by alternately stacking interlayer insulating films constituting the insulating layer  20052  and the wiring lines  20051  a plurality of times. Here, respective wiring lines including a wiring line to a Tr for reading out electric charges from the PD  20019 , such as a transfer Tr, a VSL, and the like are stacked as the wiring lines  20051  via the insulating layer  20052 . 
     A support substrate  20061  is provided on the surface of the wiring layer  20050  on the opposite side from the side on which the PD  20019  is provided. For example, a substrate including a silicon semiconductor with a thickness of several hundreds of μm is provided as the support substrate  20061 . 
     The light-blocking film  20014  is disposed on the back surface (the upper surface in the drawing) side of the semiconductor substrate  20018 . 
     The light-blocking film  20014  is designed so as to block part of the incident light  20001  traveling from above the semiconductor substrate  20018  toward the back surface of the semiconductor substrate  20018 . 
     The light-blocking film  20014  is disposed above the pixel separation unit  20030  formed inside the semiconductor substrate  20018 . Here, the light-blocking film  20014  is disposed so as to protrude in a convex form from the back surface (the upper surface) of the semiconductor substrate  20018  via an insulating film  20015  such as a silicon oxide film. On the other hand, above the PD  20019  provided inside the semiconductor substrate  20018 , the light-blocking film  20014  is not disposed, but the portion is left open so that the incident light  20001  can enter the PD  20019 . 
     That is, in a case where the solid-state imaging device is viewed from the upper surface side in the drawing, the planar shape of the light-blocking film  20014  is a grid-like shape, and an opening through which the incident light  20001  travels to the light receiving surface  20017  is formed. 
     The light-blocking film  20014  is formed with a light-blocking material that blocks light. For example, a titanium (Ti) film and a tungsten (W) film are stacked in this order, to form the light-blocking film  20014 . Alternatively, a titanium nitride (TiN) film and a tungsten (W) film are stacked in this order, to form the light-blocking film  20014 , for example. 
     The light-blocking film  20014  is covered with the planarizing film  20013 . The planarizing film  20013  is formed with an insulating material that passes light. 
     The pixel separation unit  20030  has a groove portion  20031 , a fixed charge film  20032 , and an insulating film  20033 . 
     The fixed charge film  20032  is formed so as to cover the groove portion  20031  that partitions the plurality of pixels  20010 , on the back surface (upper surface) side of the semiconductor substrate  20018 . 
     Specifically, the fixed charge film  20032  is designed to have a constant thickness and cover the inner surface of the groove portion  20031  formed on the back surface (upper surface) side of the semiconductor substrate  20018 . The insulating film  20033  is then provided (buried) so as to fill the inside of the groove portion  20031  covered with the fixed charge film  20032 . 
     Here, the fixed charge film  20032  is formed with a high dielectric material having negative fixed charges, so that a positive charge (hole) storage region is formed at the interface with the semiconductor substrate  20018 , and generation of dark current is reduced. As the fixed charge film  20032  is formed to have negative fixed charges, an electric field is applied to the interface with the semiconductor substrate  20018  by the negative fixed charges, and thus, a positive charge (hole) storage region is formed. 
     The fixed charge film  20032  can be formed with a hafnium oxide film (HfO2 film), for example. Alternatively, the fixed charge film  20032  can be formed to include at least one of oxides of hafnium, zirconium, aluminum, tantalum, titanium, magnesium, yttrium, a lanthanoid, or the like, for example. 
     In the filter layer  20012 , a color filter and a narrowband filter made of a metal are provided as described above, for example. 
     &lt;Example Configuration of a Cross-Section of the Pixel Separation Unit of a Solid-State Imaging Device to Which the Technology According to the Present Disclosure Can Be Applied&gt; 
       FIG. 68  described above also shows a first example configuration of the pixel separation unit of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
     Specifically, the pixel separation unit  20030  is formed with an insulating material so as to partition the plurality of pixels  20010 , and electrically separates the plurality of pixels  20010  from one another. 
     The pixel separation unit  20030  includes the groove portion  20031 , the fixed charge film  20032 , and the insulating film  20033 , and is formed so as to be buried in the semiconductor substrate  20018  on the side of the back surface (the upper surface in the drawing) of the semiconductor substrate  20018 . 
     That is, on the back surface (upper surface) side of the semiconductor substrate  20018 , the groove portion  20031  is formed so as to partition the n-type semiconductor regions  20020  forming the charge storage regions of the PDs  20019 . The inside of the groove portion  20031  is covered with the fixed charge film  20032 , and the groove portion  20031  is further filled with the insulating film  20033 , to form the pixel separation unit  20030 . 
     In a case where the solid-state imaging device is viewed from the upper surface side in the drawing, the planar shape of the pixel separation unit  20030  is a grid-like shape, and is interposed between the plurality of pixels  20010 . The PDs  20019  are then formed in the rectangular regions partitioned by the grid-like pixel separation unit  20030 . 
     For example, a silicon oxide film (SiO), a silicon nitride film (SiN), or the like can be used as the insulating film  20033  of the pixel separation unit  20030 . The pixel separation unit  20030  may be formed by shallow trench isolation, for example. 
       FIG. 69  is a cross-sectional view of a second example configuration of the pixel separation unit of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
     In  FIG. 69 , a first fixed charge film  21212 , a second fixed charge film  21213 , a first insulating film  21214 , and a second insulating film  21215  are buried in this order in a groove portion  21211 , to form a pixel separation unit  21210  that separates pixels  21200  from one another. The groove portion  21211  is formed to have a tapered cross-sectional shape so that the aperture diameter becomes smaller in the depth direction of a substrate  21221 . 
     Note that it is possible to form the pixel separation unit  21210  by burying the first fixed charge film  21212 , the second fixed charge film  21213 , the first insulating film  21214 , and the second insulating film  21215  not in this order in the groove portion  21211 . For example, it is possible to form the pixel separation unit  21210  by alternately burying insulating films and fixed charge films in the groove portion  21211 , such as burying the first insulating film  21214 , the first fixed charge film  21212 , the second insulating film  21215 , and the second fixed charge film  21213  in this order. 
       FIG. 70  is a cross-sectional view of a third example configuration of the pixel separation unit of a solid-state imaging device to which the technology according to the present disclosure can be applied. 
     In the solid-state imaging device in  FIG. 70 , a pixel separation unit  21310  that separates the pixels  21200  from one another has a hollow structure. In this aspect, the solid-state imaging device in  FIG. 70  differs from the case shown in  FIG. 69  where the pixel separation unit  21210  does not have a hollow structure. The solid-state imaging device in  FIG. 70  does not have a tapered groove portion  21311 . In this aspect, the solid-state imaging device in  FIG. 70  also differs from the case shown in  FIG. 69  where the groove portion  21211  has a tapered shape. Note that the groove portion  21311  can be formed in a tapered shape like the groove portion  21211  shown in  FIG. 69 . 
     The pixel separation unit  21310  is formed by burying a fixed charge film  21312  and an insulating film  21313  in this order in the groove portion  21311  formed in the depth direction from the back surface side (the upper side) of the substrate  21221 . A hollow portion (a so-called void)  21314  is formed inside the groove portion  21311 . 
     That is, the fixed charge film  21312  is formed on the inner wall surface of the groove portion  21311  and the back surface side of the substrate  21221 , and the insulating film  21313  is formed so as to cover the fixed charge film  21312 . Further, to form the hollow portion  21314  in the groove portion  21311 , the insulating film  21313  is formed to have such a film thickness that does not completely fill the groove portion  21311  inside the groove portion  21311 , and is formed so as to close the groove portion  21311  at the opening end of the groove portion  21311 . The insulating film  21313  can be formed with a material such as silicon oxide, silicon nitride, silicon oxynitride, or resin, for example. 
     &lt;Example Configuration of a Stacked Solid-State Imaging Device to Which the Technology According to the Present Disclosure Can Be Applied&gt; 
       FIGS. 71A, 71B, and 71C  are diagrams showing outlines of example configurations of stacked solid-state imaging devices to which the technology according to the present disclosure can be applied. 
       FIG. 71  shows a schematic example configuration of a non-stacked solid-state imaging device. As shown in  FIG. 71A , a solid-state imaging device  23010  has one die (a semiconductor substrate)  23011 . A pixel region  23012  in which pixels are arranged in an array, a control circuit  23013  that controls driving of the pixels and performs other various kinds of control, and a logic circuit  23014  for performing signal processing are mounted on the die  23011 . 
       FIGS. 71B and 71C  show schematic example configurations of a stacked solid-state imaging device. As shown in  FIGS. 71B and 71C , a solid-state imaging device  23020  is designed as a single semiconductor chip in which two dies, which are a sensor die  23021  and a logic die  23024 , are stacked and are electrically connected. 
     In  FIG. 71B , the pixel region  23012  and the control circuit  23013  are mounted on the sensor die  23021 , and the logic circuit  23014  including a signal processing circuit that performs signal processing is mounted on the logic die  23024 . 
     In  FIG. 71C , the pixel region  23012  is mounted on the sensor die  23021 , and the control circuit  23013  and the logic circuit  23014  are mounted on the logic die  23024 . 
       FIG. 72  is a cross-sectional view showing an example configuration of the stacked solid-state imaging device  23020 . 
     In the sensor die  23021 , photodiodes (PDs) forming the pixels constituting the pixel region  23012 , floating diffusions (FDs), Trs (MOSFETs), Trs serving as the control circuit  23013 , and the like are formed. A wiring layer  23101  having a plurality of layers, which are three layers of wiring lines  23110  in this example, is further formed in the sensor die  23021 . Note that (the Trs to be) the control circuit  23013  can be formed in the logic die  23024 , instead of the sensor die  23021 . 
     In the logic die  23024 , Trs constituting the logic circuit  23014  are formed. A wiring layer  23161  having a plurality of layers, which are three layers of wiring lines  23170  in this example, is further formed in the logic die  23024 . In the logic die  23024 , a connecting hole  23171  having an insulating film  23172  formed on its inner wall surface is also formed, and a connected conductor  23173  connected to the wiring lines  23170  and the like is buried in the connecting hole  23171 . 
     The sensor die  23021  and the logic die  23024  are bonded so that the respective wiring layers  23101  and  23161  face each other. Thus, the stacked solid-state imaging device  23020  in which the sensor die  23021  and the logic die  23024  are stacked is formed. For example, the sensor die  23021  and the logic die  23024  are stacked so that the wiring lines  23110  and  23170  are in direct contact, and heat is then applied while a required load is applied, so that the wiring lines  23110  and  23170  are bonded directly to each other. Thus, the solid-state imaging device  23020  is formed. 
     In the sensor die  23021 , a connecting hole  23111  is formed. The connecting hole  23111  penetrates the sensor die  23021  from the back surface side (the side at which light enters the PDs) (the upper side) of the sensor die  23021 , and reaches the wiring lines  23170  in the uppermost layer of the logic die  23024 . A connecting hole  23121  that is located in the vicinity of the connecting hole  23111  and reaches the wiring lines  23110  in the first layer from the back surface side of the sensor die  23021  is further formed in the sensor die  23021 . An insulating film  23112  is formed on the inner wall surface of the connecting hole  23111 , and an insulating film  23122  is formed on the inner wall surface of the connecting hole  23121 . Connected conductors  23113  and  23123  are then buried in the connecting holes  23111  and  23121 , respectively. The connected conductor  23113  and the connected conductor  23123  are electrically connected on the back surface side of the sensor die  23021 . Thus, the sensor die  23021  and the logic die  23024  are electrically connected via the wiring layer  23101 , the connecting hole  23121 , the connecting hole  23111 , and the wiring layer  23161 . 
       FIG. 73  is a cross-sectional view showing another example configuration of a stacked solid-state imaging device to which the technology according to the present disclosure can be applied. 
     In  FIG. 73 , a solid-state imaging device  23401  has a three-layer stack structure in which the three dies of a sensor die  23411 , a logic die  23412 , and a memory die  23413  are stacked. 
     The memory die  23413  includes a memory circuit that stores data to be temporarily required in signal processing to be performed in the logic die  23412 , for example. 
     In  FIG. 73 , the logic die  23412  and the memory die  23413  are stacked in this order under the sensor die  23411 . However, the logic die  23412  and the memory die  23413  may be stacked in reverse order. In other words, the memory die  23413  and the logic die  23412  can be stacked in this order under the sensor die  23411 . 
     Note that, in  FIG. 73 , PDs serving as the photoelectric conversion units of the pixels, and the source/drain regions of the pixels Tr are formed in the sensor die  23411 . 
     A gate electrode is formed around a PD via a gate insulating film, and the gate electrode and a pair of source/drain regions form a pixel Tr  23421  and a pixel Tr  23422 . 
     The pixel Tr  23421  adjacent to the PD is a transfer Tr, and one of the source/drain regions constituting the pixel Tr  23421  is an FD. 
     Further, an interlayer insulating film is formed in the sensor die  23411 , and a connecting hole is formed in the interlayer insulating film. In the connecting hole, a connected conductor  23431  connected to the pixel Tr  23421  and the pixel Tr  23422  is formed. 
     Further, a wiring layer  23433  having a plurality of layers of wiring lines  23432  connected to each connected conductor  23431  is formed in the sensor die  23411 . 
     Aluminum pads  23434  serving as electrodes for external connection are also formed in the lowermost layer of the wiring layer  23433  in the sensor die  23411 . That is, in the sensor die  23411 , the aluminum pads  23434  is formed at positions closer to the bonding surface  23440  with the logic die  23412  than the wiring lines  23432 . Each aluminum pad  23434  is used as one end of a wiring line related to inputting/outputting of signals from/to the outside. 
     Further, a contact  23441  to be used for electrical connection with the logic die  23412  is formed in the sensor die  23411 . The contact  23441  is connected to a contact  23451  of the logic die  23412 , and also to an aluminum pad  23442  of the sensor die  23411 . 
     Further, a pad hole  23443  is formed in the sensor die  23411  so as to reach the aluminum pad  23442  from the back surface side (the upper side) of the sensor die  23411 . 
     &lt;Example Configuration of a Solid-State Imaging Device Sharing a Plurality of Pixels to Which the Technology According to the Present Disclosure Can Be Applied&gt; 
       FIG. 74  is a plan view showing an example configuration of a solid-state imaging device that shares a plurality of pixels to which the technology according to the present disclosure can be applied.  FIG. 75  is a cross-sectional view taken along the line A-A defined in  FIG. 74 . 
     A solid-state imaging device  24010  has a pixel region  24011  in which pixels are arranged in a two-dimensional array. The pixel region  24011  is designed such that a total of four pixels, which are two pixels in the horizontal direction and two pixels in the vertical direction, form a sharing pixel unit  24012  that shares a pixel Tr (MOSFET) and the like, and the sharing pixel units  24012  are arranged in a two-dimensional array. 
     The four pixels of a 4-pixel-sharing pixel unit  24012  that shares the four pixels, which are two pixels in the horizontal and two pixels in the vertical direction, include photodiodes (PDs)  24021   1 ,  24021   2 ,  24021   3 , and  24021   4 , respectively, and shares one floating diffusion (FD)  24030 . The sharing pixel unit  24012  also includes pixel Trs that are transfer Trs  24041   i  for the PDs  24021   i  (i=1, 2, 3, and 4), and shared Trs to be shared by the four pixels, which are a reset Tr  24051 , an amplification Tr  24052 , and a selection Tr  24053 . 
     The FD  24030  is disposed at the center surrounded by the four PDs  24021   1  through  24021   4 . The FD  24030  is connected to a source/drain region S/D serving as the drain of the reset Tr  24051  and to the gate G of the amplification Tr  24052  via a wiring line  24071 . Each transfer Tr  24041   i  has a gate  24042   i  disposed between the PD  24021   i  for the transfer Tr  24041   i  and the FD  24030  adjacent to the PD  24021   i , and operates in accordance with a voltage applied to the gate  24042   i . 
     Here, the region including the PDs  24021   1  through  24021   4 , the FD  24030 , and the transfer Trs  24041   1  through  24041   4  of the sharing pixel units  24012  for each row is called a PD formation region  24061 . Also, the region including the reset Tr  24051 , the amplification Tr  24052 , and the selection Tr  24053  that are shared by four pixels among the pixel Trs of the sharing pixel units  24012  of each row is called a Tr formation region  24062 . The respective Tr formation regions  24062  and the respective PD formation regions  24061  that are continuous in the horizontal direction are alternately disposed in the vertical direction of the pixel region  24011 . 
     The reset Tr  24051 , the amplification Tr  24052 , and the selection Tr  24053  each include a pair of source/drain regions S/D and a gate G. One of the two source/drain regions S/D functions as a source, and the other functions as a drain. 
     The PDs  24021   1  through  24021   4 , the FD  24030 , the transfer Trs  24041   1  through  24041   4 , the reset Tr  24051 , the amplification Tr  24052 , and the selection Tr  24053  are formed in a p-type semiconductor region (p-well)  24210  formed on an n-type semiconductor substrate  24200 , for example, as shown in the cross-sectional view in  FIG. 75 . 
     As shown in  FIG. 74 , a pixel separation unit  24101  is formed in each PD formation region  24061 , and a device separation unit  24102  is formed in (the region including) each Tr formation region  24062 . As shown in  FIG. 75 , for example, the device separation unit  24102  includes a p-type semiconductor region  24211  formed in the p-type semiconductor region  24210 , and an insulating film (a silicon oxide film, for example)  24212  disposed on the surface of the p-type semiconductor region  24211 . Although not shown in the drawings, each pixel separation unit  24101  can have a similar configuration. 
     In the pixel region  24011 , well contacts  24111  for applying a fixed voltage to the p-type semiconductor region  24210  are formed. The well contacts  24111  can be designed as p-type semiconductor regions that are impurity diffusion regions formed on the surfaces of p-type semiconductor regions  24231  formed in the p-type semiconductor region  24210 . The well contacts  24111  are p-type semiconductor regions having a higher impurity concentration than the p-type semiconductor regions  24231 . The well contacts  24111  (and the p-type semiconductor regions  24231  under the well contacts  24111 ) also serve as the device separation units  24102 , and are formed between the shared Trs (the reset Trs  24051 , the amplification Trs  24052 , and the selection Trs  24053 ) of the sharing pixel units  24012  horizontally adjacent to each other. The well contacts  24111  are connected to a predetermined wiring line  24242  in a wiring layer  24240  via conductive vias  24241 . A predetermined fixed voltage is applied to the p-type semiconductor region  24210  from the wiring line  24242  through the conductive vias  24241  and the well contacts  24111 . A plurality of layers of wiring lines  24242  is disposed via an insulating film  24243 , to form the wiring layer  24240 . Although not shown in the drawings, narrowband filters, color filters, and microlenses are formed on the wiring layer  24240  via a planarizing film. 
       FIG. 76  is a diagram showing an example of an equivalent circuit of a sharing pixel unit  24012  that shares four pixels. In the equivalent circuit of the sharing pixel unit  24012  that shares four pixels, the four PDs  24021   1  through  24021   4  are connected to the sources of the corresponding four transfer Trs  24041   1  through  24041   4 , respectively. The drain of each transfer Tr  24041   i  is connected to the source of the reset Tr  24051 . The drain of each transfer Tr  24041   i  is the common FD  24030 . The FD  24030  is connected to the gate of amplification Tr  24052 . The source of the amplification Tr  24052  is connected to the drain of the selection Tr  24053 . The drain of the reset Tr  24051  and the drain of the amplification Tr  24052  are connected to a power supply VDD. The source of the selection Tr  24053  is connected to a vertical signal line (VSL). 
     Note that the technology according to the present disclosure can be applied not only to the examples described above, but also to a solid-state imaging device that shares a plurality of pixels in any appropriate arrangement such as two pixels in the horizontal direction and four pixels in the vertical direction, or one pixel in the horizontal direction and four pixels in the vertical direction, for example. 
     Further, a plurality of pixels may be shared in the normal pixel region and/or the narrowband pixel region, to reduce the area of the transistors. With this arrangement, the light reception area becomes larger, and thus, a higher image quality and a higher accuracy in detecting spectral characteristics are achieved, for example. Alternatively, the number of pixels may be increased, to achieve a higher resolution. 
     The technology according to the present disclosure can be applied to the solid-state imaging devices as described above. 
     Note that, in the filter layers shown in  FIGS. 69, 70, 72 , and  73 , for example, color filters and metallic narrowband filters are provided, as in the filter layer  20012  shown in  FIG. 68 . 
     Note that embodiments of the present technology are not limited to the embodiments described above, and various modifications may be made to them without departing from the scope of the present technology. 
     &lt;Example Combinations of Configurations&gt; 
     The present technology can also be embodied in the configurations described below, for example. 
     (1) 
     A semiconductor device including: 
     a pixel unit in which a first pixel including a metallic filter and a second pixel not including the metallic filter are disposed adjacent to each other; and 
     a reflected light reduction unit that reduces reflected light on a sidewall of the metallic filter at a boundary portion between the first pixel and the second pixel. 
     (2) 
     The semiconductor device according to (1), in which 
     the reflected light reduction unit is disposed at a position closer to a light incident surface of the semiconductor device than the metallic filter, and includes a light absorber that overlaps at least one of the first pixel or the second pixel adjacent to the boundary portion. 
     (3) 
     The semiconductor device according to (2), in which 
     the second pixel includes a non-metallic filter, and 
     the light absorber is disposed at a position closer to the light incident surface of the semiconductor device than the metallic filter and the non-metallic filter. 
     (4) 
     The semiconductor device according to (3), in which 
     the non-metallic filter is disposed at a position closer to the light incident surface of the semiconductor device than the metallic filter. 
     (5) 
     The semiconductor device according to (2) or (3), in which 
     the light absorber is a black filter. (6) 
     The semiconductor device according to (2) or (3), in which 
     the light absorber is an optical filter in which a red filter and a blue filter are stacked. 
     (7) 
     The semiconductor device according to any one of (2) to (6), in which 
     an angle between a plane and the sidewall is not smaller than a maximum incident angle of light incident on the sidewall, the plane connecting a side of a face of the light absorber that is on the opposite side from a light incident surface of the light absorber and is located on a side of the second pixel, to a side of the sidewall that is on the opposite side from a light incident surface of the metallic filter. 
     (8) 
     The semiconductor device according to any one of (1) to (7), in which 
     the reflected light reduction unit includes a light absorber that covers at least part of the sidewall. 
     (9) 
     The semiconductor device according to (8), in which 
     the light absorber is a black filter. 
     (10) 
     The semiconductor device according to (8), in which 
     the light absorber is an optical filter in which a red filter and a blue filter are stacked. 
     (11) 
     The semiconductor device according to any one of (1) to (7), in which 
     the reflected light reduction unit includes a low-reflection film that has a lower reflectance than a metal forming the metallic filter and covers at least part of the sidewall. 
     (12) 
     The semiconductor device according to any one of (1) to (7), in which 
     the reflected light reduction unit includes the sidewall that is inclined so as to move away from the boundary portion in a direction of the first pixel as a distance from a light incident surface of the metallic filter increases. 
     (13) 
     The semiconductor device according to (12), in which 
     an inclination angle of the sidewall with respect to the light incident surface of the metallic filter is not greater than (90°−the maximum incident angle of light incident on the sidewall). 
     (14) 
     The semiconductor device according to any one of (1) to (13), in which 
     an antireflective film that surrounds at least part of a periphery of the first pixel and reduces reflected light is formed on a light incident surface of the metallic filter. 
     (15) 
     The semiconductor device according to (14), in which 
     the antireflective film is a black filter. 
     (16) 
     The semiconductor device according to any one of (1) to (15), in which 
     the metallic filter is a plasmon filter. 
     (17) 
     The semiconductor device according to any one of (1) to (16), in which 
     the metallic filter is a Fabry-Perot. 
     (18) 
     An electronic apparatus including: 
     a semiconductor device; and 
     a signal processing unit that processes a signal output from the semiconductor device, 
     in which the semiconductor device includes: 
     a pixel unit in which a first pixel including a metallic filter and a second pixel not including the metallic filter are disposed adjacent to each other; and 
     a reflected light reduction unit that reduces reflected light on a sidewall of the metallic filter at a boundary portion between the first pixel and the second pixel. 
     Note that the advantageous effects described in this specification are merely examples, and the advantageous effects of the present technology are not limited to them and may include other effects. 
     REFERENCE SIGNS LIST 
     
         
           10  Imaging apparatus 
           11  Optical system 
           12 ,  12 A to  12 C Imaging device 
           14  Signal processing unit 
           31  Pixel array 
           31 A Normal pixel region 
           31 B Narrowband pixel region 
           31 C Reflected light reduction unit 
           31 D Invalid pixel region 
           51  Pixel 
           51 A Normal pixel 
           51 B Narrowband pixel 
           103  Filter layer 
           105  Photoelectric conversion element layer v 121 A to  121 E,  151 ,  171  Plasmon filter 
           201 A to  201 C Black filter 
           211  Optical filter 
           211 R Red filter 
           211 B Blue filter 
           221 A to  221 C Black filter 
           231 A to  231 C Low-reflection film 
           301  Image circle 
           402  Semiconductor chip 
           421  Antireflective film 
           501  Fabry-Perot 
           600  Electronic apparatus 
           603  Imaging device 
         CF Color filter 
         NB Narrowband filter 
         SW 1  to SW 3  Sidewall 
         PD Photodiode 
         B 1  Boundary portion