JP2019159080A - Solid-state imaging device - Google Patents

Abstract

To enable polarization information to be easily acquired for each color component.SOLUTION: A wire grid polarizer is provided as an optical element on the incidence plane of an imaging element. The array direction of the wire grid is the direction in which desired polarization information is obtained, and an array cycle is the cycle in which light of a desired wavelength is transmitted from incident light. The array direction and the array cycle are set in pixel units. For a pixel block of 2×2 pixels, for example, the array direction of each pixel is made to be four polarization directions differing from each other. For a pixel block, the array cycle in each pixel is made to be equal. For example, a pixel block of red unit UPr for acquiring polarization information of a red component is made to be an array cycle Λthat corresponds to the red component; a pixel block of green unit UPg for acquiring polarization information of a green component is made to be an array cycle Λthat corresponds to the green component; and a pixel block of blue unit UPb for acquiring polarization information of a blue component is made to be an array cycle Λthat corresponds to the blue component. The array cycle, etc., are adjusted in accordance with the incidence angle of incident light.SELECTED DRAWING: Figure 8

Description

  This technique relates to a solid-state imaging device, and makes it possible to obtain polarization information for each color component.

  Conventionally, for example, Patent Document 1 describes that an optical resonance structure is formed in a light receiving element (photoelectric conversion layer), and color separation is performed using the property of localized plasmon resonance or waveguide mode resonance. Non-Patent Document 1 describes that a visible range plasmonic filter is configured using an Al nanowire array having a periodic structure that can excite wavelengths in the visible range.

Japanese Patent No. 5300344

Hiroaki Honma “Study on anomalous transmission control technology of surface plasmon using MEMS technology” Toyohashi University of Technology Degree number No. 741 2016-03-23, Internet / 1117/00001948 /)

  By the way, in order to have multi-wavelength spectral characteristics, as in Patent Document 1 and Non-Patent Document 1, it is common to use surface plasmon characteristics. However, the techniques of Patent Literature 1 and Non-Patent Literature 1 cannot acquire polarization information indicating the polarization characteristics of the subject.

  Accordingly, an object of this technique is to provide a solid-state imaging device that can easily acquire polarization information for each color component.

The first aspect of this technology is
An optical element in which the arrangement direction of the metal wires is a direction in which desired polarization information is obtained and the arrangement period of the metal wires is a period for transmitting light of a desired wavelength from incident light is provided on the incident surface of the imaging element It is in a solid-state imaging device.

  In this technique, a wire grid polarizer is provided on the incident surface of the image sensor as an optical element. The arrangement direction of the wire grid is a direction in which desired polarization information is obtained, and the arrangement period is a period for transmitting light of a desired wavelength from incident light. The arrangement direction and arrangement period of the wire grid are set in units of pixels. For example, in a pixel block composed of a plurality of pixels, the wire grids are arranged in different directions in each pixel. In the pixel block composed of a plurality of pixels, the arrangement period of the wire grids in each pixel is set to be equal.

  Further, a lens is provided for each pixel or each pixel block, and incident light is incident on the incident surface through the lens and the wire grid. Further, the position of the lens with respect to the pixel or the pixel block is moved in the direction of the incident light according to the incident angle of the incident light. Furthermore, the arrangement period is adjusted according to the incident angle of the incident light, and light having a desired wavelength is transmitted.

  When incident light is incident through an aspheric lens, the arrangement period is adjusted according to the incident angle of the incident light through the aspheric lens.

  According to this technology, the optical element in which the arrangement direction of the metal wires is a direction in which desired polarization information is obtained, and the arrangement period of the metal wires is a period in which light having a desired wavelength is transmitted from incident light is an imaging element. Provided on the incident surface. For this reason, polarization information can be easily acquired for each color component. Note that the effects described in the present specification are merely examples and are not limited, and may have additional effects.

It is a figure for demonstrating surface plasmon. It is the figure which showed the optical arrangement | positioning of surface plasmon excitation. It is a figure which shows schematic structure of a CMOS image sensor. It is sectional drawing which shows the structural example of a CMOS image sensor typically. It is the figure which illustrated pixel arrangement | positioning of a pixel array part. It is the figure which illustrated the composition of pixel block BPa. It is the figure which illustrated pixel block BPa of the center part, and pixel block BPb of a peripheral part. It is the figure which illustrated pixel block BPa of the center part in case a pixel array part is a Bayer arrangement. It is the figure which illustrated the structure in the case of acquiring the polarization information for every color component using two or more CMOS image sensors. It is a figure which shows the other structure of a solid-state imaging device. The case where the positional relationship between the on-chip lens and the pixel is adjusted according to the incident angle is shown.

Hereinafter, embodiments for carrying out the present technology will be described. The description will be given in the following order.
1. 1. Periodic structure necessary for plasmon excitation 2. Configuration of solid-state imaging device Regarding other configurations of the solid-state imaging device,
4). Concrete example

<1. Periodic structure required for plasmon excitation>
The surface plasmon is a longitudinal wave caused by plasma electrons existing in a region near 100 nm of the metal surface, and excitation, that is, transfer of energy is performed under these conditions.

  FIG. 1 is a diagram for explaining surface plasmons. A plasmon (plasma wave) in a metal has a surface mode that interacts with light near the surface, and is called a surface plasmon. FIG. 1A is a conceptual diagram of surface plasmons. Near the surface, there is an electric field component in the surface normal direction due to the electron dense wave, and surface plasmon can be excited by using p-polarized incident light having an electric field component in the surface normal direction. It is known that It is also known that surface plasmons exhibit a dispersion relationship different from that of light propagating in free space. The dispersion relationship can be expressed as equation (1) using the surface plasmon wave number kx at the interface, the dielectric constant ε1 of the metal medium, and the dielectric constant ε2 of the peripheral medium. Here, “ω” is the angular frequency, and “c” is the speed of light in vacuum.

  FIG. 1B shows the dispersion relation of surface plasmons. Here, if it is in the region on the left side of the light line LL indicating the incident light (k = ω / c), excitation by light is possible. However, the dispersion curve of the surface plasmon on the flat metal surface is always on the right side of the light line LL and does not have an intersection with the light line LL. That is, surface plasmons cannot be excited by light propagating in free space. Therefore, for example, a diffraction grating is used to excite surface plasmons.

FIG. 2 shows the optical arrangement of surface plasmon excitation. The wave number kx of the diffracted light is represented by the formula (2). “K0” is the wave number of the propagating light, and “m” is the diffraction order, which is an integer. “K” is a lattice vector.
kx = k0 · Sinθ + mK (2)

  When the light is incident on the diffraction grating, the dispersion curve is shifted by an integral multiple of the grating vector K = 2π / Λ, and a point where the dispersion curve of the diffracted light and the surface plasmon intersect is generated. “Λ” is the period of the diffraction grating. Therefore, by adjusting the incident angle θ of the light and the period Λ of the diffraction grating, the dispersion curves of the diffracted light and the surface plasmon are made coincident so that energy transfer, that is, excitation light (transmitted light) can be generated.

  In addition, as the incident angle θ increases, the wave number shift increases as the incident angle θ increases, and the wavelength of the excitation light (transmitted light) generated by energy transfer (excitation wavelength, transmission wavelength). ) Shifts to shorter wavelengths. Therefore, in order to excite (transmit) the same wavelength, the period Λ of the diffraction grating is increased in accordance with the incident angle.

Next, the periodic structure of the diffraction grating will be described. The incident light to be excited is p-polarized light parallel to the periodic structure (periodic direction). The metal used for the diffraction grating has a wider wavelength selection (surface plasmon) range as the plasma frequency is higher. The plasma vibration is a longitudinal wave, and light having a frequency equal to or lower than the plasma frequency is totally reflected on the metal surface. Here, the plasma frequency ωp can be converted into the wavelength λ based on the equation (3).
λ = 2πc / ωp (3)

Further, the visible light wavelength λv can be converted into the angular frequency ω based on the equation (4).
ω = 2πc / λv (4)

Furthermore, the frequency dependence of the dielectric constant of the metal used for the diffraction grating can be calculated based on Equation (5), which is a lossless Drude model.
ε (ω) = 1− (ω _p ² / ω ² ) (5)

  Further, assuming that the dielectric constant ε1 of the embedded material, the period Λ of the periodic structure necessary for excitation can be calculated based on the equation (6). The dielectric constant ε2 is a dielectric constant ε (ω) calculated based on the equation (5). “M” is an integer, “k” is a wave vector, and “θ” is an incident angle.

<2. About Configuration of Solid-State Imaging Device>
FIG. 3 shows a schematic configuration of a solid-state imaging device to which the present technology is applied, for example, an XY address type CMOS image sensor. Here, the CMOS image sensor is an image sensor created by applying or partially using a CMOS process.

  The CMOS image sensor 10 includes a pixel array unit 11 formed on a semiconductor substrate (chip) (not shown) and a peripheral circuit unit integrated on the same semiconductor substrate as the pixel array unit 11. The peripheral circuit unit includes, for example, a vertical drive unit 12, a column processing unit 13, a horizontal drive unit 14, and a system control unit 15.

  The CMOS image sensor 10 includes a signal processing unit 18 and a data storage unit 19. The signal processing unit 18 and the data storage unit 19 may be mounted on the same substrate as the CMOS image sensor 10 or may be disposed on a different substrate from the MOS image sensor 10. In addition, each processing of the signal processing unit 18 and the data storage unit 19 may be processing by an external signal processing unit or software provided on a substrate different from the CMOS image sensor 10.

  The pixel array unit 11 has a configuration in which a plurality of unit pixels are arranged in the row direction and the column direction. Here, the row direction is the pixel arrangement direction (for example, horizontal direction) of the pixel row, and the column direction is the pixel arrangement direction (for example, vertical direction) of the pixel column.

  In the pixel array unit 11, the arrangement direction of the metal wires is a direction in which desired polarization information is obtained, and the arrangement period of the metal wires (corresponding to the period of the diffraction grating) is a period for transmitting light of a desired wavelength from incident light. An optical element such as a wire grid polarizer is provided on an incident surface described later, and is configured to have a polarization pixel. Details of the polarization pixel will be described later.

  The pixel array unit 11 unit pixel includes a photoelectric conversion unit (for example, a photodiode) that generates and accumulates charges according to the amount of received light, and a plurality of pixel transistors. The plurality of pixel transistors can be constituted by three transistors, for example, a transfer transistor, a reset transistor, and an amplification transistor. Alternatively, the plurality of pixel transistors can be configured by four transistors by further adding a selection transistor. Since the equivalent circuit of each pixel is the same as a general circuit, detailed description is omitted here.

  In the pixel array unit 11, pixel drive lines 16 as row signal lines are wired along the row direction for each pixel row, and vertical signal lines 17 as column signal lines are wired along the column direction for each pixel column. Yes. The pixel drive line 16 transmits a drive signal for driving when reading a signal from the pixel. In FIG. 3, the pixel drive line 16 is shown as one wiring, but is not limited to one. One end of the pixel drive line 16 is connected to an output end corresponding to each row of the vertical drive unit 12.

  The vertical drive unit 12 includes a shift register, an address decoder, and the like, and drives each pixel of the pixel array unit 11 at the same time or in units of rows. That is, the vertical drive unit 12 constitutes a drive unit that controls the operation of each pixel of the pixel array unit 11 together with the system control unit 15 that controls the vertical drive unit 12. The vertical drive unit 12 is not shown in the figure for its specific configuration, but generally has a configuration having two scanning systems, a reading scanning system and a sweeping scanning system.

  The readout scanning system selectively scans the unit pixels of the pixel array unit 11 sequentially in units of rows in order to read out signals from the unit pixels. The signal read from the unit pixel is an analog signal. The sweep-out scanning system performs sweep-out scanning on the readout line on which readout scanning is performed by the readout scanning system prior to the readout scanning by the exposure time.

  By the sweep scanning by the sweep scanning system, unnecessary charges are swept out from the photoelectric conversion unit of the unit pixel in the readout row, thereby resetting the photoelectric conversion unit. A so-called electronic shutter operation is performed by sweeping (resetting) unnecessary charges by the sweep scanning system.

  The signal read by the reading operation by the reading scanning system corresponds to the amount of light received after the immediately preceding reading operation or electronic shutter operation. A period from the read timing by the immediately preceding read operation or the sweep timing by the electronic shutter operation to the read timing by the current read operation is the charge exposure period in the unit pixel.

  A signal output from each unit pixel of the pixel row selectively scanned by the vertical driving unit 12 is input to the column processing unit 13 through each of the vertical signal lines 17 for each pixel column. The column processing unit 13 performs predetermined signal processing on signals output from the pixels in the selected row through the vertical signal line 17 for each pixel column of the pixel array unit 11, and temporarily outputs the pixel signals after the signal processing. Hold on. For example, the column processing unit 13 performs noise removal processing, A / D (analog-digital) conversion, and the like as signal processing.

  The horizontal drive unit 14 includes a shift register, an address decoder, and the like, and sequentially selects unit circuits corresponding to the pixel columns of the column processing unit 13. By the selective scanning by the horizontal drive unit 14, pixel signals subjected to signal processing for each unit circuit in the column processing unit 13 are sequentially output.

  The system control unit 15 includes a timing generator that generates various timing signals, and the vertical driving unit 12, the column processing unit 13, and the horizontal driving unit 14 based on various timings generated by the timing generator. Drive control is performed.

  The signal processing unit 18 performs various signal processes on the pixel signal output from the column processing unit 13. The pixel array unit 11 can acquire polarization information for each color component, as will be described later. Therefore, the signal processing unit 18 acquires polarization characteristic information as described later based on the polarization information for each color component. In addition, the signal processing unit 18 performs separation and extraction of the reflection component based on the polarization characteristic information by using, for example, a technique disclosed in a patent document (International Publication No. 2016/136085). Further, the signal processing unit 18 may perform subject recognition, orientation / posture determination, and the like using, for example, a technique disclosed in a patent document (International Publication No. 2016/174915).

  The data storage unit 19 temporarily stores data necessary for the signal processing in the signal processing unit 18.

  FIG. 4 is a cross-sectional view schematically showing a configuration example of a CMOS image sensor. FIG. 4 shows a cross section of the polarizing pixel portion.

  Hereinafter, the light incident side (upper side in FIG. 4) is above the CMOS image sensor 10, and the side opposite to the light incident side (lower side in FIG. 4) is below the CMOS image sensor 10.

  The CMOS image sensor 10 has a so-called back irradiation type structure in which light is incident from the back side opposite to the surface on which the wiring layer 101 of the semiconductor substrate 102 is laminated. Hereinafter, the back surface of the semiconductor substrate 102 is referred to as an incident surface or an imaging surface.

  In the wiring layer 101, the wiring 121 is laminated over a plurality of layers. A gate electrode 122 is formed for each pixel in the vicinity of the boundary between the wiring layer 101 and the semiconductor substrate 102.

  In the semiconductor substrate 102, a photoelectric conversion element 123 is formed in the region of the polarization pixel. Note that the photoelectric conversion element 123 is configured by, for example, a photodiode.

  A trench is formed between the photoelectric conversion elements 123 from the incident surface side of the semiconductor substrate 102. An insulating film 124 is formed on the incident surface of the semiconductor substrate 102 and the wall surface of the trench. A vertical portion 125 a of the light shielding film 125 is embedded in the trench of the semiconductor substrate 102.

  On the incident surface of the semiconductor substrate 102, the horizontal portion 125 b of the light shielding film 125 and the polarizer 126 are formed via the insulating film 124.

  The horizontal portion 125 b of the light shielding film 125 covers the incident surface of the semiconductor substrate 102, and an opening is formed above the photoelectric conversion element 123. That is, the horizontal portion 125b of the light shielding film 125 is formed so as to fill in between adjacent pixels. Incidence of light in an oblique direction from adjacent pixels is suppressed by the vertical portion 125a and the horizontal portion 125b of the light shielding film 125.

  The polarizer 126 is formed in the opening above the photoelectric conversion element 123 in the horizontal portion 125 b of the light shielding film 125, and covers the upper surface (incident surface) of the photoelectric conversion element 123. The polarizer 126 is, for example, a wire grid polarizer. The polarizer 126 passes a polarized wave having an electric field component perpendicular to the direction in which the wire grid extends, and suppresses the passage of a polarized wave having an electric field component parallel to the direction in which the wire grid extends. As a material of the polarizer 126, for example, aluminum, copper, gold, silver, platinum, tungsten, or an alloy containing these metals is used. The polarizer 126 has a configuration in which a wire grid is provided in a direction in which desired polarization information can be obtained, and the arrangement period of the wire grid is set according to the transmitted color and the incident angle of incident light as described later. ing. In FIG. 4 and FIGS. 10 and 11 described later, a red pixel PXr and a green pixel PXb having a shorter wavelength than the red pixel, for example, are shown.

  Next, the pixel array unit 11 will be described. The pixel array unit 11 is configured using polarized pixels or polarized images and non-polarized pixels. In the polarization pixel, the arrangement direction of the wire grid is a direction in which desired polarization information can be obtained. Further, in the polarization pixel, the arrangement period of the wire grid is a period for transmitting (exciting) light having a desired wavelength from incident light. As described above, this wire grid is provided above the photoelectric conversion element 123, that is, on the incident surface of the CMOS image sensor.

  The arrangement direction and arrangement period of the wire grid are set in units of pixels. Further, for example, in the pixel block composed of a plurality of pixels, the polarization pixels are arranged in different directions from each other in the wire grid arrangement direction of each pixel. Therefore, a plurality of pieces of polarization information having different polarization directions can be acquired for each pixel block.

  Further, the arrangement direction of the wire grid is set so that the polarization characteristic information can be acquired using the pixel values of the polarization pixels of different arrangement directions. For example, in the case of diffuse reflection, assuming that the polarization angle υpol when the maximum luminance Idmax is observed is the azimuth angle φd, a predetermined change caused by a change in the luminance Idpol observed when the polarization angle is rotated, that is, a difference in the polarization angle. The polarization model equation showing the luminance change can be expressed as equation (7).

  In Expression (7), the polarization angle υpol is obvious when the polarization image is generated, and the maximum luminance Idmax, the minimum luminance Idmin, and the azimuth angle φd are variables. Accordingly, since there are three variables, the normal vector information generation unit 35 performs fitting to the function shown in Expression (7) using the luminance of the polarization image having three or more polarization directions, and the luminance and the polarization angle. The polarization characteristic information indicating the relationship can be acquired.

  In a pixel block composed of a plurality of pixels, the arrangement period of the wire grids in each pixel is set to an equal period. Therefore, it becomes possible to acquire the polarization characteristic information for the color component corresponding to the array period of the wire grid for each pixel block.

  FIG. 5 exemplifies the pixel arrangement of the pixel array unit. In the central pixel block BPa, the incident light incident angle θa is “θa = 0 degrees”, and in the peripheral pixel block BPb, incident light is incident. The angle θb is “θb> 0 degree”.

FIG. 6 illustrates the configuration of the pixel block BPa. The pixel block of 2 × 2 pixels has any one of four directions in which the arrangement direction of the wire grids is different and is different from each other. In the 2 × 2 pixel block, the arrangement period of the wire grid is an arrangement period _Λθa . FIG. 6 shows the case where the wire grid has a horizontal direction and a tilt of 135 °, but the arrangement period is the same when the wire grid has a vertical direction and a tilt of 45 °.

FIG. 7 illustrates the pixel block BPa in the central portion and the pixel block BPb in the peripheral portion. FIG. 7A shows the configuration of the pixel block BPa in the central portion. Like FIG. 6, the wire grid has an arrangement period Λ _θa in the pixel block of 2 × 2 pixels.

FIG. 7B shows the configuration of the pixel block BPb in the peripheral portion. As described above in “Regular structure necessary for plasmon excitation”, the transmission (excitation) wavelength shifts to a short wavelength when the incident angle increases. Therefore, in order to transmit (excite) the same wavelength as the pixel block BPa in the central portion, the wire grid is set to an arrangement period Λ _θb (> Λ _θa ) corresponding to the incident angle. As described above, when the arrangement period is set in accordance with the incident angle, polarization information having the same wavelength can be acquired not only in the central portion but also in the peripheral portion of the pixel array portion.

  Further, when the pixel array unit is configured as a Bayer array, a 2 × 2 pixel block is set as a color array unit (4 × 4 pixels), and four pixel blocks are set as a red unit, a blue unit, and two green units. FIG. 8 illustrates the pixel block BPa at the center when the pixel array portion is a Bayer array.

In the 2 × 2 pixel block which is the red unit UPr, the arrangement period of the wire grid is set to an arrangement period Λ _rθa so that the red wavelength is transmitted (excited). In the 2 × 2 pixel block having the green unit UPg, the arrangement period of the wire grid is set to an arrangement period Λ _gθa so that the green wavelength is transmitted (excited). Further, in the 2 × 2 pixel block which is the blue unit UPb, the arrangement period of the wire grid is set to the arrangement period Λ _bθa so that the blue wavelength is transmitted (excited).

  As described above, by adjusting the arrangement period of the wire grid, it is possible to acquire polarization characteristic information for each color component without using a color filter. Although not shown, if the arrangement period of each color is adjusted according to the incident angle, polarization characteristic information can be acquired for each color component not only in the central part but also in the peripheral part of the pixel array part.

  In addition, in the present technology, polarization information can be acquired for each color component by using a wire grid having a thickness of 100 to several hundred nm without using a color filter having a thickness of several hundred to several hundreds of nm. For this reason, a low profile structure can be realized as compared with a CMOS image sensor in which a color filter is provided in the sensor. Further, the low-profile structure makes it possible to reduce the amount of pupil correction and realize a narrow band of a desired signal, and to secure various manufacturing margins and characteristic margins.

  6 to 8 show the case where the polarization direction is four directions. However, in the case where there is no problem even if the polarization information is coarse (for example, when only unevenness is determined), the polarization direction is changed. The basic unit may be two directions of 0 degree and 90 degrees, or two directions of 45 degrees and 135 degrees. Further, for example, 22.5 degrees, 67.5 degrees, 112.5 degrees, 157.5 degrees, and the like may be added to the polarization direction to increase the basic unit from four directions. In this case, polarization information can be acquired with high accuracy.

Further, polarization information for each color component may be acquired by using a plurality of CMOS image sensors each having a pixel array having the configuration shown in FIGS. For example, in the CMOS image sensor 10R that acquires the polarization information of the red component, the arrangement period of the wire grid in the central portion of the pixel array is set to the arrangement period Λ _rθa so that the red wavelength is transmitted (excited). In addition, the arrangement period of the wire grid in the peripheral portion is an arrangement period corresponding to the incident angle, for example, an arrangement period Λ _rθb when the incident angle is θb.

Similarly, in the CMOS image sensor 10G that acquires the polarization information of the green component, the arrangement period of the wire grid in the center portion of the pixel array is set to an arrangement period Λ _gθa so as to transmit (excite) the green wavelength. Further, the arrangement period of the wire grid in the peripheral portion is an arrangement period corresponding to the incident angle, for example, an arrangement period Λ _gθb when the incident angle is θb.

Further, in the CMOS image sensor 10B that acquires the polarization information of the blue component, the arrangement period of the wire grid in the central portion of the pixel array is set to the arrangement period Λ _bθa so that the blue wavelength is transmitted (excited). The arrangement period of the wire grid in the peripheral portion is an arrangement period corresponding to the incident angle, for example, an arrangement period Λ _bθb when the incident angle is θb.

  FIG. 9 illustrates a configuration in the case where polarization information for each color component is acquired using a plurality of CMOS image sensors. Incident light is divided into, for example, three by the light dividing unit 20. The divided light is input to the CMOS image sensor 10R that acquires the polarization information of the red component, the CMOS image sensor 10G that acquires the polarization information of the green component, and the CMOS image sensor 10B that acquires the polarization information of the blue component. . In the CMOS image sensor 10R, the polarization information of the red component is generated as described above. Further, the CMOS image sensor 10G generates green component polarization information as described above. Further, the CMOS image sensor 10B generates blue component polarization information as described above. Therefore, polarization information for each desired color component can be generated without using a color separation prism or the like. Further, by providing a CMOS image sensor for each color component, it is possible to obtain detailed polarization information while maintaining the resolution.

  Further, when a color separation prism is used instead of the light splitting unit 20 as in the past, if the arrangement period of the wire grid is adjusted according to the wavelength of the color separation light, light of a desired wavelength can be transmitted accurately ( Excitation). Furthermore, if four or more CMOS image sensors are provided, detailed polarization information can be acquired for each more detailed color component while maintaining the resolution.

<3. Other configuration of solid-state imaging device>
In the case where the CMOS image sensor has the configuration shown in FIG. 4, the incident angle becomes large in the peripheral pixels, so that it is difficult for light to enter the photoelectric conversion element 123. Therefore, in another configuration of the solid-state imaging device shown in FIG. 10, a condensing element 127, for example, an on-chip lens is formed above the wire grid (on the side opposite to the incident surface). As described above, when the light collecting element 127 is provided, incident light can be efficiently incident on the photoelectric conversion element 123.

  The on-chip lens may be provided for each pixel, for example, or may be provided for each pixel block that is greatly omitted by a plurality of polarization pixels having different polarization directions. FIG. 10 illustrates the case where each pixel is provided.

  Furthermore, when the incident angle of incident light becomes large, the position of the on-chip lens with respect to the pixel or the pixel block may be moved in the direction of incident light according to the incident angle. FIG. 11 shows a case where the position of the on-chip lens with respect to the pixel or the pixel block is moved according to the incident angle. As described above, the position of the on-chip lens with respect to the pixel or the pixel block is adjusted according to the incident angle, and as the incident angle increases, the optical axis position LPc of the on-chip lens is changed, for example, from the center position GPc of the pixel. Move more in the direction. In this case, incident light can be efficiently incident on the photoelectric conversion element 123 via the polarizer 126, compared to the case where the center position of the on-chip lens is the center position of the pixel.

  In addition, incident light may be incident on the CMOS image sensor 10 via an aspheric lens (or a lens group configured using a plurality of lenses). Here, the relationship between the incident light incident on the aspherical lens and the image height has nonlinear characteristics. Therefore, when the incident light incident on the CMOS image sensor 10 is incident through the aspheric lens, the arrangement period is adjusted according to the incident angle of the incident light through the aspheric lens.

  In the present technology, the arrangement direction and the arrangement period of the wire grid polarizer may be set so that polarization information of a desired color component can be obtained and provided on the incident surface of the image sensor. The configuration is not limited to those shown in FIGS. 4, 10, and 11. The image sensor is not limited to a CMOS image sensor, and may be an image sensor of another type (for example, a CCD image sensor).

<4. Specific example>
Next, the arrangement period of the wire grid when aluminum is used as the material of the polarizer 126 will be described. The filling material is silicon dioxide, and the dielectric constant is 2.25.

For example, when acquiring polarization information of a red component (λ = 650 nm), the wavelength of the red component is “2898 THz” when an angular frequency is set based on the equation (4). The plasma frequency of aluminum is “24000 THz”. When the Drude model is used for the frequency dependence of the dielectric constant of aluminum, the dielectric constant of aluminum at the wavelength of the red component (λ = 650 nm) is “−67.56” based on Equation (5). Therefore, based on Expression (6), the arrangement period Λ _rθa of the incident angle θa (= 0 degree) is “426.057 nm”. When the incident angle is θb (= 20 degrees), the arrangement period Λ _rθb is “549.173 nm” based on the equation (2) and the like.

When the polarization information of the green component (λ = 550 nm) is acquired, “3425 THz” is obtained when the wavelength of the green component is an angular frequency based on Expression (4). The plasma frequency of aluminum is “24000 THz”. If the Drude model is used for the frequency dependence of the dielectric constant of aluminum, the dielectric constant of aluminum at the wavelength of the green component (λ = 550 nm) is “−48.09” based on the equation (5). Therefore, based on the equation (6), the arrangement period Λ _gθa of the incident angle θa (= 0 degree) is “357.986 nm”. When the incident angle is θb (= 20 degrees), the arrangement period Λ _gθb is “460.501 nm” based on the equation (2) and the like.

When the polarization information of the blue component (λ = 450 nm) is acquired, “4187 THz” is obtained when the wavelength of the blue component is an angular frequency based on Equation (4). The plasma frequency of aluminum is “24000 THz”. When the Drude model is used for the frequency dependence of the dielectric constant of aluminum, the dielectric constant of aluminum at the wavelength of the blue component (λ = 450 nm) is “−31.86” based on Equation (5). Therefore, based on Expression (6), the arrangement period Λ _bθa of the incident angle θa (= 0 degree) is “289.213 nm”. When the incident angle is θb (= 20 degrees), the arrangement period Λ _bθb is “370.698 nm” based on the equation (2) and the like.

Thus, if the wire grid using aluminum is used as a polarizing member, and the arrangement period of the wire grid is the period shown in FIG. 10 and the arrangement direction is a predetermined number of polarization directions or more, the red component, the green component, and the blue component Polarization information can be obtained for each component. Note that the effects described in this specification are merely examples and are not limited, and there may be additional effects that are not described. Further, the present technology should not be construed as being limited to the embodiments of the technology described above. The embodiments of this technology disclose the present technology in the form of examples, and it is obvious that those skilled in the art can make modifications and substitutions of the embodiments without departing from the gist of the present technology. In other words, in order to determine the gist of the present technology, the claims should be taken into consideration.

In addition, the solid-state imaging device of the present technology can also have the following configuration.
(1) An optical element in which the arrangement direction of the metal wires is a direction in which desired polarization information is obtained, and the arrangement period of the metal wires is a period for transmitting light of a desired wavelength from incident light is defined as an incident surface of the imaging element. Solid-state imaging device provided in
(2) The solid-state imaging device according to (1), wherein the optical element is a wire grid polarizer.
(3) The solid-state imaging device according to (2), wherein the arrangement direction and the arrangement period of the wire grid are set in units of pixels.
(4) The solid-state imaging device according to (3), wherein the arrangement direction of the wire grid in each pixel is different from each other in a pixel block including a plurality of pixels.
(5) In the pixel block including the plurality of pixels, the solid-state imaging device according to (4), wherein the array period of the wire grid in each pixel is set to an equal period.
(6) A solid-state imaging according to any one of (2) to (5), wherein a lens is provided for each pixel or each pixel block, and the incident light is incident on the incident surface via the lens and the wire grid. apparatus.
(7) The solid-state imaging device according to (6), wherein the position of the lens with respect to the pixel or the pixel block is moved in the direction of the incident light according to an incident angle of the incident light.
(8) The solid-state imaging device according to any one of (1) to (7), wherein the arrangement period is adjusted according to an incident angle of the incident light, and the light having the desired wavelength is transmitted.
(9) When the incident light is incident through the aspheric lens, the arrangement period is adjusted according to an incident angle of the incident light through the aspheric lens. Solid-state imaging device.

In addition, according to the present technology, an electronic device having the following configuration can be provided. (1) The arrangement direction of the metal wires is a direction in which desired polarization information can be obtained, and the arrangement period of the metal wires is desired from incident light. A solid-state imaging device in which an optical element having a period for transmitting light of the wavelength is provided on the incident surface of the imaging element;
An electronic apparatus comprising: a signal processing unit that performs signal processing using polarization information of a desired wavelength obtained by the solid-state imaging device.

  In the solid-state imaging device and the electronic apparatus of this technology, the arrangement direction of the metal wires is a direction in which desired polarization information is obtained, and the arrangement period of the metal wires is a period in which light having a desired wavelength is transmitted from incident light. The element is provided on the incident surface of the imaging element. Therefore, polarization information can be easily acquired for each color component. In addition, since polarization information is used for each color component, various signal processes such as removal of reflection components and detection of the orientation and orientation of a subject can be performed, which is suitable for a monitoring system, a mobile control system, and the like.

10, 10R, 10G, 10B ... CMOS image sensor 11 ... Pixel array unit 12 ... Vertical drive unit 13 ... Column processing unit 14 ... Horizontal drive unit 15 ... System control unit 16 ..Pixel drive line 17... Vertical signal line 18... Signal processing unit 19... Data storage unit 20 .. light splitting unit 35. ..Semiconductor substrate 121 ... wiring 122 ... gate electrode 123 ... photoelectric conversion element 124 ... insulating film 125 ... light shielding film 126 ... polarizer 127 ... light collecting element

Claims (9)

An optical element in which the arrangement direction of the metal wires is a direction in which desired polarization information is obtained and the arrangement period of the metal wires is a period for transmitting light of a desired wavelength from incident light is provided on the incident surface of the imaging element Solid-state imaging device. The solid-state imaging device according to claim 1, wherein the optical element is a wire grid polarizer. The solid-state imaging device according to claim 2, wherein the arrangement direction and the arrangement period of the wire grid are set in units of pixels. The solid-state imaging device according to claim 3, wherein in a pixel block composed of a plurality of pixels, the arrangement direction of the wire grid in each pixel is different from each other. The solid-state imaging device according to claim 4, wherein in the pixel block composed of the plurality of pixels, the arrangement period of the wire grid in each pixel is set to be equal. The solid-state imaging device according to claim 2, wherein a lens is provided for each pixel or each pixel block, and the incident light is incident on the incident surface via the lens and the wire grid. The solid-state imaging device according to claim 6, wherein a position of the lens with respect to the pixel or the pixel block is moved in a direction of the incident light according to an incident angle of the incident light. The solid-state imaging device according to claim 1, wherein the arrangement period is adjusted according to an incident angle of the incident light, and the light having the desired wavelength is transmitted. The solid-state imaging device according to claim 8, wherein when the incident light is incident through the aspheric lens, the arrangement period is adjusted according to an incident angle of the incident light through the aspheric lens.

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