Optical element, imaging element, and imaging device

Abstract

The optical element includes: a transparent layer that covers a pixel including a first photoelectric conversion element and a second photoelectric conversion element; and a plurality of structures that are arranged in a plane direction of the transparent layer on or within the transparent layer. The transparent layer includes: a first region that guides incident light to the first photoelectric conversion element; and a second region that guides incident light to the second photoelectric conversion element. A plurality of structures are arranged in at least the second region among the first region and the second region, and the first region is smaller than the second region.

Description

Technical Field

[0001] The present invention relates to an optical element, an imaging element, and an imaging device. Background Art

[0002] In an imaging device, improvement of the dynamic range is being studied. For example, Non-Patent Document 1 discloses a method of improving the dynamic range by providing a high-sensitivity photodiode having a large size and a low-sensitivity photodiode having a small size for one pixel.

[0003] Prior Art Documents

[0004] Non-Patent Documents

[0005] Non-Patent Document 1: Boyd Fowler et al., "Automotive Image Sensors", [online], February 1, 2018, Electronic Imaging 2018, [searched on August 12, 2020], Internet <URL: http: / / www.imaging.org / Site / PDFS / Conferences / ElectronicImaging / EI2018 / Keynotes / EI2018_IMSE_Keynote_Fowler_Solhusvik.pdf> Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] When a plurality of photodiodes are provided as described above, for example, the aperture ratios of the lens and the pixel are reduced, and accordingly, the light utilization efficiency is reduced. Regarding the light utilization efficiency, no particular study has been made in Non-Patent Document 1.

[0008] An object of the present invention is to simultaneously improve the dynamic range and the light utilization efficiency.

[0009] Means for Solving the Problems

[0010] The optical element of the present invention is characterized by having: a transparent layer for covering a pixel including a first photoelectric conversion element and a second photoelectric conversion element; and a plurality of structures arranged in a plane direction of the transparent layer on or in the transparent layer, the transparent layer including: a first region for guiding incident light to the first photoelectric conversion element; and a second region for guiding incident light to the second photoelectric conversion element, and a plurality of structures are arranged in at least the second region of the first region and the second region, and the first region is smaller than the second region.

[0011] The imaging element of the present invention is characterized by including: the above optical element; and a plurality of pixels, each of which includes a first photoelectric conversion element and a second photoelectric conversion element.

[0012] The imaging device of the present invention is characterized by including: the above imaging element; and a signal processing control unit that generates an image signal based on an electrical signal obtained from the imaging element.

[0013] Advantages of the Invention

[0014] According to the present invention, it is possible to simultaneously achieve an improvement in dynamic range and an improvement in light utilization efficiency. Description of the Drawings

[0015] Figure 1 It is a diagram showing an example of the schematic structure of the optical element, imaging element, and imaging device of the embodiment.

[0016] Figure 2 It is a diagram showing an example of the schematic structure of a part corresponding to one pixel in the imaging element.

[0017] Figure 3 It is a diagram showing an example of the schematic structure of a part corresponding to one pixel in the imaging element.

[0018] Figure 4 It is a diagram showing an example of light distribution.

[0019] Figure 5 It is a diagram showing an example of the schematic configuration of a structure.

[0020] Figure 6 It is a diagram showing an example of the schematic configuration of a structure.

[0021] Figure 7 It is a diagram showing an example of the characteristics of a structure.

[0022] Figure 8 It is a diagram showing an example of the characteristics of a structure.

[0023] Figure 9 It is a diagram showing an example of the lens design of an optical element.

[0024] Figure 10 It is a diagram showing an example of the lens design of an optical element.

[0025] Figure 11 It is a diagram showing an example of the lens design of an optical element.

[0026] Figure 12 It is a diagram showing an example of the amount of light guided to the PD (detected light amount).

[0027] Figure 13It is a diagram showing an example of the amount of light (detected light amount) guided to the PD.

[0028] Figure 14 It is a diagram showing an example of the amount of light (detected light amount) guided to the PD.

[0029] Figure 15 It is a diagram showing the wavelength dependence of the light amount ratio of the light guided to each PD.

[0030] Figure 16 It is a diagram showing the wavelength dependence of the light amount ratio of the light guided to each PD.

[0031] Figure 17 It is a diagram showing the wavelength dependence of the light amount ratio of the light guided to each PD.

[0032] Figure 18 It is a diagram showing an example of the lens design of an optical element.

[0033] Figure 19 It is a diagram showing an example of the lens design of an optical element.

[0034] Figure 20 It is a diagram showing an example of the lens design of an optical element.

[0035] Figure 21 It is a diagram showing an example of the lens design of an optical element.

[0036] Figure 22 It is a diagram showing an example of the arrangement region of a structure.

[0037] Figure 23 It is a diagram showing an example of the arrangement region of a structure.

[0038] Figure 24 It is a diagram showing an example of the arrangement region of a structure.

[0039] Figure 25 It is a diagram showing an example of the arrangement region of a structure.

[0040] Figure 26 It is a diagram showing an example of the arrangement region of a structure. Detailed Description of the Invention

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The shapes, sizes, positional relationships, etc. shown in the drawings are merely schematic, and the present invention is not limited thereto. The same parts are denoted by the same reference numerals, and repeated descriptions are omitted.

[0042] Figure 1This is a diagram showing an example of the schematic structure of an optical element, an imaging element, and an imaging device according to an embodiment. The imaging device 10 captures an object 1 using the light from the object 1 (subject) as incident light. In this example, the object 1 is illustrated as a hollow arrow. The incident light enters the imaging element 12 via the lens optical system 11. The imaging element 12 includes a plurality of pixels 2 and a plurality of optical elements 6 corresponding to the plurality of pixels 2. The pixels 2 are provided for each wavelength band (for example, each color). The signal processing control unit 13 performs various controls related to the imaging element 12. Hereinafter, with reference to Figure 2 the following diagrams, the imaging element 12 will be described in detail, and then, the signal processing control unit 13 will be described.

[0043] Figure 2 This is a diagram showing an example of the schematic structure of a part corresponding to one pixel in the imaging element. In the figure, an XYZ coordinate system is shown, and the traveling direction of the incident light is schematically shown by an arrow. The Z-axis direction corresponds to the stacking direction of the PD layer 4, the filter layer 5, and the transparent layer 60 described later. The XY plane direction corresponds to the plane direction of these layers. Hereinafter, "top view" means observing along the Z-axis direction (for example, along the negative Z-axis direction), and "side view" means observing along the X-axis direction or the Y-axis direction (for example, along the positive Y-axis direction). Figure 2 This is a cross-sectional view showing an example of the schematic structure of a part of the imaging element 12 when viewed from the side.

[0044] The imaging element 12 includes a pixel 2, a filter layer 5, and an optical element 6. The pixel 2 includes a wiring layer 3 and a PD (photodiode) layer 4. An example of the optical element 6 is a metasurface. Hereinafter, the case where the optical element 6 is a metasurface will be described. A metasurface is an element composed of a plurality of microstructures having a width smaller than the wavelength of light, and can be either a two-dimensional structure or a three-dimensional structure. By using a metasurface as the optical element, there is an effect that the phase and the light intensity can be controlled according to the characteristics of light (wavelength, polarization, incident angle) only by changing the parameters of the microstructures. In the case of a three-dimensional structure, there is an effect of increasing the above-mentioned design freedom.

[0045] Starting the description from the PD layer 4 in the wiring layer 3 and the PD layer 4, the PD layer 4 includes a PD41 (first photoelectric conversion element) and a PD42 (second photoelectric conversion element) provided in the plane direction (XY plane direction) of the layer. The PD41 and the PD42 are formed on the semiconductor substrate 100. The PD41 and the PD42 may have the same size (light-receiving area) when viewed from above. The PD41 and the PD42 may have the same size (depth) when viewed from the side. The PD41 and the PD42 may have the same shape. In the case where the PD41 and the PD42 have the same shape, there are advantages such as an increase in manufacturing yield.

[0046] The charges generated by PD41 and PD42 are converted into electrical signals that serve as the basis for pixel signals by transistors (not shown) and are output to the outside of pixel 2 via wiring layer 3. Several wirings in wiring layer 3 corresponding to PD41 are illustrated as wiring 31, and several wirings corresponding to PD42 are illustrated as wiring 32.

[0047] The filter layer 5 is a color filter that allows light of the color corresponding to pixel 2 to pass through, and is provided on the upper surface (the surface on the positive Z-axis side) of the semiconductor substrate 100. In this example, the filter layer 5 is provided between the PD layer 4 and the transparent layer 60. As an example of the material of the filter layer 5, an organic material such as resin is used.

[0048] The optical element 6 guides the incident light to PD41 and PD42 respectively. The optical element 6 is provided so as to face the PD layer 4, and in this example, is provided on the upper surface (the surface on the positive Z-axis side) of the filter layer 5. The optical element 6 includes a transparent layer 60 and a plurality of structures 70. In addition, in Figure 2 the example shown, the plurality of structures 70 include a plurality of structures 71 and a plurality of structures 72 described later. The transparent layer 60 covers PD41 and PD42. The portion of the transparent layer 60 where the plurality of structures 70 are not provided may have a refractive index lower than that of the structures 70. As an example of the material of such a transparent layer 60, SiO2 or the like is used. The transparent layer 60 may also be a void, in which case the refractive index of the transparent layer 60 is the refractive index of air. The transparent layer 60 includes a region 61 and a region 62. The region 61 is a first region that guides the light incident on the region 61 to PD41. The region 62 is a second region that guides the light incident on the region 62 to PD42. "Guiding" light includes allowing the light to pass directly through, changing the traveling direction of the light (such as condensing the light), and the like.

[0049] The region 61 and the region 62 will be further described. The region 61 is a region where a plurality of structures 71 are provided. In Figure 2 the example shown, the plurality of structures 71 are provided on the upper surface (the surface on the positive Z-axis side) of the transparent layer 60, and the region 61 at least refers to a portion near the upper surface of the transparent layer 60. The region 62 is a region where a plurality of structures 72 are provided. In Figure 2 the example shown, the plurality of structures 72 are provided on the upper surface of the transparent layer 60, and the region 62 at least refers to a portion near the upper surface of the transparent layer 60. The region 61 and the region 62 may be at the same height (the same position in the Z-axis direction). In addition, there may be no plurality of structures 71, in which case the region 61 may refer to the portion of the transparent layer 60 where the plurality of structures 72 are not provided. Hereinafter, unless otherwise specified, the method in which a plurality of structures 71 are provided in the region 61 as Figure 2 shown will be described.

[0050] The description of the multiple structures 70 is repeated. The multiple structures 70 are arranged on or within the transparent layer 60 along the plane direction (XY plane direction) of the transparent layer 60. It can be said that they are arranged in a two-dimensional direction (in a two-dimensional shape). As described above, in Figure 2 the example shown, the multiple structures 70 are provided on the upper surface of the transparent layer 60. The multiple structures 70 can be arranged at unequal intervals or at equal intervals for ease of design or the like. The multiple structures 70 are each a fine structure having a size on the order of or smaller than the wavelength (nanometer level) of the incident light. The multiple structures 70 are designed to correspond to the color corresponding to the pixel 2, that is, the light of the color (transmission band) of the filter layer 5. The multiple structures 70 can be integrated into the pixel 2. In addition, when the multiple structures 70 are provided within the transparent layer 60, the region 61 at least refers to the portion within the transparent layer 60 where the multiple structures 71 are located. The region 62 at least refers to the portion within the transparent layer 60 where the multiple structures 72 are located.

[0051] The multiple structures 70 are arranged so as to converge the incident light onto the PD41 and PD42. The principle of the light concentration of the transparent layer 60, that is, the lens (on-chip lens) function, will be described later. In the present embodiment, the multiple structures 70 include multiple structures 71 and multiple structures 72. The multiple structures 71 are multiple first structures configured to converge the incident light onto the PD41. The multiple structures 72 are multiple second structures arranged to converge the incident light onto the PD42.

[0052] Figure 3 is a diagram showing an example of the schematic structure of a part corresponding to one pixel in the imaging element. In Figure 3 an example of the layout of the optical element 6, the PD41, and the PD42 in a plan view is shown. The regions 61, 62, and the PD layer 4 located below (on the negative Z-axis side) the multiple structures 70 in the transparent layer 60 are indicated by dashed lines. In addition, in order to easily distinguish the multiple structures 71 and the multiple structures 72 included in the multiple structures 70, the same hatching as Figure 2 is marked.

[0053] As Figure 3 shown, in a plan view, the arrangement area of the multiple structures 71 is smaller than the arrangement area of the multiple structures 72. That is, the region 61 is smaller than the region 62. In addition, in this example, the smaller region 61 overlaps with the PD41 so as to be located inside the corresponding PD41. The amount of converging light of the multiple structures 71 converging onto the PD41 is smaller than the amount of converging light of the multiple structures 72 in the region 62 converging onto the PD42. Regarding this, reference is also made to Figure 4 for explanation.

[0054] Figure 4 is a diagram showing an example of the light distribution. In Figure 4 , an example of the condensing distribution in the PD layer 4 when viewed from above is shown. The position where x is 0 μm corresponds to the middle position between PD41 and PD42 in the X-axis direction. The position where y is 0 μm corresponds to the center position of PD41 and the center position of PD42 in the Y-axis direction. That is, Figure 4 the roughly left half part (the part on the negative X-axis side) corresponds to PD41, and the roughly right half part (the part on the positive X-axis side) corresponds to PD42. The amount of converging light toward PD41 is smaller than the amount of converging light toward PD42. Therefore, PD41 is less likely to saturate than PD42.

[0055] Refer to Figure 5 and Figure 6 to illustrate an example of the structure of the optical element 6 that can achieve the lens function of mixing multiple lenses with different condensing positions as described above.

[0056] Figure 5 and Figure 6 are diagrams showing examples of the schematic structure of the structure body. In Figure 5 , an example of the side view of the structure body 70 is shown. In Figure 6 , an example of the top view (upper view) of the structure body 70 is shown. The structure body 70 is a columnar structure body having a rectangular columnar shape and is formed on the base 70a. The base 70a is, for example, a quartz substrate.

[0057] The height (the length in the Z-axis direction) of the structure body 70 is illustrated as the height H. The width (the length in the X-axis direction and the length in the Y-axis direction) of the structure body 70 is illustrated as the width W. In the same structure body 70, the width W can be the same or different in the X-axis direction and the Y-axis direction. Hereinafter, it is assumed that the width W is the same in the X-axis direction and the Y-axis direction.

[0058] The width (the length in the X-axis direction and the length in the Y-axis direction) of the base 70a is larger than the width W of the structure body 70. For example, the width of the base 70a can be about 320 nm. In this case, the width W of the structure body 70 is less than 320 nm. The difference between the width of the structure body 70 and the width of the base 70a gives the distance (interval) between adjacent structure bodies 70. The interval between the structure bodies 70 can be constant (equidistant) for all the structure bodies 70 or different.

[0059] The structure body 70 has a refractive index different from that of other parts, more specifically, the part between the structure bodies 70. The structure body 70 can have a refractive index higher than that of other parts. Examples of the material of the structure body 70 are SiN, TiO2, etc.

[0060] For the above-described structure 70, the characteristics can be changed by changing at least one of the width W and the refractive index. Among the width W and the refractive index, examples of changing the characteristics by the width W are described below. Examples of the characteristics of the structure 70 are the transmittance and phase (optical phase delay amount) of light passing through the structure 70. In this regard, reference is also made to Figure 7 and Figure 8 for the description. In addition, as understood from the Figure 2 and the like described above, the incident light passes through the structure 70 in the Z-axis direction. Therefore, the case where light passes through in this direction is described below.

[0061] Figure 7 and Figure 8 are diagrams showing examples of the characteristics of the structure. Figure 7 shows the relationship between the width W of the structure 70 and the transmittance of light passing through the structure 70. The wavelength of the light is 520 nm. As Figure 7 shown, in the range of the width W from 80 nm to 240 nm, a high transmittance approximately close to 1.0 is obtained. In addition, in the figure, there is a wavelength at which the transmittance is significantly reduced compared to other wavelengths, but this may occur due to the relationship with the period, the structure width, etc. of the structure 70. The period, the structure width, etc. of the structure 70 can be designed in such a way that such a reduction in transmittance is less likely to occur.

[0062] Figure 8 shows the relationship between the width W of the structure 70 and the phase of light passing through the structure 70. The structure 70 gives an optical phase delay amount corresponding to the magnitude of the width W to the incident light. By changing the width W within the range of 80 nm to 240 nm where the above-described high transmittance is obtained, the phase can be changed by more than 2π.

[0063] By using the structure 70 having the above characteristics, it is possible to perform a wide-range phase control of more than 2π while maintaining a high transmittance. By arranging a plurality of structures 70 in the plane direction of the transparent layer 60 in such a way that desired phase characteristics are obtained at each position of the optical element 6, a lens function can be obtained. In this regard, reference is made to Figures 9 - 11 for the description.

[0064] Figures 9 - 11 is a diagram showing an example of the lens design of the optical element. The design conditions are as follows.

[0065] Dimensions of PD41 and PD42 in plan view: 3.2 μm × 3.2 μm

[0066] Focal length: 4.8 μm

[0067] Design wavelength: 520 nm

[0068] Area ratio of the lens pattern: 0.08 (8%)

[0069] In addition, the area ratio of the lens pattern is the ratio of the pattern area for condensing light onto PD41 to the pattern area for condensing light onto PD41 and PD42.

[0070] The phase distribution (optical phase delay amount distribution) of the lens having a desired light condensing position is represented, for example, by the following formula.

[0071] [Mathematical formula 1]

[0072]

[0073] In the above formula (1), λ d represents the design wavelength. (x f , y f , z f ) represents the light condensing position. n sub represents the refractive index of the transparent substrate ( Figure 5 the base 70a). C represents an arbitrary constant. In the example described below Figures 9 - 11 shown, x f = ±1.6 μm, y f = 0 μm, z f = 4.8 μm (focal length). The values of the phase distribution are transformed so as to converge within the range of 0 to 2π. For example, -0.5π is transformed into 1.5π, and 2.5π is transformed into 0.5π.

[0074] Figure 9 An example of the phase distribution of the optical element 6 for condensing incident light onto PD41 is shown. The center position (lens center position) of the circularly expanding distribution corresponds to the center position of PD41. In particular, as one moves forward from this circular portion toward the right side (the positive X-axis side), the phase change occurs repeatedly. Among them, the phase distribution shown inside the quadrilateral is for the arrangement of the plurality of structures 71. The area of the quadrilateral corresponds to the arrangement area of the plurality of structures 71 (the size of the region 61). In this example, the center of the quadrilateral corresponds to the center of PD41. However, the position of the quadrilateral can be arbitrarily specified. The shape is not limited to a quadrilateral, which will be described later with reference to Figures 22 - 26 for explanation.

[0075] Figure 10An example of the phase distribution of the optical element 6 for converging incident light onto the PD42 is shown. The center position of the distribution that spreads circularly (lens center position) corresponds to the center position of the PD42. In particular, as one moves forward from this circular portion toward the left side (negative X-axis direction side), phase changes occur repeatedly. Among them, the phase distribution shown on the outer side of the quadrilateral is for the arrangement of the plurality of structures 72. The area on the outer side of the quadrilateral corresponds to the arrangement area of the structure 72 (the size of the region 62).

[0076] Figure 11 An example of the phase distribution of the optical element 6 for converging incident light onto the PD41 and PD42 is shown. This phase distribution is the one that Figure 9 combines the phase distribution inside the quadrilateral in Figure 10 with the phase distribution outside the quadrilateral in

[0077] In a manner of imparting the phase distribution shown in Figure 11 a plurality of structures 70, namely a plurality of structures 71 and a plurality of structures 72, are arranged in the transparent layer 60 of the optical element 6. Each structure 70 has a width W that imparts the phase distribution (light phase delay amount distribution) shown in Figure 11 . Therefore, when viewed from above, at least some of the plurality of structures 70 have different widths W from each other. The height H of the plurality of structures 70 can be the same. That is, when viewed from the side, the plurality of structures 70 can have the same height H.

[0078] With reference to Figures 12 - 14 , the focusing of the optical element 6 designed as above onto the PD41 and PD42 will be described.

[0079] Figures 12 to 14 is a diagram showing an example of the amount of light guided to the PD (detected light amount). Here, it will be described as the converging light amount. The wavelength of the light is 520 nm. The light amount is the average light amount of two polarized lights (for example, the polarized light in the X-axis direction and the polarized light in the Y-axis direction). This is the same in the Figures 15 - 17 described later. Figure 12 In the chart of

[0080] the horizontal axis represents the ratio of the arrangement area of the structure 71 (the size of the region 61) to the arrangement areas of the plurality of structures 71 and the plurality of structures 72 (the sizes of the region 61 and the region 62). The vertical axis of the chart represents the light amount when normalized according to the light amount of the incident light. The curve passing through the dots represents the converging light amount to the PD41. The curve passing through the diamond dots represents the converging light amount to the PD42. The curve passing through the triangle dots represents the total light amount of the converging light amount to the PD41 and the converging light amount to the PD42.

[0080] From Figure 12It can be seen that as the arrangement area of the plurality of structures 71 (the size of the region 61) increases, the amount of converging light to PD41 (circles) increases, and the amount of converging light to PD42 (diamond dots) decreases. From this, it can be known that the transparent layer 60 has a lens function capable of controlling the light condensation to PD41 and the light condensation to PD42. In addition, the total amount of converging light to the entire PD (triangles) exceeds 0.97 (97%), and a high light utilization efficiency is obtained.

[0081] Figure 13 An example of the light condensation distribution when the ratio of the arrangement area of the plurality of structures 71 is 0.32 is shown. The amount of converging light to PD41 is smaller than the amount of converging light to PD42. Figure 14 An example of the light condensation distribution when the ratio of the arrangement area of the plurality of structures 71 is 0.08 is shown. The amount of converging light to PD41 is further reduced compared to the amount of converging light to PD42. From these cases, it can also be known that the light condensation to PD41 and PD42 can be controlled by the arrangement area of the plurality of structures 71.

[0082] The lens function of the above-described optical element 6 can be designed according to the colors corresponding to PD41 and PD42. By designing according to color, as will be described next with reference to Figures 15 - 17 As described, the optical element 6 can achieve a lens function with little wavelength dependence within the wavelength range used for each pixel (in the example, the wavelength band surrounded by the dotted line where B is described). Figure 15

[0083] Figures 15 - 17 It is a graph showing the wavelength dependence of the light amount ratio (in this example, the converging light amount ratio) of the light guided to each PD. Figure 15 An example of the amount of converging light of the transparent layer 60 designed to be suitable for blue (B) to PD41 and PD42 is shown. The design range including the central wavelength of 450 nm is indicated by a dotted line. No large wavelength dependence is seen around the design wavelength, and it can be known that the pixels corresponding to blue are easy to design.

[0084] Figure 16 An example of the amount of converging light of the transparent layer 60 designed to be suitable for green (G) to PD41 and PD42 is shown. The design range including the central wavelength of 520 nm is indicated by a dotted line. No large wavelength dependence is observed around the design wavelength, and it can be known that the pixels corresponding to green are also easy to design.

[0085] Figure 17 An example of the amount of converging light of the transparent layer 60 designed to be suitable for red (R) to PD41 and PD42 is shown. The design range including the central wavelength of 635 nm is indicated by a dotted line. No large wavelength dependence is observed around the design wavelength, and it can be known that the pixels corresponding to red are also easy to design. ​

[0086] By determining these design wavelengths according to the wavelength characteristics of the color filters of each color, a structure with an optimal intensity ratio can be designed.

[0087] As described above, in the imaging element 12 of the embodiment, the optical element 6 functions as a lens that converges incident light onto the PDs 41 and 42 in each pixel 2. Referring again to Figure 2 and Figure 3 For further explanation, since the area 61 that converges incident light onto the PD 41 is smaller than the area 62 that converges incident light onto the PD 42, the amount of converged light onto the PD 41 is smaller than the amount of converged light onto the PD 42. Therefore, the PD 41 is less likely to saturate than the PD 42. In such a pixel 2, for example, by using the PD 41 as a low-sensitivity photodiode and the PD 42 as a high-sensitivity photodiode, the dynamic range can be increased. Since the ratio of the amount of converged light onto the entire PD with respect to the incident light is close to 100%, a high light utilization efficiency can also be achieved.

[0088] Referring again to Figure 1 , several examples of the control of the signal processing control unit 13 of the imaging device 10 will be described. The signal processing control unit 13 generates a pixel signal based on the electrical signal obtained from the imaging element 12. To obtain the electrical signal, the signal processing control unit 13 also controls the imaging element 12. The control of the imaging element 12 includes the exposure of the pixels 2 of the imaging element 12, the conversion of the charges accumulated in the PD layer 4 into an electrical signal, the reading out of the electrical signal, etc. The exposure of the pixel 2 includes the exposure of the PDs 41 and 42, and the exposure of the PDs 41 and 42 can be controlled separately. Since a high dynamic range is achieved by the imaging element 12 as described above, several examples of the control of the signal processing control unit 13 that utilize this will be described.

[0089] The signal processing control unit 13 can generate a pixel signal, and further generate an image signal, using the electrical signal (first electrical signal) corresponding to the charges (detected light) generated by the photoelectric conversion in the PD 41 and the electrical signal (second electrical signal) corresponding to the charges generated by the photoelectric conversion in the PD 42. For example, a pixel signal can be generated based on the composite signal of the first electrical signal and the second electrical signal. By using the first electrical signal, it is possible to cope with the shooting of bright scenes (high illuminance scenes). By using the second electrical signal, it is possible to cope with the shooting of dark scenes (low illuminance scenes). Since it is possible to shoot both bright and dark places in one shot, it is possible to shoot scenes where both low illuminance and high illuminance exist. For example, it is useful for the case where the imaging device 10 is mounted in a vehicle passing through a tunnel with different internal and external brightness.

[0090] The signal processing control unit 13 can control the exposure of PD41 and PD42 in such a way that the exposure periods of PD41 and PD42 are different. For example, transistors or the like for controlling the photoelectric conversion operations (charge reset, accumulation, etc.) of PD41 and PD42 can be arranged to enable individual control for each of PD41 and PD42. The signal processing control unit 13 drives these transistors or the like at different timings, thereby causing PD41 and PD42 to be exposed during mutually different exposure periods.

[0091] The signal processing control unit 13 can control the exposure of PD41 and PD42 in such a way that the exposure period of at least one of PD41 and PD42 is longer than a specified period. An example of the specified period is a period longer than the blinking period of lighting, signal lights, etc. (e.g., 20 ms = 1 / 50 Hz). Thereby, flicker can be suppressed.

[0092] The signal processing control unit 13 can control the exposure of PD41 and PD42 in such a way that the exposure period of PD41 is longer than the exposure period of PD42. By suppressing the exposure period of PD42 to avoid saturation, the occurrence of, for example, overexposure can be suppressed.

[0093] As described above, one embodiment of the present invention has been explained, but the imaging element and imaging device of the embodiment can be variously modified within the scope not departing from the gist of the embodiment. Several modification examples will be described.

[0094] In the above embodiment, an example of lens design of an optical element based on an asymmetric phase distribution in which the phase only repeatedly changes as it moves from the lens center position toward one side has been explained ( Figure 3 and Figures 9 - 11 etc.). However, lens design of an optical element can also be performed based on a phase distribution symmetric with respect to the lens center position. Regarding this, an explanation will be given with reference to Figures 18 - 21 for illustration.

[0095] Figures 18 - 20 is a diagram showing an example of lens design of an optical element. Figure 21 is a diagram showing an example of the schematic structure of an imaging element. Figure 18 An example of the phase distribution of the optical element for converging incident light onto PD41 is shown.

[0096] Figure 18 The shown phase distribution is the phase distribution of the optical element for converging incident light onto PD41. This phase distribution is a symmetric phase distribution in which the phase change repeatedly occurs as it moves from the center position of the circularly expanding distribution toward both sides. The phase change that repeatedly occurs as it moves toward the right side (the positive X-axis side) ends halfway, and in front of it, a phase distribution for converging incident light onto the PD of an adjacent pixel appears.

[0097] Figure 19 The phase distribution shown is the phase distribution of the optical element for converging incident light onto PD42. This phase distribution is a symmetric phase distribution in which phase changes repeatedly occur as moving from the center position of the circularly expanding distribution toward both sides. The phase change that repeatedly occurs as moving toward the left side (negative X-axis side) ends halfway, and in front of it, a phase distribution for converging incident light onto the PD of an adjacent pixel appears.

[0098] Figure 20 Shows a combination of Figure 18 and Figure 19 phase distribution. Figure 21 Shows an example of the planar layout of the optical element 6A for realizing the phase distribution shown in Figure 20 In the optical element 6A, a plurality of the structures 71A among the plurality of structures 70A are provided in the region 61A, and a plurality of the structures 72A are provided in the region 62A. When not considering the phase distribution in the region 61A, that is, except for the phase distribution in the region 61A and the positions symmetric thereto, the phase distribution in the region of the region 62A has symmetry. When not considering the phase distribution in the region 62A, that is, except for the phase distribution in the region 62A and the positions symmetric thereto, the phase distribution in the region of the region 61A has symmetry. Regarding the design method of designing the transparent layer based on the phase distribution, it is carried out as described above, and thus will not be repeated here.

[0099] According to the optical element 6A, the phase distribution has symmetry, and accordingly, the possibility of obtaining a preferable lens pattern is increased. For example, the angular range of light incident on the right side (positive X-axis side) of the lens center is likely to be the same as the angular range of light incident on the left side (negative X-axis side) of the lens center.

[0100] In the above-described embodiment, an example is described in which in the transparent layer 60, the region 61 (a plurality of structures 71) is defined as a rectangular shape part (inside the quadrilateral), and the region 62 (a plurality of structures 72) is defined as other parts. However, the regions 61 and 62 may be defined as various shapes other than this. Refer to Figures 22 - 26 for several examples.

[0101] Figures 22 - 26 is a diagram showing an example of the arrangement region of the structures. In the figure, the shapes of the respective structures are not shown, and only the arrangement regions of the structures are schematically shown.

[0102] In Figure 22In the illustrated optical element 6B, region 61B is defined as a circular-shaped portion, and region 62B is defined as the remaining portion. Region 61B corresponds to region 61 or region 61A described so far. Region 62B corresponds to region 62 or region 62A described so far.

[0103] In Figure 23 In the illustrated optical element 6C, region 61C is defined as a central rectangular-shaped portion and a rectangular ring-shaped portion that is separated from the central rectangular-shaped portion and includes the central rectangular-shaped portion inside. Region 62 is defined as the remaining portion. Region 61C corresponds to region 61 or region 61A described so far. Region 62C corresponds to region 62 or region 62A described so far.

[0104] In Figure 24 In the illustrated optical element 6D, region 61D is defined as a central circular-shaped portion and a circular ring-shaped portion that is separated from the central circular-shaped portion and includes the circular-shaped portion inside. Region 62D is defined as the remaining portion. Region 61D corresponds to region 61 or region 61A described so far. Region 62D corresponds to region 62 or region 62A described so far.

[0105] In Figure 25 In the illustrated optical element 6E, region 61E is defined as four triangular-shaped portions arranged at intervals (in this example, 90° intervals) in the rotational direction. Region 62E is defined as the remaining portion. Region 61E corresponds to region 61 or region 61A described so far. Region 62E corresponds to region 62 or region 62A described so far.

[0106] In Figure 26 In the illustrated optical element 6F, region 61F is defined as four sector-shaped portions arranged at intervals (in this example, 90° intervals) in the rotational direction. Region 62F is defined as the remaining portion. Region 61F corresponds to region 61 or region 61A described so far. Region 62F corresponds to region 62 or region 62A described so far.

[0107] In addition, the two types of regions can be configured in various shapes not shown. From the viewpoint of the continuity of the phase distribution, a shape with fewer boundaries between the two types of regions can be adopted.

[0108] In the above-described embodiment, an example in which each pixel 2 includes two PDs 41 and 42 having different converging light amounts has been described. However, each pixel may also include three, four, or a greater number of PDs having different converging light amounts. In this case, the optical element includes a plurality of structures arranged with different configuration areas according to the converging light amount to each PD. For example, in the case of using four PDs, in the transparent layer 60, a plurality of first to fourth structures are arranged in regions divided into four parts in a manner having different areas. The PDs may be arranged in one dimension or two dimensions.

[0109] In the above-described embodiment, an example in which a plurality of structures 70 are provided on the transparent layer 60 has been described. However, the plurality of structures 70 may also be provided inside the transparent layer 60. The plurality of structures 70 may also be provided on the lower surface of the transparent substrate. In this case, the transparent layer 60 is an air layer. In addition, a structure in which a plurality of structures 70 are provided on the transparent layer 60, which is the same as the above-described embodiment, can also be realized by the following method: making a portion corresponding to the plurality of structures 70 into a plurality of recesses, and making the voids of the plurality of recesses have a refractive index higher than that of the material constituting the plurality of recesses. The structure in which the portion corresponding to the plurality of structures 70 becomes a plurality of recesses can be realized by the following method: filling the voids of the plurality of recesses with a fluid having a refractive index higher than that of the material constituting the plurality of recesses, or making the material constituting the plurality of recesses a metasurface material having a refractive index lower than 1.

[0110] In the above-described embodiment, an example in which a plurality of structures 71 are arranged in the region 61 and a plurality of structures 72 are arranged in the region 62 has been described. However, a plurality of structures 71 may not be arranged in the region 61. In this case, the region 61 directly guides incident light to the PD 41. Such a region 61 may be filled with the material of the transparent layer 60. As previously referred to Figure 3 and so on, when the region 61 is located inside the PD 41 so as to overlap the PD 41 in a top view, even if the plurality of structures 71 do not have a light condensing function, the light incident on the region 61 is guided to the PD 41.

[0111] Although SiN and TiO2 are listed as the materials of the structure 70 in the above-described embodiment, the present invention is not limited thereto. For example, for light with a wavelength of 380 nm to 1000 nm (visible light to near-infrared light), SiN, SiC, TiO2, GaN, etc. can be used as the materials of the structure 70. Since they have a high refractive index and low absorption loss, they are applicable. When using light with a wavelength of 800 - 1000 nm (near-infrared light), Si, SiC, SiN, TiO2, GaAs, GaN, etc. can be used as the materials of the structure 70. Since they have low loss, they are applicable. For light in the near-infrared region of the long wavelength band (such as 1.3 μm and 1.55 μm as communication wavelengths), in addition to the above materials, InP, etc. can also be used as the materials of the structure 70.

[0112] When the structure 70 is formed by pasting, coating, etc., examples of the materials include polymers such as polyimide such as fluorinated polyimide, BCB (benzocyclobutene), photocurable resin, UV epoxy resin, acrylic resin such as PMMA, and general resists.

[0113] In the above-described embodiment, an example is shown assuming that SiO2 and an air layer are used as the materials of the transparent layer 60, but the present invention is not limited thereto. It also includes general glass materials, etc., as long as they have a refractive index lower than that of the materials of the structure 70 and are low-loss with respect to the wavelength of the incident light. The transparent layer 60 can also be a transparent layer having a laminated structure composed of multiple materials. In addition, as long as the transparent layer 60 has sufficiently low loss with respect to the wavelength that should reach the corresponding PD, it can be made of the same material as the color filter. For example, it can also be an organic material such as resin. In this case, the transparent layer 60 can be designed to have not only the same material as the color filter but also the same structure as the color filter and absorption characteristics corresponding to the wavelength of the light that should be guided to each PD.

[0114] In the above-described embodiment, the three primary colors of RGB are taken as an example to illustrate the colors corresponding to the pixel 2, but the pixel 2 can also correspond to light with wavelengths other than the three primary colors (for example, infrared light, ultraviolet light).

[0115] In the above-described embodiment, an example of providing a light phase delay amount distribution by changing the width W of the structure 70 is described. However, instead of the width W, the refractive index of the structure 70 can be changed, or the refractive index of the structure 70 and the width W can be changed together to impart a light phase delay amount distribution. In this case, the structures 70 with different refractive indices can be made of materials with different refractive indices respectively.

[0116] As described above, the present invention has been described based on specific embodiments, but the present invention is not limited to the above embodiments, and can of course be variously modified without departing from its gist.

[0117] The imaging element described above is determined, for example, as follows. As described with reference to Figures 1 - 3 and Figures 21 - 26 as well as the like, the optical element 6 includes: a transparent layer 60 for covering the pixel 2 including the PD41 and the PD42; and a plurality of structures 70 disposed on or within the transparent layer 60 along the plane direction (XY plane direction) of the transparent layer 60. The transparent layer 60 includes a region 61 for guiding incident light to the PD41 and a region 62 for guiding incident light to the PD42. A plurality of structures 70 are disposed in at least the region 62 among the regions 61 and 62. The region 61 is smaller than the region 62.

[0118] According to the imaging element 12, the region 61 is smaller than the region 62. As a result, the amount of light guided to the PD41 becomes smaller than the amount of light guided to the PD42, and thus the PD41 is less likely to saturate compared to the PD42. For example, by using the PD41 as a low-sensitivity photodiode and using the PD42 as a high-sensitivity photodiode, the dynamic range can be increased. Since the ratio of the amount of light guided to the entire PD with respect to the incident light is very large (close to 100%), a high light utilization efficiency can also be achieved. Therefore, an increase in the dynamic range and an increase in the light utilization efficiency can be achieved simultaneously.

[0119] As also described with reference to Figures 5 - 11 and Figures 18 - 20 as well as the like, the plurality of structures 70 are columnar structures having a refractive index higher than that of the portions between the plurality of structures 70. When viewed from above, at least some of the plurality of structures 70 have different widths W from each other, and when viewed from the side, the plurality of structures may have the same height. At least some of the plurality of structures 70 may have different refractive indices from each other. The plurality of structures 70 may respectively impart a light phase delay amount corresponding to the size of the width W and / or the refractive index to the incident light. The plurality of structures 70 may respectively have a width W and / or a refractive index that impart a light phase delay amount distribution for guiding the light incident on the region 61 to the PD41 and guiding the light incident on the region 62 to the PD42. The light phase delay amount distribution may be a light phase delay amount distribution for converging the light. For example, by disposing such a plurality of structures 70, the optical element 6 has a lens function, and the incident light can be guided (for example, converged) to the PD41 and the PD42. In addition, for example, compared with the case where a plurality of structures having different heights are provided, the optical element 6 can be easily manufactured.

[0120] As described with reference to Figures 18 - 21 etc., without considering the distribution of the optical phase delay amount in one of the regions 61A and 62A, the distribution of the optical phase delay amount in the other region can be symmetric. With the distribution of the optical phase delay amount being symmetric, the possibility of obtaining a preferable lens pattern is accordingly increased. For example, the angular range of light incident on the right side (positive X-axis side) of the lens center is likely to be the same as the angular range of light incident on the left side (negative X-axis side) of the lens center.

[0121] As described with reference to Figure 3 etc., in a plan view, PD41 and PD42 can have the same size. Thus, for example, compared with the case of using PDs of different sizes, each PD can be arranged without a gap, and therefore, the light utilization efficiency can be improved.

[0122] As described with reference to Figure 3 etc., in a plan view, the region 61 can be located inside the region 62. For example, in this way, the small region 61 and the large region 62 can be arranged.

[0123] The imaging element 12 described with reference to Figure 1 etc. is also an aspect of the present disclosure. That is, the imaging element 12 includes the optical element 6 and a plurality of pixels 2 each including PD41 and PD42. Thus, the imaging element 12 capable of simultaneously improving the dynamic range and the light utilization efficiency is obtained.

[0124] As described with reference to Figure 2 etc., the imaging element 12 can include the filter layer 5 provided between the pixel 2 and the optical element 6. Thus, for example, the light of the color corresponding to the pixel 2 can be guided to PD41 and PD42.

[0125] The imaging device 10 described with reference to Figure 1 etc. is also an aspect of the present disclosure. That is, the imaging device 10 includes the imaging element 12 and the signal processing control unit 13 that generates an image signal based on the electrical signal obtained from the imaging element 12. Thus, the imaging device 10 capable of simultaneously improving the dynamic range and the light utilization efficiency is obtained.

[0126] The signal processing control unit 13 can perform exposure control such that the exposure period of PD41 is different from the exposure period of PD42. For example, by making the exposure period of at least one of PD41 and PD42 longer than the blinking period of a signal lamp or the like, flicker can be suppressed. For example, by performing exposure control such that the exposure period of PD41 is longer than the exposure period of PD42, the exposure period of PD42 can be suppressed to avoid saturation, and the occurrence of overexposure or the like can be suppressed.

[0127] Symbol Explanation

[0128] 2 pixels

[0129] 3 wiring layers

[0130] 4PD layer

[0131] 5 filter layer

[0132] 6 optical element

[0133] 10 imaging device

[0134] 12 imaging element

[0135] 13 signal processing and control unit

[0136] 41PD

[0137] 42PD

[0138] 60 transparent layer

[0139] 61 area

[0140] 62 area

[0141] 70 structure

[0142] 71 structure

[0143] 72 structure

Claims

1. An optical element, characterized in that, the optical element has: a transparent layer for covering pixels including a first photoelectric conversion element and a second photoelectric conversion element; and a plurality of structures arranged in a plane direction of the transparent layer on or within the transparent layer, the transparent layer includes: a first region for guiding incident light to the first photoelectric conversion element; and a second region for guiding incident light to the second photoelectric conversion element, the plurality of structures are arranged in at least the second region among the first region and the second region, the first region is smaller than the second region, when viewed from above, the first region is located inside the second region.

2. The optical element according to claim 1, characterized in that, the plurality of structures are columnar structures having a refractive index higher than that of a portion between the plurality of structures, when viewed from above, at least a part of the plurality of structures have different widths from each other, when viewed from the side, the plurality of structures have the same height.

3. The optical element according to claim 1, characterized in that, the plurality of structures are columnar structures having a refractive index higher than that of a portion between the plurality of structures, at least a part of the plurality of structures have different refractive indices from each other, when viewed from the side, the plurality of structures have the same height.

4. The optical element according to any one of claims 1 to 3, characterized in that, each of the plurality of structures imparts a light phase delay amount corresponding to the size of the width of the structure when viewed from above to the incident light, each of the plurality of structures has a width that imparts a light phase delay amount distribution for guiding the light incident on the first region to the first photoelectric conversion element and guiding the light incident on the second region to the second photoelectric conversion element.

5. The optical element according to any one of claims 1 to 3, characterized in that, each of the plurality of structures imparts a light phase delay amount corresponding to the size of the refractive index of the structure to the incident light, each of the plurality of structures has a refractive index that imparts a light phase delay amount distribution for guiding the light incident on the first region to the first photoelectric conversion element and guiding the light incident on the second region to the second photoelectric conversion element.

6. The optical element according to claim 4, characterized in that, the light phase delay amount distribution is a light phase delay amount distribution for converging light.

7. The optical element according to claim 4, characterized in that, when not considering the light phase delay amount distribution in one of the first region and the second region, the light phase delay amount distribution in the other region has symmetry.

8. The optical element according to any one of claims 1 to 3, characterized in that, When viewed from above, the first photoelectric conversion element and the second photoelectric conversion element have the same size.

9. An imaging element, characterized in that, Comprising: The optical element according to any one of claims 1 to 8; and A plurality of pixels, each of which includes the first photoelectric conversion element and the second photoelectric conversion element.

10. The imaging element according to claim 9, wherein The imaging element has a filter layer provided between the pixel and the optical element.

11. An imaging device, characterized in that, Comprising: The imaging element according to claim 9; and A signal processing control unit that generates an image signal based on an electrical signal obtained from the imaging element.

12. The imaging device according to claim 11, wherein The signal processing control unit performs exposure control in such a manner that the exposure period of the first photoelectric conversion element is different from the exposure period of the second photoelectric conversion element.

13. An optical element, characterized in that, Comprising: A transparent layer for covering a pixel including a first photoelectric conversion element and a second photoelectric conversion element; And A plurality of recesses arranged in a plane direction of the transparent layer on the transparent layer, The transparent layer includes: A first region that guides incident light to the first photoelectric conversion element; And A second region that guides incident light to the second photoelectric conversion element, The plurality of recesses are arranged in at least the second region among the first region and the second region, The first region is smaller than the second region, When viewed from above, the first region is located inside the second region.

14. The optical element according to claim 13, wherein The voids of the plurality of recesses are filled with a fluid having a refractive index higher than that of the material constituting the plurality of recesses.

15. The optical element according to claim 13, wherein The material constituting the plurality of recesses is a metamaterial having a refractive index lower than 1.

Images