Resonator structure, imaging element, and electronic apparatus

There is provided a resonator structure that obtains a highly accurate optical spectrum. The resonator structure includes a stacked structure that includes a semiconductor layer, a first resonator, a first reflection layer, a second resonator, a second reflection layer stacked in this order, allows light of a specific wavelength band to be transmitted therethrough, the semiconductor layer having a first average refractive index, the first resonator having a second average refractive index lower than the first average refractive index, and the first reflection layer having a third average refractive index higher than the second average refractive index.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International Patent Application No. PCT/JP2019/019074 filed on May 14, 2019, which claims priority benefit of Japanese Patent Application No. JP 2018-096234 filed in the Japan Patent Office on May 18, 2018. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a resonator structure including a resonator, and an imaging element and an electronic apparatus each including the resonator structure.

BACKGROUND ART

There have been proposed solid-state imaging devices each including a multilayer interference filter that includes a plurality of Fabry-Perot resonator structures having different thicknesses, thereby allowing light of a plurality of wavelength bands to be selectively transmitted therethrough (e.g., PTL 1).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

An imaging element able to perform such multispectral dispersion preferably has a structure having superior mass productivity while acquiring a highly accurate optical spectrum.

A resonator structure that obtains a highly accurate optical spectrum while having a simple structure, and an imaging element and an electronic apparatus each including the resonator structure are therefore desired.

A resonator structure as an embodiment of the present disclosure includes a stacked structure that includes a semiconductor layer, a first resonator, a first reflection layer, a second resonator, a second reflection layer stacked in this order, allows light of a specific wavelength band to be transmitted therethrough, the semiconductor layer having a first average refractive index, the first resonator having a second average refractive index lower than the first average refractive index, and the first reflection layer having a third average refractive index higher than the second average refractive index. In addition, an imaging element and an electronic apparatus as embodiments of the present disclosure each include the resonator structure described above.

According to the resonator structure, the imaging element, and the electronic apparatus as the embodiments of the present disclosure, it is possible to obtain a highly accurate optical spectrum while having a simple configuration.

It is to be noted that the effects of the present disclosure are not limited to the effects described above, and may be any effect described below.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present disclosure are described in detail below with reference to drawings. It is to be noted that description is given in the following order.

1. First Embodiment: Example of Imaging Element Including Resonator Structure

2. Modification Examples of First Embodiment: Modification Examples of Imaging Element Including Resonator Structure

3. Second Embodiment: Example of Camera Module Including a Plurality of Imaging Elements

4. Application Examples of Imaging Device

5. Example of Practical Application to Endoscopic Surgery System

6. Example of Practical Application to In-Vivo Information Acquisition System

7. Example of Practical Application to Mobile Body

8. Other Modification Examples

1. First Embodiment: Example of Imaging Element

FIG.1is a schematic cross-sectional view of an entire configuration example of an imaging element1as a first embodiment of the present disclosure.FIG.2is a schematic enlarged cross-sectional view of any one pixel22of a plurality of pixels22included in the imaging element1. The imaging element1is, for example, a visible light spectral type CMOS (Complementary Metal-Oxide-Semiconductor) image sensor.

As illustrated inFIG.1, the imaging element1includes a photodiode PD as a photoelectric converter, the plurality of pixels22(22-1to22-4) each including a resonator structure10that transmits light of a specific wavelength band toward a photodiode PD.FIG.1illustrates four pixels22-1to22-4as an example; however, the number of pixels22included in the imaging element1is not limited thereto.

The photodiode PD is embedded in a semiconductor substrate12, for example. A wiring layer11is provided on a front surface12A of the semiconductor substrate12. The wiring layer11includes a wiring line11A included in a drive circuit that includes an MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) or the like used for driving of each of the plurality of pixels22. The semiconductor substrate12is one component included in the resonator structure10, and has a first average refractive index N1. The semiconductor substrate12includes a semiconductor material such as Si (silicon), for example. The first average refractive index N1is about 4, for example. In the present application, the “average refractive index” refers to a refractive index averaged by a volume ratio in a case where a target object, for example, the semiconductor substrate12, includes two or more kinds of components each having a different refractive index. For example, in a case where the semiconductor substrate12includes a mixture including a first material having a first refractive index n1 and a second material having a second refractive index n2 at a volume ratio of V1:V2, the average refractive index N is a value determined by:
N=(V1*n1+V2*n2)/(V1+V2).
The same applies to a case where the target object includes three or more kinds of components each having a different refractive index. In addition, in a case where the target object includes only one type of component, the refractive index of the component is the average refractive index N.
(Resonator Structure10)

The resonator structure10includes the semiconductor substrate12and a stacked structure provided on a back surface12B of the semiconductor substrate12. The stacked structure includes, in order from the back surface12B of the semiconductor substrate12, a first resonator13, a first reflection layer14, a second resonator15, a second reflection layer16, and a transparent layer17that are stacked in order. Here, the first resonator13has a second average refractive index N2lower than the first average refractive index N1. In addition, the first reflection layer14has a third average refractive index N3higher than the second average refractive index N2.

The first resonator13includes a multilayer film structure in which a plurality of films is stacked. The plurality of films includes a material containing at least one kind of silicon oxide, silicon nitride, tantalum oxide, or aluminum oxide. Specifically, the first resonator13includes, for example, a first film131including silicon dioxide (SiO2), a second film132including silicon nitride (SiN), and a third film133including silicon dioxide (SiO2) that are stacked in this order from the back surface12B side. A thickness13T of the first resonator13is desirably, for example, 400 nm or less.

The first reflection layer14, the second resonator15, and the second reflection layer16form a so-called Fabry-Perot resonator structure. Accordingly, wavelength selectivity appears in transmittance of light L transmitted through the first reflection layer14, the second resonator15, and the second reflection layer16. The first reflection layer14and the second reflection layer16each include, for example, polycrystal silicon (Si), and function as a reflection film. Each of the thickness of the first reflection layer14and the thickness of the second reflection layer16may be 50 nm or less. Polycrystal silicon (Si) has a large light absorption coefficient in a short wavelength band, which causes reduction in transmittance of transmitted light. For this reason, reducing both the thickness of the first reflection layer14and the thickness of the second reflection layer16to 50 nm or less, for example, to about 30 nm, makes it possible to minimize light absorption in the first reflection layer14and the second reflection layer16. The second resonator15includes, for example, silicon dioxide (SiO2). In the imaging element1, others, except for the first reflection layer14, the second reflection layer16, and the semiconductor substrate12, may include a material other than elemental silicon. In the imaging element1, for example, as in a schematic view of a pixel arrangement illustrated inFIG.3, the plurality of pixels22including the second resonators15having thicknesses different from each other are periodically arranged in a stacked plane (in an XY plane orthogonal to a Z-axis direction that is a stacking direction). It is to be noted thatFIG.3illustrates an example in which pixels22-1to22-16each including the second resonator15having a different thickness15T are periodically arranged.FIG.1illustrates the pixels22-1to22-4of the pixels22-1to22-16as an example. The pixels22-1to22-4respectively include the second resonators15having thicknesses15T1to15T4. That is, the pixels22-1to22-16are regarded as a pixel group22G for one cycle, and a plurality of pixel groups22G is repeatedly arranged in the stacked plane. Here, wavelength selectivity for the light L in the Fabry-Perot resonator structure including the first reflection layer14, the second resonator15, and the second reflection layer16is dependent on the thickness15T of the second resonator15. Accordingly, the plurality of pixels22including the second resonators15having different thicknesses is periodically arranged as inFIG.3, which allows for multispectral dispersion in the imaging element1.

The transparent layer17includes a transparent body including, for example, silicon dioxide (SiO2) as a main constituent material. Front surfaces17S of the transparent layers17in the plurality of pixels22are located at height positions substantially equal to each other.

Each of light shielding layers18and19may be provided in proximity to a boundary between adjacent pixels22. The light shielding layer18is embedded in the third film133of the first resonator13, for example. In addition, the light shielding layer18is provided in proximity to the back surface12B of the semiconductor substrate12, for example. This is to prevent light leakage between adjacent pixels22and avoid color mixture.

For example, a moth eye (Moth Eye) structure21is provided on a front surface17S of the transparent layer17. This is to suppress front surface reflection in the front surface17S of the transparent layer17and reduce spectrum vibration. The moth eye structure21is a structure having a plurality of pointed projections arranged on the front surface17S at a pitch of a wavelength λ or less, in particular at a pitch of 1/3×λ or less. It is possible to form the moth eye structure21as follows. First, for example, as illustrated inFIG.4A, a transparent ultraviolet curable resin layer21Z having a uniform thickness is applied by, for example, a spin coating method to cover the front surface17S of the transparent layer17. Meanwhile, a mold23in which a predetermined recessed and projected pattern23P is formed is prepared. The mold23has the fine recessed and projected pattern23formed by dry etching a substrate such as a Si substrate, which allows ultraviolet rays to be transmitted therethrough, with use of a resist pattern formed by electron beam lithography, for example. Next, as illustrated inFIG.4B, the recessed and projected pattern23P is pressed against the ultraviolet curable resin layer21Z. Further, while maintaining that state, that is, a state in which the recessed and projected pattern23P is pressed against the ultraviolet curable resin layer21Z, the ultraviolet curable resin layer21Z is irradiated with ultraviolet rays UV having a predetermined intensity for a predetermined period of time to cure the ultraviolet curable resin layer21Z. After the ultraviolet curable resin layer21Z is cured, the mold23is removed, thereby obtaining the moth eye structure21.

In the imaging element1, for example, a resonator length in the first resonator13, that is, the thickness13T (seeFIG.2) as a dimension in the Z-axis direction of the first resonator13is changed, which makes it possible to change a shape of a peak wavelength of transmitted light transmitted through the resonator structure10. As previously described, the first resonator13is provided between the semiconductor substrate12in which the photodiode PD is embedded and the first reflection layer14that forms the Fabry-Perot resonator structure. The second average refractive index N2of the first resonator13is lower than the first average refractive index N1in the semiconductor substrate12and lower than the third average refractive index N3in the first reflection layer14. Accordingly, the first resonator13exhibits coherence, and wavelength selectivity for transmitted light in the resonator structure10is improved. Si (silicon) is suitable as constituent materials of the semiconductor substrate12and the first reflection layer14. An average refractive index of silicon is about 4. For this reason, the second average refractive index N2of the first resonator13is desirably 1 or more and 4 or less. This is because a sufficient interference effect in the first resonator13is obtained. The second average refractive index N2of the first resonator13may be specifically 1 or more and 2 or less. This is because the interference effect in the first resonator13is further improved.

FIG.5illustrates an example of dependency of the first resonator13on the thickness13T at transmittance T of the light transmitted through the resonator structure10. InFIG.5, an upper left graph represents a case of the thickness13T=1100 nm, an upper right graph represents a case of the thickness13T=600 nm, a lower left graph represents a case of the thickness13T=400 nm, and a lower right graph represents a case of the thickness13T=200 nm. It is to be noted thatFIG.5illustrates results of simulating an optical spectrum by the effective Fresnel coefficient method in a case where the light L having entered the resonator structure10from the front surface17S is transmitted through the resonator structure10. In addition, in each of the cases,FIG.5corresponds to a case where the semiconductor substrate12includes Si (silicon), the first film131includes SiO2, the second film132includes SiO2, the third film133includes SiO2, the first reflection layer14includes polycrystal silicon (Si) having a thickness of 31 nm, the second resonator15includes SiO2 having a thickness of 147 nm, the second reflection layer16includes polycrystal silicon (Si) having a thickness of 31 nm, and the transparent layer17includes SiO2 having a thickness of 100 nm. As illustrated inFIG.5, it can be seen that in a case where the thickness13T of the first resonator13is 400 nm or less, an unimodal peak appearing in a wavelength band of 400 nm to 500 nm is obtained in a transmittance distribution of the light L transmitted, and wavelength selectivity suitable in performing multispectral dispersion is obtained.

In the imaging element1, for example, changing a resonator length in the second resonator15, that is, the thickness15T (seeFIG.2) as the dimension in the Z-axis direction of the second resonator15makes it possible to change the position of a peak wavelength of visible light transmitted through the resonator structure10. Specifically, in the imaging element1, for example, changing the thickness15T in a range from 147 nm to 215 nm allows for dispersion into blue light, green light, and red light.

FIG.6illustrates an example of dependency of the second resonator15on the thickness15T at the transmittance T of the light L transmitted through the resonator structure10. InFIG.6, a curve R61represents a case of the thickness15T=147 nm, a curve R62represents a case of the thickness15T=180 nm, and a curve R63represents a case of the thickness15T=215 nm. It is to be noted thatFIG.6corresponds to a case where the semiconductor substrate12includes Si (silicon), the first film131includes SiO2having a thickness of 10 nm, the second film132includes SiO2having a thickness of 56 nm, the third film133includes SiO2having a thickness of 20 nm, the first reflection layer14includes polycrystal silicon (Si) having a thickness of 31 nm, the second resonator15includes SiO2, the second reflection layer16includes polycrystal silicon (Si) having a thickness of 31 nm, and the transparent layer17includes SiO2having a thickness of 100 nm. As illustrated inFIG.6, changing the thickness15T of the second resonator15allows for dispersion into three colors of blue, green, and red, for example. In addition, it is also possible to reduce the half width of each peak to a narrow width of 50 nm or less. Accordingly, in the imaging element1, the pixels22-1to22-15including the second resonators15having different thicknesses15T are periodically arranged as illustrated inFIG.3, which allows for multispectral dispersion.

As described above, the resonator structure10of the imaging element1includes the semiconductor substrate12, the first resonator13, the first reflection layer14, the second resonator15, and the second reflection layer16that are stacked in this order, and allows the light L of a specific wavelength band to be transmitted therethrough. The first resonator13has the second average refractive index N2lower than both the first average refractive index N1in the semiconductor substrate12and the third average refractive index N3in the first reflection layer14. Accordingly, the resonator structure10and the imaging element1obtain a highly accurate optical spectrum while having a simple structure including a relatively small number of layers.

In the imaging element1, the peak wavelength of the intensity of the light L transmitted is changed, for example, depending on the thickness15T of the second resonator15provided on a side opposite to the semiconductor substrate12as viewed from the first resonator13in the resonator structure10. In the imaging element1, the pixels22including a plurality of resonator structures10having different thicknesses15T are periodically arranged with use of this property, which allows for multispectral dispersion.

In particular, in the resonator structure10, the thickness13T of the first resonator13is 400 nm or less, thereby obtaining a unimodal peak appearing in a wavelength band of 400 nm to 500 nm in the transmittance distribution of the light L transmitted, and obtaining wavelength selectivity suitable in performing multispectral dispersion.

In addition, in the resonator structure10, setting each of the thickness of the first reflection layer14and the thickness of the second reflection layer16to 50 nm or less makes it possible to minimize light absorption in the first reflection layer14and the second reflection layer16.

2. Modification Examples of First Embodiment: Modification Examples of Imaging Element

2.1 First Modification Example

FIG.7is a schematic cross-sectional view of an entire configuration example of an imaging element1A as a first modification example of the first embodiment of the present disclosure.FIG.8is a schematic enlarged cross-sectional view of an enlarged view of any one pixel22of the plurality of pixels22included in the imaging element1A. The imaging element1A is, for example, an infrared spectral type CMOS image sensor.

In the imaging element1according to the first embodiment described above, the first resonator13having a three-layer structure has been described as an example. In contrast, the imaging element1A as the present modification example includes a resonator structure10A that includes a first resonator13A having a four-layer structure. Specifically, the first resonator13A in the resonator structure10A includes the first film131, the second film132, the third film133, and a fourth film134that are stacked in this order from the back surface12B side. Each of the first film131and the fourth film134includes, for example, silicon dioxide (SiO2). The second film132includes, for example, aluminum oxide (AlO). The third film133includes, for example, tantalum oxide (TaO). A thickness13AT of the first resonator13A is desirably 400 nm or less, for example. The first resonator13A has the second average refractive index N2lower than both the first average refractive index N1in the semiconductor substrate12and the third average refractive index N3in the first reflection layer14.

In addition, the imaging element1A includes a visible light cut filter24instead of the moth eye structure21on the front surface17S of the transparent layer17.

Except for these points, the imaging element1A as a modification example 1 has substantially the same configuration as the imaging element1.

The resonator structure10A in the imaging element1A has, for example, an overall thickness of 1 μm or less, and sufficiently suppresses color mixture. Furthermore, changing the thickness15T of the second resonator15, for example, in a range from 250 nm to 350 nm makes it possible to spectrally disperse infrared light.

FIG.9is a characteristic diagram illustrating an example of dependency of the second resonator15on the thickness15T at the transmittance T of the light L transmitted through the resonator structure10A. InFIG.9, a curve R91represents a case of the thickness15T=250 nm, a curve R92represents a case of the thickness15T=275 nm, a curve R93represents a case of the thickness15T=300 nm, a curve R94represents a case of the thickness15T=325 nm, and a curve R95represents a case of the thickness15T=350 nm. It is to be noted thatFIG.9corresponds to a case where the semiconductor substrate12includes Si (silicon), the first film131includes SiO2having a thickness of 1 nm, the second film132includes AlO having a thickness of 7 nm, the third film133includes TaO having a thickness of 54 nm, the fourth film134includes SiO2having a thickness of 20 nm, the first reflection layer14includes polycrystal silicon (Si) having a thickness of 31 nm, the second resonator15includes SiO2, the second reflection layer16includes polycrystal silicon (Si) having a thickness of 31 nm, and the transparent layer17includes SiO2having a thickness of 110 nm.

In addition, in the resonator structure10A in the imaging element1A, changing the thickness15T of the second resonator15as a higher-order mode Fabry-Perot structure, for example, in a range from 500 nm to 625 nm makes it possible to obtain an optical spectrum having peaks, each with a narrow half-width.

FIG.10is another characteristic diagram illustrating an example of dependency of the second resonator15on the thickness15T at the transmittance T of the light L transmitted through the resonator structure10A. InFIG.10, a curve R101represents a case of the thickness15T=500 nm, a curve R102represents a case of the thickness15T=525 nm, a curve R103represents a case of the thickness15T=550 nm, a curve R104represents a case of the thickness15T=575 nm, a curve R105represents a case of the thickness15T=600 nm, a curve R106represents a case of the thickness15T=625 nm, a curve R107represents a case of the thickness15T=650 nm, and a curve R108represents a case of the thickness15T=675 nm. It is to be noted thatFIG.10corresponds to a case where the semiconductor substrate12includes Si (silicon), the first film131includes SiO2having a thickness of 1 nm, the second film132includes AlO having a thickness of 7 nm, the third film133includes TaO having a thickness of 54 nm, the fourth film134includes SiO2having a thickness of 20 nm, the first reflection layer14includes polycrystal silicon (Si) having a thickness of 31 nm, the second resonator15includes SiO2, the second reflection layer16includes polycrystal silicon (Si) having a thickness of 31 nm, and the transparent layer17includes SiO2having a thickness of 110 nm.

As illustrated inFIGS.9and10, changing the thickness15T of the second resonator15allows for spectral dispersion into, for example, light having five different peak wavelengths in an infrared region. It is to be noted that an optical spectrum in the resonator structure10A also includes a peak of visible light. Accordingly, a component in a visible light region R24of the light L entering the resonator structure10A is removed by the visible light cut filter24, which makes it possible to obtain an optical spectrum only in the infrared region in the imaging element1A.

In addition, the first resonator13A has the second average refractive index N2lower than both the first average refractive index N1in the semiconductor substrate12and the third average refractive index N3in the first reflection layer14. Accordingly, the resonator structure10and the imaging element1A obtain a highly accurate optical spectrum while having a simple structure.

2.2 Second Modification Example

FIG.11is a schematic cross-sectional view of an entire configuration example of an imaging element1B as a second modification example of the first embodiment of the present disclosure.FIG.12is a schematic plan view of a configuration example of the second resonator15of a resonator structure10B included in the imaging element1B.

In the imaging element1according to the first embodiment described above, a plurality of pixels each including the second resonator15having a different thickness15T are arranged, thereby changing the peak wavelength of the intensity of the light L transmitted through the respective pixels22to perform multispectral dispersion. In contrast, in the imaging element1B as the present modification example, while resonator lengths in the plurality of pixels22, i.e., the thicknesses15T of the second resonators15are uniform, microstructures different for each of the pixels22are formed in the second resonators15of the respective pixels22. Specifically, the second resonator15includes a first portion151having a first refractive index, and a second portion152as a microstructure that is dispersedly located in the first portion151in the stacked plane (in the XY plane) and has a second refractive index. Thus, the second resonator15has a refractive index distribution in the stacked plane. It is to be noted that “having a refractive index distribution” here means that the second resonator15has a different effective refractive index for each of the pixels22. Here, the first portion151includes, for example, Si3N4, and the second portion152includes, for example, SiO2.FIG.12illustrates, as an example, a state in which 16 types of pixels22-1to22-16each having a different existence ratio of the first portion151and the second portion152in the second resonator15are periodically arranged in a matrix.

[Workings and Effects of Imaging Element1B]

Even in the imaging element1B as the second modification example of the first embodiment, it is possible to obtain an optical spectrum having 16 kinds of different peak wavelengths.

3. Second Embodiment: Example of Camera Module

[Configuration of Camera Module2]

FIG.13is a schematic plan view of an entire configuration example of a camera module2as a second embodiment of the present disclosure.FIG.14is a schematic enlarged cross-sectional view of any one of a plurality of imaging elements1C (1C1to1C9) included in the camera module2. The imaging element1C is, for example, a visible light spectral type CMOS image sensor.

The camera module2includes nine imaging elements1C1to1C9arranged in, for example, three rows and three columns in the XY plane. Each of the imaging elements1C1to1C9includes an imaging lens25provided on the front surface17S of transparent layer17instead of the moth eye structure21. Here, one imaging lens25is provided common to a plurality of pixels22in each of the imaging elements1C1to1C9. The imaging lens25provides a refractive power to the light L (L1to L9) toward the resonator structure10C. It is to be noted that the shapes and refractive powers of the imaging lenses25in the imaging elements1C1to1C9may be the same as or different from each other. Except for this point, the imaging element1C (1C1to1C9) has substantially the same configuration as the imaging element1according to the first embodiment described above.

The resonator structures10C in the imaging elements1C1to1C9respectively allow the light L having different peak wavelengths, that is, lights L1to L9having wavelengths λ1to λ9to be selectively transmitted therethrough. Accordingly, the imaging elements1C1to1C9selectively obtain the lights L1to L9having the wavelengths λ1to λ9, respectively.

[Workings and Effects of Camera Module2]

As described above, the camera module2includes a plurality of imaging elements1C1to1C9that obtain respective different wavelengths. As described in the first embodiment described above, each of the imaging elements1C1to1C9has a simple structure including a relatively small number of layers, which makes it possible to achieve simplification and thinning of the camera module2as a whole. This makes it possible to manufacture the camera module2by a simple manufacturing process, which contributes to mass production. In addition, a highly accurate optical spectrum is obtained in the resonator structure10C, thereby also improving imaging performance in the camera module2.

4. Application Examples of Imaging Device

Next, applications to which the imaging element1is applicable are described with reference toFIGS.15and16.

[4.1 Application Example to Monitoring of Growth State of Agricultural Crops, Etc.]

It is possible to use the imaging element1in a spectroscopic device that performs multispectral dispersion or hyperspectral dispersion for measurement of a normalized differential vegetation index (NDVI: Normalized Difference Vegetation Index) for growth of agricultural crops and plants (hereinafter, referred to as plants and the like).FIG.15illustrates spectral characteristics of reflectance depending on a growth state of the plants and the like.

As illustrated inFIG.15, in a wavelength range from 600 nm to 800 nm, the plants and the like have a different reflectance distribution depending on the growth state thereof. That is, the reflectance distribution different depending on whether the plants and the like are healthy, weak, or dead is illustrated. This reflectance distribution is formed by reflected light mainly on leaves of the plants and the like. It is possible from the results of the reflectance distribution inFIG.15that obtaining spectral characteristics of two or more lights from the plants and the like at least in a wavelength band including wavelengths from 600 nm to 800 nm makes it possible to sense the growth state (vegetation state) of the plants and the like.

It is possible to sense the vegetation state from a relationship between two signal values with use of, for example, two imaging elements, that is, the imaging element1able to detect a wavelength band in a wavelength range of 600 nm to 700 nm, and another imaging element1able to detect a wavelength band in a wavelength range of 700 nm to 800 nm. Alternatively, to improve detection accuracy, three or more imaging elements1may be used to detect three or more plural wavelength bands and sense the vegetation state from a relationship among signal values of these wavelength bands.

The imaging element1able to detect such a wavelength band is mounted on, for example, a small unmanned aerial vehicle (a so-called drone), which makes it possible to monitor the growth state of agricultural crops from the sky, and manage and control growth of the crops.

[4.2 Application Example to Biometric Authentication]

It is possible to use the imaging element1, for example, in a spectroscopic device that performs multispectral dispersion or hyperspectral dispersion to measure reflectance of human skin in biometric authentication. In the multispectral dispersoin or hyperspectral dispersion, a plurality of spectral dispersions is performed in multiple bands of three or more primary colors of light.FIG.16illustrates optical spectrum characteristics of reflectance of human skin.

As illustrated inFIG.16, it can be seen that the reflectance greatly changes particularly in a wavelength range of 450 nm to 650 nm. These changes make it possible to authenticate whether or not a subject is human skin.

For example, detecting three spectra of a wavelength of 450 nm, a wavelength of 550 nm, and a wavelength of 650 nm with use of three imaging elements1makes it possible to authenticate whether or not the subject is human skin. For example, in a case where the subject is a material other than human skin, the spectral characteristics of the reflectance are changed, which makes it possible to distinguish the material from human skin.

Accordingly, the imaging element1able to detect such a wavelength band is mounted on, for example, a biometric authentication device, which makes it possible to apply the imaging element1to prevention of forgery of faces, fingerprints, irises, and the like, thereby enabling more accurate biometric authentication.

[4.3 Application Example to Electronic Apparatus]

The imaging element1as described above is applicable to various kinds of electronic apparatuses. Examples of the electronic apparatuses include an imaging system such as a digital still camera and a digital video camera, a mobile phone having an imaging function, and other apparatuses having imaging functions.

FIG.17is a block diagram illustrating a configuration example of an imaging device101mounted on an electronic apparatus. As illustrated inFIG.17, the imaging device101includes an optical system102, an imaging element103, a signal processing circuit104, a monitor105, and a memory106, and is able to capture a still image and a moving image.

The optical system102includes one or a plurality of lenses, and guides image light (incident light) from a subject to the imaging element103, and forms an image on a light reception surface (a sensor section) of the imaging element103.

The imaging element1described above is applied as the imaging element103. Electrons are accumulated in the imaging element103for a fixed period of time in accordance with the image formed on the light reception surface via the optical system102. Thereafter, a signal corresponding to the electrons accumulated in the imaging element103is supplied to the signal processing circuit104.

The signal processing circuit104performs various kinds of signal processing on a pixel signal outputted from the imaging element103. An image (image data) captured by performing signal processing by the signal processing circuit104is supplied to and displayed on the monitor105, or is supplied to and stored (recorded) in the memory106.

In the imaging device101configured in such a manner, applying the imaging element1described above makes it possible to obtain a highly accurate optical spectrum while having a simple structure. This makes it possible to cature an image with higher image quality.

5. Example of Practical Application to Endoscopic Surgery System

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

FIG.19is a block diagram depicting an example of a functional configuration of the camera head11102and the CCU11201depicted inFIG.18.

One example of the endoscopic surgery system to which the technology according to the present disclosure may be applied has been described above. The technology according to the present disclosure may be applied to (the image pickup unit11402of) the camera head11102, (the image processing unit11412of) the CCU11201, and the like) among the components described above. Specifically, for example, the imaging element1is applicable to the image pickup unit10402. Applying the technology according to the present disclosure to the image pickup unit10402makes it possible to capture a more accurate image of a surgical region, which allows a surgeon to reliably confirm the surgical region.

It is to be noted that the endoscopic surgery system has been described here as one example, but the technology according to the present disclosure may be additionally applied to, for example, a microscopic surgery system or the like.

6. Example of Practical Application to In-Vivo Information Acquisition System

FIG.20is a block diagram depicting an example of a schematic configuration of an in-vivo information acquisition system of a patient using a capsule type endoscope, to which the technology according to an embodiment of the present disclosure (present technology) can be applied.

The in-vivo information acquisition system10001includes a capsule type endoscope10100and an external controlling apparatus10200.

The capsule type endoscope10100is swallowed by a patient at the time of inspection. The capsule type endoscope10100has an image pickup function and a wireless communication function and successively picks up an image of the inside of an organ such as the stomach or an intestine (hereinafter referred to as in-vivo image) at predetermined intervals while it moves inside of the organ by peristaltic motion for a period of time until it is naturally discharged from the patient. Then, the capsule type endoscope10100successively transmits information of the in-vivo image to the external controlling apparatus10200outside the body by wireless transmission.

The external controlling apparatus10200integrally controls operation of the in-vivo information acquisition system10001. Further, the external controlling apparatus10200receives information of an in-vivo image transmitted thereto from the capsule type endoscope10100and generates image data for displaying the in-vivo image on a display apparatus (not depicted) on the basis of the received information of the in-vivo image.

In the in-vivo information acquisition system10001, an in-vivo image imaged a state of the inside of the body of a patient can be acquired at any time in this manner for a period of time until the capsule type endoscope10100is discharged after it is swallowed.

A configuration and functions of the capsule type endoscope10100and the external controlling apparatus10200are described in more detail below.

The capsule type endoscope10100includes a housing10101of the capsule type, in which a light source unit10111, an image pickup unit10112, an image processing unit10113, a wireless communication unit10114, a power feeding unit10115, a power supply unit10116and a control unit10117are accommodated.

The light source unit10111includes a light source such as, for example, a light emitting diode (LED) and irradiates light on an image pickup field-of-view of the image pickup unit10112.

The image pickup unit10112includes an image pickup element and an optical system including a plurality of lenses provided at a preceding stage to the image pickup element. Reflected light (hereinafter referred to as observation light) of light irradiated on a body tissue which is an observation target is condensed by the optical system and introduced into the image pickup element. In the image pickup unit10112, the incident observation light is photoelectrically converted by the image pickup element, by which an image signal corresponding to the observation light is generated. The image signal generated by the image pickup unit10112is provided to the image processing unit10113.

The image processing unit10113includes a processor such as a central processing unit (CPU) or a graphics processing unit (GPU) and performs various signal processes for an image signal generated by the image pickup unit10112. The image processing unit10113provides the image signal for which the signal processes have been performed thereby as RAW data to the wireless communication unit10114.

The wireless communication unit10114performs a predetermined process such as a modulation process for the image signal for which the signal processes have been performed by the image processing unit10113and transmits the resulting image signal to the external controlling apparatus10200through an antenna10114A. Further, the wireless communication unit10114receives a control signal relating to driving control of the capsule type endoscope10100from the external controlling apparatus10200through the antenna10114A. The wireless communication unit10114provides the control signal received from the external controlling apparatus10200to the control unit10117.

The power feeding unit10115includes an antenna coil for power reception, a power regeneration circuit for regenerating electric power from current generated in the antenna coil, a voltage booster circuit and so forth. The power feeding unit10115generates electric power using the principle of non-contact charging.

The power supply unit10116includes a secondary battery and stores electric power generated by the power feeding unit10115. InFIG.20, in order to avoid complicated illustration, an arrow mark indicative of a supply destination of electric power from the power supply unit10116and so forth are omitted. However, electric power stored in the power supply unit10116is supplied to and can be used to drive the light source unit10111, the image pickup unit10112, the image processing unit10113, the wireless communication unit10114and the control unit10117.

The control unit10117includes a processor such as a CPU and suitably controls driving of the light source unit10111, the image pickup unit10112, the image processing unit10113, the wireless communication unit10114and the power feeding unit10115in accordance with a control signal transmitted thereto from the external controlling apparatus10200.

The external controlling apparatus10200includes a processor such as a CPU or a GPU, a microcomputer, a control board or the like in which a processor and a storage element such as a memory are mixedly incorporated. The external controlling apparatus10200transmits a control signal to the control unit10117of the capsule type endoscope10100through an antenna10200A to control operation of the capsule type endoscope10100. In the capsule type endoscope10100, an irradiation condition of light upon an observation target of the light source unit10111can be changed, for example, in accordance with a control signal from the external controlling apparatus10200. Further, an image pickup condition (for example, a frame rate, an exposure value or the like of the image pickup unit10112) can be changed in accordance with a control signal from the external controlling apparatus10200. Further, the substance of processing by the image processing unit10113or a condition for transmitting an image signal from the wireless communication unit10114(for example, a transmission interval, a transmission image number or the like) may be changed in accordance with a control signal from the external controlling apparatus10200.

Further, the external controlling apparatus10200performs various image processes for an image signal transmitted thereto from the capsule type endoscope10100to generate image data for displaying a picked up in-vivo image on the display apparatus. As the image processes, various signal processes can be performed such as, for example, a development process (demosaic process), an image quality improving process (bandwidth enhancement process, a super-resolution process, a noise reduction (NR) process and/or image stabilization process) and/or an enlargement process (electronic zooming process). The external controlling apparatus10200controls driving of the display apparatus to cause the display apparatus to display a picked up in-vivo image on the basis of generated image data. Alternatively, the external controlling apparatus10200may also control a recording apparatus (not depicted) to record generated image data or control a printing apparatus (not depicted) to output generated image data by printing.

One example of the in-vivo information acquisition system to which the technology according to the present disclosure may be applied has been described above. The technology according to the present disclosure may be applied, for example, to the image pickup unit10112among the components described above. Specifically, the imaging element1inFIG.1is applicable to the image pickup unit10112. Applying the technology according to the present disclosure to the image pickup unit10112makes it possible to acquire a more accurate image of the surgical region, thereby improving inspection accuracy.

7. Example of Practical Application to Mobile Body

For example, the technology (the present technology) according to the present disclosure may be achieved as a device mounted on any type of mobile body such as a vehicle, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a vessel, or a robot.

One example of the vehicle control system to which the technology according to the present disclosure may be applied has been described above. The technology according to the present disclosure may be applied to the imaging section12031among the components described above. Specifically, the imaging element1inFIG.1is applicable to the imaging section12031. Applying the technology according to the present disclosure to the imaging section12031makes it possible to obtain a captured image that is easier to see. Hence, it is possible to reduce fatigue of the driver.

8. Other Modification Examples

The present disclosure has been described above with reference to some embodiments and modification examples; however, the present disclosure is not limited to the embodiments and the like described above, and may be modified in a variety of ways. For example, in the imaging elements1and1A according to the first embodiment described above, a case where the first resonator13or13A has a three-layer structure or a four-layer structure is described as an example; however, the present disclosure is not limited thereto, and the number of stacked layers in the first resonator is optionally settable. In addition, the materials and thicknesses of the respective layers of the resonator structure are not limited to those described above, and are optionally settable.

In addition, the imaging elements1and1A according to the first embodiment described above, the moth eye structure21is provided on the front surface17S of the transparent layer17; however, the present disclosure is not limited thereto. For example, as with an imaging element1D according to a third modification example of the first embodiment illustrated inFIG.23, an on-chip lens26may be provided for each of the pixels22on the front surface17S of the transparent layer17.

In addition, in the imaging elements1C1to1C9according to the second embodiment described above, the imaging lens25is provided on the front surface17S of the transparent layer17; however, the present disclosure is not limited thereto. For example, as with an imaging element1E according to a first modification example of the second embodiment illustrated inFIG.24, a space may be provided between the front surface17S of the transparent layer17and the imaging lens25. The imaging element1E further includes the moth eye structure21on the front surface17S. Alternatively, instead of the moth eye structure21, an on-chip lens may be provided on the front surface17S.

It is to be noted that the effects described in the present specification are merely illustrative and non-limiting, and there may be other effects. In addition, the present technology may have the following configurations.

A resonator structure comprising:

a stacked structure that includes a semiconductor layer, a first resonator, a first reflection layer, a second resonator, a second reflection layer stacked in this order, allows light of a specific wavelength band to be transmitted therethrough,

the semiconductor layer having a first average refractive index,

the first resonator having a second average refractive index lower than the first average refractive index, and

the first reflection layer having a third average refractive index higher than the second average refractive index.

The resonator structure according to (1), in which the second average refractive index is 1 or more and four or less.

The resonator structure according to (1), in which the second average refraction index is 1 or more and two or less.

The resonator structure according to any one of (1) to (3), in which the second resonator has a refractive index distribution in a stacked plane.

The resonator structure according to (4), in which the second resonator includes a first portion having a first refractive index, and a second portion being dispersedly located in the first portion in the stacked plane and having a second refractive index.

The resonator structure according to any one of (1) to (5), in which a thickness of the first resonator is 400 nm or less.

The resonator structure according to any one of (1) to (6), in which the first reflection layer and the second reflection layer include a material including polycrystal silicon.

The resonator structure according to (7), in which each of a thickness of the first reflection layer and a thickness of the second reflection layer is 50 nm or less.

The resonator structure according to any one of (1) to (8), in which the first reflection layer and the second reflection layer includes a material including polycrystal silicon, and except for the first reflection layer, the second reflection layer, and the semiconductor layer, others include a material other than elemental silicon.

The resonator structure according to (9), in which each of thicknesses of the first reflection layer and the second reflection layer is 50 nm or less.

The resonator structure according to any one of (1) to (10), further including a visible light cut filter that suppresses transmission of visible light.

The resonator structure according to any one of (1) to (11), in which the first resonator includes a multilayer film structure in which a plurality of films is stacked.

The resonator structure according to claim1.

The resonator structure according to (12), in which the plurality of films in the first resonator includes a material containing at least one kind of silicon oxide, silicon nitride, tantalum oxide, or aluminum oxide.

An imaging element comprising:

a plurality of pixels each including a photoelectric converter and a resonator structure that allows light of a specific wavelength band to be transmitted toward the photoelectric converter, the resonator structure including a semiconductor substrate, a first resonator, a first reflection layer, a second resonator, a second reflection layer stacked in this order,

the semiconductor substrate including the photoelectric layer and having a first average refractive index,

the first resonator having a second average refractive index lower than the first average refractive index, and

the first reflection layer having a third average refractive index higher than the second average refractive index.

The imaging element according to (14), further including a light shielding layer between adjacent ones of the plurality of pixels.

The imaging element according to (14) or (15), in which

the plurality of pixels is provided with a lens that provides refractive power to light L toward the resonator structure, and

the respective resonator structures in the plurality of pixels allow light of wavelength bands different from each other to be transmitted therethrough.

An electronic apparatus comprising:

an imaging element,

the imaging element including a plurality of pixels each including a photoelectric converter and a resonator structure that allows light of a specific wavelength band to be transmitted toward the photoelectric converter, the resonator structure including a semiconductor substrate, a first resonator, a first reflection layer, a second resonator, a second reflection layer stacked in this order,

the semiconductor substrate including the photoelectric layer and having a first average refractive index,

the first resonator having a second average refractive index lower than the first average refractive index, and

the first reflection layer having a third average refractive index higher than the second average refractive index.

This application claims the benefit of Japanese Priority Patent Application JP2018-96234 filed with the Japan Patent Office on May 18, 2018, the entire contents of which are incorporated herein by reference.