# US 8,570,510 B2 · Optical unit

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- Number: US 8,570,510 B2
- Document ID: US8570510B2
- Status: Granted
- Kind: B2
- Application number: 13/390,650
- Filed: 2010-07-28
- Published: 2012-06-14
- Granted: 2013-10-29
- Earliest claimed: 2009-08-25
- Assignees: NEC System Technologies, Ltd.
- Applicants: Ippei Kamimura
- Inventors: Ippei Kamimura
- Web page: https://patentgrep.com/patent/US8570510B2

## CPC

- G01J 3/18: using diffraction elements, e.g. grating (gratings per se G02B)
- G01J 3/02: Details
- G01J 3/0208: {using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction}
- G01J 3/0256: {Compact construction}
- G01J 3/1895: {using fiber Bragg gratings or gratings integrated in a waveguide}
- G01J 3/2803: {using photoelectric array detector}
- G01J 3/36: Investigating two or more bands of a spectrum by separate detectors
- G01J 3/51: using colour filters
- G02B 5/1809: {with pitch less than or comparable to the wavelength}
- G02B 5/204: {in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces (for use with wavelengths longer than the infrared light H01Q15/0006)}
- G02B 27/1013: {for colour or multispectral image sensors, e.g. splitting an image into monochromatic image components on respective sensors (spectral imaging systems G01J)}
- G02B 27/1086: {operating by diffraction only}
- G02B 27/4244: {in wavelength selecting devices (spectrometry G01J)}
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical unit has a filter member that disperses transmitted light and a photodetector that has light receiving elements. The filter member has a light transmissive substrate, protrusions including a first metallic material and formed on one surface of the substrate, and a metal film including a second metallic material having a refractive index higher than that of the first metallic material and formed so as to cover the protrusions as well as the one surface of the substrate. The metal film located between adjacent protrusions can be a diffraction grating and the protrusions can be waveguides. At least one of the grating cycle of the diffraction grating, the height of the protrusions, and the thickness of the metal film is set to a value different for each portion such that a wavelength of light transmitted through the filter member changes for each portion.

## Claims

### Claim 1

An optical unit comprising:
a filter member that separates transmitted light; and
a photodetector having a plurality of light receiving elements,
wherein the filter member includes:
a light transmissive substrate;
a plurality of protrusions formed with a first metallic material on one surface of the substrate; and
a metal film formed by a second metallic material having a higher refractive index than the first metallic material, so as to cover the one surface of the substrate along with the plurality of protrusions,
the plurality of protrusions are disposed such that the metal film located between adjacent protrusions serves as a diffraction grating and incident light that is incident the filter member from an other side of the photodetector propagates inside the protrusions as an evanescent wave,
at least one of a grating pitch of the diffraction grating, a height of the protrusions and a thickness of the metal film is set, such that a wavelength of light transmitted through the filter member changes for each portion, to a different value for each of the portions, and
the photodetector is disposed such that each of the plurality of light-receiving elements receives light transmitted through the filter member.

### Claim 2 (depends on 1)

The optical unit according to claim 1,
wherein the grating pitch of the diffraction grating is formed, for each of the portions, so as to be shorter than the wavelength of light that is required to be transmitted through the portion.

### Claim 3 (depends on 1)

The optical unit according to claim 1,
wherein a material used for the substrate includes silicon oxide, the first metallic material includes gold (Au), and the second metallic material includes titanium oxide.

### Claim 4 (depends on 1)

The optical unit according to claim 1,
wherein the plurality of protrusions are formed as rectangular columns and disposed in a matrix.

### Claim 5 (depends on 1)

The optical unit according to claim 1,
wherein the photodetector is a solid-state imaging device having a semiconductor substrate on which the plurality of light receiving elements are formed in a matrix.