# US 11,112,279 B2 · Optical module and optical encoder comprising a dummy light receiving device formed between a light receiving device and a through hole in a sensor substrate

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- Number: US 11,112,279 B2
- Document ID: US11112279B2
- Status: Granted
- Kind: B2
- Application number: 16/807,585
- Filed: 2020-03-03
- Published: 2020-09-10
- Granted: 2021-09-07
- Earliest claimed: 2019-03-07
- Assignees: Mitsumi Electric Co., Ltd.
- Applicants: Tomomitsu Ohara; Kazuki Tsutsumi; Shinji Kimura; Syuhei Suzuki; Yusuke Ohba
- Inventors: Tomomitsu Ohara; Kazuki Tsutsumi; Shinji Kimura; Syuhei Suzuki; Yusuke Ohba
- Web page: https://patentgrep.com/patent/US11112279B2

## CPC

- G01D 5/34746: {Linear encoders}
- G01D 5/30: the beams of light being detected by photocells
- G01D 5/34715: {Scale reading or illumination devices}
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR

## Abstract

An optical module includes a fixed substrate, and a sensor substrate secured to the fixed substrate and having a through-hole formed therein. A light emitting device is secured to the fixed substrate at a position in the through-hole. A light receiving device is provided in the sensor substrate. A dummy light receiving device is formed between the light receiving device and the through-hole, around the through-hole, and in the sensor substrate. The light receiving device and the dummy light receiving device are made of an impurity diffusion layer having a same conductive type as a conductive type of a surface layer of the sensor substrate. The dummy light receiving device is deeper than the light receiving device.

## Claims

### Claim 1

An optical module, comprising:
a fixed substrate;
a sensor substrate secured to the fixed substrate and having a through-hole formed therein;
a light emitting device secured to the fixed substrate at a position in the through-hole;
a light receiving device provided in the sensor substrate; and
a dummy light receiving device formed between the light receiving device and the through-hole, around the through-hole, and in the sensor substrate,
wherein the light receiving device and the dummy light receiving device are made of an impurity diffusion layer having a same conductive type as a conductive type of a surface layer of the sensor substrate, and
wherein the dummy light receiving device is formed deeper than the light receiving device.

### Claim 2 (depends on 1)

The optical module as claimed in claim 1,
wherein the sensor substrate is a semiconductor substrate, and
wherein the light receiving device and the dummy light receiving device are reverse biased pn junction type photodiodes.

### Claim 3 (depends on 2)

The optical module as claimed in claim 2, wherein the light emitting device is a light emitting diode.

### Claim 4 (depends on 3)

The optical module as claimed in claim 3, wherein the sensor substrate on the fixed substrate side is a cathode, and the light emitting device on the fixed substrate side is a cathode.

### Claim 5 (depends on 1)

The optical module as claimed in claim 1, wherein the impurity diffusion layer forming the dummy light receiving device has an impurity concentration higher than that of an impurity diffusion layer forming the light receiving device.

### Claim 6

An optical module, comprising:
a fixed substrate;
a sensor substrate secured to the fixed substrate and having a through-hole formed therein;
a light emitting device secured to the fixed substrate at a position in the through-hole;
a light receiving device provided in the sensor substrate; and
a dummy light receiving device formed between the light receiving device and the through-hole, around the through-hole, and in the sensor substrate,
wherein the light receiving device and the dummy light receiving device are made of an impurity diffusion layer having a same conductive type as a conductive type of a surface layer of the sensor substrate, and
wherein the sensor substrate is secured to the fixed substrate via a conductive adhesive layer containing a light absorbing member.

### Claim 7 (depends on 1)

An optical encoder, comprising:
the optical module as claimed in claim 1; and
a reflective scale.

### Claim 8 (depends on 6)

An optical encoder, comprising:
the optical module as claimed in claim 6; and
a reflective scale.