# US 8,772,703 B2 · Position detection system and projection display system

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- Number: US 8,772,703 B2
- Document ID: US8772703B2
- Status: Granted
- Kind: B2
- Application number: 13/417,627
- Filed: 2012-03-12
- Published: 2012-09-20
- Granted: 2014-07-08
- Earliest claimed: 2011-03-14
- Assignees: Seiko Epson Corporation
- Applicants: Kanechika Kiyose; Kogo Endo
- Inventors: Kanechika Kiyose; Kogo Endo
- Web page: https://patentgrep.com/patent/US8772703B2

## CPC

- G06F 3/0416: {Control or interface arrangements specially adapted for digitisers}
- G01B 7/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B7/30 takes precedence)
- G06F 3/0421: {by interrupting or reflecting a light beam, e.g. optical touch-screen}
- G06F 3/0425: {using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected (tracking a projected light spot to determine a position on a display surface G06F3/0386)}
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

An optical position detection system includes a light output unit that outputs lights toward a first detection target and a second detection target, and a first light receiving unit that receives a first reflected light from the first detection target and a second light receiving unit that receives a second reflected light from the second detection target having different wavelengths, wherein the first detection target has a first reflection filter that reflects the first reflected light and the second detection target has a second reflection filter that reflects the second reflected light.

## Claims

### Claim 1

A position detection system comprising:
a light output unit that outputs lights toward a first detection target and a second detection target;
a light receiving unit that receives lights reflected from the first detection target and the second detection target; and
a position detection unit that detects positions of the first detection target and the second detection target using the lights received by the light receiving unit,
wherein the first detection target has a first reflection filter that reflects a first reflected light and the second detection target has a second reflection filter that reflects a second reflected light having a different wavelength from that of the first reflected light, and
the light receiving unit has a first light receiving unit that detects the first reflected light and a second light receiving unit that detects the second reflected light by distinguishing wavelengths of the lights.

### Claim 2 (depends on 1)

The position detection system according to claim 1, wherein the first reflection filter and the second reflection filter each has a frequency filter and a retroreflector that reflects incident light in an opposite direction to an incident direction.

### Claim 3 (depends on 2)

The position detection system according to claim 2, wherein the retroreflector has a prism shape.

### Claim 4 (depends on 2)

The position detection system according to claim 2, wherein the frequency filter is provided by coating or bonding on a surface of the retroreflector.

### Claim 5 (depends on 2)

The position detection system according to claim 2, wherein the first light receiving unit and the second light receiving unit are provided in one photodetector.

### Claim 6 (depends on 5)

The position detection system according to claim 5, wherein an angle formed by a line connecting the light output unit and the first detection target and a line connecting the photodetector and the first detection target is 10 degrees or less, and an angle formed by aline connecting the light output unit and the second detection target and a line connecting the photodetector and the second detection target is 10 degrees or less.

### Claim 7 (depends on 1)

A projection display system comprising:
the position detection system according to claim 1; and
an image irradiation system that projects an image on a reference surface.

### Claim 8 (depends on 2)

A projection display system comprising:
the position detection system according to claim 2; and
an image irradiation system that projects an image on a reference surface.

### Claim 9 (depends on 3)

A projection display system comprising:
the position detection system according to claim 3; and
an image irradiation system that projects an image on a reference surface.

### Claim 10 (depends on 4)

A projection display system comprising:
the position detection system according to claim 4; and
an image irradiation system that projects an image on a reference surface.

### Claim 11 (depends on 5)

A projection display system comprising:
the position detection system according to claim 5; and
an image irradiation system that projects an image on a reference surface.

### Claim 12 (depends on 6)

A projection display system comprising:
the position detection system according to claim 6; and
an image irradiation system that projects an image on a reference surface.