# US 2014/0197306 A1 · System and method for using a linear polarizer to reduce optical crosstalk for optical proximity sensors

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- Number: US 2014/0197306 A1
- Document ID: US20140197306A1
- Status: Published application
- Kind: A1
- Application number: 14/124,235
- Filed: 2012-06-06
- Published: 2014-07-17
- Earliest claimed: 2011-06-09
- Assignees: Ams AG
- Inventors: Yu Wang; Kerry Glover; David Mehrl; Greg Stoltz; Tom Dunn
- Web page: https://patentgrep.com/patent/US20140197306A1

## CPC

- G01B 11/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00)
- H03K 17/941: {using an optical detector (H03K17/968 takes precedence)}
- H03K 2217/94108: making use of reflection
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

An optical proximity sensor often emits light, and detects the photons in the returned light signal. Because light can be reflected and scattered by cover glass and ink layer printed on the cover glass, optical crosstalk is a concern for the optical proximity sensors. In one embodiment, the present disclosure provides an optical proximity sensor including a linear polarizer to cover the photo detector, or a polarizer to cover the light emitting device, or two polarizers to cover both the photo detector and the light emitting device. The polarizer blocks the s-polarized light and only allows the p-polarized light to pass through. Because the scattered light is predominated by the s-polarization, the optical crosstalk may be reduced.

## Claims

### Claim 1

An optical proximity sensor, comprising:
a light emitting device (1);
a photon detecting device (5);
a polarization selection device (11, 51);
a transparent cover (3); and
an ink layer on the transparent cover (2).

### Claim 2 (depends on 1)

The proximity sensor according to claim 1, wherein said the light emitting device (1) is a light emitting diode.

### Claim 3 (depends on 1)

The proximity sensor according to claim 1, wherein said the photo detecting device (5) is a photodiode.

### Claim 4 (depends on 1)

The proximity sensor according to claim 1, wherein said the polarization selection device (11, 51) is a linear polarization sheet.

### Claim 5 (depends on 1)

The proximity sensor according to claim 1, wherein said the polarization selection device (11, 51) is a wire grid polarizer.

### Claim 6 (depends on 1)

The proximity sensor according to claim 1, wherein the polarization selection device is orientated in a direction such that only the p-polarized light is allowed to pass through and the s-polarized light will be blocked.

### Claim 7 (depends on 1)

The proximity sensor according to claim 1, wherein the transparent cover (2) is a glass plate.

### Claim 8 (depends on 1)

The proximity sensor according to claim 1, wherein said the transparent cover (2) is a plastic plate.

### Claim 9 (depends on 1)

The proximity sensor according to claim 1, wherein the polarization selection device is mounted between the photon detecting device (5) and the ink layer (2).

### Claim 10 (depends on 1)

The proximity sensor according to claim 1, wherein the polarization selection device is mounted between the light emitting device (1) and the ink layer (2).

### Claim 11 (depends on 1)

The proximity sensor according to claim 1, wherein an edge of a beam from the light emitting device (1) incidents upon the transparent cover/air at an angle close to the Brewster angle.