# US 2021/0333201 A1 · Fabry-perot spectrometer-based smoke detector

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- Number: US 2021/0333201 A1
- Document ID: US20210333201A1
- Status: Published application
- Kind: A1
- Application number: 16/910,332
- Filed: 2020-06-24
- Published: 2021-10-28
- Earliest claimed: 2020-04-22
- Assignees: Kidde Technologies, Inc.
- Applicants: Kidde Technologies, Inc.
- Inventors: Elbert Jeyapaul; Thambiraj Avudaiappan
- Web page: https://patentgrep.com/patent/US20210333201A1

## CPC

- G01N 21/33: using ultraviolet light (G01N21/39 takes precedence)
- G08B 17/107: for detecting light-scattering due to smoke
- B64D 45/00: Aircraft indicators or protectors not otherwise provided for
- G01J 3/14: using refracting elements, e.g. prisms (G01J3/18, G01J3/26 take precedence {prisms per se G02B5/04})
- G01J 3/26: using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
- G01J 3/2803: {using photoelectric array detector}
- G01N 21/45: using interferometric methods; using Schlieren methods
- G01N 21/534: {by measuring transmission alone, i.e. determining opacity}
- G08B 17/103: using a light emitting and receiving device
- G08B 17/113: Constructional details
- B64D 2045/009: {Fire detection or protection; Erosion protection, e.g. from airborne particles}
- G01N 2021/451: {for determining the optical absorption}
- G01N 2201/06113: Coherent sources; lasers
- G01N 2201/0636: Reflectors
- G01N 2201/0638: Refractive parts
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- 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)

## Abstract

A smoke detector includes a laser light source to provide incident light. The smoke detector also includes a Fabry-Perot etalon to transmit some incoming light, which is produced from the incident light, as transmitted light. Smoke particles in a cavity of the Fabry-Perot etalon affect an intensity of one or more wavelengths of the transmitted light.

## Claims

### Claim 1

A smoke detector comprising:
a laser light source configured to provide incident light; and
a Fabry-Perot etalon configured to transmit some incoming light, which is produced from the incident light, as transmitted light, wherein smoke particles in a cavity of the Fabry-Perot etalon affect an intensity of one or more wavelengths of the transmitted light.

### Claim 2 (depends on 1)

The smoke detector according to claim 1, further comprising a slit source configured to provide diffracted light from the incident light.

### Claim 3 (depends on 2)

The smoke detector according to claim 2, further comprising a collimating lens configured to provide parallel beams of light as the incoming light from the diffracted light.

### Claim 4 (depends on 1)

The smoke detector according to claim 1, further comprising a prism configured to refract the transmitted light from the Fabry-Perot etalon and to produce a prism output.

### Claim 5 (depends on 4)

The smoke detector according to claim 4, further comprising a collimating lens and a photodetector array, wherein the collimating lens is configured to align different wavelengths of the prism output at different portions of the photodetector array.

### Claim 6 (depends on 5)

The smoke detector according to claim 5, further comprising a controller configured to analyze a spectrometer output based on the photodetector array.

### Claim 7 (depends on 6)

The smoke detector according to claim 6, wherein the controller obtains a reference spectrometer output corresponding with a condition of no smoke or fire.

### Claim 8 (depends on 7)

The smoke detector according to claim 7, wherein the controller is configured to determine a change in intensity of one or more of the different wavelengths, corresponding with the one or more wavelengths of the transmitted light, based on a comparison of the spectrometer output with the reference spectrometer output.

### Claim 9 (depends on 8)

The smoke detector according to claim 8, wherein the controller is configured to determine a presence of smoke and a density of the smoke or a presence of fire based on the comparison.

### Claim 10 (depends on 1)

The smoke detector according to claim 1, wherein the laser light source is configured to provide the incident light as white light, and the smoke detector is disposed in an aircraft.

### Claim 11

A method of assembling a smoke detector, the method comprising:
configuring a laser light source to provide incident light; and
disposing a Fabry-Perot etalon to transmit some incoming light, which is produced from the incident light, as transmitted light, wherein smoke particles in a cavity of the Fabry-Perot etalon affect an intensity of one or more wavelengths of the transmitted light.

### Claim 12 (depends on 11)

The method according to claim 11, further comprising arranging a slit source to provide diffracted light from the incident light.

### Claim 13 (depends on 12)

The method according to claim 12, further comprising positioning a collimating lens to provide parallel beams of light as the incoming light from the diffracted light.

### Claim 14 (depends on 11)

The method according to claim 11, further comprising positioning a prism to refract the transmitted light from the Fabry-Perot etalon and to produce a prism output.

### Claim 15 (depends on 14)

The method according to claim 14, further comprising arranging a collimating lens and a photodetector array such that the collimating lens aligns different wavelengths of the prism output at different portions of the photodetector array.

### Claim 16 (depends on 15)

The method according to claim 15, further comprising configuring a controller to analyze a spectrometer output based on the photodetector array.

### Claim 17 (depends on 16)

The method according to claim 16, wherein the configuring the controller includes the controller obtaining a reference spectrometer output corresponding with a condition of no smoke or fire.

### Claim 18 (depends on 17)

The method according to claim 17, wherein the configuring the controller includes the controller determining a change in intensity of one or more of the different wavelengths, corresponding with the one or more wavelengths of the transmitted light, based on a comparison of the spectrometer output with the reference spectrometer output.

### Claim 19 (depends on 18)

The method according to claim 18, wherein the configuring the controller includes the controller determining a presence of smoke and a density of the smoke or a presence of fire based on the comparison.

### Claim 20 (depends on 11)

The method according to claim 11, further comprising disposing the smoke detector in an aircraft.