Active multi-spectral sensor

• US 9,903,757 B1
• Filed: 09/23/2016
• Issued: 02/27/2018
• Est. Priority Date: 09/25/2015
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Yap, Daniel, Neff, Brian
• Primary Examiner(s): Gaworecki, Mark R
• Application Number:
  US15/275,172
• Time in Patent Office: 522 Days
• CPC Class Codes: G01J 2003/102 Plural sources
• CPC Class Codes: G01J 2003/104 Monochromatic plural sources
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/399 Diode laser
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence
• CPC Class Codes: G01N 2201/067 Electro-optic, magneto-optic, acousto-optic elements

Abstract

A sensor includes a plurality of transmitter units, a photodetector, and an optical system coupled to the plurality of transmitter units and the photodetector. Each of the transmitter units simultaneously transmits a light beam having a plurality of wavelengths, the optical system directs the light beam from each of the transmitter units onto a same illuminated spot on a probed surface, and the optical system collects light from the same illuminated spot and directs the light to the photodetector.

Claims

1. A sensor comprising:

a plurality of laser transmitter units, wherein each of the plurality of laser transmitter units is configured to transmit a light beam having a plurality of wavelengths;

a photodetector; and

an optical system coupled to the plurality of laser transmitter units and the photodetector;

wherein the optical system directs the light beam from each of the laser transmitter units onto a same illuminated spot on a probed surface; and

wherein the optical system collects light from the same illuminated spot and directs the light to the photodetector.

2. The sensor of claim 1 further comprising:

an aperture;

wherein the optical system directs the light beam from each respective laser transmitter unit onto a portion of the aperture different from portions of the aperture onto which other light beams from other laser transmitter units are directed.

3. The sensor of claim 2:

wherein the optical system directs the light beams from different portions of the aperture to the same illuminated spot on the probed surface; and

further comprising a beam steering device coupled to the optical system for moving a spatial position of the same illuminated spot on the probed surface, and for directing the collected light to the photodetector.

4. The sensor of claim 3:

wherein the beam steering device comprises at least one single two-axis-motion fast-steering mirror, or at least a pair of one-axis-motion galvo mirrors.

5. The sensor of claim 1:

wherein each of the transmitted wavelengths of the plurality of wavelengths transmitted by each laser transmitter unit is modulated by a radio frequency that is unique for each transmitted wavelength; and

further comprising a channelizer coupled to the photodetector, the channelizer having a plurality of receiver outputs;

wherein each respective receiver output is derived using the radio frequency that is unique for each transmitted wavelength; and

wherein each respective receiver output corresponds to one of the transmitted wavelengths.

6. The sensor of claim 1 wherein each transmitted wavelength comprises a long-wave infrared (LWIR) wavelength, a mid-wave infrared (MWIR) wavelength, or a short-wave infrared (SWIR) wavelength.

7. A multi-spectral sensor comprising:

a plurality of laser devices each comprising;

a laser section having a light output;

an optical amplifier coupled to the laser section; and

an optical modulator coupled to the optical amplifier;

wherein the light output of each respective laser section of the plurality of laser devices has a respective wavelength that is different from a wavelength of the light output from each other laser section of the plurality of laser devices;

wherein each respective optical modulator of the plurality of laser devices is configured to modulate the light output of a respective laser section with a respective modulation frequency that is different from a modulation frequency of each other optical modulator of the plurality of laser devices; and

wherein the multi-spectral sensor is configured so that the plurality of laser devices simultaneously transmit a plurality of light beams, each respective light beam modulated with a respective modulation frequency; and

a photodetector for detecting received light; and

a channelizer coupled to the photodetector, the channelizer having a plurality of receiver outputs;

wherein each respective receiver output of the plurality of receiver outputs is derived using one of the respective modulation frequencies; and

wherein each respective receiver output corresponds to one of the respective wavelengths.

8. The multi-spectral sensor of claim 7:

wherein each respective laser section comprises a distributed feedback laser having a grating of a different grating period, or wherein each respective laser section comprises a distributed feedback laser having a different drive current.

9. The multi-spectral sensor of claim 7 further comprising:

a plurality of reference light outputs coupled between the plurality of laser devices and the channelizer;

wherein each respective reference light output has one of the respective wavelengths.

10. The multi-spectral sensor of claim 7 wherein each wavelength comprises a long-wave infrared (LWIR) wavelength, a mid-wave infrared (MWIR) wavelength, or a short-wave infrared (SWIR) wavelength.

11. The multi-spectral sensor of claim 7 wherein each modulation frequency is a radio frequency.

12. The multi-spectral sensor of claim 7 wherein the plurality of laser device comprises:

at least two first laser devices located adjacent to each other and separated by a first spatial spacing, wherein the at least two first laser devices each have a different wavelength, and wherein the different wavelengths of the at least two first laser devices are different by a first increment; and

at least two second laser devices located adjacent to each other and separated by a second spatial spacing, wherein the at least two second laser devices each have a different wavelength, and wherein the different wavelengths of the at least two second laser devices are different by a second increment;

wherein the first spacing and the second spacing are equal;

wherein the wavelengths of the two first laser devices are longer than the wavelengths of the second two laser devices; and

wherein first increment is smaller than the second increment.

13. The multi-spectral sensor of claim 7 further comprising:

an optical system for directing the plurality of light beams onto a same illuminated spot on a probed surface; and

a beam steering device coupled to the optical system for moving a spatial position of the same illuminated spot on the probed surface, and for directing the received light to the photodetector.

14. The multi-spectral sensor of claim 7 wherein the plurality of laser devices further comprises:

a laser array controller comprising;

a laser wavelength control coupled to each laser section for tuning the wavelength of each respective laser section;

an output level adjust coupled to each optical amplifier;

a radio frequency control coupled to each optical modulator.

15. The multi-spectral sensor of claim 7 further comprising:

at least a first substrate and a second substrate;

a first plurality of laser devices of the plurality of laser devices on the first substrate;

a second plurality of laser devices of the plurality of laser devices on the second substrate;

a top layer for providing interconnects for the first and second plurality of laser devices, wherein the first substrate and the second substrate are on the top layer;

a heat spreader coupled to the top layer; and

a cold plate coupled to the heat spreader.

16. The multi-spectral sensor of claim 13:

wherein the photodetector comprises a first photodetector and a second photodetector; and

wherein the optical system and the beam steering device direct the received light to the first photodetector and the second photodetector.

17. The multi-spectral sensor of claim 13:

wherein the beam steering device comprises a single two-axis-motion fast-steering mirror, or a pair of one-axis-motion galvo mirrors.

18. A method of sensing comprising:

simultaneously transmitting from each of a plurality of laser transmitter units a light beam, wherein each light beam comprises a plurality of wavelengths;

directing the light beam from each of the laser transmitter units onto a same illuminated spot on a probed surface using an optical system;

collecting light from the same illuminated spot and directing the collected light to a photodetector; and

detecting the collected light using the photodetector.

19. The method of claim 18 further comprising:

directing the light beam from each respective laser transmitter unit onto a portion of an aperture different from portions of the aperture onto which other light beams from other laser transmitter units are directed.

20. The method of claim 19 further comprising:

directing the light beams from different portions of the aperture to the same illuminated spot on the probed surface; and

steering the light beams using a beam steering device to move a spatial position of the same illuminated spot on the probed surface, and for directing the collected light to the photodetector.

21. The method of claim 20:

wherein the beam steering device comprises at least one single two-axis-motion fast-steering mirror, or at least a pair of one-axis-motion galvo mirrors.

22. The method of claim 18 further comprising:

modulating each of the transmitted wavelengths of the plurality of wavelengths transmitted by each laser transmitter unit by a radio frequency that is unique for each transmitted wavelength; and

channelizing an output of the photodetector to form a plurality of receiver outputs;

wherein each respective receiver output is derived using the radio frequency that is unique for each transmitted wavelength; and

wherein each respective receiver output corresponds to one of the transmitted wavelengths.

23. The method of claim 18 wherein each transmitted wavelength comprises a long-wave infrared (LWIR) wavelength, a mid-wave infrared (MWIR) wavelength, or a short-wave infrared (SWIR) wavelength.