Optical filter and sensor system

• US 9,588,269 B2
• Filed: 05/18/2016
• Issued: 03/07/2017
• Est. Priority Date: 07/16/2012
• Status: Active Grant

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Inventors: Hendrix, Karen Denise, Bradley, Richard A. Jr., Grigonis, Marius, Ockenfuss, Georg J.
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): VU, MINDY D
• Application Number:
  US15/158,191
• Publication Number:
  US 20160266289A1
• Time in Patent Office: 293 Days
• Field of Search: 359/380, 359/359, 359/489.09, 359/489.19
• US Class Current: 1/1
• CPC Class Codes: C23C 14/08 Oxides C23C14/10 takes precedence
• CPC Class Codes: C23C 14/185 by cathodic sputtering
• CPC Class Codes: C23C 14/548 Controlling the composition
• CPC Class Codes: C23C 14/5806 Thermal treatment
• CPC Class Codes: G01J 5/0802 Optical filters
• CPC Class Codes: G02B 1/11 Anti-reflection coatings
• CPC Class Codes: G02B 1/115 Multilayers
• CPC Class Codes: G02B 5/207 comprising semiconducting materials
• CPC Class Codes: G02B 5/281 designed for the infrared light
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G06V 40/20 Movements or behaviour, e.g. gesture recognition recognition of facial expressions G06V40/16
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

An optical filter having a passband at least partially overlapping with a wavelength range of 800 nm to 1100 nm is provided. The optical filter includes a filter stack formed of hydrogenated silicon layers and lower-refractive index layers stacked in alternation. The hydrogenated silicon layers each have a refractive index of greater than 3 over the wavelength range of 800 nm to 1100 nm and an extinction coefficient of less than 0.0005 over the wavelength range of 800 nm to 1100 nm.

Claims

1. An optical filter, comprising:

a filter stack comprising;

a plurality of thin film hydrogenated silicon layers, wherein the plurality of thin film hydrogenated silicon layers have a refractive index of greater than 3 over a wavelength range of 800 nm to 1100 nm; and

a plurality of thin film dielectric lower-refractive-index layers, wherein the plurality of thin film dielectric lower-refractive-index layers have a refractive index of less than 3 over the wavelength range of 800 nm to 1100 nm, and wherein the plurality of thin film dielectric lower-refractive-index layers alternate, in a one-to-one ratio, with the plurality of thin film hydrogenated silicon layers; and

wherein the optical filter has exhibits interference that creates a passband at least partially overlapping with the wavelength range of 800 nm to 1100 nm,

wherein the passband has a center wavelength that shifts by less than 20 nm in magnitude with a change in an incidence angle between 0°

to 30°

.

2. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers each have a refractive index of greater than 3.6 at a wavelength of 830 nm.

3. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers each have a refractive index of greater than 3.5 over the wavelength range of 800 nm to 1100 nm.

4. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers each have a refractive index of greater than 3.6 over the wavelength range of 800 nm to 1100 nm.

5. The optical filter of claim 1, wherein the plurality of thin film dielectric lower-refractive-index layers each have a refractive index of less than 2.5 over the wavelength range of 800 nm to 1100 nm.

6. The optical filter of claim 1, wherein the plurality of thin film dielectric lower-refractive-index layers each have a refractive index of less than 2 over the wavelength range of 800 nm to 1100 nm.

7. The optical filter of claim 1, wherein the passband has a center wavelength that shifts by less than 15 nm in magnitude with a change in the incidence angle between 0°

to 30°

.

8. The optical filter of claim 1, wherein the passband has a center wavelength that shifts by about 12.2 nm in magnitude with a change in the incidence angle between 0°

to 30°

.

9. The optical filter of claim 1, wherein the plurality of thin film dielectric lower-refractive-index layers are each composed of silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), niobium pentoxide (Nb₂O₅), tantalum pentoxide (Ta₂O₅), or a mixture thereof.

10. The optical filter of claim 1, wherein the optical filter has a transmittance level, within the passband, of greater than 90% over the wavelength range of 800 nm to 1100 nm.

11. The optical filter of claim 1, wherein the optical filter has a blocking level, outside of the passband, of greater than OD2 over a wavelength range of 400 nm to 1100 nm.

12. The optical filter of claim 1, wherein the optical filter is a long-wavelength-pass edge filter, and wherein the passband has an edge wavelength in the wavelength range of 800 nm to 1100 nm.

13. The optical filter of claim 1, wherein the optical filter is a bandpass filter, and wherein the passband has a center wavelength in the wavelength range of 800 nm to 1100 nm.

14. The optical filter of claim 1, wherein the passband has a full width at half maximum (FWHM) of less than 50 nm.

15. The optical filter of claim 1, further comprising:

a substrate, wherein the filter stack is disposed on a first surface of the substrate and a coating is disposed on a second surface of the substrate opposite the first surface.

16. The optical filter of claim 15, wherein the coating is an antireflective (AR) coating.

17. The optical filter of claim 1, wherein the optical filter has a total coating thickness of less than 10 μ

m.

18. The optical filter of claim 1, forming part of a sensor system including a light source for emitting light at an emission wavelength within the passband of the optical filter, and a sensor for detecting the emitted light,

wherein the optical filter receives the emitted light from the light source and transmits the emitted light to the sensor.

19. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers are each deposited by pulsed direct current (DC) sputtering.

20. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers are associated with an extinction coefficient of approximately 0.00055 at 800 nm.

21. The optical filter of claim 1, wherein the plurality of thin film hydrogenated silicon layers are associated with an extinction coefficient of less than 0.0003 at 800 nm.

22. A sensor system, comprising:

an optical filter, exhibiting interference that creates a passband including an emission wavelength and at least partially overlapping with a wavelength range of 800 nm to 1100 nm, being disposed to receive emitted light and transmit the emitted light,

wherein the emitted light is emitted, from a light source, at the emission wavelength in the wavelength range of 800 nm to 1100 nm, and

wherein the optical filter includes a filter stack including;

a plurality of thin film hydrogenated silicon layers,

wherein the plurality of thin film hydrogenated silicon layers each have a refractive index of greater than 3 over the wavelength range of 800 nm to 1100 nm; and

a plurality of thin film dielectric lower-refractive-index layers,

wherein the plurality of thin film dielectric lower-refractive-index layers each have a refractive index of less than 3 over the wavelength range of 800 nm to 1100 nm, and

wherein thin film dielectric lower-refractive-index layers, of the plurality of thin film dielectric lower-refractive-index layers, alternate, in a one-to-one ration, with thin film hydrogenated silicon layers of the plurality of thin film hydrogenated silicon layers,

wherein the passband has a center wavelength that shifts by less than 20 nm in magnitude with a change in an incidence angle between 0°

to 30°

.

23. The sensor system of claim 22, wherein the optical filter is disposed directly on a sensor.

24. The sensor system of claim 22, further comprising:

a sensor, wherein the sensor system is a proximity sensor system, the emitted light is directed toward a target, the optical filter is disposed to receive the emitted light after reflection by the target, and the sensor is a proximity sensor for detecting the emitted light and sensing a proximity of the target.

25. The sensor system of claim 22, further comprising:

a sensor, wherein the sensor system is a three-dimensional (3D) imaging system, the emitted light is directed toward a target, the optical filter is disposed to receive the emitted light after reflection by the target, and the sensor is a 3D image sensor for detecting the emitted light and providing a 3D image of the target.

26. The sensor system of claim 25, wherein the 3D imaging system is a gesture-recognition system, the target is a user of the gesture-recognition system, and the sensor system further includes:

a processing system for processing a 3D image of the user to recognize a gesture of the user.

27. The sensor system of claim 22, further comprising:

a sensor, wherein the sensor is a charge-coupled device (CCD) chip or a complementary metal oxide semiconductor (CMOS) chip.

28. The sensor system of claim 22, further comprising:

a sensor, wherein the optical filter is formed directly on the sensor by using wafer-level processing.

29. The sensor system of claim 22, wherein the optical filter further includes:

a substrate, wherein the filter stack is disposed on a first surface of the substrate; and

an antireflective (AR) coating is disposed on a second surface of the substrate opposite the first surface.

30. A system, comprising:

an optical filter, exhibits interference that creates a passband including an emission wavelength and at least partially overlapping with a wavelength range of 800 nm to 1100 nm;

wherein the optical filter includes a filter stack including;

a plurality of thin film hydrogenated silicon layers, wherein the plurality of thin film hydrogenated silicon layers have a refractive index of greater than 3.5 over a wavelength range of 800 nm to 1100 nm; and

a plurality of thin film dielectric lower-refractive-index layers, wherein the plurality of thin film dielectric lower-refractive-index layers have a refractive index of less than 3 over the wavelength range of 800 nm to 1100 nm, and wherein thin film dielectric lower-refractive-index layers, of the plurality of thin film dielectric lower-refractive-index layers, alternate, in a one-to-one ratio, with thin film hydrogenated silicon layers of the plurality of thin film hydrogenated silicon layers, and

wherein the passband has a center wavelength that shifts by less than 20 nm in magnitude with a change in an incidence angle between 0°

to 30°

.

31. The system of claim 30, wherein the passband has a full width at half maximum of less than 50 nm.

32. The system of claim 30, further comprising:

a substrate, wherein the filter stack is disposed on a first surface of the substrate and a coating is disposed on a second surface of the substrate opposite the first surface.