IMAGING SYSTEM AND METHOD USING A PHOTONIC BAND GAP ARRAY

• US 20080179523A1
• Filed: 01/30/2007
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Barker, Delmar L., Owens, William R., Young, Abram G.
• Granted Patent: US 8,569,696 B2
• Time in Patent Office: Days
• US Class Current: 250/338.1
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0803 Arrangements for time-dependent attenuation of radiation signals
• CPC Class Codes: G01J 5/0818 Waveguides
• CPC Class Codes: G01J 5/0853 having infrared absorbers other than the usual absorber layers deposited on infrared detectors like bolometers, wherein the heat propagation between the absorber and the detecting element occurs within a solid
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices

Abstract

An imaging system (20) includes an array (24) of photonic band gap material cells. The band gap material has an absorption edge at about the emission frequency of a source (22) of electromagnetic energy. Images from a field of view (26) directed onto the photonic band gap array (24) increase the temperature of the illuminated cells, shifting the absorption edge frequency for those cells. A focal plane array (28) detects the electromagnetic radiation transmitted through the photonic band gap array (24) from the source (22). The intensity of the transmitted radiation is proportional to the shift in the photonic band gap edge.

Claims

1. An imaging system, comprising:

a source of narrow bandwidth electromagnetic radiation having a specified wavelength;

an array of photonic band gap material cells positioned to receive the electromagnetic radiation from the source, each cell having a photonic band gap material with an absorption edge at about the emission frequency of the source of electromagnetic radiation;

an optical assembly arranged to direct electromagnetic radiation from a field of view onto the photonic band gap array and thereby shift the absorption edge of illuminated cells; and

a focal plane array positioned to receive electromagnetic radiation from the photonic band gap array and to detect electromagnetic radiation with the specified wavelength.

2. A system as set forth in claim 1, wherein the source is selected from a laser and a light emitting diode.

3. A system as set forth in claim 1, wherein the source emits electromagnetic radiation having an approximately near-infrared wavelength.

4. A system as set forth in claim 1, wherein the source is a 0.85 micrometer wavelength laser.

5. A system as set forth in claim 1, wherein the photonic band gap array is thermally isolated from the focal plane array.

6. A system as set forth in claim 1, wherein the photonic band gap array is thermally isolated from the focal plane array by an aerogel.

7. A system as set forth in claim 1, wherein the photonic band gap array includes a first material having a relatively low degree of thermal expansion and a second material having a relatively high degree of thermal expansion.

8. A system as set forth in claim 1, wherein the photonic band gap material has a high degree of absorption in a wavelength of interest to maximize absorption edge shift.

9. A system as set forth in claim 1, wherein the photonic band gap material has a high degree of absorption in an infrared wavelength of interest to maximize absorption edge shift.

11. A system as set forth in claim 1, wherein the photonic band gap material includes units of a first material dispersed within a second material at regular intervals of approximately “

a”

, each unit of the first material having a dimension of approximately 2r, and a lattice constant is defined as r/a and decreases proportionately with temperature.

12. A system set forth in claim 1, wherein the optical assembly includes a device which transmits electromagnetic radiation of a first wavelength and reflects electromagnetic radiation of a second wavelength.

13. A system as set forth in claim 1, wherein the focal plane array includes an image sensor.

14. A system as set forth in claim 1, wherein the focal plane array includes a charge-coupled device (COD).

15. A system as set forth in claim 1, wherein the photonic band gap array and the focal plane array are contained in a housing lined with a photonic band gap material that inhibits electromagnetic radiation with wavelengths of about eight to twelve micrometers.

10. A system comprising:

a source of narrow bandwidth electromagnetic radiation having a specified wavelength;

an array of photonic band gap material cells positioned to receive the electromagnetic radiation from the source, each cell having a photonic band gap material with an absorption edge at about the emission frequency of the source of electromagnetic radiation;

an optical assembly arranged to direct electromagnetic radiation from a field of view onto the photonic band gap array and thereby shift the absorption edge of illuminated cells; and

a focal plane array positioned to receive electromagnetic radiation from the photonic band gap array and to detect electromagnetic radiation with the specified wavelength,

wherein the photonic band gap material has a lattice structure that expands approximately 0.25% per 10 C temperature rise, resulting in an approximately 4 to 10 decibel change in the transmission of the electromagnetic radiation.

16. An imaging method comprising the steps of:

(a) projecting electromagnetic radiation having a specified wavelength onto an array of photonic band gap material cells, where the photonic band gap material has an absorption edge at about the same frequency as the electromagnetic radiation projected onto the photonic band gap array;

(b) receiving an image from a field of view onto the photonic band gap array, thereby increasing the temperature of cells illuminated by the image from the field of view and shifting the photonic band gap absorption edge frequency of the illuminated cells; and

(c) detecting electromagnetic radiation of the specified wavelength transmitted through the photonic band gap array.

17. A method as set forth in claim 16, wherein the projecting step includes projecting electromagnetic radiation having a wavelength of about 0.85 micrometers.

18. A method as set forth in claim 16, wherein the directing step includes directing infrared radiation from the field of view onto the photonic band gap array.

19. An imaging system comprising:

(a) means for modulating transmission of electromagnetic radiation representative of an image from a field of view;

(b) means for projecting electromagnetic radiation of a specified wavelength on the modulating means;

(c) means for receiving electromagnetic radiation forming an image from a field of view at the modulating means; and

(d) means for detecting electromagnetic radiation of the specified wavelength from the projecting means received from the modulating means.