Snapshot spatial heterodyne imaging polarimetry
Polarization based channeled images are optically demodulated to produce directly viewable images. A channeled image flux is converted to an unpolarized flux by a phosphor or other sensor, and the resulting converted flux is demodulated by modulating at a spatial frequency corresponding to a modulating frequency of the channeled image flux. After modulation, the converted flux is spatially filtered to remove or attenuate portions associated with the modulation frequency and harmonics thereof. The resulting baseband flux is then imaged by direct viewing, projection, or using an image sensor and a display.
1. An apparatus, comprising:
an optical modulation system situated to modulate an optical flux received from an object so as to produce a modulated imaging optical intensity associated with a corresponding modulation of at least one Stokes parameter associated with the optical flux; and
an optical demodulator situated to demodulate the modulated imaging optical intensity and produce a viewable image associated with at least one Stokes parameter associated with the received optical flux.
2. The apparatus of claim 1 , wherein the at least one Stokes parameter includes S 1 , S 2 , and combinations thereof.
3. The apparatus of claim 1 , wherein the optical modulation system is situated to apply a polarization dependent modulation at a first spatial frequency and the optical demodulator is situated to apply a demodulation corresponding to the first spatial frequency.
4. The apparatus of claim 3 , wherein the optical demodulator includes a grating configured to establish the demodulation associated with the first spatial frequency.
5. The apparatus of claim 4 , wherein a period of the grating corresponds to the first spatial frequency.
6. The apparatus of claim 4 , wherein the grating is a polarization grating.
7. The apparatus of claim 3 , wherein the optical demodulator includes a polarization grating having a period corresponding to the first spatial frequency and situated to produce modulation at a spatial frequency corresponding to twice the first spatial frequency.
8. The apparatus of claim 1 , wherein the optical demodulator includes a first phosphor, a grating, and a second phosphor, wherein the first phosphor is situated to produce a modulated intensity corresponding to the modulated imaging optical intensity and direct the modulated intensity to the grating so that the grating delivers a grating modulated intensity to the second phosphor.
9. The apparatus of claim 8 , wherein the optical demodulator includes a spatial filter situated to transmit a baseband portion of the grating modulated intensity.
10. The apparatus of claim 9 , further comprising an eyepiece situated for viewing the baseband demodulated optical intensity.
11. The apparatus of claim 1 , wherein the optical demodulator includes a sensor array configured to produce an electronic image associated with the modulated imaging optical intensity and a display system situated to deliver a modulated optical intensity to the optical demodulator.
12. A method, comprising:
producing an imaging optical beam having a periodic modulation associated with at least one Stokes parameter of optical radiation from an object; and
applying a corresponding optical demodulation to the periodically modulated imaging optical beam.
13. The method of claim 12 , further comprising spatially filtering the demodulated, periodically modulated optical beam.
14. The method of claim 13 , wherein the spatial filtering attenuates spatial frequency components at a spatial frequency corresponding to the periodic modulation of the imaging optical beam.
15. The method of claim 13 , wherein the spatial filtering i directs spatial frequency components at a spatial frequency corresponding to a difference between a spatial frequency of the periodic modulation of the imaging optical beam and a spatial frequency associated with the optically applied demodulation.
16. The method of claim 13 , wherein the optical demodulation is applied with a grating having a period corresponding to the periodic modulation of the imaging optical beam.
17. The method of claim 16 , wherein the periodically modulated imaging optical beam is produced by directing an optical beam from the object to a phosphor.
18. The method of claim 16 , wherein the periodically modulated imaging beam is produced by directing an optical beam from the object to an image sensor, and producing the modulated imaging beam by displaying an image based on a detected image from the image sensor.
19. The method of claim 12 , further comprising forming an image based on the demodulation applied to the periodically modulated imaging optical beam.