Scannerless loss modulated flash color range imaging
View Patent ↗Scannerless loss modulated flash color range imaging methods and apparatus are disclosed for producing three dimensional (3D) images of a target within a scene. Apparatus and methods according to the present invention comprise a light source providing at least three wavelengths (passbands) of illumination that are each loss modulated, phase delayed and simultaneously directed to illuminate the target. Phase delayed light backscattered from the target is spectrally filtered, demodulated and imaged by a planar detector array. Images of the intensity distributions for the selected wavelengths are obtained under modulated and unmodulated (dc) illumination of the target, and the information contained in the images combined to produce a 3D image of the target.
1. A method to provide a three dimensional (3D) image of a target by scannerless loss modulated flash color range imaging, the method comprising:
providing a continuously emitting light source adapted to provide illumination comprising at least three wavelengths;
modulating by a first loss modulator operated at a modulation frequency, each of the at least three wavelengths;
imparting a phase delay onto each of the at least three wavelengths, thereby creating phase delayed light comprising the at least three wavelengths;
illuminating the target with the phase delayed light;
demodulating by a second loss modulator operated at the modulation frequency, backscattered phase delayed light from the target;
obtaining with an array detector, unmodulated images of intensity distributions for each of the at least three wavelengths comprising the backscattered phase delayed light from the target, wherein the modulation frequency is substantially equal to zero;
obtaining with an array detector, modulated images of the intensity distributions for each of the at least three wavelengths comprising the backscattered phase delayed light from the target, wherein the modulation frequency is not equal to zero;
determining range information to the target based upon comparison of the unmodulated and the modulated images of the intensity distributions of the at least three wavelengths comprising the backscattered phase delayed light from the target; and,
generating the three dimensional (3D) image of the target based upon the determined range information.
2. The method of claim 1 further comprising the step of displaying the three dimensional (3D) image of the target on a display.
3. The method of claim 1 wherein the step of illuminating the target comprises illuminating the target for an exposure time ranging from approximately one microsecond up to approximately one hundred microseconds.
4. The method of claim 1 wherein the first loss modulator and the second loss modulator are embodied in one electrooptic crystal assembly.
5. The method of claim 1 wherein the at least three wavelengths comprise wavelengths of light within the visible spectrum.
6. The method of claim 5 wherein the at least three wavelengths comprise wavelengths of approximately 450 nm, approximately 560 nm and approximately 675 nm.
7. The method of claim 6 further comprising the steps of;
generating a color image of the target; and,
superimposing range information on the color image of the target.
8. The method of claim 1 wherein the step of modulating by a first loss modulator comprises an intensity loss modulation amplitude range of from approximately thirty percent up to approximately fifty percent.
9. The method of claim 1 wherein the modulation frequency has a value within the range of from approximately one megahertz up to approximately ten gigahertz.
10. The method of claim 1 wherein the step of imparting a phase delay onto each of the at least three wavelengths comprises providing a phase delay line for each of the at least three wavelengths.
11. A method to provide a three dimensional (3D) image of a target by scannerless loss modulated flash color range imaging, the method comprising:
providing a broad band light source and spectral filters, the broad band light source and spectral filters adapted to provide illumination comprising at least three wavelengths;
modulating by a first loss modulator comprising an electrooptic crystal operated at a modulation frequency, each of the at least three wavelengths;
imparting a phase delay onto each of the at least three wavelengths, thereby creating phase delayed light comprising the at least three wavelengths;
illuminating the target with the phase delayed light;
demodulating by a second loss modulator comprising an electrooptic crystal operated at the modulation frequency, backscattered phase delayed light from the target;
obtaining with an array detector, unmodulated images of intensity distributions for each of the at least three wavelengths comprising the backscattered phase delayed light from the target, wherein the modulation frequency is substantially equal to zero;
obtaining with an array detector, modulated images of the intensity distributions for each of the at least three wavelengths comprising the backscattered phase delayed light from the target, wherein the modulation frequency is not equal to zero;
determining range information to the target based upon comparison of the unmodulated and the modulated images of the intensity distributions of the at least three wavelengths comprising the backscattered phase delayed light from the target; and,
generating the three dimensional (3D) image of the target based upon the determined range information.
12. The method of claim 11 further comprising the step of displaying the three dimensional (3D) image of the target on a display.
13. The method of claim 11 wherein the step of illuminating the target comprises illuminating the target for an exposure time ranging from approximately one microsecond up to approximately one hundred microseconds.
14. The method of claim 11 wherein the first loss modulator and the second loss modulator are embodied in one electrooptic crystal assembly.
15. The method of claim 11 wherein the at least three wavelengths comprise wavelengths of light within the visible spectrum.
16. The method of claim 15 wherein the at least three wavelengths comprise wavelengths of approximately 450 nm, approximately 560 nm and approximately 675 nm.
17. The method of claim 16 further comprising the steps of;
generating a color image of the target; and,
superimposing range information on the color image of the target.
18. The method of claim 11 wherein the step of modulating by a first loss modulator comprises an intensity loss modulation amplitude range of from approximately thirty percent up to approximately fifty percent.
19. The method of claim 11 wherein the modulation frequency has a value within the range of from approximately one megahertz up to approximately ten gigahertz.
20. The method of claim 11 wherein the step of imparting a phase delay onto each of the at least three wavelengths comprises providing a phase delay line for each of the at least three wavelengths.