Method and apparatus for ultrafast time-resolved digital holography
A method for ultrafast time-resolved digital holography comprises (a) providing tunable timescale at least two tick-tock pulses arriving on a sample to be measured at various timescales, (b) spatial encoding for wavefronts of the sample by utilizing at least one optical encoder, (c) utilizing a digital holographic access unit to record a composite hologram of the spatial encoded wavefronts by the same single pulse source, (d) utilizing an encoder for obtaining at least two holograms, and (e) utilizing a compressive sensing approach or a non-linear image restoration approach and a wavefront reconstruction approach to obtain the reconstructed wavefronts information of the sample.
1. A method for time-resolved digital holography, comprising:
transmitting a first beam pulse through a sample at a first time point and a second beam pulse through said sample at a second time point, wherein an elapsed time is a period between said first time point and said second time point and said first beam pulse is created by said elapsed time previous to said second beam pulse;
separately spatially encoding for a first wavefront of said first beam pulse and a second wavefront of said second beam pulse by an optical encoder to create a first encoded spatial wavefront and a second encoded spatial wavefront;
recording a one-shot composite digital hologram of said first encoded spatial wavefront and said second encoded spatial wavefront by a digital holographic access unit in a single holographic exposing process;
decoding said composite digital hologram to obtain at least two different digital holograms by at least one decoder;
utilizing an image processing approach for processing said at least two different digital holograms to recover hologram data of said sample; and
utilizing a wavefront reconstructing approach to reconstruct said hologram data to obtain a reconstructed wavefront of said sample.
2. The method of claim 1 , wherein said optical encoder includes a spatial light modulator.
3. The method of claim 1 , wherein said optical encoder includes a micro display.
4. The method of claim 1 , wherein said digital holographic access unit includes a photodetector array.
5. The method of claim 1 , wherein said digital holographic access unit includes an image sensor.
6. The method of claim 1 , wherein said wavefront reconstructing approach includes Fourier transform approach.
7. The method of claim 1 , wherein said wavefront reconstructing approach includes convolution approach.
8. The method of claim 1 , wherein said wavefront reconstructing approach includes angular spectrum approach.
9. The method of claim 1 , wherein said wavefront reconstructing approach includes Fresnel diffraction approximation approach.
10. The method of claim 1 , wherein said image processing approach includes a compressive sensing approach.
11. The method of claim 1 , wherein said image processing approach includes a non-linear image recovery approach.
12. An apparatus for time-resolved digital holography, comprising:
a pulsed laser for creating two beam pulses with a first beam pulse and a second beam pulse which arrive on a sample at different time points;
an optical encoder for separately spatially encoding a first wavefront of said first beam pulse and a second wavefront of said second beam pulse;
a digital holographic access unit for recording a one-shot composite digital hologram of said first encoded spatial wavefront and said second encoded spatial wavefront; and
a wavefront reconstruction unit to reconstruct said first encoded spatial wavefront and said second encoded spatial wavefront.
13. The apparatus of claim 12 , wherein said optical encoder includes a spatial light modulator.
14. The apparatus of claim 12 , wherein said optical encoder includes a micro display.
15. The apparatus of claim 12 , wherein said digital holographic access unit includes a photodetector array.
16. The apparatus of claim 12 , wherein said digital holographic access unit includes an image sensor.
17. The apparatus of claim 12 , wherein said wavefront reconstruction unit includes at least one computer, used for decoding, separating wavefront of said at least two beam pulses.
18. The apparatus of claim 12 , further comprising a beam splitting element configured in front of said pulsed laser.
19. The apparatus of claim 12 , wherein said pulsed laser includes a Ti-sapphire laser.
20. The apparatus of claim 12 , further comprising at least one fiber grating to split said at least two beam pulses.