Study On Compressive Digital In-line Holography

Compared to the off-axis holography, the in-line holography has higher bandwidth utilization of digital recording device(CCD, CMOS, etc.). The in-line holographic setup takes up less space than the off-axis holographic equipment, so the in-line holography has more advantages than the off- axis holography. If we directly reconstruct the in-line hologram, image reconstructed mix real image, zeroth level image and twin image together, and it makes the image uneasy to identify. So getting rid of the zeroth level image and twin image from the in-line hologram is the key for the in-line holography further development and getting into practical applications. Compressed sensing reconstruction of digital in-line holography can remove zeroth level image and twin image from the in-line hologram, so this article researches technologies around the compressive holography, and puts forward various research results. The main contents are as follows:(1) Based on the analysis of block compressive sensing algorithms, this article proposes an adaptive sampling block compressed sensing algorithm based on DCT because the large coefficients have clear extension directions in DCT domain. The algorithm simplifies the computational procedure between two samples, and makes the time gap between two samples down to about 0.08 s. According to the simulation data, the adaptive sampling block compressed sensing algorithm proposed has better reconstruction quality than traditional block compressed sensing algorithm.(2) On the analysis of two-step phase-shift algorithms, this article proposes a new reference beam searching algorithm in order to reduce the amount of calculation of the two-step phase-shift algorithm. In this paper, the computer simulation and in-line holographic experiment validate the algorithm proposed can find out the reference light intensity quickly. At the same time, because Zhang’s algorithm is only validated by the computer simulation, this article verifies it in experiment.(3) Compressive holography is a technology removing zeroth level image and twin image in one step. In this paper, we apply this technology into fiber holographic imaging, and it makes the real-time imaging possible for fiber holographic imaging.The researches above develop the theory of compressive sensing and in-line holographic technology, and provide the convenience for further study.