Tao Shi-quan

Automatic Compensation of Total Phase Aberrations in Digital Holographic Biological Imaging

Digital holographic microscopy has been a powerful metrological technique for phase-contrast imaging. However inherent phase aberrations always exist and degrade the quality of the phase-contrast images. A surface fitting method based on an improved mathematic model is proposed, which can be used to remove the phase aberrations without any pre-knowledge of the setup or manual operation. The improved mathematic model includes not only the usual terms but also the cross terms and the high order terms to describe the phase aberrations with high accuracy. Meanwhile, a non-iterative algorithm is used to solve the parametersand thus less computational load is imposed. The proposed method is applied to the live imaging of cells. The experimental results verify its validity.

Multi-track Storage of 10000 Holograms in a Disk-Type Photorefractive Crystal

Three-dimensional disk-type holographic storage using spatioangular multiplexing with a spherical reference beam is analyzed and experimentally demonstrated. The overlapping factors between adjacent holograms in a track and between adjacent tracks in a disk are determined based on the selective angles calculated by coupled-wave theory. There are 10000 holograms stored along 5 tracks in a sector of a single iron-doped lithium niobate crystal.

Scattering Noise Properties of Holographic Photopolymers by Means of Real-Time Transmittance Analysis

We propose a simplified model to analyse the temporary behaviour of transmittance for holographic photopolymers, based on the existing first-harmonic diffusion theory, with assumptions of constant polymerization coefficient and negligible diffusion effect for noise gratings. By applying this model to measure real-time transmittance of our novel blue-sensitized photopolymer, the bleaching time constant of dye and polymerization rate are extracted, and the effect of the material composite on the noise property is revealed. This provides a prompt method to assess the performances of holographic photopolymers.

Holographic and Thermal-Fixing Characteristics of Doubly Doped Zn:Fe:LiNbO3 Crystals

We perform a comprehensive experimental study on holographic and thermal-fixing characteristics of Zn:Fe:LiNbO3. The measured hologram decay time constants, respectively caused by optical readout and under dark condition, with thermal fixing are 15 times and 75 times longer than that obtained without thermal fixing. This suggests that Zn:Fe:LiNbO3 crystals are suitable for thermal fixing. Multiplexed recordings of 300 holograms using different thermal fixing schemes verify that a proper multiplexing scheme such as track-division thermal-fixing scheme for disc-type holographic storage can effectively compensate for the negative effect of zinc-doping on the dynamic range, thus the storage density is enhanced.

The resolution characteristics of volume holographic lens

We introduce two kinds of typical volume holographic gratings into the imaging system respectively, and discuss their resolution characteristics in lateral and longitudinal defocus condition to improve the image quality.

Optical Erasure Characteristics of Holograms in Batch Thermal-Fixing

The optical erasure dynamics in a batch-thermal fixing scheme of holographic storage in photorefractive crystals is investigated theoretically and experimentally. The inter-batch optical erasure time constant τF is introduced to specify the optical erasure to compensated gratings, and measured in a sophisticated experiment. The experimental result shows that τF is much longer than the intra-batch optical erasure time constant τE. The difference between τF and τE is fundamental for enhancing nonvolatile storage density.