Ting-Chung Poon

Three-dimensional microscopy by optical scanning holography

We first briefly review a new 3-D imaging technique called optical scanning holography (OSH). We then discuss the techniques 3-D holographic magnification in the context of optical scanning and digital reconstruction. Finally, we demonstrate the 3-D imaging capability of OSH by holographically recording two planar objects at different depths and reconstructing the hologram digitally.

Three-dimensional holographic fluorescence microscope

Most commonly used methods for three-dimensional (3D) fluorescence microscopy make use of sectioning techniques that require that the object be physically scanned in a series of two-dimensional (2D) sections along the z axis. The main drawback in these approaches is the need for these sequential 2D scans. An alternative approach to fluorescence imaging in three dimensions has been developed that is based on optical scanning holography. This novel approach requires only a 2D scan to record 3D information. Holograms of 15-microm fluorescent latex beads with longitinal separation of ~2 mm have been recorded and reconstructed. To our knowledge, this is the first time holograms of fluorescent specimens have been recorded by an optical holographic technique.

Scanning holography and two-dimensional image processing by acousto-optic two-pupil synthesis

An implementation of an acousto-optic heterodyning image processor was reported earlier [ Opt. Lett.4, 317 ( 1979)]. However, details of that report are limited only to the confirmation of the basic principle of operation. In this paper, we present and emphasize the mathematical structure of the processor. We also compare this processor with other kinds of scanning and nonscanning processors. The analysis is then extended to the defocused case, where the optical transfer function is derived. A potential application of this in scanning holography is discussed.

Two-step-only quadrature phase-shifting digital holography.

Conventional methods of quadrature phase-shifting holography require two holograms and either intensity distribution of the reference wave or that of the object wave to reconstruct an original object without the zero order and the twin-image noise in an on-axis holographic recording setup. We present a technique called two-step-only quadrature phase-shifting holography in which solely two quadrature-phase holograms are required. Neither reference-wave intensity nor an object-wave intensity measurement is needed in the technique.

Holographic video at 40 frames per second for 4-million object points.

We propose a fast method for generating digital Fresnel holograms based on an interpolated wavefront-recording plane (IWRP) approach. Our method can be divided into two stages. First, a small, virtual IWRP is derived in a computational-free manner. Second, the IWRP is expanded into a Fresnel hologram with a pair of fast Fourier transform processes, which are realized with the graphic processing unit (GPU). We demonstrate state-of-the-art experimental results, capable of generating a 2048 x 2048 Fresnel hologram of around 4 × 10(6) object points at a rate of over 40 frames per second.

Twin-image elimination experiments for three-dimensional images in optical scanning holography

Twin-image elimination in the context of optical scanning holography has recently been proposed. The proposed technique involves simultaneously acquiring sine and cosine Fresnel holograms. A complex hologram is then formed by complex addition of the holograms, and twin-image rejection is predicted by computer simulations. An experimental verification of the technique by optical acquisition of the two holograms and subsequent reconstruction of the complex hologram digitally is reported. Three-dimensional image reconstruction without twin-image noise is demonstrated.

Imaging properties of scanning holographic microscopy.

Scanning heterodyne holography is an alternative way of capturing three-dimensional information on a scattering or fluorescent object. We analyze the properties of the images obtained by this novel imaging process. We describe the possibility of varying the coherence of the system from a process linear in amplitude to a process linear in intensity by changing the detection mode. We illustrate numerically the properties of the three-dimensional point-spread function of the system and compare it with that of a conventional imaging system with equal numerical aperture. We describe how it is possible, by an appropriate choice of the reconstruction algorithm, to obtain an ideal transfer function equal to unity up to the cutoff frequency, even in the presence of aberrations. Some practical implementation issues are also discussed.

Three-dimensional microscopy and sectional image reconstruction using optical scanning holography

Fast acquisition and high axial resolution are two primary requirements for three-dimensional microscopy. However, they are sometimes conflicting: imaging modalities such as confocal imaging can deliver superior resolution at the expense of sequential acquisition at different axial planes, which is a time-consuming process. Optical scanning holography (OSH) promises to deliver a good trade-off between these two goals. With just a single scan, we can capture the entire three-dimensional volume in a digital hologram; the data can then be processed to obtain the individual sections. An accurate modeling of the imaging system is key to devising an appropriate image reconstruction algorithm, especially for real data where random noise and other imaging imperfections must be taken into account. In this paper we demonstrate sectional image reconstruction by applying an inverse imaging sectioning technique to experimental OSH data of biological specimens and visualizing the sections using the OSA Interactive Science Publishing software.

Complex Fresnel hologram display using a single SLM

We propose a novel optical method to display a complex Fresnel hologram using a single spatial light modulator (SLM). The method consists of a standard coherent image processing system with a sinusoidal grating at the Fourier plane. Two or three position-shifted amplitude holograms displayed at the input plane of the processing system can be coupled via the grating and will be precisely overlapped at the systems output plane. As a result, we can synthesize a complex hologram that is free of the twin image and the zero-order light using a single SLM. Because the twin image is not removed via filtering, the full bandwidth of the SLM can be utilized for displaying on-axis holograms. In addition, the degree of freedom of the synthesized complex hologram display can be extended by involving more than three amplitude holograms.

Optical Scanning Holography - A Review of Recent Progress

Optical scanning holography (OSH) is a distinct digital holographic technique in that real-time holographic recording a three-dimensional (3-D) object can be acquired by using two-dimensional active optical heterodyne scanning. Applications of the technique so far have included optical scanning cryptography, optical scanning microscopy, 3-D pattern recognition, 3-D holographic TV, and 3-D optical remote sensing. This paper reviews some of the recent progress in OSH. Some possible further works are also discussed.