Anthony M. Tai

Incoherent image addition and subtraction: a technique

A technique of incoherent image addition and subtraction is described. The basic advantage of this technique is its use of white light processing, in which case the unavoidable artifact noise in the coherent optical processor may be removed. Although the incoherent processing technique that we have proposed is effective only in a 1-D operation, it also works for 2-D image addition and subtraction.

Spatial filtered pseudocolor holographic imaging

A technique of spatial filtered pseudocolor holographic imaging is described. The encoding process takes place at the spatial frequency plane together with the one-step rainbow holographic process. The pseudocolor hologram imaging is obtained by the white light reconstruction of the multiplexed rainbow hologram. This technique provides a simple encoding procedure and offers a wide range of pseudocolor holographic images. The potential applications of this pseudocolor holographic imaging can range from aerial photography for remote sensing to X-ray transparencies for medical diagnosis. Experimental setup of this pseudocolor encoding process is illustrated. Some experimental demonstrations of the pseudocolor encoding hologram images are also provided.

White-light pseudocolor density encoder

A simple technique utilizing a white-light processing system for the pseudocolor encoding of photographic materials by density is presented. Pseudocolored output of many different color codes is obtained by selectively spatial filtering the dispersed colors of the various high-diffraction orders of a halftone input. Besides permitting a large variety of color codes, this white-light technique would also eliminate all coherent artifact noises that plague coherent systems. Experimental results are presented, and comparison with the coherent technique is provided.

Optical logarithmic filtering using inherent film nonlinearity

Linear optical spatial filtering cannot be effectively applied to multiplied and convolved signals. One approach is to first perform a logarithmic transformation to produce a signal in additive form suitable for linear filtering processes [A. V. Oppenheim et al., Proc. IEEE 56, 1264 (1968)]. It was first suggested that a halftone screen be used to perform such a transformation [H. Kato and J. W. Goodman, Appl. Opt. 14, 1813 (1975)]. However, the maximum spatial resolution of this halftone screen technique is limited by the resolution of the screen. In this paper, we shall propose a different technique using the inherent film nonlinearity for the logarithmic transformation. Such a technique would enable the transformation of signals of very high spatial resolution, limited only by the resolution limit of the photographic film. This technique is applied to the spatial filtering and detection of signals in multiplicative noise. Experimental comparisons between linear and logarithmic filtering are presented.

Archival storage of color films by rainbow holographic technique

Abstract A technique of generating color holographic images with a one-step rainbow holographic process is described. This technique offers the capability of archival storage of color materials on a single black and white photographic film. The process is very simple to implement and it allows the reconstruction of the color image with a white light source. Although some degree of color blur is inherent with the rainbow holographic process, it can be minimized by the proper design of the optical system. A simple experimental result is also presented.

Holographic speckle reduction by complementary spatial sampling

A technique using complementary sampling in the reconstruction process is proposed for speckle reduction in holographic imaging. This method would not suffer the resolution reduction experienced with the simple random sampling method that has been proposed [F. T. S. Yu and E. Wang, Appl. Opt. 12, 1656 (1973)]. Experimental results and a theoretical explanation are presented.

Wide-band spectrum analysis with area modulation.

Nonlinearity of the film characteristics is a major problem in optical spectrum analysis with density modulation. The problem of nonlinearity can be avoided by using area modulation due to its binary recording format. The feasibility of using area modulation for wide-band signal analysis [C. E. Thomas, Appl. Opt. 5, 1782 (1966)] is demonstrated. The results obtained with area modulation is shown to be similar to that of density modulation. However, area modulation requires a larger system space. Therefore, the available space-bandwidth product for a given system size is smaller with area modulation than with density modulation.

Ultrasonic Blood Flow Spectral Analysis Using Coherent Optics

It has been shown that ultrasonic Doppler signals can be obtained easily and transcutaneously from many blood vessels in both normal and atherosclerotic subjects. The Doppler spectrum changes with time, giving rise toa distnbution of frequencies whose envelope has a waveform that is characteristic of the vessel site and closely folows the events of the cardiac cycle. This makes it very useful in diagnosing lesions of the arterial system. The paper presents a coherent optical technique for displaying and analyzing a blood-flow-generated ultrasonic Doppler spectrum. The system is highly cost-effective and produces spectrograms on-line. Other advantages include a large, continuously variable bandwidth, an instantaneous display of velocity profile, and simultaneous display of temporal spectra. The system makes use of the Fourier transformation property of converging lens and its use of processing time signals. The spectrum obtained from the brachial artery of a normal subject compares favorably with the spectrograms obtained using electronic spectrum analyzers.

Classification of the T-E Curve

The H-D curve is the most commonly used method to describe film characteristics. However, in many applications of coherent optics, the use of the H-D curve is not appropriate because the linear region of the T-E curve is used instead. In this paper, some possible classification methods for the T-E curve and their applications in spectrum analysis and holography are discussed.

One-Step Rainbow Holographic Interferometry

A one-step rainbow holographic process by using an imaging lens is presented. Results of both the pseudoscopic and orthoscopic rainbow holographic imagings are discussed. One of the most interesting and important applications of the one-step rainbow process is the holographic interferometry. Demonstrations of double exposure, time averaging, and contour generation by this one-step holographic interferometric process are provided. Extension of the one-step process to multiwavelength and multislit holographic interferometry is also included. As compared with the conventional holographic interferometry, the one-step rainbow holograph-ic process is a very simple and versatile technique, which yields the advantages of white light readout. The one-step process offers a brighter image, a lesser speckle noise, and a better fringe visibility. For multi-wavelength and multislit rainbow holographic interferometry, the techniques enable different physical holographic fringe patterns to be displayed in different colors. For multiwavelength technique, they are fringe patterns due to different physical effects, and for multislit technique, they are fringe patterns from different perspectives.