Image amplification

The process of image forming in GDC can be divided into several stages formation of a latent electron-ion image, amplification of a latent image in a pulse gas discharge and production of a visible half-tone image. 

In the following, a number of examples are presented with emphasis on how such amplified imaging device can be built in self-supporting polymer materials. The present photochromic compounds (azobenzene and spiropyran derivatives) are rather common and have been used many times in molecular assemblies without touching upon the concept of image amplification. The most recent references are given(4. - 6). 

The examples we have demonstrated so far are schematically shown in Figure 1. Although the photochemical events and the subsequent physical changes are different from system to system, a general trend is the there is a non-linear response to the degree of photochemical reaction, that is, the image amplification has been demonstrated. 

Image Amplification by Means of Photochemically Triggered Phase Transition in Liquid Crystal... 

Perhaps the most important trend at this time in ultra high-speed photography is in the increased use of image amplification (Ref 25). Image converter cameras were developed in recent years not only in the United States but also in EngTand, France, Germany, Holland the USSR (Ref 5)... 

PHYSICAL DEVELOPMENT AND OTHER IMAGE AMPLIFICATION SYSTEMS 113... 

Latent images or faint images in silver metal or other materials can be amplified by redox chemistries other than metal deposition. Several dye-forming redox chemistries have been discovered in which metal complexes serve as catalysts, catalyst precursors or one of the redox partners. The applications of coordination compounds in physical development and image amplification systems are therefore quite broad and diverse. 

In these processes, metal complexes find a number of uses as light-sensitive latent-image-catalyst formers, catalyst replacements for image silver in low-silver systems, and oxidants for various developers in image amplification baths. 

Other applications that were recently demonstrated with photorefractive polymers include homodyne detection of ultrasonic surface displacements using two-wave mixing [115]. With the development of new photorefractive polymers with response times in the millisecond range, numerous optical processing techniques can be performed at video rates. Image amplification and novelty filtering at video rates were demonstrated recently [116]. All-optical processing techniques compete with computational methods. Therefore, it is important that photorefractive polymers exhibit faster response times in the future. 

It has been Icnown for years that a decrease in the phase transition temperature of azobenzene containing LC is induced by trans -cis photoisomerization (23). Smectic LC of 4-alkyl-4 -cyano-biphenyl is subjected to phase transition by photoisomerization of azobenzene leading to a reversible change in the threshold voltage for electrohydrodynamic instability (24). None of them described the concept of image amplification. 

In view of sensitivity, the liquid crystal system is more improved than the previously mentioned systems. However, these liquid crystalline materials are viscous fluids and thus the long term image stability is not expected. To overcome this shortcoming, image amplification in a solid system has to be designed. 

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