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A brief introduction to continuous tone, dye sublimation transfer printing using a thermal head is given. Two problems that can arise in such a method of printing are discussed: density non-uniformities down the page due to the accumulation of heat in the thermal head, and density non-uniformities across the page due to variations in electrical, thermal or mechanical properties across the line of heating elements. Measurements and analyses of these effects are presented. Correction methods are proposed and implemented, and results are shown for each of these problems.

As electronic imaging becomes a mature technology, the requirements of hard copy output systems become more demanding. Currently, color hard copy output is required with a 3- or 4-bit tone scale. However, many present and future applications will require a 6- to 9-bit tone scale. Current electronic imaging systems requiring this extended color tone scale include "high-end" computer graphics, remote sensing and medical imaging. Bimodal hardcopy output systems that use dithering to achieve a tone scale will not be able to meet the requirements of these new electronic imaging systems. In order to minimize the complexity and cost of a new hardcopy output system it is desirable to have an electronic interface rather than an optical interface (as in a photographic film recorder). Thermal dye transfer hard copy (TDT HC) meets the demanding requirements necessary for affordable, high quality "continuous tone" electronic imaging output.

A discussion of the various devices used to achieve grey scales, including an overview of current technology, and applications and projected trends. The various means of exposing media, the advantages and disadvantages of dry silver processing and continuing challenges in the industry are explored.

A laser color printer has been developed to depict continuous tone color images on a photographic color film or color paper with high resolution and fidelity. We have used three lasers, He-Cd (441.6 nm), Ar4 + (514.5 nm), and He-Ne (632.8 nm) for blue, green, and red exposures. We have employed a drum scanner for two dimensional scanning. The maximum resolution of our system is 40 c/mm (80 lines/mm) and the accuracy of density reproduction is within 1.0 when measured in color difference, where most observers can not distinguish the difference. The scanning artifacts and noise are diminished to a visually negligible level. The image quality of output images compares well to that of actual color photographs, and is suitable for photographic image simulations.

Mead Imaging is commercializing Cycolor ® , a revolutionary photoimaging system which will have broad applications in color copying and reproduction, referred to as cylithography. Cycolor possesses the following characteristics: • panchromatic sensitivity • dry processing • high resolution • continuous tone • high color quality • low cost. The Cycolor system is a result of work carried out at Mead Corporation over the past several years on the microencapsulated process.

New opportunities are emerging in the graphic-arts pre-press market stimulated by the need for digitally created images. To meet this need, we have designed a cost-effective three-color digital printer using PLZT light valves. Transparent lead lanthanum zirconate titanate (PLZT) ceramic crystals when used as a linear modulator offer a number of significant benefits. The primary advantage is that the light valve is an efficient modulator of incoherent light providing a broad spectral output ranging from 400nm to well into the infrared region. In addition, light valves offer the advantages of being small, low cost, have a wide dynamic range (>1000 to 1), and can be used with simple optical designs. The characteristics of the PLZT material plays an important role in the performance of the light valve. A number of variables such as ceramic composition, electrode spacing, and ceramic thickness can be altered to affect its quadratic electrooptic behavior. Additionally, the modulator design requires a closed-loop servo to eliminate the errors caused by the device's remanent polarization and nonlinear behavior.