The effects of MPE (maximum permissible exposure) on the characteristics of electro-holographic displays are analyzed. The main effect is the reduction in the spectral range to be presented by the displays. The range will be reduced more as the pixel and hologram sizes of the displays become smaller and larger, respectively. The spectral range for the hologram size 0.5m and pixel size 0.8 µm will be about 50 nm less than that of the visible. In addition to the spectral range, the reconstructed image size should not be smaller than the value defined by 0.1 times of the diffracted intensity of the image to meet the MPE requirement for eye.

The characteristics of diffraction efficiency and spectral bandwidth of dichromated gelatin reflection holograms formed by a modified processing method are presented.

Taedok Science Town, Taejon 305-6(XL Rep. of Korea Renesse and Bouts represented the phase variations of holograms formed by conventional bleaches in which the hologram is bleached after development and fixing as a function of original density.They showed that the phase variations are determined mainly by the volume of the molecules of silver halide formed in the bleach bath. They formulated the nuer of silver halide as function of the original density.1 a a t1l (d2Nb2-diNbi) = b (1) qcos 6 qcos UIn this equation Nb2 and Nbi ae the respective partial molecular concentration of the si iver halide in the units of surface of the exposed region and unexposed region. a is absorption constant , and q indicates how many molecules of silver compound are formed from one atom of silver. Ab then represents the difference in nuer of molecules silver halide per unit of surface. di and d2 are the respective eilsion thickness of the two regions. Thus the diffraction efficiency of the phase holograms can be estimated by measuring the original optical density, and the number of formed silver halide can be explained.However, this idea can't be applied to the rehalogenating bleaches.In this study, we re-developed and measured the optical density of rather low spatial frequency gratings in which the diffusion transfer does not take 2 By comparing the difference of optical density tDr of low spatial frequency grating with the diffraction efficiency of high frequency grating, relative amount of rehalogenated silver halide and the diffusion transfer for high spatial frequency grating can be estimated. We can formolate iDr ka LAJq cos U . ln this equation k indicates how many atom of silver are formed from one molecules of silver halide. Fig. 1 shows a curve for the diffraction efficiency as a function of the concentration of potassium bromide. The values shown in Fig. 1 represent the aaxiaa efficiency for each transmission grating with spatial frequency of 1O lines/ obtained at equal exposure of 1.6 JIm' . Fig. 2 shows the optical density of the two region of low frequency grating formed at different concentration of potassiia bromide. The dashed line shows the differences of the optical densities of the two regions. The re-exposure was 1.6 JIm' Fig. 1. Diffraction efficiency for different concentrations of potassium bromide.Fig. 2. Optical density of the redeveloped grating for different concentration of potassium bromide.These experiments show additional knowledge on the rehalogenation and the diffusion transfer in the rehalogenating bleach.

We are concerned with new simplified procedures for obtaining sufficient initial bias hardness of dichromated gelatin film by inserting the dehydration process before exposure.

No abstract