A method is described to evaluate plane-wave volume hologram fringe inclination and spacing, as well as the recording material average refraction index. This evaluation allows us to estimate changes in the hologram parameters due to recording material shrinkage. The method is based on measurements of the incident and diffracted beam Bragg angles for two different wavelengths. The conditions for minimizing measurement errors are obtained. The experimental data are in good agreement with the calculated data.
A new spectrophotometric method to measure the response of spectral characteristics of reflection holograms on photopolymer materials simultaneously with the process of recording the hologram is proposed and realized. The results of experiments, in particular on the influences of shrinkage of thickness of recording media on the shift of the spectral response of the reflection hologram are considered.
The transmission type holographic screen is a special kind of scatterer, which is used to concentrate the light from the projected image into small size spot (viewing zone). As a result, different images can be delivered to each observer's eyes and it is possible to display the stereoscopic images. The most serious problem related with the holographic screen is its high dispersion and aberrations which cause the viewing zone distortions and poor color reproduction in the displayed image, especially in the screen corners. Both of the above mentioned drawbacks become more prominent when the screen size becomes larger. To compensate the screen dispersion, a diffuser in the form of a long narrow stripe directed to the reference beam axis is used for an object. The length and position of the diffuser are calculated to make the reconstructed images of it for all wavelengths of the white light projector to be superposed in the viewing zone. To solve the aberrations problem, a big size screen was composed by mosaicking many sub-screens which were recorded individually in the specially optimized setup. For example, when the sub- screen is recorded for the edge part of the screen, the diffuser was tilted different direction to provide proper superposition of the reconstructed diffuser images. For each sub-screen, the diffuser is tilted such that it is in nearly the same plane with the reference beam axis. The sub-screens are recorded on the holographic photoplates PFG-01 (Russia) with an optical set-up optimized for each sub-screen by adjusting the diffuser position and its tilt angle. All necessary parameters are calculated by considering the light beam path for different wavelengths in the visible spectrum. The size of each sub-screen is 40 X 30 cm<SUP>2</SUP>. Eight sub- screens are mosaicked to obtain a composite holographic screen with size 80 X 120 cm<SUP>2</SUP>. The screens have been used to display the full color stereoscopic images from slide projectors. The distances between the projector and the composite screen, and the screen and a viewer are set to 4 m and 3.5 m, respectively.
Holographic screen is an optical element of special kind with the directed light scattering, so that each pixel of the projected image on the screen sends light only in one observers eye (viewing zone). It is possible to record the holographic screen of two types: the reflection type screen and the transmission type one. In this paper the problem of compensation of high spectral dispersion of the transmission type holographic screen is considered. To overcome this problem the diffuse scatterer in the form of narrow long stripe, stretched in the direction to the reference beam axis, has been used. In order to simplify the recording setup, the large size holographic screen has been recorded with the diverging reference beam, because it is possible in this case to use small size optics. Experimentally the transmission type holographic screens have been recorded on the photoplates `Ilford' and PFG-01 (Russia). The screens have been used to display the stereoscopic and multiview color images from the slide-projector. The screen size was 30 X 40 cm. There is possibility to increase the screen size, if it is represented as mosaic of subscreens, each of them being recorded so, to minimize its aberrations.
The optimum sub-hologram dimension of composite Fresnel and Fourier transform holograms was found as a function of information reduction ratio. The total image blur in the reconstructed image from the composite holograms was calculated and measured experimentally. The test object used to this experiment was a plane sheet with strips of 5 different sizes drawn on it. In this strip object, the total image blur will be given as the resolution loss in the strips. The experimentally measured value of the total image blur matches reasonably with the calculated one for the case of the sub-hologram with optimum size.