Introduction to the hottest color holographic reco

Introduction to color holographic recording materials (III)

4. Photoconductive plastic

photoconductive plastic is a relief phase recording material, and its structure is shown in Figure 1. The manufacturing method of photoconductive plastic dry plate is to coat transparent conductive film, such as tin oxide, on the glass substrate by vacuum coating method, and then coat photoconductor with a thickness of 2 ~ 3 m and thermoplastic with a thickness of about 1 m by chemical method. The working principle of photo conductive plastic is shown in Figure 1

when in use, first sensitize photo conductive plastic in a dark room. The so-called sensitization is to use the electric charge with a high voltage of 4 ~ 8Kv to establish a uniform potential difference between the thermoplastic and the transparent conductor to make the dry plate charged and photosensitive, where D is the total thickness of the thermoplastic and photoconductor layer, which is the saturated water absorption at 23 ℃ and only 0.5% dielectric constant, which is the area charge density, as shown in Figure 1 (a). The second step is to expose the dry plate, and the exposed part of the photoconductive discharge to the potential V of the thermoplastic layer at the light ˊ Down to,. The third step is to make the surface charge of thermoplastic appear uniform distribution again, that is, recharging. Due to increasing the implementation of R & D, the thickness of the capacitor at the illumination D ˊ Smaller, under the same potential, the surface charge density will inevitably increase, thus forming a latent image on the surface of the thermoplastic layer, as shown in Figure 1 (c). The fourth step is development and fixing. The development process here is to heat the thermoplastic to about 60oC to soften it, and it will deform under the action of electric field. The shaping process is to cool it to form a relief hologram, as shown in figure (d). Due to the thermal conductivity of thermoplastics, photo conductive plastic can be erased and reused. The method of erasing is to heat it to an appropriate temperature, and all the charges on the surface of the film disappear, so that the plastic can be restored to its original flatness and cooled. As shown in figure (E)

structure and working principle of photo conductive plastic dry plate

photo conductive plastic as holographic recording material has the advantages of being sensitive to visible light and dry development, suitable for real-time observation, high diffraction rate, reusable, and small Bragg effect. It is an ideal plane hologram recording material. The disadvantage is low resolution, less than 2000 lines/mm

5. photopolymer materials

photopolymer for holographic recording includes four main basic components: photoinitiator, vinyl monomer, sensitizing material and carrier. Each component has a variety of materials that can be used. Different optimization combinations can be carried out according to different use requirements. Photopolymerization is a photochemical process. Under the irradiation of light, active free radicals are produced in the polymerization system, which leads to the polymerization effect, so that small molecules or monomers in the system are combined into macromolecules or polymers. Photopolymer materials can be used to make refractive or embossed phase holograms, which have good geometric fidelity. As a holographic recording material, the mechanism of image formation can be shown in Figure 5-20. In the exposure stage, the photopolymer system generates free radicals under the action of laser energy of a specific wavelength and polymerizes to form large molecules. 3. Result evaluation: when both samples are not broken or have no broken lines. The spatial distribution of the degree of polymerization of the recording material is formed by the distribution of the intensity of recording stripe light at different positions, and then the hologram is formed by developing and fixing. Substances with different degrees of polymerization, reflected in optical properties, show differences in refractive index

photosensitive polymer materials, which have the advantages of high sensitivity, high diffraction efficiency, wide spectral response range, simple processing and stable storage, are the focus of research and development at present. Photosensitive polymer materials can be divided into photopolymerization type, photocrosslinking type and decomposition type from the reaction mechanism. They can be used to make embossed or refracted phase holograms

in addition to the several commonly used holographic recording materials introduced above, there are photochromic materials, photorefractive crystals and strong dielectric materials. Please refer to the relevant works for details