The combined use of the photoelectric and electron-optic properties of BSO crystal leads to realize spatia light modulation. Under some condition BSO crystal can become birefringent depending on a local illuminance. The relationship between the distributions of illuminance and birefringence will be discussed. This spatial light modulator can work in real-time, which converts illuminance into transparence. The experiment shows, in order to increase the sensitivity of BSO crystal, an electric field 6 kv/cm at an atmosphere pressure 15 X 105 Pa should be applied to BSO crystal. With BSO crystal we have measured 3D deformation by means of real-time holography.
In this paper, the holographic recording materials is thought as a scattering object, while a laser beam illuminates to the materials, the scattering light must be emerged. For the reconstructing hologram, the scattering light is thought as the scattering noise, it comes from the scattering particles. By using a narrow laser beam illuminates to the recording plate and measures the scattering and diffraction light intensity and the size of diffraction ring, the scattering noise and the size of the particle of the recording materials can be measured respectively. As the size of the particle of the recording materials determines the resolving power of holographic plate, the resolving power determines the quality of hologram, so the measurement of the size of the particle of the recording materials is very important. This paper also presents some new methods to measure the quality of holographic plate, model plate, model plate and PET materials by using the diffraction pattern of a narrow laser beam. The experimental results shows these new methods with wide measuring range, high precision and short measuring time are very practical.
A scheme of holographic Bragg grating for achieving optical butterfly interconnection is presented in this paper. Its essential structure units are Bragg grating-slitting board of volume phase holography (splitting ratio 1:1). Photopolymer with red light is used as holographic recording medium of making gratings. The effect of the scheme has been demonstrated.
The optical technique to shoot the hologram of the flame temperature field was introduced and the factors which influence the quality of hologram were discussed. Therefore, it develops a new way to extend the research work of the flame temperature to the industrial practice.
A novel method to make lippmann color holograms recorded in DCG is introduced in this paper. The method is developed basing on the fact that the reconstruction wavelength of a DCG hologram tends to shift to longer than the recording wavelength due to the swelling of the emulsion layer. The influence of the processing procedure on the reflection bandwidth of the hologram is discussed. In this paper, successful experimental results are also presented.
The FRTH is presented in this paper and its properties are discussed. Then we make a pseudo chromatic encoding fractional Fourier transform rainbow hologram, based on its specialty in its reconstruction and that the encoding color has relationship with the order of the reconstruction FRT system, a new type of anti-counterfeiting hologram is introduced.
Non-scan holographic spectroscopy is a novel type of Fourier transform spectroscopy (FTS) which frequency modulation is implemented spatially. By the analysis of the general model of the interference of two pre-dispersing beams, it is found first time to our knowledge that the spectral resolving power of the non-scan FTS is determined by the spectral resolving power of these two coherent beams and the fringe number recorded and used for reconstruction of spectrum. As a special case, the spatial heterodyne technique with diffraction gratings used as the pre-dispersers of the coherent beams is stressed and investigated. It is shown that the symmetrical aliasing between the two side spectral regions of the harmonic spectral component can be eliminated with a 2D Fourier transform. The optical experimental results that are agreement with theoretical analyses are given.
A linear tricolor sampling leaf-shape grating is generated by computer. If a 2D color image is encoded by this grating, the trichromatic spectra of spatial frequency of the original color image will be separated from each other in space. A transmission true-color rainbow hologram with a white-light source for reconstruction will be recorded by monochromatic laser. This true-color holographic recording method is convenient and practicable for the plate-making of embossed hologram, and will be of high artistic and commercial value, the linear tricolor sampling leaf-shape grating has been invented by us recently. Up till now, the grating applied true-color holographic recording method is new.
Cleaving-etch method was presented for improving relief modulation resolution in gelatin. The principle of the method was introduced. Using the cleaving-etch method, a sine relief grating was obtained with 200 lines/mm spatial frequency and 0.4 micrometers relief depth. Comparison between enzyme-etching-imaging method and the cleaving-etch method was given and the reason why resolution of the latter much higher than the former was presented.
The problem connected with the color desaturation of reflection holograms on Russian PFG-03C panchromatic plate, has gained much attention. In this paper, we explore a new processing procedures to reduce emulsion shrinkage and wavelength shift and improve the color rendition and image quality.
In this paper, the kinetics of photosensitive initiating polymerization and photopolymer holographic recording materials were studied. Four sensitizers that could be sensitive to He-Ne (632.8 nm) laser were synthesized and chosen for this study: (1) NK-529, (2) NK-3960, (3) (MCD), (4) ECD. The long-wavelength sensitive photoinitiating system are composed of one of the four compounds above, 2- chlorohexaarrylbiimidazole(o-cl-HABI) and 3-mercapto-4- methyl-4H-1,2,4-triazole (MTA), which acted as sensitizer, initiator and hydrogen-donor respectively. The kinetic study was carried out by using dilatometer, we found the relationships between the rate of polymerization and the concentration of each component. We believe that the photopolymerization was initiated by free radicals which were produced by the electron transfer between the sensitizer and the initiator in the excited state. Comparing the monomer conversion of these four systems, we found: MCD >ECD >NK529 >NK3960. We chose the system (MCD- HABI-MTA) as a photoinitiating system of photopolymer holographic materials. The holographic material was composed of the above photoinitiating system, a binder, a mono- or multi-functional monomer, and other additives. Adding the third beam to expose the photopolymer plate simultaneously during the initial holographic exposure can increase the effective exposure sensitivity of the photopolymer plate. Mechanisms of photoinitiating polymerization and hologram formation are discussed. More than 80% of reflection grating diffraction efficiency can be obtained. The holographic gratings have a good physical and chemical stability under ambient conditions.
A newly developed plane optical element-holographic disc as an omnidirectional scanner for bar code auto-recognition, with which the incident laser beam could be realized beam deflection and focus is described. The original design parameters are also given. The experiment shows that within the length of 500 mm, the height of the arc of scanning line will not exceed 12 mm, and the focused spot size is 0.2 mm averagely in this paper.
A new method for the preparation of stratified light- sensitive film is developed and the stratified gratings are recorded in the film. The real-time splitting behavior concerning angular sensitivity and diffraction properties as a function of the normalized buffer-layer thickness in this stratified holographic optical gratings have been analyzed. It is found that by optimizing the combination of modulation of grating, spatial frequency and the total thickness of grating, the changeable number of output beams can be obtained.
The holographic optical elements (HOE) in dichromated gelatin (DCG) for airborne head-up displays are studied. The main characteristics of the HOEs are described. Some fabrication techniques of the HOEs in DCG are discussed. The large-size (max (Phi) 280) flat and spherical substrates HOEs used in our holographic head-up display prototype have been fabricated. The measured results of the HOE are as follows: approximately 95% peak diffractive efficiency, approximately 20 half spectral width and approximately 544 nm peak response wavelength.
It is an advanced Head-up Display (HUD) design approach to use Computer-Generated Hologram (CGH) construction technique to fabricate a flare-free HUD. The approach is described as determining the combiner performance at first and then designing the optical system, which finally leads to a set of wavefront polynomials to define the CGH. An interference- type binary CGH (space-bandwidth product 1.8 X 105, dimensions 5 mm X 5 mm) was designed and fabricated. Experimental results verify that CGH can be used to generate aspherical wavefront.
A method of preparing ultra-fine-grain silver halide emulsions is briefly described. It uses a computer controlled double-jet emulsifier to produce ultra-fine-grain emulsions. The average grain size is around 20 nm, which is measured by an automatic x-ray diffractometer and from TEM photographs. The emulsions have been used for recording reflection holograms, which are processed with an optimized solution physical developer. Reflection holograms of very low noise and diffraction efficiencies of over 40 percent are obtained in these emulsions without any pretreatment.
Generation and reconstruction of dot matrix hologram are theoretically described. Diffraction efficiency, reconstruction color and visual effect of the dot matrix hologram are discussed by diffraction grating principle. According to the theoretical results, a simplified experimental system is set up to generate multicolor dot matrix hologram. Two unique techniques, spot-shaping and pixel-shifting, are adopted for improving sparkling and kinetic visual effects of dot matrix hologram in our experiments.
In this paper, a new method for inversion, shearing and rotation of the reconstructed images in Fourier computer- generated hologram is proposed. This method is simple just by means of conventional coordinate transformation of the frequency spectrum. The principles of this coordinate transformation are illustrated in this paper. Good agreement between the experimental results and the theoretical solution is demonstrated.
Implementation of fractional Fourier transformation using holographic lens is presented in this paper and the conditions to use holographic lens as a transform element are discussed. The FRT and anamorphic FRT are realized and it is very convenient for holographic lens to solve the problem of focal length changes which is demanded in FRT and this approach has a practical value.
In this paper, a new kind of random phase shifter is proposed which is made of photopolymer plate by recording speckle patterns in it. The spectrum distribution of this phase shifter in 2-dimensions is measured and compared with that of random phase shifter made of silver halide plate. The result shows that the spectral distribution of the former is more intense and uniform over a more round area than the latter. An image storage experiment demonstrates that a high-quality image can be retrieved if this speckle random phase shifter is used for Fourier transform hologram recording.
The fabrication of holographic reflection gratings can be done either directly or by first making a phase transmission relief grating and then metalizing its surface by an appropriate metal. In this paper, the fabrication of reflection gratings with different spatial frequencies, from 100 L/mm to 1200 L/mm registered dissimetrically are reported and the curves of diffraction efficiency versus the slope angle are illustrated and finally the results are interpreted.
Holography is uniquely suitable as an educational tool for the middle school curriculum. By performing the simplest enjoyable experiments, students are introduced to many basic concepts of physics and myriads of technological applications. The most difficult part of introducing such a program to school is convincing educators, teachers, and parents that holography is a worthy subject. The most effective way is to find opportunities to physically demonstrate to them how to make holograms safely at a low cost and to show them applications using real hologram.
An iterative algorithm for multiple incoming wavelengths considering divergent sources is proposed to design a computer-generated holographic diffuser (CGHD) with high light utilization efficiency and uniform color mixing. We modified the conventional G-S algorithm when its input wavefront is divergent and consists of more than one wavelength. This diffuser is designed according to the Fresnel diffraction theory and can uniformly spread the different input light as far field distribution. The amplitude transmittance of this CGHD is a constant, while the phase transmittance consists of multiple phase levels. An example of designed CGHD with two divergent wavefronts is illustrated and simulated. The proposed algorithm can be used to design diffractive device for applications such as wavefront multiplexing and demultiplexing.