Waveguide Cavity Stack System And Its Application In Digital Holography Detected Image

In the application of laser material treating and processing, the high requirement is proposed for the uniformity of the laser beam distribution. In order to control the treatment region and laser energy precisely, usually, the square uniform laser distribution is required. Therefore, the study of the laser beam transformation optic system is of big significance. The square image superposition wave-guide is an optic transform system which is simple and adjustable, and the uniform square light energy distribution with shape boundary can be obtained with it. However, due to the high coherent property of laser, the fine interference fringes appear unavoidably. The existence of the intensity fringes limits the application of this optic transform system. How to eliminate these fringes is a subject worth studying. In this thesis, after studying the property of the square image superposition wave-guide system, the author has proposed a method by changing the space position of the focus spot at the entering plane of the wave-guide. The simulation experiment has performed using a parallel plane wave-guide and verified the feasibility of the approach. Considering the utilizing the laser energy efficiently and the cooling of the system, two systems suitable for practical high power laser application have been presented.With the rapid development of microelectronics, the pixels of the CCD become higher and the price become lower. The progress of these techniques has pushed the rapid development of digital holography, Digital holography has such advantages as being touch less, sensitive, and especially fulfilling the whole field measurement. Since the color digital hologram brings more information than monochromatic digital holography, for example, the measurement of three dimension displacement. Therefore the color digital holography is becoming a hot study area. At present, the wave-front reconstruction algorithm is one subject to be studied. Based on the deeply theoryitical study on the adjustable amplification reconstruction approach of the digital holography, we proposed an approach to obtain reconstruction object light field free from the zero-order diffraction interruption by filtering in frequency space. Then we applied this approach to color digital holograph and formed the non-interpolation wave-front reconstruction algorithm. The experiment result demonstrates that the quality of the reconstruction object wave field has been improved remarkably. This result has provided a useful reference for the application of color digital holography in the material testing and measurement.In the digital holography experiment, the object light waves and the reference light waves usually are obtained by laser beam filtering through pin-hole space filter, then expanding, and becoming parallel light through lens, the distribution of the expanding light is not uniform on the whole area. While the test object size is so large that it has to be placed far away from the CCD, so the light beam should be expanding even large to illuminate the whole object, and the light coming from the test object becomes very weak, under this condition, the uniformity of the light wave field distribution becomes a serious problem to affect the quality of the reconstruction image In this thesis, based on the study of the property of the square image superposition wave-guide, we first presented the ideal of applying image superposition wave-guide uniformity optical system in the digital holography, that is, the square uniform light pattern comes from image superposition wave-guide uniformity optical system is projected on the test object, the light waves scattered from the rough surface of the test object enters the window of CCD and becomes object light, since fringes separation is about several tens micrometer, the fine interference fringes on the square light pattern has no effect on the recording hologram. After passing through image superposition wave-guide optical system the light distribution become much uniform. Since the energy is concentrated within the light pattern with sharp boundary, the intensity of the object light is increased and carrying more object surface information, which is also helpful for the recording of the hologram. Due to the improvement of uniformity of the object light, the uniformity of the reconstruction image becomes better, this is valuable for the retrieve information from holograms in the proceeding treatments. In order to confirm its validation. We designed and made an image superposition wave-guide and performed digital holography experiments. The experimental results show that the quality of the reconstruction image have been improved and the fine fringes on the square light spot have no effect on the digital holography recording.In order to confirm the feasibility that the square image superposition wave-guide can be applied in the digital holography technique for large size object test, the author has designed and manufactured two test models(about80mm) with stainless steel sheet by laser processing. One is a square seal air pressure vessel; the other is a rectangular water pressure vessel. Both test models have a very high stability and repeatability while adding load or reducing load, and deformation fields are out-of-plane displacement, and the boundary is corresponding to the zero order fringes, and the results are convenient for comparing with ANSYS simulation results. The adjustable amplification reconstruction approach free from the zero-order diffraction interruption is implemented to obtain the object wave fields. The interference field of the two object waves fields under different load conditions, then the deformation field is achieved. The experiment results demonstrate that the experimental results coincide well with the ANSYS simulation results, thus approve that the square image superposition wave-guide can be applied to digital holographic detection. This research result will undoubtedly provide an effective means for digital holographic detection for large sized object. Finally, according to the fact that the maximum deformation at center of each side of square air pressure vessel has exact analytical solution and depends on the elastic modulus, Poisson ratio, thickness and the length and width geometry size, a new method for measuring the elastic modulus of plate metallic material is proposed.