Study On Dynamic Optical Three Dimensional Display Combining Digital Holography And Computer Generated Holography

Virtual reality(VR)and augmented reality(AR)are the hot display technology.And three dimensional(3D)information acquisition and display technology is the most important research direction.At present,traditional 3D display technologies such as volume 3D display,binocular parallax 3D display and multi-view 3D display have been developed.However,these 3D display technologies are not true 3D reconstruction.Optical holographic 3D display can reproduce the 3D information of the object,including the complete amplitude and phase information of the object light field.Therefor the observer can have the same stereo feeling when viewing the 3D image reconstructed by holography as they directly viewing the real 3D object or scene.Holographic 3d display is realized by diffraction imaging,which requires extremely high spatial resolution display materials or devices(about 9*107 pixels)due to the large amount of information.And wide transmission bandwidth(about 6*105MH)for dynamic display.Therefor holographic 3d display is only applied in static display.With the computer and photoelectric imaging technology rapidly developing,the research on dynamic 3D display using digital holography,computer generated holography and spatial light modulator becomes the hot topic in research field.Digital holography is a recording method using electric device to record the information of object.And generally the digital reconstruction of the recorded object is reconstructed through simulating optical diffraction process by computer.Digital holography can make full use of photoelectric imaging and computer technology to let the hologram can be reconstructed digitally.Therefor it provides a new method for 3d quantitative precision measurement.Computer generated holography encode complex amplitude of object light wave into computer generated hologram(CGH),which can be output to spatial light modulator for optical reconstruction.CGH can not only record the amplitude and phase of the light wave emitted by the real object,but also simulate the wave front of the virtual object,so it has special advantages and good flexibility.This thesis studies the research on dynamic holography.Combining digital holography and computer generated holography with spatial light modulator,we built a three-color real-time digital holographic 3D display system.The digital hologram of virtual object is obtained by computer generated holography.Real objects are recorded into digital hologram.And then two kinds of holograms are loaded into three spatial light modulators in real-time.The fusion image of real and virtual information is obtained by the diffraction of three spatial light modulators.The main contents of this thesis include the following aspects:Firstly,the development and application of digital holography and computer generated holography in 3D display are summarized.And the recording and reconstruction of lensless Fourier transform holography are analyzed.Secondly,digital hologram and CGHs are generated in different ways.In order to achieve the expected fusion effect of reconstructing images,the parameters of digital hologram and CGHs must match.We analyze the digital hologram recording condition and parameters theoretically.Then the parameters of the CGHs are set to match the parameters of the digital hologram.Finally,the corresponding CGHs are calculated by the obtained parameters.Thirdly,according to the theoretical analysis,experimental verification is carried out.Combined with the actual device parameters,we design a best light path for optical reconstruction.The digital hologram is loaded into a spatial light modulator in real time to realize the optical reconstruction of real objects.And two CGHs are loaded into the other two spatial light modulators to realize the optical reconstruction of virtual objects.Three semiconductor lasers with wavelengths of 650 nm,520nm and 462 nm are used as the reconstruction sources and three reconstructed images are combined in the space.Finally,we get the three-color holographic 3D display video in real-time through experiments,the 3D display effect of real objects is enhanced when three reconstructed images of digital hologram and CGHs are fused for final three-color 3D display through experiments.At the same time,the measurable quantitative optical reconstruction is realized.