A new expression of partially coherent light is derived. The formula of the partially coherent optical field is consisted of two terms: spatially coherent part propagated by angular spectrum and incoherent part based on the optical transfer function. Both parts are related to coherent function (degree of coherence). Then a design method for computer generated hologram based on the theory of partially coherent light is proposed. The formation process of CGH is divided into angular spectrum and optical transfer function. Both numerical simulations and optical experiments are done to verify that speckle contrast of holographic reconstructed images is improved without sacrificing in PSNR compared to traditional method. The experimental results show that the speckle contrasts are improved more than 46%, and the image quality is obviously improved. This method can be applied on three-dimensional holographic display, beam shaping and other wave-front modulation techniques.
Computer holography is based on advanced computer technology and the basic principle of wave optics, and it is widely employed in many optical fields. In the holographic display, both display systems and encoding methods of computer-generated hologram have effects on the reconstructed image quality. The high coherence of light source causes laser speckle noise that degrades modulation quality severely. We propose a novel method to encoding computer-generated hologram, in which a partially temporal coherent light with a broadband continuous spectrum is used to illuminate the object image. We consider the partially temporal coherence of an actual light source and encode the computer-generated hologram based on the extended spectrum of the actual light source. This ensures that the design source is consistent with the reconstructed source. In this paper, we compare the reconstructed images from the proposed encoding method with that obtained from the encoding method based on ideal temporal coherent light. Under the same conditions the proposed method can obtain a more accurate and clear object image with the naked eyes. The proposed method can provide a reference for various wave-front modulations.
Computer holography is based on advanced computer technology and the basic principle of wave optics, and it is widely employed in many optical fields. In the holographic display, both display systems and encoding methods of computergenerated hologram have effects on the reconstructed image quality. The high coherence of light source causes laser speckle noise that degrades modulation quality severely. The partially temporal coherent light (PTCL) has been applied to holographic reconstruction to reduce speckle noise in display systems, while the encoding methods of computergenerated hologram (CGH) based on PTCL have not been reported. We propose a novel method to encoding CGH, in which a PTCL with a broadband continuous spectrum is used to illuminate the object image.
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