tailieunhanh - OPTICAL IMAGING AND SPECTROSCOPY Phần 4

Tham khảo tài liệu 'optical imaging and spectroscopy phần 4', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 144 WAVE IMAGING Volume Holography a Plot the maximum diffraction efficiency of a volume hologram as a function of reconstruction beam angle of incidence assuming that As s 10-3 and that K p2 k0. b A volume hologram is recorded with À 532 nm light. The half-angle between the recording beams in free space is 20 . The surface normal of the holographic plate is along the bisector of the recording beams. The index of refraction of the recording material is . What is the period of grating recorded Plot the maximum diffraction efficiency at the recording Bragg angle of the hologram as a function of reconstruction wavelength. Computer-Generated Holograms. A computer-generated hologram CGH is formed by lithographically recording a pattern that reconstructs a desired field when illuminated using a reference wave. The CGH is constrained by details of the lithographic process. For example CGHs formed by etching glass are phase-only holograms. Multilevel phase CGHs are formed using multiple step etch processes. Amplitude-only CGHs may be formed using digital printers or semiconductor lithography masks. The challenge for any CGH recording technology is how best to encode the target hologram given the physical nature of the recording process. This problem considers a particular rudimentary encoding scheme as an example. a Let the target signal image be the letter E function from Problem . Model a CGH on the basis of the following transmittance function t x y 1 if arg f E u- - 0 0 otherwise where À is the intended reconstruction wavelength and d x is the intended observation range. F E is the Fourier transform of your letter E function. Numerically calculate the Fraunhofer diffraction pattern at range d when this transmittance function is illuminated by a plane wave. b A more advanced transmittance function may be formed according to the following algorithm t x y 1 if argle . x - 1 F E u x id v y id 0 0 otherwise Numerically calculate the Fraunhofer .