TAILIEUCHUNG - OPTICAL IMAGING AND SPECTROSCOPY Phần 6

Tham khảo tài liệu 'optical imaging and spectroscopy phần 6', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 250 COHERENCE IMAGING Coherent and Incoherent Imaging a Given that the impulse response for incoherent imaging is the square of the impulse response for coherent imaging does an incoherent imaging system implement a linear transformation b Does the higher bandpass of an incoherent imaging system yield higher spatial resolution than the comparable coherent imaging system c Is it possible for the image of a coherent object to be an exact replica For instance can the image be equal modulo phase constants to the input object with no blurring d Is it possible for the image of an incoherent object to be an exact replica MTF and Resolution. An f 2 imaging system with circular aperture of diameter A 1000À is distorted by an aberration over the pupil such that P x y ep x where a 10 4 AA Plot the MTF for this system. Estimate its angular resolution. Coherent and Incoherent Imaging suggested by J. Fienup . The interference of two coherent plane waves produces the field c x z 2 1 cos 2pu0x ei2pw0z The interfering field is imaged as illustrated in Fig. . As we have seen the coherent imaging system is bandlimited with maximum frequency Umax A ldị. Experimentally one observes that the image of the field is uniform . there is no harmonic modulation for A uoldi. If however one places a diffuser at the object plane then one observes harmonic modulation in the image irradiance as long as A uoldi 2. The diffuser is described by the transmittance t x eif x where f x is a random process. Diffusers are typically formed from unpolished glass. a Explain the role of the diffuser in increasing the imaging bandpass for this system. Figure Geometry for Problem . PROBLEMS 251 b Without the diffuser the image of the interference pattern is insensitive to defocus. Once the diffuser is inserted the image requires careful focus. Explain this effect. c Model this system in one dimension in Matlab by considering the coherent field f x e ỉ s 1 D cos 2 uox .

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