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1、幻 灯 片 1 Chapter 8 Analog Optical Information Processing Weimin Sun College of Science Harbin Engineering University 幻 灯 片 2 The Abbe- Porter experiments ?An object consisting of a fine wire mesh is illuminated by collimated, coherent light. ?In the back focal plane of the imaging lens appears the Fo
2、urier spectrum of the periodic mesh, and finally in the image plane the various Fourier components passed by the lens are recombined to form a replica of the mesh, it is possible to directly manipulate the spectrum of the image in a variety of ways. Mesh：网状物 Replica：复制品 Manipulate：操作，处理 幻 灯 片 3 Setu
3、p of the Abbe- Porter experiment 幻 灯 片 4 Spectrum of the mesh 幻 灯 片 5 幻 灯 片 6 幻 灯 片 7 Applications of Abbe s theory ?High- pass filter to enhance the edge of objects 幻 灯 片 8 ?To remove the background and distinguish the special points 幻 灯 片 9 ?To remove the lines 幻 灯 片 10 ?To distinguish the signals
4、 幻 灯 片 11 ?Optical differential 幻 灯 片 12 幻 灯 片 13 The Zernike phase- contrast microscope ?Many objects of interest in microscopy are largely transparent, thus absorbing little or no light (e.g. an unstained bacterium). ?When light passes through such an object, the predominant effect is the generati
5、on of a spatially varying phase shift; thus effect is not directly observable with conventional microscope and a sensor that responds to light intensity. ?A number of techniques for viewing such objects have been known for many years. ?interferometrictechniques, central dark ground method, schlieren
6、 method, Zernike method etc. Unstained：清白的，无污染的 Bacterium：细菌 Predominant：主要的，突出的，卓 越的 幻 灯 片 14 For an ordinary microscope ?A necessary condition to achieve linearity between phase shift and intensity is that the variable part of the object- induced phase shift, , be small compare with 2 radians. ),(
7、exp),(jtA= ),(1 ),( ),( += jeeet oo jjj A 1),(1 ),( 2 += jeI oj i 幻 灯 片 15 For the Zernike microscope ?A phase- changing plate can consist of a glass substrate on which a small transparent dielectric dot has been deposited. ?The dot is centered on the optical axis in the focal plane and has a thickn
8、ess and index of refraction such that it retards the phase of the focused light by either /2 radians or 3/2 radians relative to the phase retardation of the diffracted light. ),(21),(1 (),(),( 2 2 2 +=+=jjeeI j j i o ),(2-1),(-1 (-),(),( 2 2 2 3 =+=jjeeI j j i o Deposit: 堆积，存放 幻 灯 片 16 Application o
9、f Zernike s theory f Coherent light 幻 灯 片 17 Other ways f Coherent light 幻 灯 片 18 Improvement of photograph: Marchal ?For an original imaging system was badly defocused, producing an impulse response which consisted of a uniform circle of light. ?The corresponding optical transfer function was there
10、fore of the form ?where a is a constant and a aJ)( 2)( 1 H 22 YX ff+= 幻 灯 片 19 Compensating filter ?The compensating filter was synthesized by placing both an absorbing plate and a phase- shifting plate in the focal plane of the coherent filtering system. phase phase shift shift absorptionabsorption
11、 uncompensateduncompensated compensated compensated 幻 灯 片 20 幻 灯 片 21 幻 灯 片 22 Incoherent optical information processing systems ?Incoherent systems are somewhat more simple than coherent systems in their physical realization. ?On the other hand, an incoherent optical processing system has no “ freq
12、uency plane” . ?Incoherent data processing system can be broadly divided into three separate categories: ?Systems based on geometrical optics ?Systems based on diffraction ?Discrete systems 幻 灯 片 23 System based on geometrical optics ?Systems based on image casting =yxyxyxkIdd),(),( 21 Cast：投射，铸造 幻
13、灯 片 24 =yxyxyxkIdd),(),( 21 If the transparency 1is moved in the negative x direction with speed v, the detector response as a function of time will be given by =yxyxyxvtkIdd),(),( 21 幻 灯 片 25 ?Convolution without motion =yxyxyy f d xx f d kI SS dd),(),( 21 S 幻 灯 片 26 ?Impulse response synthesis with a misfocused system S L11(x,y) L22(x,y) P P 2f 2f = - 2 1 dd),;,(),(),(yxyxyxhyxkyxI dddd
