Page 175 - Introduction to Information Optics

160 2. Signal Processing with Optics
(b) Is the source encoding mask of part (a) physically realizable? Give
the reason for your answer.
(c) Design a physically realizable source encoding mask that has a
coherence distance equal to 2Ax.
2.40 Refer to the white light photographic image deblurring of Sec. 2.8. If the
linear smeared length is about 1 mm,
(a) What are the spatial and temporal coherence requirements for the
deblurring process with an incoherent source?
(b) In order to achieve the spatial coherence requirement, what is the
requirement of the light source?
(c) In order to obtain the required temporal coherence, what would be
the minimum sample frequency of the diffraction grating T(JC)?
2.41 Consider the image subtraction with the encoded source discussed in Sec,
2.8. Assume that the spatial frequencies of the input object transparencies
are about 10 lines/mm.
(a) Calculate the temporal coherence requirement.
(b) If the main separation of the two input object transparencies is 20 mm
and the focal length of the achromatic transform lenses is 300 mm,
design a spatial filter and a source encoding mask to produce point-
pair spatial coherence for the processing operation.
(c) Calculate the visibility of the subtracted image.
2.42 Assume that an integrated-circuit mask is a two-dimensional cross-
grating-type pattern. The corresponding Fourier spectrum may be repre-
sented in a finite region of a spatial frequency plane, as depicted in Fig. 2.73.
(a) Design a white light optical processing technique for the integrated-
circuit mask inspection.

Fig. 2.73.