Page 151 - Introduction to Information Optics

136 2. Signal Processing with Optics

r(x -x' )
2
2

»nc[ A- x (x 2 -x' 2 )]
x

Fig. 2.46. Image deblurring. (a) Spatial coherence function, (b) Source encoding mask.

As for the temporal coherence requirement, a sampling phase grating is used
to disperse the Fourier spectrum in the Fourier plane. Let us consider the
temporal coherence requirement for a 2-D image in the Fourier domain. A
high degree of temporal coherence can be achieved by using a higher sampling
frequency. We assume that the Fourier spectrum dispersion is along the y axis.
Since the smeared image deblurring is a 1-D processing, a fan-shaped broad-
band spatial filter to accommodate the smeared Fourier spectrum can be
utilized. Therefore, the sampling frequency of the input phase grating can be
determined by

Po

in which A and A/I are the center wavelength and the spectral bandwidth of the
light source, respectively. p m is the y-axis spatial frequency limit of the blurred
image.