Page 139 - Introduction to Information Optics

124 2. Signal Processing with Optics

I/Act

4000
d = 10mm

3000

J
8 2000
c3
I
< 1000

30 60 90 120 150 180

construction angle 2oc
(a)
X/AA,
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(C)
d = 1 Omm
•£ 30000
7mm
7 (b)
Jt
JO 20000 _
w>
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£ 10000 (a ) . - - ' . . - - - • • • • '
lmm , .
n r ,. , ,. :i: :, . H - i - r - ,- -i- -,- -, - i • ; " ; i . , i
0 30 60 90 120 150 180
construction angle 2dt
(b)
Fig. 2.40. (a) Angular selectivity, (b) Wavelength selectivity. Dash line for transmission type and
solid line for reflection type.

selectivities of which are plotted in Fig. 2.40b. We see that the wavelength
selectivity for the reflection-type hologram is quite uniform and higher than the
transmission type. Although the wavelength selectivity for both the reflection
type and the transmission type increases as the thickness of the crystal filter
increases, the increase is far more rapid for the reflection type than for the