Page 156 - Photodetection and Measurement - Maximizing Performance in Optical Systems

Control of Ambient Light

Control of Ambient Light 149

100

%T
Long-pass filters
50
405 IY – 520 IY – 560 IY – 585 IY – 650 IY –

400 600 l (nm) 800
100

%T
Bandpass- and band-blocking filters
50
555 IM – 540 IB – 555 IM –

540 IB –
400 600 l (nm) 800
100

%T

Short-pass filters
50

435 IK – 465 IK – 505 IK – 540 IK – 585 IK – 660 IK – 730 IK –
25

400 600 l (nm) 800
Figure 7.8 Dichroic filter responses. Long wave-
length-pass, short-pass and bandpass-types are avail-
able. Figure supplied and reproduced by permission of
Comar Ltd, Cambridge U.K.

(near IR). These exhibit low passband losses of the order of 8 percent (Fresnel
losses at two surface reflections), and stop-band suppression to better than 0.01
percent.
Gelatin, polyester and acrylic filters are also very useful for color correction
and control, often called generically “Wratten” filters after Eastman Kodak

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