
13
OPTICAL DETECTION
Most of our study so far has been about the manipulation of light, including reecting, refract-
ing, focusing, splitting, and recombining. In Section 12.1, we discussed quantifying the
amount of light. In this chapter, we address the detection process. Normally, detection means
conversion of light into an electrical signal for display or further processing. Two issues are of
greatest importance: sensitivity and noise.
The rst is a conversion coefcient that determines the amount of electrical signal produced
per unit of light. Typically, at the fundamental level, this is the ratio of the detected electrical
charge to optical