Spectrophotometry

Abstract

In the previous chapter we learned about optoelectronic light sensors, especially photodiode. Although many photodiodes are made to be specifically sensitive to a certain range of colors, e.g., UV-blue, red-IR, etc., they cannot tell the exact color or color combination of a light signal. Photodiodes (and most other optoelectronic light sensors) simply inform us of the intensity of light signals. Detailed information on color combination can be obtained using a technique known as spectrophotometry, which involves an instrument known as a spectrophotometer. Spectrophotometers are quite bulky, relatively expensive, and have not been considered as a topic for sensors or biosensors. In recent years, however, very small spectrophotometers (of size comparable to a smartphone) have become commercially available. Because of this, spectrophotometers are becoming an integral part of many sensor and biosensor devices.