Characteristics of Photodiode Arrays for Spectrochemical Measurements

Abstract

A rather large number of spectrochemical studies and analyses can be greatly facilitated by the simultaneous measurement of spectral information over a range of wavelengths. Of particular importance and interest to analytical spectroscopists is the development of simultaneous multielement analysis systems. The development and implementation of such analyses have been hampered by a lack of convenient and versatile multichannel spectrochemical measurement systems. New detector subsystems based on modern electronic image sensors are helping to overcome this obstacle. One type of electronic image sensor is the self-scanning linear array of silicon photodiodes. These arrays are available with densities of 1024 photodiodes per in and in lengths of up to 1 in. They are packaged in conventional dual-in-line integrated circuit packages complete with the necessary scanning circuitry. These sensors have simple and inexpensive control and measurement circuitry, and superior blooming and lag performance when compared to most other electronic image sensors. In addition, the signal integrating capability of the arrays is a flexible and powerful asset for many spectrochemical measurements. These and other operational characteristics of photodiode arrays are emphasized in this study. In addition, the measurement capability of a computer coupled photodiode array spectrometer based on a 1024 element array which is capable of simultaneously measuring over 50 nm (500 Å) of continuous spectral information anywhere from 200 to 1000 nm is illustrated.