Recent Developments in Solid-state Infra-red Image Converters

Abstract

This chapter presents developments in solid-state infrared image converters. Near-infrared images with wavelengths between 0.8 and 1.7 μm are converted into bright, visible images. An experiment was performed to examine the effectiveness of CdS as a photoconductivity-quenching materia1. CdS powder doped with copper and gallium was synthesized and bonded in a layer by plastic resin. A pair of gold electrodes 7 mm wide and separated by gap of 0.7 mm was evaporated on to the layer. The use of external bias light is not necessary if the operating voltage is suitably adjusted to obtain sufficient feedback. The input-output characteristic of the image converter are shown. The input is monochromatic light of wavelength 1.4 μm. The time response of the light output with infrared input depends on the intensity of the latter. The minimum detectable input level using photoconductivity quenching is to 10 −4 to 10 −3 W/cm 2 for 1.4-μm light and using phosphorescence quenching it is about 5 × 10 −5 W/cm 2 for 1.3-μm light. The solid-state infrared image converter can be characterized by its simplicity, ease of manipulation, and low cost.