Infrared detectors can be divided into two types : those which depend upon heating effects produced by the absorbed radiation (thermal detectors) and those which make use of photoelectric effects (photodetectors). Infrared image sensors using photodetectors show high detectivities, but must be cooled down for proper operation. Thermal detector sensors are slow responding and have relatively low sensitivity, but can operate even at room temperature. In this paper we describe our experiments and other recent works of the thermal infrared image sensors.
Improvement of sensitivity in avalanche-type image pickup tubes are examined. Sensitivities which are 1000 times higher than those of conventional tubes are attained by using thick amorphous Se layers (25.5μm) and by adopting a new electrode for high voltage operation. Noise characteristics of the avalanche-type image pickup tubes have been also investigated. It was found that the avalanche excess noise are extremely reduced by operational feature of the pickup tube, including the charge storage operation and the electron beam scanning.
Micro channel plate (MCP) have been fabricated by integrated circuits technology. Single crystalline silicon was used as the substrate of MCP. Micro channels with large aspect ratio were formed by photolithography and anisotropic etching, and secondary electron multiplying film was deposited by chemical vapor deposition (CVD) at atmospheric pressure. The gain of the fabricated MCP was 5 and 19 at the dynode voltage of 350V and 200V per stage of MCP in the single stage type and the double stage type, respectively.
This article describes recent trends of imaging technologies for invisible informations. Many kinds of invisible information imagers (IIIs) have been developed for every variety of invisible information. Above all, imagers for infrared light, X-ray and ultralow light level made remarkable progress during the past ten years. The progress of III technologies is closely associated with that of solid-state technologies and digital processings of the image information.