Laboratory Evaluation of Eleven Image Intensifiers

Abstract

A number of laboratory tests have been carried out at the image tube laboratory of the Optical Sciences Center on 11 selected image intensifiers in order to compare and evaluate their performance. The electrostatically focused tubes tested are as follows: ITT F-4708 (1 stage), two samples of a Varo 8605 (1 stage), Varo 8605DC (1 stage), ITT F -4724 (3 stages), RCA 8606 (3 stages), and Varo 8606 (3 stages). The magnetically focused tubes are EEV P829D (5 dynodes), ITT F-4089 (1 stage), RCA C33011 (2 stages), and RCA C70021AEP2 (3 stages). The tests included measurements of limiting resolution (of the intensifiers directly and of photographs obtained with the intensifiers), square -wave response, geometrical distortion, shear characteristics in fiber-optic faceplates, photographic speed gain, uniformity of response, light- induced background, dark emission, and detective quantum efficiency (DQE) of intensifier -photographic emulsion combinations. The most significant result of the tests is that a comparison among tubes with a similar number of stages (or gain) showed that the magnetically focused intensifiers were generally superior to the electrostatically focused intensifiers in resolving power, geometrical distortion, and uniformity of response. However, the electrostatically focused tubes exhibited only about one fifth the light- induced background of the magnetic tubes. Also, a mean relationship was found between the limiting resolution of the intensifier output image and the limiting resolution that is recorded on a photograph of the intensifier. Other particularly notable results include (1) the causes and characteristics of several different types of response nonuniformities, (2) the identification of sources of light -induced background, (3) the photographic speed gain required of an intensifier to obtain the highest peak DQE possible and also that required to make the system behave as a "single- photon event" detector, (4) the identification of some especially undesirable characteristics of a potassium chloride transmission secondary emission (TSE) dynode intensifier (EEV P829D), and (5) the performance of three relay lenses for intensifiers.