The Silicon Diode Array Camera Tube

A large number of electronic cameras have been developed for converting an optical image into an electrical signal.1-3 In many of these, a light-induced charge pattern is stored on a suitable image sensing target and a low velocity scanning electron beam is used to access the charge pattern. One such camera tube, the vidicon, has many desirable characteristics; it has found extensive commercial use partly because of small size and inexpensive construction.2 However, the vidicon does possess characteristics which, in many applications, can prove undesirable or even detrimental. 1481 1482 T H E BELL SYSTEM T E C H N I C A L J O U R N A L , M A Y - J U N E 1969 Recently there have been several reports of development aimed at obtaining an all solid-state image-sensing system. 4-8 Typically, these systems consist of an array of photosensitive elements scanned by solid-state logic circuits. In general, the technology associated with producing the logic circuits that must duplicate the function of the scanning electron beam is quite complicated. As a result, in all such systems reported to date, the density of photosensitive elements has been rather limited, and the resulting resolution has been small compared with what can be achieved with a vidicon and what would be required in a great many applications of interest. This paper describes a new camera tube which has the resolution, small size, and inexpensive construction of the vidicon, but not many of its undesirable features. While the vidicon has an evaporated photoconducting film as the image sensing target, the new camera has a planar array of reverse biased silicon photodiodes.9-12 The diode side of the array is scanned by a low velocity electron beam, and the electron optics are similar to that of a conventional vidicon.