Silicon diode array target with gating capabilities

The ability to electronically vary the responsivity is a valuable feature of many camera tubes. In many cases this feature eliminates the need of a variable iris and may, also, aid in discriminating pulsed light sources from background illumination. The conventional silicon vidicon does not have this feature and is, therefore, not suitable for many applications. Previously reported work described one technique for achieving an electronically controlled responsivity with a silicon vidicon by incorporating an MOS structure on the illuminated surface of the target. In general, this "front-gate" approach is unsatisfactory for several reasons: 1) The shape of the spectral response curve is changed as the responsivity is varied: 2) The change in infrared photoresponse is limited for thick targets which are useful in infrared imaging: 3) The speed of the device is limited: 4) It is difficult to fabricate structures on both sides of the target.