Patent ID: 7283166
Filing Date: 2007-10-16
Classification: H01J,H01L,H04N

Abstract:
1. An electron bombarded charge coupled device (EBCCD) sensor with automatic gain control for maintaining the EBCCD sensor within a predetermined gain or corresponding pixel count range, comprising: i) a means to image a spatially distributed photon distribution onto a photocathode whose purpose is to convert this into a similar spatial distribution of photoelectrons, ii) a means to adjust the photocathode's conversion efficiency from input photons to output photoelectrons by means of adjusting a photocathode bias voltage, iii) a means to accelerate photoelectron spatial distribution onto a focal plane array possessing one or more pixels where a number of electrons produced in an array material per incoming photoelectron may be varied by adjusting an acceleration bias voltage, iv) a means to rapidly collect electrons produced in each pixel as charge and, with analog to digital conversion, convert these to ray signal pixel counts which are promptly swept out and placed in computer memory as the data raw signal array for that time step, v) if desired, a means to automatically subtract background noise pixel counts array from the raw signal count array and, after changing each negative value to zero, to arrive at a true signal pixel counts array for the timestep, vi) a means to search desired pixel counts array for the pixel count of the pixel with maximum counts, N vii) a means to compare one or more of the pixel counts with certain pre-chosen counts that are stored in computer memory relating to the lower and upper bound counts for linear gain in the sensor, N viii) a means to store criteria for certain changes in one or both bias voltages that are commanded by those criteria to effect sensor automatic control as listed below, ix) a means to generate and store a required look-up table of bias voltages, or the functional equivalent equations, by means of prior calibration of the sensor wherein the photons from a light source of known spatial intensity distribution impinges on the sensor and the gains and pixel counts are recorded for various bias voltages, x) a means to determine the required bias voltages for certain control functions by using the feature values as determined in (vi) for the purpose of interpolation of extrapolation in the table of (ix), xi) a means to promptly adjust one or both of the voltages with digitally controlled power supplies according to values determined in (x), xii) a means for the sensor to cycle into a repeat of the above steps as it responds to a master clock signal that drives it at a repetition rate.