Dark signal compensation for diode arrays

Abstract

Three means or methods for compensating for thermal noise, also referred to as dark signal, are utilized to enhance the accuracy of a monolithic diode array. A charge-coupled linear photodiode array is used in a camera to detect densities of any image projected or reflected onto the array. After conversion, voltage variations of one/one thousandth (1/1,000) volt in a ten volt range are significant to the measurement of densities. Therefore, extremely accurate control of thermal noise, which is generated in the cell sites and in the shift registers used to obtain the data from the cell sites, is extremely important. The three methods or means of control are as follows. Temperature control maintains the temperature of the photodiode array at approximately ten degrees centigrade to minimize the generation of thermal noise. A thermistor is used to detect any temperature variations within the range controlled by the cooling means and the reading is compensated for those variations in temperature. Finally, thermal noise generated in masked cells are measured and used as a correction or calibration for the readings. The foregoing means and methods enhance the accuracy of the readings by an order of magnitude.

Dependencies are inferred from the claim text.