Patent ID: 6326603
Filing Date: 2001-12-04
Classification: G01J,H04N

Abstract:
A photodiode array having a plurality of channels, each channel comprising:a photodiode which is reverse biased such that it acts as a current source and which provides an electrical output signal in response to the light impinging on said photodiode,a signal processing unit for processing said electrical output signal of the photodiode,an A/D conversion circuit for providing a digital output signal indicative of the intensity of light impinging on said photodiode, which comprisesan integrator circuit for accumulating charge corresponding to the photocurrent provided by the photodiode,a controllable dumping circuit for dumping predefined charge packets to and/or from the integrator circuit,a comparator circuit for comparing the output signal of the integrator circuit with a predetermined signal,a logic circuit, connected to the output of said comparator circuit and to a control input of said dumping circuit for controlling said charge flow to keep the output signal of the comparator circuit within a predetermined range about the predetermined signala digital counter for counting the number of charge packets to or from the integrator circuit during a predetermined time interval,characterized in thata compensating circuit is inserted at the input side of said integrator circuit, comprising at least a switchable compensation capacitor,whereby said compensation capacitor is, in a first step, charged to a compensating-voltage corresponding to an error voltage caused by changed signal noise, which is subsequently superimposed onto the input signal of the integrator circuit to compensate said noise component of a desired signal input.