Photodiode array

US5303027A · kind A · utility

Assignee

• Hewlett-Packard Company, L.P. · US

Inventors

• Hubert Kuderer · Waldbronn, DE
• Stefan Rohrer · Glückstadt, DE

Key dates

• Filing date: Jun 18, 1992
• Grant date: Apr 12, 1994
• Expiry date: Jun 18, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G01J2001/446
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A photodiode array comprises a plurality of n channels, each channel having a photodiode which is reverse biased such that it acts as a current source. Each channel further comprises an A/D converter for providing a digital output signal (DATA) which is representative o the photo current (Iph) provided by the photodiode and therefore of the intensity of the light impinging on the photodiode. The A/D converter comprises a controllable current source, an integrator circuit, a comparator for comparing the output signal (Vout) of the integrator with a predetermined signal (Vthreshold), a logic circuit for controlling the current source in response to the output signal (Vcomp) of the comparator such that Vout is kept within a certain range. Preferably, the current source provides current in the form of charge dumps to and/or from the integrator. The number of dumps in one direction is counted by a counter and is a digital measure of the photo current (Iph). The photodiode array is particularly useful in spectrophotometers since the provision of a separate A/D converter for each channel allow simultaneous processing of all the photosignals in the array so that spectra distortions arising…