Multiple measurement channel detector circuit for interferometers

Abstract

A detector circuit for a multi-channel interferometer, typically as may be used in an optical coherence tomography device, comprising: a plurality of measurement channels () each comprising a measurement detector (); and a balance channel () comprising a balance detector (), each of the measurement detectors () and the balance detector () having a light sensitive area and an electrical output configured to output a signal indicative of the intensity of light incident on the light sensitive area, in which each measurement channel () is provided with a feedback circuit () comprising: a variable gain circuit () having an input for the signal from the measurement detector () and an output, the variable gain circuit () being configured to output at its output the signal received at its input with a variable level of gain; a difference circuit () having a first input for the output of the variable gain circuit (), a second input for the signal from the balance detector () and an output, and being configured to output at its output a signal indicative of a difference of the signals at its first and second inputs; and a controller () for each variable gain circuit () configured to vary the variable level of gain dependent upon a low frequency component of the output of the difference circuit ().