Bitmap thermal image sensor with bolometric pixel and special noise-reduction method

Abstract

The invention relates to matrix image sensors of the bolometric type, in which each pixel comprises a bolometric resistor (Rb) whose value varies according to the thermal flow received by the pixel. The resistor (Rb) is biased by a bias voltage of value Vpol. The current that passes through it is compensated for by a compensation current Icomp, the difference between these currents being integrated in order to produce a measurement signal. The bias voltage (or the compensation current) is adjusted pixel by pixel, for example during a calibration phase, so that all the pixels have an apparent identical sensitivity despite the dispersion of the nominal value of the bolometric resistor. The adjustment is carried out in an analogue manner by storing an individual voltage (VG) specific to each pixel in a sensitivity trimmer capacitor (Ca) specific to this pixel. The capacitor acts directly on the adjustment of the bias voltage or on other parameters playing a role in the sensitivity of the pixel (integration time for example). The spatial noise is thereby considerably reduced.

Description

technical field [0001] The invention relates to a matrix thermal image sensor of the bolometric type, in which each pixel comprises a bolometric resistor whose value varies according to the heat flow received by said pixel. Background technique [0002] Pixels are organized in rows and columns and the matrix can be addressed row by row. Signal readout circuits are associated with each column of pixels and there are as many readout circuits as there are columns. The signal read on each column during addressing of a row corresponds to the reading of the pixels of that row; at the same time as reading of the subsequent row is started, the signal is stored and subsequently extracted from the matrix by the multiplexer. Signal. [0003] During the addressing of a row, a bias voltage is applied to the bolometer resistor, but the value of the bolometer resistor varies according to its temperature; the temperature depends on the one hand on the bias voltage and on the other hand on...

AI Technical Summary

Problems solved by technology

[0015] In practice, however, this double correction is cumbersome to apply and, in the disclosed prior art practice, is applied by a computer that receives the image from the sensor and fully modifies it in order to remove spatial noise therein. Reprocessing; the cost of computing power is substantial

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