Electro-optical characterization of IR focal plane array sensors

This dossier covers techniques for characterizing matrix infrared detectors, known as infrared focal planes. Over the past decade, infrared detector technologies have made steady progress, and have now reached industrial maturity, enabling the production of large formats (320 × 240 pixels, 640 × 512 pixels) at increasingly affordable prices. Today, infrared system designers have a choice of detection methods (thermal or quantum).

In the first part of this dossier, aimed primarily at engineers who need to design an infrared system, we present a state-of-the-art overview of these technologies. For a given application, the designer has to choose between different components on the market. To do this, it is necessary to evaluate the electro-optical performance of these detectors. For this evaluation phase, the manufacturer's commercial or published data may suffice. However, it is essential to compile this information in order to compare the performance of the various candidates against the performance levels required by the application. We'll see that this compilation phase consists of filling in a "sensor model". Once populated, this model can be used to predict sensor performance for specific operating conditions (flux levels, integration time, spectral bandwidth, etc.). The sensor model for the main detection methods (thermal or quantum) is presented.

The second part is dedicated to electro-optical characterization techniques for infrared focal planes, and is aimed at all experimenters, whether users, experts or technologists. For the user, the characterization phase enables the sensor model to be recalibrated by means of a few test points, in order to check that the sensor is working properly and that it is delivering the performance claimed by the manufacturer.

For the expert, electro-optical characterization is a demanding job, requiring the establishment of measurement protocols, the acquisition of calibrated test benches, the development of dedicated measurement electronics and the processing of voluminous experimental data. In fact, an infrared focal plane samples a scene in several dimensions (spatial, radiometric, temporal and spectral) with associated resolutions that need to be evaluated, for conditions of use that change with the application. For the technologist, the challenge is to develop prototypes of complex, extreme-performance detectors (megapixel or multispectral arrays, etc.). In this case, fine characterizations are very useful, enabling technological parameters to be restored from the final component.