IR FPA sensors

The term IR FPA sensors (focal plane array) means array of detectors sensitive to IR light that can potentially generate electronic two dimensional image when located at focal plane of IR objective. In detail, IR FPA sensors offered on the market are built by combining array of IR detectors (raw IR FPA sensor) with read out electronic system.

IR FPA imaging sensors are the most important block of thermal imagers. The latter systems can be built using two main ways: 1)to purchase IR FPA sensor integrated with a miniaturized control/image processing electronics (thermal camera core) and later to combine it with optical objective, optional cooler, and mechanical case; 2) to purchase IR FPA sensor, to develop suitable miniaturized control/image processing electronics, and later to combine created thermal camera core with optical objective, optional cooler, and mechanical case.
    Technology of IR FPA sensors is very difficult and has been mastered only by not more than a dozen of manufacturers worldwide. However, there are dozens of scientific institutes/companies that carry out work on development of new IR FPA sensors. Both manufacturers and research institutes need scientific apparatus to characterize IR FPA sensors that they manufacture or develop.
    Testing IR FPA sensors is not standardized. However, IR FPA sensors are typically characterized using a set of parameters used to characterize thermal imagers. There are three main groups of parameters: 1)noise/sensitivity parameters, 2)image quality parameters, 3)spectral parameters. In spite of similarity of characterization parameters, the systems for testing IR FPA sensors differ a lot from systems for testing thermal imagers mainly due to one main reason. IR FPA sensors need a special electronic controller in order to generate video image in a standard electronic format when every thermal imager generates video image in one of standard electronic formats without any additional electronics. There are also other minor differences.

Inframet offers three main systems for testing  IR FPA sensors:

  1. FAPA test system
  2. MIRAD irradiator
  3. SPOT test system.

FAPA is a quasi universal system for expanded testing IR FPA sensors optimized for use by scientific institutes that carry our research on development of such imaging sensors. It is intended mainly for testing complete IR FPA sensors (array of detectors integrated with readout electronics) and thermal cameras cores but some critical parameters of raw IR FPA sensors (before integration with ROIC) can be measured, too.  In detail, FAPA system enables measurement of all important parameters (noise/sensitivity, image quality, and spectral parameters) of IR FPA sensors/thermal camera cores.

MIRAD is an infrared irradiator optimized to work as a block of machines that test semiconductor wafers used to manufacture LWIR/MWIR FPA imaging sensors. In detail, Mirad has been designed to replace IA-OPT385WL illuminator (emitting light in VIS-SWIR band) in IP750 Image Testing machine from Teradyne Inc. In other words, Mirad is a middle/far infrared radiation source that can irradiate tested wafer with regulated intensity and high uniformity. MIRAD can be also optimized to work as irradiator in other semiconductor wafers test machines offered on international market.

SPOT test station enables precision testing of  raw IR FPA sensors (sensors before integration with read out electronics).  Cooled MWIR sensors are typically tested. The system enables  direct measurement of spatial responsivity distribution function  and indirect accurate measurement of Modulation Transfer Function and cross-talk. It it offered as an independent system or as a block of bigger FAPA system.  

Fig. 6. MIRAD irradiator Fig.7.  SPOT test station

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