While it is universally recognized that image quality of a thermal sensor is a strong function of spatial uniformity, the metrics commonly used to assess performance do not adequately measure the effectiveness of non-uniformity correction (NUC). Image uniformity is generally not static, particularly if correction terms are updated intermittently (with periodic shuttering) or gradually (with scene-based NUC). Minimum Resolvable Temperature (MRT), the most prevalent test for characterizing overall imaging performance, is poorly suited for characterizing dynamic performance. The Triangle Orientation Discrimination (TOD) metric proposed by Bijl and Valeton, because of its short observation window, provides better capability for evaluating sensors that exhibit non-negligible uniformity drift. This paper compares the effectiveness of MRT and TOD for measuring dynamic performance. TOD measurements of a shutter-based thermal imager are provided immediately after shutter correction and 3 minutes later. The drift in TOD performance shows excellent correlation to drift in system noise.
The need for higher performance short wave length infrared (SWIR) cameras for the telecom industry is becoming increasingly important. This paper will discuss the measured performance and capabilities of Indigo System's near infrared cameras. These cameras are ideally suited for telecom applications because of their high quantum efficiency, uniformity, and linearity over the 1.0 to 1.65 μm wavelength band. The cameras' high dynamic range and high damage threshold to laser light also make them ideally suited for testing and characterizing S-Band, C-band, and L-band fiber optic systems used in DWDM. Measurements of the camera's sensitivity, linearity, uniformity, and dynamic range will be presented and compared to what is currently considered the industry standard, pyroelectric vidicon cameras. The performance improvement resulting from Indigo's approach for reducing the effects of the sensor package window when imaging coherent light will be demonstrated. In addition, an analysis of the camera's tolerance to high levels of laser light will be discussed.
Indigo Systems Corporation has developed a family of standard readout integrated circuits (ROIC) for use in IR focal plane arrays (FPAs) imaging systems. These standard ROICs are designed to provide a compete set of operating features for camera level FPA control, while also providing high performance capability with any of several detector materials. By creating a uniform electrical interface for FPAs, these standard ROICs simplify the task of FPA integration with imaging electronics and physical packages. This paper begins with a brief description of the features of four Indigo standard ROICs and continues with a description of the features, design, and measured performance of indium antimonide, quantum well IR photo- detectors and indium gallium arsenide imaging system built using the described standard ROICs.
This paper describes the test results for the MIRAGE read- in-integrated-circuit (RIIC) designed by Indigo Systems Corporation. This RIIC, when mated with suspended membrane, micro-machined resistive elements, forms a highly advanced emitter array. This emitter array is used by Indigo and Santa Barbara Infrared Incorporated in a jointly developed product for infrared scene generation, called MIRAGE. The MIRAGE RIIC is a 512 X 512 pixel design which incorporates a number of features that extend the state of the art for emitter array RIIC devices. These innovations include an all-digital interface for scene data, snapshot image updates (all pixels show the new frame simultaneously), frame rates up to 200 Hz, operating modes that control the device output, power consumption, and diagnostic configuration. Tests measuring operating speed, RIIC functionality and D/A converter performance were completed. At 2.1 X 2.3 cm, this die is also the largest nonstitched device ever made by Indigo's foundry, American Microsystems Incorporated. As with any IC design, die yield is a critical factor that typically scales with the size and complexity. Die yield, and a statistical breakdown of the failures observed will be discussed.
IR imaging systems require correction of detector to detector gain and offset differences to obtain high quality imagery. Ideally this correction would be performed once at the factory and would remain stable indefinitely. For most imagers, this ideal is not obtainable and some level of correction must be performed. The stability of the gain and offset characteristics of the FPA are therefore important to understand as it affects how often this correction must be updated.
KEYWORDS: Cameras, Semiconducting wafers, Staring arrays, Signal processing, Infrared cameras, Sensors, Control systems, Video, Quantum efficiency, Process control
This paper reports on continuing improvements in the performance and producibility of InSb focal plane arrays, which together with progress in self-contained dewar/cooler designs have resulted in a new level of portable infrared camera functional capability. A new camera will also take advantage of the latest advances in integrated circuit miniaturization and electronic package fabrication to achieve the lowest possible size, weight, and power consumption while meeting its design goals for ruggedness and reliability.
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