<title>Critical evaluation of test patterns for EO system performance characterization</title>

Abstract

The traditional test pattern for end-to-end EO system performance testing in the laboratory has been the static 3-or 4-bar target. This choice was governed by linear systems approach. The introduction of undersampled imagers such as IRFPAs (infrared focal plane array cameras) has challenged the testing community to develop an alternative test, because the occurrence of aliasing has a completely different effect on periodic targets (such as the bar target) and real, non-periodic targets. A new test should at least have the following properties: lab testing is objective and easy, the measure is representative for field performance, and modeling (sensor and human) the test should be relatively easy. Several alternative test methods and test patterns have already been proposed. An example is the TOD method that uses nonperiodic test patterns. Other examples are the dynamic MRT that uses a moving 4-bar target, and the MTDP that uses the traditional static target but allows that not all four bars have to be present in the image. The development of real-time scene projection allows testing with real infrared targets under controlled conditions. The authors will discuss a large number of test patterns and methods and show their advantages and disadvantages for end-to-end EO system performance testing. They conclude that simple non-periodic spatial test patterns, such as used in the TOD, are the best choice for sensor performance characterization.Keywords: Electro-Optical system performance testing, TOD, MRTD, Dynamic MRT, MTDP INTRODUCTIONA standard laboratory test to determine human performance with Electro-Optical (EO) viewing systems is required for several purposes, e.g. (i) to verify if a sensor is working properly, (ii) to compare competing sensor systems, (iii) to verify if a new type of sensor meets the expectations based on its design, or (iv) to predict field performance. Field performance can be target acquisition (TA) performance in a military or a civilian environment (security), or reading performance with the unaided eye for example.Basically, there are two approaches for such a test. The first is to measure essential physical parameters of the sensor system or parts of the system (e.g. the MTF or the NETD), and then use a model to predict human performance. However, this requires a thorough understanding of human vision with sensors, and current vision models are not sophisticated enough to cope with all target and sensor factors that affect visual performance.The second approach is to measure end-to-end sensor performance including the human observer. It is often not very practical (or even possible) to perform such measurements for a real task in a real situation. Therefore, laboratory Sensor Performance Measures (such as the MRTD 1 ) have been introduced. In the laboratory, circumstances can be controlled and measurements can be performed quicker, easier, and with higher accuracy. It is obvious that the results of such a lab test need to be representative for the corresponding tasks in the fie...

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