Johnson's guideline for visual observation

In general, random noise limits find performance, system magnification limits limit classification performance, modulation transfer functions limit recognition performance, and scan grating limits recognition performance. The number of strips required for different observation levels is quite different, and the influence on the line of sight is also very large. The line of sight of the thermal imaging system should be analyzed by different positions (system design, program argument or technical and tactical indicators). Level. On the other hand, the number of bands required for each of the above observation levels is obtained at a probability of 50%. Therefore, there will be some changes in the number of stripes corresponding to other probabilities. Using probability integral fitting, the relationship between the number of strips and the probability can be expressed as

The values corresponding to the three observed levels were found, identified, and recognized as 0.625, 1.882, and 3.529, respectively. In the line-of-sight estimation, the required number of bands can be determined by iteratively solving according to the required observation level and probability.

(3) Influence of target shape

The test pattern of the laboratory performance parameter is a 4-band target with an aspect ratio of 7:1, and the aspect ratio of the equivalent strip pattern of the actual target generally does not satisfy the above conditions. Therefore, in the estimation of the line of sight, The correction is made according to the aspect ratio of the strip corresponding to the actual target. Let the target height be, the target direction factor (aspect ratio) be, and the number of equivalent strips required for the observation level be, then the aspect ratio of the target equivalent strip pattern becomes

The aspect ratio of the strip is related to the spatial accumulation performance of the human eye. The longer the strip, the larger the accumulation, and the higher the perceived signal-to-noise ratio. As can be seen from the expression, considering the actual target of the aspect ratio change, should be corrected to

Where is the minimum discernable temperature difference obtained by the laboratory.

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