SPECTRAL SENSITIVITY STABILITY ESTIMATION OF DIGITAL COLOR CAMERAS

 The necessity for stability assessment of consumer-grade digital color cameras as imaging devices is brought about by determination of the application possibility of color aerial images in correlation-extreme aircraft navigation systems. The paper presents the results of hypothesis experimental approval about small variability of obtained photos, depending on various camera models and the change in background conditions of the survey object. During the experiments, the photographing of the object is carried out under unchanged conditions by various cameras, and then by one camera, but with the use of various colored backgrounds. Analysis of the results showed that the differences in the color coordinates of compressed images produced by cameras of different models reach 70% that is unacceptable for application in algorithms of interest. The use of color correction in the graphic editor gives the possibility to reduce the spread to about 25% that is somewhat higher than the accepted maximum permissible level of image errors (<15-20%). In the case of "raw" data processing, the swing range is reduced to 15% that meets the criterion being advanced. The change in background conditions causes a small (8% in the worst case) additive error in determination of the color coordinates. According to experiment results, the transfer characteristics of the camera can be considered stable in time and from switching on to switching on. The results obtained make it possible to assert that the use of images in compressed formats may cause errors in the operation of the correlation-extreme aircraft navigation systems algorithms. The hypothesis that the distinction in the photographic images is small relative to the camera applied is recognized to be correct in case of the reception and subsequent processing of "raw" data, as well as the presence of at least one reference object with the color coordinates known in advance in the device field of view.

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