Shinya SAKAI
An Image Improvement Study of Test Pattern Chart Image under Ultra-low Luminance Photography
Atsushi RIKIMARU , Kazuyoshi TAKAHASHI
We assume that the access to the disaster area by methods of transport on land becomes impossible by the discontinuity of the road when a large-scale disaster such as earthquakes occurs. Therefore, it is extremely useful in prompt and certain information gatherings by a fire fighting disaster prevention helicopter. However, in the night, it is difficult to figure out disaster situation by the fire fighting disaster prevention helicopter because of the debasement of contrast, resolution, and signal to noise ratio. The visibility in the night was improved by using a black-and-white shading chart in last year's research. As a result, we understood that the frame accumulation was the most useful for the visibility improvement. And we kept the resolution constant and took the image last year.
In this study, we studied the relation between the resolution and the visibility, the limit illuminance of the visibility improvement, and the relation between accumulation and the visibility about ultra-low luminance photography using a test pattern chart image. The test pattern chart is a chart made in the image of road with centerline, outline and shape of building, and color. Using this chart, we can evaluate round properties without taking a picture in air. The distance between the chart and the camera was set to 4.3m, and the angle was fixed in each illuminance 1, 0.5, 0.1, 0.05, and 0.01lx. And mading the distance between the chart and the camera 6.5m, 8.6m, and 10.8m, we did the frame accumulation to the video camera image. Next, we did subject test to evaluate the visibility of the chart and calculated the visibility score to the original image and accumulation processing image. The visibility score is a value that adds the road, the white line, the structure, the circle, and the resolution chart in the bright image. As a result, we confirmed that the visibility improved when the resolution improved. Moreover, we confirmed that the illuminance the visibility did not improve was 0.01lx(video camera) when we did the frame accumulation. In addition, we confirmed that the effect of the frame accumulation went down under ultra-low luminance.
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