D

2R sin v

x

tg AS/2

Solution of Eq. (27) yields Aft ft ft, with which the diameter

Ada Rx Aft 28

is obtained.

Pixel Value Correction

Because of the quadratic dependency between the brightness and the surface of the exposed area, the pixel value correction is obtained by multiplying the image pixel value by the square of the area enlargement rate. Its value is close to 1 in the image center. Therefore, the brightness of the central part remains unchanged. The increase of the area enlargement rate toward the periphery yields the brightening of this area. This results in improvement of the uniformity of the intensity throughout the entire image (Fig. 14).

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