| 摘要 |
PROBLEM TO BE SOLVED: To set contrast in a desired value in a short time. SOLUTION: Multiplication voltages to be impressed from a power source 10 are defined as 1V, 2V, and contrast values C1 and C2 at this time are respectively detected by a contrast value detecting circuit 15. These contrast values C1 and C2 are supplied to an operation circuit 18, and the following operation is performed. [α=ln(C1/C2)/ln(V1/V2)]. In actual automatic contrast adjusting operation, a preset value calculating circuit 16 performs operation on voltage necessary to make contrast coincide with a desired value by a supplied contrast value, photoelectron multiplying voltage impressed on a photomultiplier 8 from the power source 10 and anαvalue from operation circuit 18.
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