| 摘要 |
PURPOSE:To improve the focusing precision, by detecting sum S and difference D of integrated values of effective values of outputs of two image sensors, which detect focusing, to drive a servomotor for focusing adjustment so that D/A may be zero and by stopping driving the servomotor when S is a set value or less. CONSTITUTION:For example, in the focusing device for microscope, the image of sample 4 is focused onto A and A'. Image sensors 6a and 6b are arranged (l) back from the A point and (l') forward from the A' point, respectively. Outputs of sensors 6a and 6b pass through sample hold circuits 12a and 12b, BFFs 12a and 12b, effective value circuits 14a and 14b, and integral networks 15a and 15b, and sum S of integrated values is obtained by summing circuit 18, and ratios of respective integrated values to S are obtained by the dividing circuit, and difference of these ratios is input to differential amplifier 21, and servomotor 25 for focusing is so driven that the output may be zero. S is compared with the set value of reference voltage circuit 23 by comparing circuit 22, and switch 24 is turned off if S is smaller. As a result, the precision can be improved. |
