| 摘要 |
PURPOSE:To enable the deterioration in a gap unit to be automatically detected by a method wherein the operation time of the gap unit is compared with the previously specified reference time. CONSTITUTION:A gap unit 1a starts the gap adjustment when the operation start signal is transmitted from a controller 2 to the gap unit 1a. When the gap between a specimen and a photomask reach the specified value, the gap adjustment is stopped. During the gap adjustment process, signals are transmitted to a deterioration prediction device 3 to be outputted to a timer circuit 43 from a photocoupler 41 through IC 42a, 42b. The timer circuit 43 starts operation to output signals for actuating an alarm part 3c after the lapse of the reference time but when a reset signal is inputted within the reference time limit, no signal is outputted for the circuit 43 to be reset to the stand-by state. When a signal is inputted to the alarm part 3c, a relay thereof is actuated to sound a buzzer for informing an operator of the deterioration in the gap unit 1a. In conformity to this alarm, the gap unit 1a shall be adjusted or replaced with a new one. |
