| 摘要 |
PURPOSE:To improve inspecting accuracy by providing a means and the like, which can always control a threshold value so as to follow an actual level. CONSTITUTION:A signal generating means 52 generates a third signal corresponding to the sum of a first signal A and a second signal B, a fourth signal of the difference and a fifth signal of the rate of the sum and the difference. An analog signal alpha corresponding to the fifth signal is outputted from a height operating circuit 51. An analog signal beta corresponding to the third signal is outputted from a brightness operating circuit 52. An averaging circuit 56a of a variable-threshold-value setting circuit 52 generates and outputs a signal SIGMAalphathrough an integrating circuit. A sample-and-hold circuit 56b samples the signal SIGMAalpha from the circuit 56 at the specified timing and holds the value SIGMAalphaH. An offset circuit 56c adds a specified offset value to the SIGMAalphaH and generates a variable threshold value SL10. An accurate binary-coded signal alpha without the effect of high-frequency noises can be formed based on the variable threshold value. Thus, the inspecting accuracy of wirings and patterns can be improved. |
