| 摘要 |
PURPOSE:To correct the deterioration of a light source with age and to prevent the generation of any error in discrimination by converting the leak beam of a light source and the beam reflected irregularly from an object to be discriminated to quanties of electricity, determining the ratio between both with a calculator, and correcting the decrease in the irregularly reflected laser beam. CONSTITUTION:Part of a laser beam is transmitted through a mirror 2 of high reflectivity constituting a laser light source 1. The leak laser beam 11b is converted to quantity of electricity with a photoelectric transducer 8b and an output voltage aV is obtd. On the other hand, the laser beam 11a reflected irregularly by the ruggedness of a semiconductor wafer 9 is converted to quantity of electricity with a photoelectric transducer 8a, and an output voltage bV is obtd. Both are divided by a prescribed calcultor, whereby b/a= K is obtd. When the light source deteriorates with age, said output voltages decrease at the same ratio; therefore, if the output voltage of the irregularly reflected laser beam is corrected by determining said K value, the deterioration of the light source with age is corrected and the generation of any error in discrimination is prevented. |
