Patent ID: 6960771

Claim:
An optical measurement apparatus comprising: a photodetecting portion emitting photoelectrons that correspond to the amount of light in an incident light beam and outputting an output signal that corresponds to the number of the photoelectrons; a comparing portion comparing the output signal with a predetermined threshold value and outputting a comparison result signal when the output signal is greater than the threshold value, the comparing portion outputting no comparison result signal when the output signal is not greater than the threshold value; and a measuring portion performing measurement in accordance with the comparison result signal, wherein the threshold value is larger than an output signal that the photodetecting portion outputs when the photodetecting portion emits only one photoelectron, the threshold value being smaller than another output signal that the photodetecting portion outputs when the photodetecting portion emits two photoelectrons, whereby the measuring portion performs measurement when the photodetecting portion emits two or more photoelectrons, the measuring portion failing to perform measurement when the photodetecting portion emits only one photoelectron.