| 摘要 |
A disk-shaped object detecting system detecting the presence or absence and position of a disk-shaped object such as semiconductor wafers or magnetic disks includes a light emitting element emitting light toward a circumferential edge of the object while being moved across the object, a light receiving element receiving the light reflected on the circumferential edge of the object while being moved across the object together with the light emitting element, delivering first and second light signals each according to the received light, the first and second light signals having a ratio depending upon at what position between opposite ends the light receiving element receives the light reflected on the circumferential edge of the object, the first and second signals having a magnitude relation which is reversed when the light reflected on the circumferential edge of the object has been moved from one end side to the other end side of the light receiving element, an AND processing section supplied with the first and second light signals delivered from the light receiving element and delivering either one of the light signals having a smaller magnitude than the other as an output thereof, and a determining section determining whether the output of the AND processing section has exceeded a predetermined level.
|
