slotted optical switch
File:Mouse mechanism diagram.svg
{{about|the optoelectronic component|the optical component|Optical switch}}
The slotted optical switch, sometimes known as opto switch or optical switch but not to be confused with the optical component, is a device comprising a photoemitter (e.g. LED) and a photodetector (e.g. photodiode) mounted in a single package so that the photoemitter normally illuminates the photodetector, but an opaque object can be inserted in a slot between them so as to break the beam. Associated circuitry is provided which changes state when the beam is interrupted. For example, the carriage of a computer printer may be fitted with a projection which interrupts the beam of a slotted switch when it reaches the end of its travel, causing circuitry to react appropriately. Another application of the slotted switch is in the type of computer mouse with a rotating ball. The ball measures distances moved by rotating orthogonal shafts which drive optical chopper wheels turning in the slots of slotted switches.[https://books.google.com/books?id=Qq0CVfcAktUC&dq=mouse+opto+switch&pg=PA132 123 robotics experiments for the evil genius By Michael Predko, Myke Predko: description of wheeled mouse operation]
This device uses the same basic components as an opto-coupler, but is operated by manipulating the light path instead of the photoemitter input.
Illustrations and data on slotted optical switches are to be found in catalogues and manufacturers' data sheets.[http://www.optekinc.com/datasheets/opb610.pdf Datasheet of typical optical switch]