A "NO STRIPE" OPTICAL PAPER PATH SENSOR FOR TRANSPARENCIES AND PAPER
Original Publication Date: 1987-Feb-28
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Some copiedprinters use optical interrup sensors to detect the presence or absence of a sheet or transparency. Ordinarily, in the case of a transparency, a white stripe along a side of the transparency is sensed. This stripe is known to be an inconvenience to machine operators. Therefore, a device as shown in the Figure is disclosed which allows detection of transparencies which have no white stripe by the use of a reflective optocoupler type detector. The device consists of a light emitting diode (LED) and a Darlington photo detector (PD) mounted side-by-side in an injection molded package. Operation of the device is shown schematically in the Figure where light emitted from the LED is directed out away from the PD detector and in the absence of any refletive surface in front of the optocoupler gives no signal. As a reflecting surface is moved in front of the optocoupler, light from the LED is reflected into the PD and results in a photocurrent which is converted into a voltage by dropping across a resistor.