Abstract: An electrophotography machine is disclosed that consistently produces images of optimum image density regardless of whether an ordinary sheet of paper or a transparency is used as the recording medium. A photosensor activated in response to the recording media passing a first sensor is positioned on the paper conveyance path and detects whether or not the recording media being processed is an ordinary sheet of paper or a transparency. A controller automatically applies the appropriate transfer voltage depending on whether or not the sheet of recording media is a sheet of paper or a transparency. The special design used in this invention does not require photosensors to be placed on the photosensitive drum or near any of the image forming apparatus. Thus, the device consistently produces optimum images while being easy and inexpensive to make and manufacture.

Abstract: A paper sensor apparatus of a laser beam printer includes a LED located on the center of a substrate, obliquely positioned two-facet mirror for reflecting the light from the LED to both sides of the LED, photodiodes for receiving the light, and a paper presence detecting shutter and a paper feeding shutter located between the photodiodes and the obliquely positioned two-facet mirror, respectively for blocking or transmitting the light. Low production cost and an enhancement of productivity can be achieved because the structure of the paper presence detecting sensor and paper feeding sensor can be made cheaply and automatic assembly is possible.