Kyocera FS C5020N - Color LED Printer Service Manual page 165

A full color image is developed by recoating four colors on the primary transfer belt. If the density of each color is not kept
constant, the resultant color image will be deteriorated. The toner ID sensor mounted on the primary transfer belt to the
printer main unit side maintains the constant color fidelity.
The toner ID sensor includes a LED, deflection beam splitters of BS1 and BS2, photo diode PD2 and PD3 that scale toner
density, and associated components.
The deflection beam splitter 1 (BS1) splits the light from the LED to S wave and P wave. S wave oscillates vertically in ref-
erence to the entrance plane; whereas, P wave oscillates horizontally in reference to the entrance plane. S wave reaches
the photo diode (PD1) and acts to stabilize the luminosity of the LED by means of the feed back circuit. P wave is irradi-
ated to toner, then it produces scattered light wave S and reflection wave P which bounced on the primary transfer belt.
They reach the deflection beam splitter 2 (BS2) where they are distinguished as P wave and S wave, respectively, then
detected by photo diode 2 (PD2) and photo diode 3 (PD3).
Primary transfer belt
Toner ID sensor
Toner
PD3
Beam
spliter 2
PD2
(BS2)
Figure 2-1-31 Toner ID sensor
PD1
Beam
spliter 1
LED
(BS1)
2F3/2F4
2-1-23