LASER EXPOSURE 1 August 1996
3.3 GRADATION CONTROL (LASER POWER MODULATION)
PM
(8 levels)
Data: 0Data: 3Data: 7Data: 11 Data: 15 Data: 3Da4 ta: 63
7
5
3
1
0
PWM07 112257
(8 levels1 do)t
A193D519.wmf
Black
White
63
A193d520.wmf
To make the latent image, the laser beam illuminates the image area of the
drum surface. The longer the laser is on and the stronger its intensity is, the
darker the developed pixel becomes. Modulating (changing) the width of the
pulse makes the on time of the laser longer or shorter (PWM). There are
eight pulse width levels in this model.
While the laser is on to make one dot, the intensity of the laser is controlled
by power modulation (PM). The laser?s intensity is controlled by the amount
of current sent to the laser diode. Modulating the power makes the laser
brighter or dimmer. There 8 power levels, or laser intensity levels. The power
is modulated only on the final part of the laser pulse (example: see data 11 in
the diagram).
The machine uses the 8 pulse width levels and 8 power levels to create the
64 possible grayscale values for each pixel.
2-20 |
ACEC
RICOH
