30 March, 1999LASER EXPOSURE
Laser Exposure Control
Data 255
Detailed
Descriptions
R, G, B, and CCD output
PMPMPM
Data 0Data 48Data 255
323232
242424
161616
888
24 6 8 PWM2 4 6 8 PWM24 6 8 PWM
256 gradations
A269D099.WMF
Two modulation systems are used to produce 256 gradations of printout from the
LD output. One is pulse width modulation (PWM) in which the ON time of the laser
diode is adjusted. The other is power modulation (PM) in which the luminous
intensity (brightness) of the laser beam is controlled.
To make the latent image, the laser beam illuminates the image area on the drum
surface. The longer the laser is on and the more intense it is, the darker the
developed pixel becomes. Modulating (changing) the width of the pulse makes the
length of time that the laser is on longer or shorter. There are eight possible 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 are 32 possible power levels, or laser intensity levels.
The laser engine can use the 8 pulse width levels and 32 power levels to create
the 256 possible grayscale values for each pixel for each color.
In the printer mode, the machine carries out 1,200 dpi compatible smoothing.
2-59 |
ACEC
RICOH
