| 摘要 |
A radiographic printer has a laser diode light source which is directly modulated by an input image signal. The laser diode has two operating regions, a linear laser region and a non-linear low-level light emitting region. The laser diode is amplitude modulated in the lasing region and is pulse width modulated in the light emitting region. A programmable digital delay produces the pulse width modulating signal and a digital comparator determines whether the laser diode operates in the amplitude modulation mode or the pulse width modulation mode. A current steering circuit is used in the pulse width modulation mode to rapidly switch the diode on and off. In addition, programmable digital to analog converters are used to compensate for changes in different diode slope efficiencies and threshold currents.
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