APPARATUS AND METHOD FOR CONTROLLING A LASER DIODE TO GENERATE A LINEAR ILLUMINATIVE OUTPUT

A controller for a laser diode causes the diode to generate an illuminative output which varies linearly in response to changes in image signals which range between minimum and maximum brightness levels. A switchover point between first and second modes of operation is selected to be above the knee region of the laser diode operating curve. If the input signal values are above the switchover point, diode illuminative output is a function of these signal values. However, if the input signal values are below the switchover point, then the input signals are modulated to switch the diode several times between an "on" state which is above the knee region and an "off" state, to form one picture element (pixel). In order to vary the illuminative output as a linear function of the change in image signal level, the diode "on" time during formation of one pixel is a function of the image signal value.