The luminance of a laser diode is a function of laser diode drive current.
The luminance is also a function of other factors, such as age and
temperature. A laser projection device includes laser diodes to generate
light in response to a commanded luminance, and also includes photodiodes
to provide a measured luminance. The commanded luminance and measured
luminance are compared, and drive currents for the laser diodes are
adjusted to compensate for changes in laser diode characteristics.