Patent ID: 8289356

Claim:
A light output device comprising: an output section including a light source and configured to output light from the light source; a feedback-signal generating section configured to generate a feedback control signal to cause an output power of the light to be at a predetermined value and to supply the feedback control signal to the output section; a controller configured to generate a set signal that sets a reference voltage for determining the predetermined value in a case of power adjustment wherein in the case of power adjustment the output power is changed to a power different from a power in a case of power accuracy requirement and to control the output of the output section; a set-signal output port configured to output the generated set signal; a reference voltage generating section configured to receive the set signal from the set-signal output port and generate the reference voltage according to the set signal; and a detecting section configured to detect the reference voltage, wherein: the controller, in the case of power accuracy requirement, puts the set-signal output port in a high-impedance state, while the controller, in the case of power adjustment, generates the set signal using a predetermined voltage, the set signal alternating between a high level and a low level; the reference voltage generating section in the case of power accuracy requirement, generates the reference voltage on a basis of a level shift voltage generated by level shifting the predetermined voltage; and in a case of changing the output power from a power in the case of power accuracy requirement to a target power in the case of power adjustment, the controller changes a duty ratio of the set signal so that a detection value of the reference voltage by the detecting section is a target reference voltage corresponding to the target power.