Device for controlling the radiating output of a semiconductor laser

DETAILED DESCRIPTION It is an object of the present invention to provide a device for controlling the radiating output of a semiconductor laser, the device being of a reduced cost since it includes a photodetector of a relatively low response speed.
Another object of the present invention is to provide a device for controlling the radiating output of a semiconductor laser to reduce variations in the radiating output by failing to hold a drive current for the semiconductor laser continuously beyond a prescribed period of time.
Still another object of the present invention is to provide a device capable of accurately controlling the radiating output of a semiconductor laser.
According to the present invention, a device for controlling the radiating output of a semiconconductor laser includes a photodetector for detecting the radiating output of the semiconductor laser, a comparator for comparing an output signal from the photodetector with a reference signal, an up/down counter for counting clock signals in a count mode controlled by an output signal from the comparator, a digital-to-analog converter for converting a count output from the up/down counter into an analog signal, a semiconductor laser driver for supplying the semiconductor laser with a current proportional to the analog signal from the digital-to-analog converter, and means for controlling and holding the current supplied to the semiconductor laser to equalize the intut signals applied to the comparator.
The device may also include means for ceasing the holding of the current supplied to the semiconductor laser.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.