1. Field of the Invention
The present invention relates to an optical recording/reproducing apparatus and, more particularly, to a pulse width control apparatus which controls the pulse width of a recording light beam for an optical disk with high accuracy.
2. Description of the Related Art
As is well known, in an optical recording/reproducing apparatus, e.g., an optical disk apparatus, an optical pulse string having a specific time interval is irradiated on an optical disk to record data on the optical disk. The width of the optical pulse is controlled to an accuracy of several nsec in accordance with the characteristics of the optical disk and a recording radial position on the optical disk.
A conventional device controls an optical pulse using a CR time constant or using a delay line. In addition, a highly accurate scheme that counts high-frequency reference clocks or the like is known.
However, neither the scheme using a CR time constant nor the scheme using a delay layer can easily realize an accuracy of several nsec without any adjustment, and respective units must be adjusted. For this reason, in mass production, the cost of the adjustment increases the cost of an optical disk apparatus.
Because the scheme for counting reference clocks requires a high frequency (several hundred MHz) corresponding to the fine adjustment width of the optical pulse, a high-speed logic circuit is required. As a result, a countermeasure for removing noise generated by complicated wiring of high-frequency logic lines is also required. The design for the high-speed logic circuit, the countermeasure against noise, and the like increase the cost of the apparatus.