1. Field of the Invention
The present invention relates to a laser driving device (laser driving circuit) and an optical apparatus such as an optical disc apparatus using such a laser driving device (a recording apparatus using an optical disc).
2. Description of the Related Art
A recording/reproducing apparatus using a laser as an optical source has been used in various fields. For example, optical disc recording/reproducing apparatus (hereinafter, only referred to as an optical disc apparatus) has been attracting attention.
As a laser used as a light source, a semiconductor laser using a semiconductor material has been widely used for various kinds of devices in recent years. This is because it is very small and responses to driving current at high speed.
As a writable optical disc to be used as a medium for recording or reproducing data, a phase-change optical disc, a magnetic optical disc, and so on have been widely known in the art. These optical discs perform recording, reproducing, and erasing operations by changing the strength of irradiating laser beams. Usually, when recording information on an optical disc, a so-called optical strength modulation system that forms marks and spaces by a change in intensity of a laser beam. In the recording operation, the optical disc may receive the irradiation of a laser beam at a high peak intensity as much as 30 mW or more. In the reproducing operation, the optical disc may receive the irradiation of a laser beam at an intensity lower than that of the recording operation (e.g., 1 mW) to read the information without destroying recording marks.
Mark edge recording, which uses changes at both ends of a recording mark, has become mainstream because of superiority thereof for achieving higher density of a recent writable optical disk. In the mark edge recording, however, a data error may occur by distortion in the shape of the mark. As a technique for preventing data errors due to the mark shape distortion in the mark edge recording, a write strategy technique in which recording power is modulated into multi-leveled power by pulse division (see, for example, Japanese Published Patent Application No. 2007-141406 and “Industry-leading levels of low noise and high response: Clear a wall of achieving a technology of Blu-ray with 8× speed recording/reproduction”, CX-PAL Semiconductor & Component News No. 74 (October, 2007) published by Sony Corp. (URL:http://www.sony.co.jp/Products/SC-HP/cx pal/vol74/pdf/featuring2 bd.pdf)).