| 摘要 |
PURPOSE:To reproduce optically recorded information with a high SN ratio by setting up a semiconductor laser at a low reflection factor part of an optical recording medium to a natural radiation state, setting up the semiconductor laser at a high reflection factor part to a laser oscillation state and detecting the quantity of light in both the states by a photodetector. CONSTITUTION:Naturally radiated light 40 from the semiconductor laser 1 is radiated to the optical recording medium 4 having the high reflection factor part and the low reflection factor part, reflected light 41 from the medium 40 is made incident upon a light emitting layer of the laser 1, and when the medium 4 has a high reflection factor, the laser 1 is turned to the oscillation state by the reflected light to detect the existence of the laser oscillation state. Thus, an avalanche resonance state oscillating the semiconductor laser like avalanche on the basis of natural radiation beams radiated from the laser 1 and reflected by the part having the high reflection factor and the no-laser oscillation state of the semiconductor laser 1 based upon the reflected light from the part having the low reflection factor are detected. Since an area having large noise at a part near the oscillation threshold of the laser 1 is not used by using said method, the SN ratio and signal modulation can be improved. |
