| 摘要 |
PURPOSE:To remove probabilities of distortion of the plane half-mirror by arranging the system to accept the mirror of ample thickness. CONSTITUTION:The laser beam outputted from a laser source 1 passes through a diffraction grating 2, then reflects at a plane half mirror 3, and goes through a collimator lens 4 and an objective lens 5, and is made converge on an information recording carrier 6. The laser beam reflects from the carrier 6, becomes a reflected laser beam with modulated information, and returns as passing through the lens 5, the collimator lens 4, and the plane half mirror 3. Then, after undergoing a lens 7 and when reaching an optical detector 8, the beam is converted to an electrical signal. In this case, the laser beam lead to the detector 8, though associated with aberration due to passing the plane half mirror 3, does not require a high wave front accuracy being different from the laser beam spot converged on the information recording carrier 6. Therefore, the plane half mirror can be made to be of a thickness ample to endure the usage. |
