| 摘要 |
PURPOSE:To perform focusing while an objective is fixed by feeding a detection signal from a focusing detecting means back to piezo-elements which vary the curvature of a variable curvature mirror. CONSTITUTION:Laser light from a laser 13 forms an image on a recording medium 18 through optical systems 14-17. A light beam from a light source 20 is collimated by a lens 20 to converge to the medium through a lens 17, and its reflected light is made incident to a position sensor 25 such as CCD through the lens 17 again, generating a signal corresponding to a focusing state. The variable curvature mirror 16 has a couple of piezo-elements 19a and 19b on its reverse surface, and when a voltage V corresponding to the detection signal from a sensor 25 is applied, the piezo-elements contract to vary the curvature of the mirror 16. Thus, the focusing is performed while the objective 17 is fixed. |
