| 摘要 |
PURPOSE:To select the spot diameter of laser beam according to recording density by constituting an objective lens with a focus variable liquid crystal lens and electrically controlling a focal distance of the objective lens according to recording density of an optical disk. CONSTITUTION:A liquid crystal lens 1 is constituted by arranging two spherical concave lenses 11a and 11b, facing each other, and filling the space between them with a liquid crystal 10 and further forming transparent electrodes 12a and 12b on the internal surfaces of lenses 11a and 11b. The twocolor dyestuff having anisotropy in absorbing visible radiation is dissolved in the liquid crystal 10, and by controlling application of voltages by adjusting a variable resistor 18, a focal distance and light quantity are adjusted. So, by controlling a focal distance of the lens 1 according to the recording density of an optical disk, the spot diameter is varied for accurate reproduction of information. |
