| 摘要 |
PURPOSE:To form an optical recording medium capable of widely setting the range of the light wavelength of a light source. CONSTITUTION:A mask layer reducing the effective diameter of a spot is made to exhibit a masking effect by decreasing a light transmissivity RL to the light near the longest wavelength lambdaL in a light wavelength range capable of forming a system and made not to exhibit a masking effect so much by increasing a light transmissivity RS to the light near the shortest wavelength lambdaS. Assuming that a straight line connecting the light transmissivity RS at the shortest wavelength lambdaS to the light transmissivity RL at the longest wavelength lambdaL is Y=aX+b, the curve of light transmissivity S in this range is made to become S<=aX+b. Consequently, in an intermediate wavelength region in the wavelength range capable of forming the system, a spot having larger spot diameter than that at the longest wavelength lambdaL is not appeared and stable signal reproduction is enabled by a reproducing device provided with a light source within this range. |
