| 摘要 |
PURPOSE:To simplify the production of a lens by constituting a projection optical system of the first means which converts the divergent light from a light source to parallel rays of light and the second means which allows parallel rays of light to emit from a substrate and condenses them. CONSTITUTION:A micro-lens like a micro-Fresnel lens 2 is formed on a part of the upper face of a substrate 1, and another micro-lens 3 is formed on a position facing the lens 2 on the lower face of the substrate 1. A holder 5 is attached and fixed to the lower face of the substrate 1, and a light source like a semiconductor laser 4 is arranged and fixed on this holder 5. The light emitted from the semiconductor laser 4 goes toward the lens 3 while diverging and is converted to parallel rays of light by the lens 3. Parallel rays of light go in the substrate 1 and are emitted to the air through the lens 2 and are condensed by the lens 2 to form a minute spot (about 1mum diameter). Arrangement relations between an optical disk 20 and the substrate 1 are so determined that this spot is placed just on a pit 24 of the optical disk. |
