| 摘要 |
<p>An error detecting device for an optical head detects a focussing error and a tracking error. The error detecting device comprises optical means for converting a reflected light of a light irradiating a surface to be irradiated into an astigmatic pencil of rays having a first focal point and a second focal point, said optical means having a first focussing member for focussing said reflected light on said first focal point of said astigmatic pencil of rays, and a second focussing member for focussing said reflected light on said second focal point of said astigmatic pencil of rays, said first and said second focussing members being made integral, and means for detecting errors of said light irradiating the surface to be irradiated, based on a detecting signal of a spot of said reflected light formed by said first focussing member, and a detecting signal of a spot of said reflected light formed by said second focussing member. The error detecting device can be small-sized and light, have a small astigmatic difference, and is easy to align optical elements.</p> |
