Optical recording and reproducing apparatus having a pickup head including a main prism with reflecting surfaces for splitting the reflected beam

Claim 1

An optical recording and reproducing apparatus for optically recording information on and reproducing recorded information from a disk comprising: light source means for generating a beam of parallel rays; a movable optical system spaced from the light source means and comprising a stationary rail, a carriage radially movable along the rail relative to a disk, condensing means for condensing the beam of parallel rays from the light source means onto the disk, parallel ray forming means for forming light reflected from the disk into a beam of parallel rays, and splitting means for splitting the beam of parallel rays of light reflected from the disk into two different beams, the condensing means and the parallel ray forming means comprising an objective lens mounted on the carriage facing the disk for forming the beam of parallel rays, the splitting means comprising a prism having a beam splitting surface receiving the beam reflected from the disk, two reflecting surfaces for splitting that part of the beam reflected from the disk transmitted through the beam splitting surface into the two different beams, and a step disposed between and connecting the reflecting surfaces; split-beam detecting means spaced from the movable optical system and having two light sensing surfaces for receiving the two different beams from the movable optical system and for generating corresponding, respective output signals in response to receiving the two different beams; and control means for controlling tracking by moving the movable optical system in the radial direction relative to the disk in accordance with the respective output signals generated by the two light sensing surfaces.