Olympus Optical Company, Ltd.

Hiroyuki Hagita

Kenichi Ito

Akihiko Hashimoto

Koji Maruyama

Kenji Ichimura

Satoru Kato

An apparatus for reading information out of an optical record medium including a semiconductor laser diode for emitting a laser beam, a collimator lens, a beam splitter, an objective lens, converging lens and a photodetector. The laser beam emitted from the laser diode is made incident upon the optical record medium via the collimator lens, beam splitter and objective lens, and a light flux reflected by the optical record medium is made incident upon the photodetector via the objective lens, beam splitter and converging lens. The laser diode and collimator lens are arranged such that the laser beam is projected upon the optical record medium in a de-focused condition, while the objective lens is in-focused on the optical record medium.

Optical record medium reading apparatus having a de-focussed light beam

A bivalent signal generating circuit in which an input signal having a substantial sinusoidal waveform can be converted to a bivalent signal without causing chattering: in this bivalent signal generating circuit, the bivalent signal is generated by comparing the input signal with a hysteresis width, and the circuit is arranged such that the hysteresis width is varied in accordance with a signal level of the input signal. Therefore, even if a noise is superimposed upon the input signal and thus the level of the input signal becomes large, it is possible to generate the bivalent signal in a correct and stable manner.

Sinusoidal-to-squarewave converter with variable thereshold level

The accessing apparatus, which is to be used for an optical information recording and reproducing apparatus, controls the speed of a light spot and accesses the light spot to an object track. The apparatus includes a speed instructing device for outputting a speed instructing signal instructing the moving speed of the light spot when accessing the light spot to the object track. A track error signal detecting device detects a track error signal showing a position difference between the light spot and the track. A speed detecting device detects a speed detecting signal showing the relative speed between the light spot and the track by using the track error signal. An operating device operates the speed error signal based on the speed instructing signal and speed detecting signal. A driving device moves the light spot for the track based on the speed error signal to access the light spot to the object track by controlling the speed of the light spot. A regulating device regulates the signal from the speed detecting device to the driving device so that the speed detecting signal exceeding a predetermined range may not be used for speed control of the light spot by the driving device.

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Hachioji, Japan

Hiroyuki Hagita