Optical picking-up device able to detect stable error signal

Abstract

An optical pickup device employing a signal detection unit including a hologram element having a plurality of pattern regions for diffracting and / or focusing light reflected and incident from a recording medium, a photodetector having a plurality of light receiving regions for receiving and photoelectrically converting the light diffracted by the hologram element and a signal operation unit for generating a focus error signal and / or a track error signal from a signal detected from the photodetector. The optical pickup device can implement a stable servo operation even at deviations of the photodetector, a change in the wavelength of light emitted from the light source, and / or shift of focusing means such as an objective lens, and can record and / or reproduce high-density information on / from the recording medium.

Description

technical field [0001] The present invention relates to an optical pick-up device, and more particularly, to an optical device for detecting a stable error signal by reducing the deviation of a focusing device, such as an objective lens, when it is subject to vibration, photodetector deviation and / or temperature changes. Pick up device. Background technique [0002] In a high-capacity recording and / or reproducing optical pickup device, in order to perform a stable servo function, it is necessary to detect a focus error signal and / or a tracking error signal. Generally, an optical pickup includes a light source; an objective lens for focusing a light beam emitted from the light source onto a recording plane of a disc; Signal detection part for information signal and error signal. [0003] In the case where the optical pickup device uses an astigmatism method to detect a focus error signal, the optical structure of the above-mentioned signal detection part is as follows: fig...

AI Technical Summary

Problems solved by technology

Thus, if chromatic aberration occurs on the focusing device, e.g. an optical element such as an objective lens (in most optical elements, an increase in wavelength causes a decrease in the index of refraction), focus errors can occur even in the "in focus" state Focus deviation that signals a value other than zero

[0013] In addition, if the objective lens is displaced from its original position due to tracking or disc eccentricity, the beam on the photodetector will be shifted

In this way, the push-pull signal is also biased by

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