Optical pickup device and optical disc apparatus having the same

Abstract

Optical pickup device equipped with liquid crystal diffraction element is provided with liquid crystal diffraction element control portion, which includes detecting portions for detecting light quantities of 0 order light and 1st order light from signal of photo detector for receiving the 0 order light and 1st order light generated by liquid crystal diffraction element, processing portion for determining light quantity ratio of 0 order light to 1st order light from light quantities obtained by detecting portions and for deciding whether or not difference between light quantity ratio and prescribed light quantity ratio is within predetermined range and for determining correction value of voltage to be applied to transparent electrodes if difference is not within predetermined range, and voltage control portion for controlling the voltage value to be applied to transparent electrodes based on process result of processing portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram to show a structure of an optical disc apparatus according to a first embodiment.

FIG. 2 is a schematic diagram for explaining a structure of a liquid crystal diffraction element of an optical pickup device that is provided to the optical disc apparatus according to the first embodiment.

FIGS. 3A and 3B are schematic diagrams for explaining an action of the liquid crystal diffraction element of the optical pickup device that is provided to the optical disc apparatus according to the first embodiment.

FIG. 4 is a block diagram to show a structure of a liquid crystal diffraction element control portion that is provided to the optical disc apparatus according to the first embodiment.

FIG. 5 is a flowchart to show a process of controlling a voltage to be applied to a transparent electrode performed by a liquid crystal diffraction element control portion that is provided to the optical disc apparatus according to the first embodiment.

FIG. 6 is a block diagram to show a structure of an optical pickup device according to a second embodiment.

FIG. 7 is a diagram to show a variation of the structure of a liquid crystal diffraction element of an optical pickup device that is provided to the optical disc apparatus according to the second embodiment.

FIG. 8 is a schematic diagram to show a structure of an optical system of a conventional optical pickup device.

FIG. 9 is a graph that shows a relationship between a voltage to be applied to the liquid crystal and its refractive index at each value of the temperature.

Claims

1. An optical pickup device comprising: at least one light source;a condensing element for condensing a light beam emitted from the light source on a recording surface of an optical recording medium;a liquid crystal diffraction element disposed between the condensing element and the light source for diffracting incident light beam to generate predetermined diffracted light, the liquid crystal diffraction element including liquid crystal and two transparent electrodes sandwiching the liquid crystal; anda photo detecting portion for receiving reflection light reflected by the optical recording medium, whereinthe photo detecting portion receives at least two types of diffracted light having different order numbers of the diffracted light generated by the liquid crystal diffraction element, anda liquid crystal diffraction element control portion is provided for controlling a voltage value to be applied to the transparent electrodes based on a light quantity ratio between the diffracted light having different order numbers obtained from an electric signal from the photo detecting portion.

2. The optical pickup device according to claim 1, wherein the photo detecting portion receives 0 order light and 1st order light generated by the liquid crystal diffraction element, andthe liquid crystal diffraction element control portion includes a 0 order light quantity detecting portion connected to the photo detecting portion for detecting light quantity of the 0 order light, a 1st order light quantity detecting portion connected to the photo detecting portion for detecting light quantity of the 1st order light, a processing portion for determining a light quantity ratio of the 0 order light to the 1st order light from light quantities obtained by the 0 order light quantity detecting portion and the 1st order light quantity detecting portion and for deciding whether or not a difference between the light quantity ratio and a prescribed light quantity ratio that is input as data in advance is within a predetermined range and for determining a correction value of a voltage to be applied to the transparent electrodes if the difference is not within the predetermined range, and a voltage control portion for controlling the voltage value to be applied to the transparent electrodes based on a process result of the processing portion.

3. The optical pickup device according to claim 2, wherein the 0 order light quantity detecting portion and the 1st order light quantity detecting portion detect the light quantities at an interval of a predetermined period of time.

4. An optical disc apparatus that is equipped with the optical pickup device according to claim 1.

5. The optical disc apparatus according to claim 4, wherein the liquid crystal diffraction element control portion calculates temperature of the liquid crystal diffraction element based on the light quantity ratio and transmits information of the temperature to at least one other control portion inside the device.

6. The optical disc apparatus according to claim 5, wherein the other control portion is a light source control portion for controlling an output power of the light source.

7. An optical disc apparatus equipped with the optical pickup device comprising: at least one light source;a condensing element for condensing a light beam emitted from the light source on a recording surface of an optical recording medium;a liquid crystal diffraction element disposed between the condensing element and the light source for diffracting incident light beam to generate predetermined diffracted light, the liquid crystal diffraction element including liquid crystal and two transparent electrodes sandwiching the liquid crystal; anda photo detecting portion for receiving reflection light reflected by the optical recording medium, whereinthe photo detecting portion receives 0 order light and 1st order light generated by the liquid crystal diffraction element, anda liquid crystal diffraction element control portion is provided, which includes a 0 order light quantity detecting portion connected to the photo detecting portion for detecting light quantity of the 0 order light, a 1st order light quantity detecting portion connected to the photo detecting portion for detecting light quantity of the 1st order light, a processing portion for determining a light quantity ratio of the 0 order light to the 1st order light from light quantities obtained by the 0 order light quantity detecting portion and the 1st order light quantity detecting portion and for deciding whether or not a difference between the light quantity ratio and a prescribed light quantity ratio that is input as data in advance is within a predetermined range and for determining a correction value of a voltage to be applied to the transparent electrodes if the difference is not within the predetermined range, and a voltage control portion for controlling the voltage value to be applied to the transparent electrodes based on a process result of the processing portion.