Optical disc apparatus

Abstract

A liquid crystal element control portion of an optical disc apparatus includes a memory for storing first information concerning a relationship between a drive voltage to be applied to a liquid crystal element when an optimal reproduced signal is obtained and ambient temperature of the liquid crystal element and second information concerning a relationship between a response time characteristic of the liquid crystal element and temperature, a drive voltage obtaining portion for measuring a response time of the liquid crystal element at a predetermined timing and obtaining a drive voltage to be applied to the liquid crystal element in which an influence of temperature variation is corrected based on the obtained response time and the first and the second information, and a liquid crystal element driving circuit for driving the liquid crystal element at the drive voltage obtained by the drive voltage obtaining 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 of the present invention.

FIG. 2 is a schematic diagram of an optical system of an optical pickup that is provided to an optical disc apparatus shown in FIG. 1.

FIGS. 3A and 3B are explanatory diagrams for describing a structure of the liquid crystal element that is provided to the optical disc apparatus shown in FIG. 1; FIG. 3A is a schematic cross sectional view thereof, and FIG. 3B is a plan view thereof.

FIG. 4 is a graph to show spherical aberration and a pattern of a phase difference that is generated in the liquid crystal element for correcting the spherical aberration.

FIG. 5 is a block diagram to show a structure of a liquid crystal element control portion of the optical disc apparatus shown in FIG. 1.

FIG. 6 is a diagram to show schematically a relationship between a phase variation that is generated in the liquid crystal element and time when a predetermined drive voltage is applied to the liquid crystal element.

FIG. 7 is a diagram to show a relationship between ambient temperature of the liquid crystal element and response time of the liquid crystal element.

FIG. 8 is a flowchart to show a control method of the drive voltage to be applied to the liquid crystal element performed by the liquid crystal element control portion of the optical disc apparatus shown in FIG. 1.

FIG. 9 is a block diagram to show a structure of an optical disc apparatus according to a second embodiment of the present invention.

FIG. 10 is a block diagram to show a relationship between drive current and light output power of a semiconductor laser at each temperature.

Claims

1. An optical disc apparatus comprising: an optical pickup including a light source, a light detecting portion for receiving a light beam so as to convert light information of the light beam into an electric signal, an optical system for condensing the light beam emitted from the light source onto a recording surface of an optical recording medium and leading reflection light reflected by the recording surface to the light detecting portion, and a liquid crystal element disposed in the optical system for correcting wave aberration;a liquid crystal element driving circuit for driving the liquid crystal element by applying a voltage to the liquid crystal element;a storage portion for storing in advance first information concerning a relationship between a drive voltage for driving the liquid crystal element in a case where an optimal reproduced signal is obtained by processing the electric signal converted in the light detecting portion and ambient temperature of the liquid crystal element, and second information concerning a relationship between the characteristics or a control value for controlling the characteristics and temperature of a temperature depending component whose characteristics have temperature dependency among components disposed in the apparatus; anda drive voltage obtaining portion for obtaining the characteristics or the control value of the temperature depending component at a predetermined timing, obtaining ambient temperature of the liquid crystal element from the obtained characteristics or the control value and the second information, and obtaining the drive voltage that is supplied to the liquid crystal element driving circuit by using the temperature and the first information.

2. The optical disc apparatus according to claim 1, wherein the temperature depending component is a member that is provided to the optical pickup.

3. The optical disc apparatus according to claim 2, wherein the temperature depending component is the liquid crystal element, the second information is information concerning a relationship between a response time that is a period of time from application of a predetermined drive voltage to the liquid crystal element until a value of a predetermined signal obtained from the electric signal converted by the light detecting portion becomes substantially constant and ambient temperature of the liquid crystal element, and the drive voltage obtaining portion measures the response time by applying the predetermined drive voltage to the liquid crystal element and obtains ambient temperature of the liquid crystal element by using the obtained response time and the second information.

4. The optical disc apparatus according to claim 2, wherein the temperature depending component is a semiconductor laser that is the light source, the second information is information concerning drive current when light output power of the semiconductor laser is a predetermined value and temperature, and the drive voltage obtaining portion obtains the drive current at the predetermined timing and obtains ambient temperature of the liquid crystal element by using the obtained drive current and the second information.