JP4266006B2 - Liquid crystal drive device and optical disk device - Google Patents

Description

  The present invention relates to a liquid crystal drive device and an optical disc apparatus for driving a liquid crystal panel for aberration correction, and more particularly to a liquid crystal drive device and an optical disc device for driving a liquid crystal panel for aberration correction by a PWM signal.

  When reproducing a high-density disc such as a DVD, since the margin of tilt of the disc surface with respect to the optical axis of the optical pickup, that is, the tilt angle margin is small, it is preferable that the playback device includes a control means for the tilt angle. A liquid crystal panel for aberration correction, which is divided into two shapes, is placed on the optical axis of the laser beam, and a technique to correct aberrations caused by the disc surface tilt and disc thickness using the liquid crystal panel is proposed. Has been.

  Further, as a liquid crystal driving device for driving the liquid crystal panel, based on a PWM signal generator that generates a PWM signal under the control of the control unit, a frequency divider that divides the PWM signal, and an output signal of the frequency divider, Switching means for switching and outputting an output signal of the PWM signal generator and a signal having an intermediate level of the amplitude of the output signal of the PWM signal generator is applied to the liquid crystal panel based on the output signal of the switching means. By generating a driving voltage, a driving amount that can be varied with a simple and inexpensive circuit and does not include a direct current component has been proposed (see, for example, Patent Document 1).

However, in the prior art, it is necessary to make the integral value of the positive voltage and the integral value of the negative voltage equal to the reference potential of the PWM signal applied to the liquid crystal panel so that a signal containing a DC component is not applied to the liquid crystal panel. Therefore, it is necessary to provide a frequency divider and switching means for periodically converting the PWM signal output from the PWM signal generator into a signal having a period of positive voltage and negative voltage, which increases costs. There was a problem that it was.
JP 10-334492 A

  The present invention has been made in view of such problems, and an object of the present invention is to provide a reference potential of a PWM signal applied to a liquid crystal panel without converting the PWM signal output from the PWM signal generator. Therefore, the integrated value of the positive voltage and the integrated value of the negative voltage can be made equal to each other, and an inexpensive liquid crystal driving device with a simple configuration is provided.

In order to solve the above problems, the present invention has the following configurations.
The liquid crystal driving device of the present invention is a liquid crystal driving device for driving a liquid crystal panel, wherein the PWM signal generating means outputs a PWM signal to one electrode of the liquid crystal panel, and the PWM signal generating means outputs the PWM signal. Control means for instructing a duty ratio of the PWM signal and applying a reference voltage to the other counter electrode of the liquid crystal panel, the control means having a duty ratio corresponding to a refractive index to be set in the liquid crystal panel And instructing the PWM signal generating means while inverting the determined duty ratio for each period, and the reference voltage applied to the other counter electrode of the liquid crystal panel is the same as the timing for inverting the duty ratio. Switching is performed at timing and in the same amplitude range as the PWM signal.

  The optical disk device of the present invention is an optical disk device having a liquid crystal panel for aberration correction arranged on the optical axis of a laser beam, and includes a tilt angle detecting means for detecting a tilt angle of the optical disk, PWM signal generating means for outputting a PWM signal to one electrode, and a duty ratio of the PWM signal to be output to the PWM signal generating means, and applying a reference voltage to the other counter electrode of the liquid crystal panel Control means, and the control means obtains a duty ratio corresponding to the refractive index to be set in the liquid crystal panel in order to correct the aberration caused by the tilt angle, and inverts the obtained duty ratio for each period. While instructing the PWM signal generating means, the reference voltage applied to the other counter electrode of the liquid crystal panel In the duty ratio the same timing as the timing of reversing the, and wherein the switching by the PWM signal and the same amplitude range.

  The liquid crystal drive device according to the present invention inverts the duty ratio of the PWM signal applied to one electrode of the liquid crystal panel for each period, and the timing to invert the reference voltage applied to the other counter electrode of the liquid crystal panel. The reference potential of the PWM signal applied to the liquid crystal panel without converting the PWM signal output from the PWM signal generator by calibrating to switch at the same timing and with the same amplitude range as the PWM signal The integrated value of the positive voltage and the integrated value of the negative voltage can be made equal to each other, and an inexpensive device can be provided with a simple configuration.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an embodiment of an optical disc device according to the present invention, FIG. 2 is a block diagram showing a configuration of a liquid crystal driving device shown in FIG. 1, and FIG. It is a waveform diagram showing the waveform of the drive voltage applied to the liquid crystal panel shown,

  The optical disk apparatus according to the present embodiment is an apparatus for reproducing information recorded on an optical disk such as a DVD and recording information on the optical disk 1, and referring to FIG. 1, a laser light source 2 that emits a laser beam, The half mirror 3, the liquid crystal panel 4 for aberration correction divided into a predetermined shape, the objective lens 5, the condenser lens 6, the light receiver 7, and the tilt sensor 8 that detects the tilt of the optical disk 1. And a difference detection unit 9 and a liquid crystal driving device 10.

  The laser beam emitted from the laser light source 2 is reflected by the half mirror 3, and the laser beam reflected by the half mirror 3 passes through the liquid crystal panel 4 and forms a beam spot on the optical disk 1 by the objective lens 5. The reflected light reflected from the optical disk 1 again passes through the objective lens 5, the liquid crystal panel 4, and the half mirror 3, and is collected on the light receiver 7 by the condenser lens 6.

  The tilt sensor 8 and the difference detection unit 9 function as tilt angle detection means for detecting the tilt of the disk surface of the optical disk 1 with respect to the optical axis, that is, the tilt angle, and the tilt sensor 8 is provided adjacent to the pickup. A light emitting unit and two light receiving units are provided, the reflected light of the light irradiated on the optical disc 1 is received by each light receiving unit, and the output of each light receiving unit is supplied to the difference detecting unit 9.

  Further, the difference detection unit 9 detects the difference between the outputs of the respective light receiving units supplied from the tilt sensor 8 and outputs the detection result to the liquid crystal driving device 10 as a tilt error signal.

  The liquid crystal driving device 10 is a means for setting the refractive index of the liquid crystal panel 4 in accordance with the tilt error signal input from the difference detection unit 9 and correcting the aberration caused by the tilt angle. Referring to FIG. A PWM signal generator 11 that outputs a PWM signal applied to one electrode 41 of the liquid crystal panel 4 and a duty ratio of the PWM signal output from the PWM signal generator 11 are indicated, and the liquid crystal of the liquid crystal panel 4 is sandwiched. The controller 12 applies a reference voltage to the counter electrode 42 at a position facing the electrode 41 to which the PWM signal is applied.

The PWM signal generator 11 generates a pulse having a duty ratio instructed by the controller 12 and outputs the generated pulse as a PWM signal. As shown in FIG. 3A, the PWM signal output from the PWM signal generation unit 11 has a cycle T ₀ , and the amplitude range is from a potential V ₀ to a potential V ₁ (V ₀ <V ₁ ). It has become.

The controller 12 obtains a duty ratio for generating a liquid crystal drive amount corresponding to the refractive index of the liquid crystal panel 4 to be set, and inverts the obtained duty ratio every n * period T ₀ (n is an integer equal to or greater than 1). The PWM signal generator 11 is instructed. That is, when the obtained duty ratio is 30%, an instruction of a duty ratio of 30% and an instruction of a duty ratio of 70% obtained by inverting the duty ratio are expressed as n * cycle T ₀ (n = 1 or more integer) Do this by inverting every time. When n = 5, a PWM signal whose duty ratio is inverted every 5 * cycle T ₀ is applied from the PWM signal generator 11 to the electrode 41 of the liquid crystal panel 4 as shown in FIG. Become.

Further, as shown in FIG. 3B, the controller 12 applies the reference voltage applied to the counter electrode 42 of the liquid crystal panel 4 every n * cycle T ₀ (n is an integer equal to or greater than 1). Are switched to the potential V ₀ and the potential V ₁ which are in the same amplitude range as the PWM signal output from the signal V. The potential switching timing by the controller 12 is performed at the same timing as the timing at which the duty ratio is inverted. When the obtained duty ratio is indicated, the potential V ₀ is indicated, and when the inverted duty ratio is indicated, A potential V ₁ is applied to the counter electrode 42 of the liquid crystal panel 4.

As a result, when the counter electrode 42 of the liquid crystal panel 4 is set to the reference potential, the liquid crystal panel 4 has a positive voltage (V ₁ ) period and a negative voltage (−V ₁ ) as shown in FIG. A voltage having a period T ₁ (2n * period T ₀ ) having a period is applied, and during the period of the positive voltage (V ₁ ), the PWM signal having the obtained duty ratio is a negative voltage (−V ₁ ). During this period, since the inverted PWM signal having the duty ratio is applied to the electrode 41 of the liquid crystal panel 4, the integral value of the positive voltage and the integral value of the negative voltage are equal.

  As described above, according to the present embodiment, the duty ratio of the PWM signal applied to one electrode 41 of the liquid crystal panel 4 is inverted every period and applied to the other counter electrode 42 of the liquid crystal panel 4. By calibrating the reference voltage so that it is switched at the same timing as the timing at which the duty ratio is inverted and at the same amplitude range as the PWM signal, the liquid crystal is output without converting the PWM signal output from the PWM signal generator. The integrated value of the positive voltage and the integrated value of the negative voltage with respect to the reference potential of the PWM signal applied to the panel can be made equal to each other, and it is possible to provide an inexpensive device with a simple configuration.

  It should be noted that the present invention is not limited to the above-described embodiments, and it is obvious that each embodiment can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

1 is a block diagram showing a configuration of an embodiment of an optical disc device according to the present invention. It is a block diagram which shows the structure of the liquid crystal drive device shown in FIG. It is a wave form diagram which shows the waveform of the drive voltage applied to the liquid crystal panel shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Laser light source 3 Half mirror 4 Liquid crystal panel 5 Objective lens 6 Condensing lens 7 Light receiver 8 Tilt sensor (tilt angle detection means)
9 Difference detector (tilt angle detector)
DESCRIPTION OF SYMBOLS 10 Liquid crystal drive device 11 PWM signal generation part (PWM signal generation means)
12 Controller (control means)

Claims (2)

A liquid crystal driving device for driving a liquid crystal panel,
PWM signal generating means for outputting a PWM signal to one electrode of the liquid crystal panel;
Instructing a duty ratio of the PWM signal to be output to the PWM signal generating means, and a control means for applying a reference voltage to the other counter electrode of the liquid crystal panel,
The control means obtains a duty ratio corresponding to the refractive index to be set in the liquid crystal panel, instructs the PWM signal generating means while inverting the obtained duty ratio for each period, and also opposes the other facing of the liquid crystal panel. A liquid crystal driving device, wherein the reference voltage applied to the electrode is switched at the same timing as the timing at which the duty ratio is inverted and at the same amplitude range as the PWM signal. An optical disk apparatus having a liquid crystal panel for aberration correction arranged on the optical axis of a laser beam,
A tilt angle detecting means for detecting a tilt angle of the optical disc;
PWM signal generating means for outputting a PWM signal to one electrode of the liquid crystal panel;
Instructing a duty ratio of the PWM signal to be output to the PWM signal generating means, and a control means for applying a reference voltage to the other counter electrode of the liquid crystal panel,
The control means obtains a duty ratio corresponding to the refractive index to be set in the liquid crystal panel in order to correct the aberration caused by the tilt angle, and inverts the obtained duty ratio for each period to the PWM signal generation means. The optical disc is characterized in that the reference voltage applied to the other counter electrode of the liquid crystal panel is switched at the same timing as the timing at which the duty ratio is inverted and at the same amplitude range as the PWM signal. apparatus.

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