KR19990048278A - Optical pickup with light shield - Google Patents

Abstract

The present disclosure relates to an optical pickup that configures a separate light shielding film for the optical pickup to correct a track signal. The apparatus of the present invention comprises a laser light source, an objective lens having a function of condensing the light emitted from the laser light source into an optimal light spot on the information recording surface of the optical recording medium, and information of the optical recording medium on which the optical spot is focused. Light detecting means for detecting light reflected from the recording surface and passing through the objective lens, and a light shielding film positioned between the objective lens and the light detecting means to shield a part of the light that is formed on the light detecting means, thereby controlling the amount of track signal detection light. It consists of. Accordingly, in the present invention, in the case of the defective optical pickup in which the track offset occurs, the track offset can be easily adjusted by adjusting the light shielding film, thereby lowering the defective rate of the optical pickup, and stabilizing the track signal of the optical pickup apparatus.

Description

Optical pickup with light shield

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for correcting a track signal, and more particularly, to an optical pickup for configuring a separate light shielding film in an optical pickup to correct a track signal.

In general, the most commonly used method of tracking the optical pickup is to use three beams (one main beam and two subbeams), which are tracked using two subbeams out of three beams divided by a grating.

1 is a view showing an optical pickup of the conventional three-beam usage. The optical pickup of FIG. 1 has a typical optical system structure, and the laser diode 1 emits laser light having a specific wavelength. The grating 2 emits the incident laser light into the splitter 3 in the form of three split beams. The light splitter 3 reflects three split beams and exits the reflector 4. The reflector 4 reflects three incident beams and outputs them to the objective lens 5. The objective lens 5 forms a light spot on the information recording surface of the disk 6. In addition, the light reflected from the disk 6 passes through the objective lens 5 again, passes through the reflecting mirror 4 and the light splitter 3, and then passes through and is condensed by the light receiving lens 7. The photodiode 8 detects the reflected light collected by the light receiving lens 7. The photodiode 8 is formed by condensing three beams.

FIG. 2 is a three-beam state diagram formed on the photodiode of FIG. 1, in which three beams are focused on the photodiode 8 of FIG. 1, where A represents a main beam reading a signal from an actual track, and B And C are the boost beams for tracking. Therefore, the tracking signal is obtained as the difference between the signals detected by the beams bound to B and C of the photodiode. The signals detected here are as shown in FIGS. 3 and 4.

FIG. 3 is a graph showing a signal detected by the photodiode B of FIG. 1, and FIG. 4 is a graph showing a signal detected by the photodiode C of FIG. 1. The signals of Figs. 3 and 4 each have a phase difference of 180 degrees with each other. The difference signal between these two signals is Fig. 5, and Fig. 5 is a graph showing the detected track error signal. That is, if the objective lens 5 continues to follow the desired track, this signal has only a direct current component, and if it crosses several tracks, it will have such an alternating signal. The center value of this AC signal represents the center of the desired track and should coincide with the circuit center (usually 0).

However, when the amount of light to be formed on the photodiodes 8, B and C is different from each other or is biased to one side as shown in Fig. 9, the offset of the track error signal occurs. As shown in the track error signal having the offset shown in FIG. 6, the center of the track signal detected by an error occurring during assembly and adjustment of various optical components in the optical pickup does not coincide with the circuit center.

However, in the above characteristics adjustment, when the signal is generated based on the actual physical center position, it is possible to adjust the circuit and if the signal itself has a certain amount (if offset occurs), the playback signal is very deteriorated. There was a problem that adversely affects performance.

Accordingly, an object of the present invention is to provide an optical pickup having a light shielding film which can improve the offset of an optically generated track error signal in a track signal so as to solve the above problems.

1 is a view showing an optical pickup of the conventional three-beam usage;

2 is a three-beam state diagram formed on the photodiode of FIG.

3 is a graph showing a signal detected by the photodiode B of FIG.

4 is a graph showing a signal detected by the photodiode C of FIG.

5 is a graph showing a detected track error signal;

FIG. 6 is a graph showing a track error signal in which an offset occurs (offset: hereinafter referred to as an offset);

7 is an optical pickup having a light shielding film according to an embodiment of the present invention;

8 is an optical pickup having a light shielding film according to another embodiment of the present invention;

9 is a state in which three beams formed on the photodiode are biased to one side;

10 is a configuration diagram illustrating an example of a light shielding film;

11 is a state diagram of shielding incident light formed on the photodiode B portion;

Fig. 12 is a state diagram in which incident light formed on the photodiode C portion is shielded;

※ Explanation of code for main part of drawing

71: laser diode 72: grating

73: light splitter 74: reflector

75, 83: objective lens 76, 84: disk

77: light receiving lens 78, 82: light shielding film

79: photodiode 81: hologram module

The optical pickup having the light shielding film according to the present invention for achieving the above object has a function of condensing the laser light source and the light emitted from the laser light source into an optimal light spot on the information recording surface of the optical recording medium. Optical detection means for detecting the light reflected from the information recording surface of the optical recording medium on which the optical spot is collected and the light spot has passed through the objective lens, and between the objective lens and the optical detection means and formed on the optical detection means And a light shielding film that shields a part and adjusts the amount of light of the track signal detection light.

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

7 is an optical pickup having a light shielding film according to an embodiment of the present invention. As shown, the laser light emitted from the laser diode 71 in the apparatus of FIG. 7 is connected to be incident to the light splitter 73 through the grating 72, the light splitter 73 is the incident light is reflected mirror 74 Connected to reflect from. The light reflected by the reflector 74 is configured to form an optical spot on the information recording surface of the disk 76 via the objective lens 75. In addition, the photodiode 79 detects the light reflected from the information recording surface of the disk 76, and is condensed by the light receiving lens 77 and the light receiving lens 77 to condense the reflected light prior to the photodiode 79. And a light shielding film 78 for adjusting the amount of track signal detection light.

7 illustrates a case where the laser diode 71 is used as a light source, and the light emitted from the laser diode 71 is incident on the grating 72. The grating 72 diffracts the incident light into three beams and exits the beam splitter 73. The light splitter 73 reflects the diffracted light and exits the reflector 74. The objective lens 75 receives the reflected light reflected from the reflector 74 to form a light spot on the information surface of the disk 76. The light reflected from the information recording surface of the disk 76 passes through the objective lens 75 and the reflecting mirror 74 and then enters the light splitter 73. The light splitter 73 transmits approximately 50% of this light, and the transmitted light is condensed on the photodiode 79 by the light receiving lens 77. Here, a light shielding film 78 for adjusting the amount of track signal detection light is configured just before the light collecting of the photodiode 79. A detailed description of the light shielding film 78 will be described below with reference to the accompanying drawings.

8 is an optical pickup having a light shielding film according to another embodiment of the present invention. As shown, FIG. 8 shows a typical optical pickup device and is configured to use a hologram module 81 in which a laser diode and a photo diode are integrated as a light source. Here, the light shielding film 82 is configured to be located in front of the hologram module 81.

8 shows a case where a hologram module is used, the laser light from the laser diode of the hologram module 81 forms an optical spot on the disk 84 through the objective lens 83. The light reflected from the disk 84 passes through the objective lens 83 and focuses on the photodiode in the hologram module 81, where the light shielding film 82 adjusts the amount of track signal detection light immediately before the photodiode. As a result, the degree of shielding of light incident on the photodiode is controlled. Likewise, a detailed description of the light shielding film 82 will be described below with reference to the accompanying drawings. Since the optical pickup optical system of FIG. 8 will be well understood by those skilled in the art based on the description related to FIG.

The light shielding films 78 and 82 used in the example of the optical pickup of FIGS. 7 and 8 will be described in more detail with reference to FIGS. 10, 11 and 12.

FIG. 10 is a block diagram showing an example of a light shielding film, and is composed of a light shielding area and a light transmitting area, as shown in the figure, and has a shape having an arbitrary shape such as a circle, an ellipse, a rectangle, a rectangle, and the like. In addition, the light shielding films 78 and 82 are positioned in front of the photodiodes of the optical pickup as shown in FIGS. 7 and 8, and move in a direction perpendicular to the photodiodes B and C to adjust the amount of light incident on the B and C. That is, FIG. 11 is a state diagram of shielding incident light formed on the photodiode B, which moves in a direction perpendicular to the B and C (arrows) to shield only a part of the light going to the photodiode B to increase the detection signal at C. Can be. 12 is a state diagram in which incident light formed on the photodiode C portion is shielded, and only a portion of the light moving to the photodiode C by moving in the vertical direction (arrow notation) can be shielded to increase the detection signal at B. FIG. Accordingly, the offset of the track error signal can be prevented by adjusting the amount of incident light using the light shielding film.

As described above, in the present invention, in the case of a bad optical pickup in which a track offset occurs, the track offset can be easily adjusted by adjusting the light shielding film, thereby lowering the defective rate of the optical pickup, and stabilizing the track signal of the optical pickup apparatus. have.

Claims (6)

In the optical pickup for recording / reproduction of the optical recording medium, Laser light source; An objective lens having a function of condensing the light emitted from the laser light source into an optimal light spot on the information recording surface of the optical recording medium; Light detecting means for detecting light that has passed through the objective lens after being reflected from the information recording surface of the optical recording medium on which the light spot is focused; And And a light shielding film positioned between the objective lens and the light detecting means to shield a part of the light that is formed on the light detecting means to control the amount of light of the track signal detection light. The method of claim 1, wherein the light shielding film An optical pickup having a light shielding film, characterized in that the light shielding area and the light transmitting area. The method of claim 1, wherein the light shielding film The optical pickup having a light shielding film, characterized in that configured to be able to adjust the shielding degree of light by moving its position. The method of claim 1, wherein the light shielding film An optical pickup having a light shielding film having a structure for shielding a part of light in an arbitrary shape such as a circle, an ellipse, a rectangle, a rectangle, and the like. The optical pickup according to claim 1, further comprising an optical pickup comprising a hologram module in which the laser light source and the light detecting means are integrated. [2] The optical detection apparatus of claim 1, further comprising an optical pickup using a photodiode which detects two sub-beam signals that are collected by concentrating one main beam and two sub-beams as the light detecting means and calculates a track error signal. Optical pickup having a light shielding film.