KR100657695B1 - Method and apparatus for controlling reference beam servo in holographic rom disk - Google Patents

Abstract

The present invention is to control the reference light using the optical axis error signal of the detected reference light by further drilling two additional holes at the same distance from the center of the slit having three holes for passing only a specific track of the reproduced beam. For this purpose, the first process of generating a reference light from the light source and injecting it into the optical disk, and a plurality of track images reproduced on the optical disk by the reference light are 2 at the same distance from the center of the slit having the optical lens and three holes. And a second process of focusing on the PDIC by passing through the slit surface through two more holes. Therefore, a high level RF signal can be obtained and the linear section slope of the tracking error signal is increased, so that the servo accuracy at the time of tracking servo is also increased.

Description

Servo control method and apparatus thereof for holographic ROM disks TECHNICAL FIELD & APPARATUS FOR CONTROLLING REFERENCE BEAM SERVO IN HOLOGRAPHIC ROM DISK}

1 is a configuration diagram for a track servo of a conventional holographic ROM disk,

2 is a diagram illustrating a data recording / reproducing pattern of a conventional holographic ROM disc.

3 is a graph illustrating a measurement of intensity of track light reproduced according to an optical axis when a conventional holographic ROM disc is reproduced.

4 is a graph of tracking error signal intensity measurement in each track corresponding to the light intensity of a track reproduced during a conventional holographic ROM disc playback;

5 is an exemplary diagram of tracking error signal intensity change according to an optical axis when a conventional holographic ROM disc is played.

6 is a configuration diagram for a reference light servo control apparatus of a holographic ROM disk according to the present invention;

FIG. 7 is a view of a slit surface manufactured by further drilling two additional holes A and B at the same distance from the center of a slit having three holes E and RF F according to the present invention.

FIG. 8 is a view illustrating a case where the data pattern according to the present invention is on and off.

FIG. 9 is a diagram showing the intensity of reproduction light in which a track image reproduced from the optical disc shown in FIG. 8 has a Gaussian shape, such as a beam shape of reference light.

FIG. 10 shows an additional drilled hole 2 of the slits made by drilling two additional holes A and B at the same distance from the center of the slit having three holes E and RF shown in FIG. 7. Slit (A) holes and slit (B) holes are shown to be located so as to detect the light between the track in the playback track image,

FIG. 11 is a diagram illustrating a case where light through two slit (A) holes and a slit (B) hole is normal.

12 is a view showing that the track is reproduced at a position away from the center of the reference light so that the intensity of light passing through the three holes is lowered.

FIG. 13 is a diagram illustrating a case in which a track being tracked due to eccentricity moves to the left side of the optical axis for the same reason as in FIG. 12.

FIG. 14 is a view showing that the intensity of light passing through the slit (A) hole decreases and that of the light passing through the slit (B) hole increases compared with FIG. 11.

FIG. 15 is a diagram illustrating a normal position by controlling a reference light using a reference light error signal according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: optical disk 101: spindle motor

102: objective lens 105: optical lens

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106: slit 107: optical lens

108: focusing lens 109: PDIC

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112: reflection mirror 113: reducer

114: epitaxial 115: light source

116: amplifying unit 117: reference light servo controller

118: microcomputer 119: tracking servo controller

120: spindle controller

The present invention relates to a method for controlling a reference light servo of a holographic ROM disk, and a device thereof, and more specifically, to two reference holes by additionally drilling a slit surface for passing only a specific track of a reproduced beam. A method and apparatus for controlling reference light using an optical axis error signal of light.

As is well known, as the information industry develops, there is a demand for a larger capacity of a device for storing information and a higher processing speed. As a result, holographic ROMs, which are widely used for recording and reproducing holographic digital data, can store a large amount of information on one bit of optical discs such as CDs and DVDs. fast. Because of these advantages, holographic ROMs are in the spotlight as the next generation of mass information storage.

On the other hand, the servo operation in the holographic ROM player is different from an optical disc reproducing apparatus such as a general CD or DVD. In other words, the optical disk reproducing apparatus focuses the light to have a track size and detects the light reflected from the data pit. Therefore, the tracking servo adjusts the position of the light in the radial direction so that the focused light is accurately positioned in the data track, and the focus servo is the focus position of the light so that the reflecting surface of the disk is exactly at the focus of the light. To adjust in the optical axis direction.

However, in the holographic ROM player, the reference light is irradiated to the optical disk, and since the reference light is much larger than the data track size, it is not necessary to accurately position the light in the radial direction. That is, even if some radial run-out occurs in the rotation of the optical disc, the track to be played back is in the reference light so that a tracking servo such as an optical disc reproducing apparatus is not necessary. In addition, a large diameter light has a large depth of focus (for example, a light having a diameter of 100 μm has a depth of focus of about 4.7 mm). Since it is located within the depth of focus range of the reference light, a focus servo such as an optical disk reproducing apparatus is not necessary.

Therefore, the tracking and focus servo operation in the holographic ROM player allows the light emitted from the data pit of the optical disc to pass through the pinhole of the slit, unlike the optical disc player. Since the pinhole size has a track pitch size, the light reproduced from the data pit of a specific track is precisely drawn into the pinhole of the slit by run-out in the radial direction or the optical axis direction generated as the optical disk rotates. It's hard to come. Therefore, it is the servo operation in the holographic ROM regenerator that detects light passing through the pinhole and adjusts the light to pass correctly into the pinhole according to the detected data.

1 is a block diagram of a track servo of a conventional holographic ROM disk. Referring to FIG. 1, a green laser light source having a wavelength of 532 nm includes a light source 200 for generating laser light required for the optical disc 1, and light generated from the light source 200 to reflect the optical disc 1. Through the signal processing using the reflection mirror 206 to be incident at a predetermined angle and the reproduction signal light transmitted through the central pinhole RF of the slit 210 in the light reproduced from the optical disk 1 to the actual data. Control the conversion and track error using the reproduction signal light provided from the PDIC 214 to drive the tracking servo using the reproduction signal light transmitted through the left pinhole F and the right pinhole E of the slit 210. That is, the track servo control unit 216 controls the objective lens 208 to detect whether a track mismatch occurs and to accurately match the track error detected portion.

Here, the light source 200 and the reflection mirror 206 includes a reducer 202 for deforming the light, and an aperture 204 for irradiating the reflection mirror 206 with the light passing through the reducer 202 through the opening. An objective lens 208 is included between the optical disk 1 and the slit 210 to transmit the light reproduced from the optical disk, and a central pinhole of the slit 210 is provided between the slit 210 and the PDIC 214. And an optical lens 212 that transmits the reproduction signal light transmitted through the RF and the reproduction signal light transmitted through the left pinhole F and the right pinhole E of the slit 210. You can play the track data stored in the holographic ROM disk using.

(A), (b) and (c) of FIG. 2 show data recording / reproducing patterns of a conventional holographic ROM disk. As shown in FIG. Data is recorded in the same track form. At this time, when the reference light is irradiated to a part of the recorded interference pattern, the track pattern data pattern is reproduced from the interference pattern recorded by the reference light as shown in FIG. Thus, in order to obtain only one track information, three holes are drilled in the slit so that only the desired track is formed in the PDIC (photo detect IC).

In this case, the laser used as the reference light beam has a gaussian shape in which the shape of the beam cannot ideally become a plat-top shape, and the intensity of the beam becomes weaker as the center of the beam is the strongest and out of the center. It has a shape.

Since the track image reproduced by the Gaussian beam shape is also Gaussian, the intensity of the track image changes during the tracking servo. Therefore, the intensity of the tracking error signal required for the servo control is also changed to improve the servo control performance. There is a drawback to deterioration.

FIG. 3 is a graph showing a light intensity of a track pattern reproduced by a conventional holographic ROM disc using PDIC, and data of several tracks are reproduced by one reference light and reproduced in the same shape as the reference light. It can be seen that the intensity of the light of the track is reproduced at the highest value in the center of the reproduction light, and the intensity of the beam of the track that is reproduced gradually decreases from the center of the reference light to the outer edge.

As the intensity of the reproduction beam of the data track changes according to the shape of the beam of the reference light, the track error signal also changes. This is seen in the experimental results shown in FIG.

That is, FIG. 4 is a graph of a tracking error signal intensity measurement graph for each track corresponding to the light intensity of a track reproduced when a conventional holographic ROM disc is reproduced. As the intensity of the reproduction light of the data track is changed by the shape of the beam of the reference light, Servo control performance is reduced.

In other words, the track servo of the holographic ROM disk generates a control signal based on the track error signal in each track shown in FIG. 4, but in the case of a rotating holographic ROM disk, the track servo is similar to an existing optical disk. The track image reproduced by the disturbance condition such as eccentricity in the direction moves inside the reference light, so that the track error signal continues to change.

For example, as shown in FIG. 5, if the position of the track reproduced by the reference light is located at the center of the reference light, a track error signal of 10 is generated for a track deviation of 10 μm, but the position of the playback track is If off center, a track error signal of 8 is generated for a track deviation of 10 μm.

This causes a problem that the performance of the track servo control is degraded because another error signal is generated despite the physical deviation of the same track.

Accordingly, the present invention has been made to solve the above problems, the object of which is to drill two additional holes at the same distance from the center of the slit having three holes for passing only a specific track of the reproduced beam The present invention provides a method and apparatus for controlling a reference light servo of a holographic ROM disk capable of controlling the reference light by using an optical axis error signal of the detected reference light.

According to an aspect of the present invention, there is provided a method of controlling a reference light servo of a holographic ROM disk, the method including generating a reference light from a light source and injecting the light into an optical disk. And a second process in which the track image passes through a slit surface that drills two more holes at the same distance from the center of the optical lens and the slit having three holes, and focuses on the PDIC.

Further, in order to achieve the above object, a light source according to another aspect of the present invention generates a reference light and enters the optical disk, and a plurality of track images are reproduced from the optical disk by the reference light to reproduce the objective lens, the optical lens, and the slit. In the holographic ROM system for passing the surface to focus on the PDIC, the slit surface is characterized in that two holes are drilled at the same distance from the center of the slit having three holes.

Hereinafter, a plurality of embodiments of the present invention may exist, and a preferred embodiment will be described in detail with reference to the accompanying drawings. Those skilled in the art will appreciate the objects, features and advantages of the present invention through this embodiment.

6 is a configuration diagram for a reference light servo control apparatus of a holographic ROM disk according to the present invention. Referring to FIG. 6, the light source 115 (the vertical P polarization due to the green laser light characteristic) generates a reference light, which is a green laser light source having a wavelength of 532 nm, and passes through the reducer 113 and the epitaxial 114 to the reflective mirror ( When provided to 112, this reference light is reflected at a predetermined angle by the reflecting mirror 112 and is incident on the optical disk 100.

Then, an image of several tracks reproduced on the optical disc 100 by the reference light is made by drilling two additional holes at the same distance from the center of the objective lens 102 and the optical lens 105 and the slit having three holes. After passing through the slit 106 and focusing on the PDIC 109 via the optical lens 107 and the focusing lens 108, it is used for tracking and obtaining servo and data of the reference light.

That is, the light passing through the surface of the slit 106 is the E and F signals for generating the RF signal and the error signal for the tracking servo by the PDIC 109, and the PD-A and PD for measuring the optical axis deviation of the reproduction light. It is provided to the amplifier 116 as a -B signal. The amplifier 116 provides the signals of the E and F cells and the PD-A and PD-B signals to the tracking servo controller 119 and the reference light servo controller 117, respectively.

Then, the tracking servo controller 119 generates a tracking error using the signals of the E and F cells, and drives the objective lens 102 using this tracking error signal. Similarly, the reference light servo controller 117 receives the signals of the PD-A and PD-B cells from the amplifier 116, and then applies the signals to Equations 1 and 2 to generate a reference light error signal. In addition, the light source 115 is controlled based on the generated reference light error signal to change the position of the reference light. Here, the microcomputer 118 drives the spindle controller 120 to control the rotation of the spindle motor 101 so that the data can be stably reproduced from the optical disk 100.

Meanwhile, referring to FIG. 6, the slits 106 plane described above has the same distance from the center of the slit having three holes E (RF) F as shown in FIG. 7. Two additional holes (A) and (B) are drilled to detect off-center deviation of the regenerated light.

In this case, in order to apply the slit surface 106 having five holes shown in FIG. 7, the optical disk 100 in which the data pattern is recorded in an off form is used. Next, FIG. 8 is a diagram illustrating a case where the data pattern is On and Off, and FIG. 8A illustrates a case where the data pattern is On (that is, the track is On), and FIG. 8b. Denotes a case where the data pattern is off (that is, the track is off). That is, as shown in FIG. 8B, the track image reproduced from the optical disc 100 has a Gaussian shape like the beam shape of the reference light.

Next, FIG. 9 illustrates the intensity of the reproduced light in which the track image reproduced from the optical disc 100 shown in FIG. 8 has a Gaussian shape like the beam shape of the reference light. It can be seen that the more away from the center of the light is reduced.

FIG. 10 is an additional slit 106 made by further drilling two additional holes A and B at the same distance from the center of the slit having three holes E and RF F shown in FIG. It can be seen that the two more slit (A) holes and the slit (B) holes are positioned to detect light between the tracks in the reproduction track image.

Accordingly, the intensity of light through the two slit (A) holes and the slit (B) hole is the same, as shown in FIG.

On the other hand, if the track to be tracked by the eccentricity of the optical disk 100 is out of the center of the reference light, the tracking servo is performed to move the objective lens 102, thereby compensating for the movement of the track so that the three holes located at the center of the slit are moved. Although it is possible to prevent the deviation, although the desired track is always located in three holes by the tracking servo, since the track is played at a position outside the center of the reference light, the intensity of light passing through the three holes is lowered as shown in FIG. That is, as compared with FIG. 11, it can be seen that the intensity of light passing through the slit A hole increases and the intensity of light passing through the slit B hole decreases. Here, FIG. 13 is a diagram illustrating a case in which a track being tracked due to eccentricity moves to the left side of the optical axis for the same reason as in FIG. 12.

14, the intensity of light passing through the slit A hole decreases and the intensity of light passing through the slit B hole increases as compared with FIG. 11.

Therefore, by having the above characteristics, the deviation of the center of the reference light relative to the track tracked while the tracking servo is performed can be measured by the change in the intensity of light passing through the two slit (A) holes and the slit (B) hole. Can be.

That is, the PDIC 109 detects the intensity of light through the two slit (A) holes and the slit (B) hole. The PDIC detecting the light passing through the slit (A) hole is called PD-A, and the slit ( B) When the PDIC detecting light through the hole is called PD-B, the error signal of the reference light is calculated by Equation (1).

Error of reference light = light quantity measurement value in PD-A-light quantity measurement value in PD-B

In other words, when using the equation, if the optical axis of the regenerated light (after all, the reference light) moves to the left of the three holes, the error signal has a negative value, and as the optical axis deviates from the center of the hole, the amount is increased. Will increase. On the contrary, when the optical axis of the reproduction light moves to the right side of the three holes, the error signal has a positive value, and the amount increases as the optical axis moves away from the center of the hole.

Contrary to Equation 1, the error signal of the reference light may also be calculated by Equation 2.

Error of reference light = light quantity measurement value in PD-B-light quantity measurement value in PD-A

In the case of using Equation 1, when the optical axis of the reproduction light (after all, the reference light) moves to the left of the three holes, the error signal has a positive value, and the amount increases as the optical axis moves away from the center of the hole. Done. On the contrary, when the optical axis of the reproduction light moves to the right side of the three holes, the error signal has a negative value and increases as the optical axis moves away from the center of the hole.

If the reference light is controlled using the reference light error signals generated by the above-described Equations 1 and 2, the reference light may be positioned as shown in FIG. 15. That is, the positional change of the reproduction light generated when the objective lens 102 is moved by the tracking servo is always controlled to the center of the track being tracked by controlling the reference light using the reference light error signal calculated by Equation 1 and 2 described above. The light center of the reference light may be positioned.

Therefore, by making two additional holes at the same distance from the center of the slit having three holes for passing only a specific track of the reproduced beam, the slit 106 is fabricated to generate the reference light using the optical axis error signal of the reference light detected. By controlling so that the optical center of the reference light is always located at the center of the track being tracked, a high level RF signal can be obtained and the slope of the linear section of the tracking error signal is increased, thereby increasing the servo precision during tracking servo.

In addition, since the present invention is disclosed as a right within the spirit and claims of the present invention, the present invention may include any modification, use and / or adaptation using general principles, and the present invention as a matter deviating from the description of the present specification. It includes everything that falls within the scope of known or customary practice in the art to which it belongs and falls within the scope of the appended claims.

As described above, the present invention provides an optical axis of reference light that is detected by making two additional holes at the same distance from the center of the slit having three holes for passing only a specific track of the reproduced beam to make the slit 106. By controlling the reference light using an error signal to control the optical center of the reference light to always be located at the center of the track being tracked, a high level RF signal can be obtained and the linear section slope of the tracking error signal is increased, so that the tracking servo Servo accuracy is also increased.

Claims (16)

A first process of generating a reference light from a light source and incident the light on the optical disk; A second process in which a plurality of track images reproduced on the optical disc by the reference light passes through the slit surface through two more holes at the same distance from the center of the optical lens and the slit having three holes, and is focused on the PDIC. Reference light servo control method of the holographic ROM disk comprising a. The method of claim 1, The light focused by the second process is located on the lower left and right on the vertical axis passing through the center of the RF hole for the RF signal, the E and F signals for the tracking servo, and on the horizontal axis of the RF hole. A reference light servo control method of a holographic ROM disk, which is located at left and right sides and is a PD-A and PD-B signal for measuring a change in intensity of light. The method of claim 1, The slit surface is a hole of E and F located on the lower left and right on the vertical axis of the RF hole passing through the center of the hole for the RF signal, PD-A and PD-B holes located on the left and right on the horizontal axis of the RF hole A reference optical servo control method for a holographic ROM disk, characterized in that is located. The method of claim 3, wherein In the slit surface, a tracking error signal is generated by generating a tracking error signal from the intensity of light passing through the holes of E and F located on the lower left and the right of the vertical axis of the RF hole to perform tracking control. Way. The method of claim 4, wherein And the tracking error signal controls the horizontal position of the objective lens to position the reproduced track at the center of the hole in the slit. The method of claim 3, wherein In the slit surface, the reference light of the holographic ROM disk is generated by generating a reference light error signal from the intensity of light passing through the PD-A and PD-B holes located on the left and right sides of the horizontal axis of the RF hole. Servo control method. The method of claim 6, And the reference light error signal controls the center position of the reference light to exist in the track under tracking servo. The method of claim 7, wherein The reference light error signal is, Equation 1 Error of reference light = light quantity measurement value in PD-A-light quantity measurement value in PD-B Equation 2 Error of reference light = light quantity measured value in PD-B-reference light servo control method of a holographic ROM disc, characterized in that it is generated by using the light quantity measured value in PD-A. A holographic ROM system in which a light source generates a reference light and enters an optical disk, and the plurality of track images are reproduced by the reference light so as to focus on the PDIC through the objective lens, the optical lens, and the slit surface. , And a second hole is drilled at the same distance from the center of the slit having three holes in the slit surface. The method of claim 9, The light focused by the PDIC includes an RF signal, an E and F signal for a tracking servo located on the lower left and right sides of a vertical axis passing through the center of the RF hole for the RF signal, and a left side on the horizontal axis of the RF hole. A reference light servo control apparatus for a holographic ROM disk, which is located at the right side and is a PD-A and PD-B signal for measuring a change in intensity of light. The method of claim 9, The slit surface is a hole of E and F located on the lower left and right on the vertical axis of the RF hole passing through the center of the hole for the RF signal, PD-A and PD-B holes located on the left and right on the horizontal axis of the RF hole A reference light servo control apparatus for a holographic ROM disk, characterized in that is located. The method of claim 11, In the slit surface, a tracking error signal is generated by generating a tracking error signal from the intensity of light passing through the holes of E and F located on the lower left and the right of the vertical axis of the RF hole to perform tracking control. Device. The method of claim 12, And the tracking error signal controls the horizontal position of the objective lens to position the reproduced track at the center of the hole in the slit. The method of claim 11, In the slit surface, the reference light of the holographic ROM disk is generated by generating a reference light error signal from the intensity of light passing through the PD-A and PD-B holes located on the left and right sides of the horizontal axis of the RF hole. Servo control. The method of claim 14, And the reference light error signal controls the center position of the reference light to exist in the track under tracking servo. The method of claim 15, The reference light error signal is, Equation 1 Error of reference light = light quantity measurement value in PD-A-light quantity measurement value in PD-B Equation 2 Error of reference light = light quantity measured value in PD-B-reference light servo control apparatus of a holographic ROM disk, characterized in that it is generated by using the light quantity measured value in PD-A.

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