KR100657722B1 - Servo device of the holographic rom reading system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo device of a holographic ROM reproducing system, and in particular, a beam split that divides light reproduced from a disc by reference light from a light source, a modified plate that modifies the phase of light transmitted through the beam split, and a modified plate. Slit that transmits a part of the modified light through the pinhole, and has a reflective mirror surface on the lower surface except the pinhole, and transmits the modified light through the reflective mirror surface to the deformation plate and the beam splitter, and the light transmitted through the slit. A first light detector for detecting, a second light detector for detecting the light transmitted from the reflection mirror surface of the slit reflected through the beam splitter, and the light reflected from the beam splitter when the light is incident at a set angle The reflecting prism transmitted to the two light detectors and the light detected by the first and second light detectors, respectively, It includes a servo control unit for controlling the servo. Therefore, the present invention performs tracking and focus servo control by detecting light having the same light intensity as that of each of the two light detectors even with one reference light polarization, but adds a reflecting prism in front of the second light detector. As a result, the focus servo control of the holographic ROM reproducing apparatus can be performed accurately.

Holographic ROM playback system, servo, slit, prism, angle of incidence

Description

SERVO DEVICE OF THE HOLOGRAPHIC ROM READING SYSTEM}

1 is a configuration diagram showing an example of a servo device of a holographic ROM reproducing system according to the prior art;

2 is a configuration diagram showing another example of a servo device of a holographic ROM reproducing system according to the prior art;

3 is a block diagram showing a servo device of the holographic ROM reproducing system according to the present invention;

4 is a perspective view showing a slit structure in a servo device of a holographic ROM reproducing system according to the present invention;

5A and 5B are views for explaining the reflection or transmission form of incident light in the reflection prism in the servo device of the holographic ROM reproducing system according to the present invention;

6A and 6B illustrate off beam and on beam data reproduced in a holographic ROM reproducing system according to the present invention;

7A to 7C illustrate examples of normal focus and abnormal focus detection in the holographic ROM reproducing system according to the present invention.

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

100: disk 102: light source

110: objective lens 112: beam splitter

114: modified plate 118: slit

118c: Reflective mirror surface 122: First light detecting unit PDIC1

124: condenser lens 126: reflection prism

128: second light detection unit PDIC2 130: servo control unit

The present invention relates to a servo device of a holographic ROM (HROM) reproducing system, and more particularly, to a servo device of a holographic ROM reproducing system capable of performing servo control when reproducing data recorded on a holographic disc. It is about.

As the information industry develops, a large capacity of a device for storing information and a high speed of processing are required. As a result, the holographic ROM, which is widely known for recording and reproducing holographic digital data, can store a large amount of information in one bit of an optical disc such as a CD or a DVD, and process the stored data in one bit unit. Speed is 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 reproducing system is different from the optical disc reproducing apparatus such as 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, while in the holographic ROM reproducing system, the reference light is irradiated onto the optical disk and diffracted from the optical disk. Is detected through a pin hole of a slit. At this time, the size of the reference light is much larger than the size of the data track, and since the pinhole size of the slit has a track pitch size, a specific track is caused by run-out in the radial direction or the optical axis direction generated as the optical disk rotates. The light reproduced from the data pit of the slit hardly enters the pinhole of the slit. Therefore, it is the servo operation in the holographic ROM regeneration system that detects light passing through the pinhole and adjusts the light to pass correctly into the pinhole according to the detected data. Therefore, the tracking servo in the holographic ROM reproducing system adjusts the position of the radial direction of the light so that the focused light is precisely located in the data track, and the focus servo is the reflection surface of the disk to focus the light. It is to adjust the focus position of the light in the direction of the optical axis so that it is exactly positioned at.

1 is a configuration diagram showing an example of a servo device of a holographic ROM reproducing system according to the prior art. Referring to this, the conventional servo device includes a first polarization (for example, S polarization) S1 and a second polarization (for example, reference light). First and second light sources 10 and 24 for generating P-polarized light (S2), respectively, and a first light path for causing the first polarized light from the first light source 10 to enter the surface of the disc 2; And a second light path for causing the second polarized light from the second light source 24 to enter the surface of the disk 2 and a first light detector for detecting the second polarized light S3 of the light reproduced on the disk 2. (PDIC1) 22, a second light detector (PDIC2) 30 for detecting the first polarization S4 of the light reproduced from the disc 2, a first light detector (PDIC1) 22, and a second And a servo controller 32 which controls to perform servo control of the reproduction system according to the data detected by the light detector PDIC2 30.

Here, in the first light path, a reflection line mirror 12 that transmits a first polarization (for example, S polarization) and reflects a second polarization (for example, P polarization), and a first polarization of the reflection mirror 12 A polarizer beam splitter (PBS) for transmitting the light and reflecting the second polarized light, and a deformation plate for deforming the light transmitted from the beam splitter (PBS) 14 or the light transmitted from the disk 2 by λ / 4. (quarter wave plate) 16 and an object lens 20 for injecting the light deformed in the deforming plate 16 into the disk 2. In addition, the second light path includes a deformed plate (not shown) that deforms the second polarized light from the second light source 24 by λ / 4, and allows the light deformed by the deformed plate to be incident at the same angle as the recording angle. Reflective mirror 26. In addition, a slit 28 is further included between the reflection mirror 12 and the second light detection unit PDIC2 30, and various optical apparatuses (e.g., lenses, etc.) used in the reproducing system simplify the description. Are omitted in the drawings.

In the servo device of the holographic ROM reproducing system according to the related art configured as described above, when the respective polarizations (S polarization and P polarization) of the first and second light sources 10 and 24 are incident on the disk 2, the first light detection unit The second polarized light (for example, P polarized light, S3) reflected by the (PDIC1) 22 through the objective lens 20 and the deformable plate 16 through the beam splitter (PBS) 14 is detected and the detection data is transferred to the servo controller ( To 32). The second light detector PDIC2 30 receives first polarized light (eg, S-polarized light, S4) reflected by the reflective mirror 12 through the objective lens 20, the deforming plate 16, and the beam splitter (PBS) 14. ) Is detected and the detection data is transmitted to the servo controller 32.

The servo controller 32 horizontally shifts the position of the objective lens 20 according to the data detected by the second light detector PDIC2 30 to perform focus servo control of the holographic disc 2. Then, the position of the objective lens 20 is moved horizontally or vertically according to the data detected by the first light detector PDIC1 22 to perform tracking and focus servo control of a digital data disc such as a CD or a DVD.

Since the servo device of the conventional holographic ROM reproducing system uses two different light sources, the first and second polarization signals detected by the beam splitter (PBS) 14 and the reflection mirror 12 are respectively used. Since the second light detectors PDIC1 and PDIC2 22 and 30 detect the servos of different discs, for example, the holographic disc 2 or a digital data disc such as a CD or a DVD, the separate optical discs may be controlled. Since the light source for generating polarization and the light path are separated into two, there is a problem in that the number of optical devices required for the servo device increases.

2 is a configuration diagram showing another example of the servo device of the holographic ROM reproducing system according to the prior art. Referring to FIG. 2, another servo device of the conventional holographic ROM reproducing system includes a light source 50 generating first polarized light (eg, S-polarized light) and second polarized light (eg, P-polarized light) as reference light, and from the light source 50. A reflecting mirror 52 for reflecting the light at the surface of the disk 2, reflecting at the same angle as the recording angle, and an objective lens 54 for transmitting the light reproduced from the upper surface of the disk 2; A beam splitter (PBS) 58 that transmits the second polarized light (P polarization) of the objective lens 54 and reflects the first polarized light (S polarization), and a second transmitted from the beam splitter (PBS) 58. A slit 60 having a pinhole passing through a portion of polarized light (P polarization), a second light detector PDIC1 62 for detecting a second polarized light that has passed through the slit 60, and a beam splitter PBS ( 58 is detected by the first light detector PDIC2 64 and the second light detector PDIC1 62 and the first light detector PDIC2 64, respectively. Data And a servo control section 66 for controlling to perform servo control of the reproducing apparatus.

The other servo device of the holographic ROM reproducing apparatus according to the related art configured as described above generates the first and second polarizations (S polarization and P polarization) from the light source 50 and enters the disk 2. The light regenerated from is passed through the objective lens 54 to the beam splitter (PBS) 58. The beam splitter (PBS) 58 transmits the second polarized light (P polarized light) to the second light detector PDIC1 (62) through the slit 60, and reflects the first polarized light (S polarized light). It transmits to one light-detecting part (PDIC2) 64.

The servo controller 66 shifts the position of the objective lens 20 horizontally or vertically in accordance with the data detected by the second light detector PDIC1 62 and the first light detector PDIC2 64, respectively. Perform the focus or tracking servo control in 2).

However, the other servo device of the holographic ROM reproducing apparatus according to the related art also needs to include a light source 50 for generating two P-polarized light and an S-polarized light, and the light reproduced by the beam splitter (PBS) 58 Since it is divided and transmitted to the two light detectors, the intensity of light detected by each light detector is reduced to 1/2, which causes a problem in that the detection efficiency is lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light detection unit for detecting light regenerated from a disk as it passes through a slit as it is, and a mirror surface attached to the entire lower surface of the slit except for a pinhole. Holographic which can perform servo control by detecting the reproduced light with the same light intensity in the two light detectors by using another light by providing another light detector for detecting that the reflected light is reflected by the reflecting prism It is to provide a servo device of the ROM regeneration system.

An apparatus of the present invention for achieving the above object is a device for controlling servo by detecting light reproduced from a disc on which data is recorded in a holographic ROM reproducing system, wherein the light reproduced from the disc is divided by reference light from a light source. A beam split, a deformation plate for modifying the phase of the light transmitted from the beam split, and a portion of the light deformed from the deformation plate through a pinhole, and a reflecting mirror surface is provided on the lower surface except the pinhole. A slit for transmitting the modified light to the strain plate and the beam splitter, a first light detector for detecting light transmitted through the slit, and a second light for detecting light transmitted from the reflective mirror surface of the slit reflected through the beam splitter When the light reflected from the detector and the beam splitter is incident at a set angle, the light is reflected and transmitted to the second light detector. And a servo control unit for controlling the servo of the holographic ROM reproducing system by the prism and the light detected by the first and second light detecting units, respectively.

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

3 is a block diagram showing a servo device of the holographic ROM reproducing system according to the present invention.

Referring to FIG. 3, the servo device according to the present invention includes a light source 102 for generating reference light, a first light path S100 for causing the reference light from the light source 102 to be incident on the surface of the disk 100, and The second optical path S102 for transmitting the light reproduced from the disc 100 through the beam splitter (PBS) 112 as it is and passing it to the first light detection unit PDIC1 122 and the reproduction from the disc 100. Third light path S104 for reflecting the reflected light by the reflective mirror surface installed on the lower surface of the slit 118 and reflecting the light through the beam splitter PBS 112 to the second light detector PDIC2 128. ), And a servo control unit 130 which controls to perform servo control of the holographic ROM reproducing system according to the data detected by the first light detector PDIC1 122 and the second light detector PDIC2 128. do. Here, the first and second light detectors PDIC1 and PDIC2 122 and 128 include two or more divided sensors.

In the first optical path S100, a collimating lens 106 for converting the reference light (P polarization) from the light source 102 into parallel light and a reference light transmitted through the collimating lens 106 are recorded. A mirror 108 that is incident on the disk 100 at the same angle.

The second optical path S102 includes an objective lens 110 positioned on an upper surface of the disc 100 and a beam split (PBS) 112 for dividing light reproduced from the disc 100 through the objective lens 110. And a strain plate 114 for transforming the phase of the light transmitted from the beam split (PBS) 112 to λ / 4, and a portion of the light transformed from the strain plate 114 through the pinhole, and the entire lower surface except the pinhole. A slit 118 having a reflective mirror surface for transmitting the light modified through the reflective mirror surface to the deforming plate 114 and the beam splitter (PBS) 112, and detecting the light transmitted through the slit 118. A first light detector (PDIC1) 122 is included. At this time, an imaging lens 116 is provided between the beam splitter PBS 112 and the slit 118, and a condenser lens 120 is provided between the slit 118 and the first light detector PDIC1 122. .

In the third light path S104, the light reflected from the reflection mirror surface of the slit 118 is reflected back by the beam splitter PBS 112, and focuses the light reflected by the beam splitter PBS 112. A lens 124, a reflecting prism 126 that reflects the light when the light collected by the condenser lens 124 is incident at a predetermined threshold angle or more, and transmits the light when the incident light is below the threshold angle, and a reflecting prism And a second light detector (PDIC2) 128 for detecting the light reflected through 126.

The servo device of the holographic ROM reproducing system according to the present invention configured as described above operates as follows.

When the P-polarized light of the reference light generated by the light source 102 is converted into parallel light through the collimating lens 106 and is incident on the disc 100 by the mirror 108 at the same angle as that at the time of recording, the disc 100 enters the disc 100. The reproduction light of the recorded data is transmitted to the beam splitter (PBS) 112 via the objective lens 110 in the form of P polarization. The beam splitter (PBS) 112 transmits the P-polarized regenerated light as it is, and the deformation plate 114 deforms the P-polarized light of the incident light by λ / 4 to change the circularly polarized light.

A portion of the circular flat light formed through the imaging lens 116 is transmitted to the condensing lens 120 through the pinhole of the slit 118, and the circular polarized light condensed by the condensing lens 120 is the first light detector PDIC1. Is passed to 122.

The remaining portion of the circularly polarized light except for the pinhole of the slit 118 is reflected by the reflection mirror surface installed on the entire lower surface of the slit 118, and passes through the imaging lens 116 to be transmitted to the deformation plate 114. In the deforming plate 114, the circularly polarized light is deformed by? / 4 to be changed to S polarized light.

The S-polarized light changed by the deformation plate 114 is reflected through the beam splitter (PBS) 112 and transmitted to the condenser lens 124. S-polarized light transmitted through the condenser lens 124 is collected and transmitted to the reflecting prism 126. The reflecting prism 126 reflects the light to the second light detector PDIC2 128 when the focused light is incident at a predetermined threshold angle or higher, and when the focused light is incident below the set threshold angle. Permeate as it is.

The first light detector PDIC1 122 detects circularly polarized light quantity data from two or more divided sensors and transmits the detected value to the servo controller 130. The second light detector PDIC2 128 detects the S-polarized light quantity data reflected by the reflection prism 126 in two or more divided sensors, and transmits the detected value to the servo controller 130.

The servo controller 130 drives an actuator (not shown) according to the data detected by the first light detector PDIC1 122 to horizontally move the position of the objective lens 110 to perform tracking servo control. Then, an actuator (not shown) is driven according to the data detected by the second light detector PDIC2 128 to vertically move the position of the objective lens 110 to perform focus servo control.

4 is a perspective view showing a slit structure in a servo device of the holographic ROM reproducing system according to the present invention. Referring to FIG. 4, the slit 118 in the servo device according to the present invention is provided with a pinhole (for example, three holes) 118a for transmitting a portion of incident light and has a lower surface of the main body 118b except for the pinhole 118a. The reflection mirror surface 118c is provided in the whole.

5A and 5B are diagrams for describing a reflection or transmission form of incident light in a reflection prism in a servo device of a holographic ROM reproducing system according to the present invention.

5A and 5B, when the light passing through the beam splitter and the condenser lens is incident on the reflective prism 126, if the incident angle is greater than or equal to the set threshold angle, the reflective prism 126 material is not transmitted and is reflected as it is. If the incident angle is less than the set threshold angle, the material of the reflective prism 126 is transmitted as it is.

Therefore, as shown in the drawing, when the light S104 incident on the reflecting prism 126 is in the form of gathering or spreading, according to the angle of incidence of the reflecting prism 126, it is reflected within the material of the prism 126. It can be seen that the transmission (S106) as it is.

6A and 6B illustrate off beam and on beam data reproduced in a holographic ROM reproducing system according to the present invention. FIG. 6A shows off-beam data reproduced on a disc recorded by an off beam mask in a holographic ROM reproduction system, and FIG. 6B shows reproduction on a disc recorded by an on beam mask. Represents on beam data.

Since the servo device of the holographic ROM reproducing system according to the present invention detects the amount of light data reflected by the reflecting prism in the second light detector, both the above-described on-beam data and off-disk data are recorded.

7A to 7C illustrate examples of normal focus and abnormal focus detection in the holographic ROM reproducing system according to the present invention.

Referring to FIG. 7A, in the servo device of the present invention, the S-polarized light reflected by the beam splitter (PBS) 112 is reflected through the condenser lens 124 because the focus between the objective lens 110 and the disk 100 is exactly correct. When the angle incident on the using prism 126 becomes a set angle, for example, 90 °, all the light incident through the reflecting prism 126 is reflected and transmitted to the second light detector 128. The light amount data detected by the sensors a and b divided by the two light detectors PDIC2 128 are transmitted to the servo controller. The servo controller determines that the focus distance between the objective lens 110 and the disk 100 exactly matches the set value when the light amount data difference at the sensors a and b is a-b = 0.

However, as shown in FIG. 7B, the S-polarized light incident on the reflecting prism 126 through the beam splitter (PBS) 112 and the condenser lens 124 is not properly focused between the objective lens 110 and the disk 100. When the angle of is not a set angle, for example, 90 °, but the light spreads, part of the light incident through the reflecting prism 126 is transmitted as it is (S106) and the other part is reflected (S104) to the second light detector 128. Delivered. When the difference in the amount of light data detected by the sensors a and b of the second light detector PDIC2 128 is ab <0, the servo controller sets a focusing distance between the objective lens 110 and the disk 100. Judging from the

As shown in FIG. 7C, the S-polarized light incident on the reflecting prism 126 through the beam splitter (PBS) 112 and the condenser lens 124 is not properly focused between the objective lens 110 and the disk 100. When the angle of the light is not a set angle, for example, 90 °, but the light gathers, a part of the light incident through the reflecting prism 126 is transmitted as it is (S106) and the rest is reflected (S104) to the second light detector 128. Delivered. If the difference in the amount of light data detected by the sensors a and b of the second light detector PDIC2 128 is ab> 0, the servo controller is configured to set a focusing distance between the objective lens 110 and the disk 100. I think it is closer.

Therefore, in the servo device of the holographic ROM reproducing system according to the present invention, as shown in FIGS. 7B and 7C, the difference in light quantity data in the two divided sensors (a, b) of the second light detecting unit is ab <0 or ab> 0. In this case, focus servo control is performed to adjust a focus distance between the objective lens 110 and the disk 100 until the light amount data difference becomes ab = 0.

As described above, the present invention performs tracking and focus servo control by detecting light having the same light intensity as each of the light reproduced by the two light detectors using one reference light polarization. Regeneration efficiency can be improved.                     

Furthermore, the present invention can accurately perform the focus servo control of the holographic ROM reproducing apparatus by adding a reflecting prism to the front end of the second light detector which detects the light reflected by the mirror surface attached to the entire lower surface except the pinhole of the slit. There is an advantage to this.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

Claims (6)

An apparatus for controlling servo by detecting light reproduced from a disc on which data is recorded in a holographic ROM reproducing system, A beam split dividing the light reproduced from the disk by reference light from a light source, A deformation plate for modifying a phase of light transmitted through the beam split; A slit that transmits a portion of the light deformed in the deforming plate through a pinhole and has a reflective mirror surface on the lower surface except the pinhole to transmit the deformed light to the deforming plate and the beam splitter through the reflecting mirror surface; A first light detector for detecting light transmitted through the slit; A second light detector for detecting light transmitted from the reflection mirror surface of the slit reflected through the beam splitter; A reflecting prism reflecting the light to the second light detector when the light reflected by the beam splitter is incident at a predetermined angle; A servo control unit for controlling the servo of the holographic ROM reproducing system by the light detected by the first and second light detectors, respectively. Servo device of the holographic ROM playback system comprising a. The method of claim 1, And said reference light is P-polarized light. The method of claim 1, And the deforming plate deforms the phase of the light transmitted from the beam split to [lambda] / 4. The method of claim 1, And the first light detector comprises two or more divided sensors. The method of claim 1, And the second light detector comprises two or more divided sensors. The method of claim 1, And the reflective prism transmits the light incident at the angle outside the set angle as it is when the light reflected by the beam splitter is incident at an angle outside the set angle.

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