KR100657677B1 - 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 splitter for dividing light reproduced from a disc by reference light from a light source, a deformation plate for modifying a phase of light transmitted through the beam splitter, and a deformation in a deformation plate. A slit for transmitting a portion of the light through a pinhole and having a reflective mirror surface on the lower surface except for the pinhole to transmit the light modified through the reflective mirror surface to the deformation plate and the beam splitter, and to detect the light transmitted through the slit. A holographic ROM reproducing system by a first light detector, a second light detector for detecting the magnitude of light reflected from the reflection mirror surface of the slit and reflected by the beam splitter, and light detected by the first and second light detectors, respectively It includes a servo control unit for controlling the servo. Therefore, the present invention can accurately perform the focus servo control of the holographic ROM reproducing apparatus by the light detector for detecting the size of the light reflected by the mirror surface attached to the entire lower surface except the pinhole of the slit.

Holographic ROM playback system, servo, slit, reflective mirror surface, optical size

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 to 5C illustrate examples of normal focus and abnormal focus detection in the holographic ROM playback system according to the present invention;

6 is a diagram illustrating focus detection using a sensor for detecting light size in a servo device of a holographic ROM reproducing system according to the present invention;

7A and 7B illustrate off beam and on beam data reproduced in a holographic ROM reproducing system according to the present invention;

8A to 8C are diagrams showing focusing detection results according to off beam data use in a servo device of a 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

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 light to have a track size and detects light reflected from the data pit, while in a holographic ROM reproducing system, 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; , A second light path for causing the second polarization from the second light source 24 to enter the surface of the disc 2, and a first light for detecting the second polarization S3 of the light reproduced on the disc 2. The detection unit PDIC1 22, the second light detection unit PDIC2 30 for detecting the first polarization S4 of the light reproduced by the disc 2, the first light detection unit PDIC1 22 and the first light detector And a servo control unit 32 for controlling to perform servo control of the reproduction system according to the data detected by the two-light detection unit (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; And a beam splitter (PBS) 58 passing through the second polarized light (P polarized light) of the objective lens 54 and reflecting the first polarized light (S polarized light), and a second beam transmitted from the beam splitter (PBS) 58. A slit 60 having a pinhole passing through a part of the two polarizations (P polarization), a second light detection unit PDIC1 62 for detecting the second polarization that has passed through the slit 60, and a beam splitter PBS In the first light detection unit (PDIC2) 64, the second light detection unit (PDIC1) 62 and the first light detection unit (PDIC2) 64, which detects the first polarized light (S polarized light) reflected by (58). Detected 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. The servo device of the holographic ROM reproducing system, which is capable of performing servo control by detecting light reproduced at the same light intensity by two light detectors using one light by providing another light detector which detects the magnitude of the reflected light, To provide.

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. And a beam splitter to transform the phase of the light transmitted from the beam splitter, and a portion of the light transformed by the beam splitter to pass through the pinhole, and a reflecting mirror surface on the lower surface except the pinhole is deformed through the reflective mirror surface. A slit for transmitting the light to the strain plate and the beam splitter, a first light detector for detecting the light transmitted through the slit, and a second light detector for detecting the magnitude of the light reflected from the reflective mirror surface of the slit and reflected by the beam splitter And controlling the servo of the holographic ROM reproducing system by the light detected by the first and second light detectors, respectively. It includes a servo control unit.

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 of the holographic ROM reproducing system according to the present invention includes a light source 102 for generating reference light and a first light for causing the reference light from the light source 102 to enter the surface of the disk 100. A second optical path S102 for transmitting the light reproduced from the disk S100 and the disk 100 through the beam splitter PBS 112 as it is and passing it to the first light detector PDIC1 122; A second light detector PDIC2 for reflecting the light reproduced from the disk 100 by the reflection mirror surface provided on the lower surface of the slit 118 and reflecting it through the beam splitter PBS 112 to detect the light size ( Servo control of the holographic ROM regeneration system according to the third optical path S104 transmitted to 128 and the data detected by the first light detector PDIC1 122 and the second light detector PDIC2 128 is performed. It includes a servo control unit 130 to control to perform. Here, the first light detector PDIC1 122 is formed of two or more divided sensors, and the second light detector PDIC2 128 is formed of two divided light size 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 disk 100, a beam splitter (PBS) 112 for dividing light reproduced from the disk 100 through the objective lens 110, and The strain plate 114 transforms the phase of the light transmitted from the beam splitter (PBS) 112 to λ / 4, and a portion of the light transformed from the strain plate 114 is transmitted through the pinhole and is reflected on the entire lower surface except the pinhole. A slit 118 having a mirror surface and transmitting the light modified through the reflective mirror surface to the deforming plate 114 and the beam splitter (PBS) 112 and a first light detecting the light transmitted through the slit 118. The photo detector unit 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 and a second light detector PDIC2 128 for detecting the size of light collected by the condenser lens 124 are included.

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 these lenses 120 is the first light detector PDIC1 ( 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. The S-polarized light that has passed through the condenser lens 124 is condensed and transmitted to the second light detection unit PDIC2 128.

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 size data in the two-segmented light size detecting sensor and transfers 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 of the holographic ROM reproducing system according to the present invention is provided with a pinhole (for example, three holes) 118a for transmitting a part of the incident light. The reflective mirror surface 118c is provided in the whole lower surface except the main body 118b.

5A to 5C illustrate examples of normal focus and abnormal focus detection in the holographic ROM reproducing system according to the present invention.

Referring to FIG. 5A, the S-polarized light reflected by the beam splitter (PBS) 112 is focused when the focus between the objective lens 110 and the disk 100 is correct in the holographic ROM reproducing system according to the present invention. The focal length f1 with the second light detection unit (not shown) which is focused through 124 becomes coincident with the focal length.

However, referring to FIG. 5B, when the focus between the objective lens 110 and the disk 100 is too close, the focal length f2 between the condenser lens 124 and the second light detector (not shown) is the focal length. As close as 5C, when the focus between the objective lens 110 and the disk 100 is too far, the focal length f3 between the condenser lens 124 and the second light detector (not shown) is the focal length. As with.

Therefore, in the servo device of the holographic ROM reproducing system of the present invention, the focal length between the objective lens 110 and the disc 100 is accurately measured as the focal length in the second light detector.

6 is a diagram illustrating focus detection using a sensor for detecting light size in a servo device of a holographic ROM reproducing system according to the present invention.

Referring to FIG. 6, in the servo device of the holographic ROM reproducing system of the present invention, the second light detector 128 indicates that the S-polarized light reflected from the lower surface of the slit and again reflected by the beam splitter is collected through the condenser lens 124. The optical size is detected by the two-segmented optical size detection sensors a and b to measure the focus between the objective lens and the disk. In this case, the sensor of the second light detector 128 is installed at a distance at which the size of the light is detected, not the focal plane of the light collected by the condenser lens 124.

7A and 7B illustrate off beam and on beam data reproduced in a holographic ROM reproducing system according to the present invention. FIG. 7A shows off-beam data reproduced on a disc recorded by an off-beam mask in a holographic ROM reproduction system, and FIG. 7B shows on-beam data reproduced on a disc recorded by an on-beam mask.

Since the servo device of the holographic ROM reproducing system according to the present invention detects the light size in the second light detector, both the above-mentioned on-beam data and off-disk data are recorded.

8A to 8C illustrate a result of focusing detection according to the use of on-beam data in the servo device of the holographic ROM reproducing system according to the present invention.

Referring to FIG. 8A, the servo device of the holographic ROM reproducing system of the present invention is divided into two light sizes by a second light detector (PDIC2) 128 that detects the light size passing through the condenser lens 124 of FIG. 3. When light is incident on the detection sensors a and b as c, when the difference ab of the value of the light size detected by each of the detection sensors a and b is 0, the focusing between the objective lens and the disk is reduced. I think it's done correctly.
However, as shown in FIG. 8B, the optical size detection sensor (a, b) divided into two in the second light detector (PDIC2) 128 for detecting the light size passing through the condensing lens 124 of FIG. When the light is incident as in c ', when the difference ab of the value of the light size detected by each of the detection sensors a and b is greater than 0, it is determined that the focusing distance between the objective lens and the disk is close.
On the other hand, as shown in Figure 8c, the optical size detection sensor (a, b) divided into two in the second light detector (PDIC2) 128 for detecting the light size passed through the condensing lens 124 of FIG. When light enters as c ', it is determined that the focusing distance between the objective lens and the disk is far when the difference ab of the value of the light size detected by each of the detection sensors a and b is smaller than zero.

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Therefore, the servo control unit in the servo apparatus of the holographic ROM reproducing system of the present invention performs focus servo control by determining whether the focus between the objective lens and the disc is correct or not according to the light size data detected by the second light detector.

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 has an advantage that the focus servo control of the holographic ROM reproducing apparatus can be accurately performed by the light detector for detecting the size of the light reflected by the mirror surface attached to the entire lower surface except the pinhole of the slit.

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 (5)

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 splitter for dividing the light reproduced from the disk by reference light from a light source; A deformation plate for modifying a phase of light transmitted from the beam splitter; 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 a light size reflected by the reflective mirror surface of the slit and reflected by the beam splitter; 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 splitter to λ / 4. The method of claim 1, And the first light detector comprises two or more divided sensors. The method of claim 1, And said second light detector comprises a two-segmented light size detection sensor.

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