KR20060061644A - Servo device of the holographic rom reader - 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 apparatus, and more particularly, to a mirror for injecting reference light from a light source to a disc, a beam split for dividing light reproduced from the disc by the reference light, and a beam transmitted through the beam split. A slit for transforming the phase of the light and a portion of the light that is transformed in the deformation plate is transmitted through the pinhole, and a reflecting mirror surface is provided on the lower surface except the pinhole to transmit the modified light through the reflecting mirror surface to the deformation plate and the beam splitter. And a first light detector for detecting light transmitted through the slit, a second light detector for detecting light reflected from a reflection mirror surface of the slit reflected through the beam splitter, and a beam splitter and a second light detector. Servo for controlling the servo of the holographic ROM reproducing apparatus by the installed astigmatism lens and the light detected by the first and second light detectors. It includes a control unit. Therefore, the present invention performs tracking and focus servo control by detecting light having the same light intensity as the light reproduced by each of the two light detectors while using one reference light polarization, but accurately performs focus servo control through an astigmatism lens. can do.

Holographic ROM playback device, focus, servo, slit, reflective mirror surface

Description

SERVO DEVICE OF THE HOLOGRAPHIC ROM READER}

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

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

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

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

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

6 is a diagram illustrating focus detection using an astigmatism lens in a servo device of a holographic ROM reproducing apparatus according to the present invention;

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

8A to 8C are diagrams showing a focusing detection result according to the use of off-beam data in the servo device of the holographic ROM reproducing apparatus 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 condensing lens 126 astigmatism lens

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

The present invention relates to a servo device of a holographic ROM (HROM) reproducing apparatus, and more particularly, to a servo device of a holographic ROM reproducing apparatus 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 apparatus is different from an optical disc reproducing apparatus such as a general CD or DVD. That is, in the optical disk reproducing apparatus, the light is focused to have a track size, and the light reflected from the data pit is detected. In the holographic ROM reproducing apparatus, 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 reproducing apparatus that detects the 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 apparatus adjusts the position of the radial direction of the light so that the focused light is accurately positioned 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.

FIG. 1 is a configuration diagram showing an example of a servo device of a holographic ROM reproducing apparatus according to the prior art. Referring to this, the conventional servo apparatus 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 allowing the second polarized light from the second light source 24 to enter the surface of the disk 2, and a first light for detecting the second polarized light S3 of the light reproduced on the disk 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 controller 32 which controls to perform servo control of the reproduction device 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 apparatus simplify the description. Are omitted in the drawings.

The servo device of the holographic ROM reproducing apparatus according to the related art configured as described above has the first light detecting unit when the polarized light (S polarized light, P polarized light) of the first and second light sources 10 and 24 is incident on the disk 2. 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 moves the objective lens 20 in accordance with the data detected by the second light detector PDIC2 30 to perform servo control of the holographic disc 2. Then, the objective lens 20 is moved in accordance with the data detected by the first light detector PDIC1 22 to perform servo control of a digital data disc such as a CD or a DVD.

Since the servo device of the conventional holographic ROM reproducing apparatus 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 a servo device of the holographic ROM reproducing apparatus according to the prior art. Referring to FIG. 2, another servo device of the conventional holographic ROM reproducing apparatus 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 polarized light) of the objective lens 54 and reflects the first polarized light (S polarized light), 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 controller 66 for controlling to perform servo control of the playback 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 detection unit for detecting light that has been reproduced from a disk passing through a slit, and a detection unit for detecting light reflected from a mirror surface attached to a lower part of the slit, in order to solve the above problems of the prior art. The present invention provides a servo device of a holographic ROM reproducing apparatus capable of performing servo control by detecting light reproduced at the same light intensity by two light detectors even using one light.

An apparatus of the present invention for achieving the above object is a device for controlling servo by detecting light reproduced from a disk on which data is recorded in a holographic ROM reproducing apparatus, comprising: a mirror for injecting a reference light from a light source into a disk, and a reference light; A beam split for dividing the light reproduced from the disc by means of the light source, a strain plate for modifying the phase of the light transmitted from the beam split, and a portion of the light transformed at the strain plate through a pinhole, and a reflecting mirror on the lower surface except the pinhole. A slit having a surface and transmitting the light modified through the reflective mirror surface to the deformation plate and the beam splitter, a first light detection unit detecting the light transmitted through the slit, and a reflective mirror surface of the slit reflected through the beam splitter. A second light detector for detecting the reflected light, an astigmatism lens provided between the beam splitter and the second light detector, and a first And a servo controller for controlling the servo of the holographic ROM reproducing apparatus by the light detected by the second light detector.

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 apparatus according to the present invention.

Referring to FIG. 3, the servo device of the holographic ROM reproducing apparatus 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 be incident on 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; The light reproduced from the disk 100 is reflected by the reflection mirror surface provided on the lower surface of the slit 118, reflected by the beam splitter (PBS) 112, and transmitted to the second light detector PDIC2 128. Servo controlling to perform servo control of the holographic ROM reproducing apparatus according to the data detected by the third optical path S104 and the first light detector PDIC1 122 and the second light detector PDIC2 128. The controller 130 is included. Here, the first and second light detectors PDIC1 and PDIC2 122 and 128 are formed of 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, the deformation plate 114 for transforming the phase of the light transmitted from the beam split (PBS) 112 to λ / 4, and the lower surface except for the pinhole to transmit a portion of the light modified in the deformation plate 114 through 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 reflective mirror surface of the slit 118 is reflected by the beam splitter PBS 112 again, and is configured to detect light reflected by the beam splitter PBS 112. A two-light detector (PDIC2) 128; A condenser lens 124 and an astigmatism lens 126 are provided between the beam splitter PBS 112 and the second light detector PDIC2 128. Preferably, the second light detector PDIC2 128 uses a four-segment sensor for detecting light that has passed through the astigmatism lens 126.

The servo device of the holographic ROM reproducing apparatus 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 disk 100 by the mirror 108 at the same angle as that at the time of recording, 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 light formed through the imaging lens 116 is transmitted to the collimating lens and the condenser lens 120 through the pinhole of the slit 118, and the circularly polarized light collected by these lenses 120 is the first light detector. (PDIC1) 122 is passed.

The remaining portion of the circularly polarized light formed by the imaging lens 116 is reflected by the reflection mirror surface provided on the lower surface of the slit 118, and then 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, transmitted to the condenser lens 124, and condensed by the condenser lens 124, through the astigmatism lens 126. The second light detector 128 is transferred to the PDIC2 128.

The first light detector PDIC1 122 and the second light detector PDIC2 128 detect circularly polarized light and S-polarized light quantity data, and transmit 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 illustrating a slit structure in a servo device of the holographic ROM reproducing apparatus according to the present invention. Referring to FIG. 4, the slit 118 in the servo device of the holographic ROM reproducing apparatus according to the present invention is provided with a pinhole (for example, three holes) 118a for transmitting a part of incident light, except for the pinhole 118a. The reflective mirror surface 118c is provided in the whole lower surface of the main body 118b.

5A to 5C illustrate examples of normal focus and abnormal focus detection in the holographic ROM reproducing apparatus 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 apparatus 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 apparatus 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 an astigmatism lens in the servo device of the holographic ROM reproducing apparatus according to the present invention.

Referring to FIG. 6, in the servo device of the holographic ROM reproducing apparatus of the present invention, the condenser lens 124 and the second light detector 128, which collect the S-polarized light reflected from the lower surface of the slit and again reflected by the beam splitter, are collected. An astigmatism lens 126 is provided in between to measure the focus between the objective lens and the disk.

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

Since the servo device of the holographic ROM reproducing apparatus according to the present invention performs focus detection using an astigmatism lens, both the above-described on-beam data and off-disk data-recorded discs can be used.

8A to 8C are diagrams illustrating a focusing detection result according to the use of off-beam data in the servo device of the holographic ROM reproducing apparatus according to the present invention.

Referring to FIG. 8A, the servo device of the holographic ROM reproducing apparatus of the present invention may include a sensor divided into four by a second light detector (PDIC2) 128 that detects light passing through the astigmatism lens 126 of FIG. 3. When the amount of diagonal sensor light detected in a, b, c, d) (e.g. photodiode) is I (a + c) -I (b + d) = 0, the focusing between the objective lens and the disc is precisely performed. I think I lost.

However, as shown in FIG. 8B, when the amount of light detected by the 4-split sensor is I (a + c) -I (b + d)> 0, it is determined that the focusing distance between the objective lens and the disk is far. As shown in FIG. 8C, when the amount of light detected by the 4-split sensor is I (a + c) -I (b + d) <0, it is determined that the focusing distance between the objective lens and the disk is close.

That is, in the present invention, when the light focused accurately through the astigmatism lens is incident on the second light detector, the difference in sensor light amounts in the diagonal directions from each other in the quadrant sensor (a, b, c, d) is zero as shown in FIG. 8A. Is detected. However, when the out-of-focus light is incident through the astigmatism lens, the difference in the amount of light of the sensors is detected to be larger than or smaller than zero in any part of the four-split sensors a, b, c, and d as shown in FIGS. 8b and 8c. .

Therefore, the servo control unit in the servo apparatus of the holographic ROM reproducing apparatus of the present invention performs the focus servo control according to the light amount 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.

In addition, the present invention can accurately perform the focus servo control of the holographic ROM reproducing apparatus because the light reflected by the mirror surface attached to the entire lower surface except the pinhole of the slit is transmitted through the astigmatism lens to the light detection unit. There is an advantage.

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 apparatus, A mirror for injecting reference light from a light source into the disk, A beam split dividing the light reproduced from the disc by the reference light; 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 reflected from a reflection mirror surface of the slit reflected through the beam splitter; An astigmatism lens provided between the beam splitter and the second light detector; A servo control unit for controlling the servo of the holographic ROM reproducing apparatus by the light detected by the first and second light detectors. Servo device of the holographic ROM playback device comprising a. The method of claim 1, And said reference light is P-polarized light. The method of claim 1, And the deformation 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 four or more divided sensors.

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