KR100767932B1 - Apparatus for Reproducing Optical Information, Control Apparatus for Tracking Servo and Control Method for Tracking - Google Patents

Abstract

The present invention relates to an optical information reproducing apparatus, a tracking servo control apparatus and a tracking control method, and more particularly, a reference light providing unit for irradiating a reference light to a predetermined position of an information storage medium; A reproduction light processor for separating the reproduction light emitted from the optical information storage medium by the reference light into detection reproduction light and at least one adjacent reproduction light, and detecting light information of the separated adjacent reproduction light; An optical information detector for detecting optical information of the separated detection reproduction light; A tracking servo unit for adjusting a position of the reproduction light processor in response to a control signal; And a tracking servo controller which analyzes the optical information of the detected adjacent reproduction light to determine whether a tracking position is abnormal, and applies the control signal to the tracking servo unit according to the determination result. A servo control apparatus and tracking control method. According to the present invention, when the optical information is reproduced, the current tracking state can be determined using the adjacent reproduced light, and the tracking position can be controlled using the determination result.

Description

Optical information reproducing device, tracking servo control device and tracking control method {Apparatus for Reproducing Optical Information, Control Apparatus for Tracking Servo and Control Method for Tracking}

1 is a conceptual diagram schematically showing a configuration and operation principle of a general conventional holographic optical information reproducing apparatus.

2 is a block diagram showing the configuration of an optical information detection apparatus according to a preferred embodiment of the present invention.

3 is a perspective view showing the shape of the reflective slot shown in FIG.

FIG. 4 is an exemplary view illustrating an example of light detection by the light detection module of the reproduction light processor of FIG. 2.

FIG. 5 is an exemplary diagram illustrating an image detected in the light detection area when the optical information storage medium moves by a predetermined distance in the example shown in FIG. 4.

FIG. 6 is a graph showing the magnitude of light detected in the light detection area A and the light detection area B as the optical information storage medium rotates when tracking is normal.

7 is an exemplary view showing a detection shape of the light detection module when the track position is moved above the normal position.

FIG. 8 is an exemplary view showing a case in which the track position moves further upward than the state shown in FIG. 7 so that the track is deviated to the maximum relative to the normal position.

FIG. 9 is a graph showing a change in the light size of the light detection area A and the light detection area B when the track position is gradually moved upward from the normal position.

10 is a graph showing a change in the difference value of the light size between the light detection area A and the light detection area B. FIG.

FIG. 11 is an exemplary diagram illustrating a form of detecting light distribution of a spot image of adjacent reproduction light by using four light detection areas.

12 is a flowchart illustrating a flow of a tracking control method according to an exemplary embodiment of the present invention.

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

1: Optical information storage medium

100: reference light providing unit

200: reproduction light processing unit

210, 220, 230: first lens, second lens, third lens

240: polarized light splitter

241: light splitting surface

250: quarter wave plate

260: reflective slot

270: light detection module

300: tracking servo control

301: control module

302: tracking status determination module

400: light information detection unit

500: tracking servo unit

The present invention relates to an optical information reproducing apparatus, a tracking servo control apparatus, and a tracking control method. More particularly, an optical information reproducing apparatus can control a tracking position by using optical information of adjacent reproduction light adjacent to detection reproduction light when reproducing optical information. An information reproducing apparatus, a tracking servo control apparatus, and a tracking control method.

In general, optical information storage devices for storing optical information include compact discs (CDs), digital versatile discs (DVDs), high definition DVDs (HD-DVDs), and Blu-ray discs (BDs). Blue-ray Disc).

Recently, with the rapid development of the information and computer industry, there is an increasing demand for a next generation storage system capable of satisfying high-capacity storage capacity and high-speed input / output of data.

One of the systems that are attracting the most attention in accordance with such a demand is an optical processing system using the principle of volume holography, that is, a holographic optical information processing system.

The holographic optical information processing system is a system conceived from the principle that when two lights having different incidence angles intersect at a predetermined position of a light sensitive photosensitive medium, an interference pattern generated by the interference of the two lights is recorded in the photosensitive medium. .

That is, when a signal beam including data information and a reference beam irradiated from an angle different from the signal beam cross each other at a predetermined position of an optical information storage medium that is a photosensitive medium, a two-dimensional interference pattern generated at this time is generated. Recorded on the optical information storage medium. In addition, when the data information is reproduced, only the reference light is irradiated to the recorded interference pattern, and original data is restored by using a diffraction image generated by the interference pattern.

Such a holographic optical information processing system may record data by three-dimensionally superimposing data at the same position of the optical information recording medium using various multiplexing techniques. This superimposition recording can dramatically increase the capacity stored in a limited area, thereby realizing an ultra large storage system.

In this case, the multiplexing technique may include angle multiplexing, phase-code multiplexing, wavelength multiplexing, fractal multiplexing, shift multiplexing, and ferrotropic multiplexing. Peristrophic Multiplexing, Polytopic Multiplexing, and the like.

Holographic optical information processing systems have been studied in the direction of increasing the recording density of data by appropriately using these multiplexing techniques. For example, the holographic optical information processing system using polytopic multiplexing operates by increasing the density of the signal light and passing only the detected reproduction light by using silt during reproduction, and blocking the remaining adjacent reproduction light. Such polytopic multiplexing techniques are disclosed in U.S. Patent Publication No. 20040179251 proposed by InPhase and "Progress of the Development of High Performance Removable Storage at InPhage Technologies for Application to Archival Storage" by William L. Wilson. have.

FIG. 1 is a conceptual diagram schematically showing the structure and operation principle of a conventional conventional holographic optical information reproducing apparatus, and shows an example of reproducing optical information recorded by polytopic multiplexing.

Referring to FIG. 1, the holographic optical information reproducing apparatus irradiates the reference light R to a predetermined position of the optical information storage medium 1 on which the holographic interference pattern is recorded. In this case, the reference light R may refer to a phase conjugation reference light. Then, the reproduction light (Pd, Pn) by the interference pattern is emitted from the optical information storage medium 1 by the reference light (R).

In this case, the emitted light Pd and Pn may include a plurality of lights. That is, at least one of the detected reproduction light Pd by the interference pattern including the data information to be detected and the adjacent reproduction light Pn by the adjacent interference pattern are emitted.

The plurality of reproduction lights Pd and Pn emitted are transmitted to the slit through the lens optical systems 2 and 3. The lens optical systems 2 and 3 are composed of a first lens 2 and a second lens 3 having a predetermined focal length. In this case, when the focal length of the second lens 2 is f, the distance between the optical information storage medium 1 and the first lens 2 is f, and the distance between the first lens 2 and the second lens 3 is f. The distance can be set to 2f.

An optical splitter may be provided between the first lens 2 and the second lens 3, which facilitates the placement of a spatial light modulator (SLM) when recording optical information, thereby recording optical information. And to increase the efficiency of the regeneration module configuration. Related matters are described in the above-mentioned polographic multiplexing literature.

On the other hand, the slit 5 passes only the detected reproduction light Pd among the reproduction light Pd and Pn transmitted through the lens optical system, and blocks the rest. Therefore, in the CMOS (Complementary Metal-Oxide Semiconductor) 8, only an image of data included in the detection reproduction light Pd is detected.

However, such a holographic optical information processing apparatus is sensitive to environmental changes such as shaking of the apparatus because the detected reproduction light Pd passes through the fine through hole of the slit 5.

Therefore, accurate tracking servo control is required. In other words, it is required to check whether the reproduced light of the desired track is correctly detected when the optical information is reproduced, and if the track position is not correct, moving to the correct position through servo control is required.

If the tracking servo control is not performed properly, the desired detection reproduction light Pd does not pass through the slit 5 so that the CMOS 8 cannot acquire an image of the light information properly, which in turn results in an error rate. It may cause to increase. Therefore, there is an urgent need for a technique capable of performing accurate and efficient tracking control in reproducing holographic optical information.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and provides an optical information reproducing apparatus capable of accurately detecting optical information by performing efficient tracking servo control using optical information of adjacent reproduction light when optical information is reproduced. There is one purpose.

It is also a second object of the present invention to provide a tracking servo control apparatus of an optical information reproducing apparatus that makes it possible to detect tracking servo control information by using optical information of adjacent reproduction light when reproducing optical information.

Another object of the present invention is to provide a tracking control method of an optical information reproducing apparatus that can control a tracking position by using optical information of adjacent reproduction light when reproducing optical information.

An optical information reproducing apparatus according to the present invention for achieving the first object of the present invention comprises a reference light providing unit for irradiating a reference light to a predetermined position of the optical information storage medium; A reproduction light processor for separating the reproduction light emitted from the optical information storage medium by the reference light into detection reproduction light and at least one adjacent reproduction light, and detecting light information of the separated adjacent reproduction light; An optical information detector for detecting optical information of the separated detection reproduction light; A tracking servo unit for adjusting a position of the reproduction light processor in response to a control signal; And a tracking servo controller which analyzes the optical information of the detected adjacent reproduction light to determine whether a tracking position is abnormal and applies the control signal to the tracking servo unit according to the determination result.

The reproduction light processing unit may include a polarization light splitter configured to transmit reproduction light emitted from the optical information storage medium; A reflection type slit for transmitting the detected reproduction light out of the reproduction light transmitted by the polarization light splitter to the optical information detection unit, and reflecting the adjacent reproduction light; A quarter-wave plate disposed between the polarized light splitter and the reflective slit; And a light detection module detecting light information of the adjacent reproduction light. In this case, the polarized light splitter reflects the adjacent reproduction light, which is reflected by the reflective slit and transmitted from the quarter wave plate, to the light detection module.

The light detection module may include a plurality of light detection areas for detecting adjacent reproduction light reflected by the polarized light splitter. The tracking servo controller may determine the tracking state by using a distribution of light sizes detected in the plurality of light detection areas.

The polarizing light splitter may have a light splitting surface that transmits light having P-polarized light and reflects light having S-polarized light.

The reproducing light processor comprises: a first lens disposed between the optical information storage medium and the polarized light splitter to focus light; A second lens disposed between the polarized light splitter and the quarter wave plate to focus light; And a third lens disposed between the polarized light splitter and the light detection module to focus light.

The tracking servo control unit may include: a tracking state determination module configured to determine a current tracking state by using light information of adjacent reproduction light detected by the reproduction light processing unit; And a control module configured to apply the control signal to the tracking servo unit to adjust a tracking position to a normal position in response to the tracking state determined by the tracking state determination module.

The tracking state determination module may detect at least one of a first track and an end track of the optical information storage medium by using a plurality of detected optical information of the adjacent reproduction light.

On the other hand, the tracking servo control apparatus of the optical information reproducing apparatus according to the present invention for achieving the above-described second object of the present invention is a tracking servo control apparatus for controlling a tracking servo that adjusts a tracking position when optical information is detected. A tracking state determination module for collecting light information of at least one adjacent reproduction light adjacent to the detected reproduction light to determine a current tracking position; And a control module for applying a control signal to the tracking servo for adjusting the tracking position to the normal position in consideration of the current tracking position when the current tracking position determined by the tracking state determination module is not a normal position. It includes.

In this case, the light information of the adjacent reproduction light is light information respectively detected by a plurality of light detection areas, and the tracking state determination module uses the distribution of light sizes of the plurality of light detection areas to determine the current tracking position. Can be determined.

On the other hand, the tracking control method according to the present invention for achieving the above-described third object of the present invention is to separate at least one adjacent reproduction light adjacent to the detection reproduction light from the reproduction light emitted from the optical information storage medium by the reference light. Steps; Detecting optical information of the separated adjacent reproduction light; Analyzing light information of the detected adjacent reproduction light to determine a current tracking state; And if the determined current tracking state is not normal, adjusting to the normal tracking position by using the current tracking state information.

Preferably, in the optical information detecting step, the optical information of the separated adjacent reproduction light may be detected through a plurality of light detection regions.

In this case, the plurality of light detection areas are two light information areas. In this case, in the tracking state determination step, the current tracking state may be determined by analyzing a difference between the light sizes detected by the two light detection areas. .

For example, if there is little difference in the light size detected in the two light detection areas, the current tracking state is determined to be normal, and if the difference in the light size is large, the current tracking state is determined to be abnormal. At this time, in the tracking position adjusting step, when there is a large difference in the light size detected in the two light detection areas, the tracking position is adjusted in a direction of reducing the difference in the light size.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In addition, in describing the preferred embodiment of the present invention illustrated in the drawings, specific technical terms are used for clarity of content. However, it is to be understood that the invention is not limited to these specific selected terms, and that each specific term includes all technical synonyms that operate in a similar manner to achieve a similar purpose.

2 is a block diagram showing the configuration of an optical information detection apparatus according to a preferred embodiment of the present invention.

2, the optical information detecting apparatus according to the preferred embodiment of the present invention may include a reference light providing unit 100. The reference light providing unit 100 irradiates the reference light R to a predetermined position of the optical information storage medium 1 having a disc shape. At a predetermined position of the optical information storage medium 1, there are a plurality of spots recorded by polytopic multiplexing. In this case, each spot may mean a holographic interference pattern.

Therefore, in the optical information storage medium 1, the plurality of reproduction lights Pd and Pn are emitted by the incident reference light R. In this case, the emitted reproduction light Pd and Pn may have P-polarized light.

The reproduction light processing unit 200 separates the plurality of reproduction lights Pd and Pn emitted from the optical information storage medium 1 by the reference light R into the detection reproduction light Pd and the adjacent reproduction light Pn, The detected reproduction light Pd is provided to the optical information detection unit 400, and the adjacent reproduction light Pn detects the optical information.

The reproduction light processing unit 200 includes a first lens 210, a polarization beam splitter (PBS) 240, a second lens 220, and a quarter plate 250. And a reflective slit 260, a third lens 230, and a light detection module 270. In this case, the second lens 220 and the third lens 230 have the same focal length 'f'. In addition, the distance between the first lens 210 and the second lens 220 may be determined as '2f'.

The plurality of reproduction lights Pd and Pn emitted from the optical information storage medium 1 are transmitted to the polarized light splitter 240 through the first lens 210. The polarized light splitter 240 transmits the plurality of reproduction lights Pd and Pn transmitted from the first lens 210 to the second lens 220.

Preferably, the polarized light splitter 240 has a light splitting surface 241 that transmits light having P-polarized light and reflects light having S-polarized light. Therefore, as described above, the reproduction light Pd and Pn transmitted from the first lens 210 have P-polarized light and thus are transmitted to the second lens 220.

A reflective slit 260 is provided at a position separated by the focal length 'f' from the second lens 220, and a quarter wave plate 250 is disposed between the second lens 220 and the reflective slit 260. Is provided. Therefore, the plurality of reproduction lights Pd and Pn passing through the second lens 220 are transmitted to the reflective slit 260 via the quarter wave plate 250. In this case, the plurality of reproduction lights Pd and Pn are focused at a position where the reflective slit 250 is installed. That is, the plurality of reproduction lights Pd and Pn have a minimum size at the position of the reflective slit 260.

FIG. 3 is a perspective view illustrating the shape of the reflective slot 260 shown in FIG. 2.

2 to 3, the reflective slot 60 has a plate-shaped body, the center of the body of the plurality of reproduction light (Pd, Pn) to be transmitted from the second lens 220 to be detected The through groove 262 is formed so that only the detected reproduction light Pd having data information can pass therethrough.

The detection reproduction light Pd passes through the slit through the through groove 220 and then is transmitted to the optical information detection unit 400. At this time, the optical information detector 400 detects the optical information of the detection reproduction light (Pd). Therefore, it is possible to reproduce the data information included in the detected reproduction light Pd by using the detected light information.

Meanwhile, a reflective part 261 having a predetermined size is formed on an upper surface of the body of the reflective slot 260, that is, a surface facing the quarter wave plate 250. In this case, the reflector 261 may be realized by coating a material capable of reflecting light on the body surface.

The reflector 261 may include at least one quarter wavelength plate 250 of at least one adjacent reproduction light Pn except for the detection reproduction light Pd among the plurality of reproduction lights Pd and Pn transmitted from the second lens 220. To reflect). For example, the reflector 260 illustrated in FIG. 3 may reflect eight reproduction light Pn except for the detection reproduction light Pd among the plurality of reproduction lights Pd and Pn.

Accordingly, only the detection reproduction light Pd is selected by the reflective slot 260 and transmitted to the optical information detection unit 400, and the remaining adjacent reproduction light Pn is reflected to the quarter wave plate 250.

On the other hand, the adjacent reproduction light Pn transmitted to the quarter wave plate 250 is converted to S-polarized light by changing its polarization direction. That is, the adjacent regenerated light Pn, which has passed through the quarter-wave plate 250 through the polarized light splitter 240, is reflected and passes through the quarter-wave plate 250 again, thereby changing its polarization direction.

Adjacent regenerated light Pn converted to S-polarized light is transmitted to the polarized light splitter 240 via the second lens 220. The light splitting surface 241 of the polarized light splitter 240 has the P- Since the polarized light is transmitted and the S-polarized light is reflected, the adjacent reproduction light Pn converted into the S-polarized light is reflected by the third lens 230.

The adjacent reproduction light Pn transmitted to the third lens 230 is focused on the light detection module 270 provided at a position spaced apart by the focal length “f ′”. At this time, "f '" is a numerical value that can be appropriately set according to the implementation environment. "F '" may be the same as "f".

The light detection module 270 detects light information of at least one adjacent reproduction light Pn transmitted from the third lens 230. In this case, the light detection module 270 may detect light information of the adjacent reproduction light Pn using a plurality of light detection areas. The structure of this light detection module 270 will be described in detail later.

The tracking servo unit 500 adjusts the position of the reproduction light processing unit 200 in response to a control signal Ctrl. That is, the tracking position is adjusted. In this case, the control signal Ctrl is applied by the tracking servo controller 300.

The tracking servo controller 300 determines the current tracking state by monitoring the optical information of the adjacent reproduction light Pn detected by the light detection module 270, and controls the tracking servo unit 500 according to the determination result. Apply the signal Ctrl.

The tracking servo controller 300 may include a tracking state determination module 302 and a control module 301.

The tracking state determination module 302 monitors the light information of the adjacent reproduction light Pn detected by the light detection module 270 to determine the current tracking state. Preferably, the tracking state determination module 300 determines the tracking state by using the light distribution of adjacent reproduction light Pn detected by the plurality of light detection regions of the light detection module 270. In this case, the light distribution may mean a distribution of light intensity.

The control module 301 applies a control signal Ctrl to the tracking servo unit 500 in consideration of the tracking state determined by the tracking state determination module 302.

Detailed operation concepts of the trackcane state determination module 302 and the control module 301 are described in detail below.

4 is a diagram illustrating an example of optical information detection by the optical detection module 270 of the reproduction light processing unit 200 illustrated in FIG. 2. When the tracking position is correct, one adjacent reproduction is performed by the optical detection module 270. The example in which the light spot image Pn1 was detected correctly is shown. In this case, it is assumed that the adjacent reproduction light is provided by the reflective slot 260 illustrated in FIG. 3.

As illustrated in FIG. 4, the light detection module 270 has a light detection area corresponding to a size capable of completely detecting one spot image Pn1 among the spot images of eight adjacent reproduction light incident thereto. In this case, the light detection area may be divided into two areas, that is, the light detection area A and the light detection area B. That is, the light detection module 260 may use a two-part photo detector.

In the example shown in Fig. 4, since the tracking state is good, the spot image Pn1 of the one adjacent reproduction light is accurately detected by the light detection area. Therefore, in the light detection area A and the light detection area B, light corresponding to 1/2 of the adjacent reproduction light spot image Pn1 is detected. That is, when tracking is accurate (On Track), the light size detected in the light detection area A and the light detection area B is the same.

FIG. 5 is an exemplary diagram illustrating an image detected in the light detection area when the optical information storage medium moves by a predetermined distance in the example shown in FIG. 4. In this case, the movement refers to the rotation of the optical information storage medium. In fact, since the spot image of the adjacent reproduction light is much smaller than the rotation radius of the optical information storage medium, the spot image of the adjacent reproduction light is horizontally moved when the optical information is detected. It may be considered. In this embodiment, it is assumed that the optical information storage medium rotates counterclockwise. Therefore, it can be seen that the spot image of the adjacent reproduction light moves to the left. Therefore, the arrow shown at the top of FIG. 5 indicates the moving direction of the optical information storage medium.

Referring to FIG. 5, the light information storage medium is slightly rotated so that the spot images Pn1 and Pn2 of two adjacent reproduction lights enter the light detection region in half. Therefore, due to the distance between the two spot images, the size of light detected by the light detection area is smaller than the size of light detected in FIG. 4.

However, the magnitudes of light detected in the light detection area A and the light detection area B are the same. That is, when the track position is normal, the optical information detected in the light detecting region A and the light detecting region B has the same size regardless of the rotation of the optical information storage medium.

FIG. 6 is a graph showing the magnitude of light detected in the light detection area A and the light detection area B as the optical information storage medium rotates when tracking is normal. In the graph shown in FIG. 6, the Y axis represents light intensity and the X axis represents time.

As shown in Fig. 6, when the tracking position is correct, the light detected in the light detection area A and the light detection area B repeatedly increases and decreases. That is, when the spot image Pn1 of the adjacent reproduction light exactly enters the middle of the light detection region as shown in FIG. 4 described above, the size of the light is maximized, and as shown in FIG. When the spot images Pn1 and Pn2 enter the light detection area in half, the size of light is minimized.

However, it can be seen from the graph of FIG. 6 that the magnitude of the optical information detected in the optical detection area A and the optical detection area B is always the same regardless of the rotation of the optical information storage medium if the track position is correct.

7 is an exemplary view illustrating a detection shape of the light detection module when the tracking position is moved above the normal position.

Referring to FIG. 7, it can be seen that the tracking position is moved above the normal position so that the size of light detected in the light detection area A is larger than the size of light detected in the light detection area B. FIG. This is because the center portion of the spot image Pn1 is detected in the light detection area A, and the spot image Pn1 and a part of (Pn3) present in the lower track are detected little by little in the light detection area B.

Therefore, when the light detection area A is larger than the light detection area B, the tracking servo unit 500 is controlled to move the reproduction light processing unit 200 to adjust the tracking position down.

Similarly, if the size of the light detected in the light detection area B is larger than the size of the light detected in the light detection area A, the position of the track is moved downward than normal. In this case, the reproduction light processor 200 is moved. You must move the tracking position up.

FIG. 8 illustrates a case in which the tracking position moves further downward than the state shown in FIG. 7 so that the track is deviated to the maximum position compared to the normal position.

Referring to FIG. 8, it can be seen that the position of the track to be detected is moved higher than the position shown in FIG. 7 so that the magnitude of the light detected in the light detection area A and the magnitude of the light detected in the light detection area B are the same. .

In this case, since the light size of the light detection area A and the light detection area B is the same, it is difficult to distinguish it from the state shown in FIG. 4 described above. However, when the track position before and after is monitored, the light of the light detection area A and the light detection area B Even if the size is the same, it is possible to determine when the track position is normal and when the track position is deviated to the maximum.

FIG. 9 is a graph showing a change in the light size of the light detection area A and the light detection area B when the track position is gradually moved upward from the normal position. In the graph shown in FIG. 9, the Y axis represents light size and the X axis represents time.

Referring to FIG. 9, the light size of the light detection area A and the light size of the light detection area B are the same at the point “a”, and the tracking position is normal. By the way, after the point "a", the light size of the light detection area A becomes larger than the light size of the light detection area B. In other words, this may mean that the tracking position is moving upward.

On the other hand, as the track position continues to move up, the light size of the light detection area A and the light size of the light detection area B become equal again at the " b " point. This case may be considered to be the same as the state shown in FIG. 8. That is, it may mean that the tracking position is deviated to the maximum upward.

These points "a" and "b" can be distinguished by monitoring the light distribution before and after. That is, before the "b" point, the light size of the light detection area A is larger than the light size of the light detection area B. After the "b" point, the light size of the light detection area A is the light size of the light detection area B. Becomes smaller. Therefore, the same point of the light size located between the points where the light size of the light detection area A is cut and smaller than the light size of the light detection area B is determined as the position of the track is moved upward as shown in FIG. Therefore, the position of the track can be adjusted downward through the tracking servo unit 500.

FIG. 10 is a graph showing a change in the difference between the light sizes of the light detection area A and the light detection area B. FIG. Is showing.

Referring to FIG. 10, at the point "a", since the light size of the light detection area A and the light detection area B is the same, the difference value of the light size is "0". In other words, the track position is normal.

Then, when the position of the track moves upward, the light size difference between the light detection area A and the light detection area B increases and decreases and becomes the same again at the point "b". However, in this case, since the same point of the light size located in the front and rear state where the difference in light size is reduced as described above, the position of the track is moved upward as shown in FIG. Therefore, the position of the track must be adjusted down.

In this way, by monitoring the light distribution of the light detection area A and the light distribution of the light detection area B, the current tracking state can be determined, and accordingly, the tracking state can be adjusted by controlling the tracking servo unit 500. This determination and control operation may be performed by the tracking state determination module 302 and the control module 301, respectively.

4 to 8 described above, the case where the light detection module 270 includes a single split photodetector having a light detection area A and a light detection area B has been described. 270 may include a plurality of bipartite photodetectors or photodetectors having more than two photodetection regions.

FIG. 11 is an exemplary diagram illustrating a form of detecting light distribution of a spot image of adjacent reproduction light by using four light detection areas.

Referring to FIG. 11, the light detector has four light detection regions, for example, a light detection region A, a light detection region B, a light detection region C, and a light detection region D. FIG. That is, the light detection module may be provided with two two split photo detectors.

Also in this case, the position of the track can be determined in consideration of the difference in the light size detected in the light detection area A and the light detection area B and the difference in the light size detected in the light detection area C and the light detection area D. For example, the tracking state may be determined by averaging the difference between the light size difference between the light detection area A and the light detection area B and the difference between the light size between the light detection area C and the light detection area D. FIG.

In addition, by using the light detection area structure, it is possible to determine the end of the track or the start of the track of the optical information storage medium.

That is, if the sum of the light magnitudes detected in the light detection area A and the light detection area B and the sum of the light magnitudes detected in the light detection area C and the light detection area D have little difference, the currently detected track stores the optical information. It can be determined to be an intermediate track rather than the first track or the end track of the medium. This is because in the intermediate tracks, each track has a relatively constant light size.

On the other hand, if the sum of the light sizes detected in the light detection area A and the light detection area B and the sum of the light sizes detected in the light detection area C and the light detection area D show a great difference for a predetermined time, the currently detected track is light. The first track or the last track of the information storage medium can be determined. This is because, in the start track or the end track of the light detection area, light information is not detected in the track immediately before or after the track.

Therefore, the use of a plurality of two-segment photodetectors enables not only accurate determination of the tracking state but also detection of the first track and the last track.

12 is a flowchart illustrating a flow of a tracking control method according to an exemplary embodiment of the present invention. The tracking control method illustrated in FIG. 12 may be performed based on the above-described optical information reproducing apparatus.

Referring to Fig. 12, first, in order to obtain current tracking information, it is necessary to obtain light information of adjacent reproduction light. Therefore, at least one adjacent reproduction light adjacent to the detection reproduction light is separated from the reproduction light emitted from the optical information storage medium by the reference light (step S1), and the optical information of the separated adjacent reproduction light is detected (step S2). ).

In this case, the light information of the separated adjacent reproduction light may be detected using a plurality of light detection areas. For example, as described above, light information of one adjacent reproduction light is detected through two light detection areas. Further, the light information of two adjacent reproduction lights may be detected through two light detection areas, respectively, and in this case, the start track and the end track may be discriminated. At this time, the two adjacent reproduction light means the reproduction light by the spot which exists in different tracks (the previous track and the next track of the track currently detected).

The light information of the detected adjacent reproduction light is analyzed to determine the current tracking state (step S3), and to determine whether tracking servo control is necessary (step S4). At this time, if the control of the tracking servo is required as a result of the determination, the tracking position is adjusted in consideration of the current tracking position (step S5). If the control of the tracking servo is not necessary, the current tracking state is maintained (step S6).

For example, a difference in light size detected in the two light detection areas is calculated and the current tracking state is maintained when there is no difference in light size, while the current tracking position is considered when a difference in light size occurs. To perform tracking servo control. That is, to perform tracking adjustment.

For example, when the track position moves above the normal position, the tracking position is moved downward through tracking servo control, and when the track position moves below the normal position, the tracking position position is moved upward.

Although the present invention has been described above with reference to its preferred embodiments, those skilled in the art will variously modify the present invention without departing from the spirit and scope of the invention as set forth in the claims below. And can be practiced with modification. Accordingly, modifications to future embodiments of the present invention will not depart from the technology of the present invention.

As described above, according to the present invention, when the optical information is reproduced, the current tracking state can be determined using the adjacent reproduction light, and the tracking servo control can be performed using the determination result. Therefore, efficient tracking servo control can be achieved through a simple structure, and the reliability of the reproduction data can be improved by reducing the bit error rate through the tracking servo control.

Claims (15)

A reference light providing unit for irradiating the reference light to a predetermined position of the optical information storage medium; A reproduction light processor for separating the reproduction light emitted from the optical information storage medium by the reference light into detection reproduction light and at least one adjacent reproduction light, and detecting light information of the separated adjacent reproduction light; An optical information detector for detecting optical information of the separated detection reproduction light; A tracking servo unit for adjusting a position of the reproduction light processor in response to a control signal; And And a tracking servo controller which analyzes the optical information of the detected adjacent reproduction light to determine whether a tracking position is abnormal and applies the control signal to the tracking servo unit according to the determination result. The method of claim 1, wherein the reproduction light processing unit, A polarized light splitter configured to transmit reproduction light emitted from the optical information storage medium; A reflection type slit for passing the detected reproduction light out of the reproduction light transmitted by the polarization light splitter to the optical information detection unit, and reflecting the adjacent reproduction light; A quarter-wave plate disposed between the polarized light splitter and the reflective slit; And A light detection module for detecting light information of the adjacent reproduction light; And the polarizing light splitter reflects the adjacent reproduction light reflected by the reflective slit and transmitted from the quarter wave plate to the light detection module. The optical information reproducing apparatus according to claim 2, wherein the light detecting module includes a plurality of light detecting regions for detecting adjacent reproduced light reflected by the polarized light splitter. The optical information reproducing apparatus according to claim 3, wherein the tracking servo control unit determines the tracking state by using distributions of light sizes detected in the plurality of light detection areas. The optical information reproducing apparatus according to claim 2, wherein the polarizing light splitter includes a light splitting surface that transmits light having P-polarized light and reflects light having S-polarized light. The method of claim 2, wherein the reproduction light processing unit, A first lens disposed between the optical information storage medium and the polarized light splitter to focus light; A second lens disposed between the polarized light splitter and the quarter wave plate to focus light; And And a third lens disposed between the polarized light splitter and the light detection module to focus light. The method of claim 1, wherein the tracking servo control unit, A tracking state determination module for determining a current tracking state by using light information of adjacent reproduction light detected by the reproduction light processing unit; And And a control module for applying the control signal for adjusting the tracking position to the normal position to the tracking servo unit in response to the tracking state determined by the tracking state determination module. The method of claim 7, wherein the tracking state determination module, And at least one of a first track and an end track of the optical information storage medium using a plurality of detected optical information of the adjacent reproduction light. A tracking servo control apparatus for controlling a tracking servo that adjusts a tracking position when detecting optical information, A tracking state determination module for collecting light information of at least one adjacent reproduction light adjacent to the detection reproduction light to determine a current tracking position; And If the current tracking position determined by the tracking state determination module is not a normal position, the control module for applying a control signal for adjusting the tracking position to the normal position in consideration of the current tracking position to the tracking servo; A tracking servo control apparatus for an optical information reproducing apparatus, comprising: 10. The apparatus of claim 9, wherein the light information of the adjacent reproduction light is light information respectively detected by a plurality of light detection areas, and the tracking state determination module uses the distribution of light sizes of the plurality of light detection areas. A tracking servo control apparatus for an optical information reproducing apparatus, characterized in that it determines a tracking position of the optical information reproducing apparatus. Separating at least one adjacent reproduction light adjacent to the detection reproduction light from the reproduction light emitted from the optical information storage medium by the reference light; Detecting optical information of the separated adjacent reproduction light; Analyzing light information of the detected adjacent reproduction light to determine a current tracking state; And And if the determined current tracking state is not normal, adjusting to a normal tracking position using the current tracking state information. 12. The tracking control method according to claim 11, wherein in the optical information detecting step, optical information of the separated adjacent reproduction light is detected through a plurality of optical detection areas. The method of claim 12, wherein the plurality of light detection areas are two light detection areas, The tracking state determination step is a tracking control method of the optical information reproducing apparatus, characterized in that for determining the current tracking state by analyzing the difference in the light size detected in the two light detection area. 15. The method of claim 13, wherein the current tracking state is determined to be normal when the difference between the light sizes detected in the two light detection areas is smaller than a predetermined reference value, and the current tracking when the difference between the light sizes is larger than the predetermined reference value. A tracking control method for an optical information reproducing apparatus, characterized in that it is determined that the state is abnormal. 15. The method of claim 14, wherein the adjusting of the tracking position comprises adjusting the tracking position in a direction of reducing the difference in the light size when the difference in the light size detected in the two light detection areas is larger than a predetermined reference value. A tracking control method of an optical information reproducing apparatus.

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