KR20090002584A - Method of controlling tracking servo for optical information reproducting apparatus and apparatus of optical information reproducting - Google Patents

Abstract

An optical information reproduction device and a tracking servo control method thereof are provided to improve the reproduction efficiency by making the reproduction reference beam incident to the right position of the recording region without a separate light source. A tracking servo control method of an optical information reproduction device comprises a step of projecting reproduction reference beam to a recording region of a recording medium while moving the reproduction reference beam in the tracking direction, a step of reproducing the incident reproduction reference beam according to the moving distance in the tracking direction, a step of detecting the reproduction beam in divided detection regions and detecting the total intensity of the reproduction beam detected in each detection region, and a step of producing tracking error signal by using the total beam intensity and performing tracking servo control.

Description

Method of controlling tracking servo for optical information reproducting apparatus and apparatus of optical information reproducting

The present invention relates to a tracking servo control method and an optical information reproducing apparatus of an optical information reproducing apparatus, and more particularly, to an optical information reproducing apparatus which performs tracking servo control without having a light source for a separate tracking servo control and the same. A tracking write control method is used.

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

Therefore, it is an optical information storage device capable of high-capacity storage and high-speed input / output of data using optical, and it is a compact disc (CD), a digital versatile disc (DVD), a high definition DVD (HD-DVD), Blue-ray discs (BD), holographic (Holographic) and the like are in the spotlight.

The optical information processing apparatus using holographic intersecting a signal beam on which data is loaded and a reference beam having an incident angle different from that of the signal light, and recording an interference pattern generated by the interference of two lights. To record.

In order to reproduce optical information from the recording area, that is, the interference fringe stored in the recording medium as described above, the reproduction reference light which is restored to the reference light incident upon recording the optical information into the recording area is incident to the recording area. When the reproduction reference light enters the recording area, the reproduction light diffracted in the recording area is reproduced, and the reproduction information is detected to reproduce the optical information.

Here, in order for the reproduction reference light to enter the recording area in the correct position, a tracking servo control for controlling the reproduction reference light to enter the correct position along the plurality of recording areas, an angle servo control for controlling the incident angle of the reproduction reference light, There is a need for servo control such as a focusing servo control for controlling the distance between the objective lens for condensing the reproduction reference light to the recording area and the recording medium.

Conventional servo control is performed by separately providing a light source for servo control with a light source for recording and reproducing optical information. In addition, an optical detector for detecting the optical information from the reproduction light and a servo optical detector for receiving the servo control signal are provided separately.

Conventional servo control has a separate light source for servo control and has to provide a separate optical path for injecting light into the recording area. Therefore, the configuration of the optical information processing apparatus becomes complicated, and accordingly, the increase of optical devices There is a problem that the construction cost of the optical information processing device is increased.

Tracking servo control method of the optical information reproducing apparatus according to an embodiment of the present invention for achieving the above object is an incident step of moving the reference light for reproduction in the tracking direction and incident to the recording area of the recording medium; A reproduction step of reproducing the reproduction light according to the moving distance in the tracking direction, the reproduction light being detected in the divided detection area, and detecting the sum of the light intensities of the reproduction light detected in each divided detection area; Detecting step; And a tracking servo control step of generating a tracking error signal using the sum of the light intensities and performing tracking servo control.

The detecting step divides the detection area into a first detection area and a second detection area to detect the reproduced light by dividing, and the tracking servo control step includes a sum of the light intensities of the reproduced light detected in the first detection area. And calculating the difference in the sum of the light intensities of the reproduction lights detected in the second detection region to generate the tracking error signal.

In the tracking servo control step, the incident position of the reference reference light for reproducing is set to a side where the sum of the light intensities of the reproduced light detected in the first detection area and the difference in the sum of the light intensities of the reproduced light detected in the second detection area are detected as zero. I can regulate it.

The first detection area and the second detection area may be signal light detection areas for detecting data loaded on signal light detected from the reproduction light when optical information is reproduced.

On the other hand, the optical information reproducing apparatus according to an embodiment of the present invention includes an optical system for moving the reproduction reference light in the tracking direction and incident to the recording area of the recording medium; detecting the signal light from the reproduction light reproduced by the reproduction reference light An optical detector having a first detection area and a second detection area for dividing and detecting the light intensity of the reproduction light; the detection signal detected by the first detection area and the second detection area; A control unit for generating a tracking error signal using the sum of the light intensities of the reproduction lights; And an actuator for moving the incident position of the reproduction reference light under the control of the controller.

The signal light detection area may be formed to have the same pixel pitch as the pixel pitch of the signal light pattern area modulated by the signal light when optical information is recorded, and the first detection area and the second detection area may each consist of one cell.

The actuator may move at least one of the optical system and the recording medium under the control of the controller.

The servo light detector may be further provided in the path of the reproduced light reflected by the photo detector, and the servo light detector may detect the light intensity of the reproduced light reflected by the photo detector in a divided detection region.

The tracking servo control method and the optical information reproducing apparatus of the optical information reproducing apparatus according to the present invention as described above perform tracking servo control without providing a separate light source for tracking servo control, so that the reference light for reproduction is defined in the recording area. Since the light enters the position, the reproduction efficiency can be increased.

Hereinafter, an optical information reproducing apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram briefly showing an optical information reproducing apparatus according to an embodiment of the present invention. Referring to FIG. 1, the optical information reproducing apparatus 100 includes an optical system 110, a photo detector 130, a controller 150, and an actuator 170.

The optical system 110 is provided to restore the reference light L incident upon optical information recording and provide the reference light L for reproduction. The optical system 110 includes a light source 111, a spatial filter 112, a first wavelength plate 113, a light modulator 115, a polarized light separator 116, a condenser lens 119, and a second wavelength plate 118. It may be provided.

The light source 111 is provided to provide light L for reproducing optical information. The spatial filter 112 is provided after the light source 111 to remove unnecessary light L that may be included in the light L provided from the light source 111. After the spatial filter 112, the first wave plate 113 for changing the polarization of the light L is provided. The first wave plate 113 may be a half wave plate (λ / 2 wave plate) that provides light L with P polarization. After the first wave plate 113, a mirror 114 may be provided to guide the light L to the light modulator 115 between the first wave plate 113 and the light modulator 115.

The light modulator 115 is provided in the path of the light L guided by the mirror 114. The light modulator 115 may include a reference light pattern area (not shown) for modulating the light L into the reference light L incident upon optical information recording. The reference light pattern area (not shown) is composed of a plurality of pixels, so that the reference light pattern can be displayed by dividing the pixels into on / off pixels.

Such a light modulator 115 may be adopted as a reflective spatial light modulator such as a digital micro-mirror device (DMD). Here, in another embodiment, the optical modulator 115 may include a transmissive spatial light modulator such as twisted nematic liquid crystal (TN-LC), super twisted nematic liquid crystal (STN-LC), and thin film transistor liquid crystal (TFT-LC). It can be adopted as either. As such, when the optical modulator 115 is adopted as a transmissive spatial light modulator, the configuration of the mirror 114 is omitted, and the optical modulator 115 is installed on the path of the light L provided from the light source 111. Can be.

After the light modulator 115, a polarized light splitter 116 is provided, which is provided with a reflective surface 116a that transmits light of P-polarized light and reflects light of S-polarized light. As long as there is focus at the reflecting surface 116a of the polarizing light separator 116 between the light modulator 115 and the polarizing light separator 116 and between the polarizing light separator 116 and the second wave plate 118. Pairs of lenses 117a and 117b may be provided.

A second wave plate 118 for changing the polarization of the light may be provided in the path of the light L passing through the polarized light separator 116. When recording the optical information, the second wave plate 118 converts the light L of the P-polarized light into circularly polarized light and enters the recording medium 10, and reproduces the reproduced light P reflected from the recording medium 10. It may be a quarter wave plate (λ / 4 wave plate) to change from polarized light to S polarized light.

The condenser lens 119 is provided between the second wave plate 118 and the recording medium 10, and is used as an objective lens for condensing the reproduction reference light R to the recording area Ra of the recording medium 10. Can be.

On the other hand, the recording medium 10 includes a recording layer 10a and a reflective layer 10b. In the recording layer 10a, the recording area Ra is recorded by an interference pattern in which the reference light L and the signal light L intersect, and are made of an optical refractive material such as a photopolymer. The reflective layer 10b is made of a light reflective material such as aluminum to reflect the reproduction light P to which the reproduction reference light R is incident and reproduced in a direction opposite to the incident direction of the reproduction reference light R. . The recording medium 10 may be installed to be coupled to the spindle motor 11 to rotate in the tracking direction.

On the other hand, an imaging lens 131 may be provided in the path of the reproduction light P reflected by the polarized light splitter 116. The imaging lens 131 is provided to image the reproduced light P passing through the photo detector 130 at the photo detector 130. The photo detector 130 may be adopted as any one of a charge coupled device (CCD) and a low power consumption type imaging device having a complementary metal oxide semiconductor structure (CMOS).

2 is a conceptual diagram illustrating a configuration of a detection area of a photo detector according to an embodiment of the present invention. Referring to FIG. 2, the photodetector 130 may include a signal light detection region 140, and the signal light detection region 140 may be divided into a first detection region 141 and a second detection region 143. .

The signal light detecting region 145 has the same pitch as the signal light pattern region (not shown) displayed on the optical modulator 115 at the time of optical information recording so that the signal light can be detected from the reproduction light P after the tracking servo control is performed. It may be provided with a plurality of pixels (not shown) having.

The first detection area and the second detection area are provided for detecting the light intensity of the reproduced light formed in the photo detector during tracking servo control. The first detection region 141 and the second detection region 143 divide the detection region 140 of the photodetector 130 to the left and right to detect the light intensity of the detected reproduction light P, respectively. Each cell may be provided as one cell.

Referring back to FIG. 1, the controller 150 generates a tracking error signal by using the sum of the light intensities detected in the first detection region 141 and the second detection region 143 of the photo detector 130. The actuator 170 is provided to control the actuator 170 according to the tracking error signal. The actuator 170 is fastened to the optical system 110 and the spindle motor 11, and moves one of the optical system 110 or the spindle motor 11 under the control of the controller 150 to perform tracking servo. do.

Hereinafter, a tracking servo control method of an optical information reproducing apparatus according to an embodiment of the present invention will be described in detail.

3 is a flowchart illustrating a tracking servo control method of an optical information reproducing apparatus according to an exemplary embodiment of the present invention. Referring to FIG. 3, the light L emitted from the light source 111 is removed from the spatial filter 112, is reflected by the mirror 114, and is incident to the light modulator 115. At this time, the light L emitted from the light source 111 is changed to P polarized light which is horizontally polarized light while passing through the first wave plate 113. The light L is incident on the light modulator 115 and modulated to the reproduction reference light R by a reference light pattern (not shown) displayed on the light modulator 115.

In this way, the light L provided from the light source 111 is provided as the reference light R for reproduction. The reproduction reference light R is incident to the polarized light separator 116. The reproduction reference light R incident to the polarized light separator 116 is P-polarized light that is horizontally polarized, and thus passes through the polarized light separator 116 and enters the recording medium 10. At this time, the reproduction reference light R is changed from P-polarized to circularly polarized light while passing through the second wave plate 118 and is incident on the condensing lens 119. The reproduction reference light R is incident on the recording area Ra of the recording medium 10 by the condensing lens 119 (step S11).

When the reproduction reference light R enters the recording area Ra of the recording medium 10, the reproduction light P is reproduced (step S13). The reproduction light P is reflected by the reflective layer 10b and reflected in the direction opposite to the incident direction of the reproduction reference light R. As shown in FIG. The regenerated light P passes through the second wave plate 118 and changes from circularly polarized light to vertically polarized S polarized light and is incident to the polarized light separator 116. At this time, since the reproduction light P is S-polarized light, it is reflected by the reflective surface 116a of the polarized light separator 116 and is incident on the imaging lens 131. The reproduction light P is imaged to the photodetector 130 by the imaging lens 131, and the photodetector 130 detects the reproduction light P. FIG.

On the other hand, in order to reproduce the optical information, the spindle motor 11 rotates the recording medium 10 in the tracking direction so that the reproduction reference light R enters the recording area Ra to be reproduced, or the actuator 170 The optical system 110 may be moved in the tracking direction (hereinafter referred to as tracking movement).

 4 is an operation diagram showing an operation in which the reproduction reference light is moved in the tracking direction with respect to a predetermined recording area and is incident according to an embodiment of the present invention. Referring to FIG. 4, it can be seen that, in accordance with the tracking movement, the reproduction reference light R is moved from the left side of the recording area Ra to the right side of the recording area Ra. That is, the reproduction reference light R1 incident to the left side of the recording area Ra, the reproduction reference light R2 incident to the right position to be concentric with the recording area Ra, and the right side of the recording area Ra It can be seen that the reproducing reference light R3 is incident.

5A is a photograph of a detection image of the reproduction light detected by the photo detector when the incident position of the reproduction reference light is shifted to the left. Referring to FIG. 5A, when the reproduction reference light R is incident to the left side of the recording area Ra, the left side of the detection image 160 of the reproduction light P detected by the photodetector 130 is clearly detected. It can be seen that the right side is blurred. That is, the light intensity detected in the first detection region 141 of the photo detector 130 is detected to be larger than the light intensity detected in the second detection region 143.

5B is a photograph of a detection image of the reproduction light detected by the photodetector when the incident position of the reproduction reference light is incident to the right. Referring to FIG. 5B, when the reproduction reference light R is incident to the right side of the recording area Ra, the right side of the detection image 160 of the reproduction light P detected by the photodetector 130 is clearly detected. You can see that the left side is blurred. That is, the light intensity detected in the second detection region 143 of the photo detector 130 is detected to be larger than the light intensity detected in the first detection region 141.

6A is a graph illustrating a distribution of light intensity sums detected in the first detection area according to a tracking movement distance. Referring to FIG. 6A, the reproduction reference light R enters to the left of the recording area Ra, and the sum of the light intensities of the reproduction light detected in the first detection area 141 gradually increases, and then the reproduction reference light R It can be seen that the light intensity sum of the reproduction light P detected in the first detection area 141 decreases rapidly as it is moved to the center of the recording area Ra, that is, the point "0" of the graph horizontal axis. Subsequently, as the reproduction reference light R exits to the right of the recording area Ra, it can be seen that the sum of the light intensities of the reproduction light P detected in the first detection area 141 gradually increases.

6B is a graph illustrating a distribution of light intensity sums detected in the second detection area according to a tracking movement distance. Referring to FIG. 6B, it can be seen that the distribution of the light intensity sum detected in the second detection area 143 is different from the distribution of the light intensity sum detected in the first detection area 141 according to the tracking movement distance.

In other words, the reproduction reference light R enters to the left of the recording area Ra, so that the sum of the light intensities of the reproduction light P detected in the second detection area 143 gradually decreases, and the reproduction reference light R It can be seen that the sum of the light intensities of the reproduction light Ps detected in the second detection area 143 is rapidly increased as () is moved to the center of the recording area Ra. Subsequently, as the reproduction reference light R exits to the right of the recording area Ra, it can be seen that the sum of the light intensities of the reproduction light P detected in the second detection area 143 gradually decreases (step). ; S15).

The tracking error signal may be generated using the sum of the light intensities that are differently detected in the first and second detection regions 141 and 143.

FIG. 7A is a graph illustrating a tracking error signal generated by using the sum of the light intensities detected in the first detection area and the second detection area, respectively. FIG. 7B shows a reference light for reproduction to the correct position of the recording area under tracking servo control. It is a photograph showing the detected image of the incident light which is incident and detected. 7A to 7B, the tracking error signal is generated by calculating the difference between the sum of the light intensities detected in the second detection area 143 and the sum of the light intensities detected in the first detection area 141.

The tracking error signal decreases gradually as the reproduction reference light R enters the left side of the recording area Ra and moves to the center of the recording area Ra, and then decreases in the 500 nm section of the center of the recording area Ra. It can be seen that it is increased in a curved shape and gradually decreases as the reproduction reference light R exits from the center of the recording area Ra to the right.

The controller 150 generates the tracking error signal, and controls the actuator 170 based on the tracking error signal so that the actuator 170 performs tracking control. In other words, when the tracking error signal is detected to be smaller than "0", the controller 150 controls the actuator 170 to move the recording medium 10 or the optical system 110 to the right, and the tracking error signal is If greater than "0", the actuator 170 may be controlled to move the recording medium 10 or the optical system 110 to the right (step S17).

As described above, when the reproduction reference light R enters the correct position of the recording area Ra through the tracking servo control, the left and right signals are clearly detected as shown in the detection image 160 of FIG. 7B. At this time, the photodetector 130 detects data from the signal light detected by the signal light detection region 140 to reproduce the optical information.

Here, in the above description, the first detection region 141 and the second detection region 143 are divided into two parts to the left and the right, and the actuator 170 moves the recording medium 10 or the optical system 110 to the left and right. Although it is described as moving and performing tracking servo control, this is only in accordance with an embodiment of the present invention, and the divided positions of the first detection region 141 and the second detection region 143 and the actuator 170 are described. The direction to be moved may be changed as many as possible within the technical scope of those skilled in the art.

Hereinafter, an optical information reproducing apparatus according to another embodiment of the present invention will be described. Components similar to those of the above-described optical information reproducing apparatus 100 among the components described below are denoted by the same reference numerals, and detailed description thereof will be omitted. Therefore, among the components of the optical information reproducing apparatus 100 which will be described below, components which have not been described in detail will be understood with reference to the above description.

8 is a configuration diagram schematically showing an optical information reproducing apparatus according to another embodiment of the present invention. Referring to FIG. 8, the optical information reproducing apparatus 200 may include a third wavelength plate 231 in the path of the reproducing light P reflected from the reflecting surface 216a of the first polarized light splitter 216 of the optical system 100a. ), A first imaging lens 131, a second polarized light splitter 233, and a fourth wave plate 234. The third wave plate 231 may be a half wave plate for converting the regenerated light of S polarized light into P polarized light, and the second polarized light separator 233 transmits the regenerated light P of P polarized light and reproduces the regenerated light P ) Is provided at the photodetector 130 by the first imaging lens 131. At this time, between the second polarized light separator 233 and the photo detector 130, the regenerated light P incident on the photo detector 130 is changed into circularly polarized light, and the regenerated light reflected by the photo detector 130 is changed. A fourth wave plate 234 provided with a quarter wave plate for changing to S polarization is provided.

On the other hand, the second imaging lens 251 and the servo light detector 250 are provided in the path of the reproduction light P reflected by the reflective surface 233a of the second polarized light separator 233. The second imaging lens 251 is provided to form the reproduction light P reflected by the second polarized light separator 233 at the servo light detector 250. The servo light detector 250 divides the detection area (not shown) of the reproduction light P into two or four parts, and detects the sum of the light intensities of the reproduction light P for each detection area (not shown). It may be provided as a photodiode so as to.

The optical information reproducing apparatus 200 detects the reproduction light P reflected by the optical detector 130 and performs tracking servo control. That is, the detection light P reflected by the photodetector 130 is dividedly detected by the servo light detector 250 to detect the sum of the light intensities of the reproduction light P which is dividedly detected, and the sum of the detected light intensities is determined. The difference is calculated to perform tracking servo control, and optical information can be reproduced.

As described above, the optical information reproducing apparatus 100 or 200 divides the detection region 140 of the reproduction light P, and generates a track error signal by using a difference in the light intensity sum detected in the divided detection regions 141 and 143, respectively. Using this, track servo control is performed.

1 is a configuration diagram briefly showing an optical information reproducing apparatus according to an embodiment of the present invention.

2 is a conceptual diagram illustrating a configuration of a detection area of a photo detector according to an embodiment of the present invention.

3 is a flowchart illustrating a tracking servo control method of an optical information reproducing apparatus according to an exemplary embodiment of the present invention.

4 is an operation diagram showing an operation in which the reproduction reference light is moved in the tracking direction with respect to a predetermined recording area and is incident according to an embodiment of the present invention.

5A is a photograph of a detection image of the reproduction light detected by the photo detector when the incident position of the reproduction reference light is shifted to the left.

5B is a photograph of a detection image of the reproduction light detected by the photodetector when the incident position of the reproduction reference light is incident to the right.

6A is a graph illustrating a distribution of light intensity sums detected in the first detection area according to a tracking movement distance.

6B is a graph illustrating a distribution of light intensity sums detected in the second detection area according to a tracking movement distance.

FIG. 7A is a graph illustrating a tracking error signal generated using the sum of the light intensities detected in the first and second detection areas, respectively.

Fig. 7B is a photograph showing a detected image of the reproduced light detected by the reproduction reference light entering the correct position in the recording area under the tracking servo control.

8 is a configuration diagram schematically showing an optical information reproducing apparatus according to another embodiment of the present invention.

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

100: optical information reproducing apparatus 110: optical system

130: light detector 150: control unit

170: actuator

Claims (8)

An incident step of moving the reproduction reference light in the tracking direction and entering the recording area of the recording medium; A reproducing step in which the reproducing reference light is incident on the recording area to reproduce the reproducing light according to the moving distance in the tracking direction; A detection step of detecting the reproduced light in the divided detection regions and detecting a sum of the light intensities of the reproduced light detected in each divided detection region; And a tracking servo control step of generating a tracking error signal using the sum of the light intensities and performing tracking servo control. The method of claim 1, wherein the detecting step divides the detection area into a first detection area and a second detection area, and detects the reproduced light separately. The tracking servo control step may generate the tracking error signal by calculating a difference between the sum of the light intensities of the reproduction light detected in the first detection area and the sum of the light intensities of the reproduction light detected in the second detection area. A tracking servo control method of an optical information reproducing apparatus. The reproducing control method as claimed in claim 2, wherein the tracking servo control step is performed such that the difference between the sum of the light intensities of the reproduction light detected in the first detection area and the sum of the light intensities of the reproduction light detected in the second detection area is detected as 0. Tracking servo control method, characterized in that for adjusting the incident position of the reference light. The method of claim 2, wherein the first detection area and the second detection area are And a signal light detection area for detecting data loaded on the signal light detected from the reproduced light when optical information is reproduced. An optical system which moves the reproduction reference light in the tracking direction and enters the recording area of the recording medium; And a signal light detection area for detecting signal light from the reproduction light reproduced by the reproduction reference light, wherein the signal light detection area is provided with a first detection area and a second detection area for dividing and detecting the light intensity of the reproduction light. Detectors; A controller configured to generate a tracking error signal by using a sum of light intensities of the reproduction light detected in the first detection area and the second detection area; And an actuator for moving the incident position of the reproduction reference light under the control of the controller. The method of claim 5, wherein the signal light detection area is When recording optical information, the pixel pitch is formed to have the same pixel pitch as the pixel pitch of the signal light pattern region to be modulated by the signal light. And the first detection area and the second detection area each comprise one cell. The method of claim 5, wherein the actuator And at least one of the optical system and the recording medium under the control of the controller. The method of claim 5, wherein the servo light detector is further provided in the path of the reproduction light reflected by the photo detector, And the servo light detectors respectively detect the light intensity of the reproduced light reflected by the light detector in a detection area divided therein.

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