KR20100030894A - Tilt controlling method and apparatus - Google Patents

Abstract

A tilt control method according to an aspect of the present invention comprises the steps of measuring the vertical displacement between the recording medium and the lens unit, measuring the linear distance from the lens unit to the center of the recording medium and the measured vertical displacement and straight line And measuring the tilt amount of the recording medium with respect to the lens unit by using a distance.

Description

Tilt control method and apparatus {TILT CONTROLLING METHOD AND APPARATUS}

The present invention relates to a method and apparatus for measuring and controlling the amount of tilt between a recording medium and an optical pickup.

A recording / reproducing apparatus using light records data on the recording medium or reproduces the recorded data by using a recording medium such as various disc types. Recently, high-quality video processing is required due to the advancement of consumer's preference, and as the video compression technology is developed, the recording medium is also required to be high in density. To this end, as a technology for high-density recording media, recently, near-field recording (Near Field Recording) by near-field optics such as Blue-ray Disc, HD-DVD, etc. NFR) devices are being developed. In addition, a recording medium having a multilayer recording layer has been developed.

NFR applies SIL to the objective lens of the optical unit to increase the NA (opening number) for recording and reproduction. This NFR is a Gap Servo Controller that records the SIL and the media at a few tens of nanometers while recording the gap between the SIL and the media, the size of the beam reaching the disk, and the recording characteristics of certain pulses. The performance of the recording and playback device will be determined.

Since NFR has a very small gap between the disk and the SIL, there is a high risk of collision between them. If a collision occurs, not only will the servo become impossible, but it may also cause damage to the disk and SIL.

An object of the present invention is to calculate the amount of tilt by controlling the tilt.

The tilt control method according to the present invention for achieving the above object comprises the steps of measuring the vertical displacement between the recording medium and the lens unit, measuring the linear distance from the lens unit to the center of the recording medium and the measured And measuring the tilt amount of the recording medium with respect to the lens unit by using the vertical displacement and the linear distance.

The vertical displacement may be measured using an actuator transfer function.

The actuator transfer function is characterized in that the following function.

A: constant. B, C, D: Coefficients arbitrarily set by the user. s: magnitude and frequency value of the signal input.

The linear distance is calculated based on the driving distance of the sled motor which moves the lens portion in the radial direction of the recording medium.

The tilt amount is measured using the following formula.

X: straight line distance from the lens portion to the center of the recording medium

Y: vertical displacement between the tilted recording medium and the lens portion

The tilt amount between the lens unit and the recording medium is determined by comparing the measured tilt amount with the tilt reference amount set by the user.

The tilt control device according to the present invention includes a lens unit for irradiating light to a recording medium and condensing the light reflected from the recording medium, a sled motor for moving the lens unit in the radial direction of the recording medium, and the recording medium; The vertical displacement between the lens unit and the linear distance from the lens unit to the center of the recording medium are measured, and the tilt amount of the recording medium based on the lens unit is measured using the measured vertical displacement and linear distance. It includes a control unit.

According to the tilt control method and apparatus according to the present invention as described in detail above, by estimating the absolute amount of the tilt error for the active tilt control to prevent the collision of the NFR recording medium and the lens, it is applied to the recording / playback device further improved The effect of obtaining a recording / playback apparatus with reliability is obtained.

Hereinafter, an embodiment of the tilt control device of the present invention will be described in detail. In adding reference numerals to the components of the following drawings, the same components are used the same reference numerals as much as possible even if they are displayed on different drawings. In this specification, for convenience of description, an example of a recording method and apparatus will be described in detail.

1 is a block diagram illustrating a tilt control device according to an embodiment of the present invention. This will be described in detail with reference to the other drawings.

Referring to FIG. 1, the tilt control apparatus according to the present invention includes an optical pickup 100, a signal processor 110, a controller 120, a gap servo driver 130, a sled motor 140, a tilt servo driver 150, The main controller 160, the interface 170, and the spindle motor 180 may be included.

The optical pickup 100 is a portion for irradiating light to a recording medium and receiving light reflected on the recording medium to generate an electrical signal corresponding to the reflected light. The configuration of the optical pickup 100 will be described in detail later with reference to FIG. 2.

The signal processor 110 generates a recording / playback signal (also referred to as an “RF signal”) necessary for data reproduction and a gap error signal or a tilt error signal necessary for servo control by using the electrical signal generated by the optical pickup 100. . In addition, the gap error signal is processed and converted into a drive signal for controlling the gap between the lens unit 104 and the recording medium and outputted to the gap servo driver 130.

The controller 120 measures the tilt amount of the recording medium based on the lens unit 104 and determines whether the tilt control is performed between the lens unit and the recording medium according to the measured tilt amount. The tilt amount is measured from the linear distance from the lens portion 104 to the center of the recording medium and the vertical displacement between the tilted recording medium and the lens portion 104, and the user sets an arbitrary reference value and the measured tilt amount. By comparison, tilt control is determined. In addition, the control unit 120 transmits a driving signal to the motor driving unit to control the sled motor 140 to move the optical pickup 100 in the radial direction of the recording medium.

As shown in FIG. 1, the part processed by a thin dotted line shows a tilt control loop. A part of the driving signal of the gap servo driver 130 is transmitted to the controller 120, and the controller 120 measures the tilt amount. And tilt control, and the controller 120 converts the tilt error signal into a driving signal for tilt control and outputs the tilt error signal to the tilt servo driver 150.

The gap servo driver 130 moves the lens unit 104 of the optical pickup 100 or the optical pickup illustrated in FIG. 2 by driving the actuator 107 in the optical pickup 100. As a result, the distance between the lens unit 104 and the recording medium can be kept constant.

In FIG. 1, a portion treated with a thick dotted line shows a servo control loop. The signal processor 110 receives an electrical signal from the optical pickup 100, converts it into a gap error signal, and then converts the signal into a gap error driver 130. By transmitting, the optical servo driver 100 may control the optical pickup 100. In the present invention, a part of the driving signal of the gap servo driver 130 may be transmitted to the controller 120 to allow the controller 120 to measure the tilt amount.

The tilt servo driver 150 corrects the inclination between the lens unit 104 to be described later of the optical pickup 100 and the recording medium by driving or giving an offset to the actuator 107 in the optical pickup 100. Through this, an error due to the tilt between the lens unit and the recording medium (hereinafter referred to as tilt), which occurs when the recording medium itself is bent or tilted and seated on the drive, can be corrected.

The interface 170 receives a recording or reproducing command of the user from the main controller 160 and transmits the command to the controller 120 so that the controller 120 controls each component.

The main controller 160 transmits a recording / playback command to the interface 170 and controls the entire system. The main controller 160 may be a main controller of a computer, a server, an audio device, or a video device.

Spindle motor 180 is involved in recording / reproducing data by rotating the recording medium.

The recording / playback apparatus according to the embodiment of the present invention is applicable to both an optical drive and a player used as a single product mounted and operated inside a PC.

2 is a block diagram showing an embodiment of the optical pickup 100 provided in the tilt control device of the present invention.

Referring to FIG. 2, the optical pickup 100 may include a light source 101, a separate combining unit 102 and 103, a lens unit 104, a light detecting unit 105 and 106, an actuator 107, and the like.

As the light source 101, a laser or the like having good linearity may be used. Therefore, the light source 101 is specifically a laser diode. The light emitted from the light source 101 to be irradiated onto the recording medium may be composed of parallel light. Therefore, it can be configured to include a lens, such as a collimate, to parallel the path of light on the path of light emitted from the light source.

The separate combining units 102 and 103 separate portions of paths of light incident in the same direction or synthesize paths of light incident in different directions. In the present embodiment, since the first separation synthesis unit 102 and the second separation synthesis unit 103 are provided, each of them will be described. The first separation composition part 102 is a part that passes a part of incident light and reflects a part of the incident light. In addition, the second separation synthesis unit 103 is a portion that passes only the polarization in a specific direction according to the polarization direction. For example, when using linear polarized light, the second separation synthesis unit 103 may be configured to pass only the polarization component in the vertical direction and reflect the polarization component in the horizontal direction. Alternatively, it may be configured to pass only the polarization component in the horizontal direction and reflect the polarization component in the vertical direction.

The lens unit 104 is a portion that irradiates the recording medium with the light emitted from the light source 100 and condenses the light reflected from the recording medium again. In the present embodiment, the lens unit is a portion forming a near field, which will be described below in detail with reference to FIG. 3.

The light detectors 105 and 106 are parts for receiving and photoelectrically converting the reflected light to generate an electrical signal corresponding to the light amount of the reflected light. The first light detector 105 and the second light detector 106 may be constituted by two light detectors PDA and PDB that are specifically divided, for example, divided into two in the signal track direction or the radial direction of the recording medium. . The photodetectors PDA and PDB generate electrical signals A and B proportional to the amount of light received. Alternatively, the light detectors 105 and 106 may be composed of four light detectors (PDA, PDB, PDC, PDD) divided into two in the signal track direction and the radial direction of the recording medium. Here, the configuration of the photodetecting elements constituting the photodetectors 105 and 106 is not limited to this embodiment, and various modifications may be made as necessary.

The actuator 107 has a shape surrounding the lens unit 104 with a coil, and receives a drive signal from the servo drivers 130 and 150. In the case of the present invention, as shown, in particular, a drive signal is received from the gap servo driver 130, and some of the signals are transmitted to the controller 120, so that the controller 120 can detect the tilt amount and control the tilt.

3 is a cross-sectional view schematically showing the lens unit 104 of the optical pickup constituting an embodiment of the present invention.

Referring to FIG. 3, the lens unit 104 may include an objective lens 104a and a high refractive index lens 104b.

The lens unit 104 further includes a lens having a high refractive index in addition to the objective lens 104a to increase the numerical aperture, thereby forming an evanescent wave, thereby forming a near field. Specifically, as shown in Fig. 3, the high light provided on the objective lens 104a and the path through which the objective lens 104a enters the recording medium (the portion corresponding to C indicated by a dotted line) is provided. Refractive index lens 104b. In the present invention, the objective lens 104a and the high refractive index lens 104b provided in the lens unit 104 may be variously modified.

Here, the high refractive index lens 104b is referred to as a "near lens forming lens" for convenience of description. In a recording and reproducing apparatus using a near field, the near field forming lens 104b needs to be located very close to the recording medium. As shown in Fig. 3, the spacing (the spacing indicated by H) between the near field forming lens 104b and the recording medium should be maintained at the nanometer to micrometer level spacing. Specifically, the relationship between the lens unit 104 and the recording medium will be described as an example.

When the lens unit 104 and the recording medium are brought close to about 1/4 (or λ / 4) or less of the optical wavelength, a part of the light incident on the lens unit 104 at a critical angle or more is formed at the surface of the recording medium. A dissipation wave is formed without total reflection, and passes through the recording medium to reach the recording layer. The dissipated wave that has reached the recording layer can be used for recording and reproducing. This makes it possible to store high density bit information with light below the diffraction limit. However, when the distance between the lens unit 104 and the recording medium is greater than λ / 4 or more, the wavelength of the light loses the property of the dissipation wave and returns to the original wavelength, and the surface of the recording medium or the near field forming lens 104b Total reflection at the surface. In this case, dissipation waves cannot be formed, and recording and reproduction by the near field cannot be performed. Therefore, in the recording / reproducing apparatus using the near field, the lens section 104 is controlled so that the distance from the recording medium does not exceed approximately? / 4. Is the limit of the near field. That is, in order to use the near field, the lens unit 104 and the recording medium need to maintain a nanometer distance. In this embodiment, a gap error signal (hereinafter, referred to as 'GE') may be used as a method of maintaining the nanometer-level spacing. In addition, the objective lens 104a must maintain an alignment relationship with the near field forming lens 104b, and this alignment relationship can be easily disturbed when the objective lens 104a is moved. Therefore, the objective lens 104a is configured to be fixed and not to move. For example, one lens unit may be set by combining the objective lens 104a and the near field forming lens 104b with a barrel (not shown). SIL may be used as the high refractive index near field forming lens 104b.

4 is a diagram illustrating a concept for measuring a tilt error according to an embodiment of the present invention.

As shown in Fig. 4, X, a straight line distance from the SIL to the center of the recording medium, can be calculated based on the driving distance of the sled motor. In addition, Y, which is a vertical displacement between the tilted recording medium and the lens unit 104, is in real time from the control input and the actuator 107 transfer function which is a part of the driving voltage transmitted from the gap servo driver 130 to the optical pickup 100 in real time. Can be calculated Here the transfer function is

Where A is a constant, B, C, and D are coefficients arbitrarily set by the user, and s is the magnitude and frequency of the signal input. This function may be obtained by modeling the actuator 107 and the order or coefficient of the transfer function may change according to the characteristics of the actuator 107. The unit of function is the unit of distance per voltage input, such as meter / volt.

The absolute tilt amount is measured by the vertical displacement between the tilted recording medium and the lens unit 104 measured using the distance from the SIL and the center of the recording medium and the function of equation (1).

The equation for measuring the absolute tilt amount is as follows.

FIG. 5 is a flowchart showing a method of recording / reproducing data on a recording medium with tilt control according to an embodiment of the present invention.

As shown in FIG. 5, the recording medium is loaded (S10) to perform a gap servo for driving the lens unit 104 up and down so that the distance between the lens unit 104 and the recording medium is constant (S20). For example, the distance between the SIL and the recording medium can be maintained at about 30 nm. When the recording medium is inclined with respect to the lens unit 104 while maintaining a gap with the gap servo, the vertical displacement between the tilted recording medium and the lens unit 104 is measured after measuring the distance between the SIL and the center of the recording medium. Measure (S30, S40) The vertical displacement may be measured, and then the distance between the SIL and the center of the recording medium may be measured. The distance from the SIL to the center of the recording medium may be calculated based on the driving distance of the sled motor as described above, and the vertical displacement between the tilted recording medium and the lens unit 104 is determined by the optical pickup in the gap servo driver 130. It may be calculated in real time from the control input and the actuator 107 transfer function that is part of the driving voltage transmitted to the (100). The tilt amount of the recording medium based on the lens unit is measured using the measured vertical displacement and the linear distance (S50).

After calculating the tilt value, it is determined whether the tilt control between the lens unit 104 and the recording medium is controlled according to the measured tilt amount (S60). In this case, it is possible to determine whether the tilt is controlled by comparing the measured tilt amount with an arbitrary reference value set by the user. If the tilt value is equal to or greater than an arbitrary reference value set by the user (S60), data is recorded / reproduced after the active tilt control (S70) (S80). On the other hand, when the tilt value is smaller than an arbitrary reference value set by the user (S60), the data is immediately recorded / reproduced without going through the tilt control. (S80) For example, the recording medium refers to the lens unit 104. Tilt control is performed only when the angle of inclination is greater than or equal to 0.1 degrees. When the user sets it, the tilt control can be performed only when the angle is inclined above this angle.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings, and the present invention is also provided. Naturally, it belongs to the range of.

1 is a block diagram of a tilt control device according to an embodiment of the present invention.

Figure 2 is a block diagram showing one embodiment of an optical pickup provided in the tilt control device of the present invention.

3 is a sectional view schematically showing a lens unit of an optical pickup constituting an embodiment of the present invention.

4 is a view showing a tilt amount measuring method according to the present invention.

5 is a flowchart illustrating a tilt control method according to an embodiment of the present invention.

Claims (12)

Measuring a vertical displacement between the recording medium and the lens portion; Measuring a straight line distance from the lens portion to the center of the recording medium; And And measuring the tilt amount of the recording medium with respect to the lens unit by using the measured vertical displacement and the linear distance. The method of claim 1, Tilt control method for measuring the vertical displacement using the actuator transfer function. The method of claim 2, The actuator transfer function is a tilt control method, characterized in that the following function.

A: constant. B, C, D: Coefficients arbitrarily set by the user. s: magnitude and frequency value of the signal input. The method of claim 1, A tilt control method for calculating the linear distance based on a driving distance of a sled motor for moving the lens unit in the radial direction of the recording medium. The method of claim 1, The tilt control method of measuring the said tilt amount using the following formula.

X: straight line distance from the lens portion to the center of the recording medium Y: vertical displacement between the tilted recording medium and the lens portion The method of claim 1, And a tilt control method for determining whether the tilt is controlled between the lens unit and the recording medium by comparing the measured tilt amount with a tilt reference amount set by the user. A lens unit for irradiating light to the recording medium and condensing light reflected from the recording medium again; A sled motor for moving the lens portion in the radial direction of the recording medium; And Measuring the vertical displacement between the recording medium and the lens unit and the linear distance from the lens unit to the center of the recording medium, and using the measured vertical displacement and linear distance, the recording medium based on the lens unit And a controller for measuring a tilt amount of the tilt control device. The method of claim 7, wherein The control unit, Tilt control device for measuring the vertical displacement using the actuator transfer function. The method of claim 8, The control unit, Tilt control device for measuring the vertical displacement using the actuator transfer function.

A: constant. B, C, D: Coefficients arbitrarily set by the user. s: magnitude and frequency value of the signal input. The method of claim 7, wherein The control unit, Tilt control device for calculating the linear distance based on the drive distance of the sled motor. The method of claim 7, wherein The control unit is a tilt control device for measuring the amount of tilt using the following equation.

X: straight line distance from the lens portion to the center of the recording medium Y: vertical displacement between the tilted recording medium and the lens portion The method of claim 7, wherein The control unit, And a tilt control device for determining whether the tilt is controlled between the lens unit and the recording medium by comparing the measured tilt amount with a tilt reference amount set by a user.

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