KR20050040100A - Optical disc device and method for compensating tilt of disc - Google Patents

Abstract

It is an object to realize accurate tilt correction with a simple configuration by using radial contrast.

Means for converting the return light from the optical disk into an electrical signal, means for generating land signals and groove signals from the converted electrical signals, means for detecting the amplitude of the generated signals, and radial contrast values from the detected amplitudes. A means for calculating, a means for correcting the tilt amount of the objective lens with respect to the optical disk, a means for storing the radial contrast value when the tilt amount is corrected by the tilt amount correcting means, and a value of the radial contrast stored in the storage means. There is provided an optical disc apparatus which realizes accurate tilt correction by means for detecting a maximum value in the and means for setting the tilt amount when the radial contrast is maximum to the tilt amount correction means.

Description

Optical disc device and method for compensating tilt of disc}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc apparatus, and more particularly, to an optical disc apparatus suitable for tilt correction and a tilt correction method of an optical disc.

Conventionally, in order to accurately read recording information from an optical disc, it is necessary to irradiate a read beam from an optical pickup perpendicular to the recording surface of the optical disc. However, if the optical disc itself is warped or the assembly error of the mechanical system becomes large, the read beam from the optical pickup cannot be irradiated perpendicularly to the recording surface of the optical disc, and a tilt may occur, resulting in deterioration of information reading or writing information from the optical disc. There was a problem (see FIG. 3).

In order to cope with such a problem, in an optical disk apparatus which performs the control of the track direction of the optical pickup by the push-pull method, a tilt correction signal is generated based on the push-pull signal obtained from the optical pickup, and the generated tilt correction signal is adjusted for tilt correction. A method of correcting the tilt by supplying the circuit has been proposed (see Patent Document 1, for example).

[Patent Document 1] Japanese Patent Laid-Open No. 2002-170265 (pages 2 to 11, FIG. 1)

However, in the method of generating a tilt correction signal based on the push-pull signal and correcting the tilt based on the generated correction signal, since the influence of the lens shift of the objective lens is reflected on the push-pull signal, a simple push-pull signal is used. There is a problem that a tilt signal cannot be obtained and as a result, accurate tilt correction cannot be executed.

Therefore, the present invention has been made in view of the above problems, and the optical disc apparatus and the tilt correction method of the optical disc which realize accurate tilt correction with a simple configuration by using the radial contrast which is not affected by the lens shift of the objective lens and the uneven adjustment of the light receiving optical system. The purpose is to provide.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention proposes the following means.

The invention according to claim 1 includes: light detecting means for converting the return light from the optical disk into an electrical signal, a radial contrast calculating means for calculating a radial contrast value from the electrical signal converted by the light detecting means, and an object for the optical disk. A tilt amount correcting means for correcting the tilt amount of the lens, a radial contrast value storing means for storing the radial contrast value when the tilt amount is corrected by the tilt amount correcting means, and a radial contrast stored in the storing means. There is proposed an optical disk apparatus comprising a maximum value detecting means for detecting a maximum value from a value, and a tilt amount setting means for setting the tilt amount when the radial contrast is maximum to the tilt amount correcting means.

The invention according to claim 4 converts the return light from the optical disk into an electrical signal and generates an electrical signal (hereinafter referred to as a land signal and a groove signal) by the return light from the land portion and groove portion formed on the optical disk from the electrical signal. Detecting the amplitude of the generated signal, calculating a radial contrast value from the amplitudes of the land signal and the groove signal, and correcting the amount of tilt of the objective lens with respect to the optical disc. Storing a contrast value, detecting a maximum value from the stored radial contrast value, and determining a tilt amount based on the tilt amount when the radial contrast is maximum A tilt correction method is proposed.

According to these inventions, the radial contrast value is calculated by converting the return light from the optical disk into an electrical signal and detecting the amplitude of the electrical signal by the return light from the land portion and groove signal formed on the optical disk. Since the radial contrast value has a strong correlation with the jitter value of the reproduction signal, the tilt correction can be appropriately performed by obtaining a tilt amount at which the radial contrast value is maximum.

An invention according to claim 2 includes an optical pickup moving means for moving an optical pickup with respect to the optical disc apparatus according to claim 1, wherein the radial contrast calculating means moves the optical pickup to a predetermined recording and reproducing apparatus. And calculating the maximum value of the radial contrast at the same time, wherein the tilt amount setting means sets the tilt amount when the radial contrast is maximum to the tilt amount correcting means to execute the recording / reproducing operation of the optical disc. An optical disk device is proposed.

The invention according to claim 5 includes the steps of moving the optical pickup to a predetermined position, converting the return light from the optical disc at the predetermined position into an electrical signal and detecting the amplitude of the land signal and groove signal from the electrical signal; Calculating a radial contrast value from amplitudes of the land signal and groove signal, storing the radial contrast value when the tilt amount of the objective lens for the optical disc is corrected, and storing the radial contrast value at There is proposed a tilt correction method for an optical disc comprising the steps of detecting a maximum value and determining a tilt amount based on the tilt amount when the radial contrast is maximum.

According to these inventions, when the optical pickup is moved to a predetermined position, the maximum value of the radial contrast value is obtained at the moved position, and the tilt correction is performed on the basis of the tilt correction amount corresponding to this value, thereby making it optimal for all circumferences of the optical disc to be reproduced. Tilt correction can be performed.

The invention according to claim 3 relates to an optical pickup moving means for moving an optical pickup, an optical disc apparatus according to claim 1, and a maximum value and a tilt amount of the radial contrast at the correction position and the correction position in the optical pickup. And a storage means for storing the optical disc, wherein the radial contrast calculating means calculates the maximum value of the radial contrast at a predetermined position of the optical disc before the recording / reproducing operation of the optical disc, and the tilt amount setting means sets the tilt amount and supplies this information. There is proposed an optical disc apparatus characterized in that the recording and reproducing of the optical disc is executed based on the information stored in the storage means and at the same time.

The invention according to claim 6 includes the steps of moving the optical pickup to a predetermined position, converting the return light from the optical disc at the predetermined position into an electrical signal and detecting the amplitude of the land signal and groove signal from the electrical signal; Calculating a radial contrast value from amplitudes of the land signal and groove signal, storing the radial contrast value when the tilt amount of the objective lens for the optical disc is corrected, and storing the radial contrast value at Detecting the maximum value, storing the tilt amount at the maximum radial contrast together with the positional information of the optical pickup, and reproducing the optical pickup based on the stored information. A tilt correction method is proposed.

According to these inventions, an optical disc which is reproduced while maintaining the original reproduction time for calculating and storing a tilt correction amount for maximizing radial contrast over all the circumferences of the optical disc before the reproduction operation of the optical disc and executing the reproduction operation based thereon Optimal tilt correction can be performed at all perimeters.

The optical disk apparatus according to the present embodiment uses the radial contrast which is not affected by the lens shift of the objective lens and the uneven adjustment of the light receiving system for the tilt correction. Generally, the tilt (tilt) of the objective lens and the optical disc in the optical pickup is evaluated by the jitter of the reproduced signal. 2 (a) and 2 (b) show the relationship between the radial contrast and the jitter and tilt amounts. In FIG. 2 (a), when the jitter is the minimum, the radial contrast becomes the maximum and the radial contrast decreases from the maximum value. It can be seen that the relationship also increases accordingly. Also, as shown in Fig. 2B, the relationship between the angle at which the radial contrast is maximum and the angle at which the jitter is minimum becomes almost straight. Hereinafter, the optical disk apparatus of the present invention for correcting the tilt using the radial contrast will be described in detail with reference to FIGS. 1 to 4.

As shown in FIG. 1, an optical disc apparatus according to an embodiment of the present invention includes an optical disc 1, an optical pickup 2, an optical detector 3, an RF amplifier 4, a signal processing circuit 5, and a driver ( 6), a CPU (Central Processing Unit) 7, a RAM (Random Access Memory) 8, and a tilt correction drive 9 are provided.

The optical disc 1 is a recording medium capable of recording, reproducing and erasing information by a semiconductor laser, for example, a CD-R, a CD-RW, a DVD-R, a DVD-RW, or the like.

The optical pickup 2 includes a laser light source such as a laser diode (not shown), optical parts such as an objective lens, a polarizing beam splitter, a cylindrical lens, and the like driven by a collimator lens, a focus actuator or a tracking actuator.

The photodetector 3 is provided with a four-segment photodetector PD, a sub-beam photodetector, etc., which is built into the optical pickup and is divided into four areas A, B, C, and D to convert light into an electric signal.

The RF amplifier 4 detects the reflected light from the optical disk 1, calculates the reflected light amount from the detected reflected light, generates an RF signal indicating the total amount of reflected light to each region of the 4-split PD, and at the same time the optical pickup 1 A focus error signal (FE), which is a signal for detecting a focus shift of the irradiation laser of R, is generated by astigmatism and a tracking error signal (TE), which is a signal for detecting a track shift of the irradiation laser of the optical pickup (1). Produced by the push-pull method. The servo circuit 5 generates the focus drive signal FODDR and the tracking drive signal TRDRV based on the FE, TE, and RF generated by the analog signal processor 4.

In the RF amplifier 4, an unshown peak bottom detection circuit is provided to detect the envelope of the generated RF signal. In addition, the detected envelope signal detects the top level and the bottom level of the envelope signal that changes in correspondence with the reflected light intensity in the groove and the land, and calculates the difference value (see FIG. 5). The calculated value is output to the CPU 7 to calculate the radial contrast. In addition to the radial contrast is when the level of the signal level of the lands I _l, the groove signal to I _g appear as normalized by the average value the following formula (1), wide in the present invention as described above means (I _{g l} -I) It shall be included in radial contrast.

[Equation 1]

2 (I _g -I _l ) / (I _l + I _g )

The signal processing circuit 5 inputs the EFM signal generated from the RF signal, processes the data, has a PLL signal not shown, and controls the rotation of the spindle motor. It also has a function of incorporating a servo circuit including a phase compensation circuit and the like to turn on / off the servo circuit.

The driver 6 inputs the focus drive signal FODV generated by the RF amplifier 4, the tracking drive signal TRDRV, or the spindle control signal generated by the signal processing circuit 5, and amplifies it to a desired size. Supply to a focus actuator, tracking actuator or spindle motor not shown.

The CPU 7 executes control of the entire apparatus based on a control program stored in a ROM (Read Only Memory) or the like. In this embodiment, the radial contrast is calculated from the difference between the peak and the bottom based on the envelope of the RF signal input from the RF amplifier 4. In addition, the tilt correction amount is changed to store the corresponding radial contrast in the RAM 8, the values of these radial contrasts are compared, the maximum value is obtained, and the tilt correction amount at that time is supplied to the tilt correction driver.

The RAM 8 is an overwritable storage device and has a data table which stores the radial contrast in association with the corresponding tilt correction amount. It also has a data table relating to the predetermined track address of the optical disc 1 and the tilt correction amount corresponding thereto.

The tilt correction driver 9 supplies a voltage or the like corresponding to the tilt correction amount input from the CPU 7 to a tilt actuator not shown in the optical pickup 2, and performs tilt correction. In the present embodiment, the tilt actuator is exemplified as the tilt correction means, but the present invention is not limited thereto. For example, a liquid crystal panel method may be used. As for the tilt actuator, any method may be used, such as tilting the pickup itself or tilting only the objective lens.

Next, the tilt correction procedure of the present invention will be described with reference to FIG.

First, when the insertion of the optical disc is confirmed (step 101), the CPU 7 instructs the setup operation (step 102). Upon completion of the setup operation, the CPU 7 issues a search command to the signal processing circuit 5 to move the optical pickup 2 to the desired track on the optical disc (step 103).

When moving to the desired track of the optical pickup 2, the CPU 7 instructs the signal processing circuit 5 to turn off the tracking control to turn off the track servo (step 104). When the track servo is 0FF, the objective lens in the optical pickup 2 alternates the return light from the land portion and the groove portion to the photodetector 3 due to the eccentricity of the disk 1 so as to maintain a neutral position with respect to the tracking direction. Appears. Therefore, the RF signal obtained by inputting the signal from the photodetector 3 and calculating by the RF amplifier 4 is a wave which is waved corresponding to the return light from the land portion and the groove portion (see FIG. 5).

The generated RF signal is supplied to the peak bottom detection circuit in the RF amplifier, and the difference between the peak and the bottom is calculated. The calculated difference value is input to the CPU 7 to calculate the radial contrast. The calculated radial contrast is stored in the RAM 8 together with the tilt amount. The CPU 7 then varies the tilt correction value of the initials and supplies it to the tilt correction driver 9 to vary the tilt amount, and calculates the radial contrast at this time by the same method as above, and associates it with the tilt amount. It is stored in RAM8. This operation is executed continuously and the maximum value of the radial contrast at the predetermined address of the optical disc 1 is calculated (step 105).

The tilt correction amount that maximizes the radial contrast is stored in a predetermined data table together with the address correction of the optical disc 1 (step 106). When the series of processing is finished at the predetermined address of the optical disc 1, the CPU 7 issues a search command to the signal processing circuit 5 to move the optical pickup 2 to the next desired track and from there the series of processing The operation is executed to find a tilt correction amount that maximizes the radial contrast (step 107). When the next track to be searched is the first track to be searched, the CPU 7 judges that a series of operations have been completed for all the predetermined tracks of the optical disc 1, and ends the processing, and then the track to be searched next. If this is not the first track searched, a series of operations are continued on the predetermined track.

In the reproduction operation of the optical disc 1, the tilt amount at each address is corrected by the value of the data table which stores the relationship between the address and the tilt correction amount obtained by the series of operations. In the data table, an increase in the number of samplings of the addresses in the optical disc 1 enables accurate tilt correction in proportion to the data table. From the characteristics of the optical disc 1, for example, when the number of samplings is small, the amount of tilt correction for the addresses in the meantime is determined. You may calculate by linear approximation. In the present embodiment, the execution of the processing for creating the data table before the reproduction operation has been described, but the above operation may be performed together with the reproduction of the optical disc.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments and includes design changes and the like without departing from the gist of the present invention. For example, in the present embodiment, the method of calculating the radial monttra using only the RF signal has been described. In the tracking control using the push-pull signal, when there is a sub spot such as a DPP signal (Differential Push Pull), The radial contrast based on the calculation result of the sub spot signal may be included.

According to the present invention, the radial contrast that is not affected by the lens shift of the objective lens or the uneven adjustment of the light receiving optical system has the effect that it can be realized at all the circumferences of the optical disc which reproduces the accurate tilt correction with a simple configuration.

1 is a configuration diagram of an optical disk device according to the present invention.

2 is a diagram illustrating a relationship between a tilt angle, a radial contrast, and a jitter value.

3 is a diagram showing a relationship between an optical disc and an optical pickup.

4 is a process flow diagram of the present invention.

5 shows RF signals in an unrecorded area and a completed recording area.

[Description of the code]

1 optical disc

2 optical pickup

3 photodetector

4 RF Amplifier

5 Signal Processing Circuit

6 driver

7 CPU

8 RAM

9 Tilt Correction Driver

Claims (6)

Light detecting means for converting the return light from the optical disk into an electrical signal; Radial contrast calculating means for calculating a radial contrast value from the electric signal converted by the light detecting means; Tilt amount correction means for correcting a tilt amount of the objective lens with respect to the optical disc; A radial contrast value storing means for storing the radial contrast value when the tilt amount is corrected by the tilt amount correcting means; Maximum value detecting means for detecting a maximum value from the value of the radial contrast stored in the storage means; And a tilt amount setting means for setting the tilt amount when the radial contrast is maximum to the tilt amount correcting means. An optical pickup moving means for moving an optical pickup, The radial contrast calculating means calculates the maximum value of the radial contrast in the apparatus when the optical pickup is moved to the predetermined recording / reproducing apparatus, and the tilt amount setting means calculates the tilt amount when the radial contrast is the maximum. And recording and reproducing the optical disc by setting the tilt amount correcting means. An optical pickup moving means for moving an optical pickup; Memory means for storing the correction position in the optical pickup, the maximum value of the radial contrast and the tilt amount in association with the correction position; Before the recording / reproducing operation of the optical disc, the radial contrast calculating means calculates the maximum value of the radial contrast at a predetermined position of the optical disc, and the tilt amount setting means sets the tilt amount and stores these information in the storage means. And recording and reproducing the optical disc on the basis of the information stored in the storage means. Converting the return light from the optical disk into an electrical signal and generating an electrical signal (land signal, groove signal) by the return light from the land portion and groove portion formed on the optical disk from the electrical signal; Detecting an amplitude of the generated signal; Calculating a radial contrast value from amplitudes of the land signal and the groove signal; Storing the radial contrast value when the tilt amount of the objective lens with respect to the optical disc is corrected; Detecting a maximum value from the stored radial contrast value; And determining the tilt amount based on the tilt amount when the radial contrast is maximum. Moving the optical pickup to a predetermined position; Converting the return light from the optical disk into an electrical signal at the predetermined position and detecting the amplitude of the land signal and the groove signal from the electrical signal; Calculating a radial contrast value from amplitudes of the land signal and the groove signal; Storing the radial contrast value when the tilt amount of the objective lens with respect to the optical disc is corrected; Detecting a maximum value from the stored radial contrast value; And determining the tilt amount based on the tilt amount when the radial contrast is maximum. Moving the optical pickup to a predetermined position; Converting the return light from the optical disk into an electrical signal at the predetermined position and detecting the amplitude of the land signal and the groove signal from the electrical signal; Calculating a radial contrast value from amplitudes of the land signal and the groove signal; Storing the radial contrast value when the tilt amount of the objective lens with respect to the optical disc is corrected; Detecting a maximum value from the stored radial contrast value; Storing the tilt amount when the radial contrast is maximum together with the position information of the optical pickup; And tilting the optical pickup based on the stored information.