JP2006018898A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve stability and reliability of an optical disk device by avoiding the adverse effect of reflected light beams from the surface of an optical disk and by enabling to conduct stable pull-in control even at an accurate position of the recording surface of an optical disk having low reflectivity. <P>SOLUTION: In the optical disk device, information is recorded or reproduced by conducting focus servo pull-in control using focus error signals being detected while moving an objective lens along an optical axis direction by focus sweep and reflection sum signals. The device is provided with a storage means which stores the peak value of the reflection sum signals of the recording surface by the disk search of an optical disk arbitrarily loaded and a threshold value setting means which outputs an arbitrarily set low level, that is equal to or less than the peak value of the stored reflection sum signals, as the threshold of the focus servo pull-in control. Thus, focus servo pull-in control for different kinds of optical disks is made possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention enables focus servo pull-in control of a plurality of types of optical disks having different recording surface reflectivities in an optical disk apparatus that drives an optical disk to record or reproduce information. The optical disk with a low rate can be reliably controlled to be pulled in.

  In an optical disc apparatus that records information by forming pits on the recording surface of a disc-shaped optical disc, which is an information recording medium, or reproduces information by reading the recorded pits, the optical beam is focused on the pits. It must be accurately focused. Conventionally, focus servo pull-in control has been generally adopted as an operation for this purpose. This pull-in control is forcibly moving the objective lens of the optical pickup of the optical disk apparatus up and down in the optical axis direction (focus direction) of the light beam. The focus servo loop is turned on at a position where the detected reflection sum signal (RF signal) is equal to or higher than a predetermined level and the focus error signal (FE signal) is “0” (zero cross). is there.

  FIG. 7 is a diagram showing a basic configuration for performing the above operation. A light beam emitted from the semiconductor laser element of the optical pickup 100 is irradiated onto the optical disk D rotated by the spindle motor 101, and the reflected light is received. It is incident on a four-split optical detector 100a that is an element. In the optical pickup 100, the objective lens is elastically supported, and the actuator is driven by the control current supplied from the focus driver 102, and the objective lens is moved up and down in the optical axis direction of the light beam to record the recording surface of the optical disc D. The focus servo is performed so that the beam spot is accurately focused.

  The light reception signal output from the quadrant optical detector 100a is input to the FE signal generation unit 103 for generating a focus error signal and the RF signal generation unit 104 for generating a reflection sum signal. In the quadrant optical detector 100a, the light receiving element is divided into four as shown in FIG. 8, and the difference signal is detected by the astigmatism method. That is, the signal detected by the four-split optical detector 100a is subjected to (A + C)-(B + D) calculation in the FE signal generation unit 103, and a focus error signal FE obtained by calculating the difference in light amount sum is output. On the other hand, the signal detected by the four-split optical detector 100a is subjected to the calculation of A + B + C + D in the RF signal generation unit 104, and a reflected sum signal RF in which the total amount of reflected light is calculated is output.

  In this way, the focus error signal FE generated by the FE signal generation unit 103 is input to the switching circuit 106 via the phase compensation filter 105 and also to the zero cross detection unit 107, and is detected by the zero cross detection unit 107. The zero cross signal and the reflection sum signal RF generated by the RF signal generation unit 104 are input to the lead-in signal generation unit 108. Further, the search signal generator 109 outputs a search signal SS for performing a focus sweep for moving the objective lens of the optical pickup 100 up and down with respect to the optical disc D, and the search signal SS is input to the switching circuit 106.

  FIG. 10 shows the form of each signal when the above configuration is driven. FIG. 10 (a) is a search signal SS, (b) is a focus error signal, (c) is a reflection sum signal, (d). Indicates a pull-in signal PS. First, when the optical disk D is loaded, a search signal SS whose signal level gradually increases is output from the search signal generator 109 based on an instruction from the system controller. When this search signal SS is input to the focus driver 102 via the switching circuit 106, the focus driver 102 gradually raises the objective lens of the optical pickup 100 to perform a focus sweep.

  At this time, a light beam is emitted from the objective lens of the optical pickup 100, and therefore the focal point gradually approaches the surface d1 of the optical disc D. Then, when the focal point of the light beam reaches the surface d1 of the optical disc D as shown in FIG. 9, the four-split light detector 100a detects the reflected light by surface reflection, and as shown in FIGS. 10 (b) and 10 (c). A weak focus error signal fe and a reflection sum signal rf are output. At this time, the reflection sum signal rf is at a very low level as compared with the reflection sum signal RF from the recording surface d3. Does not exceed the threshold value SL set in the pull-in signal generation unit 108, and the output signal from the pull-in signal generation unit 108 is maintained at a low level, so that the switching circuit 106 does not operate and malfunction due to reflected light occurs. There is no induction.

  When the focal point of the light beam passes through the surface d1 of the optical disc D and enters the protective layer d2, the reflected light from the surface d1 of the optical disc D disappears, so the output from the RF signal generation unit 104 also disappears. Then, as the focal point of the light beam further enters and approaches the recording surface d3, the focus error signal FE calculates the difference in the sum of the light amounts. The level is “0”, that is, a zero cross signal, and the reflection sum signal RF has a maximum value as shown in FIG.

  At this point, the pull-in signal generation unit 108 is in the state of both signals, that is, under the condition that the focus error signal FE is “0” and the maximum value of the reflection sum signal RF exceeds the threshold SL. The output signal becomes high level as shown in FIG. 10 (d), and the pull-in signal PS is output. When the pull-in signal PS is output from the pull-in signal generation unit 108, this signal activates the switching circuit 106, cuts off the transmission of the search signal SS from the search signal generation unit 109, and the focus error input from the phase compensation filter 105 The signal FE is sent to the focus driver 102, the focus servo is turned on, a focus servo loop is formed, and the pull-in control is completed.

As is clear from the above description, in the pull-in control in the optical disc apparatus, the threshold of the reflection sum signal in the pull-in signal generation unit becomes a gate, and the timing of the pull-in control is determined by detecting the zero cross of the focus error signal. There has been proposed a method for performing pull-in control of optical discs having different recording surface reflectances using such characteristics. This is because the objective lens is brought close to the optical disc by focus sweep during focus servo pull-in control, and the signal level of the reflection sum signal is measured near the in-focus point, and the reflectivity of the optical disc is detected from this signal level. , And the amplification factor of the RF signal generator is switched based on the determination result, and pull-in control is performed again to turn on the focus servo (for example, Patent Document 1).
JP 11-203691 A

  The method according to the above conventional example is to discriminate the type of the optical disc and to uniquely change the amplification factor of the RF amplifier according to the result. Pull-in control is made possible. However, even if it is the same type of optical disc, the reflectivity differs depending on the individual optical disc, and even if the amplification factor is simply changed according to the type of the optical disc, if it is fixed, pull-in control is not possible There is. In addition, when the amplification factor is changed, in the case of an optical disc with a low reflectance, reflected light from the surface is also amplified, and there is a possibility that the pull-in control is erroneously performed on the disc surface.

  By the way, in recent years, optical discs driven by optical disc apparatuses have been proposed based on many standards, and information recording forms are diversified. For example, when compared with a CD (Compact Disc), a DVD (Digital Versatile Disc) achieves a large capacity by increasing the recording density by reducing the track pitch and the shortest pit length to ½ or less. Therefore, it is necessary to reduce the spot size of the light beam from about 1.6 μm to 0.8 μm of the CD, and for this reason, the wavelength of the light beam is set to 780 nm to 650 nm of the CD. Further, in the case of CD, there are a plurality of types such as CD-ROM, CD-RW, CD-R, etc., and in the case of DVD, there are a plurality of types such as DVD-RAM, DVD-ROM 1 layer, DVD-ROM 2 layer, With different reflectivity.

  FIG. 11 shows a reflection sum signal obtained when such various optical discs are detected by a light beam for CD (wavelength 780 nm). DVD-RAM, DVD-ROM (two layers), CD- It can be recognized that the signal level of DVD-ROM, CD-ROM, and CD-R is higher than that of RW. FIG. 12 shows a reflection sum signal obtained when each of the above optical disks is detected by a DVD light beam (wavelength 650 nm), compared with DVD-RAM, DVD-ROM, and CD-ROM. It can be seen that the signal level of DVD-ROM (two layers) and CD-RW is low, and the signal level of CD-R is low.

  As described above, the reflectivity of the optical disc according to various standards is greatly different. For example, in the case of a stamper disc such as a CD-ROM, the reflectivity of the recording surface is high (about 12 db). The reflection sum signal is large when the focal position is on the recording surface, and the threshold can be set high. On the other hand, in the case of a phase change type disk such as a CD-RW, since the reflectance of the recording surface is low (about 6 db), the reflection when the focal position of the light beam is on the recording surface during pull-in control. The sum signal becomes smaller and the threshold must be set lower.

  FIG. 13 illustrates an aspect in which a plurality of types of optical discs (two types in the illustrated example) with low reflectivity on the recording surface and close to the level of the reflection sum signal are controlled with a common threshold. 2 shows the generation state of the first focus error signal FE1, the second focus error signal FE2, and the first reflection sum signal RF1 and the second reflection sum signal RF2. In this case, as is apparent from the figure, since the threshold value SL of the first reflection sum signal RF1 and the second reflection sum signal RF2 is a common threshold value, the threshold level is the first obtained from the optical disk having a low reflectance. Must be set low so as to correspond to the reflection sum signal RF1. The threshold SL is set to be higher than the peak value of the reflection sum signal rf2 generated by the reflected light generated when the pull-in control is performed.

  When the threshold value SL is set based on such conditions, for example, the focus error signal and the reflected sum signal due to the reflected light due to the eccentricity, warpage, or individual difference of the optical disk are usually as indicated by the phantom lines in FIG. May be generated higher than the peak value. When such a state is reached, the reflected sum signal reaches the threshold value SL at the time of zero crossing of the focus error signal generated by the reflected light as shown in the figure, and erroneous pull-in control is performed in focusing on the surface of the optical disk. It will end up. That is, when performing pull-in control of a plurality of types of optical disks having a low reflectance with a common threshold, there is a high probability that correct pull-in control on the recording surface cannot be performed. Such a problem is likely to occur when the level of the reflection sum signal is low due to an optical disc having a low reflectivity on the recording surface. However, even in the same type of optical disc, the reflectivity may be different, which is a problem. It is a cause to promote.

  The present invention has been made in view of the above-described conventional problems, avoids the influence of reflected light from the surface of the optical disk, and enables stable pull-in control at an accurate position on the recording surface even in an optical disk with low reflectance. In this way, the stability and reliability of the operation of the optical disk apparatus are improved.

  Therefore, the present invention solves the above problems by means described below. That is, according to the first aspect of the present invention, an optical disk which performs focus servo pull-in control by a focus error signal and a reflection sum signal detected by moving the objective lens in the optical axis direction by focus sweep, and records or reproduces information. In the apparatus, storage means for storing a peak value of a reflection sum signal of a recording surface detected by a disk search of an arbitrarily loaded optical disc, and an arbitrarily defined low level below the peak value of the stored reflection sum signal Threshold setting means for outputting as a threshold value in focus servo pull-in control is provided to enable focus servo pull-in control of different types of optical discs.

  According to the second aspect of the present invention, there is provided an optical disc apparatus in which focus servo pull-in control is performed by a focus error signal and a reflection sum signal detected by moving an objective lens in the optical axis direction by a focus sweep, and information is recorded or reproduced. In the pull-in control of the optical disc loaded arbitrarily, storage means for storing the peak value of the reflection sum signal due to the reflected light from the surface of the optical disc and the reflection sum signal due to the reflected light from the recording surface, and each stored And a threshold value setting means for outputting an arbitrarily defined level between the peak values of the reflection sum signals as a threshold value in focus servo pull-in control, so that focus servo pull-in control of different types of optical disks can be performed. .

  The invention according to claim 3 is the reflection sum signal from the recording surface obtained by the disk search of the newly loaded optical disk in the state where the threshold value is set in the invention according to claim 1 or 2. There is provided collation means for collating the peak value of the current and the peak value of the reflection sum signal stored in the storage means.

  According to the present invention, it is possible to avoid the influence of reflected light from the surface of an optical disc, and to perform stable pull-in control at an accurate position on the recording surface even for an optical disc with low reflectivity, thereby providing a highly reliable optical disc apparatus. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of the present invention. A light beam emitted from a semiconductor laser element of an optical pickup 1 is irradiated onto an optical disk D rotated by a spindle motor 2, and its reflected light is received by a light receiving element. Is incident on the quadrant detector 1a. In the optical pickup 1, the objective lens is elastically supported, and the actuator is driven by a control current supplied from the focus driver 3, and the objective lens is moved up and down in the optical axis direction of the optical beam to beam onto the recording surface of the optical disc D. Focus servo is performed so that the spot is accurately focused.

  The light reception signal output from the four-split optical detector 1a is input to the FE signal generation unit 4 for generating a focus error signal and the RF signal generation unit 5 for generating a reflection sum signal. Then, as in the conventional calculation process, the FE signal generation unit 4 calculates (A + C) − (B + D), and outputs a focus error signal obtained by calculating the difference in the amount of light. On the other hand, the RF signal generation unit 5 calculates A + B + C + D and outputs a reflection sum signal obtained by calculating the total amount of reflected light.

  Thus, the focus error signal generated by the FE signal generation unit 4 is input to the switching circuit 7 via the phase compensation filter 6 and also to the zero cross detection unit 8. Further, the reflection sum signal generated by the RF signal generation unit 5 is input to the variable level comparator 9 and the system controller 13 and also to the RF signal determination unit 10.

  The RF signal discriminating unit 10 compares the peak value of the reflection sum signal detected and stored by the disk search of the optical disk performed in the past with the peak value of the reflection sum signal by the disk search of the optical disk thereafter. The process flow in the system controller 13 is determined based on the result. Here, the disk search is a processing operation for determining the presence or absence of the optical disk and the type of the loaded optical disk when the optical disk apparatus is started, and applying a sweep signal to the focus coil as in the case of performing the pull-in control. Thus, the objective lens is brought closer to the optical disc, and the reflection sum signal of the optical disc at this time is detected.

  The variable level comparator 9 sets a threshold specified by the system controller 13, and outputs a signal to the pull-in signal generator 11 when the reflection sum signal input from the RF signal generator exceeds this threshold. The pull-in signal generator 11 sends a pull-in signal to the switching circuit 7 when the zero-cross signal is input from the zero-cross detector 8 while the signal from the variable level comparator 9 is input, and turns on the focus servo.

  The search signal generator 12 sends a search signal SS necessary for disk search when the optical disk is loaded to the switching circuit 7 based on an instruction from the system controller 13, and the search driver SS amplifies the search signal SS with the focus driver 3. A focus sweep of the optical pickup 1 is performed by the control current.

  Next, the flow of processing when the above-described configuration is operated will be described with reference to FIGS. In the figure, when an optical disk D is loaded, the system controller 13 detects this and sends a signal instructing activation to the search signal generator 12. When the search signal generator 12 is activated, the search signal SS is output to the focus driver 3 via the switching circuit 7, and a control current is output from the focus driver 3 to the actuator of the optical pickup 1 to start disc search. (Step ST1).

  As the disk search proceeds, the RF signal generation unit outputs the reflection sum signal rf due to the surface reflection of the optical disc D, and then generates and outputs the reflection sum signal RF due to the recording surface of the optical disc D (step ST2). At this time, the focus error signal FE is output from the FE signal generation unit 4, but the system controller 13 prevents the pull-in signal generation unit 11 from operating due to, for example, output prohibition processing of the variable level comparator 9.

  The reflection sum signal RF generated and output by the RF signal generation unit 5 is input to the RF signal determination unit 10, and the peak value of the reflection sum signal whose peak value of the RF signal has been detected and stored by the previous disk search is stored. (Step ST3). If the result of discrimination in the RF signal discriminating unit 10 does not coincide with the stored peak value, a corresponding threshold value is set for the peak value (step ST4) and stored in the storage means in the system controller 13. (Step ST5). The threshold value set for each peak value depends on the level of the peak value of the reflection sum signal RF, such as a sufficiently higher value than the reflection sum signal rf, particularly when the reflection sum signal RF is a low value. Set the optimal value. The threshold value thus stored in the storage means is set from the system controller 13 to the variable level comparator 9 (step ST6).

  On the other hand, in the discrimination of the reflection sum signal RF in step ST3, the peak value of the reflection sum signal RF from the recording surface obtained by the disk search of the loaded optical disc is compared with the reflection sum signal stored in the storage means (step If a match is stored as a result of ST7), the threshold value set for the peak value is read from the storage means (step ST8), and the threshold value is set in the variable level comparator 9 (step ST6).

  When the disk search is completed as described above and the threshold value suitable for the loaded optical disk is set in the variable level comparator 9, the system controller 13 operates the search signal generator 12 and outputs the search signal SS again. Then, the focus sweep is started (step ST9). When the focus sweep is started, the RF signal generation unit 5 generates the reflection sum signal rf1 due to the surface reflection of the optical disc D. At this time, the peak value pl1 does not exceed the set threshold value SL1. It will not be accidentally controlled. In addition, by performing the threshold setting process in the disk search processing operation at the time of starting the optical disk apparatus, it is not necessary to perform a separate sweep operation for the threshold setting process, and this process does not take time.

  When the focus sweep further proceeds, the focus error signal FE1 is output from the FE signal generation unit 4 (step ST10), and the reflection sum signal RF1 from the recording surface of the optical disc D is output from the RF signal generation unit 5 (step ST11). Then, the focus error signal FE1 is input to the zero cross detection unit 8 to detect the zero cross signal (step ST12), and is input to the pull-in signal generation unit 11. On the other hand, the reflection sum signal RF1 is input to the variable level comparator 10 and compared with the set threshold value SL1 (step ST13), and a signal is output to the pull-in signal generation unit 11 when the reflection sum signal RF1 exceeds the threshold value SL1. To do.

  Since the signal input from the variable level comparator 9 to the pull-in signal generation unit 11 becomes a gate signal of the zero-cross signal, the zero-cross signal is input from the zero-cross detector 8 to the pull-in signal generation unit 11 and at the same time the pull-in from the pull-in signal generation unit 11 Signal PS is output to switching circuit 7. When the switching circuit 7 is actuated by the pull-in signal PS, the phase compensation filter 6 is switched to input the focus error signal FE1, and thereby the focus servo is turned on and the focus is locked, so that the recording surface of the optical disc D is recorded. The spot of the light beam is focused and information can be read or written.

  As described above, in the present invention, the optimum threshold value is set in the variable level comparator 9 for the reflection sum signal detected each time the optical disc is loaded. It is possible to prevent the signal from being affected. That is, as shown in FIG. 4, by setting the threshold value SL1 of the reflection sum signal RF1 of the optical disk having a low reflectivity on the recording surface, the reflection sum signal due to surface reflection becomes a virtual line due to the eccentricity, warpage or individual difference of the optical disk Since the threshold value SL1 is not reached even when the level shown occurs, no signal is output from the variable level comparator 9.

  Further, as shown in FIG. 5, when it is assumed that the reflection sum signal due to surface reflection of two types of optical disks with low reflectance is rf1 and rf2, the peak values are pl1 and pl2, and the threshold is only SL1. Since the peak value pl2 of the reflection sum signal rf2 is very close to the reflection sum signal SL1, the probability of malfunctioning increases, and the optical disk that generates the reflection sum signal RF2 is based on the threshold value SL1, so the gate width becomes large. The accuracy of the pull-in control decreases. However, in the present invention, since the threshold value is set in the variable level comparator 9 for each optical disc as described above, for example, when a reflection sum signal RF2 higher than the reflection sum signal RF1 is detected as shown in FIG. The threshold SL2 that is optimal for this is set in the variable level comparator 9, which enables highly accurate pull-in control.

  FIG. 6 shows another example of the present invention, in which a reflection sum signal generated by surface reflection is detected at the initial stage of disc search (step ST1), and the peak value is a lower limit for determining a threshold value in step ST4. The reference value is used. That is, in the above-described embodiment, the threshold value is determined based on the reflection sum signal from the recording surface of the optical disc. However, in the case of the processing in FIG. Can be accurately determined.

It is a block diagram which shows the structure of the optical disk apparatus of this invention. It is a flowchart which shows the flow of the operation | movement process of this invention. It is a figure explaining the aspect of the signal processing of this invention. It is a figure explaining the aspect of the signal processing of this invention. It is a figure explaining the aspect of the signal processing of this invention. It is a figure which shows the other example of the flow of the process of this invention. It is a block diagram which shows the structure of the conventional optical disk apparatus. It is a figure which shows a 4 division | segmentation optical detector. It is a figure explaining the aspect of a focus sweep. It is a figure explaining the aspect of the conventional signal processing. It is a figure explaining the reflectance of an optical disk. It is a figure explaining the reflectance of an optical disk. It is a figure explaining the aspect of the conventional signal processing. It is a figure explaining the state of the malfunction in the conventional signal processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Optical pick-up 2 .... Spin motor 3 .... Focus driver 4 .... FE signal generation part 5 .... RF signal generation part 6 ················································································································································· ··· Pull-in signal generator 12 ··· Search signal generator 13 ··· System controller (microcomputer)
D ... Optical disc

Claims (3)

In an optical disc apparatus in which focus servo pull-in control is performed by a focus error signal and a reflection sum signal detected by moving an objective lens in the optical axis direction by a focus sweep, and information is recorded or reproduced.
Storage means for storing the peak value of the reflection sum signal of the recording surface detected by the disk search of an optical disk loaded arbitrarily;
A threshold setting means configured to output a arbitrarily defined low level below the peak value of the stored reflection sum signal as a threshold in focus servo pull-in control,
An optical disc apparatus characterized by enabling focus servo pull-in control of different types of optical discs. In an optical disc apparatus in which focus servo pull-in control is performed by a focus error signal and a reflection sum signal detected by moving an objective lens in the optical axis direction by a focus sweep, and information is recorded or reproduced.
Storage means for storing the peak value of the reflection sum signal due to the reflected light from the surface of the optical disc and the reflection sum signal due to the reflected light from the recording surface in the pull-in control of the optical disc loaded arbitrarily,
Threshold value setting means configured to output an arbitrarily determined level between the peak values of each stored reflection sum signal as a threshold value in focus servo pull-in control,
An optical disc apparatus characterized by enabling focus servo pull-in control of different types of optical discs.   Collating means for collating the peak value of the reflection sum signal from the recording surface obtained by the disk search of the newly loaded optical disc with the peak value of the reflection sum signal stored in the storage means in a state where the threshold is set The optical disk apparatus according to claim 1, wherein the optical disk apparatus is provided.

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