JP2006323885A - Evaluation system and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate reproducing characteristics of a pickup of an optical disk device by driving the optical disk in CAV (Constant Angular Velocity). <P>SOLUTION: The pickup 16 is evaluated by using the optical disk 10 wherein only 3T continuous data are formed and pit length is varied so that the frequency of a reproducing signal is always constant when being driven in CAV as the optical disk 10 used for evaluation. The reproducing signal when the driving revolution for CAV drive of the optical disk 10 is changed is supplied from the pickup 16 to a system controller 32. The system controller 32 analyzes frequency characteristics of the reproducing signal by using a spectrum analyzer and evaluates the frequency characteristics of the pickup 16. The optical pickup 16 is made to seek while the optical disk is driven in CAV to detect the waveform of the reproducing signal in each radial position. A spot diameter of a laser beam is evaluated by a pit length in the radial position where the waveform of the reproducing signal shows a waveform deviated from a sine wave. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an evaluation system, and more particularly to a reproduction evaluation technique for a pickup of an optical disk drive.

  Reproduction evaluation of an optical disk drive, particularly a pickup, includes laser diode light emission stability evaluation, detector evaluation, pickup FPC (flexible printed circuit board) transmission characteristic evaluation, and the like. For these evaluations, a ROM disk on which signals are recorded is prepared, mounted on the optical disk drive to be evaluated, servo controlled to focus ON and tracking ON, and then driven at a constant linear velocity (CLV) to reproduce data. The evaluation is performed by measuring the eye pattern and jitter amount of the reproduced signal waveform output from the pickup.

  Although the following patent documents are not directly related to the evaluation technique, the reference clock of the EFM modulation signal for modulating the recording laser beam is set to a frequency lower than the reference clock at the inner periphery of the disk, and the reference clock at the outer periphery of the disk. Paying attention to the fact that the pit length in the outer circumferential direction of the disc changes by setting the frequency higher than the clock, a variable clock signal that rotates the optical disc at a constant speed and makes the clock signal of the recording signal changing encoder proportional to the recording position Thus, a technique for recording and reproducing data in the CLV format is described.

JP-A-9-17115

  When performing reproduction evaluation of an optical disk drive, the spindle motor must be controlled by a clock signal obtained by decoding the reproduction signal in order to drive the disk on which the signal is recorded as described above, and the configuration of the evaluation system itself There is a problem that becomes complicated. In order to simplify the configuration of the evaluation system, it is sufficient that the disk can be driven at a constant angular velocity (CAV). However, when an EFM modulation signal is recorded on the optical disk, signals of various data lengths (3T to 11T signals) are reproduced signals. Therefore, there is a problem that it is difficult to specify which is a noise signal component and which is a regular signal component even if the reproduced signal is analyzed by the spectrum analyzer.

  In addition, as a characteristic of the pickup, there is also an evaluation of whether or not the laser beam is accurately focused on the disc surface of the optical disc, and the laser beam condensing state on the disc surface, specifically, the spot diameter of the laser beam is simplified. It is hoped that it can be evaluated.

  An object of the present invention is to provide a system capable of simplifying the configuration of an evaluation system itself by driving an optical disk at a constant angular velocity (CAV), and reliably evaluating the reproduction characteristics of the optical disk drive, and an optical disk used therefor There is to do.

  The present invention reproduces the data by irradiating the optical disk with laser light and driving means for driving the optical disk on which data is formed so that the reproduction signal frequency is constant when driven at a constant angular velocity (CAV). It is characterized by comprising reproduction means for outputting a reproduction signal and evaluation means for evaluating the frequency characteristic of the reproduction means based on the reproduction signal obtained by changing the driving rotational speed with a constant angular velocity.

  In the present invention, further, means for detecting a waveform deviation from the sinusoidal shape of the reproduction signal when the reproduction radius position of the optical disk is changed, and the laser beam based on the reproduction radius position where the waveform deviation has occurred. Means for evaluating the spot diameter. The optical disk used in the system of the present invention corresponds to the data length so that only data corresponding to a predetermined data length is continuously formed and the reproduction signal frequency is constant when driven at a constant angular velocity. This is an optical disc formed such that the pit length to be increased sequentially from the inner periphery toward the outer periphery.

  According to the present invention, by using a special optical disc in which data is formed so that the reproduction signal frequency is constant when driven at a constant angular velocity, the configuration of the evaluation system is simplified, and the normal signal and noise are reduced. Can be easily identified and the evaluation accuracy can be improved. In addition, the spot diameter of the laser beam can be easily evaluated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the configuration of an optical disk drive pickup evaluation system in the present embodiment. The optical disk drive to be evaluated includes a spindle motor (SPM) 12 that rotationally drives the optical disk 10, a driver 14 that drives the spindle motor 12, and a laser beam applied to the optical disk 10, and the reflected light from the optical disk is received as a reproduction signal. The pickup 16 to be output, the sled motor 18 that drives the pickup 16 in the radial direction of the optical disk 10, the driver 20 that drives the sled motor 18, the driver 22 that drives the laser diode (LD) in the pickup 16, and the reproduction signal from the pickup 16 Based on the RF circuit 26 for generating the focus error signal and the tracking error signal, the pickup 16 is in the tracking ON state and the focus ON state based on the focus error signal and the tracking error signal from the RF circuit 26. Having a servo processor 30 servo-controlling the.

  The evaluation system for evaluating the reproduction characteristics of the pickup 16 includes a system controller 32 including an interface for inputting a reproduction signal from the pickup 16 and outputting a drive signal to the driver 14 and a spectrum analyzer. A spectrum analyzer may be provided separately from the system controller 32, and the analysis result of the spectrum analyzer may be supplied to the system controller 32. The system controller 32 outputs a control signal to the driver 14 to drive the optical disc 10 at a constant angular velocity (CAV). Further, the reproduction signal from the pickup 16 is input, and the reproduction characteristic of the pickup 16 is evaluated based on the frequency characteristic and waveform of the input reproduction signal. The evaluation result is displayed on, for example, a display device.

  In the present embodiment, the system controller 32 drives the optical disk 10 by CAV. However, since a normal optical disk includes signals of various data lengths (3T to 11T signals in EFM modulation), the reproduced signal is converted into a spectrum analyzer. However, it is difficult to specify which is a noise signal component and which is a normal signal component.

  Therefore, in this embodiment, the characteristics of the pickup 16 are evaluated using the optical disc 10 on which only data having a specific data length is recorded as the optical disc 10. That is, the optical disc 10 in the present embodiment is not formed with 3T to 11T as in the prior art, only a specific T signal (for example, 3T) is formed and no synchronization signal or the like is formed, and When the CAV drive is performed, the reproduction signal frequency is constant at all radial positions of the optical disk 10. In the CAV drive, the linear velocity increases in proportion to the radius of the optical disc 10, so in order to make the reproduction signal frequency constant at all radial positions, the pit length is sequentially proportional to the linear velocity from the inner circumference to the outer circumference. Therefore, it is necessary to form data so as to be long. For example, assume that an optical disk for DVD is assumed as the optical disk 10 and 3T continuous data is formed. In the DVD standard, the CLV standard speed is 1388 rpm at the innermost circumference, 574 rpm at the outermost circumference, the reference data length T = 133.3 nm, and the reproduction signal frequency of 3T is 4.36 MHz. When the CAV drive is performed at 1388 rpm by forming data so that the outermost peripheral pit length is 133.3 × 3 × 1388/574 = 967 nm by sequentially increasing the pit length according to the radius with .3 × 3 = 400 nm. Therefore, a reproduction signal of 4.36 MHz is always obtained. Of course, instead of forming only 3T continuous data, only 4T continuous data or only 5T continuous data may be formed.

  In this way, by sequentially setting the pit length in accordance with the radius, a reproduction signal having one frequency is always generated even when the optical disk 10 is CAV-driven, and the system controller 32 reproduces the reproduction signal from the pickup 16. Even when the signal is input and analyzed, the regular signal and the noise component can be easily separated and identified. Since the frequency of the reproduction signal is constant at all radial positions of the optical disk 10, the pickup 16 is sought at an arbitrary radial position, for example, a predetermined radial position (predetermined track position) on the inner circumference side, and is reproduced by CAV driving at that position. In addition to inputting a signal, a reproduction signal is sequentially input by sequentially changing the rotation speed during CAV driving. The reproduction signal frequency at a certain rotational speed is one frequency, which corresponds to 1: 1. Therefore, when analyzing with the spectrum analyzer, the normal reproduction signal level for each frequency can be detected accurately, and thereby the frequency characteristic of the pickup 16 can be accurately evaluated. In a normal optical disk, only 3T signals can be reproduced by recording 3T continuous data on a certain track and repeatedly reproducing the track, but it is necessary to perform a still jump to the track. In this embodiment, since a reproduction signal having the same frequency is obtained at all radial positions, it is not always necessary to perform a still jump. It can be said that the evaluation can be performed using not only the same track but also a plurality of tracks. However, in the outer track, the reproduction signal waveform changes from a sine wave to a rectangular wave and a different frequency component appears as will be described later. Therefore, it is preferable to evaluate the frequency characteristics on the inner track side.

  FIG. 2 shows pits (a) in the innermost track of the optical disc 10 and pits (c) in the outermost track. As described above, 400 nm pits are formed on the innermost track, and 967 nm pits are formed on the outermost track. Data other than 3T continuous data, for example, ECC code data or a synchronization pattern (SYNC) is not formed on the optical disc 10. The optical disc 10 can be said to be an evaluation-dedicated optical disc in which only 3T continuous data is formed. In this embodiment, since evaluation is performed by CAV driving, it is not necessary to decode the reproduction signal to generate a clock signal and control the spindle motor 12 as in the case of evaluation by CLV driving, and signals other than 3T continuous data are unnecessary. It is. FIG. 2 also shows the reproduction signal waveforms (b) and (d) of the inner track and the outer track, respectively. The inner waveform has a sine wave shape at the outer periphery, but the sine wave shape at the outermost track. It will shift.

  FIG. 3 shows a reproduction signal waveform 100 for the innermost track and a reproduction signal waveform 200 for the outermost track. As long as the evaluation-dedicated optical disk 10 of this embodiment is CAV-driven, the reproduction signal frequency of the innermost track and the reproduction signal frequency of the outermost track are the same. However, in the reproduced signal waveform 200 of the outermost track, a concave portion 202 is generated at the peak position and the bottom position. The recess 202 is generated due to the magnitude relationship between the pit length and the spot diameter of the laser beam. That is, returning to FIG. 2 again, as shown in FIG. 2A, when the spot diameter is larger than the pit length, the recess 202 does not occur, and the reproduced signal waveform shows a sine wave shape. However, as shown in FIG. 2 (c), when the spot diameter is smaller than the pit length, the concave portion 202 is formed, resulting in a deviation from the sine wave shape. The pit length is set so as to increase sequentially according to the radius, and has a known length according to the radial position. On the other hand, the spot diameter may change due to the distortion of the optical system of the pickup or the inclination of the optical axis. In order to satisfy the pit length ≦ spot diameter up to a certain radial position of the optical disc 10, the reproduced signal waveform becomes a sine wave waveform. However, at a certain threshold radius, the pit length> spot diameter, and the reproduced signal waveform is derived from the sine wave waveform. It will shift. Therefore, the size of the spot diameter can be evaluated by detecting the threshold radius at which the reproduction signal waveform shifts from a sine wave to a non-sine wave (rectangular wave). Specifically, the pit length at each radial position of the optical disk 10 is stored as a table in the memory of the system controller 32, and when the reproduction signal waveform deviates from a sine wave at a certain radial position, the pit length at the radial position is determined. Read from the memory and evaluate the pit length as the spot diameter. Since the spot diameter is normally set to a predetermined value, if the spot diameter evaluated in this way is different from the predetermined value, it can be evaluated that the optical system of the pickup 16 is abnormal.

  FIG. 4 shows an evaluation processing flowchart in the present embodiment. First, the evaluation-dedicated optical disc 10 is mounted on the optical disc apparatus (S101), and the optical disc 10 is driven by CAV (S102). The rotational speed of the CAV drive is set to 1388 rpm, for example. The pickup 16 seeks to a predetermined position of the optical disk 10 driven by the CAV, for example, a predetermined track on the inner circumference side (S103), and 3T continuous data formed on the optical disk 10 is reproduced and output from the pickup to the system controller 32 (S104). ).

  Next, it is determined whether or not the current CAV drive rotational speed is a predetermined upper limit rotational speed (S105). If the upper limit is not reached, the system controller 32 controls the driver 14 to rotate the CAV drive. The number is increased by a predetermined amount (S106), and 3T continuous data on the optical disc 10 is reproduced again. The tracks during playback may be the same track or different tracks. The above processing is repeatedly executed up to the upper limit of the rotational speed, and a reproduction signal for each rotational speed is supplied to the system controller 32. The system controller 32 performs frequency analysis on the obtained reproduction signal with a spectrum analyzer and displays the analysis result on the display device (S107). Needless to say, the starting rotational speed and the upper limit of the CAV drive are set according to the frequency to be subjected to frequency analysis.

  Next, the optical disk 10 is again driven by CAV at a certain rotational speed, for example, 1388 rpm (S108), and the pickup 16 is sought toward the outer periphery while maintaining the rotational speed (S109). The reproduction signal is sequentially output from the pickup to the system controller 32 while seeking toward the outer periphery (S110), and the system controller 32 detects the presence or absence of deviation from the sine wave shape of the reproduction signal waveform. The presence or absence of the recess 202 in FIG. 3 may be directly detected. When the reproduction signal waveform deviates from a sine wave at a certain radius position r1, that is, when there is a recess 202, the radius position r1 is detected (S111), and a table defining the pit length for each radius position previously recorded in the memory , The pit length D corresponding to the radial position r1 is read, and the pit length D is evaluated as the spot diameter D (diameter) of the laser beam (S112). For spot diameter evaluation, the spot diameter value obtained by referring to the table may be output as it is, or the specified value required for the spot diameter is compared with the evaluation value, and the spot diameter is within the allowable range. It may be judged as abnormal when normal and the allowable range is exceeded, and the result may be output. Since it is possible to calculate the radial position r0 when the spot diameter is assumed to be normal, the spot diameter may be evaluated by comparing r1 and r0 when the radial position r1 is detected in S111.

  After evaluating the frequency characteristics and spot diameter of the pickup 16, the optical disk 10 is further CAV-driven at a certain rotational speed, and the output of the pickup 16 → FPC (flexible printed circuit board) → PCBA (printed circuit board assembly) → front end A signal from each point in the process of transmitting the IC and the reproduction signal is supplied to the system controller 32, and the reproduction signal waveform and frequency characteristics in each process are evaluated. As a result, it is possible to evaluate the characteristics of each point of the transmission path of the reproduction signal and to facilitate troubleshooting when an abnormality occurs in the reproduction signal. For example, it becomes easy to execute a frequency analysis at each point to extract frequency components that are noises and specify a noise source.

  Although the embodiment of the present invention has been described above, the evaluation system of the present embodiment can be incorporated into the optical disc drive itself to provide an optical disc drive having an automatic evaluation function. In this case, the controller of the optical disk drive functions as the system controller 32 in FIG. When the evaluation-dedicated optical disk 10 is loaded, the controller drives the optical disk 10 by CAV, and evaluates the frequency characteristics of the pickup and the spot diameter of the laser beam. In addition, a reproduction signal from each point is input, a noise source is specified, and an abnormal part is displayed on the display.

  In this embodiment, 3T continuous data is formed at all radial positions from the innermost circumference to the outermost circumference. However, in order to evaluate the frequency characteristics of the pickup 16, only the inner circumference or only the inner circumference to the middle circumference. Alternatively, 3T continuous data may be formed. However, in order to evaluate the spot diameter of the laser beam, it is desirable to form it at all radial positions. When 4T or 5T continuous data is formed instead of 3T, the radius position satisfying the pit length> spot diameter is shifted to the inner circumference side than 3T, so that 4T or 5T continuous data is formed. In this case, an upper limit radius position for forming continuous data may be set according to the data length, and it is not always necessary to form the uppermost radius position.

It is a block diagram of the evaluation system in embodiment. It is explanatory drawing which shows the relationship between the pit length and spot diameter in an innermost track and an outermost track. It is a reproduction signal waveform explanatory view of the innermost track and the outermost track. It is an evaluation processing flowchart of an embodiment.

Explanation of symbols

1 optical disk, 12 spindle motor, 16 pickup, 18 thread motor, 20, 22 driver, 26 RF circuit, 30 servo processor, 32 system controller.

Claims (4)

Driving means for driving the optical disk on which data is formed so that the reproduction signal frequency is constant when driven at a constant angular velocity;
Reproducing means for reproducing the data by irradiating the optical disk with a laser beam and outputting a reproduction signal;
An evaluation means for evaluating the frequency characteristics of the reproduction means based on a reproduction signal obtained by changing the driving speed at a constant angular velocity;
An evaluation system characterized by comprising: The system of claim 1, further comprising:
Means for detecting a waveform deviation from a sine wave shape of the reproduction signal when the reproduction radius position of the optical disc is changed;
Means for evaluating the spot diameter of the laser beam based on the reproduction radius position where the waveform shift has occurred;
An evaluation system characterized by comprising: Only data corresponding to a predetermined data length is continuously formed, and the pit length corresponding to the data length is directed from the inner circumference to the outer circumference so that the reproduction signal frequency is constant when driven at a constant angular velocity. Driving means for driving the optical disk formed so as to increase sequentially at a constant angular velocity;
A pickup that irradiates the optical disc with a laser beam to reproduce the data and output a reproduction signal;
The frequency characteristic of the pickup is evaluated by analyzing the frequency characteristic of a reproduction signal output from the pickup when the rotational speed having a constant angular velocity is sequentially changed in a predetermined track of the optical disc, and the pickup is A controller that evaluates the spot diameter of the laser beam based on a change in a reproduction signal waveform output from the pickup when seeking in the radial direction of the optical disc;
An evaluation system characterized by comprising: Only data corresponding to a predetermined data length is continuously formed, and the pit length corresponding to the data length is directed from the inner circumference to the outer circumference so that the reproduction signal frequency is constant when driven at a constant angular velocity. An optical disc formed so as to increase sequentially.

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