JPH0432025A - Method for evaluating reliability of optical disk - Google Patents

Abstract

PURPOSE:To evaluate the reliability of an optical disk with a high precision by calculating the self-recorded C/N (ratio of carrier to noise) value of an arbitrary track at the initial time in accordance with self-recorded C/N measured values of two or more specific tracks and checking the difference from the measured value of the arbitrary track at each evaluation time. CONSTITUTION:When an innermost peripheral track and the outermost peripheral track are taken as C/N value measurement tracks at the initial time, the self-recorded C/N value at the initial time for a measurement track position at each evaluation time is accurately calculated in accordance with measured values of these tracks, and therefore, the variation of the C/N value for an arbitrary track position is accurately obtained though the C/N value is measured in the arbitrary track position at each evaluation time. Thus, the evaluation precision of the C/N value of an optical disk of the CAV system is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a reliability evaluation method for estimating the lifespan of an optical disk, and in particular to self-recording of a CAV type optical disk that is driven at a constant rotation speed regardless of the recording position. The present invention relates to a method for evaluating C/N value (carrier-to-noise ratio).

2. Description of the Related Art One of the reliability evaluation items for this type of optical disc is a self-recorded C/N value. Conventionally, the evaluation method of this self-recorded C/N value was as follows.

First, track A on which the optical disc is located at the initial point in time, that is, in the initial state, is stored under normal temperature and humidity environmental conditions (for example, 23C).
, 55% RH) to measure the self-recorded C/N value. Next, this optical disc is placed under high temperature and high humidity environmental conditions (e.g. 80C).
, 85% RH) for a certain period of time, and then the self-recorded C/N of track B, which is different from track A, under normal temperature and normal humidity conditions.
By measuring the value, the amount of change (amount of deterioration) from the self-recorded C/N value at the initial time point is evaluated.

This self-recorded C/N value is evaluated at a plurality of evaluation points, such as after 1000 hours, 2000 hours, and 3000 hours, and is used to determine the lifespan of the optical disk. Naturally, it is necessary to measure the self-recorded C/N value at each evaluation point on different tracks.

Problems to be Solved by the Invention However, according to this evaluation method, changes (deterioration) in the self-recorded C/N value at the same recording position cannot be directly evaluated;
In the case of CAV type optical discs, it has been difficult to improve evaluation accuracy. The cause will be explained below.

In a CAV type optical disc, the linear velocity differs between the inner track and the outer track, so in order to record a stable signal over the entire circumference of the optical disc, the recording track is set as shown in Figure 2. The recording power is proportionally increased as the position moves from the inner circumference to the outer circumference. This also applies to the recording of a signal (carrier) for self-recording C/N value measurement, so the difference in recording power depending on the track position is naturally reflected in self-recording, which is one of the indicators for evaluating the signal quality of optical discs. This appears as a difference in C/N value, and the self-recorded C/N value changes depending on the measurement position, that is, the recording track position, as shown in FIG.

However, in the past, it was necessary to directly compare the self-recorded C/N values measured at different track positions to evaluate the amount of deterioration, so it was necessary to directly compare the self-recorded C/N values measured at different track positions to evaluate the amount of deterioration. evaluation errors will inevitably occur. Moreover, in order to avoid tarostalk between tracks, it is necessary to shift the track positions at the initial point and each measurement point by several tracks, so the evaluation error due to the difference in track positions is small, and if this is ignored, the evaluation accuracy will be high. I can't expect that.

The present invention has been made in view of the above-mentioned problems.
It is an object of the present invention to provide a method for evaluating a self-recorded CZN value with high accuracy even in the case of a V-system optical disc.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides self-recording C of two or more specific tracks of an optical disc to be evaluated at an initial point in time.
/N value is measured, and from this measured value, the self-recorded C/N value of other tracks at the initial time point is calculated, and at each evaluation time point, the self-recorded C/N value of each different track other than the specific track of the optical disc is calculated. /N value is measured, and the difference between this measured value and the initial self-recorded C/N value calculated for the same track is investigated.

Effect The present invention has the above-mentioned configuration, so that the C/N at the initial point is
If the value measurement tracks are, for example, the innermost track and the outermost track, it is possible to accurately calculate the self-recorded C/N value at the initial point in time for the measurement track position at each evaluation point based on the measured values. Even if the C/N value is measured at any track position at each evaluation time, it is possible to accurately determine the amount of change in the C/N value for the same track position. The accuracy of value evaluation can be significantly improved compared to conventional methods.

Embodiment FIG. 1 is a schematic diagram of an optical disk reliability evaluation apparatus according to an embodiment of the present invention. Note that this optical disk reliability evaluation apparatus is also capable of physical evaluation of thickness, thickness, etc., but the configuration related to this is omitted in FIG.

In FIG. 1, 1 is an optical disk to be evaluated, 2 is a motor with an encoder that rotates the set optical disk 1 at a constant rotation speed, and 3 is a disk drive circuit that drives the motor 2. 4 is an optical head equipped with a tracking mechanism, a focus mechanism, and a mechanism for moving the optical disk in the radial direction;
Reference numeral 5 denotes a recording/reproducing circuit for recording and reproducing signals on the optical disk 1 via the optical head 4; 6, a C/N for measuring a self-recorded C/N value by inputting the reproduction signal from the recording/reproducing circuit 5;
The value measurement circuit 7 is a tracking/focus servo circuit for tracking and focus control of the optical head 4. Reference numeral 8 denotes an arithmetic unit that calculates the self-recorded C/N value at the initial point of time and the amount of deterioration of the self-recorded C/N value, etc., 9 the data storage unit for storing evaluation data, etc., and 10 the evaluation data, etc. Reference numeral 11 denotes an operation section through which an operator inputs operating instructions and data into the apparatus, and reference numeral 12 denotes a control section that controls the operation of each part of the apparatus and the operation sequence of the entire apparatus.

The self-recorded C/N value evaluation process and procedure by the optical disk reliability evaluation apparatus configured as described above will be explained.

First, the initial point will be explained.

The optical disc 1 to be evaluated is set, and necessary data such as the optical disc percentage is entered through the operation unit 11 to start the system. After instructing the disk drive circuit 3 to drive the motor 2, the control unit 12 specifies the innermost track to the tracking/focus servo circuit 7, and moves the optical head 4 to the innermost track. Next, the control unit 12 instructs the recording/reproducing circuit 5 to record a carrier, thereby recording a carrier signal on the innermost track of the optical disc 1. Note that since the CAv method is used, the recording power is controlled according to the track position as shown in FIG. When this carrier recording is completed, the control section 12 instructs the recording/reproducing circuit 5 to reproduce the signal from the innermost track. The reproduced signal is sent to the C/N value measuring circuit 6.
and input the self-recorded C of the innermost track at the initial point in time.
/ N (OE is required.

After storing this self-recorded C/N value in the data storage unit 9, the control unit 12 sequentially moves the optical head 4 to the outermost track of the optical disc 1, performs carrier recording, and reproduces the measured outermost track. The self-recorded C/N value of the track is stored in the data storage section 9.

Next, the control unit 12 gives the self-recorded C/N values of the innermost track and the outermost track to the calculation unit 8 to calculate the self-recorded C/N values of other necessary tracks, and converts the calculation results into data. It is stored in the storage unit 9.

This calculation is based on the recording position (track position) shown in Figure 3.
This is done based on the proportional relationship between the C/N value and the self-recorded C/N value. That is, by dividing the difference between the self-recorded C/N value of the outermost track and the self-recorded C/N value of the innermost track by the predetermined total number of tracks, up to 1
Since the amount of increase in the self-recorded C/N value per track can be calculated, it is possible to calculate the amount of increase corresponding to the required track by proportional calculation and add it to the self-recorded C/N value of the innermost track. You can obtain the self-recorded C/N value of the track you need.

Note that this calculation may be performed on all tracks other than the innermost track and the outermost track, but it is sufficient to perform this calculation only on a specific track selected in advance as an evaluation target.

In this way, in the data storage unit 9, the self-recorded C/N values of the innermost track and the outermost track at the initial point in time, and the calculated self-recorded C/N values of the other tracks are associated with the disk M. will be saved.

Note that it is also possible to print out the data at this initial point using the printer 10.

Next, the evaluation point will be explained. Set the optical disc 1 that has been left in an accelerated environment of high temperature and high humidity for 1,000 hours, for example, and input the disc M and specified data at the time of evaluation (for example, indicating that 1,000 hours have passed) through the operation unit 11 to start the system. . Incidentally, by recording the disc M on the optical disc 1 in advance and having the disc percentage automatically read at the time of evaluation, or by making the evaluation order correspond to the disc percentage, it is possible to eliminate the need for disc delay input operations. You can also do that.

This also applies at the initial time point.

The control unit 12 includes a tracking/focus servo circuit 7
The optical head 4 is then moved to the required track, the recording and reproducing circuit 5 records and reproduces the carrier signal, and the self-recorded C/N value obtained by the C/N value measuring circuit 6 is read as data. It is stored in the storage unit 9. The same process is repeated for the necessary tracks. In parallel with this process, or
After this process is completed, the control unit 12 controls the measured self-record C.
/N value and the self-recorded C/N value at the initial point calculated for the same track are transferred from the data storage section 9 to the calculation circuit 8, the difference between them, that is, the amount of deterioration is calculated, and the result is transferred to the data. The information is stored in the storage unit 9 in correspondence with the disk position.

For example, by performing similar measurements (track positions are different) and calculations at each evaluation time point, such as after 2000 hours and 3000 hours, evaluation data 1 as shown in Figure 1 can be obtained.
3 is obtained in the data storage section 9 for each disk number. This data can be printed out to the printer 10 by giving an instruction from the operation unit 11.

In addition, the evaluation device records the C/N at the initial point and each evaluation point.
If you print out only the self-recorded C/N value without calculating the amount of deterioration in the value, and then calculate the amount of deterioration, input the data of the self-recorded C/N value into an external converter. It can also be changed to calculate the amount of deterioration.

Furthermore, it is also possible to measure the initial self-C/N values of three or more specific tracks, and use the measured values to calculate the self-C/N values of other tracks.

Effects of the Invention As is clear from the above description, the present invention measures, for example, the self-recorded C/N values of the innermost track and the outermost track at an initial point of time, and calculates the self-recorded C/N values of other tracks at the initial point of time from this measured value. The self-recorded C/N value is determined by calculation, the self-recorded C/N value of other tracks is measured at each evaluation point, and this measured value is combined with the self-recorded C/N value at the initial point calculated for the same track. By examining the difference in C/N value, it is possible to accurately determine the amount of deterioration in the self-recorded C/N value, eliminating errors caused by differences in measurement track positions as in the past. This has the effect of significantly improving the evaluation accuracy of the N value.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an optical disk reliability evaluation apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between recording position and recording power, and FIG. 3 is a recording position and self-recorded C. FIG. 3 is a characteristic diagram showing the relationship with /N value. DESCRIPTION OF SYMBOLS 1... Optical disc, 2... Motor, 3... Disk drive circuit, 4... Optical head, 5... Recording/reproducing circuit, 6... C/N value measurement circuit, 7... Tracking /
Focus servo circuit, 8... Arithmetic unit, 9... Data storage unit, 10... Printout, 11... Operation unit, 12... Control unit. Name of agent: Patent attorney Shigetaka Awano and 1 other person (Figure 2) Figure 31 /3t1 Sukeguichime

Claims (1)

[Claims] Measuring the self-recorded C/N values of two or more specific tracks of the optical disc to be evaluated at an initial point in time, and calculating the self-recorded C/N values of other tracks at the initial point of time from these measured values,
At each evaluation time, the self-recorded C/N value of each different track other than the specific track of the optical disc is measured, and this measured value is combined with the self-recorded C/N value at the initial time calculated for the same track. A method for evaluating the reliability of an optical disc, which is characterized by examining the difference between the two.