JPH03296931A - Device for inspecting information recording medium - Google Patents

Abstract

PURPOSE:To rapidly and highly accurately measure amplitude by providing the information recording medium inspecting device with a means for reproducing inspecting data for recording prescribed recording frequency, a means for forming the envelope signal of a reproduced signal, a means for setting up timing for sampling the envelope signal, and a means for measuring the value of the envelope signal to be sampled. CONSTITUTION:An optical disk driving device 1 records a recording signal with a fixed frequency band in an optical disk, reproduces the recorded signal to measure an amplitude value and a smoothing circuit 2 smooths the reproduced signal and converts the smoothed signal to an envelope signal. The envelope signal is sampled by an A/D converter 3 at a prescribed period based upon the timing determined by a timing circuit and a computer 5 controls an optical disk driving device 1 and an A/D converter 3 to control the recording, reproducing and sampling operation of testing information. In addition, the computer 5 automatically measures the sampled amplitude value and executes the data processing of the measured result. Consequently, the amplitude of the reproduced signal can be measured by the simple circuit and rapid and highly accurate amplitude measurement can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information recording medium inspection device for inspecting large capacity recording media such as optical discs.

[Prior Art] Conventionally, the recording film of this type of recording medium has been evaluated by reproducing the information recorded on the recording medium, measuring the amplitude value, and evaluating whether the value is within the inspection standard. It is common to do so. As a method for measuring the amplitude value of such a reproduced signal, for example, there is a method of visually measuring it using a broadband and high-brightness analog oscilloscope. In addition, automatic measurement is also performed using a high-speed sampling digital oscilloscope.

[Problems to be Solved by the Invention] However, when measuring visually with an analog oscilloscope, the measured value is affected by differences in tube surface brightness and individual differences among the measurers, and there is a problem in terms of measurement accuracy. In addition, staring at the oscilloscope tube surface for long periods of time caused significant eye fatigue.

On the other hand, automatic measurement using a digital oscilloscope
Due to software control, it takes a long time for sampling, and especially in large-capacity recording media such as optical discs, it is necessary to take a large number of samples, so there is a problem that the measurement time becomes long. Also, broadband oscilloscopes are expensive, so any of the measurement methods mentioned above
Installing many identical measuring devices required a high cost.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an information recording medium inspection device that can inspect at high speed and with high precision, and can also inspect at low cost with a simple configuration.

[Means for Solving the Problem] In order to achieve the above object, there is provided a means for reproducing test data recorded on a recording medium at a predetermined recording frequency and generating an envelope signal of the obtained reproduced signal; There is provided an information recording medium inspection device characterized by having means for setting timing for sampling an envelope signal and means for measuring a value of the sampled envelope signal.

[Operation] According to the present invention, the amplitude of the reproduced signal is measured by converting the reproduced signal into an envelope signal and sampling this signal at a predetermined timing, thereby making it possible to measure the amplitude of the reproduced signal with a simple circuit. It is designed to be able to perform amplitude measurements at high speed and with high accuracy.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the information recording medium inspection apparatus of the present invention.

In FIG. 1, reference numeral 1 denotes an optical disk drive device that writes information to an optical disk (not shown) or reproduces recorded information. For example, IMH, ~20MH! A recording signal of a constant frequency is recorded, and then reproduced to measure the amplitude value. Smoothing circuit 2
is a circuit that smoothes the reproduction signal reproduced by the optical disk drive device 1 and converts it into an envelope signal. This smoothing circuit 2 will be described in detail later.

The A/D converter 3 is a sampling circuit that samples the envelope signal output from the smoothing circuit 2, and the timing circuit 4 is a pulse generation circuit that generates timing pulses for the sampling.

Therefore, the envelope signal output from the smoothing circuit 2 is sampled by the A/D converter 3 at a predetermined period at a timing determined by the timing circuit 4. The computer 5 is a measurement control computer that operates under program control, and controls the optical disk drive device 1 and the A/D converter 3 to control recording, reproduction, and sampling operations of test information. In addition, the calculator 5 automatically measures the sampled amplitude values, performs data processing on the measurement results, that is, performs statistical processing on the signal amplitude distribution, displays histograms and waveforms, and displays data based on these results. A pass/fail judgment is made to determine whether the optical disc satisfies the standard values.

FIG. 2 shows a specific circuit example of the smoothing circuit 2.

In the figure, 6 is a differential amplifier, C3 is a capacitor for cutting the DC component, and D is a diode for half-wave rectification. Furthermore, R and CI are charging/discharging resistors and capacitors for smoothing the half-wave rectified signal, and 7 is a low-pass filter that removes high frequency components from this smoothed signal to generate a smooth envelope signal.

Although not shown in FIG. 2, the smoothing circuit 2 is composed of another circuit in which the direction of the diode D is reversed. That is, by performing half-wave rectification, smoothing, and filtering on both the positive reproduction signal and the negative reproduction signal, positive and negative envelope signals of the original reproduction signal are generated.

Next, the operation will be explained. First, a reproduction signal reproduced by the optical disk drive device 1 is input to the input terminal A. This reproduced signal is input to the child terminal of the differential amplifier 6 after the DC component is removed by the capacitor C1. Since the differential amplifier 2 has a voltage follower configuration, the input reproduced signal is output as is. Then, the signal is half-wave rectified by diode D, and a half-wave rectified signal shown as S in FIG. 3 is generated. As described above, since the reproduced signal is subjected to half-wave rectification by the smoothing circuits in both the positive and negative directions, a signal S, which is a composite of the half-wave rectified signals in both the positive and negative directions, is obtained as shown in FIG. Furthermore, the circuit shown in FIG. 2 has a circuit configuration that compensates for the nonlinear characteristics of the diode D, since the output side of the diode D is connected to one terminal of the differential amplifier 6. Therefore, as a half-wave rectified output, the reproduced signal is output as it is without being affected by the characteristics of the diode D, with the same amplitude value maintained.

After this, the half-wave rectified signal S1 is connected to the resistor R and the capacitor C8.
The signal is smoothed by a low-pass filter, and high-frequency components are removed by a low-pass filter. As a result, as shown in Fig. 3, a smooth positive and negative envelope signal S connecting the maximum amplitude points of the reproduced signal is obtained.
8 is output from output terminal B. Since the obtained envelope signal is a signal connecting the maximum amplitude points of the reproduced signal, it is possible to measure the amplitude value of the reproduced signal no matter which point is sampled. This envelope signal is output to the A/D converter 3 as described above and sampled at a predetermined timing.

As described above, in this embodiment, a high frequency reproduction signal is converted into a low frequency envelope signal, and the envelope signal is sampled to measure the amplitude value of the reproduction signal. Thereby, it is not necessary to match the sampling timing to the maximum value of the reproduced signal, and even if the timing is slightly off, the reproduced signal amplitude value can be accurately measured. Therefore, automatic measurements that were conventionally impossible without a high-performance digital oscilloscope are now possible using simple smoothing circuits, timing circuits, and inexpensive A/D converters.

Additionally, generally, optical discs have concentric or spiral tracks formed, and each track is divided into a plurality of sectors. In such an optical disc, if sampling is performed several dozen times per sector at equal intervals, the amplitude distribution within the circumference of the optical disc can be known in detail. In addition, the sector is further divided by the synchronization pattern (in many cases it is divided into a few blocks, so it is necessary to sample while avoiding the synchronization pattern position.The synchronization pattern position is determined by the type of optical disc. Therefore, the timing pulse generation of the timing circuit 4 can be changed depending on the type of optical disc.

In addition, in the above embodiment, an example was shown in which an optical disk is inspected as an information recording medium, but the present invention is not limited to this, and can of course be applied to, for example, a magnetic disk, magnetic tape, or optical card. .

[Effects of the Invention] As explained above, according to the present invention, since the reproduced signal is converted into an envelope signal and the envelope signal is sampled to measure the amplitude value of the reproduced signal, timing alignment is not particularly necessary. You can easily measure the amplitude value of the reproduced signal.

Therefore, without using a conventional expensive digital oscilloscope, it is possible to measure amplitude values at high speed and with high accuracy by simply providing a simple circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the information recording medium inspection device of the present invention, FIG. 2 is a circuit diagram showing a specific example of a smoothing circuit, and FIG. 3 is a half of the reproduced signal of the smoothing circuit in FIG. FIG. 3 is a waveform diagram showing a wave rectified signal and an envelope signal. DESCRIPTION OF SYMBOLS 1... Optical disk drive device, 2... Smoothing circuit, 3... A/D converter, 4... Timing circuit, 5... Computer, 6...
Differential amplifier, 7...Low pass filter.

Claims (1)

[Claims] means for reproducing test data recorded on a recording medium at a predetermined recording frequency and generating an envelope signal of the obtained reproduced signal; means for setting timing for sampling the envelope signal; and sampling. An information recording medium inspection device comprising means for measuring the value of the envelope signal.