JPH0476193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for recording and reproducing digital signals on a recording medium such as a tape or a disk.

Conventional Structure and Problems In recent years, digital signal recording and reproducing apparatuses have been trending toward higher density and larger capacity due to the development of recording media and recording element technology. For example, optical disks can be approximately 10 to 100 times more dense than magnetic recording media. Because the head and disk are non-contact, both have long lifespans and high-speed access, making it promising as a high-density, large-capacity memory medium.

The recording and reproducing process of an optical disc will be explained using the example shown in FIG. In FIG. 1, laser light 100 from a semiconductor laser is focused by a lens thread into a spot with a diameter of about 1 μm, and is irradiated onto a recording film 101 on a disk rotating at high speed. As a result, the recording film 10
A minute portion of the recording bit 103 is instantaneously heated and undergoes melting, evaporation, or thermal transformation, thereby forming a recording bit 103 that causes a change in refractive index and reflectance. After such a recording process, the power of the same laser beam is then lowered, and changes in the reflectance or transmittance of the recorded bits are read and used as a reproduced signal. Note that 104 is a laser guide groove.

In the recording process described above, the shape of the recording bits is greatly influenced by the thermal conductivity of the material used. As a result, the recording bit length is different from the length of the "1" and "0" sections of the digital data before recording, and this is particularly noticeable when thermal transformation of the material is used, due to the transition temperature characteristics of the material. FIG. 2 shows an example in which the recording bit length is shortened due to the above-mentioned reasons. In Figure 2, when recording
During playback, the bit length that was recorded at t _r becomes short to t _p (t _r > t _p ), and in the case of digital recording, it becomes "1" and "0".
Since the length of is used as information, if t _r −t _p exceeds the detection window width, false detection will occur.

Conventionally, in order to correct the displacement of the bit interval, a method has been adopted in which the length of recording bits is changed during recording. In other words, as shown in Fig. 3, if the length t _r of the bit "1" is corrected in advance to a longer value t _r ', then upon reproduction, depending on the characteristics of the material, the reproduction will be t _p = t _r . I can get a signal.

However, when performing the above recording correction, the amount of correction (t _r '-t _r in FIG. 3) must be determined. Conventionally, a large number of optical disks have been actually recorded and reproduced, and the amount that provides the best correction effect within the range of variations in their characteristics has been determined. However, in order to stably perform recording and reproduction on a high-density, large-capacity optical disk, a correction method that is more suited to the characteristics of the disk is required at any position on the surface of the optical disk.

Conventionally, there was no such method, and there was a problem in that correction information could only be obtained for specific locations or average locations on the disk surface, making it impossible to deal with fine variations in characteristics. In addition, in order to perform correction during recording, it is necessary to perform recording in order to know the characteristics of the disk, and there is also the problem that the effective recording area becomes narrow.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
It is an object of the present invention to provide a digital signal recording and reproducing device that records and reproduces digital data at high density on a recording medium such as a tape disk.

Composition of the Invention The present invention is a digital signal recording and reproducing device having means for recording and reproducing a signal for obtaining correction information, means for generating correction information, and means for performing reproduction correction, and the apparatus includes a means for recording and reproducing a signal for obtaining correction information, and a means for performing reproduction correction. By recording the signal for the reproduction clock in the clock line that helps synchronize the reproduced clock or in the amble section provided for starting recording, this original purpose and the purpose of obtaining correction information can be achieved at the same time. There is no need to record correction information in a separate location in advance to obtain the information, and the recording area can be used efficiently. Further, since the amble sections are located before and after the data recording area, the reproduced signal can be corrected before data reproduction starts, and correction can be performed in accordance with the characteristics of the recording area.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a block diagram of the recording side of a digital signal recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 7 is a block diagram of the reproduction side. In FIG. 4, 1 is a recording format configuration circuit, 2 is a modulation circuit,
3 is an ampoule section addition circuit, 4 is a recording amplification circuit,
5 is a recording laser. In FIG. 7, 6 is a reproduction light detection element, 7 is a preamplifier circuit, 8 is an equalization circuit, 9 is a waveform shaping circuit, 10 is a correction circuit, 11 is an amble section detection circuit, 12 is a correction signal detection circuit, 13 is a correction constant generation circuit.

The operation of the digital signal recording/reproducing apparatus of this embodiment configured as described above will be described below.

Data to be recorded is rearranged in a recording format configuration circuit 1 into a format for error control during reproduction, and redundant data is added. Then, the output is sent to the modulation circuit 2,
It undergoes modulation for recording on a recording medium. For example, it is digital recording modulation such as MFM modulation. Next, the amble section addition circuit 3 adds amble sections before and after the data modulation signal, that is, the data recording section, as shown in FIG. The amble section is essential for clock running in for data reproduction and for starting recording. As shown in FIG. 6, the signal in this amble section is composed of a pattern that does not occur in the data modulation signal. For example, in the case of MFM modulation, only three types of level inversion signals appear: 1T, 1.5T, and 2T (T is the bit period). There are repeating patterns etc. The following explanation uses a 2.5T repeating pattern. The signal configured as shown in FIG. 5 is amplified by a recording amplifier circuit 4 and drives a laser 5 that records the signal on a recording medium.

The recording signal on the recording medium detected by the reproduction light detection element 6 is amplified in a preamplifier circuit 7, then equalized by an equalization circuit 8 to remove deterioration in frequency characteristics, and then amplified by a waveform shaping circuit 9. The signal is made into a rectangular wave, and a reproduced modulated signal is obtained.

As shown in FIG. 2 of the conventional example, this reproduced signal has a shorter length of bit "1" than when recorded. It has been confirmed through experiments that the amount of change in length is always constant regardless of frequency. The reproduced signal is input to the amble section detection circuit 11, which detects the section of the 2.5T repeating pattern. Here, due to the above-mentioned phenomenon that the length of bit "1" becomes shorter, the 2.5T repeating pattern becomes 2T,
However, since this repeating pattern does not occur in the data modulation signal, that is, in the data recording section, it is possible to detect the amble section. Since it is necessary to obtain correction information in the amble section, a signal indicating that the reproduced signal is in this section is created from the detection signal, and the period in which the correction signal detection circuit 12 and the correction constant generation circuit 13 operate is determined.

Correction signal detection circuit 12, correction constant generation circuit 13
The operation will be explained using FIGS. 8A and 8B, which are one example.

The amble signal a is input to the differentiating circuit 14, and edge signals b at the rising and falling parts are created.
The counter circuit 15 calculates the time interval of the edge signal b, that is, the length of each bit "1" period and bit "0" period of the amble signal a by counting the clock signal of a constant frequency. The count value of the counter circuit 15 is stored in the memory circuit 16 when the amble signal a rises, and is stored in the memory circuit 17 when the amble signal a falls. As a result, memory circuit 1
The output of the memory circuit 17 is held as d, and the output of the memory circuit 17 is held as c. The difference between c and d is determined by the difference circuit 18, and e is obtained as its output. The above is the part of the correction signal detection circuit 12. Based on the output of the difference circuit 18, that is, the counted value of the difference between the bit "1" period and the bit "0" period, a constant generating circuit 19 creates a correction amount, an averaging circuit 20 calculates the average value of the correction amount, Output as correction information. The above is the correction constant generation circuit 13
This is the part. The above operation of determining the amount of correction is performed only during the amble signal period, and the correction information is held thereafter until the next amble signal, that is, during the data recording section.

Correction is performed in the correction circuit 10 using the correction information output from the correction constant generation circuit 13. The operation of the correction circuit will be explained using FIG. 9, which is an example.

The reproduced signal from the waveform shaping circuit 9 is delayed in a delay circuit 21. Then, as an output of the delay circuit, a signal delayed by the time interval necessary for correction is obtained and input to the selector circuit 22. Based on the correction information, the selector circuit 22 selects a signal with a necessary amount of delay. As a result, the first
A signal g having the necessary delay amount Δt is obtained with respect to the signal f before correction in FIG. By ORing f and g in the OR circuit 23, a corrected signal h is obtained, and a signal that is the same as the recording modulation waveform is obtained.

Here, the delay circuit of the correction circuit 10 is composed of a delay line with a tap, and a signal having the necessary delay amount is obtained by selecting its output with a selector circuit. However, using a variable delay line as the delay circuit, Even with a configuration in which the amount of delay is controlled based on correction information, the effect obtained is the same or better.

As described above, according to this embodiment, a certain pattern of repeating signals is recorded before and after the data recording section in order to obtain correction information, as well as for the clock line and recording start, and this portion is detected during playback. Then, by detecting the deviation of a fixed pattern of the playback signal from the recorded signal pattern during recording, calculating the average of the deviations, obtaining correction information, and performing correction during playback of the data recording section based on this, it is possible to You can get the same signal.

In the explanation of this embodiment, a constant pattern in which the bit "1" section and the bit "0" section are the same is used, but even if the pattern is different as shown in FIG. 6, the operation will still work. It's the same.

In addition, in order to detect the amble section, the signal of the amble section uses a pattern that does not appear in the data recording section, and a configuration is used to detect this, but the amble section is shown separately from the recorded signal on the recording medium. If a signal is already provided and the amble section can be detected by a method other than using the reproduced signal, a configuration as shown in FIG. 11 is also possible. In this case as well, the operation of each part is the same as that already shown.

Effects of the Invention The digital signal recording and reproducing apparatus of the present invention includes means for recording and reproducing a signal for obtaining correction information, means for generating correction information, and means for performing reproduction correction, and is provided with a means for recording and reproducing a signal for obtaining correction information, and a means for performing reproduction correction. When recording a signal for the clock line or the amble section provided for recording start, the correction information can be obtained by making the signal combine the original purpose of this amble section and the purpose of obtaining the correction information. Therefore, no separate recording signal is required in advance, and the recording area can be used efficiently. Furthermore, since the amble section is located before and after the data recording area, the correction of the reproduced signal is determined before the start of the data recording section, so even if there are variations in the characteristics on the recording medium, the correction can be made in accordance with the characteristics. can be done, and its practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the recording and reproducing process of an optical disc, Fig. 2 is a diagram showing the recording signal, recording state, and reproduction signal of the disc, and Fig. 3 is a diagram for explaining the conventional signal correction method. , FIG. 4 is a block diagram of the recording side of the digital signal recording and reproducing apparatus according to the embodiment of the present invention, FIG. 5 is a block diagram of the recording signal, FIG. 6 is a diagram showing signals in the amble section, and FIG. Figures 8A and 8B are diagrams of the correction signal detection circuit and correction constant generation circuit, respectively, and timing charts for explaining their operations. Figure 9 is a diagram of the correction circuit, and Figure 10 is a diagram of the correction circuit. A timing chart for explaining the operation of the circuit, and FIG. 11 is a block diagram of the reproducing side of a digital signal recording/reproducing apparatus according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Recording format configuration circuit, 2... Modulation circuit, 3... Amble section addition circuit, 4... Recording amplifier circuit, 5... Recording laser, 6... Reproduction light detection element, 7... Preamplification Circuit, 8...Equalization circuit,
9... Waveform shaping circuit, 10... Correction circuit, 11...
... Amble section detection circuit, 12 ... Correction signal detection circuit, 13 ... Correction constant generation circuit.

Claims (1)

[Claims] 1. Means for recording and reproducing a repeating signal of a predetermined pattern in amble sections existing at predetermined intervals on a recording medium, and performing reproduction correction from the repeating signal of the predetermined pattern before data reproduction. 1. A digital signal recording and reproducing apparatus comprising: means for obtaining information for performing reproduction correction; and means for performing reproduction correction based on the information for performing this reproduction correction. 2. The digital signal recording and reproducing apparatus according to claim 1, wherein the reproduction correction information is obtained by counting the pulse interval of a reproduction signal of a repeating signal of a predetermined pattern.