JPS6152482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a storage device for signal waveforms having periodic changes such as control signals of a feedback control system.

For example, Japanese Patent Application No. 54-91868 (Japanese Unexamined Patent Publication No. 56-16918),
Patent application 1987-91870 (Japanese Patent Application No. 1983-16946), Patent application 1983
-82238 (Japanese Unexamined Patent Publication No. 56-7247) etc., contains recorded information such as mechanical eccentricity that occurs when a disk-shaped recording medium is attached and detached during recording, erasing, and retrieval (reproduction) in magnetic or optical recording and reproducing devices. An eccentricity compensation method is described to compensate for the distorted shape of the track. These eccentricity compensation methods perform tracking control to follow the distortion shape of the information track distortion (track bending caused by eccentricity) caused by the insertion and removal of a disk-shaped recording medium, and generate a tracking control signal (corresponding to the distortion shape). A periodic signal whose basic period is the time required to reproduce one revolution of the information track is obtained, this tracking control signal is stored in a waveform storage device, and the readout signal of the signal stored in the waveform storage device is used to perform the above-mentioned tracking control signal. The tracking control system is excited to perform eccentricity compensation corresponding to the distortion of the information track.

The present invention aims to improve the precision of a waveform storage device for control signals used for eccentricity compensation and the like.

First, with reference to FIG. 1, an example of an eccentricity compensation method in an optical recording/reproducing apparatus for recording still images will be described. In FIG. 1, a light beam 2 is emitted from a light source 1.
is emitted, and the light beam 2 is made into a light beam 2a with an appropriate intensity by a modulator 3, enters a focusing objective lens 6 via a beam splitter 4 and a rotating mirror 5, is condensed to a minute spot diameter, and is focused on a disk. A disk-shaped recording medium 8 rotated by a drive motor 7 is irradiated with light. When the intensity of the irradiated light beam 20 is strong, the disk-shaped recording medium 8
A material such as a well-known amorphous material is used, which has optical properties that change through chemical changes, allows optical recording, and when strengthened, can be optically erased.
In this type of material, when the intensity of the irradiated light beam 2a is weaker than that during recording, there is no physical or chemical change in the recording medium, and neither recording nor erasing occurs. The information track is reproduced by irradiating this weakened light beam. Further, a still image signal of one frame is concentrically recorded on one information track on the disk-shaped recording medium 8, and the disk drive motor 7 rotates in synchronization with a frame synchronization signal in the video signal, and uses the NTSC system. For television signals
1800RPM (30 revolutions per second), PAL or SECAM
1500 RPM (25 rpm per second) for standard television signals
It is rotating in synchronization with the rotation reference signal at a rotation speed of (rotation). The disk-shaped recording medium 8 is rotationally driven by a disk drive motor 7, and the distance from the objective lens 6 changes due to surface wobbling caused by its poor flatness, resulting in the light beam 2a not being focused into a sufficiently small spot. may be irradiated. For this purpose, a movable coil 9 is provided to control the position of the focusing objective lens 6 so that the signal recording surface of the disk-shaped recording medium 8 is located on the focal point where the irradiated light beam 2a is focused to the minimum diameter. This moving coil 9 is already controlled by a well-known convergence control method. Furthermore, in addition to convergence control, tracking control is performed in which the light beam 2a is scanned by following the distortion of the information track, and many well-known methods have already been proposed for this tracking control. Therefore, detailed explanation will be omitted. In FIG. 1, reflected light 2 of a light beam 2a irradiated onto an information track is shown.
A well-known optical system is constructed in which the beam is reflected by a beam splitter 4 via a focusing objective lens 6 and a rotating mirror 5, and is irradiated onto a photodetector 11 via a cylindrical lens 10. 2a
A tracking signal corresponding to the distortion shape of the information track that occurs in response to the amount of tracking deviation of
S ₁ is obtained. This tracking signal S ₁ is applied to the tracking control circuit 12 and becomes a tracking control signal S ₂ which undergoes signal processing. This tracking control signal _S2 is applied to the waveform storage device 3, and is stored for one round of the information track in correspondence with the position in the longitudinal direction of the track.
The readout signal _S3 of the waveform storage device 13 is applied to the B contact of SW. During tracking control, the signal changeover switch SW is connected to contact A, and the tracking control signal _S2 is supplied to the rotating mirror drive circuit 14, which excites the rotating mirror 5 to create a feedback control loop that follows the distortion shape of the information track. Tracking control is being performed.

Now, as mentioned above, the tracking control signal _S2 is a signal having information corresponding to the distortion of the information track caused by eccentricity, etc., and corresponds to the period for reproducing one revolution of the information track, that is, one It is a periodic signal whose basic period is the period required for rotation. This signal _S2 is sent to the rotating mirror drive circuit 14.
In addition, a tracking control system is constructed in which the rotating mirror 5 is excited and the light beam 2a scans the signal recording surface of the disk-shaped recording medium 8 by following the distorted shape of the information track. Also, the signal S ₂ and the output signal S ₃ of the waveform storage device 13 that stores it are equivalent, so the signal changeover switch SW is switched to the B contact, and the signal S ₃ is rotated instead of the signal S ₂ . Even if the rotary mirror 5 is excited in addition to the mirror drive circuit 14, the light beam 2a scans the information track on the disk-shaped recording medium 8, which has been subjected to the tracking control, following the distorted shape of the information track. Eccentricity compensation is performed to compensate for the distorted shape of the information track due to eccentricity that occurs when the disk-shaped recording medium 8 is attached or removed.

The tracking control signal like this is stored in waveform,
In the eccentricity compensation method in which the tracking control system is excited by the stored signal to compensate for eccentricity, the compensation accuracy depends on the storage accuracy of the waveform storage device.
In order to perform highly accurate compensation, it is necessary to improve the storage accuracy of the signal waveform storage device.

Now, what was used as this waveform storage device, for example, Japanese Patent Application No. 54-91870 (Japanese Unexamined Patent Publication No. 56-56
The waveform storage device described in No. 16946 stores tracking control signals during one revolution of the information track (the period required for one revolution of the disk drive motor). Alternatively, measures were taken such as averaging the memorization over several laps. However, in these methods, the analog-
Quantization errors caused by the resolution of digital converters (hereinafter abbreviated as ADC), semiconductor digital memories (for example, using well-known random access memory, hereinafter abbreviated as RAM), digital-to-analog converters (hereinafter abbreviated as DAC), etc. , offset voltage and nonlinear distortion that occur in analog circuit systems (including ADCs and DACs), gain errors that occur when there is an amplitude difference between the stored signal and the stored signal, and phase errors that occur when there is a phase difference between these two signals, etc. Waveform storage accuracy The deterioration factors are not corrected and directly result in waveform memory errors. To improve memory accuracy, it is necessary to take measures to improve the resolution of the ADC, DAC, and RAM mentioned above, adjust the offset voltage, use analog circuits with good linearity, and increase the gain. Adjustment, phase adjustment that reduces the phase error by adjusting the phase of the read signal by shifting the timing of reading and writing to RAM
91870 (Japanese Patent Publication No. 56-16946))
etc., resulting in increased circuit cost and complicated adjustment. Moreover, even if these precision improvement measures were taken, there were limits.

In view of the drawbacks of such waveform storage devices, the present invention provides two
A difference signal between the signal whose waveform has been stored in the first storage means and the signal to be stored (waveform storage error of the first storage means) is obtained, and this difference signal is stored in the second storage means. By mixing the storage signal of the first storage means with the storage signal of the second means and using the signal corrected for the storage error caused by the first storage means as the storage, an inexpensive circuit with simple adjustment can be achieved. The present invention provides a waveform storage device that uses components (circuit components that are not highly accurate) and has fewer errors.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram that can be applied to the waveform storage device 13 of FIG. 1, for example.
In FIG. 2, the waveform storage device 13 includes a first waveform storage means 15, a second waveform storage means 16, a differential amplifier 17, a control circuit 19, and a mixing amplifier 18. The waveform storage means 15 and 16 can be constituted by waveform storage means as shown in the above-mentioned Japanese Patent Application No. 54-91870 (Japanese Unexamined Patent Publication No. 56-16946), and each includes a low-pass filter for input signal processing. 20, 26, sample and hold circuits 21, 27,
ADC22, 28, RAM23, 29, DAC24,
30, low-pass filter 25 for output signal processing,
31, and storage and reading of waveforms are controlled by a control circuit 19.

In FIG. 2, _the first waveform storage means ₁₅ receives a periodic signal S ₂ (information The waveform is stored for a period of time (the time required to read out one track round as a basic period), and a first read signal _S5 is obtained from t3 through a transition time _{t2 to t3} . This signal S ₅ is applied to the mixing amplifier 18 and also to the differential amplifier 17,
An output signal S ₆ corresponding to the difference between the signal S ₂ and the signal S ₅ is obtained. The relationship between the signal S ₆ and the signals S ₂ and S ₅ is as shown in the following equation (1).

S ₆ =S ₂ −S ₅ (1) Then, the signal S ₆ is applied to the second waveform storage means 16, and after passing through the transition period t ₃ to t ₄ , it is stored in the period t ₄ to _{t 5} (information track). The waveform of the signal _S6 is stored during the period required to read out one round, and after a transition period from _t5 to _t6 , a second readout signal _S7 is obtained from _t6 onwards.
This signal _S7 is simultaneously read out and sent to the mixing amplifier 1.
8, the first read signal S ₅ and the second
An output signal _S3 is obtained by mixing the readout signal _S7 .
The signal S ₃ becomes a read signal for the waveform storage circuit 13.

Note that in FIG. 2, the signal to be applied to the differential amplifier 17 is not the output signal S ₅ of the first waveform storage means 15 and the signal S ₂ , but the output signal S ₃ of the mixing amplifier 18 is added together with the signal S ₂ , and both The signal _S6 may be obtained as a difference signal. However, in this case, the input terminal to which the signal S ₇ of the mixing amplifier 18 is applied is connected at least to t ₃ in FIG.
The base potential (usually zero potential) must be maintained during the period leading up to _t5 . After the signal S ₆ is stored in the second waveform storage means 16, this stored signal is read out and added to the mixing amplifier 18 as a signal S ₇ for error correction. Using this method, errors in the input signal _S5 of the mixing amplifier 18 can be corrected.

The waveform storage error of the waveform storage device 13 shown in FIG. 2 will be described. The spectrum of the periodic signal _S2 , which is the signal under test, is divided into DC components.
A ₂₀ , the fundamental wave component A ₂₁ , and the n-th high frequency component (the n-th high frequency component with respect to the fundamental wave) are A _2o , and the spectrum of the signal S ₅ in which these are stored is the DC component, respectively.
A ₅₀ , fundamental wave component A ₅₁ , n-th high frequency component A _5o becomes. However, δ ₁₀ , δ ₁₁ , and δ _1o are storage errors of the first waveform storage means 15 in each spectrum. Also, from the relationship in equation (2), signal S ₂ and signal S ₅
The signal S _{6 ,} which is _the difference _between becomes. If this signal S ₆ is stored in the second waveform storage means 16 and the spectra of the read signal S ₇ are respectively designated as a DC component A ₇₀ , a fundamental wave component A ₇₁ , and an n-th high frequency component A _7o becomes. However, δ ₂₀ , δ ₂₁ , and δ _2o are storage errors of the second waveform storage means 16 in each spectrum. Further, the read signal S ₃ of the waveform storage device 13 is a mixture of the signal S ₂ and the signal ₇ ,
If the spectra are respectively a DC component A ₃₀ , a fundamental wave component A ₃₁ , and an n-th high frequency component A _3o Therefore, the storage error of the signal S ₃ with respect to the signal S ₂ in each spectrum is the storage error of the first storage means 15 and the storage error of the second storage means 16 (1
), and can be reduced to a very small value. For example, when both δ _1o and δ _2o are 3%=0.03, the memory error δ _1o of A _3o is
δ _2o is 0.03×0.03=0.0009=0.09%. Also
The same applies to A ₃₀ and A ₃₁ .

For example, when using the waveform storage device 13 shown in FIG. 2 for the eccentricity compensation shown in FIG. Device 1
3, a device with a very small memory error of ±0.1% (=±1/1000) or less must be used. However, in a waveform storage device that does not perform error correction, it is extremely difficult to suppress the error to ±0.1% or less when the above-mentioned resolution distortion, drift amplitude error, phase error, etc. are considered. However, if the present invention is applied, even if the error that each of the first and second waveform storage means individually has is large, the storage error generated by the first waveform storage means can be corrected by the second storage means. Therefore, due to the synergistic effect, the final error of the storage device can easily achieve the tolerance value of ±0.1% even if the error of each of the waveform storage devices described above is about 3%. In reality, errors also occur in the differential amplifier 17 and the mixing amplifier 18, and are added to the storage error in the waveform storage device 13. However, these can be easily achieved with a high precision of 0.1% or less using commercially available general-purpose operational amplifiers without using particularly high-precision and expensive parts.

Further, in FIG. 2, the signal S ₆ is generally a low level signal for comparison with the signal S ₂ or the signal S ₅ when S ₆ =S ₂ -S ₅ . Therefore, in order to effectively utilize the resolution of the ADC 28 of the second waveform storage means 16, the differential amplifier 17 is provided with a gain so that S ₆ =
When the signal S ₆ of Sα·(S ₂ −S ₅ ) (α is 1 or more) is stored in the second waveform storage means 16 and the read signal is mixed by the mixing amplifier 18, the signal S 6 of the mixing amplifier 18 is By mixing the signals at a gain of 1/α with respect to the gain of the signal S ₅ , the resolution of the waveform storage device 13 can be equivalently improved. For example ADC
22, 28, DAC24, 30, and RAM2
If the resolution of the waveform storage device 13 is set to 8 bits and the gain α of the differential amplifier 17 is set to α=16, the resolution of the waveform storage device 13 will be 12 bits.
The method for improving this resolution is not limited to the gain of the differential amplifier 17, but also the low-pass filter 26 for input signal processing, the sample hold circuit 27, and the ADC 2.
It may be realized by the gain of the system up to 8, and as a means to reduce the read signal _S7 to 1/α, the DAC3
0, the gain of the low-pass filter 31 for output signal processing, or the gain of the mixing amplifier 18 for the signal _S7 .

In Figure 2, two independent waveform storage means are used.
Although we have described an example in which a low-pass filter 32 (second filter) for input signal processing is used, as shown in FIG.
30, 26) in the figure, sample and hold circuit 33,
(21, 27 in Figure 2), ADC34 (2 in Figure 2)
2, 28), DAC36 (24, 30 in Figure 2),
The low-pass filter 37 (25, 31 in FIG. 2) for output signal processing may be shared by the first and second waveform storage means to simplify the circuit.

At this time, for example, the first waveform storage means connects the changeover switch SW ₂ to the C contact, and when the memorized signal S ₂ (periodic signal similar to FIG. 2) is input from the C contact, the first waveform storage means The waveform storage means includes a low-pass filter 32 for input signal processing and a sample hold circuit 3.
3. It is composed of ADC 34, RAM 35, DAC 36, and low-pass filter 37 for output signal processing, and when the first waveform storage means performs waveform storage operation,
RAM 40 and adder 41 do not operate. The first waveform storage means having the above structure stores the stored signal S ₂ and supplies the read signal S ₃ together with the stored signal S ₂ to the differential amplifier 39 to generate a signal corresponding to the difference between the two.
Get _S3 . The signal _S8 becomes a storage error by the first waveform storage means. Next, connect the changeover switch SW ₂ to the D contact to store the error, and when inputting the signal S ₈ , use the low-pass filter 3 for input signal processing.
2. A second waveform storage means is formed which stores the converted signal S ₉ in the RAM 40 (the signal S ₉ is converted into a digital signal S ₉ via the sample and hold circuit 33 and the ADC 34 and the signal S 9 is not stored). After the storage is completed, the signals S'9 and _S'9 stored at the addresses corresponding to RAM40 and RAM35, respectively, are
_S10 is read out and added to the adder 41, and a digital signal _S11 obtained by adding the two is stored in the RAM 35.
At this time, the waveform storage signal stored in the RAM 35 by the first waveform storage means is stored in the first and second waveform storage means.
A digital signal that is the addition result of the waveform storage means of
Rewritten to S ₁₁ , RAM after this rewriting is completed
The read signal S ₁₀ of 35 is equal to the signal S ₁₁ ,
It is equal to the sum of the waveform storage signals from the first and second waveform storage means. After adding and storing the addition results in the RAM 35 for all stored data (data equivalent to one revolution of the information track),
The digital signal which is the addition result stored in the RAM 35 is read out. The read addition signal S ₁₀ from the RAM 35 passes through a low-pass filter 37 for processing the output signal of the DAC 36 and becomes a signal S ₃ . Further, the read addition signal _S10 is the sum of the storage result of the first waveform storage means and the storage result of the signal _S8 ,
The memory error caused by the first waveform storage means is corrected, and a signal with good memory accuracy and error correction is obtained as the signal _S3 . Note that the control circuit 38 controls each circuit in FIG. 4 described above.

Also, in the embodiment shown in FIG.
Similarly to the figure, in order to increase the resolution of the waveform storage circuit 13, the gain of the differential amplifier 17 is multiplied by α (α is 1 or more), and the signal _S8 is stored in the RAM 40.
At the time of addition to 1, read signal S ₁₀ of RAM35
In contrast, the digit of the read signal S' ₉ of the RAM 40 may be lowered to 1/α and added. In order to add the signal S' ₉ and the signal S ₁₀ , which are digital signals, in the adder 41, the above α is 2 ⁿ ( (n is an integer greater than or equal to 1), signal processing during addition becomes easier. On this occasion,
The resolution of RAM35 and DAC36 is changed to ADC3
4. Must be higher than RAM40. For example, when α=16 (=2 ⁴ ), ADC34 and RAM4
0 resolution 8 bits, RAM35 and DAC3
The resolution of the signal S'9 is set to 12 bits, and the adder 41 shifts (lowers) the most significant digit of the signal _S'9 by 4 bits and adds it to the most significant digit of the signal _S10 .

Further, although the signal S ₂ is a periodic signal, for example, in the case of a signal such as the tracking control signal S ₂ shown in FIG. 1, in addition to the periodic signal component indicating the distortion of the information track, It also includes non-periodic signal components caused by vibrations and the like. Storing this non-periodic signal component is harmful when performing eccentricity compensation, so in order to prevent this non-periodic component from being stored, the second waveform storage means stores it multiple times, averages the results, and then mixed with the storage result of the waveform storage means,
It may also be used for eccentricity compensation.

In addition, in FIGS. 2 and 4, the RAM 23,
29 and RAMs 35 and 40 may be located at different addresses within the same integrated circuit. for example
When storing 1024 points, RAM with a capacity of 2048 addresses is used, and RAM 3 is used for addresses 0 to 1023.
Memorize the information that should be entered in 5 and enter addresses 1024-2047.
Information to be stored in the RAM 40 may be stored.

Furthermore, the scope of application of the present invention is as follows:
As shown in the figure, digital information obtained by performing analog-to-digital conversion is stored in a semiconductor memory, and this is converted to digital-to-analog and read out as analog information.It is not only a waveform storage device, but also a charge transfer device. It can also be applied to waveform storage devices using analog memories. At least two waveform storage means are required, and devices having two or more waveform storage means fall within the scope of the present invention as long as they perform error correction, which is the basic concept of the present invention.

In addition, the RAM 40 shown in FIG. 4 can be replaced with a register, and each time the signal S ₈ is digitally converted by the ADC 34, it is stored in the register, added to the adder 41 at the same time, and the result of addition with the signal S ₁₀ is added to the RAM 35. It's okay.

2 and 4, and the number of samples possessed by the second waveform storage means (1
The number of samples for sampling and storing a signal may vary during the period. Furthermore, in the waveform storage device that shares the ADC and DAC shown in FIG. Stored in the third RAM,
The storage result of this third RAM may be converted into an analog signal by a DAC to obtain an error-corrected waveform storage signal. In this case, three independent RAM
These storage operations may be performed by one RAM having a storage capacity equal to or larger than the sum of the storage capacities of the three RAMs.

Further, it is desirable that the first waveform storage means 15 and the second waveform storage means 16 are set or designed so that the waveform storage accuracy of each of them is maximized. For example, in the embodiments shown in FIGS. 2 and 4, the phase error caused by the phase delay caused by the low-pass filter used for input/output signal processing is more advanced when reading RAM addresses than when writing them. By setting the timing, phase errors can be reduced and accuracy can be improved. The time to advance when reading this RAM address than when writing it (RAM R/W address timing)
must be determined in accordance with the phase characteristics of the low-pass filter used for input/output signal processing, and in the first and second waveform storage means, the characteristics of the low-pass filter for input/output signal processing must be determined. If they are different,
The timing of the R/W address of the RAM must also be set to different values depending on the performance of each filter.

Note that the digital signal processing operation of the present invention may be combined with an electronic computer system called a microcomputer.

Additionally, the present invention provides a method for using one ADC or multiple ADCs.
It is also applicable to a waveform storage device that includes an ADC and stores waveforms of multiple input signals.

The present invention can be applied to devices other than waveform storage devices for eccentricity compensation as long as the signals to be stored have known periodicity, and when used for eccentricity compensation, magnetic disks other than the optical disk shown in FIG. A device having a recording or reproducing medium that performs physical or capacitive recording and reproducing, a device having a recording or reproducing medium in the shape of a tape, sheet, drum, etc. other than a disk, and an information track with a recording trajectory other than concentric circles. The present invention can be applied regardless of the device in which recording is performed, the type of information recorded on the information track or the recorded information at the time of recording, the tracking control means, etc.

As described above, according to the present invention, it is possible to provide a highly accurate waveform storage device using inexpensive circuit elements (circuit elements that do not require high accuracy) and with simple adjustment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a waveform storage device that compensates for eccentricity of a recording medium, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a timing diagram showing its operation timing, and FIG. The figure is a block diagram showing another embodiment of the invention. 8... Recording medium, 12... Tracking control circuit, 13... Waveform storage device, 14... Rotating mirror drive circuit, 15, 16... First and second waveform storage means, 17, 39... Differential Amplifier, 18... Mixing amplifier, 20, 26, 32... Low pass filter, 21, 27, 33... Sample hold circuit, 22, 28, 34... ADC, 23, 29,
35...RAM, 24, 30, 36...DAC, 2
5, 31, 37...Low pass filter, 40...
RAM, 41...Adder.

Claims (1)

[Claims] 1. A first storage means that stores a first signal having a known period and obtains a second signal that is a read signal, and a difference between the first signal and the second signal. error detection means for obtaining a third signal corresponding to the third signal;
and a mixing means for mixing the fourth signal and the second signal to obtain the signal of Problem 5. , a signal waveform storage device characterized in that the fifth signal is used as a waveform storage signal. 2. The signal waveform storage device according to claim 1, further comprising second storage means for averaging and storing the third signal for each known period of the first signal. 3. The storage gain for storing the third signal in the second storage means is increased by α times (α is 1 or more) than the storage gain for storing the first signal in the first storage means, and the storage gain is increased by α times (α is 1 or more), and the storage gain is increased in the mixing means. 3. The signal waveform storage device according to claim 1, wherein the mixing ratio of the fourth signal to the first signal is 1/α. 4. The signal waveform storage device according to claim 3, wherein α is 2 ⁿ (n is an integer of 1 or more).