JPH0441402B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is directed to pressing a reproduction needle against the surface of a disk-shaped information recording carrier (hereinafter referred to as a disk) on which information signals are recorded as concentric or spiral recording trajectories. The present invention relates to a stylus pressure applying device for a regenerated needle that obtains a good regenerated output.

BACKGROUND TECHNOLOGY In a device in which reproduction is performed by a reproduction needle that comes into sliding contact with a disk on which various information signals are recorded,
In particular, in a method (hereinafter referred to as capacitance method) in which an electrode is provided on the reproducing needle and the reproducing needle is scanned along the recording trajectory of the disk to read the recorded information signal as a change in capacitance (hereinafter referred to as the capacitance method), It is required that the signal surface on which the information signal is recorded be in close contact with the sliding contact surface of the electrode.

For example, the height of the unevenness on the signal surface of a disk on which information signals are recorded is several thousand Å and the width is about 10,000 Å, and the thickness of the sliding contact surface of the electrode is several 1000 Å and the width is also about 1000 Å.
Even if there is a minute gap between the signal surface and the sliding contact surface of the reproducing needle electrode, it is possible to successfully detect changes in capacitance corresponding to the information signal recorded on the disk. It becomes impossible. for example,
It has been experimentally confirmed that if the distance between the signal surface and the electrode sliding surface is approximately 700 Å, the detected signal level will be reduced by approximately 30% in terms of noise ratio compared to when they are in close contact. ing. The cause of the gap between the signal surface and the sliding contact surface of the electrode is due to the geometrical characteristics (undulations) of the surface of the disk itself, and the disk material and other dust in the air may act as foreign objects on the signal surface. This is due to the fact that the needle is interposed between the surface and the recycled needle slide contact surface, but the latter accounts for a larger proportion than the former.

Therefore, various proposals have been made to maintain uniform contact between the disk and the regenerated needle.

An example of the conventional stylus pressure application circuit for the above-mentioned regenerated needle will be described below with reference to the drawings.

FIG. 5 shows a block diagram of a conventional stylus pressure application circuit for a regenerated needle. In FIG. 5, 1 is a disk, 2 is a reproducing needle, 3 is a detector, 4 is a head amplifier, 5 is a signal processing circuit, 6 is a display means, 7,
Reference numerals 8, 9, 10, 11, 12, and 13 indicate needle pressure increasing circuits that increase needle pressure when a foreign object is present between the sliding surface of the regenerating needle and the disk surface, resulting in a decrease in output.
Reference numeral 4 denotes an addition circuit of the steady needle pressure circuit 15 and the needle pressure increasing circuit, 16 a needle pressure drive circuit, 17 a needle pressure applying coil, and 18 a cantilever for holding the regenerating needle.

The operation of the conventional stylus pressure application circuit for a regenerated needle configured as described above will be described below.

To reproduce a capacitive disk, the irregularities on the signal surface of the disk 1 are read as changes in capacitance between the electrode sliding surface of the playback needle 2, and the detector 3 converts the changes in capacitance into an electrical signal. This is done by sending the signal through a head amplifier 4 and a signal processing circuit 5 to a display means 6 consisting of a speaker, a video tube, etc. If a foreign object intervenes between the sliding surface of the playback needle and the signal surface of the disk, the RF signal level output from the head amplifier 4 will change depending on the degree of the foreign object. The presence of foreign matter is detected, and the contact pressure between the regeneration needle and the disk during regeneration is controlled to increase or decrease in order to remove the foreign matter.

The operation when a foreign object is present between the disk surface and the sliding surface of the reproduction needle will be explained in more detail with reference to FIG. 6.

FIG. 6 is an explanatory diagram of the operation of each main part of the conventional needle pressure applying circuit for the regenerated needle shown in FIG.

In FIGS. 5 and 6, the DC converter 7
The DC voltage after DC conversion and LP amplification of the RF signal is compared with the DC voltage as a reference voltage by a level hold 9 made of a CR and an attenuator 10 made of resistance division, and the DC voltage is compared with the DC voltage as a reference voltage. The comparator 11 is configured to output a foreign object detection output when the following conditions occur, and the output is input to the waveform shaping circuit 13 via the diode 12. The output of this waveform shaping circuit 13 is
is added to the constant stylus pressure applying circuit 15, and the added output is sent to the stylus pressure applying coil 1 via the drive circuit 16.
7. (Disclosed in Japanese Patent Application Laid-Open No. 59-36343) Problems to be Solved by the Invention However, in such a conventional circuit configuration,
When a foreign object is present between the disk surface and the regenerated needle, there is only one level of increased pressure retention level for the contact pressure between the disk and the regenerated needle, so even if the maximum stylus pressure is maintained, the foreign object may not be removed. If the increased pressure retention level is increased in order to improve the ability to remove foreign matter, the maximum stylus pressure is reached even when a slight foreign matter is present, resulting in frequent disk deterioration.

In view of the above-mentioned problems, the present invention provides a stylus pressure application circuit for a regenerated needle that can completely remove foreign matter interposed between the disk surface and the regenerated needle during regeneration.

Means for Solving the Problems In order to solve the above problems, the regeneration needle pressure application circuit of the present invention increases the contact pressure when the regeneration signal of the re-biopsy falls below a predetermined value. The structure has a plurality of retention levels.

Effects The present invention has the above-mentioned structure and has multiple contact pressure holding levels during pressure increase, so that even foreign objects firmly interposed between the playback needle and the disk surface can have a negative effect on the screen being played back. This means that it can be removed without any problems.

Embodiment A stylus pressure applying circuit for a regenerated needle according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a stylus pressure applying circuit for a regenerated needle in an embodiment of the present invention. In FIG. 1, 1 is a disk, 2 is a reproducing needle, 3 is a detector, 4 is a head amplifier, 5 is a signal processing circuit, 6 is a display means,
7, 8, 9, 10, 11, 12, 19, 20, 2
Reference numerals 1, 22, and 23 refer to a needle increasing pressure circuit unit that increases the contact pressure between the regeneration needle and the disk when a foreign object is interposed between the sliding surface of the regeneration needle and the disk and the output decreases; 15 is an addition circuit of the steady stylus pressure circuit 15 and the stylus pressure increasing circuit; 16 is a stylus pressure drive circuit;
17 is a needle pressure applying coil, and 18 is a cantilever that holds the regenerated needle 2.

The operation of the stylus pressure applying circuit for the regenerated needle in one embodiment of the present invention constructed as described above will be explained below with reference to FIG. 2.

FIG. 2 explains the operation of the stylus pressure increasing circuit section according to the embodiment of the present invention shown in FIG. 1.

The RF output during reproduction is converted to a DC voltage via a DC converter 7 and an LF amplifier 8, and a reference voltage is further set by a level hold 9 and an attenuator 10.
The DC voltage and the reference voltage are connected to a comparator 11.
When the DC voltage becomes less than the reference voltage value, it is detected that a foreign object is present between the disk 1 and the reproduction needle 2, and a foreign object detection output is output to the comparator 11. be done.
The foreign matter presence detection output is input to a first constant time holding circuit 22 which operates according to the rising edge of the pulse, and a holding output for a holding time _T1 is output. In addition, if a foreign object is not removed even after a certain period of time _T1 has elapsed, the signal obtained by inverting the output of the first fixed time holding circuit 11 by the inverter 20 and the foreign object detection output of the comparator 11 are malfunctioned. AND with the signal obtained through the delay circuit 19 for _the purpose of preventing
Even after this period has passed, it is still detected due to the presence of foreign matter. The detection output is input to a second fixed time holding circuit 23, and a holding output for a holding time _T2 is obtained. the first and second fixed time holding circuits 22;
The output of 23 is sent to the steady stylus pressure circuit 1 by the adding circuit 14.
5 is added.

For example, the addition level at this time is approximately the steady contact pressure.
100 mg, the contact pressure when the output of the first fixed time holding circuit 22 is added is approximately 180 mg, and the contact pressure when the output of the second fixed time holding circuit 23 is added is approximately 250 mg. With this setting, if the foreign matter interposed between the disc and the regeneration needle can be removed by increasing the contact pressure between the first stage disc and the regeneration needle during the holding time T ₁ , only the first stage pressure increase is required. The steady contact pressure returns, but if the foreign object remains present even after the holding time T ₁ , the second step of pressure increase is performed for the holding time T ₂ , and then the steady stylus pressure is restored. Return.

As described above, according to this embodiment, when the reproduction output falls below a predetermined value, first the contact pressure between the disk and the reproduction needle is increased at a relatively small level for a certain period of time, and then If the intervening foreign matter is removed by increasing the pressure and holding it, the pressure will return to steady contact pressure, but if the foreign matter is still present even after the first stage pressure has been increased for a certain period of time, the second stage with a higher level will be applied. By increasing the pressure, it becomes possible to remove even strong foreign substances that cannot be removed using conventional circuit configurations. In addition, although the stylus pressure application circuit for the regenerated needle in one embodiment of the present invention has two types of contact pressure holding levels during pressure increase, it is also possible to have the same configuration and add a fixed time holding circuit. By doing so, it is possible to increase the holding level during pressure increase to 3 or 4 types, which makes it possible to set the pressure increase level more precisely, but on the other hand, an increase in cost cannot be avoided. There is a problem. However, it has been experimentally confirmed that even if the contact pressure is maintained at two levels during pressure increase, a practically sufficient foreign matter removal effect can be obtained and that there is no adverse effect on the disk.

FIG. 3 shows a block diagram of another embodiment of the present invention, in which the foreign object detection output from the comparator 11 is inputted to a fixed time holding circuit 24 and a waveform shaping circuit 26, and the outputs obtained respectively are is added to the constant stylus pressure circuit 15 by the adding circuit 14, so that two types of holding levels are provided when the contact pressure is increased.

The operation of another embodiment configured as described above will be explained using FIG. 2-2.

FIG. 4 explains the operation of the stylus pressure increasing circuit section of another embodiment of the present invention shown in FIG. 3.

When the playback output becomes less than a predetermined value, it is detected that a foreign object is present between the disk and the playback needle, and a positive foreign object detection output is output to the comparator 11. The detection output is provided by a falling operation type constant time holding circuit 24 and a waveform shaping circuit 2.
6 is input. The holding time T 3 is outputted by the constant time holding circuit 24, and the holding time T ₃ is outputted and ORed with the detection output, so that the one with the longer time width is selected. In addition, in a waveform shaping circuit consisting of a CR charging/discharging circuit, for example, the charging time constant is approximately
By setting it from 100 msec to several 1000 msec,
If the time width of the foreign object detection output is smaller than the charging time constant, a pressure increase level corresponding to the time width is obtained, and if it is equal to or greater than the charging time constant, a constant pressure increase level output is obtained. The output of the constant time holding circuit 24 and the output of the waveform shaping circuit 26 are added to the constant stylus pressure circuit 15 by the adding circuit 14, and when the foreign object is removed immediately after increasing the pressure, the charging time constant of the waveform shaping circuit 26 becomes Since it is relatively large, ranging from several hundred milliseconds to several thousand milliseconds,
The output of the waveform shaping circuit 26 hardly changes, and only the pressure increase and holding at the first stage is performed for the sum of the output of the comparator 11 and the output of the fixed time holding circuit 24. In addition, in the case of a strong foreign object that cannot be removed by increasing the pressure in the first stage, two
When the pressure is increased in the second step and becomes equal to or higher than the charging time constant of the waveform shaping circuit 26, the second step pressure increase level is maintained.

As described above, according to another embodiment of the present invention, the presence of a foreign object between the disk surface and the regenerating needle is detected, and the contact pressure between the disk and the regenerating needle, which is at a relatively small level, is first reduced. In the case of stubborn foreign matter that cannot be removed even after increasing the pressure, a second stage of pressure increase that changes in accordance with the time width of the foreign matter detection output is applied, so that it cannot be removed using the conventional circuit configuration. It is also possible to remove stubborn dirt particles.

Furthermore, with the above configuration, the pressure increase in the second stage changes in accordance with the time width of the foreign object detection output, so that the maximum stylus pressure retention level is not reached every time. Therefore, it is also possible to set the maximum pressure increase holding level of the second stage to approximately 300 mg, for example, and use it as an emergency measure in the worst case when foreign matter is present.

Effects of the Invention As described above, according to the present invention, the disc surface is It is possible to remove foreign matter that is firmly interposed between the disk and the regeneration needle, and since the pressure is increased gradually only when it cannot be removed by increasing the pressure in the first stage, it does not damage the disk and is extremely useful in practical terms. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a stylus pressure application circuit for a regenerated needle in an embodiment of the present invention, FIG. 2 is an output waveform diagram for explaining the operation of each main part in FIG. 1, and FIG. A block diagram of a stylus pressure application circuit for a regenerated needle in another embodiment, FIG. 4 is an output waveform diagram for explaining the operation of the main parts in FIG. 3, and FIG. 5 is a conventional stylus pressure application circuit for a regenerated needle. FIG. 6 is an output waveform diagram for explaining the operation of the main parts of FIG. 5. 1...Disc, 2...Regeneration needle, 3...Detector, 4...Head amplifier, 5...Signal processing circuit,
6...Display means, 15...Addition circuit, 16...Stylus pressure drive circuit, 17...Stylus pressure application coil, 18
...cantilever.

Claims (1)

[Scope of Claims] 1. A playback needle that comes into contact with a rotationally driven disc-shaped information recording carrier to play back a signal, and a detection means that detects that the playback signal of the playback needle has fallen below a predetermined level. and stylus pressure applying means for changing the contact pressure between the reproducing needle and the disc-shaped information recording carrier according to the detection output of the detecting means, the reproducing needle having a reproduction signal below a predetermined value. A stylus pressure applying device for a regenerated needle, characterized in that it has a plurality of holding levels of contact pressure that is increased when the stylus pressure is increased. 2 When the regeneration signal of the regeneration needle falls below a predetermined value, first the contact pressure of the first stage is increased and maintained, and after a certain period of time, if the regeneration signal recovers to the predetermined value or more, steady state is established. The stylus pressure of the regenerated needle according to claim 1 is characterized in that when the contact pressure is restored and the contact pressure is still below the specified value, the next stage contact pressure is increased and maintained for a certain period of time. Application device. 3 When the regeneration signal of the regeneration needle falls below a predetermined value, the first stage is first held to increase the pressure, and if the regeneration signal immediately recovers to the specified value or more by the first stage increase and hold, the pressure is increased for a certain period of time thereafter. After maintaining the contact pressure, the pressure returns to steady contact pressure, and if it still does not recover to above the specified value, the next step of pressure increase is performed corresponding to the time period during which it remains below the specified value, and the maximum holding state is reached after several hundred milliseconds to several seconds. The stylus pressure applying device for a regenerated needle according to claim 1, characterized in that the stylus pressure applying device for a regenerated needle is configured to reach the stylus pressure of a regenerated needle.