JPS6213235Y2 - - Google Patents

Description

[Detailed explanation of the idea]

In recent years, high-density recording of various information signals,
Research on the development and practical application of information recording media and its reproduction using disks (hereinafter sometimes referred to as disks) has become active.
Various methods for recording and reproducing information signals using disks have been announced so far. The applicant company is also promoting development research and practical research on a high-density recording and reproducing method for information signals using grooveless disks, which have many advantages, and has developed a method for reading (detecting) information signals. , which adopts the detection format of changes in capacitance value as
In addition, we published research results on recording/reproducing systems using magnetic heads and many other systems (for example, Japanese Patent Application Laid-open No. 123205/1983, Japanese Patent Publication No.
Publication No. 32415, Japanese Patent Application Laid-Open No. 1983-29617, Japanese Patent Application Publication No. 1987-29617
-128303, Utility Model Application Publication No. 168803/1983, and many others). By the way, when reproducing information signals from a non-grooved disc, it is assumed that the information signal reading element (hereinafter sometimes referred to as reading element) always accurately follows the recording trace on the disc. A tracking control means is required for this purpose, and the reading element is driven and displaced in the width direction of the recorded trace by a drive device of the tracking control system. In addition, since discs are inevitably subject to mechanical deformation (distortion) due to various reasons during manufacture, even if the disc is rotated at a constant number of revolutions during playback, the disc The existing mechanical deformation causes a change in the relative velocity between the recording trace and the reading element, and as a result, the reproduced signal contains so-called jitter (time axis error). For this reason, conventionally, in order to remove jitter in the disc playback signal, a jitter correction signal obtained by comparing a reference signal in the playback signal with a standard signal is used to control the jitter component correction of the reading element. The signal is applied to a driving device of the circuit, thereby driving and displacing the reading element in the direction in which the recording trace extends, thereby preventing jitter from occurring in the reproduced signal. In this way, when reading and reproducing information signals from a non-grooved disk, two types of control, jitter correction control and tracking control, are used to control the reading element in the direction in which the recording trace extends and the recording trace. It is necessary to drive and displace the reading element two-dimensionally in both the width direction and the applicant company also drives and displaces the reading element two-dimensionally when reading and reproducing information signals from a grooveless disk. Regarding drive devices for reading devices capable of 54−
Many proposals have been made in publications such as Publication No. 168803. By the way, in a reading element designed to read the information signal of the disk while in sliding contact with the disk surface, wear naturally occurs due to the sliding contact with the disk rotating at high speed. These types of reading elements, such as regenerative needles and magnetic heads, need to be replaced with new ones when they wear out and reach the end of their service life. In an information signal pickup device using a reading element, it is desirable that the reading element can be easily attached to and removed from the drive unit described above. In view of this, the applicant company has decided to
As disclosed in Publication No. 55401, Japanese Utility Model Application Publication No. 168803/1983, and many other publications, there is information that allows the drive device part and the pick-up arm part to which the reading element is attached to be easily attached and detached. We are proposing a signal pickup device. FIGS. 1 to 4 show the structure, operation, and operation of an example of the previously proposed pick-up device described above, in which the drive device part and the pick-up arm part to which the reading element is attached can be easily attached and detached.
These are drawings for explaining the location of problems, etc., in which Fig. 1 is a perspective view of cartridge B coupled to drive device A, Fig. 2 is a perspective view of cartridge B, and Fig. 3 is a perspective view of cartridge B in use. FIG. 4 is a vertical side view for explaining the cartridge mounting process in this state, and FIG. 4 is a side view for explaining the state in which information signals are being read from the disk D. The specific structure and operation of the drive device A portion and the cartridge B portion shown in FIGS. 1 to 4 are disclosed in, for example, Japanese Unexamined Utility Model Publication No. 54-168803 and Japanese Unexamined Patent Publication No. 55-132541. Since some of these points have been described in detail in other publications, detailed explanations of these points will be omitted in this specification, and a general explanation will be given. The drive device A detects the current flowing through the coil when a drive signal for tracking control and a drive signal for jitter correction are supplied to the coil which is supported in a displaceable state in a DC magnetic field. The electromagnetic force generated between the device and the DC magnetic field causes linear movement in the Y direction in the figure and rotational movement that can displace the reading element in the X direction in the figure. The cartridge part B is provided with a movable part, and the cartridge part B is connected to the cartridge part B through the end of the pick-up arm 2 which is pressed against the pivot receivers 1a and 1b provided in the movable part.
By driving and displacing the pick-up arm 2 in two orthogonal directions, the reading element 3 attached to the tip of the pick-up arm 2 can be driven and displaced in the two orthogonal directions in the figure. Further, as shown in FIG. 2, the cartridge B has a magnetic field between it and a second permanent magnet 7 fixed in a position regulating groove 6 in a bracket 5 attached to the cartridge base 4. A first permanent magnet 8 that exerts an attractive force on each other is attached to a bridging member 9 provided to bridge between the legs 2a and 2b of the pick-up arm 2, so that the cartridge B is separated from the drive device A. In the state shown in the second figure, the first and second permanent magnets 8 and 7 are attracted to hold the pick-up arm 2 at a specific position. When the cartridge B and the drive device A are connected by the pivots 2a 1 and 2b 1 at the tips of the legs _2a and _2b of the arm 2 in the cartridge B and the pivot receivers 1a and 1b in the drive device A, as shown in FIG. , due to the magnetic attraction between the first and second permanent magnets 8 and 7, the pick-up arm 2
The pivots 2a ₁ and 2b ₁ of the drive unit A are brought into pressure contact with the pivot receivers 1a and 1b of the drive device A with a predetermined pressure contact force, and the reading element 3 is pressed against the surface of the disk D in the operating condition as shown in the fourth figure. The contact is made with a predetermined contact pressure. The drive device A is fixed to a guide base 11 to be attached to a cover 10, and the cover 10 is attached to a transfer body 12 as shown in FIGS.
It is rotatably attached to the shaft 13. The transfer body 12 is transferred at a predetermined transfer speed in the radial direction of the disk D rotated by the turntable T, and as shown in the fourth figure, the reading element 3 is brought into sliding contact with the disk D to perform a reproducing operation. In this state, the first and second permanent magnets 8 and 7 are
Due to the magnetic attraction force at , the reading element 3 comes into contact with the surface of the disk D with a predetermined contact pressure, reads the information signal of the disk D, and sends it to the subsequent electric circuit via the conductor 14. That is, the electrode section provided on the reading element 3 is connected to the central conductor 15 of the semi-coaxial resonator via the conducting wire 14, and the resonant frequency of the semi-coaxial resonator is the same as that of the electrode section of the reading element 3. Change in capacitance value between (e.g. 3×
10 ^-16 F). Then, the center conductor 1 of the above-mentioned semi-coaxial resonator
5 is coupled by a coupler (not shown) to an oscillator that oscillates an oscillation wave with a frequency value near the resonant frequency of the semi-coaxial resonator (for example, 925 MHz), and a sufficiently large high-frequency electric field is applied to the reading element 3. ing. Therefore, when the capacitance value between the electrode part of the reading element 3 and the disk changes depending on the pit on the disk, the resonant frequency of the semi-coaxial resonator changes, and as a result, the high-frequency electromagnetic field within the semi-coaxial resonator changes. The intensity changes depending on the sharpness Q of the resonance of the semi-coaxial resonator. Since a detection circuit is provided in the center conductor of the semi-coaxial resonator via a coupler, the change in the capacitance value according to the information signal detected by the reading element 3 described above is caused by AM detection in the detection circuit. It is sent as an output to the subsequent signal processing circuit. As is clear from the above, in order for the reading element 3 to read the information signal well, a large high-frequency electric field must be applied to the reading element 3.
If the pick-up arm 2 to which the is attached is made of a material that exhibits conductivity in a high frequency band, the pick-up arm 2 will act as an antenna, increasing the load on the semi-coaxial resonator and lowering the Q value. At the same time, in order to reduce the magnitude of the high-frequency electric field applied to the reading element 3, the reading element 3 no longer reads the information signal, so the pick-up arm is configured as a non-conductor in the high frequency band. It is necessary to In addition, in FIGS. 3 and 4, reference numeral 16 indicates a conductive wire for supplying a drive signal to the drive device A. In FIG. 3, solid lines indicate the state immediately before the side edges 4a, 4b of the cartridge base 4 of the cartridge B are inserted into the grooves 11a, 11b of the guide base 11, and the state in which the cartridge B is coupled to the drive device A is shown. The pick-up arm 2 is shown with an imaginary line. Further, an arrow E in the figure indicates the direction of movement of the cartridge B as the cover 10 is opened and closed. Note that the pivot receivers 1a and 1b provided on the side of the drive device A smoothly engage the pivots 2a ₁ and 2b ₁ of the pick-up arm 2 in the cartridge B, and
In order that a ₁ and 2b ₁ can be brought into pressure contact with the pivot receivers 1a and 1b at the correct position, the pivot receivers are formed with valley supports or conical recesses. During a playback operation in which the reading element 3 in the pickup device is in sliding contact with the disk D rotating at high speed, the reading element 3 is in sliding contact with the surface of the disk D with a predetermined contact pressure (for example, 100 mg), and The reading element 3 is driven by the driving device A.
is in sliding contact with the surface of disk D and is driven and displaced in two directions: the direction in which the recorded trace extends and the direction orthogonal to the aforementioned direction, so that the jitter-free reproduction signal accurately tracks the recorded trace. During the above playback operation, the pickup arm 2 of the cartridge B has (1) a sliding contact between the reading element 3 and the surface of the disk D; (2) Vibration caused by the driving force applied from the drive device A is applied to the pickup arm 2.
causes a flexural vibration as shown in FIGS. 5a and 6a and 6b at the resonance frequency of its flexural mode. Fig. 5 shows the state of deflection that occurs in the pick-up arm 2 when the pick-up arm 2 is rotated in a plane parallel to the surface of the disk D by the drive device A for tracking control {Fig. 5 a }, the frequency characteristic of the displacement amount of the reading element 3 with respect to the tracking error signal {FIG. 5b}, and
Frequency characteristics of residual tracking error {Figure 5c
Figure } is shown. The characteristics shown in Fig. 5b are the round transfer characteristics of the system including the compensation characteristics of the tracking control system, and
The peak 17 in Figure b is made to occur at a frequency position corresponding to the rotation speed of disk D (15Hz in the example shown), and the characteristic curve is 12db/oct in the low range,
The gain is set at 6 dB/oct in the middle range and 12 dB/oct or more in the high range, and the round transfer gain in the DC range is set to be about 70 dB, for example. Now, if the pick-up arm 2 causes a deflection vibration as shown by the dotted line in FIG. A peak 18 as shown by 18 in FIG. 5b occurs at the frequency position. Then, by a tracking control system having a loop transfer characteristic as shown in FIG. 5b,
When a tracking control operation is performed to reduce the tracking error to zero, a large residual error as shown at 18' in Figure 5c occurs at the resonant frequency of the deflection of the pickup arm 2. This emphasizes the movement of the reading element 3 at 18' in Figure 5c, and sometimes makes the operation of the tracking control system unstable, making tracking impossible. FIG. 6 is a curve diagram showing the frequency characteristics of the remaining tracking error δ when D is intentionally shaken in the width direction of the recording trace. } In the tracking control system, the degree of improvement is
About 1000 times more is required {for example, at 15Hz,
This is the degree of improvement necessary to reduce the track deviation of 300 μm to 0.3 μm. The disk track pitch is
If the distance is approximately 1.4μm, the tracking control system will reduce the track deviation to 0.3μm.
It is necessary to keep it within m. In addition, in an actual tracking control system, the degree of improvement is estimated to be about 3000 times (70 dB), so even a slight deflection that occurs in the pick-up arm 2 will have a large effect on the tracking control characteristics. . As is clear from the above, the pickup arm 2 is required to have a sufficiently small amount of lateral deflection due to standing waves. Next, the deflection of the pick-up arm in a direction perpendicular to the above-mentioned lateral direction will be considered. The reading element 3 is designed to come into sliding contact with the disk via the pick-up arm 2 with a sliding contact pressure of about 100 mg.
For example, when a bending vibration as shown in FIGS. 6a and 6b occurs, the sliding contact between the reading element 3 and the disk surface changes, and the signal level of the reproduced signal changes to the sixth level.
It fluctuates as shown in Figure c. If pick-up arm 2 is a completely rigid body,
Whether the reading element 3 is separated from the disk is determined by
It is determined by the frequency spectrum of the amount of vertical deflection of the disk surface when the disk rotates, the moment of inertia of the entire pickup arm and reading element 3 around the pivot fulcrum, the sliding contact pressure, and the spring constant of the permanent magnet in the rotational direction. Fig. 6a,
b When a standing wave of deflection occurs in the deflection mode as shown in the figure, the sliding contact pressure of the reading element 3 fluctuates at the resonance frequency of the deflection as described above, causing a signal level fluctuation of the reproduced signal, which improves the reproduction quality. deteriorate. This means that when the pick-up arm 2 vibrates in the deflection mode, there is a very small gap between the reading element and the disk in the state of contact between them.
For example, this causes a gap drift of about 100 angstroms, which causes fluctuations in the level of the read reproduction signal and the frequency characteristics of the reproduction signal, impairing the reproduction quality. A portion where the signal level is low corresponds to a case where the gap is large, and the signal in this portion exhibits frequency characteristics in which the high frequency region is lowered. As described above, the deflection of the pickup arm 2 in the surface deflection direction (vertical deflection) has a significant effect on the quality of the reproduced signal, so the amount of this deflection must also be sufficiently small. By the way, if we consider the case where the pick-up arm 2 is deflected in the lateral direction as shown in FIG. 5a, if the resonance frequency of the deflection becomes high in this case, as can be seen from FIG. Since the peak occurs in a small portion of the loop transfer gain G, the tracking control characteristics are improved. On the other hand, if the pick-up arm 2 is deflected in the vertical direction as shown in FIGS. 6a and 6b, as the resonant frequency of the deflection becomes higher, the fluctuation frequency of the envelope of the reproduced signal becomes higher, as shown in FIG. (c) Even if the frequency of the undulations in the reproduced signal waveform shown in the figure increases, the quality of the reproduced signal still deteriorates, and there is no advantage in terms of longitudinal flexural vibration even if the flexural resonance frequency increases. Does not occur. As is clear from the description so far, the vibration in the deflection mode that occurs in the pick-up arm 2 is
It is necessary to dampen the flexural vibration generated in the pickup arm 2 as much as possible since it causes deterioration in the tracking performance and the quality of the reproduced signal. Therefore, the legs 2a and 2b of the pick-up arm 2
An elastic member having a vibration absorbing function is provided between the first permanent magnet 8 and the bridging member 9 provided with the first permanent magnet 8, so as to damp the flexural vibration of the pick-up arm 2 described above (see Fig. 1). (see FIG. 2), or an elastic member having a vibration absorbing function may be provided between the pick-up arm 2 and a suitable fixed part to damp the deflection vibration of the pick-up arm 2 (not shown). Attempted. FIG. 7 is a partially vertical side view of the pick-up arm 2 shown in FIGS. 1 and 2, in which 20a and 20b are cylindrical bodies, 21a and 21b are are elastic members having a vibration absorbing function filled in the cylindrical bodies 20a, 20b, and for example, butyl rubber can be used as the elastic members 21a, 21b. For example, alumite-treated aluminum pipes can be used as the cylindrical bodies 20a and 20b, and the outer peripheries of the cylindrical bodies 20a and 20b are fixed to the bridging member 9. Legs 2a, 2 of pick-up arm 2
b extends through the center of the elastic members 21a, 21b filled inside the cylindrical bodies 20a, 20b. Now, in the pick-up arm 2 configured as described above, even if the pick-up arm 2 is excited for some reason and bending vibration occurs in the pick-up arm 2, the bending vibration is absorbed by the elastic members 21a and 21b having a vibration absorbing function. Therefore, good braking is achieved. That is, the elastic members 21a, 21b and the cylindrical body 2
0a, 20b, the bridging member 9, the first permanent magnet 8, etc. are the legs 2a, 20b of the pick-up arm 2,
A resonant system added to 2b is configured, and the resonant frequency of this additional resonant system is set to 600Hz, for example.
Assuming that the frequency band in which the pick-up arm 2 causes bending vibration is 1.5KHz or higher, in the frequency band in which the pick-up arm 2 causes bending vibration, the bridging member 9 and the cylindrical body 20a,
20b hardly moves, so the vibration caused by the deflection of the pick-up arm 2 deforms the elastic members 21a and 21b filled inside the cylindrical body.
Vibration is efficiently damped by converting vibration energy into heat. From what has been explained so far, the pick-up arm is made of a material that is lightweight and does not exhibit conductivity in the high frequency band, and can effectively damp standing waves of flexural vibration in both the horizontal and vertical directions. It will be understood that the By the way, one type of material that is required to be lightweight and resistant to bending due to bending vibrations is the cantilever used for picking up disc records. Since there are no such requirements, it is possible to use materials made of various materials with high specific stiffness as shown in Table 1. Among the various materials shown in Table 1, all other materials except boron have high conductivity and are therefore unsuitable for use in the pick arm of the information signal reading element that is the subject of the present invention. It is.

[Table] In addition to the materials listed in Table 1 above, duralumin and magnesium, which are used as materials for cantilevers, are also metals and good conductors of electricity, and are suitable for the information signal reading element that is the subject of the present invention. Cannot be used for pick-up arms. Among the materials listed in Table 1, boron is a trivalent nonmetallic element and has no conductivity, but it is difficult to mold it into a pipe suitable for the arm shape. The specific stiffness values for boron shown in Table 1 are for the case where boron is a complete whisker (whisker-like crystal), but it is extremely difficult to obtain this whisker. Then,
Usually, boron is used by mixing it with other organic substances and sintering it, making it into a boride with carbon or metal, or making it into fibers and making it into a composite material with a binder. By the way, the metal boride mentioned above is a conductor similar to a metal, and the carbon boride (which is often in this form even when sintered with an organic substance) is a semiconductor, but in the high frequency band of about 1 GHz, it becomes a conductor. Therefore, these materials cannot be used as materials for the pick-up arm of the information signal reading element, which is the object of the present invention. In addition, as mentioned above, fibers formed into fibers and hardened using epoxy resin as a binder have good insulation properties, but are currently not available due to cost considerations. Therefore, as a means of constructing the pick-up arm of the information signal reading element using the materials shown in Table 1 above, a so-called cantilever, such as that used in the cantilever of an ordinary audio pick-up cartridge, is proposed. It is conceivable to construct a pick-up arm as a joint type. Fig. 8 is a partial plan cross-sectional view showing an example of a pick-up arm configured as a joint type.
In the pick-up arm shown in FIG. Alternatively, pipes 22a and 22b made of glass are used, and the base sides 23a and 23b of the arms are, for example, aluminum pipes 23a and 23b that have been subjected to oxidation treatment.
is made using. In this case, pipe 22
The lengths of a and 22b are preferably 1 cm or more so that the high frequency electric field applied to the reading element 3 is not coupled to the aluminum pipes 23a and 23b. Here, we will consider how the joint-type pick-up arm as shown in FIG. That is, even in the joint type pick-up arm as shown in Fig. 8, lateral deflection occurs as shown by the dotted line in Fig. 5a described above. In a joint type pick-up arm such as, the specific rigidity of the tip side portions 22a and 22b is small, so
These portions 22a and 22b are bent significantly as shown by dotted lines in FIG. 8a. In the joint type pick-up arm, two parts 22a, 22b, 23a, and
23b are joined, the characteristic impedance of the medium changes suddenly at the joining portion of the two portions described above, and therefore vibrations are reflected at the joining portion and standing waves are generated in the portions 22a and 22b. The standing wave vibrations generated in the portions 22a, 22b described above are caused by the reading element 3 and the two portions 22a, 22b,
23a and 23b, this vibration is damped by the elastic members 21a and 21b which have a vibration absorption function in the additional resonance system provided at the base end of the pick-up arm. It is not done. Naturally, the resonant frequency of the flexural vibration in the tip portions 22a, 22b described above is higher than the resonant frequency of the flexural vibration of the entire pick-up arm.
If 2b is a cylindrical glass pipe with a length of 10 mm, an outer diameter of 0.8 mm, and a wall thickness of 0.1 mm, the parts 22a and 2
The resonant frequency at 2b is approximately 8KHz. In the lateral flexural vibration shown in Figure 8a, the loop gain G shown in Figure 5b is
The position of peak 18 in the characteristic increases, and the absolute value of the peak value decreases, so that the peak value shown in Figure 3c also becomes smaller than peak 18' in the figure. The servo characteristics are improved. On the other hand, even in the case of longitudinal flexural vibration as shown in Fig. 8b, the resonance frequency of the flexural vibration is higher than that in the state shown in Fig. 6a for the reasons mentioned above, but this vibration also As mentioned above, the elastic member 21 has the function of absorbing vibrations in the additional resonance system.
Since absorption braking is not applied to parts 22a and 21b, taking as an example the case where parts 22a and 22b are glass pipes having the above-mentioned dimensions, it is approximately 8K.
Hz, the envelope of the reproduced signal fluctuates and the quality of the reproduced signal deteriorates. The 8KHz deflection resonance described above not only causes fluctuations in the signal level of the reproduced signal, but also causes a scale-like striped pattern on the disk surface due to the reading element 3 hitting the disk surface at a frequency of 8KHz. , which will gradually damage the disk. As described above, it is not possible to provide a pick-up arm with good performance even if the pick-up arm is of a joint type construction. The inventors of the present invention believe that materials that exhibit conductivity in high frequency bands cannot be used as the pick-up arm to which the reading element to which a high-frequency electric field is applied is attached, and that the pick-up arm must be made of a lightweight and highly rigid material. Although it is said that
Conventionally, the cantilever material for audio pick-up cartridges, which has a high specific stiffness and has been commonly used, cannot be used due to its conductivity, processability, and cost. In view of various points such as the difficulty of constructing a pick-up arm,
By using alumina porcelain (alumina ceramic) for the pick-up arm, which has excellent insulation properties in high frequency bands, high specific rigidity, light weight, and excellent workability, the problems of the conventional methods mentioned above have been successfully solved. This made it possible to provide a pick-up arm that could be used. Alumina ceramic is a white, dense-looking material made of Al ₂ O ₃ , and is highly corrosion resistant and highly hard. Although its density is somewhat high at 3.8, its Young's modulus is second only to boron. specific stiffness
It is an insulating material that exhibits a high value of about 9.210× ¹⁰⁸ dyneg/cm, and can be manufactured using a processing method that involves firing after extrusion molding, making it easy to manufacture pipe-like products with a thin cross-sectional shape and having the required shape and dimensions. It is possible to obtain a pick-up arm easily and at low cost. Therefore, by using alumina ceramic, the first
The pick-up arm 2 has a configuration as shown in Figs. It is also easy to configure, and in this case, the characteristic impedance of the medium in each part of the arm is constant, so there is no reflection of vibration in the arm, and the vibration can be excited by various causes. Flexural vibrations occurring in the arm can also be well absorbed and damped by the elastic member that is added to the arm and has a vibration absorbing function in the additional resonance system. Note that the alumina ceramic may be porous, but by making the arm from porous alumina ceramic, it is possible to provide a pick-up arm with even higher specific rigidity. FIG. 9 shows a leg 2 in which the diameter of the arm made of alumina ceramic gradually increases from the mounting part of the reading element 3 to the base of the arm.
This is a partial plan cross-sectional view showing an example of a case where the pick-up arm is configured by a and 2b, and when the cross-sectional shape of the arm is gradually changed like the pick-up arm shown in FIG. Since the reflection of generated vibrations can be made relatively small, the present invention may be implemented as a pickup arm configured as shown in FIG. 9. As is clear from the detailed explanation above, in the pick-up arm of the information signal reading element of the present invention, the area extending from the mounting part of the reading element 3 to the area where the elastic members 21a and 21b having a vibration absorbing function come in contact with each other. Since the arm is made of alumina ceramic, the high-frequency electric field applied to the reading element 3 is not affected in any way because the arm is non-conductive, and the reading element 3 receives a sufficiently large high-frequency electric field. The information signal is picked up with high reading sensitivity, and the deflection vibration generated in the arm is well absorbed and damped by the elastic member having a vibration absorption function in the additional resonance system added to the arm. , there will be no deterioration in the playback quality due to level fluctuations in the playback signal, or damage to the disk.Furthermore, the pick-up arm has high specific rigidity, so good tracking control operation and reading element It is easy to realize good sliding contact between the disk and the pick-up arm of the present invention, and the pick-up arm of the present invention can provide this at a low cost. All the problems with the pick-up arm of 2008 are successfully solved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a state in which the drive device and the cartridge are combined, Fig. 2 is a perspective view of the cartridge, Figs. 3 and 4 are partial longitudinal side views of the pick-up device, and Fig. 5a. FIG. 8a is a partial plan cross-sectional view of the pick-up arm to explain the deflection vibration in the lateral direction of the pick-up arm, FIGS. 5 b and c are characteristic curve examples, and FIGS. 6 a and b are 8b is a partial side cross-sectional view of the pick-up arm to explain the vertical deflection vibration of the pick-up arm, FIG. 6 c is a waveform example of the reproduced signal, and FIG. FIG. 9 is a partial side cross-sectional view, and FIG. 9 is a partial plan cross-sectional view of the pick-up arm. A... Drive device, B... Cartridge, D...
Disk, 1a, 1b... Pivot holder, 2... Pick up arm, 2a, 2b... Leg, 2a ₁ , 2
b ₁ ...Pivot, 3...Reading element, 4...Cartridge base, 5...Bracket, 7...Second permanent magnet, 8...First permanent magnet, 9...Bridging member, 10... ...Cover, 20a, 20b...Cylindrical body, 21a, 21b...Elastic member.

Claims (1)

[Scope of utility model registration request] The pick-up arm is attached to one end of the pick-up arm, and a high-frequency electric field is applied to read the information signal as an electric quantity corresponding to a change in capacitance value from a recording trace consisting of an array of pits caused by the information signal on the information recording medium disk. drive the information signal reading element in a predetermined direction on the information recording medium disc so that the information signal reading element having an electrode portion is brought into sliding contact with the information recording medium disc surface with a predetermined contact pressure; The other end of the pick-up arm is brought into pressure contact with a driving device for displacing the pick-up arm with a predetermined pressure contact force, and an elastic member having a vibration absorbing function is brought into contact with the pick-up arm. In the pick-up arm of an information signal reading element such as the above, at least the part extending from the mounting part of the information signal reading element to the range where an elastic member having a vibration absorbing function comes into contact is made of alumina porcelain. .