JPH031753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup device for reproducing information signals of an information recording carrier (hereinafter referred to as a disk) reproducing device such as a video disc or an audio disc.

Recording and reproducing methods for video disks, audio disks, etc. include mechanical, optical, and capacitance methods.In particular, in the case of capacitance methods, the disk has grooves to guide the transfer of information signal reading elements. There are grooved types and non-grooved types. When reproducing information signals from a non-groove type disc, the pick-up must follow the radial distortion (eccentricity) of the information signal caused by the mechanical characteristics of the disc and perform accurate signal reproduction. Control means such as tracking control for driving and displacing the arm in a predetermined direction is required.

FIG. 1 shows a principle diagram of signal reading using the grooveless capacitive method.

Although not shown, the disk 1 includes a main signal 2, tracking guide signals 3a and 3b, and 1
A third signal for alternately switching the tracking guide signals 3a and 3b is recorded during tracking control signal processing once per rotation. These signals are transmitted to the electrode 5 provided on the stylus 4.
It is extracted as a change in capacitance that occurs between Then, in order for the electrode 5 to accurately trace the main signal 2 and to accurately extract the main signal, the position of the stylus 4 is corrected and displaced in the X direction along the above-mentioned tracking guide signal.

In addition, fluctuations appear in the relative velocity between the signal recorded on the disk and the information signal reading element due to eccentricity or vertical waviness (face runout) caused by mechanical deformation of the disk, etc. This causes a time axis error (jitter) in the reproduced signal. This uses the jitter correction signal to change the position of the stylus 4 to Y.
A corrective displacement is made in the direction.

FIG. 2 is a perspective view showing the structure of a conventional signal pickup device, partially shown in cross section. The stylus 4 is attached to the tip of a pick-up arm 7 via a stylus holder 6, and a magnet 9 is inserted into the other end of the pick-up arm 7. It is supported by a suspension 8 made of material. needle pressure coil 10,
Tracking coil 11 and jitter coil 12
are arranged near the magnet 9 so as to be magnetically coupled with the magnet 9, and by attracting and repelling the magnet, a pressing force is applied to the stylus 4 against the disk, and at the same time, the stylus 4 is moved in the X direction and the Y direction. movement, tracking and jitter correction control.

In the pickup device of the information signal reproducing apparatus having the above-mentioned configuration, the characteristics of the pickup arm have a great influence on the performance of the entire reproduction device.

Now, the important characteristics that a pick-up arm should have can be broadly divided into two.

One of them is surface runout following characteristics, and the other is tracking drive characteristics.

First, I will explain the former. Disks often undergo mechanical deformation during manufacturing or due to subsequent environmental conditions, and there are two types of deformation depending on the direction of deformation. Waviness in the thickness (vertical) direction of the disk is called surface runout. In addition to this surface runout, the disk
It rotates at high speed (for example, 900 rpm) and produces undulations with large accelerations in the vertical direction. Pressure force is applied to the stylus against the disk via a pick-up arm in order to prevent the stylus from flying off the disk surface due to surface runout of the disk. In order to reduce this, it is desirable that the pressing force of the stylus be as small as possible. In that case, the pick-up arm is required to have a small equivalent mass at the point of contact with the disk (stylus).

Next, we will discuss the latter case. Another type of mechanical deformation of the disk mentioned in the former explanation is undulation in the radial (horizontal) direction of the disk, which is called eccentricity. If the disk becomes eccentric, the recorded trace of the information signal will naturally also become eccentric, and in order to make the electrode provided on the stylus follow the undulations of the information signal,
Tracking control is applied, but in this case, in order to accurately transmit the drive signal to the stylus, the pick-up arm has a high frequency and a low resonance level at that point regarding its own resonance, and other unnecessary resonances. It is required that this does not occur.

In order to satisfy the above characteristics, the pick-up arm has traditionally been made of aluminum or light alloy pipes, but the resonance level of the pick-up arm is high, especially in the tracking control system.
In order to compensate for the phase delay of the drive, an emphasized drive signal is supplied in the high frequency range, so the resonance of the pickup arm and other resonances that exist in the high frequency range will cause oscillation phenomena at these resonance points. , reduce tracking control performance,
This has the disadvantage of impairing the quality of the reproduced signal.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide a pickup arm for an information signal reproducing device that is stable and highly reliable.

Next, an embodiment of the pickup arm of the information signal reproducing apparatus according to the present invention will be described with reference to FIGS. 3, 4, and 5.

The basic configuration in FIGS. 3 to 5 is the same as that in FIG. 2 of the conventional example, so it is omitted, and the reference numerals of each component are also the same as in FIG. 2.

FIG. 3 shows the first part of the pick-up arm of the present invention.
is a perspective view showing an embodiment of the invention, in which a pipe is filled with a viscoelastic body, for example, an arm damper 13a, in the middle of the hollow arm and near the support part in order to minimize the influence of the mass added to the arm. ing.

FIG. 4 shows another embodiment in which a damper sheet 13b is attached to a part of the arm 7.

5 and 6 further show an embodiment of the present invention, in which openings 7a are provided near the viscoelastic members 13a and 13b disposed on the arms in FIGS. 3 and 4, respectively. .

Arm damper 13 made of the viscoelastic member
a. The damper sheet 13b has viscoelasticity and functions to absorb vibrations of the pickup arm 7. Therefore, by disposing these in the pick-up arm 7, the resonance level of the pick-up arm can be suppressed in a relatively high frequency range (for example, several kilohertz). As a result, in particular, the tracking control characteristics for the pickup disk are improved as follows.

By comparing the characteristics of the pick-up arm of the information signal reproducing device according to the present invention with the characteristics of the pick-up arm of the conventional example described above, it has been found that the drawbacks that were a problem in the explanation of the conventional example described above can be very well improved. Explain that.

FIG. 7 is a tracking drive characteristic diagram of the pick-up arm in the conventional example. It shows the frequency response (14 to 18) and the phase characteristic 19 of the stylus displacement with respect to the drive signal. 1 in the diagram
5 is the stakeness of suspension 8 (1 in the diagram).
4 indicates this region) and the pickup arm 7, the magnet 9 attached thereto, and other masses.
In the frequency range higher than the resonance frequency 15, the frequency decreases at a slope of -12 dB/octave, and if the pickup arm were a completely rigid body, this slope would continue up to the high frequency range as shown by the broken line 18. However, the pickup arm causes its own resonance, producing a peak such as 17 in the figure. If the peak of this resonance is high, the tracking control performance and others will be greatly degraded, as explained above.

Therefore, attempts have been made to improve the pick-up arm by changing the material of the pick-up arm, but no major improvements have been made.

FIG. 8 is a characteristic diagram showing the tracking drive characteristics of the pick-up arm according to the present invention. The characteristics of the arm without the arm damper 13a or seat 13b in the pick-up arm 7 are roughly similar to those shown in FIG. It is being That is, depending on the configuration of the pickup arm, an improvement of about 10 to 30 dB is achieved at this peak. Further, although not shown, resonance caused by other constituent members in a higher frequency range is also well suppressed.

Therefore, by employing the pick-up arm according to the present invention, it is possible to suppress oscillation of the tracking control system at a relatively high resonance frequency, resulting in advantages such as stabilization of tracking control and improvement in the quality of reproduced signals.

Furthermore, when performing still image playback or trick playback, it is necessary to make the playback element (stylus, etc.) attached to the pick-up arm jump to a predetermined signal track on the disk, as shown in Figure 9a. In this case, there is a method of adding a kick pulse signal as shown in FIG. 9b to the tracking control signal. Observing the tracking error signal at this time, it is found that when using the conventional pick-up arm, a transient phenomenon as shown in c is observed. This makes still image playback and trick playback unstable, and the amount of loss in the playback signal increases, which is one of the factors that degrades the quality of the playback image and sound.

However, when the pick-up arm according to the present invention is used, a response as shown in d is exhibited, and stable static playback and trick playback are possible.

As described above, by employing the pick-up arm of the device according to the present invention, the conventional problems can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the original configuration of a signal reading system using a grooveless capacitive method, FIG. 2 is a partially cutaway perspective view showing a conventional example of a signal pickup device, and FIGS. 5 and 6 are respectively perspective views showing embodiments of the pick-up arm of the present invention, FIG. 7 is a characteristic diagram showing the tracking drive characteristics of the pick-up arm in the conventional example, and FIG. 8 is a diagram showing the tracking drive characteristics of the pick-up arm according to the present invention. FIG. 9 is a characteristic diagram showing tracking drive characteristics, and is an explanatory diagram of operation regarding skipping of signal tracks. 1... Disc, 2... Main signal, 4... Stylus, 7... Pick up arm, 7a...
Opening, 8... Suspension, 9... Magnet, 10, 11, 12... Coil, 13a... Arm damper, 13b... Damper sheet.

Claims (1)

[Claims] 1. A device having a reading element for reading information signals recorded on an information recording carrier at one end, supported by an elastic body at the other end, and having a permanent magnet in a part of the carrier. An electromagnetic coil arranged externally so as to be magnetically coupled obtains a rotational driving force centered around the elastic body, and arbitrarily selects the position of the reading element on the information recording carrier in the horizontal direction. A hollow pick-up arm having the function of
A pick-up arm characterized in that a viscoelastic member is disposed at least in a portion of the pick-up arm between the reading element and the permanent magnet. 2. The pick-up arm according to claim 1, wherein an opening is provided in a part of the pick-up arm near the viscoelastic part.