JPH0136179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup device for a video disc player, and more particularly to an improvement in the mounting structure between an arm and a stylus holder that supports a stylus for detecting video signals.

A video disc is a system that reproduces video and audio on a television receiver or the like using the same principle as a record disc, and various systems are currently being developed.

One of them is the so-called grooveless capacitance variable type.
In other words, pits are formed on the surface of the conductive band that forms the disk, and an extremely thin insulator is coated on top of the pits to record information as changes in capacitance. For example, Safaya needle)
This is a VHD (Video High-
density disc) method. FIG. 1 is a schematic bottom plan view of a video disc player according to the above-described system, and FIG. 2 is a side sectional view taken along the line - in FIG.

The structure and operation of a conventional pickup device will be explained with reference to FIGS. 1 and 2.

The pick-up device 10 includes an outer frame 1 fixed to a pick-up device moving device (not shown).
A needle pressure coil 12, an arm stretcher coil 4, and tracking coils 3a, 3b, 3c, and 3d are attached to the upper inner surface and three inner surfaces of the outer frame 1, respectively. The arm 7 is attached so that its rear end coincides with a portion surrounded by the end faces of the needle pressure coil 12, arm stretcher coil 4, and tracking coils 3a, 3b, 3c, and 3d. The arm 7 is tapered and becomes thinner toward the tip. A stylus holder 8 made of an insulating material is attached to the tip of the arm 7, and a needle 9 is held by the stylus holder 8.

The rear end of the arm 7 is inserted into a suspension cylindrical portion 6B provided at the center of the suspension 6,
The entire arm 7 is thereby held by the suspension 6. As described above, the suspension 6 has a cylindrical portion 6B in the center thereof, and has arm portions 6A extending from the cylindrical portion 6B to both ends, and each end of the arm portion 6A is attached to the inner frame 5. It is being This inner frame 5 is fixed to the outer frame 1.

The suspension 6 is made of a flexible material such as silicone rubber, and in its natural state keeps the arm 7 horizontal (Fig. 2), but when an external force is applied to the arm 7, the direction of the applied external force changes. The holding state of the arm 7 can be changed by.

Further, a permanent magnet 11 is embedded inside the rear end of the arm 7 as shown by a dotted line.

The operation of the video disk player pickup device 10 having the above configuration is as follows.

First, as a turntable (not shown) rotates, the disk 2 placed on the turntable rotates. Subsequently, when a DC voltage is applied to the needle pressure coil 12, the needle pressure coil 12 and the permanent magnet 11
A magnetic force acts between the arm 7 and the arm 7, so that the arm 7 is tilted about the suspension 6 to the position shown by the dashed line 16, and the needle 9 comes into contact with the surface of the disk 2.

On the surface of the disk 2, tracks on which video signals and the like are recorded are formed in a spiral shape, and the needle 9 moves sequentially from the outer track to the inner track each time the disk 2 rotates once. A pick-up cartridge moving device (not shown) is used to move the contacts. The needle 9 then electrically detects the video signal from the track as a change in capacitance.

Incidentally, in such a conventional pick-up device 10, polypropylene is generally used as the material for the stylus holder 8. This is because when the stylus holder 8 is made of polypropylene, the arm 7 and the needle 9 can be completely electrically insulated, and the needle 9 can be easily attached.

However, through repeated detailed experiments and measurements, it has been found that the stylus holder 8 as described above has the following drawbacks.

The natural frequency of the stylus holder 8 is several k
Hz, and this natural frequency decreases as the elastic modulus decreases with increasing temperature. In other words, polypropylene has a larger change in elastic modulus and natural frequency with respect to temperature changes than metals such as iron and aluminum. Now, when we consider the temperature environment in which video disc players are used, the temperature is close to 0°C at the beginning of use in the winter, and when used for long periods in the summer, due to the fact that there is a motor inside the video disc player, etc. Ambient temperatures are expected to reach approximately 40°C or higher. Therefore, the natural frequency of the stylus holder 8 also changes significantly.

On the other hand, it has been found that when the natural frequency of the stylus holder 8 is around 1/2 of the horizontal synchronization frequency of the television screen, that is, around 7875 Hz, the quality of the reproduced television image deteriorates. The reason for this is that slight vibrations and shocks near the pick-up device 10 excites the natural vibration of the stylus holder 8, and the vibration component of the stylus holder 8 of the video signal reproduced from the needle 9 is superimposed, however slight, and the image is distorted. It is considered to be a disturbance.

Therefore, in order to prevent such a deterioration in image quality, even if the temperature conditions around the pickup device 10 change, the natural frequency of the stylus holder 8 must be 1/2 of the horizontal synchronization frequency, that is, 7875
Just keep it away from Hz.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a pickup device for a video disc player that satisfies the above-mentioned conditions.

Simply put, this invention has two parts at the tip of the arm.
This is a pickup device for a video disc player which is divided into parts and a stylus holder is attached to the tip of the divided arm.

The above-mentioned features of the invention will become clearer from the following description of embodiments with reference to the drawings.

FIG. 3 is a partial bottom plan view of one embodiment of the invention. In FIG. 3, only the parts necessary for explaining this embodiment are depicted, and other parts, that is, the outer frame 1 are depicted.
, coils, etc. are omitted.

A feature of this embodiment is that the tip of the tapered cylindrical arm 7 is divided into two parts.
That is, the distal end of the arm 7 is configured such that two halves 7A each having a U-shaped cross section face each other. A stylus holder 8 is mounted between the halves 7A. In other words, at least both sides of the stylus holder 8 are divided into two parts 7.
The structure is reinforced by A.

FIG. 4 is a sectional view taken along line - in FIG. 3. With reference to FIGS. 4 and 3, arm 7
The structure of the tip will be explained in more detail. The left and right side surfaces and a portion of the upper and lower surfaces of the stylus holder 8 are held by an arm halves 7A having a U-shaped cross section. Note that the needle 9 is held by penetrating the stylus holder 8, as in the conventional case. The arm 7 is made of aluminum, for example. With such a configuration, at least both sides of the stylus holder 8 are tightly held by the aluminum material of the arm 7, so the rigidity of the stylus holder 8 is increased. .

As a result, the natural frequency of the stylus holder 8 attached to the distal end portion 7A of the arm 7 hardly changes with respect to changes in ambient temperature. Therefore, due to the influence of ambient temperature changes, the natural frequency of the stylus holder 8 decreases to 7875.
It will no longer come close to Hz.

As described above, the present invention provides a pick-up system for a video disc player that can stably reproduce high-quality images without deteriorating the quality of the reproduced image on a television over the entire temperature range in which the video disc player is used. equipment can be provided.

[Brief explanation of drawings]

FIG. 1 is a bottom plan view of a conventional pickup device for a video disc player. FIG. 2 is a side sectional view taken along line - in FIG. 1. FIG. 3 is a partial bottom plan view of one embodiment of the invention. Fourth
The figure is a side sectional view taken along line - in FIG. 3. In the figure, 7 is an arm, 7A is divided into two parts, and 8
indicates a stylus holder, and 9 indicates a needle. In the figures, the same or corresponding parts are designated by the same numbers.

Claims (1)

[Scope of Claims] 1. A pickup device for a capacitive video disk player in which a stylus holder for supporting a needle for detecting video signals is provided at the tip of an arm, the tip of the arm being divided into two parts; 1. A pickup device for a video disc player, characterized in that the stylus holder is attached to a distal end of an arm.