JPS6252386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for manufacturing a recording master disc for a video disc (hereinafter referred to as a cutting machine), and in particular to an apparatus for improving the accuracy of adjacent track pitches of information signals recorded on a master disc. It is.

The video and audio signals of a video disc are recorded in a spiral on a resin disc, similar to audio records, but the recording density is
It's so expensive that it can't be compared to audio records. For example, on a VHD format video disc,
The track pitch of adjacent spirals is 1.35μ.

This video disc record is produced by molding resin using a mold called a stamper, but the recording master from which the stamper is made is a glass disc with photoresist applied to the surface. It is created by irradiating a coated master disc with a laser beam carrying video and audio signals while scanning it along a spiral (hereinafter referred to as cutting).

Therefore, the signal recording accuracy of a video disc record is determined by the accuracy of this cutting.

FIG. 1 shows a schematic configuration of a device for cutting, that is, a cutting machine.

The master disc 1 is fixed to a rotating shaft 2 that is rotatably supported by a bearing 3, and is given rotational motion by a rotational drive means (not shown) such as a DD motor. The feed table 4 on which the bearing 3 is mounted is given linear motion via a nut 5 fixed to the feed table 4 by rotation of a feed screw 6 combined with the nut. The feed screw 6 is driven by a drive motor 10 via a reduction gear 9 and a shaft coupling 8. 7 is a support base that rotatably supports the feed screw. 11 is a slide bearing that guides the linear movement of the feed base 4.

A laser beam 18 used for recording the signal is generated by a laser oscillator 14, and the video and audio signals to be recorded are conveyed into the laser beam by a modulator 5. Reference numeral 17 denotes a mirror fixed on the optical bench 19, which allows the laser beam 18 to be incident perpendicularly onto the master disc. Furthermore, the surface plate 12 on which the above-mentioned apparatus is mounted is supported by an air damper 13, so that vibrations from the floor are not transmitted to the cutting apparatus.

With the above configuration, the fixed laser beam 2
1, the master disc 1 simultaneously performs linear and rotational movements relative to the master disc 1, and a spiral recording is made on the master disc. For example, when cutting a VHD video disc, the rotational speed of master disc 1 is
900 rpm, and the moving speed of the feed table 4 is 1.215/min.

Now, the signals recorded on the master disk by the cutting machine are transferred as they are to the video disk, but the track pitch accuracy of this recorded signal has a significant effect on the quality of reproduced images and sounds. That is, in a cutting machine, if the master disc and the recording laser beam do not properly perform a predetermined relative movement, the recorded spiral track will fluctuate and the track pitch will vary.
This variation in track pitch makes it difficult for the playback pick-up to run correctly on the recording track when playing back signals from a video disc, and in extreme cases, adjacent tracks may overlap, causing signal distortion. Recording and playback becomes impossible.

Therefore, the mechanical precision required of a cutting machine is to ensure that the recording laser beam and the master disk perform the correct relative movement.1. 2. The rotational speed of the master must be constant and the rotational accuracy must be high.

Generally, in a cutting machine, when the master 1 is set on the rotating shaft 2, the center of the master and the center of the rotating shaft may be misaligned due to dimensional errors during installation, and the rotation shaft and the master may not be combined. The rotating body becomes an unbalanced rotating body, and as the master disk rotates, it generates an unbalanced centrifugal force that is synchronized with the rotation, causing the master disk to whirl around, reducing rotation accuracy, and causing The unbalanced centrifugal force of
Furthermore, vibrations are generated in the entire structure of the cutting machine, reducing the recording track pitch accuracy.

To solve this problem, when setting the master,
Conventionally, a rotating body consisting of a master disk and a rotating shaft is balanced.

FIG. 2 shows a conventional balancing method.

The vibration of the feed base 4 that occurs as the master disk 1 rotates is detected using the displacement detection means 23, and the amount of unbalance and the unbalance position are calculated using the detection signal. Balance is achieved by attaching it to a groove 27 provided on the outer periphery.

However, with the conventional balancing method described above, balance can only be achieved within the range of displacement detection accuracy of the displacement detector 23. Therefore, for example, errors caused by unbalanced track pitch vibration can be
In order to maintain a balance so that the displacement is 1 μ or less, a displacement detector having a resolution of 1 μ or more is naturally required.

The track pitch of a video disc recording signal is, for example, 1.35 μ in the VHD system. Therefore, if the track pitch tolerance is set to ±5%, only a track pitch error of ±0.0675 μ is allowed. Naturally, the resolution of the displacement detector during balancing requires an extremely high resolution of 0.0675μ or more.

Conventional balancing methods for cutting machines use Michelson interferometry using laser beams to detect this displacement, but unlike normal displacement detection means such as differential transformers, it is sensitive to external vibrations. In addition, the signal processing becomes complicated, and the configuration of the device itself is complicated, resulting in an increase in costs.

The present invention solves the problems of the above-mentioned conventional balancing method in cutting machines.

FIG. 3 shows an embodiment of the present invention.

In FIG. 3, the feed base 4 is connected to the slide bearing 1.
A gas discharge opening 63 is provided on the sliding surface of the feed base so as to supply compressed gas toward the sliding surface that slides on the slide surface 1. External compressed air source 60
Therefore, high-pressure air is discharged from the gas discharge opening onto the sliding surface through the air supply path 61, and the feed table 4 is supported by floating above the sliding surface of the slide bearing 11. Moreover, in the air supply path 61,
Valve 6 for turning on and off the flow of compressed air
2 is provided. In the above configuration, in the balancing step when setting the master disk, the valve 62 is opened and the feed table 4 is floated and supported, so that the amplitude of vibration of the feed table 4 caused by unbalanced rotation is expanded, and the unbalanced rotation is In order to facilitate the detection of the amount, in the cutting process after the completion of balancing, the valve is closed and the feed table 4 is brought into normal sliding contact with the slide bearing.

Next, the principle of improving the accuracy of balancing and thus improving the track pitch accuracy of recording signals in cutting will be explained with the configuration of the present invention.

FIG. 4 shows a model of a feed table system during balancing in a conventional cutting machine. In other words, the object 56 with mass m _p represents the mass of the feed table and the bearing mounted on the feed table, and the spring 57 with spring constant k _p represents the feed screw or slide bearing that supports the feed table. Furthermore, the damper 58 with a viscous damping coefficient C _p replaces the viscous resistance and frictional resistance associated with sliding between the feed table and the slide bearing with equivalent viscous resistance. be. The centrifugal force caused by the unbalanced rotation of the rotating body is expressed here as a forced vibration external force F _p sinωt.

Note that 52 is a detector for detecting unbalanced vibrations.

In the above conventional configuration, the damper 58 is
It has an important role. In other words, due to unbalanced rotation, the feed table receives a forced vibration external force and generates vibration, but the damper absorbs this vibration energy.
It has the effect of suppressing the vibration of the feed base. This effect must be effectively utilized in the cutting process, but on the other hand, during balancing, unbalanced vibrations are suppressed, making it difficult to detect unbalanced, and becoming a factor that hinders the improvement of balancing accuracy.

Next, FIG. 5 shows a model of the structure of the balancing system of the cutting machine according to the present invention shown in FIG.
(Fig. 3) shows the case in the open state. In other words, by opening the valve 62, the feed base is supported without contact with the slide bearing through air pressure, and the slide bearing has a relationship with the slide bearing represented by the viscous damping coefficient C _p in FIG. The viscous resistance and frictional resistance that occur with sliding between the two no longer exist.

If the rotating body is balanced in this state, it becomes possible to easily detect unbalanced vibrations, which were conventionally attenuated by the damper 58 and difficult to detect, and the balancing accuracy is improved.

After balancing is achieved with a predetermined accuracy, the vibration is damped by closing the valve 62 and returning the feed table and slide bearing to their normal sliding state, that is, the state shown in Figure 4. This effectively utilizes the effect to suppress the vibration of the feed table.

In the cutting machine of the present invention having the above configuration, if the vibration displacement detector used for balancing when setting the master has the same resolution as the conventional one, the balancing accuracy can be dramatically improved. It is clear that you can obtain
On the other hand, if the goal is to achieve the same balancing accuracy as before, unbalanced vibrations that could only be detected with a conventional laser-based length measuring device can be detected using a conventional differential transformer or capacitive displacement meter. It becomes possible to detect the displacement using a displacement detecting means such as the above, and it is possible to simplify the device and reduce the cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a video disk cutting machine, FIG. 2 is a side view of the configuration of a conventional cutting machine, FIG. 3 is a side view of a cutting machine according to an embodiment of the present invention, and FIG. 4 5 is an explanatory diagram of a conventional unbalance correcting method, and FIG. 5 is an explanatory diagram of an unbalance correcting method according to the present invention. DESCRIPTION OF SYMBOLS 1...Glass master disc, 2...Rotating shaft, 3...Bearing, 4...Feeding stand, 28...Displacement detection means, 63
...Opening for gas discharge.

Claims (1)

[Claims] 1. A bearing supporting a rotating shaft having a rotation drive means is mounted on a feed base that performs linear motion, and a disk-shaped glass master disk attached to the rotating shaft is given rotational and linear motion, and a recording signal is transmitted to the glass master disk. In the disk recording master production device that processes and records information signals in a spiral shape on the glass master disc by irradiating a laser beam having The glass master disc,
It is attached to the rotary shaft, discharges compressed air from the compressed air discharge opening, floats and supports the feed base, rotates a rotary body consisting of a glass master and the rotary shaft, and eliminates rotational unbalance existing in the rotary body. After detecting the vibration of the feed table caused by the amount of air, the discharge of compressed air from the compressed air outlet is stopped, and predetermined information is recorded while the feed table and the slide bearing are in sliding contact. A disk recording master production device characterized by the following.