JPS6252387B2 - - 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 spirally (hereinafter referred to as cutting).

Therefore, the accuracy of signal recording on 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 stand 4 on which the bearing 3 is mounted is the feed stand 4.
A linear motion is applied through a nut 5 fixed to the shaft 5 by rotation of a feed screw 6 combined with the nut 5. 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
This is a slide bearing that guides the linear movement of the feed table 4. A laser beam 17 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 15. 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 21
On the other hand, the master disc 1 simultaneously performs linear and rotational movements relative to the original disc, 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 mm/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 correctly 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 reproducing pick-up to run correctly on the recording track when reproducing signals from the video disk.
In extreme cases, adjacent tracks overlap, making it impossible to record or reproduce signals.

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. To perform linear motion.

2. The rotational speed of the master disc is constant and the rotational accuracy is high.

It is.

Now, in general, in cutting machines, 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 when the rotating shaft and the master are 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 an appropriate displacement detection means 23, and the detection signal is used to calculate the amount of unbalance and the unbalance position, and the counterbalance is set on the rotary table. 22
Balance is achieved by attaching it to a groove 27 provided on the outer periphery of the cylinder.

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, the error caused by unbalanced vibration of the track pitch can be
In order to maintain a balance so that it is less than 0.05μ,
Naturally, a displacement detector with a resolution of 0.05μ or more is 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 a laser beam to detect this displacement, but unlike ordinary displacement detection means such as differential transformers, it is sensitive to external vibrations. , and signal processing becomes complicated.
Further, the structure of the device itself is complicated, which causes a problem of increased 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, a bearing 3 supporting a rotating shaft 2 on which a master 1 is mounted is a spring member 2 made of a plate spring or the like.
It is supported via blocks 9 and 30 by blocks 31 and 34 fixed to the feed base 4. Reference numeral 32 denotes an air cylinder, and a block 33 is attached to the tip of the piston rod to abut against the outer peripheral surface of the bearing 3. Pressurized air is supplied to the air cylinder 32 from a compressed air source 37. By supplying the bearing 3, the bearing 3 is firmly clamped between the bearing abutting surface 36 provided on the block 31 and the block 33.

Now, in the cutting machine having the above configuration, balancing when setting the master is performed in the following manner.

First, fix the master disc 1 on the turntable 22,
The rotating shaft 2 is driven to rotate using a driving means (not shown) such as a DD motor. The displacement detection means 28 is used to detect the vibration amplitude of the bearing 3 that occurs as the bearing 3 rotates, and the phase shift with respect to the rotation of the rotating shaft, thereby determining the magnitude and position of the unbalance in the rotating body. Calculate. Based on this result, a predetermined amount of correction weight is attached to a predetermined position in a groove provided on the outer periphery of the rotary table 22 in order to correct the unbalance. The above procedure is repeated until the vibration amplitude of the bearing 3 caused by the unbalanced rotation becomes equal to or less than a predetermined value, thereby correcting the amount of unbalance of the rotating body.

After performing the balancing as described above, the bearing 3 is clamped to the feed base using the air cylinder 32, and the actual cutting process begins.

The reason why the accuracy of balancing is improved by achieving balance with the above configuration and procedure, and therefore the accuracy of recording track pitch during cutting is improved will be described below.

FIG. 4 is a model of the mechanical structure used in balancing, which will be described later. That is, the mass
The object 50 with m ₀ represents the mass of the feed table and the bearings mounted on the feed table, and the spring 51 with a spring constant k ₀
represents the support rigidity of the feed screw, slide bearing, etc. that supports the feed base. The centrifugal force caused by the unbalanced rotation of the rotating body is expressed here as a forced vibration external force F ₀ sinωt. here
F ₀ has the following relationship, where mr is the unbalance amount of the rotating body and ω is the rotational speed.

F ₀ =mrω ² (1) The equation of motion of this mechanical system is expressed by equation (2), where x is the position coordinate of the center of gravity of the object 50 with mass m ₀ .

m ₀ x＋k ₀ x＝mrω ² sinωt (2) By solving equation (2), the object 50 of mass m ₀
The vibration amplitude x ₀ is given by equation (3).

If equation (3) is expressed using a graph, it will look like curve A in Figure 5.

Now, as a specific example, if the total weight of the feed table and the object mounted on the feed table, that is, the weight of the object 50 corresponding to m ₀ , is 70 Kgf, and the equivalent spring constant of the support system is 2 Kg/μ, then the system The resonance speed of is approximately 5060r.p.
m. Since the rotational speed of the rotating body is 900 rpm, it is lower than the resonance point and corresponds to point P in the figure.

Now, the feed table generates vibrations as the unbalanced rotating body rotates, but if the allowable amplitude of this vibration is 0.05μ, then from equation (3), the amount of unbalance allowed for the rotating body is It must be approximately 10 g cm or less. Of course, in balancing, the detection resolution of the vibration displacement detector must be 0.05μ or more.

Next, FIG. 6 is a model of the mechanical structure of the balancing according to the present invention shown in FIG. 3. Similarly to FIG. 4, the spring 51 represents the rigidity of the feed screw or slide bearing that supports the feed base. The object 53 with mass m ₁ represents the mass of the feed table and objects fixed to the feed table, that is, the masses of 4, 31, 32, 33, 34, etc. in FIG. 3,
Similarly, an object 54 having a mass m ₂ represents the masses of the bearing 3, the rotating shaft 2, the master disc 1, etc. Spring constant k ₂
The spring 55 represents the spring members 29 and 30 that support the bearing 3.

This system is a two-degree-of-freedom vibration system with two mass points, but the spring stiffness of the spring members 29 and 30 is set so that k ₂ ≪ k ₀ , and approximately consists of m ₂ and k ₂ It is considered a vibrating system with one degree of freedom. Therefore, the vibration amplitude _x20 in this case is approximately expressed by the following equation.

Here, if the weight of the object corresponding to m ₂ is 30 Kgf and the spring stiffness k ₂ of the spring members 29 and 30 is 50 Kgf/cm, the resonance speed of the system is 386 r.pm, and the above
If there is an unbalance of 10 g cm, the vibration amplitude x ₂₀ is
If calculated using equation (3), it will be the 4th μ.

In other words, by using a displacement meter with a detection resolution of 4μ, it is possible to achieve balancing with an accuracy of 10g·cm. In other words, the accuracy of balancing has been improved by approximately 80 times.

This is because by reducing the spring stiffness of the support system and the mass of the supported object, the frequency characteristics of the vibration amplitude change as shown by curve B in Figure 5, and at the same test speed (Fig. This is because the vibration amplitude changes from point P to point Q under ω _s ), and the vibration amplitude is expanded.

Now, if cutting is performed with the system as it is, the system will naturally generate vibrations with an amplitude of 4 μ due to the residual unbalance of 10 g cm.
After balancing, the present invention firmly clamps the object 54 to the object 53 and makes the spring stiffness k ₂ almost infinite, thereby returning to the same support structure as before, thereby reducing the vibration amplitude. This is to suppress it to 0.05μ. That is why, as shown in FIG. 3, the bearing 3 is clamped to the feed base using an air cylinder during cutting.

The key point is that only in the balancing process when setting the master, the spring stiffness of the support system is reduced and the vibration amplitude generated by unbalanced rotation is expanded, which would otherwise be necessary without using a laser length measuring device. This makes it possible to easily achieve the previously possible balancing accuracy using an ordinary displacement detector (for example, a differential transformer, etc.).

In the above explanation, the resonance speed ω ₂ of the system when supported flexibly is smaller than the test speed ω _s , but even if ω _s < ω ₂ < ω ₀ , the vibration amplitude is It is clear that this can be expanded to a corresponding degree.

However, if ω ₂ is close to ω _s , the system enters a resonance state and the phase may become unstable, so care must be taken.

Furthermore, in the above explanation, it was stated that by using the balancing of the present invention for the same allowable unbalance amount, the detection resolution required of the displacement detector is relaxed. It is clear that when using this method, the accuracy of the balancing of the rotating body is improved, the vibrations accompanying the unbalanced rotation are reduced, and the track pitch accuracy during cutting can be improved.

FIG. 7 shows another embodiment of the invention, in which the bearing 3 is supported by an air bearing holder 35 fixed to the carriage 4. In FIG. 44 is a compressed air source, which supplies compressed air to the gas supply port of the air bearing holder through the air supply path 40. The supplied compressed air is connected to the inner wall surface of the air bearing holder,
Narrow clearance 42, 43 between the outer peripheral surface of the bearing 3
A pressure film of air is formed inside the bearing 3 to support the bearing 3 without contact. In other words, the spring member 2 of the embodiment shown in FIG.
In this embodiment, air bearings are used as equivalents to the bearings 9 and 30. Further, 45 is a vacuum suction source, which removes the gas in the gap 43 formed on the bottom surface of the bearing 3 through the exhaust path 41, and
is suctioned and fixed to the bottom surface of the air holder 35. In other words, during balancing, the valve 46
is opened, the valve 47 is closed, the bearing 3 is supported flexibly by the air bearing, and during cutting,
46 is closed and 47 is opened to firmly fix the bearing 3 to the feed base.

Of course, in FIG. 6, the outer shape of the bearing 3 is a quadrangular prism, and the bearing 3 is structured so that it does not rotate within the air bearing holder.

As detailed above, according to the present invention, it is possible to easily perform highly accurate balancing, and it is possible to suppress vibrations caused by unbalanced rotation during master cutting. Vibration detection, which could only be detected with a length measuring device, can now be performed with a normal displacement detector (e.g., capacitive displacement meter, differential transformer type displacement meter), simplifying the equipment and reducing costs. You can aim for down.

[Brief explanation of the drawing]

Fig. 1 is a side view of a schematic configuration of a video disk cutting machine, Fig. 2 is a side view 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 the conventional unbalance correction method, FIG. 5 is an explanatory diagram of the unbalance correction method according to the present invention, FIG. 6 is an explanatory diagram of the relationship between test speed and vibration amplitude during balancing, and FIG. 7 is an explanatory diagram of the present invention. It is a side view of the cutting machine of another Example. DESCRIPTION OF SYMBOLS 1...Glass master disc, 2...Rotating shaft, 3...Bearing, 4...Feeding stand, 28...Displacement detection means, 2
9, 30... Spring member.

Claims (1)

[Claims] 1. A bearing that supports a rotating shaft having a rotational drive means is mounted on a feed table that performs linear motion, and a disk-shaped glass master disk attached to the rotating shaft is given rotational and linear movement, and the glass master disk is subjected to rotational and linear movement. In a 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 a recording signal, the bearing is connected to the feed base through a spring element such as a plate spring. The glass master is supported by a flexible support structure that supports the glass master softly, and a rigid support structure that firmly supports the glass master using a method such as mechanical clamping or vacuum suction. The support structure is set as a flexible support structure and rotated, the vibration of the bearing generated by the amount of rotational unbalance is detected by the vibration detection means, the support structure is set as a rigid support structure, and predetermined information is recorded. A disk recording master production device characterized by performing the following.