JP2000339715A - Automatic focusing device using static pressure air bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely automatically focus a lens barrel to which an objective lens is fixed using compressed air. SOLUTION: In this automatic focusing device 1B, a first static pressure air bearing 10A which supports a small diameter cylindrical part 2b of a lens barrel 2 within a through hole 11a of a bearing casing 11 so as to be vertically movable in a floating state by a static pressure of compressed air and a second static pressure air bearing 10B which moves upward the lens barrel 2 relative to the bearing casing 11 until the lens barrel 2 comes into contact with an upper limit stopper 26 are separately provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus adjusting device which is applied to an optical disk master device and uses a static pressure air bearing for narrowing a recording beam or a reproducing beam.

[0002]

2. Description of the Related Art Conventionally, an automatic focus adjusting device using a static pressure air bearing has a large movable range of the objective lens by guiding a lens barrel for fixing the objective lens with a static pressure air bearing using compressed air. Since the objective lens has good follow-up performance in the optical axis direction, it is applied to an optical disk master device.

An example of this type of conventional automatic focusing device using a static pressure air bearing will be described with reference to FIG.

FIGS. 2A and 2B are views for explaining a conventional automatic focus adjusting device using a static pressure air bearing. FIG.
(B) is a longitudinal sectional view.

[0005] In the conventional automatic focusing device 1A using a static pressure air bearing shown in FIGS.
Is formed in a stepped cylindrical shape, and the upper flange portion 2a
Is formed to have a large diameter and a small thickness.
Below the upper flange portion 2a, a small-diameter cylindrical portion 2b having a smaller diameter than the upper flange portion 2a is formed. A through hole 2c is formed in the center of the inside of the lens barrel 2, and the objective lens 3 is fixed in the through hole 2c using an adhesive or the like.

Further, as described later, the above-mentioned lens barrel 2 is supported in a state of being floated by compressed air while being directed in the direction of gravity in a fixed ring-shaped bearing housing 11. . At the lower end of the lens barrel 2, a disc-shaped optical disc master 7 is placed on a turntable (not shown), and is rotatable integrally with the turntable. A photoresist for recording information signals is applied to the upper surface of the optical disk master 7.

Reference numeral 4 denotes a recording main beam for recording an information signal. In this case, a blue & ultraviolet laser is used. On the other hand, reference numeral 5 denotes a sub-beam for focus adjustment, in which a red laser is used here. At this time, the sub-beam 5 for focus adjustment includes a forward sub-beam 5a for irradiating the optical disk master 7 and a return sub-beam 5b in which the forward sub-beam 5a is reflected by the optical disk master 7.

The recording main beam 4 emitted from a laser light source (not shown) is converged by the objective lens 3 and irradiated on the optical disc master 7 to record and expose information signals on the photoresist. On the other hand, the sub-beam 5 for focus adjustment is emitted from a laser light source (not shown) different from the laser light source of the main beam 4, where the incoming sub-beam 5 a is narrowed by the objective lens 3 and the optical disc master 7 The return sub-beam 5b reflected by the optical disc master 7 is taken into a two-segment photodetector (not shown) to obtain focus information of the objective lens 3. At this time, a laser (red laser) having a wavelength having a low sensitivity characteristic with respect to the photoresist for information recording is used as the sub-beam 5 for focus adjustment.

A small-diameter cylindrical portion 2b formed below the upper flange portion 2a of the lens barrel 2 has a through-hole 1 formed in the center of a ring-shaped bearing housing 11 in which a hydrostatic air bearing 10 is formed.
The lens barrel 2 is fitted in a floating state by a static pressure of compressed air with a slight gap therebetween so that the lens barrel 2 can move up and down along the optical axis of the objective lens 3.

The bearing housing 11 of the above-described hydrostatic air bearing 10
Is formed in a ring shape by using an aluminum material or the like. A ring-shaped air passage 11e is formed on the lower surface 11b, and the lower side of the ring-shaped air passage 11e is shielded by a shielding disk 12. Further, an outer peripheral portion 11c is provided inside the bearing housing 11.
The first and second horizontal air passages 11f and 11g are divided at substantially equal intervals along the circumference and are radially formed in two stages of a lower stage and an upper stage toward the central through hole 11a, and The outer peripheral sides of the first and second lateral air passages 11f and 11g are closed by a shield material 13 except for a compressed air inlet 11h described below, and the first and second lateral air passages 11g and 11g are closed.
f, 11g of the through-hole 11a side are narrowed and the through-hole 1
1a. Also, the lower first horizontal air passage 11f
One of them is connected to a compressed air inlet 11h formed in the outer peripheral portion 11c. Also, the lower surface 1 of the bearing housing 11
A plurality of first vertical airways 11i are formed to connect the ring-shaped airway 11e formed in 1b to the first and second horizontal airways 11f and 11g. Further, a second vertical air passage 11j is formed upward from the upper second horizontal air passage 11g, and the second vertical air passage 11j is a ring-shaped air passage formed on a lower surface 23c of a center pole 23 described later. 2
It communicates with 3d.

Then, the clean compressed air pressure that has passed through a filter (not shown) is applied to the compressed air inlet 11 of the bearing housing 11.
h, the air is guided from one of the first horizontal air passage 11f and the first vertical air passage 11i communicating with the compressed air inlet 11h to the lower ring-shaped air passage 11e. Via the road 11i, the first and second lower and upper stages
Compressed air flows into the through hole 11a formed in the center of the bearing housing 11 from the lateral air passages 11f and 11g, and passes through the small-diameter cylindrical portion 2b of the lens barrel 2 through the through hole 11a of the bearing housing 11. Suspended by static pressure.

Next, between the lower part of the upper flange portion 2a of the lens barrel 2 and the upper surface 11d of the bearing housing 11, there is provided an electromagnetic driving means 20 by an electromagnetic circuit for moving the lens barrel 2 up and down.
Is attached.

In the above-mentioned electromagnetic driving means 20, a ring-shaped coil bobbin 21 is attached to the outer peripheral portion of the upper flange portion 2a of the lens barrel 2 so as to fall down, and a driving coil 22 is wound around the coil bobbin 21.

A center pole 23 is mounted on the upper surface 11d of the bearing housing 11. The center pole 23 is formed of a large-diameter portion 23a and a small-diameter portion 23b in a stepped ring shape using a soft magnetic material. Is formed.

The large-diameter portion 23 of the center pole 23 described above
A ring-shaped permanent magnet 24 and a ring-shaped yoke 25 are laminated on a, and the ring-shaped yoke 25 faces the drive coil 22 wound around the coil bobbin 21. Further, an upper limit stopper 26 for restricting upward movement of the lens barrel 2 is mounted on the yoke 25.

The drive coil 22 and the yoke 25
, The permanent magnet 24 and the center pole 23 form an electromagnetic circuit. In this electromagnetic circuit, a control current is supplied to the drive coil 22 based on focus information to the objective lens 3 corresponding to the return sub-beam 5b for focus adjustment reflected by the optical disk master 7 and an electromagnetic force output. The lens barrel 2 is moved up and down along the optical axis of the objective lens 3.

The small diameter portion 23b of the center pole 23
Enters the inside of the ring-shaped coil bobbin 21 and protrudes to near the lower surface of the upper flange portion 2a of the lens barrel 2.

The lower surface 23c of the center pole 23 is mounted on the upper surface 11d of the bearing housing 11, and the lower surface 23c of the center pole 23 is
3d, and the ring-shaped air passage 23d communicates with the second vertical air passage 11j of the bearing housing 11.

A plurality of vertical air passages 23e are formed from the ring-shaped air passages 23d formed in the center pole 23 upward in the small diameter portion 23b.
The upper end of 3e is narrowed and communicates with the gap S on the lower surface side of the upper flange portion 2a of the lens barrel 2.

Here, the compressed air inlet 1 of the bearing housing 11
The compressed air entering from 1h and reaching the second vertical air passage 11j flows into the ring-shaped air passage 23d of the center pole 23 from the second vertical air passage 11j, and this ring-shaped air passage 23d
Is sent out to the gap S on the lower surface side of the upper flange portion 2a of the lens barrel 2 through the vertical air passage 23e communicating with the upper portion 2a.
Is pushed up until the lens barrel 2 comes into contact with the upper limit stopper 26 and the compressed air sent out passes through a small gap between the coil bobbin 21 and the center pole 23 and flows out into the atmosphere. are doing. At this time, the vertical movable amount of the lens barrel 2 to which the objective lens 3 is fixed is approximately 3 mm.
If there is, it can be easily confirmed by visual inspection, which is sufficient. If the movable amount of the lens barrel 2 is about 3 mm, the entire automatic focus adjustment device 1A is raised by a mechanical vertical movement mechanism (not shown) when the optical disk master 7 is mounted in the optical disk master. In addition, a mechanism for releasing the lower end of the lens barrel 2 from the optical disk master 7 becomes unnecessary, and the rigidity of the apparatus can be increased.

[0021]

According to the above-mentioned conventional automatic focusing device 1A using a static pressure air bearing, the main beam for recording condensed by the objective lens 3 fixed in the lens barrel 2 is used. While recording and exposing an information signal on the optical disc master 7 by the optical disc 4, an object corresponding to the return sub-beam 5b for focus adjustment reflected by the optical disc master 7 on the defocus due to the surface deflection of the optical disc master 7 or the like. A control current is supplied to the drive coil 22 based on the focus information on the lens 3 to move the lens barrel 2 up and down, thereby performing focusing of the objective lens 3. Normally, this focal position is set at about the middle point of the range in which the lens barrel 2 to which the objective lens 3 is fixed can move in the vertical direction, but it is formed on the center pole 23 even during this focusing operation. Compressed air is constantly discharged from the vertical air passage 23e, and the lens barrel 2 receives a rising force until the lens barrel 2 is restricted in contact with the upper limit stopper 26. For this reason, it is necessary to always supply a downward drive force for canceling the rising force to the drive coil 22 as an offset coil current.
The load on the drive coil 22 increases.

On the other hand, the discharge of the compressed air from the vertical air passage 23e formed in the center pole 23 is accompanied by acoustic vibration, and furthermore, the center pole 23 of the fixed part, the lens barrel 2 of the movable part, and the coil bobbin 21 is pressurized by compressed air from the vertical air passage 23e, and
When the small-diameter cylindrical portion 2b floats in the through hole 11a formed in the center of the bearing housing 11 in a non-contact manner by compressed air and moves slightly up and down to perform focusing operation, The coil bobbin 21 is more likely to abnormally vibrate. These abnormal vibrations are recorded on the optical disk master 7 as abnormal signals,
This abnormal signal may cause deterioration of the recording quality of the optical disk master 7 as deterioration of focus and tracking performance.

Further, a static pressure air bearing function for floating the lens barrel 2 with respect to the bearing housing 11 with compressed air inserted through one compressed air inlet 11h formed in the bearing housing 11, and The following problem also arises because it also serves as an up-moving function for up-moving the bearing housing 11.

That is, the adjustment to move the lens barrel 2 upward until the lens barrel 2 comes into contact with the upper limit stopper 26 attached above the bearing housing 11 is regulated. The vertical air passage 23 formed in the center pole 23 is adjusted.
e, which is mainly determined by the diameter of the vertical air passage 23e and the pressure of the compressed air.
It is fine adjustment of pressure that adjusts the upward movement amount by absorbing the imbalance of the diameter of 3e.

On the other hand, in order to float the small-diameter cylindrical portion 2b of the lens barrel 2 in the through-hole 11a of the bearing housing 11, it is necessary to set the static pressure of the compressed air to the best pressure value.
The vertical air passage 23e formed in the pole 23 is swung due to fine adjustment, so that the best air bearing performance cannot be exhibited.
Due to the positional relationship between the vertical air passage 23e of the center pole 23 and the upper flange portion 2a of the lens barrel 2, a change in the amount of compressed air discharged from the vertical air passage 23e causes a slight change in the pressure of the compressed air. . This also causes abnormal micro-vibration of the lens barrel 2, and this vibration is recorded on the optical disk master 7 as an abnormal signal, and this abnormal signal is degraded as focus and tracking performance deterioration.
Therefore, in the present invention, the above-mentioned disadvantages are solved, the best hydrostatic air bearing performance can be exhibited, and a hydrostatic air bearing having good focus and tracking performance is used in the present invention. There is a need for an automatic focus adjustment device.

[0026]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a large-diameter upper flange portion which is directed in the direction of gravity and has an upper portion formed thereon. A lens barrel in which an objective lens is fixed in a small-diameter cylindrical part formed below and a small-diameter cylindrical part of the lens barrel are fitted in a through hole of a fixedly installed bearing housing in a floating state by static pressure of compressed air. A first static pressure air bearing for vertically supporting the lens barrel by discharging the compressed air into the through hole through a first air path means formed in the bearing housing; and An electromagnetic circuit is formed by the drive coil attached to the motor and the permanent magnet and the yoke attached to the bearing housing in opposition to the drive coil, and the electromagnetic circuit outputs the electromagnetic circuit based on the focus information to the front objective lens. Up and down movement of the lens barrel by electromagnetic force Discharging the compressed air toward an upper flange portion of the lens barrel through an electromagnetic driving means to be driven and a second air path means different from the first air path means formed in the bearing housing; And a second static pressure air bearing that moves the bearing up to the upper limit stopper with respect to the bearing housing.

In the automatic focus adjusting apparatus using the static pressure air bearing according to the invention, the second static pressure air bearing is provided when the automatic focusing on the objective lens is not performed, when the automatic focusing operation is performed, and when the automatic focusing operation is completed. When the auto-focus operation is abnormal, the compressed air is discharged toward the upper flange portion of the lens barrel, while the auto-focus pull-in operation to the objective lens is completed and the discharge of the compressed air is stopped during the auto-focus operation. An automatic focus adjusting device using a static pressure air bearing.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an automatic focusing device using a hydrostatic air bearing according to the present invention will be described below in detail with reference to FIG.

FIGS. 1A and 1B are views for explaining an automatic focus adjusting device using a static pressure air bearing according to the present invention, and FIG. 1A is a view taken along the line NN of FIG. FIG.
(B) is a longitudinal sectional view. For the sake of convenience, the same components as those shown in the conventional example will be denoted by the same reference numerals, and the description will be appropriately made, and the points different from the conventional example will be mainly described.

In the automatic focusing device 1B using the static pressure air bearing according to the present invention shown in FIGS. 1A and 1B, the lens barrel 2 is floated on the bearing housing 11 by compressed air. The pressurized air bearing function and the upward movement function of moving the lens barrel 2 upward with the compressed air with respect to the bearing housing 11 are not performed by the compressed air inserted from the same compressed air inlet as described in the related art. The static pressure air bearing function is performed by the compressed air inserted from the first compressed air inlet 11h formed in the bearing housing 11, while the upward movement function is performed by the compressed air inserted from the second compressed air inlet 11p formed in the bearing housing 11. It is characterized by performing with air.

That is, in the automatic focus adjusting device 1B using the static pressure air bearing according to the present invention, a large-diameter upper flange portion 2a is formed above the lens barrel 2 oriented in the direction of gravity.
The objective lens 3 is fixed using an adhesive or the like in a through hole 2c formed in the small-diameter cylindrical portion 2b formed below the upper flange portion 2a. At the lower end of the lens barrel 2, a disc-shaped optical disc master 7 is mounted on a turntable (not shown), and is rotatable integrally with the turntable. The small-diameter cylindrical portion 2b formed below the upper flange portion 2a of the lens barrel 2 has a small diameter in a through hole 11a formed in the center of a ring-shaped bearing housing 11 constituting the first hydrostatic air bearing 10A. The lens barrel 2 is fitted in a floating state by the static pressure of the compressed air with a gap therebetween, so that the lens barrel 2 can move up and down along the optical axis of the objective lens 3. The main beam 4 for recording and the sub-beam 5 for focus adjustment are squeezed by the objective lens 3 and irradiated on the optical disc master 7. At this time, the return for focus adjustment reflected on the optical disc master 7 is performed. Is taken into a two-segment detector (not shown) to obtain focus information for the objective lens 3.

Further, between the lower part of the upper flange portion 2a of the lens barrel 2 and the upper surface 11d of the bearing housing 11, an electromagnetic driving means 20 by an electromagnetic circuit for moving the lens barrel 2 up and down is provided.
Is attached.

The above-described electromagnetic drive means 20 includes a coil bobbin 21 attached to the upper flange 2a of the lens barrel 2,
A drive coil 22 is wound around the coil bobbin 21. A center pole 23 is mounted on the upper surface 11d of the bearing housing 11, and a permanent magnet 24 and a yoke 25 are laminated on the large-diameter portion 23a of the center pole 23. The yoke 25 is wound around the coil bobbin 21. The drive coil 22 and the yoke 2
5, the permanent magnet 24, and the center pole 23 form an electromagnetic circuit. In this electromagnetic circuit, a control current is supplied to the drive coil 22 based on focus information to the objective lens 3 corresponding to the return sub-beam 5b for focus adjustment reflected by the optical disk master 7 and an electromagnetic force output. The lens barrel 2 is moved up and down along the optical axis of the objective lens 3. The lens barrel 2 is placed on the yoke 25.
The upper limit stopper 26 for restricting the upward movement of the upper end is mounted. In the embodiment, the upper limit stopper 26 is fixed on the yoke 25. However, the present invention is not limited to this. The upper limit stopper 26 can restrict the upward direction of the lens barrel 2 with respect to the fixedly installed bearing housing 11. Is fine.

Here, differences from the conventional example will be described.

First, the small-diameter cylindrical portion 2b of the lens barrel 2 is fitted into the through hole 11a of the fixedly mounted bearing housing 11 in a floating state by the static pressure of compressed air.
The first static pressure air bearing 10A that supports the lens barrel 2 so that it can move up and down by being discharged into the inside of the bearing housing 11 uses the static pressure of the compressed air taken in from the first compressed air inlet 11h formed in the bearing housing 11. I have.

Here, as first air passage means for operating the first static pressure air bearing 10A, a ring-shaped air passage 11e, a first lateral air passage 11f, and a second lateral air passage 11g are provided in a bearing housing 11. , First compressed air inlet 11h, first vertical air passage 1
1i is formed. That is, the outer peripheral portion 1 of the bearing housing 11
The compressed air taken in from the first compressed air inlet 11h formed in 1c is transferred from one first horizontal air passage 11f and the first vertical air passage 11i communicating with the first compressed air inlet 11h to the ring-shaped air passage 11e. Led, after which a plurality of first
The compressed air is discharged from the lower and upper first and second horizontal air passages 11f and 11g into the through-hole 11a formed in the center of the bearing housing 11 through the vertical air passage 11i, thereby reducing the diameter of the lens barrel 2. The lens barrel 2 is vertically movably supported in a state where the cylindrical portion 2b is floated by the static pressure of compressed air in the through hole 11a of the bearing housing 11.

Next, the lens barrel 2 is compressed by the compressed air into the bearing housing 1.
The second static pressure air bearing 10B, which is moved upward until it comes into contact with the upper limit stopper 26, uses the static pressure of the compressed air taken in from the second compressed air inlet 11p formed in the bearing housing 11.

Here, as a second air passage means for operating the second hydrostatic air bearing 10B, a second compressed air inlet 11p, a third horizontal air passage 11q, a third vertical air passage are provided in the bearing housing 11. 11r is formed. That is, a second compressed air inlet 11p different from the first compressed air inlet 11h is formed in the outer peripheral portion 11c of the bearing housing 11, and the second compressed air inlet 11p is formed in the outer peripheral portion 11c.
A third lateral air passage 11q communicating with the compressed air inlet 11p is formed without reaching the inside of the through hole 11a.
Third vertical airway 11r upward from horizontal airway 11q
Are formed. These second compressed air inlets 11p,
The second air path means for the second hydrostatic air bearing 10B by the third horizontal air path 11q and the third vertical air path 11r is located at a different position from the first air path means for the first static pressure air bearing 10A. Because they are formed, they do not cross each other.

The third vertical air passage 11r of the bearing housing 11
Communicates with a ring-shaped air passage 23d formed on the lower surface 23c of the center pole 23, and further, the ring-shaped air passage 23d
Communicates with the vertical air passage 23e in the small diameter portion 23b.

Therefore, the second static pressure air bearing 10B
In the air passage means, clean compressed air that has passed through a filter (not shown) is supplied to the second compressed air inlet 11 p of the bearing housing 11.
From the third horizontal airway 11q and the third vertical airway 11q.
and 23d of a ring-shaped air passage of the center pole 23
The compressed air flows into the upper flange portion 2 of the lens barrel 2 through the vertical air passage 23e communicating with the ring-shaped air passage 23d.
Since the compressed air is sent out to the gap S on the lower surface side of the lens a, the sent compressed air pushes up the lower surface of the upper flange portion 2a of the lens barrel 2 to move the lens barrel 2 upward until the contact with the upper limit stopper 26 is restricted. The sent compressed air passes through a minute gap between the coil bobbin 21 and the center pole 23 and flows out to the atmosphere.

With the above arrangement, the first compressed air inlet 11h of the first air passage means formed in the bearing housing 11 and the second compressed air inlet 11h
Since the second compressed air inlet 11p of the air passage means is separately provided, the pressure of the compressed air can be adjusted by the first static pressure air bearing 10A.
And the second static pressure air bearing 10B
It can be adjusted separately from the time of the upward movement function.
In particular, the first hydrostatic air bearing 10B has the first
The pressure setting value at which the bearing performance of the hydrostatic air bearing 10A becomes the best is not affected, and the best air bearing performance can be exhibited. In addition, during the upward movement function by the second static pressure air bearing 10B, the second compressed air inlet is independent of the line of the first static pressure air bearing 10A that communicates with the first compressed air inlet 11h to which compressed air is always supplied. The upward movement of the lens barrel 2 is turned on / off by the compressed air by turning on / off the compressed air supplied to the 11p by an electromagnetic valve or the like (not shown).
Can control.

For example, before recording on the optical disk master 7, during standby, and during mounting of the optical disk master 7, the lens barrel 2 is raised so that the lower end of the lens barrel 2 does not contact the optical disk master 7. At this time, the lens barrel 2 is brought into contact with the upper limit stopper 26 with the compressed air supplied to the second compressed air inlet 11p, instead of the ascending operation by the DC current supplied to the drive coil 22, which causes a problem due to heat generation. And keep it raised upward until it does.

Next, at the start of recording with the optical disc master 7 mounted, the automatic focus adjusting device 1B starts an automatic focus pull-in operation. While the lens barrel 2 is floated with respect to the bearing housing 11 with the compressed air taken in from the first compressed air inlet 11h formed in the bearing housing 11, the DC to the drive coil 22 is increased.
The lens barrel 2 to which the objective lens 3 is fixed is moved downward by energization, and the focus information of the objective lens 3 is obtained by the return sub-beam 5b for focus adjustment reflected by the optical disk master 7, and the optical disk master 7 is obtained. A control current is applied to the drive coil 22 so that the focal position of the objective lens 3 coincides with and follows the resist surface, and an automatic focusing operation is started. Thereafter, the main beam 4 for recording enters the objective lens 3. Then, the automatic focusing operation during the exposure recording, in which the exposure recording on the resist surface of the optical disk master 7 is started, is continued. When the automatic focusing operation is completed, the compressed air supplied to the second compressed air inlet 11p is turned off to stop the discharge of the compressed air. Therefore, the gap S surrounded by the center part 23 of the fixed part, the lens barrel 2 of the movable part, and the coil bobbin 21 changes from a pressurized state to a normal pressure state, and abnormal vibration occurs when the lens barrel 2 is pressurized. Is gone. Therefore, the signal recorded on the optical disk master 7 has no abnormal signal in both focus and tracking performance, and a high quality recording master can be obtained.

When recording on the optical disk master 7 is completed and when recording is stopped due to an abnormality, the main beam 4 for recording is
Of the objective lens 3 is stopped, the automatic focus following operation is stopped at the same time, and the lens barrel 2 is separated from the optical disk master 7. A time constant until the compressed air supplied to the second compressed air inlet 11p is turned on and the discharge amount of the compressed air until the lens barrel 2 contacts the upper limit stopper 26 can be secured, for example, 5 seconds. Drive coil 22 that causes adverse effects due to heat generation.
Is stopped, and the lens barrel 2 is raised and held so as to contact the upper limit stopper 26 only by discharging the compressed air from the second compressed air inlet 11p.

As described above, the second hydrostatic air bearing 10B is
Compressed air is discharged toward the upper flange portion 2a of the lens barrel 2 when the automatic focusing on the objective lens 3 fixed in the lens barrel 2 is not performed, when the automatic focusing operation is performed, when the automatic focusing operation is completed, and when the automatic focusing operation is abnormal. Therefore, in each of the above operations, the drive coil 22 of the electromagnetic drive means 20 is not energized,
By discharging the compressed air, the lens barrel 2 to which the objective lens 3 is fixed can be floated and held above the optical disk master 7.

On the other hand, the second static pressure air bearing 10B
When the automatic focusing operation to the objective lens 3 fixed inside is completed and the discharge of the compressed air is stopped during the automatic focusing operation, the recording and reproduction on the optical disk master 7 during the automatic focusing operation are performed. This has the effect of preventing adverse effects due to the discharge of compressed air by the second static pressure air bearing 10B.

In the above-described embodiment, the automatic focus adjusting device 1B using the static pressure air bearing according to the present invention has been described as applied to the optical disk master device. However, the present invention is not limited to this. The present invention can be applied to any object in which a lens barrel to which an objective lens is fixed is floated by a static pressure air bearing in a bearing housing.

[0048]

According to the first aspect of the present invention, there is provided an automatic focusing device using a hydrostatic air bearing according to the present invention, wherein a small diameter cylindrical portion of a lens barrel is fixedly installed. The lens barrel can be moved up and down by being fitted into the through hole in a floating state by the static pressure of the compressed air, and discharging the compressed air into the through hole through the first air path means formed in the bearing housing. By discharging the compressed air toward the upper flange portion of the lens barrel through a first static pressure air bearing that is supported by the first and second air path means different from the first air path means formed in the bearing housing, Since the second static pressure air bearing for moving the lens barrel up with respect to the bearing housing until it comes into contact with the upper limit stopper is provided separately, the first static pressure air bearing and the second static pressure air bearing are separated. Each can be operated independently.

According to the second aspect, the second hydrostatic air bearing supplies compressed air to the objective lens at the time of non-automatic focusing operation, at the time of automatic focusing operation, at the end of the automatic focusing operation, and at the time of abnormal automatic focusing operation. Since the discharge is performed toward the upper flange portion of the lens barrel, the lens barrel to which the objective lens is fixed can be floated and held upward by discharging compressed air instead of energizing the electromagnetic driving means during each of the above operations.

On the other hand, the second static pressure air bearing stops the discharge of the compressed air during the automatic focusing operation after the automatic focusing operation to the objective lens is completed, so that the recording and reproduction during the automatic focusing operation are performed. At this time, there is an effect of preventing adverse effects due to the discharge of compressed air by the second static pressure air bearing.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining an automatic focus adjustment device using a static pressure air bearing according to the present invention;
(A) is an NN cross-sectional view of (B), and (B) is a longitudinal cross-sectional view.

FIGS. 2A and 2B are views for explaining a conventional automatic focusing device using a static pressure air bearing, and FIG. 2A is a cross-sectional view taken along line MM of FIG. FIG. 4B is a longitudinal sectional view.

[Explanation of symbols]

1B: automatic focus adjustment device using a static pressure air bearing, 2: lens barrel, 2a: upper flange portion, 2b: small diameter cylindrical portion, 3: objective lens, 4: main beam for recording, 5: focus adjustment Sub beam, 7: optical disk master, 10A: first
Static pressure air bearing, 10B: second static pressure air bearing, 11: bearing housing, 11a: through hole, 11e: ring-shaped air path, 11
f: 1st horizontal airway, 11g ... 2nd horizontal airway, 11h ... 1st compressed air inlet, 11i ... 1st vertical airway, 11p ... 2nd compressed air inlet, 11q ... 3rd horizontal airway, 11r ... Third vertical airway, 11e, 11f, 11g, 11h, 11i
... first airway means, 11p, 11q, 11r ... second airway means, 20 ... electromagnetic drive means, 21 ... coil bobbin,
Reference numeral 22: drive coil, 23: center pole, 23d: ring-shaped airway, 23e: vertical airway, 24: permanent magnet, 2
5: yoke, 26: upper limit stopper.

Claims (2)

[Claims] 1. A lens barrel which is directed in the direction of gravity, has a large-diameter upper flange formed at an upper part thereof, and has an objective lens fixed in a small-diameter cylindrical part formed below the upper flange. The small-diameter cylindrical part of the lens barrel is fitted in the through hole of the fixedly installed bearing housing in a floating state by the static pressure of compressed air,
A first static pressure air bearing for vertically supporting the lens barrel by discharging the compressed air into the through-hole through a first air path means formed in the bearing housing; An electromagnetic circuit is formed by the attached drive coil, the permanent magnet and the yoke attached to the bearing housing in opposition to the drive coil, and the electromagnetic circuit is output by the electromagnetic circuit based on focus information to the front objective lens. Compressed air is directed to an upper flange of the lens barrel via electromagnetic driving means for moving the lens barrel up and down by force, and second air path means different from the first air path means formed in the bearing housing. By discharging, the lens barrel is moved up to the bearing housing until it comes into contact with an upper limit stopper.
An automatic focus adjustment device using a static pressure air bearing, comprising: a static pressure air bearing. 2. An automatic focus adjusting device using a static pressure air bearing according to claim 1, wherein said second static pressure air bearing operates automatically when said objective lens is not automatically focused, when automatically focused, and when said automatic focus pull-in operation is performed. The compressed air is discharged toward the upper flange portion of the lens barrel at the end of the focus operation and at the time of an abnormal auto focus operation, and the compressed air is discharged during the auto focus operation when the automatic focus pull-in operation to the objective lens is completed. Automatic focusing device using a static pressure air bearing, characterized in that it stops the discharge of fluid.