JPH10269599A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently shorten a focal position in the constitution using a variable focus lens and adjusting the focal position. SOLUTION: A variable focus lens part 13 is constituted of the variable focus lens 14 and a fixed objective lens 15. The variable focus lens 14 is constituted so that a piezoelectric element 26 is film formed on a glass diaphragm 25, and silicon oil 28 is sealed in the inside. Then, the curvature of the glass diaphragm 25 is changed by driving the piezoelectric element 26, and the focal position of the variable focus lens part 13 is changed. In such a case, laser light from a semiconductor laser is made incident on the variable focus lens 14 in the state converged by being made incident on the fixed objective lens 15. Thus, the focal distance of the variable focus lens part 13 is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device for reading pit information formed on an optical information storage surface of an optical information storage medium such as a CD-ROM or DVD.

[0002]

FIG. 11 shows an example of this type of optical pickup device. In FIG. 11, a focus coil 3 is wound around an outer periphery of a bobbin 2 holding an objective lens 1, and a drive current is supplied to the focus coil 3 from a control circuit (not shown). The bobbin 2 is elastically supported on a head base 5 by a suspension spring 4. A tracking coil 6 is mounted on the side surface of the bobbin 2, and a driving current is supplied to the tracking coil 6 from a control circuit (not shown).

On the other hand, a pair of permanent magnets 7 are fixed to the head base 5 so as to face the tracking coil 6.
When a drive current is applied from the control circuit to the focus coil 3, the bobbin 2 moves up and down in the focusing direction due to the magnetic action of the focus coil 3 and the permanent magnet 7, so that the condensing position of the objective lens 1 is moved in the focusing direction. Can be adjusted. The tracking coil 6
When the drive current is supplied from the control circuit to the bobbin, the bobbin 2 moves in the tracking direction due to the magnetic action of the tracking coil 6 and the permanent magnet 7, so that the focusing position of the objective lens 1 can be adjusted in the tracking direction.

However, in the above-described configuration, when the condensing position of the objective lens 1 is adjusted in the focusing direction, the entire bobbin 1 is moved up and down. Therefore, focusing is adjusted due to its weight. There is a problem that the response time is long. In addition, since the entire bobbin 2 is moved, stress is applied to the lead wire of the focus coil 3 led out of the bobbin 2 to cause a problem that the focus coil 3 may be disconnected.

Accordingly, the applicant of the present invention has proposed a means for adjusting the focusing position without moving the optical system as disclosed in Japanese Patent Application No. 8-348.
No. 83 was filed. This embodiment relates to a camera device incorporating a variable focus lens. As an example, a pressing elastic film 9 integrally provided with an annular piezoelectric element 8 as shown in FIG. A configuration in which a transparent operating liquid is sealed in the space between the elastic film for pressurization 9 and the light-transmitting elastic film 10 while being arranged on the opposite side of the liquid crystal display device 10 has been proposed. In this case, the focal position of the varifocal lens can be adjusted by changing the curvature of the translucent elastic film 10 by piezoelectrically driving the piezoelectric element 8.

Incidentally, the aforementioned Japanese Patent Application No. 8-34883 is disclosed.
No. 1 proposes a variable focus lens in which the optical aberration is reduced by giving the light-transmitting elastic film 10 a film thickness distribution. The point which should be devised from is left.
In other words, the focal length of the variable focus lens is determined by the curvature of the translucent elastic film 10 as a member thereof, but there is a structural limit to reducing the curvature of the translucent elastic film 10. Was difficult to reduce to a practical distance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical pickup device capable of sufficiently shortening a focal length in a configuration in which a focal position is adjusted using a variable focus lens. Is to do.

[0008]

According to the first aspect of the present invention, by adopting a method of changing the curvature of the translucent elastic film as the variable light condensing means, the lens can be collected without moving the lens in the focusing direction. The light position can be adjusted.

In this case, since the configuration is only to change the shape of the light-transmitting elastic film, a high-speed response is possible, and the possibility of sound skipping during reproduction due to defocus is reduced. Further, since the focusing coil which is necessary for the focus adjustment in the related art becomes unnecessary, the fear of disconnection of the focusing coil is removed, and the durability and the reliability can be improved.

According to the second aspect of the present invention, the driving means is a piezoelectric element integrally provided on the light-transmitting elastic film.
A thin varifocal lens can be easily manufactured.
Therefore, a thin variable-focus lens can be easily manufactured from the variable-focus lens and the fixed objective lens, which contributes to a reduction in the overall size and space.

According to the third aspect of the present invention, since the light-transmitting elastic film is formed so as to have a film thickness distribution so as to reduce optical aberration, it is possible to improve the accuracy of the light-converging position.

According to the fourth aspect of the invention, when the light source of the optical pickup device is an infrared laser, silicon having a high infrared light transmittance is used as the translucent elastic film, so that a batch process using a semiconductor process is performed. The process simplifies the manufacturing process of the translucent elastic film, and enables low cost and mass production.

According to the fifth aspect of the present invention, when the fixed objective lens is disposed between the light source and the variable focus lens, the light condensed by the fixed objective lens enters the variable focus lens. That is, the angle of incidence on the varifocal lens increases. In this case, since the translucent elastic film of the varifocal lens is a silicon diaphragm having a large refractive index, when the incident angle on the varifocal lens is large, the interface between the translucent elastic film and the translucent substance is formed. Light is not incident on the translucent material of the varifocal lens due to total reflection. Therefore, by arranging the variable focus lens between the light source and the fixed objective lens, light from the light source can effectively enter the variable focus lens.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, the present invention will be described with reference to a CD-ROM or a DV.
A first embodiment applied to the optical pickup device of D will be described with reference to FIGS. FIG. 2 is a perspective view showing a condensing optical unit constituting the optical pickup device, and FIG. 3 is a schematic diagram showing a configuration of the entire optical pickup device. 2 and 3, the optical pickup device includes a condensing optical section 11 and a peripheral optical section 12 (shown only in FIG. 3). First, the condensing optical section 11 will be described first. The same parts as those in the technology are denoted by the same reference numerals, and description thereof is omitted. That is, the condensing optical unit 11 is mainly composed of the bobbin 2 and the varifocal lens unit 13
Is provided. The varifocal lens unit 13 includes a varifocal lens 14 and a fixed objective lens 15, and these lenses 14, 15 are integrally fixed to the bobbin 2 by bonding or the like. A tracking coil 6 is attached to the side surface of the bobbin 2 by bonding or the like.

The bobbin 2 is supported by an elastic support spring 16 while being separated from the head base 5. As shown in FIG. 2, the elastic support spring 16 has a center portion fixed to the bobbin 2 and an end portion fixed to the head base 5, thereby restricting the movement of the bobbin 2 in the focusing direction, and restricting the movement of the bobbin 2 in the tracking direction. It is characterized by a structure that enables movement. That is, since the elastic support spring 16 has an appropriate width, it does not deform in the focusing direction, but the curved portion can be elastically deformed in the tracking direction.
A pair of permanent magnets 7 are fixed to the head base 5 so as to face the tracking coil 6 provided on the bobbin 2. With the above configuration, the bobbin 2 is elastically supported between the pair of permanent magnets 7 fixed to the head base 5.

The peripheral optical section 12 shown in FIG. 3 is an optical system for reproducing the information recorded on the optical disk, and since its configuration is general, it will be briefly described. That is, a semiconductor laser 17 as a light source emits a laser beam, and the laser beam passes through optical components such as a collimator lens 18, a diffraction grating 19, and a polarizing beam splitter 20, and then a varifocal lens of the condensing optical unit 11. Light enters the unit 13. Then, the light is reflected by the varifocal lens unit 13 while being focused on the optical information storage surface of an optical disk 21 (see FIG. 6) as an optical information storage medium, and the reflected light travels straight through the polarization beam splitter 20 to be focused. The light condensed by the lens 22 is detected by the light detection unit 23. Therefore, an output signal corresponding to the intensity of light reflected on the optical information storage surface of the optical disk 21 provides focusing servo information, and the focal position of the varifocal lens unit 13 is adjusted based on the information.

FIG. 1 is a detailed view of the varifocal lens unit 13 provided on the bobbin 2. The varifocal lens unit 13 is configured as follows in order to make it thinner with respect to the focal length of the fixed objective lens 15. That is, a thin glass diaphragm 25 as a translucent elastic film is joined to the annular silicon spacer 24 by anodic bonding. On the glass diaphragm 25, a piezoelectric element 26 as driving means such as PZT is formed in an annular shape by a film forming method such as sputtering. Although not shown, the glass diaphragm 25 is formed so as to have a film thickness distribution in which the film thickness gradually becomes thinner toward the center, thereby reducing the optical aberration of the varifocal lens unit 13. It has become.

The piezoelectric element 26 has an initial shape as shown in FIG. 4 when no voltage is applied, and the glass diaphragm 25 is not deformed in the initial shape. On the other hand, when a voltage is applied to the piezoelectric element 26, compression occurs as shown in FIG.
Is deformed into a curved shape, and the glass diaphragm 25 is also deformed into a curved shape along with the curved shape.

As shown in FIG. 1, an integrated body comprising the silicon spacer 24 and the glass diaphragm 25 is bonded to each other by means of bonding or the like so that a space is formed between the glass diaphragms 25. Have been.

Here, two fine through-holes 27 are formed on the side surface of the silicon spacer 24, and a silicone oil 28 as a light-transmitting substance is supplied to the space between the glass diaphragms 25 through the through-holes 27. It is enclosed. In other words, when one through-hole 27 is immersed in silicone oil and the other through-hole 27 is evacuated,
Silicone oil 28 is introduced into the space between the glass diaphragms 25. After that, by sealing the two through holes 27 with resin or the like, the varifocal lens 14 in which the silicone oil 28 is sealed can be formed.
In this case, since the refractive index of the silicone oil 28 is substantially the same as that of the glass diaphragm 25, the silicone oil 28 is selected for the purpose of avoiding reflection at the interface between the silicone oil 28 and the glass diaphragm 25. Furthermore, as described in Japanese Patent Application Laid-Open No. H08-114703, the glass diaphragm 25 has a film thickness distribution to reduce optical aberrations. However, since the technology is the same, the description thereof is omitted. Omitted.

The fixed objective lens 15 includes a lens holder 29
Are fixed by means such as adhesion while being sandwiched between the inner peripheral step portion and the holding ring 30. The outer peripheral portions of the variable focus lens 14 and the fixed objective lens 15 are joined to each other by means such as adhesion or the like to be integrated. In this case, the variable focus lens 14 and the fixed objective lens 1
The vertical relationship in arrangement with 5 is arbitrary.

Next, the principle of focusing will be described with respect to the focusing direction. When the semiconductor laser 17 is driven, a laser beam is emitted from the semiconductor laser 17.
This laser light is converted into parallel light by a collimator lens 18, passes through a diffraction grating 19, is then reflected by a polarizing beam splitter 20 in an orthogonal direction, and is condensed by a condensing optical unit 11.
Of the variable focus lens unit 13 of FIG.

When a voltage is applied to the piezoelectric element 26 from an external power supply, the piezoelectric element 26 is deformed as shown in FIG.
Accordingly, the glass diaphragm 25 integrated with the piezoelectric element 26 is elastically deformed. Thereby, the varifocal lens unit 1
The laser light incident on 3 is incident on the varifocal lens 14 so as to pass through the fixed objective lens 15 and converge on the focal position of the fixed objective lens 15. Then, the laser light that has passed through the fixed objective lens 15 is applied to the optical disc 21 while being further focused by the variable focus lens 14.

In this case, the focal length of the varifocal lens unit 13 changes due to the change in the curvature of the glass diaphragm 25, and accordingly, the focal length of the condensing optical unit 11 changes. Therefore, it is possible to focus on the optical information storage surface of the optical disk 21 based on the servo signal from the light detection unit 23 that receives the reflected light from the optical disk 21.

As shown in FIG. 7, when the focus position of the varifocal lens unit 13 deviates from the optical information storage surface of the optical disk 21 due to the influence of the warp of the optical disk 21, the servo signal from the light detection unit 23 is used. Variable focus lens 14
A large servo voltage is applied from an external power supply to the piezoelectric element 8 constituting. Thereby, the curvature of the piezoelectric element 8 and thus the glass diaphragm 25 is increased, and the focal length of the variable focus lens unit 13 is reduced, so that the optical information storage surface of the optical disk 21 can be focused. In this case, the varifocal lens 1
Since the configuration of the glass diaphragm 25 of No. 4 is changed, the focal length of the varifocal lens 14 can be adjusted at high speed.

The tracking direction is adjusted by the entire bobbin 2 moving in the tracking direction due to the interaction between the magnetic field generated when the tracking coil 6 provided on the side surface of the bobbin 2 is energized and the magnetic field generated by the permanent magnet 7. .

According to the above configuration, the variable focus lens unit 13 is constructed by combining the variable focus lens 14 and the fixed objective lens 15, so that the variable focus lens unit 14
Is provided, the thickness of the bobbin 2 and, consequently, the condensing optical unit 11 is reduced, so that the variable focal length lens unit 14 has a shorter focal length than a configuration using only the variable focal length lens 14. Can be planned.

The piezoelectric element 8 is connected to the glass diaphragm 2.
Since the variable focus lens portion 14 is formed by the film forming method, the varifocal lens portion 14 can be reduced in thickness and can be mass-produced without variation in product quality.

(Second Embodiment) When the optical information storage surface of the optical disk 21 is a two-layer DVD, the variable focus lens is adjusted by adjusting the drive voltage for the piezoelectric element 8 as shown in FIGS. This can be dealt with by switching the focal position of the unit 13 between the upper optical information storage surface and the lower optical information storage surface. Further, even if the optical information storage surface of the optical disk 21 has three or more layers, it is possible to cope with it.

(Third Embodiment) When the wavelength of the light from the light source used in the optical pickup device is not visible light but infrared light,
Since light can be transmitted and refracted even with silicon, it is not necessary to bond the glass diaphragm 25 and the annular silicon spacer 24 as described above, and a translucent elastic member having a thick outer peripheral portion as shown in FIG. A structure in which the piezoelectric element 26 is formed on a silicon diaphragm 31 as a film may be bonded to each other by means such as adhesion or the like, and the silicone oil 28 may be sealed therein.

According to such a configuration, Japanese Patent Laid-Open No.
Batch processing using a semiconductor process described in JP-A No. 2185 or JP-A-6-300899 enables low-cost and mass production. In this case, as shown in FIG.
5 is preferable. This is because the refractive index of silicon, 3.4, is significantly higher than the refractive index of silicone oil, 1.5. That is, when the fixed objective lens 15 is disposed between the light source and the varifocal lens 14, light refracted by the fixed objective lens 15 is incident on the interface between the silicon diaphragm 31 and the silicone oil 28 at an incident angle equal to or greater than the critical angle. This is because there is a possibility that the light may be incident, and in such a case, it is feared that the light is totally reflected and does not enter the silicone oil 28.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. As the varifocal lens 14, the translucent elastic film 9 may be provided only on one side.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a variable focus lens unit according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a condensing optical unit.

FIG. 3 is a schematic diagram showing the entire configuration.

FIG. 4 is a schematic view showing an initial shape of a piezoelectric element and a glass diaphragm.

FIG. 5 is a schematic diagram showing deformed shapes of a piezoelectric element and a glass diaphragm.

FIG. 6 is a schematic view showing focusing by a variable focus lens.

FIG. 7 is a diagram corresponding to FIG. 6, showing a state following the movement of the optical disk;

FIG. 8 is a schematic diagram showing focusing by a variable focus lens on an optical information storage surface below a two-layer optical disc in a second embodiment of the present invention.

FIG. 9 is a view corresponding to FIG. 8, showing focusing on the upper optical information storage surface.

FIG. 10 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 11 is a diagram corresponding to FIG. 2 showing a conventional example.

FIG. 12 is a perspective view showing a varifocal lens in section.

[Explanation of symbols]

2 is a bobbin, 6 is a tracking coil, 7 is a permanent magnet,
11, a condensing optical unit, 12 a peripheral optical unit, 13 a variable focus lens unit, 14 a variable focus lens, 14 a fixed objective lens, 17 a semiconductor laser (light source), 21 an optical disk (optical information storage medium), 25 is a glass diaphragm (light transmitting elastic film), 26 is a piezoelectric element (driving means), 27 is silicone oil (light transmitting material), 31 is a silicon diaphragm (light transmitting elastic film), and 32 is a variable focus lens. is there.

Claims (5)

[Claims] An optical pickup device for reading pit information formed on an optical information storage surface of an optical information storage medium by irradiating light from a light source to the optical information storage medium, wherein the optical information storage medium is arranged on an optical axis of the light source. A variable light-collecting means in which a deformable light-transmitting substance is sealed in an internal space closed by a pair of light-transmitting films, at least one of which is made of a light-transmitting elastic film; A driving means for changing the curvature of the translucent elastic film provided; and a fixed objective lens arranged on an optical axis of the light source, wherein the light from the light source is variably collected by the variable condensing means and the fixed light source. An optical pickup device, wherein the light is focused on an optical information storage surface of the optical information storage medium via an objective lens. 2. The optical pickup device according to claim 1, wherein said driving means is an annular piezoelectric element provided integrally with said translucent elastic film. 3. The optical pickup device according to claim 1, wherein the light-transmitting elastic film is formed to have a film thickness distribution for reducing optical aberration. 4. The optical pickup device according to claim 1, wherein the light source emits infrared light, and the light-transmitting elastic film is a silicon diaphragm. 5. The optical pickup device according to claim 4, wherein said variable focus lens is disposed between said light source and said fixed objective lens.