JP2590306B2 - Information reading device - Google Patents

Description

The present invention relates to optical information for recording and reproducing information on optical recording media such as optical disks such as compact disks and video disks and magneto-optical disks. It relates to improvement of a reading device.

[Conventional technology]

Japanese Utility Model Laid-Open No. 58-62486 (prior art A) describes an optical information reading apparatus. In this apparatus, an optical block (reference numeral 11) serving as a base is in a tracking direction (A, FIG.
(B direction). This optical block has a rectangular parallelepiped box shape surrounded by six plate members. On the other hand, the tooth arrangement direction is along the direction traversing the information track and the tooth width (the rack 8a in the direction perpendicular to the medium surface of the disk 13 in the prior art A Figs. 2 and 4;
A U-shaped rack plate member (reference numeral 10) formed with a rack whose direction (direction of 8b) is perpendicular to the medium surface of the disk 13 as a recording medium is fixed to the side surface of the optical block. I have. This rack plate member is a motor (reference numeral 1).
The driving force for moving the optical block is transmitted by engagement with the pinions (symbols 6a and 6b) that are rotated.

[Problems to be solved by the invention]

 However, the above device has the following disadvantages.

There is no clear description in the above-mentioned prior art A about the actuator for moving the lens in two directions. If the actuator is to be installed in the apparatus disclosed in the prior art A, the name of the optical block and the light beam entrance / exit portion (reference numeral 12, passing through the light beam) are provided on the surface of the optical block facing the medium surface of the recording medium (reference numeral 13). Considering that a simple opening is simply formed, an actuator is assumed to be installed inside the optical block. However, the optical block has four side portions (a side portion to which the rack plate member 10 is fixed and a side portion having the height dimension clearly larger than the size of the actuator in the direction perpendicular to the medium surface of the recording medium). 2 is formed with through-holes formed in the side portions and the guides 14 and 15 opposed to each other.
(If the actuator is installed in an optical block having such a configuration, the optical block is viewed in one direction perpendicular to the direction perpendicular to the medium surface.) At this time, the appearance of the actuator is invisible.) Installing an actuator inside such a box-shaped container has a disadvantage in that the operation of installing the actuator becomes complicated.

In addition, since the optical block and the rack plate member are composed of separate and independent members, it is necessary to combine the two with high precision in order to obtain predetermined dimensions, and as a result, the assembly of the apparatus becomes complicated. However, there are disadvantages that the number of parts is increased and it is not suitable for mass production.

On the other hand, Japanese Utility Model Laid-Open No. 58-43675 (Prior Art B) describes a configuration in which a rack (reference numeral 13) is formed integrally with a cartridge storage portion (reference numeral 15) as a base. The detection cartridge (reference numeral 9) corresponding to the actuator of the prior art B has a configuration in which the appearance of the detection cartridge is not visible when the cartridge storage portion is viewed in one direction perpendicular to the direction perpendicular to the medium surface. It has become. The installation of the actuator inside such a storage container has a drawback that the installation work of the actuator becomes complicated as in the device disclosed in the above-mentioned prior art A.

An object of the present invention is to provide an optical head that has solved the above-mentioned disadvantages.

[Means for solving the problem]

The information reading apparatus according to the present invention is configured to irradiate a light beam from a light source as convergent light by a lens onto a medium surface of a disk-shaped recording medium on which information is recorded in a track shape, and to read the information by reflected light, A lens arranged in the base so as to be movable in both a first direction perpendicular to the surface and a second direction parallel to the medium surface and across the information track, and a rack and a motor arranged on the base; The base is brought into contact with the second
In an information reading device configured to move in the direction of, an actuator configured to move the lens in both of the first direction and the second direction (at least,
A mechanism that steps on a lens, a focusing coil, a tracking coil, and a magnetic field generating means. Lens and 2
If a cover that covers at least the type of coil and the magnetic generating means is arranged, the cover is also included in the actuator) on the surface of the base opposite to the medium surface,
The base is formed by integral molding of a plastic material and the arrangement of teeth ("the arrangement of teeth" refers to a form in which a plurality of teeth are arranged, in other words, a form in which a plurality of teeth form a row). The direction is along the second direction (in other words, "along" means in a direction substantially parallel to the second direction) and the tooth width (tooth direction perpendicular to the above "teeth arrangement direction"). The rack whose dimension (dimension) direction is along the first direction is integrally formed with the base ("integrally formed" means a rack plate member 10 as shown in FIG. Excluding a configuration that connects the two members of the optical block 11 and the optical block 11 and forming a rack on the base itself)
By arranging the actuator so as to protrude from the surface toward the disc-shaped recording medium, the actuator can be arranged in one direction perpendicular to the first direction (one of the directions perpendicular to the first direction). Looking toward the base,
Almost appearance of the actuator (if the actuator has a cover, the cover corresponds to the appearance)
(In order to eliminate the form in which the actuator is incorporated in a box-shaped storage container having a depth dimension larger than the height dimension of the actuator as in the prior arts A and B). It is characterized by having comprised.

〔Example〕

FIG. 3 shows a configuration of an example of an optical head developed up to the present invention, and FIG. 3A is a diagram showing an arrangement of a laser diode, a photodiode, and an optical system arranged therein; FIG. 3B is a perspective view showing the configuration of the entire optical head.

As shown in FIG. 3A, a light beam emitted from a laser diode 1 constituting a light source is focused by a collimator lens 2 into a parallel beam, and is incident on a polarizing prism 3 having a polarizing film 3a. The incident light beam is reflected by the polarizing film 3a, passes through the quarter-wave plate 4, enters the objective lens 6 displaced by the actuator 5 in the optical axis direction and in the tracking direction orthogonal thereto, and forms a spot on the recording medium 7 as a spot. Irradiated. In this example, it is assumed that the information track recorded on the recording medium 7 is reproduced. The reflected light beam from the recording medium 7 modulated by the information on the information track is condensed by the objective lens 6, passes through the quarter-wave plate 4, and enters the polarizing prism 3 again. Since this light beam passes through the quarter-wave plate 4 twice, the polarization plane is rotated by 90 °, transmits through the polarization film 3a, and the reflection plane 8a is set at a substantially critical angle with respect to the optical axis of the incident light. The detected light enters the detection prism 8. The light beam reflected by the reflecting surface 8a is made incident on a photodiode 9 constituting a light receiving element having a light receiving area divided into four. Although the internal structure of the actuator 5 is not shown in FIG. 3A for clarity, the objective lens 6 is supported by a leaf spring so as to be displaceable in its optical axis direction and in a direction orthogonal thereto. The objective lens 6 can be displaced in the optical axis direction and the tracking direction by supplying a current corresponding to the focusing error and the tracking error to the coil and the tracking coil. The detailed configuration of such an actuator is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-94311. Further, a focusing error and tracking error detecting mechanism including a detecting prism 8 whose reflecting surface 8a is set to a substantially critical angle and a light receiving element 9 divided into four parts is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 57-66533. .

In the above-described optical head, the light source 1 composed of a laser diode, the optical systems 2, 3, and 4 for guiding the light beam emitted from the light source to the objective lens 6, and the objective lens in the optical axis direction and a direction substantially orthogonal thereto. An actuator 5 that performs focusing control and tracking control by displacing, an optical head body that supports a light receiving element 9 including a photodiode that receives a light beam reflected from a recording medium 7 through an objective lens 6 and a detection prism 8, and the like. Reference numeral 10 is formed of a molded body of a metal such as aluminum or zinc.
A lid 11 is fixed to the lower portion of the optical head body 10 with screws 12 to close the opening.

Further, in order to drive the optical head in a direction orthogonal to the information tracks recorded on the recording medium 7, a bearing block 14 is attached to the optical head body 10 with screws 13, and a bearing 15 is fitted to the bearing block. The guide shaft 16 is slidably inserted through the guide shaft 16. Also, on the upper surface of the bearing block 14,
A rack plate 17 having a rack 17a formed on the side surface is fixed, a pinion 18 is engaged with the rack 17a, and the pinion is rotated by a motor 19.
The optical head body 10 is integrally formed with a guide portion 10 a, which is mounted on a support member 20. By moving the support member 20 in the vertical direction as shown by the arrow A, the entire optical head is rotated around the guide shaft 16 as shown by the arrow a, and the optical axis of the objective lens 6 is moved in the track direction. Can be adjusted.

In the above-described optical head, the surface of the optical head main body 10 is formed in order to obtain a desired positional relationship between various components mounted on the optical head main body 10 formed of a molded body of aluminum or zinc metal. Accuracy and dimensional accuracy must be achieved,
For this reason, there is a disadvantage that cutting is required after molding, the number of steps increases, and the cost increases.

In addition, the optical head body 10 constituted by a metal molded body
The weight of the optical head is, for example, as heavy as about 30 g, and the weight of the entire optical head is about 60 g.In accordance with this, the inertia increases, and the optical head is moved in a direction perpendicular to the track of the recording medium,
That is, a power source having a large output is required as a power source for driving the disk-shaped recording medium in the radial direction, and high-speed feeding becomes difficult, and there is a disadvantage that an access time until the optical head is moved to a desired track position is lengthened. .

Usually, the actuator 5 for driving the objective lens 6 is provided with a coil, and a current is supplied to the coil to drive the objective lens in the optical axis direction or the tracking direction. In the case of 10, since the heat conductivity is large, the heat generated in the coil is transmitted to the laser diode 1 of the light source via the optical head main body, so that the life of the laser diode is shortened. It is desirable that the temperature rise of the laser diode 1 be suppressed to about 3 ° C. or less. In order to satisfy this requirement, the magnitude of the drive current flowing through the coil of the actuator 5 is limited, which is one of the restrictions on the optical head design. Was.

Further, in the optical head shown in FIG. 3, the bearing block 14 and the rack plate 17 are provided separately from the optical head body 10.
Is formed, the number of parts is increased, assembly adjustment is troublesome, and the manufacturing cost is increased. Especially when the optical head body 10 and the bearing block 14 are separate,
Guide shaft as reference for position as shown in FIG. 3A
There is a disadvantage that the dimensional error of the distance H between the center line of 16 and the optical axis of the objective lens 6 increases. That is, the above distance H
Is the distance α between the center line of the guide shaft 16 and the mounting reference plane of the bearing block 14, the distance β between this mounting reference plane and the mounting reference plane of the actuator 5, and the distance β between this mounting reference plane and the objective lens 6. The distance H is equal to the sum of the distance γ and the optical axis, but since there is an error in each of these distances α, β and γ, the distance H is the sum of these errors and has the disadvantage of being extremely large. .

FIG. 1 shows an optical head obtained by improving the optical head shown in FIG. 3, and also shows an example of the configuration of an optical head developed up to the present invention similarly to the optical head shown in FIG. . FIG. 1A is a sectional view, and FIG. 1B is a plan view. In this embodiment, the optical head main body and the bearing portion are formed of an integrally molded plastic body. The internal structure of the optical head is the same as that of the optical head shown in FIG.
, And reflected by the polarizing film 23a of the polarizing prism 23.
After passing through a / 4 wavelength plate 24, the light is made incident on an objective lens 26 which is displaced by an actuator 25 in a focusing direction parallel to the optical axis and a tracking direction orthogonal thereto. The objective lens 26 focuses the laser beam and focuses it on the information track of the recording medium 27 as a spot. In this example, the recording medium has a disk shape, and the information tracks have a spiral shape. The light reflected by the recording medium 27 is collected by the objective lens 26,
The light passes through the polarizing prism 23 through the four-wavelength plate 24, is reflected by the reflecting surface 28a set at a substantially critical angle of the detection prism 28,
The light enters the photodiode 29.

This optical head supports a laser diode 21, a collimator lens 22, a polarizing prism 23, an optical system integrally configured with a quarter-wave plate 24 and a detection prism 28, an actuator 25, and a photodiode 29. The optical head main body 30 and the bearing portions 30a and 30b to be formed are constituted by an integrally molded plastic body. That is, the bearing portions 30a, 30b
The optical head body 30 having PPS (poly phenyl sulfide), PEEK (poly ether ether ketone), PES (poly ether sulfone), PEI (poly ether imide), PC (polycarbonate) And a plastic such as an epoxy resin or a material formed by mixing a fiber such as a carbon fiber or a glass fiber with these materials to increase the strength. Such a molded body of plastic material can be molded very accurately as long as the dimensional accuracy of the mold is ensured. Therefore, after molding, as in the case of the optical head body composed of the metallic molded body in FIG. In addition, it is not necessary to perform a cutting process to obtain dimensional accuracy. Therefore, the cutting step can be omitted from the manufacturing process, and the manufacturing cost can be reduced. further,
Since the plastic material is about 1/2 to 1/3 lighter than metal, the weight of the optical head can be reduced. Therefore, the power source for driving the optical head in the direction perpendicular to the information tracks, that is, in the radial direction of the disk-shaped recording medium, requires only a low output, and can move at high speed, thereby shortening the access time. Can be. Furthermore, since the plastic material has a lower thermal conductivity than metal, the heat generated by the coil of the actuator 25 is less likely to reach the laser diode 21 through the optical head body 30 and effectively suppress the temperature rise of the laser diode. And the life of the laser diode can be extended.

In addition, since the bearings 30a and 30b are formed integrally with the optical head main body 30, the number of parts is reduced, assembly and adjustment are simplified, and manufacturing costs can be reduced. Further, the error of the distance H between the reference line of the bearing portion, that is, the center line of the guide shaft and the optical axis of the objective lens is reduced.

That is, the distance H is a distance δ between the center line of the guide shaft 32 and the mounting reference plane of the actuator 25,
The error of the distance H is the sum of the respective errors of the distances δ and γ, which is the sum of the distance γ between the mounting reference plane and the optical axis of the objective lens 26. H is significantly smaller than the error of H, and the dimensional accuracy is improved.

However, the optical head of FIG.
And the rack unit 35 are formed by combining separate and independent members. Therefore, in such a configuration, the number of components increases, and a highly accurate joining operation between the optical head main body 30 and the rack unit 35 is required. As a result, there is a disadvantage that the apparatus becomes expensive and unsuitable for mass production.

FIG. 2 shows an embodiment of the present invention in which the optical head of FIG. 1 is improved. 2A is a schematic sectional view, FIG. 2B is a plan view, and FIG. 2C is a front view. In this example, the bearing part 40a, the rack part 40b, and the guide part 40c are integrally formed with the optical head body 40 with a plastic molded body. That is, a hole is formed in the bearing portion 40a, and
And the guide shaft 32 is slidably passed through the shaft.
Also, a rack is integrally formed on the side surface of the rack portion 40b,
This is engaged with a pinion 36, and this pinion is
Connect to The guide portion 40c has the same width as the rack portion 40b, and the guide portion 40c is supported from above and below by supporting members 38 and 39.
To be sandwiched between. Other configurations are almost the same as those of the embodiment shown in FIG. 1, and therefore, the same portions are denoted by the same reference numerals and detailed description thereof will be omitted.

As described above, when the bearing portion 40a is integrally formed of plastic with the optical head main body 40, a dimensional error between the bearing and the optical head main body is eliminated, so that the center line of the guide shaft 32 supported by the bearing 31 and the objective lens Distance H between 26
Is only the sum of the dimensional error of the actuator 25 with respect to the optical head body 40 and the dimensional error of the objective lens 26 with respect to the actuator 25, but since these errors are small, the dimensional error of the entire optical head is extremely small. be able to.

The present invention is not limited only to the above-described embodiment, and various modifications and changes are possible. For example, there are various types of light sources, optical systems and light receiving elements, and there are various types of actuators. For example, a light source which emits three light beams can be used as the light source, and a light receiving element having a light receiving area divided into six can be used as the light receiving element. In the above-described example, the focusing error information is detected using the detection prism having the reflection surface set at the critical angle. However, the focusing error is detected by, for example, an astigmatism method using a cylindrical lens. You can also.

〔The invention's effect〕

The information reading apparatus according to the present invention is configured to irradiate a light beam from a light source as convergent light by a lens onto a medium surface of a disk-shaped recording medium on which information is recorded in a track shape, and to read the information by reflected light, A first direction perpendicular to the medium surface and a second direction parallel to the medium surface and across the information track (for example, the extending direction of the guide shaft 32 in FIG. 2C;
In other words, the lens is arranged on a base (for example, the optical head body 40 of the embodiment) so as to be movable in both directions of the guide shaft 32 (axial direction of the guide shaft 32), and a rack (for example, the embodiment is arranged on the base). Of the racks 17a, 35a and the rack portion 40b) and a gear (for example, the pinion 36 of the above-described embodiment) driven by the motor 37 (for example, the pinion 36 of the above-described embodiment). 2. An information reading apparatus which moves in two directions, wherein the lens moves in both directions of the first direction and the second direction (for example, the actuator 25 of the embodiment, a more detailed configuration As described above, for example, as shown in FIG. 5 of JP-A-56-94311, the surface of the base opposed to the medium surface (for example, FIGS. 2A and 2B)
The upper surface of the optical head pair 40, or the upper surface of the optical head body 10 on which the actuator 5 of FIG. 3B is mounted, in other words, the surface in contact with the leading end of each of the lead wires 40 and 10. ), The base is formed by integral molding of a plastic material, and a row of teeth (for example, a row of many teeth formed on the rack portion 40b in the axial direction of the shaft 32 in FIG. 2C). ) Direction is along the second direction and the tooth width (e.g., corresponding to the vertical dimension of the rack portion 40b in FIGS. 2A and 2B) is the first direction.
The rack is formed integrally with the base, and the actuator is disposed so as to protrude from the surface toward the disc-shaped recording medium, so as to be perpendicular to the first direction. The present invention is characterized in that the base is configured such that the external appearance of the actuator is substantially visible when the base is viewed in one direction, and thus the present invention has the following effects.

An actuator adapted to move the lens in both the first direction and the second direction is provided on a surface of the base opposite to the medium surface, and the base is viewed in one direction perpendicular to the first direction. When the base is configured so that the external appearance of the actuator can be viewed substantially, the work of assembling the actuator into the base becomes extremely simple, and as a result, the optical information reading device of the present invention is suitable for mass production. There is an advantage that will be.

Also, since the base is formed by integral molding of a plastic material, the device of the present invention is lightweight,
As a result, there is an advantage that high-speed and high-precision information reading can be expected. Moreover, since the rack is integrally formed on the base made of the plastic material, high-precision dimensional accuracy between the members can be obtained instantaneously, and the gear drive is smooth due to the characteristic of the material surface peculiar to the plastic material. As a result, the optical head of the present invention has an advantage that it can be read out with a very simple configuration at low cost, suitable for mass production, and with high accuracy.

[Brief description of the drawings]

1A and 1B are diagrams showing the configuration of an optical head developed up to the present invention, FIGS. 2A to 2C are diagrams showing the configuration of an embodiment of the present invention, and FIGS. It is sectional drawing and a perspective view which show the structure of the optical head developed up to the invention. 10, 30, 40… Optical head body 30a, 30b, 40a… Bearing part 35, 40b,… Rack part 40c… Guide part 17a, 35a… Rack 36… Pinion 21… Laser diode 22… Collimator lens 23 Polarizing prism 24 Quarter wave plate 25 Actuator 26 Objective lens 27 Recording medium 28 Detection prism 29 Photodiode

Claims (1)

(57) [Claims] A light beam from a light source is irradiated as convergent light by a lens onto a medium surface of a disk-shaped recording medium on which information is recorded in a track shape, and when the information is read by the reflected light, the light beam is perpendicular to the medium surface. A first direction and a second direction that is parallel to the medium surface and crosses the information track.
In an information reading apparatus, the base is moved in the second direction by engagement of a rack arranged on the base and a gear that is driven to rotate by a motor, wherein the lens is moved in the first direction and the second direction. An actuator adapted to move in both of the two directions is installed on a surface of the base opposed to the medium surface, and the base is integrally formed of a plastic material, and the teeth are arranged in the second direction. And the width direction of the teeth is the first direction.
The rack is formed integrally with the base, and the actuator is disposed so as to protrude from the surface toward the disc-shaped recording medium, so as to be perpendicular to the first direction. An information reading device, wherein the base is configured so that the external appearance of the actuator can be viewed substantially when the base is viewed in one direction.