JPS62279529A - Lens holder for optical head - Google Patents

Abstract

PURPOSE:To prevent two lenses from having optical axes shifted from each other and being inclined by fitting the optical lens, which determines the focus position of return light beams, and the optical lens, which gives the astigmatism to the return light beams, into the holder in two directions orthogonal to each other. CONSTITUTION:A lens holder 20 is pierced by a center hole 200, through which the return light beams from a beam splitter passes, in the axial direction. A plano-concave lens 10 which determines the focus position of the return light beams are fitted to an attaching recessed part 21 in one end of the holder 20 in the axial direction. A cylindrical lens 11 which gives the astigmatism is fitted to an attaching groove 22 on the inside of the recessed part 21 in the direction orthogonal to the axial direction. Lenses 10 and 11 are fixed by adhesion with respective plane sides matched and are adjusted. Thus, optical axis deviation and inclination of lenses 10 an 11 are eliminated, and the deviation of the focus position from a photodetector is reduced.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention is directed to DAD (Digital Audio Disk)
- Relates to an optical head for optically reproducing information or recording and reproducing information applied to optical discs such as DRAW (recordable once) discs.

Conventional technology Optical heads applied to DAI) and the like have conventionally been, for example, 6
The optical system is configured as shown in the figure.

A semiconductor laser 2 is disposed at one end of the opto base 1 so as to emit laser light parallel to the surface of the base 1 toward the other end. On the optical base 1 along the optical axis direction of the laser light emitted from the semiconductor laser 2, a collimator lens 3. A beam deflector, a 4-degree mirror, and a 45-degree mirror 5 are arranged in this order. On the other hand, a two-axis actuator 6 is disposed at the other end of the optical base 1 to drive the objective lens in orthogonal two-dimensional directions. An objective lens 7 is supported on the two-axis actuator 6 so as to be located directly above the 45-degree mirror 5. The laser beam emitted from the semiconductor laser 2 is converted into a parallel beam through a collimator lens 3, passes through a beam splitter 4, is reflected through a 45-degree mirror 5, and is then focused by an objective lens 7 and directed onto a disk medium. is irradiated.

The return light from the disk medium is polarized by 90 degrees through the beam splitter 4 and guided to the light receiving element 8 disposed at the side end of the optical base 1. The optical axis from the beam splitter 4 to the light receiving element 8 includes a convex lens 9 for condensing a parallel beam, a plano-concave lens 10 for adjusting the focal position of the laser beam focused by the convex lens 9, and A cylindrical lens 11 is provided that causes astigmatism in the laser beam.

The plano-concave lens 10 and the cylindrical lens 11 are assembled in a lens holder 12, and are mounted on the opto base 1 via the lens holder 12 so as to be adjustable in the optical axis direction and in the direction of rotation around the optical axis. Preferably, both lenses 10.11 are in close proximity or in contact. However, both these lenses10. The optical distance between il and the beam splitter 4 can only be about several millimeters due to constraints on the configuration of the optical system.

Conventionally, a lens holder 12 for incorporating the plano-concave lens 10 and the cylindrical lens 11 as described above has been configured as shown in FIG. 7, for example.

The lens holder 12 has a disk body 12a that is attached to the plano-concave lens 10 and the cylindrical lens 11 with their flat sides aligned, and a disk body 12a that is attached to the opto base 1 with a stable structure in the longitudinal direction to ensure stability. It is constructed by bonding together a certain cylindrical body 12b. Disc body 1
A hole 12c for mounting the plano-concave lens 10 is formed in the hole 2a. A mounting groove 12c for the cylindrical lens 11 is cut out on the opposite surface. Disc body 12
In a, after the plano-concave lens 10 and the cylindrical lens 11 are assembled with their respective lower surfaces aligned with the mounting hole 12c and the mounting groove 12d, they are aligned and adhesively fixed to one end side of the cylindrical body 12b.

A cylindrical lens 11 is provided at one end of the cylindrical body 12b.
A recess 12 for receiving a portion protruding from the disc body 12a.
e is formed.

Problems to be Solved by the Invention The plano-concave lenses 10 and 7 lindrical lenses 11 assembled to the lens holder 12 in the manner described above are installed on the opto base 1 via this holder 12, and are then installed on the opto base 1 during subsequent setting. , yji adjustment is performed in the optical axis direction and around this forward axis via the holder. However, since the conventional lens holder is constructed by combining two members as described above, each member and the lens rP1
Even if the body is processed with high precision, the lens can be made into a disc body 12a.
Errors occur when assembling this into the cylindrical body 12b, errors when assembling it to the opto base, etc., and due to the accumulation of these errors, the central axis of the lens itself and the optical axis of the laser beam There are also problems such as the lens being tilted with respect to the plane orthogonal to the optical axis, and the focal length relative to the light receiving element being misaligned.

In this way, if the optical axis of the lens shifts, or the lens tilts in the optical axis direction or in a direction perpendicular to this,
This causes an optical axis shift and a shift in the focal point position relative to the light receiving element 8, making it impossible to perform stable signal reproduction and error signal detection.

The present invention has been made in view of the above points, and an object of the present invention is to provide a structure in which optical axis misalignment is less likely to occur, and to improve the stability of reproduced signals.

Amnion to Solve the Problems The present invention irradiates a disk medium with laser light emitted from a semiconductor laser, and guides the return light from the disk medium to a light receiving element, thereby optically reproducing or recording/reproducing information. An optical lens that determines the focal position of the returned light guided to the light receiving element and an optical lens that causes astigmatism in the returned light are fitted into each other from two orthogonal directions. to optics consisting of cylindrical members.

The lens holder has the following features:

According to the present invention, since the 2N lenses of different shapes are fitted into the lens holder made of a single cylindrical member from two directions orthogonal to each other, when assembled into the optical head body, there is no problem of accumulated errors as in the conventional case. Without causing large assembly errors, there is no optical axis misalignment between the two lenses, no lens tilt with respect to the optical axis, no deviation in focal position, etc., and signal reproduction is stabilized, while at the same time detecting focus and tracking error signals. is also stable.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the following description, the details of the optical head will be omitted, and the lens holder, which is the main part, will be mainly described.

FIG. 1 is a perspective view showing a lens holder of an optical head according to the present invention, FIG. 2 is a side sectional view thereof, and FIG. 3 is a front view thereof.
FIGS. 4 and 5 are a front view and a plan view showing how the lens holder according to the present invention is assembled to the optical head.

The lens holder 20 is formed of a single cylindrical member. A center hole 200 through which the return light from the beam splitter 4 passes is formed through the lens holder 20 in the axial direction. The length of the lens holder 20 is approximately twice as large as its diameter, so that stability can be obtained when the lens holder 20 is installed on the optical base 1.

A mounting recess 21 for mounting the plano-concave lens 10 in the axial direction is bored in one end surface of the lens holder 20. The mounting recess 21 is formed in a cylindrical shape that is concentric with the center hole 200 and has approximately the same diameter as the plano-concave lens 10 . The mounting recess 21 has a depth that is approximately the same as the thickness of the plano-concave lens 10. The cylindrical lens 11 is attached to the lens holder 2 inwardly from the outer periphery of one end of the lens holder 20.
A mounting groove 22 is formed for mounting from a direction perpendicular to the direction of the central axis of 0. The mounting groove 22 is formed at one end of the lens holder 20 in the shape of a substantially rectangular rectangular parallelepiped square hole having a depth that allows the cylindrical lens 11 to be inserted, and is orthogonal to the central axis of the lens holder 20. The attachment communicates with one end side of the recess 21 and the center hole 200. The mounting groove 22 is formed into a step deeper than the edge of the center hole 200, so that the outer shape of the mounting recess 21 is substantially inscribed in the square hole inside the holder.

The lens holder 20 is attached by an annular groove 23 extending in the circumferential direction on the outer peripheral surface opposite to the recess 21 and the attachment groove 22. Moreover, a groove 24 is formed linearly on the outer circumferential surface along the holder axial direction. a23 and a24 are formed so as to be orthogonal to each other in the circumferential direction and the axial direction of the circumferential surface of the lens holder 20. The groove 24 along the axial direction has a diameter of 4 with respect to the mounting direction of the cylindrical lens 11 with respect to the mounting groove 22.
It is formed at a 5 degree tilt.

The lens holder 20 configured as described above is integrally molded by resin molding. Therefore, manufacturing is easy. This lens holder 20 includes a plano-concave lens 1.
0 and the cylindrical lens 11 are fitted into the mounting recess 21 and the mounting groove 22 from two mutually orthogonal directions, axial and radial.

The plano-concave lens 10 and the cylindrical lens 11 are fitted into the mounting recess 21 and the mounting groove 22 of the lens holder 20, respectively, with their flat sides aligned.
2 are adhesively fixed to the inner surfaces of the respective parts. Thereby, the lens centers of the two lenses 10.11 and the central axis of the lens holder 20 are aligned. The mounting recess 21 and the mounting groove 22 are formed to be continuous with each other so as to have such a relationship.

At this time, since the mounting recess 21 and the mounting groove 22 are continuous with each other, the plano-concave lens 10 and the cylindrical lens come into contact with each other on their plane sides. Furthermore, even if the diameter of the plano-concave lens 10 and the height of the cylindrical lens 11 are the same, the cylindrical lens has a mounting recess w on the mounting groove 22 side.
The holder is fixed at the four corners of the J21 periphery, so once it is installed, it will not fall off accidentally.

As described above, the plano-concave lens 10 and the cylindrical lens 1
The lens holder 20 to which 1 is assembled is shown in FIGS.
As shown in the figure, an upright wall 100 is formed on the optical base 1 between the condensing convex lens 9 and the light receiving element 8 that constitute the return destination optical system. The peripheral surface is positioned and installed at the corner where the base surface and the wall surface are in contact with each other. The lens holder 20 has one end rising from the wall 1.
It is pressed and held at the corner of the opto base 1 by a leaf spring 101 screwed to the opto base 1. Lens holder 2
0 is movable and rotatable in the axial direction along the return light optical axis and in the circumferential direction orthogonal to this.

Openings are formed in the optical base 1 and the rising wall 101 at positions corresponding to the grooves 23 and 24 formed in the lens holder 20, and the adjustment pins 25 and 26 of the lens holder 20 are inserted into the openings so that the center axis It is fitted so that it can rotate around it. A lens holder 20 is attached to one end of the adjustment pin 25° 26.
Eccentric pins 251 and 261 protruding toward the peripheral surface are formed with their central axes eccentric.

Eccentric pin 251 of adjustment pin 25 provided on opto base 1
is fitted into a groove 24 formed in the axial direction of the lens holder 20 so as to be eccentrically rotatable. The eccentric pin 261 of the adjustment pin 26 provided on the rising wall 100 is fitted into a groove 23 formed in the circumferential direction of the lens holder 20 so as to be eccentrically rotatable.

When attaching the lens holder 20 onto the optical base 1, first, the lens holder 20 is roughly aligned and installed so that its central axis coincides with the optical axis of the return light from the beam splitter 4 to the light receiving element 8. At that time, cylindrical lens 1
1 is arranged with its central axis inclined at 45 degrees around the optical axis with respect to the direction perpendicular to the base surface.

After the lens holder 20 is installed on the opto base 1 as described above, the return light is received through the beam splitter 4 by adjusting the inclination of the cylindrical lens 11 around the optical axis and finely moving the plano-concave lens 10 and the cylindrical lens 11. The imaging position for the element 8 is adjusted, that is, the focal position is adjusted. The adjustment is performed using an adjustment jig 30 as shown in FIGS. 4 and 5.

First, as shown in FIG. 4, when the adjustment pin 25 fitted into the axial groove 24 of the lens holder 20 is rotated by a predetermined angle around the axis using the adjustment jig 30, the eccentric pin 25
The lens holder 20 is rotated by a predetermined angle around the optical axis in accordance with the amount of eccentricity. As a result, the cylindrical lens 11 is rotated by a small amount around the optical axis, and the cylindrical lens 11 is tilted at an angle of 45 degrees around the tip axis! Adjustments will be made to

Next, as shown in FIG. 5, the adjustment pin 26 inserted into the groove 23 along the circumferential direction of the lens holder 20 is inserted into the adjustment jig
When the lens holder 20 is rotated by a predetermined amount using
Depending on the amount of eccentricity of the eccentric pin 261, the eccentric pin 261 is moved by a required amount in one or the other direction of the axis. Now, the plano-concave lens 0 and the cylindrical lens 11 are finely adjusted in the optical axis direction, resulting in beam splitting.

The focal position of the returning laser beam that has passed through the laser beam 4 is adjusted with respect to the light receiving element 8.

The above adjustments can be made by displaying the signal extracted from the light receiving element 8 on the screen of, for example, an Otsu 70 scope and viewing the signal waveform. That is, the adjustment is made so that the zero-crossing point of the signal waveform coincides with the 0 point.

As described above, the plano-concave lens 10 and the cylindrical lens 11 are finely adjusted via the lens holder 20, and the plano-concave lens 10. The focal position of the return laser beam from the beam splitter 4 passing through the cylindrical lens 11 with respect to the light receiving element 8 is adjusted.

It should be noted that the adjustment operation around the optical axis shown in FIG. 4 and the adjustment operation in the optical axis direction shown in FIG. It is best to do them in the same order as described.

As described above, the lens holder 20 of the embodiment structure is composed of a single cylindrical member, and the four mounting parts 2 formed therein are
Since the plano-concave lens 10 and the cylindrical lens 11 are fitted into the mounting groove 22 from two directions perpendicular to the axial direction and the circumferential direction, the above-mentioned optical The cumulative error when assembling into the head body can be extremely small, and the plano-concave lens 10
In addition, optical axis deviation at the center of the cylindrical lens, inclination of each lens, deviation of the focal position with respect to the light receiving element 8, etc. are almost eliminated. Therefore, beam splitter 4
The return laser beam from the disk that has passed through the lens is guided onto the light receiving surface of the light receiving element 8 through the plano-concave lens 10 and the cylindrical lens 11 in a correctly focused state.
Stable and reliable signal reproduction and error signal detection are possible.

Furthermore, since the lens holder 20 is formed as a single unit, the number of separate parts is reduced.

As described in detail, according to the present invention, there is no optical axis deviation or inclination of the two lenses with respect to the optical axis of the optical system when the lens holder is assembled to the optical head main body, and there is no optical axis deviation or inclination relative to the light receiving element. The deviation of the focal point position can be made extremely small.This allows for stable signal reproduction and error signal detection operations.Furthermore, fine adjustment via the lens holder of the two lenses can be made using the lens itself. Since there is no optical axis shift or tilt, this can be done easily.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a lens holder of an optical head according to the present invention, FIG. 2 is a side sectional view thereof, and FIG. 3 is a front view thereof.
FIG. 4 is a front view showing how the lens holder according to the present invention is attached to the optical head body, FIG. 5 is a plan view thereof, and FIG.
The figure is a perspective view showing an example of a general optical head to which the present invention is applied, and FIG. 7 is an exploded perspective view showing a conventional lens holder. 20... Lens holder, 10... Plano-concave lens, 11... Cylindrical lens, 21.22.
... Lens mounting recess, 23.24 ... Groove. Patent Applicant NEC Home Electronics Co., Ltd. Agent Patent Attorney Tadashi Saeki Occupation 1 Figure 2 Figure 3 Figure 4 Figure 5 6 Figure 6

Claims (2)

[Claims] (1) In an optical head that irradiates a disk medium with laser light emitted from a semiconductor laser and guides return light from the disk medium to a light receiving element to reproduce or record/reproduce optical information, the light receiving element An optical head lens consisting of a single cylindrical member into which an optical lens that determines the focal position of the returned light guided by the lens and an optical lens that causes astigmatism in the returned light are fitted from two orthogonal directions. holder. (2) The optical lens that determines the focal position is a plano-concave lens, and the optical lens that causes astigmatism is a cylindrical lens, and these two lenses are fitted with their flat sides facing each other. A lens holder for an optical head according to claim (1), which is constructed as follows.