JPH04329Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a lens positioning mechanism for fixing a lens used in an optical pickup or the like so that its optical axis is aligned with high precision.

[Technical background and conventional technology]

FIG. 8 is a layout diagram showing the optical system portion of an optical pickup installed in a compact disc player.

A laser beam emitted from a laser diode 1 passes through a beam splitter 2, is converted into parallel light by a collimating lens 3, and is further converted into a parallel beam by an objective lens 4.
The light is focused and irradiated onto the recording surface of the optical disk D. The reflected beam reflected from the recording surface of the optical disk D is reflected by the beam splitter 2 in the right angle direction, passes through the concave lens 5 and the cylindrical lens 6, and is detected by the photodiode 7. Digital information is recorded on the recording surface of the optical disk D by pits, and when the laser beam hits the pits, the light intensity modulation of the reflected beam is detected by the photodiode 7 and the information is read. It's summery.

In addition, as shown in FIG. 9, the photodiode 7
has four divided light receiving and detecting sections a, b, c, and d, and the cylindrical lens 6 is positioned so as to be rotated by 45 degrees with respect to the dividing line of the photodiode 7. When a focus error occurs in the laser beam irradiated onto the recording surface of the optical disk D, the receiving spot S of the laser beam detected by the photodiode 7 becomes vertically elongated due to the astigmatism of the cylindrical lens 6 as shown in FIG. takes shape. The shape of the light-receiving spot S is detected by comparing the amount of light received by the four-divided light-receiving detection sections a, b, c, and d of the photodiode 7. Based on the focus error signal detected in this way, the position of the objective lens 4 is controlled and servoed so that the focus of the laser beam on the recording surface of the optical disk D is always in a normal state.

[Problems with conventional technology]

As described above, the concave lens 5 and the cylindrical lens 6 are important elements for detecting the focus error of the laser beam with high accuracy. Therefore, both lenses 5 and 6 must be assembled to an optical member such as the photodiode 7 with their optical axes aligned with high precision. The need to align the optical axis with high precision in this way also applies to other lenses. In addition, in the case of the cylindrical lens 6,
The inclination angle of 45 degrees must be adjusted to the photodiode 7 with high accuracy.

Conventionally, it has been common to assemble the concave lens 5, the cylindrical lens 6, or other lenses by storing them in a holder. Moreover, in this holder, lenses such as the concave lens 5 and the cylindrical lens 6 must be accurately aligned and fixed with respect to the optical axis of other optical systems.
In the case of the cylindrical lens 6, it must be accurately positioned and fixed at a position rotated by 45 degrees with respect to the photodiode 7 within the holder.
Therefore, a holder for storing this type of lens must be machined with high precision, and the cylindrical lens 6 and the like must be attached to this holder with high precision. Conventionally, the lens is positioned using a holder, which not only complicates the structure of the lens support but also complicates the work for positioning the lens during the assembly process, resulting in an overall increase in manufacturing costs. is getting higher.

[Purpose of invention]

The present invention was developed by focusing on the above-mentioned conventional problems, and allows lenses installed in optical pickup optical systems to align the optical axis with high precision without using a holder to store the lenses. It is an object of the present invention to provide a lens positioning mechanism which allows the lens to be assembled in a fixed state, and which also facilitates the installation work.

[Summary of the idea]

In the present invention, a lens such as a glass press lens is formed with a tapered surface that is a part of a cone whose virtual apex is a point on the optical axis, and the lens support member has a tapered surface that is formed with a conical part whose virtual apex is a point on the optical axis. A positioning protrusion arranged in a circular shape is provided, and the lens and the lens support member are fixed with the tapered surface in contact with the positioning protrusion.

In the present invention, by simply bringing the tapered surface of the lens into contact with the positioning protrusion of the lens support member, the lens can be fixed while being aligned with the optical axis with high precision. Furthermore, since there is no need for a holder for storing the lens, the structure becomes simpler and a simple optical system can be constructed.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings of FIGS. 1 to 6.

1 to 4 show a first embodiment of the present invention. FIG. 1 shows a press lens 10 in a perspective view. This press lens 10 corresponds to the conventional example shown in FIG. 8, in which the concave lens 5 and the cylindrical lens 6 are integrated. FIG. 2 shows the press lens 10 in a supported state. FIG. 3 is an enlarged sectional view showing the positioning portion of the press lens 10, and FIG. 4 is a front view of the press lens 10 viewed from the cylindrical surface side.

The press lens 10 is formed by pressing a glass material. One side of the press lens 10 (the top side in Fig. 1 and the second side
The cylindrical surface 1 (right side of Fig. 3)
1 is formed. The back side of this (Fig. 2,
A concave spherical surface 12 is formed on the left surface in FIG. Further, a plane 13 perpendicular to the optical axis OO is formed around the cylindrical surface 11. Further, a tapered surface 14 is formed around the concave spherical surface 12. This tapered surface 14 is a portion of a cone whose virtual apex is a point A located on the optical axis OO. Furthermore, a pair of small holes 15 are provided in the plane 13 around the cylindrical surface 11.
As shown in detail in FIG. 4, the line X--X connecting the pair of small holes 15 and 15 is rotated by 45 degrees with respect to the axis Y--Y of the cylindrical surface 11.

In the molding process of this press lens 10, a cylindrical surface 11, a flat surface 13, and an uneven part corresponding to the small hole 15 are formed on one press mold used in the molding process, and a concave spherical surface 1 is formed on the other press mold.
2 and a convex portion corresponding to the tapered surface 14 are formed. By pressing the glass material from both sides with this pair of press dies, a cylindrical surface 11, a flat surface 13, a small hole 15 and a concave spherical surface 1 are formed.
2. The tapered surface 14 is formed with high precision. Also,
In the pressing process, the glass material escapes toward the side surface of the lens, and an extra wall portion 16 is formed.

In FIG. 2, reference numeral 20 designates a lens support member within the optical pickup. A support plate 21 is fixed to one surface of this lens support member 20, and a thin plate-shaped beam splitter 22 is fixed to this support plate 21. Further, the lens support member 20 has grooves 2 to avoid the beam splitter 22.
0a is formed. Beam splitter 22
is installed at an angle of 45 degrees with respect to the optical axis O-O. The beam splitter 22 is formed by depositing a semi-transparent film on a thin plate made of glass material. A lens positioning protrusion 23 is provided on the opposite surface of the lens support member 20.
is provided, and the press lens 10 is positioned and fixed by this lens positioning protrusion 23.

In Fig. 2, the beam is reflected by the beam splitter 22 in a direction perpendicular to the optical axis O-O (A).
The laser diodes face each other in this direction. Also,
A photodiode faces the (b) direction of the optical axis O-O. An objective lens is provided facing the optical disk in the (c) direction of the optical axis OO.

As shown in FIG. 3, an edge portion 23a is formed around the tip of the positioning protrusion 23. As shown in FIG. This edge portion 23a is located on a circle centered on the optical axis OO. In the embodiment shown in FIG. 3, the edge portion 23a is formed continuously around the entire circumference around the optical axis O-O, but the edge portion 23a has a shape in which a middle portion on the circumference is cut off. It may be hot.

Next, the positioning and fixing work of the press lens 10 will be explained.

A jig 25 shown in FIG. 3 is used to attach the press lens 10. A pair of small protrusions 25a are formed at the tip of this jig 25.

The small protrusion 25a of the jig 25 is fitted into the small hole 15 of the press lens 10. In this state, the press lens 10 is positioned by bringing the tapered surface 14 of the press lens 10 into contact with the edge portion 23a of the positioning protrusion 23. Further, an ultraviolet curing adhesive 26 is applied between the outer surface of the positioning protrusion and the press lens 10.

By bringing the tapered surface 14 into contact with the entire circumference of the edge portion 23a of the positioning protrusion 23,
The optical axis of the press lens 10 is the optical axis of the entire optical system O-
An exact match can be made for O. This point will be explained in detail.

For example, as shown in FIG. 7, when the edge portion 23a of the positioning protrusion 23 is brought into contact with the concave spherical surface 12 of the press lens 10, the entire circumference of the edge portion 23a and the concave spherical surface 12 are brought into contact. Even in this state, the press lens 10 moves at α along the concave spherical surface 12 with radius R.
This means that it can move in the −β direction. Therefore,
It is impossible to accurately align the optical axis of the press lens 10 with the optical axis of the optical system. In contrast, in the present invention, as shown in FIG.
With the entire circumference of the tapered surface 14 in contact with the tapered surface 14, point A, which is the virtual vertex of the tapered surface 14, is always aligned with the optical axis O-
It will be located on O. That is, by simply bringing the entire circumference of the edge portion 23a into contact with the tapered surface 14, the optical axis of the press lens 10 can be aligned with the optical axis O- of the optical system.
It becomes possible to precisely match O.

Furthermore, as shown in Fig. 4, the axis Y-Y of the cylindrical surface 11 must be rotated by 45 degrees with respect to the four-part photodetection section of the photodiode (see Fig. 9), but this adjustment is not necessary. This can be done by rotating the jig 25.

Whether or not the press lens 10 is in the correct position can be confirmed by applying parallel light from the (c) side of the optical axis OO and viewing the image of the light transmitted through the press lens 10 on a monitor. By checking the astigmatism image on this monitor, it is possible to check whether the axis Y-Y of the cylindrical surface 11 is accurately rotated by 45 degrees. At the same time, it is also possible to check whether the optical axis of the press lens 10 coincides with the optical axis OO of the optical system. After these checks, the adhesive 26 is cured by irradiating the adhesive 26 with ultraviolet rays, and the press lens 10 is fixed.

FIG. 5 shows a second embodiment of the invention. In this embodiment, a tapered surface 14 is formed on the outer periphery of the concave spherical surface 12 of the press lens 10, and a point A is the virtual apex of a conical shape that includes this tapered surface 14.
is located outside the concave spherical surface, contrary to the embodiment shown in FIG. Of course, this point A is located on the optical axis OO. Also in this embodiment, the entire circumference of the edge portion 23a of the positioning protrusion 23 is connected to the tapered surface 1.
4, the optical axis of the press lens 10 can be accurately aligned with the optical axis OO of the optical system.

FIG. 6 shows a third embodiment of the invention. This embodiment is applied to an objective lens 10a facing an optical disk D in an optical pickup. This objective lens 10a is a pressed lens made of glass material. This objective lens 10a also has a spherical or aspherical convex surface 1.
A tapered surface 14a is formed on the outer periphery of 7. This tapered surface 14a is part of a conical shape whose virtual apex is a point A located on the optical axis. The lens holder 30 is provided with a circular positioning protrusion 31 centered on the optical axis. The tapered surface 14
By abutting the entire circumference of the positioning protrusion 31, the objective lens 10a can be accurately positioned and fixed.

Furthermore, the present invention can be applied to the positioning of other lenses such as the collimating lens 3 (see FIG. 8).

[Effect of idea]

As described above, according to the present invention, the following effects can be achieved.

(1) Since the lens has a tapered surface corresponding to a part of a cone whose virtual apex is a point on the optical axis, by bringing this tapered surface into contact with the positioning protrusion, the lens aligns with the optical axis. can be fixed in an accurately aligned state. Therefore, the work for adjusting the optical axis becomes unnecessary, and the lens can be positioned and fixed with high precision with simple work.

(2) The tapered surface of the lens can be brought into contact with the positioning protrusion and the lens can be fixed with adhesive, etc.
No need for a holder to store the lens. Therefore, there is no need to provide a holder that requires highly accurate machining, and the structure of the lens attachment can be simplified, resulting in cost reduction.

[Brief explanation of the drawing]

Figures 1 to 4 show a first embodiment of the present invention. Figure 1 is a perspective view showing a press lens that integrates a concave lens and a cylindrical lens, and Figure 2 is a perspective view showing a press lens in which a concave lens and a cylindrical lens are integrated. 1 is a cross-sectional view showing the state in which the press lens is supported, FIG. 3 is an enlarged cross-sectional view showing the lens positioning mechanism, and FIG.
The figure is a front view showing the positioning state of the press lens from the cylindrical surface side, FIG. 5 is a sectional view showing the lens positioning mechanism according to the second embodiment of the present invention, and FIG. A cross-sectional view showing a positioning mechanism of an objective lens facing the
Fig. 7 is a cross-sectional view showing problems in conventional lens positioning, Fig. 8 is a configuration diagram showing the optical system of an optical pickup installed in a compact disc player, and Fig. 9 is a cylindrical lens and photodiode facing each other. It is an enlarged front view showing a position. 10, 10a...Press lens, 14, 14a
... Tapered surface, 20 ... Lens support member, 23,
31...Positioning protrusion, 23a...Edge part,
A... Point that becomes the virtual vertex, O-O... Optical axis.

Claims (1)

[Claims for Utility Model Registration] (1) A tapered surface consisting of a portion of a cone whose virtual apex is a point on the optical axis is formed on the outer periphery of the optical surface of the lens; is provided with a positioning protrusion arranged in a circle centered on the optical axis, and the lens and lens support member are fixed with the tapered surface in contact with the positioning protrusion. A lens positioning mechanism consisting of (2) The lens positioning mechanism according to claim 1, wherein the lens is pressed from a glass material, and the tapered surface is formed by a pressing process.