JPH03203045A - Lens and optical head - Google Patents

Abstract

PURPOSE:To reduce the thickness of the optical head by executing the effect of changing the direction of light and the effect of convergence, etc. of light by means of one lens. CONSTITUTION:Both of the incident surface 18a and exit surface 18b of the lens 18 have a convex face shape and this lens is made into the shape having a flat intra-lens body reflecting surface 18c, the normal of which is the bisector of the intersection angle of the optical axis K1 of the incident surface 18a and the optical axis K2 of the exit surface 18b. The light emitted from a laser light source 15 is refracted by the incident surface 18a and is reflected in a perpendicular direction by the reflecting surface 18c. This light is refracted by the exit surface 18b and is converged to the signal surface of a disk 1. The return light reflected by the disk surface is diffracted by a hologram element 17. The primary diffracted light thereof heads toward a photodetector 16. The detector 16 receives this light as a reproducing signal or focusing/ tracking control signal. The thickness of the objective lens part is reduced in this way and the formation of the optical head to the smaller thickness is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to a lens suitable as an objective lens of an optical head, an optical head using this lens, and an optical head using a concave mirror.

[Prior Art] Conventional lenses, whether convex or concave, have a shape in which the optical axis of the entrance surface and the optical axis of the exit surface are on the same straight line, that is, the entrance surface and the exit surface face each other.

By the way, in an optical disk device that optically reads information recorded on an optical disk, an optical head that reads signals from the optical disk includes a laser light source, an incident and reflection optical system,
It is equipped with a photodetector, etc., but in order to make this optical head thinner, a 45° mirror 3 is placed directly below the objective lens 2 facing the signal surface of the optical disk 1, as shown in FIG. Generally, a configuration is adopted in which the directions of the light beam from the laser light source as shown and the light beam directed toward the photodetector as shown are set horizontally (parallel to the disk surface).

[Problems to be Solved by the Invention] However, in the configuration in which the 45° mirror is placed directly below the objective lens, two optical components, the objective lens and the 45° mirror, are placed above and below, so the height cannot be set sufficiently. cannot be lowered.

In addition, in order to make the optical head even thinner, the entire optical system from the laser light source to the photodetector, including the objective lens, is configured as a movable part, and the movable part, including the entire optical system, is used for focusing control and tracking. An optical head for controlling the optical head has been developed, but when trying to reduce the thickness of the layers in such a thin optical head, the height of the objective lens portion in particular becomes an obstacle.

The present invention has been made in view of the above circumstances, and primarily aims to provide a lens and optical head that can further reduce the thickness of an optical head, and also to provide a lens that can be used for general purposes. The purpose is to

[Means for Solving the Problems] The invention of claim 1 which solves the above problems has an entrance surface and an exit surface, each of which has optical axes that intersect with each other, at least one of which is a curved surface, and an angle of intersection between the two optical axes. This lens has an internal reflection surface whose normal is the equal dividing line.

According to a second aspect of the invention, the lens according to the first aspect is configured as a convex lens.

The invention according to claim 3 is such that the lens according to claim 1 is configured as a concave lens.

The invention according to claim 4 is an optical head using the lens according to claim 2 as an objective lens, in which the angle of intersection of the two optical axes is a right angle.

According to a fifth aspect of the invention, the lens according to the fourth aspect is applied to an optical head in which the entire optical system from a laser light source to a photodetector is a movable part capable of controlling focusing and tracking.

According to a sixth aspect of the invention, there is provided an optical head including a concave mirror for converging a light beam on a disk signal surface.

[Action] In the lens according to the first aspect, the action of changing the direction of light and the lens action of converging light are performed simultaneously.

In the optical head according to claim 4, the lens functions as a 45° mirror that bends the direction of the light beam from the laser light source and the light beam directed toward the photodetector by 90°, and converges the light beam onto the disk signal surface. A single component functions as an objective lens. Therefore, the height of the objective lens portion can be made sufficiently low, and the thickness of the optical head can be significantly reduced.

In the optical head of the present invention, the concave mirror functions as an objective lens and a 45° mirror. Therefore, similar to the above, it is possible to significantly reduce the thickness of the optical head.

[Examples] Examples of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 2 is a perspective view showing an embodiment of the optical head of the present invention.
The movable part 10 of the optical head is supported by the carriage 11 via four suspension wires 12 so as to be movable in the focusing direction (two directions in FIG. 2) and in the tracking direction (X direction in the same figure). is movable in the disk radial direction (X direction) along the illustrated guide shaft passing through the guide hole 12a. Reference numeral 13 denotes a printed wiring board to which wiring to the movable part 10 of the optical head is connected. .

The movable part 10 of the optical head is equipped with a laser light source 15, a photodetector 16, and a hologram element 17 integrated inside, as shown in ta-th, and a lens 18 according to an embodiment of the present invention.
It is equipped with The laser light source 15 directs the laser light horizontally (
The photodetector 16 is arranged so as to emit light parallel to the disk surface (parallel to the disk surface), and the photodetector 16 is arranged to form a plane parallel to the disk surface together with the laser light source 15 (for convenience, in the figure, it is above the laser light source 15). (as illustrated).

This lens 18 has a convex entrance surface 18a and an exit surface 18b.
is also convex, and intersects the optical axis of the entrance surface 18a and the optical axis of the exit surface 18b at an angle of 90°, and at the intersection, the optical axis Kl and the optical axis Kl form an angle of 2 and 45°. (In other words, the bisector of the intersecting angle of 2 to both optical axes Kl is the normal line.) A flat internal reflection surface of the lens (note that the surface of the lens body viewed from the inside of the lens body is the reflection surface inside the lens body). 18c (referred to as a surface).In other words, the entrance surface 18c
A and the exit surface 18b constitute a convex lens, and the internal lens reflection surface 18c constitutes a 45° mirror.

In the optical head having the above configuration, a light beam parallel to the disk surface emitted from the laser light source 15 enters the entrance surface 18a of the lens 18 and is refracted, and is refracted by the lens internal reflection surface 18c.
The light is reflected in the right angle direction, refracted by the exit surface 18b, and converged onto the signal surface of the disk 1. The return light reflected from the disk signal surface follows the same path and reaches the hologram element 17, and the first-order diffracted light at the hologram element 17 is transmitted to the photodetector 1.
The photodetector 16 receives this light as a reproduction signal and as a focusing/tracking control signal. The entire movable part 18 supported by the suspension wire 11 is controlled in the focusing direction (two directions) and the tracking direction (X direction) according to the focusing/tracking control signal.

In the above-mentioned optical head, the direction of the light beam emitted from the laser light source 15 and the direction of the light beam directed toward the photodetector 16 are parallel to the disk surface, which not only makes it easy to make the optical head thinner, but also makes it possible to make the optical head thinner. Since 18 is a single optical component that serves as both an objective lens and a 45° mirror, the number of parts can be reduced, and the thickness of the objective lens can be made significantly thinner than in the past, making the optical head even more compact. This makes it possible to achieve even thinner optical disk devices.

Also, since the part corresponding to the 45° mirror is integrated,
Compared to the conventional 45° mirror installed separately,
Installation accuracy will be improved.

When the lens of the present invention is configured as a convex lens, as shown in FIG.
Both b are not limited to having a convex shape, but one surface, for example, the entrance surface 18', may be flat as shown in FIG.

In short, any material may be used as long as the entrance surface and the exit surface function as convex lenses.

Alternatively, as shown in FIG. 4, for example, a portion A on the exit surface 18b side and a portion B including the entrance surface 18a and the lens internal reflection surface 18c may be made separately by, for example, plastic molding, and the two may be in contact with each other. .

Alternatively, as shown in FIG. 5, for example, a portion C on the incident surface 18a side and a portion including the exit surface 18b and the lens internal reflection surface 18c may be made separately by, for example, plastic molding, and the two may be joined together. .

FIG. 6 shows the present invention applied as a concave lens.

That is, in this lens 28, the entrance surface 28a is concave, and the exit surface 28b is also concave. The lens internal reflection surface 28c is the same as described above.

This lens 28 functions as a concave lens and changes the direction of light by 90 degrees with a single optical component.

FIG. 7 shows an embodiment of the optical head according to claim 8.

Laser light source 15 provided in the movable part 10A of the optical head
, a photodetector 16, a hologram element 17, etc. are the same as those shown in FIG.
is arranged.

In the optical head described above, the light beam emitted from the laser light source 15 is transmitted through the hologram 17, and the concave mirror 30
Then, the returned light is reflected by the concave mirror 30, diffracted by the hologram element 17, and received by the photodetector 16.

According to this configuration, the concave mirror 30 alone serves the dual functions of a conventional objective lens and a 45° mirror, thereby reducing the number of parts and making the optical head even thinner.

In each embodiment, the intersection angle between the optical axis of the incident surface and the optical axis of the exit surface is 90', but the angle is not necessarily limited to this. However, it is usually most appropriate for Mhfz applied to the optical head to be 90°.

Note that the lens of the present invention is not limited to optical heads, and can be used for various purposes.

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

According to the lens of claim 1, since the action of changing the direction of light and the lens action of converging light are performed by one optical component, it is an optical device that needs to change the direction of light at the same time as converging light. When used in a field, etc., various useful effects such as reduction in the number of parts and space saving can be obtained.

According to the optical head of the fourth aspect, since the height of the objective lens portion can be made sufficiently low, combined with the configuration in which the directions of the light beam from the laser light source and the light beam directed toward the photodetector are set horizontally, The height near the objective lens portion can be made sufficiently low, and the optical head can be made significantly thinner. Further, the present invention can be easily applied to an optical head in which the entire optical system is a movable part, as in the fifth aspect, in which the number of parts is reduced.

In the optical head according to claim 6, since the concave mirror functions as an objective lens and a 45° mirror,
Similarly to the above, it is possible to significantly reduce the thickness of the optical head and to reduce the number of parts.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of the movable part of an optical head using a lens according to an embodiment of the present invention, FIG. 2 is a perspective view of the same optical head, and FIG.
The figure is a side view showing another embodiment of the lens of the present invention, FIG. 4 is a side view showing still another embodiment of the same lens, and FIG. 5 is a side view showing still another embodiment of the same lens. FIG. 6 is a side view showing an embodiment of the lens according to claim 3, FIG. 7 is a schematic configuration diagram showing an embodiment of the optical head according to claim 6, and FIG. 8 is an objective view of a conventional optical head. What is the configuration diagram of the lens part? ). 1], O, lOA...Movable part of optical head, 15...Laser light source, 16...Photodetector, 1.8.28...Lens, 18a, 18a', 28...・Incidence surface, 18b,
28b--output surface, 18c, 28c--lens internal reflection surface, 30... concave mirror.

Claims (6)

[Claims] (1) A lens comprising an entrance surface and an exit surface, at least one of which is a curved surface, each having optical axes that intersect with each other, and a reflective surface within the lens body whose normal is the bisector of the intersection angle of both optical axes. (2) The lens according to claim 1, wherein the entrance surface and the exit surface are curved surfaces for a convex lens. (3) The lens according to claim 1, wherein the entrance surface and the exit surface are curved surfaces for a concave lens. (4) An optical head characterized in that the lens according to claim 2 is used as an objective lens, in which the angle of intersection of the two optical axes is a right angle. (5) The optical head according to claim 4, wherein the lens according to claim 4 is applied to an optical head in which the entire optical system from a laser light source to a photodetector is a movable part capable of controlling focusing and tracking. head. (6) An optical head characterized by comprising a concave mirror for converging a light beam on a disk signal surface.