JPS62162248A - Optical reader - Google Patents

Abstract

PURPOSE:To omit a collimator lens for turning light beams to parallel beams and to reduce the size of a device by forming a beam splitter unitedly with an objective lens and shielding excess light out of the light beams irradiated from a light emitting source at the peripheral wall part of an objective lens exposure opening part of a cover to cover an optical system member. CONSTITUTION:The objective lens 2 opposed to the surface of a recording medium disk 31 is arranged on the upper surface of a rectangular prism 1 and formed unitedly with a triangular prism 1, i.e. the beam splitter, or directly fixed with the prism 1. Another triangular prism 3 is sticked to one inclined surface of the prism 1 to constitute the beam splitter and a sealing prism. A convex lens 4 is sticked to the other side of the prism 1. Consequently, the optical path of the light emitting system is shortened and the whole size can be reduced. The cover 10 for protecting these optical system member is also provided with a function as a heat discharging plate for heat generated in the light emitting source 5, the opening part 11 for exposing a prescribed area of the objective lens 2 is formed on the upper wall and a diaphragm structure for shielding the excess light of the irradiated light from the light emitting source 5 is formed on the peripheral wall part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical reading device used for optically reading recorded information optically recorded on a disk-shaped recording medium. be.

[Prior art]

In conventional optical reading devices of this type, a light beam emitted from a light source passes through a beam splitter and reaches a collimating lens, and the light beam that passes through this collimating lens and becomes parallel light is focused by an objective lens. This focused light is
The beam is reflected on the disk surface of the disk on which information is optically recorded, passes through the objective lens, passes through the collimating lens, and is then guided to the photodetector by the beam splitter, A photodetector reads information recorded on the disk surface.

However, in the conventional optical reading device described above, only the objective lens is driven in the focus/tracking direction, so a collimating lens is arranged between the beam splitter and the objective lens to make the light beam parallel. It becomes. For this reason, the number of parts increases, and it becomes necessary to increase the distance between the beam splitter and the objective lens, resulting in the problem that it is difficult to downsize and reduce the cost of the device.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and eliminates the collimating lens from the optical system members and eliminates the distance between the beam splitter and the objective lens, thereby reducing the size and cost of the device. The purpose of this invention is to provide an optical reading device that makes it possible to

[Structure of the invention]

In order to achieve the above object, an optical reading device according to the present invention includes a light emitting source, and focuses light emitted from the light emitting source onto a recording medium on which information is optically recorded. an objective lens placed so as to be exposed to the light, and a light emitting source placed between the objective lens and the light emitting source, which guides the light from the light source to the objective lens, reflects the light from the recording medium, and focuses the light on the objective lens. In an optical reading device equipped with a beam splitter for guiding a reflected light beam to a photodetector, the beam splitter and the objective lens are integrated, and a cover that covers the optical system member has a predetermined surface area of the objective lens. By forming an opening that exposes the light, and by providing a peripheral wall around the opening to block excess light emitted from the light emitting source, it is possible to downsize the device and reduce costs. It is characterized by being configured as follows.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 to 5.

As shown in FIG. 5, a base 32 fixed by vibration isolating members 33, etc. is disposed in close proximity to the disk surface of a disk 31 which is rotatable by a motor 30. The disk 31 described above constitutes a recording medium in which information is optically recorded on the disk surface. Two guide shafts 18, 18 are provided on the base 32, which are installed in parallel at a predetermined interval.
The movable part main body 16 is supported by guide shafts 18, 18 so as to be movable in the axial directions of the movable parts 8, 18. That is, as shown in FIG. 2, the movable part main body 16 has square holes 19 and 20 in which the two guide shafts 18 and 18 can be inserted, respectively, in the vicinity of both sides of the movable part main body 16. It is formed in a penetrating shape. The one square hole 19 has a regular square shape, which eliminates backlash between the movable part main body 16 and the guide shaft 18 and enables accurate movement, and also reduces the contact area with the guide shaft 18. It is configured to reduce the coefficient of friction by making it as small as possible. In addition, the other square hole 20 has a rectangular shape to reduce the contact area with the guide shaft 18, and to reduce the width of the gap between the guide shafts 18 and 18, the dimensional error thereof, and the dimensional error of the double square holes 19 and 20. Designed to absorb.

As shown in FIGS. 1 to 3, a triangular prism 1 made of glass, plastic, or the like is disposed inside the movable body 16, which has an overall U-shape. An objective lens 2 is provided on the upper surface of the optical disc 1 so as to face the disc surface of the disc 31 as a recording medium. This objective lens 2
is made of glass or plastic, and the objective lens 2 is either integrally molded with the triangular prism 1, that is, the beam splitter, or is constructed separately from the triangular prism 1, and the two are directly fixed. It has a solid structure. Another triangular prism 3 is bonded to the slope on one side of the triangular prism 1, thereby forming a beam splitter and a Tuukola prism. Further, a concave lens 4 is bonded to the other side surface of the triangular prism 1, thereby shortening the optical path of the light emitting system, resulting in a structure that can be miniaturized. The above concave lens 4
A recess 4a for installing a light emitting source is formed on the side surface opposite to the triangular prism 1, and a light emitting source 5 such as a laser is incorporated and mounted in the recess 4a, and a light emitting source 5 such as a laser is installed in the recess 4a. The stepped portion 4b formed on the surface determines the insertion depth of the light emitting source 5 into the recess 4a.

That is, the positioning and setting of the light emitting source 5 can be performed with high precision by the formation positions and shapes of the concave portion 4a and its stepped portion 4b of the concave lens 4. Moreover, on the bonding surface A of the triangular prism 1 and the concave lens 4,
On the cemented surface of either the triangular prism 1 and the concave lens 4,
If the material is made of glass, a large number of grooves are provided by etching or by molding if it is made of plastic, thereby providing the function of a diffraction grating. moreover,
A light-receiving element substrate 9 is fixed to the reference surfaces 6, 6 formed on the bottom surface of the triangular prism 3, which is a pair of combinations, with a predetermined distance between it and the inner bottom of the movable part main body 16. On the light-receiving element substrate 9, a light-receiving element 8 serving as a photodetector is disposed in a space 7 surrounded by both triangular prisms 3 in a fixed state. still,
Adjustment of the setting position of the light receiving element 8 is performed by adjusting the setting position of the light receiving element 8.
The light-receiving element substrate 9, which is disposed facing the space 7 side, is brought into contact with the reference surfaces 6, 6, and in this state, the light-receiving element substrate 9
This is done by finely adjusting and positioning it at a predetermined position while horizontally moving it, and after positioning it in this way, it is fixed to the reference surfaces 6 by any means.

On the other hand, in order to protect the optical system members such as the objective lens 2, the triangular prism 3, and the concave lens 4, the surroundings of these incorporated components are covered with a cover 10. This cover 10 also has a function as a heat sink so that heat generated from the light emitting source 5 can be released. An opening 11 is formed in the clay wall of the cover 10 so as to expose a predetermined surface area of the objective lens 2, and the peripheral wall around the opening 11 absorbs excess light from the light emitting source 5. It has an aperture structure that blocks out light.

On one side of the cover 10, that is, on the cover outer wall surface B near the triangular prism 3, a thin rectangular tube 12 is fixedly installed. As shown in FIG. 1, this rectangular tube 12 has a length such that its both ends slightly protrude from the end of the cover 10, and a track is provided on the outer periphery of each of these protruding ends. - The knocking operation coils 13 are fixed in a wound state. Further, on one outer surface of the rectangular tube 12, that is, on the outer surface opposite to the direction in which the triangular prism 3 is arranged, both the tracking operation coils 13 are provided.
- A focus operation coil 14 having a rectangular tube shape as a whole is fixed so as to be arranged between the coils 13.

and a cover 10 that encloses each of the optical system members described above;
The rectangular tube 12 holding the tracking operation coils 13 and the focus operation coil 14 is connected to the cover 1.
A pair of upper and lower leaf springs 15 whose base ends are fixed to the upper and lower parts of 0
- It is elastically supported in a cantilevered state by each free end side of 15, and these leaf springs 15, 15 allow the above-mentioned optical system members, etc. to move slightly in parallel in the vertical direction. The leaf springs 15 have base end portions fixed to the upper end portion 16a and stepped shoulder portion 16b of the movable portion main body 16, respectively. In addition, the above-mentioned movable part main body 16 includes:
A pair of different tracking operation coils 17, 17 are fixed in the vicinity of the tracking operation coils 13, 13, respectively. As a result, in the trunking direction, it is driven by the two tracking operation coils 13, 13 and the two tracking operation coils 17, 17 described above, that is, a total of four tracking operation coils. . In order to perform a tracking operation, the entire tracking drive section can be driven with only two tracking operation coils 17, 17, but in this case, the leaf springs 15, 1
It is difficult to accurately transmit the tracking driving force to the optical system member supported at 5. This is because distortion and deflection occur at the fixed points between the tracking operation coils 17 and the movable part main body 16, distortion and deflection of the leaf springs 15 and 15 themselves, and fixed points between the leaf springs 15 and the movable part main body 16 and the plate springs. Due to distortion at the fixed location between 15 and cover 10,
This is because the optical system members operate slightly differently in response to the driving force of the tracking operation coils 17, 17, which adversely affects frequency characteristics, sensitivity, and the like. In order to avoid such a situation, as described above, the weight of the focus drive unit, which is supported by the same leaf springs 15 near the incorporated optical system members, can be driven in the tracking direction. A pair of tracking operation coils 13.
13. For this reason, the tracking operation coils 13 are attached to the focus drive unit, but since the number of turns of the coils is small, the overall weight is light, so there is no negative effect on the focus drive, and the tracking drive can be optically Since the information can be accurately transmitted to system members, it is possible to sufficiently respond to minute movements.

Further, the outer yoke 22 and the magnet 21 fixed to the outer yoke 22 are provided so as to pass through the insides of the tracking operation coils 17, 17, and these extend parallel to the guide shaft 18. There is. On the other hand, an inner yoke 23 is provided penetrating inside the rectangular tube 12, and this inner yoke 23 also extends parallel to the outer yoke 22 and the like. Furthermore, as shown in FIGS. 4 and 5, end yokes 24 are fixed to both end surfaces of the magnet 21, the outer yoke 22, and the inner yoke 23, respectively.

The magnet 21, the outer yoke 22, the inner yoke 23, and the end yokes 24, 24 constitute a magnetic circuit for driving focus and tracking. This magnetic circuit includes a tracking operation coil 13.
・13.17・17, and focus operation coil 14
The lens is arranged in the configuration described above, and is configured to perform focus tracking drive. Further, a magnetic plate 25 is embedded and fixed in the inner bottom of the movable part main body 16, and this magnetic plate 25 attracts the magnetic circuit by using leakage magnetic flux of the magnetic circuit. There is. As a result, the weight of the entire parts assembled in the movable part main body 16 is reduced due to the action of repelling and canceling out the gravity, so that the square holes 19, 20 and each guide shaft 18, 1
By reducing the frictional force caused by gravity that acts between
It is possible to perform a tracking operation with high sensitivity.

In the above configuration, the light emitted from the light emitting source 5 passes through the concave lens 4, is guided to the triangular prism 3 as a beam splitter, and directly reaches the objective lens 2, and is focused by the objective lens 2. The light is irradiated onto the disk surface of a disk 31, which is a recording medium, and which faces the disk. After this light is reflected by the disk 31, the reflected light beam condensed by the objective lens 2 is directly guided to the beam splitter and received by the light receiving element 8 as a photodetector. Recorded information optically recorded on the disk surface is read. The movable part main body 16, which includes optical system members such as the triangular prism 1, the objective lens 2, the triangular prism 3, and the concave lens 4, has a total of four tiger knocking operation coils 13, 13, 17, 17.
The two guide shafts 18, 18 in the tracking direction by
while being driven along the focus operation coil 14 and a focus tracking magnetic circuit consisting of a magnet 21, an outer yoke 22, an inner yoke 23, and end yokes 24, 24. The recorded information recorded on the disk 31 described above is read sequentially.

〔Effect of the invention〕

As described above, the optical reading device according to the present invention includes a light emitting source and a device that focuses the light emitted from the light emitting source and directs it onto a recording medium on which information is optically recorded. and an objective lens disposed between the objective lens and the light emitting source, which guides the light from the light emitting source to the objective lens and directs the reflected light beam reflected from the recording medium and condensed by the objective lens. In an optical reading device equipped with a beam splitter for guiding the beam to a detector, the beam splitter and the objective lens are integrated, and a predetermined surface area of the objective lens is exposed to a cover that covers an optical system member. This is a configuration in which an opening is formed and a peripheral wall around the opening blocks excess light from the light emitted from the light emitting source. This eliminates the need for a collimating lens to make the beam parallel, which not only reduces the number of parts, but also eliminates the distance between the beam splitter and the objective lens, making the device more compact and reducing costs. This has the effect of making it possible to realize

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a plan view of the main part, FIG. 2 is a central vertical sectional view of FIG. 1, and FIG. 3 is an assembly thereof. FIG. 4 is an exploded perspective view, and FIG. 5 is a plan view showing the entire optical reading device. 1 and 3 are triangular prisms (beam splitters), 2 is an objective lens, 4 is a concave lens, 5 is a light emitting source, and 8 is a light receiving element (
10 is a cover, 11 is an opening, and 31 is a disk (recording medium).

Claims (1)

[Claims] 1. A light emitting source, and an objective lens arranged to focus the light emitted from the light emitting source and project it onto a recording medium on which information is optically recorded. , a beam disposed between the objective lens and the light emitting source, for guiding light from the light emitting source to the objective lens, and guiding a reflected light flux reflected from the recording medium and condensed by the objective lens to a photodetector. In an optical reading device equipped with a splitter, the beam splitter and the objective lens are integrated, and an opening that exposes a predetermined surface area of the objective lens is formed in a cover that covers the optical system member. What is claimed is: 1. An optical reading device characterized in that a peripheral wall portion around the portion blocks excess light emitted from a light emitting source. 2. The optical reading device according to claim 1, wherein the beam splitter is fixed to an objective lens. 3. The optical reading device according to claim 1, wherein the beam splitter is integrally formed with the objective lens. 4. The optical reading device according to claim 1, wherein the objective lens is made of glass. 5. The optical reading device according to claim 1, wherein the objective lens is made of plastic.