JPS62162251A - Optical reader - Google Patents

Abstract

PURPOSE:To reduce the size of a device and to provide the device with the function of a diffraction grating by joining a concave lens with the end surface of a beam splitter on the light emitting source side and forming grooves for applying the function of the diffraction grating on any one of joint surfaces between the beam splitter and the concave lens. CONSTITUTION:An objective lens 2 is arranged on the upper surface of a beam splitter consisting of two triangular prisms 1, 3 oppositely to the surface of a disk 31 to be a recording medium and the concave lens 4 is sticked to the end surface of the beam splitter on the light emitting source side, so that the optical of the light emitting system can be shortened and the size of the device can be reduced. Many grooves are formed on any one of joint surfaces between the prism 1 and the lens 4 to provide the device with the function of the diffraction grating. The positioning of the light emitting source 5 can be attained highly accurately on the basis of the recessed part 4a of the concave lens 4 and the forming position, shape, etc. of the stepped part 4b.

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. .

[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 splinter, A photodetector reads information recorded on the disk surface.

In recent years, there has been a demand for miniaturization of such optical reading devices. As one measure to miniaturize optical reading devices, a light emitting source, Heems 7' IJ
It is possible to shorten the distance of the light emitting system optical path in optical system members such as the footer, collimating lens, and objective lens. In this case, the distance between the objective lens and the collimating lens should be made as close as possible, and It is also necessary to bring the collimating lens and the light source close to each other.However, it is unreasonable to bring the collimating lens and the light source close to each other.The reason is as follows.

For example, in the case of a pickup for a compact disc, the objective lens needs to have an NA of about 0.45, and the collimator lens needs to have an NA of about 0.14. The former is a limitation due to the optical cutoff frequency, and the latter is determined by the need to correct the elliptical far-field pattern of the laser diode. Therefore, if the distance between the light emitting source and the collimating lens is to be shortened, the effective diameters of the collimating lens and the objective lens should be set small, in view of the need to satisfy the determined NA.
In addition, it is required to shorten the focal length.

However, since the distance between the objective lens and the disk (working distance) is usually required to be about 21 m1 according to standards, there is a natural limit to reducing the focal length.

For these reasons, there is a limit to how close the light emitting source and the collimating lens can be, making it difficult to miniaturize the device.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and the present invention is an optical reading device that allows the distance between the light emitting source and the collimating lens to be set short, thereby realizing miniaturization of the device. The purpose is to provide the following.

[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, a concave lens is bonded to the end surface of the beam splitter on the side of the light emitting source, and either the beam splitter or the concave lens The device is characterized in that a groove for providing the function of a diffraction grating is provided on the bonding surface to enable miniaturization of the device, and the device is configured to have the function of a diffraction grating. be.

〔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 I8 and 18 are provided on the base 32 and are installed in parallel with 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 recording medium so as to face the disk surface of the disk 31 as a recording medium. This objective lens 2
is formed integrally with the triangular prism 1, or is fixed to the triangular prism 1 in a separate structure. Another triangular prism 3 is bonded to the slope on one side of the triangular prism 1, and this makes it possible to create a beam splitter.
and a Tsuukola prism is constructed.

In addition, a concave lens 4 is bonded to the other side surface of the triangular prism 1, that is, the end surface on the light source side of the beam splinter, thereby shortening the optical path of the light emitting system, resulting in a structure that can be miniaturized. Note that the bonding of the concave lens 4 to the beam splitter is not limited to the above-described attachment structure, but may be a structure in which, for example, the concave lens 4 made of plastic is fixed by an outsert. Further, the triangular prism 1 and the concave lens 4 forming a beam splitter are also provided.
The joining surface A of either the triangular prism 1 or the concave lens 4 is etched if the material is glass, or by molding if it is made of plastic.
A large number of grooves are provided, and the structure is configured to have the function of a diffraction grating.

The concave lens 4 has a recess 4a for installing a light emitting source formed on the side opposite to the triangular prism 1, and a light emitting source 5 such as a laser is installed and installed in the recess 4a. Stepped portion 4b formed on the circumferential surface of 4a
Accordingly, the insertion depth of the light emitting source 5 into the recess 4a is determined. That is, the concave portion 4a of the concave lens 4
And depending on the formation position and shape of the stepped portion 4b,
This makes it possible to position and set the light emitting source 5 with high precision. Further, the reference surfaces 6, 6 formed on the bottom surface of the triangular prism 3, which is configured as a pair of combinations, have
A light-receiving element substrate 9 is fixed at a predetermined distance from the inner bottom of the movable part main body 16, and on this light-receiving element substrate 9,
A light-receiving element 8 serving as a photodetector is placed in a space 7 surrounded by both triangular prisms 3 in a fixed state. To adjust the set position of the light receiving element 8, the light receiving element board 9, which is placed with the light receiving element 8 facing the space 7, is brought into contact with the reference surfaces 6, 6, and in this state, the light receiving element board 9 is adjusted. 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 1O 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 tracking is provided on the outer periphery of each of these protruding ends. The operating 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 and
A focus operation coil 14 having a rectangular tube shape as a whole is fixed so as to be disposed between the focus operation 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 tracking/knocking direction, it is driven by the two tracking operation coils 13 and the two tracking operation coils 17 and I7 described above, that is, a total of four tracking operation coils. Become. To perform the tracking operation, the entire trunking drive section can be driven with just the two tracking operation coils 17, 17, but in this case, the leaf springs 15 and 17 are sufficient to drive the entire trunking drive section.
It is difficult to accurately transmit the tracking driving force to the optical system member supported by the optical system member 15. 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. 15 and the cover 10, 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, etc. It is from. 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 section, but since the number of turns of the coils is small, the overall weight is light, so that the focus drive is not adversely affected, and the tracking drive can be carried out by optical system components. Since the information can be transmitted accurately, 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, reaches the objective lens 2, and is focused by the objective lens 2. The light is irradiated onto the disk surface of the disk 31 serving as the opposing recording medium. After this light is reflected by the disk 31, the reflected light beam condensed by the objective lens 2 is guided to the beam splitter and received by the light receiving element 8 as a photodetector. Recorded information optically recorded on the surface is read. The movable part main body 16, which includes optical system members such as the triangular prism 1, objective lens 2, triangular prism 3, and concave lens 4, is moved in the trunking direction by a total of four tracking operation coils 13, 13, 17, and 17. A focus/tracking magnetic circuit is driven along two guide shafts 18, 18, and is composed of a focus operation coil 14, a magnet 21, an outer yoke 22, an inner yoke 23, and end yokes 24, 24. This operates continuously to sequentially read the recorded information recorded on the disk 31 described above.

〔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 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 reader equipped with a beam splitter for transmitting to a detector, a concave lens is bonded to the end surface of the beam splitter on the side of the light emitting source, and the bonded surface of either the beam splitter or the concave lens is It has a structure in which a groove is provided to provide the function of a diffraction grating. As a result, the distance between the light emitting source and the collimating lens can be set short, making it possible to downsize the device and also having the function of a diffraction grating.

[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. l.3 is a triangular prism (beam splinter), 2 is an objective lens, 4 is a concave lens, A is a cemented surface, 5 is a light source, 8
is a light receiving element (photodetector), 31 is a disk (recording medium)
It is.

Claims (1)

[Claims] 1. A light emitting source, an objective lens arranged so as to focus the light emitted from the light emitting source and projecting it onto a recording medium on which information is optically recorded; A beam splitter disposed between a light emitting source and guiding light from the light emitting source to an objective lens and guiding a reflected beam reflected from the recording medium and condensed by the objective lens to a photodetector. In the optical reading device, a concave lens is bonded to the end surface of the beam splitter on the light emitting source side, and a groove is provided on the bonded surface of either the beam splitter or the concave lens to provide a function of a diffraction grating. optical reader.