JPH10177733A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin optical pickup. SOLUTION: This optical pickup is provided with a light source emitting light, a photodetector light receiving reflection light from an optical recording medium 4 and an objective lens 3 converging the emitted light on the recording surface of the optical recording medium, and the objective lens 3 is formed integrally with a convergent action part 3b substantially performing a convergent action and a flange part 3a thinner than the convergent action part 3b along the outer periphery of the convergent action part by resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording and reproducing information on an optical disk, and more particularly, to recording and reproducing on an optical disk such as a compact disk (CD), a CD-ROM, and a digital video disk (DVD). Regarding possible optical pickups.

[0002]

2. Description of the Related Art In recent years, personal computers (hereinafter, referred to as personal computers)
The amount of data handled by a personal computer (PC) is steadily increasing, and a conventionally used storage device such as a floppy disk device cannot accommodate large-capacity computer software and programs. Instead of floppy disks, now 300-400 floppy disks
A CD-ROM drive using a compact disk having twice the storage capacity as a memory has come to be mounted on most desktop PCs. By the way, desktop type P
Along with C, notebook PCs have been increasingly used because of their space saving and portability. Due to the small volume of the notebook PC, the CD-ROM device to be mounted is required to be thin and small, and the optical pickup which is a key component of the CD-ROM device is also thin and small. Has been requested.

Hereinafter, a conventional optical pickup will be described. FIG. 3 is a sectional view of a conventional optical pickup.

An optical unit 201 has a stem 210 on which a semiconductor laser and a light receiving element (not shown) are mounted. 211 is the stem 210
The terminal 211 is electrically connected to a flexible printed board (not shown) or the like, and supplies power to the semiconductor laser, outputs a signal from the light receiving element, and the like. The stem 212 is covered with a cap 212 for accommodating a diffraction grating in addition to the semiconductor laser and the light receiving element described above. The cap 212 protects the semiconductor laser, the light receiving element, and the diffraction grating from outside. Further, a cover glass 213 is adhered to a hole provided on the cap. A hologram (not shown) is formed on the cover glass 213. The optical unit 201 alone can emit laser light and receive reflected light from an optical recording medium. The optical unit 201 is fixed to the carriage 206 so as to have an optical axis parallel to the recording surface of the optical recording medium 204.

Reference numeral 202 denotes a rising mirror, which emits light from the optical unit 201 to the recording surface 2 of the optical recording medium 204.
The light is reflected by the reflection surface 202r so as to be substantially perpendicular to the surface 04r. The rising mirror 202 is fixed to the bottom surface 205 of the carriage by inclining its reflection surface 202r by 45 ° with respect to the recording surface 204r of the optical recording medium 204. Here, the rising mirror 202 has a rectangular plate shape in cross section, and has a protruding portion 202t protruding more toward the bottom surface 205 of the carriage than the bottom of the inclined reflecting surface 202r.
The protrusion 202t and the bottom surface 205 of the carriage are fixedly arranged.

[0006] Reference numeral 203 denotes an objective lens which condenses outgoing light reflected from the rising mirror 202 with a minute spot on the recording surface 204 r of the optical recording medium 204. Although optical glass, resin, and the like are used as the material of the objective lens 203, the cost of the optical pickup can be reduced.
In recent years, resin has been used as the material of the objective lens 203 in order to reduce the inertia weight. Acrylic resin is used as the resin. FIG. 4 is a sectional view of an objective lens used in a conventional optical pickup. The objective lens 203 is provided with a light condensing section 20 that substantially performs a light condensing action.
3b and a brim portion 20 protruding along the outer periphery of the light collecting section.
3a are integrally formed of resin.

Reference numeral 207 denotes an objective lens holding cylinder.
The objective lens 203 is held by engaging with the protruding flange portion 203a of the objective lens 203. The objective lens holding cylinder 207 is elastically held by the carriage 206 via a suspension (not shown), and can be finely moved in the focus direction and the tracking direction.

The projecting flange 203a of the objective lens 203 has a projecting structure due to the expansion and contraction characteristics of the acrylic resin used as the material of the objective lens 203. Expansion / contraction occurs mainly when the acrylic resin absorbs moisture. The protruding brim portion 203a has a shape that easily absorbs the stress generated by the expansion and contraction of the objective lens 203 and is easily deformed. As a result, the objective lens 203 itself does not undergo distortion or the like due to stress, and does not change in optical characteristics. Further, the adhesion with the objective lens holding cylinder 207 does not come off.

The operation of the optical pickup configured as described above will be described. Emitted light emitted from a semiconductor laser, which is a light source built in the optical unit 201, is divided into three beams by a diffraction grating (not shown), and also passes through a hologram (not shown) and rises up to a mirror 2
The light is reflected at 02 and becomes an optical axis substantially perpendicular to the recording surface 204r of the optical recording medium 204, and is converged by the objective lens 203 to form a spot on the recording surface 204r of the optical recording medium 204. The reflected light including the pit information of the recording surface 204r of the optical recording medium 204 passes through the objective lens 203 again, is reflected by the rising mirror 202, and is reflected by the recording surface 20r of the optical recording medium 204.
4r, and is diffracted by a hologram (not shown), received by a light receiving element (not shown) built in the optical unit 201, and is recorded on the recording surface 204 of the optical recording medium 204.
The pit information of r is reproduced. The focus detection is performed by the known hologram Foucault method, and the track detection is performed by the known 3
This is performed by a beam method.

[0010]

However, in the conventional optical pickup, the objective lens 203 engages with the holding portion 207a of the objective lens holding tube 207 through the protruding flange portion 203a. It was not possible to reduce the height together with the cylinder, which hindered the overall reduction in the thickness of the optical pickup.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical pickup which has good responsiveness, is low in cost, and can be easily made thin.

[0012]

According to the present invention, there is provided a light source for emitting light, a light receiving element for receiving light reflected from an optical recording medium, and a light receiving element for transmitting the emitted light to the optical recording medium. An optical lens having an objective lens for condensing light on a recording surface, wherein the objective lens substantially performs a condensing action, and the condensing action section is formed along an outer periphery of the condensing action section. It is configured such that a brim portion having a smaller thickness than the action portion is integrally formed of resin.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claims 1 and 2 is directed to a light source for emitting light, a light receiving element for receiving light reflected from an optical recording medium, and a light emitting element for emitting light to a recording surface of the optical recording medium. An optical pickup having an objective lens for condensing light, wherein the objective lens has a light-condensing section that substantially performs light-condensing action and a light-condensing section along the outer periphery of the light-condensing section. It is characterized in that the brim portion having a small thickness is integrally formed of resin, so that the objective lens becomes lightweight and the optical pickup can be made thin. Further, the responsiveness of the optical pickup can be improved.

According to a third aspect of the present invention, there is provided a light source for emitting light, a light receiving element for receiving light reflected from an optical recording medium, and an objective lens for focusing the emitted light on a recording surface of the optical recording medium. An optical pickup comprising: an objective lens holding unit that holds the objective lens; and a carriage that fixes the light source and the light receiving element and elastically supports the objective lens holding unit. A light-collecting portion that substantially performs a light-collecting operation, and a brim portion having a smaller thickness than the light-collecting portion along the outer periphery of the light-collecting portion are integrally formed of a resin having a low water absorption. And the collar portion of the objective lens is engaged with the objective lens holding means, and the objective lens and the objective lens holding means are structured such that the collar portion does not protrude. The combined height can be lowered as compared with the conventional. Accordingly, the thickness of the optical pickup can be reduced.

According to a fifth aspect of the present invention, there is provided an optical unit in which a semiconductor laser for emitting a laser beam and a light receiving element for receiving reflected light from an optical recording medium are at least integrated with each other; A plate-shaped rising mirror that reflects the emitted light and guides it to the recording surface of the optical recording medium, an objective lens that focuses the laser light passing through the rising mirror on the recording surface of the optical recording medium, and holds the objective lens. An optical pickup comprising: an objective lens holding cylinder to be fixed; and a carriage that fixes the optical unit and the rising mirror and supports the objective lens holding cylinder so as to be finely movable. And the optical axis of the light emitted from the optical unit is inclined so as to be inclined with respect to the recording surface of the optical recording medium. An optical unit is fixed to the carriage, an angle between a recording surface of the optical recording medium and a reflecting surface of the rising mirror is set to less than 45 °, and the objective lens substantially performs a condensing operation. A portion and a flange portion having a smaller thickness than the light collecting portion along the outer periphery of the light collecting portion are integrally formed of a resin having a low water absorption rate, and the collar portion of the objective lens is The optical pickup is characterized in that it is engaged with the objective lens holding cylinder, and the optical pickup is further reduced in thickness by reducing the thickness of the rising mirror, increasing the efficiency of disposing the optical unit, and reducing the thickness of the objective lens. Can be.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an optical pickup according to Embodiment 1 of the present invention. Reference numeral 1 denotes an optical unit. The optical unit 1 has a stem 10 on which a semiconductor laser, which is a light source (not shown), and a light receiving element are mounted. Reference numeral 11 denotes a terminal that protrudes from the stem 10. The terminal 11 is electrically connected to a flexible printed circuit (not shown) or the like to supply power to the semiconductor laser, output a signal from the light receiving element, and the like. The stem 10 is covered with a cap 12 for accommodating a diffraction grating in addition to the semiconductor laser and the light receiving element described above.
The cap 12 protects the semiconductor laser, the light receiving element, and the diffraction grating from outside. Further, a cover glass 13 is adhered to a hole provided on the cap 12. A hologram (not shown) is formed on the cover glass 13.
The optical unit 1 alone can emit laser light and receive reflected light from an optical recording medium. The optical unit 1 is fixed to the carriage 5 so that the optical axis 14 of the light emitted from the optical unit 1 is inclined at a predetermined angle θ11 with respect to the recording surface 4 r of the optical recording medium 4. Thus, the optical unit 1 is fixed to the carriage 6 at a position closer to the optical recording medium 4 than the reflection unit 2. In this embodiment, the optical axis 14 of the light emitted from the optical unit 1 is set to the recording surface 4r of the optical recording medium 4.
Is fixed to the carriage 6 so as to be inclined at an angle of about 4 °. Thus, the optical unit 1 is moved to the carriage 6
To the stem 1 of the conventional optical unit 1.
0, the light beam could not be brought close to the bottom surface 5 of the carriage due to interference of the cap 12, etc.
Since the optical unit 1 is closer to the optical recording medium than the reflection means 2, the light beam can be arranged closer to the bottom surface 5 of the carriage. Thus, the surplus portion 20 of the carriage 6 can be made as thin as possible, and the carriage 6 can be made thinner, that is, the optical pickup can be made thinner.

Note that the optical unit 1 does not necessarily have to be integrally formed, and the necessary optical elements as described above may be appropriately arranged along the optical path. The predetermined angle θ11 between the optical axis 14 of the light emitted from the optical unit 1 and the recording surface 4r of the optical recording medium 4 can be changed in accordance with design conditions. Is preferably in the range of approximately 0 ° <θ11 ≦ 6 °.

Reference numeral 2 denotes a reflecting means, for example, a rising mirror using a reflecting mirror having a reflectance increased to about 95% by depositing a silver thin film or a dielectric film on one surface of a plate-shaped optical glass is used. The reflection means 2 reflects the light emitted from the optical unit 1 arranged obliquely so as to be substantially perpendicular to the recording surface 4r of the optical recording medium 4. Since the optical unit 1 is fixed to the carriage 6 at a predetermined angle θ11 as described above, the reflecting means 2 also needs to be arranged on the carriage 6 corresponding to the arrangement of the optical unit 1. Specifically, the reflecting means 2 is fixed to the bottom surface 5 of the carriage in a state where the angle θr1 between the recording surface 4r of the optical recording medium 4 and the reflecting surface 2r of the reflecting means 2 is less than 45 °.

In this embodiment, θr1 is set to 43 ° in correspondence with θ11 = 4 °.

Here, in the reflecting means 2, a portion protruding from the state of the plate having a rectangular cross section and facing the bottom surface 5 of the carriage is removed by chamfering. Due to this chamfering, the reflecting means 2 has a slope 2t which is parallel to the bottom surface 5 of the carriage and forms almost one surface with the bottom surface 5 of the carriage when arranged. Since the reflecting means 2 has the slope 2t, the reflecting surface 2r of the reflecting means 2 is arranged substantially continuously with the bottom surface 5 of the carriage. Furthermore, the angle θr1 between the recording surface 4r of the optical recording medium 4 and the reflecting surface 2r of the reflecting means 2 corresponding to the inclined arrangement of the optical unit 1.
Is less than 45 °.

By arranging the reflecting means 2 on the bottom surface 5 of the carriage at an angle of less than 45 ° with respect to the recording surface 4r of the optical recording medium 4, the height of the reflecting means 2 can be set low. The optical path of the light emitted to the optical recording medium can be designed in a space-saving manner. That is, the optical pickup can be made thinner and smaller.

Reference numeral 3 denotes an objective lens which focuses outgoing light reflected from the reflecting means 2 on the recording surface 4r of the optical recording medium 4 with a minute spot. As the objective lens 3, a lightweight resin objective lens is suitable for reducing the inertia of the entire optical pickup. In the present invention, a resin material having a particularly low water absorption is used as the material of the objective lens 3. For example, polyolefin resin has low water absorption,
Since it has excellent moisture resistance, it is suitable as a material for the objective lens in the present invention. When a resin material having a low water absorption is used, the swelling factor can be reduced in the design items of the objective lens as compared with a conventionally used acrylic resin having a water absorption of 0.21% and a high water supply. .

Further, details of the objective lens 3 will be described with reference to the drawings. FIG. 2 is a sectional view of an objective lens used in an optical pickup according to one embodiment of the present invention. The objective lens 3 has a light-condensing portion 3b that substantially performs a light-condensing operation, and a flange portion 3a having a smaller thickness and a rectangular cross section along the outer periphery of the light-condensing portion 3b. It is integrally formed of resin. As described above, since the flange portion 3a of the objective lens 3 is configured not to protrude from the light collecting section 3b, the objective lens 3 is lightweight, and the response characteristics of the optical pickup can be improved.
Further, since the height when the objective lens 3 is engaged with an objective lens holding cylinder 7 described later can be designed to be low, the optical pickup can be made thin.

Reference numeral 4 denotes an optical recording medium having a recording surface 4r. For example, an optical disk or the like provided with pit information having projections and depressions corresponding to recording information on a reflective film as a recording surface is applied.

Reference numeral 6 denotes a carriage.
Is an optical unit 1 and a reflecting means 2 fixed, and an objective lens 3
Are elastically supported via a suspension (not shown) and the objective lens holding means 7 so as to be finely movable in the focus direction and the tracking direction. The carriage 6 is movable from one end to the other end of the optical recording medium 4 by integrally holding the optical unit 1, the reflecting means 2, and the objective lens 3 by moving means (not shown).

Reference numeral 7 denotes an objective lens holding means, for example, a cylindrical objective lens holding cylinder corresponding to the outer shape of the objective lens 3 is applied. The objective lens holding means 7 includes a holding unit 7
The objective lens 3 is bonded and held while a is engaged with the flange 3a of the objective lens 3. Compared with the conventional height of the combination of the objective lens 203 and the objective lens holding cylinder 207 shown in FIG. 4, the height of the combination of the objective lens 3 and the objective lens holding means 7 for holding the objective lens 3 is lower. can do. This is because the flange 3a of the objective lens 3 in the present invention has a structure that does not protrude. Therefore, the objective lens 3 and the objective lens holding means 7
Can be made lower than before.

An objective lens holding means 7 holding the objective lens 3 is elastically supported by a carriage 6 via a suspension (not shown), and moves the objective lens 3 to the optical recording medium 4 via an actuator (not shown) in a focusing direction. , In the tracking direction.

The operation of the optical pickup configured as described above will be described. The emitted light emitted from a light source (not shown) in the optical unit 1 at a predetermined angle θl1 in a direction away from the recording surface 4r of the optical recording medium 4 is
The beam is divided into three beams by a diffraction grating (not shown), passes through a hologram (not shown), is reflected by the reflection means 2, becomes an optical axis substantially perpendicular to the recording surface 4 r of the optical recording medium 4, and is focused by the objective lens 3 for optical recording. Three spots are formed on the recording surface 4r of the medium 4. The reflected light from the recording surface 4r including the pit information of the recording surface 4r of the optical recording medium 4 passes through the objective lens 3 again, is reflected by the reflection means 2 and approaches the recording surface 4r of the optical recording medium 4. The optical axis is inclined by a predetermined angle θ11, is diffracted by a hologram (not shown) in the optical unit 1, is received by the light receiving element, and is
The pit information on the recording surface 4r is reproduced. Note that a known hologram Foucault method and three-beam method are used for focus detection and track detection.

[0029]

According to the present invention, the objective lens includes a light-condensing portion which substantially performs a light-condensing operation, and a brim portion having a smaller thickness than the light-condensing portion along the outer periphery of the light-condensing portion. Are integrally formed of resin, so that the optical pickup can be made thinner. Further, the response characteristics of the optical pickup can be improved with a lightweight objective lens. Further, by using a low-cost objective lens made of resin, a low-cost optical pickup can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an objective lens used in the optical pickup according to one embodiment of the present invention;

FIG. 3 is a cross-sectional view of a conventional optical pickup.

FIG. 4 is a cross-sectional view of an objective lens used in a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical unit 2 Reflecting means 2r Reflecting surface 2t Inclined part 3 Objective lens 3a Collar part 3b Condensing action part 4 Optical recording medium 4r Recording surface 5 Bottom of carriage 6 Carriage 7 Objective lens holding means 10 Stem 11 Terminal 12 Cap 13 Cover glass Reference Signs List 14 optical axis 201 optical unit 202 rising mirror 202r reflecting surface 202t projecting portion 203 objective lens 203a projecting brim portion 203b light collecting section 204 optical recording medium 204r recording surface 205 bottom surface of carriage 206 carriage 207 objective lens holding tube

Claims (5)

[Claims] An optical pickup comprising: a light source that emits light; a light receiving element that receives light reflected from an optical recording medium; and an objective lens that focuses the emitted light on a recording surface of the optical recording medium. In the objective lens, a light-condensing portion that substantially performs a light-condensing operation, and a brim portion having a smaller thickness than the light-condensing portion along the outer periphery of the light-condensing portion are integrally formed of resin. An optical pickup characterized by being made. 2. The optical pickup according to claim 1, wherein the resin has a low water absorption. 3. A light source for emitting light, a light receiving element for receiving reflected light from an optical recording medium, an objective lens for focusing the emitted light on a recording surface of the optical recording medium, and an objective for holding the objective lens. An optical pickup comprising: a lens holding unit; and a carriage that fixes the light source and the light receiving element and elastically supports the objective lens holding unit. A light action portion and a flange portion having a smaller thickness than the light collection action portion along the outer periphery of the light collection action portion are integrally formed of a resin having a low water absorption, and the collar of the objective lens is formed. An optical pickup wherein a portion is engaged with the objective lens holding means. 4. The optical pickup according to claim 3, wherein said objective lens uses a polyolefin resin. 5. An optical unit in which a semiconductor laser that emits laser light and a light receiving element that receives reflected light from an optical recording medium are at least integrated with each other, and the light that is emitted from the optical unit is reflected. A plate-shaped rising mirror that guides to the recording surface of the recording medium, an objective lens that focuses the laser beam passing through the rising mirror on the recording surface of the optical recording medium, and an objective lens holding barrel that holds the objective lens. An optical pickup, comprising: a carriage that fixes the optical unit and the rising mirror and finely supports the objective lens holding cylinder, wherein a reflection surface of the rising mirror and a bottom surface of the carriage are substantially continuous. The optical unit is arranged so that the optical axis of the light emitted from the optical unit is inclined with respect to the recording surface of the optical recording medium. Fixed to a ridge, the angle between the recording surface of the optical recording medium and the reflecting surface of the rising mirror is less than 45 °, the objective lens is a light-condensing section that substantially condenses light, A collar portion having a smaller thickness than the light collecting portion is integrally formed of a resin having a low water absorption along the outer periphery of the light collecting portion, and the collar portion of the objective lens is held by the objective lens. An optical pickup characterized by being engaged with a tube.