JP2001167463A - Laser beam emitting unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of an optical pickup device by maintaining precision in positioning of the emitting direction of outgoing laser beams, especially Z axis adjustment. SOLUTION: The laser beam emitting unit 1 is composed of a laser diode 3, a laser diode holder 4, and a laser diode base 5 which is provided with a hollow part of the same shape as the cross section shape in the thickness direction of the laser diode holder 4 and the both ends of which are opened. The Z axis of the beams is adjusted by slightly moving the laser diode holder 4 holding the laser diode 3 in the direction of the Z axis using a coil spring 6 and a Z axis adjusting screw 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam emitting unit used for an optical pickup, and more particularly, to a laser beam emitting unit.
The present invention relates to a laser beam emitting unit suitable for a writable optical recording medium such as DR and MO.

[0002]

2. Description of the Related Art As is well known, various peripheral devices are connected to an electronic device such as a personal computer, and one of them is a storage device (recording medium). There are various types of storage devices (recording media), one of which is a CD.
-R (compact disc recordable). The CD-R is a recordable recording medium, and is compatible with a CD-ROM and an audio CD (CD-DA). Although writing to the CD-R requires a dedicated device and a writing application, reading from the CD-R can be performed with a normal CD-ROM drive. Once written, data cannot be erased, but can be appended many times.

[0003] A magneto-optical disk (MO) is also known as a kind of erasable / rewritable optical disk.
That is, the MO is a disk-shaped optical memory that writes information (data) using the thermo-magnetic effect of a magnetic thin film and reads information (data) using the photo-magnetic effect.

In order to write information (data) on or read information (data) from an optical disk such as a CD-R or MO, a recording / reproducing light for irradiating a laser beam onto the optical disk is required. Pickup is required.

In general, this type of optical pickup includes a laser light source for emitting a laser beam and an optical system for guiding the emitted laser beam to a recording medium such as an optical disk.

[0006] The optical pickup has a laser section which is a laser light source for emitting a laser beam. The laser beam emitted from the laser unit is a diffraction grating (described later),
The light passes through a beam splitter (to be described later), a collimator lens (to be described later), and an objective lens, and is irradiated onto an optical disk (CD-R) (to be described later) as an optical storage medium. Here, in the current DVD pickup, the optical axis is set to Z in order to correctly position the laser for the optical disk.
With the width of the axis and the bottom of the laser diode holder as the X axis and the depth as the Y axis, adjustment of the X, Y, and Z axes was indispensable.

A conventional method of adjusting the X, Y, and Z axes will be described with reference to FIG. The illustrated laser beam emitting unit 21 includes a cylindrical optical base 25 that holds a beam shaping lens (not illustrated) inserted therein, and a laser diode holder 24 that is bonded to one end of the optical base 25 with a UV adhesive 22. And a diffraction grating 28 (GRT) mounted on the optical base 25. Diffraction grating 28
Is held down by a spring 26. The laser diode 23 is fixed by a laser diode holder 24.

[0008] The positioning of the laser beam emitted from the laser beam emitting unit having the above structure is performed by adjusting the X-axis, Y-axis, and Z-axis of the laser diode holder 24 and then attaching the laser diode holder 24 to the optical base 25. U
It is performed by fixing with a V adhesive.

As another conventional example, as shown in FIG. 3, a laser diode holder 34 for holding a laser diode 33 is finely moved in the Z-axis direction using a coil spring 36 and a Z-axis adjusting screw 49, and In some cases, the Z-axis of the laser diode holder 24 is adjusted. The illustrated laser beam emitting unit 31 includes a laser diode 33.
And a laser diode holder 34 for holding the laser diode 33, and a hollow portion having the same shape as the cross-sectional shape of the laser diode holder 34 in the thickness direction. One end is open, and the other end has a through hole 42. And a laser diode base 35. Laser diode holder 2
4, a heat radiating plate 39 for releasing heat radiated from the laser diode 33 is provided at an end on the base side of the laser diode 33. Laser diode base 3
A damping plate 43 is fixed to the opening side of the fifth plate 5. A thread is formed at the center of the damping plate 43, and the damping plate 43 functions as a female screw portion. Further, a Z-axis adjustment screw 49 which is screwed into the thread of the damping plate 43 and functions as a male screw portion is provided.

A diffraction grating 38 (GRT) is mounted in the laser diode holder 24 on the beam emitting side of the laser diode 33 of the laser diode holder 24. A washer 37 is provided adjacent to the end face of the diffraction grating 38 in the beam irradiation direction. A coil spring 36 is provided between the washer 37 and the through hole 42 of the laser diode base 35.

Hereinafter, a method of positioning the emitted laser beam in the laser beam emitting unit having the above configuration will be described. The Z-axis position is adjusted by turning the Z-axis adjusting screw 49 rightward or leftward in the figure. When the laser diode 33 is turned rightward in the Z axis, the coil spring 36 contracts, and when the laser diode 33 is turned leftward in the Z axis, the coil spring 36 is expanded by the reaction force.

In the case of the configuration shown in FIG. 3, the laser diode 33 is located substantially at the center of the laser diode base 35, so that the heat radiated from the laser diode 33 is released. It is necessary to use a material having a high thermal conductivity as the material 35.

One laser beam emitted from the laser diode LD in the horizontal right direction is split into three laser beams by the diffraction grating GRT, and the polarized beam splitter PB
S, collimator lens CL, and quarter-wave plate QWP
, Is bent at a right angle by the rising mirror MIR, travels vertically upward, and is irradiated onto the optical disc DISC via the objective lens OL.

Incidentally, of the three laser beams separated by the diffraction grating GRT, the central one laser beam is used for signal reading, and the remaining two laser beams are used for tracking servo. .

The reflected light from the optical disk DISC travels vertically downward, passes through the objective lens OL, is bent at a right angle by the rising mirror MIR, and travels horizontally to the left.
Through the 波長 wavelength plate QWP and the collimator lens CL,
The light is bent at a right angle by the polarizing beam splitter PBS, travels in the horizontal front direction, and is received by the photodiode PD through the sensor lens SL.

[0016]

However, in the conventional laser beam emitting unit shown in FIG.
Adjustment of Y axis and Z axis is performed after adjustment of X axis, Y axis and Z axis in laser diode holder assembly.
Since it was fixed with UV adhesive at the position after the adjustment, if the Z-axis adjustment before fixing with the adhesive was not good, it is impossible to readjust it after fixing Met. In addition, since fixing is performed using an adhesive, there is a problem that reliability is poor and accuracy is unstable.

Although the conventional laser beam emitting unit shown in FIG. 2 does not use an adhesive as compared with the laser beam emitting unit shown in FIG. 2, the above problem caused by using an adhesive is solved. In the case of adjustment in the left direction of the Z-axis, fine adjustment is performed by the reaction force of the spring, so that there is a problem that the adjustment accuracy is reduced due to the time-dependent settling of the spring.

Therefore, an object of the present invention is to position the emitted laser beam in the emission direction, and particularly to adjust the Z-axis.
An object of the present invention is to provide a laser beam emitting unit which maintains the accuracy even after a predetermined use time has elapsed, and further improves the reliability of the optical pickup device.

[0019]

According to the present invention, a laser diode, a hollow first base and a first leg are provided, and the first base is provided with a female for adjusting an optical axis (Z axis). A screw portion is formed in the optical axis direction, and a laser diode holder that holds and holds the laser diode from the first base portion to the first leg portion, and a hollow second base portion and a second leg portion. A concave portion for fixing a head portion of a male screw portion screwed to the female screw portion is formed in the second base portion, and the first base portion extends from the second base portion to the second leg portion. And a laser diode base that houses and holds the legs.

Further, according to the present invention, the laser diode holder and the laser diode base have a cross section T.
And the female screw portion is a through hole having a female screw thread to be screwed with a male screw thread of the male screw portion, and the concave portion has a U-shaped cross section formed at a base of the laser diode holder. A laser beam emitting unit characterized by having a concave shape is obtained.

Further, according to the present invention, the Z-axis adjustment of the laser beam emitted from the laser diode is performed by screwing the male screw into the female screw and turning the male screw. A laser beam emitting unit is obtained by slightly moving the laser diode holder in the Z-axis direction.

Further, according to the present invention, the laser diode held in the hollow portion of the laser diode holder is provided with a coil spring, a washer, and a diffraction grating in this order. A unit is obtained.

Further, according to the present invention, there is provided a laser beam emitting unit in which a concave portion having a shape necessary and sufficient for turning a screw is formed in the head of the male screw portion.

[0024]

Embodiments of the present invention will be described below in detail with reference to FIG. With reference to FIG. 1, a laser beam emitting unit according to an embodiment of the present invention will be described. In FIG. 1, (a) is a longitudinal sectional view,
(B) is a plan view of a Z-axis adjustment screw, and (c) is a diagram illustrating three axes that are beam adjustment directions. The Z-axis adjustment of the beam in the laser beam emitting unit 1 according to the present embodiment is performed by using the Z-axis adjustment screw 9 to slightly move the laser diode holder 4 holding the laser diode 3 in the Z-axis direction.

The illustrated laser beam emitting unit 1 has a laser diode 3 and a hollow portion having the same cross-sectional shape in the thickness direction. One end is open, and the other end is a through hole 11.
A laser diode holder 4 for holding the laser diode 3, a laser diode base 5 having a hollow portion having the same shape as the cross-sectional shape in the thickness direction of the laser diode holder 4, and having both ends open. It is composed of A laser diode 3, a coil spring 6, a washer 7, a diffraction grating 8
Are arranged in this order. The laser diode holder 4 has a T-shaped cross section and includes a hollow base and legs. A through hole 13 having a female screw thread to be screwed with a male screw thread of the Z-axis adjusting screw 9 is formed in the base on the side of the laser diode 3. Like the laser diode holder 4, the laser diode base 5 also has a T-shaped cross section, and includes a hollow base and legs. At the base of the laser diode 3 side,
A concave portion 14 having a U-shaped cross section is formed, and the head of the Z-axis adjusting screw 9 is housed in the concave portion 14.

The through hole 13 functions as a female screw portion. The thread of the Z-axis adjusting screw 9 functioning as a male thread is screwed into the thread of the through hole 13. Laser diode holder 4
The diffraction grating 8 (GRT) is mounted at the end of the hollow portion of the laser diode 3 on the side of the through hole 11. A washer 7 is provided on the end face of the diffraction grating 8 toward the laser diode 3.
Are provided adjacent to each other. A coil spring 6 is provided between the washer 7 and the laser diode 3.

Hereinafter, a method of positioning the emitted laser beam in the laser beam emitting unit according to the present embodiment will be described. The Z-axis position is adjusted by turning the Z-axis adjustment screw 9 clockwise or counterclockwise so as to face the right or left direction in the figure. Specifically, when the laser diode 3 is turned rightward in the Z-axis, the Z-axis adjustment screw 9 is turned clockwise to move the laser diode holder 4 rightward in FIG. The fixed laser diode 3 moves rightward in the figure. When the laser diode 3 is turned to the left in the Z-axis direction, the Z-axis adjustment screw 9 is turned counterclockwise to move the laser diode holder 4 to the left in the figure, and the laser fixed to the laser diode holder 4. The diode 3 moves to the left in the figure. Here, the head of the Z-axis adjusting screw 9 is formed with a hexagonal concave portion as shown in FIG. When turning the screw, it is performed using a hexagonal screwdriver having the concave shape. Any shape other than the hexagonal shape may be used as long as the shape is necessary and sufficient for turning the screw.

In the case of the configuration shown in FIG. 1, the laser diode 3 is located at the end of the laser diode base 5, so that the heat radiated from the conventional laser diode is released. Although it is necessary to use a material having a high thermal conductivity as the material, in the present embodiment, a material having a low thermal conductivity such as a resin may be used.

[0029]

According to the present invention, since the Z-axis adjustment is all performed by the screw leads, the laser diode base and the laser diode holder can be press-fitted, and the position of the emitted laser beam in the emitting direction can be determined. In the axis adjustment, the accuracy can be maintained even after a predetermined use time has elapsed, and thus the reliability of the optical pickup device can be improved.

According to the present invention, since the laser diode is located at the end of the laser diode base, the material of the laser diode base has a high thermal conductivity in order to release the heat radiated from the conventional laser diode. Although it was necessary to use something, in this embodiment,
A resin or the like having a low thermal conductivity may be used. Further, a heat radiating plate or the like is unnecessary due to the above-described structure, and the number of components can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a laser beam emitting unit according to an embodiment of the present invention, wherein FIG.
(B) is a figure which shows the head shape of the Z-axis adjustment screw 9,
(C) shows an adjustment direction necessary for positioning of the laser emission direction.

FIG. 2 is a front sectional view showing a configuration of a conventional laser beam emitting unit.

FIG. 3 is a front sectional view showing the configuration of another conventional laser beam emitting unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser beam emitting unit 2 optical axis 3 laser diode 4 laser diode holder 5 laser diode base 5 6 coil spring 7 washer 8 diffraction grating 9 Z-axis adjustment screw 10, 11, 13 through hole 12 recess 14 recess

Claims (5)

[Claims] 1. A laser diode, comprising a hollow first base and a first leg, wherein the first base has an optical axis (Z
An axial) female screw portion for adjustment is formed in the optical axis direction;
A laser diode holder that holds and holds the laser diode from the base to the first leg, a hollow second base and a second leg, and the second base has a female screw part. A concave portion for fixing the head of the male screw portion to be screwed is formed, and the laser diode base is configured to house and hold the first leg portion from the second base portion to the second leg portion. A laser beam emitting unit characterized in that: 2. The laser diode holder and the laser diode base have a T-shaped cross section, and the female screw portion is a through hole having a female screw thread to be screwed with a male screw thread of the male screw portion, 2. The laser beam emitting unit according to claim 1, wherein the recess is a U-shaped recess formed in a base of the laser diode holder. 3. The Z-axis adjustment of the laser beam emitted from the laser diode is performed by screwing the male screw into the female screw and turning the laser diode holder by turning the male screw. The laser beam emitting unit according to claim 1, wherein the laser beam is emitted by slightly moving in a direction. 4. The laser beam according to claim 2, wherein a coil spring, a washer, and a diffraction grating are arranged in this order in the laser diode held in the hollow portion of the laser diode holder. Emission unit. 5. A concave portion having a shape necessary and sufficient for turning a screw is formed in a head portion of the male screw portion.
5. The laser beam emitting unit according to any one of claims 4 to 4.