KR100438723B1 - Laser optical module and method for controlling angle between major axis of laser and pit - Google Patents

Abstract

Disclosed are a laser optical module structure and a method for adjusting the long axis and the pit angle of a laser.

In the disclosed laser light module, the first laser light source and the second laser light source for irradiating light of different wavelengths are arranged at predetermined intervals on the same line of the mount, and each laser exit port of the first and second laser light sources is provided. Is mounted to be inclined at a predetermined angle with respect to the horizontal direction.

According to the above configuration, the laser long axis and the pit angle are adjusted to form an angle of approximately 45 degrees, so that the reproduction signal characteristics are excellent and the responsiveness to the birefringent disc is improved.

Description

Laser optical module and method for controlling angle between major axis of laser and pit}

The present invention relates to a laser optical module having a good reproduction signal characteristic by adjusting a long angle between a long axis of a laser and a pit to achieve a predetermined angle, and a method for adjusting the long angle between the long axis and a pit of a laser.

1 is a related art of the present invention, in which a first and second laser light sources 3 and 5 for irradiating the first light I and the second light II having different wavelengths are formed in a package ( The optical pickup apparatus provided with 1) is shown. The optical pickup apparatus includes an optical module 1, a beam splitter 10 for changing an optical path by reflecting or transmitting light emitted from the optical module 1, and reflected by the beam splitter 10. An objective lens 15 for focusing light onto a relatively thin disk 17 or a relatively thick disk 18, and a photodetector for receiving and detecting the light reflected from the disks 17 and 18. 23).

The optical module 1 is configured by mounting the first laser light source 3 and the second laser light source 5 having different wavelengths on the mount 2 together. The first laser light source 3 is, for example, a laser diode for irradiating light of 650 nm wavelength, and is used for the relatively thin disk 17, for example, DVD. The second laser light source 5 is, for example, a laser diode for CD for irradiating light of 780 nm wavelength, and is used for the relatively thick disk 18, for example for CD. These first and second laser light sources 3 and 5 are arranged approximately (110 ± 2) μm apart.

A grating 7 is provided on the optical path between the optical module 1 and the beam splitter 10 to spectroscopic light emitted from the second laser light source 3 into three beams. This is for tracking error detection using the tribeam method which will be described later.

Light reflected from the disks 17 and 18 passes through the objective lens 15, the collimating lens 13, and the beam splitter 10 to be formed on the photodetector 23. Here, the concave lens 20 may be further provided between the beam splitter 10 and the photodetector 23. The concave lens 20 works together with the collimating lens 13 to increase the size of the light spot formed on the photodetector and to remove the coma aberration generated in the light passing through the beam splitter. Is inclined in the opposite direction.

On the other hand, the light reflected from the disks 17 and 18 is bound to the photodetector 23. The photodetectors 23 are provided for the first and second laser light sources 3 and 5, respectively, as shown in FIG. 2A. For example, the first photodetector 25 in which light irradiated from the first laser light source 3 is detected and the second photodetector 26 in which light irradiated from the second laser light source 5 are detected. Can be configured. The first photodetector 25 is a four-segment photodetector, and the second photodetector 26 is composed of a four-segment main optical sensor 26a and first and second sub-light sensors 26b and 26c. .

Tracking and focus servo implementations are performed by using the signals detected by the first and second photodetectors 25 and 26 to detect tracking errors and focusing errors.

Focusing servo for the disks of the first and second laser light sources 3 and 5 is implemented by the astigmatism method using the defocusing effect of the optical disk, and the first disk by the DPD (Differential Phase Detection) method. The tracking servo (17) is implemented by the three-beam method for the tracking servo of the second disk 18, respectively. Here, the three-beam method is received by the grating (7) to the three-beam light is reflected on the disk 18 and then received by the main photodetector and the sub-photodetector of the second photodetector 26 respectively detected Use the signal.

The principle of reproducing the information recorded on the disc as the light passes along the track formed on the disc using the first and second photodetectors 25 and 26 is as follows.

2B, information is recorded on the first and second disks 17 and 18 in the form of pits 33 formed along the track 30. Reference numeral 35 denotes a first light spot in which light irradiated from the first laser light source 3 forms a disc, and reference numerals 36a, 36b and 36c denote light that is emitted from the second laser light source 5. 7) shows a second main light spot, first and second side light spots, respectively, which are spectroscopically beamed into three beams and formed on the disk.

However, since the first and second laser light sources 3 and 5 are arranged in parallel in the optical module, the photodetectors corresponding thereto are arranged in parallel. Since the first and second side light spots 36b and 36c are used for tracking purposes, they lie side by side in the track direction T, that is, the pit direction pit. Accordingly, the direction in which the first and second side light spots 36b and 36c form on the photodetector shown in FIG. 2A represents the track direction T, and the direction perpendicular to the track direction is the disc radial direction R. FIG. Indicates.

Meanwhile, as shown in FIG. 3A, the laser light emitted from the first and second laser light sources 3 and 5 is emitted through the narrow laser exit port 6, and the laser light passes through the exit port 6. Diffraction occurs when The smaller the size of the exit port 6, the larger the diffraction angle. As shown in FIG. 3B, when the exit port of the laser light source is viewed, the distance between the exit ports from which light is emitted in the horizontal direction (M) and the vertical direction (L) is different from each other. Diffracted at different angles. At this time, the light in the longitudinal direction L looks as if it is emitted from the front of the laser light source, and the light in the lateral direction M appears as if it is emitted from the front of the laser light source as much as ΔZ. As such, the path difference between the light in the vertical direction and the light in the horizontal direction is represented by astigmatism. Is the angle spreading in the horizontal direction, and θ⊥ represents the angle spreading in the vertical direction.

In general, the longitudinal direction L is referred to as the long axis direction of the laser. In this way, the light emitted from the laser light source is arranged such that the long axis direction L of the laser is parallel to the pit 33 on the disk. In Fig. 4, the cross-sections of the first and second light (I) (II) emitted from the laser light source are somewhat exaggerated. However, in general, when the laser long axis does not form 45 degrees with the pit, it is widely known that defocusing occurs and signal characteristics are deteriorated and signal reproduction is difficult when playing a disc having a large birefringence.

Accordingly, various methods have been sought to have the long axis direction of the light spot formed on the pit at an angle of 45 degrees with respect to the pit. First, as shown in FIG. 5A, the optical module can be rotated 45 degrees so that the longitudinal direction L of the laser exit port can be rotated 45 degrees, so that the long axis and the pit of the optical spot formed on the disk can be 45 degrees. have. However, when the CD laser light source 5 is rotated 45 degrees around the DVD laser light source 3, the position of the light spot formed on the disk is not affected, but the CD laser light source is rotated 45 degrees on the photodetector. As a result, the light reflected from the disk is rotated by 45 degrees to form a photodetector. Therefore, as shown in FIG. 5B, as the laser light source is rotated by 45 degrees, the photodetector 23 should also be rotated by 45 degrees to correspond to the position variation of the laser.

Here, the first and second sub-light sensors (26b, 26c) of the photodetector should always be parallel to the track direction (T), that is, the pit direction in order to implement tracking servo, if the photodetector is rotated as described above Since the side beam no longer bears parallel to the track direction T on the photodetector, tracking cannot be realized. Therefore, this method cannot be the ultimate solution for making the long axis of the laser 45 degrees with respect to the pit.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and improved laser chip arrangement structure for irradiating light of different wavelengths so that the laser optical module can easily adjust the angle formed by the long axis of the pit and the laser light spot. And it aims to provide a method for adjusting the laser angle between the long axis and the pit.

1 illustrates an optical pickup apparatus as a related art of the present invention.

Figure 2a shows a conventional photodetector structure.

Fig. 2B shows the pit formed in the track of the disc and the laser light spot formed on the disc.

3A and 3B show a cross-sectional shape of a conventional laser optical module and light irradiated from the laser optical module.

4 shows a state in which a conventional optical module and light irradiated from the optical module are formed on a disk.

5A and 5B are views illustrating a state in which light emitted from an optical module is formed on a disc and a photodetector arrangement state when the optical module is rotated according to a conventional method of adjusting the long axis and the pit angle of a laser.

Figure 6 schematically shows a laser optical module according to the present invention.

<Description of Symbols for Major Parts of Drawings>

50, 55 ... laser light 56 ... laser exit

60 ... mount 62 ... ft

17, 18 Optical disc T (pit) ... Track direction (pit direction)

L ... laser long axis direction

In order to achieve the above object, the laser optical module according to the present invention includes a first laser light source and a second laser light source for irradiating light of different wavelengths arranged at a predetermined distance apart from the same line of the mount, and the first and second Each laser exit port of the laser light source is mounted so as to be inclined at a predetermined angle with respect to the horizontal direction.

The exit openings of the first and second laser light sources are inclined at an angle of approximately 45 degrees with respect to the horizontal direction.

In order to achieve the above object, the method according to the present invention, the first axis and the second laser light source for irradiating light of different wavelengths and the long axis of the laser light spot irradiated from the optical module formed in the package formed on the disk and In the method for adjusting the angle formed by the pit formed in the disk, the first and second laser light source is arranged at a predetermined interval apart on the same line of the mount, and the exit port of each laser light source is inclined at a predetermined angle with respect to the horizontal direction And attach to the mount.

Hereinafter, a laser optical module structure and a method of adjusting an angle formed by a long axis of a pit and an optical spot according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The laser optical module structure improved according to the present invention is applicable to, for example, the optical pickup apparatus shown in FIG. Therefore, with reference to the optical pickup device of Figure 1 will be described a method of adjusting the angle between the laser optical module and the long axis of the pit and the light spot according to the present invention.

In the optical module according to the present invention, as shown in FIG. 6, a first laser light source 50 and a second laser light source 55 for irradiating light of different wavelengths are formed as a package, and the first and second lasers are packaged. The light sources 50 and 55 are each made of one chip and attached to the mount 60.

The first laser light source 50 and the second laser light source 55 are spaced apart at predetermined intervals on the same line of the mount 60, and each exit port 56 has a predetermined angle θ with respect to the horizontal direction. It is mounted to be inclined at. The interval between the first laser light source 50 and the second laser light source 55 is approximately (110 ± 2) μm, and the inclination angle θ of the exit port 56 is preferably about 45 degrees.

As described above, as the exit holes 56 of the first and second laser light sources 50 and 55 are disposed to be inclined at about 45 degrees with respect to the horizontal direction, the light exiting through the exit holes 56 is The long axis direction L of the laser (see FIG. 3B) has a shape inclined at 45 degrees. Therefore, when light emitted from the first and second laser light sources 50 and 55 forms on the disc, as shown in FIG. 7, the laser long axis L is formed along the disc track 61. ) Is inclined at an approximately 45 degree angle with respect to the arranged pit row direction (pit). Here, the track direction T and the pit row direction pit represent the same direction, and L represents the laser long axis direction.

On the other hand, the first and second laser light source 50, 55 is because the inclination of the exit port is changed only in each original position when compared with the conventional optical module is arranged when the light emitted from each laser light source is formed on the disk Only the long axis direction of the laser light is changed, and the position where the focus is achieved remains unchanged. Reference numeral 63 denotes a laser light spot emitted from the first laser light source 50 and formed on the disk, and 65a, 65b, and 65c are emitted from the second laser light source 55, divided into three beams, and then attached to the disk. The main light spot and the first and second side light spots are respectively shown.

Therefore, referring to FIG. 1, not only can the photodetector 23 which receives the light reflected from the disks 17 and 18 be used as it is, but also the laser long axis and the pit row by the structure of the optical module as described above. The angle formed by the direction can be easily adjusted as desired. In the present invention, the angle between the laser long axis and the pit means an acute angle between the laser long axis direction L shown in FIG. 3B and the pit row direction pit formed along the track, and is indicated by θ in FIG. 7.

When manufacturing the optical module according to the present invention, the groove (60) for mounting the first and second laser light source (50, 55) formed of a chip is formed in the mount (60). The groove 58 has a shape in which the first and second laser light sources 50 and 55 can be seated such that the exit port 56 is inclined at a predetermined angle θ. That is, when the first and second laser light sources 50 and 55 are inclined at a predetermined angle θ on the mount 60, the first and second laser light sources 50 and 55 are disposed. The groove 58 is formed to have a shape that can be stably supported. At this time, the first and second laser light source 50, 55 is installed so as to be located on the same line of the mount 60 so that only the direction of the laser long axis is changed, the position of the light spot on the disk does not change. desirable. In addition, the groove 58 is preferably formed so as to penetrate the laser light exit direction so as not to interfere with the laser light exit.

As described above, the laser optical module structure according to the present invention is improved so that the angle between the long axis and the pit of the laser can be easily adjusted, and thus the angle between the long axis and the pit of the laser is adjusted to form an angle of about 45 degrees, thereby reproducing signal characteristics. It is excellent and the response to a birefringent disc is improved.

In addition, the method of adjusting the long axis and the pit angle of the laser according to the present invention has the advantage that can be simply implemented by changing only the internal arrangement in the existing optical module structure.

Claims (4)

The first laser light source and the second laser light source for irradiating light of different wavelengths are arranged at predetermined intervals on the same line of the mount, and each laser exit port of the first and second laser light sources has a predetermined angle with respect to the horizontal direction. Laser light module, characterized in that mounted to be inclined to position. The method of claim 1, Wherein the exit holes of the first and second laser light sources are inclined at an angle of about 45 degrees with respect to the horizontal direction. In the method of adjusting the angle between the long axis of the laser light spot formed on the disk and the pit formed on the disk irradiated from the optical module formed by the package of the first laser light source and the second laser light source for irradiating light of different wavelengths, And arranging the first and second laser light sources at a predetermined interval apart on the same line of the mount, and attaching the first and second laser light sources to the mount such that the exit port of each laser light source is inclined at a predetermined angle with respect to the horizontal direction. The method of claim 3, And wherein the exit openings of the first and second laser light sources are inclined at an angle of approximately 45 degrees with respect to the horizontal direction.