KR20000003393A - Apparatus of controlling optical pick-up and method of the same - Google Patents

Abstract

PURPOSE: An apparatus of controlling an optical pick-up and a method of the same is provided to determine a reference optical line and to correct a combination of optical elements. CONSTITUTION: The apparatus of controlling the optical pick-up and the method of the same comprises the steps of providing a horizontal setting block and a vertical setting block, which is disposed to be perpendicular. setting a vertical optic path and a horizontal optic path using the horizontal setting block and the vertical setting block, mounting a pick-up base on the vertical and the horizontal setting block to dispose the center of a prism to be agreed with the cross section of the vertical optic path and the horizontal optic path and combining the optical pick-up to be agreed with the center of the vertical optic path and a center of a reference lens.

Description

Apparatus For Assembling / Aligning Optical Pickup And Methods Of Thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for optically accessing a recording medium. In particular, in assembling an optical component of an optical pickup, an optical pickup assembling / adjusting apparatus is set so that the optical components are assembled with their center aligned with the reference optical axis. And to a method.

In optical recording media such as CD and DVD, which have already been generalized as a recording medium using light, laser light is irradiated onto the recording layer to record or reproduce data. Such optical recording media are classified into read-only and rewritable media. In the former case, there are ROM types such as CD-ROM and DVD-ROM. In the latter case, WORM (Write Once Read Many) type and Rewritable type according to the number of rewritable times. , RAM type, etc. An optical disk drive apparatus for recording / reproducing information on such an optical recording medium is provided with an optical pickup for optically accessing the optical recording medium. In recent years, optical pick-up has been in the trend of being compatible so that different optical recording media can be accessed together. Therefore, the optical pickup requires a lot of optical parts and requires high precision during assembly. Fig. 1 schematically shows a CD / DVD combined optical pickup, wherein a CD / DVD combined optical pickup is a DVD laser diode (hereinafter referred to as "DVD LD") that generates a light beam having a wavelength of 635 to 650 nm. 2) a hologram module (hereinafter referred to as "CD HOM") 20 in which a CD laser diode (hereinafter referred to as "CD LD") and a CD photodetector incorporating a light beam having a wavelength of 780 nm are integrated. An objective lens 14 for focusing the light beam on the recording surface of the optical disc 1, a right angle mirror prizm (RAMP) 10 for guiding the light beam from the light source toward the objective lens 14, and a right angle The first and second beam splitters 4 and 6 positioned between the prism 10 and the light source, the collimating lens 12 positioned between the objective lens 14 and the right prism 10, and the right prism 10 and A λ / 4 plate 8 positioned between the second beam splitter 6 and a light beam reflected from the optical disc 1 positioned at the lower end of the first beam splitter 6. And a and a light detector 18 for the DVD to convert a signal term, the sensor lens 16 for focusing a light beam toward the light detector (18) for DVD. The right angle prism 10 is positioned between the light source and the objective lens 14 of the DVD LD 2 and the CD HOM 20 to receive the light beam generated from the DVD LD 2 or the CD HOM 20. The light beam reflected from the optical disc 1 is reflected toward the DVD photodetector 18 or the CD HOM 20. The first beam splitter 4 transmits the light beam from the DVD LD 2 toward the objective lens 14 and reflects the light beam reflected from the optical disk 1 toward the photodetector 18 for DVD. The second beam splitter 6 transmits the light beam generated from the CD LD toward the objective lens 14 and reflects the light beam reflected from the optical disk 1 toward the photodetector for the CD. The collimation lens 12 propagates the light beam generated from the DVD LD 2 or the CD LD in parallel toward the objective lens 14. The λ / 4 plate 8 serves to convert the polarization characteristics of the light beam generated from the DVD LD 2 or the CD LD. For example, the λ / 4 plate 8 converts the light beam having the linear flatness characteristic generated from the light source into circularly polarized light. can do. The optical pickup having such a configuration realizes miniaturization by accessing the disk 1 with light beams having different wavelengths with one objective lens 14 by folding the optical path using the right-angle prism 10. The combined optical pickup accesses a DVD, which is an infinite optical system, and a CD, which is a finite optical system, by means of one objective lens 14, and has an optical transfer function (hereinafter referred to as "OTF") and a modulation transfer function (hereinafter referred to as "Modulation Transfer Function"). Due to the deterioration of the MTF and the like, there is a problem such as a phase shift such as a phase transfer function, which requires high accuracy in setting, assembling, or adjusting the optical pickup. For example, if the distance between the collimation lens 12 and the collimation lens 12 does not match the design value, the light beam passing through the collimation lens 12 becomes a converging light instead of a parallel beam, and the OTF and the MTF are dropped to record / play back Instability, such as instability, has a significant adverse effect on optical performance. In addition, the optical pickup for combined DVD / CD uses a dichroic polarizing beam splitter (DPBS) as a beam splitter, so that a wavelength change / incident angle change / tilt occurs, and thus PTF dependence such as phase shift The larger the angle dependence of the beam splitter, the larger the tilt is caused.

FIG. 2 is a view showing a conventional optical pickup assembling / adjusting apparatus, which is a vertical laser 24 for setting a right angle prism 10 in parallel between a major axis and a minor axis 22, 22 '. And a horizontal laser 26 for setting the perpendicular prism 10 perpendicular to the optical disk. The major and minor axes 22 and 22 'serve to guide the optical pickup in the radial direction so that the optical pickup is linearly driven radially with respect to the optical disc, and also support the entire optical pickup. The optical pickup setting / adjustment method uses a vertical laser 24 and a horizontal laser 26 to adjust the position so that the right-angle prism 10 is perpendicular to the optical disc 1 and set the parallel position between the PUH axes 22. After that, the other parts needed for the optical system are assembled. Therefore, when assembling other optical parts, the assembly and adjustment are performed in a state that includes errors occurring during initial setting and adjustment of the optical pickup. However, since the optical pickup adjustment method as described above does not know the optical center of the rectangular prism 10, optical path differences (dL, dL ′) from the optical system to the collimating lens are generated depending on the position of the rectangular prism in the optical system. Since the light beam passing through the lens does not become parallel light and converges, the reflection and diffraction on the optical disk 1 do not work properly, and each part deteriorates OTF such as tilt, and the accurate signal cannot be read from the photodetector side. Will fall. The optical pick-up setting / adjustment method does not affect the performance in the optical system with the numerical aperture NA of 0.45 like the optical disc of the CD series, but in the optical system with the numerical aperture of 0.6 as the DVD such as the DVD. As the numerical aperture (NA) increases, optical performance becomes sensitive due to a two-, three-, and four-square relationship depending on the focal point, tilt, and distance. In addition, as the recording density becomes higher, the numerical aperture (NA) increases, and in order to stabilize recording and reproducing of the high density optical recording medium, high precision setting / adjustment is required during initial setting / adjustment of the optical pickup.

Accordingly, it is an object of the present invention to provide an optical pickup assembling / adjusting apparatus and method for improving the accuracy of horizontal and vertical degrees of an optical system.

1 is a view schematically showing a CD / DVD combined optical pickup.

2 is a view showing a conventional optical pickup assembly / adjustment device.

Figure 3 is a longitudinal cross-sectional view showing an optical pickup assembly / adjustment device according to an embodiment of the present invention.

4 is a view showing in detail the setting block shown in FIG.

5 is a view showing an optical pickup assembly / adjustment method according to an embodiment of the present invention.

6 is a view showing the trajectory of the light beam incident surface in the optical pickup assembly / adjustment method according to an embodiment of the present invention.

<Description of the reference numerals for the main parts of the drawings>

1: optical disc 2: laser diode for DVD

4,6 beam splitter 8 λ / 4 plate

10: right angle prism 12: collimation lens

14: objective lens 16: sensor lens

18: photodetector for DVD 20: hologram module

22: main axis 22 ′: minor axis

24,40: vertical laser 26,46: horizontal laser

32: vertical setting block 34: horizontal setting block

36: 5-axis stage 38: optical table

42: vertical laser stage 44: interference induction barrel

48: horizontal laser stage 50,52: target

In order to achieve the above object, the optical pickup assembly / adjustment device according to the present invention is a horizontal laser and vertical laser to form a horizontal optical axis and a vertical optical axis is mounted on the front surface of the interference pattern forming member for forming an interference fringe pattern, and optical The parts are assembled and provided with a setting block for providing a reference plane for the horizontal optical axis and the vertical optical axis, and supporting means for supporting the setting block.

The optical pickup assembly / adjustment method according to the present invention comprises the steps of providing a horizontal / vertical setting block making a right angle to each other, setting a vertical light path and a horizontal light path using a horizontal / vertical setting block, and a vertical light path And mounting the pickup base on the horizontal / vertical setting block such that the center of the perpendicular prism coincides with the intersection point of the optical path and the horizontal light path, and assembling the center of the vertical light path and the center of the collimating lens. It is done.

Other objects and advantages of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 to 6.

Figure 3 is a longitudinal cross-sectional view showing an optical pickup assembly / adjustment device according to an embodiment of the present invention.

The optical pickup assembly / adjustment device according to the present invention in the configuration of FIG. 3 includes a vertical setting block 32 forming a vertical reference plane, a horizontal setting block 34 forming a horizontal reference plane, a vertical setting block 32 and 5-axis stage 36 for supporting the horizontal setting block 34 to be driven in the 5-axis direction, vertical laser 40 for measuring the perpendicularity of the right-angle prism 10, and setting the vertical path of the optical axis. An interference inducing barrel 44, a horizontal laser 46 for measuring the horizontality of the rectangular prism 10, and a first target 50 for setting the horizontal path of the optical axis. The optical pickup assembly / adjustment device according to the present invention includes a vertical laser stage 42 supporting the vertical laser 46, a horizontal laser stage 48 supporting the horizontal laser 46, and a 5-axis stage 36. And an optical table 38 for supporting the vertical laser stage 42 and the horizontal laser stage 48. The vertical and horizontal setting blocks 32 and 34 are assembled to be perpendicular to each other by a three-dimensional measuring device as shown in FIG. The vertical setting block 32 supports optical components constituting an optical system between the major and minor axes 22 and 22 'and the major and minor axes 22 and 22'. Here, the surface formed by the major and minor axes 22 and 22 'is parallel to the vertical setting block 32. The 5-axis stage 36 serves to support the vertical and horizontal setting blocks 32 and 34 to be driven in the 5-axis direction in the X, Y, Z, tilt, and rotation directions as shown in FIG. 5. The right angle prism 10 is installed at a position that reflects the light beam incident from the vertical laser 40 (or the horizontal laser) on the vertical setting block 32 toward the horizontal laser 46 (or the vertical laser). The vertical laser 40 is mounted on the vertical laser stage 42 to be perpendicular to the vertical setting block 32 and to be perpendicular to the optical table 38. An interference inducing barrel 44 is provided at the front end of the vertical laser 40 on the vertical optical axis. The interference inducing barrel 44 is provided with a second target 52 which forms an interference fringe pattern. The second target 52 forms an interference fringe pattern having a concentric shape according to the tilt angle of the light beam incident on the second target 52 so that the vertical path of the optical axis is set. The horizontal laser 46 is mounted on the horizontal laser stage 48 to be perpendicular to the horizontal setting block 34 and to be horizontal to the optical table 38. In front of the horizontal laser 46 on the horizontal optical axis, a first target 50 for setting the horizontal path of the optical axis is provided by forming an interference fringe pattern having a concentric shape according to the incident angle of the light beam incident on the horizontal laser 46. These first and second targets 50 and 52 are composed of an iris for extending and contracting the effective diameter of the incident light beam and a beam extender for sharpening the contrast of the formed interference fringe pattern.

The setting and assembly procedure of the optical pickup is as follows. This will be described with reference to FIGS. 5 and 6.

First, the vertical and horizontal setting blocks 32 and 34 are perpendicular to each other by a 3D measuring instrument, and then the vertical and horizontal setting blocks 32 and 34 are mounted on the 5-axis stage 36. Then, after installing the reflection mirror on the surface of the vertical setting block 32 on the vertical optical axis, the vertical laser 40 is operated so that the light beam reflected from the reflection mirror is incident on the center of the vertical laser 40. The tilt is adjusted so that is perpendicular to the vertical setting block 32. Then, the reflective mirror is removed and the horizontal laser 46 is operated so that the light beam irradiated from the horizontal laser 46 is directed toward the vertical reference plane of the horizontal setting block 34 so that the light beam reflected from the vertical reference plane is the center of the horizontal laser 46. Adjust the horizontal laser 46 to be incident on. At this time, the horizontal laser 46 can be adjusted by adjusting the tilt of the block using the horizontal laser stage 48. Then, the 5 axis stage 36 is used to adjust the Z axis of the vertical setting block 32 so that the light beam irradiated from the vertical laser 40 or the horizontal laser 46 is irradiated to the center of the main axis 22. . When one of the vertical laser 40 and the horizontal laser 46 is operated to irradiate the light beam to the main axis 22, the light beam reflected from the main axis 22 forms 90 ° from the center of the main axis 22 as shown in FIG. 6. It becomes the plane of. Referring to FIG. 6, the light beam irradiated from the horizontal laser 46 is reflected at one point of the main axis 22 to become one plane in the entire space on the Z plane including the trajectory of the incident light. Therefore, the light beam irradiated on the main axis 22 passes through the centers of the vertical / horizontal lasers 40 and 46 and the right angle prism 10 and passes through three centers at the same time. In this way, the setting of the vertical laser 40, the horizontal laser 46 and the vertical / horizontal setting blocks 32 and 34 is completed. After marking the center of the vertical laser 40 formed on the optical table 38 with reference to the center of the interference fringe, the right angle prism is formed at the intersection of the horizontal light path and the vertical light path in the vertical setting block 32. 10) Insert the pickup base 100 so that the center of the target coincides, and mount the collimation lens 12 on the pickup base 100. Then, the center of the vertical laser 40 and the center of the interference pattern of the collimating lens 12 are aligned. The 5-axis stage 36 is adjusted to X, Y plane direction. The Z axis is adjusted in the 5-axis stage 36 so that the optical axis center and the setting center coincide with each other so that the photodetector hole center coincides with the horizontal laser 46. Finally, each light component is assembled to the pickup base 100 one by one so that the center of the reflected light beam reflected from each optical component coincides with the optical axis center of the light beam emitted from the horizontal laser 46 or the vertical laser 40. The parts are assembled to the pickup base 100.

As described above, according to the optical pickup assembly / adjustment apparatus and method of the present invention, it is possible to know the exact center of the right-angle prism on the vertical / horizontal optical path, thereby improving the accuracy of horizontal and vertical degrees. Optical components are assembled / adjusted at distance.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

A horizontal laser and a vertical laser each having an interference pattern forming member for forming an interference pattern pattern to be mounted on the front surface to form a horizontal optical axis and a vertical optical axis, respectively; A setting block for assembling the optical parts and providing a reference plane for the horizontal and vertical optical axes, And an supporting means for supporting the setting block. The method of claim 1, The support means includes a five-axis support means that the setting block is supported to be movable in the five axis direction, Vertical laser support means for supporting the vertical laser at a constant height in the vertical direction in the setting block; And a horizontal laser support means for rotatably supporting the horizontal laser at a constant distance in the horizontal direction from the setting block. The method of claim 1, The interference fringe forming member includes an iris for expanding and contracting an effective diameter of an incident light beam; And a beam expander for sharpening the interference fringe pattern. Preparing a horizontal / vertical setting block perpendicular to each other; Setting a vertical light path and a horizontal light path using the horizontal / vertical setting block; Mounting a pickup base on the horizontal / vertical setting block such that the center of the perpendicular prism coincides with the intersection of the vertical light path and the horizontal light path; And assembling the center of the vertical optical path and the center of the collimating lens to coincide with each other. The method of claim 4, wherein The vertical optical path is set in accordance with the interference pattern of the reflected light beam by mounting a reflection mirror on the horizontal / vertical setting block on the vertical optical path and irradiating a vertical light beam on the reflection mirror. How to adjust. The method of claim 4, wherein And the horizontal light path is set according to an interference fringe pattern of the reflected light beam by irradiating a light beam on a vertical reference plane of the horizontal / vertical setting block.