This application claims the benefit of Korean Patent Application No. 2004-49706, filed on Jun. 29, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical pickup and an apparatus for and a method of assembling a lens.
2. Description of the Related Art
In an optical recording and/or reproducing apparatus for recording arbitrary information on an optical information storage medium and/or reproducing the information recorded on the optical information storage medium using a light spot obtained by condensing laser light using an objective lens, a recording capacity is determined by a size of the light spot condensed by the objective lens. The condensed spot size S is given by Equation 1 with a wavelength λ of the laser light used and a numerical aperture (NA) of the objective lens.
S∝λ/NA (1)
Therefore, to reduce the light spot size focused onto the optical information storage medium for a high density of the optical information storage medium, research on an optical recording and/or reproducing apparatus is being conducted in a direction that adopts a light source of a short wavelength such as a blue laser and an objective lens having NA of more than 0.6.
Intensive research for increasing information storage capacity by increasing a recording density has been made since a compact disc (CD), where recording and/or reproducing of information is performed using light of a wavelength of 780 nm and an objective lens having an NA of 0.45 or 0.5, was introduced. As a result of the research, a digital versatile disc (DVD), where recording and/or reproducing of information is performed using light of a wavelength of 650 nm and an objective lens having an NA of 0.6 or 0.65, has been developed.
Currently, research on a high-density optical information storage medium having a recoding capacity of more than 20 giga bytes (GB) using light of a blue wavelength, e.g., a wavelength of 405 nm is constantly carried out.
Standardization of the high-density optical information storage medium is being actively carried out and part of the standards whose development has been almost completed, uses light of a blue wavelength, e.g., a wavelength of 405 nm. At this point, the NA of the objective lens for the high-density optical information storage medium is 0.65 or 0.85 as described below.
A thickness of the CD is 1.2 mm. The reason why a thickness has been reduced to 0.6 mm in for the DVD is that since the NA has been raised from 0.45 for the CD to 0.6 for the DVD, a tilt tolerance of the optical information storage medium should be secured.
Further, if the NA of the objective lens for the high-density optical information storage medium is raised to 0.85 in case of the high-density optical information storage medium having a large capacity greater than the DVD, a thickness of the high-density optical information storage medium should be reduced to about 0.1 mm.
For a medium such that the NA of the objective lens is raised and the thickness of the optical information storage medium is made thin, there exists a Blu-ray disc (referred to as BD hereinafter). In a BD standard, a wavelength of a light source is 405 nm, an NA of the objective lens is 0.85, and a thickness of the optical information storage medium is about 0.1 mm.
For a high-density optical information storage medium currently under development, there exists a high definition digital versatile disc (HD DVD) besides the BD. An HD DVD standard is a standard such that a substrate thickness is the same as the DVD, the NA of the objective lens is the same as the DVD, but a wavelength of the light source is a blue wavelength, e.g., 405 nm as is in the BD standard.
What is problematic in developing an optical disc of a new standard is a compatibility with a conventional optical disc.
To perform recording/reproducing using optical discs having different recording densities in a compatible manner, a working distance (WD) of the objective lens focusing a light spot onto the optical disc should be different, so that at least two objective lenses need to be provided.
An actuator for an optical pickup includes a magnetic circuit so as to operate in both focus and track directions. The magnetic circuit maintains constant an interval between the optical disc and the objective lens in the focus direction and moves the objective lens to a desired track position (track center) in the track direction.
A compatible optical pickup adopting a plurality of optical discs having different recording densities requires objective lenses that correspond to the plurality of optical discs having the different recording densities, respectively.
Therefore, at least two objective lenses are arranged in a radial direction of the optical disc in a single lens holder so that compatibility may be secured.
In case of the optical pickup where only one objective lens is mounted in the lens holder of a moving unit of the actuator, the objective lens is assembled to the lens holder and then an alignment between the objective lens and an optical axis is accurately obtained using an actuator skew supported by a mold of the lens holder. In case of mounting two objective lenses in the lens holder, since only an alignment between one of the two objective lenses and an optical axis can be obtained using the actuator skew and a tilt allowance angle between the two objective lenses should be strictly limited, there is a possibility that an optical pickup performance cannot be secured.
A Japanese patent publication No. 10-11765 discloses an optical disc apparatus having an adjusting device adjusting an inclination of an objective lens so that central axes of two objective lenses may be parallel. In case of the Japanese patent publication, the objective lens to be adjusted is mounted in a separate lens housing and the lens housing is inclination-adjusted with respect to a lens holder, so that an inclination adjustment between the two objective lenses may be performed.
However, since the separate lens housing should be mounted according to the Japanese patent publication, a lens holder structure having no limitations in a space for adjusting an inclination is required and a lens housing part should be added separately to a conventional lens holder part. Further, a number of assembling processes is increased and a number of the assembly parts is increased.
An aspect of the present invention provides an optical pickup, a method of lens alignment and an apparatus for adjusting relative inclinations of a plurality of objective lenses without increase in a number of parts or in a number of separate assembly processes.
According to an aspect of the present invention, an optical pickup includes: a plurality of objective lenses; a lens holder having a plurality of installation holes for receiving the plurality of objective lenses and having a seat surface of at least one of the installation holes formed as a curved surface so that an inclination adjustment of the objective lens installed in the curved seat surface can be performed.
The seat surface may be formed as a spherical surface.
An inner diameter or an outer diameter of the seat surface may be at least 0.05 mm smaller or 0.05 mm greater, respectively, than a medium position of the seat surface.
The outer diameter of the seat surface may be at least 0.05 mm greater than an outer diameter of the objective lens.
The plurality of objective lenses may include a first objective lens appropriate for a BD; a second objective lens appropriate for a HD DVD, a DVD, or a CD.
Further, the plurality of objective lenses may include a first objective lens appropriate for at least one of a BD or an HD DVD and a second objective lens appropriate for at least one of a DVD and a CD.
According to another aspect of the present invention, an objective lens assembling apparatus, for assembling a plurality of objective lenses in a plurality of installation holes of the lens holder of the above-described optical pickup so that central axes of the objective lenses are parallel to one another, includes: a mount having a seat part on which the lens holder where the objective lenses are respectively inserted into the plurality of installation holes is seated; a plurality of lens jigs pressing the plurality of objective lenses respectively installed into the installation holes; an inclination adjustment device adjusting an inclination of the objective lens inserted into the installation hole having the curved seat surface using the lens jig; a laser light illumination unit setting a reference point and illuminating laser light for aligning central axes of the objective lenses with respect to the reference point; and a base on which the mount, the plurality of lens jigs, the inclination adjustment device are mounted.
One of the installation holes formed on the lens holder may be formed to have a non-curved seat surface, a reference point may be set by using laser light illuminated onto the objective lens inserted into the installation hole having the non-curved seat surface, and a central axis of the remaining objective lenses may be aligned with the reference point.
All of the plurality of installation holes may be formed to have curved seat surfaces, a reference point may be set by using laser light illuminated onto a predetermined position of the lens holder, and central axes of a plurality of objective lenses installed in the plurality of installation holes may be aligned with the reference point.
A linear movement device changing a position on which the laser light is illuminated may be further provided.
The linear movement device may be installed at the base so as to change a position on which laser light is illuminated by moving the mount.
The objective lens assembling apparatus may further comprise at least one of an X-stage, a Y-stage, or an X-Y stage matching a center of at least one objective lens with a center of a respective opening in the lens holder by moving the objective lens with respect to the center of the installation hole of the lens holder after relative inclination adjustment between the plurality of objective lenses.
The inclination adjustment device may include a gonio stage.
A front end of the lens jig pressing the objective lens may be formed to expose a partial portion of an outer periphery of the objective lens so that the light illuminated to the objective lens from the laser light illumination unit may be reflected by the partial portion of the outer partial periphery of the objective lens.
A front end of the lens jig may be formed such as to expose at least three regions of the outer periphery of the objective lens.
According to another aspect of the present invention, a method of assembling a plurality of objective lenses in a plurality of installation holes of the lens holder of an optical pickup, so that central axes of the objective lenses may be parallel, includes: configuring the lens holder such that a seat surface of at least one of the plurality of installation holes is formed as a curved surface to adjust an inclination of an objective lens installed in the installation hole having the curved seat surface and another installation hole has a non-curved seat surface; seating the lens holder in which the objective lenses are respectively inserted into the plurality of installation holes on a seat part of a mount; pressing and fixing a reference objective lens inserted into the installation hole having the non-curved seat surface using one lens jig; illuminating laser light onto the reference objective lens to set a reference point on a target; illuminating the laser light onto an objective lens inserted into an installation hole having the curved seat surface and pressurized with another lens jig; comparing an optical path of light reflected by the objective lens inserted in the installation hole having the curved seat surface with the reference point on the target; and adjusting an inclination of the objective lens inserted in the curved seat so that central axes of the reference objective lens and the objective lens inserted in the curved seat are in parallel, using an inclination adjustment device.
The method may further include matching a center of at least one of the objective lenses with the center of a respective installation hole in the lens holder by moving the objective lens with respect to the center of the respective installation hole in lens holder after a relative inclination adjustment between the plurality of objective lenses.
According to another aspect of the present invention, a method of assembling a plurality of objective lenses in a plurality of installation holes of the lens holder of the optical pickup so that central axes of the objective lenses may be in parallel includes: configuring the lens holder such that a seat surface of the each of a plurality of installation holes is formed as a curved surface to adjust an inclination of an objective lens installed in a respective installation hole; seating the lens holder on a seat of a mount, pressing the respective objective lenses into respective installation holes using lens jigs; illuminating laser light onto a predetermined position of the lens holder to set a reference point on a target; illuminating the laser light onto the respective objective lenses; comparing an optical path of light reflected by each objective lens with the reference point on the target; and adjusting an inclination of each objective lens so that central axes of the respective objective lenses may be aligned, using an inclination adjustment device.
The method may further include matching a center of at least one of the objective lenses with the center of the respective installation hole of the lens holder by moving the objective lens with respect to the center of the installation hole of the lens holder after a relative inclination adjustment between the plurality of objective lenses.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The above and/or other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
Referring to
The first and second objective lenses 45 and 41 have different specifications. For example, the first objective lens 45 may be formed to have a high NA, e.g., about 0.85 for the BD (Blu-ray Disc) and optimized in recording and/or reproducing the BD whose thickness is about 0.1 mm using light having a blue wavelength region, e.g., a wavelength of 405 nm The second objective lens 41 may be optimized for recording and/or reproducing at least one of the HD DVD, the DVD, and the CD.
For example, the first objective lens 45 may be formed to have an NA of about 0.85 and optimized in recording and/or reproducing the BD whose thickness is about 0.1 mm using light having a wavelength of 405 nm and the second objective lens 41 may be formed to have an NA of about 0.65 and optimized for recording and/or reproducing the HD DVD whose thickness is about 0.6 mm using light having a wavelength of 405 nm.
Further, the first objective lens 45 may be formed to be appropriate for recording and/or reproducing the HD DVD or the BD and the HD DVD, and the second objective lens 41 may be formed to be appropriate for recording and/or reproducing at least one of the DVD and the CD in a compatible manner.
A seat surface of at least one installation hole of the first and second installation holes 55 and 57 may be formed as a curved surface, such as for example, a spherical surface so that an inclination of the objective lens installed therein can be adjusted.
Where the seat surface 55a is formed as a spherical surface, a middle position of the spherical surface in the seat surface 55a of the first installation hole 55 line-contacts an outer edge of a bottom (reference plane) on an outer periphery of the first objective lens 45. The line-contact position may deviate slightly from the middle position of the spherical surface depending on an inclination adjustment of the first objective lens 45. An inner diameter or an outer diameter of the seat surface 55a may be at least 0.05 mm smaller or greater, respectively, than the middle position of the spherical surface.
Further, the outer diameter of the seat surface 55a may coincide with an outer diameter of the first installation hole 55 of the lens holder 50 supporting an outer periphery of the first objective lens 45 and may be at least 0.05 mm greater than an outer diameter of the first objective lens 45.
Where the lens holder 50 is formed as illustrated in
With the first and second objective lenses 45 and 41 inserted into and seated on the first and second installation holes 55 and 57, respectively, the second objective lens 41 is fixed. After that, an inclination of the first objective lens 45 is adjusted so that a central axis of the first objective lens 45 is parallel with a central axis of the second objective lens 41 using the second objective lens 41 as a reference. Since the seat surface 55a of the first installation hole 55 is a curved surface, if the first objective lens 45 is pressed so that force applied to at least one point on an outer periphery of the first objective lens 45 is different from force applied to other points, the first objective lens 45 slides a little along the curved surface, whereby the inclination is adjusted. During the adjustment, when the central axis of the first objective lens 45 becomes parallel with the central axis of the second objective lens 41, the first objective lens 45 is fixed. The first and second objective lenses 45 and 41 may be fixed with an adhesive.
Alternatively, the seat surface 55a of the first installation hole 55 may be formed as a plane and the seat surface 57a of the second installation hole 57 may be formed as a curved surface, so that a relative inclination of the second objective lens 41 is adjustable with respect to the first objective lens 45 so that the central axes thereof are parallel.
Further, referring to
As described above, since the optical pickup according to an aspect of the present invention has the lens holder 50 or 50-1 such that the seat surface of at least one installation hole of the first and second installation holes 55 and 57 in which the first and second objective lenses 45 and 41 are inserted is formed in a curved plane, the first and second objective lenses 45 and 41 may be assembled to the lens holder 50 or 50-1 so that the relative inclination is not generated between the central axes of the assembled lenses 45 and 41.
The first and second objective lenses 45 and 41 may be assembled to the lens holder 50 or 50-1 without a relative inclination between the central axes of the lenses 45 and 41 in the above-described optical pickup using a lens assembling apparatus that is described below.
As described above, the optical pickup according to an aspect of the present invention includes a plurality of objective lenses mounted in the single lens holder such that a curved seat surface is formed in at least one installation hole so as to perform inclination adjustment. Other optical construction and construction of the actuator may be modified in various ways.
Referring to
The optical unit 5, for example, may comprise: first and second optical units 10 and 20 emitting first and second lights 11a and 21a, respectively, of wavelengths appropriate for the high-density optical disc and the DVD and receiving the first and second light 11a and 21a returning after being reflected by the optical disc 1 (
With the above construction, the optical pickup according to an aspect of the present invention may adopt the high-density optical disc and the DVD in a compatible manner.
The optical unit 5 may further comprise: a third optical unit 30 emitting third light 31a of a wavelength appropriate for a CD and receiving the third light 31a returning after being reflected by the optical disc 1 (
With the above construction, the optical pickup can compatibly adopt the CD, the high-density optical disc, and the DVD.
Referring to
The detection lens 16 may be an astigmatism lens generating an astigmatism for the incident first light 11a to allow a focus error signal by an astigmatism method to be detected.
In order to control an optical power of the blue light source 11, the optical unit 10 may further comprise a monitoring photodetector 26, detecting the first light 11a emitted from the first source 11 and partially reflected by the polarizing beam splitter 13. Further, the first optical unit 10 may further comprise a condensing lens 14 condensing the first light 11a reflected by the polarizing beam splitter 13 to allow the light to be properly gathered to the monitoring photodetector 26.
For the second optical unit 20, a holographic optical module for a red wavelength, e.g., a wavelength of 650 nm appropriate for the DVD may be provided.
Further, for the third optical unit 30, a holographic optical module for a near infrared wavelength, e.g., a wavelength of 780 nm appropriate for the CD may be provided.
A typical holographic optical module includes: a light source emitting light of a predetermined wavelength, e.g., a wavelength of 650 nm or 780 nm; a photodetector arranged on one side of the light source to receive light returning after being reflected by the optical disc 1 and to detect an information signal and/or an error signal; a hologram optical element transmitting in a straight manner most of the light incident from the light source and diffracting by +1 or −1 degree the light returning back by being reflected from the optical disc 1 to direct the diffracted light to the photodetector. The holographic optical module may further include a grating generating a sub-beam so as to detect a tracking error signal using, for example, a differential push-pull method.
Where the grating is provided, the photodetector of the holographic optical module has a structure for detecting a tracking error signal using the differential push-pull method.
Like the case of the first optical unit 10, the second and the third optical units 20 and 30 may have an optical construction where the light source and the photodetector are separated, instead of having a construction of the holographic optical module.
Further, the first optical unit 10 may have a holographic optical module for a blue wavelength, e.g., a wavelength of 405 nm intended for a high-density optical disc.
The first optical path changer 25 is arranged between the second and the third optical units 20 and 30 and the second objective lens 41 to direct the second and the third lights 21a and 31a incident from the second and the third optical units 20 and 30 to the second objective lens 41 and allow the second and the third lights 21a and 31a returning after being reflected by the optical disc 1 to return to the second and third optical units 20 and 30. The first optical path changer 25 may be a plate-type beam splitter having a mirror plane that transmits the second light 21a and total-reflects the third light 31a.
The first collimating lens 18 is arranged between the first optical unit 10 and the first objective lens 45 to change the first light 11a incident in a form of diverging light from the first optical unit 10 into parallel light to allow the light to be incident to the first objective lens 45.
Where the first collimating lens 18 changing the first light 11a into the parallel light is provided as described above, the first objective lens 45 is designed to be optimized for the first light 11a which is the parallel light.
The second collimating lens 23 is arranged between the second optical unit 20 and the first optical path changer 25. The second collimating lens 23 changes the second light 21a incident in form of diverging light from the second optical unit 20 into the parallel light.
The third collimating lens 33 is arranged between the third optical unit 30 and the first optical path changer 25. The third collimating lens 33 changes the third light 31a incident in form of diverging light from the third optical unit 30 into the parallel light.
In the above, although description has been made for a case where the optical pickup has the first through the third collimating lenses 18, 23, and 33 to allow the parallel light to be incident to the first and second objective lenses 45 and 41, the optical pickup may not have at least one of the first through the third collimating lenses 18, 23, and 33 or can allow a little converging or diverging light to be incident to the first and/or the second objective lenses 45 and 41 so that the optical system for at least one of the high-density optical disc, the DVD, and the CD may be a finite optical system.
The optical unit 5 may further include the monitoring photodetector 27 for monitoring optical output quantity of the second and/or the third optical units 20 and 30 on one side of the first optical path changer 25.
The first objective lens 45 may be formed to generate an optimized light spot for recording and/or reproducing the high-density optical disc having the highest density among the high-density optical disc, the DVD, and the CD.
For example, where the first light source 11 emits the first light 11a of a bluish-purple wavelength, e.g., a wavelength of 405 nm and the high-density optical disc has a thickness of 0.1 mm, i.e. the optical disc is the BD, the first objective lens 45 may have a high NA of 0.85. Here, the high-density optical disc is the HD DVD, the first objective lens 45 may have an NA of 0.65.
The second objective lens 45 may be formed to generate an optimized light spot for recording and/or reproducing the low-density optical disc, i.e., the DVD and/or the CD.
That is, where the optical pickup adopts the CD compatibly as well as the high-density optical disc and the DVD as illustrated in
Further, where the optical pickup is of a high-density optical disc and DVD-compatible type, the second objective lens 41 may be optimized for the DVD.
Further, where the optical pickup is of a BD and HD DVD-compatible type, the first objective lens 45 may be optimized for the BD and the second objective lens 41 may be optimized for the HD DVD.
The actuator 40 may be a single actuator structure mounting the first and second objective lenses 45 and 41 to the single lens holder 50 or 50-1.
The actuator 40 includes: a base (not shown) where a holder (not shown) is fixedly installed; the single lens holder 50 or 50-1 in which the first and second objective lenses 45 and 41 are installed; a plurality of suspensions (not shown) whose one end (not shown) is fixedly combined to the lens holder 50 or 50-1 and whose other end (not shown) is fixedly combined to the holder (not shown), and movably supporting the lens holder 50 and 50-1; and a magnetic circuit (not shown) operating the lens holder 50 and 50-1 to a focus direction, a track and/or tilt directions.
Except for the first and second objective lenses 45 and 41, the remaining optical parts are arranged on the base. Further, part of the magnetic circuit, for example, coils are installed in the lens holder 50 or 50-1 and the remaining magnetic parts, i.e., a magnet and yokes are arranged on the base. The lens holder 50 or 50-1, the first and second objective lenses 45 and 41, and the part of the magnetic circuit installed in the lens holder 50 or 50-1 constitute a moving unit of the optical pickup assembly.
Hereinafter, a detailed embodiment of an objective lens assembling apparatus and a method therefor, assembling the plurality of objective lenses 45 and 41 to the lens holder 50 or 50-1 of the optical pickup without the relative inclination between the objective lenses 45 and 41 will be described.
Referring to
Except for the laser light illuminating unit, i.e., the lens fixing jig 210, the lens adjustment jig 200, the inclination adjustment device 140, the mount 150, the remaining elements are all mounted on the base 100. Of course, the laser light illumination unit may also be installed on the mount 100.
As described above with reference to
Referring now to
During the lens assembling process, a bottom portion of an outer peripheral part of the second objective lens 41 is fixed closely to the seat surface 57a of the second installation hole 57 and the fixed state is maintained.
The lens adjustment jig 200 is configured such that one side of the lens adjustment jig is combined to the inclination adjustment device 140 and a front end 201 of the lens adjustment jig 200 pressurizes the first objective lens 45 inserted into the first installation hole 55 of the lens holder 50 by spring force. The first installation hole 55 has the seat surface 55a formed as a curved surface.
The lens adjustment jig 200 is adjusted by the inclination adjustment device 140, whereby forces pressing various portions of the first objective lens 45 are varied and thus the first objective lens 45 slides along the curved seat surface 55a to adjust the inclination of the first objective lens 45.
The front ends 201 and 211 of the lens adjustment jig 200 and the lens fixing jig 210, pressing the first and second objective lenses 45 and 41 are formed such as to expose peripheral regions (45a, 41a) of the first and second objective lenses 45 and 41 as shown in
The front ends 201 and 211 of the lens adjustment jig 200 and the lens fixing jig 210 are formed such as to expose at least three peripheral regions (41a, 45a) of the first and second objective lenses 45 and 41 so that the front ends 201 and 211 may press the first and second objective lenses 45 and 41 using relatively uniform force.
For the inclination adjustment device 140, a gonio stage may be provided. The inclination adjustment device 140 is configured such that the lens adjustment jig 200 is rotated within a predetermined angle range so that pressure applied to the first objective lens 45 by the lens adjustment jig 200 may be varied depending on the position and accordingly the first objective lens 45 slides a little along the curved seat surface 55a of the first installation hole 55 so that inclination of the first objective lens may be adjusted.
The laser light illumination unit includes: a laser light source 230 emitting laser light; and a reflection mirror device 240 reflecting laser light emitted from the laser light source 230 to a lower direction to direct the laser light to the lens holder 50 mounted on the mount 150.
The laser light emitted from the laser light source 230 is bent about 90 degree in by the reflection mirror device 240 and progresses to the lens holder 50 positioned in a lower direction. The laser light is illuminated onto one of the lens holder 50, the first objective lens 45, and the second objective lens 41 and the light reflected by one of them is reflected again by the reflection mirror device 240 and returns back to the laser light source 230.
A target 245 such as a section paper may be placed in front of the laser light source 230 in order to check a position of the light that has returned back to the laser light source 230. The target 245 is used in setting the reference point before the lens inclination adjustment. If an inclination of a lens is adjusted so that a path of light reflected by the lens to be adjusted (the first lens 45 in the present embodiment) coincides with the reference point on the target 245, the central axes of the first and second objective lenses 45 and 41 may be made in parallel to each other.
In the present embodiment, the laser light is illuminated onto the second objective lens 41 and the laser light reflected by the second objective lens 41 passes through the target 245. The position on the target where the laser light passes through is used for the reference point. After that, the position to which the laser light is illuminated is horizontally moved, the laser light is illuminated onto the first objective lens 45, and it is confirmed whether the laser light reflected from the first objective lens 45 passes through the reference point on the target. If the laser light does not pass through the reference point, the inclination of the first objective lens 45 is adjusted by rotating the lens adjustment jig 200 using the inclination adjustment device 140 until the laser light passes through the reference point on the target 245. When the laser light passes through the reference point on the target 245, the central axis of the first objective lens 45 becomes parallel with the central axis of the second objective lens 41.
The objective lens assembling apparatus may further include a linear movement device 110, i.e., a linear stage linearly moving the position to which the laser light is illuminated.
As shown in
The objective lens assembling apparatus may further include: the X-stage and/or the Y-stage 120 and 130 performing an operation of matching a center of the first objective lens 45 with an opening's center of the lens holder 50 by moving the first objective lens 45 with respect to the opening's center of the first installation hole 55 of the lens holder 50 after relative inclination adjustment between the plurality of objective lenses. In
The objective lens assembling apparatus may further include the X and/or Y stages mounting the lens fixing jig 210 so as to perform an operation of matching the central axis of the second objective lens 41 with the center of the opening of the second installation hole 57. In that case, the X and/or Y stages are mounted on the linear movement device 110 and the lens fixing jig 210 is installed on the X and/or the Y stages. Since the arrangement may be sufficiently inferred from the above description with reference to FIGS. 5 to 6, detailed description thereof will be omitted.
Hereinafter, a process of assembling the first and second objective lenses 45 and 41 in the lens holder using the objective lens assembling apparatus according to an aspect of the present invention described above will be described.
First, the lens holder 50 is seated on the seat part 151 of the mount 150. The second objective lens 41 is inserted into the second installation hole 57 having the non-curved seat surface 57a and pressed using the lens fixing jig 210 so that the second objective lens 41 is maintained in a fixed state. The first objective lens 45 is inserted into the first installation hole 55 having the curved seat surface 55a and pressed using the lens adjustment jig 200.
The laser light is illuminated onto the second objective lens 41 to set a reference point on the target 245.
The linear movement device 110 is operated so that the laser light is illuminated onto the first objective lens 45 and a path of the light reflected by the first objective lens 45 is compared with the reference point on the target 245. If the path of the reflected light from the first objective lens is different from the reference point on the target 245 as a result of comparison, the inclination of the first objective lens 45 is adjusted by incrementally rotating the lens adjustment jig 200 using the inclination adjustment device 140 until the path of the light reflected by the first objective lens 45 coincides with the reference point on the target 245. By the above operation, the central axis of the first objective lens 45 may be made parallel with the central axis of the second objective lens 41.
After the relative inclination adjustment between the first and second objective lenses 45 and 41, the X and/or the Y stages 120 and 130 are adjusted so that the lens adjustment jig 200 is moved within a horizontal plane. By this operation, the first objective lens 45 pressed by the lens adjustment jig 200 is moved with respect to the center of the first installation hole 55. The adjustment by the X and/or the Y stages is performed until the center of the first objective lens 45 coincides with the center of the first installation hole 55.
Where the X and/or the Y stages mounting the lens fixing jig 210 are provided, it is possible to match the center of the second objective lens 41 with the center of the second installation hole 57 through adjustment of the X and/or the Y stages.
In described above, although description and illustrating have been made taking, as an example, the objective lens assembling apparatus appropriate where the lens holder 50 of the optical pickup according to an aspect of the present invention has the construction of
Referring to
Referring to
The lens holder 50-1 is seated on the seat part 151 of the mount 150. The first and second objective lenses 45 and 41 are inserted and pressed using the lens adjustment jigs 200, respectively.
After that, the laser light is illuminated onto a predetermined position of the lens holder 50-1 so that the reference point on the target 245 may be set.
Next, the linear movement device 110 is operated so that the laser light is illuminated onto the second objective lens 41 and the inclination of the second objective lens 41 is adjusted until the path of the light reflected by the second objective lens 41 coincides with the reference point on the target 245.
Then, the linear movement device 110 is operated so that the laser light is illuminated onto the first objective lens 45 and the inclination of the first objective lens 45 is adjusted until the path of the light reflected by the first objective lens 45 coincides with the reference point on the target 245. By the above operation, the central axis of the first objective lens 45 becomes parallel with the central axis of the second objective lens 41.
In addition, after relative inclination adjustment between the first and second objective lenses 45 and 41, the first and second objective lenses 45 and 41 are moved with respect to the respective centers of the first and second installation holes 55 and 57 of the lens holder 50-1, whereby the centers of the first objective lens 45 and the second objective lens 41 are matched with the centers of the first and second installation holes 55 and 57, respectively.
Referring to
The optical pickup 300 includes an optical system having the first and second objective lenses 45 and 41 condensing light emitted from a light source to the optical disc; and an optical pickup actuator driving the first and second objective lenses 45 and 41. For the optical pickup, the above-described optical pickup is provided.
The light reflected by the optical disc 1 is detected by a photodetector provided in the optical pickup 300 and photoelectric-transformed into an electrical signal. The electrical signal is inputted to the controller 309 through the driving unit 307. The driving unit 307 controls a rotational speed of the spindle motor 312, amplifies the inputted signal, and drives the optical pickup 300. The controller 309 sends a focusing and a tracking servo commands controlled based on a signal input from the driving unit 307, back to the driving unit 307 to allow focusing and tracking servo operations to be realized.
According to the optical recording and/or reproducing apparatus according to an aspect of the present invention, since the first and second objective lenses 45 and 41 are mounted on the single lens holder so that the central axes thereof are in parallel with each other and alignment between the first and second objective lenses 45 and 41 and an optical axis is adjustable using only the actuator skew adjusting an inclination of the actuator itself, whereby optical pickup performance may be secured. Here, if an actuator having a tilt operation is provided for the actuator, an adjustment of the inclination of the actuator may be performed.
According to the technique for assembling the plurality of objective lenses of the optical pickup, an inclination between the plurality of objective lenses can be completed within five minutes, so that deterioration in reproducing or recording performance for the optical discs that correspond to the respective objective lenses may be prevented.
According to an aspect of the present invention, since the lens seat surface of at least one installation hole of the plurality of installation holes formed in the lens holder is formed as the curved surface so that the inclination adjustment can be properly performed, the inclination adjustment between the plurality of objective lenses may be performed without an increase in the number of the parts or an increase in the number of the assembling processes.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Number | Date | Country | Kind |
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2004-49706 | Jun 2004 | KR | national |