KR20090011899A - Compensating apparatus for numerical aperture of optical pickup - Google Patents

Compensating apparatus for numerical aperture of optical pickup Download PDF

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Publication number
KR20090011899A
KR20090011899A KR1020070075936A KR20070075936A KR20090011899A KR 20090011899 A KR20090011899 A KR 20090011899A KR 1020070075936 A KR1020070075936 A KR 1020070075936A KR 20070075936 A KR20070075936 A KR 20070075936A KR 20090011899 A KR20090011899 A KR 20090011899A
Authority
KR
South Korea
Prior art keywords
lens
compensation
numerical aperture
boss
seating
Prior art date
Application number
KR1020070075936A
Other languages
Korean (ko)
Inventor
김영훈
Original Assignee
엘지전자 주식회사
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지전자 주식회사 filed Critical 엘지전자 주식회사
Priority to KR1020070075936A priority Critical patent/KR20090011899A/en
Publication of KR20090011899A publication Critical patent/KR20090011899A/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/139—Numerical aperture control means
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
    • G11B2220/2537—Optical discs

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)

Abstract

The present invention relates to a numerical aperture compensation device for an optical pickup. The present invention includes a lens holder 32 is provided with a pair of mounting boss 34 protruding in parallel in the vertical direction; A compensation lens 40 which is seated to be in line contact with the mounting boss 34 and is mounted on the mounting boss 34 to compensate for the numerical aperture of light emitted from the laser diode 20; The elastic lens 50 is installed on the mounting boss 34 to cover the compensation lens 40 and the elastic lens 50 provides elastic force in a direction in which the compensation lens 40 is in close contact with the mounting boss 34. do. According to the present invention as described above, even if the compensation lens is moved in the optical axis direction to adjust the focal length together with the lens holder, the compensation lens is prevented from tilting in the vertical direction of the optical axis direction.

Description

Compensating apparatus for numerical aperture of optical pickup

The present invention relates to an optical pickup, and more particularly, to an optical pickup numerical aperture compensation device for increasing the numerical aperture by adjusting the focal length of the light emitted from the laser diode.

An optical pickup apparatus refers to an apparatus that reproduces information recorded on an optical disc or records information on an optical disc by using optical characteristics. In such an optical pickup device, information stored on an optical disc is made higher by digitizing data and increasing capacity.

In line with this trend, the development of compact discs (CDs), which are mainly used as conventional optical discs, as well as DVDs and Blu-rays having shorter wavelengths and higher numerical apertures (NAs). This is accelerating.

Looking at the configuration of a general optical pickup device, a laser diode that emits light, an optical splitter that reflects or transmits light, a collimator lens that makes light incident from the optical splitter, and a light incident from the collimator lens An objective lens for condensing on the optical disk, and a photodetector for detecting light reflected by the optical splitter as an electrical signal.

Here, the light emitted from the laser diode passes through the numerical aperture compensation device for compensating the numerical aperture before passing through the optical splitter. A detailed configuration of the numerical aperture compensator will be described below with reference to the accompanying drawings.

1 is a perspective view showing the configuration of a numerical aperture compensation device for an optical pickup according to the prior art.

As shown, the numerical aperture compensation device 1 is provided with a lens holder (2). The lens holder 2 has a substantially flat rectangular hexahedral shape. The center of the lens holder 2 is formed to be open so that light can pass.

The mounting boss 4 protrudes from one surface of the lens holder 2. The mounting boss 4 is a portion on which the compensation lens 10 to be described below is mounted. The mounting bosses 4 protrude in parallel in a direction perpendicular to the lens holder 2. In addition, the mounting boss 4 is formed so that the lower ends thereof protrude in a direction facing each other so that the compensation lens 10 can be more stably fixed.

At least one fixing protrusion 6 is provided on an outer surface of the seating boss 4. The fixing member 6 is to hang the elastic member 18 to be described below.

The compensation lens 10 is seated on the mounting boss 4 of the lens holder 2. The compensating lens 10 serves to increase the numerical aperture NA. The numerical aperture described above is a reference value closely related to the light efficiency, and the light efficiency increases as the numerical aperture increases. That is, the compensation lens 10 adjusts the numerical aperture by adjusting the focal length of the collimator lens.

In addition, seating parts 12 are provided at both sides of the compensation lens 10. The seating portion 12 is a portion that is substantially seated on the seating boss (4). The compensation lens 10 has a structure that is difficult to be seated on the structure because the cross section is formed in a circular shape. Therefore, in the injection process, the seating portion 12 is made to have a shape that is joined to the seating boss 4.

On the other hand, the top and bottom of the front of the compensation lens 10 is provided with a mounting protrusion 14 for mounting the grating element 16 to be described below. The seating protrusions 14 are formed to correspond to the shape of the grating element 16.

The grating element 16 is installed on the mounting protrusion 14 of the compensation lens 10. The grating element 16 divides the light into a plurality of light by using the diffraction phenomenon of the light.

On the other hand, the lens holder 2 is provided with an elastic member 18 for fixing the compensation lens 10 to the mounting boss (4). The elastic member 18 is formed by bending both ends of the rectangular leaf spring. The elastic member 18 provides an elastic force in a direction in which the compensation lens 10 is in close contact with the mounting boss (4). The elastic member 18 surrounds the mounting boss 4 and the compensation lens 10 as a whole, and both ends of the elastic member 18 are fixed to the fixing protrusion 6.

However, the prior art as described above has the following problems.

In the prior art, the lens holder 32 is moved in the optical axis direction (arrow direction) to adjust the focal length of the collimator lens. In this process, the compensation lens 10 installed in the lens holder 32 adjusts the focal length to prevent defocusing from occurring.

As described above, the two mounting surfaces of the mounting boss 4 and the compensation lens 10 are coupled to each other by surface contact with each other. The plane perpendicular to the surface of the seating boss 4 and the seating portion 12 in contact with the surface has a slight tolerance in the design process. This is to reduce the friction generated between the contact surface in the process of seating the seating portion 12 to the mounting boss (4).

As such, since there is a tolerance between the surfaces where the seating boss 4 and the seating portion 12 come into contact with each other, the compensation lens 10 is in the optical axis direction when the seating portion 12 is coupled to the seating boss 4. The tilting in the vertical direction may occur. In precision and environmentally sensitive products such as optical pickups, tilting at very small angles can have a significant impact on performance.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and to provide a numerical aperture compensation device for an optical pickup having a structure for increasing the numerical aperture to increase the light efficiency.

According to a feature of the present invention for achieving the object as described above, the present invention includes a lens holder having a pair of mounting boss protruding in parallel in the vertical direction; A compensation lens seated in line with the seating boss and configured to compensate for the numerical aperture of light emitted from the laser diode by being seated on the seating boss; It is installed on the mounting boss to cover the compensation lens, characterized in that it comprises an elastic member for providing an elastic force in the direction in which the compensation lens is in close contact with the mounting boss.

Both sides of the compensation lens is characterized in that each mounting portion corresponding to the shape of the mounting boss is provided.

A round surface is formed at an upper end of the seating boss, and a pair of flat surfaces are formed at a lower end of the seating portion to have a predetermined angle so that the round surface is in line contact with the two parts.

A round surface is formed at a lower end of the seating portion, and a pair of flat surfaces are formed to have a predetermined angle at an upper end of the seating boss, and the line surface is in line contact with the two parts.

The elastic member is a leaf spring bent at both ends in the vertical direction, characterized in that the engaging projection formed on the outside of the mounting boss.

It is installed on the seating protrusion provided on the front surface of the compensation lens, characterized in that it further comprises a grating element for dividing the light.

In the numerical aperture compensation device of the optical pickup according to the present invention as described in detail above, the following effects can be expected.

In the present invention, the shape of the mounting boss and the mounting portion is designed so that both sides of the compensation lens mounted on the lens holder can be installed in line contact. Therefore, even if the compensation lens is moved in the optical axis direction to adjust the focal length together with the lens holder, the compensation lens is prevented from tilting in the vertical direction of the optical axis direction.

Hereinafter, a preferred embodiment of the numerical aperture compensation device for optical pickup according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a configuration diagram of an optical pickup apparatus employing the numerical aperture compensation device of the optical pickup according to the present invention, Figure 3 is a perspective view showing a preferred embodiment of the numerical aperture compensation apparatus of the optical pickup according to the present invention, Figure 4 Is a front view of the numerical aperture compensation device for optical pickup according to the present invention.

As shown in these figures, the optical pickup apparatus is provided with laser diodes 20, 21, 22 for generating light irradiated onto the disc. Three laser diodes 20, 21, and 22 are installed in this embodiment, in order to provide an optical pickup apparatus that can be used for all of CD, DVD, and Blu-ray recording media. Thus, the laser diodes 20, 21, and 22 generate light of different wavelengths, respectively. In this embodiment, CD light is generated in the first laser diode 20, Dive light is generated in the second laser diode 21, and blue ray light is generated in the third laser diode 22. .

First, the light generated by the first laser diode 20 is incident on the numerical aperture compensator 30. The configuration of the numerical aperture compensator 30 will be described below in detail with reference to FIG. 3.

The numerical aperture compensation device 30 is provided with a lens holder 32. The lens holder 32 is formed in a substantially flat rectangular hexagonal shape. Although not specifically illustrated in the drawing, the center of the lens holder 32 is formed to be opened to a predetermined width so that light can pass therethrough. The lens holder 32 is moved in the optical axis direction to allow the compensation lens 40 to be described below to adjust the focal length.

A mounting boss 34 protrudes from one side of a relatively wide surface of the lens holder 32. The mounting boss 34 is a portion where the compensation lens 40 is substantially fixed. The mounting boss 34 is formed by projecting a pair in parallel in a direction perpendicular to the lens holder 32. In addition, the mounting boss 34 is formed so that the lower ends thereof protrude in a direction facing each other so that the compensation lens 40 can be more stably fixed.

At least one fixing protrusion 36 is provided on an outer surface of the seating boss 34. In the present embodiment, two fixing protrusions 36 are provided to fix the elastic member 50 to the seating boss 34 to be described below.

On the other hand, the upper end of each of the seating boss 34 is rounded to form a round surface 34 'to be in line contact with the compensation lens 40 to be described below. However, the round surface 34 ′ is not required to be formed on the mounting boss 34, and the round surface 34 ′ may be formed on the compensation lens 40. That is, it is important that the mounting boss 34 and the compensation lens 40 are coupled to each other in line contact with each other.

The compensation lens 40 is mounted on the mounting boss 34 of the lens holder 32. The compensation lens 40 increases the numerical aperture NA. The numerical aperture described above is a value that is closely related to the light efficiency, and the light efficiency increases as the numerical aperture increases. That is, the compensation lens 40 adjusts the numerical aperture by adjusting the focal length of the collimator lens 62 to be described below. The numerical aperture is generally inversely proportional to the focal length. The compensation lens 40 adjusts the focal length while moving in the optical axis direction together with the lens holder 32.

Mounting parts 42 are provided at both sides of the compensation lens 40. The seating portion 42 is a portion which is substantially seated on the seating boss 34. The compensation lens 40 has a structure that is difficult to be mounted on the structure because the cross section is formed in a circular shape. Therefore, it is made to have a shape that is matched to the mounting boss 34 in the process of ejecting the compensation lens 40.

The lower surface of the seating portion 42 is formed with a flat surface 42 ′ in line contact with the upper end of the seating boss 34. To this end, the flat surface 42 'is formed such that two planes are adjacent to each other to form a predetermined angle, and the upper end of the seating portion 42 is in contact with each flat surface 42'. As shown in FIG. 4, the flat surface 42 ′ is in linear contact with the round surface 34 ′ of the seating boss 34 at two portions. As described above, the round surface 34 ′ and the flat surface 42 ′ may be formed to be replaced by the mounting boss 34 and the mounting portion 42.

In addition, a mounting protrusion 44 for protruding the grating element 46 to be described below is provided at the top and bottom of the front surface of the compensation lens 40. The seating protrusions 44 are formed to correspond to the shape of the grating element 46. In the present embodiment, portions of the seating protrusions 44 contacting the grating element 46 are inclined.

A grating element 46 is installed on the mounting protrusion 44 of the compensation lens 40. The grating element 46 serves to divide the light into a plurality of light using a diffraction phenomenon of light. On the other hand, the grating element 46 is not to be installed with the compensation lens 40 in the lens holder 32 as shown in the figure, it may be installed in a structure separate from the compensation lens 40.

On the other hand, the lens holder 32 is provided with an elastic member 50 for fixing the compensation lens 40 to the mounting boss 34. The elastic member 50 is formed by bending both ends of the rectangular leaf spring. The elastic member 50 provides an elastic force in a direction in which the compensation lens 40 is in close contact with the mounting boss 34. The elastic member 50 has a shape surrounding the mounting boss 34 and the compensating lens 40 as a whole, and both ends of the elastic member 50 are fixed to the fixing protrusions 36.

Referring back to FIG. 2, the light passing through the numerical aperture compensator 30 is incident on the first prism 60. The first prism 60 serves to reflect or transmit light. The first prism 60 reflects the light passing through the numerical aperture compensator 30 toward the collimator lens 62 to be described below, and transmits the light reflected from the disk.

The light reflected by the first prism 60 is incident to the collimator lens 62. The collimator lens 62 serves to make the light generated by the laser diodes 20, 21, and 22 into parallel light. As described above, the focal length of the collimator lens 62 is adjusted by the movement of the compensation lens 40.

The light passing through the collimator lens 62 is reflected by the total reflection mirror 64 and is incident on the objective lens 68. A filter 66 is installed between the total reflection mirror 64 and the objective lens 66 to adjust the amount of light incident on the objective lens 68. The objective lens 68 collects light onto the disk.

The light reflected from the disk is incident on the second prism 70 through the total reflection mirror 64, the collimator lens 62, and the first prism 60. The light passing through the second prism 70 is incident on the first photodetector 76 through the half mirror 72 and the sensor lens 74.

The half mirror 72 serves to reflect or transmit light, and the sensor lens 74 has a coma aberration (COMA) generated while the light passes from the objective lens 68 to the first photodetector 76. ) To remove

Meanwhile, looking at the path of the light generated by the second laser diode 21, the light generated by the second laser diode 21 passes through the sensor lens 78 and the grating element 80 and the half mirror 72. Is incident on. The light reflected by the half mirror 72 is reflected by the second prism 70 to pass through the first prism 60. The subsequent path of the light generated by the second laser diode 21 is the same as the path of light generated by the first laser diode 20.

The light generated by the third laser diode 22 is incident on the wave plate 82. The wave plate 82 converts polarized light by using birefringence of a medium. Light passing through the wave plate 82 passes through the second prism 70 and passes through the collimator lens 84. Light passing through the collimator lens 84 is reflected by the total reflection mirror 64 and is incident on the objective lens 88 through the grating element 86. Light condensed on the disk in the objective lens 88 is reflected and moved in the reverse order of the above-described process. Then, the second prism 70 is reflected and detected as an electrical signal to the second photodetector 92 via the sensor lens 90.

Hereinafter, the operation of the numerical aperture compensator of the optical pickup according to the present invention having the configuration as described above will be described in detail.

First, the process of assembling the numerical aperture compensation device for optical pickup according to the present invention will be briefly described. The compensation lens 40 is mounted on the mounting boss 34 of the lens holder 32. Substantially, the mounting portions 42 formed on both sides of the compensation lens 40 are seated on the mounting boss 34. At this time, the round surface 34 'of the seating boss 34 and the flat surface 42' of the seating portion 42 are in line contact with each other.

In addition, the grating element 46 is installed on the mounting protrusion 44 formed on the front surface of the compensation lens 40. Then, the elastic member 50 is coupled to the lens holder 32. The elastic member 50 is fixed to the fixing boss 36 formed on the outer side of the compensation lens 40 so that the compensation lens 40 is firmly fixed to the mounting boss 34.

In the numerical aperture compensation device 30 assembled as described above, the compensation lens 40 and the mounting boss 34 are in linear contact with each other. Therefore, the compensation lens 40 is prevented from being tilted in the vertical direction in the optical axis direction while the compensation lens 40 moves in the optical axis direction to adjust the focal length of the collimator lens 62. In other words, the compensation lens 40 is in close contact with the mounting boss 34 by the elastic member 50 and the compensation lens 40 and the mounting boss 34 are in line contact with each other in the direction perpendicular to the optical axis direction. It can be prevented from tilting.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self-evident.

1 is a perspective view showing the configuration of a numerical aperture compensation device for optical pickup according to the prior art.

2 is a block diagram of an optical pickup apparatus employing the numerical aperture compensation device of the optical pickup according to the present invention.

Figure 3 is a perspective view showing a preferred embodiment of the numerical aperture compensation device of the optical pickup according to the present invention.

4 is a front view of the numerical aperture compensation device of the optical pickup according to the present invention.

Explanation of symbols on the main parts of the drawings

20: first laser diode 30: numerical aperture compensation device

32: lens holder 34: seating boss

34 ': round face 36: fixing protrusion

40: compensation lens 42: seating portion

42 ': flat surface 44: seating protrusion

46: grating element 50: elastic member

60: first prism 62: collimator lens

64: total reflection mirror 66: objective lens

70: second prism 72: half mirror

74 sensor lens 76 first photodetector

82: wave plate 92: second photodetector

Claims (6)

A lens holder provided with a pair of mounting bosses which protrude in parallel in the vertical direction; A compensation lens seated in line with the seating boss and configured to compensate for the numerical aperture of light emitted from the laser diode by being seated on the seating boss; And a resilient member installed on the mounting boss to cover the compensation lens and providing an elastic force in a direction in which the compensation lens is in close contact with the mounting boss. The method of claim 1, Opposite number compensation device of the optical pickup, characterized in that each side of the compensation lens is provided with a mounting portion corresponding to the shape of the mounting boss. The method of claim 2, A round surface is formed at an upper end of the seating boss, and a pair of flat surfaces are formed at a lower end of the seating portion to have a predetermined angle, so that the linear surface is in line contact with the round surface in two parts. Device. The method of claim 2, A round surface is formed at a lower end of the seating portion, and a pair of flat surfaces are formed at a predetermined angle at an upper end of the seating boss so that the round surface is in line contact with the round surface in two parts. Device. The method according to any one of claims 1 to 4, The elastic member is a leaf spring bent both ends in the vertical direction, the numerical aperture compensation device of the optical pickup, characterized in that the engaging projection formed on the outside of the mounting boss. The method of claim 5, wherein The numerical aperture compensation device of the optical pickup, characterized in that the mounting projection is provided on the front surface of the compensation lens, further comprising a grating element for dividing the light.
KR1020070075936A 2007-07-27 2007-07-27 Compensating apparatus for numerical aperture of optical pickup KR20090011899A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020070075936A KR20090011899A (en) 2007-07-27 2007-07-27 Compensating apparatus for numerical aperture of optical pickup

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020070075936A KR20090011899A (en) 2007-07-27 2007-07-27 Compensating apparatus for numerical aperture of optical pickup

Publications (1)

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KR20090011899A true KR20090011899A (en) 2009-02-02

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KR1020070075936A KR20090011899A (en) 2007-07-27 2007-07-27 Compensating apparatus for numerical aperture of optical pickup

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