KR20100055836A - Optical pick-up apparatus using free curved-surface prism - Google Patents

Abstract

PURPOSE: An optical pick-up device using free curved-surface prism is provided to simplify the manufacturing process by reducing the number of parts. CONSTITUTION: An optical pick-up device comprises a light source(11), a splitter(15), a free curved-surface prism(20), objective lens and a photodetector(33). The splitter is installed on the path of the light produced from the light source and splits from the light transferred to an optical recording medium the light reflected from the optical recording medium. The free curved-surface prism changes the light path of the dispersed light incoming through the splitter to be perpendicular to the recording medium and changes the dispersed light to a parallel light. The objective lens collects the light passed the free curved-surface prism at the optical recording medium in a spot type. The photodetetor detects the light which is reflected from the recording medium and passed the splitter.

Description

Optical pick-up apparatus using free curved-surface prism}

The present invention relates to an optical pickup device, and more particularly, to an optical pickup device using a free curved prism.

An optical pickup apparatus generates light from a light source to form pit information on a surface of a disk, which is a recording medium, or reproduces recorded data using light reflected from the formed pit information.

At this time, there are various types of recording media used, and most commonly used CD (Compact Disc) and DVD (Digital Versatile Disc).

1 is a block diagram of a conventional optical pickup apparatus according to the prior art. According to this, the optical pickup device is provided with a light source 1 for emitting the generated light. A laser diode or the like may be used as the light source 1.

The diffraction grating 2 is provided on a path along which the light emitted from the light source 1 travels. The diffraction grating 2 serves to diffract the light emitted from the light source 1 to divide the amount of incident light by a predetermined ratio. In general, the diffraction grating 2 is designed to perform tracking to separate the incident light into three so that the light is accurately irradiated onto the track on the disc.

The light passing through the diffraction grating 2 is incident on the optical separator 3. The optical separator 3 serves to change the path of incident light, transmits the light incident from the light source 1 toward the disk D, and transmits the light reflected from the disk D to the photodetector 9. ) It separates and delivers to the side.

Meanwhile, the light generated by the light source 1 and passing through the optical separator 3 passes through a collimator lens 4. The collimator lens 4 serves to convert the incident light into parallel light. This is because the light emitted from the light source 1 is distributed light so that it can be converted into parallel light so that it can be used for recording and reproduction on the disc.

Light passing through the collimator lens 4 is transmitted to the rerouting mirror (5). The path changing mirror 5 serves to change the path of the light in a direction in which the light transmitted from the light source 1 can be incident perpendicularly to the disk.

The light whose path is changed in the path changing mirror 5 is condensed on the disk by the objective lens 6. The objective lens 6 collects light onto the disk D in the form of spots.

The light irradiated onto the disk D by the objective lens 6 forms a pit on the disk D to record data or is reflected by the formed pit.

On the other hand, the light reflected on the disk (D) is transferred to the optical splitter (3) in the reverse path of the path that the light is transmitted from the light source (1) to the disk (D). In the optical separator 3, light is transmitted in a direction other than the direction of the light source 1.

In addition, a sensor lens 8 is installed on a path through which the light reflected by the disk D and passed through the optical separator 3 is transmitted. The sensor lens 8 causes incident light to be focused on the photodetector 9 in the form of a spot.

When the light collected through the sensor lens 8 is irradiated to the photodetector 9, the photodetector 9 detects the irradiated light and plays a role of reproducing the signal recorded on the disc D. . In this case, the photodetector 9 includes a plurality of cells, and includes a photodetector such as a photo diode integrated chip (PDIC) that photoelectrically converts light irradiated to the cells to be output as an electrical signal. Can be configured.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup apparatus which minimizes the number of components except for the configuration of a collimator lens using a free-curved prism.

Another object of the present invention is to provide an optical pickup device which is competitive in price by minimizing the number of parts.

It is still another object of the present invention to provide an optical pickup apparatus capable of simplifying a manufacturing process by simplifying the configuration of parts.

According to a feature of the present invention for achieving the above object, the present invention comprises a light source for generating light of a specific wavelength; An optical separator installed on the path of the light emitted from the light source to separate and transmit the light transmitted from the light source and the light reflected from the recording medium; A free curved prism for converting the optical path of the scattered light from the light source through the optical splitter so as to be perpendicular to the recording medium and at the same time converting the scattered light into parallel light; An objective lens for condensing the light passing through the free-curved prism from the light source on the optical recording medium in a spot shape; And a photodetector for detecting light reflected from the recording medium and passing through the optical separator.

The free curved prism may include a first curved surface formed such that light incident from the light source is refracted toward a second curved surface; A second curved surface in which the light refracted by the first curved surface is totally reflected inside the free curved prism to be incident to the third curved surface, and the light reflected by the third curved surface is refracted to be transmitted to the outside of the free curved prism; And a third curved surface that totally reflects into the free curved prism so that the light reflected from the second curved surface is incident on the second curved surface.

Herein, the first to third curved surfaces may be defined by the following equation.

≪ Equation &

In the above equation,

z is the sag of the surface parallel to the Z axis,

cux is the basic curvature in the X-axis direction,

kx is the cone coefficient in the X-axis direction,

cuy is the base curvature in the Y axis direction,

ky is the cone coefficient in the Y axis direction,

AR, BR, and CR are the rotational symmetry coefficients of the 4th, 6th, and 8th aspherical terms, respectively,

AP, BP and CP are the non-rotational symmetry coefficients of the fourth, sixth and eighth aspherical terms, respectively.

In this case, a diffraction grating may be further provided on the path from which the light from the light source is transmitted to the optical separator so as to perform the tracking operation with the light from the light source.

In addition, a sensor lens for condensing the light reflected from the recording medium to the cell of the photodetector in the form of a spot may be further provided.

As described in detail above, according to the optical pickup device according to the present invention, the following effects can be expected.

That is, there is an advantage in that the optical pickup apparatus which minimizes the number of components except for the configuration of the collimator lens by using the free-curved prism can be provided.

In addition, according to the optical pickup device according to the present invention, there is an advantage that the price competitiveness of the optical pickup device can be secured by minimizing the number of components.

In addition, the optical pickup apparatus according to the present invention has an advantage in that the configuration of the components is simplified, thereby simplifying the manufacturing process, thereby reducing the defective rate occurring in the manufacturing process.

Hereinafter, with reference to the accompanying drawings a specific embodiment of the optical pickup device according to the present invention as described above will be described in detail.

2 is a configuration diagram schematically showing the configuration of an optical pickup apparatus according to a specific embodiment of the present invention, Figure 3 is a perspective view showing the configuration of the optical pickup apparatus according to a specific embodiment of the present invention and the light movement path thereby 4 is a perspective view showing the configuration of a free-form surface prism used in the optical pickup device according to a specific embodiment of the present invention, and FIG. 5 is a free-form surface prism used in the optical pickup device according to a specific embodiment of the present invention. It is an exemplary figure which shows the path | route of the light which injects into.

As shown in Fig. 2 and 3, the optical pickup device according to a specific embodiment of the present invention is provided with a light source (11). The light source 11 is provided with a light emitting element such as a laser diode. In addition, the monitor PD 12 may be provided in the opposite direction in which the light of the light source 11 is emitted. The monitor PD 12 receives a portion of the light emitted from the light source 11, converts the amount of optical power emitted from the light source 11 into an electrical signal, and outputs the converted electrical signal, which is a wavelength control circuit. Is transmitted to the light source to control the wavelength of the light generated from the light source 11 again.

In this case, the wavelength of the light generated by the light source 11 depends on the type of storage medium to record or reproduce data using the optical pickup device. For example, the light source 11 may generate light for a CD having a wavelength of about 780 nm, or light for a DVD having a wavelength of about 650 nm.

Light emitted from the light source 11 is incident to the diffraction grating 13. The diffraction grating 13 diffracts the light emitted from the light source 11 and divides the amount of incident light by a predetermined ratio. In general, the diffraction grating 13 is designed to perform tracking to separate the incident light into three so that the light is accurately irradiated onto the track on the disc.

An optical separator 15 is provided on a path through which the light emitted from the light source 11 is projected through the diffraction grating 13. The optical separator 15 changes the path of incident light, transfers the light incident from the light source 11 toward the disk D, and transmits the light reflected from the disk D to the photodetector 33. ) It separates and delivers to the side.

The light passing through the optical separator 15 is incident to the free curved prism 20. The free curved prism 20 redirects the light incident from the light source 11 through the optical splitter 15 to the free curved prism 20 in a direction perpendicular to the disk D. At the same time, it serves to convert light incident as jet light into parallel light.

As shown in FIGS. 4 and 5, the free curved prism 20 is formed with a first curved surface 21, a second curved surface 22, and a third curved surface 23. In this case, the curvatures of the first curved surface 21, the second curved surface 22, and the third curved surface 23 are exaggerated than the actual free curvature prism according to the embodiment of the present invention.

Light passing through the diffraction grating 13 and the optical separator 15 is incident from the light source 11 into the first curved surface 21. In this case, light incident on the first curved surface 21 is referred to as incident light L1, L1 ′, and L1 ″.

The incident light (L1, L1 ', L1 ") is a scattered light that is dispersed as they proceed without being parallel to each other, as shown in the drawing. Incident light (L1, L1', L1") incident on the first curved surface 21 Is refracted by the first curved surface 21 and passes through the free curved prism 20. Here, the incident light (L1, L1 ', L1 ") is refracted in accordance with Snell's law in the first curved surface 21. The incident light (L1, L1', L1") is in the first curved surface 21 It is refracted to pass through the free curved prism 20 to reach the second curved surface 22.

The second curved surface 22 reflects the light reaching the second curved surface 22 from the inside of the free curved prism 20 back into the free curved prism 20. In this case, the second curved surface 22 is formed such that the light that is refracted by the first curved surface 21 and is incident to total internal reflection. Accordingly, the light reflected from the second curved surface 22 passes through the free curved prism 20 and reaches the third curved surface 23.

The third curved surface 23 reflects the incident light back into the free curved prism 20. Accordingly, the reflected light is refracted when the light passes through the inside of the free curved prism 20 and reaches the second curved surface 22, and is transmitted to the outside of the free curved prism 20. In this case, hereinafter, the light passing through the inside of the free curved prism 20 and transmitted to the outside is referred to as transmitted light (L2, L2 ', L2 ").

The transmitted light L2, L2 ′, L2 ″ is incident on the free curved prism 20 by the incident light L1, L1 ′, L1 ″, and is converted into parallel light while repeating refraction and reflection. At this time, the incident light (L1, L1, L1 ") is converted to the transmitted light (L2, L2 ', L2" in parallel to each other via the free-curved prism 20, the transmitted light (L2, L2', L2 "). This result is obtained by setting the curvatures of the respective curved surfaces 21, 22, and 23 of the free curved prism 20 so as to be parallel light, wherein the curved surfaces 21, 22, and 23 are asymmetrical. Since it is a shape, it is formed as an asymmetrical curved surface such as anamorphic aspherical surface.

The parallel light passing through the free curved prism 20 is incident to the objective lens 17. Accordingly, the light incident on the objective lens 17 is irradiated to the disk D. Herein, light irradiated to the disk D in the form of a spot passing through the objective lens 17 may form a pit on the disk D. That is, the pit information is formed on the disk D by light, so that data is recorded on the disk D. FIG. In addition, the light is irradiated onto the disk D by the objective lens 17 so that the light may be reflected at the already formed pits. That is, when the light is reflected on the already formed pit, the light is transferred to the photodetector 33 through the objective lens 17, the free-curved prism 20, and the optical separator 15. The data can be decrypted.

In this case, the photodetector 33 may use a PDIC as a light receiving element for converting light reflected from the disk D into an electrical signal. The photodetector 33 may use various kinds according to the type of the light source 11 and the function of the optical pickup device.

In addition, a sensor lens 31 may be installed between the photodetector 33 and the optical separator 15. The sensor lens 31 reflects the light reflected from the recording medium disk D and passed through the optical separator 15 to the photodetector 33 in a spot shape.

One embodiment of the design of such a free-form surface prism is shown in the following table. Table 1 is optical design data of the first curved surface 21 of the free curved prism according to an embodiment of the present invention, Table 2 is optical design data of the second curved surface 22, and Table 3 is the third curved surface 23 ) Is optical design data.

At this time, the progress of the light according to the free-form surface prism by the optical design data is shown in FIG. The axial direction of the optical design data shown here is also shown in FIG. 6.

First surface RDX -11.48260 GLA BK7_SCHOTT RMD RDY -10.34534 GL2 AIR Eccentricity XDE 0.000000 YDE 2.500000 ZDE 1.000000 ADE 61.244183 BDE -0.000000 CDE 0.000000 Aspheric coefficient KX 15.111110 KY 17.287864 AR 0.742859E-03 BR 0.654958E-04 CR 0.759273E-04 AP 0.129416E + 01 BP -.895435E + 00 CP 0.208012E + 00

Second surface RDX -1909.20468 GLA AIR RMD TIR RDY -795.16091 GL2 BK7_SCHOTT Eccentricity XDE 0.000000 YDE 1.000000 ZDE 0.000000 ADE 25.143655 BDE -0.000000 CDE 0.000000 Aspheric coefficient KX -0.558167E45 KY -0.133438E19 AR 0.565810E-06 BR 0.525953E-04 CR 0.674776E-08 AP 0.199343E + 02 BP -.121791E + 00 CP 0.102653E + 01

3rd surface RDX -54.36143 GLA BK7_SCHOTT RMD REFL RDY -56.70119 GL2 AIR Eccentricity XDE 0.000000 YDE 1.000000 ZDE 1.609351 ADE -9.920431 BDE -0.000000 CDE 0.000000 Aspheric coefficient KX -183.475362 KY -431.897134 AR 0.282472E-06 BR -.653662E-10 CR 0.593969E-05 AP -.276629E + 02 BP -.495354E + 02 CP 0.186958E + 00

As shown in Tables 1 to 3, each curved surface of the free curved prism 20 has a predetermined curvature (RDX = X-axis curvature radius, RDY = Y-axis curvature radius) in the X-axis and Y-axis directions. It has a curved surface. At this time, the symbol "En" means "10 ^-n ".

Here, the 'XDE', 'YDE', 'ZDE', 'ADE', 'BDE', 'CDE' is a translation and rotation in the coordinate system starting from the point where the light is irradiated to the disk (D) in FIG. It shows the amount of eccentricity. In particular, the 'XDE', 'YDE', 'ZDE' represents the vertex coordinates of each curved surface, and individually represents the amount of translational eccentricity in the X, Y and Z directions, respectively. 'ADE', 'BDE', and 'CDE' represent the rotation angles of the curved surfaces, respectively, and represent the rotation eccentricity in the X, Y, and Z directions.

Also, 'KX' and 'KY' represent cone coefficients in the X and Y directions, respectively, and 'AR', 'BR', 'CR', 'AP', 'BP' and 'CP' are aspherical surfaces of the respective curved surfaces. Indicates coefficients. Where 'AR', 'BR' and 'CR' are the rotational symmetry coefficients of the 4th, 6th and 8th aspherical terms, respectively, and 'AP', 'BP' and 'CP' are the 4th, 6th, Non-rotational symmetry coefficients of the eighth-order aspherical terms.

Each of the curved surfaces 21, 22, and 23 of the free curved prism 20 having such data is determined by a deformation aspheric equation as shown in Equation 1 below.

In this case, 'z' is defined as a sag of a surface parallel to the Z axis, and 'CUX' and 'CUY' represent basic curvatures in the X-axis and Y-axis directions, respectively. It is the inverse of 'RDX' and 'RDY'.

Looking at the path of the light passing through the free-form surface prism 20 by substituting design data as shown in Tables 1 to 3 in the equation as shown in FIG. 6, in this case, the free-form surface prism 20 Looking at the axial aberration and 1 degree non-axial aberration of the aberration characteristics as shown in Figures 7 and 8.

7 is a graph illustrating aberration characteristics on the axis of the free-formed prism in the optical pickup apparatus according to an embodiment of the present invention, and FIG. 8 is a graph of the free-formed prism in the optical pickup apparatus according to the embodiment of the present invention. It is a graph showing 1 degree stockpile aberration characteristics.

First, referring to FIG. 7, the aberration characteristics when the free-curved prism 20 is on the optical axis will be described with reference to FIG. 7. The graph on the left is the aberration in the Y-axis direction, and the graph on the right is the aberration in the X-axis direction. The resulting RMS aberration was sufficiently small, about 2mλ _rms .

In addition, referring to FIG. 8, a non-axial aberration characteristic when the free-curved prism 20 deviates 1 degree from the optical axis is shown. The graph on the left is the aberration in the Y-axis direction, and the graph on the right is the aberration in the X-axis direction. And it can be seen that the RMS aberration as shown in the figure is about 10 mλ _{rms, which} is also sufficiently small that there is no problem in the optical performance of the free curved prism 20 in the optical pickup device.

Meanwhile, another embodiment and another embodiment of the optical pickup apparatus using the free-curved prism according to the present invention as described above will be described in detail with reference to the drawings.

9 is a configuration diagram schematically showing the configuration of an optical pickup apparatus according to another embodiment of the present invention, Figure 10 is a configuration diagram schematically showing the configuration of an optical pickup apparatus according to another embodiment of the present invention. .

As shown in FIG. 9, the optical pickup apparatus according to another embodiment of the present invention includes two light sources, that is, a first light source 11a and a second light source 11b, each providing light having a different wavelength. . This is to provide both recording and reproducing functions for storage media using different wavelengths.

Each monitor PD 12a, 12b and diffraction gratings 13a, 13b for each light source 11a, 11b are provided. In addition, a first light separator 15a is provided on a path of the light generated from the first light source 11a. The first optical separator 15a refracts the light incident from the first light source 11a to the disk D side.

On the other hand, the second optical separator 15b is provided on the traveling path of the light generated from the second light source 11b. The second optical separator 15b refracts the light incident from the second light source 11b to the disk D side.

In this case, the first light separator 15a is emitted from the second light source 11b and refracted by the second light separator 15b to be incident on the first light separator 15a to receive the first light source 11a. Is refracted toward the disk D in the same way as the path for refracting the light incident on the disk D side.

In this way, the light starting from the first light source 11a or the second light source 11b and passing through the first light separator 15a is incident to the free curved prism 20. The free curved prism 20 changes the direction of the light so that the incident light can be irradiated in the direction perpendicular to the disk D via the objective lens 17, and simultaneously converts the incident light in the form of scattered light. Release in form. To this end, each curved surface of the free curved prism 20 is designed so that the emitted light can be parallel light perpendicular to the disk D.

The light incident through the free curved prism 20 and incident on the objective lens 17 is irradiated in a spot shape to the point of the disk D by the objective lens 17.

When the light irradiated onto the disk D is reflected, the sensor passes through the objective lens 17, the free curved prism 20, the first light separator 15a, and the second light separator 15b in sequence. Incident on the lens 31.

The sensor lens 31 collects the incident light in the form of a spot on the photodetector 33.

Accordingly, when the light reaches a certain point of the photodetector 33, the photodetector 33 decrypts it to generate an electrical signal.

Therefore, data can be recorded on the recording medium by using light formed from a light source generating an appropriate wavelength according to the type of recording medium, and the data recorded on the recording medium can be reproduced. For example, the first light source 11a may form a CD light, and the second light source 11b may form a DVD light to form a CD and DVD combined optical pickup. However, this is just one example, and one of the first or second light sources 11a and 11b is a blue ray disc (BD) or an HD VD using blue light of a blue laser diode, for example, light having a wavelength of 400 nm. It can also be a light of the (High Definition Video Disc) series.

On the other hand, the optical pickup apparatus according to another embodiment of the present invention, as shown in Figure 10 is provided with two optical pickup means for recording and reproducing to a different type of storage medium, respectively on the left and right sides. At least one of the two optical pickup means includes a free curved prism 20 according to an embodiment of the present invention as shown on the right side of the drawing.

For example, the optical pickup means on the left side of FIG. 10 is an optical pickup means for BD and includes both the collimator lens 14 and the path changing mirror 16 as in the prior art. On the other hand, the optical pickup means on the right side of the figure includes only the free curved prism 20 instead of the collimator lens 14 and the path changing mirror 16 as the optical pickup means for the CD and DVD. At this time, the free curved prism 20 is the same as described in the specific embodiment and the other embodiment of the present invention.

Accordingly, an optical pickup apparatus having a simpler configuration can be designed, and the optical pickup apparatus having a complicated configuration, such as an optical pickup apparatus supporting recording and reproducing for various storage media, as in another embodiment of the present invention. It makes the function simpler.

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

1 is a configuration diagram briefly showing the configuration of an optical pickup apparatus according to the prior art.

Figure 2 is a schematic diagram showing the configuration of an optical pickup apparatus according to a specific embodiment of the present invention.

Figure 3 is a perspective view showing the configuration of the optical pickup apparatus according to a specific embodiment of the present invention and the movement path of the light thereby.

Figure 4 is a perspective view showing the configuration of a free-form surface prism used in the optical pickup device according to a specific embodiment of the present invention.

5 is an exemplary view showing a path of light incident on a free-curved prism used in an optical pickup apparatus according to a specific embodiment of the present invention.

6 is an exemplary view showing the progress of light according to the design data of the free-form curved prism in the optical pickup device according to an embodiment of the present invention.

7 is a graph illustrating aberration characteristics on an axis according to design data of a free-form curved prism in the optical pickup apparatus according to an embodiment of the present invention.

8 is a graph illustrating first-degree axle aberration characteristics according to design data of a free-form curved prism in the optical pickup apparatus according to an embodiment of the present invention.

9 is a configuration diagram schematically showing a configuration of an optical pickup apparatus according to another embodiment of the present invention.

10 is a configuration diagram schematically showing the configuration of an optical pickup apparatus according to another embodiment of the present invention.

** Description of the symbols for the main parts of the drawings **

11, 11a, 11b: light source 12: monitor PD

13, 13a, 13b: diffraction grating 14: collimator lens

15, 15a, 15b: Optical Separator 16: Rerouting Mirror

17, 17a, 17b: objective lenses 18a, 18b; 1/4 wavelength plate

20: free-surface prism 21: first surface

22: second surface 23: third surface

31, 31a, 31b: sensor lens 33, 33a, 33b: photodetector

D: disks L1, L1 ', L1 ": incident light

L2, L2 ', L2 ": transmitted light

Claims (5)

A light source for generating light of a specific wavelength; An optical separator installed on the path of the light emitted from the light source to separate and transmit the light transmitted from the light source and the light reflected from the recording medium; A free curved prism for converting the optical path of the scattered light incident through the optical splitter from the light source so as to be perpendicular to the recording medium and simultaneously converting the scattered light into parallel light; An objective lens for condensing the light passing through the free-curved prism from the light source on the optical recording medium in a spot shape; And And a photo detector for detecting light reflected from the recording medium and passing through the optical separator. The method of claim 1, The free curved prism is, A first curved surface formed such that light incident from the light source is refracted toward a second curved surface; A second curved surface that reflects the light refracted by the first curved surface into the free curved prism to be incident to the third curved surface and refracts the light reflected by the third curved surface to be transmitted to the outside of the free curved prism; And And a third curved surface totally reflected inside the free curved prism such that the light reflected from the second curved surface is incident on the second curved surface. The method of claim 2, The first curved surface to the third curved surface, Optical pickup device, characterized in that defined by the following equation. ≪ Equation &

In the above equation, z is the sag of the surface parallel to the Z axis, cux is the basic curvature in the X-axis direction, kx is the cone coefficient in the X-axis direction, cuy is the base curvature in the Y axis direction, ky is the cone coefficient in the Y axis direction, AR, BR, and CR are the rotational symmetry coefficients of the 4th, 6th, and 8th aspherical terms, respectively, AP, BP and CP are the non-rotational symmetry coefficients of the fourth, sixth and eighth aspherical terms, respectively. The method according to any one of claims 1 to 3, And a diffraction grating for dividing the light to perform a tracking operation with the light from the light source on a path from which the light from the light source is transmitted to the optical separator. The method according to any one of claims 1 to 3, And a sensor lens for condensing the light reflected from the recording medium to the cells of the photodetector in the form of spots.

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