KR100421011B1 - Optical pickup comprising a polygon prism and method of compensating optical axes using the same - Google Patents

Abstract

An optical pickup apparatus having a polygonal prism and an optical axis correction method using the same are disclosed. The disclosed optical pickup apparatus is provided on a light source, an objective lens, a photodetector, a beam splitter, and an optical path between the light source and the beam splitter for generating first and second light beams parallel to each other. The first and second surfaces inclined at a predetermined angle with respect to the optical axis so that two lights are incident and refracted, and the optical axes of the first and second beams refracted by the first and second surfaces are refracted. And polygonal optical axis correction means having a matching third surface. The refractive index of the beam splitter and the angle at which the first and second surfaces are inclined with respect to the optical axis may be adjusted to facilitate optical axis correction and increase the thickness tolerance.

Description

Optical pickup comprising a polygon prism and method of compensating optical axes using the same

The present invention relates to an optical pickup device and an optical axis correction method using the same, and more particularly, to an optical pickup device and an optical axis correction method using the same that can increase the thickness tolerance.

Although a DVD (Digital Versatile Disc) player is a device capable of playing DVDs, it is generally manufactured to be able to play both CDs and DVDs in consideration of compatibility with a conventional compact disc (CD). In the conventional optical pickup apparatus, since each laser diode for CD and DVD is provided as a light source for reproducing both CD and DVD as described above, the structure of the optical pickup device is complicated and the number of parts increases.

Conventional optical pickup apparatus uses a laser diode having a wavelength of 650nm and a laser diode emitting a light of 780nm to reduce the number of parts, but using a two-wavelength laser diode, but the distance between the two laser diodes This 110μm is separated so that the two light beams are not coincident.

In the conventional optical pickup apparatus, when the photodetector and the other optical elements are aligned with the optical axis of either one of the two light beams, the other light having different optical axes focused on the photodetector due to the distance tolerance between the two light sources is collimated. When the lens 21 passes through the optical axis, the shape of the light is stabbed on the disk, so that signal reproduction is poor, and the optical signal is not detected normally because the focus is not focused on the photodetector.

Referring to FIG. 1, in the conventional optical pickup apparatus, in order to correct such optical axis deviation, CDs having different wavelengths emitted from the light source 11 on the optical path between the light source 11 and the collimating lens 21 are different from each other. A double plate beam splitter 19 for arranging the optical axes of the reproduction reproduction light 13a (hereinafter referred to as first light) and the DVD reproduction light 15a (hereinafter referred to as second light) in a row is provided.

The double plate beam splitter 19 has a first surface on which the DVD reflection coating mainly reflects the first light 13a and a second surface on which the CD reflection coating mainly reflects the second light 15a. .

After entering the first surface of the first light 13a beam splitter 19 emitted from the first light source 13 at a 45 degree angle, most of the light is reflected at a 45 degree angle to the objective lens 23.

The second light 15a emitted from the second light source 15 is incident on the first surface of the beam splitter 19 at a 45 degree angle and then refracted at a predetermined angle so as to interface between the first layer and the second layer of the beam splitter. Mostly reflected off. The reflected second light is incident on the first surface of the beam splitter again. In the conventional optical pickup apparatus, the optical axis and the second light beam of the second light emitted as shown are controlled by adjusting the refractive index and the thickness of the first layer of the beam splitter. The optical axis correction method is used to match the optical axis of one light.

In the conventional optical pickup apparatus, since the thickness of the first layer of the double plate beam splitter 19 is as thin as 150 μm, the thickness tolerance becomes strict, which makes it difficult to manufacture the double plate beam splitter. In addition, since the thickness of the double plate beam splitter is very thin, a small thickness error is also large, and the optical axis is shifted by the thickness error.

Accordingly, an object of the present invention is to provide an optical pickup device and an optical axis correction method using the same, which can increase the thickness tolerance of the beam splitter and reduce the effect of the distance tolerance between the two lights.

1 is a view schematically showing a conventional optical pickup device;

2 is a view showing an optical pickup apparatus according to an embodiment of the present invention;

3 is an enlarged view illustrating A of FIG. 2 and illustrates an optical axis correction method according to an exemplary embodiment of the present invention;

4 is a view showing the principle of the optical axis correction method according to an embodiment of the present invention,

5 is a view showing a beam splitter that may be employed in an optical pickup apparatus according to an embodiment of the present invention;

6 illustrates a beam splitter that may be employed in an optical pickup apparatus according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

7, 67, 77: page 1 9, 69, 79: page 2

10, 60, 70: 3rd surface 11, 51: light source

13, 23: first light source 13a, 23a: first light

15, 25: second light source 15a, 25a: second light

17, 57: diffraction grating 19: double-beam beam splitter

21, 41: collimating lens

23, 43: objective lens

25, 55: recording medium 27, 47: concave lens

29, 49: photodetector 33: beam splitter

31: isosceles triangle prism

61: trapezoidal prism 71: pentagonal prism

In order to achieve the above technical problem, the present invention provides a recording medium comprising: first and second light sources for generating first and second light beams having parallel optical axes; and recording the first and second light beams emitted from the first and second light sources. An objective lens for concentrating the light source; a photodetector configured to receive and photoelectrically convert the first and second light beams reflected from the recording medium; an optical path between the light source and the objective lens provided on the optical path; A beam splitter for converting the furnace; And first and second surfaces provided on an optical path between the light source and the beam splitter, and inclined at the same angle with respect to an optical axis such that the first and second light are incident and refracted, respectively. And a polygonal optical axis correcting means having a third surface in which the optical axes of the first light to be refracted and the second light to be refracted by the second surface are coincident with each other.

In addition, in order to achieve the above technical problem, the present invention, the first step of emitting the first and second light beams parallel to the optical axis from the first and second light sources; first and second inclined at the same angle with respect to the optical axis A second step of injecting the first and second light into the first or second surface of the polygonal optical axis correction means having a surface; the first and second refracted on the first or second surface And a third step of matching the optical axis of the light at the third surface of the optical axis correcting means and outputting the light axis.

In the optical pickup apparatus, the first and second surfaces may be set such that the first and second lights are incident at the same angle, and a polygonal prism having such first and second surfaces may be used. have. In particular, an isosceles triangular prism may be used as the optical axis correction means.

The first light or the second light may be reproduction light for CD or reproduction light for DVD.

In the optical pickup apparatus and the optical axis correction method using the same, the optical axis correction means is a polygonal prism, the first and second surfaces inclined at a predetermined angle so that at least the first and second light is incident; And a third surface in which the optical axes of the first and second light refracted by the first and second surfaces coincide with each other.

Such a polygonal prism, as described above, may preferably be an isosceles triangular prism. In the present invention, an isosceles triangle-shaped prism is defined as having first and second surfaces inclined at the same angle with respect to the optical axis, and having a third surface where light refracted by the first and second surfaces exits.

Hereinafter, exemplary embodiments of an optical pickup apparatus and an optical axis correction method using the same will be described in detail with reference to the accompanying drawings.

2 is a view showing an optical pickup apparatus according to a first embodiment of the present invention.

2, the optical pickup apparatus according to the embodiment of the present invention, on the optical path between the light source 51 and the beam splitter 33, the same angle of inclination with respect to the optical axis (does not have the same inclination in some embodiments) A first surface 7 and a second surface 9 having a third surface 10 which is perpendicular to the optical axis (may have a predetermined angle of inclination rather than vertical in some embodiments). An isosceles triangular prism 31 is provided.

The light source 51 is a two-wavelength laser diode and includes a first light source 53 and a second light source 55 which are located adjacent to each other at a predetermined interval, for example, d = 110 μm. The first light (CD reproduced light, 23a) is emitted from the first light source 53, and the second light (DVD reproduced light, 25a) in which the first light and the optical axis are parallel to each other is emitted from the second light source 55. It is emitted. The lights can be interchanged so that the first light can be the reproduction light for DVD or the second light can be the reproduction light for CD.

On the optical path between the light source 51 and the beam splitter 35, a CD grating 57 is further provided to branch the first light 33a into three beams. The three beams are necessary for detecting the tracking error signal in the photodetector 29 which photoelectrically converts the light reflected from the CD disk.

At a predetermined angle from the light source 51, the first and second light beams 23a and 25a parallel to each other incident on the first surface 7 and the second surface 9 at the same angle in the present embodiment are the first. The surfaces 7 and 2 are refracted at different angles, respectively, and the optical axes are emitted from the third surface 10 in a coincident manner.

The first and second light beams 23a and 25a having the same optical axis are reflected by the beam splitter 33 and sequentially passed through the collimating lens 41 and the objective lens 43 and focused on the recording medium 55. . The first and second light 55 reflected from the recording medium 55 travels backward through the path and is received by the photodetector 49.

On the optical path between the beam splitter 33 and the photodetector 49, a concave lens 47 is further provided to correct coma aberration in which parallel rays of the first and second lights 23a and 25a bend toward the optical axis and Adjust

3 is a view showing an optical axis correction method according to an embodiment of the present invention.

3, an optical axis correction method according to an embodiment of the present invention, the first step of emitting the first or second light (23a, 25a) from the first or second light source (23, 25), The first and second light beams 23a and 25a emitted from the first or second light sources 23 and 25, respectively, are inclined at a predetermined angle with respect to the optical axis at the same angle in this embodiment. A second step of injecting the first surface 7 or the second surface 9 of the isosceles triangle-shaped prism 31 having the surfaces 7 and 9, and the first surface 7 or the second surface 9 The third or second light beams 23a and 25a refracted by the light beams are emitted from the third surface 10 of the isosceles triangular prism 31 perpendicular to the optical axis so that the optical axis and the optical path coincide with each other. Steps.

The first light 23a and the second light 25a incident on the first surface 7 and the second surface 9 of the isosceles triangular prism 31 at the same angle θ _{1 and} θ ₁ ′, respectively, After refracting at angles θ _{2 and} θ ₂ ′, the light is incident on the third surface 10 of the polygonal prism at angles θ _{3 and} θ ₃ ′, and the optical axes coincide with each other.

The angles θ ₁ , θ ₁ ′, θ _2, θ ₂ ′ and θ _3, θ ₃ ′ for matching the optical axes of the first light 3 and the second light 5 are represented by the following equations 1 to 6 Can be obtained by Where α is the angle at which the first surface 7 is inclined with respect to the optical axis, and α 'is the angle at which the second surface 9 is inclined with respect to the optical axis.

Θ _1, and θ ₁ ′ obtained in Equations 1 and 2 have the same value, and according to Equation 3, the slopes α and α ′ of the prism have the same value.

The first light 23a and the second light 25a in which the optical axis deviation is corrected in the above manner are directed toward the beam splitter.

4 is a diagram showing the principle of obtaining the thickness t of the prism. 3, the slope of the prism α, the first light the incident angle of the three-sided θ ₃ and the optical axis (x = d / 2) distance from the point A from the 20 thickness t by the following equation 4 and 5, from Can be obtained.

In the optical pickup device having an isosceles triangle-shaped prism according to an embodiment of the present invention and the optical axis correction method using the same, an advantage of the isosceles triangle prism is that by adjusting the angle α to have a constant thickness t, The incidence angles and refraction angles of the first light and the second light are the same, so that the optical axis deviation can be easily corrected. The distance tolerance between the two lights can minimize the distance tolerance by adjusting the triangular prism 31 in the optical axis direction.

An isosceles triangular prism according to an embodiment of the present invention may be applied in other forms.

5, in the optical pickup apparatus according to the embodiment of the present invention, the optical axis correction means provided on the optical path between the light source 51 and the beam splitter 33, the first light and the second optical axis is parallel to each other In the first surface 67 and the second surface 69 having a first surface 67 and a second surface 69 inclined at predetermined angles α, α 'so that light 23a, 25a is incident. Each of the first and second light beams 23a and 25a refracted has a third surface 60 where the points coincide with each other, and further includes a fourth surface 62 corresponding to the third surface 60. It is a rhombic prism 61.

Referring to FIG. 6, in the optical pickup apparatus according to the exemplary embodiment of the present invention, the optical axis correction means provided on the optical path between the light source 51 and the beam splitter 33 includes first and second optical axes parallel to each other. It has a first surface 77 and a second surface 79 inclined at a predetermined angle (α, α ') for the light (23a, 25a) to enter, at the first surface 77 and the second surface 79 A fourth surface 72 and a first surface 70 having a third surface 70 at which a point where the optical axes of the refracted first and second lights 23a and 25a coincide, respectively, is positioned. A hexagonal prism further includes a fifth surface 74 connecting the 77 and the third surface 70 and a sixth surface 76 connecting the second surface 79 and the third surface 70. (71).

The prism of the type shown in FIGS. 5 and 6 may also correct the optical axis by adjusting the first and second surfaces to have a predetermined angle with respect to the optical axis, and when used in the optical pickup device, its configuration and function, and The optical axis correction method used is as described above with reference to FIGS.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. For example, one of ordinary skill in the art will be able to align the optical axis using another type of prism instead of the polygonal prism. Because of this variety of the invention the scope of the invention should not be defined by the described embodiments, but should be defined by the technical spirit described in the claims.

As described above, an advantage of the optical pickup apparatus and the optical axis correction method using the same according to the present invention is that the optical axis can be easily used by using a polygonal prism having first and second surfaces inclined at a predetermined angle with respect to the optical axis and having a predetermined refractive index. The optical pickup device can be easily manufactured, and the thickness tolerance can be increased, thereby making it easy to manufacture an optical pickup device that can cancel the effect of the distance tolerance between the two lights.

Claims (10)

First and second light sources for generating first and second light beams parallel to each other; An objective lens for focusing the first and second light emitted from the first and second light sources onto a recording medium; A photodetector configured to receive and photoelectrically convert the first and second light reflected from the recording medium; A beam splitter provided on an optical path between the light source and the objective lens to convert optical paths of the first light and the second light; And First and second surfaces provided on an optical path between the light source and the beam splitter and inclined at the same angle with respect to an optical axis such that the first and second light are incident and refracted, respectively, and refracted at the first surface And a polygonal optical axis correction means having a third surface in which the optical axes of the first light and the second light refracted by the second surface are coincident with each other. delete delete The method of claim 3, wherein And the first and second surfaces are set such that the first and second lights are incident at the same angle. The method of claim 4, wherein The optical axis correction means is an optical pickup device, characterized in that the isosceles triangular prism. A first step of emitting first and second light having parallel optical axes from the first and second light sources; A second step of injecting the first and second light into the first or second surface of the polygonal optical axis correction means having first and second surfaces inclined at the same angle with respect to the optical axis; And a third step of matching the optical axes of the first and second light refracted by the first surface or the second surface with the third surface of the optical axis correcting means and outputting the same. delete delete The method of claim 8, And the light is incident at the same angle with respect to the first surface or the second surface. The method of claim 9, And the optical axis correction means is an isosceles triangular prism.