KR100693094B1 - Optical pick-up - Google Patents

Abstract

An optical pickup is provided to dispose two mirrors which are located by adjoining together so that the disposed mirrors do not interfere with each other, thereby controlling focusing and tracking even in a simple and inexpensive optical system structure. The first optical system(10) is composed of the first light source(11) for recording/reproducing of the first recording medium(D1), and the first objective lens(12). The second optical system(20) has an optical axis inclined at certain angle for an optical axis of the first optical system(10), and is composed of the second light source(21) for recording/reproducing of the second recording medium(D2), and the second objective lens(22). The first optical system(10) has the first mirror(30) for changing a path of a beam emitted from the first light source(11) toward the first objective lens(12). The second optical system(20) has the second mirror(40) for changing a path of a beam emitted from the second light source(21) toward the second objective lens(22). The first and second mirrors(30,40) are disposed on different horizontal surfaces.

Description

Optical pickup {OPTICAL PICK-UP}

1 is a view schematically showing the configuration of an optical system in a conventional compatible optical pickup.

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

     3 is a view showing the configuration of an optical system in the optical pickup according to a second embodiment of the present invention.

     4 is a view showing the configuration of an optical system in the optical pickup according to a third embodiment of the present invention.

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

      10: first optical system 11: first light source

      12: first objective lens 20: second optical system

      21: second light source 22: second objective lens

      25: beam splitter 30: first mirror

      40: second mirror

      The present invention relates to an optical pickup, and more particularly to an optical pickup having two objective lenses for compatibility of the recording medium.

      An optical disk refers to a storage medium for recording / reproducing data such as voice, image, document, etc. by an optical method, and typically, a compact disk (CD) or a digital versatile disk (DVD). In recent years, research on high-density recording media with higher recording capacities as next-generation optical discs has been actively conducted. Such high-density recording media include BD (Blu-ray Disc) and HD-DVD (High Definition Digital Versatile Disc).

      Optical pickup refers to a device for reproducing information stored in the optical disk as described above using a semiconductor laser in a non-contact manner. The problem in developing a new recording medium is its compatibility with existing recording media. Recently, in line with the development of a new recording medium, researches on optical pickups that make it possible to be compatible with existing recording media (CD, DVD) and next-generation high-density recording media (BD, HD-DVD).

      1 is a view schematically showing the configuration of an optical system in a conventional compatible optical pickup. As shown in FIG. 1, the conventional optical pickup has a first optical system 1 for recording / reproducing CDs and DVDs, and a second optical system 2 for recording / reproducing BD, a next-generation recording medium.

The first optical system 1 comprises a twin light source 1a that emits light of two wavelengths suitable for CD and DVD, and a light spot that is formed on the CD or DVD by condensing the light incident from the twin light source 1a. Reflects the light emitted from the single objective lens 1b, the first photodetector 1c for receiving and detecting the light returned from the CD or DVD, and the light emitted from the twin light source 1a toward the first objective lens 1b. It has a first mirror 1d. On the optical path connected from the twin light source 1a to the first photodetector 1c, optical elements such as a diffraction grating 1e, a cubic beam splitter 1f, a collimation lens 1g, and an astigmatism lens 1i Are placed. Similarly, the second optical system 2 includes a light source 2a for emitting light of a suitable wavelength of the BD, a second objective lens 2b for condensing the light emitted from the light source 2a, and the light source 2a. With a second mirror 2c for reflecting light incident from the side toward the second objective lens 2b, various optical elements are arranged on the optical path between the light source 2a and the objective lens 2b.

      However, the conventional optical pickup having two objective lenses for compatibility of recording media has the following problems. In order to apply the general focusing error signal detection method (astigmatism method) and tracking error signal detection method (PP, DPP) in the first optical system 1 of the conventional optical pickup as described above, A photodetector may be used or the astigmatism lens 1i should be disposed in front of the first photodetector 1c as shown in FIG. 1. This raises the cost of parts, which leads to a problem that the price competitiveness of the product becomes worse.

      The problem is that in FIG. 1, the cubic beam splitter 1f is replaced with a plate beam splitter, and the optical axis of the first optical system 1 is moved in the direction through or through the ground or in the 'R' direction in FIG. 1. This can be solved by rotating (1j) at a constant angle.

However, when the optical axis of the first optical system 1 is rotated in the direction of the electrons, the overall thickness of the optical pickup becomes thicker, which in turn counters the current trend of slimming down the product. In addition, when the optical axis of the first optical system 1 is rotated in the latter direction (R direction), there is a problem that the first mirror 1d and the second mirror 2c interfere with each other.

      SUMMARY OF THE INVENTION The present invention has been made in view of the above problem, and provides two optical mirrors positioned adjacent to each other so as not to interfere with each other to provide an optical pickup capable of controlling focusing and tracking even with a simple and inexpensive optical system structure.

The optical pickup according to the present invention for achieving the above object in the optical pickup to be compatible with at least two recording media having a different recording density, the first light source for recording / reproduction of the first recording medium, A second optical system having a first optical system having a first objective lens and an optical axis inclined at an angle (θ, 30 ° ≤θ≤60 °) with respect to the optical axis of the first optical system, and for recording / reproducing the second recording medium A second optical system having a light source and a second objective lens, wherein the first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, and the second optical system And a second mirror for changing the path of the light emitted from the second light source toward the second objective lens, wherein the first mirror and the second mirror are disposed on different horizontal planes.

In addition, the optical pickup according to the present invention in the optical pickup to be compatible with at least two recording media having different recording density, the first light source, the first objective lens for recording / reproduction of the first recording medium A second optical source and a second object having a first optical system and an optical axis inclined at an angle (θ, 30 ° ≤θ≤60 °) with respect to the optical axis of the first optical system, and for recording / reproducing the second recording medium And a second optical system having a lens, wherein the first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, and the second optical system includes the second light source. And a second mirror for changing the path of the light emitted from the lens toward the second objective lens, wherein the first mirror and the second mirror have their respective centers spaced apart from each other in the tangential direction (Y direction) of the recording medium. Characterized in that .

In addition, the optical pickup according to the present invention in the optical pickup to be compatible with at least two recording media having different recording density, the first optical source and the first objective lens for recording / reproduction of the first recording medium And a first optical system having an optical axis inclined at an angle (θ1, 30 ° ≤θ1≤60 °) with respect to the tangential direction (Y direction) of the first recording medium, and for recording / reproducing the second recording medium. A second optical system having a second light source and a second objective lens and having an optical axis inclined at a predetermined angle (θ2, 30 ° ≤θ2≤60 °) with respect to the tangential direction (Y direction) of the second recording medium, And the first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, and the second optical system transmits a path of light emitted from the second light source to the second mirror. A second mirror for shifting toward the objective lens, Group the first mirror and the second mirror is characterized in that the side by side arranged in the radial direction of the first recording medium or the second recording medium.

The plate-shaped beam splitter is disposed on the optical path between the first light source and the first objective lens.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. 2 is a diagram showing the configuration of an optical system in the optical pickup according to the first embodiment of the present invention.

      As shown in FIG. 2, the optical pickup according to the first exemplary embodiment of the present invention allows the first optical system 10 and the second optical system 20 to be compatible with at least two recording media having different recording densities. ) The first optical system 10 is for recording / reproducing the first recording medium. In the present embodiment, the case where BD is applied as the first recording medium will be described as an example. The second optical system 20 is for recording / reproducing the second recording medium. In this embodiment, a CD or DVD is applied as the second recording medium by using a twin light source capable of emitting different wavelengths. Listen and explain. In other words, the second optical system 20 may be referred to as a CD / DVD shared optical system.

      The first optical system 10 focuses on a first light source 11 that emits light having a wavelength suitable for BD, and a first objective lens that condenses the light incident from the first light source 11 to form a spot on the BD D1. (12), the first mirror 30 for changing the path of the light emitted from the first light source 11 toward the first objective lens 12, and the light reflected from the BD (D1) and returned to detect the optical A first photodetector 13 for converting the signal into an electrical signal is provided.

      In addition, the first optical system 10 includes a diffraction grating 14, a cubic beam splitter 15, a collimating lens 16, an astigmatism lens 17, a condensing lens 18, and a feedback photodetector 19. do. The diffraction grating 14 is positioned in front of the first light source 11 to diffract the light emitted from the first light source 11 to form a 3-beam for detecting the tracking signal. The cubic beam splitter 15 transmits the light emitted from the first light source 11 to be directed toward the first objective lens 12, and transmits the light reflected from the BD D1 and returned to the first light detector ( 13). The collimating lens 16 is disposed between the cubic beam splitter 15 and the first objective lens 12 to convert the divergent light emitted from the first light source 11 into parallel light, and the feedback photodetector 19 The light emitted from the first light source 11 is received to monitor the output of the first light source 11. The astigmatism lens 17 is disposed in front of the first photodetector 13 to generate astigmatism necessary for detecting the focusing error signal, and the condensing lens 18 is disposed in front of the feedback photodetector 19 to make it a first. The divergent light emitted from one light source 11 is focused on the feedback photodetector 19.

      The second optical system 20 focuses the second light source 21 as a twin light source for emitting light having a wavelength suitable for the CD (D2) or the DVD (D3), and the light incident from the second light source 21 to condense the CD ( D2) or the second objective lens 22 forming a spot on the DVD D3, and the second mirror 40 for changing the path of the light emitted from the second light source 21 toward the second objective lens 22. And a second photodetector 23 which detects light returned from the CD D2 or DVD D3 and converts the optical signal into an electrical signal. At this time, the first objective lens 12 and the second objective lens 22 are mounted side by side in the radial direction (X direction) of the recording mediums D1, D2, and D3 by one actuator (not shown). The first mirror 30 and the second mirror 40 are also arranged side by side in the radial direction (X direction) of the recording mediums D1, D2, and D3.

      The second optical system 20 has a diffraction grating 24, a plate-shaped beam splitter 25, and a collimating lens 26 similarly to the case of the first optical system 10. In particular, in the present invention, the optical axis 20a of the second optical system 20 is inclined at a predetermined angle (θ, 30 ° ≦ θ ≦ 60 °) with respect to the optical axis 10a of the first optical system 10. Thus, when the plate-shaped beam splitter 25 is used and the optical axis 20a of the second optical system 20 is inclined at an angle, the astigmatism method and the DPP do not need to be used without using an astigmatism lens or a special optical detector. The same general error detection method can detect a focusing error signal and a tracking error signal.

      However, when the optical axis 20a of the second optical system 20 is inclined at an angle as described above, the first mirror 30 and the first mirror 30 must be rotated according to the direction of the optical axis 20a. The two mirrors 40 may interfere with each other or light emitted from the second light source 21 may be blocked by the first mirror 30. In order to solve this problem, in this embodiment, the first mirror 30 and the second mirror 40 are disposed on different horizontal planes. That is, the first mirror 30 and the second mirror 40 are disposed to be spaced apart by a predetermined distance in the vertical direction (Z direction) so as not to interfere with each other. In FIG. 2, the second mirror 40 is disposed above the first mirror 30, but on the contrary, the first mirror 30 may be disposed above the second mirror 40.

      3 is a diagram illustrating a configuration of an optical system in an optical pickup according to a second exemplary embodiment of the present invention. This embodiment has the same configuration as most of the embodiment of FIG. 2, but differs from the embodiment of FIG. 2 in the arrangement method of the first mirror 30 and the second mirror 40.

      As shown in Fig. 3, the first mirror 30 and the second mirror 40 in this embodiment have their respective centers O and O 'shots of the recording mediums D1, D2, and D3. It is arrange | positioned so that a predetermined distance d may be spaced in a gent direction (Y direction). Then, since the 'a' portion of the first mirror 30 is located above the 'b' portion of the second mirror 40 in three dimensions, the first mirror 30 and the second mirror 40 do not interfere with each other. In addition, a phenomenon in which light incident from the second light source 21 is blocked by the first mirror 30 does not occur.

4 is a diagram illustrating a configuration of an optical system in an optical pickup according to a third exemplary embodiment of the present invention. 2 and 3, the optical mirror 10b and the second optical system of the first optical system 10 may be replaced with the first mirror 30 and the second mirror 40 instead of linearly moving in a specific direction. This is a case where the optical axis 20b of (20) is rotated at an angle in the tangential direction (Y direction) of the recording mediums D1, D2, and D3.

As shown in FIG. 4, in the present embodiment, the second optical system 20 has a predetermined angle (θ ₂ , 30 ° ≦ θ ₂ ≦ with respect to the tangential direction (Y direction) of the recording mediums D1, D2, and D3. 60 °) has an inclined optical axis 20b. Similarly, the first optical system 10 also tilts the optical axis 10b inclined at an angle (θ ₁ , 30 ° ≤θ ₁ ≤60 °) with respect to the tangential direction (Y direction) of the recording mediums D1, D2, and D3. Have

Then, as shown in FIG. 4, the second mirror 40 and the first mirror 30 are respectively rotated by an angle along the inclination of the optical axis. Accordingly, since the 'a' portion of the first mirror 30 is located above the 'b' portion of the second mirror 40 in three dimensions, the first mirror 30 and the second mirror 40 do not interfere with each other. In addition, a phenomenon in which light incident from the second light source 21 is blocked by the first mirror 30 does not occur.

      In the present embodiment, as the optical axis 10b of the first optical system 10 rotates by a predetermined angle, the configuration of the first optical system 10 is different from those of FIGS. 2 and 3. That is, the cubic beam splitter of FIG. 2 is replaced by a plate beam splitter 15a, and a concave lens 17a is disposed between the first photodetector 13 and the beam splitter 15a.

      As described above, the present invention properly modifies the positions of the two mirrors disposed adjacent to each other so that the two mirrors do not interfere with each other or one of the mirrors blocks light incident to the other mirror. It works.

      Therefore, focusing control and tracking control can be easily performed without an optical element such as a special photodetector or astigmatism lens, thereby improving the price competitiveness and quality of the product.

Claims (5)

In the optical pickup to be compatible with at least two recording media having different recording density, A first optical system having a first light source for recording / reproducing the first recording medium, a first objective lens, and an optical axis inclined at an angle (θ, 30 ° ≤θ≤60 °) with respect to the optical axis of the first optical system; And a second optical system having a second light source and a second objective lens for recording / reproducing the second recording medium, The first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, The second optical system includes a second mirror for changing a path of light emitted from the second light source toward the second objective lens. And the first mirror and the second mirror are disposed on different horizontal planes. In the optical pickup to be compatible with at least two recording media having different recording density, A first optical system having a first light source for recording / reproducing the first recording medium, a first objective lens, and an optical axis inclined at an angle (θ, 30 ° ≤θ≤60 °) with respect to the optical axis of the first optical system; And a second optical system having a second light source and a second objective lens for recording / reproducing the second recording medium, The first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, The second optical system includes a second mirror for changing a path of light emitted from the second light source toward the second objective lens. And the centers of the first mirror and the second mirror are spaced apart by a predetermined distance in the tangential direction (Y direction) of the recording medium. In the optical pickup to be compatible with at least two recording media having different recording density, Having a first light source and a first objective lens for recording / reproducing the first recording medium, and inclining the predetermined angle (θ1, 30 ° ≤θ1≤60 °) with respect to the tangential direction (Y direction) of the first recording medium A first optical system having a true optical axis, a second light source for recording / reproducing the second recording medium, and a second objective lens, and having a predetermined angle θ2, relative to the tangential direction (Y direction) of the second recording medium; 30 ° ≦ θ2 ≦ 60 °) and having a second optical system having an inclined optical axis, The first optical system includes a first mirror for changing a path of light emitted from the first light source toward the first objective lens, The second optical system includes a second mirror for changing a path of light emitted from the second light source toward the second objective lens. And the first mirror and the second mirror are arranged side by side in the radial direction of the first recording medium or the second recording medium. The method according to any one of claims 1 to 3, And a plate type beam splitter is disposed on an optical path between the first light source and the first objective lens. The method of claim 4, wherein       And the first recording medium is BD, and the second recording medium is CD or DVD.

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