KR100459154B1 - Optical pickup device for different kinds of optical disks, especially correlated to enabling recording/reproducing compatibility between different optical disks while easily realizing thin and light properties - Google Patents

Abstract

PURPOSE: An optical pickup device for different kinds of optical disks is provided to separately configure light sources having different wavelengths, respectively while comprising a concave-mirror objective lens, thereby enabling recording/reproducing compatibility between different optical disks while removing the spherical aberration of the object lens with respect to the wavelengths. CONSTITUTION: The first light source(11) generates a DVD optical beam. A collimator lens(12) collimates the beam in certain direction. A beam splitter(13) transmits or reflects an incident beam according to the wavelength of the incident beam. The second light source(14) generates a CD-R optical beam. A collimator lens(15) collimates the beam toward the beam splitter(13). A reflecting mirror(16) passes a certain amount of the incident beam while reflecting the rest. An objective lens(17) controls an aperture ratio according to the wavelength of the beam passing through the reflecting mirror(16), and condenses the beam on one point positioned on a surface of an optical disk(18) via the reflecting mirror(16) again.

Description

Optical pickup device for different optical discs

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for heterogeneous optical disks having different substrate thicknesses and wavelengths. In particular, a compact disc (CD) and a digital multifunction device are used in the same optical pickup device by using an objective lens of concave diameter and two light sources. The present invention relates to an optical pickup apparatus for heterogeneous optical discs that enables recording / playback of not only a disc (Digital Versatile Disc; DVD) but also a recordable CD, that is, CD-R (Compact Disc Recordable).

Usually, the light source used for the optical pickup for DVD has a wavelength of 635 to 650 nm (visible light, red), but a light source having a wavelength of 780 nm (infrared light) is required to simultaneously read a CD-R disc in the same player.

In other words, in the case of CD-R, the medium of the disc uses cyanine (blue pigment) dye, which has a property of having a reflectance only at 780 nm.

Therefore, since a light source of 780 nm is necessarily required, it cannot be used as a DVD light source.

At this time, the CD can be read at both 780 nm and 635 to 650 nm wavelengths.

As a result, in order to use the CD-R as a combined use, a light source for the CD-R and a light source for the DVD are respectively required.

In addition, in order to read a CD or CD-R in a DVD player, it is necessary to adjust the aperture ratio NA of the objective lens.

In other words, in the case of a combined CD / DVD, a light source having the same wavelength may be used, but since the thickness of the disk is different (for example, 1.2 μm for a CD and 0.6 μm for a DVD), spherical aberration is changed, and it is necessary to correct this.

For example, the aperture ratio NA1 of the objective lens required for CD should be smaller than the aperture ratio NA2 required for DVD (NA2 > NA1).

Therefore, conventionally, a twin-lens method using two light sources separately for such a CDR / CD / DVD combined use, and separately using an DVD objective lens and a CD objective lens to adjust the aperture ratio has been proposed.

However, in the twin lens method, two objective lenses and a separate optical device for driving the respective lenses must be added, so that the product is heavy and complicated, so that the light and small is difficult and the price increases.

In addition, since the optical path of the beam generated from the light source and the beam incident to the objective lens is vertical, that is, the pickup type is L-shaped, the pickup height becomes high and the optical pickup device cannot be made thin (slim).

In addition, since the objective lens is a convex lens made of plastic, the incident beam passes through the objective lens regardless of the wavelength to form a spot on one surface of the optical disk. When the beam having the beam passes through the objective lens, the refractive index is affected.

In other words, the spherical aberration of the objective lens relatively increases the beam intensity of the side lobes, thereby increasing the crosstalk from the signals recorded in the adjacent tracks.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to separately configure light sources having different wavelengths and to configure concave objective lenses, thereby eliminating spherical aberration of objective lenses at different wavelengths. An optical pickup apparatus for heterogeneous optical disks, which enables recording / playback compatibility of optical disks having different wavelengths.

Another object of the present invention is to provide an optical pickup apparatus for heterogeneous optical disks, which is configured by making the optical pickup apparatus straight, thereby reducing the height of the pickup and making the optical pickup apparatus slim.

Another object of the present invention is to coat the dichroic mirror which transmits or reflects the beam according to the wavelength on the inner concave diameter of the objective lens and the beam splitter of the beam splitter, so that the aperture ratio of the objective lens can be easily adjusted to different thicknesses and recordings. An optical pickup apparatus for heterogeneous optical disks capable of recording / playback compatibility of optical disks having a density.

Features of the optical pickup device for heterogeneous optical disk according to the present invention for achieving the above object, the first light source for emitting a beam of the first wavelength and the beam generated from the first light source in parallel run in a predetermined direction A first collimator lens, a second light source that emits a beam of a second wavelength different from the first wavelength, a second collimator lens that propagates a beam generated by the second light source in parallel in a predetermined direction, and a first or A beam splitter that transmits or reflects an incident beam according to the wavelength of the beam incident in parallel from the second collimator lens, a reflective mirror that transmits only a predetermined amount of the beam reflected or transmitted by the beam splitter and reflects the rest, and a concave lens After adjusting the aperture ratio of the light beam passing through the reflection mirror, the light beam on the surface of the optical disk having a different wavelength and thickness through the reflection mirror It is configured to include an objective lens for condensing.

Features of the optical pickup apparatus for heterogeneous optical disks according to the present invention include a light source for generating a light beam to be irradiated on the surface of the optical disk, a reflection mirror for transmitting only a predetermined amount of the beam generated from the light source, and reflecting the rest, and a concave lens. And an objective lens for adjusting the aperture ratio of the light beam passing through the reflection mirror and then condensing the light beam on the corresponding surface of the optical disk having a different recording density and thickness through the reflection mirror.

1 is a configuration diagram of an optical system of an infinite optical pickup apparatus for a heterogeneous optical disk according to a first embodiment of the present invention.

2 is an optical system configuration diagram of a finite optical pickup apparatus for heterogeneous optical disks according to a second embodiment of the present invention.

3 is a view illustrating an example in which beam spots are simultaneously formed in FIG. 2;

4 is a diagram illustrating an example in which interference due to the simultaneous beam spot of FIG. 3 is removed;

Explanation of symbols for the main parts of the drawings

11: first light source 12,15 collimator lens

13 beam splitter 13a beam split surface

14 second light source 16 reflection mirror

17: objective lens 17a: inner surface

17b: outer surface 18: optical disk

18a: first information recording surface 18b: second information recording surface

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First embodiment

1 is an optical system configuration diagram of an infinite optical pickup apparatus for heterogeneous optical disks according to a first embodiment of the present invention, wherein the first light source 11 and the first light source 11 generate a DVD light beam. The collimator lens 12 for advancing parallel to the predetermined direction, the beam separator 13 for transmitting or reflecting the incident beam according to the wavelength of the incident beam, the second light source 14 for generating the light beam for CD-R, and the second Regardless of the wavelength or polarization direction passing or reflecting the collimator lens 15 and the beam splitter 13, which propagates the beam generated by the light source 14 to the beam splitter 13 in parallel, The rest is adjusted to the reflecting mirror 16 for reflecting and the wavelength of the beam passing through the reflecting mirror 16, and then focused on a point on the surface of the optical disk 18 via the reflecting mirror 16 again. It consists of an objective lens 17.

At this time, the dichroic mirror for passing or reflecting the incident beam according to the wavelength is coated on the beam splitting surface 13a of the beam splitter 13, and the reflective mirror 16 has the incident beam regardless of the polarization direction or wavelength. Non Polarizing Beam Splitter (NPBS) coated to pass a certain amount of light and reflect the rest.

The objective lens 17 is a concave lens, and is a dichro that reflects or transmits an incident beam according to a wavelength of an incident beam on a surface on which the beam passing through the reflective mirror 16 is incident, that is, on an inner surface 17a. The blade mirror is coated, and a reflection mirror for unconditionally reflecting the incident beam is coated on the opposite surface 17b of the surface 17a on which the beam passing through the reflection mirror 16 is incident.

At this time, the dichroic coating surface formed on the beam separation surface 13a of the beam splitter 13 and the inner surface 17a of the objective lens 17 has a plurality of optical coatings, and a beam having a specific wavelength passes therethrough. Beams of different wavelengths have the property of reflecting.

That is, in the present invention, it is assumed that the dichroic coating is performed so that the wavelength for the DVD is transmitted and the wavelength for the CD-R is reflected.

Therefore, recording / playback compatibility of heterogeneous disks having different wavelengths and heterogeneous disks having different aperture ratios is made possible by using the same optical pickup apparatus.

That is, when the CD series uses a wavelength of 780 nm, the DVD series uses a wavelength of 635-650 nm, the aperture ratio (NA) required for the CD series is 0.45, the NA required for the DVD series is 0.6, and the beam of the CD series is objective. The reflectance is reflected on the inner surface 17a of the lens 17 and the DVD-based beam is designed to reflect on the outer surface 17b so that the aperture ratio can be adjusted.

1, the first information recording surface 18a of the optical disc 18 is an information recording surface of a DVD, the second information recording surface 18b is an information recording surface of a CD, and the second information recording surface 18b is a first information. It is located 0.6 mm further from the surface of the optical disk 18 than the recording surface 18a.

On the other hand, after focusing on the first information recording surface 18a or the second information recording surface 18b of the optical disk 18, the reflected beam is incident to each photodetector via the opposite path.

In this case, it is assumed that the light detector is integrally formed in the light source package.

That is, the laser diode and the photo detector are disposed side by side in the package of the light source, and the reflected signal from the optical disk can be detected by diffracting the beam incident into the light source package using the hologram element toward the photo detector.

In the present invention configured as described above, the wavelength of the light beam generated by the first light source 11 is 635-650 nm used for the DVD-based optical disc, and the wavelength of the light beam generated by the second light source 14 is used for the CD-based optical disc. Assume that it is 780nm.

The beam splitting surface 13a of the beam splitter 13 and the inner surface 17a of the objective lens 17 are coated with a dichroic mirror to reflect light of 780 nm wavelength and reflect light of 635-650 nm wavelength. Assume that there is.

Here, 780 nm is a wavelength for CD-R, and 635-650 nm is a wavelength for DVD.

At this time, the CD can be read in both 780nm or 635-650nm, but in the present invention uses 780nm for CD-R / CD / DVD combined use.

Hereinafter, the recording / reproducing of the DVD-based optical disc and the recording / reproducing of the CD-based optical disc will be described separately.

i) DVD series optical disc

The light beam having a wavelength of 635-650 nm generated by the first light source 11 is parallel light by the collimator lens 12 and is incident to the beam splitter 13.

At this time, the beam of the wavelength for DVD is parallel-beamed by the collimator lens 12, and an image height does not generate | occur | produce.

Since the dichroic mirror is coated on the beam splitting surface 13a of the beam splitter 13, the light beam of the DVD passes through the beam splitter 13 and is incident to the reflecting mirror 16.

The reflective mirror 16 is an NPBS coated mirror, and only a predetermined amount of the beam passing through the beam splitter 13 is irrelevant to the wavelength of the beam passing through the beam splitter 13 or the polarization direction. It enters into the inner surface 17a.

That is, the NPBS-coated reflecting mirror 16 has a property of reflecting 50% unconditionally and transmitting the remaining 50% irrespective of the property of the incident beam.

Since the inner surface 17a of the objective lens 17 is dichroic coated, the incident beam passes through the inner surface 17a and enters the outer surface 17b.

Since the outer surface 17b has a total reflection coating that unconditionally reflects the beam, the beam incident on the outer surface 17b is reflected and incident on the reflection mirror 16.

At this time, the beam reflected from the outer surface 17b is imaged at the position of a.

The position of a is half of the curvature R of the outer concave mirror 17b of the objective lens 17.

Therefore, the beam diameter of the beam for DVD incident on the reflection mirror 16 is not reduced.

That is, since the beam diameter of the light beam is not reduced, the original numerical aperture (i.e., 0.6) is maintained.

Therefore, a certain amount of light beams reflected by the reflecting mirror 16 is accurately focused on the first information recording surface 18a of the optical disk 18, that is, the information recording surface of the DVD, so that the information is recorded on the DVD or the recorded information is accessed. do.

ii) CD series optical disc

The light beam having the 780 nm wavelength generated by the second light source 14 becomes parallel light by the collimator lens 15 and is incident to the beam separator 13.

At this time, the beam of the wavelength for CD-R is parallel-beamed by the collimator lens 15, and an image height does not generate | occur | produce.

Since the dichroic mirror is coated on the beam splitting surface 13a of the beam splitter 13, the light beam of the CD is reflected from the beam splitting surface 13a of the beam splitter 13 to the reflecting mirror 16. Incident.

The reflection mirror 16 is an NPBS coated mirror, and a predetermined amount of the beam reflected from the beam splitter 13 regardless of the wavelength or polarization direction of the beam reflected from the beam splitting surface 13a of the beam splitter 13. The light is incident on the inner surface 17a of the objective lens 17.

At this time, since the inner surface 17a of the objective lens 17 is dichroic coated, the incident beam is reflected from the inner surface 17a and is incident again to the reflective mirror 16.

At this time, the beam reflected from the inner surface 17a is imaged at the position of b.

The position b is half of the curvature R of the internal concave mirror 17a of the objective lens 17.

Therefore, the beam diameter of the CD-R beam incident on the reflection mirror 16 is reduced.

When the beam diameter of the light beam is reduced, the numerical aperture is reduced to the CD numerical aperture (i.e. 0.45), so that a certain amount of the light beam reflected from the reflecting mirror 16 causes the second information recording surface 18b of the optical disk 18, i.e., the information of the CD. Since the light is condensed accurately on the recording surface, information can be recorded on the CD series optical disk or the recorded information can be accessed.

As described above, the first embodiment of the present invention is ideal because the quality of the beam is almost perfect (corresponding to aberration) by the convex objective lens as it is formed by the parallel beam. If only the height is secured, there is no problem in the pick-up operation, so the thickness can be reduced.

Second embodiment

2 is an optical system configuration diagram of a finite system optical pickup apparatus for a heterogeneous optical disk according to a second embodiment of the present invention, which is effective when recording / reproducing heterogeneous optical disks having different aperture ratios.

2, the light source 21, the NPBS-coated reflecting mirror 22, and the concave objective lens 23 are provided on the same optical path.

In this case, the inner surface 23a of the objective lens 23 has a NPBS coating for passing 50% of the incident beam and reflecting the remaining 50%.

The outer surface 23b of the objective lens 23 is provided with an optical coating for totally reflecting the incident beam.

That is, the light beam generated by the light source 21 is incident on the reflection mirror 22.

At this time, since the reflecting mirror 22 is coated with NPBS, only a predetermined amount of incident light passes through the reflecting mirror 22 and is incident on the inner surface 23a of the objective lens 23.

Since the inner surface 23a of the objective lens 23 is also NPBS-coated, 50% of the incident beam is reflected and is incident on the reflection mirror 22.

At this time, the beam reflected from the inner surface 23a is imaged at the position of d.

The point d is always located at a point between the half point of the curvature R of the inner concave mirror 23a of the objective lens 23 and the curvature R of the inner concave mirror 23a in the optical axis.

Therefore, even if the objective lens 23 is moved up and down by a focusing operation or the like, the d point is always located on the optical axis, and thus no image is generated.

In addition, the beam diameter of the beam incident on the reflection mirror 22 is reduced.

When the beam diameter of the light beam is reduced, the numerical aperture is reduced to the CD numerical aperture (i.e., 0.45), so that 50% of the light beams reflected from the reflecting mirror 22 are applied to the second information recording surface 24b of the optical disk 24, i.e. Since the light is condensed accurately on the information recording surface, information can be recorded on the CD series optical disk or the recorded information can be accessed.

Meanwhile, the remaining 50% of the light beams passing through the inner surface 23a of the objective lens 23 is incident on the outer surface 23b.

Since the outer surface 23b has an optical coating that reflects the incident beam unconditionally, the beam incident on the outer surface 23b is reflected and incident on the reflecting mirror 22.

At this time, the beam reflected from the outer surface 23b is imaged at the position of c.

The point c is always located at a point between the point 1/2 of the curvature R of the outer concave mirror 23b of the objective lens 23 and the curvature R of the outer concave mirror 23b in the optical axis.

Therefore, even if the objective lens 23 moves up and down by a focusing operation or the like, the c point is always located on the optical axis, so that no image is generated.

Therefore, the beam diameter of the beam incident on the reflection mirror 22 is not reduced.

That is, since the beam diameter of the light beam is not reduced, the original numerical aperture (i.e., 0.6) is maintained.

Therefore, 50% of the light beams reflected by the reflecting mirror 22 are accurately focused on the first information recording surface 24a of the optical disk 24, that is, the information recording surface of the DVD, so that the information is recorded on the DVD or the recorded information is accessed. Be sure to

As described above, in the second embodiment of the present invention, beam spots are simultaneously formed on heterogeneous disks having different aperture ratios using one beam as shown in FIG. 3, but interference does not occur.

That is, when the disc is reproduced using the beam formed at the position of d, the beam path is the same as that of f of FIG. 4, and when the disc is reproduced using the beam formed at the position of c, the beam path is represented by e of FIG. 4. Since they are the same, they are scattered on the disk and do not interfere with the focusing operation of the pickup.

That is, it does not act as signal noise.

Therefore, the finite system optical pickup apparatus according to the second embodiment of the present invention can achieve simplicity and slimming.

As described above, according to the optical pickup device for heterogeneous optical disks according to the present invention, by constructing a plurality of light sources that generate different wavelengths separately, and by configuring the objective lens using a concave mirror and a concave lens, objectives for different wavelengths It eliminates the spherical aberration of the lens and eliminates the need for a separate optical device, thereby enabling recording / playback compatibility of CD-based optical discs / DVD-based optical discs using different wavelengths with the same high speed and thinner optical pickup.

In addition, since the optical pickup device is constructed in a straight type by securing only the height of the concave diameter of the objective lens, the height of the pickup can be reduced to make the optical pickup device slim.

In addition, by coating a dichroic mirror which transmits or reflects the beam according to the wavelength on the inner concave diameter of the objective lens and the beam separation surface of the beam splitter, the beam separation of different wavelengths and the aperture ratio of the objective lens are controlled to separate optical components. Since the numerical aperture can be easily adjusted without the need for this, the optical pickup device can be easily and lightly shortened, and recording / playback compatibility of optical discs having different thicknesses and recording densities is possible.

Claims (8)

First light emitting means for emitting a beam of a first wavelength; A first collimator lens for traveling the beam generated by the first light emitting means in parallel in a predetermined direction; Second light emitting means for emitting a beam of a second wavelength different from the first wavelength; A second collimator lens for traveling the beam generated by the second light emitting means in parallel in a predetermined direction; Beam separation means for transmitting or reflecting the incident beam according to the wavelength of the beam incident in parallel from the first or second collimator lens; A reflection mirror which transmits only a predetermined amount of the beam reflected or transmitted by the beam separation means and reflects the rest; And a focusing means for adjusting the aperture ratio of the light beam passing through the reflective mirror and condensing the light beam on a corresponding surface of the optical disk having a different wavelength and thickness through the reflective mirror. Optical pickup device. The method of claim 1, wherein the first and second light emitting means An optical pickup apparatus for heterogeneous optical disks, characterized by emitting light beams of wavelengths used for CD-based optical disks and beams of wavelengths used for DVD-based optical disks. The method of claim 1, And a dichroic mirror for passing or reflecting the incident beam according to the wavelength of the incident beam, wherein the beam splitting surface of the beam splitter is coated. The method of claim 1, And the dichroic mirror for passing or reflecting the incident beam according to the wavelength of the incident beam is coated with an internal concave diameter of the focusing means to which the beam passing through the reflecting mirror is incident. The method of claim 1, And an outer concave mirror opposite the inner concave mirror of the focusing means is optically coated to reflect the incident beam unconditionally. The method of claim 1, And a non-polarization beam separation (NPBS) coating for passing only a predetermined amount of the incident beam and reflecting the rest, irrespective of the wavelength of the incident beam and the polarization direction of the reflective mirror. A light source for generating a light beam to be irradiated to the surface of the optical disk, A reflecting mirror coated with a non-polarization beam separation (NPBS) to pass only a predetermined amount of the beam incident from the light source and reflect the rest; It is made of a concave lens, the inner concave diameter of the concave lens to which the beam passing through the reflecting mirror is incident non-polarization beam separation (NPBS) coating to pass only a certain amount of the incident beam, and reflect the rest, and transmits through the reflecting mirror And focusing means for adjusting the aperture ratio of the light beam and focusing the light beam on a corresponding surface of the optical disk having a different recording density and thickness through the reflecting mirror. 8. An optical pickup apparatus for heterogeneous optical discs as claimed in claim 7, wherein the outer concave opposite the inner concave of the focusing means is optically coated to unconditionally reflect the incident beam.