KR19980059971A - Optical pickup device for heterogeneous optical discs. - Google Patents

Abstract

The present invention relates to an optical pickup device for heterogeneous optical disks having different substrate thicknesses and wavelengths. In particular, a plurality of light sources generating different wavelengths are separately formed, and an objective lens is formed by using a concave mirror and a concave lens. It eliminates the spherical aberration of the objective lens, eliminating the need for a separate optical device, making it possible to record / play back compatible CD-based optical discs / DVD-based optical discs using different wavelengths with the same high-speed and thin optical pickup. By coating a dichroic mirror that 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, separate optical components are controlled by adjusting beam separation of different wavelengths and aperture ratio of the objective lens. Easy adjustment of the numerical aperture without the need for easy and light weight reduction of optical pickup devices It is possible to record / play back compatible optical discs having degrees.

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).

Therefore, since a light source of 780 nm is required, it cannot be used as a light source for DVD. For example, the aperture ratio NA1 of the objective lens required for a CD must be smaller than the aperture ratio NA2 required for a DVD (NA2 > NA1).

The present invention is to solve the above problems, an object of the present invention by separately configuring the light source having a different wavelength and by configuring an objective lens of the concave diameter, to eliminate the spherical aberration of the objective lens for different wavelengths An optical pickup apparatus for heterogeneous optical disks capable of making recording / playback compatibility of optical disks having different wavelengths possible. An aspect of the optical pickup apparatus for heterogeneous optical disks according to the present invention is an optical beam to be irradiated onto the surface of the optical disk. A light source for generating a light source, a reflection mirror that transmits only a predetermined amount of the beam generated from the light source, and reflects the rest of the light beam, and a concave lens to adjust the aperture ratio of the light beam passing through the reflection mirror, It is configured to include an objective lens for focusing the light beam on the surface of the optical disk of different thicknesses .

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.

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

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. The incident beam irrespective of the wavelength A predetermined amount is passed through and the rest is a non-polarization beam splitter for reflecting; is (Non Polarizing Beam Splitter NPBS) coating.

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.

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.

That is, by placing the laser diode and the photo detector side by side in the package of the light source and diffracting the beam incident into the light source package toward the photo detector using the hologram element, it is possible to detect the reflected signal from the optical disk.

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 / playback of the DVD-based optical disc and the recording / playback of the CD-based optical disc will be described separately. I) DVD-based optical disc

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 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 117b is reflected and incident on the reflecting mirror 16.

The position of a is half of the curvature R of the outer concave mirror 17b of the objective lens 17. A predetermined amount of light beams reflected from the reflecting mirror 16 is applied to the optical disk 18. 1 The information recording surface 18a, i.e., the information recording surface of the DVD, is condensed accurately so that the information is recorded on the DVD or the recorded information is accessed.

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 reflection mirror 16. Incident.

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

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.

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.

Here, the inner surface 23a of the objective lens 23 is coated with an NPBS that passes 50% of the incident beam and reflects the remaining 50%.

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

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.

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. 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.

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 half point 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.

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.

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 Since the spherical aberration of the lens is eliminated and a separate optical device is not required, recording / playback compatibility of CD-based optical discs / DVD-based optical discs using different wavelengths is possible with the same high speed and thin 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 (10)

First light emitting means for emitting a beam of a first wavelength, a first collimator lens for advancing the beam generated by the first light emitting means in parallel in a predetermined direction, and a beam of a second wavelength different from the first wavelength; The incident light beam is transmitted or transmitted according to the second light emitting means, the second collimator lens for traveling the beam generated by the second light emitting means in parallel in a predetermined direction, and the wavelength of the beam incident in parallel from the first or second collimator lens. A beam splitting means for reflecting, a reflecting mirror for transmitting only a predetermined amount of the beam reflected or transmitted by the beam separating means, and reflecting the rest, and a concave lens to adjust the aperture ratio of the light beam passing through the reflecting mirror, And focusing means for condensing a light beam on a corresponding surface of an optical disk having a different wavelength, thickness, or the like. The optical pickup device for an optical disk. 2. The heterogeneous optical disc according to claim 1, wherein the first and second light emitting means emit a beam of a wavelength used for a CD optical disc and a beam of a wavelength used for a DVD optical disc. Optical pickup. The optical pickup apparatus of claim 1, wherein the beam splitting surface of the beam splitting means is coated with a dichroic mirror which passes or reflects the incident beam according to the wavelength of the incident beam. The heterogeneous light according to claim 1, wherein the internal concave diameter of the focusing means to which the beam passing through the reflecting mirror is incident is coated with a dichroic mirror for passing or reflecting the incident beam according to the wavelength of the incident beam. Optical pickup device for discs. 2. An optical pickup apparatus for heterogeneous optical discs as claimed in claim 1, wherein the outer concave opposite the inner concave of the focusing means is optically coated to unconditionally reflect the incident beam. 2. The heterogeneous optical disc of claim 1, wherein the reflective mirror is coated with a non-polarization beam separation (NPBS) coating that passes only a predetermined amount of the incident beam and reflects the rest regardless of the wavelength of the incident beam and the polarization direction. Optical pickup device. A light source for generating a light beam to be irradiated to the surface of the optical disk, a reflecting mirror that transmits only a predetermined amount of the beam generated from the light source and reflects the rest, and a concave lens to adjust the aperture ratio of the light beam passing through the reflecting mirror. And focusing means for condensing a light beam on a corresponding surface of the optical disk having different recording densities and thicknesses through a reflective mirror. 8. The heterogeneous optical disc of claim 7, wherein the reflective mirror is coated with a non-polarization beam separation (NPBS) coating that passes a predetermined amount of the incident beam and reflects the rest regardless of the wavelength of the incident beam and the polarization direction. Optical pickup device. The non-polarization beam separation method according to claim 7, wherein the internal concave diameter of the focusing means to which the beam passing through the reflecting mirror is incident passes only a predetermined amount of the incident beam and reflects the rest regardless of the wavelength of the incident beam and the polarization direction. NPBS) optical pickup device for heterogeneous optical disk, characterized in that the coating. 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.