KR20010105826A - Optical Pick-up Device - Google Patents

Abstract

Useful catalyst compositions are produced by treating substituted molecular sieves with reactive titanium compounds such as titanium tetrahalides, preferably in the vapor phase at elevated temperatures. The molecular sieve starting materials contain tellurium, boron or germanium oxides in addition to silicon and titanium oxides. Olefins are efficiently transformed to epoxides using these catalyst compositions and an oxidizing agent such as hydrogen peroxide or an organic hydroperoxide.

Description

Optical Pick-up Device

The present invention relates to an optical disc player and a recording / reproducing method thereof, and more particularly, to an optical disc player and a recording / reproducing method thereof capable of recording and reproducing different types of optical discs using a single optical pickup device.

In general, a recording / playback method of an optical disc player for recording / reproducing an optical disc such as an optical disc such as a compact disc (CD) (or a recordable compact disc (CD-R)) or a digital video disc (DVD) or the like is as follows. Same as

1 is a schematic diagram showing an optical pickup apparatus for recording / reproducing a conventional optical disc.

As shown in FIG. 1, a beam is irradiated from the laser diode 1 to reproduce the optical disc D. FIG. For example, in order to reproduce the DVD disc D, a 650 nm P-polarized beam is irradiated from the laser diode 1. The beam emitted from the laser diode 1 is divided by the diffraction grating 2 into three beams of 0th order beam and ± 1st order beam so that it can be used as a tracking servo. The beam passing through the diffraction grating 2 is transmitted or reflected by the flat plate beam splitter 3. The flat plate beam splitter 3 is formed with a coating layer for reflecting or transmitting the beam depending on the wavelength and polarization. For example, the flat plate beam splitter 3 may be coated so as to battle when the 650 nm wavelength beam is P-polarized and totally reflect when the beam is S-polarized. The P-polarized beam divided into three beams by the diffraction grating 2 is totally reflected by the flat beam splitter 3.

This totally reflected beam is converted into circularly polarized light while passing through the λ / 4 wave plate 4, and the beam is focused into parallel light by the converging lens 5. This parallel light is focused on the recording surface of the optical disc D via the objective lens 5.

The beam focused on the recording surface of the optical disc D is reflected and passes again through the objective lens 6 and the converging lens 5.

This beam is then converted into S-polarized light while passing through the [lambda] / 4 wave plate 4, and this S-polarized beam undergoes the beam splitter 3. The beam passing through the beam splitter 3 converges to an optical signal having astigmatism for use as a focusing servo while passing through the converging lens 8 and enters the photodetector 9. The beam incident on the photodetector 9 is detected by the photodetector 9 and used as an image / audio signal and an electrical signal of the tracking and focusing servo.

By the way, the λ / 4 wave plate used in the optical pickup device as described above is very expensive, which increases the cost of the product.

However, when the lambda / 4 wave plate is not used, a beam splitter having the characteristics described above cannot be used. When not using a λ / 4 wave plate, the beam splitter should have a property of partially transmitting and partially reflecting a predetermined polarized beam. For example, when the beam splitter is coated with a diagonal surface to transmit and reflect at a ratio of T _p : R _p = 6: 4 (T _p : P polarization transmittance and R _p : P polarization reflectance) with respect to the P polarized incident beam It is preferable.

However, in the case of applying a beam splitter having some reflection and some transmissive characteristics due to polarization, it is impossible to solve the problem that distortion occurs in the disc reproduction signal due to the birefringence phenomenon in the disc.

That is, when the pressure conditions, etc., during injection molding of the disk are not precisely controlled, the stress is partially generated. Accordingly, the beams incident on the disk are partially different from each other depending on the position of the beam on the disk according to the polarization direction. A different phenomenon will occur. There is a problem that the amount of light detected by the photo detector cannot be accurately controlled due to the partially different refractive index on the disk.

For example, in the case where the λ / 4 wave plate is not applied in FIG. 1, when the P-polarized beam is incident on the beam splitter, 40% of the incident beams are reflected by the beam splitter toward the disk. This beam enters the disc via the objective lens. The beam returned therefrom enters the beam splitter again, and 60% of the incident beams enter the photodetector. When the disk is an ideal disk that does not cause birefringence, the amount of light detected by the photodetector is 0.24 light amount (= 0.4 * 0.6) with respect to the total light amount. On the other hand, if the disk converts 100% P-polarized light into a beam of 50% P-polarized light and 50% S-polarized light due to the birefringence effect, the light detected by the photodetector is 0.12 light amount (= 0.4 * (0.6) * 0.5 + 0.5 * 0)), the amount of light is greatly reduced. Since the birefringence phenomenon changes irregularly according to the partial position of the disk, it becomes difficult to accurately recognize the reproduction signal in the photodetector.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to set up the coating conditions of the reflection and transmission for the P-polarized light and the S-polarized light of the beam splitter to be the same within the error range. An optical pickup apparatus capable of accurate recording / reproducing for an optical disc exhibiting birefringence without using an element.

1 is a schematic diagram showing an optical pickup apparatus for recording / reproducing a conventional optical disc;

2 is a schematic diagram showing an optical pickup apparatus for recording / reproducing one type of optical disc according to the present invention.

3 is a schematic diagram showing an optical pickup apparatus for recording / reproducing a plurality of different types of optical discs according to the present invention.

Figure 4a is a graph showing the transmission spectrum of the flat panel beam splitter in the optical pickup device of the present invention, Figure 4b is a graph showing the transmission spectrum of the cubic beam splitter in the optical pickup device of the present invention.

Explanation of symbols on the main parts of the drawings

10; First laser diode 12; Diffraction grating

13; Flat beam splitter 14; Adjustable iris

15; Converging lens 16; Objective

18; Converging lens 19; Photo detector

20; Second laser diode 22; Diffraction grating

In order to achieve the object as described above, the present invention,

A laser light source for irradiating a laser beam of predetermined polarization;

Reflects the laser beam of the predetermined polarization irradiated from the laser light source with a first reflectance of 40 to 60% and transmits it to the remaining beams, and for other polarizations, at the predetermined first reflectance with respect to the predetermined polarization of the laser beam. A beamsplitter coated to reflect at a second reflectance within a predetermined error range and to transmit for the remaining beams;

An objective lens for focusing a beam directed to the optical disc via the beam splitter on the recording surface of the optical disc; And

An optical pickup apparatus including a photo detector for detecting a laser beam reflected from the optical disc is provided.

The error range is ± 5%.

In addition, in order to achieve the above object, the present invention

In order to record / reproduce a plurality of optical discs of different densities, a first laser light source and a second laser light irradiating a first laser beam having a first polarization and a first wavelength and a second laser beam having a second polarization and a second wavelength, respectively. A laser light source unit having a laser light source;

Is disposed on the optical path of the first laser beam irradiated from the first laser light source, reflects the first laser beam of the first wavelength and the first polarization with a first reflectance of 40 to 60% and transmits to the remaining beam The laser beam of the second polarized light having the same wavelength is reflected to the first polarized light of the first laser beam at a first 'reflectance within a predetermined error range with respect to the predetermined first reflectance, and transmitted to the remaining beams. A first beamsplitter coated to be coated;

Disposed on the optical path of the second laser beam of the second polarization irradiated from the second laser light source, reflecting the second laser beam of the second wavelength and the second polarization at a second reflectance of 40 to 60%, and remaining The light beam is transmitted through the beam, and the laser beam of the first polarization of the same wavelength is reflected by the second 'reflectance within a predetermined error range with respect to the predetermined second reflectance with respect to the second polarization of the second laser beam and the remaining beams. A first beamsplitter coated to transmit about;

An objective lens for focusing a beam directed to the optical disc via the beam splitter on the recording surface of the optical disc; And

An optical pickup apparatus including a photo detector for detecting a first or second laser beam reflected from the disk is provided.

The first beamsplitter combats the laser beam of the second wavelength, and the second beamsplitter is coated to totally reflect the laser beam of the first wavelength.

The error range is ± 5%.

According to the optical pickup apparatus as described above, even if the polarization of the beam reflected from the optical disk is changed by setting the coating conditions of the reflection and transmission for the P- and S-polarized light of the beam splitter within the error range, the photodetector accordingly is changed accordingly. The amount of light of the received beam at can be kept constant. Therefore, accurate recording / reproducing is possible for discs showing birefringence without using expensive elements such as lambda / 4 wavelength plates.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Embodiment 1 is a case of recording / reproducing one type of optical disc, and Embodiment 2 is a case of recording / reproducing a plurality of different types of optical discs.

Example 1

2 is a schematic diagram showing an optical pickup apparatus for recording / reproducing one type of optical disc according to an embodiment of the present invention. Figure 4a is a graph showing the transmission spectrum of the flat plate beam splitter in the optical pickup device of the present invention.

Reference numeral 10 denotes a laser diode for irradiating a laser beam of a predetermined polarization. The laser diode 10 irradiates a P-polarized beam having a wavelength of 650 nm, for example, to record / reproduce a DVD disc.

The diffraction grating 12 is installed on the front surface of the laser diode 10. The diffraction grating 12 divides the laser beam irradiated from the laser diode 10 into three beams, i.e., a 0th order beam and a ± 1st order beam, respectively for tracking servo.

As shown in FIG. 4A, the beam splitter 13 reflects the laser beam of the P-polarized light emitted from the laser diode 10 at a first reflectance of 40 to 60% and transmits the remaining beam. Coated. In addition, the S-polarized beam of 650 nm is coated to transmit and reflect within an error range of ± 5%. For example, a 650 nm P polarized beam is transmitted and reflected at a ratio of T _p : R _p = 6: 4, and the S polarized beam of 650 nm is also at the same ratio as the P polarized beam, that is, T _s : R _s = 6: 4 Permeate and reflect at the ratio of.

The beam reflected by the beam splitter 13 is focused into parallel light by the converging lens 15. This parallel light is focused on the recording surface of the DVD disc D via the objective lens 16. The P-polarized component and the S-polarized component are changed due to the birefringence effect caused by the generation of stress or the like during the molding of the disk D while the P-polarized beam focused on the recording surface of the DVD disc D is reflected. The amount of change is irregular depending on the position of the image on the disk. For example, the P polarization component and the S polarization component can be changed to 50%.

The beam in which the polarization component is converted by this birefringence effect passes through the objective lens 16 and the converging lens 15 again.

This 650 nm beam then passes through the beam splitter 13, with the 650 nm P polarized beam at the ratio of T _p : R _p = 6: 4 and the S polarized beam of T _s : R _s = 6: 4 Permeate and reflect in proportion.

The transmitted beam converges to an optical signal having astigmatism for use as a focusing servo while passing through the converging lens 18 and enters the photodetector 19. The beam incident on the photodetector 19 is detected by the photodetector 19 and used as an image / audio signal and an electrical signal of the tracking and focusing servo.

Here, if the disk is reflected after the beam is incident to a position where the birefringence does not occur, the light detected by the photodetector detects 0.24 light amount (= 0.4 * 0.6) with respect to the total light amount at the corresponding position. On the other hand, if the disk is incident to 100% P polarized light at a predetermined position on the disk due to the birefringence effect and is converted and reflected into a beam of 50% P polarized light component and 50% S polarized light component, the light detected by the photodetector is correspondingly The amount of light does not change as 0.24 amount of light (= 0.4 * (0.6 * 0.5 + 0.5 * 0.6)) with respect to the total amount of light at the position to be.

Therefore, even if the disc exhibits a birefringent effect that varies irregularly according to its partial position, the amount of light detected by the photodetector is constant, so that the reproduction signal can be accurately recognized.

Example 2

3 is a schematic diagram showing an optical pickup apparatus for recording / reproducing a plurality of different types of optical discs according to an embodiment of the present invention. Figure 4a is a graph showing the transmission spectrum of the flat panel beam splitter in the optical pickup device of the present invention, Figure 4b is a graph showing the transmission spectrum of the cubic beam splitter in the optical pickup device of the present invention.

Reference numeral 10 is a first laser diode that irradiates a first laser beam of a first wavelength and a first polarization. The first laser diode 10 is, for example, a P-polarized beam having a wavelength of 650 nm for recording / reproducing DVD discs. When the first disc is to be recorded / reproduced, the first laser diode 10 is driven. A P-polarized beam of 650 nm wavelength is emitted.

Reference numeral 20 is a second laser diode for irradiating a second laser beam of a second wavelength and a second polarization. The second laser diode 20 is, for example, an S-polarized beam having a wavelength of 760 nm for recording / reproducing CD-R discs. When the second laser diode 20 is to be recorded / reproduced, the second laser diode 20 ) And emits an S-polarized beam having a wavelength of 760 nm.

Diffraction gratings 12 and 22 are respectively provided on the front surfaces of the first and second laser diodes 10 and 20. The diffraction gratings 12 and 22 divide the respective laser beams irradiated from the first and second laser diodes 10 into three beams, i.e., zero-order beam and ± first-order beam, respectively for tracking servo.

The flat panel beam splitter 13 is disposed on the 650 nm wavelength irradiated from the first laser diode 10 and the optical path of the first laser beam of P polarization, and the 650 nm wavelength irradiated from the first laser diode 10. The P-polarized laser beam is reflected at a first reflectance of 40 to 60% and coated to transmit the remaining beam. In addition, the S-polarized beam of 650 nm is coated to transmit and reflect within an error range of ± 5%. On the other hand, a beam of 760 nm is coated to combat.

For example, a 650 nm P polarized beam is transmitted and reflected at a ratio of T _p : R _p = 6: 4, and the S polarized beam of 650 nm is also at the same ratio as the P polarized beam, that is, T _s : R _s = 6: 4 Since it is coated to transmit and reflect at a ratio of, 40% of the beams emitted from the first laser diode 10 are reflected by the flat plate beam splitter 13.

A cubic beam splitter 23 is disposed on the optical path of the 760 nm wavelength irradiated from the second laser diode 20 and the second laser beam of P polarization, and the P of 760 nm wavelength irradiated from the laser diode 20. It is coated to reflect the laser beam of polarization at a first reflectance of 40-60% and transmit it for the remaining beams. In addition, the S-polarized beam of 760 nm is coated to transmit and reflect within an error range of ± 5%. For example, a 760 nm P polarized beam is transmitted and reflected at a ratio of T _p : R _p = 6: 4, and the S polarized beam of 760 nm is also the same ratio as the P polarized beam, that is, T _s : R _s = 6: 4 Since it is coated to transmit and reflect at a ratio of, 40% of the beams emitted from the second laser diode 20 are reflected by the cubic beam splitter 23.

The beam reflected by the flat beam splitter 13 or the cubic beam splitter 23 passes through a coaxially arranged variable aperture 14, a converging lens 15 and an objective lens 16 to a DVD disc D2 or CD. -Focusing on the recording surface of the R disc D1.

Therefore, when the DVD disc D2 is to be played back, 40% of the 650 nm P-polarized beams emitted from the first laser diode 10 are reflected by the flat panel beam splitter 13, and the beams are cubic. Combat the beam splitter 23. This beam is then focused on the recording surface of the DVD disc D2 via the variable stop 14, the converging lens 15 and the objective lens 16. As shown in FIG.

On the other hand, when the CD-R disc D1 is to be reproduced, 40% of the 760 nm S-polarized beams emitted from the first laser diode 10 are reflected by the cubic beam splitter 23, and the beams Via the variable stop 14, the converging lens 15 and the objective lens 16, the focusing is performed on the recording surface of the CD-R disc D1.

The converging lens 15 focuses the beam into parallel light, and the focused beam is focused on the disc D1 or D2 by the objective lens 16.

On the other hand, since the recording density of the CD-R disc D1 and the recording density of the DVD disc D2 are different from each other, the variable aperture 15 has a difference in size of the beam spot to be focused. It is used to control the size. The variable stop 14 passes both the 650 nm wavelength beam and the 780 nm wavelength beam in the inner region of the predetermined numerical aperture (for example, 0.45) and the 650 nm wavelength without passing the 780 nm wavelength beam in the outer region (the aperture number 0.6). The coating is formed to pass only the beam, and is installed in front of the objective lens 16 and the converging lens 15. In addition, the recording surface of the CD-R disc D1 is arranged farther from the optical pickup apparatus than the recording surface of the DVD disc D2. Thus, in the case of the DVD disc D2, a beam of 650 nm wavelength passes through the 0.6 aperture variable aperture 14 to form a smaller beam spot for the DVD on the recording surface of the DVD disc D2. Meanwhile, in the case of the CD-R disc D1, a beam of 780 nm wavelength passes through only the inner region (opening number 0.45) of the variable stop 14 to form a large beam spot for the CD-R on the disc. In addition, since the focusing distance is larger as the focusing position increases, the focusing position can be accurately focused on the recording surface of the CD-R disc D1 disposed farther than the DVD recording surface.

After focusing on the optical disk D1 or D2, the beams passing through the objective lens 16, the converging lens 15, and the objective lens 16 beam the cubic beam splitter 23 and the flat beam splitter 13. According to the wavelength and polarization of the light transmits at a predetermined transmittance.

That is, when the DVD disc D2 is to be played back, 40% of the 650 nm P-polarized beams from the first laser diode 10 are reflected by the flat beam splitter 13 and then the cubic beam splitter ( 23) is battled and focused on the DVD disc D2. The 650 nm beam is then reflected from the disk to combat the cubic beam splitter 23 via the objective lens 16, the converging lens 15 and the variable aperture 14, and the flat beam splitter 13 In the 650 nm beam, the P-polarized beam is transmitted and reflected at a ratio of T _p : R _p = 6: 4 and the S polarized beam is at a ratio of T _s : R _s = 6: 4.

On the other hand, when the CD-R disc D1 is to be reproduced, 40% of the 760 nm P-polarized beams from the second laser diode 20 are reflected by the cubic beam splitter 23 and the CD-R disc ( Focused on D1). The 760 nm beam is then reflected from the disc so that the P-polarized beam of the 760 nm beam is T by the cubic beam splitter 23 via the objective lens 16, the converging lens 15 and the variable aperture 14. _At the ratio _p : R _p = 6: 4 and the S polarized beam is transmitted and reflected at the ratio T _s : R _s = 6: 4. This beam then battles the flat beam splitter 23.

Thus, the DVD recording / reproducing or CD-R recording / reproducing beam that has passed through the flat panel beam splitter 23 passes through the converging lens 18 and has astigmatism for use as a focusing servo. The signal converges to the photodetector 19.

The beam incident on the photodetector 19 is detected by the photodetector 19 and used as an image / audio signal and an electrical signal of the tracking and focusing servo.

Here, in the case where the DVD disc D2 is to be played back, if the 650 nm P-polarized beam is reflected after being incident to a position that does not cause birefringence on the disc, the light detected by the photodetector is the total amount of light at the corresponding position. The amount of 0.24 light (= 0.4 * 0.6) for is detected. On the other hand, if the disk is converted into a beam of 50% P polarization component and 50% S polarization component after being incident to a predetermined position on the disk due to the birefringence effect, the light detected by the photodetector Is 0.24 light quantity (= 0.4 * (0.6 * 0.5 + 0.5 * 0.6)) with respect to the total light quantity at the corresponding position, so that the light quantity does not change.

The same effect is also provided when the CD-R disc D1 is to be played back.

Therefore, even if the disc exhibits a birefringent effect that varies irregularly according to its partial position, the amount of light detected by the photodetector is constant, so that the reproduction signal can be accurately recognized.

Therefore, according to the optical pickup apparatus as described above, even if the polarization of the beam reflected from the optical disk is changed by setting the coating conditions of the reflection and transmission for the P- and S-polarized light of the beam splitter to be the same within the error range, The amount of light of the received beam at the photodetector can be kept constant. Therefore, accurate recording / reproducing is possible for discs showing birefringence without using expensive elements such as lambda / 4 wavelength plates.

Claims (5)

A laser light source for irradiating a laser beam of predetermined polarization; Reflects the laser beam of the predetermined polarization irradiated from the laser light source with a first reflectance of 40 to 60% and transmits it to the remaining beams, and for other polarizations, at the predetermined first reflectance with respect to the predetermined polarization of the laser beam. A beamsplitter coated to reflect at a second reflectance within a predetermined error range and to transmit for the remaining beams; An objective lens for focusing a beam directed to the optical disc via the beam splitter on the recording surface of the optical disc; And And a photo detector for detecting the laser beam reflected from the optical disc. The optical pickup apparatus of claim 1, wherein the error range is ± 5%. In order to record / reproduce a plurality of optical discs of different densities, a first laser light source and a second laser light irradiating a first laser beam having a first polarization and a first wavelength and a second laser beam having a second polarization and a second wavelength, respectively. A laser light source unit having a laser light source; Is disposed on the optical path of the first laser beam irradiated from the first laser light source, reflects the first laser beam of the first wavelength and the first polarization with a first reflectance of 40 to 60% and transmits to the remaining beam The laser beam of the second polarized light having the same wavelength is reflected to the first polarized light of the first laser beam at a first 'reflectance within a predetermined error range with respect to the predetermined first reflectance, and transmitted to the remaining beams. A first beamsplitter coated to be coated; Disposed on the optical path of the second laser beam of the second polarization irradiated from the second laser light source, reflecting the second laser beam of the second wavelength and the second polarization at a second reflectance of 40 to 60%, and remaining The light beam is transmitted through the beam, and the laser beam of the first polarization of the same wavelength is reflected by the second 'reflectance within a predetermined error range with respect to the predetermined second reflectance with respect to the second polarization of the second laser beam and the remaining beams. A first beamsplitter coated to transmit about; An objective lens for focusing a beam directed to the optical disc via the beam splitter on the recording surface of the optical disc; And And a photo detector for detecting the first or second laser beam reflected from the disk. 4. The optical pickup apparatus of claim 3, wherein the first beamsplitter combats a laser beam of a second wavelength and the second beamsplitter is coated to totally reflect a laser beam of a first wavelength. The optical pickup apparatus of claim 3, wherein the error range is ± 5%.