KR100226853B1 - An optical pickup device for two kinds of optical disk - Google Patents

Abstract

The present invention relates to an optical pickup device for heterogeneous optical disks having different substrate thicknesses and wavelengths, and in particular, to one side, a color separation coating having a characteristic of unconditionally reflecting a CD-R wavelength beam and transmitting a DVD wavelength beam. The junction surface has a different thickness by using a λ / 4 plate combined with DPBS and CSF formed by dichroic coating so as to have NPBS function for the wavelength for CD-R and PBS function for the wavelength for DVD. Recording / playback compatibility of optical discs having wavelengths and recording densities, while reducing optical elements, makes the optical pickup device thin and short, and facilitates the assembly process, thereby lowering the price of the optical pickup device. [lambda] / 4 plate prevents malfunction of [lambda] / 4 plate due to temperature change by adjusting the phase delay amount so as to change by [lambda] / 4 phase simultaneously with respect to the wavelength for CD-R and the wavelength for DVD. .

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, and more particularly to compact discs (CDs) and digital versatile discs (DVDs) in the same optical pickup device. The present invention relates to an optical pickup apparatus for heterogeneous optical discs, which enables recording / playback compatibility of a CD, that is, CD-R (Compact Disc Recordable).

The light source used for the optical pickup for DVD has a wavelength of 635 to 650 nm (visible light, red). 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.

1 is an optical system configuration diagram of such a conventional optical pickup apparatus for heterogeneous optical disks.

1, a correction lens for correcting aberrations of a first laser diode (LD) package 11 for generating a light beam for a CD-R, a second LD 12 for generating a light beam for a DVD, and a light beam for a CD-R (13), a polarizing beam splitter (PBS) 14 for transmitting or reflecting an incident beam according to the polarization direction of the beam incident from the second LD 12 or the optical disk 21, and the PBS ( The collimator lens 15 which advances the beam which passes through 14 in parallel in a predetermined direction, and the (lambda) / 4 plate 16b which changes the direction of polarization to the surface in which the beam radiated in parallel from the collimator lens 15 is incident. Is attached, and a dichroic beam splitter (DBS) for transmitting or reflecting the incident beam according to the wavelength and polarization direction of the beam incident through the λ / 4 plate 16b or the correction lens 13 ( 16) a prism mirror for reflecting a beam incident from the DBS 16 in a vertical direction; PM) 17, a color separation filter (CSF) 18 for selectively transmitting a part of the incident beam according to the wavelength of the beam reflected from the prism mirror 17 to adjust the beam diameter of the light beam; The objective lens 19 for condensing the light beam passing through the CSF 18 at a point on the surface of the optical disc 21, and the reflected light beam from the optical disc 21 are the objective lens 19, CSF 18, It includes a prism mirror 17, a DBS 16, a collimator lens 15, and a photo detector 23 that detects and converts the reflected light into an electrical signal when reflected through the PBS 14.

At this time, the objective lens 19 is provided with an actuator 20 for moving the objective lens 19 in the horizontal and vertical directions, the focus by the astigmatism between the PBS 14 and the photo detector 23 A sensor lens 22 for detecting an error signal is provided.

The first LD package 11 integrates an LD 11a for generating a beam of 780 nm wavelength and a photo detector 11c for detecting the reflected light beam from the disk 21 in the package. And the photodetector 11c are arranged side by side, and the beam incident into the first LD package 11 is diffracted toward the photodetector 11c using the hologram 11b.

Here, the photo detector 11c for detecting the reflected light beam of 780 nm wavelength is integrated in the first LD package 11, and the photo detector 23 for detecting the reflected light beam of 635-650 nm wavelength is reflected by the PBS 14. Is provided separately from the second LD (12) on the optical path.

Since the objective lens 19 needs to be corrected for a DVD having a large numerical aperture NA, the aberration is corrected for a wavelength of 635-650 nm. Therefore, when the CD or CD-R is reproduced, the wavelength is different. Therefore, a correction lens 13 for correcting aberrations caused by this is provided between the first LD package 11 and the DBS 16.

The DBS 16 is formed by bonding two glass substrates and applying a dichroic coating to the bonding surface 16a.

In this case, as shown in FIG. 2A, when the polarization direction is S wave, the bonding surface 16a transmits unconditionally to a beam of 635-650 nm wavelength and unconditionally reflects to a beam of 780 nm wavelength, as shown in FIG. 2B. If the direction is P-wave, it has the characteristic of transmitting unconditionally about the beam of 635-650nm wavelength and the beam of 780nm wavelength.

The beam transmitted or reflected through the DBS 16 is focused on one surface of the optical disc 21 through the objective lens 19. For the CD / CD-R / DVD playback compatibility, aperture ratio adjustment is required.

In this case, since beams having different wavelengths are incident on the CD / CD-R and the DVD, the CSF 18 uses the difference to adjust the size of the incident mirror.

That is, by forming an optical coating film for blocking a specific wavelength, for example, the wavelength for the CD, in the remaining region except for the portion corresponding to the opening ratio (NA) for the CD, the wavelength for the DVD is transmitted as it is and the wavelength for the CD is incident by the optical coating film. Since the diameter of the mirror is adjusted, the incident light is not large, and spherical aberration is not large.

Here, the optical coating is a dichroic coating.

That is, when the CD series uses a wavelength of 780 nm, the DVD series uses a wavelength of 635-650 nm, the NA required for the CD series is 0.45 and the NA required for the DVD series is 0.6.

Accordingly, as shown in FIG. 3A, the dichroic film reflecting the beam of the CD wavelength is coated on the region except for the incident diameter corresponding to the case where the NA for the CD is 0.45, that is, the coating region 18b.

FIG. 3B is a graph showing the transmission characteristics of the optical coating film applied to the coating region 18b, and shows reflection at 780 nm, which is the wavelength of the CD.

Therefore, since the wavelength for CD passes through only the uncoated region 18a in the center portion as shown in FIG. 3A, and the wavelength for DVD passes through both the uncoated region 18a and the optical coating region 18b, one objective lens is used. Both CD and DVD can be played.

The first information recording surface 21a of the optical disc 21 is an information recording surface of a DVD, the second information recording surface 21b is an information recording surface of a CD, and the second information recording surface 21b is a first information recording surface 21a. ) 0.6 mm further from the surface of the optical disk 21.

In the conventional optical pickup apparatus for heterogeneous optical disks configured as described above, the wavelength of the light beam generated in the first LD package 11 is 780 nm, the polarization direction is S-wave, and the wavelength of the light beam generated in the second LD 12 is 635. Assume that -650nm and polarization direction is P wave.

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 at both 780nm and 635-650nm, but here 780nm is used for CD-R / CD.

Hereinafter, the case of recording and reproducing a CD optical disc and the case of recording and reproducing a DVD optical disc will be described separately.

i) CD series optical disc

In the LD 11a of the first LD package 11, when a light beam having a wavelength of 780 nm and a linear polarization direction S-wave is generated through the hologram 11c, the aberration is corrected by the correcting lens 13 and then incident on the DBS 16. do.

At this time, since the bonding surface 16a of the DBS 16 has a characteristic of unconditionally reflecting when the wavelength is 780 nm and the polarization direction is S wave, as shown in FIG. 2A, the light beam generated by the first LD package 11 is It is reflected by the bonding surface 16b of the DBS 16 and is incident on the prism mirror 17.

The prism mirror 17 vertically reflects a beam incident from the DBS 16, which is incident on the CSF 18.

3A and 3B, the CSF 18 is an uncoated region 18a that transmits both a CD wavelength and a DVD wavelength, and an optical coating region 18b that reflects only a CD wavelength and reflects the CD wavelength. The optical coating region 18b is formed with a dichroic coating film that reflects or transmits an incident beam depending on the wavelength.

Therefore, the beam for the CD / CD-R reflected by the prism mirror 17 and incident on the CSF 18 is transmitted in the uncoated region 18a and reflected in the optical coating region 18b, thereby reducing the beam diameter of the light beam. .

When the beam diameter of the light beam is reduced, the objective lens 19 receives the light beam that passes through the uncoated region 18a because the numerical aperture is reduced to the CD numerical aperture (i.e., 0.45). In other words, it focuses accurately on the information recording surface of the CD.

On the other hand, the light beam reflected from the second information recording surface 21b is incident on the DBS 16 via the objective lens 19, the CSF 18, and the prism mirror 17.

In this case, the junction surface 16a of the DBS 16 has a characteristic of unconditionally reflecting when the wavelength is 780 nm and the polarization direction is S wave, as shown in FIG. 2A, and the reflected light beam incident on the DBS 16 is S pi. While having a wavelength of 780 nm, the reflected light beam is unconditionally reflected at the bonding surface 16a and is incident to the first LD package 11 through the correction lens 13.

At this time, the LD 11a and the photodetector 11c are mounted side by side in the first LD package 11, and the beam incident on the first LD package 11 is diffracted by the hologram 11b to emit light. Incident to the detector 11c.

The photo detector 11c converts the incident light beam into an electrical signal to obtain a high frequency signal, a focus error signal, and a tracking error signal.

ii) DVD series optical disc

A light beam having a wavelength of 635-650 nm and a linearly polarized P wave generated in the second LD 12 is incident on the PBS 14.

Since the PBS 14 reflects the S-wave and transmits the P-wave, the light beam generated by the second LD 12 passes through the PBS 14 and is incident to the collimator lens 15.

The collimator lens 15 propagates a diverging light beam of P waves passing through the PBS 14 in parallel to the λ / 4 plate 16b of the DBS 16.

At this time, when the P-wave, which is a linearly polarized beam, passes through the λ / 4 plate 16b, it is converted into a right-turning circularly polarized beam, and the right-turning circularly polarized beam is incident on the joining surface 16a of the DBS 16.

As shown in FIGS. 2A and 2B, when the wavelength is 650 nm, the bonding surface 16a transmits the incident beam irrespective of P and S waves. It passes through the bonding surface 16a as it is and enters into the prism mirror 17.

The prism mirror 17 enters the CSF 18 by vertically reflecting the light beam passing through the DBS 16.

At this time, the CSF 18 is composed of an uncoated region 18a that transmits both the wavelength for the CD and the wavelength for the DVD, and an optical coating region 18b that reflects the wavelength for the CD and transmits only the wavelength for the DVD. The light beam passes through both the uncoated region 18a and the optically coated region 18b of the CSF 18.

Therefore, the objective lens 19 maintains the original numerical aperture (i.e., 0.6) since the beam diameter of the light beam is not reduced.

Therefore, the objective lens 19 transmits a light beam passing through both the uncoated region 18a and the optical coating region 18b of the CSF 18 by the movement of the actuator 20 provided with the objective lens 19. The first information recording surface 21a of (21), that is, the information recording surface of the DVD is accurately focused.

On the other hand, the light beam reflected from the first information recording surface 21a is incident on the DBS 16 through the objective lens 19, the CSF 18, and the prism mirror 17.

At this time, when the right rotating circularly polarized beam is reflected from the first information recording surface 21a, it is diffracted by the information carrier on the information recording surface and converted into the left rotating circularly polarized beam.

The bonding surface 16a of the DBS 16 has a property of transmitting unconditionally regardless of the polarization direction when the wavelength is 650 nm, as shown in FIGS. 2A and 2B. The bonding surface 16a of the DBS 16 is provided. Since the incident light beam is also a left-rotating circularly polarized beam having a wavelength of 635-650 nm, the left-rotating circularly polarized beam passes through the bonding surface 16a as it is and enters into the λ / 4 plate 16b.

When the left rotating circularly polarized beam passes through the λ / 4 plate 16b, it is converted into an S-wave which is a linearly polarized beam, and the S-wave is incident on the collimator lens 15.

At this time, since it is assumed that the aberration of the objective lens is aligned with the DVD, the reflected beam is focused again by the collimator lens 15 and is incident on the PBS 14.

The PBS 14 reflects all incident S-waves, and the S-waves reflected from the PBS 14 are incident toward the sensor lens 22, and the sensor lens 22 corrects spherical aberration of the reflected beam. The light is then focused on the surface of the photo detector 23.

The photo detector 23 converts the incident light beam into an electrical signal to obtain a high frequency signal, a focus error signal, and a tracking error signal.

However, the conventional optical pickup device for heterogeneous optical discs requires PBS, correction lens, and CSF for CD / CD-R / DVD recording / playback compatibility, thus having a large number of optical elements and a complicated structure, thereby assembling the process. This complicated and bulky optical pickup device becomes difficult to compact the optical pickup device, and therefore, when applied to a laptop, the size of the laptop becomes larger and thicker, and the cost increases.

In addition, since the λ / 4 plate can be used for only one wavelength, a phase change occurs when the wavelength changes with temperature change, and the amount of phase retardation increases, thereby causing a problem that the λ / 4 plate cannot change the direction of polarization.

The present invention is to solve the above problems, an object of the present invention is a dichroic polarizing beam splitter (DPBS) for transmitting or reflecting the beam according to the wavelength and polarization direction, CSF is combined By using the λ / 4 plate, recording / reproducing compatibility of optical discs having different thicknesses, wavelengths and recording densities is possible, while the optical elements are reduced, so that the optical pickup device can be easily and lightly shortened and assembled, and the cost is reduced. An optical pickup apparatus for heterogeneous optical disks is provided.

Another object of the present invention is to provide an optical pickup device for a heterogeneous optical disc which prevents the malfunction of the λ / 4 plate by adjusting the phase delay amount so as to change by λ / 4 phase simultaneously with respect to the wavelength for the CD-R and the wavelength for the DVD. Is in.

A feature of the optical pickup device for heterogeneous optical disks according to the present invention for achieving the above object is a first LD for emitting a beam of a first wavelength, and for emitting a beam of a second wavelength different from the first wavelength A dichroic polarizing beam splitter that reflects or transmits an incident beam according to the polarization direction and wavelength of the incident beam, and a collimator lens for condensing a diverging beam incident from the dichroic polarizing beam splitter into parallel beams; And a prism mirror for reflecting the parallel beam incident from the collimator lens at a predetermined angle, and converting the polarization direction of the parallel beam reflected and incident from the prism mirror and selectively selecting all or part of the incident beam according to the wavelength of the parallel beam. The wavelength and recording density by maintaining a numerical aperture different from each other according to the polarization conversion and light shielding portion to be passed through The thickness, etc. may consists of including an objective lens for condensing the light beam on the surface of different optical disc.

1 is a configuration diagram of an optical system of a conventional optical pickup apparatus for heterogeneous optical disks.

FIG. 2A is a graph showing reflection characteristics of an S wave of the dichroic beam splitter (DBS) of FIG.

FIG. 2B is a graph showing reflection characteristics of P waves of the dichroic beam splitter (DBS) of FIG.

3A is a view illustrating a relationship between a beam blocking area and a transmission area of the color separation filter CSF of FIG. 1.

3B is a graph illustrating transmission characteristics of a beam blocking region of the color separation filter (CSF) of FIG. 1.

4 is an optical system configuration diagram of an optical pickup device for heterogeneous optical disks according to the present invention;

FIG. 5A is a graph showing the transmission characteristics with respect to the wavelength of the color separation coating surface of the dichroic polarizing beam splitter (DPBS) of FIG.

FIG. 5B is a graph showing transmission characteristics with respect to the wavelength and polarization direction of the junction surface of the dichroic beam splitter (DPBS) of FIG. 4.

6A is a detailed cross-sectional view of the polarization conversion and light shielding unit;

FIG. 6B is a view illustrating a relationship between an optical coating region and a non-optical coating region of the polarization conversion and light shielding portion of FIG. 4.

FIG. 6C is a graph showing transmission characteristics versus wavelength of the optical coating region of FIG. 6B.

FIG. 6D is a graph of transmission characteristics versus wavelength of the non-optical coating region of FIG. 6B.

FIG. 6E is a graph showing the characteristics of the λ / 4 plate of polarization conversion and light shielding portion of FIG. 6A

Explanation of symbols for the main parts of the drawings

41: first laser diode (LD) package 41a: LD

41b: hologram 41c: photo detector

42: second LD

43: Dichroic Polarized Beam Separator (DPBS)

43a: bonding surface 43b: color separation coating surface

44: collimator lens 45: prism mirror

46: polarization conversion and light shield

46a: non-optical coating area 46b: optical coating area

46c: λ / 4 plate 47objective lens

48: optical disc 48a: first information recording surface

48b: second information recording surface 49: sensor lens

50: light detector

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

4 is an optical system configuration diagram of an optical pickup device for heterogeneous optical disks according to the present invention.

4, a first laser diode (LD) package 41 for generating a light beam for a CD-R, a second LD 42 for generating a light beam for a DVD, and a light beam emitted from the second LD 42 Color Separation Coating is applied to the incident surface to form a color separation coating surface 43b, and to the wavelength and polarization direction of the beam emitted from the color separation coating surface 43b or the first LD package 41. A dichroic polarizing beam splitter (DPBS) 43 for transmitting or reflecting an incident beam, a collimator lens 44 for advancing the diverging beams incident from the DPBS 43 in parallel in a predetermined direction; A prism mirror (PM) 45 for reflecting the parallel beam incident from the collimator lens 44 in the vertical direction, and simultaneously converts the polarization direction of the beam reflected from the prism mirror 45 and is incident Depending on the wavelength of the beam A polarization conversion and light shielding portion 46 for selectively transmitting the light beam's beam diameter, and an objective lens 47 for condensing the light beam passing through the polarization conversion and light shielding portion 46 at one point on the surface of the optical disk 48. And a reflected light beam for DVD from the optical disk 48 through the objective lens 47, the polarization conversion and light shielding portion 46, the prism mirror 45, the collimator lens 44, and the DPBS 43. It is configured to include a photo detector 50 for detecting this and converting it into an electrical signal.

In this case, a sensor lens 49 is installed between the DPBS 43 and the photo detector 50 to detect a focus error signal due to an astigmatism range.

The first LD package 41 integrates the LD 41a for generating a beam of 780 nm wavelength and the photodetector 41c for detecting the reflected light beam from the disk 21 in the package. And the photodetector 41c are arranged side by side, and the beam incident into the first LD package 41 is diffracted toward the photodetector 41c using the hologram 41b.

Here, the photo detector 41c for detecting the reflected light beam of 780 nm wavelength is integrated into the first LD package 41, and the photo detector 23 for detecting the reflected light beam of 635-650 nm wavelength is reflected by the PBS 44. It is installed separately from the second LD 42 on the optical path.

In addition, the DPBS 43 is formed by bonding two glass substrates and applying a dichroic coating to the bonding surface 43a.

In this case, as shown in FIG. 5B, when the polarization direction is S wave, the junction surface 46a reflects a beam of 635-650 nm wavelength and transmits 50% and reflects 50% of a beam of 780 nm wavelength. When the polarization direction is P wave, it transmits for the beam of 635-650nm wavelength and transmits 50% and reflects 50% for the beam of 780nm wavelength.

That is, the junction surface 43a has a PBS characteristic of separating P / S waves for beams of 635-650 nm wavelength, and passes through a certain amount of light beams and reflects the rest, regardless of polarization direction, for beams of 780 nm wavelength. Non Polarizing Beam Splitter (NPBS) characteristics.

The beam transmitted or reflected through the DPBS 43 is focused on one surface of the optical disk 48 through the objective lens 47. For the CD / CD-R / DVD playback compatibility, aperture ratio adjustment is required.

In this case, since beams having different wavelengths are incident on the CD / CD-R and the DVD, the polarization conversion and light blocking unit 46 adjusts the size of the incident mirror by using the difference.

The polarization conversion and light blocking portion 46 is formed by color separation coating on the λ / 4 plate 46c as shown in FIG. 6A.

That is, the color separation coating surface of the polarization conversion and light blocking part 46 is also referred to as CSF, and this CSF excludes an optical coating film that blocks a specific wavelength, for example, a wavelength for CD, except for a portion corresponding to the opening ratio (NA) for CD. By forming in the remaining region, the wavelength for the DVD is transmitted as it is, and the wavelength for the CD is incident by adjusting the size of the incident diameter by the optical coating film, so that spherical aberration is not large even when the CD is reproduced, thereby enabling proper reproduction.

Here, the optical coating is a dichroic coating.

That is, when the CD series uses a wavelength of 780 nm, the DVD series uses a wavelength of 635-650 nm, the NA required for the CD series is 0.45 and the NA required for the DVD series is 0.6.

Accordingly, as shown in FIG. 6B, the dichroic film reflecting the CD wavelength beam is coated on the region except for the incident diameter corresponding to the case where the NA for CD is 0.45, that is, the coating region 46b.

FIG. 6C is a graph showing the transmission characteristics of the optical coating film applied to the coating area 46b, and it can be seen that only the beam of 780 nm wavelength is reflected.

FIG. 6D is a graph showing transmission characteristics applied to the uncoated region 46a, and it can be seen that the incident beam is unconditionally transmitted regardless of the wavelength.

Therefore, the wavelength for CD passes through only the uncoated region 46a in the center portion as shown in FIGS. 6C and 6D, and the wavelength for DVD passes through both the uncoated region 46a and the optical coating region 46b. The lens can be used to play both CDs and DVDs.

However, in the non-coated region 46a and the optical coating region 46b, a path difference due to the thin film thickness may occur, which may distort the beam spot. Therefore, a coating for compensating for the phase difference is applied to the non-coated region 46a. After passing through the blade film, the phase difference between the uncoated region 46a and the light passing through the optical coating region 46b is adjusted to be λ / 10 or less.

On the other hand, the λ / 4 plate 46c of the polarization conversion and the light shielding portion 46 is manufactured to have the same phase retardation for the two wavelengths as shown in FIG. 6E to reduce the amount of phase change due to the wavelength change.

In other words, the phase delay amount is adjusted so that the wavelength for the CD-R and the wavelength for the DVD are changed by λ / 4 phase at the same time, so that the amount deviating from λ / 4 according to the external temperature change is reduced.

In addition, the collimator lens 44 and the objective lens 47 are designed for a DVD having a large numerical aperture. The collimator lens 44 and the DPBS 43 and the CD-R light beam pass through both the collimator lens 44 and the CD-R light beam. By providing between the polarization conversion and the light shielding portion 46, aberration does not occur even for the light beam for the CD-R.

That is, the light beam for the CD-R comes within a desired aberration range.

Therefore, there is no need for a correction lens for correcting the aberration of the light beam for the CD-R.

The first information recording surface 48a of the optical disk 48 is an information recording surface of a DVD, the second information recording surface 48b is an information recording surface of a CD, and the second information recording surface 48b is a first information recording surface 48a. ) 0.6 mm further from the surface of the optical disk 48.

In the present invention configured as described above, the wavelength of the light beam generated in the first LD package 41 is 780 nm, and the polarization direction may be P wave or S wave, and the wavelength of the light beam generated in the second LD 42 is 635-650 nm. And the polarization direction is P.

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 at both 780nm and 635-650nm, but here 780nm is used for CD-R / CD.

Hereinafter, the case of recording and reproducing a CD optical disc and the case of recording and reproducing a DVD optical disc will be described separately.

i) CD series optical disc

A light beam having a wavelength of 780 nm generated by the LD 41a of the first LD package 41 is incident on the bonding surface 43a of the DPBS 43 through the hologram 41c.

In this case, the bonding surface 43a of the DPBS 43 has a property of transmitting 50% and reflecting 50% regardless of the polarization direction when the wavelength of the incident beam is 780 nm, as shown in FIG. 5B. 50% of the beam reflected at the light incident on the color separation coating surface 43b.

Since the color separation coating surface 43b has a characteristic of unconditionally reflecting when the wavelength of the incident beam is 780 nm as shown in FIG. 5A, the beam reflected from the bonding surface 43a is reflected back from the color separation coating surface 43b. And enters into the bonding surface 43a.

Of the beams incident on the bonding surface 43a, only a predetermined amount of light passes through the bonding surface 43a and is incident to the collimator lens 44.

The collimator lens 44 propagates the beam passing through the bonding surface 43a in parallel to the prism mirror 45, and the prism mirror 45 polarizes the parallel beam by reflecting the parallel beam vertically. The light is incident on the conversion and light blocking unit 46.

The λ / 4 plate 46c of the polarization conversion and light shielding portion 46 converts the parallel linearly polarized beam incident from the prism mirror 45 into a circularly polarized beam.

In addition, the CSF of the polarization converting and shielding part 46 includes an uncoated region 46a that transmits both a wavelength for a CD and a wavelength for a DVD, and an optical coating region 46b that reflects a wavelength for a CD and transmits only a wavelength for a DVD. The optical coating area 46b is formed with a dichroic coating film that reflects or transmits an incident beam depending on the wavelength.

Therefore, since the circularly polarized beam for CD / CD-R converted in the λ / 4 plate 46c is transmitted in the uncoated region 46a and reflected in the optical coating region 46b, the beam diameter of the light beam is reduced.

When the beam diameter of the light beam is reduced, the objective lens 47 receives the light beam passing through the uncoated area 46a because the numerical aperture is reduced to the CD numerical aperture (i.e., 0.45). In other words, it focuses accurately on the information recording surface of the CD.

On the other hand, the light beam reflected from the second information recording surface 48b enters the DPBS 44 through the objective lens 47, the polarization converting and shielding portion 46, the prism mirror 45, and the collimator lens 44. do.

At this time, the circularly polarized beam reflected by the second information recording surface 48b of the optical disk 48 is converted into a linearly polarized beam once passing through the polarization direction and the λ / 4 plate 46c of the light shielding portion 46.

5B, the bonding surface 43a of the DPBS 43 has a characteristic of transmitting a predetermined amount of light in the incident beam and reflecting the rest, regardless of the polarization direction, when the wavelength is 780 nm as shown in FIG. 5B. Only a certain amount of light, that is, 50%, of the 780 nm wavelength beam reflected from the second information recording surface 48b penetrates the bonding surface 43a and enters the color separation coating surface 43b.

Since the color separation coating surface 43b has a property of reflecting a beam having a wavelength of 780 nm as shown in FIG. 5A, the beam passing through the bonding surface 43a is again reflected from the color separation coating surface 43b and is a bonding surface. Incident on 43a.

Only a certain amount of light from the beam incident back to the bonding surface 43a is reflected at the bonding surface 43a and is incident to the first LD package 41.

At this time, the LD 41a and the photodetector 41c are mounted side by side in the first LD package 41, and the beam incident on the first LD package 41 is diffracted by the hologram 41b to emit light. Incident to the detector 41c.

The photo detector 41c converts the incident light beam into an electrical signal to obtain a high frequency signal, a focus error signal, and a tracking error signal.

ii) DVD series optical disc

A light beam having a wavelength of 635-650 nm and a linear polarization direction P wave generated in the second LD 42 is incident on the color separation coating surface 43b of the DPBS 43.

At this time, since the color separation coating surface 43b has a property of transmitting about 635-650nm wavelength as shown in FIG. 5A, the light beam of P wave generated in the second LD 42 is the color separation coating surface 43b. It penetrates and enters into the bonding surface 43a.

Since the bonding surface 43a has a wavelength of 635-650 nm as shown in FIG. 5B and the linear polarization direction transmits the P pie surface, the incident beam passes through the bonding surface 43a as it is to the collimator lens 44. Incident.

The collimator lens 44 advances the light beam passing through the bonding surface 43a of the DPBS 43 toward the prism mirror 45 in parallel.

The prism mirror 45 is incident on the polarization conversion and the light shield 46 by reflecting the incident parallel beam vertically.

At this time, when the linearly polarized beam of parallel P waves incident from the prism mirror 45 passes through the λ / 4 plate 46c of the polarization conversion and light shielding portion 46, it is converted into a right-turning circularly polarized beam, and this right-turning circularly polarized light The beam is incident on the CSF.

Since the CSF is composed of an uncoated region 46a that transmits both the wavelength for CD and the wavelength for DVD and an optical coating region 46b that reflects the wavelength for CD and transmits only the wavelength for DVD, the incident right-turn circularly polarized beam The silver penetrates both the uncoated region 46a and the optically coated region 46b.

Therefore, since the beam diameter of the light beam is not reduced, the objective lens 47 maintains the original numerical aperture (i.e., 0.6).

Therefore, the objective lens 47 transmits the light beam passing through both the uncoated region 46a and the optical coating region 46b of the polarization conversion and light shielding portion 46 to the first information recording surface 48a of the optical disk 48. That is, it concentrates on the information recording surface of the DVD accurately.

On the other hand, the light beam reflected from the first information recording surface 48a is bonded to the DPBS 43 through the objective lens 47, the polarization conversion and light shielding portion 46, the prism mirror 45, and the collimator lens 44. Incident on the surface 43a.

At this time, when the right rotating circularly polarized beam is reflected from the first information recording surface 48a, it is diffracted by the information carrier on the information recording surface and converted into the left rotating circularly polarized beam.

When the left rotating circularly polarized beam passes through the λ / 4 plate 46c of the polarization conversion and light shielding portion 46, it is converted into a linearly polarized beam of S wave.

On the other hand, since the junction surface 43a of the DPBS 43 has a characteristic of unconditionally reflecting the S-plane if the wavelength is 650 nm and the linear polarization direction is as shown in Fig. 5B, the S wave for DVD incident on the junction surface 43a is used. The beam is reflected at the bonding surface 43a and is incident on the sensor lens 49.

The sensor lens 49 condenses the spherical aberration of the reflected beam and then condenses it on the surface of the photo detector 50.

The photo detector 50 converts the incident light beam into an electrical signal to obtain a high frequency signal, a focus error signal, and a tracking error signal.

As described above, according to the optical pickup device for the heterogeneous optical disk according to the present invention, one side has a color separation coating so as to have a characteristic of unconditionally reflecting the CD-R wavelength beam and transmitting the DVD wavelength beam. The junction surface has NPBS function for the wavelength for CD-R and PBS function for the wavelength for DVD, and DPBS formed by dichroic coating and λ / 4 plate combined with CSF can be used for different thickness, While recording / reproducing compatibility of optical discs having wavelengths and recording densities is possible, the optical elements can be reduced and the light and small size and assembly process of the optical pickup device is easy, thereby lowering the price of the optical pickup device.

Further, the λ / 4 plate has an effect of preventing the λ / 4 plate from malfunctioning by changing the temperature by adjusting the phase delay amount so as to change by the λ / 4 phase simultaneously with respect to the wavelength for the CD-R and the wavelength for the DVD. .

Claims (11)

First light emitting means for emitting a beam of a first wavelength; Second light emitting means for emitting a beam of a second wavelength different from the first wavelength; Dichroic polarizing beam separation means for reflecting or transmitting the incident beam according to the polarization direction and the wavelength of the incident beam; A collimator lens for condensing a diverging beam incident from the dichroic polarizing beam separating means into a parallel beam; A prism mirror for reflecting the parallel beam incident from the collimator lens at a predetermined angle; Polarization conversion and light blocking means for converting the polarization direction of the parallel beam reflected and reflected from the prism mirror and selectively passing all or part of the incident beam according to the wavelength of the beam in which the polarization direction is converted; A heterogeneous optical disk comprising an objective lens for condensing a light beam on a corresponding surface of an optical disk having a different wavelength, recording density and thickness by maintaining different numerical apertures according to the amount of light passing through the polarization conversion and light shielding means 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 dichroic polarizing beam separation means according to claim 1, Two glass substrates are bonded to each other, and the bonding surface is coated with an optical coating for transmitting or reflecting an incident beam according to the wavelength of the incident beam and the polarization direction, and the surface on which the beam of the second wavelength generated by the second light emitting means is incident. The optical pickup device for a heterogeneous optical disk, characterized in that formed by an optical coating that transmits the beam of the second wavelength and reflects the beam of the first wavelength unconditionally. The method of claim 3, wherein the joining surface Regardless of the polarization direction, the optical coating transmits a predetermined amount of light and reflects the remaining amount of light regardless of the polarization direction, and the optical coating unconditionally transmits or totally reflects the incident beam according to the polarization direction. Optical pickup device for heterogeneous optical disk, characterized in that. The method of claim 3, wherein the joining surface Regardless of the polarization direction, the beam of CD-R wavelength transmits a certain amount of light of the incident beam and reflects the remaining amount of light. For the beam of wavelength of DVD, the polarization direction is P pie surface. An optical pickup apparatus for heterogeneous optical disks, characterized in that the dichroic coating is coated to have a reflecting property. The dichroic polarizing beam separation means according to claim 1, Only a predetermined amount of light of the beam of the first wavelength emitted from the first light emitting means is reflected to the color separation coating surface through the bonding surface, the color separation coating surface reflects the beam reflected from the bonding surface back to the bonding surface, An optical pickup device for heterogeneous optical disks, characterized in that only a certain amount of light of the beam reflected from the color separation coating surface is transmitted to the collimator lens. The method of claim 1, wherein the dichroic polarizing beam separating means When the linearly polarized light beam of the second wavelength is incident on the second light emitting means, the optical pickup device for heterogeneous optical disks, characterized in that it is sequentially transmitted from the color separation coating surface and the bonding surface to enter the collimator lens. The method of claim 1, wherein the polarization conversion and shading means An optical pickup device for heterogeneous optical disks, characterized by being formed by color separation coating on a λ / 4 plate. The method of claim 8, wherein the λ / 4 plate An optical pickup apparatus for a heterogeneous optical disc, characterized in that the amount of phase delay is adjusted so as to be changed by? / 4 phases simultaneously with respect to the first and second wavelengths. The method of claim 8, wherein the color separation coating surface An optical pickup apparatus for heterogeneous optical discs, characterized in that it is divided into a blocking region for blocking a specific wavelength and a transmission region for transmitting an incident beam regardless of the wavelength. The method of claim 10, And a phase difference corrected by the coating of the transmission region is lambda / 10 or less.

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