WO2012157795A1

WO2012157795A1 - Multi-optical pickup

Info

Publication number: WO2012157795A1
Application number: PCT/KR2011/003657
Authority: WO
Inventors: 한현석; 강도원; 김현준; 이인우; 박호만; 김용상; 임부빈
Original assignee: 엘지전자 주식회사
Priority date: 2011-05-17
Filing date: 2011-05-17
Publication date: 2012-11-22

Abstract

The multi-optical pickup according to the present invention uses a general grating (Normal Grating) with a uniform array of lattices within various types of Multi- optical pickups, for example, a CD / DVD combined optical pickup; DVD and video (DVD / BD) combined optical pickup; CD and video (CD / BD) combined optical pickup; CD, DVD and video (CD / DVD / BD) combined optical pickup; and the like, and does not require the use of specially produced, high price optical devices, such as phase shift grating; wavelength-selectable grating; double-sided grating; and the like, which reduces the manufacturing costs for the optical pickup, and which is able to improve the productivity and performance of the optical pickup.

Description

Multi optical pickup

The present invention relates to a multi-optical pickup for recording or reading data on various types of optical discs such as CDs, DVDs, BDs and the like, for example.

FIG. 1 shows a configuration of an embodiment for a general optical pickup. For example, the optical pickup includes an objective lens 11, a collimator lens 12, a beam splitter 13, and a grating ( 14), laser diode 15, photo detector 16, actuator 17, and the like.

In addition, the optical pickup radiates a laser beam onto various types of optical discs 10, such as CDs, DVDs, BDs, etc., to record or read data. do.

The laser diode (LD) 15 is a light emitting device. For example, in the case of a CD-LD, a laser diode (LD) emits a red laser beam having a wavelength of 785 nm, and uses a laser diode for a DVD. DVD-LD) emits a red laser beam of 660nm wavelength, and BD-LD emits a blue laser beam of 405nm wavelength.

In addition, the grating (GT) 14 is a grating element, and the laser beam emitted from the laser diode 15 receives a main beam, a first beam, and a second sub beam. The beam splitter (BS) is diffracted and separated, respectively, and the beam splitter (BS) 13 reflects the separated main beam and the sub beams.

In addition, the collimator lens (CL) 12 converts the reflected main beam and the sub-beams from diffused light into parallel light, and the object lens (OL) 11 converts the parallel light. The main beams and the sub-beams, which have been converted into, are condensed on a track formed on the optical disk 10, for example, as shown in FIG.

After the light is collected on the track of the optical disk, the reflected main and sub beams pass through the objective lens 11, the collimator lens 12, and the beam splitter 13 to transmit the photo detector PD. Photo Detector) 16 is received.

For example, as shown in FIG. 2, the photo detector 16 may be a light receiving element, and a 12 split photo detector may be used, and the main beams A and B are formed at the center of the photo detector. Received in the C, D regions, and a first sub beam 1 of the sub beams is received in the E, F, G, H regions formed on the left side of the photo detector, and a second sub beam 2 Is received in the I, J, K, L regions formed on the right side of the photo detector.

The A, B, C, and D signals photoelectrically converted by the A, B, C, and D regions are output by a subtractor (unsigned) as a main push pull (MPP) signal, and the main The push-pull signal has a value of MPP = (A + D)-(B + C).

In addition, the E, F, G, and H signals photoelectrically converted by the E, F, G, and H regions are output as a first sub push pull 1 (SPP1) signal by a subtractor (unsigned). The first sub-push pull signal is a value of SPP1 = (E + H)-(F + G), and the I, J, K, L signals photoelectrically converted by the I, J, K, L regions. Is output as a second sub push pull (SPP2) signal by a subtractor (unsigned), and the second sub push pull signal is represented by SPP2 = (I + L)-(J + K). Value.

Meanwhile, the first sub push pull signal SPP1 and the second sub push pull signal SPP2 are summed and amplified by an adder (unsigned) and a predetermined gain (Gain = k) (k (SPP1 +). SPP2) and a subtractor (unsigned), which are subtracted from the main push pull signal MPP and output as a differential push pull signal (DPP), which is a DPP signal. = MPP-k (SPP1 + SPP2).

The differential push-pull (DPP) signal, as is widely known, controls a driving voltage applied to the actuator 17 to move the objective lens 11 in a horizontal direction. Tracking) Servo control operation, for example, as shown in Figure 3, the main push pull (MPP) signal, the first push pull (SPP1) signal and the second push pull (SPP2) signal and 180 Also has a phase difference value.

On the other hand, the main push-pull (MPP) signal and the differential push-pull (DPP) signal have the same phase value with each other, for example, the main push-pull (MPP) signal and the sub-push-pull (SPP) signal are abnormal. Even if there are offset values, the differential push-pull (DPP) signal is calculated with the value of DPP = MPP-k (SPP1 + SPP2), so that the offset present in the main push-pull signal and the sub-push-pull signal The values cancel each other out so that a stable differential push-pull signal is always output.

Accordingly, the tracking servo control operation is performed by using the differential push-pull (DPP) signal which is not affected by the abnormal offset value as described above.

Recently, Multi-Pick Up for recording or reading data on different types of optical discs, such as CDs and DVDs, or DVDs and BDs, etc. This development is released and commercialized.

4 illustrates an embodiment of a general multi-optical pickup. For example, the multi-pickup includes an objective lens 21, a collimator lens 22, a beam splitter 23, The multi-grating 24, the multi-laser diode 25, the multi-photo detector 26, the actuator 27, and the like are included.

The multi-laser diode 25 is to selectively emit a unique laser beam corresponding to the type of optical disk, for example, the multi-laser diode 25, CD and DVD combined laser diode (CD / DVD) -LD), it emits a red laser beam of 785nm wavelength for CD, or emits a red laser beam of 660nm wavelength for DVD.

When the multi-photo detector 26 is, for example, a CD and DVD photo detector (CD / DVD-PD), as shown in FIG. 4, a CD photo detector (for example, PD1 = CD-). PD) and DVD photodetector (eg PD2 = DVD-PD) are integrally formed.

In addition, when the multi-grating 24 is, for example, CD and DVD combined grating (CD / DVD-GT), as shown in FIG. 4, a phase shift grating manufactured in a special shape is shown. This can be used.

However, since the phase shift grating is a high-priced optical element specially manufactured in the shape of a grating in order to make the phase difference between the main beam and the sub beams 180 degrees as is well known, the manufacturing cost of the multi-optical pickup increases. There is a problem.

In addition, since the phase shift grating has a poor radial shift characteristic, as is widely known, the optical efficiency is extremely lowered unless it is precisely placed in the center of the laser beam, thereby improving productivity and performance of the optical pickup. There is a problem that is reduced.

As the multi-grating 24, in addition to the phase shift grating specially manufactured as described above, wavelength-selective grating or double-sided grating may be used, as is well known. In the case of the wavelength-selective grating or double-side grating, Since it is a specially manufactured high-cost optical element, the manufacturing cost of the multi-optical pickup is increased, and precise design and control are required, and thus there is a problem that the productivity and performance of the optical pickup are deteriorated.

The present invention is, for example, a CD and DVD (CD / DVD) optical pickup, or a DVD and BD (DVD / BD) optical pickup, or a CD and BD (CD / BD) optical pickup, or CD and DVD And the use of normal gratings in which gratings are uniformly arranged in various types of multi-optical pickups such as a combined optical pickup (CD / DVD / BD) and the like, so as to improve productivity and maintain performance of the optical pickup. It is to provide a multi-optical pickup for.

The multi-optical pickup of an embodiment according to the present invention includes a light emitting device for emitting any one of a plurality of wavelength laser beams, and a grating device for dividing the emitted laser beam into a main beam and first and second sub beams. In the multi-optical pickup comprising a, the grating element, the gratings are uniformly arranged, arranged in front of the light emitting element vertically, the track of the optical disk focused on the main beam, and the first and second Rotate counterclockwise or clockwise so that the separation distance between the tracks of the optical discs on which one of the sub-beams is focused is either 1.5 tracks, 2.5 tracks or 3.5 tracks, depending on the type of the optical disc Characterized in that,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 1.5 tracks of the CD, provided that the optical disk is a CD having a track pitch of 1.6 um. ,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 2.5 tracks of the DVD when the optical disk is a DVD having a track pitch of 0.74 um. ,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 3.5 tracks of the video if the optical disk has a track pitch of 0.32 um. It is done.

On the other hand, the multi-optical pickup according to another embodiment of the present invention, a light emitting device for emitting any one of a plurality of wavelength laser beam, and for dividing the emitted laser beam into a main beam and the first and second sub-beams In the multi-optical pickup comprising a grating element, the grating element is a track of an optical disk in which the gratings are uniformly arranged, arranged vertically in front of the light emitting element, the main beam is focused, and the first And a counterclockwise or clockwise direction such that the distance between the tracks of the optical disks on which one of the second sub-beams is focused is one of 2.5 tracks, 4.5 tracks, and 6.5 tracks, depending on the type of the optical disks. It is characterized in that it is rotated in the direction,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 2.5 tracks of the CD, provided that the optical disk is a CD having a track pitch of 1.6 um. ,

The grating element may be rotated counterclockwise or clockwise so that the separation distance is 4.5 tracks of the DVD when the optical disk is a DVD having a track pitch of 0.74 um. ,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 6.5 tracks of the video if the optical disk has a track pitch of 0.32 um. It is done.

The multi-optical pickup according to the present invention does not require the use of a specially manufactured high-cost optical element by using a normal grating in which gratings are uniformly arranged in various types of multi optical pickups. In addition to reducing the manufacturing cost of the optical pickup, it is possible to improve the productivity and performance of the optical pickup.

1 illustrates an embodiment of a general optical pickup,

2 illustrates an embodiment of an output process of a general differential push-pull (DPP) signal.

3 shows a graph of an embodiment for general push-pull signals,

4 illustrates an embodiment of a general multi-optical pickup,

5 illustrates an embodiment of a multi-optical pickup according to the present invention,

Figure 6 illustrates an embodiment in which the general grating applied to the present invention is rotated in the clockwise direction,

FIG. 7 illustrates an embodiment in which the main beam and the sub beams are spaced apart as the general grating applied to the present invention is rotated.

FIG. 8 is a table illustrating a separation distance between a main beam and a sub beam for each type of optical disc according to the present invention.

Hereinafter, exemplary embodiments of a multi-optical pickup according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention is, for example, a CD and DVD (CD / DVD) optical pickup, or a DVD and BD (DVD / BD) optical pickup, or a CD and BD (CD / BD) optical pickup, or CD and DVD And various types of multi optical pickups such as a CD / DVD / BD combined optical pickup and the like.

In the multi-optical pickup to which the present invention is applied, for example, as shown in FIG. 5, the objective lens 21, the collimator lens 22, the beam splitter 23, the general grating 14, and the multi laser diode ( 25, the multi-photo detector 26, and the actuator 27 may be included.

In addition, the multi-laser diode 25 is a light emitting device, and selectively emits a unique laser beam corresponding to the type of the optical disk. For example, the multi-laser diode 25 is a combination of CD and DVD. In the case of a laser diode (CD / DVD-LD), either a red laser beam of 785 nm wavelength for CD or a red laser beam of 660 nm wavelength for DVD is selectively emitted.

In the case where the multi-laser diode 25 is a DVD and a BD laser diode (DVD / BD-LD), either a red laser beam of 660 nm wavelength for the DVD or a blue laser beam of 405 nm wavelength for the DVD is selectively selected. In the case of CD and BD combined laser diode (CD / BD-LD), either a red laser beam of 785 nm wavelength for CD or a blue laser beam of 405 nm wavelength for video is selectively emitted.

In addition, when the multi-laser diode 25 is a CD, DVD, and DVD laser diode (CD / DVD / BD-LD), a red laser beam of 785nm wavelength for CD, or a red laser beam of 660nm wavelength for DVD, Alternatively, any one of the 405 nm wavelength blue laser beams for the video may be selectively emitted.

In addition, the multi-photo detector 26 includes a plurality of photo detectors corresponding to the types of laser beams emitted by the multi-laser diode 25, for example, the multi-laser diode 25. In the case of the CD and DVD combined photo detector (CD / DVD-PD), as shown in Fig. 5, the photo detector for CD (eg PD1 = CD-PD) and the photo detector for DVD (eg PD2 = DVD) -PD) is integrally formed.

On the other hand, the grating 14 is, for example, as shown in Figure 5, the normal grating (Normal Grating) is used is uniformly arranged in a linear grating, the general grating 14 is a grating element As a vertical, it is disposed vertically in front of the multi-laser diode 25, the rotation is adjusted in a counterclockwise or clockwise direction by any predetermined angle.

For example, as shown in FIG. 6, the position in the optical disk where the main beam M diffracted by the general grating 14 is collected and among the first and second sub beams S1 and S2. The separation distances d1 and d2 between the positions in the optical disc on which one sub-beam is focused is at least N + 0.5 (N = 0,1), depending on the type of optical disc (eg CD, DVD, BD). , 2,3 ..) Rotate in a counterclockwise or clockwise direction to match the track.

That is, in the manufacturing process for manufacturing the multi-optical pickup according to the present invention, the position in which the main beam is formed on the optical disk and the position in which the sub-beam is formed while rotating the general grating 14 counterclockwise or clockwise. By adjusting the separation distance therebetween to be at least 0.5 tracks, the main push pull (MPP) signal generated by the main beam and the sub push pull generated by the sub-beams, as described above with reference to FIG. 3. The (SPP) signals have a 180 degree phase difference value with each other, so that a normal differential push-pull (DPP) signal is generated.

On the other hand, the separation distance between the main beam and the sub-beam diffracted by the normal grating 14, depending on the wavelength of the laser beam, for example, as shown in Figure 7, the general grating 14 is half When the laser beam of 660 nm wavelength for DVD is emitted while being rotated clockwise or clockwise by a certain angle, the separation distance between the position where the main beam forms on the DVD disk and the position where the sub beam forms on the DVD disk (d_dvd) Is 1.85 um, which corresponds to 2.5 tracks of DVD with a 0.74 um track pitch.

On the other hand, when the 785nm wavelength laser beam for the CD is radiated, the separation distance (d_cd) between the position where the main beam and the sub beam are in the CD disc is 2.2um, which is a CD having a track pitch of 1.6um. It is an approximation corresponding to 1.5 tracks (2.4um) of. If this is expressed as a formula, d_dvd: 660nm = d_cd: 785nm, where d_dvd is 1.85um, d_cd becomes 2.2um.

On the other hand, when the laser beam of the 405nm wavelength for the video is radiated, when the distance (d_bd) between the position of the main beam and the position of the sub-beam on the video disk is calculated using the above formula, d_dvd: 660nm = d_bd Since d_dvd is 1.85 um, it can be seen that d_bd is 1.13 um, which is an approximation to 3.5 tracks (1.12 um) of a video having a 0.32 um track pitch.

That is, for example, based on the CD (CD) having a track pitch of 1.6um, when adjusting the position by rotating the general grating 14, while emitting a laser beam of 785nnm wavelength for the CD, When the general grating 14 is rotated counterclockwise or clockwise so that the separation distance d_cd between the position where the main beam is formed and the position where the sub beam is formed is 1.5 track, in the case of DVD, The spacing distance (d_dvd) between this forming position and the position where the sub beams form is 2.5 tracks, and in the case of a video, the spacing distance (d_bd) between the position where the main beam forms and the position where the sub beams form is 3.5 tracks. As a result, a normal differential push-pull (DPP) signal can be generated for CD, DVD, and BD.

Therefore, in the manufacturing process for manufacturing the multi-optical pickup according to the present invention, as described above, the separation distance between the position where the main beam is formed and the position where the sub beam is formed is 1.5 tracks for CD, 2.5 for DVD. In the case of tracks and videos, the general grating 14 is rotated counterclockwise or clockwise so as to be 3.5 tracks.

On the other hand, as another embodiment of the present invention, as shown in Figure 8, the separation distance between the position of the main beam and the position of the sub-beam is 2.5 tracks in the case of CD, 4.5 tracks, video in the case of DVD In this case, the general grating 14 may be rotated counterclockwise or clockwise so as to be 6.5 tracks.

For reference, it is advantageous for the tracking servo control operation that the phase difference between the main beam and the sub beam is close to 180 degrees and the phase difference between the main beam and the sub beam is as close as possible, as shown in FIG. 8. It is preferable to rotate the general grating so that it becomes 2.5 tracks for tracks and DVDs and 3.5 tracks for DVDs.

Preferred embodiments of the present invention described above have been disclosed for the purpose of illustration, and those skilled in the art will be further improved, modified, and other various embodiments within the spirit and technical scope of the present invention disclosed in the appended claims. Replacement or addition may be possible.

Claims

A light emitting device for emitting any one of a plurality of wavelength laser beams,

In the multi-optical pickup comprising a grating element for dividing the emitted laser beam into a main beam and first and second sub-beams,

The grating element, the gratings are uniformly arranged, disposed in front of the light emitting element,

The separation distance between the track of the optical disk on which the main beam is focused and the track of the optical disk on which any one of the first and second sub beams are focused is 1.5 tracks, 2.5 depending on the type of the optical disk. A multi-optical pickup, which is rotated counterclockwise or clockwise so as to be any of tracks and 3.5 tracks.
The method of claim 1,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 1.5 tracks of the CD, provided that the optical disk is a CD having a track pitch of 1.6 um. Multi optical pickup.
The method of claim 1,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 2.5 tracks of the DVD when the optical disk is a DVD having a track pitch of 0.74 um. Multi optical pickup.
The method of claim 1,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 3.5 tracks of the video, if the optical disk has a track pitch of 0.32 um. Multi optical pickup.
A light emitting device for emitting any one of a plurality of wavelength laser beams,

In the multi-optical pickup comprising a grating element for dividing the emitted laser beam into a main beam and first and second sub-beams,

The grating element, the gratings are uniformly arranged, disposed in front of the light emitting element,

The separation distance between the track of the optical disk on which the main beam is focused and the track of the optical disk on which any one of the first and second sub beams are focused is 2.5 tracks, 4.5 depending on the type of the optical disk. A multi-optical pickup, which is rotated counterclockwise or clockwise so as to be any of tracks and 6.5 tracks.
The method of claim 5,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 2.5 tracks of the CD if the optical disk is a CD having a track pitch of 1.6 um. Multi optical pickup.
The method of claim 5,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 4.5 tracks of the DVD when the optical disk is a DVD having a track pitch of 0.74 um. Multi optical pickup.
The method of claim 5,

The grating element is rotated counterclockwise or clockwise so that the separation distance is 6.5 tracks of the video if the optical disk has a track pitch of 0.32 um. Multi optical pickup.