CN1161538A - Multi beam track system and method for optical memory - Google Patents
Multi beam track system and method for optical memory Download PDFInfo
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- CN1161538A CN1161538A CN96104607A CN96104607A CN1161538A CN 1161538 A CN1161538 A CN 1161538A CN 96104607 A CN96104607 A CN 96104607A CN 96104607 A CN96104607 A CN 96104607A CN 1161538 A CN1161538 A CN 1161538A
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- track system
- polarization
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Abstract
A multi beam track system and method is used for the retrieving of information stored in optical memories like optical disks. The information carrying beams reflected on the surface of such a optical disk results in spots on the surface of a detector array. Because these beams are very close to each other, the resulting spots tend to overlap so that cross talk conditions between neighboring channels occur. As result the S/N ratio becomes worse. The polarization angle of neighboring beams differ by 90 degree. After reflection on the surface of the optical disk the row of reflected laser beams is separated into two rows by an separating means. Such a separator can be a polarizing beamsplitter or a birefringent prism crystal. As a result two rows of laser beams are achieved, which can be detected by two separate detectors. As result no overlap between neighboring spots occurs on the surface of the detectors, resulting in the elimination of crosstalk.
Description
The present invention relates to a kind of multi beam track system and relate to a kind of method that is used for recovering the information of optical memory, for example method that multi-beam is reflected by stored CD.
For storing and recovering a large amount of numerical datas, can adopt so-called CD, these CDs can be ROM (read-only memory), as form with CD-ROM or digital video disk (DVD), or can wipe, CD-RW.Usually this class CD comprises a plurality of top annular sessions that can store numerical information.One laser beam is incorporated on this session, just can from the light beam that usually reflects by optical disc surface, recovers numerical information.For improving to being stored in the acquisition speed of the numerical information in the CD, both can increase the linear velocity of CD, also can adopt a kind of many track systems, that is to say simultaneously and a plurality of sessions are read with multi-beam.
System known per shows following defective:
If the CD linear velocity is high more, shake is severe more (signal to noise ratio (S/N ratio) S/N variation) just, and focusing and tracking servo become difficulty and complexity.On the other hand, in the many track systems that adopt multiple beam, be difficult to separate the multi-beam that reflection (or transmission) goes out.Therefore, interference has aggravated.
Therefore, one object of the present invention just provides a kind of multi beam track system and is used to recover the method for optical memory information, wherein, separate fully penetrate carry information carrying beam and avoid adjacency channel or session between interference be possible.
This purpose is to be resolved by the subject matter according to claim 1 and 14.
The multi beam track system that is used for optical memory according to the present invention comprises that one is used for producing the multiple beam generating means of multiple beam, the pick-up unit that is used to separate the tripping device that carries information carrying beam of ejaculation and is used to detect outgoing beam.
Adjacent beams can be distinguished by for example different polarization states and/or different wavelength.Therefore, employing one is used for separating the tripping device that carries information carrying beam of ejaculation, is possible according to its polarization state and/or its wavelength with these beam separation.This tripping device can for example reflect these light beams according to polarization state and/or wavelength.Can also adopt based on other principle, as birefringent tripping device.
Usually adopt the linear polarization of light beam, these light beams all are laser in most of devices, and wherein the polarization direction of adjacent beams differs 90 °, and promptly adjacent beams will be by linear polarization vertically.
Furtherly, it is possible allowing polarization state between a branch of light and adjacent that Shu Guang change a fixed amount Δ φ who is different from 90 °.
In addition, light beam circular polarization be can make, a branch of right-hand circular polarization, and another bundle Left-hand circular polarization made in the two bundle adjacent light.
This multiple laser is normally produced by a diode laser matrix that is arranged in delegation.
Be incorporated into the tripping device usually carrying the information carrying beam that carries that the one side of information reflects from CD, this device responds laser in different polarization states Shu Jinhang.Utilize the different polarization states of adjacent beams, it is possible spatially separating folded light beam.For example, adopt vertical light beam, just can be with a polarization beam splitter with the light beam that the penetrates light beam that is divided into two lines, they spatially are perpendicular to one another.Reason is that a branch of polarized light is reflected on the inclined-plane of beam splitter, and another bundle polarized light passes through beam splitter along incident direction.Therefore, it is lip-deep overlapping in relevant detection adjacent beams can not occur, has also just avoided the interference between adjacency channel.
Another kind of possibility of separating different polarization light is utilized birefringence or optical anisotropy phenomenon exactly, particularly adopts the birefringent prism crystal, and wherein amount of refraction depends on polarization state.Therefore on the whole, optical anisotropy can be used to the angle of a Δ φ of polarization state change of adjacent beams, for example 45 ° situation.
Can adopt known device,, be used to separate different wave length as light filter.
And, be used for the method that optical storage reads being comprised the following steps: according to the present invention by multi beam track system
-preferably the mode with row produces many light beams, and wherein adjacent beams has different polarization states.
-described many light beams are incorporated on the optical storage.
-utilize a tripping device of deciding on polarization state that folded light beam is separated.
-utilize a pick-up unit that the information carrying beam of separating that carries is detected.
Provided the further preferred embodiment of the present invention in the dependent claims.
In the following drawings, the preferred embodiments of the present invention are described, wherein
Fig. 1 illustrates a kind of principle of many sessions optical memory system;
Fig. 2 illustrates the example of a diode laser matrix;
Fig. 3 is illustrated in not the overlapping situation that arrives the folded light beam on the detecting device under the situation of separating according to its polarization state;
Fig. 4 illustrates the embodiments of the invention of an employing linear polarized beam and a polarization beam splitter;
Fig. 5 illustrates the another embodiment of the present invention that adopts the birefringent prism crystal.
Fig. 1 has comprised Fig. 1 a and Fig. 1 b.
Fig. 1 a has represented to have the Concentric plate 1 of a plurality of concentric sessions 2.Utilize the multi-beam (not shown) in the zone 3 of CD 1, these sessions to be read.
Fig. 1 b is that to be read regional 3 one diagrammatic sketch that has amplified (is also seen Fig. 1 a), wherein, for ease of explanation, session 2 is expressed as being parallel to each other.Use the laser spots (4 of multiple beam respectively
1-4
n) irradiation session (2
0-2
N+1).Find out by Fig. 1 b, comprise the multiple beam point 4 of n bundle laser beam
1-4
nBe arranged in straight line, this straight line is with respect to session 2
0-2
N+1Direction tilt.Be coated with full round dot (those round dots that promptly have the odd number footnote) and have the vertical polarization attitude in this example, and the round dot (the grey flakey round dot with even number footnote) of those band points has the horizontal linearity polarization state in this example.
Can make polarization state differ 90 °, and can differ a 45, the polarization state of each round dot and adjacent round dot differs 45 in other words.And, for example can allow round dot have the right-hand circular polarization attitude and round dot with even number footnote has the Left-hand circular polarization attitude with odd number footnote.
Usually the line 5 that connects round dot tilts with respect to the radius 6 that coils, so that session 2
1-2
nOn luminous point 4
1-4
nCan be not overlapping.
Fig. 2 illustrates a kind of diode laser matrix 7 that can be used in many track systems.This diode laser matrix 7 comprises a plurality of laser diodes 7 with line spread
1-7
nBe used for diode laser matrix 7 of the present invention and comprise n the little laser diode with linear polarization state of checker, wherein n is a natural number.
Fig. 3 shows each the laser beam round dot 9 that lists at a detector array
1-9
nOverlapping 8.Because the reflection of laser beam on the CD session, the round dot size changes so that list at detector array, the round dot 9 of different light beams
1-9
nTrend towards overlapped one-tenth overlapping region 8.Can cause the reduction of undesirable interference and signal to noise ratio (S/N ratio) (S/N) like this.If the light beam round dot can be separated better, perhaps, for example, if per second round dot all will be shifted into another locus, just interference problem can not appear.
Fig. 4 shows first embodiment of multiple beam piece-rate system.Allow laser beam round dot 4
1-4
nBe incident on the session 2 of CD 1
1-2
nOn.Corresponding to round dot 4
1-4
nThe linear polarization direction of laser beam change 90 °.The light beam that is gone out by CD reflection is collimated by lens 10 and is introduced on the polarization beam splitter 11, beam splitter 11 has such characteristic, be that those light beams with vertical linear polarisation attitude (being those light beams with odd number footnote) are reflected on the 45 plane 12 of beam splitter, and those have the plane 12 of light beam (being those light beams with even number footnote) the transmitted beam separation vessel 11 of horizontal polarization attitude.As a result, obtain the round dot 9 of the two capable information of carrying of spatially separating
1-9
N-1(being those points) and 9 with odd number footnote
2-9
n(point that promptly has the even number footnote).Therefore, can with have the horizontal polarization attitude round dot that the row luminous point be incorporated in the detector array, and will have corresponding vertical polarization attitude that the row luminous point be incorporated in another detector array.
Fig. 5 illustrates second embodiment of multiple beam piece-rate system.A plurality of laser beam 4 that will have as shown in Figure 4, different polarization states
1-4
nBe incorporated into the corresponding session 2 on the CD 1
1-2
nOn.Collimate and be incorporated on the birefringent prism crystal with 10 pairs of folded light beams of lens, wherein the reflection angle of different polarization states light beam is the function of crystal birefringence.The polarization state that this birefringent phenomenon can produce according to laser beam spatially is separated into two row light beam 9 separately with delegation's light beam
1-9
N-1With 9
2-9
nBecause in each row, per second round dot all disappears, therefore the interference problem of adjacent session can not appear.Can utilize two row separate detector array (not shown) that information is detected.
Claims (24)
1, a kind of multi beam track system that is used for optical memory (1) comprises:
The multiple beam generating means, be used for producing the multi-beam be used for reading the information that is stored in optical memory (1) and
Pick-up unit is used for detecting the information carrying beam that carries of ejaculation,
Also comprise:
A tripping device (12,13) is used for separating the information carrying beam that carries of ejaculation,
Wherein adjacent beams has different polarization states and/or wavelength.
2, multi beam track system as claimed in claim 1, wherein light beam is a linear polarization.
3, multi beam track system as claimed in claim 2, wherein the polarization state of adjacent beams differs a Δ φ angle.
4, multi beam track system as claimed in claim 3, wherein the polarization angle of adjacent beams differs 90 °.
5, multi beam track system as claimed in claim 1, wherein light beam is a circularly polarized light.
6, as the multi beam track system in any one claim of front, wherein light beam is a laser beam.
7, multi beam track system as claimed in claim 6 wherein utilizes diode laser matrix (7) to produce multiple laser.
8, as any one described multi beam track system of claim 1～7, wherein said tripping device (12,13) separates the information carrying beam that carries that sends from optical storage (1) according to the polarization state and/or the wavelength that carry information carrying beam.
9, multi beam track system as claimed in claim 8, wherein tripping device (12,13) will carry information carrying beam and spatially separate.
10, multi beam track system as claimed in claim 9, wherein tripping device (12,13) comprises a polarization beam splitter (11).
11, multi beam track system as claimed in claim 9, wherein tripping device (12,13) comprises a birefringent device (13).
12, as the multi beam track system of claim 11, wherein birefringent device (13) is a birefringent prism crystal (13).
13,, wherein carry information carrying beam and be from a surface of stored CD (1) and be reflected as any one described multi beam track system in the claim of front.
14, a kind of employing one multi beam track system recovers the method for the information in the optical storage (1) that is stored in, and comprises the following steps:
Produce a plurality of light beams, wherein adjacent beams has different polarization states and/or wavelength;
Multi-beam is incorporated on the optical storage (1);
Utilize tripping device (12,13) according to polarization state and/or wavelength to carrying of penetrating information carrying beam separates and
Utilize pick-up unit to detect isolated light beam.
15, as the method for claim 14, wherein said light beam by rows.
16, as the method for claim 14 or 15, wherein said light beam is a laser beam.
17, as any one described method in the claim 14 to 16, the polarization state of wherein said adjacent laser beam differs a Δ φ angle.
18, as the method for claim 17, wherein Δ φ angle is 90 °.
19, as the method for claim 14, wherein said light beam is a circularly polarized light.
20, as any one described method in the claim 14 to 19, wherein carry the laser beam of the ejaculation of information and spatially separate.
21, as the method for claim 20, wherein said tripping device is made of a polarization beam splitter (12).
22, as the method for claim 20, wherein said tripping device is made of a birefringent device.
23, as the method for claim 22, wherein birefringent device (13) is a birefringent prism crystal (13).
24, as any one described method in the claim 14 to 23, wherein said multi-laser beam is reflected on the surface of stored CD (1).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96104607A CN1161538A (en) | 1995-05-06 | 1996-04-08 | Multi beam track system and method for optical memory |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9509306.8 | 1995-05-06 | ||
| CN96104607A CN1161538A (en) | 1995-05-06 | 1996-04-08 | Multi beam track system and method for optical memory |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1161538A true CN1161538A (en) | 1997-10-08 |
Family
ID=5118399
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN96104607A Pending CN1161538A (en) | 1995-05-06 | 1996-04-08 | Multi beam track system and method for optical memory |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1161538A (en) |
-
1996
- 1996-04-08 CN CN96104607A patent/CN1161538A/en active Pending
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