TW200818159A - Holographic storage system with multiple reference beams - Google Patents

Abstract

The present invention relates to a coaxial type apparatus (1) for reading from and/or writing to holographic storage media (18) with multiple reference beams (7", 7'''). The invention further relates to a beam generator (21) and a filter (12) for use in such an apparatus (1). According to the invention, in an apparatus (1) for reading from and/or writing to a holographic storage medium (18), with a coaxial arrangement of three or more focused reference beams (7", 7''') and an object beam (6) or a reconstructed object beam (26), the foci of the focused reference beams (7", 7''') are arranged on a circle around the object beam (6) in a Fourier plane of the apparatus (1). A beam generator (21) generates the three or more reference beams (7", 7''') from an incoming reference beam (7). A filter (12) low-pass filters the object beam (6) and rotates the polarization of the three or more reference beams (7", 7''').

Description

200818159 IX. Description of the Invention: [Technical Field] The present invention is directed to a holographic storage medium read/write device 像ί" like a storage medium coaxial read/write device. The beam business of the present invention, and the use of such a device [Filter] [Previous technique] In the holographic data storage, the digital material is stored by using the records of the interference generated by the same, and the local strength of the type of ^^ is determined. = Line. Causes the reconstruction of the recorded beam. One of the advantages of the King is to increase the data capacity. Contrary to the conventional optical media, the capacity of the holographic storage medium is used for a few The holographic data storage has the advantage that it is the same as t :: can be stored in multiples of the data 'for example, between two beams: with: Ο, etc. In addition, the data is stored in the data page, generation; single =;: early (three) The net number will be written to the stone horse. If Ά + =, increase the data rate. The data page is used as empty: =) Ρβ has been on the object beam and detected by the detector array.

U 624 451 discloses a holographic configuration with a coaxial configuration in which a plurality of reference beams are disposed around the object beam. According to this solution, the object beam and the reference beam system are respectively 物, 隹1, f in the object plane and the image plane. This configuration is a so-called split aperture configuration J part and reference part. This configuration has a circular symmetry: excellent. However, the Fourier lens of the Fourier lens is used for reference = ^^ 200818159. The overlap only partially begins with the pulse of the holographic storage medium starting from the distance of the full side JL 姊 Fourier Wei's miscellaneous g = face about 200-400 μηι, and the silk cocoons are not superimposed.攸得立千千 shows a kind of 12f^ in WO 2006/003077

The Fourier plane of the confocal configuration. Here, the SI and the three-Fourier plane are coupled and coupled out. reference

Ο ίίΐ ίί Millennium. More precisely, the diffraction pattern is formed, ί = rational (Any) _. This configuration is the so-called normal aperture, ί:=? plane, the object beam and the reference beam fill aperture are the same as the Si aperture, the entire aperture of the light ilif objective. The disclosed configuration can be applied to shift multi-system, multi-process, phase write code multiplexing, or such multi-work beam is a pair (or pairs) of semi-conical beams, in pairs In the infinite hologram, the displacement selectivity curve is sin t. See, for example, G. Ba Touch athis #人 <Shifting Work with a Spherical Reference Wave> (APP1. 〇Pt. 35, pp. 2403-2417). The diffraction efficiency of the shifted hologram at the Shishitian Bragg distance is zero. In 2006/003077, the distance between the reference beams along the tip of the two lines is equivalent to this Bragg distance. Assume an infinite-diameter hologram, a shifting multiplex, a selective and non-selective direction. See also G. Barbastathis et al. The selective direction is the direction in which the reference beam tip forms a line. In the so-called non-selective direction (straight in the hologram plane and the selective direction), the shift distance is unlimited. However, in a real storage system, the hologram capacity is limited. In fact, the magnitude of the total &amp; graph J is about (0.4-0.6) x (0.4-0.6) x (0.2_0.6) mm 丨. Detailed studies have shown that there is a large contradiction between the shift selectivity curves of infinite and finite holograms. In the case of a finite-capacity hologram, there is no Bragg distance. ^ 6 200818159 The selectivity of the semi-conical reference beam is multiplexed. The problem is in non-selection in the two-way string, south. This limits the multiplexed sequence that can be achieved in this direction and thus limits the total capacity of the holographic storage medium. The number of t-pictures, [Summary of the contents] There is a change in the purpose of the holographic read-and-write device. The realization of the bud-set is to use the holographic storage medium to read/write 2' with two or more focuss. The reference beam and the object beam in the 2 plane, such as (4) or ellipse, circle. The crosstalk between the Fourier holograms can be applied in both directions by two or more = balance. The tip of the beam is placed around the object beam in the Fourier plane ===: In terms of a circle, the displacement distance is the same in the γ• direction, and &amp;, and the direction is different. At least three reference beams are used, the circumference of the aperture is distributed. From the point of view of geometric optics, the reference beam in the ^ plane is a single point, or more accurately, in the center, the intensity of the ride. The tip of the reference beam or the peak of the bribe is ^ week/circle or elliptical. The diameter of the circle _ _ 傅 傅 傅 器 器 器 器 , , , , , 器 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径 孔径The %^ large diameter allows the reference beam and the filament to be coupled into and out of the optical system, such as an optical system. The solution of the present invention is an improvement of the solution disclosed in No. 6/003077, in which pairs of reference beams are arranged along the line. According to the invention, the circle around the beam of matter in the leaf plane of the Fourier 200818159 is arranged. There are at least four reference beams, and they are equally spaced along the circle: ίί: Gong 2: It is better to achieve the same crosstalk between the holograms. ... straight up: to: three incoming reference beams or holograms or thick multi-components are preferred. For example, the computer generates the above reference beam, which does not require complex diagrams to occur efficiently.

Light; 8: In this way, the overlap between the Wenjin County and the reference beam can be reduced in the ninth, and the symbol error rate (SER) of the Xigong all-image is reduced. And 5ί 5-bit i Fourier plane, as a low-light illuminator for the object beam, one or more polarization-rotating elements of the reference beam. For this purpose, the filter is crying «there is a beam block, the object beam is low-pass filter-like central aperture, and ^^ ΐίΓΜ and the ring-shaped half-wave plate for turning the pole of three or more reference beams = 丄ί! Central aperture. These filters are easy to tie the object beam to green silk. At the same time, the filter and light 11 can interfere with the zero-order reference beam generated by the diffracted light. Of course, the efficacy of the low pass filter and the polar rotating element can be performed using separate components. For a more detailed description of the invention, reference is made to the accompanying drawings in detail. It is to be understood that the invention is not limited to the specific embodiments, and the specific features may be combined and varied without departing from the scope of the invention. [Embodiment] Fig. 1 is a simplified diagram showing a coaxial reflection type hologram storage medium of the present invention. For the sake of clarity, the integrated feeding system is omitted from the figure. In an embodiment, the holographic storage system is a 12f system. The laser beam 3 emitted by the laser 2 is expanded by the optical beam expander 4 to be divided into the object beam 6 and the reference beam 7 by a polarized beam splitter (ρΒ§;) cube 5. The half-wave plate 27 is located between the beam expander 4 and the 200818159 master w, 5. Laser 2 emits a linearly polarized laser beam 3. Turn PRS 2: Touch 7 ' to turn the polarization direction of the laser beam 3 to any direction. Christine (4)^\5 divides the laser beam 3 into orthogonal polarizations (p and s polarization): tick t: ° rotate the half-wave plate 27 to control the P and S polarized beams, fy! The intensity ratio of the object arm to the reference arm. In order to make the readout around ‘ί I, the intensity ratio is optimal. The object beam 6 utilizes the second [BS two-in-one 8 to reflect the reflection type _9. After reflection from (4) 9, the object beam body 8, using the third pbs cube ig and the reference light port. &gt; The test beam 7 uses the mirror 20 to point to the third PBS cube! Hey. In the optical path of ίίΐΐί, there are secret plates 22 and beam generators 2 such as beam generation 11. Beam generator 21 (for its function, see Figures 2 to 4 Ο I ff complex reference beam 7, 7, 7,,, as described above, object beam &>&gt; light beam 7, 7'" using the third pBS cube 1〇face into the main coaxial configuration. After the PBS body 10, there is a first long focal length objective n. In this case, the long focal length means that the focal length is long enough to place another light f component between the lens and the focus. , * There will be * large aberrations. The advantages of the health and distance objective lens are simple to make. 'There are few optical components required. In addition, the Fourier plane of the long focal length objective lens is straight and large, which can be simplified and placed in Fourier due to the reduced manufacturing tolerances. State in the plane. This first object 11 is in its back focal plane, ie, the Fourier of SLM; the Fourier transform of SLM 9 occurs. The first objective n also has a complex number of light, 7&quot;:7"' Focusing on the Fourier plane. Located in this Fourier plane is the inner light filter state, as shown in Fig. 6. The design of the internal coupling filter 12 is such that the beam of light is passed through the beam 7, and the reference beam 7, 7, ," Polarization. After the internal lighter! 2, the object beam 6 and the reference beam 7", 7... through the fourth PBS After the PBS is accessed, the second long focal length objective 14 converts the sm shadow to the intermediate plane 15. The high να Fourier objective 16 (for example, na^ 〇·6) converts the SLM image to the hologram. On the mirror layer 19 of the storage medium 18. At the time of writing, the object beam 6 interferes with the direct beam 7", 7"' and the reference beam 7", 7&quot; reflected by the mirror layer 19 in the holographic storage medium 18. Reading the Reconstruction 9 200818159 The beam 26 is converted to the intermediate image plane 15 using a sorghum Fourier objective ι6. The quarter wave plate 17 is between the sorghum Fourier objective 16 and the holographic storage medium 18. The beam passes through the quarter-wave plate 17 twice, and the polarization direction of the reconstructed object beam 26 is orthogonal to the polarization direction of the original object beam 6. The reconstructed object beam 26 is again subjected to Fourier using the first long focal length objective lens ι4. Conversion. Due to the polarization rotation, the PBS cube η puts the reconstructed beam beam in the third Fourier plane of the system. The object optoelectronics 23 blocks Ο ϋ mm and thus only the reconstructed beam 26 utilizes a third focal length objective; Detect (4) on column 25. In the towel, the focal length of the objective lens 24, and the object

The Hi distance is different. This optical configuration is a so-called out-of-focus system. In the case of the objective lens 1U4, 24 which can be used with different focal lengths, the focal length of the objective lens 11 * 14 can be appropriately selected, and between the _ 9 ^ between the object beams 15 to appropriately select the pupil distances of the objective lenses 14 and 24, ί When the intermediate plane 15) and the detector are connected to magnify the size of the SLM 9 and the size of the detector 25, ί:: sampling and oversampling is expressed as a number of variations of the -slm primitive specified 'transmission type SLM. In this case, Fig. 2 shows that the beam generator 21 ^ 18 taper slams 7丨7,7," lL , t 〒 〒 / / / and the knives are 稷 ± ± ± ^ 21 LL · , b The semi-conical reference beam 7,,, 7" is generated by using the diffractive element as a reference beam. The three-dimensional figure in the figure is represented by the ^ direction $. Divided into the right half cone 7" and the left half cone 'body J. With if: beam 7,, riding efficiency is low. Age test light thousand 7, = ^ j zero-order tea test two H inner ΐ + specific examples, use within The dimming light is achieved by the devices 12 and 1 13. The diffractive element should be the full side of the computer or the I-IS, 200818159. The symbol of the beam generator 21 should be 11 and the reference beam 7 ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, The object beam 6 is subjected to Fourier on this plane, and the grating is filtered by the Yoshiguchi. The light beam 7'·, 7''' is disposed around the circle of the object beam 6 by the inner surface ί光 k'fL1. The zero-order reference beam 7, which is not directly blocked by the light, is located within the same area of the object beam 6. Ο Directly 'after reflection of the mirror layer 19 of the holographic storage medium 18, the =+ cone reference beam 7",7,&quot; together with the reflective half-cone reference beam 7"7&quot;,, 2 ΐίίΠ, ie substantially complete _ . That is to say, the group of such beams has a substantially circular cross section close to the plane of the passing leaves.滹光Ϊ Hi is located in the inner surface of the first Fourier plane of the optical system. Including the beam block 12〇, for example, 7 in the thin, with the wire, the object 6 and the reference beam 12] Γ s22 (diameter 〇 3)' and the reference beam 7, 7, 7,, sit with holes, 4! d). The ring type half wave plate 123 is disposed on the beam block 120. The toroidal beam ϋΐΓϋ '124 ' diameter &amp; The object beam 6 and the zero-order reference 匕 central aperture 124, without any change, also cry through the beam block nm. The central aperture 122 acts as a higher Fourier component of the tilting light 1^ of the object beam 6. The rest of the reference beam - Fu beam 7", 7 &quot;, the polarization direction. In the first ΐ ΐ ί ί,, the object beam 6 and the reference beam 7', 7', 7, and the polarization direction of the beam The 3L half-wave plate 123 rotates and diffracts the reference beam 7&quot;, 7&quot;, and the low-energy zero-order reference beam 7 preserves its polarization direction. The ring around it (diameter Di) is the first beam 7 Hole 7 (2). Therefore, the first Fourier plane is crying 12' transmission diffraction reference beam 7", 7"', and the zero-order reference beam 7,, ^2 low through the filtered object beam 6. Because the ring-shaped half-wave plate 12; 3, the zero-order reference beam is 11 200818159 and the polarization direction of the other f-beams 6,7 is orthogonal. Therefore, the secret shot m is after filtering, light is 12, and the transmission is low through the filter. The wire 6 and ϊ /, 7"', and the zero-order reference beam 7 is reflected by the mouth, and the optical system circle ^ ^ # ^ 122 壬 81 shape, preferably with the optically set lens 7" 7 ^, and The aperture 122 may also have an elliptical shape, for example, a reference beam Ο Ϊΐ ΐ ΐ ΐ 1 31. The diameter of the central aperture 122 is D3. The diameter difference is ^ / (^ Γ) about A0 · (four). Reference light 7V, "The hole 121 is straight" = gram 7" Γ #然' reference beam 7'7," the number is not limited to four or eight to four or eight to test light 7 &quot; 7,,,... ϊϊ Qiaozha money. Use the dryness of the semaphore to match the homogenization of the crosstalk between the hologram and the top view. The central aperture is such that QV: Medium 2 satisfies the relationship of (Dl_d) &gt; 〇 2 &gt; ε &gt; A section of the outer dimmer and 23. External dimmer 23 bits 2^0, ΐΐί the second Fourier plane. The outer ablower 23 is a beam block 230, and its central aperture 231 has a diameter D3. η尤来块 Upstroke the ii0 diagram to indicate the modification of the setting in Figure 1. In this modified setting, the = = = 21 is a mirror beam generator. As a result, the ί point required to change = i in the half-wave plate 22 is further simplified by the optical system: no 12 200818159 [Simple description of the drawing] ί f _+ like the setting of the dimension of the Wei; the brother 2 chart does not refer to the beam generator and The spring beam of the test is carried out. The cone opens the m-face in the fine society. The sigh beam and the four semi-conical beams are shown in the joint material (4) Newt beam and eight half-shaped beam beam; Table 7^ Fourier plane object beam and eight her double cone

F6 is a cross-sectional view of an inner filter having a ring-shaped half-wave plate; 7 is a top view of a coupling filter of four reference beam cases; and FIG. 8 is a plan view of a ring-shaped half-wave plate;

U Figure 9 shows a cross-sectional view of the external consumption filter; Figure 10 shows a modification of the setting of Figure 1. [Main component symbol description] 1 holographic storage system 2 laser 3 laser beam 4 beam expander 5 beam splitter cube 6 object beam 7,7',7",7"' reference beam 8 second beam splitter cube 9 Reflective spatial dimmer 10 Third beam splitter cube 11, 14, 24 Objective lens 12 Internally coupled filter 13 Fourth beam splitter cube 15 Intermediate plane 16 High NA Fourier objective 17, 28 Quarter A wave plate 18 hologram storage medium 19 mirror layer 20 mirror 21 beam generator 22, 27 half wave plate 23 outer filter, light mirror 25 detector 26 reconstructed object beam, D3, d diameter 120, 230 beam block 121 hole 122,124,231 central aperture 123 ring half wave plate 13

Claims (1)

200818159 X. Patent application scope: 1, 1 A holographic storage medium (18) read/write device (1) with three or more focused reference beams (7,,, 7,,) and object beams (6) Or a coaxial arrangement of the reconstructed beam (26) characterized by focusing the focus of the reference beam (7", 7,,,) on a circle I around the object beam (4) in the Fourier plane of the device (1). 2. The device (1) of claim 1 of the scope of the patent application, the reference beam (7) having the beam generator generates three or more reference lights S Ο 3 as in the device of claim 2 (1) Where the beam is crying (21) is a diffractive element. 4. The device (1) of claim 2, wherein the holographic storage medium (18) is a reflective medium and the beam generator ( 21) The reference beam (7", 7'&quot;) occurs. 5. The device (1) of claim 2 or 3, wherein the holographic storage medium (18) is a reflective medium, and the beam generator (21) is a cone beam (7&quot;, 7 m) .夕6·, as in the device of claim 1 (1), having a filter (I (12) 'located in the Fourier plane for low pass filter beam (6) and for rotating three or more reference beams (7,,,7",) The direction of polarization. 7. As in the device (1) of claim 6, the filter (12) has a beam block (120) with a low pass filter The central aperture (122) of the beam (6), and the aperture (121) for the reference beam (7", 7,"), and the annular half-wave plate (123) for rotating three or more reference beams ( The polarization direction of 7",7,"), the central aperture (124) of the object beam (6). 8. The beam generator (21), three or more from the incoming beam (7) a beam (7, 7) characterized in that the beam generator (21) is adapted to generate two or more beams (7'', 7&quot;'), arranged around the central beam (7,) 14 200818159 9·A beam generator according to item 8 of the patent application, wherein the beam generator ^21) emits elements for three or more cones or half cones Light &amp; !〇·- kind of central beam (4) and low-pass filter arranged around the central beam (4) (7V,,,) (12) 5 5 center beam (6), and three (7", 7 "," the polarization of the rotating element. Chiyou 11. The filter (12 (120) of the first application of the patent scope, with a central aperture (122) (third straight rear D block diameter (m ) The hole around the circle (121) (the first 置 = placed in the central hole type half-wave plate (123), its central aperture (124) d ^ ring three diameter (D3) is the largest. - Straight only (3⁄4 ) ϋ 15