Coaxial holographic storage system and torquer device thereof

Abstract

The invention discloses a coaxial holographic storage system and a torquer device thereof, the torquer device comprises an objective lens, a first support, a first frame, a focusing moving mechanism, a reflector and a tracking moving mechanism, the objective lens is arranged on the first support, the first support is arranged on the first frame through the focusing moving mechanism, and the reflector is arranged on the first frame through the tracking moving mechanism. The focusing moving mechanism is used for enabling the first support and the objective lens to move in the focusing direction, the reflecting mirror is arranged on the first frame and can rotate relative to the first frame, the first frame is arranged on the tracking horizontal moving mechanism, and the tracking horizontal moving mechanism is arranged on the second frame. The tracking moving mechanism is used for enabling the first frame, the reflecting mirror and the objective lens to move in the tracking direction, and the focusing direction is perpendicular to the tracking direction. Compared with a direct movement holographic optical disc and a motor for driving the holographic optical disc to rotate, focusing and tracking are realized by moving the objective lens and the reflector which are relatively light in weight, and the precision is easy to control.

Description

Technical Field

[0001] The present invention relates to the technical field of coaxial holographic storage, and in particular to a coaxial holographic storage system and a torquer device thereof. Background Art

[0002] With the development of the Internet of Things and artificial intelligence technology, the data generated by people in their lives is also growing explosively. According to the forecast of IDC, the world will generate 159.2ZB of data in 2024, and it will more than double to 384.6ZB in 2028. Among them, most of the data information is cold data that is not frequently read. Therefore, the development of low-energy, long-life, and large-capacity cold data storage technology is imminent. Traditional optical storage has become an important means of cold data storage with its advantages of low cost, low energy consumption, and long life. In recent years, the emerging holographic storage can solve the problems of low capacity and slow reading speed of traditional optical storage.

[0003] The coaxial holographic storage system is a three-dimensional data storage technology that uses laser beams and holograms to record data. In the coaxial holographic storage system, the position of the objective lens is usually fixed, and in order to achieve focusing, the holographic disc is adjusted to achieve the desired focusing effect. However, the holographic disc is driven by a motor to rotate, and the overall mass is large, making it difficult to achieve high-precision and fast control when the entire disc moves. Summary of the invention

[0004] Therefore, it is necessary to provide a coaxial holographic storage system and a torque device thereof to solve the problem that the holographic optical disc is driven to rotate by a motor, the overall mass is large, and it is difficult to achieve good control when the overall movement.

[0005] To achieve the above-mentioned purpose, the present embodiment provides a torquer device of a coaxial holographic storage system, comprising an objective lens, a first bracket, a first frame, a focusing movement mechanism, a reflector and a tracking movement mechanism, wherein the objective lens is arranged on the first bracket, and the first bracket is arranged on the first frame through the focusing movement mechanism, and the focusing movement mechanism is used to move the first bracket and the objective lens along a focusing direction, and the reflector is arranged on the first frame, and the reflector is rotatable relative to the first frame, and the first frame is arranged on the tracking movement mechanism, and the tracking movement mechanism is used to move the first frame, the reflector and the objective lens along a tracking direction, wherein the focusing direction is perpendicular to the tracking direction.

[0006] Furthermore, it also includes a second frame, and the tracking movement mechanism includes two tracking movement components, and the tracking movement components include a permanent magnet, a tracking coil and a tracking wire. The permanent magnet is arranged on the second frame, and the permanent magnet is located on one side of the tracking coil. The tracking coil is arranged on the first frame, and the tracking wire is arranged on the first frame and the second frame. The tracking coil is elastic and has a curved part, wherein the tracking coil generates a magnetic field when energized, and interacts with the magnetic field where the permanent magnet is located to generate an electromagnetic force in the tracking direction, which cooperates with the elastic force of the tracking wire to move the tracking coil along the tracking direction.

[0007] Furthermore, the focusing movement mechanism includes two focusing movement components, the two focusing movement components are located on both sides of the objective lens, the focusing movement components include a focusing coil and a focusing suspension wire, the two focusing movement components share one focusing coil, the focusing coil is located on the inner side of the tracking coil, the focusing coil is arranged on the first bracket, and the first bracket is arranged on the first frame through the focusing suspension wire, the focusing suspension wire is elastic and has a curved part, wherein the focusing coil generates a magnetic field when energized, and interacts with the magnetic field where the permanent magnet is located to generate an electromagnetic force in the focusing direction, which cooperates with the elastic force of the focusing suspension wire to move the focusing coil along the focusing direction.

[0008] Furthermore, the focusing moving assembly also includes a first fixed block, the focusing suspension wire is connected to the first fixed block, the first fixed block is plugged into the first bracket, so that the focusing suspension wire is arranged on the first frame through the first fixed block, the focusing suspension wire and the first fixed block are conductors, and the focusing suspension wire / the tracking suspension wire, the first fixed block, and the focusing coil / the tracking coil are electrically connected through wires.

[0009] Furthermore, it also includes a yoke, which is a U-shaped structure. The permanent magnet, the tracking coil, and the focusing coil are all located inside the yoke, and the permanent magnet is plugged into the yoke.

[0010] Furthermore, the focusing wire extends along the tracking direction, the tracking wire is perpendicular to the focusing wire, and the extending direction is perpendicular to the focusing direction, and the focusing wire and the tracking wire are staggered up and down.

[0011] Furthermore, the tracking moving component has two tracking suspension wires, namely an upper tracking suspension wire and a lower tracking suspension wire, and the cross-sectional area of ​​the upper tracking suspension wire is different from the cross-sectional area of ​​the lower tracking suspension wire.

[0012] Furthermore, the tracking moving component also includes a second fixed block, the tracking wire is connected to the second fixed block, and the second fixed block is plugged into the first frame so that the tracking wire is arranged on the first frame through the second fixed block, the tracking wire and the second fixed block are conductors, and the tracking wire, the second fixed block, and the tracking coil are electrically connected through wires.

[0013] Furthermore, the tracking moving component has two tracking coils, which are arranged side by side and plugged into the first frame.

[0014] To achieve the above purpose, this embodiment further provides a coaxial holographic storage system, including:

[0015] A semiconductor laser, configured to emit a first light beam;

[0016] a single longitudinal mode laser, for emitting a second light beam;

[0017] a polarization beam splitter, disposed on one side of the semiconductor laser, and used for reflecting the first light;

[0018] a collimating lens, disposed at one side of the polarization beam splitter, and used for collimating the first light reflected by the polarization beam splitter;

[0019] A dichroic beam splitter, disposed on one side of the collimating lens, for combining the first light and the second light;

[0020] A quarter wave plate, disposed on one side of the dichroic beam splitter, for allowing the combined light beam to pass through;

[0021] A torquer device, such as the torquer device of the coaxial holographic storage system described in any one of the above embodiments, wherein the torquer device is arranged on one side of the 1 / 4 wave plate, the reflector of the torquer device is used to reflect the combined light beam passing through the 1 / 4 wave plate, and the objective lens of the torquer device is used to converge the first light beam of the combined light beam on the ideal focal plane corresponding to the holographic optical disc, and converge the second light beam of the combined light beam on the ideal focal plane corresponding to the holographic optical disc;

[0022] Among them, the torquer device also includes a four-quadrant detector and a controller, the four-quadrant detector is used to detect the focusing error signal and the tracking error signal carried by the first light, and the controller is used to control the focusing movement mechanism according to the focusing error signal to move the first bracket and the objective lens along the focusing direction, and control the tracking movement mechanism according to the tracking error signal to move the first frame, the reflector and the objective lens along the tracking direction.

[0023] Different from the prior art, the above technical solution has the following beneficial effects:

[0024] Compared with directly moving the holographic disc and the motor driving it to rotate, the present application realizes focusing and tracking by moving the objective lens and the reflector with relatively light mass, which is easy to operate and the precision is easy to control. In addition, the synchronous tracking method of the objective lens and the reflector can keep the incident light at the same incident angle during the tracking servo, which meets the requirement that the incident angles of the read and write light in the coaxial holographic storage system need to be consistent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a three-dimensional diagram of the torquer device in this embodiment;

[0026] Figure 2 is a stereoscopic diagram of the objective lens, the first bracket and the focus moving assembly in this embodiment;

[0027] Figure 3 is a three-dimensional diagram of the yoke, permanent magnet, and tracking coil in this embodiment;

[0028] Figure 4 is a front perspective view of the focusing movement mechanism and the tracking movement mechanism in this embodiment;

[0029] Figure 5 is a rear perspective view of the focusing movement mechanism and the tracking movement mechanism in this embodiment;

[0030] Figure 6 is a schematic structural diagram of the coaxial holographic storage system in this embodiment;

[0031] Figure 7 is a schematic diagram of an astigmatism error signal FE in this embodiment;

[0032] Figure 8 is a schematic diagram showing that the value of the focus error signal FE in this embodiment is an S curve;

[0033] Fig. 9 It is a schematic diagram of determining the direction and distance of the focus spot offset from the optical disc track according to the push-pull method in this embodiment.

[0034] Description of reference numerals:

[0035] 1. objective lens; 11. first bracket;

[0036] 2. Focus moving mechanism; 21. Focus moving assembly; 211. Focus coil; 212. Focus suspension wire; 2121. First upper focusing suspension wire; 2122. Second upper focusing suspension wire; 2123. First lower focusing suspension wire; 2124. Second lower focusing suspension wire; 213. First fixing block; 214. Copper rivet 1; 215. Wire 2; 216. Wire 4;

[0037] 3. reflector; 31. second bracket;

[0038] 4. Tracking mechanism; 41. Tracking assembly; 411. Tracking coil; 4111. Second tracking coil; 4112. Fourth tracking coil; 412. Tracking wire; 4121. First upper tracking wire; 4122. Second upper tracking wire; 4123. First lower tracking wire; 4124. Second lower tracking wire; 413. Second fixed block; 414. Permanent magnet; 415. Third fixed block; 416. Wire one; 417. Wire three; 418. Wire five; 419. Wire six;

[0039] 5. First frame; 51. Winding column 1; 52. Winding column 2;

[0040] 6. Second frame;

[0041] 7. yoke iron; 71. groove;

[0042] 8. Semiconductor laser;

[0043] 9. Polarization beam splitter;

[0044] 100. Collimating lens;

[0045] 110. Dichroic beam splitter;

[0046] 120, 1 / 4 wave plate;

[0047] 130. Four-quadrant detector;

[0048] 140, holographic optical disc; 1401, substrate; 1402, color separation reflection layer; 1403, holographic medium layer; 1404, protective layer; 1405, address information pit; 1406, pre-groove;

[0049] 150. Motor;

[0050] 160, first light;

[0051] 170. Second ray. DETAILED DESCRIPTION

[0052] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0053] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0054] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0055] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0056] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0057] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0058] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0059] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0060] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0061] See also Figures 1 to 5 The present embodiment provides a torquer device of a coaxial holographic storage system, comprising an objective lens 1, a first bracket 11, a focusing movement mechanism 2, a reflector 3 and a tracking movement mechanism 4, wherein the objective lens 1 is arranged on the first bracket 11, and the first bracket 11 is arranged on the first frame 5 through the focusing movement mechanism 2, and the focusing movement mechanism 2 is used to move the first bracket 11 and the objective lens 1 along a focusing direction, and the reflector 3 is arranged on the first frame 5, and the reflector 3 is rotatably arranged relative to the first frame 5, and the first frame 5 is arranged on the tracking movement mechanism 4, and the tracking movement mechanism 4 is used to move the first frame 5, the reflector 3 and the objective lens 1 along a tracking direction, wherein the focusing direction is perpendicular to the tracking direction.

[0062] See also Figure 6, the objective lens 1 is used to focus the combined light beam onto the holographic optical disc 140, and the combined light beam includes the first light beam 160 for focusing, tracking and addressing functions, and the second light beam 170 for reading and writing holographic information. The holographic optical disc 140 includes a substrate 1401, a color separation reflection layer 1402, a holographic medium layer 1403 and a protective layer 1404 arranged in sequence, wherein the color separation reflection layer 1402 will reflect the second light beam 170 and transmit the first light beam 160, and the color of the first light beam 160 is different from the color of the second light beam 170; the substrate 1401 is pre-engraved with address information pits 1405; the holographic medium layer 1403 will store the data information carried by the green light; and the protective layer 1404 is responsible for protecting the holographic optical disc 140.

[0063] See also Figure 4 and Figure 6 The reflector 3 is disposed on the first frame 5 and can rotate relative to the first frame 5 to change the direction of the optical path so that the light emitted from the laser can be accurately focused onto the holographic optical disc 140 through the objective lens 1.

[0064] See also Figure 1 and Figure 6 The focusing moving mechanism 2 moves the first bracket 11 and the objective lens 1 thereon in the focusing direction (i.e., a direction perpendicular to the surface of the holographic optical disc 140) for precise focusing. The tracking moving mechanism 4 moves the first frame 5 and the reflector 3 and the objective lens 1 thereon in the tracking direction (i.e., a direction parallel to the surface of the storage medium) for data reading and writing operations. In actual use, the holographic optical disc 140 is on top and the torquer device is on the bottom, i.e., the focusing direction is in the vertical direction and the tracking direction is in the horizontal direction.

[0065] Compared with directly moving the holographic optical disc 140 and the motor 150 driving the rotation, the present application realizes focusing and tracking by moving the objective lens 1 and the reflector 3 with relatively light mass, which is easy to operate and the precision is easy to control. In addition, the synchronous tracking method of the objective lens 1 and the reflector 3 can keep the incident light at the same incident angle during the tracking servo, which meets the requirement that the incident angles of the read and write lights in the coaxial holographic storage system need to be consistent.

[0066] See also Figure 1 , Figure 4 and Figure 5In this embodiment, the torquer device also includes a second frame 6, and the tracking movement mechanism 4 includes two tracking movement components 41. The tracking movement component 41 includes a permanent magnet 414, a tracking coil 411 and a tracking suspension wire 412. The permanent magnet 414 is arranged on the second frame 6, and the permanent magnet 414 is located on one side of the tracking coil 411. The tracking coil 411 is arranged on the first frame 5, and the tracking suspension wire 412 is arranged on the first frame 5 and the second frame 6. The tracking suspension wire 412 is elastic and has a curved part. The tracking coil 411 is energized to generate a magnetic field, which interacts with the magnetic field where the permanent magnet 414 is located to generate an electromagnetic force in the tracking direction, and cooperates with the elastic force of the tracking suspension wire 412 to move the tracking coil 411 along the tracking direction.

[0067] The second frame 6 carries the permanent magnet 414 and is used in conjunction with the first frame 5. The two ends of the tracking wire 412 can be fixed to the two side walls of the second frame 6 by rivets, specifically, a standard copper rivet can be put on the tracking wire 412, and then the middle part is fixed to the first frame 5. The tracking wire 412 is connected to the first frame 5 to support the first frame 5. The tracking wire 412 has a curved part, and the tracking wire 412 is elastic and can be deformed, so that the first frame 5 can follow the tracking wire 412 when it moves along the tracking direction, while the second frame 6 is not affected. Figure 1 As shown, the tracking wire 412 has a straight portion and an S-shaped curved portion, and the S-shaped curved portion can have redundancy. The S-shaped curved portion can also avoid the copper rivet 214 and the focusing wire 212.

[0068] The tracking mechanism 4 is designed with a permanent magnet 414, a tracking coil 411 and a tracking suspension wire 412, which is small in size and easy to install and integrate. The material of the permanent magnet 414 can be selected as N52, which has a very high magnetic energy product and can provide a strong magnetic field. The tracking mechanism 4 driven by electromagnetic force has a fast response speed. By controlling the magnitude and direction of the current, the distance and speed of the tracking movement can be accurately controlled, thereby achieving high-precision tracking operation.

[0069] See also Figure 1 , a spatial rectangular coordinate system is constructed, the focusing direction is the up-down direction (such as the direction indicated by the arrow z), the tracking direction is the front-back direction (such as the direction indicated by the arrow y), and the left-right direction is the direction indicated by the arrow x. Among them, the tracking suspension wires 412 corresponding to the two tracking moving components 41 are symmetrically arranged on the front and back sides of the first frame 5, and the focusing suspension wires 212 corresponding to the two focusing moving components 21 are symmetrically arranged on the left and right sides of the first bracket 11.

[0070] In this embodiment, the tracking moving component 41 has two tracking coils 411 . The two tracking coils 411 are arranged side by side and plugged and glued to the first frame 5 . Figure 1As shown, the two tracking coils 411 of the tracking movable component 41 are arranged side by side along the tracking direction (front and back direction, as indicated by arrow y), and the two tracking movable components 41 are symmetrically arranged on the left and right sides of the first frame 5. The two tracking movable components 41 have a total of four tracking coils 411.

[0071] In some embodiments, the tracking movement mechanism 4 can be a linear motion mechanism such as an oil cylinder, an air cylinder, or an electric cylinder. Similarly, the focusing movement mechanism 2 can also be a linear motion mechanism such as an oil cylinder, an air cylinder, or an electric cylinder.

[0072] See also Figure 1 , Figure 2 , Figure 4 and Figure 5 In this embodiment, the focus moving mechanism 2 includes two focus moving components 21, which are located on both sides of the objective lens 1. The focus moving components 21 include a focus coil 211 and a focus suspension wire 212. The two focus moving components 21 share one focus coil 211, which is located on the inner side of the tracking coil 411. The focus coil 211 is arranged on the first bracket 11, and the first bracket 11 is arranged on the first frame 5 through the focus suspension wire 212. The focus suspension wire 212 is elastic and has a curved part. The focus coil 211 is energized to generate a magnetic field, which interacts with the magnetic field where the permanent magnet 414 is located to generate an electromagnetic force in the focusing direction, and cooperates with the elastic force of the focus suspension wire 212 to move the focus coil 211 along the focusing direction.

[0073] In order to save the volume of the torquer and optimize the internal space, the focusing moving assembly 21 and the tracking moving assembly 41 share a permanent magnet 414. There are two focusing moving assemblies 21 and two tracking moving assemblies 41, and there are two corresponding permanent magnets 414. In some embodiments, the focusing moving assembly 21 and the tracking moving assembly 41 can each use a permanent magnet 414.

[0074] The two ends of the focusing wire 212 can be fixed to the two side walls of the first frame 5 by rivets, specifically, a standard copper rivet 214 can be put on the focusing wire 212, and then the middle part is fixed to the first frame 5. The focusing wire 212 is connected to the first bracket 11 to support the first bracket 11 and the objective lens 1 thereon. The focusing wire 212 has a curved part, and the focusing wire 212 is elastic and can be deformed, so that when the focusing coil 211 moves along the focusing direction, the first bracket 11 can move with it, and the first frame 5 is not affected. Figure 1 As shown, the focusing wire 212 has a straight portion and an S-shaped curved portion, and the S-shaped curved portion can have a redundancy.

[0075] The focus moving mechanism 2 design using the permanent magnet 414, the focus coil 211 and the focus suspension wire 212 is small in size and easy to install and integrate. The focus moving mechanism 2 driven by the electromagnetic force has a fast response speed. By controlling the magnitude and direction of the current, the distance and speed of the focus movement can be accurately controlled, thereby achieving a high-precision focusing operation.

[0076] In this embodiment, the two permanent magnets 414 are symmetrically arranged, and the polarities of the two ends facing each other are the same. For example, the S pole of the left permanent magnet 414 is at the left end and the N pole is at the right end, and the S pole of the left permanent magnet 414 is at the right end and the N pole is at the left end, and the N poles are arranged facing each other. The controller adjusts the movement direction by controlling the direction of the current applied to the focusing coil 211 and the tracking coil 411. For example, if the current direction is positive, the focusing coil 211 is upward and the tracking coil 411 is forward; the controller adjusts the stroke length by controlling the magnitude of the current applied to the focusing coil 211 and the tracking coil 411.

[0077] See also Figure 1 , Figure 2 , Figure 4 and Figure 5 In this embodiment, the focus moving assembly 21 further includes a first fixing block 213, the focus suspension wire 212 is connected to the first fixing block 213, and the first fixing block 213 is plugged into the first bracket 11, so that the focus suspension wire 212 is arranged on the first frame 5 through the first fixing block 213, the focus suspension wire 212 and the first fixing block 213 are conductors, and the focus suspension wire 212 / tracking suspension wire 412, the first fixing block 213, the focus coil 211 / tracking coil 411 are electrically connected through wires, and then connected to a controller on one side to form a loop, so that the controller can input current to the focus coil 211 and the tracking coil 411. The mechanical support and electrical connection functions are effectively integrated, multiple functions are realized through a small number of components, and the structure of the device is simplified.

[0078] Preferably, Figure 2 It is shown that two focusing wires of a focusing moving assembly 21 share a first fixed block 213, that is, the upper and lower sides of the first fixed block 213 are respectively connected to the two focusing wires 212. In order to avoid a short circuit caused by the connection between the two focusing wires 212, part of the first fixed block 213 is a conductor and part is an insulator. The insulated part can prevent the two focusing wires 212 from being conductive.

[0079] Preferably, the focusing wire 212 and the tracking wire 412 can be made of C17200 beryllium copper, which has certain strength and elasticity, can play a good supporting role, and has a good deformation margin. The focusing coil 211 is wound by a wire, and all the tracking coils 411 can be wound by a wire. The focusing wire 212 and the first fixed block 213 can be welded, so that the first fixed block 213 moves with the movement of the position of the focusing wire 212. Similarly, the tracking wire 412 and the second fixed block 413 can be welded, so that the second fixed block 413 moves with the movement of the position of the tracking wire 412.

[0080] Figure 1 As shown, the focusing direction is the up-down direction (as indicated by the arrow z), the tracking direction is the front-back direction (as indicated by the arrow y), there are two first fixing blocks 213, and one focusing moving assembly 21 has one first fixing block 213. The first fixing block 213 is provided with a first fixing groove on one side close to the first bracket 11, and the left and right sides of the first bracket 11 are clamped by the first fixing groove, and then can be fixed by gluing. Preferably, the first fixing block 213 is made of a circuit board, and the pads on the circuit board serve as conductive parts, that is, the pads are respectively connected to the required focusing suspension wire 212 and the wire. In some embodiments, the first fixing block 213 can be a metal block.

[0081] See also Figure 2 and Figure 5 In this embodiment, the tracking moving component 41 has two tracking wires 412, which are an upper tracking wire (such as the first upper tracking wire 4121 and the second upper tracking wire 4122 described below) and a lower tracking wire (such as the first lower tracking wire 4123 and the second lower tracking wire 4124 described below), which are located on the upper and lower sides of the first bracket 11, and the upper tracking wire is located above the lower tracking wire. The cross-sectional area of ​​the upper tracking wire is different from that of the lower tracking wire, so that the vertical axis torquer can remain stable during the tracking servo process without tilting to a large extent, thereby avoiding affecting the incident angle of the focusing spot. Optionally, the cross-sectional area of ​​the upper tracking wire is larger than that of the lower tracking wire. Or in some embodiments, the cross-sectional area of ​​the upper tracking wire is smaller than that of the lower tracking wire.

[0082] See also Figures 1 to 5 In this embodiment, the torquer device further includes a yoke 7, which is a U-shaped structure. The permanent magnet 414, the tracking coil 411, and the focusing coil 211 are all located in the yoke 7, and the permanent magnet 414 is plugged into the yoke 7. The function of the yoke 7 is to limit the magnetic field within a certain range and keep the magnetic field stable within the range. Preferably, the material of the yoke 7 can be 1j85 Permalloy, which has the characteristics of high magnetic permeability and low hysteresis loss, and can effectively guide and concentrate the magnetic field.

[0083] Figure 1 , Figure 3 As shown, the yoke 7 is in an inverted U-shape, with a total of two tracking moving components 41, and a total of two yokes 7, and the two yokes 7 are located on the left and right sides of the first bracket 11. The permanent magnet 414 is located in the middle of the yoke 7, and a groove 71 is provided at the top of the yoke 7 (inverted U-shaped space), and the permanent magnet 414 is inserted into the groove 71 to achieve fixation. The yoke 7 and the permanent magnet 414 form a mountain shape, and the two spaces inside the mountain shape respectively contain the focusing coil 211 and the tracking coil 411. The focusing coil 211 is in a square shape, and the opening in the center extends up and down. The two sides of the focusing coil 211 are respectively located in a yoke 7 (U-shaped space), specifically in the direction where the permanent magnet 414 is close to the first bracket 11. The tracking coil 411 is in a square shape, and the opening in the center extends left and right. There are protrusions on the left and right side walls of the first frame 5, respectively, and the tracking coil 411 is inserted into the protrusions to achieve fixation. Optionally, a gluing step can be performed after plugging to further increase the stability of the connection.

[0084] See also Figure 1 In this embodiment, the focusing wire 212 extends along the tracking direction, the tracking wire 412 is perpendicular to the focusing wire 212, and the extending direction is perpendicular to the focusing direction, and the focusing wire 212 and the tracking wire 412 are staggered up and down. Figure 1 As shown, the focusing direction is the up-down direction, the tracking direction is the front-back direction, the focusing wire 212 extends along the tracking direction, and the tracking wire 412 extends along the left-right direction. The orthogonality of the focusing wire 212 and the tracking wire 412, as well as the up-down misalignment design, enables the movement in the two directions (focusing direction, tracking direction) to be independently controlled, reducing the interference between different movement directions.

[0085] See also Figure 1 , Figure 4 and Figure 5 In this embodiment, the tracking moving assembly 41 further includes a second fixing block 413, the tracking wire 412 penetrates the second fixing block 413, and the second fixing block 413 is plugged with the first frame 5, so that the tracking wire 412 is arranged on the first frame 5 through the second fixing block 413. The tracking wire 412 and the second fixing block 413 are conductors, and the focusing wire 212 / tracking wire 412, the second fixing block 413, the focusing coil 211 / tracking coil 411 are electrically connected through wires, and then connected to a controller on one side to form a loop, so that the controller can input current to the focusing coil 211 and the tracking coil 411. The mechanical support and electrical connection functions are effectively integrated, multiple functions are realized through a small number of components, and the structure of the device is simplified.

[0086] Figure 1As shown, the focusing direction is the up-down direction, the tracking direction is the front-back direction, the tracking moving assembly 41 has two tracking suspension wires 412 arranged up and down, a total of two tracking moving assemblies 41, a total of four tracking suspension wires 412, and the structure is as follows Figure 4 , Figure 5 As shown. One tracking wire 412 corresponds to one first fixed block 213, and one tracking moving assembly 41 has two second fixed blocks 413. The second fixed block 413 is provided with a second fixed groove on the side close to the first frame 5. The front and right sides of the first frame 5 are clamped by the second fixed groove, and then fixed by gluing. Preferably, the second fixed block 413 is made of a circuit board, and the pads on the circuit board serve as conductive parts, that is, the pads are respectively connected to the required focusing wire 212 and wires. In some embodiments, the second fixed block 413 can be a metal block.

[0087] See also Figure 1 In this embodiment, the tracking moving assembly 41 further includes a third fixing block 415, which is located outside the second frame 6. The tracking wire 412 sequentially passes through the second frame 6 and the fourth fixing block, and can be fixed by rivet 2. The shape of the third fixing block 415 can be adapted to the shape of the side wall of the second frame 6, and the third fixing block 415 can be covered on the side wall of the second frame 6, wherein the third fixing block is preferably insulated from the second frame. Figure 1 It is shown that the third fixing block 415 and the side wall of the second frame 6 are both in the shape of a concave. Preferably, the third fixing block 415 is a conductor, which can be made of a circuit board, or made of metal or non-metal, and is electrically connected to the controller. Part of the third fixing block 415 is a conductor, and part is insulated, and the insulated part can avoid causing a short circuit.

[0088] See also Figure 4 and Figure 5 In this embodiment, the four focusing suspension wires 212 can be divided into a first upper focusing suspension wire 2121, a second upper focusing suspension wire 2122, a first lower focusing suspension wire 2123, and a second lower focusing suspension wire 2124. The four tracking suspension wires 412 can be divided into a first upper tracking suspension wire 4121, a second upper tracking suspension wire 4122, a first lower tracking suspension wire 4123, and a second lower tracking suspension wire 4124. The four tracking coils 411 can be divided into a first tracking coil, a second tracking coil 4111, a third tracking coil, and a fourth tracking coil 4112, which are made of a wire. The first tracking coil and the second tracking coil 4111 are the same tracking moving component 41, located on the left side, and the third tracking coil and the fourth tracking coil 4112 are the same tracking moving component 41, located on the right side.

[0089] The second fixed block 413 assembled together with the first upper tracking wire 4121 is electrically connected to the copper rivet 214 sleeved on the second upper focusing wire 2122 through the wire 416, wherein the wire 416 can be wound around the winding pole 51 on the outer wall of the first frame 5, and then the first fixed block 213 assembled together with the second upper focusing wire 2122 is connected to the focusing coil 211 through the wire 215.

[0090] The second fixed block 413 assembled together with the first lower tracking suspension wire 4123 is electrically connected to the copper rivet 214 on the second lower focusing suspension wire 2124 through the wire 3 417, wherein the wire 3 417 can be wound around the winding column 2 52 on the outer wall of the first frame 5, and then the first fixed block 213 assembled together with the second lower focusing suspension wire 2124 is connected to the focusing coil 211 through the wire 4 216.

[0091] The second fixing block 413 assembled with the second upper tracking wire 4122 is electrically connected to the fourth tracking coil 4112 via a fifth wire 418 , and the second fixing block 413 assembled with the second lower tracking wire 4124 is electrically connected to the second tracking coil 4111 via a sixth wire 419 .

[0092] The controller located on one side can be electrically connected to the tracking suspension wire 412 through an electric wire, and the focusing coil 211 and the tracking coil 411 are pressurized through the above-mentioned circuit structure. The controller can receive the focusing error signal, tracking error signal, address signal, etc. reflected by the holographic optical disk 140 to the four-quadrant detector 130, and process these signals according to the control algorithm, and apply the processed signals to the focusing coil 211 and the tracking coil 411.

[0093] See also Figure 4 In this embodiment, the reflector 3 is rotatably arranged relative to the first frame 5, that is, the reflector 3 can rotate on the first frame 5 to adjust the trajectory of the incident light. The reflector 3 can be hinged to the first frame 5 through the second bracket 31. The side of the second bracket 31 has two cylinders, so that it can rotate after being connected to the first frame 5, thereby adjusting the direction of the optical axis incident on the objective lens 1.

[0094] In this embodiment, the second frame 6 may be made of metal, preferably 1j85 Permalloy.

[0095] In this embodiment, the material of the first bracket 11 and the first frame 5 can be red wax for 3D printing.

[0096] See also Figures 1 to 6 This embodiment provides a coaxial holographic storage system, including:

[0097] A semiconductor laser 8, used for emitting a first light beam 160, wherein the first light beam 160 carries a focusing error signal and a tracking error signal;

[0098] A single longitudinal mode laser, used to emit a second light 170, the second light carrying holographic data information;

[0099] A polarization beam splitter 9, disposed on one side of the semiconductor laser 8, for reflecting the first light 160;

[0100] A collimating lens 100 is provided on one side of the polarization beam splitter 9 and is used to collimate the first light 160 reflected by the polarization beam splitter 9;

[0101] A dichroic beam splitter 110 is disposed on one side of the collimating lens 100 and is used to combine the first light 160 and the second light 170;

[0102] A quarter wave plate 120 is provided on one side of the dichroic beam splitter 110 and is used for allowing the combined light beam to pass through;

[0103] A torquer device, such as the torquer device of the coaxial holographic storage system described in any one of the above embodiments, the torquer device is arranged on one side of the 1 / 4 wave plate 120, the reflector 3 of the torquer device is used to reflect the combined light beam passing through the 1 / 4 wave plate 120, and the objective lens 1 of the torquer device is used to converge the first light beam 160 of the combined light beam on the ideal focal plane corresponding to the holographic optical disc 140, and converge the second light beam 170 of the combined light beam on the ideal focal plane corresponding to the holographic optical disc 140;

[0104] Among them, the torquer device also includes a four-quadrant detector 130 and a controller. The four-quadrant detector 130 is used to detect the focusing error signal and the tracking error signal carried by the first light 160. The controller is used to control the focusing movement mechanism 2 according to the focusing error signal to move the first bracket 11 and the objective lens 1 along the focusing direction, and control the tracking movement mechanism 4 according to the tracking error signal to move the first frame 5, the reflector 3 and the objective lens 1 along the tracking direction.

[0105] The first light 160 may be red light, and the second light 170 may be green light. It should be noted that this embodiment is not limited to these two colors of light, and can be adjusted according to actual conditions. The red light is responsible for focusing, tracking and addressing, and the green light is responsible for reading and writing holographic information.

[0106] See also Figure 6 The holographic optical disc 140 includes a substrate 1401, a color separation reflection layer 1402, a holographic medium layer 1403 and a protective layer 1404 arranged in sequence, wherein the color separation reflection layer 1402 is a red-transmitting and green-reflecting layer, which reflects green light and transmits red light.

[0107] See also Figure 6The red light emitted by the semiconductor laser 8 is reflected by the polarization beam splitter 9 (PBS), collimated by the collimating lens 100, and combined with the green light by the dichroic beam splitter 110 (DBS). Previously, the green light is emitted by a single longitudinal mode laser. After the red light and the green light are combined, they pass through the 1 / 4 wave plate 120 and the reflector 3. The red light is focused between the substrate 1401 and the red-transmitting and green-reflecting layer of the holographic optical disc 140 (i.e., the ideal focal plane of red light) through the converging effect of the objective lens 1, and the green light path is focused between the red-transmitting and green-reflecting layer and the holographic medium layer 1403 (i.e., the ideal focal plane of green light). The ideal focal plane of red light and the ideal focal plane of green light are at the same radial position of the holographic optical disc, but are located in different layers.

[0108] When the holographic optical disc 140 deviates from the ideal focal plane of the red light in the focusing direction, the four-quadrant detector 130 will detect a focusing error signal. At this time, the controller will receive the information and change the current applied to the focusing coil 211, so that the objective lens 1 moves in the focusing direction, so that the foci of the red light and the green light fall on their respective ideal focal planes. This process is called focusing servo.

[0109] When the holographic optical disc 140 completes the focusing servo, the light spot at the focus of the red light may not fall accurately on the track where the address information pit 1405 is located. At this time, the four-quadrant detector 130 will detect a tracking error signal, and the controller will receive the information and change the current applied to the tracking coil 411, so that the first frame 5 moves in the tracking direction, thereby making the focus of the red light fall on the track of the holographic optical disc 140. This process is called tracking servo.

[0110] In this embodiment, the focusing error signal can be realized by the astigmatism method. The astigmatism method uses astigmatism elements such as cylindrical mirrors to generate astigmatism. When the objective lens 1 is defocused, the astigmatism element will convert different defocus amounts into changes in light energy distribution in different directions, and the error signal is obtained after detection by the photodetector. The four-quadrant detector 130, also known as PDIC, can be adjusted in position so that when it is in focus, the light spot is a perfect circle, and the error signal FE (Focusing Error) output is 0. When it is defocused, the light spot is an ellipse in the horizontal or vertical direction, and the error signal FE output is not 0, thereby obtaining a defocus error signal, such as Figure 7 When the torquer is controlled to perform focusing motion, the current will drive the objective lens 1 to move up and down. When the optical disc approaches or moves away from the focal position, the value of the focusing error signal FE will fluctuate accordingly. Therefore, this signal becomes the basis for focusing control.

[0111] When the torquer device is controlled by the controller to perform focusing movement, the current will drive the objective lens to move up and down. When the optical disc approaches or moves away from the focal position, the value of the focus error signal FE will fluctuate accordingly. Therefore, this signal becomes the basis for focusing control. Because its appearance is similar to the letter S, it is named S curve. Figure 8 shown.

[0112] Tracking error signal detection can be achieved through the push-pull method. In order to cooperate with the push-pull method, a wobble groove (Wobble) will be left when the holographic optical disc 140 is made. The raised part is called the land, and the concave part is called the groove. Usually, the user signal is recorded in the groove, and sometimes it is recorded on the groove and the land at the same time. When the light spot is correctly focused on the center line of the pre-groove 1406, the returned light spot will fall exactly in the center of the four quadrants of the PDIC. After photoelectric conversion, the radial push-pull signals (RPP: Radial Push-Pull) output by the four quadrants A, B, C, and D are satisfied; when the light spot deviates downward from the center line of the pre-groove 1406, more light energy hits the land below the pre-groove 1406, and the returned light spot will fall more in the D and C quadrants. At this time; when the light spot deviates upward from the center line of the pre-groove 1406, more light energy hits the land above the pre-groove 1406, and the returned light spot will fall more in the A and B quadrants. According to the positive and negative, size of the RPP signal, the direction and distance of the focus spot offset from the optical disc track can be determined. Fig. 9 As shown, the tracking coil 411 is controlled to move according to the signal. Since the RPP signal also reflects the tracking error, it is also called TE (Tracking Error) signal.

[0113] It should be mentioned that, compared with the torquer device used in the past on ordinary optical discs, this method solves the problem that the classic torquer device cannot drive the large-mass objective lens 1 and cannot keep the incident light at the same incident angle during tracking servo. It meets the requirement that the incident angles of the read and write lights need to be consistent in the coaxial holographic storage system. If a single objective lens 1 is used for tracking servo, the angle of the incident light near the holographic optical disc 140 will change. If the reflector 3 and the objective lens 1 of the present application move synchronously, the angle of the incident light near the holographic optical disc 140 will not change. The imaging quality of red light and green light on the imaging surfaces of their respective detectors can be improved.

[0114] It should be noted that, although the above embodiments have been described in this article, the patent protection scope of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, changes and modifications made to the embodiments described herein, or equivalent structures or equivalent process changes made using the contents of the present invention specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included in the patent protection scope of the present invention.

Claims

1. A torquer device for a coaxial holographic storage system, characterized in that: It includes an objective lens, a first bracket, a first frame, a focusing movement mechanism, a reflector and a tracking movement mechanism, the objective lens is arranged on the first bracket, the first bracket is arranged on the first frame through the focusing movement mechanism, the focusing movement mechanism is used to move the first bracket and the objective lens along a focusing direction, the reflector is arranged on the first frame, the reflector is rotatable relative to the first frame, the first frame is arranged on the tracking movement mechanism, and the tracking movement mechanism is used to move the first frame, the reflector and the objective lens along a tracking direction, wherein the focusing direction is perpendicular to the tracking direction.

2. The torque device according to claim 1, characterized in that: It also includes a second frame, and the tracking movement mechanism includes two tracking movement components, and the tracking movement component includes a permanent magnet, a tracking coil and a tracking suspension wire. The permanent magnet is arranged on the second frame, and the permanent magnet is located on one side of the tracking coil. The tracking coil is arranged on the first frame, and the tracking suspension wire is arranged on the first frame and the second frame. The tracking suspension wire is elastic and has a curved part, wherein the tracking coil generates a magnetic field when energized, and interacts with the magnetic field where the permanent magnet is located to generate an electromagnetic force in the tracking direction, which cooperates with the elastic force of the tracking suspension wire to move the tracking coil along the tracking direction.

3. The torque device according to claim 2, characterized in that: The focusing movement mechanism includes two focusing movement components, and the two focusing movement components are located on both sides of the objective lens. The focusing movement components include a focusing coil and a focusing suspension wire. The two focusing movement components share one focusing coil, and the focusing coil is located on the inner side of the tracking coil. The focusing coil is arranged on the first bracket, and the first bracket is arranged on the first frame through the focusing suspension wire. The focusing suspension wire is elastic and has a curved part. The focusing coil generates a magnetic field when energized, and interacts with the magnetic field where the permanent magnet is located to generate an electromagnetic force in the focusing direction, which cooperates with the elastic force of the focusing suspension wire to move the focusing coil along the focusing direction.

4. The torque device according to claim 3, characterized in that: The focusing moving assembly also includes a first fixed block, the focusing suspension wire is connected to the first fixed block, the first fixed block is plugged into the first bracket, so that the focusing suspension wire is arranged on the first frame through the first fixed block, the focusing suspension wire and the first fixed block are conductors, and the focusing suspension wire / the tracking suspension wire, the first fixed block, and the focusing coil / the tracking coil are electrically connected through wires.

5. The torque device according to claim 3, characterized in that: It also includes a yoke, which is a U-shaped structure. The permanent magnet, the tracking coil, and the focusing coil are all located inside the yoke, and the permanent magnet is plugged into the yoke.

6. The torque device according to claim 3, characterized in that: The focusing suspension wire extends along the tracking direction, the tracking suspension wire is perpendicular to the focusing suspension wire, and the extending direction is perpendicular to the focusing direction, and the focusing suspension wire and the tracking suspension wire are staggered up and down.

7. The torque device according to claim 2, characterized in that: The tracking moving component has two tracking suspension wires, namely an upper tracking suspension wire and a lower tracking suspension wire. The cross-sectional area of ​​the upper tracking suspension wire is different from the cross-sectional area of ​​the lower tracking suspension wire.

8. The torque device according to claim 2, characterized in that: The tracking moving component also includes a second fixed block, the tracking wire is connected to the second fixed block, and the second fixed block is plugged into the first frame so that the tracking wire is arranged on the first frame through the second fixed block. The tracking wire and the second fixed block are conductors, and the tracking wire, the second fixed block, and the tracking coil are electrically connected through wires.

9. The torque device according to claim 2, characterized in that: The tracking moving component has two tracking coils, which are arranged side by side and plugged into the first frame.

10. A coaxial holographic storage system, characterized in that: include: A semiconductor laser, configured to emit a first light beam; a single longitudinal mode laser, for emitting a second light beam; a polarization beam splitter, disposed on one side of the semiconductor laser, and used for reflecting the first light; a collimating lens, disposed at one side of the polarization beam splitter, and used for collimating the first light reflected by the polarization beam splitter; A dichroic beam splitter, disposed on one side of the collimating lens, for combining the first light and the second light; A quarter wave plate, disposed on one side of the dichroic beam splitter, for allowing the combined light beam to pass through; A torquer device, as claimed in any one of claims 1 to 9, wherein the torquer device is arranged on one side of the 1 / 4 wave plate, the reflector of the torquer device is used to reflect the combined light beam passing through the 1 / 4 wave plate, and the objective lens of the torquer device is used to converge the first light beam of the combined light beam on the ideal focal plane corresponding to the holographic optical disc, and converge the second light beam of the combined light beam on the ideal focal plane corresponding to the holographic optical disc; Among them, the torquer device also includes a four-quadrant detector and a controller, the four-quadrant detector is used to detect the focusing error signal and the tracking error signal carried by the first light, and the controller is used to control the focusing movement mechanism according to the focusing error signal to move the first bracket and the objective lens along the focusing direction, and control the tracking movement mechanism according to the tracking error signal to move the first frame, the reflector and the objective lens along the tracking direction.

Images