Optical disc drives, memory, and electronic devices for optical discs having a single servo layer and multiple recording layers

Abstract

An optical disc drive, memory, and electronic device are provided for an optical disc having a single servo layer and multiple recording layers. A dichroic mirror is present inside the optical disc drive. The beam of a first light source is irradiated onto the surface of one side of the dichroic mirror and then reflected onto the recording medium of the optical disc for reading and writing data. The beam of a second light source may pass directly through the dichroic mirror and be transmitted to the servo layer of the recording medium of the optical disc. The dichroic mirror may be fastened inside the optical disc drive via a movable component. The movable component may change the orientation of the dichroic mirror to adjust the relative position between the propagation direction of the beam of the first light source and the propagation direction of the beam of the second light source, thereby eliminating errors that occur during the installation and use of the optical disc drive. The optical disc drive in this application has advantages such as fewer changes to the internal structure, a simpler implementation process, and high control accuracy. When servo control is performed accurately and at low cost via the beam of the second light source in the servo layer, the beam of the first light source is irradiated onto the center of the data track of each recording layer of the optical disc.

Description

Technical Field

[0004] , , , ,

[0003]

[0001] This application claims priority to Chinese Patent Application No. 202311050409.X, titled "OPTICAL DISC DRIVE OF OPTICAL DISC WITH SINGLE SERVO LAYER AND MULTIPLE RECORDING LAYERS, MEMORY, AND ELECTRONIC DEVICE", filed with the China National Intellectual Property Administration on August 18, 2023, the entire content of which is incorporated herein by reference.

[0002] The present invention relates to the field of optical disc technology, and more particularly, to an optical disc drive, a memory, and an electronic device of an optical disc having a single servo layer and multiple recording layers.

Background Art

[0003] An optical disc drive is a device for reading data from and writing data to an optical disc. An optical disc drive is typically any component of a computer or another electronic device and is configured to read data from and write data to various types of optical discs such as compact discs (CDs), digital versatile discs (DVDs), Blu-ray Discs (registered trademark, BD), etc. The operating principle of an optical disc drive is to read and write the surface of an optical disc via a laser beam. When an optical disc drive reads data from an optical disc, the reflected light of the laser beam is detected by a sensor and converted into a digital signal to retrieve the data in the optical disc. Also, the optical disc drive may write additional data to the optical disc by adjusting the intensity and focus of the laser beam.

[0004] In related optical disc drives, when writing data to an optical disc having a single servo layer and multiple recording layers, servo control is performed via a red laser beam on a pre-pressed single guide layer, and the depth of focus of a coaxial blue laser beam is changed to record on the multiple recording layers. The direction of the red laser beam and the blue laser beam may change during installation and use of the optical disc drive. As a result, the red laser beam and the blue laser beam may not be coaxial, which may affect the quality of data written to and read from the optical disc drive. [Overview of the project]

[0005] To solve the above problems, embodiments of the present application provide an optical disc drive for an optical disc having a single servo layer and multiple recording layers, enabling an internal dichroic mirror to be movably fastened inside the optical disc drive to adjust the relative position between the guide beam and the recording beam, thereby eliminating errors that occur during installation, use, etc., of the optical disc drive. In addition, the present application further provides memory and electronic devices corresponding to an optical disc drive for an optical disc having a single servo layer and multiple recording layers. [Means for solving the problem]

[0006] Therefore, the following technical solutions are used in the embodiments of this application.

[0007] According to a first aspect, one embodiment of the present application provides an optical disc drive for an optical disc having a single servo layer and a plurality of recording layers, comprising: a first light source configured to generate a first beam for reading data from the recording layers and writing data to the recording layers; a second light source configured to generate a second beam for performing focusing and tracking servo control on the servo layers, wherein the propagation direction of the second beam intersects with the propagation direction of the first beam; a dichroic mirror positioned at the intersection of the propagation direction of the second beam and the propagation direction of the first beam, which reflects the first beam and transmits the second beam; and a movable component configured to movably fasten the dichroic mirror inside the optical disc drive and change the orientation of the dichroic mirror to adjust the relative position between the propagation direction of the first beam and the propagation direction of the second beam.

[0008] In this implementation, a dichroic mirror is used to transmit and reflect laser light of different wavelengths, and the dichroic mirror may be designed to be movably mounted inside the optical disc drive. The beam generated by the second light source may be transmitted directly through the dichroic mirror, and its propagation direction is not altered by the orientation of the dichroic mirror. After irradiating the surface of the dichroic mirror, the beam generated by the first light source is reflected. The propagation direction of the reflected beam is altered by the orientation of the dichroic mirror. If the propagation direction of the beam from the first light source irradiating the optical disc and the propagation direction of the beam from the second light source irradiating the optical disc are not coaxial, the orientation of the dichroic mirror may be changed by changing the movable component to adjust the propagation direction of the beam from the first light source irradiating the optical disc. Optical disc drives have advantages such as fewer changes to the internal structure, a simpler implementation process, and high control accuracy. When servo control is performed accurately and at low cost via the beam of a second light source in the servo layer, the beam of the first light source illuminates the center of the data track in each recording layer of the optical disc.

[0009] In one implementation, the movable component includes at least one piezoelectric actuator, each of which one end is fastened to a different position on the dichroic mirror, and each of which one end is fastened to a different position inside the optical disc drive, and each piezoelectric actuator is separately configured to change the orientation of the dichroic mirror when it receives an electrical signal.

[0010] In this implementation, piezoelectric actuators are very common components with advantages such as low cost, convenient control, and precise control. After the dichroic mirrors are fastened inside the optical disc drive via piezoelectric actuators, the orientation of the dichroic mirrors can be changed simply by altering the electrical signals flowing through each piezoelectric actuator. The entire process is very simple, and the control costs are low.

[0011] In one implementation, the dichroic mirror includes a frame, the frame includes two frame structures, the edges on the same side of the two frame structures are separated from each other, the opposite edges of the two frame structures are connected to each other, the connected edges on the sides of the two frame structures are fastened inside an optical disc drive, and the movable component includes at least one piezoelectric actuator positioned between the separated edges on the sides of the two frame structures and configured to change the orientation of the dichroic mirror when it receives an electrical signal.

[0012] In this implementation, if the dichroic mirror frame includes two frame structures, with the edges on the sides of the two frame structures separated from each other and the opposite edges of the two frame structures connected to each other, the piezoelectric actuator may be positioned between the separated edges on the sides. The orientation of the dichroic mirror can be changed simply by changing the electrical signal flowing through each piezoelectric actuator. The overall process is simpler and the control costs are lower.

[0013] In one implementation, the optical disc drive further includes a controller connected to a piezoelectric actuator, configured to detect a value representing the degree of deviation between the light spot of a first beam and the light spot of a second beam, and to transmit an electrical signal of the corresponding value to the piezoelectric actuator.

[0014] In this implementation, the controller is a hub unit that precisely controls the orientation of the dichroic mirrors, and may adjust the relative position between the first and second beams by changing the electrical signals flowing to each piezoelectric actuator based on the deviation between the light points of the first and second beams, thereby precisely changing the orientation of the dichroic mirrors. This ensures that when the servo layer completes servo control accurately, the first beam, which is used to read data from and write data to the recording layer, always remains centered on the data track, thereby eliminating deviations caused by installation errors and coaxiality of different actuators.

[0015] In one implementation, the optical disc drive further includes a first photodetector configured to receive a first beam and convert the focusing deviation signal and / or tracking deviation signal of the first beam into corresponding values / corresponding electrical signals / electrical signals.

[0016] In this implementation, after receiving the first beam, the first photodetector converts the first beam into an electrical signal of a corresponding value in order to detect the light intensity of the first beam. The photodetector's light-receiving aperture generally has four quadrants, with a photosensitive detector placed in each quadrant. If focusing and tracking errors exist, the four quadrants of the photodetector receive different light intensities, and the photodetector detects the focusing and tracking errors by performing different addition and subtraction operations on the light intensities of the four quadrants.

[0017] In one implementation, the optical disc drive further includes a first focus servo circuit and a first tracking servo circuit, wherein the first focus servo circuit is configured to adjust the focal position of a first beam based on a change in an electrical signal corresponding to a focusing deviation signal of a first photodetector, and the first tracking servo circuit is configured to adjust the direction of a first beam based on a change in an electrical signal corresponding to a tracking deviation signal of a first photodetector.

[0018] In this implementation, the first focus servo circuit may make slight displacement adjustments to the objective lens based on changes in the light intensity signal of the first beam, thereby enabling the focus of the first beam to reach an optimal position. The first tracking servo circuit may also adjust the direction of the objective lens based on changes in the light intensity signal of the first beam, thereby enabling the objective lens to accurately follow changes in the position of the first beam and maintain the correct direction of the first beam.

[0019] In one implementation, the optical disc drive further includes a first polarizing beam splitter positioned in the propagation direction of the first beam, configured to split the first beam into two identical sub-beams, irradiating one sub-beam onto the light-receiving aperture of a first photodetector and the other sub-beam onto a dichroic mirror.

[0020] In this implementation, the first polarization beam splitter may split the first beam into two sub-beams of the same intensity, and as a result, the first polarization beam splitter can detect the intensity of the first beam irradiated onto the recording medium.

[0021] In one implementation, the optical disc drive further includes a second photodetector configured to receive a second beam and convert the focusing deviation signal and / or tracking deviation signal of the second beam into corresponding values / corresponding electrical signals / electrical signals.

[0022] In this implementation, after receiving the second beam, the second photodetector converts the second beam into an electrical signal of a corresponding value in order to detect the light intensity of the second beam. If focusing and tracking errors exist, the four quadrants of the photodetector receive different light intensities, and the photodetector detects the focusing and tracking errors by performing different addition and subtraction operations on the light intensities of the four quadrants.

[0023] In one implementation, the optical disc drive further includes a second focus servo circuit and a second tracking servo circuit, the second focus servo circuit being configured to adjust the focal position of a second beam based on a change in an electrical signal corresponding to a focusing deviation signal of a second photodetector, and the second tracking servo circuit being configured to adjust the direction of a second beam based on a change in an electrical signal corresponding to a tracking deviation signal of a second photodetector.

[0024] In this implementation, the second focus servo circuit may make slight displacement adjustments to the objective lens based on changes in the light intensity signal of the second beam, thereby enabling the focus of the second beam to reach an optimal position. The second tracking servo circuit can adjust the direction of the objective lens based on changes in the light intensity signal of the second beam, so that the objective lens accurately follows changes in the position of the second beam and maintains the correct direction of the second beam.

[0025] In one implementation, the optical disc drive further includes a second polarizing beam splitter positioned in the propagation direction of the second beam, configured to split the second beam into two identical sub-beams, illuminating one sub-beam onto the light-receiving aperture of the second photodetector and the other sub-beam onto a dichroic mirror.

[0026] According to a second aspect, one embodiment of the present application provides a memory including at least one optical disk having a single servo layer and a plurality of recording layers, and at least one optical disk drive configured to read data from and write data to at least one optical disk having a single servo layer and a plurality of recording layers, which may be implemented according to each embodiment of the first aspect.

[0027] According to a third aspect, one embodiment of the present application provides an electronic device including at least one memory that may be implemented according to each embodiment of the second aspect, and at least one controller connected to the at least one memory and configured to control the at least one memory to read and write data.

[0028] Hereinafter, the accompanying drawings necessary for the description of the embodiments or the prior art will be briefly described.

Brief Description of the Drawings

[0029] [Figure 1] FIG. shows the principle of an optical disk drive reading data from and writing data to an optical disk having a single servo layer and a plurality of recording layers. [Figure 2] FIG. shows the structure of an optical disk drive in the related art. [Figure 3] FIG. shows the structure of an optical disk drive according to one embodiment of the present application.

[0030] [Figure 4(a)] FIG. shows the coaxial propagation of the blue laser sub-beam 1 and the red laser sub-beam 1 on a dichroic mirror according to one embodiment of the present application. [Figure 4(b)] FIG. shows the non-coaxial propagation of the blue laser sub-beam 1 and the red laser sub-beam 1 on a dichroic mirror according to one embodiment of the present application. [Figure 4(c)]This is another diagram of non-coaxial propagation of a blue laser subbeam 1 and a red laser subbeam 1 on a dichroic mirror according to one embodiment of the present application. [Figure 5] This figure shows the deformation that occurs when a deformation block of a piezoelectric actuator receives different electrical signals, according to one embodiment of this application. [Figure 6] This is a diagram of an assembly between a movable component and a dichroic mirror according to one embodiment of the present application. [Figure 7] This is another diagram of the assembly between a movable component and a dichroic mirror according to one embodiment of the present application. [Figure 8(a)] This figure shows the coaxial propagation of a blue laser subbeam 1 and a red laser subbeam 1 in a single orientation on a dichroic mirror according to one embodiment of this application. [Figure 8(b)] This figure shows the non-coaxial propagation of a blue laser subbeam 1 and a red laser subbeam 1 in a single orientation on a dichroic mirror according to one embodiment of this application. [Figure 8(c)] This figure shows the non-coaxial propagation of a blue laser subbeam 1 and a red laser subbeam 1 in a different orientation on a dichroic mirror according to one embodiment of this application. [Modes for carrying out the invention]

[0031] The following describes the technical solutions in the embodiments of this application with reference to the accompanying drawings.

[0032] In this specification, the term "and / or" describes a relationship between related objects, indicating that three relationships may exist. For example, A and / or B represents the following three cases: A alone exists, both A and B exist, and B alone exists. In this specification, the letter " / " indicates an "or" relationship between related objects. For example, A / B represents A or B.

[0033] In the specification and claims of this application, terms such as “first,” “second,” etc., are intended to distinguish different objects, but do not indicate a particular order of objects. For example, “first response message,” “second response message,” etc., are used to distinguish different response messages, but do not indicate a particular order of response messages.

[0034] In embodiments of this application, words such as “example” or “for example” are used to indicate that an example, illustration, or explanation is being given. Embodiments or design methods described as “example” or “for example” in embodiments of this application should not be described as being preferable to other embodiments or design methods, or as having more advantages than other embodiments or design methods. More precisely, the use of words such as “example” or “for example” is intended to present the relevant concepts in a particular way.

[0035] In the description of embodiments of this application, unless otherwise specified, “multiple” means two or more. For example, “multiple processing units” means two or more processing units, and “multiple elements” means two or more elements.

[0036] An optical disc having a single servo layer and multiple recording layers is an optical disc structure and has the capability of single-sided multilayer data storage. Based on the transparency between different data layers of an optical disc having a single servo layer and multiple recording layers, an optical disc drive may read data from multiple data layers of an optical disc having a single servo layer and multiple recording layers and write data to multiple data layers by adjusting the focus of the laser beam and selecting the appropriate data layer. The optical disc drive switches the focal position of the laser beam or adjusts the laser wavelength to allow the read / write head to select a specific data layer for operation.

[0037] Figure 1 illustrates the principle by which an optical disc drive reads data from an optical disc having a single servo layer and multiple recording layers, and writes data to the optical disc. As shown in Figure 1, a red laser beam, acting as a guide beam, passes through the objective lens and the multiple recording layers of the optical disc having a single servo layer and multiple recording layers, and illuminates the guide layer of the optical disc having a single servo layer and multiple recording layers. The servo control operation by the red laser beam is performed based on the irregularities, lines, and markings of the guide layer. This enables the function of precisely positioning and tracking a target within the optical device. A blue laser beam, used as a recording beam, passes through the objective lens and illuminates a specific recording layer of the optical disc having a single servo layer and multiple recording layers. The recording beam is focused onto the recording layer and interacts with the recording layer to read data from the recording layer and write data to the recording layer.

[0038] When an optical disc drive reads data from and writes data to an optical disc having a single servo layer and multiple recording layers, the guide beam and the recording beam always remain coaxial, and the paths of the guide beam and the recording beam remain coincided in the optical system. This helps to better align and calibrate the beams to ensure that both beams are precisely focused to the focal point, in order to achieve optimal optical performance and recording quality. "Coaxial" means that the propagation direction of the guide beam is the same as the propagation direction of the recording beam, and the center of the guide beam is at the same location as the center of the recording beam. The guide beam and the recording beam share a single optical path. This may improve the stability and reliability of the optical system by reducing the number of components and the complexity of installation in the optical system.

[0039] Figure 2 shows the structure of an optical disc drive in related technology. As shown in Figure 2, red laser light emitted from a red laser diode (RLD) passes through various lenses and irradiates the guide layer of the optical disc. Blue laser light emitted from a blue laser diode (BLD) passes through various lenses and a group of relay lenses and irradiates the recording medium of the optical disc. The optical disc drive may adjust the relay lens group to a set orientation to allow the red laser light and the blue laser light to be coaxial. The coaxial red laser light and blue laser light may share a single drive mechanism, which performs focusing and tracking control on the objective lens to adjust the depth of focus of the blue laser light and operate on the recording medium of different layers.

[0040] In related technologies, the coaxiality of red and blue laser beams depends on the assembly precision of the optical disc drive and the precision of the internal components of the optical disc drive. After the optical disc drive is assembled, the position of the internal dichroic mirror is fixed and cannot be adjusted. When manufacturing optical disc drives, it is difficult to make the red and blue laser beams coaxial in all optical disc drives, and errors in different directions always exist. An optical disc drive may eliminate focusing errors by adjusting the relay lens group. An optical disc drive may eliminate tracking errors by adjusting the objective lens and drive mechanism. However, since the red and blue laser beams share the same objective lens and drive mechanism, if the optical disc drive adjusts the objective lens and drive mechanism based on the blue laser beam, the red laser beam will have a tracking error. As a result, an optical disc drive cannot simultaneously eliminate tracking errors for both the red and blue laser beams.

[0041] To address the shortcomings of optical disc drives in related technologies, embodiments of this application provide an optical disc drive, memory, and electronic device for an optical disc having a single servo layer and multiple recording layers. Generally, a dichroic mirror (dichroic prism or dichroic mirror) is present inside the optical disc drive. Red laser light may be transmitted directly through the dichroic mirror to the recording medium of the optical disc. Blue laser light is irradiated onto one side of the dichroic mirror and then reflected to the recording medium of the optical disc. The dichroic mirror may be fastened inside the optical disc drive, for example, inside the optical head of the optical disc drive, via a movable component. The movable component may change the orientation of the dichroic mirror to adjust the relative position of the propagation directions of the red laser light and the blue laser light, so that the red and blue laser lights always remain coaxial, thereby eliminating errors that occur during installation, use, etc., of the optical disc drive.

[0042] Figure 3 is a diagram of the structure of an optical disc drive according to one embodiment of the present application. As shown in Figure 3, the optical disc drive 300 may include a first light source 301, a second light source 302, a dichroic mirror 303, a movable component 304, a deformable prism 305, a polarizing beam splitter (PBS) 306, a PBS 307, a photodetector 308, a photodetector 309, a focus servo circuit 310, a tracking servo circuit 311, a focus servo circuit 312, a tracking servo circuit 313, a dichroic aperture 313, a quarter-wave plate 314, and an objective lens 315.

[0043] In this embodiment of the present application, the wavelength of the light emitted by the first light source 301 is different from the wavelength of the light emitted by the second light source 302. One of the first light source 301 and the second light source 302 is used as a recording light source. The recording beam generated by the recording light source may be focused onto the recording layer and interact with the recording layer to read data from the recording layer and write data to the recording layer. The other of the first light source 301 and the second light source 302 is used as a guide light source. Focusing and tracking servo control is performed in the servo layer via a guide beam generated by the guide light source. This can enable the function of precisely positioning and tracking a target within the optical device. In this embodiment of the present application, the first light source 301 is used as a recording light source and may emit blue laser light. The second light source 302 is used as a guide light source and may emit red laser light.

[0044] The blue laser light may pass through optical components such as a deformable prism 305, a PBS 306, and a convex lens to illuminate one side of a dichroic mirror 303. The deformable prism 305 is a specially designed optical component used to change the aspect ratio of the input beam in order to deform or compress the beam to achieve the desired deformation effect. In this embodiment of the present application, after the blue laser light passes through the deformable prism 305, the light in the optical path is deformed or compressed, and as a result the blue laser light is deformed or compressed to achieve the set deformation effect, thereby satisfying the requirement to write data to a recording medium of an optical disk via the blue laser light.

[0045] A PBS is an optical component, generally made of a special optical material via a reflective coating. A PBS can split an input beam into two split beams perpendicular to each other and having the same intensity, based on a set polarization direction. In this embodiment of the present application, a PBS 306 can split a blue laser beam into two blue laser subbeams perpendicular to each other and having the same intensity, irradiating one blue laser subbeam 1 onto one surface of a dichroic mirror 303 and irradiating the other blue laser subbeam 2 onto the light-receiving aperture of a photodetector 308.

[0046] A photodetector is a device that converts light energy into an electrical signal and is configured to detect and measure light intensity. In this embodiment of the present application, after receiving the blue laser subbeam 2, the photodetector 308 converts the blue laser subbeam 2 into an electrical signal of a corresponding value in order to detect the light intensity of the blue laser subbeam 2. After detecting the light intensity of the blue laser subbeam 2, the photodetector 308 may adjust the position and direction of the optical path based on the light intensity signal.

[0047] The photodetector 308 may be connected to a focus servo circuit 310 and a tracking servo circuit 311. The photodetector 308 may generate a control signal based on the light intensity signal of the blue laser subbeam 2 and transmit the control signal to the focus servo circuit 310 and the tracking servo circuit 311 to control the movement of the optical components and adjust the phase position and relative direction of the blue laser subbeam 1 irradiating the optical disk. In this embodiment of the present application, the photodetector's light-receiving port generally has four quadrants, with photosensitive detectors located in each quadrant. When the blue laser subbeam 2 irradiates the input port of the photodetector 308, if focusing and tracking errors exist, the four quadrants of the photodetector 308 receive different light intensities. The photodetector 308 can detect the focusing and tracking errors of the blue laser subbeam 2 by performing different addition and subtraction operations on the light intensities of the four quadrants. The photodetector 308 can convert the focusing deviation signal into an electrical signal of a corresponding value and transmit the electrical signal to the focus servo circuit 310, and convert the tracking deviation signal into an electrical signal of a corresponding value and transmit the electrical signal to the tracking servo circuit 311.

[0048] The focus servo circuit 310 may adjust the focal position of the optical path by controlling the positions of optical components (e.g., the objective lens 315, the dichroic aperture 313, and the quarter-wave plate 314). In this embodiment of the present application, the focus servo circuit 310 may be connected to the objective lens 315. After receiving an electrical signal corresponding to the focusing deviation signal of the photodetector 308, the focus servo circuit 310 may enable the servo system to make slight displacement adjustments to the objective lens 315 based on changes in the electrical signal corresponding to the focusing deviation signal of the photodetector 308, thereby enabling the blue laser subbeam 1 to reach its optimal focal position.

[0049] The tracking servo circuit 311 may track the position of a light source or a moving target by controlling the orientation of optical components (e.g., the objective lens 315, the dichroic aperture 313, and the quarter-wave plate 314). In this embodiment of the present application, the tracking servo circuit 311 may be connected to the objective lens 315. After receiving an electrical signal corresponding to the tracking deviation signal of the photodetector 308, the tracking servo circuit 311 may also allow the servo system to adjust the orientation of the objective lens 315 based on the change in the electrical signal corresponding to the tracking deviation signal of the photodetector 308, so that the objective lens 315 can accurately track changes in the position of the blue laser subbeam 1 and maintain the correct orientation of the blue laser subbeam 1.

[0050] The red laser light may pass through optical components such as the PBS 307 and a convex lens and irradiate the dichroic mirror 303. The PBS 307 may split the red laser light into two red laser subbeams perpendicular to each other and having the same intensity, irradiating the dichroic mirror 303 with one red laser subbeam 1 and the other red laser subbeam 2 with the light-receiving aperture of the photodetector 309. After receiving the red laser subbeam 2, the photodetector 309 converts the red laser subbeam 2 into an electrical signal of a corresponding value in order to detect the light intensity of the red laser subbeam 2. After detecting the light intensity of the red laser subbeam 2, the photodetector 309 may adjust the direction of the optical path based on the light intensity signal.

[0051] The photodetector 309 may be electrically connected to the focus servo circuit 312 and the tracking servo circuit 313. The photodetector 309 can detect the light intensity signal of the red laser subbeam 2 based on the light intensity of the red laser subbeam 2 irradiated into four quadrants and generate a control signal. The photodetector 309 transmits the control signal to the focus servo circuit 312 and the tracking servo circuit 313 to control the movement of the optical components and adjust the phase position and relative direction of the red laser subbeam 1 irradiated onto the optical disk.

[0052] In this embodiment of the present application, the focus servo circuit 312 may be connected to the objective lens 315. After receiving an electrical signal corresponding to the focusing deviation signal of the photodetector 309, the focus servo circuit 312 may enable the servo system to make slight displacement adjustments to the objective lens 315 based on the change in the electrical signal corresponding to the focusing deviation signal of the photodetector 309, thereby enabling the focus of the red laser subbeam 1 to reach the optimal position.

[0053] After receiving an electrical signal corresponding to the tracking deviation signal of the photodetector 309, the tracking servo circuit 313 may allow the servo system to adjust the direction of the objective lens 315 based on the change in the electrical signal corresponding to the tracking deviation signal of the photodetector 309. As a result, the objective lens 315 can accurately track changes in the position of the red laser subbeam 1 and maintain the correct direction of the red laser subbeam 1.

[0054] The dichroic mirror 303 is an optical component, also known as a polarizing filter or birefringent filter. The dichroic mirror 303 selectively transmits or blocks light in a specific direction using different refractive indices (refractive indexes) based on the birefringent properties of the material. In other words, the dichroic mirror 303 is an optical component that can transmit a beam of a set wavelength and reflect a beam of another wavelength. In this embodiment of the present application, the dichroic mirror 303 can transmit long-wavelength red laser light and reflect short-wavelength blue laser light. That is, the red laser light is irradiated onto the surface of the dichroic mirror 303 and then passes directly through the dichroic mirror 303. The blue laser light is irradiated onto the surface of the dichroic mirror 303 and then reflected, changing its direction. The propagation direction of the red laser light irradiated by the dichroic mirror 303 and the propagation direction of the reflected blue laser light are coaxial, and the red laser light and the reflected blue laser light are irradiated onto the optical disk via optical components such as the dichroic aperture 313, quarter-wave plate 314, and objective lens 315.

[0055] A dichroic aperture is an optical component that generally comprises an aperture and a series of filters that separate colors. The filters of a dichroic aperture have specific optical properties, allowing only light within a specific wavelength range to pass through and reflecting or absorbing light of other wavelengths, and are controlled using the aperture. In this embodiment of the present application, coaxial red and blue laser beams pass through a dichroic aperture 313, separating different wavelength components in the incident beam to improve the purity of the two types of laser beams.

[0056] A quarter-wave plate is an optical component configured to change the polarization state of an incident beam. The quarter-wave plate is a wave plate made of a special material, and its thickness is approximately one-quarter the wavelength of light. In this embodiment of the present application, after coaxial red laser light and blue laser light pass through the quarter-wave plate 314, the quarter-wave plate 314 can adjust and change the polarization state of the coaxial red laser light and blue laser light by converting linear polarization of light in one direction to circular polarization in another direction, or converting circular polarization in one direction to linear polarization.

[0057] The objective lens is an optical component configured to focus and illuminate light. In this embodiment of the present application, after coaxial red and blue laser beams pass through the objective lens 315, the objective lens 315 precisely focuses the coaxial red and blue laser beams onto the data track on the surface of the optical disc, maintaining accurate data reading or writing. The objective lens 315 provides accurate and stable optical performance to the optical disc drive by using functions such as focusing, tracking, and shape control of the light spot.

[0058] The dichroic mirror 303 may be movably positioned at the intersection of the propagation directions of the red laser subbeam 1 and the blue laser subbeam 1. In this embodiment of the present application, the propagation direction of the red laser subbeam 1 is perpendicular to the plane of the optical disc. When the dichroic mirror 303 is positioned between the second light source 302 and the optical disc, the propagation direction of the red laser subbeam 1 is not altered by the position and angle of the dichroic mirror 303.

[0059] If the propagation direction of the blue laser subbeam 1 and the propagation direction of the red laser subbeam 1 are different, the blue laser subbeam 1 is irradiated onto the surface of the dichroic mirror 303, then reflected off the surface of the dichroic mirror 300, and the propagation direction of the blue laser subbeam 1 is changed. The propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the red laser subbeam 1 are coaxial.

[0060] In a possible embodiment, as shown in Figure 4(a), the propagation direction of the blue laser subbeam 1 is perpendicular to the propagation direction of the red laser subbeam 1. The angle between the surface of the dichroic mirror 303 and the propagation direction of the red laser subbeam 1 is 45°. The blue laser subbeam 1 is irradiated onto the surface of the dichroic mirror 303 and then reflected by the surface of the dichroic mirror 303. The propagation direction of the reflected blue laser subbeam 1 coincides with the propagation direction of the transmitted red laser subbeam 1, and as a result, the two beams are coaxial.

[0061] Note that in Figure 4(a), the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 are not coaxial, which is to make it easier for the reader to see the two beams. Essentially, the propagation direction of the reflected blue laser subbeam 1 coincides with the propagation direction of the transmitted red laser subbeam 1.

[0062] As shown in Figure 4(b), if the angle between the propagation direction of the blue laser subbeam 1 and the propagation direction of the red laser subbeam 1 is greater than 90°, then after the blue laser subbeam 1 is irradiated onto the surface of the dichroic mirror 303, the propagation direction of the reflected blue laser subbeam 1 will not coincide with the propagation direction of the transmitted red laser subbeam 1. The propagation direction of the reflected blue laser subbeam 1 will be lower than the propagation direction of the transmitted red laser subbeam 1.

[0063] The orientation of the dichroic mirror 303 may be adjusted to enable the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 to be coaxial, and the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1 may be changed to adjust the relative position between the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1. In this way, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 remain coaxial. In this embodiment of the present application, the dichroic mirror 303 may be tilted slightly forward within the optical disc drive 300 to change the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1, so that the angle of the blue laser subbeam 1 incident on the surface of the dichroic mirror 303 is 45°. After the reflection angle of the blue laser subbeam 1 is reduced, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 are coaxial.

[0064] As shown in Figure 4(c), if the angle between the propagation direction of the blue laser subbeam 1 and the propagation direction of the red laser subbeam 1 is less than 90°, then after the blue laser subbeam 1 is irradiated onto the surface of the dichroic mirror 303, the propagation direction of the reflected blue laser subbeam 1 does not coincide with the propagation direction of the transmitted red laser subbeam 1. The propagation direction of the reflected blue laser subbeam 1 is higher than the propagation direction of the transmitted red laser subbeam 1.

[0065] The orientation of the dichroic mirror 303 may be adjusted to enable the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 to be coaxial, and the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1 may be changed to adjust the relative position between the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1. In this way, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 are coaxial. In this embodiment of the present application, the dichroic mirror 303 may be tilted slightly backward within the optical disc drive 300 to change the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1, so that the angle of the blue laser subbeam 1 incident on the surface of the dichroic mirror 303 is 45°. After the reflection angle of the blue laser subbeam 1 is increased, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 become coaxial.

[0066] The movable component 304 can movably fasten the dichroic mirror 303 inside the optical disc drive 300. The movable component 304 may fasten the position of the dichroic mirror 303, thereby preventing the dichroic mirror 303 from moving inside the optical disc drive 300 and affecting the reliability of the product. The movable component 304 may change the orientation of the dichroic mirror 303 to adjust the relative position between the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1, thereby keeping the propagation directions of the reflected blue laser subbeam 1 and the transmitted red laser subbeam 1 coaxial.

[0067] The movable component 304 may be a piezoelectric actuator. A piezoelectric actuator is a device that controls or drives a device using the piezoelectric effect. The piezoelectric effect means that when certain crystalline or ceramic materials are subjected to pressure or pressure action, the charge distribution changes, resulting in an electric field or potential difference. A piezoelectric actuator can use the piezoelectric effect to control or drive a corresponding device by applying pressure or pressure action.

[0068] As shown in Figure 5, the piezoelectric actuator may include a deformation block. The deformation block may be made of lead barium zirconate titanate (PZT). Both ends of the deformation block are electrically connected to the positive and negative terminals of the power supply, respectively. When the power supply does not apply an electrical signal to both ends of the deformation block, the deformation block is not deformed. When the power supply applies an electrical signal to both ends of the deformation block, the deformation block is deformed, resulting in a deformation block with a large radius and a small axial length. Within a reasonable range, a larger electrical signal applied by the power supply indicates a greater deformation of the deformation block. In other words, a larger radius of the deformation block indicates a shorter axial length.

[0069] Figure 6 shows an assembly between a movable component and a dichroic mirror according to one embodiment of the present application. As shown in Figure 6, the movable component 304 includes four piezoelectric actuators. One end of each of the four piezoelectric actuators is fastened to each of the four corners of the frame of the dichroic mirror 303. The other end of each of the four piezoelectric actuators is fastened to the inner surface of the housing of the optical disc drive 300 or to the surface of another component. The four piezoelectric actuators are electrically connected separately to a controller. The controller may randomly change the orientation of the dichroic mirror 303 by applying electrical signals of different values ​​to the four piezoelectric actuators. Optionally, the number of piezoelectric actuators included in the movable component 304 is not limited to the four shown in Figure 6, but may be a different value. The installation positions of the piezoelectric actuators are not limited to those shown in Figure 6, but may be other positions.

[0070] For example, if the dichroic mirror 303 needs to be tilted to the left by a specific angle (left side as shown in Figure 6), the controller may apply the same electrical signal to the upper left piezoelectric actuator and the lower left piezoelectric actuator, but may not apply an electrical signal to the upper right piezoelectric actuator and the lower right piezoelectric actuator. Alternatively, the same electrical signal applied by the controller to the upper left piezoelectric actuator and the lower left piezoelectric actuator may be greater than the same electrical signal applied to the upper right piezoelectric actuator and the lower right piezoelectric actuator.

[0071] As another example, if the dichroic mirror 303 needs to be tilted by a specific angle to the lower left, the controller does not need to apply an electrical signal to the lower left piezoelectric actuator, but not to the upper left, upper right, and lower right piezoelectric actuators. Alternatively, the controller could apply the same electrical signal to the upper left and lower right piezoelectric actuators, and this signal would be smaller than the signal applied to the lower left piezoelectric actuator. Alternatively, the controller could apply an electrical signal to the upper right piezoelectric actuator, and this signal would be smaller than the signals applied to the upper left and lower right piezoelectric actuators.

[0072] Figure 7 is another diagram of the assembly between a movable component and a dichroic mirror according to one embodiment of the present application. As shown in Figure 7, the dichroic mirror 303 has a frame. The frame includes two frame structures, the edges of the two frame structures on the same side separated from each other, and the edges of the two frame structures on opposite sides connected to each other. The dichroic mirror 303 is embedded inside the frame structure. The movable component 304 includes two piezoelectric actuators. The two piezoelectric actuators are positioned at the two ends of the separated edges of the two frame structures on the side and are fastened to the adjacent edges of the two frame structures. The two piezoelectric actuators are electrically connected separately to a controller. The controller may randomly change the orientation of the dichroic mirror 303 by applying electrical signals of different values ​​to the two piezoelectric actuators. Optionally, the number of piezoelectric actuators included in the movable component 304 is not limited to the two shown in Figure 7, but may alternatively be another value. The installation positions of the piezoelectric actuators are not limited to the positions shown in Figure 7, but may be other positions.

[0073] Typically, the two piezoelectric actuators are positioned between the edges of two frame structures on the side and push the edges of the two frame structures on the side apart. When the axial length of the piezoelectric actuators is shortened, the restoring force of the two frame structures causes the edges of the two frame structures on the side to move closer together.

[0074] As shown in Figure 8(a), after fastening one side of the frame of the dichroic mirror 303 to a set position within the optical disc drive 300, the two frame structures of the frame return to their normal state. That is, the edges of the two frame structures on the side are spread apart. The red laser subbeam 1, after being irradiated onto the dichroic mirror 303, is transmitted directly from the dichroic mirror 303, and its propagation direction remains unchanged. The blue laser subbeam 1, after being irradiated onto the surface of the dichroic mirror 303, is reflected from the surface of the dichroic mirror 303, and its propagation direction is changed. In this case, the propagation direction of the reflected blue laser subbeam 1 coincides with the propagation direction of the transmitted red laser subbeam 1, and as a result, the two beams are coaxial.

[0075] As shown in Figure 8(b), when the propagation direction of the blue laser subbeam 1 is changed, the propagation direction of the reflected blue laser subbeam 1 after it irradiates the surface of the dichroic mirror 303 does not coincide with the propagation direction of the transmitted red laser subbeam 1. The propagation direction of the reflected blue laser subbeam 1 is to the left of the propagation direction of the transmitted red laser subbeam 1.

[0076] To enable the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 to be coaxial, the orientation of the dichroic mirror 303 may be adjusted, and the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1 may be changed to adjust the relative position between the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1. In this way, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 remain coaxial. In this embodiment of the present application, the controller may reduce the electrical signal applied to the piezoelectric actuator between the two frame structures. After the electrical signal at both ends of the piezoelectric actuator is reduced, the axial length is increased and the indentation distance between the edges of the two frame structures on the side surface is increased. The frame structure, in which the dichroic mirror 303 is mounted, moves slightly upward due to the restoring force of the piezoelectric actuator, thereby reducing the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1. After the reflection angle of the blue laser subbeam 1 is increased, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 become coaxial.

[0077] As shown in Figure 8(c), when the propagation direction of the blue laser subbeam 1 is changed, the propagation direction of the reflected blue laser subbeam 1 after it has irradiated the surface of the dichroic mirror 303 does not coincide with the propagation direction of the transmitted red laser subbeam 1. The propagation direction of the reflected blue laser subbeam 1 is to the right of the propagation direction of the transmitted red laser subbeam 1.

[0078] To enable the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 to be coaxial, the orientation of the dichroic mirror 303 may be adjusted, and the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1 may be changed to adjust the relative position between the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1. In this way, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 remain coaxial. In this embodiment of the present application, the controller may increase the electrical signal applied to the piezoelectric actuator between the two frame structures. After the electrical signal at both ends of the piezoelectric actuator is increased, the axial length is shortened and the indentation distance between the edges of the two frame structures on the side surface is reduced. The two frame structures are subjected to a restoring force and move slightly downward, increasing the angle between the surface of the dichroic mirror 303 and the propagation direction of the blue laser subbeam 1. After the reflection angle of the blue laser subbeam 1 is reduced, the propagation direction of the reflected blue laser subbeam 1 and the propagation direction of the transmitted red laser subbeam 1 are coaxial.

[0079] In this embodiment of the present application, the electrical signal applied to the piezoelectric actuator by the controller is related to the degree to which the light spot of the blue laser subbeam 1 deviates from the recorded data track. This relationship can be studied and determined experimentally. Generally, a greater degree of deviation of the light spot of the blue laser subbeam 1 from the recorded data track indicates a larger electrical signal applied to the piezoelectric actuator by the controller. A smaller degree of deviation of the light spot of the blue laser subbeam 1 from the recorded data track indicates a smaller electrical signal applied to the piezoelectric actuator by the controller.

[0080] The controller can use a push-pull method to detect deviations in the light spot of the blue laser subbeam 1 from the recorded data track. The basic principle of the push-pull method is to apply an AC voltage to a piezoelectric material to generate mechanical vibrations in the piezoelectric material. These vibrations can cause slight changes in the light propagation path, resulting in a deviation in the light spot. The degree of deviation in the light spot can be controlled by adjusting the frequency and amplitude of the applied voltage. After the controller determines that the light spot of the blue laser subbeam 1 is deviating from the center of the data track, photosensitive detectors in four quadrants will detect the degree of deviation. A low-pass filter removes the high-frequency response and noise in the output from the photosensitive detectors in the four quadrants, and the output low-frequency portion is a fixed deviation between the propagation direction of the blue laser subbeam 1 and the propagation direction of the red laser subbeam 1. After converting the fixed deviation into an electrical signal of the corresponding value, the controller inputs the electrical signal to a piezoelectric actuator to adjust the orientation of the dichroic mirror 303, so that the propagation direction of the blue laser subbeam 1 and the propagation direction of the red laser subbeam 1 always remain coaxial.

[0081] In this embodiment of the present application, the dichroic mirror 303 is used to transmit and reflect laser light having different wavelengths, and the dichroic mirror 303 may be designed to be movably fastened inside the optical disc drive 300. The beam generated by the second light source 302 may be transmitted directly through the dichroic mirror 303, and its propagation direction is not altered by the orientation of the dichroic mirror 303. After being irradiated onto the surface of the dichroic mirror 303, the beam generated by the first light source 301 is reflected. The propagation direction of the reflected beam is altered by the orientation of the dichroic mirror 303. If the propagation direction of the beam from the first light source 301 irradiating the optical disc and the propagation direction of the beam from the second light source 302 irradiating the optical disc are not coaxial, the orientation of the dichroic mirror 303 may be changed to adjust the relative position of the propagation directions of the beams from the first light source 301 and the second light source 302, so that the propagation directions of the beams from the first light source 301 and the second light source 302 remain coaxial. The optical disc drive 300 protected in this application has advantages such as fewer changes to the internal structure, a simpler implementation process, and high control accuracy. When servo control is performed accurately and at low cost via the beam of the second light source 302 in the servo layer, the beam of the first light source 301 irradiates the center of the data track of each recording layer of the optical disc.

[0082] One embodiment of this application provides a memory. The memory includes an optical disc drive and an optical disc, the optical disc drive being able to read data from and write data to the optical disc. The optical disc drive may be an optical disc drive having an optical disc having a single servo layer and multiple recording layers, as shown in Figures 3 to 8(c). The optical disc may be an optical disc having a single servo layer and multiple recording layers or other types of optical discs. Since the memory includes an optical disc drive, the memory has all or at least some of the advantages of an optical disc drive. The memory may be a CD, DVD, BD, etc. The memory may be a type of dedicated optical disc, for example, an optical disc image file or an optical disc mirror file. The memory may be a storage medium based on optical technology, for example, an optical memory and an optical disc array.

[0083] The number of memory components, the types of components, etc., provided in this embodiment of the present application are not limited to the embodiments described above. All technical solutions implemented in accordance with the principles of this application fall within the scope of protection of this solution. Any one or more embodiments or figures in this specification, combined in an appropriate manner, fall within the scope of protection of this solution.

[0084] One embodiment of this application provides an electronic device. The electronic device includes at least one memory. The memory includes an optical disc drive as shown in Figures 3 to 8(c). Since the electronic device includes an optical disc drive, the electronic device has all or at least some of the advantages of an optical disc drive. The electronic device may be a desktop computer, a server, a portable notebook computer, etc.

[0085] The number, types, and other characteristics of components of the electronic device provided in this embodiment of the present application are not limited to the embodiments described herein. All technical solutions implemented in accordance with the principles of this application fall within the scope of protection of this solution. Any technical solution combined in an appropriate manner for any one or more embodiments or figures herein falls within the scope of protection of this solution.

[0086] Finally, it should be noted that the embodiments described above are used solely to illustrate in detail the technical solutions of this application. Those skilled in the art will understand that although this application is described in detail with reference to the embodiments described above, the technical solutions described in those embodiments may still be modified, or some of their technical features may be replaced by equivalents. Such modifications or substitutions will not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of this application. [Explanation of Symbols]

[0087] 300 Optical Disc Drives 301 First light source 302 Second light source 303 Dichroic Mirror 304 Movable Components 305 Deformable Prism 306 Polarizing Beam Splitter 307 Polarizing Beam Splitter 308 Photodetectors 309 Photodetector 310 Focus Servo Circuit 311 Tracking Servo Circuit 312 Focus Servo Circuit 313 Tracking Servo Circuit 313 Dichroic Aperture 314 1 / 4 wave plate 315 Objective lens

Claims

1. An optical disc drive for an optical disc having a single servo layer and multiple recording layers, A first light source (301) configured to read data from the recording layer and generate a first beam for writing data to the recording layer, A second light source (302) configured to generate a second beam for performing focusing and tracking servo control in the servo layer, wherein the propagation direction of the second beam intersects with the propagation direction of the first beam, and the second light source (302) A dichroic mirror (303) is positioned at the intersection of the propagation direction of the second beam and the propagation direction of the first beam, which reflects the first beam and transmits the second beam. A movable component (304) is configured to movably fasten the dichroic mirror inside the optical disc drive and change the orientation of the dichroic mirror to adjust the relative position between the propagation direction of the first beam and the propagation direction of the second beam, An optical disc drive equipped with this feature.

2. The movable component comprises at least one piezoelectric actuator, one end of each of the at least one piezoelectric actuators fastened to different positions on the dichroic mirror, and the other end of each of the at least one piezoelectric actuators fastened to different positions inside the optical disc drive. The optical disc drive according to claim 1, wherein the at least one piezoelectric actuator is separately configured to change the orientation of the dichroic mirror when it receives an electrical signal.

3. The dichroic mirror comprises a frame, the frame comprises two frame structures, the edges of the two frame structures on the same side are separated from each other, the edges of the two frame structures on opposite sides are connected to each other, and the connected edges on the sides of the two frame structures are fastened inside the optical disc drive. The optical disc drive according to claim 1, wherein the movable component comprises at least one piezoelectric actuator positioned between the separated edges on the sides of the two frame structures and configured to change the orientation of the dichroic mirror when an electrical signal is received.

4. The optical disc drive is connected to the piezoelectric actuator and configured to detect the degree of deviation between the light spot of the first beam and the light spot of the second beam, and to transmit an electrical signal of the corresponding value to the piezoelectric actuator. The optical disc drive according to claim 2 or 3, further comprising:

5. The optical disc drive according to any one of claims 1 to 4, further comprising a first photodetector (308) configured to receive the first beam and convert the focusing deviation signal and / or tracking deviation signal of the first beam into corresponding values / corresponding electrical signals / electrical signals.

6. The system further comprises a first focus servo circuit (310) and a first tracking servo circuit (311). The first focus servo circuit is configured to adjust the focal position of the first beam based on the change in the electrical signal corresponding to the focusing deviation signal of the first photodetector. The optical disc drive according to claim 5, wherein the first tracking servo circuit is configured to adjust the direction of the first beam based on the change in the electrical signal corresponding to the tracking deviation signal of the first photodetector.

7. The optical disc drive according to claim 5 or 6, further comprising a first polarizing beam splitter (306) positioned in the propagation direction of the first beam, configured to split the first beam into two identical sub-beams, irradiating one sub-beam onto the light-receiving port of the first photodetector and the other sub-beam onto the dichroic mirror.

8. The optical disc drive according to any one of claims 1 to 7, further comprising a second photodetector (309) configured to receive the second beam and convert the focusing deviation signal and / or tracking deviation signal of the second beam into corresponding values / corresponding electrical signals / electrical signals.

9. The system further comprises a second focus servo circuit (312) and a second tracking servo circuit (313), The second focus servo circuit is configured to adjust the focal position of the second beam based on the change in the electrical signal corresponding to the focusing deviation signal of the second photodetector. The optical disc drive according to claim 8, wherein the second tracking servo circuit is configured to adjust the direction of the second beam based on the change in the electrical signal corresponding to the tracking deviation signal of the second photodetector.

10. The optical disc drive according to claim 8 or 9, further comprising a second polarizing beam splitter (307) positioned in the propagation direction of the second beam, configured to split the second beam into two identical sub-beams, irradiating one sub-beam onto the light-receiving port of the second photodetector and the other sub-beam onto the dichroic mirror.

11. An optical disc having a single servo layer and multiple recording layers, At least one optical disc drive according to any one of claims 1 to 10, the at least one optical disc drive configured to read data from the at least one optical disc having a single servo layer and a plurality of recording layers, and to write data to the at least one optical disc, Memory equipped with this feature.

12. At least one memory according to claim 11, Each of the at least one memory is connected to at least one controller configured to control the at least one memory to read and write data, An electronic device equipped with the following features.

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