A method and apparatus for reading data from an optical disc

Abstract

The application belongs to the field of optical storage, and specifically discloses an optical disc data reading method and device. The optical disc involved in the application comprises a plurality of data layers, each data layer comprising a plurality of data blocks. The optical disc data reading method comprises the following steps: focusing imaging light to a preset data layer of the optical disc; obtaining images of each data block in the preset data layer based on the imaging light when the optical disc rotates; controlling the imaging light to stably focus on the preset data layer according to the brightness and the definition of each data block image, and then reading corresponding data information based on the images of each data block. According to the application, the defocus distance and direction can be accurately predicted in combination with the definition evaluation function, and real-time focus control can be performed in the process of continuous rotation of the optical disc. Data is read in a pure image mode, and focus servo control can be completed without making a data recording layer with a track in the optical disc, so that reading of hundreds of layers of data in a multi-dimensional storage optical disc can be realized.

Description

Technical Field

[0002] This application belongs to the field of optical storage, and more specifically, relates to a method and apparatus for reading optical disc data. Background Technology

[0003] Traditional optical discs record data by etching "pits" into the information recording layer. When reading information, the light spot must be accurately focused onto the information recording layer of the disc and strictly tracked within the channel. Focusing error and track tracking error must be controlled at the nanometer level. To achieve the required focusing accuracy, an information recording layer with tracks needs to be fabricated on the disc. Due to limitations in the reflectivity of the recording layer and manufacturing processes, it is difficult for conventional optical discs to have more than four layers, thus limiting the maximum capacity of the optical disc.

[0004] Multidimensional optical storage technology utilizes femtosecond lasers to fabricate micro- and nano-structures within transparent materials to store information, eliminating the need for pre-fabricating information recording layers within the medium. Depending on the fabrication depth, hundreds of data layers can be easily written within transparent materials, significantly increasing data storage capacity. However, these data layers lack reflective surfaces and tracks similar to blue light, making it impossible to use servo technology like blue light to accurately focus the read light onto the data points, resulting in unsuccessful data reading. Therefore, novel data reading methods need to be developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide an optical disc data reading method and apparatus, which aims to solve the problem that existing multidimensional optical storage optical discs do not have a pre-made reflective layer and cannot use data point reflection to read information.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for reading optical disc data, wherein the optical disc includes multiple data layers, each data layer includes multiple data blocks, and includes the following steps: The imaging light is focused onto the preset data layer of the optical disc; When the optical disc rotates, images of each data block within a preset data layer are acquired based on the imaging light; The imaging light is controlled to be stably focused onto the preset data layer based on the brightness and sharpness of each data block image, and then the corresponding data information is read based on the image of each data block.

[0007] In one possible implementation, controlling the imaging light to be stably focused onto the preset data layer based on the brightness and sharpness of each data block image includes: The focus of the imaging light is determined based on the brightness of the data block image to determine whether the focus surface of the imaging light deviates from the preset data layer and the direction of deviation from the preset data layer; if the brightness of the image is in the first brightness range, the focus surface is above the preset data layer; if the brightness of the image is in the second brightness range, the focus surface is below the preset data layer. When the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and the preset optimal sharpness; the preset optimal sharpness is determined by the sharpness of the corresponding data block image obtained when the imaging light is focused onto the preset data layer. The position of the imaging light's focal plane is finely adjusted based on the direction and distance of the focal plane deviating from the preset data layer, so that it is stably focused on the preset data layer.

[0008] In one possible implementation, each data block includes multiple data points; The first brightness range is defined as follows: the average gray level of the data point images in the data block image is less than the average gray level of the background area in the data block image; The second brightness range is defined as follows: the average gray level of the data point images in the data block image is greater than the average gray level of the background area in the data block image.

[0009] In one possible implementation, the distance Δd between the focusing surface and the preset data layer is: Δd = K × (Fbest − Fcur) Where Fbest is the preset optimal resolution, Fcur is the resolution of the data block image, and K is the preset scaling factor.

[0010] In one possible implementation, the sharpness of the data block image is obtained through the following steps: The array of data points composed of multiple data points in the data block image is set as the Region of Interest (ROI). The image of the ROI in the current data block image is extracted, and the ROI image is standardized to obtain the standardized image. Based on the pre-calibrated single data point pixel size, the standardized image is divided into multiple sub-blocks that match the single data point pixel size. Abnormal sub-blocks are removed by grayscale variance verification, and valid sub-blocks are retained. For each valid sub-block, a preset gradient operator is used to calculate the grayscale gradient value of each pixel within it. The grayscale gradient values ​​of all pixels in the valid sub-block are weighted and summed to obtain the sharpness value of the valid sub-block. The weighted value of each pixel during the weighted summation is proportional to the degree to which the grayscale value of each pixel is close to the average grayscale value of its valid sub-block. The sharpness of the current data block image is determined by combining the average sharpness of all valid sub-blocks.

[0011] In one possible implementation, for each valid sub-block, a preset gradient operator is used to calculate the grayscale gradient value of each pixel, including: Obtain the grayscale gradient value of each pixel, which is the horizontal grayscale gradient and the vertical grayscale gradient of that pixel; the horizontal grayscale gradient and the vertical grayscale gradient correspond to the Sobel operators in the horizontal and vertical directions, respectively.

[0012] In one possible implementation, determining the sharpness of the current data block image includes: After frequency domain constraint correction of the mean sharpness of all valid sub-blocks, the image is linearly normalized to a preset value range to obtain the sharpness of the current data block image.

[0013] In one possible implementation, the data information of each data block in the preset data layer includes the address information of the data layer in which it resides. Secondly, this application provides an optical disc data reading device, the optical disc comprising multiple data layers, each data layer comprising multiple data blocks, including: An illumination unit is used to focus imaging light onto a preset data layer of the optical disc; Control unit, used to control the rotation of the optical disc; The image acquisition unit is used to acquire images of each data block within a preset data layer based on the imaging light; The illumination unit is also used to control the imaging light to be stably focused onto the preset data layer according to the brightness and sharpness of each data block image; The reading unit is used to read the corresponding data information based on the image of each data block.

[0014] In one possible implementation, the illumination unit determines whether the focusing surface of the imaging light deviates from a preset data layer and the direction of deviation from the preset data layer based on the brightness of the data block image; if the brightness of the image is in a first brightness range, the focusing surface is above the preset data layer; if the brightness of the image is in a second brightness range, the focusing surface is below the preset data layer; when the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and a preset optimal sharpness; the preset optimal sharpness is determined by the sharpness of the corresponding data block image acquired when the imaging light is focused onto the preset data layer; and the position of the focusing surface of the imaging light is finely adjusted based on the direction and distance of the focusing surface of the imaging light deviating from the preset data layer, so that it is stably focused onto the preset data layer.

[0015] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: This application provides a method and apparatus for reading optical disc data. It reads data using a pure image-based approach, eliminating the need to create tracked data recording layers on the optical disc for focus servo control. This allows for the reading of hundreds of layers of data from multidimensional storage optical discs. The automatic focus detection process incorporates data point brightness judgment, combined with a sharpness evaluation function, to accurately predict defocus distance and direction. The automatic focusing speed is faster than traditional algorithms, and real-time focus control can be performed during continuous optical disc rotation. Attached Figure Description

[0016] Figure 1 This is a flowchart of the optical disc data reading method provided in the embodiments of this application; Figure 2 This is an architectural diagram of an optical disc reading device provided in an embodiment of this application; Figure 3 These are schematic diagrams illustrating the sharpness at different focus positions provided in the embodiments of this application; Figure 4a This is a schematic diagram of an image of a data point when the imaging light is focused above the data point, as provided in an embodiment of this application. Figure 4b This is a schematic diagram of an image of a data point when the imaging light is focused below the data point, as provided in an embodiment of this application. Figure 5a This is a schematic diagram of a blurred image obtained when the imaging light is not focused on the data point, as provided in an embodiment of this application. Figure 5b This application provides an embodiment of the method for... Figure 5a A schematic diagram showing the results of identifying data points in the blurred image. Figure 5c This is a schematic diagram of a clear image obtained when the imaging light is focused on a data point, as provided in an embodiment of this application. Figure 5d This application provides an embodiment of the method for... Figure 5c A schematic diagram showing the results of identifying data points in the clear image. Figure 6 This is another architectural diagram of the optical disc reading device provided in the embodiments of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0019] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0020] The purpose of this application is to develop an image-based multi-layer optical disc data reading method based on the characteristics of multi-dimensional optical storage data, in order to solve the problem of difficult focus control during the reading process of multi-layer optical discs.

[0021] Figure 1 This is a flowchart of the optical disc data reading method provided in an embodiment of this application; as shown... Figure 1 As shown, it includes the following steps: Step S101: Focus the imaging light onto a preset data layer of the optical disc; the optical disc includes multiple data layers, and each data layer includes multiple data blocks; Step S102: When the optical disc rotates, images of each data block in the preset data layer are acquired based on the imaging light; Step S103: Control the imaging light to be stably focused onto the preset data layer according to the brightness and sharpness of each data block image, and then read the corresponding data information based on the image of each data block.

[0022] In one embodiment, controlling the imaging light to be stably focused onto the preset data layer based on the brightness and sharpness of each data block image includes: The focus of the imaging light is determined based on the brightness of the data block image to determine whether the focus surface of the imaging light deviates from the preset data layer and the direction of deviation from the preset data layer; if the brightness of the image is in the first brightness range, the focus surface is above the preset data layer; if the brightness of the image is in the second brightness range, the focus surface is below the preset data layer. When the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and the preset optimal sharpness; the preset optimal sharpness is determined by the sharpness of the corresponding data block image obtained when the imaging light is focused onto the preset data layer. The position of the imaging light's focal plane is finely adjusted based on the direction and distance of the focal plane deviating from the preset data layer, so that it is stably focused on the preset data layer.

[0023] Optionally, each data block includes multiple data points; The first brightness range is defined as follows: the average gray level of the data point images in the data block image is less than the average gray level of the background area in the data block image; The second brightness range is defined as follows: the average gray level of the data point images in the data block image is greater than the average gray level of the background area in the data block image.

[0024] In one embodiment, the distance Δd between the focusing surface and the preset data layer is: Δd = K × (Fbest − Fcur) Where Fbest is the preset optimal resolution, Fcur is the resolution of the data block image, and K is the preset scaling factor.

[0025] In one embodiment, the sharpness of the data block image is obtained through the following steps: The array of data points composed of multiple data points in the image block is set as the region of interest (ROI). The image of the ROI in the current data block image is extracted, and the ROI image is standardized to obtain the standardized image. Based on the pre-calibrated single data point pixel size, the standardized image is divided into multiple sub-blocks that match the single data point pixel size. Abnormal sub-blocks are removed by grayscale variance verification, and valid sub-blocks are retained. For each valid sub-block, a preset gradient operator is used to calculate the grayscale gradient value of each pixel within it. The grayscale gradient values ​​of all pixels in the valid sub-block are weighted and summed to obtain the sharpness value of the valid sub-block. The weighted value of each pixel during the weighted summation is proportional to the degree to which the grayscale value of each pixel is close to the average grayscale value of its valid sub-block. The sharpness of the current data block image is determined by combining the average sharpness of all valid sub-blocks.

[0026] More specifically, the sharpness Fcur of the aforementioned data block image is obtained through the following steps: a) Region of Interest (ROI) extraction: From the acquired original data block image, a region of interest containing only the data point array is cropped. The ROI is then subjected to grayscale conversion, grayscale normalization, and edge-preserving filtering to obtain a standardized image; b) Valid sub-block selection: Based on the pre-calibrated single data point pixel size, the standardized image is divided into several atomic blocks matching the single data point size. Abnormal atomic blocks corresponding to blanks, scratches, and stains are removed through grayscale variance verification, retaining valid computational sub-blocks; c) Edge enhancement gradient calculation: For each valid computational sub-block, a preset gradient operator is used to calculate the pixel gradient value. High gradient pixels corresponding to the data point edges are weighted and amplified, and the sharpness values ​​of each valid sub-block are accumulated. The average sharpness of all valid sub-blocks is then taken; d) Normalized output: After frequency domain constraint correction, the average sharpness value is linearly normalized to a preset value range to obtain the sharpness Fcur of the current data block image.

[0027] In one embodiment, for each valid sub-block, the grayscale gradient value of each pixel is calculated using a preset gradient operator, including: Obtain the grayscale gradient value of each pixel, which is the horizontal grayscale gradient and the vertical grayscale gradient of that pixel; the horizontal grayscale gradient and the vertical grayscale gradient correspond to the Sobel operators in the horizontal and vertical directions, respectively.

[0028] For example, the data information of each data block in the preset data layer includes the address information of its respective data layer. In a specific embodiment, this application uses a transmission microscopy imaging optical path to read information, and utilizes an autofocus algorithm in conjunction with data point brightness information to achieve focus control. A schematic diagram of the optical disc reading device is shown below. Figure 2 As shown.

[0029] in, Figure 2 The spindle motor controls the optical disc to rotate at a constant speed, and the linear slide controls the optical disc to move radially. The two work together to make the imaging spot scan the data layer along a spiral.

[0030] The illumination source provides illumination, the objective lens performs microscopic imaging of the data points, and the torque converter is used to fine-tune the focal plane and compensate for jitter on the disk surface. The focusing lens, driven by a linear motor, can move up and down to adjust the depth of focus in conjunction with the objective lens, ensuring the image plane is focused on the correct data layer. The tube lens projects the image onto the camera sensor (i.e., the image acquisition module). The computer (i.e., the data reading and control module) runs image processing algorithms to achieve focus control and data extraction.

[0031] Traditional optical disc reading must solve two key problems: focusing and track tracking. This application uses a camera to capture images, allowing data from multiple tracks to be captured simultaneously. Therefore, a redundant design with overlapping scan area edges ensures that all tracks are read, eliminating track tracking issues. The focusing steps of the device are as follows: 1. Based on the calibration values, a linear motor is used to move the focusing lens to the designated position, focusing the imaging plane near the data layer. Combined with a focus detection algorithm, the torque is fine-tuned to find the position where the image is sharpest. Commonly used sharpness evaluation functions, such as the Brenner and Tenengrad functions, can be used to evaluate the focusing situation and the image sharpness at different focus positions. Figure 3 As shown, the resolution can be considered to be 1.3e. 9 It achieves good focusing effect.

[0032] 2. Read the image data and determine the data layer number based on the address information in the data. If the number is correct, proceed to the data reading stage. If the number is incorrect, adjust the linear motor according to the difference to move the imaging plane to the correct data layer, and repeat the focusing steps above.

[0033] Specifically, the data information of each data block in the preset data layer includes the address information of its respective data layer. The data read is then pre-recorded servo data or address information for positioning on the optical disc. Furthermore, the aforementioned data layer number is directly encoded in the address field. The optical disc is layer-coded, with each layer having a corresponding layer code. For example, if the address information is L01-xxx, L01 indicates that the current physical layer is layer 1. The xxx field represents the corresponding data layer code.

[0034] In one embodiment, the above-mentioned control of focusing the imaging light onto a preset data layer includes the following steps: (1) Setting the target: When a user or device needs to read data from the 3rd layer (N=3), the “target layer number=3” is issued to the aforementioned device.

[0035] (2) Coarse positioning and focusing: The device controls the linear motor to move the focusing lens to the vicinity of the theoretical 3rd layer position, and then the torque device is used to fine-tune the initial focusing to make the image clearer.

[0036] (3) Reading and Verification: Action: The device decodes the clear image and extracts the address information. Let's assume the decoded address is L02 (i.e., the current layer number M=2).

[0037] Decision: The control device performs a simple comparison: Is the current layer number M (2) equal to the target layer number N (3)? (4) Error correction actions: The device determines that "the data layer number is incorrect". This means that the imaging plane actually falls on the wrong second layer. The device immediately calculates the difference: D = 3 - 2 = 1. Based on the difference (+1), the device knows that it needs to move the imaging plane one layer deeper.

[0038] So, it controls the linear motor to move the focusing lens by a preset "single-layer step amount". After the movement is completed, the device returns to the "initial focusing" step, refocuses and reads the address information again for verification. If the address decoded this time is L03, then 3 == 3 is True, and the device determines that the data layer number is correct and then enters the formal data reading stage.

[0039] 3. After entering the data reading stage, the motor is used to rotate the optical disc to move the camera imaging plane to the next data block position. Due to the tilt of the disc surface or the jitter of the device, the imaging plane may deviate from the data layer. When focusing on the data point, the data point is black, as Figure 4a shown. When focusing below the data point, the data point is white, as Figure 4b shown. According to the brightness of the data point, the deviation direction of the focal plane can be judged. Combining with the clarity evaluation function, the defocus distance can be estimated. Just move the actuator to return the focal plane to the correct position to complete the focusing control.

[0040] In one embodiment, the deviation direction of the focal plane is judged according to the brightness of the data point in the image (this step uses the Figure 4a and Figure 4b shown contrast inversion characteristics): Extract the average gray value Idot of the data point area and the average gray value Ibg of the background area.

[0041] If Idot < Ibg (the data point is black), the focal plane is above (the object distance is too close).

[0042] If Idot > Ibg (the data point is white), the focal plane is below (the object distance is too far).

[0043] Furthermore, combining the clarity value and the direction, estimate the defocus distance Δd that needs to be adjusted. There are two common methods: Inverse derivation based on the calibration curve: Combining the Figure 3 shown curve, the clarity value F corresponding to different defocus positions d can be measured in advance through experiments, and the curve F = f(d) can be fitted. Substitute the current Fcur into the curve to inversely solve the current defocus position dcur, then the defocus amount Δd = dcur - dbest, where dbest is the best focal plane position (at the clarity peak).

[0044] Linear approximation formula (applicable to small-range defocus): Δd = K × (Fbest − Fcur) In the formula, Fbest is the optimal focal plane sharpness value (obtained and calibrated through initial coarse adjustment), and K is the device scaling factor (unit: μm / sharpness unit), which is obtained by pre-calibrating the depth of field and curve slope of the optical device.

[0045] When the optical disc is in a large defocus range, the corresponding defocus amount can be determined by a pre-fitted nonlinear formula (a function of sharpness and focus position). For the specific nonlinear fitting calculation process, please refer to existing curve fitting methods; this application does not specifically limit this process.

[0046] Furthermore, the estimated defocus amount Δd is multiplied by the direction sign (obtained from step 3): If the focal plane is too high (data points are black), the object distance needs to be increased, and the torque should be moved away from the optical disc, taking Δd as a positive value; If the focal plane is too low (data points are white), the object distance needs to be reduced, and the torque device should be moved closer to the optical disc, taking Δd as a negative value.

[0047] The final control quantity D = sign × |Δd| is converted into a voltage signal and output to the torque drive.

[0048] Repeat the above steps for each captured image block, adjusting the torque in real time to keep the focal plane locked in the optimal position.

[0049] 4. The above-described focusing control process only involves simple sharpness evaluation function calculation and data point brightness calculation. The algorithm can be easily implemented using an FPGA to achieve real-time control. Under real-time control conditions, the area scan camera can be replaced by a line scan camera. When the lens scans at a constant speed along a spiral, the line scan camera can obtain the same two-dimensional image as the area scan camera, while reducing device costs.

[0050] To adapt to variations in grayscale gradients across multiple directions when calculating sharpness, the Tenengrad function, which incorporates Sobel operators in both horizontal and vertical directions, is used for improvement. Furthermore, to enhance the sensitivity of the evaluation function, the maximum value of the grayscale gradients in these two directions is selected as the grayscale gradient value for that pixel. When the edge direction of the image changes, the function automatically selects the direction with the largest change in grayscale gradient, significantly improving the stability of autofocus. Simultaneously, by weighting image pixels, the differences between background and content pixels are highlighted, further enhancing the sensitivity and noise resistance of the evaluation function.

[0051] The expression for calculating the gray-level gradient value of an image pixel is: Where g(x, y) represents the grayscale value of the pixel at coordinates (x, y). Indicates level x Sobel operators in direction Indicates vertical y Sobel operators in direction Represents the horizontal grayscale gradient. Represents the vertical grayscale gradient. This represents the grayscale gradient value of the pixel at coordinates (x, y).

[0052] To improve the noise resistance of the Tenengrad function while preserving gray-level gradient features, an optimization method combining it with a variance function is employed. First, the variance of the gray-level gradient value G(x, y) for each pixel in the image is calculated. The variance measures the degree of deviation of G(x, y) from the mean; a larger deviation indicates a stronger gray-level gradient in that region. The expression for calculating the variance D(x, y) is as follows: Where G represents the average gray-level gradient value G(x, y) of all pixels in the image. M This represents the total number of pixels in the horizontal direction. N This represents the total number of pixels in the vertical direction.

[0053] Because the grayscale values ​​of background, noise pixels, and content pixels differ, background pixels and content pixels are weighted separately. This increases the weight of content pixels and decreases the weight of background and noise pixels, thereby improving the sensitivity and noise resistance of the focus evaluation function. The improved Tenengrad focus evaluation function is calculated as follows: Where g(x, y) represents the gray value of the pixel at (x, y), S represents the average gray value of the image pixels, and F represents the sharpness of the pixel at (x, y).

[0054] It can be seen that the closer the gray value g(x, y) is to the gray mean S, the greater the weighting value at the corresponding pixel.

[0055] Furthermore, by combining the sharpness evaluation function and data point brightness information, the focus position of the optical disc is adjusted. The specific steps are as follows: Control flow: The computer (or FPGA) runs the focus detection algorithm and calculates the required adjustment amount D for each frame of image acquired.

[0056] Signal conversion: The D signal is converted into an analog voltage signal by a digital-to-analog converter (DAC) and output to the torque drive circuit.

[0057] Action performed: The torque device moves the objective lens a corresponding distance along the optical axis according to the voltage magnitude and polarity, so that the imaging plane returns to the data layer.

[0058] Real-time closed-loop: During the continuous rotation of the optical disc, the algorithm continuously calculates and drives at the frame rate (such as the line frequency of a line scan camera) to form a closed-loop servo control, which effectively suppresses defocusing errors caused by disc tilt and vibration.

[0059] Furthermore, in one embodiment, to verify the effectiveness of the optical disc focus position adjustment method proposed in the embodiments of this application, Figure 5a , Figure 5b Provide the corresponding comparative examples. Figure 5c , Figure 5d Corresponding implementation examples are provided.

[0060] Figure 5a This is a schematic diagram of a blurred image acquired when the imaging light is not focused on the data points; by Figure 5a It is evident that the images of the acquired data blocks are relatively blurry; the clarity of the data points has not yet been achieved. Figure 3 The peak value or the vicinity of the peak value is shown.

[0061] Figure 5b Yes Figure 5a The diagram shows the result of identifying data points in the blurred image; as shown. Figure 5b As shown, green circles represent valid data points, and yellow circles represent no data points. The positions of the valid data points are marked with the corresponding symbols. Figure 5a The difference is significant. It is evident that when the imaging light is not focused on the data points, the data information on the optical disc cannot be effectively identified.

[0062] Figure 5c This is a schematic diagram of a clear image obtained when the imaging light is focused on a data point, as provided in an embodiment of this application; combined with Figure 5d The data point identification results show that the valid data points corresponding to the green circles are... Figure 5c All the gray dots in the image match perfectly. This demonstrates that data information on the optical disc can only be effectively identified when the imaging light is focused on the data points.

[0063] In summary, the optical disc data reading method provided in this application incorporates data point brightness judgment during the automatic focus detection process. Combined with a sharpness evaluation function, it can accurately predict the defocus distance and direction. Real-time and effective focus control can be performed during continuous optical disc rotation, enabling this application embodiment to read data from the optical disc using only image processing. Without the focus control method for optical disc rotation provided in this application embodiment, it would be impossible to effectively read optical disc data using only image processing, resulting in a higher error rate.

[0064] Figure 6This is another architectural diagram of the optical disc reading device provided in the embodiments of this application, such as... Figure 6 As shown, it includes: The illumination unit 610 is used to focus the imaging light onto the preset data layer of the optical disc; Control unit 640 is used to control the rotation of the optical disc; The image acquisition unit 620 is used to acquire images of each data block within a preset data layer based on the imaging light when the optical disc rotates; The illumination unit 610 is also used to control the imaging light to be stably focused onto the preset data layer according to the brightness and sharpness of each data block image; The reading unit 630 is used to read the corresponding data information based on the image of each data block.

[0065] In one embodiment, the illumination unit 610 determines whether the focusing surface of the imaging light deviates from a preset data layer and the direction of deviation from the preset data layer based on the brightness of the data block image; if the brightness of the image is in a first brightness range, the focusing surface is above the preset data layer; if the brightness of the image is in a second brightness range, the focusing surface is below the preset data layer; when the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and a preset optimal sharpness; the preset optimal sharpness is determined by the sharpness of the corresponding data block image obtained when the imaging light is focused on the preset data layer; and the position of the focusing surface of the imaging light is finely adjusted based on the direction and distance of the focusing surface of the imaging light deviating from the preset data layer, so that it is stably focused on the preset data layer.

[0066] It should be understood that the above-described device is used to execute the methods in the above embodiments. The corresponding program units in the device are implemented in a similar manner and have similar technical effects as described in the above methods. The working process of the device can be referred to the corresponding process in the above embodiments, and will not be repeated here.

[0067] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0068] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0069] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for reading data from an optical disc, wherein the optical disc comprises multiple data layers, each data layer comprising multiple data blocks, characterized in that, Includes the following steps: The imaging light is focused onto the preset data layer of the optical disc; When the optical disc rotates, images of each data block within a preset data layer are acquired based on the imaging light; The imaging light is controlled to be stably focused onto the preset data layer based on the brightness and sharpness of each data block image, and then the corresponding data information is read based on the image of each data block.

2. The optical disc data reading method according to claim 1, characterized in that, The step of controlling the imaging light to be stably focused onto the preset data layer based on the brightness and sharpness of each data block image includes: The brightness of the data block image determines whether the focusing surface of the imaging light deviates from the preset data layer and the direction of deviation from the preset data layer; if the brightness of the image is in the first brightness range, the focusing surface is above the preset data layer; if the brightness of the image is in the second brightness range, the focusing surface is below the preset data layer. When the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and the preset optimal sharpness; the preset optimal sharpness is determined by the sharpness of the corresponding data block image obtained when the imaging light is focused onto the preset data layer. The position of the imaging light's focal plane is finely adjusted based on the direction and distance of the focal plane deviating from the preset data layer, so that it is stably focused on the preset data layer.

3. The optical disc data reading method according to claim 2, characterized in that, Each data block includes multiple data points; The first brightness range is defined as follows: the average gray level of the data point images in the data block image is less than the average gray level of the background area in the data block image; The second brightness range is defined as follows: the average gray level of the data point images in the data block image is greater than the average gray level of the background area in the data block image.

4. The optical disc data reading method according to claim 2, characterized in that, The distance Δd between the focusing surface and the preset data layer is: Δd = K × (Fbest − Fcur) Where Fbest is the preset optimal resolution, Fcur is the resolution of the data block image, and K is the preset scaling factor.

5. The optical disc data reading method according to any one of claims 1 to 4, characterized in that, The sharpness of the data block image is obtained through the following steps: The array of data points composed of multiple data points in the data block image is set as the region of interest (ROI). The image of the ROI in the current data block image is extracted, and the ROI image is standardized to obtain the standardized image. Based on the pre-calibrated single data point pixel size, the standardized image is divided into multiple sub-blocks that match the single data point pixel size. Abnormal sub-blocks are removed by grayscale variance verification, and valid sub-blocks are retained. For each valid sub-block, a preset gradient operator is used to calculate the grayscale gradient value of each pixel within it. The grayscale gradient values ​​of all pixels in the valid sub-block are weighted and summed to obtain the sharpness value of the valid sub-block. The weighted value of each pixel during the weighted summation is proportional to the degree to which the grayscale value of each pixel is close to the average grayscale value of its valid sub-block. The sharpness of the current data block image is determined by combining the average sharpness of all valid sub-blocks.

6. The optical disc data reading method according to claim 5, characterized in that, For each valid sub-block, the grayscale gradient value of each pixel is calculated using a preset gradient operator, including: Obtain the grayscale gradient value of each pixel, which is the horizontal grayscale gradient and the vertical grayscale gradient of that pixel; the horizontal grayscale gradient and the vertical grayscale gradient correspond to the Sobel operators in the horizontal and vertical directions, respectively.

7. The optical disc data reading method according to claim 5, characterized in that, Determine the sharpness of the current data block image, including: After frequency domain constraint correction of the mean sharpness of all valid sub-blocks, the image is linearly normalized to a preset value range to obtain the sharpness of the current data block image.

8. The optical disc data reading method according to any one of claims 1 to 4, characterized in that, The data information of each data block in the preset data layer includes the address information of the data layer in which it belongs.

9. An optical disc data reading device, wherein the optical disc comprises multiple data layers, each data layer comprising multiple data blocks, characterized in that, include: An illumination unit is used to focus imaging light onto a preset data layer of the optical disc; Control unit, used to control the rotation of the optical disc; The image acquisition unit is used to acquire images of each data block within a preset data layer based on the imaging light; The illumination unit is also used to control the imaging light to be stably focused onto the preset data layer according to the brightness and sharpness of each data block image; The reading unit is used to read the corresponding data information based on the image of each data block.

10. The optical disc data reading device according to claim 9, characterized in that, The illumination unit determines whether the focusing surface of the imaging light deviates from a preset data layer and the direction of deviation from the preset data layer based on the brightness of the data block image; if the brightness of the image is in the first brightness range, the focusing surface is above the preset data layer; if the brightness of the image is in the second brightness range, the focusing surface is below the preset data layer; when the focusing surface of the imaging light deviates from the preset data layer, the distance of the focusing surface from the preset data layer is determined based on the sharpness of the data block image and the preset optimal sharpness. The preset optimal sharpness is determined by the sharpness of the corresponding data block image acquired when the imaging light is focused onto the preset data layer; and the position of the imaging light focusing surface is finely adjusted based on the direction and distance of the focusing surface of the imaging light from the preset data layer, so that it is stably focused onto the preset data layer.

Images