Virtual image distance measurement method and system

Abstract

The application provides a virtual image distance measurement method and system, and belongs to the technical field of near-eye display devices.The system comprises a displacement sensing module, which is used to obtain measurement information of the back intercept of a lens; a driving module, which is used to adjust the back intercept of the lens; an image sensing module, which is used to collect a projection image generated by a to-be-measured object under different focusing states of the lens; and a calculation module, which is in signal connection with the displacement sensing module, the driving module and the image sensing module, and is used to determine the virtual image distance of a target projection image according to a pre-constructed virtual image distance measurement model and target measurement information corresponding to the target projection image under a preset focusing state; wherein the virtual image distance measurement model is established according to a preset calibration distance and corresponding measurement information of the back intercept.The application can provide higher measurement accuracy, improve the consistency and repeatability of measurement results, and has strong universality.

Description

Technical Field

[0001] This invention relates to the field of near-eye display technology, and in particular to a method and system for measuring virtual image distance. Background Technology

[0002] Virtual reality products include VR, AR, and MR. They have different applications in different fields, such as: VR games and entertainment: providing highly immersive virtual gaming experiences and virtual tours; AR navigation and positioning: displaying real-time navigation information, such as arrows and paths, in map applications.

[0003] Virtual reality (VR) uses projection technology to project a virtual image onto a target area within a certain distance in front of the viewer. The projection distance is adjusted based on the specific application scenario, adjusting the lens characteristics to project at different distances. Therefore, the projection distance is a crucial metric for AR / VR / MR products.

[0004] However, existing virtual image distance measurement schemes suffer from poor measurement accuracy and poor measurement repeatability. Summary of the Invention

[0005] This invention provides a virtual image distance measurement method and system to solve the defects of poor measurement accuracy and poor measurement repeatability in the prior art.

[0006] In a first aspect, the present invention provides a virtual image distance measurement system, comprising:

[0007] The displacement sensing module is used to acquire measurement information of the lens back focal length;

[0008] The drive module is used to adjust the back focal length of the lens;

[0009] The image sensing module is used to acquire projected images of the object under test under different focusing states of the lens;

[0010] The calculation module, which is connected to the displacement sensing module, the driving module and the image sensing module, is used to determine the virtual image distance of the target projection image based on the pre-built virtual image distance measurement model and the target measurement information corresponding to the target projection image under the preset focus state.

[0011] The virtual image distance measurement model is established based on the measurement information of the preset calibration distance and the corresponding back intercept.

[0012] According to the present invention, a virtual image distance measurement system determines the virtual image distance of a target projection image based on a pre-constructed virtual image distance measurement model and using target measurement information corresponding to a target projection image under a preset focus state. The system includes: controlling a drive module to adjust the back focal length of the lens; determining the projection image under a preset focus state as the target projection image from received measurement information under different focus states and corresponding projection images; wherein the preset focus state is determined based on preset parameters of the projection image; and inputting the measurement information corresponding to the target projection image as target measurement information into the pre-constructed virtual image distance measurement model to obtain the virtual image distance of the target projection image.

[0013] According to the present invention, a virtual image distance measurement system and a method for constructing a virtual image distance measurement model include: placing a calibration plate at a preset calibration distance; acquiring test images of the calibration plate under different focusing states by adjusting the back crop of the lens; determining the target test image under the preset focusing state and the corresponding back crop measurement information from the test images under different focusing states; acquiring multiple sets of different preset calibration distances and corresponding measurement information; fitting the virtual image distance and measurement information to obtain a virtual image distance measurement model.

[0014] According to the present invention, a virtual image distance measurement system is provided, wherein the displacement sensing module includes a grating ruler and a grating probe, and the image sensing module is a camera; the grating ruler body is disposed on the lens, and the grating probe is disposed at the lens mount of the camera, so as to use the pulse value output by the displacement sensing module as the measurement information of the back intercept.

[0015] According to the present invention, a virtual image distance measurement system is provided, wherein when the measurement information is a pulse value, the virtual image distance and the measurement information are fitted to obtain a virtual image distance measurement model, comprising: fitting the virtual image distance and the pulse value to obtain a corresponding relationship curve between the virtual image distance and the pulse value; and using the relationship curve as the virtual image distance measurement model.

[0016] According to the present invention, a virtual image distance measurement system is provided, in which a calibration plate is placed at a preset calibration distance, and test images of the calibration plate under different focusing states are obtained by adjusting the back focal length of the lens, including: setting the moving distance of the calibration plate; moving the calibration plate according to the moving distance, and obtaining test images of the calibration plate under different focusing states after each movement.

[0017] The virtual image distance measurement system provided by the present invention further includes: taking the image with the highest sharpness value as the image under a preset focus state.

[0018] Secondly, the present invention also provides a virtual image distance measurement method, which applies any of the virtual image distance measurement systems described above, and includes the following measurement steps: placing the device under test at a preset position in the optical path; controlling the drive module to adjust the back focal length of the lens; determining the projection image in the preset focal state as the target projection image from the measurement information received under different focal states and the corresponding projection images; wherein the preset focal state is determined according to the preset parameters of the projection image; inputting the measurement information corresponding to the target projection image as target measurement information into a pre-constructed virtual image distance measurement model to obtain the virtual image distance of the target projection image.

[0019] Thirdly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the virtual image distance measurement method as described above.

[0020] The virtual image distance measurement method and system provided by this invention have the following advantages compared with the prior art:

[0021] This invention avoids the backlash or hysteresis errors that often exist in traditional geared motor drive systems. By directly monitoring the actual displacement distance of the mirror assembly, these sources of mechanical error are bypassed. This method can provide higher measurement accuracy and improve the consistency and repeatability of measurement results.

[0022] This invention is applicable to a variety of AR / VR / MR products and lenses with different focusing methods, and has strong versatility. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the virtual image distance measurement system provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the calibration method provided by the present invention;

[0026] Figure 3 This is a schematic diagram illustrating the relationship between virtual image distance and pulse number provided by the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] It should be noted that in the description of the embodiments of the present invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The terms "upper," "lower," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more.

[0031] The following is combined with Figures 1-4 The present invention describes the virtual image distance measurement method and system provided in the embodiments of the present invention.

[0032] As an optional embodiment, the virtual image distance measurement system provided by the present invention includes: a displacement sensing module, a driving module, an image sensing module, and a calculation module;

[0033] The primary function of the displacement sensing module is to acquire measurement information of the lens's back focal length. Back focal length refers to the distance from the last optical surface of the lens to the focal point, and it is one of the key parameters determining the imaging position. In this system, the displacement sensing module may employ different types of sensor technologies, such as potentiometer-based, inductive-based, and Hall effect-based sensors, to ensure accurate capture of changes in lens position.

[0034] The drive module is responsible for adjusting the lens position, thereby changing its back focal length. This typically involves using a motor or other mechanical transmission device to precisely move the lens. By adjusting the lens position, the distance to the virtual image can be changed, allowing the projected image to form a sharp image at different distances.

[0035] The image sensing module is used to acquire projected images of the object under test under different focusing states of the lens; the image sensing module can be a camera or other imaging device; the object under test can be AR / VR / MR products, etc.

[0036] The calculation module, which is connected to the displacement sensing module, the driving module and the image sensing module, is used to determine the virtual image distance of the target projection image based on the pre-built virtual image distance measurement model and the target measurement information corresponding to the target projection image under the preset focus state.

[0037] The virtual image distance measurement model is established based on the measurement information of the preset calibration distance and the corresponding back intercept.

[0038] Based on the above embodiments, as an optional embodiment, the virtual image distance measurement system provided by the present invention determines the virtual image distance of the target projection image by using target measurement information corresponding to the target projection image under a preset focus state, according to a pre-constructed virtual image distance measurement model, including:

[0039] (1) Control the drive module to adjust the back focal length of the lens.

[0040] In practice, the system requires a control drive module to adjust the lens's back focal length. This is achieved by precisely moving the lens using a motor or other mechanical transmission device. Different back focal lengths result in images of varying sharpness on the imaging plane, making this process crucial for finding the optimal focus position.

[0041] (2) From the measurement information received under different focus states and the corresponding projected images, determine the projected image under the preset focus state as the target projected image; wherein, the preset focus state is determined according to the preset parameters of the projected image.

[0042] In practice, the system collects measurement information and corresponding projected images under different focus states. This data is used to analyze which projected image was obtained under the preset focus state, the so-called "target projected image." The preset focus state is usually defined based on specific image quality standards or parameters, such as image contrast, sharpness, or clarity. These parameters reflect whether the current focus is accurate, thus helping the system identify the sharpest image as the target projected image.

[0043] (3) The measurement information corresponding to the target projection image is used as the target measurement information and input into the pre-constructed virtual image distance measurement model to obtain the virtual image distance of the target projection image.

[0044] Once the target projection image and its corresponding measurement information (such as the lens's specific back clipping) are determined, this data will be input into a pre-built virtual image distance measurement model. This model is typically built based on a large amount of experimental data and theoretical calculations, and it can predict the actual virtual image distance of the target projection image based on the input data.

[0045] Finally, after processing by the above model, the system outputs the virtual image distance of the target projection image. This means that users can understand how far away the observed virtual image is actually located under specific focusing conditions.

[0046] The virtual image distance measurement system provided by this invention offers a systematic and automated method for measuring virtual image distance, which not only improves measurement accuracy but also enhances operational convenience and efficiency. Furthermore, due to the use of a pre-calibrated model, high measurement reliability and repeatability are ensured even in complex optical environments.

[0047] Based on the above embodiments, as an optional embodiment, the virtual image distance measurement system provided by the present invention includes a method for constructing a virtual image distance measurement model, comprising:

[0048] (1) Place the calibration plate at the preset calibration distance and obtain test images of the calibration plate under different focusing states by adjusting the back crop of the lens.

[0049] First, a calibration plate with known geometric characteristics is selected and placed at a predetermined distance (i.e., the preset calibration distance). This distance is pre-set to facilitate subsequent calculations and verification. Then, by adjusting the lens's back focal length, the system will capture test images of the calibration plate under different focus conditions.

[0050] Optionally, the movement interval of the calibration plate is set; the calibration plate is moved according to the movement interval, and test images of the calibration plate under different focus states are acquired after each movement. Specifically:

[0051] 1) Moving the calibration plate: Move the calibration plate sequentially according to the set moving interval. After each movement, the calibration plate will be at a new preset calibration distance.

[0052] 2) Adjusting the lens back focal length: For each new position, the focus is changed by adjusting the lens back focal length. This step aims to simulate different focus conditions in order to collect as many data points as possible for subsequent analysis.

[0053] 3) Acquire test images: Take test images of the calibration board at each position and with the corresponding focus state. These images will be used as raw data to construct the virtual image distance measurement model.

[0054] (2) From test images under different focusing states, determine the target test image under the preset focusing state and the corresponding back intercept measurement information.

[0055] Next, from these test images under different focus conditions, identify those that are in optimal focus. This typically involves analyzing image quality metrics such as edge sharpness and contrast. Optimal focus means the sharpest part of the image, where the lens's back focal length corresponds to the position closest to the ideal focus.

[0056] (3) Obtain multiple sets of different preset calibration distances and corresponding measurement information, fit the virtual image distance and measurement information to obtain a virtual image distance measurement model.

[0057] Finally, multiple sets of different preset calibration distances and corresponding back intercept measurement information are collected. Using these data for fitting, a mathematical model describing the relationship between virtual image distance and measurement information can be obtained. This fitting process can employ linear regression, nonlinear regression, or other statistical methods, as well as intelligent learning methods. With such a model, unknown virtual image distances can be predicted based on new measurement information.

[0058] Optionally, the present invention uses the image with the highest sharpness value as the image under a preset focus state.

[0059] This invention provides a reliable model based on experimental data, which can maintain high measurement accuracy even in complex optical environments and has strong applicability.

[0060] Figure 1 This is a schematic diagram of the virtual image distance measurement system provided by the present invention, as shown below. Figure 1As shown, the displacement sensing module includes a grating ruler and a grating probe. The grating ruler can be directly mounted on the movable part of the lens to monitor the physical displacement of the lens back intercept in real time. The grating probe (connected to the camera in the figure) is fixed at the camera lens mount and generates a pulse signal by scanning the grating ruler, converting the mechanical displacement into a high-precision digital pulse value.

[0061] The "camera lens mount" can be understood as the location where the camera lens is installed (connected).

[0062] The drive module (displacement motor) is connected to the lens via a mechanical transmission mechanism (not detailed in the figure) and executes instructions from the calculation module to fine-tune the lens back focal length.

[0063] The image sensing module (camera) acquires projected images of the object under test under different lens focusing states (controlled by the drive module).

[0064] The calculation module (computing unit) receives the pulse signal (back intercept measurement value) from the grating probe and the image data from the camera, and runs the virtual image distance measurement model.

[0065] When the measurement information is a pulse value, the virtual image distance and the measurement information are fitted to obtain a virtual image distance measurement model, including:

[0066] (1) Fit the virtual image distance and pulse value to obtain the curve of the correspondence between the virtual image distance and the pulse value.

[0067] The goal of fitting is to find a function or curve that can describe the relationship between the two. Specifically, linear regression, multinomial regression, or other models can be chosen for fitting depending on the characteristics of the data.

[0068] (2) Use the relationship curve as the virtual image distance measurement model.

[0069] To improve the practicality and accuracy of the model, it can be validated and optimized. For example, the model's performance can be evaluated using techniques such as cross-validation, and the model parameters can be adjusted according to the actual situation.

[0070] Figure 2 This is a schematic diagram of the calibration method provided by the present invention. The following is in conjunction with the attached diagram. Figure 2 Explanation:

[0071] A physical target plate is placed at the first working distance (preset calibration distance), such as 300mm. Then, the motor is adjusted to adjust the lens, while the image sensor captures images to determine the focus status or focus value. When the optimal focus is achieved, the motor rotation is stopped, and the first pulse value measured by the displacement sensing module at this moment is recorded (hereinafter, pulse values ​​will be used to describe this). This gives the correspondence between the first pulse count and the 300mm working distance.

[0072] Move the target plate to the 500mm position, repeat the previous step, and record the second pulse value measured by the displacement sensing module at this time. The number of second pulses corresponds to the 500mm working distance.

[0073] Repeat the above steps, increasing the distance to the target plate sequentially. Record the pulse value at each position when the lens is in optimal focus.

[0074] This allows us to obtain a curve showing the correspondence between pulse value (pulse number) and virtual image, such as... Figure 3 As shown, Figure 3 This is a schematic diagram illustrating the relationship between virtual image distance and pulse number provided by the present invention.

[0075] The denser the target plate movement spacing, the higher its accuracy. Furthermore, the pulse value-virtual image distance variation curve for discrete points can be obtained by fitting a limited number of movement positions.

[0076] The present invention also provides a virtual image distance measurement method, which is applied to any of the above-mentioned virtual image distance measurement systems, including calibration steps and measurement steps, which are described in detail below.

[0077] The calibration steps include:

[0078] (1) Place the calibration plate at the preset calibration distance and obtain test images of the calibration plate under different focusing states by adjusting the back focal length of the lens;

[0079] (2) From test images under different focusing states, determine the target test image under the preset focusing state and the corresponding back intercept measurement information;

[0080] (3) Obtain multiple sets of different preset calibration distances and corresponding measurement information, fit the virtual image distance and measurement information to obtain a virtual image distance measurement model.

[0081] The measurement steps include:

[0082] (1) Place the device under test at the preset position in the optical path;

[0083] (2) Control the drive module to adjust the back focal length of the lens;

[0084] (3) From the measurement information received under different focus states and the corresponding projected images, determine the projected image under the preset focus state as the target projected image; wherein, the preset focus state is determined according to the preset parameters of the projected image.

[0085] (4) The measurement information corresponding to the target projection image is used as the target measurement information and input into the pre-constructed virtual image distance measurement model to obtain the virtual image distance of the target projection image.

[0086] Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention, such as... Figure 4 As shown, the electronic device may include a processor 410, a communication interface 420, a memory 430, and a communication bus 440. The processor 410, communication interface 420, and memory 430 communicate with each other via the communication bus 440. The processor 410 can call logical instructions from the memory 430 to execute a virtual image distance measurement method.

[0087] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the virtual image distance measurement method provided in the above embodiments.

[0088] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0089] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A virtual image distance measurement system, characterized in that, include: The displacement sensing module is used to acquire measurement information of the lens back focal length; The drive module is used to adjust the back focal length of the lens; The image sensing module is used to acquire projected images of the object under test under different focusing states of the lens; The calculation module, which is connected to the displacement sensing module, the driving module and the image sensing module, is used to determine the virtual image distance of the target projection image based on the pre-built virtual image distance measurement model and the target measurement information corresponding to the target projection image under the preset focus state. Among them, the virtual image distance measurement model is established based on the measurement information of the preset calibration distance and the corresponding back intercept; The methods for constructing a virtual image distance measurement model include: Place the calibration board at the preset calibration distance, and obtain test images of the calibration board under different focus states by adjusting the back crop of the lens; From test images under different focusing states, determine the target test image under the preset focusing state and the corresponding back intercept measurement information; Multiple sets of different preset calibration distances and corresponding measurement information are obtained, and the virtual image distance and measurement information are fitted to obtain a virtual image distance measurement model.

2. The virtual image distance measurement system according to claim 1, characterized in that, Based on a pre-built virtual image distance measurement model, the virtual image distance of the target projection image is determined using target measurement information corresponding to the target projection image under a preset focus state, including: The control drive module adjusts the back focal length of the lens; From the measurement information received under different focus states and the corresponding projected images, the projected image under the preset focus state is determined as the target projected image; wherein, the preset focus state is determined based on the preset parameters of the projected image; The measurement information corresponding to the target projection image is used as the target measurement information and input into the pre-built virtual image distance measurement model to obtain the virtual image distance of the target projection image.

3. The virtual image distance measurement system according to claim 1, characterized in that, The displacement sensing module includes a grating ruler and a grating probe, and the image sensing module is a camera; The grating ruler body is mounted on the lens, and the grating probe is mounted at the camera lens mount, so that the pulse value output by the displacement sensing module is used as the measurement information of the back intercept.

4. The virtual image distance measurement system according to claim 1, characterized in that, When the measurement information is a pulse value, the virtual image distance and the measurement information are fitted to obtain a virtual image distance measurement model, including: By fitting the virtual image distance and the pulse value, a curve showing the correspondence between the virtual image distance and the pulse value is obtained; The relationship curve is used as the virtual image distance measurement model.

5. The virtual image distance measurement system according to claim 1, characterized in that, Place the calibration board at a preset calibration distance, and obtain test images of the calibration board under different focus conditions by adjusting the back crop of the lens, including: Set the movement distance of the calibration plate; The calibration board is moved according to the moving interval, and test images of the calibration board under different focus states are obtained after each movement.

6. The virtual image distance measurement system according to claim 1, characterized in that, Also includes: The image with the highest sharpness value is selected as the image under the preset focus state.

7. A method for measuring virtual image distance, characterized in that, The virtual image distance measurement system as described in any one of claims 1 to 6 includes the following measurement steps: Place the device under test at the preset position in the optical path; The control drive module adjusts the back focal length of the lens; From the measurement information received under different focus states and the corresponding projected images, the projected image under the preset focus state is determined as the target projected image; wherein, the preset focus state is determined based on the preset parameters of the projected image; The measurement information corresponding to the target projection image is used as the target measurement information and input into the pre-built virtual image distance measurement model to obtain the virtual image distance of the target projection image.

8. The virtual image distance measurement method according to claim 7, characterized in that, Including calibration steps: Place the calibration board at the preset calibration distance, and obtain test images of the calibration board under different focus states by adjusting the back crop of the lens; From test images under different focusing states, determine the target test image under the preset focusing state and the corresponding back intercept measurement information; Multiple sets of different preset calibration distances and corresponding measurement information are obtained, and the virtual image distance and measurement information are fitted to obtain a virtual image distance measurement model.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the virtual image distance measurement method as described in any one of claims 7 to 8.

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