Virtual image distance measurement method and system

Abstract

The invention provides a virtual image distance measurement method and system, and belongs to the technical field of near-to-eye display equipment, and the system comprises a displacement sensing module which is used for obtaining the measurement information of the rear intercept of a lens; the driving module is used for adjusting the rear intercept of the lens; the image sensing module is used for collecting projection images generated by the to-be-detected object in different focusing states of the lens; the calculation module is in signal connection with the displacement sensing module, the driving module and the image sensing module, and is used for determining the virtual image distance of the target projection image by utilizing target measurement information corresponding to the target projection image in a preset focusing state according to a pre-constructed virtual image distance measurement model; wherein the virtual image distance measurement model is established according to the preset calibration distance and the measurement information of the corresponding back intercept. According to the invention, higher measurement precision can be provided, the consistency and repeatability of the measurement result are improved, and the method has strong versatility.

Description

Technical Field

[0001] The present invention relates to the technical field of near-eye display devices, and in particular to a virtual image distance measurement method and system. Background Art

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

[0003] Virtual reality uses projection technology to project virtual images within a certain distance of the user's eyes. Depending on the application scenario, lens characteristics are adjusted to achieve different projection distances. Therefore, the projected virtual image distance is a crucial metric for AR / VR / MR products.

[0004] However, existing virtual image distance measurement solutions have the disadvantages of poor measurement accuracy and poor measurement repeatability. Summary of the Invention

[0005] The present invention provides a virtual image distance measurement method and system, which are used 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] A displacement sensing module is used to obtain measurement information of the back focus of the lens;

[0008] A driving module, used to adjust the back focus of the lens;

[0009] An image sensing module is used to collect projection images of the object to be measured under different focus states of the lens;

[0010] a calculation module, signal-connected to the displacement sensing module, the driving module, and the image sensing module, for determining the virtual image distance of the target projection image based on a pre-established virtual image distance measurement model and using target measurement information corresponding to the target projection image in a 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 is provided. Based on a pre-constructed 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 in a preset focus state. The system includes: controlling a drive module to adjust the back focus distance of a lens; determining, from received measurement information under different focus states and corresponding projection images, a projection image in a preset focus state as a target projection image; 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, and obtaining test images of the calibration plate in different focus states by adjusting the back focus distance of a lens; determining, from the test images in different focus states, a target test image in a preset focus state and corresponding back focus distance measurement information; obtaining multiple sets of different preset calibration distances and corresponding measurement information, and fitting the virtual image distances and the measurement information to obtain a virtual image distance measurement model.

[0014] According to a virtual image distance measurement system provided by the present invention, 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 set on the lens, and the grating probe is set 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.

[0015] According to a virtual image distance measurement system provided by the present invention, 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: 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 a virtual image distance measurement system provided by the present invention, a calibration plate is placed at a preset calibration distance, and test images of the calibration plate in different focus states are obtained by adjusting the back focus distance of the lens. The system includes: setting a movement spacing of the calibration plate; moving the calibration plate according to the movement spacing, and obtaining test images of the calibration plate in different focus states after each movement.

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

[0018] In a second aspect, the present invention also provides a virtual image distance measurement method, which uses any of the above-mentioned virtual image distance measurement systems, including the following measurement steps: placing the device to be measured at a preset position in the optical path; controlling the drive module to adjust the back focus of the lens; determining the projection image in a preset focus state as the target projection image from the received measurement information under different focus states and the 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 a pre-constructed virtual image distance measurement model to obtain the virtual image distance of the target projection image.

[0019] In a third aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the above-described virtual image distance measurement methods.

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

[0021] The present invention avoids the problems of backlash or return errors often present in traditional gear motor drive systems. By directly monitoring the actual displacement distance of the mirror group, these mechanical error sources are bypassed. This method can provide higher measurement accuracy and improve the consistency and repeatability of the measurement results.

[0022] The present invention can be applied to a variety of AR / VR / MR products and lenses with different focusing methods, and has strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

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

[0026] Figure 3 Schematic diagram of the corresponding relationship between virtual image distance and pulse number provided by the present invention;

[0027] Figure 4 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0029] It should be noted that in the description of the embodiments of the present invention, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "comprises a..." does not preclude the presence of additional identical elements in the process, method, article, or device comprising the element. The terms "upper," "lower," and the like, used to indicate orientations or positional relationships based on those shown in the accompanying drawings, are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the system or element referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be broadly construed, for example, to mean a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or internal communication between two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] The terms "first," "second," and the like in this application are used to distinguish similar objects, and are not used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in orders other than those illustrated or described herein. Furthermore, the objects distinguished by "first," "second," and the like generally refer to a class of objects and do not limit the number of objects. For example, the first object may be one or more.

[0031] The following combination Figure 1-Figure 4 The virtual image distance measurement method and system provided by the embodiments of the present invention are described.

[0032] As an optional embodiment, the present invention provides a virtual image distance measurement system, which 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 obtain information on the back focus of the lens. Back focus refers to the distance from the last optical surface of the lens to the focal point and is a key parameter that determines the image position. In this system, the displacement sensing module may use different types of sensor technologies, such as potentiometers, inductors, and Hall effect sensors, to ensure accurate capture of changes in lens position.

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

[0035] The image sensing module is used to capture the projection images generated by the object to be measured under different focus states of the lens; the image sensing module can be a camera or other imaging device; the object to be measured can be an AR / VR / MR product.

[0036] a calculation module, signal-connected to the displacement sensing module, the driving module, and the image sensing module, for determining the virtual image distance of the target projection image based on a pre-established virtual image distance measurement model and using target measurement information corresponding to the target projection image in a 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 contents of the above embodiments, as an optional embodiment, the present invention provides a virtual image distance measurement system, which determines the virtual image distance of a target projection image based on a pre-established virtual image distance measurement model and using target measurement information corresponding to the target projection image in a preset focus state, including:

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

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

[0041] (2) Determine a projection image in a preset focus state as a target projection image from the received measurement information in different focus states and the corresponding projection images; wherein the preset focus state is determined according to preset parameters of the projection image.

[0042] In practice, the system collects measurement information and corresponding projected images at different focus states. This data is used to analyze which projected image was obtained at a preset focus state, known as the "target projected image." Preset focus states are typically defined based on specific image quality criteria or parameters, such as contrast, sharpness, or clarity. These parameters indicate whether the current focus is accurate, 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-built 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 specific back focus distance of the lens) are determined, this data is input into a pre-built virtual image distance measurement model. This model is usually built based on a large amount of experimental data and theoretical calculations. It can predict the actual virtual image distance of the target projection image based on the input data.

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

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

[0047] Based on the contents of the above embodiment, as an optional embodiment, the present invention provides a virtual image distance measurement system and a method for constructing a virtual image distance measurement model, including:

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

[0049] First, a calibration target with known geometric characteristics is selected and placed at a predetermined distance (the preset calibration distance). This distance is pre-set to facilitate subsequent calculations and verification. Then, by adjusting the back focus distance of the lens, the system captures test images on the calibration target at different focus states.

[0050] Optionally, a moving distance of the calibration plate is set; the calibration plate is moved according to the moving distance, and test images of the calibration plate in different focus states after each movement are obtained. Specifically:

[0051] 1) Move the calibration plate: Move the calibration plate one by one according to the set moving distance. After each move, the calibration plate will be at a new preset calibration distance.

[0052] 2) Adjust the lens back focus: For each new position, adjust the lens back focus to change the focus state. This step is intended to simulate different focus conditions in order to collect as many data points as possible for subsequent analysis.

[0053] 3) Acquire test images: Capture test images of the calibration plate at each position and corresponding focus state. These images will serve as raw data for constructing the virtual image distance measurement model.

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

[0055] Next, from these test images at different focus states, identify those that are in optimal focus. This typically involves analyzing image quality metrics such as edge sharpness and contrast. The optimal focus state is defined as the sharpest portion of the image, where the lens' back focus corresponds to the position closest to ideal focus.

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

[0057] Finally, multiple sets of preset calibration distances and corresponding back intercept measurements are collected. Using this data, a fitting process can be performed to develop a mathematical model describing the relationship between virtual image distance and measurement information. 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 largest sharpness value as the image in a preset focus state.

[0059] The present 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 Schematic diagram of the structure of the virtual image distance measurement system provided by the present invention. Figure 1As shown in the figure, the displacement sensing module includes a grating scale and a grating probe. The grating scale body can be directly installed on the movable part of the lens to monitor the physical displacement of the lens back focus in real time. The grating probe (connected to the camera in the figure) is fixed on the camera lens mount and generates a pulse signal by scanning the grating scale, thereby converting the mechanical displacement into a high-precision digital pulse value.

[0061] The camera lens mount can be understood as the installation (connection) position of the camera lens.

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

[0063] The image sensing module (camera) collects the projection image of the object to be measured under different focus states of the lens (controlled by the driving module).

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

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

[0066] (1) Fit the virtual image distance and pulse value to obtain the corresponding relationship curve 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, polynomial regression and other models can be selected for fitting based on the characteristics of the data.

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

[0069] In order to improve the practicality and accuracy of the model, it can also be verified and optimized, such as evaluating the performance of the model through techniques such as cross-validation, and adjusting the model parameters according to actual conditions.

[0070] Figure 2 This is a schematic diagram of the calibration method provided by the present invention. Figure 2 To explain:

[0071] The physical target plate is placed at a first working distance (preset calibration distance), such as 300mm. The motor is then adjusted to adjust the lens while the image sensor captures the image and determines the image's focus state, or focus value. When the image reaches the optimal focus state, the motor is stopped and the first pulse value (hereinafter referred to as pulse value) measured by the displacement sensor module is recorded. This indicates the correspondence between the first pulse number and the 300mm working distance.

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

[0073] Repeat the above steps, increasing the distance between the target plate and the lens. Record the pulse value at each position when the lens is in the most focused state.

[0074] Thus, a curve of the corresponding relationship between the pulse value (pulse number) and the virtual image can be obtained, such as Figure 3 As shown, Figure 3 It is a schematic diagram of the corresponding relationship between the virtual image distance and the pulse number provided by the present invention.

[0075] The closer the target plate moves, the higher its accuracy. At the same time, the pulse value-virtual image distance variation curve of discrete points can be fitted through limited movement positions.

[0076] The present invention also provides a virtual image distance measurement method, which is applied to any of the above virtual image distance measurement systems and includes a calibration step and a measurement step, which are described one by one below.

[0077] The calibration steps include:

[0078] (1) Place the calibration plate at a preset calibration distance and obtain test images of the calibration plate in different focus states by adjusting the back focus distance of the lens;

[0079] (2) determining, from the test images in different focus states, a target test image in a preset focus state and corresponding back intercept measurement information;

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

[0081] The measurement steps include:

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

[0083] (2) controlling the drive module to adjust the back focus of the lens;

[0084] (3) determining, from the received measurement information under different focus states and the corresponding projection images, a projection image in a preset focus state as a target projection image; wherein the preset focus state is determined based on preset parameters of the projection image;

[0085] (4) 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.

[0086] Figure 4 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, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other via the communication bus 440. The processor 410 may call logic instructions in the memory 430 to execute the virtual image distance measurement method.

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

[0088] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units. They may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0089] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A virtual image distance measurement system, characterized in that: include: A displacement sensing module is used to obtain measurement information of the back focus of the lens; A driving module, used to adjust the back focus of the lens; An image sensing module is used to collect projection images of the object to be measured under different focus states of the lens; a calculation module, signal-connected to the displacement sensing module, the driving module, and the image sensing module, for determining the virtual image distance of the target projection image based on a pre-established virtual image distance measurement model and using target measurement information corresponding to the target projection image in a preset focus state; The virtual image distance measurement model is established based on the measurement information of the preset calibration distance and the corresponding back intercept.

2. The virtual image distance measurement system according to claim 1, characterized in that: According to a pre-built virtual image distance measurement model, the virtual image distance of the target projection image is determined by using target measurement information corresponding to the target projection image in a preset focus state, including: Control the drive module to adjust the back focus of the lens; Determining, from the received measurement information under different focus states and the corresponding projection images, a projection image in a preset focus state as a target projection image; wherein the preset focus state is determined based on preset parameters of the projection image; The measurement information corresponding to the target projection image is used as target measurement information and input into a 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 method for constructing a virtual image distance measurement model includes: Place the calibration plate at a preset calibration distance, and obtain test images of the calibration plate in different focus states by adjusting the back focus distance of the lens; Determining, from the test images in different focus states, a target test image in a preset focus state and corresponding back intercept measurement information; A plurality of different sets of preset calibration distances and corresponding measurement information are obtained, and the virtual image distance and the measurement information are fitted to obtain a virtual image distance measurement model.

4. The virtual image distance measurement system according to claim 1, 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 set on the lens, and the grating probe is set 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.

5. The virtual image distance measurement system according to claim 3, characterized in that: When the measurement information is a pulse value, fitting the virtual image distance and the measurement information to obtain a virtual image distance measurement model includes: Fitting the virtual image distance and the pulse value to obtain a corresponding relationship curve between the virtual image distance and the pulse value; The relationship curve is used as the virtual image distance measurement model.

6. The virtual image distance measurement system according to claim 3, characterized in that: Place the calibration plate at the preset calibration distance and adjust the back focus distance of the lens to obtain test images of the calibration plate in different focus states, including: Set the moving distance of the calibration plate; Move the calibration plate according to the moving distance, and obtain test images of the calibration plate in different focus states after each movement.

7. The virtual image distance measurement system according to claim 1, wherein: Also includes: The image with the largest sharpness value is regarded as the image in the preset focus state.

8. A method for measuring virtual image distance, characterized in that: The virtual image distance measurement system according to any one of claims 1 to 7 is used, comprising the steps of: Place the device under test at a preset position in the optical path; Control the drive module to adjust the back focus of the lens; Determining, from the received measurement information under different focus states and the corresponding projection images, a projection image in a preset focus state as a target projection image; wherein the preset focus state is determined based on preset parameters of the projection image; The measurement information corresponding to the target projection image is used as target measurement information and input into a pre-built virtual image distance measurement model to obtain the virtual image distance of the target projection image.

9. The method for measuring virtual image distance according to claim 8, wherein: The calibration steps include: Place the calibration plate at a preset calibration distance, and obtain test images of the calibration plate in different focus states by adjusting the back focus distance of the lens; Determining, from the test images in different focus states, a target test image in a preset focus state and corresponding back intercept measurement information; A plurality of different sets of preset calibration distances and corresponding measurement information are obtained, and the virtual image distance and the measurement information are fitted to obtain a virtual image distance measurement model.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the virtual image distance measurement method according to any one of claims 8 to 9 are implemented.

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