Three-dimensional topography measurement method and system based on high-speed phase shift method

Abstract

The application discloses a three-dimensional topography measurement method and system based on a high-speed phase shift method, projects all fringe images to a measured target surface in sequence, acquires at least one group of phase shift fringe images modulated on the measured target surface, divides the phase shift fringe images into multiple groups according to phase difference values, determines the cut-off phase of each group of phase shift fringe images, eliminates errors, and then performs fusion to obtain fused cut-off phase, and adopts a phase unwrapping method to perform phase unwrapping on the fused cut-off phase to obtain unwrapped phase of the measured target outer contour information.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional measurement of industrial environments, specifically to a three-dimensional topography measurement method and system based on the high-speed phase-shifting method. Background Technology

[0002] With the continuous upgrading of processing technology, the processing efficiency of industrial products is also constantly improving. Existing line laser 3D scanning and traditional phase-shifting methods both suffer from low detection efficiency. Line laser scanning can only calculate the 3D coordinates of all points on the laser line at a time, requiring continuous laser movement until the entire measurement area is scanned before 3D reconstruction can be completed. While traditional phase-shifting methods can project multiple phase-shifted fringe images onto the measurement area, and after capturing all fringe images, calculate the unfolded phase of a region including the target's outer contour using phase unfolding, the algorithm is complex and computationally intensive, still failing to achieve efficient 3D topography measurement.

[0003] Therefore, to address the above issues, it is necessary to design a high-speed phase-shifting method for measuring the three-dimensional shape of workpieces, so as to achieve accurate and rapid measurement of products. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a three-dimensional topography measurement method and system based on the high-speed phase-shifting method, enabling efficient and accurate measurement of products.

[0005] This invention is achieved through the following technical solution:

[0006] A three-dimensional topography measurement method based on high-speed phase shift method includes the following steps:

[0007] Acquire at least one set of phase-shifted fringe images projected onto the surface of the target object;

[0008] The phase-shifted fringe images are divided into multiple groups based on the phase difference value. The truncated phase of each group of phase-shifted fringe images is determined and the error is eliminated before fusion to obtain the fused truncated phase.

[0009] The phase unfolding method is used to unfold the fused truncated phase to obtain the unfolded phase of the outer contour information of the target under test.

[0010] In a further preferred embodiment, the phase difference between two adjacent phase-shifted fringe images in each group is π / 2, and the phase-shifted fringe images in each group are represented as [I n ,I n+π / 2 ,I n+π ,I n+3×π / 2 ].

[0011] A further preferred embodiment is the method for calculating the truncated phase, as follows:

[0012]

[0013] A further preferred embodiment is the fusion method for the truncated phases, as follows:

[0014] Calculate the phase difference between each group of truncated phases and the last group of truncated phases. Based on the phase difference, compensate all truncated phases to the same initial phase and then fuse them to obtain the fused truncated phases.

[0015] A further preferred embodiment is the expression for the fused truncated phase, as follows:

[0016]

[0017] in, For phase difference, The truncated phase after fusion The truncated phase after eliminating errors.

[0018] To further optimize the scheme, the complementary Gray code phase expansion method is used to expand the fused truncated phase to obtain the expanded phase of the outer contour information of the target under test.

[0019] A further preferred embodiment is the complementary Gray code phase expansion method as follows:

[0020] The Gray code series phases are obtained from the Gray code encoded fringe image projected onto the surface of the target under test, and another set of Gray code series phases is generated by combining the mapping method. At the same time, a set of complementary Gray code series phases is generated.

[0021] The fused truncated phase is expanded using another set of Gray code series phases and complementary Gray code series phases generated by mapping to obtain the expanded phase containing the outer contour information of the measured target.

[0022] Further optimization of the scheme involves using the three-frequency heterodyne phase expansion method to expand the phase of the fused truncated phase of multiple sets of phase-shifted fringe images at different frequencies, thereby obtaining the expanded phase containing the outer contour information of the target under test.

[0023] To further optimize the scheme, the phase derivative variance phase expansion method is used to expand the fused truncated phase to obtain the expanded phase containing the outer contour information of the measured target.

[0024] This invention also provides a three-dimensional topography measurement system based on the high-speed phase-shifting method, comprising:

[0025] The acquisition module is used to acquire stripe images projected onto the surface of the target being measured;

[0026] The fusion module is used to divide the phase-shifted fringe image into multiple groups based on the phase difference value, determine the truncated phase of each group of phase-shifted fringe images, eliminate errors, and then fuse them to obtain the fused truncated phase.

[0027] The phase unwrapping module is used to unwrap the fused truncated phase using the phase unwrapping method to obtain the unwrapped phase of the outer contour information of the target under test.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] The three-dimensional topography measurement method based on the high-speed phase-shifting method provided by this invention groups the projected phase-shifting fringe images according to the phase difference value, calculates the truncated phase of each group of phase-shifting fringe images, fuses all the truncated phases, and then uses the phase unfolding method to unfold the fused truncated phases to obtain the final unfolded phase containing the outer contour of the target. This method reduces the amount of computation by grouping the phase-shifting fringe images, thus improving the computational efficiency. Under the premise of the same projected image and the same detection accuracy, the detection efficiency is improved by about 15% compared with the traditional phase-shifting method. Attached Figure Description

[0030] Figure 1 This is a flowchart of the three-dimensional topography measurement method of the present invention;

[0031] Figure 2 This is a flowchart of the three-dimensional topography measurement method of Embodiment 1 of the present invention;

[0032] Figure 3 This is a hardware structure diagram of the three-dimensional topography measurement method of the present invention;

[0033] Figure 4 This is a rendering of the three-dimensional topography measurement method based on the high-speed phase-shifting method of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0035] See Figure 1 A three-dimensional topography measurement method based on high-speed phase shift method is proposed. The method acquires at least one set of phase shift fringe images projected onto the surface of the target under test; divides the phase shift fringe images into multiple groups according to the phase difference value, determines the truncated phase of each group of phase shift fringe images, and fuses them after eliminating errors to obtain the fused truncated phase; and uses the phase unfolding method to unfold the fused truncated phase to obtain the unfolded phase of the outer contour information of the target under test.

[0036] The following section provides a detailed explanation of this three-dimensional topography measurement method based on the high-speed phase shift method, employing various phase expansion techniques.

[0037] Example 1

[0038] See Figure 2 , one A three-dimensional topography measurement method based on high-speed phase shifting includes the following steps:

[0039] Step 1: Obtain the stripe image projected onto the surface of the target being tested.

[0040] See Figure 3 A DLP projector is used to sequentially project all fringe images onto the surface of the target object. The fringe images include phase-shifted fringe images and Gray code-encoded fringe images. Then, an industrial camera is used to sequentially acquire the modulated phase-shifted fringe images I1~I2 of the target surface. N Gray code encoded stripe image

[0041] Step 2: Based on the set phase difference, the phase-shifted fringe images I1 to I2 are... N Divided into N / 4 groups, where N is an integer multiple of 4, the phase difference between two adjacent phase-shifted fringe images in each group is π / 2.

[0042] Each group of phase-shifted fringe images is represented as [I] n ,I n+π / 2 ,I n+π ,I n+3×π / 2 ].

[0043] Step 3: Determine the cutoff phase corresponding to each group of phase-shifted fringe images using the phase-shifting method. The calculation method is as follows:

[0044] Substitute each group of images into formula (1) according to their numbers to obtain the truncated phase of each group of moving stripe images.

[0045]

[0046] Step 4: To avoid introducing additional errors, the truncated phase needs to be processed to obtain the processed truncated phase. The solution is as follows:

[0047] Substituting each group of truncated phases into formula (2) yields .

[0048]

[0049] Step 5: Fuse all the processed truncated phases to obtain the fused truncated phase.

[0050] Since there is a phase difference between each truncated phase obtained from each set of phase-shifted fringe images, it is necessary to calculate... and The phase difference is added during the truncated phase fusion process to compensate all truncated phases to the same initial phase. The fusion method is as follows:

[0051]

[0052] in, for and The phase difference.

[0053] Step 6: Encode the stripe image using Gray code. The conversion yields the Gray code series phase Ge. M Its expression is as follows:

[0054]

[0055] Step 7: Generate Gray code series phase Ge using a mapping method. M The corresponding other set of Gray code series phase Ge M-1 Simultaneously, a set of complementary Gray code series phases is generated based on the Gray code series phases.

[0056] Specifically, Gray code series phase Ge M Since it cannot be directly used for phase expansion, a mapping relationship is used to generate another set of Gray code series phases Ge. M-1 The method is as follows:

[0057]

[0058] According to the phase of the Gray code series Ge M Generate a set of complementary Gray code series phases The method is as follows:

[0059]

[0060] Step 8: Perform phase expansion on the fused truncated phase using another set of Gray code series phases and complementary Gray code series phases generated by mapping, to obtain the expanded phase corresponding to the truncated phase, and determine the three-dimensional shape of the target based on the expanded phase.

[0061] Specifically, the phase will be truncated. Gray code series phase Ge M-1 and Substituting into formula (7), we obtain the unfolded phase ψ of the target under test.

[0062] The method for calculating the unfolded phase of the target under test is as follows:

[0063]

[0064] See Figure 4 The image shows a simulation of the three-dimensional topography measurement method based on the high-speed phase-shifting method provided by this invention. The simulation shows that this invention can obtain the unfolded phase of the target being measured. Moreover, by using the high-speed phase-shifting method provided by this invention, the detection efficiency is improved by about 15% compared with the traditional phase-shifting method under the premise of the same projected image and the same detection accuracy, which greatly improves the practicality of the phase-shifting method.

[0065] Example 2

[0066] The present invention relates to a three-dimensional topography measurement method based on the high-speed phase-shifting method in Embodiment 1, and also provides a three-dimensional topography measurement system based on the high-speed phase-shifting method, including an acquisition module, a fusion module, a Gray code phase module and a phase unrolling module;

[0067] The acquisition module is used to acquire phase-shifted fringe images and Gray code-coded fringe images projected onto the surface of the target under test.

[0068] The fusion module is used to divide the phase-shifted fringe image into multiple groups based on the phase difference value, determine the truncated phase of each group of phase-shifted fringe images, eliminate errors, and then fuse them to obtain the fused truncated phase.

[0069] The Gray code phase module is used to generate another set of Gray code series phases based on the Gray code series phases of the Gray code encoded stripe image and a mapping method, while simultaneously generating a set of complementary Gray code series phases.

[0070] The phase expansion module is used to expand the fused truncated phase using another set of Gray code series phases and complementary Gray code series phases generated by mapping, so as to obtain the expanded phase corresponding to the truncated phase.

[0071] Example 3

[0072] A three-dimensional topography measurement method based on high-speed phase shift method includes the following steps:

[0073] Step 1: Obtain three sets of stripe phase-shift images of different frequencies projected onto the surface of the target object.

[0074] The frequency of three different frequencies is 1 after being superimposed using the superposition principle.

[0075] Step 2: Based on the set phase difference, generate each group of phase-shifted fringe images I1~I N The images are divided into N / 4 groups, and the phase difference between two adjacent phase-shifted fringe images in each group is π / 2.

[0076] Step 3: Determine the truncation phase corresponding to each image group according to the phase shift method.

[0077] Step 4: In order not to introduce additional errors, the errors of the truncation phase corresponding to each image are eliminated to obtain the processed truncation phase.

[0078] Step 5: Fuse the truncated phases of each image group in the same stripe phase-shifted image group after processing to obtain the fused truncated phases of each group.

[0079] Step 6: Using the superposition principle and heterodyne principle, calculate the phase difference of the unit phase and the three different frequency phases for the three fused truncated phases respectively. Calculate the period number k of the principal phase value based on the phase difference and the unit phase. Recover the unfolded phase of the truncated phase calculated from the highest frequency fringe phase-shift image based on the period number k. Determine the three-dimensional shape of the target based on the unfolded phase.

[0080] It should be noted that the calculation methods of steps 1-5 in this embodiment 3 are the same as those in embodiment 1. The difference is that it requires the fusion of three sets of stripe phase-shifted images of different frequencies and the truncated phase. The calculation method of each set of fused truncated phases is the same as that in embodiment 1. In this embodiment 3, the three fused truncated phases are combined with the three-frequency heterodyne phase expansion method to expand the phase and obtain the expanded phase.

[0081] Example 4

[0082] A three-dimensional topography measurement method based on high-speed phase shifting is disclosed. The method in this embodiment differs from steps 1-5 of the measurement method in Embodiment 1, specifically in that the truncated phase after fusion is expanded using the phase derivative variance phase expansion method, as detailed below:

[0083] Phase points whose derivative variance of the truncated phase after fusion is greater than a threshold are obtained. Then, phase compensation is performed on these phase points to make them continuous with adjacent phase points. The unfolded phase of the target under test is quickly obtained based on all the compensated phase points. The three-dimensional shape of the target under test is determined based on the unfolded phase of the target under test.

[0084] The present invention also provides a three-dimensional topography measurement system based on the high-speed phase shift method, including an acquisition module, a fusion module and a phase unfolding module;

[0085] The acquisition module is used to acquire stripe images and Gray code-encoded stripe images projected onto the surface of the target being measured.

[0086] The fusion module is used to divide the phase-shifted fringe image into multiple groups based on the phase difference value, determine the truncated phase of each group of phase-shifted fringe images, eliminate errors, and then fuse them to obtain the fused truncated phase.

[0087] The phase unwrapping module is used to unwrap the fused truncated phase using the phase unwrapping method to obtain the unwrapped phase containing the outer contour information of the target being measured.

[0088] The module division in this embodiment of the invention is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in the various embodiments of the invention can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0089] In another embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used for the operation of a complex environment three-dimensional topography measurement method based on high-speed phase-shifting method.

[0090] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the complex environment three-dimensional topography measurement method based on the high-speed phase-shifting method in the above embodiments.

[0091] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0092] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A three-dimensional topography measurement method based on high-speed phase shifting, characterized in that, Includes the following steps: Acquire at least one set of phase-shifted fringe images projected onto the surface of the target object; The phase-shifted fringe images are divided into multiple groups based on the phase difference value. The truncated phase of each group of phase-shifted fringe images is determined and the error is eliminated before fusion to obtain the fused truncated phase. The phase difference between two adjacent phase-shifted fringe images in each group is The phase-shifted fringe images in each group are represented as follows: ; The method for calculating the truncated phase is as follows: The method for fusing the truncated phases is as follows: Calculate the phase difference between each group of truncated phases and the last group of truncated phases. Compensate all truncated phases to the same initial phase based on the phase difference, and then fuse them to obtain the fused truncated phase, as shown in the following expression: in, For phase difference, The truncated phase after fusion The truncated phase after eliminating errors; The phase unfolding method is used to unfold the fused truncated phase to obtain the unfolded phase of the outer contour information of the target under test.

2. The three-dimensional topography measurement method based on high-speed phase shifting method according to claim 1, characterized in that, The complementary Gray code phase expansion method is used to expand the fused truncated phase to obtain the expanded phase of the outer contour information of the target under test.

3. The three-dimensional topography measurement method based on the high-speed phase-shifting method according to claim 2, characterized in that, The complementary Gray code phase expansion method is as follows: The Gray code series phases are obtained from the Gray code encoded fringe image projected onto the surface of the target under test, and another set of Gray code series phases is generated by combining the mapping method. At the same time, a set of complementary Gray code series phases is generated. The fused truncated phase is expanded using another set of Gray code series phases and complementary Gray code series phases generated by mapping to obtain the expanded phase containing the outer contour information of the measured target.

4. The three-dimensional topography measurement method based on the high-speed phase-shifting method according to claim 1, characterized in that, The phase unwrapping method of three-frequency heterodyne phase unwrapping is used to unwrap the fused truncated phase of multiple sets of phase-shifted fringe images of different frequencies to obtain the unwrapped phase containing the outer contour information of the target under test.

5. The three-dimensional topography measurement method based on the high-speed phase-shifting method according to claim 1, characterized in that, The phase expansion method based on the phase derivative variance is used to expand the fused truncated phase, resulting in an expanded phase that includes information about the outer contour of the target being measured.

6. A system for implementing the three-dimensional topography measurement method based on the high-speed phase-shifting method according to any one of claims 1-5, characterized in that, include, The acquisition module is used to acquire stripe images projected onto the surface of the target being measured; The fusion module is used to divide the phase-shifted fringe image into multiple groups based on the phase difference value, determine the truncated phase of each group of phase-shifted fringe images, eliminate errors, and then fuse them to obtain the fused truncated phase. The phase unwrapping module is used to unwrap the fused truncated phase using the phase unwrapping method to obtain the unwrapped phase of the outer contour information of the target under test.

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