Method for obtaining phase required for three-dimensional measurement using frequency multiplexing
Patent Information
- Application Number
- CN202411720530.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-28
- Publication Date
- 2025-12-16
- Estimated Expiration
- 2044-11-28
Smart Images
Figure CN119687826B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to optical three-dimensional measurement method in photoelectric detection technology, and particularly relates to a method for obtaining phase required by three-dimensional measurement using frequency multiplexing. BACKGROUND
[0002] Fringe projection profilometry (FPP) is a widely used optical three-dimensional measurement (3D) technology in the fields of industrial quality inspection, biomedical, machine vision, navigation, etc., which has the advantages of fast speed, high precision, non-contact, etc. The FPP system generally uses a projection-camera device to project a sinusoidal fringe pattern, and then acquires a distorted fringe image for phase calculation and final three-dimensional measurement. In order to exclude the interference of ambient light, when using fringe structured light for three-dimensional measurement, phase information is usually used to restore the height.
[0003] With the advent of CCD cameras and digital projectors, the method of frequency multiplexing is used to make composite fringe patterns for high-speed three-dimensional measurement. However, the large amount of high-frequency information loss caused by separating the composite fringe greatly reduces the measurement accuracy. Therefore, how to solve or skip this problem has become a big problem for the application of this method. SUMMARY
[0004] The present application provides a method for obtaining phase required by three-dimensional measurement using frequency multiplexing, so as to realize high-speed measurement without separating the composite fringe pattern, thereby reducing the loss of high-frequency information and improving the three-dimensional measurement accuracy at high speed.
[0005] In order to achieve the above purpose, the present application adopts the following technical scheme. A method for obtaining phase required by three-dimensional measurement using frequency multiplexing, the steps are as follows:
[0006] 1) According to the requirements of three-frequency heterodyne method using four-step phase shift method, make phase shift fringe pattern, and the phase shift fringe pattern of each phase shift angle is divided into three frequencies;
[0007] 2) Starting from the phase shift angle of 0, arrange the fringe pattern made in step 1) according to the phase shift angle from small to large, and mark the phase shift angle as , , and ;
[0008] 3) After sorting in step 2), extract three different frequency fringe patterns of phase shift angle , and combine the three pictures of phase shift angle to make a composite fringe pattern;
[0009] 4) Use the composite fringe pattern made in step 3) to replace the fringe pattern of a certain frequency with the phase shift angle of the rest two pictures remain unchanged to make a composite fringe pattern; and the above same method is operated on the three frequencies respectively;
[0010] 5) After the sorting of step 2), three fringe patterns with different frequencies of phase shift angle of are extracted, and the three pictures with phase shift angle of are combined to make a composite fringe pattern;
[0011] 6) using the composite fringe pattern made in step 5), a fringe pattern with a certain frequency is replaced by a fringe pattern with phase shift angle of , and the rest two pictures remain unchanged to make a composite fringe pattern; and the above method is operated on the three frequencies respectively;
[0012] 7) the composite fringe patterns made in steps 3) to 6) are projected onto the object to be measured by a projector, and the fringe is collected by a CCD camera;
[0013] 8) the gray matrix of each composite fringe pattern made in step 4) is collected by a CCD camera, and the gray matrix of the composite fringe pattern made in step 3) is directly subtracted; at the same time, the gray matrix of each composite fringe pattern made in step 6) is collected by a CCD camera, and the gray matrix of the composite fringe pattern made in step 5) is directly subtracted to calculate the phase displacement;
[0014] 9) the phase displacement is substituted into the formula of the phase shift method: to obtain the truncated phase diagram of the object to be measured;
[0015] wherein θ is the wrapped phase, represents the intensity matrix of the mth sine fringe pattern photographed by the CCD camera;
[0016] 10) the three-frequency heterodyne method is used to obtain the continuous phase of the object to be measured.
[0017] Compared with the single fringe three-dimensional measurement scheme, the required projection and shooting time is less; compared with other composite fringe picture schemes, since the composite fringe pattern does not need to be separated, the information loss is less, the accuracy of high-speed three-dimensional measurement is improved, and the scheme has potential application prospect and practical value in the field of optical three-dimensional measurement. BRIEF DESCRIPTION OF DRAWINGS
[0018] Fig. 1 a picture coding and making scheme relationship diagram in the embodiment of the application;
[0019] Fig. 2 a phase displacement calculation scheme relationship diagram in the embodiment of the application;
[0020] Fig. 3 A measurement physical diagram in the embodiment of the present application. DETAILED DESCRIPTION
[0021] The present application is further illustrated in the following drawings and examples. Referring to Figs. 1 to 3 A method for obtaining phase required by three-dimensional measurement using composite fringe pattern, comprising the following steps:
[0022] 1) According to the requirement of three-frequency heterodyne method using four-step phase shifting method, phase shifting fringe patterns are made [1]-
[12] , and the phase shifting fringe patterns of each phase shifting angle are divided into three frequencies (such as Fig. 1 shown).
[0023] 2) From the phase shifting angle of 0, the fringe patterns made in step 1) are arranged according to the phase shifting angle from small to large, and the phase shifting angles are recorded as , , and .
[0024] 3) After the arrangement in step 2), the fringe patterns of different frequencies with the phase shifting angle of are extracted, and there are three, and the three pictures with the phase shifting angle of are combined to make a composite fringe pattern [1].
[0025] 4) Using the composite fringe pattern made in step 3), the fringe pattern of a certain frequency is replaced by the fringe pattern with the phase shifting angle of , and the remaining two are kept unchanged, to make a composite fringe pattern [2] in figure (1). The above operation is performed on the three frequencies respectively.
[0026] 5) After the arrangement in step 2), the fringe patterns of different frequencies with the phase shifting angle of are extracted, and there are three, and the three pictures with the phase shifting angle of are combined to make a composite fringe pattern [3].
[0027] 6) Using the composite fringe pattern made in step 5), the fringe pattern of a certain frequency is replaced by the fringe pattern with the phase shifting angle of , and the remaining two are kept unchanged, to make a composite fringe pattern [4]. The above operation is performed on the three frequencies respectively, until a composite fringe pattern [8] is made.
[0028] 7) The composite fringe patterns made in steps 3) to 6) are projected onto the object to be measured C by the projector A, and the fringe is collected by the CCD camera B (as shown in Fig. 3 ).
[0029] 8) subtracting each gray matrix of the composite fringe pattern made in step 4) from the gray matrix of the composite fringe pattern made in step 3) and subtracting each gray matrix of the composite fringe pattern made in step 6) from the gray matrix of the composite fringe pattern made in step 5) using CCD camera B to calculate the phase shift (as shown in Fig. 2
[0030] 9) substituting phase shift 1 and phase shift 4 into the phase shift method formula to obtain the truncated phase of f1, substituting phase shift 2 and phase shift 5 into the phase shift method formula to obtain the truncated phase of f2, and substituting phase shift 3 and phase shift 6 into the phase shift method formula to obtain the truncated phase of f3, and directly using the phase shift method to obtain the truncated phase pattern of the measured object 3 (as shown in Fig. 2
[0031] 10) using the phase unwrapping step in the three-frequency heterodyne method to unwrap the truncated phase of f1, f2 and f3 into continuous phase (as shown in Fig. 2
[0032] The present application acquires the phase required for three-dimensional measurement by frequency multiplexing, and compared with the traditional similar method, the number of projected pictures is less, and the measurement speed is faster.
Claims
1. A method for obtaining the phase required for three-dimensional measurement using frequency multiplexing, comprising the following steps: 1) producing phase-shifted fringe patterns according to the requirements of three-frequency heterodyne method using four-step phase-shifting method, the phase-shifted fringe pattern of each phase shift angle being divided into three frequencies; 2) from the phase shift angle of 0, the stripe pattern in step 1) is arranged according to the phase shift angle from small to large, and the phase shift angle is recorded as , , and ; 3) After sorting in step 2), extract three phase-shifted angle different frequency fringe patterns, and combine these three phase-shifted angle pictures to make a composite fringe pattern 1. 4) Extract three phase shift angles of different frequency fringe patterns, replace the fringe pattern of a certain frequency with the fringe pattern of the corresponding frequency whose phase shift angle is , and keep the other two unchanged to make a composite fringe pattern; and operate the above same method on the three frequencies respectively to obtain composite fringe pattern two, composite fringe pattern three, and composite fringe pattern four; 5) After the sorting of step 2), three fringe patterns with phase shift angles of at different frequencies are extracted, and the three images with phase shift angles of are combined to make a composite fringe pattern five; 6) extract three fringe patterns with phase shift angle of at different frequencies, replace the fringe pattern with a frequency with a fringe pattern with phase shift angle of at the corresponding frequency, and keep the other two unchanged to make a composite fringe pattern; and perform the above method for the three frequencies respectively to obtain composite fringe pattern six, composite fringe pattern seven, and composite fringe pattern eight; 7) projecting the composite fringe patterns produced in steps 3) to 6) onto the object to be measured by a projector, and collecting the fringes by a CCD camera; 8) using the gray scale matrix of each composite fringe pattern produced in step 4) to directly subtract the gray scale matrix of the composite fringe pattern produced in step 3) collected by the CCD camera, and using the gray scale matrix of each composite fringe pattern produced in step 6) to directly subtract the gray scale matrix of the composite fringe pattern produced in step 5) collected by the CCD camera, so as to calculate the phase shift; 9) Substituting the phase shift into the phase shift method formula: ; obtaining the truncated phase patterns of the object to be measured at three frequencies; where: θ is the wrapping phase, represents the intensity matrix of the mth sinusoidal fringe image captured by the CCD camera, m = 1, 2, 3, 4. 10) obtaining the continuous phase of the object to be measured by using three-frequency heterodyne method.