CN-118129639-B - Structured light coding and decoding method and system based on multiple spiral stripes

CN118129639BCN 118129639 BCN118129639 BCN 118129639BCN-118129639-B

Abstract

The invention provides a structured light coding and decoding method and system based on multiple spiral stripes, and relates to the technical field of three-dimensional measurement and machine vision, wherein the method comprises the steps of projecting an object to be measured, generating a group of concentric circle sine stripe phase shift diagrams coded along the radial direction, generating another group of concentric circle sine stripe phase shift diagrams with different frequencies, and generating two groups of spiral stripe phase shift diagrams coded along the radial direction and the circumferential direction at the same time with different frequencies; the method comprises the steps of acquiring stripe coding patterns modulated by the surface of an object to be measured through a camera, calculating to obtain the corresponding radius phase and angle phase of the surface point of the object to be measured under a camera image coordinate system, and obtaining the real depth information of each object point according to a triangulation principle. The invention obviously improves the resolution of the angle phase by using the multi-spiral stripe patterns with different spiral numbers, and reduces errors in the measuring process by an improved angle phase unwrapping technology, thereby realizing high-precision three-dimensional measurement.

Inventors

WU QINGYANG
JIANG YIFAN
ZHANG BAICHUN
GUO WENFENG
ZOU YIFENG

Assignees

深圳技术大学
深圳市百旸科技有限公司

Dates

Publication Date: 20260505
Application Date: 20240403

Claims (10)

1. The structured light coding and decoding method based on the multi-spiral stripes is characterized by comprising the following steps: Step 1) projection preparation: Projecting to an object to be detected to generate a group of concentric circle sine stripe phase shift diagrams along the radial direction; projecting to an object to be detected to generate another group of concentric circle sine stripe phase shift diagrams with different frequencies; projecting to an object to be detected to generate a group of P spiral stripe phase shift diagrams which are coded along the radial direction and the circumferential direction simultaneously; Projecting to an object to be detected to generate a group of Q spiral stripe phase shift diagrams which are coded along the radial direction and the circumferential direction simultaneously; Step 2) projection and capture: Sequentially projecting the phase shift patterns to the surface of the object to be measured through a projector; collecting a stripe coding pattern modulated by the surface of an object to be measured by a camera; Step 3) phase computation Calculating to obtain a radius phase and an angle phase corresponding to the surface point of the object to be measured under a camera image coordinate system; step 4) three-dimensional point cloud reconstruction: according to the obtained radial phase and angle phase, combining the geometric relationship between the camera and the projector, and according to the principle of triangulation, obtaining the real depth information of each object point.
2. The structured light encoding and decoding method based on multiple spiral stripes according to claim 1, wherein the projection onto the object to be measured adopts an N-step phase shift method, and the phase shift is performed according to a predetermined number of steps N to obtain N phase shift patterns, and each group of stripe phase shift patterns includes a plurality of phase shift states.
3. The structured light encoding and decoding method based on multiple spiral stripes according to claim 2, wherein the radial phase and the angular phase are obtained, comprising the steps of: resolving the projected two groups of concentric circle stripe patterns with different frequencies to obtain two truncated phase diagrams of concentric circles; Performing phase unwrapping processing on the first concentric circle truncated phase according to the phase difference of the two truncated phase maps by adopting a double-frequency heterodyne method to obtain a radius phase covering the whole view field; resolving the projected multi-spiral stripe patterns of two groups of spiral lines with different numbers to obtain two multi-spiral truncated phase diagrams; performing difference calculation on the two multi-spiral truncated phase maps and a first concentric circle truncated phase map with the same frequency to obtain two angle phase maps for dividing a view field into a plurality of sector areas; and according to the two angle phase diagrams dividing the view field into a plurality of sector areas, performing unfolding processing on the first angle phase diagram to obtain an angle phase.
4. The multi-spiral stripe-based structured light encoding and decoding method according to claim 3, wherein when the first angular phase map is expanded, the first angular phase map is an angular phase map of the P-spiral stripe phase shift map, and the range of values of the angular phase is expanded compared with an angular phase map of the Q-spiral stripe phase shift map.
5. The multi-spiral stripe-based structured light codec method according to claim 1, wherein the multi-spiral stripe-based structured light codec method performs three-dimensional measurement using a double-frequency heterodyne method, comprising the steps of: sinusoidal phase shift coding is carried out along the radial direction by taking the origin of a camera image coordinate system as a starting point, and a phase shift diagram is generated; solving a truncated phase corresponding to each pixel point of the camera by applying a classical phase shift solution formula; unwrapping the truncated phase to enable the phase distribution to cover the whole camera field of view; Sinusoidal phase shift encoding is carried out along the radial direction to generate a spiral phase shift diagram, angle information is added into a phase main value to obtain a truncated phase distribution diagram, and meanwhile, the truncated phase distribution diagram comprises radius phase information and angle phase information; And combining the radius phase information to obtain an angle phase so as to mark the position information of all object points in the camera field under an image coordinate system.
6. The multi-spiral stripe-based structured light encoding and decoding method according to claim 5, wherein the unwrapping process of the truncated phase uses a dual-frequency unwrapping method or a gray code assisted unwrapping method, where the dual-frequency unwrapping method is to re-project a set of concentric circular stripes with different periods, and the gray code assisted unwrapping method is to re-project a set of concentric circular gray codes.
7. The structured light encoding and decoding method based on multiple spiral stripes according to claim 1, wherein each object point in the camera image coordinate system has a unique radius phase value, and an object point in the space is uniquely marked according to the obtained angle phase value of each object point.
8. The structured light encoding and decoding method based on multiple spiral stripes according to claim 7, wherein the obtained truncated phase distribution map is subjected to a difference processing with respect to the truncated phase corresponding to the first set of concentric stripes to obtain an angular phase of 0 to 2 pi.
9. The structured light encoding and decoding method based on multiple spiral stripes of claim 8, wherein when obtaining the angle phase, further comprising projecting four additional multiple spiral patterns with different spiral numbers to perform a secondary expansion process on the angle phase map, and expanding the range of angle phase values to An angular phase map is obtained.
10. A multi-spiral stripe based structured light codec system for performing the multi-spiral stripe based structured light codec method of any one of claims 1-9, the multi-spiral stripe based structured light codec system comprising: the projection module is a projector controlled by programming and used for generating and sequentially projecting a concentric sine stripe phase shift diagram and a spiral stripe phase shift diagram on the surface of an object to be detected, and adjusting the projected stripe patterns to generate stripe patterns with different frequencies and different spiral numbers; The image acquisition module is one or more high-resolution cameras and is used for capturing a stripe pattern modulated by the surface of the object to be detected; the control and synchronization module is used for synchronously controlling the work of the projector and the camera and ensuring the projection of the fringe pattern and the acquisition of the image under the correct time sequence; The data processing module is used for executing the algorithm of phase calculation and three-dimensional point cloud reconstruction, calculating the radius phase and the angle phase by receiving the image data acquired by the camera, and finally obtaining the real three-dimensional coordinates of each object point.

Description

Structured light coding and decoding method and system based on multiple spiral stripes Technical Field The invention relates to the technical field of three-dimensional measurement and machine vision, in particular to a structured light coding and decoding method and system based on multiple spiral stripes. Background In the field of three-dimensional measurement and machine vision, structured light technology is an important non-contact measurement method. It generally involves projecting a specific optical pattern (such as a stripe, grid or lattice) onto a target object and then capturing reflected images from different perspectives using a camera. By analyzing the deformation of the projected pattern on the surface of the object, three-dimensional shape information of the object can be deduced. In the traditional structured light system, the marking precision of the angle phase in the practical application is low in the used coding scheme, the angle phase value range distribution [0,2 pi ] of the whole measurement space, and the slight jitter of the angle phase has a great influence on the final reconstruction precision. Furthermore, when structured light systems are subjected to measurement tasks with high accuracy requirements, such as in precision engineering or biomedical imaging, the angular resolution of conventional fringe patterns is insufficient to meet the requirements. Therefore, researchers have been required to develop a new structured light encoding method to improve the resolution of angular phase and reduce measurement errors caused by minute jitter in the image acquisition process. In summary, in view of the problems of low angular resolution and sensitivity to dynamic errors existing in the current structured light three-dimensional measurement technology, the application of the three-dimensional measurement technology in the field of high-precision measurement is limited. Therefore, how to develop new codec methods and systems to overcome these limitations is of great importance to drive the development of three-dimensional measurement techniques. Disclosure of Invention In view of this, in order to improve the accuracy, the range of the angular phase is extended, and the influence of the jitter on the reconstruction accuracy is reduced by the extension. The invention provides a structured light coding and decoding method and a structured light coding and decoding system based on multiple spiral stripes, which remarkably improve the resolution of angle phases by using multiple spiral stripe patterns with different spiral numbers, and reduce errors in the measuring process by an improved angle phase unwrapping technology, thereby realizing high-precision three-dimensional measurement. The invention is realized by adopting the following technical scheme: in a first aspect, the present invention provides a structured light encoding and decoding method based on multiple spiral stripes for high-precision three-dimensional measurement, the method comprising the steps of: Step 1, projection preparation: Projecting to an object to be detected to generate a group of concentric circle sine stripe phase shift diagrams along the radial direction; projecting to an object to be detected to generate another group of concentric circle sine stripe phase shift diagrams with different frequencies; projecting to an object to be detected to generate a group of P spiral stripe phase shift diagrams which are coded along the radial direction and the circumferential direction simultaneously; Projecting to an object to be detected to generate a group of Q spiral stripe phase shift diagrams which are coded along the radial direction and the circumferential direction simultaneously; step 2, projection and capture: Sequentially projecting the phase shift patterns to the surface of the object to be measured through a projector; collecting a stripe coding pattern modulated by the surface of an object to be measured by a camera; Step3, phase calculation Calculating to obtain a radius phase and an angle phase corresponding to the surface point of the object to be measured under a camera image coordinate system; Step4, reconstructing three-dimensional point cloud: according to the obtained radial phase and angle phase, combining the geometric relationship between the camera and the projector, and according to the principle of triangulation, obtaining the real depth information of each object point. As a further scheme of the invention, an N-step phase shift method is adopted for projection of an object to be detected, and phase shift is carried out according to a preset step number N so as to obtain N phase shift patterns, wherein each group of stripe phase shift patterns comprise a plurality of phase shift states. As a further aspect of the present invention, obtaining the radial phase and the angular phase includes the steps of: resolving the projected two groups of concentric circle stripe patterns with different f