Heliostat surface shape detection system and method based on multi-view image recognition

Abstract

A heliostat surface shape detection system and a method based on multi-view image recognition are described. The system includes a multi-view image collector array, a bracket and a computer. The multi-view image collector array is arranged on the bracket so that the main optical axes of image collectors are parallel to each other and point to the heliostat; the multi-view image collector array is connected with the computer via data lines, and transmits the collected image data to the computer for heliostat surface shape calculation.

Claims

1. A surface shape detection method of a heliostat based on multi-view image recognition, a 3D surface shape of the heliostat being reconstructed by measuring a pitch angle and a roll angle of each sub-mirror of the heliostat, the method comprising: (1) determining a distance from the heliostat to a bracket and the number of image collectors in a multi-view image collector array according to an external dimension of the heliostat; (2) mounting the multi-view image collector array on the bracket and adjusting each image collector so that main optical axes of the image collectors are parallel to each other and aligned with the heliostat; (3) collecting, by the multi-view image collector array, heliostat images of a field of view corresponding to the multi-view image collector array and transmitting the heliostat images to a computer respectively; (4) performing feature matching on the collected image data through a feature recognition technology in an image recognition technology to determine corresponding feature points in a common field of view of a plurality of image collectors, wherein a feature point of the heliostat has a real image on each image collector corresponding to the multi-view image collector array; (5) wherein a deviation between the real image of the feature point in each image collector and an image center in an image coordinate system is (X.sub.i, Y.sub.i), where i represents a number of the image collector; a center of the multi-view image collector array is an origin of a multi-view measurement coordinate system satisfying the right-hand rule, and a Z axis of the multi-view measurement coordinate system points to the heliostat; center coordinates of each image collector are (x.sub.i, y.sub.i, 0), and a distance between image collectors is L, coordinates of the multi-view measurement coordinate system of each real image point are (x.sub.i+X.sub.i.Math.Size.sub.Pixel, y.sub.i+Y.sub.i.Math.Size.sub.Pixel, 0); (6) given a focal length of the multi-view image collector array is f, coordinates of an equivalent lens center of each image collector are (x.sub.i, y.sub.i, f); a 3D linear equation involving the equivalent lens center and the corresponding real image is $\begin{array}{cc}\frac{x-x_i}{X_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{y-y_i}{Y_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{z-f}{-f}& \end{array}$ (7) according to the equation $\frac{x-x_i}{X_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{y-y_i}{Y_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{z-f}{-f},$ a single feature point of the heliostat establishes a plurality of 3D linear equations in the multi-view image collector array, and relative coordinates (x.sub.i, y.sub.i, z.sub.i) of linear intersection points in the multi-view measurement coordinate system are obtained by concatenating the plurality of 3D linear equations, the relative coordinates (x.sub.i, y.sub.i, z.sub.i) of linear intersection points are the relative coordinates of the single feature point of the heliostat; and (8) repeating the steps (3)-(7) to obtain a relative position information of a mirror surface of the heliostat in the multi-view measurement coordinate system, and calculating the surface shape of the heliostat.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings described herein are intended to provide a further understanding of the present invention and form a part of this application, but do not constitute an undue limitation on the present invention, in which:

(2) FIG. 1 is a schematic diagram of the detection system of the present invention;

(3) FIG. 2 is a schematic diagram of the multi-view image collector array of the present invention;

(4) FIG. 3 is a schematic diagram of multi-view imaging of the present invention;

(5) FIG. 4 is a schematic diagram of the deviation of the real image of the same feature point in multiple image collectors from the image center in the image coordinate system of the present invention.

(6) In the figures: 1. multi-view image collector array; 2. bracket; 3. computer; 4. heliostat; 5. real image.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) The present invention will now be described in detail with reference to the accompanying drawings and embodiments, in which the illustrative embodiments and descriptions are only for the purpose of explaining the present invention, and are not to be taken as limiting the present invention.

(8) As shown in FIGS. 1-4, a heliostat surface shape detection system based on multi-view image recognition, comprising a multi-view image collector array 1, a bracket 2 and a computer 3, wherein the multi-view image collector array 1 is arranged on the bracket 2 so that the main optical axes of image collectors are parallel to each other and point to the heliostat 4; the multi-view image collector array 1 is connected with the computer 3 via data lines, and transmits the collected image data to the computer 3 for heliostat surface shape calculation. The image collectors of the multi-view image collector array 1 are stably installed on the bracket 2 at equal intervals, and the number of image collectors in the multi-view image collector array 1 is determined according to the external dimensions of the measured heliostat 4 and the image collectors can be installed in the form of modules. The number of image collectors in the multi-view image collector array 1 is at least 2.

(9) A heliostat surface shape detection system based on multi-view image recognition, characterized in that the 3D surface shape of the heliostat to be measured is reconstructed by measuring the pitch angle and roll angle of each sub-mirror, including the following steps:

(10) (1) As shown in FIG. 1, determining the distance from the heliostat 4 to the bracket 2 and the number of image collectors (at least 2) in the multi-view image collector array 1 according to the external dimensions of the heliostat 4;

(11) (2) Stably mounting the multi-view image collector array 1 on the bracket 2 and adjusting each image collector so that their main optical axes are parallel to each other and aligned with the heliostat 4;

(12) (3) The multi-view image collector array 1 collects heliostat images of the corresponding field of view and transmits them to the computer 3 respectively;

(13) (4) Performing feature matching on the collected image data through the feature recognition technology in the image recognition technology to determine corresponding feature points in the common field of view of a plurality of image collectors; as shown in FIG. 3, a feature point of the heliostat 4 will have a real image 5 on each image collector corresponding to the multi-view image collector array 1;

(14) (5) As shown in FIG. 4, the deviation between the real image 5 of the same feature point in multiple image collectors and the image center in the image coordinate system is (X.sub.i, Y.sub.i), where i represents the image collector number; the center of the multi-view image collector array (1) is the origin of the multi-view measurement coordinate system (satisfying the right-hand rule), and the Z axis points to the heliostat; the center coordinates of each image collector are (x.sub.i, y.sub.i, 0), and the distance between image collectors is L (unit: m); therefore, the coordinates of the multi-view measurement coordinate system of each real image point are (x.sub.i+X.sub.i.Math.Size.sub.Pixel, y.sub.i+Y.sub.i.Math.Size.sub.Pixel, 0);

(15) (6) Given the focal length of the multi-view image collector array (1) is f, the coordinates of the equivalent lens center of each image collector are (x.sub.i, y.sub.i, f); the 3D linear equation involving the equivalent lens center and the corresponding real image 5 is

(16) $\begin{array}{cc}\frac{x-x_i}{X_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{y-y_i}{Y_i.Math.{\mathrm{Size}}_{\mathrm{Pixel}}}=\frac{z-f}{-f};& \left(2\right)\end{array}$

(17) (7) According to Formula (1), a single feature point of the heliostat 4 can establish a plurality of 3D linear equations in the multi-view image collector array 1, and the relative coordinates (x.sub.j, y.sub.j, z.sub.j) of the linear intersection points in the multi-view measurement coordinate system can be obtained by concatenating the above equations, that is, the relative coordinates of the single feature point of the heliostat 4; and

(18) (8) By repeating the above process, the relative position information of the mirror surface of the heliostat 4 in the multi-view measurement coordinate system can be obtained, and the surface shape of the heliostat 4 can be calculated.

(19) The embodiments are only the preferred embodiments of the present invention. Therefore, the equivalent changes or modifications made in accordance with the structure, features and principles in the scope of patentable claims of the present invention shall also fall within the scope of the present invention.