A profile tilt correction method for measuring inner groove of eyeglass frames

Abstract

The present invention discloses a contour tilt correction method for measuring the inner groove of a spectacle frame, which relates to the field of measurement technology and includes the following steps: S1, establishing a line structured light measurement system based on laser triangulation; S2, extracting the contour edge and characteristic edge of the groove; S3, performing least squares fitting on the contour data points of two straight edge parts in sequence by setting an error threshold. S4, determining the rotation point for the contour tilt correction of the frame groove; S5, performing correction. The contour tilt correction method for measuring the inner groove of a spectacle frame is based on the least squares tilt correction principle, and after extracting the characteristic points of the edge contour, the least squares method is used to fit the characteristic points into a straight line, thereby obtaining the image tilt angle and performing tilt correction on the image. It can be used for the tilt correction of the distorted contour obtained by measuring the inner groove of the spectacle frame, and effectively completes the tilt correction of the inner groove of the frame.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, in particular to a contour tilt correction method for measuring a groove inside a spectacle frame. Background Art

[0002] The current research on frame scanners in the glasses market or domestic enterprises and scientific research universities is basically aimed at measuring the shape of the inner contour of the frame or the outer contour of the lens template, and rarely measures the groove of the frame. Optical detection technology is widely used in various fields due to its advantages of non-contact, high precision and high speed. The contour data of the inner groove of the glasses frame can be obtained by a non-contact measurement method based on the principle of optical detection. When projecting the inner groove of the frame, due to the compact structure of the glasses frame, the sensor usually cannot extend into the frame. In order to avoid the obstruction of the contour measurement effect by the frame groove part opposite to the measured inner groove part of the frame during laser projection, the sensor can only project the required inner groove part of the frame as vertically as possible from the outside of the frame. This inevitably causes the contour distortion of the inner groove contour of the frame obtained due to the tilt measurement. Therefore, it is of great significance to correct the distorted inner groove contour of the frame obtained by the sensor scanning at a certain tilt angle.

[0003] Existing image processing-based tilt correction methods have been developed in fields such as license plate character extraction, but there are few methods to solve the problem of contour tilt measurement. When the sensor scans the inner groove of the eyeglass frame, due to the compact structure of the frame and the influence of the sensor measurement range, the scanned inner groove contour of the frame has a tilt distortion problem. For this reason, we propose a contour tilt correction method for measuring the inner groove of the eyeglass frame. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a contour tilt correction method for measuring the inner groove of the eyeglass frame, which solves the problem that the tilt correction method based on image processing proposed in the above background technology has been developed in the field of license plate character extraction, but there are few methods to solve the contour tilt measurement problem. When the sensor scans the inner groove of the eyeglass frame, due to the compact structure of the frame and the influence of the sensor measurement range, the scanned inner groove contour of the frame has a tilt distortion problem.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solutions: a contour tilt correction method for measuring the inner groove of a spectacle frame, comprising the following steps:

[0006] S1. Establish a line structured light measurement system based on laser triangulation;

[0007] S2, extraction of groove contour edge and feature edge;

[0008] S3, performing least square fitting on the contour data points of the two straight line edges in sequence by setting an error threshold;

[0009] S4, determining a rotation point for tilt correction of the frame groove profile;

[0010] S5. Perform calibration.

[0011] Optionally, the contour tilt correction method for measuring the inner groove of the eyeglass frame comprises the following specific steps:

[0012] S1. Establish a line structured light measurement system based on laser triangulation.

[0013] Scan the inner groove of the frame to obtain the contour point data of the inner groove of the frame;

[0014] S2, extraction of groove contour edge and feature edge;

[0015] The data of the inner groove contour points of the frame are subjected to Gaussian filtering to remove noise points, and different geometric shape curves of the contour curve are segmented according to the discrete approximate curvature of the groove contour points. First, the contour of the frame groove part is obtained by segmentation. Then, in order to further obtain the inclination angle of the inner groove contour of the frame, the segmentation points are extracted according to the discrete approximate curvature curve, so as to determine the characteristic edge, that is, the contour of the two straight edges of the V-shaped groove inside the frame;

[0016] S3, performing least square fitting on the contour data points of the two straight line edges in sequence by setting an error threshold;

[0017] The inclination angles of the two straight line edges are calculated by the slopes of the two fitted straight lines, and the inclination angle of the groove profile of the frame can be deduced;

[0018] S4, determining a rotation point for tilt correction of the frame groove profile;

[0019] The intersection point of the two fitted straight lines in step 3 is taken as the rotation point based on which the tilt correction is performed;

[0020] S5, perform calibration;

[0021] A two-dimensional coordinate rotation model is established for the contour coordinate transformation before and after rotation, and the inclined contour data points are corrected through software calculation.

[0022] Furthermore, in step S1, the mirror frame is placed on the surface of the supporting stand.

[0023] Furthermore, the portion of interest in step S2 is two straight edges of the V-shaped groove inside the frame.

[0024] Furthermore, the operation function of step S5 is:

[0025]

[0026] In the formula, (x 0 ,y 0 ) is the rotation center of the two-dimensional coordinates, (x, y) is the original contour coordinates, (x', y') is the original contour coordinates around (x 0 ,y 0 ) is the coordinate after rotating it clockwise by an angle θ.

[0027] The present invention provides a contour tilt correction method for measuring the inner groove of a glasses frame, which has the following beneficial effects: the tilt correction method based on the least squares method straight line fitting is to extract the feature points of the edge contour and then use the least squares method to fit the feature points into a straight line to obtain the image tilt angle and perform tilt correction on the image, which can be used for tilt correction of the distorted contour obtained by measuring the inner groove tilt of the glasses frame. At the same time, by establishing a line structured light measurement system based on the laser triangulation method, the inner groove of the frame is scanned to obtain the contour point data of the inner groove of the frame, so that the eye frame data can be obtained more comprehensively, and the inner groove of the eye frame can be tilt corrected without contact. A two-dimensional coordinate rotation model can be established for the acquired contour coordinate data, so that the tilt contour data points can be corrected by software calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a groove profile curve and a discrete approximate curvature curve of a profile tilt correction method for measuring a groove inside a spectacle frame according to the present invention;

[0029] Figure 2 Schematic diagram of calculating the groove profile inclination angle from two straight edges of the V-shaped groove on the inner side of the frame according to the present invention;

[0030] Figure 3 Schematic diagram of calculating the tilt correction rotation point by the least square fitting straight line of the two straight line edges of the V-shaped groove inside the frame of the present invention;

[0031] Figure 4 The present invention is a schematic diagram of a two-dimensional coordinate model structure of a contour tilt correction method for measuring a groove inside a spectacle frame.

[0032] Figure 5 The present invention is a schematic diagram of a contour tilt correction method for measuring a groove inside a glasses frame before and after correction of the contour of the groove inside the glasses frame. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] A profile tilt correction method for measuring a groove inside a spectacle frame comprises the following steps:

[0035] S1. Establish a line structured light measurement system based on laser triangulation;

[0036] S2, extraction of groove contour edge and feature edge;

[0037] S3, performing least square fitting on the contour data points of the two straight line edges in sequence by setting an error threshold;

[0038] S4, determining a rotation point for tilt correction of the frame groove profile;

[0039] S5. Perform calibration.

[0040] A profile tilt correction method for measuring a groove inside a spectacle frame comprises the following specific steps:

[0041] S1. Establishing a line structured light measurement system based on laser triangulation. In step S1, the mirror frame is placed on the surface of a supporting stand.

[0042] Scan the inner groove of the frame to obtain the contour point data of the inner groove of the frame;

[0043] S2, extraction of groove contour edge and feature edge;

[0044] Perform Gaussian filtering on the contour point data of the inner groove of the frame to remove noise, refer to Figure 1 , according to the discrete approximate curvature of the groove contour points, the contour curves of different geometric shapes are segmented. First, the contour of the frame groove is obtained by segmentation. Then, in order to further obtain the inclination angle of the groove contour inside the frame, the segmentation points are extracted according to the discrete approximate curvature curve, so as to determine the characteristic edges, that is, the contours of the two straight edges of the V-shaped groove inside the frame;

[0045] The portion of interest in step S2 is the two straight edges of the V-shaped groove inside the frame;

[0046] S3, performing least square fitting on the contour data points of the two straight line edges in sequence by setting an error threshold;

[0047] Reference Figure 2 , the inclination angles of the two straight line edges are calculated by the slopes of the two fitted straight lines, and the inclination angle of the groove profile of the frame can be deduced;

[0048] S4, determining a rotation point for tilt correction of the frame groove profile;

[0049] Reference Figure 3, take the intersection point of the two fitting lines obtained in step 3 as the rotation point based on the tilt correction;

[0050] S5, perform calibration;

[0051] Reference Figure 4 , a two-dimensional coordinate rotation model is established for the contour coordinate transformation before and after the rotation, and the inclined contour data points are corrected through software calculation. The operation function of step S5 is:

[0052]

[0053] In the formula, (x 0 ,y 0 ) is the rotation center of the two-dimensional coordinates, (x, y) is the original contour coordinates, (x', y') is the original contour coordinates around (x 0 ,y 0 ) is the coordinate after rotating clockwise by angle θ. Figure 5 The figure shows the comparison of the results before and after correction of the groove profile on the inside of the frame.

[0054] In summary, the contour tilt correction method for measuring the inner groove of the eyeglass frame comprises the following specific steps when used: firstly, a line structured light measurement system based on laser triangulation is established to scan the inner groove of the frame to obtain the contour point data of the inner groove of the frame;

[0055] Then, the discrete approximate curvature of the discrete contour points is calculated; according to the discrete approximate curvature diagram, the different geometric shape curves of the contour curve are segmented, and the partial contour of the frame groove is first obtained by segmentation, and then in order to further obtain the inclination angle of the inner groove contour of the frame, the segmentation points are extracted according to the discrete approximate curvature curve, so as to determine the characteristic edge, that is, the two straight edge partial contours of the V-shaped groove inside the frame, and then the two straight edge partial contour data points are sequentially least squares fitted by setting an error threshold; the inclination angle of the two straight edges is calculated by the slope of the two fitted straight lines obtained, and the inclination angle of the frame groove contour can be inferred, and then the rotation point for the frame groove contour inclination correction is determined; the intersection point of the two fitted straight lines obtained in step three is taken as the rotation point based on the inclination correction, and finally correction is performed; a two-dimensional coordinate rotation model is established for the contour coordinate transformation before and after the rotation, and the inclined contour data points are corrected by software calculation.

[0056] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A contour tilt correction method for measuring the inner groove of a spectacle frame, characterized in that: The following steps are involved: S1. Establish a line structured light measurement system based on laser triangulation: scan the inner groove of the frame to obtain the contour point data of the inner groove of the frame; S2. Extraction of groove contour edge and characteristic edge: Gaussian filtering is performed on the contour point data of the inner groove of the frame to remove noise points, and different geometric shape curves of the contour curve are segmented according to the discrete approximate curvature of the groove contour points. First, the contour of the groove of the frame is obtained by segmentation. Then, in order to further obtain the inclination angle of the contour of the groove of the inner side of the frame, segmentation points are extracted according to the discrete approximate curvature curve, thereby determining the characteristic edge, that is, the contour of the two straight edges of the V-shaped groove of the inner side of the frame; S3, performing least square fitting on the contour data points of the two straight line edges of the V-shaped groove on the inner side of the frame in sequence by setting an error threshold: calculating the inclination angles of the two straight line edges by the slopes of the two fitted straight lines, and inferring the inclination angle of the groove contour of the frame; S4, determining a rotation point for tilt correction of the frame groove profile: taking the intersection of the two fitting straight lines obtained in step S3 as the rotation point based on which the tilt correction is based; S5. Correction: Establish a two-dimensional coordinate rotation model for the contour coordinate transformation before and after the rotation, and correct the inclined contour data points through software calculation.

2. A contour tilt correction method for measuring the inner groove of a spectacle frame according to claim 1, characterized in that: In step S1, the mirror frame is fixed on the surface of the displacement platform and placed on the surface of the support frame.

3. The contour tilt correction method for measuring the inner groove of the eyeglass frame according to claim 1, characterized in that: The portion of interest in step S2 is the two straight edges of the V-shaped groove inside the frame.

4. The method for correcting the profile tilt of the inner groove of the eyeglass frame according to claim 1, characterized in that: The step S5 operation function is: Where (x0, y0) is the rotation center of the two-dimensional coordinates, (x, y) is the original contour coordinates, and (x', y') is the coordinates of the original contour after rotating clockwise around (x0, y0) by an angle of θ.

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