CN106950399B - Automatic calibration device and method for large-range surface flow field image testing system - Google Patents
Automatic calibration device and method for large-range surface flow field image testing system Download PDFInfo
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- CN106950399B CN106950399B CN201710200559.2A CN201710200559A CN106950399B CN 106950399 B CN106950399 B CN 106950399B CN 201710200559 A CN201710200559 A CN 201710200559A CN 106950399 B CN106950399 B CN 106950399B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
- G01P21/02—Testing or calibrating of apparatus or devices covered by the preceding groups of speedometers
- G01P21/025—Testing or calibrating of apparatus or devices covered by the preceding groups of speedometers for measuring speed of fluids; for measuring speed of bodies relative to fluids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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Abstract
The invention discloses an automatic calibration device of a large-range surface flow field image testing system, which comprises two groups of lasers and a matched rotating device, wherein the lasers are respectively arranged on a rotating disc at intervals, the centers of the lasers are positioned on the same plane, the angles of the lasers are adjusted to enable the two lasers to be completely overlapped, and the positions and the angles of the rotating disc are recorded. And respectively rotating the two laser beams to enable the two laser beams to intersect in the shooting range of the camera, acquiring an intersection point image by the camera, and then rotating the laser beams again to acquire the intersection point image. Because the rotation angle and the distance between the two groups of lasers are known, the coordinates of the intersection points of the lasers are obtained by utilizing a trigonometric function, so that the actual distance between the two intersection points is calculated; and acquiring coordinates of the laser intersection points in the image through image processing, and calculating to obtain image distances of the two intersection points, wherein the actual distances correspond to the image distances, so that system calibration can be completed. The method realizes the automatic conversion between the unit pixels of the image test system and the actual distance, and improves the accuracy of the image speed measurement system.
Description
Technical Field
The invention relates to an automatic calibration device and method for a large-range surface flow field image testing system, and belongs to the field of flow velocity measurement.
Background
The large-scale surface flow field image testing system is widely applied to laboratory river model or prototype river surface flow velocity measurement. The principle is as follows: the tracer particles with good following performance are scattered on the surface of the water flow, follow the water flow to move, the CCD camera is used for recording flow field images with a certain time interval, the tracer particle images are extracted through image processing, particle matching is carried out on two adjacent flow field images, and t is found out 1 The trace particle at time t after the delta t time 2 And (3) calculating the particle displacement L in the deltat time according to the image at the moment, so as to obtain the speed of the trace particle, namely the speed v corresponding to the water flow point: v=l/Δt, the unit of the displacement L is a pixel, in order to obtain the actual flow velocity, a relation between the pixel and the actual scale needs to be established, the process is called calibration, a=l/N, α is the actual size corresponding to the unit pixel, and L and N are the actual length of the water flow surface and the number of pixels corresponding to the image respectively.
Fig. 1 is a block diagram of a surface flow field image testing system, in which a camera can only be erected on a beach when a prototype river is applied, and in order to obtain the flow velocity of the center of the river, the camera needs to be obliquely arranged at a certain angle, so that different areas of the acquired image have different deformations. Therefore, an automatic calibration device is urgently needed, and the automatic calibration is realized by tracking the intersection point of two laser beams and establishing the conversion relation between the image pixels and the actual scale by using the geometric relation.
Disclosure of Invention
The invention aims to: in order to overcome the defects in the prior art, the invention provides an automatic calibration device and method suitable for a large-scale surface flow field image testing system, which are used for realizing automatic calibration by tracking the intersection point of two laser beams and establishing an image pixel and actual scale conversion relationship by using a geometric relationship.
The technical scheme is as follows: in order to solve the technical problems, the automatic calibration device of the large-range surface flow field image testing system comprises a first rotary tray, a second rotary tray, a first laser emitting device and a second laser emitting device, wherein the first laser emitting device is positioned on the first rotary tray, the second laser emitting device is positioned on the second rotary tray, and a camera is installed on a river bank.
Preferably, the first rotating tray is located on the first lifting frame, the second rotating tray is located on the second lifting frame, the first lifting frame and the second lifting frame are installed on the river side, and the lowest descending position is the lowest river water level.
A method suitable for the automatic calibration device of a large-scale surface flow field image testing system comprises the following steps:
(1) Adjusting the first laser and the second laser emitted by the first laser emitting device and the second laser emitting device to the same plane;
(2) The first rotary tray and the second rotary tray are adjusted to enable the first laser beam and the second laser beam to coincide, the distance between the center points of the first laser beam and the second laser beam is A, the center of the first laser beam is used as an origin, the connecting line between the center points of the first laser beam and the second laser beam is used as an X axis, and a prototype coordinate system is established according to a right-hand rule;
(3) The first rotary tray has a rotation angle a 11 The second rotary tray has a rotation angle a 21 The camera shoots a laser image M1, and the coordinate of the intersection point P1 of the two laser beams on an image coordinate system is (x) M1 ,y M1 ) The coordinates on the prototype coordinate system are (x 1 ,y 1 ) The following steps are:
y 1 ＝A/(cot a 11 +cot a 21 )
x 1 ＝y 1 cot a 11 ；
(4) First rotary tray rotation a 12 The second rotary tray rotates a 22 The camera shoots a laser image M2, and the coordinate of the intersection point P2 of the two laser beams on the image coordinate system is (x) M2 ,y M2 ) The coordinates on the prototype coordinate system are (x 2 ,y 2 ) The following steps are:
y 2 ＝A/(cot a 12 +cot a 22 )
x 2 ＝y 2 cot a 12 ；
(5) The actual distance between P1 and P2 is:
(6) The pixel distance on the image between P1 and P2 is:
(7) The relationship between the unit pixel and the actual scale is:
α＝l/N。
in the invention, the lasers are respectively arranged on the rotating disk at a certain distance, the centers of the lasers are positioned on the same plane, the angles of the lasers are adjusted to ensure that the two lasers are completely overlapped, and the positions and the angles of the rotating disk are recorded. And respectively rotating the two laser beams to enable the two laser beams to intersect in the shooting range of the camera, acquiring an intersection point image by the camera, and then rotating the laser beams again to acquire the intersection point image. Because the rotation angle and the distance between the two groups of lasers are known, the coordinates of the intersection points of the lasers are obtained by utilizing a trigonometric function, so that the actual distance between the two intersection points is calculated; and acquiring coordinates of the laser intersection points in the image through image processing, and calculating to obtain image distances of the two intersection points, wherein the actual distances correspond to the image distances, so that system calibration can be completed. The invention adopts only one camera and two laser emission devices, the structural system is simple in composition, the calibration method is ingenious, the configuration requirement on the system is low, the cost of the device is greatly saved, and the calibration accuracy is high.
The beneficial effects are that: according to the automatic calibration device of the large-range surface flow field image testing system, the superposition surface regulated by the first laser and the second laser is parallel to the water surface, the intersection point of the two lasers is tracked in real time through the camera, the geometrical relationship is utilized to establish the conversion relationship between the image pixels and the actual scale, automatic calibration is realized, and then the calibration result is fed back to the camera, so that the flow velocity is measured and calculated more accurately.
Drawings
Fig. 1 is a diagram of a surface flow field image testing system.
Fig. 2 is an angular view of the first laser light and the second laser light rotated.
FIG. 3 is a computational schematic;
fig. 4 is a schematic diagram of an embodiment.
FIG. 5 is a schematic diagram of the system of the present invention.
Detailed Description
As shown in fig. 5, the automatic calibration device of the large-range surface flow field image testing system comprises a first rotary tray 2, a second rotary tray 5, a first laser emitting device 3 and a second laser emitting device 4, wherein the first laser emitting device 3 is positioned on the first rotary tray 2, the second laser emitting device 4 is positioned on the second rotary tray 5, the first rotary tray 2 is positioned on a first lifting frame 1, the second rotary tray 5 is positioned on a second lifting frame 6, and a camera 7 is installed on a river bank.
The method for automatically calibrating the device of the large-range surface flow field image testing system comprises the following steps of:
(1) Adjusting the first laser light and the second laser light emitted by the first laser light emitting device 3 and the second laser light emitting device 4 to the same plane;
(2) The first rotary tray 2 and the second rotary tray 5 are adjusted to enable the first laser beam and the second laser beam to coincide, the distance between the center points of the first laser beam and the second laser beam is A, the center of the first laser beam is taken as an origin, the connecting line between the center points of the first laser beam and the second laser beam is taken as an X axis, and a prototype coordinate system is established according to a right-hand rule, as shown in fig. 2;
(3) The first rotary tray 2 rotates by an angle a 11 The second rotary tray 5 rotates by an angle a 21 The camera 7 captures a laser image M1, and the coordinates of the intersection point P1 of the two laser beams on the image coordinate system are (x) M1 ,y M1 ) The coordinates on the prototype coordinate system are (x 1 ,y 1 ) The following steps are:
y 1 ＝A/(cot a 11 +cot a 21 )
x 1 ＝y 1 cot a 11 ；
(4) The first rotary tray 2 rotates a 12 The second rotary tray 5 rotates a 22 As shown in fig. 3, the camera 7 captures a laser image M2, and the coordinates of the intersection point P2 of the two laser beams on the image coordinate system are (x M2 ,y M2 ) The coordinates on the prototype coordinate system are (x 2 ,y 2 ) The following steps are:
y 2 ＝A/(cot a 12 +cot a 22 )
x 2 ＝y 2 cot a 12 ；
(5) The actual distance between P1 and P2 is:
(6) The pixel distance on the image between P1 and P2 is:
(7) The relationship between the unit pixel and the actual scale is:
α＝l/N。
example 1
1) Rotating the second rotary tray 5 by 90 deg., as shown in fig. 4, the first rotary tray 2 rotates by an angle a 1 The camera 7 captures a laser image M1, and the coordinates of the intersection point of the two laser beams on the image are (x) 1 ,y 1 ) The following steps are:
B 1 ＝A*tan a 1 ；
2) The first rotary tray 2 rotates by an angle a 2 The camera 7 captures a laser image M2, and the coordinates of the intersection point of the two laser beams on the image are (x) 2 ,y 2 ) The following steps are:
B 2 ＝A*tan a 2 ；
3) The relationship between the unit pixel and the actual scale is:
the foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (2)
1. The automatic calibration method of the large-range surface flow field image testing system is characterized by adopting an automatic calibration device of the large-range surface flow field image testing system, wherein the automatic calibration device of the large-range surface flow field image testing system comprises a first rotary tray, a second rotary tray, a first laser emission device and a second laser emission device, the first laser emission device is positioned on the first rotary tray, the second laser emission device is positioned on the second rotary tray, and a camera is installed on a river bank;
the automatic calibration method of the large-range surface flow field image testing system comprises the following steps:
1) Adjusting the first laser and the second laser emitted by the first laser emitting device and the second laser emitting device to the same plane;
2) The first rotary tray and the second rotary tray are adjusted to enable the first laser beam and the second laser beam to coincide, the distance between the center points of the first laser beam and the second laser beam is A, the center of the first laser beam is used as an origin, the connecting line between the center points of the first laser beam and the second laser beam is used as an X axis, and a prototype coordinate system is established according to a right-hand rule;
3) The first rotary tray has a rotation angle a 11 The second rotary tray has a rotation angle a 21 The camera shoots a laser image M1, and the coordinate of the intersection point P1 of the two laser beams on an image coordinate system is (x) M1 ，y M1 ) The coordinates on the prototype coordinate system are (x 1 ，y 1 ) The following steps are:
y 1 ＝A/(cot a 11 +cot a 21 )
x 1 ＝y 1 cot a 11
4) First rotary tray rotation a 12 The second rotary tray rotates a 22 The camera shoots a laser image M2, and the coordinate of the intersection point P2 of the two laser beams on the image coordinate system is (x) M2 ，y M2 ) The coordinates on the prototype coordinate system are (x 2 ，y 2 ) The following steps are:
y 2 ＝A/(cot a 12 +cot a 22 )
x 2 ＝y 2 cot a 12
5) The actual distance between P1 and P2 is:
6) The pixel distance on the image between P1 and P2 is:
7) The relationship between the unit pixel and the actual scale is:
α＝1/N。
2. the method for automatically calibrating a large-scale surface flow field image testing system according to claim 1, wherein the first rotary tray is located on a first lifting frame, the second rotary tray is located on a second lifting frame, the first lifting frame and the second lifting frame are installed on a river side, and the lowest descending position is the lowest river water level.
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