Computer image measuring system and measuring method
阅读说明：本技术 一种计算机图像测量系统及测量方法 (Computer image measuring system and measuring method ) 是由 马国欣 于 2019-07-25 设计创作，主要内容包括：本发明公开了一种计算机图像测量系统及测量方法,系统包括照明光源、承物台、投影光学组件、显示屏、计算机,待测工件放置在承物台上,测量时,照明光源照明待测工件,投影光学组件将工件的图像投射在显示屏的显示平面上；计算机控制显示平面上显示预存工件参考标尺图形,将参考标尺图形与工件的投影进行比对,实现测量。本发明通过设置参考标尺,在利用标准工件进行标定过程中可以实现将显示屏的像素细分,得到更准确的单个像素单元刻度值,在进行测量时,利用参考标尺对待测工件图像进行像素细分,得到更准确的像素个数,从而提高准确度。该系统和方法适用于工件几何量的快捷图形测量,也可方便地应用于精密机械加工过程的实时测量。(The invention discloses a computer image measuring system and a measuring method, wherein the system comprises an illumination light source, an object bearing table, a projection optical assembly, a display screen and a computer, wherein a workpiece to be measured is placed on the object bearing table; and controlling a display plane to display a prestored workpiece reference scale pattern by the computer, and comparing the reference scale pattern with the projection of the workpiece to realize measurement. According to the invention, by arranging the reference scale, the pixels of the display screen can be subdivided in the calibration process by using the standard workpiece, so that a more accurate scale value of a single pixel unit is obtained, and during measurement, the reference scale is used for subdividing the pixels of the workpiece image to be measured so as to obtain more accurate pixel number, thereby improving the accuracy. The system and the method are suitable for rapid graphic measurement of the geometric quantity of the workpiece, and can also be conveniently applied to real-time measurement of the precision machining process.)
1. a computer image measuring system is characterized by comprising an illumination light source, an object bearing table, a projection optical assembly, a display screen and a computer, wherein a workpiece to be measured is placed on the object bearing table; and controlling a pre-stored workpiece reference scale pattern to be displayed on the display plane by the computer, and comparing the reference scale pattern with the projection of the workpiece to be measured to realize measurement.
2. A computer image measurement system as claimed in claim 1, wherein the object table is adjustable in position in three dimensions.
3. The computer image measuring system of claim 1, wherein the projection optical assembly comprises a main projection objective and a light splitter, the display screen is a transparent display screen, the projection light beam is transmitted to the light splitter through the main projection objective, reflected by the light splitter and imaged on the transparent display screen, and a display screen backlight source is arranged behind the light splitter.
4. the computer image measuring system of claim 1, wherein the projection optical assembly comprises a front objective, a coaxial light splitting plate, a main projection objective and a light splitting plate, a coaxial light source is arranged on one side of the coaxial light splitting plate, light emitted by the coaxial light source is reflected by the coaxial light splitting plate and collimated on the surface of the workpiece through a front objective, and a projection light beam reflected on the surface of the workpiece sequentially passes through the front lens, the coaxial light splitting plate, the main projection objective and the light splitting plate and then is imaged on a transparent display screen;
The front lens adopts a double telecentric lens with the multiplying power of 1.
5. The computer image measuring system of claim 1, wherein the projection optics assembly comprises a projection objective and a beam splitter, the projection beam passes through the projection objective and then is transmitted to the beam splitter, the projection beam is transmitted through the beam splitter and then is imaged on a conventional display screen, and a viewing window is arranged in the reflection direction of the beam splitter.
6. a computer image measuring system as claimed in claim 1, wherein the computer image measuring system is a box structure, an extension opening is left at the position of the object bearing platform, an observation window is arranged at the corresponding box above the display screen, a reading magnifier is arranged at the observation window, or a camera capable of simultaneously acquiring the image of the reference scale image boundary and the corresponding image of the workpiece image boundary is arranged.
7. A computer vision measurement method, comprising the steps of:
Acquiring a standard workpiece image displayed on a display plane by a standard workpiece; displaying a pre-stored standard workpiece reference scale corresponding to the design size of a standard workpiece on a display plane, calibrating the standard workpiece reference scale according to the standard workpiece image to obtain an actual size value corresponding to each pixel on the display plane, and simultaneously obtaining the magnification of the projection optical assembly;
The method comprises the steps of obtaining an image of a workpiece to be measured displayed on a display plane of the workpiece to be measured, displaying a pre-stored reference scale of the workpiece to be measured corresponding to the design size of the workpiece to be measured on the display plane, determining the position of the image of the workpiece to be measured through an observation window by taking pixels on a display screen as a measurement unit, obtaining the number of pixels covered by the image of the workpiece to be measured according to the reference scale of the workpiece to be measured, and calculating to complete the size measurement of the current workpiece to be measured according to the actual size value corresponding to each pixel.
8. A computer vision measurement method as claimed in claim 7, wherein the calibration of the reference scale of the master artefact is performed from the master artefact image by:
(1-1) acquiring a standard workpiece image, wherein boundaries at two ends of the image are A respectively0′、B0' and displaying a standard workpiece reference scale which is prestored and corresponds to the design size of the standard workpiece on a display plane, wherein the boundaries of two ends of the standard workpiece reference scale are A respectivelys、Bs；
(1-2) obtaining the reference scale length (A) of the standard workpiecesBs) Number of pixels m involveds；
(1-3) comparing the reference scale of the standard workpiece with one end boundary A of the image of the standard workpiecesAnd A'0Obtaining the pixel subdivision difference value Deltam between the twos1Reference scale for standard workpieceand the other end boundary B of the standard workpieceSand B0', obtaining a pixel subdivision difference value Deltam between the twos2；
The obtained standard workpiece image has the following calibrated magnification ratio relative to the standard workpiece:
In the formula, L0Representing the actual length of the standard workpiece, wherein sigma is the unit pixel size of the display screen;
Through the calibration, the unit scale value of a single pixel of the display screen relative to the workpiece is as follows:
9. A computer image measuring method according to claim 8, wherein the number of pixels covered by the workpiece image to be measured is obtained according to the reference scale of the workpiece to be measured, and further the dimension measurement of the current workpiece to be measured is completed, the steps are as follows:
(2-1) acquiring an image of the workpiece to be detected, wherein the boundaries of two ends of the image are A 'and B' respectively, a prestored reference scale of the workpiece to be detected corresponding to the design size of the workpiece to be detected is displayed on a display plane, and the boundaries of two ends of the reference scale of the workpiece to be detected are A, B respectively;
(2-2) acquiring the number m of pixels contained in the reference scale A, B of the workpiece to be detected;
(2-3) comparing the reference scale of the workpiece to be detected with the boundary A and A 'at one end of the image of the workpiece to be detected to obtain the pixel subdivision difference value delta m between the reference scale and the boundary A and A' at one end of the image of the workpiece to be detected1Similarly, the reference scale of the standard workpiece and the boundary B and B 'at the other end of the standard workpiece are compared to obtain the pixel subdivision difference value Deltam between the reference scale and the boundary B and B' at the other end of the standard workpiece2；
Further obtaining the measurement length of the workpiece to be measured as follows:
10. A computer image measurement method as claimed in claim 8 or 9, wherein a reading magnifier or a camera is provided at the observation window, and the reading magnifier or the camera is used to read the next digit of the pixel subdivision difference.
Technical Field
the invention relates to the field of geometric quantity measurement, in particular to a computer image measurement system with a transparent display screen and a measurement method.
Background
optical projection image measurement techniques have been widely used for geometric measurements. Compared with the traditional contact coordinate measurement or tool microscopic alignment measurement, the image projection measurement has the characteristics of rapidness, non-contact and convenient measurement, is always concerned by the industry, and particularly shows obvious advantages in the beginning of the rapid improvement of the modern computer image technology.
The chinese invention patent publication No. 01139045 provides a method for rapid pattern measurement of a mold, which has an integral measurement feature and is much more efficient than contact measurement or point-by-point coordinate measurement. However, in the method, a camera is used for shooting the workpiece, and then the workpiece is displayed on a computer display screen and compared with a workpiece design drawing prestored in a computer to obtain the difference between the workpiece and the workpiece. Therefore, the size of the camera area array device and the pixels greatly limit the measurement range and the measurement precision. When the standard pattern of the workpiece is used for comparison measurement, the size of the display pixels of the display screen directly influences the alignment precision, and the pattern positioning reference needs to be determined indirectly, so that the method is not suitable for measurement with higher precision (such as micron-scale) and precise real-time measurement.
another common device is a contour projector, in which a workpiece standard drawing is printed on a transparent film according to the magnification of a projection lens, and the printed workpiece standard drawing is compared with the transparent film on a projection screen of the contour projector. The limitations of such measurement systems are that high objective magnification is often required to achieve higher accuracy measurements, and the size of the workpiece to be measured is therefore very limited. The contourgraph can realize high measurement accuracy in principle, but needs to print out a film accurately, which brings inconvenience to actual measurement.
in summary, the existing computer graphics measurement method has the advantages of rapidness and convenience, but the pixel size of an image sensor and a display screen in a camera greatly affects the alignment precision of images, the precision is far lower than that of the profile projector, even if a 50-time magnification lens is used, the precision is generally 5-10 micrometers, and the measurement range is greatly limited at the same time. During measurement, a base line needs to be measured accurately, then a workpiece standard design graph is positioned on a display screen, measurement uncertainty is increased, and complicated system calibration needs to be performed frequently.
At present, the requirement of industrial geometric quantity measurement on precision is higher and higher, the precision geometric quantity measurement and the on-line measurement of precision mechanical parts generally need to reach the level of 1 micron or higher, and the requirement is convenient and quick as much as possible, and the existing computer image measurement method is difficult to simultaneously measure high precision and larger size.
Disclosure of Invention
in order to overcome the defects, the invention combines the fine alignment characteristic of a contour projector and the rapid and flexible measurement characteristic of computer graphics with the development of a computer image processing technology and a high-definition computer display technology in recent years, provides a computer image measurement system and a measurement method which simultaneously use a display screen as a projection screen.
the purpose of the invention is realized by the following technical scheme: a computer image measuring system comprises an illumination light source, an object bearing table, a projection optical assembly, a display screen and a computer, wherein a workpiece to be measured is placed on the object bearing table; and controlling a pre-stored workpiece reference scale pattern to be displayed on the display plane by the computer, and comparing the reference scale pattern with the projection of the workpiece to be measured to realize measurement. The image of the workpiece to be measured is directly projected on the display screen, the projection is directly compared with the reference scale image, the display pixel of the display screen is taken as the minimum indexing unit, the image measurement is realized, and the method has the advantages of high precision and convenience in operation.
Preferably, the object bearing platform is adjustable in three-dimensional direction position. Therefore, the positions of the workpiece and the projection optical assembly can be adjusted according to different workpieces to be measured, the workpiece focusing is realized, and the projection of the workpiece on the display screen is more accurate.
preferably, the projection optical assembly comprises a projection objective, one side of the projection objective is a plane, the other side of the projection objective is a convex surface, the workpiece to be measured is arranged in front of the plane, and at the focal position of the projection objective, light passes through the convex surface and then is focused on the transparent display screen.
Preferably, the projection optical assembly comprises a main projection objective and a light splitting plate, the display screen adopts a transparent display screen, the projection light beam is transmitted to the light splitting plate through the main projection objective and reflected by the light splitting plate to be imaged on the transparent display screen, and a display screen backlight source is arranged behind the light splitting plate. By adopting the structure, the illumination on the display screen is more uniform during projection imaging, and the purpose of beneficial measurement can be achieved.
preferably, the projection optical assembly comprises a front objective, a coaxial light splitting plate, a main projection objective and a splitting plate, wherein a coaxial light source is arranged on one side of the coaxial light splitting plate, light emitted by the coaxial light source is reflected by the coaxial light splitting plate and collimated on the surface of the workpiece through a front objective lens, and a projection light beam reflected on the surface of the workpiece sequentially passes through the front objective, the coaxial light splitting plate, the main projection objective and the splitting plate and then is imaged on the transparent display screen. By adopting the optical component, a larger working distance can be obtained when a workpiece with a concave or convex structure is measured, and the total length of an optical path is reduced.
Furthermore, the front lens adopts a double telecentric lens with the multiplying power of 1.
Preferably, the projection optical assembly comprises a projection objective and a light splitting plate, the projection light beam is transmitted to the light splitting plate through the projection objective, and is imaged on a conventional display screen after being transmitted through the light splitting plate, and an observation window is arranged in the reflection direction of the light splitting plate. With this optical assembly, the image imaged on the display screen can be observed and measured through the spectroscopic plate through the observation window.
Preferably, the computer image measuring system adopts a box structure, an extension opening is reserved at the position of the object bearing platform, an observation window is arranged at the corresponding box above the display screen, a reading magnifier is arranged at the observation window, or a camera capable of simultaneously acquiring the image boundary of the reference scale and the image boundary of the corresponding workpiece image is arranged. The method is used for assisting in positioning the boundary of the workpiece projection image, and further improving the reading accuracy.
A computer image measurement method, comprising the steps of:
Acquiring a standard workpiece image displayed on a display plane by a standard workpiece; displaying a pre-stored standard workpiece reference scale corresponding to the design size of a standard workpiece on a display plane, calibrating the standard workpiece reference scale according to the standard workpiece image to obtain an actual size value corresponding to each pixel on the display plane, and simultaneously obtaining the magnification of the projection optical assembly;
The method comprises the steps of obtaining an image of a workpiece to be measured displayed on a display plane of the workpiece to be measured, displaying a pre-stored reference scale of the workpiece to be measured corresponding to the design size of the workpiece to be measured on the display plane, determining the position of the image of the workpiece to be measured through an observation window by taking pixels on a display screen as a measurement unit, obtaining the number of pixels covered by the image of the workpiece to be measured according to the reference scale of the workpiece to be measured, and calculating to complete the size measurement of the current workpiece to be measured according to the actual size value corresponding to each pixel.
Preferably, the calibration of the reference scale of the standard workpiece is performed according to the standard workpiece image, and the steps are as follows:
(1-1) acquiring a standard workpiece image, wherein boundaries at two ends of the image are A respectively0′、B0' and displaying a standard workpiece reference scale which is prestored and corresponds to the design size of the standard workpiece on a display plane, wherein the boundaries of two ends of the standard workpiece reference scale are A respectivelys、Bs；
(1-2) obtaining the reference scale length (A) of the standard workpiecesBs) Number of pixels m involveds，msis an integer;
(1-3) comparing the reference scale of the standard workpiece with one end boundary A of the image of the standard workpiecesand A'0obtaining the pixel subdivision difference value Deltam between the twos1the reference scale of the standard workpiece and the boundary B of the other end of the standard workpiece are comparedSAnd B0', obtaining a pixel subdivision difference value Deltam between the twos2；
The obtained standard workpiece image has the following calibrated magnification ratio relative to the standard workpiece:
In the formula, L0Representing the actual length of the standard workpiece, wherein sigma is the unit pixel size of the display screen;
Through the calibration, the unit scale value of a single pixel of the display screen relative to the workpiece is as follows:
The invention reads the Delta m by setting a reference scales1、Δms2The pixel subdivision difference values are all less than 1, which is equivalent to subdividing the pixels of the display screen, so that the alignment precision is improved.
preferably, the number of pixels covered by the workpiece image to be measured is obtained according to the reference scale of the workpiece to be measured, so as to complete the size measurement of the current workpiece to be measured, and the steps are as follows:
(2-1) acquiring an image of the workpiece to be detected, wherein the boundaries of two ends of the image are A 'and B' respectively, a prestored reference scale of the workpiece to be detected corresponding to the design size of the workpiece to be detected is displayed on a display plane, and the boundaries of two ends of the reference scale of the workpiece to be detected are A, B respectively;
(2-2) acquiring the number m of pixels contained in the reference scale A, B of the workpiece to be detected, wherein m is an integer;
(2-3) comparing the reference scale of the workpiece to be detected with the boundary A and A 'at one end of the image of the workpiece to be detected to obtain the pixel subdivision difference value delta m between the reference scale and the boundary A and A' at one end of the image of the workpiece to be detected1Similarly, the reference scale of the standard workpiece and the boundary B and B 'at the other end of the standard workpiece are compared to obtain the pixel subdivision difference value Deltam between the reference scale and the boundary B and B' at the other end of the standard workpiece2；
Further obtaining the measurement length of the workpiece to be measured as follows:
the invention compares the reference scale of the workpiece to be measured with the boundary of the image of the workpiece to be measured by setting the reference scale of the workpiece to be measured, and reads the delta m1、Δm2The pixel subdivision difference values are all smaller than 1, which is equivalent to subdividing the pixels of the display screen, so that the alignment precision is improved, and the obtained length is more accurate.
Preferably, a reading magnifier or a camera is arranged at the observation window, and the reading magnifier or the camera is used for reading the next digit for the pixel subdivision difference. Therefore, alignment errors caused by the size of the pixel unit of the display screen are further reduced, the reading accuracy is improved, and the boundary of the image of the workpiece to be measured is more accurately positioned.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. The invention directly projects the image of the workpiece to be measured on the display screen, and firstly, the defect of secondary imaging of the camera is eliminated. Because the workpiece image is directly imaged on the display screen, the boundary of the workpiece image is clearly determined on the display screen, and the limitation of the image obtained by the camera to the measurement range in the past is avoided.
2. The invention realizes the graph measurement by setting a reference scale and taking the display pixels of the display screen as the minimum graduation unit. After the system is calibrated, the influence of pixel quantization errors can be reduced and the measurement accuracy is improved by subdividing the boundary pixels of the reference scale. The invention can achieve micron-scale precision, is suitable for rapid graph measurement of workpiece geometric quantity, and can be conveniently applied to real-time measurement of precision machining process.
3. The invention takes the boundary of the direct projection of the workpiece on the display screen as the measurement reference, takes the pixels of the display screen as the basic measurement unit, and obtains the accurate measurement result by the amplification of the reference scale. The method can be used for quickly calibrating the system by using the workpiece with the known length before measurement, so that the method does not require very strict lens power and has the advantages of high precision, lower cost and convenient construction.
Drawings
FIG. 1 is a schematic structural view of example 1.
FIG. 1-a is a schematic diagram of the calibration process in example 1.
FIG. 1-b is a schematic view of the measurement process in example 1.
FIG. 2 is a schematic structural view of example 2.
FIG. 3 is a schematic structural view of embodiment 3.
FIG. 4 is a schematic structural view of example 4.
description of the sequence numbers: 1-an illumination light source, 2-an object bearing table, 3-a workpiece to be measured, 4-a main projection objective, 5-a display screen, 6-a computer, 7-a standard workpiece image, 8-a standard workpiece reference scale, 9-a computer marking cross line, 10-a workpiece image to be measured, 11-a workpiece reference scale to be measured, 12-a light splitting plate, 13-a display screen backlight source, 14-a front objective, 15-a coaxial light source, 16-a coaxial light splitting plate and 17-a conventional display screen.
Detailed Description
the present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
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