CN110567391A - Computer image measuring system and measuring method - Google Patents
Computer image measuring system and measuring method Download PDFInfo
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- CN110567391A CN110567391A CN201910677102.XA CN201910677102A CN110567391A CN 110567391 A CN110567391 A CN 110567391A CN 201910677102 A CN201910677102 A CN 201910677102A CN 110567391 A CN110567391 A CN 110567391A
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2433—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring outlines by shadow casting
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Abstract
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.
Description
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.
Example 1
As shown in fig. 1, the present embodiment discloses a computer image measuring system, which includes an illumination light source 1, an object stage 2, a projection objective, a display screen 5, a computer 6, a display screen backlight 13, and the like, wherein the display screen 5 is a transparent display screen. The illumination light source 1, the object bearing table 2, the projection objective and the transparent display screen are arranged on one light path, when calibration or measurement is carried out, a workpiece is placed on the object bearing table 2, and the computer can control the object bearing table 2 to move in the three-dimensional direction, so that focusing of the workpiece is realized. During measurement, the illumination light source 1 illuminates a workpiece, and the projection objective projects the workpiece 3 to be measured on the display plane of the transparent display screen. Each structure will be specifically described below.
In the present embodiment, the illumination light source 1 is a transmission light source. The central axis of the illumination light beam, the center of the workpiece to be measured and the optical axis of the projection objective are on the same straight line.
In this embodiment, the object-bearing table 2 includes a three-dimensional movement mechanism and a support frame, and the workpiece to be measured is fixed on the support frame during measurement in many ways, for example, by an embedded snap-fit manner, by a thread fixing manner, by a magnetic seat fixing manner, and so on, which will not be described in detail herein. The three-dimensional motion mechanism is used for realizing X, Y, Z-axis direction movement, and the final purpose of the movement is that a workpiece to be measured placed on the support frame is convenient for measurement. The controller of the three-dimensional motion mechanism is connected with a computer.
The computer 6 in this embodiment may be a general computer, an industrial computer, or a notebook computer, a single chip microcomputer, or other controllers, and the functions realized by the computer mainly include controlling the display, processing, and storage of images on the transparent display screen. In addition, according to actual needs, the on and off of the transparent screen backlight source can be controlled.
in this embodiment, the transparent display screen is connected to the computer, the image of the workpiece to be measured is directly projected onto the transparent display screen, and the transparent display screen also receives information transmitted by the computer to display the reference scale pattern, which is usually displayed by using a CAD drawing. The user can move the CAD drawing or projection of the reference scale on the transparent display screen for calibration or measurement. Because the workpiece image is directly imaged on a transparent display screen, the boundary of the workpiece image is clearly determined on the display screen, and the limitation of the image obtained by a camera to the measurement range in the past is avoided.
In order to avoid the influence of ambient light, temperature and humidity, etc., the computer image measuring system of the embodiment adopts a box structure, and an extension port is reserved at the position of the object bearing platform 2 and used for placing or taking out a standard workpiece and a workpiece to be measured. And an observation window is arranged at the corresponding box body above the transparent display screen and used for the user to compare, calibrate the position of the workpiece to be measured and the like. In addition, a reading magnifier can be arranged at the observation window for improving the discrimination capability of human eyes on boundary positions. Or, a camera which can simultaneously acquire the graph boundary of the reference scale and the corresponding graph boundary image of the workpiece is arranged for auxiliary positioning.
In this embodiment, when the magnification of the projection lens is 20 times, the display screen is a 27-inch transparent display screen, and the magnification of the reference scale is 10 times of the projection pattern of the workpiece, the error caused by a single pixel of the high-definition transparent screen is about 1 micron.
The computer image measuring method of the embodiment comprises the following steps:
(1) Acquiring a standard workpiece image 7 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;
(2) 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.
The reference scales are all set according to the integer of the pixel number of the display screen, the boundary is an accurate whole-pixel boundary when the reference scales are displayed on a display plane, and compared with the boundary of a projection image, the reference scales can realize graph measurement by taking the pixel size of the transparent display screen as a minimum indexing unit.
In order to reduce alignment errors caused by the size of a pixel unit of the display screen, the projection boundary of a workpiece to be measured and the boundary of a reference scale can be synchronously amplified by a magnifying glass or a digital camera according to needs, so that the subdivision of the display pixels of the reference screen is realized, and the influence of the pixel unit on the measurement is limited within an allowable precision range. The invention does not require very strict lens power, and only needs to use a standard component with known length to quickly calibrate the system before measurement.
after the system is calibrated, the system adapts to different measurement accuracy and measurement ranges by selecting projection lenses (components) with different multiplying powers.
The invention is further explained below in relation to length measurements (cf. FIGS. (1-a), (1-b)).
Firstly, calibrating the system by using a standard workpiece.
To perform image measurement, an actual size value corresponding to each pixel on a display plane in the computer image measurement system is obtained. The display plane is an array formed by a plurality of pixels, the pixels can be regarded as a small square, the small square has a definite position and assigned color numerical value, and the color and the position of the small square determine the appearance of the image to be presented and are regarded as an integral unit in the whole image. In practical applications, the projected image does not exactly fall on the border of a pixel when it falls on the display screen, and exactly occupies a complete grid, and in practice, the projected image is more or less misaligned, and if the projected image is measured only according to the number of the occupied complete pixels, the measurement and calculation are not accurate.
Referring to fig. 1-a, the present invention proposes the following calibration method:
(1) A known length dimension of L0The standard workpiece 3 is fixed on a three-dimensionally movable (focusing) object-bearing table 2, the illumination light source 1 illuminates the standard workpiece 3, and the projection objective 4 projects an image 8 (A) of the standard workpiece0′B0') on the display plane of the transparent display screen 5. Reference numeral 9 in the figure denotes a computer icon reticle.
(2) a standard workpiece reference scale 8 which is pre-stored and corresponds to the design size of the standard workpiece is displayed on the display screen 5, and the boundaries at two ends are A respectivelys、BsRecording the number of pixels included in the length of the reference scale as ms。
(3) Comparing the reference scale of the standard workpiece with the boundary A of one end of the standard workpiece image 7sAnd A'0Obtaining the pixel subdivision difference value Deltam between the twos1The reference scale 8 of the standard workpiece and the boundary B of the other end of the standard workpiece are compared with each otherSand B0', obtaining a pixel subdivision difference value Deltam between the twos2；
The obtained standard workpiece image 7 has a calibration magnification ratio relative to the standard workpiece of:
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 calibration parameters are stored in the computer 6, the standard workpiece 3 is taken out, and the calibration step is completed.
and secondly, measuring the workpiece to be measured.
The measurement method is as follows:
(1) A workpiece 3 with the length L to be measured is fixed on an adjustable object bearing table 2, an illumination light source 1 illuminates the workpiece 3, and a projection objective 4 projects an image 10(A 'B') of the workpiece to be measured on a display plane of a display screen 5.
(2) And displaying a pre-stored workpiece reference scale 11 to be detected corresponding to the designed size of the workpiece to be detected on the display plane, and acquiring the number m of pixels contained in the workpiece reference scale A, B to be detected.
(3) Comparing the reference scale of the workpiece to be measured with the boundary A and A 'at one end of the image of the workpiece to be measured to obtain the pixel subdivision difference value Deltam between the reference scale and the boundary A and A' at one end of the image of the workpiece to be measured1Similarly, 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:
It is worth noting that the alignment of the workpiece image boundary with the reference scale pattern boundary can be done solely by manual judgment. And a camera capable of simultaneously acquiring the boundary of the reference scale and the corresponding boundary image of the workpiece graph to be detected can be arranged, and the alignment of the boundary of the workpiece graph and the boundary of the reference scale graph is independently realized by the camera. Of course, the method can also be completed by manual judgment and assistance of a camera.
According to the invention, through selecting the reference scale and properly amplifying the reference scale, the scale value of the workpiece corresponding to the unit pixel of the transparent display screen can be refined, so that the quantization error of the pixel size of the display screen on the measurement result is reduced.
The invention effectively reduces the quantization error of the pixel size of the display screen to the measurement result by selecting the reference scale and further subdividing and compensating the two ends of the reference scale.
In conclusion, the measurement method of the embodiment images the workpiece to be measured on the transparent display screen to obtain the clear projection boundary, and the limitation of secondary imaging of the camera on the measurement range and boundary alignment is avoided. The pixels of the display screen are used as basic measurement units, the reference scale is set, the pixels at two ends are subjected to subdivision alignment, the influence of the pixel size on measurement is effectively reduced by combining the multiplying power of the projection lens, and therefore the measurement precision is effectively improved.
Example 2
The embodiment 1 is only one basic device and a basic using method of the invention, and in practical application, the invention can meet different using requirements through obvious change and optimization. In embodiment 1, the projection light is also a backlight of the transparent display panel. In this embodiment, in order to make the display effect of the display screen better, a dedicated transparent display screen backlight 13 is added.
Meanwhile, the projection optical assembly of the present embodiment includes a main projection objective 4 and a light splitting plate 12, the display screen is a transparent display screen, the projection light beam is transmitted to the light splitting plate 12 through the main projection objective 4, and is reflected by the light splitting plate 12 to be imaged on the transparent display screen, and the display screen backlight 13 is disposed behind the light splitting plate 12.
In this embodiment, the light splitter 12 has partial reflection and partial transmission functions, and the projection light beam is reflected by the light splitter and then imaged on the transparent display screen, and the light source is lighted. The light passes through the light splitting plate and then illuminates the transparent display screen. When the normal projection imaging is carried out, the illumination on the transparent display screen is more uniform, and the purpose of beneficial measurement is achieved.
Example 3
The present embodiment has the same structure as embodiment 1 except for the following features:
In actual measurement practice, workpieces with concave or convex structures are often encountered, and the size of the depth of the concave structure needs to be measured, and a system is required to have a larger measurement working distance (namely, the distance between the workpiece and a projection lens). The direct design of a main projection lens with a large working distance is a solution, but the volume and the total length of an optical path are greatly increased. For this purpose, the present embodiment proposes that a low-power pre-objective 14 can be added in front of the projection objective 4. The structure is shown in fig. 3.
In this embodiment, the front objective lens is designed as a large-working-distance double telecentric lens with a magnification of 1, and distortion and other aberration corrections are performed. Because of the adoption of the front lens, the front working distance of the projection lens is shortened, and the total length of a projection light path is compressed. After the front objective lens is introduced, the projection is an erect image, which is beneficial to operation and measurement.
In this embodiment, the projection optical assembly has a coaxial light source 15, and the coaxial light source 15 is reflected by a coaxial light splitting plate 16, collimated on the surface of the workpiece by a front objective 14, reflected by the surface of the workpiece, and projected and imaged on a transparent display screen. The projection optics assembly has a coaxial light source to ensure geometric measurements of the surface features.
Example 4
the present embodiment has the same structure as embodiment 1 except for the following features:
Referring to fig. 4, in the present embodiment, the basic functions of embodiment 1 can also be realized by replacing the transparent display screen 5 with the conventional display screen 17. The projection optical assembly comprises a projection objective and a light splitting plate, projection light beams are transmitted to the light splitting plate through the projection objective, the projection light beams are imaged on a conventional display screen 17 after being transmitted by the light splitting plate, and then the images are convenient to observe and measure through the light splitting plate 12. Considering that the observation window is far away from the display screen, an auxiliary camera or a measuring magnifier can be arranged at the observation window for auxiliary measurement if necessary.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
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.
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