National Instruments IMAQ Vision for LabWindows TM /CVI manual

IMAQ TM IMAQ Vision for LabWindows TM /CVI TM User Manual IMAQ Vision f or LabW indows/CVI User Manual August 2004 Edi tion Part Number 3712 66A-01[...]

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© National Instruments Cor poration v IMAQ Vision for LabWindows/CVI User Manual Contents About This Manual Conventions ............ .............. ........... .............. ............ .............. .............. ........... ............. i x Related Documentation ............ .............. ........... .............. .............. .........[...]

Contents IMAQ Vision for LabWindow s/CVI User Manual vi ni.com Chapter 3 Making Grayscale and Color Measurements Define Regions of Interest .............. .............. ........... .............. .............. .............. ............ 3-1 Defining Regions Interactively ................. ... .............. ........... .............. ...........[...]

Contents © National Instruments Cor poration vii IMAQ Vision for LabWindows/CVI User Manu al Defining a Search Area .............. .............. ........... .............. .............. .. 5-16 Setting Matching Parameters and Tolerances ..... .............. ................ 5-17 Testing the Search Algorithm on Test Images ..................... .[...]

Contents IMAQ Vision for LabWindows/ CVI User Manual viii ni.com Appendix A Technical Support and Professional Services Glossary Index[...]

© National Instruments Corporation ix IMAQ Vision for LabWindows/CVI U ser Manual About This Manual The IMAQ Vision for LabWin dows/CVI User Manual is inten ded for engineers and scientists who have kno wledge of the LabW indo ws ™ /CVI ™ programming en vironment and need to create machine vi sion and image processing applications using C func[...]

About This Manual IMAQ Vision for LabWindow s/CVI User Manual x ni.com Related Documentation In addition to this manual, the fol lo wing documentatio n resources are av ailable to help you create your vision application. IMAQ Vision • IMAQ Vision C o ncepts Man u al — I f y ou are n e w to m achi n e v i sion and imaging, read this manual to un[...]

About This Manual © National Instruments Corporation xi IMAQ Vision for LabWindows/CVI U ser Manual Other Documentation • Y our National Instru ments image acquisition (I MA Q) de vice user manual—If you need installation instructions and device-specif ic information, refer to your device user manual. • Getting St arted With Yo ur IMAQ Syste[...]

© National Instruments Corporation 1-1 IMAQ Vision for LabWindows/CVI User Manual 1 Introduction to IMAQ Vision This chapter describes the IMAQ Vision for LabWin dows/CVI software, outlines the IMAQ Vision fu nction organization, and lists the steps for making a machine vision application. Note Refer to the Vision Development Mo dule Release Notes[...]

Chapter 1 Introductio n to IMAQ Vision IMAQ Vision for LabWindows/ CVI User Manual 1-2 ni.com IMAQ Vision Function T ree The IMAQ Vision funct ion tree ( NIVision.lfp ) contains separate classes corresponding to groups or type s of functions. Table 1 -1 lists the IMAQ Vision function types and gives a description of each type. Table 1-1. IMAQ Visio[...]

Chapter 1 Introductio n to IMAQ Vision © National Instruments Corporation 1-3 IMAQ Vision for LabWindows/CVI User Manual IMAQ Machine Vision Function T ree The IMAQ Machine Vision function tree ( NIMachineVision.fp ) contains separate classes corresponding to g roups or types of functions. Table 1-2 lists the IMAQ Machine Vision function types and[...]

Chapter 1 Introductio n to IMAQ Vision IMAQ Vision for LabWindows/ CVI User Manual 1-4 ni.com Creating IMAQ Vision Applications Figures 1-1 and 1-2 illustrate the step s for creating an application with IMAQ Vision. Figure 1-1 describ es the general steps to designing a Vision application. The last step in Figure 1-1 is expanded u pon in Figure 1-2[...]

Chapter 1 Introductio n to IMAQ Vision © National Instruments Corporation 1-5 IMAQ Vision for LabWindows/CVI User Manual Figure 1-1. General Steps for Designi ng a Vision Application Note Diagram items enclosed with da shed lines are optional steps. Set Up Y our Imaging System Calibrate Y our Imaging System Create an Image Acquire or Read an Image[...]

Chapter 1 Introductio n to IMAQ Vision IMAQ Vision for LabWindows/ CVI User Manual 1-6 ni.com Figure 1-2. Inspection Steps for Building a Vision Application Note Diagram items enclosed with da shed lines are optional steps. Define Regions of Interest Chapter 4: Grayscale and Color Measurements Measure Grayscale Statistics Measure Color Statistics 2[...]

© National Instruments Corporation 2-1 IMAQ Vision for LabWindows/CVI User Manual 2 Getting Measurement-Ready Images This chapter describes how to set up your imagin g system, acquire and display an image, analyze the image, and prepare the image for additional processing. Set Up Y our Imaging System Before you acquire, analyze, and process images[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/ CVI User Manual 2-2 ni.com 3. Select an IMA Q device that meet s your needs. National Instruments of fers se veral IMA Q devices, includi ng analog color and monochrome devices as well as digital de vices. V isit ni.com/imaq for more information about IMA Q devices. 4. Configu[...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Corporation 2-3 IMAQ Vision for LabWindows/CVI User Manual Y ou can create multiple images b y ex ecuting imaqCreateImage() as many times as you want. Determine the number of required images through an analysis of your intended application. The decision is based on different process[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/ CVI User Manual 2-4 ni.com Source and Destination Images Some IMAQ Vision func tions that modify the contents of an image have source image and destination image in put parameters. The source image receives the image to process. Th e destination image recei ves the processing [...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Corporation 2-5 IMAQ Vision for LabWindows/CVI User Manual • imaqAdd(myImageA, myImageA, myIma geB); This function adds two source images and stores t he result in the first source image. • imaqAdd(myImageB, myImageA, myIma geB); This function adds two source images and stores t[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/ CVI User Manual 2-6 ni.com Acquiring an Image Use one of the following methods to acquire images with a Nation al Instruments IMAQ devi ce. • Acquire a single image using imaqEasyAcquire() . When you call this function, it initializes the IMA Q de vice and acquires the next [...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Corporation 2-7 IMAQ Vision for LabWindows/CVI User Manual Use imaqReadVisionFile() to open an image file containing additional information, such as calibration info rmation, template inform ation for pattern matching, or overlay information. For more information about pattern match[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/ CVI User Manual 2-8 ni.com Attach Calibration Information If you want to attach the calibratio n information of the curr ent setup to each image you acquire, use imaqCopyCalibr ationInfo() . This function takes in a source image contai ning the calibration inform ation and a d[...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Corporation 2-9 IMAQ Vision for LabWindows/CVI User Manual If the image quality meets your needs, use the histogram to determine the range of pixel v alues that correspond to objects in the image. Y o u can use this range in processing functions, such as determining a threshold rang[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/CVI U ser Manual 2-10 ni.com Lookup T ables Apply lookup table (LUT) transformati ons to highlight image details in areas containing significan t information at the expense of other areas. A LUT transformation converts in put gr ayscale values in the source image into other gra[...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Cor poration 2-11 IMAQ Vision for LabWi ndows/CVI User Manual Convolution Filter The imaqConvolve() function allows you to use a predefined set of lowpass and highpass filters. Each filter is defined by a kernel of coefficients. Use imaqGetKernel() to retrieve predefin ed kernels. I[...]

Chapter 2 Getting M easure ment-Ready Images IMAQ Vision for LabWindows/CVI U ser Manual 2-12 ni.com • Closing—Removes d ark pixels isolated in bright regions and smoot hs boundaries. • Proper -openi ng—Removes brig ht pixels isol ated in dark regio ns and smooths the inner contours of particles. • Proper-closing—Removes dark pixels iso[...]

Chapter 2 Getting Measurement-Ready Images © National Instruments Cor poration 2-13 IMAQ Vision for LabWi ndows/CVI User Manual attenuation increases. This oper ation preserv es all of the zero frequency information. Zero frequ ency information correspond s to the DC co mponent of the imag e or the av erage intensity of the image in the spatial do[...]

© National Instruments Corporation 3-1 IMAQ Vision for LabWindows/CVI User Manual 3 Making Grayscale and Color Measurements This chapter describes how to take m easurements from grayscale and color images. You can make inspection decisi ons based on image statistics, such as the mean intensity level in a region. Based on the image statistics, you [...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/ CVI User Manual 3-2 ni.com T a ble 3-1 describes each of the tool s and the manner in which you use them. Table 3-1. T ools Palette Functions Icon T ool Name Function Selection T ool Select an R OI in the image and adjust the position of its control points and contours. A[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Corporation 3-3 IMAQ Vision for LabWindows/CVI User Manual Hold down the <Shift> ke y while drawing an R OI to const rain the R OI to the horizontal, vertical, or diagonal axes. Use the Selection T ool to position an R OI by its control points or vertic es. R OIs are c[...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/ CVI User Manual 3-4 ni.com Y ou can display the IMA Q V ision tools palette as part of an R OI constructor window or in a separate, floating w indow . Follow these steps to in v oke an R OI constructor and define an R OI from within the R OI constructor window: 1. Use ima[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Corporation 3-5 IMAQ Vision for LabWindows/CVI User Manual 3. Click OK to populate a struct ure representing the R OI. Y ou can use this structure as an input to a variety of functions, such as the following functions that measure grayscale intensity . • imaqLightMeterPoin[...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/ CVI User Manual 3-6 ni.com The following list describes ho w you can display the tools palette in a separate window and manipulate the palette. •U s e imaqShowToolWindow() to display the tools palette in a floating window . •U s e imaqSetupToolWindow() to conf igure t[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Corporation 3-7 IMAQ Vision for LabWindows/CVI User Manual or a labeled version of the binary im age as a mask image to the intensity measurement functi on. If you want to make color comp arisons, con vert the binary image i nto an R OI descriptor usin g imaqMaskToROI() . Me[...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/ CVI User Manual 3-8 ni.com Figure 3-4. Primar y Components of a 32-Bit Color Image Figure 3-5. Primar y Components of a 64-Bit Color Image Use imaqExtractColorPlanes() to extract the red, green, blue, hue saturation, intensity , luminance, or v alue plane of a color image[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Corporation 3-9 IMAQ Vision for LabWindows/CVI User Manual Comparing Colors You can use the color matching capabilit y of IMAQ Vision to compare or evaluate the color content of an image or regions in an image. Complete the f ollo wing step s to compare co lors using c olor [...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/CVI U ser Manual 3-10 ni.com Figure 3-6. T emplate Color Information The following sections explain when to learn the color information associated with an entire image, a reg ion in an image, or multiple regions in an image. Using the Entire Image You can use an entire ima[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Cor poration 3-11 IMAQ Vision for LabWi ndows/CVI User Manual Figure 3-8. Using a Single Region to Learn Color Distribution Using Multiple Regions in the Image The interaction of light w ith the objec t surface creates the observed color of that object. The color of a surfac[...]

Chapter 3 Making Grayscale and Color Measurements IMAQ Vision for LabWindows/CVI U ser Manual 3-12 ni.com Figure 3-9. Using Multiple Regions to Learn Color Distribution Choosing a Color Repr esentation Sensitivity When you learn a color, you need to sp ecify the sensi tivity required to specify the color information. An imag e containing a few, wel[...]

Chapter 3 Making Graysca le and Color Measurements © National Instruments Cor poration 3-13 IMAQ Vision for LabWi ndows/CVI User Manual Ignoring Learned Colors Ignore certain color components in color matching by rep lacing the corresponding componen t in the input color spectrum array to –1. For example, by replacing the last component in the c[...]

© National Instruments Corporation 4-1 IMAQ Vision for LabWindows/CVI User Manual 4 Performing Particle Analysis This chapter describes how to perfor m particle analysis on you r images. Use particle analysis to find statistical informat ion about particles—such as the area, location, and pres ence of particles. With this i nformation, you can p[...]

Chapter 4 Per forming Particle Analysis IMAQ Vision for LabWindows/ CVI User Manual 4-2 ni.com If all the objects in your grayscale image are either brighter or dark er than your background, you can use imaqAutoThreshold() to automati cally determine the optimal threshold range and threshol d your image. Automatic thresholding techniques offer more[...]

Chapter 4 Per forming Particle Analysis © National Instruments Corporation 4-3 IMAQ Vision for LabWindows/CVI User Manual Removing Unwanted Particles Use imaqRejectBorder() to remove particles that touch the border of the image. Reject particles on the bo rder of the image when you suspect that the information about tho se particles is incomplete.[...]

Chapter 4 Per forming Particle Analysis IMAQ Vision for LabWindows/ CVI User Manual 4-4 ni.com isthmuses while close widen s the isth muses. Close and proper-close fill small holes in the particle. Auto-m edian removes isthm uses and fills holes. Refer to Chapter 9, Binary Morphology , of the I M AQ Vision Concepts Manu a l for m o re in f or m at [...]

Chapter 4 Per forming Particle Analysis © National Instruments Corporation 4-5 IMAQ Vision for LabWindows/CVI User Manual IMAQ_MT_BOUNDING_RECT_LEFT X-coordinate of the leftmost particle point IMAQ_MT_BOUNDING_RECT_RIGHT X-coordinate of the rightmost particle po int IMAQ_MT_BOUNDING_RECT_HEIGHT Distance between the y-coordinate of highest particle[...]

Chapter 4 Per forming Particle Analysis IMAQ Vision for LabWindows/ CVI User Manual 4-6 ni.com IMAQ_MT_EQUIVALENT_ELLIPSE_MAJOR_AXIS Length of the major axis of the ellipse with the same perimeter and area as the particle IMAQ_MT_EQUIVALENT_ELLIPSE_MINOR_AXIS Len gth of the minor axis o f the ellipse with the same perimeter and area as the particle[...]

Chapter 4 Per forming Particle Analysis © National Instruments Corporation 4-7 IMAQ Vision for LabWindows/CVI User Manual IMAQ_MT_HU_MOMENT_5 Fifth Hu moment IMAQ_MT_HU_MOMENT_6 Sixth Hu mome nt IMAQ_MT_HU_MOMENT_7 Se v enth Hu moment IMAQ_MT_HEYWOOD_CIRCULARITY_FACTOR Perimeter di vided b y the circumference of a circle with the same area IMAQ_MT[...]

Chapter 4 Per forming Particle Analysis IMAQ Vision for LabWindows/ CVI User Manual 4-8 ni.com IMAQ_MT_MAX_FERET_DIAMETER_START_Y Y -coordinate of the start of the line segment connecting the tw o perimeter points that are the furthest apart IMAQ_MT_MAX_HORIZ_SEGMENT_LENGTH_LEFT X-coordinate of the leftmost pixel in the longest row of contiguous pi[...]

Chapter 4 Per forming Particle Analysis © National Instruments Corporation 4-9 IMAQ Vision for LabWindows/CVI User Manual IMAQ_MT_NORM_MOMENT_OF_INERTIA_XXX Normaliz ed moment of inertia in the x direction three times IMAQ_MT_NORM_MOMENT_OF_INERTIA_XXY Normaliz ed moment of inertia in the x direction twice and the y directio n once IMAQ_MT_NORM_MO[...]

Chapter 4 Per forming Particle Analysis IMAQ Vision for LabWindows/CVI U ser Manual 4-10 ni.com IMAQ_MT_SUM_XX Sum of all x-coordinates squared in the particle IMAQ_MT_SUM_XY Sum of all x-coordinates multiplied by y-coordinates in the particle IMAQ_MT_SUM_YY Sum of all y-coordinates squared in the particle IMAQ_MT_SUM_XXX Sum of all x-coordinates c[...]

© National Instruments Corporation 5-1 IMAQ Vision for LabWindows/CVI User Manual 5 Performing Machine Vision Ta s k s This chapter describes how to perform many common machi ne vision inspection tas ks. The most common inspection tasks are detecting the presence or absence of parts in an image an d measuring the dim ensions of parts to see if the[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/ CVI User Manual 5-2 ni.com Figure 5-1 ill ustrates the basic st eps involved in perfor ming machine visio n inspection tas ks. Figure 5-1. Steps to Performing Machine Vision Note Diagram items enclosed with da shed lines are optional steps. Locate Objects to Inspect In a typic[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Corporation 5-3 IMAQ Vision for LabWindows/CVI User Manual it appears shifted and rotated in the image you need to process. This coordinate system is referred to as the measurement co ordinate system. The measurement methods automatically mov e the R OIs to the correct position usi[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/ CVI User Manual 5-4 ni.com Using Edge Detection to Build a Coordinate T ransform You can build a coordinate transform using two edge detection techn iques. Use imaqFindTransformRect() to define a coordinate system using one rectangular region. Use imaqFindTransformRects() to d[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Corporation 5-5 IMAQ Vision for LabWindows/CVI User Manual b . If you use imaqFindTransformRects() , specify two rectangular objects, each contai ning one separate, straight boundary of the object, as shown in Figure 5-3. The boundaries cannot be parallel. The regions must be large[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/ CVI User Manual 5-6 ni.com Using Pattern Matching to Bu ild a Coordinate T r ansform You can build a coordinate transform using patt ern matching. Use imaqFindTransformPattern() to define a coordinate system based on the location of a reference feature. Us e this technique whe[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Corporation 5-7 IMAQ Vision for LabWindows/CVI User Manual Choosing a Method to Build the Coordinate T ransform Figure 5-4 guides you through cho osing the best method for bui lding a coordinate transform for your appl ication. Figure 5-4. Building a Coordinate T ransform Start Ye [...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/ CVI User Manual 5-8 ni.com Set Search Areas You use ROIs to define search areas in your images and limit the areas in which you perform your processing and inspection. You can define ROIs interactivel y or programmati cally. Defining Regions Interactively Complete the f ollowi[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Corporation 5-9 IMAQ Vision for LabWindows/CVI User Manual Defining Regions Programmatically When you have an automated application, you need to define ROIs programmatically. You can programmatical ly define regions in two ways: • Specify the contours of the R OI. • Specify ind[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-10 ni.com Finding Lines or Circles If you want to find points along the edge of an object and find a line describing the edge, use imaqFindEdge() and imaqFindConcentricEdges() . The imaqFindEdg e() function finds edges based on rectangular search areas, as sh[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-11 IMAQ Vision for LabWi ndows/CVI User Manual If you want to find points along a circular edge an d find the circle that best fits the edge, as sho wn in Figure 5-6, use imaqFindCircularEdge() . Figure 5-6. Finding a Cir cular Feature Use imaqFindEdge() and imaqFind[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-12 ni.com These functions require you to input th e coordinates of the points along the search contour . Use imaqROIProfile() to obtain the coordinates along the edge of each contour in an R OI. If you hav e a straight line, use imaqGetPointsOnLine() to obtai[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-13 IMAQ Vision for LabWi ndows/CVI User Manual Finding Points Usin g Pattern Matching The pattern matching algorithms in IM A Q V ision measure the similarity between an idealized representation of a feature, called a template, and the feature that may be presen t in[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-14 ni.com Symmetry A rotationally symmetric temp late, shown in Fig ure 5-7a, is less sensi tive to changes in rotation than one that is rotat ionally asymmetric, shown in Figure 5-7b. A rotati onally symmetric temp late provides good position ing information[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-15 IMAQ Vision for LabWi ndows/CVI User Manual Positional Information A template with strong edges in both th e x and y directions is easier to locate. Figure 5-9a sho ws good posi tional information in both t he x and y directions, whi le Figure 5-9b sho ws insuffic[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-16 ni.com the template that are necessary for shift-inv ariant matching. Howe ver, if you want to match the template at any ori entation, use rotation-invariant matching. Use the lear ningMode parameter of imaqLearnPattern2() to specify which type of learning[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-17 IMAQ Vision for LabWi ndows/CVI User Manual Figure 5-11. S electing a Sear ch Area for Grayscale P attern Matching Setting Matching Parameters and T olerances Every pattern matching algor ithm makes assumptions about th e images and pattern matching parameters use[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-18 ni.com Minimum Contrast The pattern matching algorit hm ignores all image region s in which contrast values fall below a set minimum contrast value. Contrast is the difference between the smallest and largest pi xel va lues in a region. Set the minContrast[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-19 IMAQ Vision for LabWi ndows/CVI User Manual Using a Ranking Method to V erify Results The manner in which you interp ret the pattern matching algo rithm depends on your application. For typ ical alignm ent applications, such as finding a fiducial on a wafer, the m[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-20 ni.com 5. Set the t olerances and p arameters to specify h ow t he algorithm operates at run time using the options parameter of imaqMatchColorPattern() . 6. T est the search algorith m on test images using imaqMatchColorPattern() . 7. V erify the results [...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-21 IMAQ Vision for LabWi ndows/CVI User Manual Background Information Unique background information in a template improves search performance and accuracy during the grayscale pattern matching phase. This requirement could conflict with the color information requirem[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-22 ni.com Defining a Search Area Two equally important factors define the success of a color pattern matching algorithm—accuracy and speed . You can define a search area to reduce ambiguity in the search proce ss. For example, if your image has multiple ins[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-23 IMAQ Vision for LabWi ndows/CVI User Manual The time required to locate a pattern in an image depends on both the template size and the search area. By reducing the search area or increasing the template size, you can reduce the required search time. Increasing th[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-24 ni.com Choose from the followi ng search strategies: • IMAQ_CONSERVATIVE —Uses a very small ste p size, the least amount of subsampling, and all the color in formation present in the tem plate. The conservati v e strategy is the most reliable method to[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-25 IMAQ Vision for LabWi ndows/CVI User Manual Rotation Angle Ranges Refer to the Setting Matchin g Parameters a nd Tolerances section of this chapter for informati on about rotation angle ran ges. T esting the Search Algorithm on T e st Images To determine if your s[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-26 ni.com 6. T est the color location algorithm on test images using imaqMatchColorPattern() . 7. V erify the results using a ranking method. Y ou can sav e the template image using imaqWriteV isionFile() . Convert Pixel Coordinates to Real-W orld Coordinates[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-27 IMAQ Vision for LabWi ndows/CVI User Manual Analytic Geometr y Measurements Use the following functions to make geometrical measurements from the points you detect in the image: • imaqFitLine() — Fits a line to a set of points and comp utes the equation of the[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-28 ni.com Use imaqFindLCDSegments() to calculate the R OI around each digit in an LCD or LED. T o find the area of each digit, all the segments of the indicator must be activ ated. Use imaqReadLCD () to read multip le digits of an LCD or LED. Identify Parts U[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-29 IMAQ Vision for LabWi ndows/CVI User Manual The following code sample provides an example of a typical classif ication application. ClassifierSession* session; Image* image; ROI* roi; char* fileName; // The classifier fi le to use. ClassifierReport* report; sessio[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-30 ni.com Reading Barcodes Use barcode reading functions to read values encoded int o 1D barcodes, Data Matrix barcodes, and PDF417 barcodes. Reading 1D Barcodes To read a 1D barcode, locate the barcode in the image using one of the techniques described in th[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-31 IMAQ Vision for LabWi ndows/CVI User Manual By default, imaqReadDataMatrixBarcode() assumes the barcode cells are square. If the barcodes you need to read hav e round cells, set the cellShape element of the options paramet er to IMAQ_ROUND_CELLS . Note Specify rou[...]

Chapter 5 Per forming Mac hine Vision T asks IMAQ Vision for LabWindows/CVI U ser Manual 5-32 ni.com Use the following functions to ov erlay search re gions, inspection results, and other information, such as text and bitmaps. • imaqOverlayPoints() — Overlays points on an image. Specify a point by its x-coordinate and y-coordinate. • imaqOver[...]

Chapter 5 Per forming Machine Vision T asks © National Instruments Cor poration 5-33 IMAQ Vision for LabWi ndows/CVI User Manual The following list contains the kinds of information you can overlay with the pre vious functions except imaqFindPattern() , imaqCountObjects() , and imaqFindTransformPatte rn() . • The search area input into the funct[...]

© National Instruments Corporation 6-1 IMAQ Vision for LabWindows/CVI User Manual 6 Calibrating Images This chapter describes how to calibrate yo ur imaging system, save calibration information , and attach calibration in formation to an image. After you set u p your imaging system , you may want to cal ibrate your system. If your imaging setup is[...]

Chapter 6 Calibrating Images IMAQ Vision for LabWindows/ CVI User Manual 6-2 ni.com Refer to Chapter 5, Performing Machine Vision Tasks , fo r more information about applying calibratio n information before making measurements. Defining a Calibration T emplate You can define a calibration tem plate by supply ing an image of a grid or providing a li[...]

Chapter 6 Calibr ating Images © National Instruments Corporation 6-3 IMAQ Vision for LabWindows/CVI User Manual Defining a Reference Coordinate System To express measurements in real-w orld units, you need to d efine a coordinate system in the imag e of the grid. Use the CoordinateSystem structure to define a coordinate sy stem by its origin, angl[...]

Chapter 6 Calibrating Images IMAQ Vision for LabWindows/ CVI User Manual 6-4 ni.com Figure 6-3. A Calibration Grid and an Image of the Grid Note If you specify a list of points instead of a grid for the calibration process, the software def ines a default coordinate system, as follo ws: 1. The origin is placed at the point in the li st with the lo [...]

Chapter 6 Calibr ating Images © National Instruments Corporation 6-5 IMAQ Vision for LabWindows/CVI User Manual Figure 6-4. Defining a Coordinate System Learning Calibration Information After you define a calibration grid and reference axis, acquire an image of the grid using the current imaging se tup. For information about acqu iring images, ref[...]

Chapter 6 Calibrating Images IMAQ Vision for LabWindows/ CVI User Manual 6-6 ni.com Specifying Scaling Factors Scaling factors are the real-world distances between the dots in the calibration grid in the x and y direction s and the units in which the distances are measured. Use the GridDescriptor structure to specify the scaling factors. Choosing a[...]

Chapter 6 Calibr ating Images © National Instruments Corporation 6-7 IMAQ Vision for LabWindows/CVI User Manual Choose the perspecti ve projection algo rithm when your system exhibits perspecti ve errors only . A perspectiv e projection calibration has an accurate transformation e ven in areas not co ve red by the calibration grid, as sho wn in Fi[...]

Chapter 6 Calibrating Images IMAQ Vision for LabWindows/ CVI User Manual 6-8 ni.com If the learning process returns a learni ng score below 600, try the follo wing: 1. Make sure your grid co mplies with t he guidelines listed in the Defining a Calibration Tem plate section of this chapter . 2. Check the lighting condition s. If you have too much or[...]

Chapter 6 Calibr ating Images © National Instruments Corporation 6-9 IMAQ Vision for LabWindows/CVI User Manual Simple Calibration When the axis of your camera is perpendicular to the image plane and lens distortion is negligibl e, use simple calibration. In simpl e calibration, a pixel coordinate is transformed to a real-wor ld coordinate through[...]

Chapter 6 Calibrating Images IMAQ Vision for LabWindows/CVI U ser Manual 6-10 ni.com Save Calibration Information After you learn th e calibration informatio n, you can save it so that yo u do not have to relearn the informatio n for subsequent processing. Use imaqWriteVisionFile() to save the image of the grid and its associated calibration inform[...]

© National Instruments Corporation A-1 IMAQ Vision for LabWi ndows/CVI User Manual A T echnical Support and Professional Ser vices Visit the following sections of the National Instruments Web site at ni.com for technical support an d professional services: • Support —Online technical support resources at ni.com/support include the following: ?[...]

© National Instruments Corporation G-1 IMAQ Vision for LabWind ows/CVI User Manual Glossar y Numbers 1D One-dimensional. 2D T wo-dimensional. 3D Three-dimensional. A AIPD The National Instrument s internal image file format used for saving complex images and calib ration information associ ated with an image (extension APD). alignment The process [...]

Glossary IMAQ Vision for LabWindows/ CVI User Manual G-2 ni.com barycenter The grayscale value repres enting the centroid of the range of an image’ s grayscale v alues in the image histogram. binary image An image in which the objects usually have a pix el intensity of 1 (or 255) and the background has a pixel intensity of 0. binary morphol ogy F[...]

Glossary © National Instruments Corporation G-3 IMAQ Vision for LabWind ows/CVI User Manual C caliper (1) A function in the NI V ision Assistant and in NI V ision Buil der for Automated Inspection that calculates di stances, angles, circular f its, and the center of mass based on positio ns giv en by edge detection, particle analysis, centroid, an[...]

Glossary IMAQ Vision for LabWindows/ CVI User Manual G-4 ni.com connecti vity-4 O nly pixels adjacent in the horizon tal and v ertical direc tions are considered neighbors. connecti vity-8 A ll adjacent pixe ls are considered neighbors. contrast A constant multiplication factor applied to the lu ma and chroma components of a color pixel in the colo[...]

Glossary © National Instruments Corporation G-5 IMAQ Vision for LabWind ows/CVI User Manual edge steepness The number of pixels that corr esponds to the slope or transition area of an edge. energy center The center of mass of a grayscale image. See also center of mass . equalize function See histogram equalization . erosion Reduces the size of an [...]

Glossary IMAQ Vision for LabWindows/ CVI User Manual G-6 ni.com gradient filter An edge detection algorithm that extracts the contours in gray-le vel v alues. Gradient filters include the Pr e witt and Sobel filters. gray lev el The brightness of a pixel in an image. gray-lev el dilation Increases the brightness of pi xels in an image that are surr[...]

Glossary © National Instruments Corporation G-7 IMAQ Vision for LabWind ows/CVI User Manual hit-miss function Locates objects in the image similar to the patt ern defined in the structuring element. HSI A color encoding scheme in hue, saturation, and intensity . HSL A color encoding scheme using hue, saturation, and luminance information where eac[...]

Glossary IMAQ Vision for LabWindows/ CVI User Manual G-8 ni.com image enhancement The process of improving the quality of an i mage that you acqu ire from a sensor in terms of signal-to-noise ratio, imag e contrast, edge definition, and so on. image file A f ile containing pixel data and additional information about the image. image format Defines [...]

Glossary © National Instruments Corporation G-9 IMAQ Vision for LabWind ows/CVI User Manual intensity calibration A ssigns user -defined quantities such as optical densities or concentrations to the gray-le vel v alues in an image. intensity profile The gray-lev el distribution of the pix els along an R O I in an image. intensity range Defines the[...]

Glossary IMAQ Vision for LabWindow s/CVI User Manual G-10 ni.com line gauge Measures the distance between selected edges with hig h-precision subpixel accuracy along a line in an image. For e xample, this function can be used to measure distances between points and edges. This function also can step and repeat its measurements across the image. lin[...]

Glossary © National Instruments Cor poration G-11 IMAQ Vision for LabWindows/CVI User Manu al luminance See luma . LUT Lookup table. A table containing v alu es used to transform the gray-le v el v alues of an image. For each gray -lev el v alue in the image, the corresponding new v alue is obtained from the lookup table. M M (1) Mega, the standar[...]

Glossary IMAQ Vision for LabWindow s/CVI User Manual G-12 ni.com N neighbor A pixel whose v alue af fects the v alue of a nearb y pix el when an image is processed. The neighbors of a pixel are usually def ined by a k ernel or a structuring element. neighborhood operations Operations on a point in an image that take into considerat ion the values o[...]

Glossary © National Instruments Cor poration G-13 IMAQ Vision for LabWindows/CVI User Manu al of fset The coordinate positi on in an imag e where you want to place the origin of another image. Setting an offset is useful when performing mask operations. opening An erosion followed b y a dilation. An openin g removes small objects and smooths bound[...]

Glossary IMAQ Vision for LabWindow s/CVI User Manual G-14 ni.com PNG Portable Network Graphic. An image file format for storing 8-bit, 16-bit, and color images with lossless compre ssion. PNG images ha ve the f ile extension PNG . Prewitt filter An edge detection algorith m that extracts the contours in gray-lev el v alues using a 3 × 3 filter ker[...]

Glossary © National Instruments Cor poration G-15 IMAQ Vision for LabWindows/CVI User Manu al R OI Region of inter est. (1) An area of the image that is graphically selected from a windo w displaying the image. This area can be used focus further processing. (2) A hardware-program mable rectangular portion of the acquisition window . R OI tools A [...]

Glossary IMAQ Vision for LabWindow s/CVI User Manual G-16 ni.com spatial filters Alter the intensity of a pixel relative to variations in intensities of its neighboring pixels. Y ou can use these filters for edge detection, image enhancement, noise reduction, smoothing, and so forth. spatial resolution The number of pix els in an image, in terms of[...]

Glossary © National Instruments Cor poration G-17 IMAQ Vision for LabWindows/CVI User Manu al V v alue The grayscale intensity of a color pixel computed as the av erage of the maximum and min imum red, green, an d blue v alues of that pixel. VI V irtual Instrument. (1) A combination of hard ware and/or software elements, typically used with a PC, [...]

© National Instruments Corporation I-1 IMAQ Vision for LabWindows/CVI User Manual Index Numerics 1D barcodes, reading, 5-30 2D arrays, converting to images, 2-5, 2-7 A acquiring, images, 2-5 analyzing components of color images, 3-7 images, 2-8 particles, 4-1 applications, creating Vision , 1-4 applying, LUTs, 2-10 applying to images, 2-10 arrays,[...]

Index IMAQ Vision for LabWindows/ CVI User Manual I-2 ni.com color information learning, 3-9 specifying, 3-9 color location, using to find points, 5-25 color representation sensitivity, specifying, 3-12 color score weight, 5-24 comparing, color content in images, 3-9 computing energy center of an image, 3-7 energy center of an ROI in an image, 3-7 [...]

Index © National Instruments Corporation I-3 IMAQ Vision for LabWindows/CVI User Manual error maps, learning, 6-8 examples (NI resources), A-1 external windows, displaying im ages, 2-7 extracting, planes of color images, 3-8 F Fast Fourier Transform, 2-12 features, finding in images, 5- 13 FFT, 2-12 filtering grayscale features of an image, 2-11 i[...]

Index IMAQ Vision for LabWindows/ CVI User Manual I-4 ni.com improving binary images, 4-2 improving sharpn ess of transitions, 2-10 inspecting, 2-8 learning color info rmation, 3-9 learning the color distribution , 3-10 loading from file, 2-5 measuring light intensity, 3-7 modifying complex im ages, 2-13 processing components, 3-7 reading, 2-5 read[...]

Index © National Instruments Corporation I-5 IMAQ Vision for LabWindows/CVI User Manual N National Instruments support and services, A-1 NI Vision Assistant, x NI Vision Builder for Automated I nspection, x NI-IMAQ, xi Nth order fi lter, 2-11 O objects, 5-2 inspecting, 5-2 locating, 5-2 open operation, 4-3 opening, particles, 4-3 P particle analys[...]

Index IMAQ Vision for LabWindows/ CVI User Manual I-6 ni.com search algorithm, testing, 5-18, 5-25 search areas, 5-10 defining, 5-16, 5-22 ROIs, defining search areas, 5-8 search strategies, se lecting for pattern matching, 5-23 selecting, pattern match ing search strategies, 5-23 separating, touching particles, 4-3 setting color sensitivity, 5-23 [...]