Manuals / Brands / Computer Equipment / Network Card / National Instruments / Computer Equipment / Network Card

National Instruments IMAQ Vision for Measurement Studio Learning the Error Map, Learning the Correction Table, Setting the Scaling Method, Calibration Invalidation

1 114

Download 114 pages, 1.93 Mb

Chapter6 Calibration

IMAQVision for LabWindows/CVI User Manual 6-8 ni.com

Also, adjust the range parameter to distinguish the dots from the

background.

3. Select another learning algorithm. When nonlinear lens distortion is

present,using perspective projection sometimes results in a low

learning score.

Note Ah igh score does not reflect the accuracyof your system.

Learning the Error Map

An errorm ap helps you gauge the quality of your complete system.

The errormap returns anestimated error range to expect when a pixel

coordinateis transformed into a real-world coordinate. The transformation

accuracymay be higherthan the value the error rangeindicates. Set the

learnMapelement of the options parameter to TRUE to learn the error

map.

Learning the Correction Table

Ifthe speed of image correction is a critical factor for your application , use

acorrection table. T he correction table is a lookup table stored in memory

that contains the real-world location information of all the pixels in the

image.The extra memory requirements for this option are based on the size

ofthe image. Use this o ption when you want to correct several images at a

time in your vision application. Set the learnTable element of the

options parameter to TRUE to learn the correction table.

Setting the Scaling Method

Usethe method element of the options parameter to choose the appearance

ofthe corrected image.Select either IMAQ_SCALE_TO_FITor

IMAQ_SCALE_TO_PRESERVE_AREA.For more information a bout the

scalingmethods, see Chapter 3, System Setup and Calibration,intheIMAQ

Vision Concepts Manual.

Calibration Invalidation

Anyimage processing operation that changes the ima ge size or orientation

voids the calibration information in a calibrated image. Examples of

functions that void calibration information include imaqResample(),

imaqScale(),imaqArrayToImage(),andimaqUnwrap().

Contents

Main IMAQ Page Important Information Warranty Copyright Trademarks WARNINGREGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS Conventions Contents Chapter 1 Introduction to IMAQ Vision Chapter 2 Getting Measurement-Ready Images Chapter 3 Grayscale and Color Measurements Chapter 4 Blob Analysis Chapter 5 Machine Vision Page Introduction to IMAQ Vision About IMAQ Vision Documentation and Examples Application Development Environments IMAQ Vision Function Tree Page IMAQ Machine Vision Function Tree Creating IMAQ Vision Applications Chapter1 Introductionto IMAQ Vision Figure1-2. InspectionSteps for Building a Vision Application IMAQVision for LabWindows/CVI User Manual 1-6 ni.com Getting Measurement-Ready Images Set Up Your Imaging System Calibrate Your Imaging System Create an Image Page Source and Destination Images AcquireorReadanImage Acquiring an Image Reading a File Converting an Array to an Image Display an Image Attach Calibration Information Analyze an Image Improve an Image Lookup Tables Filters Convolution Filter Nth Order Filter Grayscale Morphology FFT Page Complex Image Operations Grayscale and Color Measurements Define Regions of Interest Interactively Defining Regions Page Page Page Page Programmatically Defining Regions Defining Regions with Masks Measure Grayscale Statistics Measure Color Statistics Figure3-4. Primary Components of a Color Image Comparing Colors Learning Color Information Choosing the Right Color Information Specifying the Color Information to Learn Using the Entire Image Using a Region in the Image Using Multiple Regions in the Image Choosing a Color Representation Sensitivity Ignoring Learned Colors Blob Analysis Correct Image Distortion Create a Binary Image Improve the Binary Image Removing Unwanted Blobs Separating TouchingBlobs Improving Blob Shapes Make Particle Measurements Page Page Convert Pixel Coordinates to Real-World Coordinates Machine Vision Locate Objects to Inspect UsingEdgeDetectiontoBuildaCoordinateTransform Page Using Pattern Matching to Build a Coordinate Transform Page Chapter5 MachineVision NationalInstruments Corporation 5-7 IMAQVision for LabWindows/CVI User Manual ChoosingaMethodtoBuildtheCoordinateTransform Figure5-4. Buildinga Coordinate Transform Set Search Areas Interactively Defining Regions Programmatically Defining Regions Find Measurement Points Finding Features Using Edge Detection Finding Lines or Circles Figure5-5. Findinga Straight Feature Finding Edge Points Along One Search Contour Finding Edge Points Along Multiple Search Contours Finding Points Using Pattern Matching Defining and Create Good TemplateImages Symmetry Feature detail Positional information Background information Trainingthe Pattern Matching Algorithm Defining a Search Area Setting Matching Parameters and Tolerances Match Mode Minimum Contrast Rotation Angle Ranges Testingthe Search Algorithm on Test Images Using a Ranking Method to Verify Results Finding Points Using Color Pattern Matching Defining and Creating Good Color TemplateImages Color Information Symmetry Feature Detail Positional Information Trainingthe Color Pattern Matching Algorithm Defining a Search Area Setting Matching Parameters and Tolerances Color Sensitivity Search Strategy Color Score Weight Minimum Contrast Rotation Angle Ranges Testingthe Search Algorithm on Test Images Finding Points Using Color Location Convert Pixel Coordinates to Real-World Coordinates Make Measurements Distance Measurements Analytic Geometry Measurements Instrument Reader Measurements Display Results Page Calibration Perspective and Nonlinear Distortion Calibration Defining a Calibration Template Defining a Reference Coordinate System Page Page Learning Calibration Information Specifying Scaling Factors Choosing a Region of Interest Choosing a Learning Algorithm Using the Learning Score Learning the Error Map Learning the Correction Table Setting the Scaling Method Calibration Invalidation Simple Calibration Save Calibration Information Attach Calibration Information A Technical Support Resources Web Support NI Developer Zone Customer Education System Integration Worldwide Support Glossary Numbers/Symbols A B C Page D E F G H I Page J K L M N O P Page Q R S T Page Index A B C D E F G H I Page Page L M N O P R S T V W Z