National Instruments IMAQ Vision for LabWindows TM /CVI Chapter 6 Calibrating Images

Contents

Defining a Search Area.....................................................................5-16

Setting Matching Parameters and Tolerances...................................5-17

Testing the Search Algorithm on Test Images..................................5-18

Using a Ranking Method to Verify Results......................................5-19

Finding Points Using Color Pattern Matching................................................5-19

Defining and Creating Good Color Template Images...................... 5-20

Training the Color Pattern Matching Algorithm...............................5-21

Defining a Search Area.....................................................................5-22

Setting Matching Parameters and Tolerances...................................5-23

Testing the Search Algorithm on Test Images..................................5-25

Finding Points Using Color Location..............................................................5-25

Convert Pixel Coordinates to Real-World Coordinates.................................................5-26

Make Measurements......................................................................................................5-26

Distance Measurements...................................................................................5-26

Analytic Geometry Measurements..................................................................5-27

Instrument Reader Measurements...................................................................5-27

Identify Parts Under Inspection.....................................................................................5-28

Classifying Samples........................................................................................5-28

Reading Characters..........................................................................................5-29

Reading Barcodes............................................................................................5-30

Reading 1D Barcodes........................................................................5-30

Reading Data Matrix Barcodes.........................................................5-30

Reading PDF417 Barcodes...............................................................5-31

Display Results..............................................................................................................5-31

Chapter 6Calibrating Images

Perspective and Nonlinear Distortion Calibration.........................................................6-1

Defininga Calibration Template .....................................................................6-2

Defininga Reference Coordinate System .......................................................6-3

Learning Calibration Information....................................................................6-5

Specifying Scaling Factors................................................................6-6

Choosing a Region of Interest...........................................................6-6

Choosing a Learning Algorithm.......................................................6-6

Using the Learning Score..................................................................6-7

Learning the Error Map.....................................................................6-8

Learning the Correction Table..........................................................6-8

Setting the Scaling Method...............................................................6-8

Calibration Invalidation....................................................................6-8

Simple Calibration.........................................................................................................6-9

Save Calibration Information.........................................................................................6-10

Attach Calibration Information......................................................................................6-10