How to Correct False Positive Readings from IMAQ Read LCD VIPrimary Software: Vision Development ModulePrimary Software Version: 1.0 Primary Software Fixed Version: N/A Secondary Software: N/A
Problem: I am using IMAQ Read LCD VI to read the digits from my LCD but some of the segements that are not illuminated are being detected as being on. Is there any preprocessing I can do to minimize these false positive readings? Solution: First, ensure you are using the appropriate lighting for your application. For more information, please refer to A Practical Guide to Lighting - Part I, Part II and Part III. Even with the proper lighting you may still be seeing uneven coloring on segments. To minimize this, use the IMAQ Local Threshold VI to differentiate the segments from the background. This VI thresholds the image into a binary image based on the specified local adaptive thresholding method. By thresholding the image prior to IMAQ Read LCD VI we have made the pixels in each segment uniform, reducing and possibly eliminating false positive readings.  For more information on this method please see: Adaptive Thresholding in IMAQ Vision. Related Links: Developer Zone Tutorial: A Practical Guide to Machine Vision Lighting - Part I Developer Zone Tutorial: A Practical Guide to Machine Vision Lighting - Part II Developer Zone Tutorial: A Practical Guide to Machine Vision Lighting - Part III Developer Zone Tutorial: NI Recommended Camera, Lighting, and Optics Providers Developer Zone Tutorial: Control Advanced Illumination Strobe Lighting with LabVIEW Developer Zone Tutorial: Adaptive Thresholding in IMAQ Vision Developer Zone Example: LCD Example Attachments:  LCD threshold.gif
Report Date: 09/12/2008 Last Updated: 09/16/2008 Document ID: 4PBCJ58Q |
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