7.3.1 Measurement Accuracy and Depth of Field
Telecentric lenses have a large focus range, also known as depth of field. Within this range, the instrument is expected to measure with an accuracy of about ten microns or better for a one-inch artifact.
However, the most repeatable results can be achieved by taking the time to adjust focus using digital zoom.
To do this, digitally zoom in on an edge and adjust focus until the pixels appear on that edge. This will ensure the best and most repeatable measurements are obtained. See images below.
Poor Focus
Good Focus
7.4 Lighting Strategy
Once the image has been properly focused, adjust front and back lighting using the on- screen sliders provided by M3 software. You can also utilize room lighting, or shield the system from room lighting, as appropriate. Correct lighting is paramount to accurate measurement with any video-based measurement system. A clear image with lighting toward the low side is recommended. Lighting that is too low will result in a dark, low-contrast image with indiscernible features. Lighting that is too bright might result in a washed-out image and in hot spots (or blooms) that provide false edges. When adjusting lighting, start with light that is lower than desired, then increase lighting while viewing the image on the computer monitor. Maintain constant lighting for consistent results. Do not change light levels between points used to measure the same geometrical feature.
Made with FlippingBook - professional solution for displaying marketing and sales documents online