Optical filters are critical components for machine vision applications. They’re used to maximize contrast, improve color, enhance subject recognition and control the light that’s reflected from the object being inspected. A machine vision filter is not just a machine vision filter. Here’s what to look for when choosing a filter for your machine vision system:
1) Wavelength Control
Short-shifting occurs when conventional filters are placed in front of industrial imaging lenses with focal lengths of 12mm or less. StablEDGE® filters utilize absorptive filter glass to form the leading edge of the filter passband. This assures no shifting in this region, even when the lens field-of-view exceeds 100 degrees.
2) Passband Performance
Some filters on the market have a high, flat transmission profile. With this design, an overwhelming amount of ambient light is able to pass through at the weaker tail ends of the LED spectral output curve. To ensure maximum performance, the position, height and width of the passband should emulate the bell-shaped spectral output curve of the LED illumination being used.
3) High Transmission
When a ray of light passes through a glass surface, a portion of the light is reflected, resulting in a 4% transmission loss per surface. MidOpt uses anti-reflection coating on all filter designs, reducing surface reflection to less than .1%. This improves the efficiency of the vision system by increasing transmission, enhancing contrast and eliminating ghost images.
4) Quality Assurance & Repeatability
MidOpt sets the quality standard for machine vision filters. Every filter is examined to ensure near-flawless surface quality and is 100% inspected by state-of-the-art spectrophotometer technology to ensure optimal performance and repeatability. They are also one of the only manufacturers to use controlled torque when securing filters into their mounts, eliminating distortion and guaranteeing optical flatness.
5) Mounting Solutions
MidOpt offers same-day shipping and stocks over 20,000 mounted filters, ranging in size from M13.25 to M105. A variety of other mounting solutions are also available, including options for applications without filter threads, custom mounting solutions and the MidOpt exclusive 25.4® C-Mount filter.
This article was featured in Automation.