Lasers are often used to make distance measurements, sometimes in three dimensions, but may not be capable of high accuracies. A special type of laser called a “diode laser” can be strobed. Lasers are highly collimated light sources which have high intensity, allowing them to be mounted a distance from the object being inspected. Using high frequency ballasts can help reduce the amount of flicker but can’t eliminate it entirely. Fluorescent lights also flicker due to the frequency of the AC power source, which can affect the image quality of vision inspection applications. The limiting factors here are that fluorescent lights can’t be strobed, they degrade over time, and it’s difficult to dim them. They are available in many shapes and sizes and provide diffuse light that minimizes glare. If halogen light is to be used for an inspection application, it would be beneficial to run the lights at 80% of their maximum power to extend their life, keeping the voltage constant to avoid color changes, and using fiber optics to enable mounting the lamp remotely if the application is sensitive to the heat produced.įluorescent lighting sources are relatively inexpensive. They tend to run very hot and lose intensity over time. Halogen lights are also limited by their poor strobing capability. Halogen lights are good for applications where very bright lighting is required. Illumination choices for machine vision system designers now include halogen, incandescent, fluorescent, compact-fluorescent, plasma-type, high-intensity discharge (HID), Xenon, and light-emitting-diode (LED), fiberoptic, and structured light sources. For this reason, it is important to understand how the material, size, shape, color, and surface finish of the object you are illuminating will affect light reflected off the object, and what challenges these physical characteristics of the object(s) under inspection may pose. Lighting is a pivotal factor in the design of a machine vision system because these systems create images by analyzing the reflected light from an object, not by analyzing the object itself. This is unsurprising when we consider how often the importance of lighting as a factor in the success of a machine vision application has been discussed thus far. Vision System Design’s online Buyer’s Guide lists well over 100 different suppliers of lighting and illumination products.
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