Machine vision lights require accurate and robust illumination. Typically installed close to the target object, LED fixtures are currently the lighting system of choice for such applications. The placement of the LED lamps dictate how the light is casted on the object. LED illumination methods covered below include full bright field, partial bright field and dark field lighting techniques.
Full Bright Field Configuration
Full bright field is applicable to machine vision operations when the sample requires multi-directional illumination. A common setup entails the use of a dome accessory, which diffuses the light beams for maximum reflectivity. Furthermore, the LED lamp must be positioned close to the target (but does not have to be pointed directly at the sample), with the sides of the dome serving as a reflector. By comparison, a flat diffuse configuration incorporates a straight diffusing accessory.
For detecting object orientation and inconsistencies (quality assurance), LED back lighting is the preferred technique. A colored LED light, such as blue, green or red, may be used by the operator for distinguishing markings on labels. Flexibility is introduced to LED machine vision lights when the units are equipped with several lighting features. For example, an LED light bar may offer high-color temperature white light, with an optional red beam that can be toggled.
Partial Bright and Dark Field Illumination
Partial bright field illumination utilizes traditional illumination methods. An LED spotlight is applied to the sample, in the same way individuals point a flashlight at an object. This lighting technique is effective for producing contrast and inspecting detail on the surface of the sample.
In machine vision, dark field illumination refers to angled lighting methods, which can be directional, linear or circular. Glare reduction is one of the greatest benefits of dark field illumination, due to the way light is reflected away from the monitoring device (camera).