What is the difference between a machine vision filter and a narrow band filter?
Tolerance Shift Each LED lamp has a nominal peak wavelength at which it is intended to operate. Due to manufacturing tolerances, however, that peak can vary +/- 10nm and 20-30nm on the tail ends of the output curve. A narrow bandpass filter will not cover all of that tolerance shift and will block some, if not most, of the light’s output. The MidOpt broad bandpass filter will easily accommodate a normal tolerance shift in either direction. Blue Shift When a subject is viewed at an angle to a filter, the reflected light travels a path through the filter that is significantly longer (say, 1.4x) than if it’s straight-in. Each layer of coating is then optically thicker which creates a phenomenon known as “blue shifting.” At 45º, this equates to a shift of about 30nm; a 20nm bandpass filter doesn’t have enough width to allow for that shift. Therefore, the scene gets darker, often much darker as it moves toward the edge of the frame. MidOpt filters are broad enough that the blue shift effect
