Wavelength (Color) Separation
In monochrome imaging the value of each pixel is composed exclusively of shades of gray, varying from black to white. Maximum contrast in imaging is achieved when black pixels (the weakest signal) are measured against white pixels (the strongest signal). Ideal contrast results by passing (highlighting) only relevant wavelengths from the item being inspected and blocking (darkening) the area not needed for inspection. The reverse can work just as well by blocking the wavelengths of the items being inspected and passing the background wavelengths. When contrast is maximized, errors in interpreting results will be minimized. This can greatly improve a system’s accuracy and reliability.
Color cameras may be the first thought when separating items by color, but it can be more efficient and effective to use a monochrome camera with a color bandpass filter. As shown above, to brighten or highlight an items that’s predominantly red, transmission in the red portion of the spectrum must be maximized and all other portions of the spectrum blocked. The reverse can work just as well by using a blue filter to pass blue wavelengths while blocking red.