Lighting techniques to help read the toughest codes
Cognex DataMan and MX series of industrial, image-based barcode readers decode 1-D and 2-D codes, from printed labels to the hardest to read direct part mark (DPM) codes, and deliver industry-leading read rates.
Eric Andersen, 10-07-2014
Your ID reader has to be able to see the code in order to extract the data. When codes are printed with high contrast – such as a black code printed on a white background – seeing or imaging the code is easy. But when codes are permanently marked on parts using Direct Part Mark (DPM) methods such as dot peen, laser, or electro-chemical etching, the codes are much more difficult to read. DPM codes often require special lighting to get a good image and extract the data out of the code.
Historically, DPM-code illumination has been a challenge that required testing different lighting techniques. Once it was determined whether bright-field, dark field or diffuse-on-axis lighting gave the best results, the proper lighting components would have to be purchased and installed. While this process is not too difficult for a single application, many factories and distribution centers have many different DPM applications and testing and deploying the optimal lighting solution for each one would be a very time-consuming and expensive process.
Cognex® UltraLight® illumination technology solves this problem by combining bright-field, dark field and dome illumination in a single device that can read virtually any code on any part or surface. Bright-field lighting projects at 90 degrees to the marked surface and then reflects back up to the image to handle high-contrast labels and marks. Dark field lighting projects light at angles of 30 degrees to the marked surface which then reflects back up to the imager. This effect increases the contrast of dot peen or laser marks that are difficult to see in bright-field lighting. Dome lighting, also known as cloudy-day or diffused-off-axis illumination, projects light from many different directions to negate reflections and shadows. This technique provides even lighting across curved reflective surfaces to simulate flat objects.
It is easy to take advantage of the power of UltraLight. Out of the box, the DataMan 8600 comes with 4 preset defaults enabled and the device can read a wide variety of codes. Additionally, you can enable extended read attempts mode though the auxiliary button and this enables 4 additional read setups. Of course, you can adjust UltraLight settings manually as well by turning on and off lighting quadrants and adjusting the light intensity. The end result is that you will be able to read a wide range of marked surfaces – dot peen, laser etched, ink jet, on glass, smooth or rough metal and shiny surfaces – without having to determine your lighting needs up front.