Aluminum components and housings used for Optical products, are oftentimes subject to stray light, strong UV light, or outgassing when used in a vacuum with high intensity light exposure, such as in satellites.
Traditionally, black anodize has been used for Optical components without regard to stray light. Traditional black anodize is comprised of a clear anodic oxide film (anodize) , which is then immersed in a dye stuff to color it black. Dye stuffs come in a variety of formulations, but they all have organic components, and some have metallic components as well. These organic components in the black dye are subject to degradation under strong light, and are typically not suited to long term outdoor or high intensity UV light applications. UV and sunlight degrade the organic material in the dye, and the response to this degradation is for the black color to fade.
Depending on the dye selected, the color will fade toward the base color of the black dye, and the resulting faded anodic surface will appear purple, brown, green, or grey. The exposure time for a dyed surface to fade can be weeks, to months, to a year or more, but in the end, all anodized films dyed with black dye will fade to some degree.
The anodizer can select specific dye chemistry and sealing techniques to minimize the fading effect of traditional dye, and Pioneer has developed a very robust black dye system with the highest fade resistance in the industry. However, it is not totally fade resistant, and will outgas in specific applications.
Optical Black® from Pioneer Metal Finishing solves this issue. It does not fade. It does not outgas, and it has very interesting spectral absorbance characteristics when compared to traditional black anodize films.
LIDAR systems can also benefit from the properties of Pioneer’s Optical Black®. Up to 85% of reflected light absorbed in the critical 900-1600nm wavelengths. This improves the sensitivity and discrimination in these critical safety systems.
Optical Black® is produced under strict controls. The anodic film is .7 Mils – 1.0 Mils thick, and then colored using a proprietary system which provides a completely fade resistant coloring system. There are no organic components in the anodize film to break down, so the Optical Black® anodize coating is extremely stable and robust in any high intensity light environment.
In addition to the fade resistance properties in this coating system, reflectivity across the Visible and Ultra-Violet spectrums is significantly reduced compared to traditional black anodize. Reductions in reflectivity are reduced as much as 85% times compared to traditional black anodize. At 1500 nm, Optical Black® has been measured at 4% reflectivity vs 23% for traditional Black Anodize.
Tested with N&K Technology’s Olympian Scatterometry System
The graph above, created with results from N&K Technology Olympian Series Scatterometry System shows the difference between standard black anodize, and Pioneer’s Optical Black system. The difference in performance is significant. The standard black anodize sample was produced per Mil A-8625 Type II, Class 2 Black Anodize.
Optical Black® has been successfully used in many optical systems including cameras, lenses, night vision, IR scanning equipment, satellite vision and sensor systems, laser systems, and other highly critical optical applications where reduced reflectivity, greater absorbance, and elimination of outgassing is needed to the optical system performance.
Pioneer can successfully coat parts up to 24” x 24” with Optical Black® in 6000 and 5000 series alloys. Extensive masking and plugging services are also available for complex components.
For more information on Optical Black®, or all the finishing options from Pioneer Metal Finishing, please Click Here.