ColorLock® filters are angle insensitive absorbing glass filters used for wide-area imaging. These filters are designed using various substrate elements to create a filter configuration that meets specific requirements in spectral performance and durability, passing MIL-SPEC severe abrasion and temperature/humidity.
Datasheet available for more information.
ColorLock® Filter Stacks are a unique product offered by Reynard that utilizes the optical characteristics of filter glass to produce a precision optical component. These filters are designed utilizing our proprietary ColorLock® software to determine a merit function and an optical layer thickness prescription of two or more glass types that meet your requirements. Once the glass types are identified, the raw materials are processed and the single optical component is produced. These filters are manufactured to meet your spectral needs for long wave pass, short wave pass, or band pass filtering, or can be custom specified for an arbitrary filtering configuration.
ColorLock® Filter Stacks perform best in bright conditions where angle insensitivity is crucial and performance is demanding. These filters are pin-hole free and offer extended out-of-band blocking, sometimes to an order >OD10.
As demonstrated in the animation below, ColorLock® Filter Stacks can achieve upwards of +/-50 degrees in angle performance without any shift in the transmitted color spectrum (upper animation). In comparison, dielectric coated filters (lower animation) perform very well only at or near zero degrees. However, as angle increases, coated filters show a significant shift to smaller wavelengths, turning an orange filter to green. If your system requires large cone angle, or wide angle performance, then ColorLock® filters are your best choice for consistant spectral performance.
When the same real filters are imaged at 0-degrees and 45-degrees, the difference in color is significant:
Dielectric Filter ColorLockTM Filter
Since the glass itself provides all of the blocking, coatings are not necessary. However, there does exist a small Frasnel loss on each air-to-substrate surface (internal surfaces do not have loss), which exists in all optical components. A broadband anti-reflection (BBAR) coating can be added to recover this approximate 8% total loss in transmission. Since the BBAR spectral range is much wider than the active spectral region of the filter, changes in angle of the filter will not affect the stabilty of the transmission band. Additionally, blocking coatings can also be added to create steeper edges for in-band performance.
Since ColorLock® Filter Stacks do not require any thin film coating on the outside surfaces, they are as durable as the glass itself. Hence, they are able to pass MIL-PRF- 13830B Temperature and Humidity testing, as well as severe abrasion and salt/fog testing.
ColorLock® Filter Stacks are ideal solutions for fluorescence imaging, in that they offer extreme out-of-band blocking levels. A ColorLock® Filter Stack can reject excitation wavelengths at OD10 levels or better at the detector, while allowing peak emission wavelengths to traverse to the detector.
Published in Laser Focus World Nov. 2014