Case Study: Collaborative Filter Design Enables Multispectral Imaging
Overview
A customer developing a multispectral fluorescence imaging system for biological tissue needed custom optical filters capable of resolving seven fluorescent dyes across eight image volumes. Engaged from the beginning of the project, Chroma Technology provided initial proposals, modeled spectral curves alongside, and refined the filter set through iterative design reviews over two years. Close collaboration resolved spectral, mechanical, and scheduling challenges—delivering filters that matched expected performance at first assembly.
The Technology Focus was custom multi-notch filters, bandpass filters, dichroics, and compensation plates for multi-camera fluorescence detection
The Challenge
Without early collaboration with Chroma, the system risked being designed around filter performance that couldn’t realistically be achieved.
The instrument used four cameras and three dichroic beam splitters to separate fluorescence signals across multiple detection paths. This created compounding requirements:
- Multi-notch filters required >OD6 blocking at several excitation laser lines while maintaining high transmission in adjacent emission bands.
- Several filters also served as compensation plates, demanding tight thickness tolerances alongside demanding spectral performance.
- Components up to 4” × 4” required high-quality reflected wavefronts after coating—sensitive to coating stress and uniformity across large apertures.
- Staged deliveries to teams in Germany and the United States added coordination complexity under a tight schedule.
The Solution
Rather than quoting against the initial specification alone, Chroma provided modeled spectral curves with its first proposal. This let the customer’s engineers run realistic system simulations early, revealing spectral overlaps that could have degraded dye separation had they gone unaddressed.
Over multiple design iterations, the teams refined the full filter set. Key adaptations included:
- Redistributing performance requirements across two filter elements when single-filter designs exceeded manufacturing margins.
- Replacing dicing with precision milling for thick substrates, improving dimensional accuracy and enabling recovery of partially damaged components.
- Multiple coating iterations on multi-notch filters to achieve the required blocking depth across large substrates.
Key Features of the solution included:
- Alignment – Compensation elements aligned correctly within the optical assembly.
- Spectral measurements – Matched modeled performance, supporting the planned fluorescence separation strategy.
- Delivery – Staged international deliveries were coordinated successfully, keeping the program on schedule.
- Process improvements – Milling vs dicing reduced scrap and recovered usable components.
Implementation Sequence
The implementation included the following steps:
- Specification Hand-Off
- Joint Design Review
- Prototype Fabrication Validation
- Staged Delivery and Final Integration
Conclusion
The most successful multispectral filter programs engage specialists early, design at the system level, and build in flexibility — because trade-offs between blocking depth, edge slope, and manufacturability rarely surface in simulation alone. As spectral architectures grow more complex, filters are no longer a late-stage procurement decision. The most reliable path to a working instrument starts with solving the filter problem together.
About Chroma Technology
Chroma Technology is a leading manufacturer and OEM supplier of high performance optical filters used in a wide range of applications, such as communications, inspection and metrology, astronomy, life sciences and health care, microscopy, calorimetry, machine vision, and Raman spectroscopy. Chroma offers an extensive selection of optical filter sets and filter accessories, as well as custom solutions tailored to customer-specific needs
For more information or a quotation for Chroma products, contact IL Photonics.