Optimizing Optical Filter Components for Subassemblies Navigating Challenges in Optical Filter Subassemblies Manufacturing is more than just putting parts together. It’s coming up with ideas, testing principles and perfecting the engineering, as well as final assembly. ― James Dyson Abstract: Navigating Challenges in Optical Filter Subassemblies Achieving the right balance between individual component performance and overall system design is essential to reducing development times, controlling costs, and achieving peak performance. System designers who seek to enhance the performance of not just individual components but entire subassemblies will find that an optimized approach to multiple components yields superior results. This paper explores strategies for optimizing filter subassemblies through both system-level and component-specific considerations, offering practical tools for overcoming design challenges. System-Level Design Considerations for Subassemblies In designing optical filter subassemblies, every system requires unique consideration to optimize both performance and cost. System designers looking for cohesive, optimized subassemblies should consider how a carefully selected set of components can maximize overall system performance, ensuring each element works in concert for peak efficiency. Balancing factors such as filter placement, beam shape, environmental conditions, and integration with light sources and detectors is critical to achieving efficient, high- performance optical systems. A comprehensive approach to system-level design—one that evaluates each element holistically—can simplify assembly, minimize costs, and streamline development. Here are some fundamental areas for system-level optimization: Imaging vs. Non-Imaging Systems Understanding whether an optical system is designed for imaging is essential when specifying filters, as imaging and non-imaging systems have distinct requirements. In imaging systems, where spatial information is preserved, filters must minimize transmitted wavefront distortion to maintain image quality. Components such as dichroic mirrors and other reflective optics also need minimal reflected wavefront distortion to avoid degrading the final image. Additionally, for imaging systems requiring precise image registration, particularly where filters or dichroics are swapped in and out, low wedge angles and tight thickness control are important. In contrast, non-imaging systems using detectors, such as photomultiplier tubes (PMTs) or photodiodes, function as “light buckets” with no spatial information. For these non-imaging systems, requirements for wavefront distortion and registration are typically more relaxed. However, non-imaging systems may still require specific considerations based on the spectral and intensity characteristics of the light. For filters positioned near an imaging plane, factors such as surface quality, defects, and pinholes are particularly important, as they can cause visible artifacts in the image. Accounting for 1 Optimizing Optical Filter Components for Subassemblies whether a system is imaging or non-imaging early in the design process ensures that filters meet the application’s specific needs without unnecessary costs or over-specification. Light Source and Detector Matching When integrating filters with light sources and detectors, understanding both the spectral output of the light source and the sensitivity of the detector is essential. Different combinations, such as a xenon arc lamp with a photomultiplier tube (PMT) versus a laser with a CMOS sensor, present distinct filtering requirements. With a broad-spectrum source such as a xenon lamp, filters are typically used to select or block certain regions of the spectrum, ensuring that the detector only receives wavelengths of interest. This is essential when using sensitive detectors such as PMTs, which can detect a wide range of wavelengths but may be susceptible to noise from unwanted wavelengths. On the other hand, a narrow-spectrum light source, such as a laser, emits light at a very specific wavelength but has spurious (unwanted) emissions sometimes very close to the primary laser line wavelength, so a filter might need very steep transitions and high blocking “near-band”, but would not necessarily need blocking far from the band. In this case, narrow bandpass filters are used to further isolate the laser wavelength, preventing interference from ambient light or other spectral noise. In both cases, understanding the overlap between the light source’s emission spectrum and the detector’s sensitivity profile is crucial. This allows for selecting appropriate filters—such as bandpass, longpass, or shortpass filters—that enhance the desired signal, minimize noise, and improve overall detection accuracy. Filter Placement and Optical Path Considerations Strategically positioning filters within the optical path is essential for achieving an optimal balance of performance and cost. Each potential filter location in the optical path offers distinct benefits and limitations, influenced by factors such as beam shape, cone angle, and intensity distribution. Identifying the ideal position often allows designers to maximize efficiency while minimizing the size and cost of the filter, though the best location varies based on the system’s unique design requirements. The key point regarding filter placement in the optical path is to consider filters early in the design process, rather than as an afterthought, to avoid costly redesigns and ensure that they integrate seamlessly within the broader system architecture. System designers that treat optical filters as a key component of the optical system are more likely to develop a practical, cost-effective solution that prevents filters from being pushed beyond their limits, which would otherwise increase costs or compromise functionality. Environmental and Operational Conditions Environmental factors—such as temperature, humidity, vacuum conditions, and potential exposure to radiation—are important to address for long-term filter stability and durability. Systems that operate in high-intensity light conditions, Chroma Technology Corp whether from lasers or intense arc lamps, may require filters with specialized coatings and robust thermal management. Taking environmental conditions into account at the start of design avoids premature filter degradation and ensures consistent performance across a range of operational settings. By considering system-level factors such as these early in the design process and collaborating closely with manufacturers, system designers can optimize optical filter subassemblies for both performance and cost. Establishing these foundational elements at the outset simplifies the subsequent task of fine-tuning individual components, leading to a well-balanced, efficient, and cost-effective optical filter subassembly. Optimizing Optical Filter Components for Performance and Cost Optical filters are essential components that directly impact the performance of complex optical systems. However, achieving optimal performance often involves trade-offs in cost and product lead time. Deciding between catalog filters and custom solutions is a key step in balancing these considerations. Both options have unique advantages—catalog filters offer off-the-shelf availability, while custom filters can be tailored to meet specific system requirements. Understanding when to utilize the two available options provides distinct advantages for system designers in terms of both cost and performance. Catalog vs. Custom Filters: Choosing the Right Option Catalog Filters: Pre-designed and readily available. Catalog filters are ideal for prototyping, quick replacements, or standard applications. However, they are pre-designed for general use, often including features such as deep blocking and high surface quality that may exceed the needs of specific applications thus making them more costly. Custom Filters: Designed to meet the exact performance specifications of an application. Custom solutions are particularly advantageous for subassemblies where multiple components must work together, which catalog options might not be able to address as effectively. Custom filters eliminate unnecessary requirements, ensuring efficient manufacturing and lower costs. Customization allows for flexibility in performance characteristics—such as angle of incidence, blocking levels, and substrate material—ensuring that only what is essential is included in the design. Collaboration with manufacturers early in the design phase helps customers determine when a custom filter will provide better performance and cost-efficiency compared to catalog options. Both catalog and custom filter options benefit from carefully considering key filter characteristics that directly impact cost, lead time, and optical performance. For custom filters, small adjustments to these parameters can deliver substantial savings, while with catalog filters, selecting the right specifications avoids unnecessary expense. 3 Optimizing Optical Filter Components for Subassemblies Key Characteristics to Optimize for Optical Filters After deciding between catalog and custom filters, adjusting specific filter characteristics can further align performance with system requirements while controlling costs. In many cases, relaxing certain specifications— such as AOI range, blocking levels, or surface quality—provides sufficient performance without the added expense of over-engineering. To optimize the relationship between the performance and cost of the filter component, consider the following filter parameters for your subassembly: Filter Parameter Challenge Solution Angle of Incidence (AOI) and Cone-angle Filters that accept a wide range of AOI or have to be used with an incident beam having a large cone- angle require advanced coatings, increasing complexity and cost. Narrow the AOI range or collimate the beam (use filter in infinity space) to simplify design and reduce costs. Blocking Requirements Deep out-of-band blocking in catalog filters is often unnecessary for certain applications. Customize blocking levels based on the light source and detector to reduce coating layers, minimizing production time and costs. Edge Steepness Steep edges require thicker coatings increasing cost. Relax steepness when sharp transitions aren’t critical to save on manufacturing costs. Wavelength Tolerance Tight wavelength tolerances mean lower yields and therefore more cost. Loosen wavelength tolerances where they can to improve yield and reduce cost. Filter Shape Custom shapes increase processing time. Opt for rectangular shapes to improve throughput and reduce costs. Packaging Individual packaging increases inspection time. Choose bulk packaging to reduce inspection time. Substrate Material High-end substrates such as fused silica are costly but not always required. Use cost-effective substrates or relaxed specifications especially for non-imaging systems. Surface Quality Strict scratch/dig requirements decrease yield. Relax surface quality requirements for non- imaging systems to reduce costs. Aligning specifications with actual system needs can be a complex process. System designers should collaborate with manufacturers to optimize performance while controlling costs. Chroma Technology Corp Collaboration as the Foundation for Effective Optical Solutions Success in developing custom optical subassemblies relies on collaboration between system designers and manufacturers. Providing comprehensive system information—such as performance goals, environmental conditions, and system constraints—allows your manufacturing partner to tailor solutions to meet your needs. Manufacturers routinely sign NDAs to protect proprietary information, ensuring that even sensitive data can be safely shared. With early engagement, manufacturers can help align designs with system requirements from the start, minimizing costly redesigns. In addition, experienced engineers can also uncover opportunities that might otherwise go unnoticed, ensuring that even ambitious design goals are achievable within reasonable timelines and costs. budgets. Rapid Prototyping: Custom on a Catalog Timeline Prototyping is key in developing optical filter subassemblies, offering precision-engineered custom solutions on timelines comparable to catalog filters. Early prototypes help validate designs with system requirements, ensuring that key elements perform as expected. By identifying potential issues early, rapid prototyping reduces the risk of redesigns and delays, making even complex projects manageable. Manufacturers like Chroma and 89 North combine engineering expertise with advanced prototyping capabilities to fine-tune designs and streamline integration. By delivering custom solutions quickly, they help customers meet performance objectives without compromising speed or quality. About Chroma Technology Chroma Technology is a leading manufacturer of very durable and highly precise optical filters. Chroma has been supplying highly precise optical filters for industries ranging from the life sciences to astronomy, industrial inspection, security, and aerospace for over 30 years. Chroma Technology’s reputation is built on dedicated customer service, including free technical and application support. About 89 North Chroma Technology’s Collaboration Chroma Technology and 89 North combine decades of experience in optical filter manufacturing and system design to deliver high-performance subassemblies tailored to your specific needs. Our collaborative approach ensures that every project benefits from thoughtful consultation, advanced prototyping, and precise engineering. With the ability to provide custom optical solutions on catalog-like timelines, we help customers streamline development and achieve their goals without compromising quality or speed. Whether you need a custom filter or complete system-level support, we partner with you from concept to completion, ensuring that your project is optimized for performance, cost, and seamless integration. Phone: +1 800.824.7662 Email: [email protected] Website: www.chroma.com/request-a-quote For more info visit: https://www.chroma.com 100% Employee Owned 5 Optimizing Optical Filter Components for Subassemblies November 2024 Advancements in biomedical imaging, automation, remote sensing, and many other photonics applications have increased the complexity of optical systems. These demands require higher performance and tighter tolerances while managing costs, environmental constraints, and system-level challenges. US Corporate Headquarters 10 Imtec Lane Bellows Falls, Vermont 05101 US [email protected] Tel: +1-800-824-7662 +1-802-428-2500 Chroma Technology GmbH Maximilianstrasse 33 D-82140 Olching, Germany [email protected] Tel: +49-8142-2847525 Chroma China Rm 803, Building No.16 Yuanbo Wuli Xingjin Road, Jimei District Xiamen City, Fujian Province 361021 Phone: +86-0592-5062089 [email protected] Chroma Technology Japan 8F Yokohama Onoecho Building 4-57 Onoecho Naka-ku Yokohama 231-0015 Japan Phone: +81 (0) 45 285 1583 Fax: +81 (0) 45 285 1501 [email protected] ®