Improving the cost/performance ratio for optical filters
Filters are a critical element in the design of most optical systems. However, optimizing the trade-off between cost and performance isn’t obvious. With nearly a half century of experience in the business, Andover Corporation has a few tips to help you reduce your overall spend while still maintaining the required performance of your system design.
So, before you finalize your filter specifications, consider the following questions:
What is your application? Are you imaging or detecting energy? In most cases, the most effective way to reduce coating cost for custom filters is to avoid over-specifying your filter requirements. Extended blocking, high transmission, ultra-narrow bandwidths, steep slopes, and imaging requirements are all price drivers.
What do you want to do to the light (energy)? Knowing your transmission, reflection, and absorption requirements can allow for optimization of your coating to reduce cost.
What is your light source? Depending on the range and intensity of your light source, you may be able to specify more economic transmission specifications. Many light sources have limited spectral ranges, which allow for cost savings by choosing the appropriate out-of-band blocking range. Lesser blocking requirements allow for better transmission with fewer layers and lower cost.
What is your detector and its range? Base your blocking requirements on your detector’s response range. Many CCD and PMT detectors do not detect light above 1200 nm, so there is no need to extend the blocking range of your filter. Blocking longer wavelengths requires additional layers and increases cost.
In what environment does your optical filter operate? Temperature range, corrosive or abrasive atmosphere, vibration and angle of incidence, are just a few examples of environmental conditions that can drive optical filter cost.
Dynamic Range. What is the dynamic range the filter will be operating in? This is usually determined by the detector’s dynamic range. A filter with very high blocking can have a slightly lower transmission but a higher dynamic range. Higher dynamic range is achieved at the expense of some transmission loss. For example, a filter with a transmission of 95% and a blocking of OD 4 will have a dynamic range of 39.8 dB. A filter with a transmission of 70% and a blocking of OD 5 will have a dynamic range of 48.5 dB. Therefore, higher dynamic ranges are still possible even with a lower transmission. The allowance for a lower transmission can significantly improve the manufacturability of the filter allowing for lower cost.
Coating technology. By being open to multiple coating technology solutions, you may be able to reduce the total filter cost by using the optimal technology or technologies to meet your requirements.
Strategic ordering. Based on your expected forecast, quantities and lot sizes can be optimized allowing for a less expensive solution.
SUMMARY:Providing the above information to your Andover design engineer will let us minimize the need for expensive coating stacks and propose the best material match for your bandwidth of interest. Optimizing optical filter costs is a collaborative process between Andover and our customers. We look forward to working with you.