What are Optical Homogenizers, and What Applications do they Serve?
Homogenizers, also known as ‘light pipes’, are examples of optical waveguides that are designed to combine and integrate a number of sources – and power levels – of light, including lasers; even out a single source of light input (homogenize), and reduce coherence. Homogenizers accomplish this feat via total internal reflection to consolidate multiple disparate optical wavelength sources into one uniform output throughout the cross-section of the waveguide.
Since they can combine sources of the same or different wavelengths and/or power levels, homogenizers are found in diverse applications. These uses can range from automotive display backlighting to medical device imaging, to wafer inspection–And that’s just scratching the surface.
Factors and Specs to Consider When Designing Custom Optical Homogenizers
Oftentimes, componentry design specs are driven by budget. Optical engineers have several parameters to specify when designing a homogenizer within cost constraints – among them, cost, quality, size, material, shape, and end-face angle. And while stock products are also available on the market and ‘off-the-shelf’, these offerings rarely provide the highest levels of efficiency or optimal size for enclosure packaging.
Optical homogenizers are designed as shapes along the length axis to achieve customer-specified efficiency. Round, square, hexagonal, tapers, round to square taper, and octagonal homogenizers are among the most common variants. In general, efficiency increases with the number of facets a homogenizer features; for example, a homogenizer with a hexagonal cross-section provides 35% greater transmission than the equivalent-size rectangular rod.
Another critical aspect of homogenizer design is edge-face coating and angles. In many cases, homogenizers are designed and manufactured such that the input face of the rod is perpendicular to the side faces. This is done in the interest of device packaging, as this configuration enables easier coupling between an input and the homogenizer. Likewise, many homogenizers also use a perpendicular output face. That said, many other designs utilize a tilted facet at a Brewster’s angle to mitigate surface reflection losses
Furthermore, depending on application, many homogenizers also utilize a custom optical coating on both end faces to improve light throughout and to reduce optical noise in their system.
Quality and Cost
Like with most items, high product complexity and performance carries a cost. More facets necessitate more handling and more surfaces to inspect for defects. For example, an octagonal homogenizer, with twice the number of surfaces and edges than a rectangular homogenizer, is substantially more complex to produce, though more efficient.
Ultimately, determining the optimal balance of traits, capability, and cost for your project is a unique and holistic process.
Having a knowledgeable optics manufacturing partner with whom you can whiteboard ideas is key to beating your competition in the market while also optimizing performance. IRD’s approach is to provide customers with unlimited access to our technical people, “engineer to engineer”, to produce a design that not only meets performance requirements but does so at the lowest lifetime cost and most consistent quality.
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