Lambda 721

In the diagram below the optical paths are outlined for each position including the reflections that occur:

Optical path for each light source position from 0 through 7

The Lambda 721 was designed to keep the size of the beam combiner small and the optical path short and efficient. Thin-film bandpass filters, such as Semrock®’s STR, reflect greater than 90% of out-of-band light. If the band pass of each light source does not overlap, it is possible to use the filters for both attenuation and reflection of the light from the other sources. By arranging the filters and sources into a double pentagon, we were able to combine seven light sources in a compact design with lower losses than previously achievable. As an added benefit, the last position in the optical train does not require any filter since no other input reflects from that position. This position can be used with LED’s that have broad spectral output, such as the 561nm LED, and may allow the excitation of more than single channel of fluorescence from a single LED. (raw spectra available upon request)

Notes:
• The light from position #1 goes directly to the device output without being reflected. This position might be preferred for the source with the greatest desired output.
• The filter for the seventh light source is not used as a reflective surface and could be used with LED cubes with broader outputs.
• In configurations with fewer than 7 light sources, sources should be filled from lowest to highest number of reflections to ensure the greatest light output.
• This filter is installed at 18° angle-of-incidence to the collimated beam of the LED cube. This will cause a small shift in the band pass toward shorter wavelengths. While it would be ideal to have a coating optimized for this application, we have found that stock -STR filters can be used if you correct for the shift in the band pass when selecting the filters.
• The Lambda optical beam combiner is designed for flexibility and expandability. Should your illumination need change over time a simple configuration change and possibly additional filters can produce an entirely different output.