Laser light delivery for a diagnostic test cartridge

Challenge

A laser diode had to excite a small sensing well inside a disposable cartridge. The existing lens delivered only about a quarter of the light into the detection area. Any change had to fit the cartridge's mechanical limits and work at both near and far cartridge positions.

Approach

We modeled the baseline in non-sequential ray tracing, normalized to 1 W, to track efficiency and peak irradiance together. We then optimized the lens and a new lightguide as one system and iterated with the client's mechanical team on fit. Each candidate was checked at near and far positions and with the cartridge film in place.

Result

The final lens and lightguide reached about 90% efficiency at both positions, with a large gain in peak irradiance on the target. That design was built.

Key figures

• 25% to 90%

  optical efficiency into the detection area

• ~30x

  peak irradiance on target