Imaging lens for a 4K otoscope

Challenge

A 4K sensor with small pixels needed a lens that would not waste its resolution, in a package that fits inside a standard ear speculum with peripheral illumination. Distortion had to stay low for accurate anatomy. The client also wanted a low-cost path to first prototypes.

Approach

We ran a first-order analysis to set realistic resolution targets, then compared front-stop, center-stop, and reimaging concepts. With the client we set 10% modulation at 100 lp/mm as the target and optimized a custom center-stop design to it, with a stray light check. We then worked the design down to off-the-shelf catalog lenses for prototyping.

Result

A five-element prototype built from catalog lenses held average MTF above 10% at 100 lp/mm. The prototype was built and performed as intended, and a custom design is ready for production quoting.

Key figures

• 5

  catalog lenses in the prototype design

• >10%

  average modulation at 100 lp/mm

• <0.1%

  stray light relative to incident light