ASE Optics' GM Christopher Cotton is featured in a video on Laser Focus World discussing techniques to improve performance of lens systems for aerial applications. Vibration control is the primary detractor to the image quality that these systems demand.

In aerial applications, cameras are focused weeks in advance in a warm lab, and rely on the hardware to maintain focus and prevent lens motion. On the ground, in commercial applications and for the amateur photographer, this is easy. People don't vibrate, fingers make for a soft mount and refocusing is usually possible.

For aerial camera systems we design and build, we built the lens in a fixture separate from the camera. We focus the lens separately in the lab with an interferometer. Our customer can then mount it to the camera, ready to be used in flight.

Bayonet mounts commonly used on commercial cameras tend to wobble. They are just not meant to survive in an aerial environment.

Accurate and repeatable mounting of the lens to the camera is required to negate the need for recalibration when removing and remounting the lens on the camera.

We have overcome this problem by attaching the lenses with a hydrostatic mounting technique. We have also designed the focusing mechanism for the lens to be secured by a compressible clamp with fingers that exert pressure on the barrel. Loctite is then used as a final securing mechanism. The Loctite can be broken apart later if changes are needed.

Temperature changes from the lab to the aerial platform will cause the focus of the lens to change. The correct choice of materials and design are critical to getting our passive thermal compensation scheme correct.

Weight is especially important for UAV applications. You need to use just enough metal to maintain stability. Glass lenses have less thermal stability issues, exacerbating the weight issue. We have had the best success using off the shelf lenses in the $50-3000 price range . These lenses can be ruggedized and athermalized. This can be very economical for quantities less than 10. They can be taken off the shelf, taken apart and then reengineered.

We have used these techniques in designing lenses for Geospatial Systems, whose high-definition imaging technology was used to map the regions of Haiti devastated by the 2010 earthquake. Aid workers used these maps to determine the full extent of the damage to this small country.

Questions about your application? Comment and ask us or contact us directly.