Design of an in-line, digital holographic imaging system for airborne measurement of clouds

The airborne environment constrained the design space to the simple optical layout that in-line non-beam-splitting holography affords. The desired measurement required the largest possible sample volume in which the smallest desired particle size (~5 μm) could still be resolved, and consequently the magnification requirement was driven by the pixel size of the camera and this particle size.

The resulting design was a seven-element, double-telecentric, high-precision optical imaging system used to relay and magnify a hologram onto a CCD surface. The system was designed to preserve performance and high resolution over a wide temperature range. Details of the optical design and construction are given.