How to specify a lens for defence applications

To deliver a robust and reliable optical system suitable for a defence application your specification should include sections detailing required optical, mechanical and environmental performance.

The optical specification should clearly define performance factors including the required field of view (FOV), f/#, working distance, resolution, sensor size and pixel pitch plus distortion and vignetting. An optical specification will often also detail any optical test reports that are required to be supplied with the qualification lenses.

Lenses used in defence applications are typically designed to meet military standards (e.g. MIL SPEC), often requiring increased durability and resistance to harsh environmental conditions.

The mechanical specification for a defence application should state the available space envelope, Motorisation requirements (if any), Method of focus required, Register distance, lens camera interface, Preferred construction materials and coatings, grounding points for static drain and preferred mounting arrangement on camera / sensor / instrument.

An environmental specification should cover all aspects of required vibration and shock testing during both the qualification and production phase of creating the new lens / optical system. This specification should also consider the temperature extremes the lens will be exposed to plus required ingress protection (IP standards) to ensure it is protected from water, dust, and other environmental factors.

Read Interview: ‘Designing and Proving Optics for Military Applications’.