A paper by variable focus lens manufacturer Optotune presents a focal sweep telephoto camera which is potentially of interest in defence and security applications, among others.
The system is enabled by Optotune’s liquid polymer based deformable optics.
A focal stack is a sequence of images captured with different focus settings. A number of cameras have been introduced that sweep the focal plane using mechanical motion in order to capture a focal stack. However, mechanical motion makes video capture impractical and is unsuitable for long focal length cameras, as large sensor travel poses serious practical issues.
This new Optotune paper presents a focal sweep telephoto camera that uses a variable focus lens to sweep the focal plane. The camera requires no mechanical motion and is capable of sweeping the focal plane periodically at high speeds. Optotune’s prototype camera has been used to capture Extended Depth of Field (EDOF) videos at 20fps, and to capture periodic focal stacks which can be used for several interesting applications such as video refocusing and trajectory estimation of moving objects, potentially of interest in security and defence applications. Telephoto imaging (e.g., scenes with depth range on the order of 10’s to 100’s of meters) is an area where focal sweep could be particularly useful because telephoto lenses typically have a narrow DOF.
Deformable optics can open the door for focal sweep videography. The fast response time of deformable optics enables periodic focal sweep at high frequencies. As a result, deformable lenses are particularly well suited for focal sweep cameras with large focal lengths, which would require large sensor motion using the swept-sensor approach.
More information here on Optotune’s deformable optics