Multi-focus camera optics with 5˟ extending the depth of field

Extending the depth of field (DOF) of imaging optics is a longstanding challenge in machine vision, microscopy, photography and cinematography. This paper presents a method to extend DOF of camera lenses up to 5 times by using foto-foXXus - multi-focus quasi afocal optics. The foto-foXXus devices are implemented as achromatic aplanatic optical systems installed in front of camera lenses in such a way that the combined optical system has simultaneously several focuses separated along the optical axis. When applied for imaging a scene, such a combined optical system forms along the optical axis several images of each object of the extended DOF. The inevitable decrease in contrast of the common image, resulting from defocusing of some images from the plane of camera sensor (or film), can be enhanced using specific algorithms in the stage of image processing, which is nowadays an obligatory part of image capture in machine vision or microscopy. This method is very effective in capturing black-and-white objects, such as QR-codes, or in computer vision-based robotic arms for detecting the shape and size of objects. Direct measurements of the modulation transfer function (MTF) and through-focus MTF curves for a system consisting of a foto-foXXus and a state-of-the-art machine vision objective confirm the increase in depth of focus of the combined optical system and, consequently, depth of field in the Object space. The paper presents description of the foto-foXXus devices, measurements data of MTF and through-focus MTF-curves using the MTF test bench, as well as examples of imaging real objects demonstrating effective extending depth of field.