Increasing the depth of focus in mirror optical systems using high-order aspheric coefficients

Depth of focus (DoF) is a fundamental property of optical systems, as it influences key aspects such as image quality, resolution, and tolerance. A method is presented to increase the DOF by adding high-order aspherical coefficients to one of the mirrors of the optical system. The developed method applies to finite and infinite conjugate mirror systems. Using the focal length function, the rays are positioned to determine the aspheric deformation, based on exact ray tracing and the proposed condition of equalizing the optical paths of a marginal and a paraxial ray. Two optical systems are presented. First, a microscope objective with a light sheet length increased by 390% compared to a classic system. Second, a Telescope with a DoF of 1000 μ m was designed. The results demonstrate the method's versatility, quickly and easily extending the DoF. • A method to extend the depth of focus to avoid affecting resolution and image quality. • Mirror systems are deformed aspherical by equalizing the optical paths. • A method to compute aspheric coefficients on a single mirror to extend focus depth. • A method to design telescopes and microscopes with an increased depth of focus. • Increased depth of focus in reflective optical systems with near and far objects.