Breaking the Diffraction Limit in Optical Edge Estimation Problem
Introduction: Diffraction is a fundamental limit for object geometry measurement accuracy in conventional optical systems. Due to diffraction, high-frequency components of an image are fully attenuated, and groups of small-sized details become non-resolvable. Edge estimation results obtained by known algorithms become smoothed compared against actual edge geometry. Purpose: Development of a method to estimate an object edge with a compensation of the diffraction impact on the image. Results: To compensate for the diffraction, a method of 2D image approximation by а numerical model is proposed. The proposed model reconstructs а camera-acquired image with subpixel accuracy, taking into account the optical system’s 2D point spread function along with the non-uniformity of the object intensity. The model implementation is based on the Fourier image synthesis algorithm for the measured object’s bounding polygon. In real optical systems, the method provides the opportunity to compensate not only for the diffraction but also for lens aberrations by means of point spread function measurement. Numerical simulation results are presented, along with the results and technique for a real system application. Practical relevance: The edge estimation error for 2D image approximation corresponds to 2- or 3-fold improvement in optical resolution as compared to the conventional 1D edge estimation algorithms.