Millipixel accuracy optical localization for point-like targets on pixelated image sensors

Localizing point-like targets, such as stars and single molecules on pixelated image sensors, are of great importance in optical measurement fields, including astronomy and microscopy. To date, a localization accuracy of 0.01 pixels has been considered high in practical applications. It is difficult to assess or achieve a higher accuracy (e.g., millipixel level) using experimental data due to noise from conventional setups or environment. Here, we propose a millipixel-scale localization accuracy assessment and realization method. The method combines organic light emitting diode subpixel precise motion control and large-ratio optical scaling to form spot array motion with ultrahigh accuracy in digital images for localization assessment and uses effective point spread function (PSF) modeling and maximum likelihood estimation fitting to realize millipixel localization performance. A localization accuracy better than 0.001 pixels has been demonstrated on two types of practical spots. The work not only provides an experimental assessment method for localization techniques with ultrahigh accuracy but also verifies the ability of optical localization as a powerful tool to measure 2D displacements at nano-scale accuracy in advanced manufacturing.