Defocused speckle imaging using digital image correlation for lensless tip and tilt measurements with experimental validation

This paper introduces an optical instrument leveraging a defocused speckle pattern for angular measurements of a sample orientation. The technique involves illuminating the sample with the speckle pattern and capturing the reflected pattern using a camera. With an uncertainty level of 0.4 µrad and repeatability of 0.47 µrad, this system is modestly comparable to the traditional autocollimators but with a wider angular range advantage. One of the key innovations of this system is its cost-effectiveness, offering a significant reduction in expense compared to conventional autocollimators. This paper outlines the design, operational principles, and performance evaluation of the instrument, highlighting its potential as a cost-efficient alternative in the field of optical metrology.