Ultra-Compact Optical Microscopes Made of Liquid Crystal Pancharatnam-Berry Optical Elements

Ultra-compact optical systems are increasingly sought after for applications such as consumer electronics and medical imaging. Here, we present a design and manufacturing approach for ultra-compact bright field and dark field optical microscopes entirely made of flat liquid crystal optical elements. Both systems utilize a liquid crystal PB lens as the objective, achieving a numerical aperture of up to 0.25. The dark-field optical microscope also incorporates a Q-plate with a +1 topological defect to filter zero-order light, all within an overall thickness of just 5 mm. The system can achieve high imaging performance with a maximum resolution of 7 μm using the USAF 1951 resolution chart. In addition, we demonstrate an exemplary application in biological imaging, to effectively enhance edge contrast in imaging onion epidermal cells with integrated dark-field optical microscope. This work presents an example in exploiting the flatness and high quality of liquid crystal optical elements to achieve both compactness and high-quality promising for various other applications.