Monochromatic Wide‐Angle Optical Edge Detection Enabled by a Three‐Dimensional Soft Photonic Crystal

Abstract Optical edge detection is attractive in real‐time image information compression, image recognition, and three‐dimensional reconstructions due to its fast response and low power consumption. Liquid crystal planar optics is widely used to carry out optical differentiation due to its dynamic functionality. However, it still suffers from edge distortions and contrast reductions for oblique incidence, severely restricting its application in monochromatic wide‐angle optical edge detections. Here, a blue phase liquid crystal q ‐plate based 4 f imaging system is developed to solve the above problems. With the photopatterned three‐dimensional photonic crystal, the same spiral phase is encoded omnidirectionally to all reflected light, thus avoiding oblique incidence‐induced edge distortions and image contrast reduction. Moreover, the electrostriction‐induced lattice extension is further adopted to compensate for the angle‐dependent wavelength shift, thus realizing a monochromatic wide‐angle optical edge detection. The inherent circular polarization‐dependent phase modulation enables simultaneous optical edge imaging and bright‐field imaging, which makes the image detection more accurate. This work explores the potential of three‐dimensional soft photonic crystals in optics and photonics, supplies a practical platform for active monochromatic wide‐angle optical edge detection, and will be widely applied in LiDAR, machine vision, and biomedical imaging.