A wavefront sensor is an instrument used in optics and astronomy to measure the wavefront of light, which refers to the shape and orientation of the light waves as they propagate through space. Wavefront sensors are commonly used to analyze aberrations in optical systems, such as telescopes and microscopes, and to correct for those aberrations in real-time. By measuring the wavefront of light, wavefront sensors can provide valuable information about the quality and performance of optical systems, and can be used to improve the resolution and clarity of images in various applications.