Wavefront sensors are devices used to measure the wavefront of light, which is the shape of the light waves as they travel. They help in assessing optical systems by detecting distortions in the wavefront caused by imperfections in lenses or mirrors. This information is crucial for applications in fields like astronomy, where precise measurements are needed to improve image quality. These sensors work by analyzing how light waves deviate from an ideal shape. Common types include Hartmann sensors and Shearing interferometers, each employing different techniques to capture wavefront data. The information gathered can be used to correct optical errors and enhance imaging systems.