Definition: An autocollimator is a type of optical instrument that uses light to create an image on a screen or other surface. It works by collimating the incoming light, which is then directed towards a detector, and causing it to emit a signal that can be detected by a camera or other device. Autocollimators are commonly used in medical imaging equipment such as ultrasound systems, where they are used to create images of internal organs and structures. They also have applications in various fields such as engineering,