Active autofocus is a camera focusing system that uses an infrared or similar beam to measure the distance to a subject and adjust the lens accordingly. This method works well when the subject is within the effective range of the beam and unobstructed by reflective surfaces, but it can be less accurate if the subject is behind glass or beyond the system's maximum distance. In some cases, the camera may default to infinity focus, potentially resulting in slightly out-of-focus images. Active autofocus systems are commonly used in point-and-shoot cameras, compact digital cameras, and early autofocus designs, offering quick and convenient focus for everyday photography while highlighting the importance of understanding system limitations for precise image capture.