An active sensor is a type of sensor that emits its own energy, such as radio waves, light, or sound, to detect and measure objects or environmental conditions. Unlike passive sensors, which rely on external energy sources like sunlight or ambient radiation, active sensors generate and transmit signals, then analyze the reflected or returned data to determine characteristics such as distance, speed, shape, or composition. Common examples include radar, LiDAR, and sonar, which are widely used in applications such as remote sensing, autonomous vehicles, industrial automation, and security systems. The ability of active sensors to function independently of ambient light or environmental conditions makes them particularly valuable in low-visibility or high-precision scenarios.