Laser sensor for detecting the presence of an object in continuous motion

摘要

A laser based noncontact detection system is disclosed which is useful in automated manufacturing. The sensor system detects the presence or absence of an object that is either rotating or in some other continuous repetitive motion such as a rotating drill bit. This device is especially useful for detecting broken or absent drill bits used for drilling printed circuit boards. The system projects a laser beam onto the concave face of the flute near the tip of a drill bit and the amount of light which is reflected by the drill bit is sensed by a detector. The sensor is located at an angle oblique to the axis of rotation. Due to the rotation of the drill bit, fluctuating electronic signals are produced, detected and analyzed to determine the presence of the drill bit. The system automatically compensates for dust, debris and ambient light. Sensor positioning allows for greater drilling machine throughput since there is no need to fully retract the drill bit for breakage or damage detection. The laser beam may be focused into a stripe of light allowing for the detection of rotating drills of differing diameters without refocusing the light source when the sensor is used on a drilling machine using different and interchangeable drill sizes. The system can be used for detecting any continuously revolving object or any object in any other continuous repetitive motion. The presence of the object may be verified after each repetitive motion sequence.