Laser scanning and power control in a rapid prototyping system

A method for controlling the amount of laser power to which a working surface of a heat-fusible material is exposed in a rapid-prototyping system having a laser light source that creates a laser beam and a scanning system comprising a first mirror coupled with a first rotary motive device for positioning the first mirror, the laser beam being directed from the first mirror onto a second mirror of the scanning system and then onto the working surface to form a laser spot thereon, the second mirror being coupled with a second rotary motive device for positioning the second mirror, the mirrors having an acceleration time less than about 1 millisecond, the method comprising the steps of:

• periodically measuring an instantaneous power of the laser beam on a real-time basis using a first power meter having a response time less than the acceleration time of the mirrors;
• regulating operation of the laser light source in real time based on the measured instantaneous power of the laser beam;
• and
• calibrating the first power meter on a periodic basis using a second power meter having a response time greater than that of the first power meter.

A method for controlling the amount of laser power to which a working surface of a heat-fusible material is exposed in a rapid-prototyping system having a laser light source that creates a laser beam and a scanning system comprising a first mirror coupled with a first rotary motive device for positioning the first mirror, the laser beam being directed from the first mirror onto a second mirror of the scanning system and then onto the working surface to form a laser spot thereon, the second mirror being coupled with a second rotary motive device for positioning the second mirror, the mirrors having an acceleration time less than about 1 millisecond, the method comprising the steps of:

• periodically measuring an instantaneous power of the laser beam on a real-time basis using a power meter having a response time less than the acceleration time of the mirrors;
• periodically determining Instantaneous positions of the mirrors;
• and
• using a digital signal processor to regulate operation of the laser light source in real time based on digitized data representing at least the measured instantaneous power of the laser beam.

A method for tuning a laser light source in a rapid-prototyping system wherein the laser light source creates a laser beam and the laser beam is vector-scanned by a scanning system along a working surface of a heat-fusible material, the scanning system comprising a first mirror coupled with a first rotary motive device for positioning the first mirror, the laser beam being directed from the first mirror onto a second mirror of the scanning system and then onto the working surface to form a laser spot thereon, the second mirror being coupled with a second rotary motive device for positioning the second mirror, the method comprising the steps of:

• scanning the laser beam along at least one vector on the working surface;
• at each of a plurality of sequential times during the scanning of the laser beam along the at least one vector, measuring an instantaneous position of each of the mirrors and deducing an instantaneous position of the laser beam on the working surface at each of said plurality of sequential times;
• at each of said plurality of sequential times, measuring an instantaneous power of the laser beam using a power meter, such that power versus position data are derived along the at least one vector;
• calculating exposure of the heat-fusible material to laser energy based on the power versus position data, such that calculated exposure versus position data are derived;
• and
• tuning the laser light source based on the calculated exposure versus position data.