03. Medical Laser50 Watts of Invisible Light
Three microcontroller sub-systems, and a supervisory microprocessor cooperate to treat patients.
 The heart of the system is ten laser diodes, each capable of delivering approximately 5W of light ouput. Those diodes require as much as 150W of input power. To keep the wavelength of the Laser diodes constant, they are kept at a constant temperature by 300W of Peltier coolers (Thermo Electric Coolers - TECs). The result is electronics that have an input power of almost 500W. This powerful sub-system is supervised and commanded by a single microcontroller that monitors dozens of signals associated with the drive electronics for the laser diodes and TECs. The output of the ten laser diodes are combined into four separate treatment outputs through fiber optics and mirrors. We implemented electronics at the distal end of the fiber optics that would only enable the Laser diode if the electronics sensed a response from a Flex PCB embedded in the sterile disposable. A very small microcontroller (4mm x 4mm package) was also incorporated for redundant temperature sensing at the site of the laser treatment. The system includes another microcontroller sub-system used to verify the proper light output for each laser. Each of the four "home" positions houses a low-cost optical integrator and a photodiode sensor. The system's power on self-test verifies proper laser output at several drive levels. Any problem with the light delivery system (broken or damaged fiber, faulty laser diode, dirty mirror, etc) is detected as an improper light level at the light sensor.  Lastly the micro-processor responsible for the overall control of the system monitors the state of all the other microcontrollers in the system, the state of the power supplies, and a switch that can be used by the patient to interrupt treatment if discomfort is felt. This processor utilizes a color display and touchscreen as the human interface and uses a simple serial interface to communicate with each of the sub-systems. |