Our project was proposed by the Laser Plasma Laboratory (LPL) at the Center for Research and Education in Optics and Lasers (CREOL) here at the University of Central Florida (UCF). The project was to create an automated setup that involves the rotation of an optical element that the laser beam passes through. After passing through this optical element a sensor will measure the intensity of the laser beam. The purpose of wanting this process to be automated is for convenience, time, and accuracy. A computer is also able to do this faster and with a higher degree of accuracy then a human doing this by hand. Furthermore, making the whole process much simpler.
The basic setup for this project involves using a mount which contains two motors and a pivot point to rotate the object in the holder, whether it is a mirror or some other optical element. These two motors will be connected to a controller which is then connected to a computer along with a series of amplifiers coming from a light sensor that measures the intensity of the laser beam. The primary experiment this setup will be used for is called an Optical Parametric Oscillator (OPO) but will also be used for experiments such as Difference Frequency Generation (DFG). Some of these experiments may require the crystal be placed in an air seal camber or be confined to a small space via an optical cavity; therefore a mount with small motor was desired. The basics of the OPO experiment involves a laser firing into a crystal and, as long as the orientation of the crystal is descent, a new wavelength will be emitted from the crystal which will be longer in wavelength then the original beam. The orientation of this crystal will affect how strong the intensity of this new beam will be. A problem is that this intensity will be very small; therefore amplifiers are needed. This is were we had an opportunity to design hardware to amplify the small signal and digitize it for a computer.
Designed PCB with cascading amplifiers, USB communication and a display. (click for full size)
The project was motivated and inspired by the desire to aid UCF’s laser department to better its tests. Currently, optical elements are manually tweaked through various mechanics that hold the optical elements in place. This method is unreliable and requires time to achieve a desired position which often changes, usually due to noise. If the time to achieve precise positions for the experiment is reduced, many experiments will be run in the same amount of time. This will undoubtedly improve the overall experiment. The primary goal of our project was to design a device that rotates an optical element accurately on various axes depending on the user’s input. This reduces the possibilities of human errors in manually tweaking the mechanics. The device has two primary features. The first feature was to have a friendly user interface to accept the two rotational angle inputs.
Left: Full Scan LabVIEW GUI Right: Precise scan GUI (click for full size)
One angle was responsible for rotating about the horizontal axis (Φ). The other angle was responsible for rotating about the vertical axis (Θ). These values were determined by a raster scan of the optical element in two ways. One way was to start at one of the limits and then scan the entire object. Another way is to choose a position that would seem to be the zero point and then make rectangular point scans until the true point is determined. With the scan, an algorithm calculates the ideal position and communicated to the motors with information on how far they need to move. This is the second feature which takes in information from the motors and light sensor. The motors relayed back their position and the light sensor relayed back the amplitude of detected laser beam. This light sensor is highly precise due to the short band of wavelengths produced from the test. The goal was to have this device be able to scan and correct itself in real time without jumping too much or frying the motors. Even with a good algorithm the calculated coordinates could still be off; therefore a person, using the UI, will be able to increase and decrease the rotation of each axis by a desired amount. Algorithms were written to communicate with the motors on how to move, how quickly to move, and how long to move for. This algorithm was then be used for the automated adjusting the scanning procedure. An accurate feedback of the optical element’s position is displayed to the user.
Biography
Chris Nergard will graduate with a Bachelor’s in Computer Engineering and continue to a Ph.D. in Electrical Engineering at the University of Central Florida (UCF). At the time of his graduation he would have had over two and half years of experience in the field of optics and lasers plus some prior research experience in various fields of computer science. He was also the Chair of the Institute of Electrical and Electronics Engineers (IEEE) student branch at UCF and Vice President of the American Society for Engineering Education at UCF.
Duy-Hung Pham is a 22 year old who will graduate with a Bachelor's of Science in Electrical Engineering in December 2012 at the University of Central Florida (UCF). He has done over 3 semesters of co-op works at the Aviation and Missile Research, Development and Engineering Center (AMRDEC) in Huntsville, Alabama. He is both a member of the Engineering Honor Society, Tau Beta Pi, and the Honor Society Phi Kappa Phi. After receiving his degree, he plans to start his engineering career while pursuing a Master degree in Electrical Engineer.
Roberto Borja will be graduating with a B.S. in Electrical Engineering and may continue his education after a few years of work experience. He has interned at Earthrise Space inc. on research park for a semester developing a lunar rover. He has been working fulltime as an intern for the past six months at NDI-RS in Longwood developing the firmware for a linux based intelligent camera that identifies license plates for law enforcement.