Introduction - University of Central Florida



Initial Project DocumentVE-NIRVisible Emission Near-Infrared Up-Conversion SpectrometerAn optical spectrometer that analyzes near infrared spectrums with a visible spectrum detector utilizing up-converting phosphors.The University of Central FloridaCollege of Optics and Photonics (CREOL) and Department of Electrical EngineeringDr. Lei WeiSenior Design ISean Crystal - PSEJason Owens – PSEArgeny Batista – EEIntroductionPartnershipFor this project our team will be working with a local company and a UCF faculty member. Ocean Optics is a dominating player in the world of practical spectrometers. Ocean Optics products are based on being high quality, but relatively inexpensive, compact, portable, and customizable. Ocean Optics will be the customer setting their desired specifications/requirements for the device. Ocean Optics will also be providing equipment for this project. In addition to Ocean Optics, Dr. Stephen Kuebler will be a faculty mentor assisting us with the technical science and design aspects of this project. He is a faculty member in CREOL, The College of Optics and Phonics as well as in The Department of Chemistry. SummarySpectroscopy is a standard and highly developed technique used to analyze the optical spectrum of an input light. There are many variations of this technique such as absorption or transmission spectroscopy and two much more complicated techniques such as Raman or mass spectroscopy. The applications of such techniques are almost limitless. Spectrometers are used in every day applications such as water testing all the way to more elaborate applications like explosive detection and nuclear radiation analysis. The more common spectroscopy techniques of absorptions, transmission and emission spectroscopy will be the focus of this project. These relatively simple techniques are very important. Almost every optical company or lab has one available and in addition many non-optical companies utilize these devices because how widely they are used. For many applications, a simple, rugged, user friendly and cost effective spectrometer is a must. Many companies currently specialize in making such devices. While each individual application has many specifications, one specification that is always of interest is the wavelength range of interest for the user. Theoretically, spectroscopy can be performed in all wavelength ranges but there has been a surge of interest in Infrared spectroscopy. In this project we will develop a spectrometer that works in the near infrared spectral range but utilizes a visible spectrum detector. This can be accomplished through frequency up-conversion. Such a device would meet the simple, rugged, user friendly and cost effective parameters that are desired for so many applications while being able to analyze the infrared spectrum.MotivationWith such interest in infrared spectroscopy, the market for such spectrometers is very large. The complication is that the higher the wavelength of the infrared signal, the more expensive the components get. The optical components such as lens coatings and grating periods are more complicated which leads to a higher cost but the main increase in price comes from the detector. In the visible spectrum Silicon (Si) detectors are used. These are simple, cheap and made in bulk. Once you move into the near infrared spectrum, Si detectors no longer work and the commonly used detector is Indium Gallium Arsenide (InGaAs). This is a much more expensive detector. Also, often detector arrays are used in spectrometers so the increase in cost of the detector is multiplied by the size of the array. In addition InGaAs detectors are usually cooled which adds another expense. It can easily be seen how a near infrared spectrometer can cost exponentially more than a visible spectrometer. It would be ideal to develop an infrared spectrometer that uses a visible spectrum Si detector. Attempting to push the sensitivity of the Si detector to further wavelengths is not an option because this has been done for many years and its limit of roughly 1.1μm is well accepted. They key is to change the incoming infrared light into visible light and be able to correlate the two different wavelengths. This change in light wavelength/frequency is called frequency up-conversion. There are many different methods to do this such as sum-frequency generation, non-linear optical processes and some unique materials. The option we have found to be most practical and will work the best is utilizing a unique material called a phosphor. When the material is pumped properly by a light emitting diode (LED), impinging near infrared light can linearly be converted to visible light. In addition, these materials are relatively cheap and simple to work with.In order to do this the proper phosphor must be found, and an efficient manner to pump it, control the system, detect/amplify the signal, analyze/correlate the spectrum must be designed. This will encompass the disciplines of optics, photonics, electrical engineering and computer science. Such a device will fill a place in the market for a cheap and simple near infrared spectrometer.SpecificationsGeneral SpecificationsWavelengths .9 um to 1.6 um continuousResolutionStill to be determined by customerDevice Size (PCB Dimension)PortableVoltage Source (volts)3.3-8VSignal-to-Noise ratio250 +/- 2%Additional Electrical SpecificationsA reliable Voltage source is needed to power the microcontrollers, the diodes, the UV pump, and any other sensor or part used in the device. In the case of photodiodes, LEDs need about a 1.7 minimum input voltage to operate. A UV LED would need about 3 V. The voltage used by the LEDs would affect the luminosity and thus the intensity of the light. Most op-amps have a maximum rail of 15V so this would need to be taken into consideration.Market/Engineering RequirementsMarketingRequirements1) Phosphor Response2) LED Pulse Speed3) Spectrum Range4) Resolution5) Sensitivity6) Cost7) Output Power+-+++--Engineering Requirements1) Phosphor Responses+↑↑↑↑2) LED Pulse Speed+↓↑3) Spectrum Range+↓↑↑4) Resolution+↓↑↓↑5) Sensitivity+↓↑↓↓↑↑6) Cost-↓↓↓↑↑7)Output Power+↑↓↑Block DiagramBudgetPart DescriptionPrice ($) QuantityCost ($)Provider1Visible Spectrometer (includes lens, Bragg grating, silicon detector, fiber)303213032Ocean Optics2UV Filter15-35115-35N/A3UV LEDs1.2055N/A4Upconverting Phosphors40-100140-100N/A5Infrared Laser SourceN/A1N/ACREOL Faculty6Microncontroller10-50220-100N/A7Custom PCB layout/DesignN/A1-550-250N/A8Total130-490NOTE: The largest costs (seen in the first and fifth row) will be provided and are therefore left out of the total cost. Ocean Optics currently uses, in their visible spectrometers, the equipment mentioned in the first row so it is not only good for cost of the project but it is a positive to use the same equipment for later integration purposes. CREOL is home to the Townes Laser Institute, therefore we plan to work with CREOL faculty due to the numerous amount of near infrared laser sources there. This will allow us to be cost effective and perform testing over many wavelengths. NOTE: Typically it seems that for the cost of ordering 1 PCB is higher than ordering in bulk. In many of the sites I looked at this was held to be true, hence the wide range in cost. I will look more in depth into this as time goes on. It would also probably depend on the size of the PCB. Seeing as we are using 2 microcontrollers we could probably house both on the same PCB in order to save on costsSchedule WeekDescription1Project Idea2-3Initial project documentation and requirement specs/ group meeting on roles and tasks4Decide on phosphor and microcontroller.5Work on PCB layout5-7Build uv and microcontroller stage.8-10Write and Finalize the ponent check.Work on Labview and ultraviolet photodetector.10-12Experiments on test phosphorsEnd of Summer Semester13-14Ir and Bragg grating15-17Ir and phosphor design and uv filter design18-20Detect ir signal and compare to actual spectrum21-23Labview and Matlab coding24-26Fine tuning27Present ................
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