1. Objective Our goal is to create a radically inexpensive spectrometer for educational purposes using a Raspberry Pi. The prototype is housed in a black enclosed project box and consists of a Pi NoIR camera aimed at a broken fragment of a CD-ROM that is illuminated through a slit. Finding the optimal slit width, diffraction grating angle, and camera focus is essential in order to generate a full visible spectrum of the light source. Taking advantage of the Raspberry Pi capabilities and MATLAB programming software, a plot of intensity versus wavelength is produced. The resolution, sensitivity, and cost of our spectrometer are compared to the commercially available instruments manufactured by Ocean Optics. We expect to achieve a 1 nanometer/pixel dispersion. Future work includes further optimization of the prototype, the addition of photosensitive diodes, and 3-D printing. Background: What Is Spectroscopy? Spectroscopy is the study of the interaction between matter and energy. The source of energy used for spectroscopic studies is called electromagnetic radiation, which is composed of oscillating electric and magnetic fields that serve to transfer energy through space. This energy propagates in the form of a wave. The distance between successive crests in a wave is called its wavelength. Frequency refers to the number of wave cycles that travel past a fixed point per unit of time. An inverse relationship exists between wavelength and frequency. One of the fundamental principles in spectroscopy is the decomposition of electromagnetic radiation into its component wavelengths. The perception of color can be thought of as a physiological response of the eye to light waves of a specific frequency. The retina of the eye is lined with color-sensing cells called cones. Three kinds of cones exist- red, green, blue- each sensitive to a range of wavelengths within the visible light spectrum. When light of a particular wavelength strikes the cones of the retina, a chemical reaction occurs which results in an electrical impulse being sent along the nerves to the brain. It is the visible light that is reflected and not absorbed that contributes to the color appearance. White light is perceived when all the wavelengths of the visible light spectrum strike the eye simultaneously. Building a Radically Inexpensive Spectrometer Using a Raspberry Pi Will Brogdon, Sundee Olson, Russell Pina & Brian Rasnow California State University Channel Islands, Camarillo, California m Acknowledgements This work was supported by: References Conclusions Red Tide Spectrometer USB650 Intensity Versus Wavelength Plot Spectrometer Prototype Challenges / Future Work What Is A Raspberry Pi? Single board computer: $35 Dimensions: 3.37” x 2.21” x 0.83” Pre-packaged with Linux and Python programming language Pi NoIR camera module capable of taking photos up to 5 megapixels (2592 x 1944 pixels) - Insert picture of apparatus - Insert screenshot of images of spectrum - Insert intensity vs. wavelength graph Figure 1: Regions of the electromagnetic spectrum and corresponding wavelengths, frequencies, and energies. The visible light spectrum is of particular interest. Figure 2: Range of wavelengths associated with colors of the visible spectrum. Figure 3: Component colors of the visible spectrum separated by passing light through a prism, which bends the light in differing degrees according to wavelength. Figure 4: Cone sensitivity curve depicting the range of wavelengths and sensitivity level for the three kinds of cones. The Red Tide has a wavelength range of 350-1000 nm, and utilizes a detector with 650 active pixels; that’s 650 data points in one full spectrum, or one data point per nanometer. Configured with a 25 µm entrance slit, the Red Tide offers ~2.0 nm optical resolution (FWHM). Retail Value: $1200