Transcript Building a Radically Inexpensive Spectrometer

Building a Radically Inexpensive Spectrometer Using a Raspberry Pi
Will Brogdon, Sundee Olson, Russell Pina & Brian Rasnow
California State University Channel Islands, Camarillo, California
Objective
Spectrometer Prototype
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.
Red Tide Spectrometer USB650
- Insert picture of apparatus
- Insert screenshot of images of spectrum
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
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.
Intensity Versus Wavelength Plot
- Insert intensity vs. wavelength graph
What Is A Raspberry Pi?
• Single board computer: $35
m
• Dimensions: 3.37” x 2.21” x 0.83”
• Pre-packaged with Linux and
Python programming language
Figure 1: Regions of the electromagnetic spectrum and corresponding wavelengths,
frequencies, and energies. The visible light spectrum is of particular interest.
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.
• Pi NoIR camera module capable
of taking photos up to 5 megapixels
(2592 x 1944 pixels)
Challenges / Future Work
Conclusions
References
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.
Acknowledgements
This work was supported by: