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DIY Webcam Diffraction Grating Spectrometer

TabletAndSpectrometer

In this post we propose the construction of a diffraction grating spectrometer based on webcam and software Theremino Spectrometer. The spectrometer is a fundamental tool that allows measurement of the spectrum of a light source, ie the properties of light as a function of its wavelength. The spectrometer that we propose uses the principle of interference in a diffraction grating in order to decompose the light radiation in its wavelengths and subsequently measuring its intensity with a high-resolution webcam.

Diffraction Grating

A monochromatic light beam that is incident on a grating gives rise to a transmitted beam and various diffracted beams, at angles that depend on the ratio between the distance between the lines of the grating and the wavelength of the light. So, if the light beam is composed of multiple wavelengths, the decomposition of the beam into its components is obtained.

The light with a longer wavelength is deflected to a larger angle with respect to the incident direction (angle of diffraction ) . For each wavelength more rows can be observed. The number of rows that are counted from the middle line, which is not skewed with respect to the incident beam and is taken as a reference , it is said “order” and is often denoted by the letter m.

reticolo
Light Beam Diffracted by a Grating
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Lamp Spectrum obtained from a Diffraction Grating

Design and Components

Webcam : NEW TRUST MEGAPIXEL WEBCAM PRO 1.3MP 1024×1280
Diffraction Grating : olographic grating 1000 lines/mm monoaxial
Optics: Telescope Lens
Optical Slit : manual micrometric slit

spettrometro

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Spectrometer Internal View with Grating, Lens and Webcam
SpecSlit
Spectrometer external view with the micrometric slit

Spectra Examples

Fluorescence Lamp

CFL_Spettro

CFL_COLD_1
Imagine and Spectrum of a fluorescence lamp (mercury UV emission at 546nm, 438nm and 406nm andRed Europium fluorescence)

Neon Lamp

NEON_1
Neon lamp spectrum (Discrete Spectral lines)

Alogen Lamp

ALOGENA
Halogen lamp spectrum (continuos spectrum)

Sodium Lamp

“cold” lamp- detail of sodium doublet at 589nm

Warming up Lamp

“warm” lamp – sodium absorption line at 589nm

Wood UV Lamp

LAMPADA_WOOD_3
Wood lamp spectrum (UV emission)

Candle

Near infrared emission

Laser and LED

Comparison between Red LED and Red Laser

Electric Arc Plasma

Near UV Emission

Quinine Fluorescence

Blu quinine fluorescence – UV lamp excited

Uranium Glass Fluorescence

Green Uranium glass fluorescence – UV lamp excited

Sun Spectrum

SUN_SPETTRO_1

SUN_2
Imagine and solar spectrum with absorption Fraunhofer lines

Pdf document with complete description of the spectrometerSpettrometro_ENG

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