Optical spectrometer and C++ Builder.

Physical bases

Building

Software

Observations

Home pages ...

Internet camera from recent is basic equipment of standard computer. We won't to use camera, what the manufacturer prepared her. We will do from camera optical spectrometer.

What is the spectrum analysis? White light consist of the whole mosaic of colours - is containing the rainbow in onself. Colours of the World surrounding us usually decompose for component, another colours. At least screen of the computer, shining with milion of colours, is only shining really with pixels red, green and blue ...

Our eyes don't have spectral properties. They aren't able to notice, that the white of solar light is the whole rainbow of colours, and the white of TV screen is the suitable combination of tree other colours. Optical spectrometer reduces all mixtures of light and measure content of each simple colour components in them. Speaking strictlier - spectrometer is able to separate waves from the light about the determined length.

Spectrogram of the white light is showing equal intensity of all waves from the visible range.

The light of the bulb contains more longer waves.

Internet camera will be so analyser the rainbow - she will be measuring participation of each colours in some concrete radius of light.

Physical bases

There are medium, in whom radii abaut various colours (strictlier - various lengths of waves) are moving at the various speeds. These are centres called dispersive. Dispersive medium is the surface coast, which sea waves are breaking on, because their longer components are laging behind shorter. Glass, which longer red waves are ahead short blue.

The prism is the cut suitably and smoothed bit of glass. Falling radius of the light is bending twice - one time at entering, other at leaving glass. Thanks to dispersion properties of glass radii about various colours are separated.

Diffraction grating is dividing light stream into separate radii. Here are two radii, and one has to travel longer way, then second. If the dissimilarity of ways is equal to the multiple of total wavelegth, waves will meet on the camera in consistent phases and will increment.

Waves about various length are getting stronger (they are interfering constructively) in various places of the camera eye. In diffraction grating red light is bending more than blue - the other way than in the prism.

Building

Spectrometer schemma: slot, lens, prism or diffraction grating and the sensor of internet camera.

From left to right: lamp, slot, lens, camera widh small diffraction grating.

Camera with turned off lens. The small bit of diffraction grating is glued in the place of lens.

The slot has precise adjustment the vertical arrangment.

Optical lens.

Software

The rainbow is rising on the sensor. The arrow is showing the trend of summation of amplitudes of lighting system.

The first application read the picture and is calculating the amplitude of the light in column pointed by mouse cursor. The active area of image may be cutted to values shown in 4 editors.

Download first application (173 kB, polish only)

Next application is presenting amplitudes of the light in form of the plot (spectrogram). The plot is not calibrated. We are able to choose the colour which is scanned ...

Download application (177 kB, polish only)

This application is showing the plot in separate window. Horizontal axis (wavelength) is calibrated. Two characteristic points of the spectra are the basis of scaling, advisable left and right mouse button.

Download this application (179 kB, polish only)

Observations

We will get shining diodes (LED) in every electronic shop literally for pennies. Red, green, yellow, but recently even blue.

Wien's Law - what the source of light has higher temperature, the light is more blue (the wavelength is shorter).

Downloads examples of spectra (856 kB)