Integral sphere

A integral sphere , (also called sphere of integration ) is component a consistent Optique in a cavity digs of which the interior is covered of a painting having a factor of reflection diffuses high and having exit and relatively small input ports. For the applications in the visible field, the coating more used is the sulfate of Baryum (BaSO4) white. In the Infra-red field, the usual coating is gold. The shape of the cavity is generally a Sphère. The beams of light coming from any point of the internal surface of the sphere, are distributed, because of the multiple diffuse reflections, equally at all the other points of the sphere and this independently of the original direction of the Lumière. An integral sphere can be regarded as a diffuser which preserves the power but destroyed space information. The integral spheres are typically used as source of light and system of measurement of the optical power. One finds them in a great number of optical measurements, photometric or radiometric such as:

  • quantification of the total luminous power emitted by a lamp in all the directions.
  • measurement of the factor of reflection (reflectance) of surfaces while realizing correctly according to all the angles of illumination and observation,
  • creation of a source of light with a Luminous intensity connects uniform in all the directions inside its opening circular, and independent of the excluded direction the function cosine inherent in an ideal diffuse radiant surface (Surface Lambertienne).
  • Mesure specifies sum of all the incidental ambient light on a small circular opening.
  • Measurement of the power of a Laser beam , independently of the structure of the beam, its form of its position and incidental direction.

The majority of the marketed integral spheres have diameters from 20 to 50 cm. There exist integral spheres much larger, until several meters in diameter to measure lamps of public lighting or to produce a uniform source of light very broad. The united image presents a sphere developed by NASA for tests of uniformity on the Spectroradiomètre imagor MISR.

See too

Related articles

  • Photometry
  • Radiometry

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