Confocal Sensor
Definition
It is a micro-optical technique which increases the resolution and contrast of a micrograph by using point illumination and a space pinhole to eliminate out-of-focus light.
Components:
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Confocal microscopy was first developed by Marvin Minsky in 1957.
The lateral scanning and depth slicing using a LASER pointer was achieved by Thomas and Cristoph Cremer.
Types and variants:
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Physical Principle
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The polychromatic white light beam irradiated by the source is dispersed to a series of monochromatic light (wavelengths λo to λn) through an optical system of multiple lenses. The monochromatic point images (with wavelength of λi) is focalized Due to the confocal configuration of the pinhole, only the light of wavelength λi is reflected through the objective lenses |
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High resolution can therefore be achieved as the interfering wavelengths are rejected.
Advantages
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Advantages against other surface analysis techniques such as acoustic nucleonic and electricalmethods:
- Non-intrusiveness
- Higher resolution in space and time
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Advantages against other optical methods such as fluoresce, dispersive and diffractive conventional (full-field illumination) microscopy:
- Pinhole: Monochromatic resolution.
- Point Illumination: Non interfering lectures of inner excited particles´ emissions. (higher resolution and contrast)

Applications
- Microorganisms study and biological research (cells, organelles, DNA )
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Medical applications:
- Brain microcirculation
- Cornea visualization
- Scanning of the materials used for orthopedic implants.
- Semiconductors´ properties.
- Composition and patterns of dispersed solid conglomerations and colloidal suspensions.
- Characterization of polymers and plastics.
- For opaque specimens surface 3D topology can be assed and for transparent specimens inner structure can be imaged.
- Geometrical parameters such as volume, area, perimeter, roughness, convexity, roundness, indentations, porosity of irregular shaped objects can be calculated
- The surface film or coating thickness can be measured with a depth scanning, and also its variation in time as when assessing for example liquid layer evaporation or surface/coating corrosion.




