Confocal

Confocal sensors

Tree axis scanning system
Time and Space measures
Optical sectioning in depth
Point illumination and analysis
Monochromatic detection
2D and 3D images

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:

  • Light source
  • Graduated lenses
  • Object plaque
  • Pinhole (collimator)
  • Detector
  • Analyzer/Computer
Microptik confokal sensor optoNCDT-2402

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:

  1. Confocal Laser Scanning Microscopes
  2. Spinning disks (Nipkow disk)
  3. Programmable Array microscopy (PAM)
  4. Confocal theta microscopy
  5. STED microscopy
confocal marvin minsky scheem

Physical Principle

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
on the object surface.

Due to the confocal configuration of the pinhole, only the light of wavelength λi is reflected through the objective lenses
and directed towards the spectrometer with high efficiency, being all other wavelengths out of focus.

physical principle of confocal microscopy

High resolution can therefore be achieved as the interfering wavelengths are rejected.


Advantages

  1. Advantages against other surface analysis techniques such as acoustic nucleonic and electricalmethods:
    • Non-intrusiveness
    • Higher resolution in space and time
  2. 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)
confocal sensor

Applications

  1. Microorganisms study and biological research (cells, organelles, DNA )
  2. Medical applications:
    • Brain microcirculation
    • Cornea visualization
    • Scanning of the materials used for orthopedic implants.
  3. Semiconductors´ properties.
  4. Composition and patterns of dispersed solid conglomerations and colloidal suspensions.
  5. Characterization of polymers and plastics.
  6. For opaque specimens surface 3D topology can be assed and for transparent specimens inner structure can be imaged.
  7. Geometrical parameters such as volume, area, perimeter, roughness, convexity, roundness, indentations, porosity of irregular shaped objects can be calculated
  8. 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.