martedì 27 marzo 2012

INPUT/OUTPUT PHENOMENON

In theory for a straight fiber whose end faces are perpendicular to its axis, a small collimated beam of rays entering the fiber at 25 degrees off axis will exit the fiber at 25 degrees off axis.






In practice, multiple internal reflections, fiber length, micro-bending (external surface features) and manufacturing defects will spread collimated rays out to fill an annulus (or doughnut) of a cone whose total angle is twice that of the input angle. The thickness of the annulus will equal the diameter of the input beam. If the input beam is conical and focused on the face of the fiber, the output beam will still form an annulus of a cone whose nominal angle is twice the input angle, but the thickness of the annulus will now be determined by the angle of the input beam cone.



Temporal imaging system. Input and output dispersions play the role of free-space diffraction while quadratic phase modulation acts as a time lens. Output wave form envelope is a magnified version of the input envelope.
Schematic diagram of up-conversion time microscope. Input wave form I(t) is a 4 bit 100 Gb/s word. Input and output dispersion is obtained by two sets of diffraction grating pairs. The up-conversion time lens is achieved by sum frequency generation of the input wave form and a linearly chirped pump E(t). The output wave form is the magnified and inverted I(t/M).




giovedì 22 marzo 2012

Microscopes


What is a microscope ?
A microscope is a high precision optical instrument that uses a lens or a combination of lenses to produce highly magnified images of small specimens or objects especially when they are too small to be seen by the naked (unaided) eye.  A light source is used (either by mirrors or lamps) to make it easier to see the subject matter.

Who invented the microscope ?
A Dutchman, Anton van Leeuwenhoek, is considered the father of microscopes because of the advances he made in microscope design and use.  He worked as an apprentice in a dry goods store where magnifying lenses were used to count the threads in cloth.  Anton was inspired by these glasses and he taught himself new methods for grinding and polishing small lenses which magnified up to 270x.  This led to the first practical microscopes.  In 1674, Anton was the first to see and describe bacteria, yeast, plants, and life in a
drop of water.

What can you do with a microscope ?
A microscope can be used for numerous things:
  •  hobbyists have an interest in microscopic worlds from learning and having fun to using a microscope for the study of stamps, coins, gems, insects, etc
  •  children can view a fantastic world of discovery
  •  students have an interest in pursuing knowledge anywhere from middle school through the university level
  •  medical uses from analysis to advanced research in many and varied disciplines
  •  industrial uses as inspection and measurement tools
  •  government and scientific uses for public safety and discovery
  •  imaging of whatever you are looking at