Difference between revisions of "Microscope"

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(Types of illumination)
m (Pinpoint-source illumination)
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Good gemological microscopes will have an adjustable iris diaphragm which will enable you to reduce the light source by  closing the diaphragm to a small pinpoint opening.
 
Good gemological microscopes will have an adjustable iris diaphragm which will enable you to reduce the light source by  closing the diaphragm to a small pinpoint opening.
  
This makes it easier to sopt curved striae and other structures inside the gemstone.
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This makes it easier to spot curved striae and other structures inside the gemstone.
  
 
When you would open the diaphragm to just less than the diameter of the gemstone, this will also work as a "shadowing technique".
 
When you would open the diaphragm to just less than the diameter of the gemstone, this will also work as a "shadowing technique".
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[[image:lightfield.png|left|150px|thumb|Lightfield illumination]]
 
[[image:lightfield.png|left|150px|thumb|Lightfield illumination]]
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====Lightfield illumination====
 
====Lightfield illumination====
  

Revision as of 09:17, 2 October 2006

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This section is currently under construction, do not edit until this message is gone
--Doos 06:18, 2 October 2006 (PDT)

The microscope is next to the refractometer and the loupe probably the most used instrument amongst gemologists. It's obvious use is for magnification of internal end extrenal features in gemstones which gives the gemologist extra information about the identity and quality of the stone.

Basic

Microscope.png


Gemologists usually use binocular microscope with zoom capabilities ranging from about 10 to 90 times magnification. In most circumstances a magnification of 45x is sufficient for day to day operation. These binocular zoom microscopes are the most expensive pieces of identification equipment used in the standard gemological laboratory.
When handled with care they will last a lifetime and are well worth the investment.

Some binocular microscopes do not have a zoom feature and these are far less expensive. Typically the magnification ranges from 10 to 30 to 60 times (in steps). For these steps of magnification the oculars (eyepieces) need to be exchanged.

A good gemological microscope should atleast have lightfield, darfkfield and overhead illumination with an adjustable iris. A stoneholder is also preferable.



Types of illumination

Most gemological microscopes provide a whole range of illumination and associated techniques which all have their characteristic uses.

Pinpoint-source illumination

Pinpoint-source illumination

Good gemological microscopes will have an adjustable iris diaphragm which will enable you to reduce the light source by closing the diaphragm to a small pinpoint opening.

This makes it easier to spot curved striae and other structures inside the gemstone.

When you would open the diaphragm to just less than the diameter of the gemstone, this will also work as a "shadowing technique".



Lightfield illumination

Lightfield illumination


Darkfield illumination

Darkfield illumination


Overhead illumination

Overhead illumination


Diffused illumination

Diffused illumination


Horizontal illumination

Horizontal illumination


Polarized illumination

Polarized illumination


Oblique illumination

Oblique illumination


Shadowing technique

Shadowing technique