Phase telescope
Encyclopedia
A phase telescope
or Bertrand lens is an optical device used in aligning the various optical components of a light microscope. In particular it allows observation of the back focal plane of the objective lens and its conjugate focal planes. The phase telescope/Bertrand lens is inserted into the microscope in place of an eyepiece
to move the intermediate image plane to a point where it can be observed.
Phase telescopes are primarily used for aligning the optical components required for Köhler illumination
and phase contrast microscopy. For Köhler illumination the light source and condenser diaphragm should appear in focus at the back focal plane of the objective lens. For phase contrast microscopy the phase ring (at the back focal plane of the objective) and the annulus (at the back focal plane of the condenser lens) should appear in focus and in alignment.
Bertrand lenses find use in creating interference figures and assisting in aligning a microscope to generate interference figures. The name Bertrand lens commemorates French mineralogist Emile Bertrand
(1844-1909), for whom the mineral Bertrandite
is also named.
Phase telescope
A phase telescope or Bertrand lens is an optical device used in aligning the various optical components of a light microscope. In particular it allows observation of the back focal plane of the objective lens and its conjugate focal planes...
or Bertrand lens is an optical device used in aligning the various optical components of a light microscope. In particular it allows observation of the back focal plane of the objective lens and its conjugate focal planes. The phase telescope/Bertrand lens is inserted into the microscope in place of an eyepiece
Eyepiece
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings...
to move the intermediate image plane to a point where it can be observed.
Phase telescopes are primarily used for aligning the optical components required for Köhler illumination
Köhler illumination
Köhler illumination is a method of specimen illumination used for transmitted and reflected light optical microscopy. Köhler illumination acts to generate an extremely even illumination of the sample and ensures that an image of the illumination source is not visible in the resulting image...
and phase contrast microscopy. For Köhler illumination the light source and condenser diaphragm should appear in focus at the back focal plane of the objective lens. For phase contrast microscopy the phase ring (at the back focal plane of the objective) and the annulus (at the back focal plane of the condenser lens) should appear in focus and in alignment.
Bertrand lenses find use in creating interference figures and assisting in aligning a microscope to generate interference figures. The name Bertrand lens commemorates French mineralogist Emile Bertrand
Emile Bertrand
Emile Bertrand was a French mineralogist, in honour of whom Bertrandite was named by Alexis Damour. He also gave his name to the Bertrand lens or phase telescope.-References:...
(1844-1909), for whom the mineral Bertrandite
Bertrandite
Bertrandite is a beryllium sorosilicate hydroxide mineral with composition: Be4Si2O72. Bertrandite is a colorless to pale yellow orthorhombic mineral with a hardness of 6-7. It is commonly found in beryllium rich pegmatites and is in part an alteration of beryl. Bertrandite often occurs as a...
is also named.