Oil Immersion | Oil Immersion

Key Words: N.A., resolution, live cell imaging, depth of field, working distance

Definition:An oil immersion objective is designed to be used with oil between the front lens and the glass coverglass thereby effectively making full use of the N.A. of the objective

TECHNOLOGY:

N.A. is possibly the most important criterion when selecting an objective. As the N.A. increases across a series of objectives of the same magnification, light gathering capability and resolution increase. Unlike air, immersion oil has a refractive index that is similar to that of the glass coverglass. By placing immersion oil between the front lens of an objective (designed for use with immersion oil) and the coverglass, the angular range of the diffracted rays captured by the lens increases and, in effect, increases the N.A. of the objective. Light rays passing through the specimen, coverglass and oil are not refracted as they enter the lens but only as they leave its upper surface. Objectives that use water and/or glycerin as an imaging medium are also available.

Different microscope manufacturers produce objectives with tight tolerances to refractive index and dispersion and require matching values in the oil (or other media) placed between the cover glass and objective front lens. Users should, therefore, only use the oil (or other medium) recommended by the manufacturer.

APPLICATIONS:

The greater resolution gained through the use of immersion oil enables users to focus on very small objects that would be unresolved using dry objectives. Oil immersion objectives are used for the observation of very small objects, such as individual bacteria and in high resolution applications, such as TIRF and confocal fluorescence applications.

MICROSCOPE CONFIGURATION:

Nikon's CFI Plan Apochromat TIRF oil immersion objectives provide the highest N.A. of all Nikon objectives and have been designed specifically for TIRF applications (CFI Plan Apochromat TIRF 60x oil, N.A. 1.45; CFI Plan Apochromat TIRF 100X oil, N.A. 1.45). The TIRF Plan Apo 60x NA 1.45 oil objective incorporates a temperature change correction ring. Nikon's CFI Plan Apochrmat VC (violet corrected) 60x oil (N.A. 1.40) and 100x oil (N.A. 1.40) are the ideal choice for multicolor-stained, fluorescence confocal applications.

Nikon manufactures two types of immersion oil: Type A is a general purpose oil used for brightfield, darkfield, phase and fluorescence while Type NF helps to improve signal-to noise ratios in fluorescence microscopy, particularly in low-light applications or those between 340-380nm, typically associated with calcium or deep UV imaging.

RECOMMENDED SYSTEM:

Please consult your local Nikon representative for the objectives best suited for your imaging application.

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