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Optical units are dimensionless units of length used in optical microscopy. They are used to express distances in terms of the numerical aperture of the system and the wavelength of the light used for observation. Using these units allows comparison of the properties of different microscopes. [1]
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century.
The single lens with its attachments, or the system of lenses and imaging equipment, along with the appropriate lighting equipment, sample stage, and support, makes up the basic light microscope. The most recent development is the digital microscope, which uses a CCD camera to focus on the exhibit of interest. The image is shown on a computer ...
In both cases the numerical aperture of the objective is 1.49 and the refractive index of the medium 1.52. The wavelength of the emitted light is assumed to be 600 nm and, in case of the confocal microscope, that of the excitation light 500 nm with circular polarization. A section is cut to visualize the internal intensity distribution.
E 0 is a vector in the x-y plane, with the units of an electric field (the vector is in general a complex vector, to allow for all possible polarizations and phases); ω is the angular frequency of the wave; k is the angular wavenumber of the wave; Re indicates real part; e is Euler's number.
Memorial in Jena, Germany to Ernst Karl Abbe, who approximated the diffraction limit of a microscope as = , where d is the resolvable feature size, λ is the wavelength of light, n is the index of refraction of the medium being imaged in, and θ (depicted as α in the inscription) is the half-angle subtended by the optical objective lens (representing the numerical aperture).
Luminous energy per unit time Luminous intensity: I v: candela (= lumen per steradian) cd (= lm/sr) J: Luminous flux per unit solid angle: Luminance: L v: candela per square metre: cd/m 2 (= lm/(sr⋅m 2)) L −2 ⋅J: Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit ...
The ability of a lens to resolve detail is usually determined by the quality of the lens, but is ultimately limited by diffraction.Light coming from a point source in the object diffracts through the lens aperture such that it forms a diffraction pattern in the image, which has a central spot and surrounding bright rings, separated by dark nulls; this pattern is known as an Airy pattern, and ...