objective lens

optics

Also known as: objective

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Last updated

July 1, 2026

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An objective lens is a lens or system of lenses in an optical instrument, such as a microscope or telescope, that forms an image of an object. In a compound microscope, the objective lens has a short focal length and is placed close to the object being examined. It works with an eyepiece to relay an image, with the total magnification being the product of the objective and eyepiece magnifications. The resolution of a microscope is determined by the objective's numerical aperture (N.A.), which indicates its ability to collect diffracted light and resolve detail. In telescopes, the objective lens is the first lens that light from a celestial object passes through, and its diameter is called the aperture.12345

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microscope
The objective
The optics of the microscope objective are defined by the focal length, N.A., and field of view. Objectives that have been corrected for aberrations are further defined by the wavelength requirements and the tube length of the microscope.
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The optics of the microscope objective are defined by the focal length, N.A., and field of view. Objectives that have been corrected for aberrations are further defined by the wavelength requirements and the tube length of the microscope.
Read More

microscope
The compound microscope
One of them, the objective, has a short focal length and is placed close to the object being examined. It is used to form a real image in the front focal plane of the second lens, the eyepiece or ocular. The eyepiece forms an enlarged virtual image that can…
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One of them, the objective, has a short focal length and is placed close to the object being examined. It is used to form a real image in the front focal plane of the second lens, the eyepiece or ocular. The eyepiece forms an enlarged virtual image that can…
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telescope
Refracting telescopes
…object passes is called the objective lens. It should be noted that the light will be inverted at the focal plane. A second lens, referred to as the eyepiece lens, is placed behind the focal plane and enables the observer to view the enlarged, or magnified, image. Thus, the simplest…
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…object passes is called the objective lens. It should be noted that the light will be inverted at the focal plane. A second lens, referred to as the eyepiece lens, is placed behind the focal plane and enables the observer to view the enlarged, or magnified, image. Thus, the simplest…
Read More