A report on Objective (optics)

Several objective lenses on a microscope.
Objective lenses of binoculars
Two Leica oil immersion microscope objective lenses; left 100×, right 40×.
Camera photographic objective, focal length 50 mm, aperture 1:1.4
The segmented hexagonal objective mirror of the Keck 2 Telescope

Optical element that gathers light from the object being observed and focuses the light rays to produce a real image.

- Objective (optics)
Several objective lenses on a microscope.

18 related topics with Alpha

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A 200 mm refracting telescope at the Poznań Observatory

Refracting telescope

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A 200 mm refracting telescope at the Poznań Observatory
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Optical diagram of Galilean telescope
y – Distant object; y′ – Real image from objective; y″ – Magnified virtual image from eyepiece;
D – Entrance pupil diameter; d – Virtual exit pupil diameter;  L1 – Objective lens;  L2 – Eyepiece lens e – Virtual exit pupil – Telescope equals
Engraved illustration of a 150 ft focal length Keplerian astronomical refracting telescope built by Johannes Hevelius.
Alvan Clark polishes the big Yerkes achromatic objective lens, over 1 meter across, in 1896.
This 12 inch refractor is mounted in dome and a mount the rotates with the turn of the Earth
The Greenwich 28-inch refractor is a popular tourist attraction in 21st century London
The Apochromatic lens usually comprises three elements that bring light of three different frequencies to a common focus
The 102 cm refractor, at Yerkes Observatory, the largest achromatic refractor ever put into astronomical use (photo taken on 6 May 1921, as Einstein was visiting)
The "Große Refraktor" a double telescope with a 80cm (31.5") and 50 cm (19.5") lenses, was used to discover calcium as an interstellar medium in 1904.
Astronaut trains with camera with large lens
Touristic telescope pointed to Matterhorn in Switzerland
The Yerkes Great refractor mounted at the 1893 World's Fair in Chicago; the tallest, longest, and biggest aperture refactor up to that time.
The 68 cm refractor at the Vienna University Observatory

A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope).

Stratospheric Observatory for Infrared Astronomy

Reflecting telescope

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Telescope that uses a single or a combination of curved mirrors that reflect light and form an image.

Telescope that uses a single or a combination of curved mirrors that reflect light and form an image.

Stratospheric Observatory for Infrared Astronomy
24-inch convertible Newtonian/Cassegrain reflecting telescope on display at the Franklin Institute
A replica of Newton's second reflecting telescope that he presented to the Royal Society in 1672
The great telescope of Birr, the Leviathan of Parsonstown. Modern day remnants of the mirror and support structure.
Gran Telescopio Canarias
An image of Sirius A and Sirius B by the Hubble Space Telescope, showing diffraction spikes and concentric diffraction rings.
Main mirror of James Webb Space Telescope assembled at Goddard Space Flight Center, May 2016.
Light path in a Gregorian telescope.
Light path in a Newtonian telescope.
Light path in a Cassegrain telescope.
A prime focus telescope design. The observer/camera is at the focal point (shown as a red X).
Cassegrain design
Nasmyth/coudé light path.

Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives.

The 100-inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe.

Telescope

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Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

The 100-inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe.
17th century telescope
The 60-inch Hale (debuted in 1908) considered to be the first modern large research reflecting telescope.
The primary mirror assembly of James Webb Space Telescope under construction. This is a segmented mirror and its coated with Gold to reflect (orange-red) visible light, through near-infrared to the mid-infrared
Modern telescopes typically use CCDs instead of film for recording images. This is the sensor array in the Kepler spacecraft.
A 1.2-meter (47 in) reflecting telescope
Binoculars
The Very Large Array at Socorro, New Mexico, United States.
Einstein Observatory was a space-based focusing optical X-ray telescope from 1978.
The Compton Gamma Ray Observatory is released into orbit by the Space Shutte in 1991, and it would operate until the year 2000
The reflectors of HEGRA detect flashes of light in the atmosphere, thus detecting high energy particles
Equatorial-mounted Keplerian telescope
A diagram of the electromagnetic spectrum with the Earth's atmospheric transmittance (or opacity) and the types of telescopes used to image parts of the spectrum.
Six views of the Crab nebula supernova remnant, viewed at different wavelengths of light by various telescopes
The Five-hundred-meter Aperture Spherical radio Telescope in Guizhou, China, is the world's largest filled-aperture radio telescope

The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope.

A collection of different types of eyepieces.

Eyepiece

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Type of lens that is attached to a variety of optical devices such as telescopes and microscopes.

Type of lens that is attached to a variety of optical devices such as telescopes and microscopes.

A collection of different types of eyepieces.
A 25 mm Kellner eyepiece
Simulation of views through a telescope using different eyepieces. The center image uses an eyepiece of the same focal length as the one on the left, but has a wider apparent field of view giving a larger image that shows more area. The image on the right has the same apparent field of view as the center eyepiece but has a shorter focal length, giving the same true field of view as the left image but at higher magnification.
The Plössl, an eyepiece with a large apparent field of view
Examples (from left to right) of 2" (51 mm), 1.25" (32 mm), and 0.965" (24.5 mm) eyepieces.
The eye relief. 1 Real image 2 - Field diaphragm 3 - Eye relief 4 - Exit pupil
Negative lens
Convex lens
Huygens eyepiece diagram
Ramsden eyepiece diagram
Kellner eyepiece diagram
Plössl eyepiece diagram
Orthoscopic eyepiece diagram
Monocentric eyepiece diagram
Erfle eyepiece diagram
König eyepiece diagram
RKE eyepiece diagram
Nagler type 2 eyepiece diagram
Nagler type eyepieces

The objective lens or mirror collects light and brings it to focus creating an image.

8×42 roof prism binoculars

Binoculars

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Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.

Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.

8×42 roof prism binoculars
A typical Porro prism binoculars design
Galilean binoculars
Cross-section of a relay lens aprismatic binocular design
Double Porro prism design
Porro prism binoculars
Schmidt–Pechan "roof" prism design
Abbe–Koenig "roof" prism design
Roof prism binoculars with the eyepieces in line with the objectives
Parameters listed on the prism cover plate describing 7 power magnification binoculars with a 50 mm objective diameter and a 372 foot field of view at 1000 yards
The small exit pupil of a 25×30 telescope and large exit pupils of 9×63 binoculars suitable for use in low light
Central-focusing binoculars with adjustable interpupillary distance
People using binoculars
Binoculars with red-colored multicoatings
Special reflective coatings on large naval ship 20×120 binoculars
Tower Optical coin-operated binoculars
Vector series laser rangefinder 7×42 binoculars can measure distance and angles and also features a 360° digital compass and class 1 eye safe filters
German U.D.F. 7×50 blc U-boat binoculars (1939–1945)
7×50 marine binoculars with dampened compass
US Naval ship 'Big eyes' 20×120 binoculars in fixed mounting
25 × 150 binoculars adapted for astronomical use
A simulated view of how the Andromeda Galaxy (Messier 31) would appear in a pair of binoculars
Beam path at the roof edge (cross-section); the P-coating layer is on both roof surfaces
Porro type, external eyepiece bridge central-focusing binoculars with adjustable interpupillary distance set for about 63 mm
thumb|right|Binoculars diagram showing a Schmidt–Pechan roof prism design
thumb|Binoculars diagram showing an Abbe–Koenig roof prism design

Most early binoculars used Galilean optics; that is, they used a convex objective and a concave eyepiece lens.

Optical microscope used at the Wiki Science Competition 2017 in Thailand

Microscope

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Laboratory instrument used to examine objects that are too small to be seen by the naked eye.

Laboratory instrument used to examine objects that are too small to be seen by the naked eye.

Optical microscope used at the Wiki Science Competition 2017 in Thailand
18th-century microscopes from the Musée des Arts et Métiers, Paris
Carl Zeiss binocular compound microscope, 1914
Electron microscope constructed by Ernst Ruska in 1933
Fluorescence microscope with the filter cube turret above the objective lenses, coupled with a camera.
Types of microscopes illustrated by the principles of their beam paths
Evolution of spatial resolution achieved with optical, transmission (TEM) and aberration-corrected electron microscopes (ACTEM).
Unstained cells viewed by typical brightfield (left) compared to phase-contrast microscopy (right).
Modern transmission electron microscope
Transmission electron micrograph of a dividing cell undergoing cytokinesis
Leaf surface viewed by a scanning electron microscope.
First atomic force microscope

The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620.

Principle of immersion microscopy. Path of rays with immersion medium (yellow) (left half) and without (right half). Rays (black) coming from the object (red) at a certain angle and going through the cover-slip (orange, as is the slide at the bottom) can enter the objective (dark blue) only when immersion is used. Otherwise, the refraction at the cover-slip-air interface causes the ray to miss the objective and its information is lost.

Oil immersion

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Technique used to increase the resolving power of a microscope.

Technique used to increase the resolving power of a microscope.

Principle of immersion microscopy. Path of rays with immersion medium (yellow) (left half) and without (right half). Rays (black) coming from the object (red) at a certain angle and going through the cover-slip (orange, as is the slide at the bottom) can enter the objective (dark blue) only when immersion is used. Otherwise, the refraction at the cover-slip-air interface causes the ray to miss the objective and its information is lost.
Two Leica oil immersion objective lenses. Oil immersion objective lenses look superficially identical to non-oil immersion lenses.
Oil-immersion objective in use

This is achieved by immersing both the objective lens and the specimen in a transparent oil of high refractive index, thereby increasing the numerical aperture of the objective lens.

Simple ray diagram showing typical chief and marginal rays

Numerical aperture

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[[Image:Numerical aperture.svg|thumb|The numerical aperture with respect to a point

[[Image:Numerical aperture.svg|thumb|The numerical aperture with respect to a point

Simple ray diagram showing typical chief and marginal rays
Numerical aperture of a thin lens

Numerical aperture is commonly used in microscopy to describe the acceptance cone of an objective (and hence its light-gathering ability and resolution), and in fiber optics, in which it describes the range of angles within which light that is incident on the fiber will be transmitted along it.

Index-matching material

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Index-matching material is a substance, usually a liquid, cement , or gel, which has an index of refraction that closely approximates that of another object (such as a lens, material, fiber-optic, etc.).

Index-matching material is a substance, usually a liquid, cement , or gel, which has an index of refraction that closely approximates that of another object (such as a lens, material, fiber-optic, etc.).

This is achieved by immersing both the objective lens and the specimen in a transparent oil of high refractive index, thereby increasing the numerical aperture of the objective lens.

The largest non-segmented mirror in an optical telescope in 2009, one of the Large Binocular Telescope's two mirrors

Primary mirror

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The largest non-segmented mirror in an optical telescope in 2009, one of the Large Binocular Telescope's two mirrors
Six of the 18 primary mirrors of the James Webb Space Telescope being prepared for acceptance testing
The correctly ground backup primary mirror built by Eastman Kodak for the Hubble space telescope (the mirror was never coated with a reflective surface, hence its honeycomb support structure is visible). It now resides in the National Air and Space Museum in Washington, DC.
Artists's Rendering of the primary mirror of the ELT.

A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope.