Provided the electron gun can generate a beam with sufficiently small diameter, a SEM could in principle work entirely without condenser or objective lenses, although it might not be very versatile or achieve very high resolution.

He made use of it to work out the shapes of lenses that focus light with no geometric aberrations, known as anaclastic lenses.

Corrective lenses can also be added to work masks or eyeglasses used in sports.

The principal breakthrough in soft lenses was made by the Czech chemists Otto Wichterle and Drahoslav Lim who published their work " Hydrophilic gels for biological use " in the journal Nature in 1959.

Monovision is the use single vision lenses ( one focal point per lens ) to focus one eye for distance vision ( typically the person's dominant eye ) and the other eye for near work.

Later work that used these ChromaGen lenses with dyslexics in a randomised, double-blind, placebo controlled trial showed highly significant improvements in reading ability over reading without the lenses This system has been granted FDA approval in the USA.

Very few lenses, such as the Konica M-Hexanon Dual or Leica Tri-Elmar, let the user select among two or three focal lengths ; the viewfinder must be designed to work with all focal lengths of any lens used.

Macro lenses, ring flash, high-saturation colour film, and since it became an easier format to work in, digital photography, all allow him to put his subjects " under the microscope " in their own environment, giving them space to expose their lives and values in ways that often involve inadvertent humour.

Since the longer devices tended to work correctly on the first try, there must have been some difficulty in flattening the two high explosive lenses enough to achieve the desired length-to-width ratio.

Hall wished to keep his work on the achromatic lenses a secret and contracted the manufacture of the crown and flint lenses to two different opticians, Edward Scarlett and James Mann.

Johannes Hevelius described an early periscope with lenses in 1647 in his work Selenographia, sive Lunae descriptio or an account of the Moon.

The theoretical basis for curved mirrors behaving similar to lenses was probably established by Alhazen, whose theories had been widely disseminated in Latin translations of his work.

Schmidt corrector plates work because they are aspheric lenses with spherical aberration that is equal to but opposite of the spherical primary mirror they are placed in front of.

* The Holga TIM camera has two fixed focus plastic lenses which work simultaneously, allowing for the capture of 3D images.

This work was followed by that of the Russian scientist, Svyatoslav Fyodorov ( 1920-2000 ), who developed the Radial keratotomy ( RK ) in the 1970s and designed the first posterior chamber implantable contact lenses ( phakic intraocular lens ) in the 1980s.

Photographic lenses and the human eye work in the same way, therefore perspective projection looks most realistic.

Eyeglass lenses are usually much weaker, because eyeglasses do not work by magnifying ; they work by correcting focus.

He nevertheless uses his remaining hand to work wonders when polishing high quality lenses and mirrors for astronomical telescopes.

Revised grille work with fewer vertical bars, a stand-up hood ornament and revised taillight lenses with " GP " logos highlighted the 1977 Grand Prix, which was the final year for the 1973-vintage bodyshell which was set to be replaced by a downsized GP for 1978.

Rhoads critically analyzes the work of Yoshimitsu Banno in Godzilla vs. Hedorah through three lenses to properly analyze the film's reach: its place as a work of Japanese science fiction, specifically kaiju cinema ; the time and place of its creation, specifically the horrific industrial pollution present in postwar Japan ; and its creation after the collapse of the Japaneses film industry in the 1960s due to the proliferation of television.

Certain specific conditions are excluded as disabilities, such as current substance abuse and visual impairment that is correctable by prescription lenses.

Combustion generated by focusing sunlight over flammable materials using lenses, an experiment conducted by Lavoisier in the 1770s

The Gaussian theory, however, is only true so long as the angles made by all rays with the optical axis ( the symmetrical axis of the system ) are infinitely small, i. e. with infinitesimal objects, images and lenses ; in practice these conditions are not realized, and the images projected by uncorrected systems are, in general, ill defined and often completely blurred, if the aperture or field of view exceeds certain limits.

The largest opening of the pencils, which take part in the reproduction of O, i. e. the angle u, is generally determined by the margin of one of the lenses or by a hole in a thin plate placed between, before, or behind the lenses of the system.

In addition, overwash by tsunamis and tropical storms has corrupted lenses in the Maldives and several Pacific islands.

Because the porosity of the surface soil results in virtually zero runoff, lenses are easily polluted by fecal waste, burials, and chemical spills.

Primary power for the mission was produced by a new solar array technology, the Solar Concentrator Array with Refractive Linear Element Technology ( SCARLET ), which uses linear Fresnel lenses made of silicone to concentrate sunlight onto solar cells.

Geometric optics uses Euclidean geometry to analyze the focusing of light by lenses and mirrors.

Transmission electron microscopes function in a manner similar to overhead projector, with a beam of electrons passing through a slice of material then being projected by lenses on a photographic slide or a charge-coupled device.

These lenses are analogous to but different from the glass lenses of an optical microscope that form a magnified image by focusing light on or through the specimen.

The electron beam is accelerated by an anode typically at + 100 keV ( 40 to 400 keV ) with respect to the cathode, focused by electrostatic and electromagnetic lenses, and transmitted through the specimen that is in part transparent to electrons and in part scatters them out of the beam.

Niles Eldredge ’ s study of the Phacops trilobite genus supported the hypothesis that modifications to the arrangement of the trilobite ’ s eye lenses proceeded by fits and starts over millions of years during the Devonian.

Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eye glasses.

In early lighthouses, the light source was a kerosene lamp or, earlier, an animal or vegetable oil Argand lamp, and the lenses rotated by a weight driven clockwork assembly wound by lighthouse keepers, sometimes as often as every two hours.

With the creation of the United States Lighthouse Board in 1852, all U. S. lighthouses received Fresnel lenses by 1860.

Humans with natural eye lenses removed, as well as many animals with eyes that do not require lenses ( such as insects and shrimp ) are able to directly detect ultraviolet visually, by quantum photon-absorption mechanisms, in much the same chemical way that normal humans detect visible light.

* Photograph subjects wearing contact lenses with UV filtering.

The connection between spatial and angular bandwidth in the far field is essential in understanding the low pass filtering property of thin lenses.

A Pacific University research study of 36 participants found significant differences in irritation or burning of the eyes, tearing, or watery eyes, dry eyes, and tired eyes, that were each improved by filtering lenses versus placebo lenses.

Refraction occurs when light travels through an area of space that has a changing index of refraction ; this principle allows for lenses and the focusing of light.

This permits accurate viewing, composing and focusing, especially useful with interchangeable lenses.

Binoculars have a focusing arrangement which changes the distance between ocular and objective lenses.

Leica also offered focusing systems, such as the Focorapid and Televit, that could replace certain lenses ’ helicoid mounts for sports and natural-life telephotography.

The M6 could be optionally ordered with a. 85 magnification viewfinder for easier focusing with long lenses and more accurate focusing with fast lenses, such as the 50mm / f1. 0 Noctilux and 75mm / f1. 4 Summilux.

A series of new Leica lenses is manufactured specifically for the S2 and Leica claims they offer unsurpassed resolution and contrast at all apertures and focusing distances, even exceeding the sensor's capabilities.

The lack of a rangefinder on the Robot and Robot Star required zone focusing of these long lenses: every shot had to be estimated or premeasured.

The standard 38 mm f / 2. 8 Xenar lenses were extremely sharp, even by today's standards, and zone focusing worked well on rapid action with short focal length lenses.

The retrofocus lenses addressed this situation by shifting the focal plane further back than where it would normally be, thus making wider-angle lenses usable while retaining normal viewing and focusing.

It is often considered to be an imperfection of telescopes and other instruments which makes their focusing less than ideal due to the spherical shape of lenses and mirrors.

Electron lenses are designed to act in a manner emulating that of an optical lens, by focusing parallel rays at some constant focal length.

All lenses can be focused by moving the lens assembly towards or away from the film (" unit focusing "), and the Tessar is no exception.

It is similar to the focusing of a photographic camera via movement of its lenses.

When no delay line detector is used focusing the ions onto a detector can be accomplished through the use of two or three einzel lenses placed in the vacuum tube located between the ion source and the detector.

* Add on correction or magnifying lenses to help focusing or composition through the viewfinder.