Dichroism

Some of the light coming from the sky is polarized (bees use this phenomenon for navigation[2]). The electrons in the air molecules cause a scattering of sunlight in all directions. This explains why the sky is not dark during the day. But when looked at from the sides, the light emitted from a specific electron is totally polarized.[3] Hence, a picture taken in a direction at 90 degrees from the sun can take advantage of this polarization. Actually, the effect is visible in a band of 15° to 30° measured from the optimal direction.

Birefringence

World-class Nikon objectives, including renowned CFI60 infinity optics, deliver brilliant images of breathtaking sharpness and clarity, from ultra-low to the highest magnifications.

For modern cameras, a circular polarizer (CPL) is typically used, which has a linear polarizer that performs the artistic function just described, followed by a quarter-wave plate, which further transforms the linearly polarized light into circularly-polarized light. The circular polarization avoids problems with autofocus and the light-metering sensors in some cameras, which otherwise may not function reliably with only a linear polarizer.

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P-polarized light

Some companies make adjustable neutral density filters by having two linear polarizing layers. When they are at 90° to each other, they let almost zero light in, admitting more as the angle decreases.

There are two types of polarizing filters readily available, linear and circular, which have exactly the same effect photographically. But the metering and auto-focus sensors in certain cameras, including virtually all auto-focus single-lens reflex cameras (SLRs), will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent. Linearly-polarized light may also defeat the action of the anti-aliasing filter (low-pass filter) on the imaging sensor.

If an auxiliary lens is inserted between the objective and eyepiece, the magnification factor of this lens should also be employed in the equation by multiplication with the objective magnification (prior to the division operation). Although the field number is usually limited by the magnification and field diaphragm (stop) size of the eyepiece, there is clearly a limit that is also imposed by the design of the objective lens system. In early microscope objectives, the maximum usable field diameter tended to be about 18 millimeters or considerably less, but with modern plan apochromats and other specialized flat-field objectives, the maximum usable field can sometimes exceed 26 millimeters. Correspondingly, the field of view through microscope camera ports has risen in step with larger objective field numbers and larger camera sensors. The Nikon Eclipse Ti2 inverted microscope in particular offers a 25mm field of view through the camera ports.

Photon polarization

The Eclipse Ti2 inverted microscope delivers an unparalleled 25mm field of view (FOV) that revolutionizes the way you see.

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Polarization

Much light is differentiated by polarization, e.g. light passing through crystals like sunstones (calcite) or water droplets producing rainbows. The polarization of the rainbow is caused by the internal reflection. The rays strike the back surface of the drop close to the Brewster angle.[6]

Polymer optical fibers (POF) have a number of advantages over glass fibers, such as low cost, flexibility, low weight, electromagnetic immunity, good bandwidth, ...

Linear polarizing filters can be easily distinguished from circular polarizers. In linear polarizing filters, the polarizing effect works (rotate to see differences) regardless of which side of the filter the scene is viewed from. In "circular" polarizing filters, the polarizing effect works when the scene is viewed from the male threaded (back) side of the filter, but does not work when looking through it backwards.

Threaded rings of thickness ranging from 2 mm to 20mm can be selected for convenient applications. Spanner slots are provided for easy fastening of optics.

The diameter of the view field in an optical microscope is termed the field number and represents the diameter of the field measured in millimeters at the intermediate image plane. This interactive tutorial explores the effect of varying the field of view size on the viewable specimen area.

Use of a polarizing filter, in the correct direction, will filter out the polarized component of skylight, darkening the sky; the landscape below it, and clouds, will be less affected, giving a photograph with a darker and more dramatic sky, and emphasizing the clouds.[4] Perpendicularly incident light waves tend to reduce clarity and saturation of certain colors, which increases haziness. The polarizing lens effectively absorbs these light waves, rendering outdoor scenes crisper with deeper color tones in subject matter such as blue skies, bodies of water and foliage.[5]

A polarizing filter or polarising filter (see spelling differences) is a filter that is often placed in front of a camera lens in photography in order to darken skies, manage reflections, or suppress glare from the surface of lakes or the sea. Since reflections (and sky-light) tend to be at least partially linearly-polarized, a linear polarizer can be used to change the balance of the light in the photograph. The rotational orientation of the filter is adjusted for the preferred artistic effect.

Thorlabspolarizer

In most cases, the eyepiece field diaphragm opening diameter determines the view field size. The field size in the specimen plane is then defined as the field number divided by the magnification of the objective:

Half wave plate

Mar 5, 2024 — Depth of field: Refers to how much of a scene appears acceptably in focus ... Depth of field (DOF) describes the distance between the nearest and ...

John C. Long and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.

The benefits of polarizing filters are the same in digital or film photography. While software post-processing can simulate many other types of filter, a photograph does not record the light polarization, so the effects of controlling polarization at the time of exposure cannot be replicated in software.

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Polarizing filters reduce the light passed through to the film or sensor by about one to three stops (2–8×) depending on how much of the light is polarized at the filter angle selected. Auto-exposure cameras will adjust for this by widening the aperture, lengthening the time the shutter is open, and/or increasing the ASA/ISO speed of the camera. Polarizing filters can be used deliberately to reduce available light and allow use of wider apertures to shorten depth of field for certain focus effects.

Circular polarizing photographic filters consist of a linear polarizer on the front, with a quarter-wave plate on the back. The quarter-wave plate converts the selected polarization to circularly polarized light inside the camera. This works with all types of cameras, because mirrors and beam-splitters split circularly polarized light the same way they split unpolarized light.[7]

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How to use the DoF Calculator · Hyperfocal distance: The closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp.

Polarizing filters can be rotated to maximize or minimize admission of polarized light. They are mounted in a rotating collar for this purpose; one need not screw or unscrew the filter to adjust the effect. Rotating the polarizing filter will make rainbows, reflections, and other polarized light stand out or nearly disappear depending on how much of the light is polarized and the angle of polarization.

Light reflected from a non-metallic surface becomes polarized; this effect is maximum at Brewster's angle, about 56° from the vertical for common glass. A polarizer rotated to pass only light polarized in the direction perpendicular to the reflected light will absorb much of it. This absorption allows glare reflected from, for example, a body of water or a road to be reduced. Reflections from shiny surfaces (e.g. vegetation, sweaty skin, water surfaces, glass) are also reduced. This allows the natural color and detail of what is beneath to come through. Reflections from a window into a dark interior can be much reduced, allowing it to be seen through. (The same effects are available for vision by using polarizing sunglasses.)

polarizer中文

Nikon offers a range of eyepiece options featuring magnification and field of view combinations tailored towards a variety of applications.

The tutorial initializes with a randomly selected specimen visible in the virtual microscope viewport and the field number set to a value of 20. Use the Field of View slider to adjust the field size between 10 and 28 millimeters, and note how the viewable specimen area increases or decreases with the field number. After viewing a specimen, use the Choose A Specimen pull-down menu to select another specimen.