Infinity corrected plan achromatic microscope objectives are ideal for collimating and focusing laser beams in the visible spectrum.

Opticallens

[3] P. Swolana, Ch. Weigel, T. Geiling, L. Dittrich, D. Frese: Wetting and roughness - What to do if Wenzel does not work? KRÜSS Application Report AR295, 2020.

Focal length

A telephoto lens provides an effective focal length \(efl\) that is longer than its overall length \(s_{ol}\) as measured from the front of the lens to the image plane. The telephoto ratio is defined as \(s_{ol}/efl\), thus a lens with a ratio less than one is a telephoto lens.

An extreme form of the reverse telephoto lens is the fish-eye or sky lens. Such lenses have a total field of view of 180° or more. The image formed by these lenses has very large barrel distortion.

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Telephotolens

where θ* is the measured contact angle. This is called the apparent contact angle for a rough surface because it is the angle of the droplet contour with an apparently straight profile line. θ is the contact angle that would exist on a smooth surface of the same material and corresponds to the ideal contact angle according to Young's equation. r' is called the roughness coefficient and indicates the ratio of the total surface area to the surface geometrically projected onto a plane.

telephoto是什么

At contact angles below 90°, wetting of the surface is energetically advantageous overall for the two phases involved. Since a rough material has a larger total surface area than a smooth one due to the tiny depressions and thus offers a larger wetting area, the wettability increases.

It seems to be obvious to calculate a "roughness-corrected" contact angle using the Wenzel formula in order not to have to investigate the roughness influence on wetting separately. In practice, however, such an approach is fraught with great uncertainties. A study carried out by KRÜSS [3] on the basis of surfaces with defined roughness shows that the roughness influence can deviate considerably from the behavior to be expected according to Wenzel - up to a trend reversal, in which a well-wettable material is less wetted in the rough state.

When most telephoto lenses are used to view objects that are relatively close, the image quality degrades rapidly due to the typical unsymmetrical lens configuration. Some modern telephoto lenses include one or more elements that move as the lens is focused for the purpose of aberration correction.

This wetting behavior is also known as the lotus effect since the lotus leaf is one of the least wettable non-technical surfaces. There are many industrial applications for superhydrophobic materials or coatings, for example for fouling and wetness protection or for self-cleaning textiles or building walls.

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Recalling that the image height for a distortionless lens on a flat image surface is \(f\tan\theta\), the reverse telephoto lens has mapping relationships such as \(f\theta\) and \(f\sin\theta\).

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telephoto lens中文

Roughness affects the wettability of a solid and thus the contact angle of a liquid as well as adhesion. A rule of thumb states that roughness improves wettability at small contact angles (angle becomes smaller), and reduces it at large contact angles (angle becomes larger). The limiting contact angle of wettability, which determines the deflection in one direction or the other, is 90°. The roughness-related reduction in wetting comes into play on superhydrophobic surfaces; it is often referred to as the Lotus Effect.

The basic concept of a telephoto lens is illustrated by the dialyte lens configuration in which a negative lens is inserted between the objective lens and the image plane. This concept goes back to Kepler, but Peter Barlow developed the idea in the early 1800s by including a negative achromat in telescopes to increase their magnification.

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Fisheyelens

Extremely low wettability, also known as superhydrophobicity, results from the rough surface texture of a material where the smooth surface is already non-wettable. Put simply, the liquid avoids the depressions in the surface, which is enlarged by roughness, instead of filling them up. The technical term for this effect is capillary depression in contrast to capillary adhesion - in an unwettable capillary, the capillary force does not pull the liquid inward, but pushes it outward.

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Result parameters for roughness and suitable measuring methods are defined in the ISO 25178 standard. Non-destructive measurements by non-contact optical methods, for example confocal microscopy, should be emphasized. Other methods use, for example, an air stream or even vacuum and make use of the gas permeability on contact between a smooth and a rough surface.

Barlow type lenses are widely used today. As the telephoto ratio is made smaller, the design of the lens becomes more difficult, primarily due to the Petzval sum increasing.

Widelens

A reverse telephoto lens has a telephoto ratio greater than unity and exhibits a shorter focal length than its overall length, a larger \(bfl\) than is provided by normal lenses of the same \(efl\), lenses with generally large apertures and wide fields of view, and lens elements of physically larger size that allow easier manufacture and handling.

The basic configuration has a large negative lens located in front of a positive objective lens. Since the negative lens makes the object appear closer to the objective lens, the resultant image moves beyond the focal point, thereby making the \(bfl\) greater than the \(efl\).

Based on the Wenzel equation, it can be seen why the critical angle for the transition from wetting enhancement to reduction is 90°. Since cos θ assumes negative values above 90°, the apparent contact angle becomes larger. However, the Wenzel equation can then be applied only to a limited extent because, at low wetting, not all the depressions of the rough surface are usually filled with liquid. Cassie and Baxter [2] have formulated the following relationship for a condition where only parts of the entire surface are in contact with the liquid:

Primelens

After World War II, the Russian designer M. M. Roosinov patented a double-ended reverse-telephoto lens that was nearly symmetrical with large negative lenses surrounding a pair of positive lenses with a central stop. Although the back focal length is quite short, it provides relatively large aperture with a wide field of view and essentially no distortion. Lenses of this type have found significant use in aerial photography and photogrammetry.

The use of this effect is part of everyday practical knowledge, for example when components are ground before painting or bonding to increase wetting and adhesion. For surface tension measurements using the Wilhelmy plate method, the platinum plate is roughened to optimize wetting by the sample.

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Roughness (surface roughness) is the degree of unevenness of a solid surface below the size scale of its shape or waviness, but above the irregularity of crystal lattice structures. The roughness has an influence on the wettability of a solid.

When the barrel distortion is given by \(f\sin\theta\), the illumination across the image will be constant if such effects as vignetting and stop distortion are absent.

Barrel distortion has the effect of compressing the outer portions of the image towards the central portion, thereby increasing the flux density appropriately.