Lensdistortioncorrection

Operating compressed air systems can be expensive. By managing them more efficiently or taking a few proactive steps, you can lower your energy costs and save.

Use compressed air only when and where it is necessary. Shut down your central compressor during non-working hours. If small amounts of compressed air are required, separate those uses from the main system and supply them from a smaller compressor, such as fire sprinkler systems.

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On a continual basis, monitor, check and inspect all components of your compressed air systems for wear, proper temperatures and settings, leaks, proper lubrication and clogged filters.

Maintain air pressure at the lowest pressure acceptable. Evaluate your pressure requirements carefully. Some facilities operate at higher working pressures to satisfy small high-pressure applications or to compensate for pressure drops from undersized piping.

Radialdistortion

The tutorial starts with an aberration-free point spread function close to the cover glass when using a water immersion objective to image an embedded sample of higher refractive index (ƞ sample > ƞ water i.e. ƞ sample > 1.33). Use the Specimen Penetration Depth slider to transform the point spread function through a series of specimen depths and their corresponding aberrations. The higher the penetration depth, the higher the spherical aberration will be. The same will happen if an oil objective with an oil of RI (refractive index) >1.33 would be used to image a water sample, only that the spherical aberration caused asymmetries would be reversed along the optical axis.

This foundational knowledge article explores the concept of focus depth and spherical aberration in microscopy. An aberration-free optical system produces symmetrical diffraction images of an object at varying focal levels. However, when a microscope objective shows non-symmetric optical behavior, the wavefront leaving the objective lens is distorted and deviates from ideal behavior, resulting in an asymmetric distribution of the point spread function. Even if the objective itself is free of spherical aberrations, the optical system might not. An example for such a setting would be a mismatch between the refractive indices of the objective immersion and the sample embedding media. This article discusses the effects of spherical aberration on image quality and explains the use of water immersion objectives for critical work.

Water immersion objectives are a type of microscope objective lens that are designed for use with samples embedded in aqueous media. They have a higher refractive index than air, which allows them to capture more light and provide higher numerical apertures than dry objectives. This results in higher resolution and better image quality. With water immersion objectives you may overcome spherical and chromatic aberration caused by non-optimal sample depth and/or refractive index mismatch. Although they do not offer the highest numerical apertures of their oil immersion counterparts, they better overcome both types of aberration.

Coma aberration

A theoretical, aberration-free optical system produces a symmetrical diffraction image of an infinitely small and light emitting/diffracting object – called a “point source” – at varying focal levels. The lateral resolution for an Airy diffraction pattern generated by an illuminated small pinhole-shaped object is defined within a single plane of focus at the intermediate image position of the microscope. When a microscope objective shows a non-symmetric optical behavior, as in the case of spherical aberration (as well as astigmatism and/or coma), the wavefront leaving the objective lens is no longer symmetric with a center at the point of focus in the image plane. Instead, the wavefront is distorted and deviates from ideal behavior in a manner that depends on the nature of the aberration and/or image filters and the conditions present in the optical system. At the intermediate image plane, the point spread function yields an asymmetric distribution where the intensity ratio between the central peak and the surrounding rings is shifted, with the latter becoming much more prominent. Likewise, a mismatch in refractive index between immersion and sample can cause spherical aberrations.

Perspectivedistortion

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Chromatic aberration

To avoid image aberrations caused by non-optimal sample conditions, the use of correction collar immersion objectives is recommended. However, for best results, the cleanliness of the whole setup also has a strong impact on the image quality. In addition, tiny water or oil droplets, smeared films, or air bubbles in the immersion oil, as well as non-uniform illumination of the condenser or objective aperture, can degrade image quality. Hence, care should be taken when applying immersion media and to carefully remove any immersion media from the objective lens after use.

Lendistortion

Maintain the air receiver in good condition and ensure it is drained effectively at regular intervals. A timer and solenoid valve can help. Install compressor air intakes where they will receive the coolest air available.

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Oil immersion objectives are more sensitive to spherical aberration when used with samples embedded in aqueous media. Therefore, water immersion objectives are recommended for such critical work: Although these objectives do not offer the highest numerical apertures of their oil immersion counterparts, they better overcome spherical and chromatic aberration caused by non-optimal sample depth and/or refractive index mismatch. High-end water immersion objectives can focus through approximately 200-400 micrometers of aqueous media and still maintain excellent optical correction.

In the presence of spherical aberration (e.g. caused by non-optimal sample conditions), the diffraction image of a point source extends periodically above and below the intermediate image plane into a three-dimensional pattern that is not symmetrical: This diffraction pattern expands and spreads asymmetrically from the center along the optical axis. Cross-sections along the optical axis near the focal plane with residual spherical aberration are illustrated in the shown image. You can see that the diffraction images above and below the exact focus (the so-called “paraxial focal point”), are not symmetric. The asymmetry of the sectioned diffraction rings is particularly evident when the image of a point source is rapidly focused above and below the paraxial focal point: This procedure requires considerable practical experience. It can be used to detect the presence of small amounts of spherical and other aberrations.

To avoid image aberrations caused by non-optimal sample conditions – e.g. objects too far from the cover glass underside or too thick, wrong embedding medium, cover glass thickness not 0.17 +/- 0.05 mm or better –, the use of correction collar immersion objectives is recommended. However, for best results, the cleanliness of the whole setup also has a strong impact on the image quality. In addition, tiny water or oil droplets, smeared films, or air bubbles in the immersion oil, as well as non-uniform illumination of the condenser or objective aperture, can degrade image quality.

Spherical aberration causes diffraction images to expand and spread asymmetrically, affecting image quality. It occurs when a microscope objective shows non-symmetric optical behavior and the wavefront leaving the objective lens is distorted, deviating from ideal behavior.

Sphericalaberration

If your facility relies on compressed air, you already know how energy-hungry compressors can be. In fact, the cost to run one can easily exceed the purchase cost within a single year.

Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20 to 30% of the compressor's output. Compressed air leaks can also contribute to problems with system operations. Fluctuating system pressures cause air tools and other air-operated equipment to function less efficiently, possibly affecting production.

Consider replacing your old drain valves with new electronic sensing drains which discharge only when necessary. This can save you five times the purchase price in wasted air each year. Older mechanical float type drain valves often get stuck open and timer-based drains open when not needed.