As an additional note: Lens magnification is based on standard microscope sizes, including the size of the tube the lenses are installed in. If this standard size is changed, so will the magnification.

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Angular Apertures of Objectives Compared. The 3x objective is at a longer focal length, taking in a larger area at a smaller angle. The 95x objective is at a shorter focal length, taking in a smaller area in a larger angle.

In summary, the significance and advantages of aspheric lenses are primarily related to their ability to correct optical aberrations, provide clearer and sharper vision, and offer improved peripheral vision. They also come with aesthetic benefits such as a slimmer profile and better appearance. However, they have some limitations, including a smaller light area and potential adjustments needed for individuals used to spherical lenses. Advances in manufacturing have made aspheric lenses more affordable and versatile, allowing them to replace multiple spherical lenses in various applications, resulting in cost-effective and high-performance optical systems.

Aspheric lenses offer significant advantages over traditional spherical lenses due to their unique shape and optical properties. Let’s delve into these advantages and also consider some of their disadvantages, as discussed in the provided articles.

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negative lenses are thinner in the middle so that rays of light passing through them are made divergent termed biconcave, plano-concave, concave (diverging) meniscus

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Magnification in the compound microscope is achieved by the use of simple lenses. There are two broad categories of simple lenses: positive lenses, which are thicker in the middle (convex), cause light to converge. Negative lenses are thinner in the middle (concave) and cause light to diverge.

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All these factors determine the resolving power, or the minimum separation of two objects such that they appear distinct and separate when viewed through a microscope or telescope. The numerical aperture (NA) is a measure of the resolving power of the objective lens only. The upper limit of resolving power, of an objective lens or the whole microscope, ultimately depends on the wavelength of light used. Why can't we just magnify the image?

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The image we see through the eyepiece is the aerial image formed by the microscope objective in the tube. This image has a limit, where useful magnification ends and the empty magnification begins. There is a good parallel with the grain of a photographic film. As soon as the image details reach the same size as the image grain, no further detail can be gained by magnifying the image. In the same way, as you move closer and closer to the photographic image on a projector screen, you reach the point where you can no longer see the actual details on the photograph. The performance limit of the microscope is determined by the NA, so that the total magnification of the microscope is the objective magnification multiplied by the eyepiece magnification  times NA.

The eyepiece actually has two functions: to magnify and correct. The need for correction comes from the different colours of light that are refracted. If the eyepiece is over-corrected or under-corrected, the different colours of light will not be balanced and the resulting image will show up as coloured.

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We have discussed the objective and eyepiece lenses, but another part of the microscope has lenses also: the condenser. Unlike the objective and eyepiece lenses, which serve to magnify the image to the viewer, the lenses in the condenser are there to focus the light on the sample. This is accomplished by combining several simple lenses together. The combinations of lenses used in the condenser can vary, from something like this:

The microscope is the fundamental tool of the cytologist. In order to use it effectively, you need to understand key concepts, like:

At Avantier, we manufacture a wide variety of aspheric lenses for applications from smartphones to lasers and fiber optics, from research and industry to medicine. If you have more questions about aspheric lenses, don’t hesitate to contact us. Our experienced optical designers are always available to discuss a custom order.

positive lenses are thicker in the middle and therefore capable of converging light to a focus. These are termed biconvex, plano-convex, and convex (converging) meniscus.

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Comparison of dry and oil immersion objectives. The values for NA range from 0.1 to 0.95 for dry objectives and up to 1.5 for oil immersion lenses. Air has a refractive index of 1. So for air, the image scatters beyond the aperture angle.  Immersion oil fills the space between the cover glass and the front lens of the microscope has a refractive index of 1.5. Oil keeps the image within the aperture angle of the objective lens.

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NA is calculated using a mathematical formula devised by Ernst Abbe for the direct comparison of the resolving power of dry and all types of immersion objectives.

The most important part of the microscope are the objective lenses. These different lenses allow the viewer to see the specimen at different magnifications and easily switch between the lenses with the revolving nosepiece. The objective lenses in modern compound microscopes are also parfocal, which means that switching from a lower to a higher magnification lens keeps the image roughly in focus. While the fine focus knob may be needed for adjustment, the image stays in view when switching lenses.

Optical Advantages: Aspheric lenses are designed to reduce aberrations, especially spherical aberration. Spherical aberration is a distortion that occurs when light passes through a spherical surface, causing blurriness and reduced image quality. These lenses focus light to a single point, regardless of the entry angle, resulting in clearer and sharper vision.

These broad categories contain three lenses each, to make the six simple lenses. Positive lenses are biconvex, planoconvex, and convex (converging) meniscus, while negative lenses are biconcave, planoconcave, and concave (diverging) meniscus.

The compound microscope allows the observer to see greater detail in small objects by magnifying and resolving the image. Although chromosomes cannot be seen by the naked eye, even a relatively low-power compound microscope will allow a scientist to resolve individual chromosomes in the eukaryotic cell.

The effect that the simple lenses has on the light is fundamental to the production of a useful image. Without a condenser, the microscope would be a magnifying glass with no resolving power of its own. The student microscopes are fitted with Abbe (chromatic) condensers. They are simply constructed and transmit a large amount of light.

Earlier on, we said that the microscope is able to magnify and resolve an image, to allow the viewer to see tiny details in the sample. The lenses accomplish the magnification of the image, but the resolution is more complex. Many factors influence the highest resolution a microscope can achieve, such as: