The next task is to find real glasses to replace the model glasses. OSLO has a special command, accessible from the lens spreadsheet, that substitutes the nearest real glass for a model glass.

Gausslens

Final Solution (dblgauss5.len) The lens shown below (public/len/demo/tutorial/dblgauss5.len) is the result of about an hour's investigation of various options for improving the design using the GENII error function (with different weights on selected operands). It is not feasible to trace the course of this optimization explicitly. You should try to see if you can match, or improve on, the final design shown below. Note that checked apertures have been inserted to provide vignetting at the edge of the field.

Gauss' signature

Tutorial example - Optimizing a double-Gauss objective The double-Gauss objective can serve as a starting system to illustrate the techniques for lens optimization with the GENII error function, specifically using the OSLO LT program (although the same system can be optimized similarly using any of the OSLO programs). It is assumed that the lens is to be optimized for f/2, 50mm focal length, 20 degrees field coverage, i.e. the same as the example system. The results will be different because the example system was created using a different optimization procedure. The example is presented as a series of explicit steps that you should duplicate on your computer. The OSLO user interface has been especially constructed to provide an easy-to-use interaction during optimization, if you follow the recommended procedure. As you progress through the design, you should save your lens so that you can recover to a given point rather than start over, if you make a mistake. The tutorial directory in public/len/demo contains lens files showing the design at various stages. You should expect your lens data to be similar, but not necessarily identical, to that in the tutorial files.

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The objective lens is the most important optical component of the microscope. It’s the part that sits in closest proximity to the specimen being examined, gathering light to produce optimal images for observation and analysis. This lens creates the first magnification by spreading out the light’s rays to make the object appear considerably larger by the time it meets your field of view at the other end of the eyepiece. Such a critical piece of equipment doesn’t come in a one-size-fits-all package. Below, we will discuss some of the different types of microscope objective lenses and the unique roles they play in microscopy.

Doublegaussian lens

Specialized microscopes, such as metallurgical microscopes, require their own specific metallurgical objective lenses. These devices are most often used to examine structural detail of ceramics, metals and other non-living materials. Another common microscope objective accessory is a Barlow lens. These can be added to the bottom of an objective lens to either increase or decrease its working distance, field of view or magnification. Since they can be interchanged between lenses, they are a cost-effective way to change the power and magnification of lenses you already own. Lastly, if all these lenses are starting to seem overwhelming, remember one quick trick for determining magnification at a glance: look at the band of color near the bottom of your objective lens. While the magnification number is usually written right on the lens, you can also quickly determine its strength by the color ring. Red indicates 5x magnification, while yellow means 10x, light blue means 40x and white can mean 100-250x.

DoubleGaussian function

At this point, the optimization has proceeded to the point of a default solution. Now, various trials can be conducted to improve the design, such as trying additional glasses. Other possibilities for additional optimization are to remove the edge contact solves to see whether the positive elements still want to get too thin, to change the weights on selected terms in the error function, or to re-enter the error function with different rays. The general approach to optimization using OSLO is illustrated by the steps of this example: you should approach the optimization cautiously and change only a few things at a time, working interactively, until you are confident that the combination of variables and operands can be trusted to produce a system of high quality. You should always maintain a way to restore your system to an earlier state, such as using the revert capability of OSLO spreadsheets.

For the design exercise in this tutorial, we will just vary the glasses in the inner doublets. After trying this, you can proceed on your own to make a final design by varying all the glasses. To vary glasses, it is necessary to first replace the catalog glasses with model glasses.

At this stage, we have only used curvatures as variables. This has the advantage that the system is still in the same general solution region as the starting system, and the disadvantage that the performance is not improved very much. The next stage of the design is to add the thicknesses as variables. When you add thicknesses, you must take extra care to provide boundary conditions to prevent the system from "blowing up", i.e. wandering off to a solution that is either non-physical or in a totally different solution region from the starting system.

There are hundreds of unique objective lenses to choose from, but once you have a greater understanding of the most common types, you can make a more informed decision regarding which lens is right for you. Whether you are a hobbyist or whether you require the use of a microscope in your day-to-day research, it’s important to gain an understanding of the strengths and weaknesses across the spectrum of objective lenses. Once you know exactly what you’re looking for, you’ll be well on your way to obtaining the best results and having an optimal viewing experience.

Sonnar vsdouble Gauss

Achromatic lenses are used to diminish chromatic and spherical aberrations which are the loss of color and focus that can happen when light wavelengths refract in direct light. These aberrations can be controlled by using an objective lens that contains both a convex and concave lens inside. Mounting these two different types of lenses to each other can bring wavelengths of red and blue light closer together, which puts them in the same focus and cancels out chromatic aberration. Another type of lens used to correct for both color and spherical aberration is the plan (or planar) lens. These produce a flatter field and can also give you a much larger working distance. However, they can be more expensive than achromatic lenses, so choosing between the two depends largely on how much power you need in your objective lens, and whether or not you need to adjust for field curvature, which only plan lenses can do. Achromatic lenses and plan lenses both come in dozens of magnifications and types, accommodating a wide variety of microscopy needs.

Infinity objective lenses did not become common until the 1980s but have since carved out a permanent spot in the microscope objective market. Previously, all microscopes had a standard tube length–the distance from the eyepiece to the objective lens was always 160 mm. Once microscope manufacturers began developing microscopes with varying tube lengths, lens manufacturers had to catch up with the changing technology. New tube lengths meant that microscopy equipment developers needed to adjust for these changes in their accessories, including objective lenses. Infinity optical systems use multiple sets of lenses within the lens house to correct a wide range of tube lengths–typically from 160-200 mm. This enables the lenses to be more versatile between microscopes of varying tube lengths.

Obtaining high-contrast images of transparent specimens is difficult, especially when your specimen is alive and moving on a slide. Phase-contrast lenses allow you to observe microorganisms without having to fix and stain them. When your specimens are kept alive, a variety of biological functions can be examined and analyzed in real-time. Phase plates at the top of the objective lens diffract light, allowing these specialized lenses to tap into tiny changes in wavelength amplitude, which appears to the viewer as starker contrast on the slide. This makes the specimen much easier to view and observe.