Over the years we have seen some interesting asphere designs. We preface the following comments by stating; clearly, we are not optical designers; so please use your best judgment when designing. With that said, here are 10 considerations to keep in mind when you are designing your next asphere from a manufacturing perspective. Some of these tips are specific to ground and polished aspheres.

Natural zinc is a mixture of five stable isotopes: 64Zn (48.6 percent), 66Zn (27.9 percent), 67Zn (4.1 percent), 68Zn (18.8 percent), and 70Zn (0.6 percent).

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Aspheres geometry can come in several different flavors. Each class presents specific challenges and considerations for manufacturers. These challenges will also be different for each type of manufacturing process. For example, a gull-wing asphere with mounting flanges may not be very difficult for precision molding, but the same lens would be impossible to manufacture using a grinding/polishing method. Below is a table that highlights different potential geometries along with benefits and considerations for each.

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3 days ago — The meaning of OBJECTIVE LENS is a lens or system of lenses in a microscope, telescope, etc., that forms an image of an object.

Metallic zinc is produced by roasting the sulfide ores and then either leaching the oxidized product in sulfuric acid or smelting it in a blast furnace. Zinc is won from the leach solution by electrolysis or is condensed from the blast furnace gas and then distilled of impurities. For specific information on the mining, recovery, and refining of zinc, see zinc processing.

Goal: To provide an introductory overview of each topic we will be addressing in this blog series.  As a result, we will be able to dive deeper into each item to better understand aspheres and how they are manufactured.

Hot-dip galvanizing is the most common procedure for coating steel with zinc. This may be a batch process known as general galvanizing or a continuous coating of coils of steel strip. In general galvanizing, steel is pickled in acid, treated with fluxing agents, and then dipped in a bath of molten zinc at about 450 °C (840 °F). Layers of iron-zinc alloy are formed on the surface and are topped with an outer layer of zinc. Objects so treated range from small nuts and bolts to steel window frames and large girders used in construction. An ordinary grade of zinc containing up to 1.5 percent lead is normally used in this process.

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Departure is the distance from the BFS to the aspheric form. Form error can be explained by how much the manufactured asphere contrasts with the theoretical aspheric form. Slope error is the derivative of form error and quantifies how quickly the form error changes. The aspheric surface is typically defined using an even aspheric equation. Other forms of defining aspheric surfaces exist although most optical fabrication machines utilize the even aspheric equation.

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How do you know that your asphere meets design specifications? What if your design needs to be tweaked explicitly to each lens to squeeze that last bit of performance from your system? Furthermore, inspection data can be extremely beneficial. We have a complete guide on inspection data that explains all aspects of qualifying optics. The industry standard has been a profilometer trace for aspheric-specific inspection data. A profilometer trace involves using a precision stylus that has been atomically balanced, which traces the surface of the lens. The resulting trace is compared with the theoretical design of the aspheric surface and the form error, vertex radius error and slope error can also be identified. Feel free to check out interferometry blog if interested in learning more about the various forms of interferometry and optical measurements.

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There are several different methods of manufacturing aspheres. Each method has strengths and weaknesses, which depends on material, specifications, size, and quantity to name a few. Below is a table highlighting each technique.

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The negative electrode (outside can) in one common type of electric dry cell is composed of zinc. Another important series of alloys are those formed by the addition of 4 to 5 percent aluminum to zinc; these have a relatively low melting point but possess good mechanical properties and can be cast under pressure in steel dies. Considerable quantities of zinc in the rolled form are used for roofing, particularly in Europe; small additions of copper and titanium improve creep resistance—i.e., resistance to gradual deformation.

In electrogalvanizing, zinc is deposited on a steel strop in as many as 20 consecutive electrolytic coating cells. There are several successful cell designs; the simple vertical cell is discussed here to explain the principle. The strip, connected to the negative side of a direct current through large-diameter conductor rolls located above and between two cells, is dipped into a tank of electrolyte by a submerged sink roll. Partially submerged anodes, opposing the strip, are connected to the positive side of the electric current by heavy bus bars. Zinc cations (i.e., positively charged zinc atoms) present in the electrolyte are converted by the current into regular zinc atoms, which deposit on the strip. The bath is supplied with zinc cations either by zinc anodes, which are continuously dissolved by the direct current, or by zinc compounds continuously added to the electrolyte. In the latter case the anodes are made of insoluble materials, such as titanium coated with iridium oxide. The electrolyte is an acidic solution of zinc sulfide or zinc chloride with other bath additions to improve the quality of the coating and the current efficiency. Coating thickness is easier to control than in the hot-dip process because of the good relationship between electrical current and deposited zinc.

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Materials are typically chosen based on the end user application. Several considerations need to be accounted for such as the wavelength of the application, thermal and mechanical stability, cost, manufacturing method, and any other possible concerns. Each material presents manufacturing challenges that need to be in consideration. Below is a chart that provides which materials can be made with each process.

Our hope with this series is to shed light on aspheric manufacturing; specifically, to help enable optical designers and engineers to gain a better understanding of how aspheric lenses are manufactured as well as how to properly tolerance aspheres to meet their performance goals and obtain manufacturable lenses. Optics is an exciting field, and we are passionate about helping you with your next project. Please contact one of our engineers today if you have a project you would like some feedback or a ROM quote.

Ultraviolet laser beams radiated and scanned on a thin layer of photopolymerizing polymer solution can produce two-dimensional structures.

Aspheres have allowed optical designers to create systems and products that push the limitations of performance across several fields. These systems find application in products such as night vision goggles, laser rangefinders, high power laser fabrication tools, medical instruments, and many more. Aspheres are not limited to specific applications; instead, they can increase performance by correcting aberrations with fewer surfaces than would be required using only spherical lenses. Along with new possibilities, aspheric lenses have also brought much disruption to the design and fabrication processes. It's one process to design an asphere that works in an optical system, and it's another process to develop an asphere that is manufacturable.  The purpose of this blog series is to address the following topics:

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A little more abundant than copper, zinc makes up an average of 65 grams (2.3 ounces) of every ton of Earth’s crust. The chief zinc mineral is the sulfide sphalerite (zinc blende), which, together with its oxidation products smithsonite and hemimorphite, constitute nearly all of the world’s zinc ore. Native zinc has been reported from Australia, New Zealand, and the United States, and the leading early 21st-century producers of zinc are China, Australia and Peru. For zinc’s mineralogical properties, see native element.

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Two potential problems with profilometry can occur. First is you can potentially miss out on asymmetric error induced on your part; and second, it is possible you can scratch the surface of the part with the stylus. 3D non-contact metrology is an excellent alternative for this potential risk. LaCroix specifically uses an Optipro Ultrasurf to provide 3D measurements of aspheric surfaces. This instrument is capable of seeing the entire surface of the asphere rather than a single trace. With the complete data set, we can correct the asymmetric error and provide a higher quality 3D aspheric surface. The data below is of a 6-inch asphere that our profilometer showed a peak to valley form error measurement of roughly 0.4 um of form error; however, the profilometer did not capture the asymmetric error of the part. Our 3D analysis revealed the asymmetry and form error was 1.3407 um. After a quick 3D correction, the 3D form error was reduced to .294um and .133 um in 2D with less than 0.1 um/mm of slope error using a 1 mm integration window.

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zinc (Zn), chemical element, a low-melting metal of Group 12 (IIb, or zinc group) of the periodic table, that is essential to life and is one of the most widely used metals. Zinc is of considerable commercial importance.

The major uses of zinc metal are in galvanizing iron and steel against corrosion and in making brasses and alloys for die-casting. Zinc itself forms an impervious coating of its oxide on exposure to the atmosphere, and hence the metal is more resistant to ordinary atmospheres than iron and corrodes at a much lower rate. In addition, because zinc tends to oxidize in preference to iron, some protection is afforded the steel surface even if some of it is exposed through cracks. The zinc coating is formed either by hot-dip galvanizing or electrogalvanizing.

Let us start by discussing what an aspherical lens is. An aspherical lens is a spherical lens with a constantly changing local radius. In our illustration below an asphere has the best fit sphere (BFS), which is a radius that touches the edge and center of the lens.

Tolerancing an aspheric lens is perhaps the single most significant point of confusion, and one could easily write an entire article on each tolerance. Over the course of the next few blogs that are we what we are planning to do. In the meantime, here is a chart that describes several asphere specific tolerances along with a button below to download our tolerancing chart on precision optics for spherical and aspherical tolerances.

Turn the coarse adjustment knob to raise the body tube. 4. Revolve the nosepiece until the low-power objective lens clicks into place. 5. Adjust the diaphragm.

Freshly cast zinc has a bluish silver surface but slowly oxidizes in air to form a grayish protective oxide film. Highly pure zinc (99.99 percent) is ductile; the so-called prime western grade (99.8 percent pure) is brittle when cold but above 100 °C (212 °F) can be rolled into sheets that remain flexible. Zinc crystallizes in the hexagonal close-packed structure. When iron and zinc together are exposed to a corrosive medium, they constitute an electrolytic cell, and the zinc is attacked (oxidized to the Zn2+ ion) preferentially because of its higher electrode potential. This so-called sacrificial protection, coupled with the much greater corrosion resistance of zinc under atmospheric conditions, is the basis for galvanizing.

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Zinc is an essential trace element in the human body, where it is found in high concentration in the red blood cells as an essential part of the enzyme carbonic anhydrase, which promotes many reactions relating to carbon dioxide metabolism. The zinc present in the pancreas may aid in the storage of insulin. Zinc is a component of some enzymes that digest protein in the gastrointestinal tract. Zinc deficiency in nut-bearing and fruit trees causes such diseases as pecan rosette, little leaf, and mottle leaf. Zinc functions in the hemosycotypsin of snails’ blood to transport oxygen in a way analogous to iron in the hemoglobin of human blood.

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