You want excellent optics for your project, and one of your big questions is: how much will a custom lens cost? The answer is, of course, “it depends.” In his optical design courses, Warren Smith was known to show a fifteen page program he used to estimate cost. We won’t go into that level of detail, but let’s discuss some of the major cost contributions in optics. Important factors include schedule, complexity, size, quantity, materials and manufacturing location. If you’re in a big hurry and need to ignore the factors, just start by assuming that each prototype lens or prism will cost $1000. At the other extreme, plastic lenses in production would be closer to $2.
The lens design process starts with a lens specification. If you don’t know how to specify a custom lens, you’re in good company. We have worked with many excellent engineers who have never been through this process and we are happy to assist. However, if you do know at least some of the specifications, it would be helpful for you to fill out as much of the form on our Custom Lens Specification page as you can. If you are looking for a number, designing a custom lens will cost at least $2000 (US $) and often costs considerably more, especially if the specifications change during the design process.
A straightforward but important cost factor is schedule. Normal production time for glass optics is 8-10 weeks. If you need them sooner, there are suppliers who can make them in as little as 1-2 weeks for about 3X the normal price. If you can wait 4 weeks, the price goes down to only 2X the normal price. All of these times are for production only; don’t forget that the lenses must be designed and specified before production can begin.
Production times for plastic optics are different from glass in the sense that production method changes with schedule. If you need prototype plastic optics, they can be diamond-turned in as little as 2-3 weeks, but you can expect to pay $2000 each. In production, the lenses are molded, which means that it is necessary to make molds. Typical time for making molds is 6 weeks for “first article” and another 6 to get the molds to the point where they are making exactly what you want every time. Molds will run from as little as $10k for a single cavity mold to over $50k for multiple cavity production molds.
Complexity & Size
Complexity is another important factor in cost. Lenses vary from simple equiconvex magnifying glasses to semiconductor projection lithography lenses with a couple dozen elements. Most lenses fall between these extremes, with 3-6 elements being most common.
Normal lenses fall in the range of 10 to 50 mm diameter. Within this range, there is not much variation in price until the volume gets into the hundreds. However, outside of this range, size will affect price. Making lenses smaller than 3 mm is quite an art, so tiny lenses command a premium. Larger lenses require glass that is better annealed as well as needing special attention in the polishing process to keep the surfaces accurate over their larger areas, so the price also goes up for lenses larger than normal.
As with anything, price is dependent on quantity. If you are buying single lenses that are custom made, you can expect to pay around $1000 each. The same lens in quantities of 100 could cost less than $50. Normally, price reductions come at quantities of 5, 10, 20, 50 and so on. Given this information, it is wise to plan ahead and order a year’s supply. Manufacturers will often quote a price for a certain quantity and agree to ship and bill at intervals. That allows them to choose how to best allocate their manufacturing capacity.
Material selection also affects price. Magnifying glasses can be made of window glass, but anything more demanding requires better materials. If your lens will be used in the infrared, the lens designer will have to use exotic crystals like silicon, germanium or zinc selenide. These cost significantly more than optical glasses. Similarly, in the ultraviolet the designer will have to use fused silica or calcium fluoride. Within the visible range, there is a much broader selection of materials available. Plastic lenses can be made from acrylic, the most common optical plastic, polycarbonate or a cyclic olefin such as Zeonex™ or Topas™. Lower quality glass lenses can be made of an ophthalmic crown such as Schott B270, but higher quality lenses must be made from optical quality glasses. These range in price from Schott BK7, which sells for around $15/lb to high index specialty glasses that sell for hundreds of dollars per pound. A good lens designer can usually design a lens using glasses that cost no more than 5X the price of BK7.
The last variable cost we’ll consider is manufacturing location. For quick turnaround optics, it is difficult to beat the U.S., but prices tend to be high because making lenses involves a lot of skilled labor. On the other end of the spectrum, it’s difficult to beat the price of lenses made in China, but caveat emptor. There are some suppliers who deliver consistent quality for a very good price and others that will sell you whatever they think they can get away with. It’s best to build a relationship with one or two suppliers and not shop around based on price alone. Other reputable lens manufacturers are located in Germany, Japan and Taiwan.
If better optics or a custom designed lens would enhance your product, Eckhardt Optics will work with you to design and manufacture a custom tailored solution. Contact or call us for a consultation.