You want excellent optics for your project. Of course, your first question is “how much will a custom lens cost?” Well, 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 that will affect how much you spend.
If you’re in a big hurry and need to ignore the factors, just start by assuming that each prototype lens or prism costs $1000. At the other extreme, plastic lenses in production are closer to $2.
Before we can estimate custom lens cost, we need to know what kind of product you’re looking for. Thus, lens specification is the first step of the process. If you don’t know how to specify a custom lens, you’re in good company. We’ve worked with many excellent engineers who have never been through this process and we’re happy to assist. However, if you do know at least some of the specifications, filling out as much of the form on our Custom Lens Specification page would be helpful. If you’re looking for a number, designing a custom lens will cost at least $2000 USD, often more, especially if the specifications change during the design process. If your application requires a more complex lens like a conoscope it’s going to be much more expensive than a simple machine vision assembly.
Schedule is a straightforward but important cost factor. Normal production time for glass optics is eight to ten weeks. If you need them sooner, there are suppliers who can make them in as little as one-to-two weeks for about three times the normal price. If you can wait four weeks, the price goes down to only two times 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 two to three 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 six weeks for “first article” and another six 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. We don’t manufacture plastic optics, but we can point you toward some friends in the industry who are great at what they do.
Complexity and Size
Complexity also affects cost. Lenses vary from simple equiconvex magnifying glasses to semiconductor projection lithography lenses with a couple dozen elements. Most lenses contain three to six elements, falling between these extremes.
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, size will affect price outside of this range. Making lenses smaller than 3 mm is quite an art, so tiny lenses command a premium. Larger lenses require glass that is better annealed. Also, large lenses need special attention in the polishing process to keep the surfaces accurate over their larger areas. Both these factors will increase the price of larger lenses.
As with anything, price is dependent on quantity. You can expect to pay around $1000 each if you’re buying single custom made lenses. The same lens in quantities of 100 could cost less than $50. Normally, price reductions come at quantities of five, ten, twenty, fifty, and so on. Given this information, it’s 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’s a much broader selection of materials available. 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.
Finally, the chosen manufacturing location affects price. For quick turnaround optics, it’s difficult to beat the U.S., but the skilled labor required will raise prices. On the other end of the spectrum, it’s difficult to beat the price of lenses made in China. However, this can be a bit of a 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.