At Kingsview we pride ourselves on having first hand experience of the complete optical production process. This means we design with manufacturing at the forefront of our mind. This leads to a more economic design and better real world performance.
Zemax is a great software package but it is not a substitute for manufacturing experience. Some common problems we see a lot.
There are hundreds of different optical glasses out there but they don’t behave the same and they certainly don’t cost the same. All optical glasses process slightly differently.
Some are prone to cracking due to a change in temperature which is a problem as there are many instances in the manufacturing process that add heat.
Others are extremely soft which makes it difficult to keep a good surface finish and hold tight centre thickness tolerances.
Letting Zemax optimise your material choice it will usually pick the most expensive glass it can without thought for it’s production characteristics. This can lead to increases in production costs which aren’t necessary.
This happens when lens surfaces are added too quickly. The problem with adding more surfaces the tighter your lens tolerances need to be. As the deviation from the normal start to multiply the performance can drop off a cliff if not met.
This results in higher costs as the number of optical components, metalwork and assembly time go up. If the complexity gets too much and the tolerances get too tight for a manufacturer to hold consistently this actually gives you worse real world performance but still at that high price.
The key is knowing what is good enough and what is manufacturable. There are actually times where it is better to have slightly worse theoretical performance that is met 95% of a production run then one that is slightly higher where in production only 20% are acceptable.
Zemax can tell you what is a perfect design but it can’t tell you if it can be manufactured or to what tolerance is possible.
Some lenses with small edge thicknesses can be a particular problem as lenses are generally manufactured to a bigger diameter and final edged and centred last. So a steep bivex lens might have to be manufactured to a knife edge leading to chipping and an increase in rejects.
Large diameter lenses with thin centre thicknesses can cause problems holding tight irregularity tolerances.
Very shallow radii are extremely difficult to hold tight radii tolerances on.
These just offer a snapshot of some of some of the potential difficulties for the manufacturer if not allowed for in the design. Most of them are common sense but if you don’t have experience of manufacture you don’t see these potential problems.