Section 2 - Manufacturing tolerances, Mechanical and Thermal disturbing effects

Up to this moment, we have found two parameters in the case of air spaced lenses that must be manufactured very precisely: the metal spacers between the air spaces, and the curvature radii of surfaces surrounding the air spaces. Keeping this second parameter perfect is not a problem in reality, as the curvarures can be measured optically to extreme precision if the manufacturer has test plates with proper curvature radiuses. Also, it is possible to make very precise metal spacers, but the manufacturer must be very careful with this parameter.

So, we can conclude, that in the case of oil spaced lenses we have found no parameters that should be manufactured very precisely, but in the case of air spaced lenses there are two of them. Though, with some care, there are usable methods to set these parameters with proper tolerances, so they are not prohibitive in any meaning. Both lens types can be used to make excellent lenses, so in this regard these are roughly equivalent - at least before examining their error tolerances outside the laboratory.

We might mention that there are several other problems that can occur, but these are not specific to a lens type (e.g. internal inhomogenities of optical glass, or optical material not matching the manufacturer specification). To spare space, we do not examine them one by one, as they can be commonly present in all lenses.

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