What is Perfect Optical Performance?

They say that beauty is in the eye of the beholder, however, perfection is often more difficult to define. In lens systems the diffraction limit is often used to describe the limits of optical resolution. In visible optics this is rarely relevant but in the 8-14 micron waveband, this is a very real limitation on what can be done in any optical system and can, conveniently, define perfection.

The diffraction limit is a consequence of the laws of physics and it can be shown that the diffraction limit is related to only two system properties. It is proportional to the wavelength of light used and inversely proportional to the f-number of the imaging system. The wavelength of light is not normally a system variable, being fixed by the detector. However, shorter wavelengths will give sharper images with everything else equal.  So the only real variable to define your perfect system is the f-number of your lens assembly. Here, a faster lens (for example f/1.3 rather than f/1.5) gives a sharper image.

In the real world the choice of f-number is much more complex than “how sharp do I want my image?”. The consequences of fast lenses are optical complexity (more lens elements), lens diameter (size and weight) and tighter manufacturing tolerances. All of these will drive the cost of a lens assembly. Other considerations include: how much energy is needed, faster systems collect more energy; what depth of focus is needed, slow systems are in focus over a longer distance; and how good is the detector, since detector resolution should match the lens resolution.

Well, perfection was always going to be difficult to define and even harder to design! However, Umicore has a range of lenses available “off-the-shelf” which we hope comes close to your idea of perfection. If you would like to get even closer to perfection, you can always talk to our designers, and perhaps between us we can achieve your goals.

(JF)