For many years JB has been trying to improve every part of the optical path of our spectroscopy system. Among many other improvements, one major step forward was the development of a new cosine receptor.
The operating principle of a cosine receptor is aimed towards the collection of the incoming radiance. The standard way to do so, is a white panel that reflects almost 100% of the light perfectly diffuse which is also known as Lambertian diffusion. White panels work good for manual measurements, but their surface is very sensitive and attracts dust and flies, so it´s tricky to use a white panel for permanent installation.
The solution is a cosine diffuser which is pretty much an opaque diffuser that collects the incoming light of the whole hemisphere and leads it toward an optical fibre below. However to mimic the Lambertian diffusion of the white panel, the light throughput has to follow a cosine function depending on the incident angle. This is quite tricky to realize especially if you want to make a robust weatherproof optic that at the same time has a high light throughput but also has a constant cosine function over the whole spectral range of interest.
There were no market ready cosine diffusers available so within JB we developed our own optical diffusers. Of cause this required many many prototypes and a special device called Goniometer which basically allows to characterize the cosine function of a diffuser.
In the end, we´ve manufactured a cosine diffuser that works surprisingly well and we´re in the process of replacing all diffusers in any instruments with the new type. The development and characterization of the new optic has been patented and is described and published in the following paper: “Iterative design of a high light throughput cosine receptor fore optic for unattended proximal remote sensing”.
Since the cosine diffusers have a standard SMA thread, they can be used on any kind of spectroscopy setup so following multiple inquiries, we have added these optics as a product. Please send us a note if you´re interested.