The above should include a shutter mechanism and timer for achieving different exposures.
It is linear as follows:
Light > Shutter > Monochromator > Step Wedge / object being tested.
The optical items are all mounted on a flat plate of metal for a sturdy makeup and to give optical alignment. The monochromator has a range from about 300 nm - 900 nm with an adjustment for which range - ie UV, visible or IR. It also has a filter drawer next to the shutter for any desired filter combination.
I have posted examples here of exposures. I have no good photos of the device itself.