How to specify UV high brightness LEDs?
The datasheets can be a bit all over the place in terms of these units, especially with luminous intensity which is a function of how well the eye perceives the particular wavelength.
Since the application is a box, I would not worry too much about directivity (or the eye), and focus more on getting an LED with a respectable &quot;Radiant power&quot; (total radiated power) to electrical power ratio.
I have used &quot;VLMU1610-365-135&quot; (the datasheet is quite good in my opinion) for a project where it has P_rad=23mW at 20 mA. And it states a forward voltage of 3.5 V at 20 mA. So P_in=70mW, and thus we are around 33 % efficient in radiating light. I might have seen some with 50 % which seems to be around the top.
About this box, remember to be able to dissipate the heat from the LED's through the sides. LED's lose quite a lot of radiant performance when they run hot and the consultant who helped me said that it was the most common error in power LED applications.