Bentham has supplied many systems for detector responsivity measurements (from 200nm to 30µm). A typical system, configured for both Detector Responsivity and Source Measurements, is described below.
The key features include:-
Software includes calculation of quantum efficiency.
The optics is used to both produce a focused spot at the surface of the detector and to relay a general view of the detector back to the operator via an eyepiece.
For the measurement, the mirrored aperture at the exit slit of the monochromator forms the object for the image produced at the detector.
For setting up, a floodlight is used to illuminate the detector. Light reflected from the detector is sent “backwards” through the optics to be imaged at the mirrored aperture.
The camera’s image displayed on PC’s screen, allows the operator to see most of the image of the detector surface reflected by the mirrored aperture, but not the part which falls into the aperture.
Because the same optical path is used in both directions, the missing section of the image corresponds precisely to the area of the detector illuminated during the measurement.
The operator therefore, has an accurate and unambiguous method for positioning the illuminating spot on the detector area.
During manufacture, the focusing and collimating mirrors are adjusted to give concentric beams at the sample. The setting up facility can thus be used for accurately positioning the collimated beam.
