Gerhard Fuernkranz wrote:
You make me curious. Do you know, how X-Rite's DRS (Dynamic Rotational Sampling?) spectral engine basically works? I asked Google, and "DRS" is mentioned in many product brochures and descriptions, but I did not find a technical description or white paper of the technology. Does it mean, that these are filter spectrometers, and not based on a grating and a photo diode array?
(The following from taking a look at a DTP41 with the cover off:) It has a filter wheel that is rotated over the sensor. Naturally there is a synchronization element so that it knows which filter is over the sensor at any point in time. I would guess that the filter wheel contains dichroic filters with cut-offs at various wavelengths, possibly chosen optimize precision at critical wavelengths. Add appropriate maths to convert the filter/sensor responses to spectral data, and you're done. The DTP20 seems to be a variation on this, with a smaller set of (duplicated) fixed filters "viewing" the illuminant image (6 x 3 I think). I would guess that X-Rite have used this approach due to technical, cost or patent reasons (Quite a few companies seem to offer grating/CCD type spectrometer modules though, so I wouldn't have thought patents come into it). Graeme Gill.