[argyllcms] Re: Use of DTP-22 digital swatchbook with Argyll CMS

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.

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