What is in the DLP NIRscan EVM?
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DLPU016C – April 2014 – Revised April 2019
Copyright © 2014–2019, Texas Instruments Incorporated
DLP NIRscan Evaluation Module Overview
1.2.1 Optical Engine
The DLP NIRscan EVM spectrometer optical engine is mounted on top of a thermal plate which acts as a
stable platform for mounting the optics. The configuration is a post-dispersive architecture where the
broadband light from the tungsten lamp is directed through a transmissive sample. In this specific
implementation, the lamp or sample holder module allows insertion of standard cuvettes. These cuvettes
are designed to hold liquid samples. There is also a slit in the sample holder, which allows insertion of
various thickness NIR transmissive samples such as plastic sheets and coated glass.
Each sample passes (and absorb) a specific amount of NIR light through the sample. The amount passed
(and absorbed) depends on the molecular makeup of the material, and is specific to that material, similar
to a fingerprint. The light which passes through the sample enters the engine through the input slit. Slit
size is relative to the desired wavelength resolution of the spectrometer. This spectrometer uses a 25-µm
wide slit, which is approximately 4.2-mm tall. After light passes through the slit, the light then passes
through a collimating lens, through a 1350- to 2450-nm bandpass filter where the light then strikes a
reflective grating. This grating, in combination with the focusing lens, disperses the NIR wavelengths
across the DLP4500NIR DMD in a horizontal fashion, with 1350 nm projected to one side of the DMD,
2450 nm to the other end, and all wavelengths dispersed between. When specific DMD columns are
selected as 'on', or tilted to the +12º position, the energy reflected by the selected columns diverts through
the collection optics to the single pixel detector. All other DMD columns which are not selected as 'on' are
by default 'off' (tilted to the –12º position). 'Off' DMD pixels divert the unselected wavelengths away from
the detector optical path so as not to interfere with the selected wavelength measurement.
The DLP NIRscan EVM size is mostly driven by the size of the optical engine and measures
approximately 197-mm long, 112-mm wide, and 96-mm tall.
Figure 1-2. DLP NIRscan EVM Optical Engine
