Slew Scan Mode
30
DLPU016C – April 2014 – Revised April 2019
Copyright © 2014–2019, Texas Instruments Incorporated
Operating the DLP NIRscan EVM
up overall scan times.
Below are the steps to setup and execute a Slew Scan. This example uses 3 regions which are not
contiguous, have different exposure times per pattern in each region, and different digital resolutions for
each region. The configuration is located above in
. Graphical output results are shown below in
1. Determine the number of distinct spectral segments required and enter that number in the
Number of
Regions
box. Now click the
Apply
button and the entry table expands or contracts to provide one row
for each Region. Now the user can enter the desired configuration settings for each of the desired
regions:
•
Lambda Start (nm)
: is the starting wavelength for the region N. The starting wavelength must be
≥
1350 and must be
> the Region (N-1)'s Lambda Stop value.
•
Lambda Stop (nm)
: is the stopping wavelength for the region N. The stopping wavelength must
be > the region N Lambda start value, and must be
≤
2450.
•
Exposure time per pattern (µs)
: The minimum exposure time is 600 µs. Ensure that [maximum
allowed exposure time (µs/pattern)] × [the number of wavelength points] is less than or equal to 1
second. The NIRscan EVM software design limits the exposure time constraints. Because the DLP
patterns applied to the DMD are inherently programmable, customer systems can implement much
longer integration times for applications which require them.
•
Wavelength Points
: The number of wavelength points defines the number of the patterns being
applied to the DMD within this region only. [Lambda stop – Lambda Start] / # wavelength points) =
the Digital Resolution for which the DMD is programmed
•
Digital Resolutions is only one of the contributors to the true spectral resolution of a DLP based
spectrometer. See
DLP Spectrometer Design Considerations
for more information regarding
spectrometer resolution as a function of DMD digital resolution, input slit width, and optical point
spread function.
2. As in the other scan modes, the user can change the scan name, or leave the default name in place.
The sfotware embeds in the resulting filenames for imminent scans, which can be downloaded from
the DLP NIRscan after the scans are complete.
3. As in the Custom Scan mode, whenever new configuration data are entered, or existing settings are
modified, the NIRscan generates new patterns defined by the new configuration data. The Generate
Patterns button turns green when the configuration data changes to indicate new patterns are needed.
•
Click
Generate Patterns
. This step is complete when the
Set Reference
button turns green and
the message
Patterns Generated - Set New Reference!
message displays.
4. Click
Set Reference
.
•
If planning to measure a liquid sample in a cuvette, first run the reference scan with an empty
cuvette in the sample holder. This scan allows the absorbance of the cuvette material to be
negated when the absorbance of the material is calculated.
•
When measuring a solid transmissive material such as sheet plastic by inserting the plastic into the
sample holder, ensure the sample holder remains empty during the reference scan.
5. Insert the sample in the sample holder (with or without cuvette).
6. Click
Perform Scan
. The DLP NIRscan EVM scans the sample, calculates the sample material
absorbance, and displays the absorbance in graphical format on the next screen.
shows an
example of this output.
