High Throughput Fourier Transform Spectrometer
for diffuse reflected light.
The Arcspectro HT is a static
Fourier transform spectrometer
(FTS) that is based on a licensed concept that uses the
polarization properties of the light and the optical properties of crystals). It
provides a extremely high throughput (sensitivity) and does not need external
optics to be used. The Arcspectro HT is ideal for the measurement of low light,
diffuse reflection
and also
in fields like fluorescence or Raman spectroscopy.
What makes the ARCspectro-HT
spectrometer
so
exclusive?
ARCspectro HT
is ideal for low
light applications or for the spectral analysis of diffusing light sources (or samples). Its unique design permits to
gather a maximum of light over a large
diffusing surface (several millimeters!) and over a large angle (±10°).
This gives a tremendous throughput advantage (~100x more) compared to the most
powerful grating spectrometers (also well-known Jaquinot advantage)
which are intrinsically limited by a small
entrance slit (typically 0.025mm). This makes this unique device ideal for applications were small light
intensities has to be analyzed (fluorescence or Raman spectroscopy).
Overview
of the ARCSpectro HT Models:
Choose the right model for
your needs!
ARCSpetro HT series contains three different models with different detector
arrays having different properties. The table below gives an overview:
|
ARCSpetro Models |
Detector Array |
Features |
Applications |
HT-HR
High
Resolution |
Toshiba TCD
1304 3648 Pixels CCD.Also available
with extended UV detector. |
- High
Throughput
- < 1nm @ 550nm
|
- Peak
position Measurement
- Need for Higher resolution |
HT-U
High Sensitivity |
Hamamatsu
S9840
2048x14 Pixels back-thinned
CCD |
- High
Throughput
- High sensitivity
- UV sensitive |
- Low light
applications
- Raman Spectroscopy
- Fluorescence Spectroscopy |
HT-2D
2D detector
High SNR
High dynamic |
CMOS 2D camera
1024x1248 Pixels |
- High
Throughput
- 1024
Measurements
in one shot
- Compact
- Short Integration
Time (50ms)
- High Dynamic range |
- Diffuse
Reflection with
sufficient
light
- High SNR, High Stability
- Need for High dynamic
range |
Compared with a conventional grating
Spectrometer?
Compared to conventional grating spectrometers,
The arcspectro-HT (and all the other FT spectrometerrs) has many advantages. The
most important is its a high resolution (0.7
nm @ 500nm) for
a broad wavelength range (400nm-1050nm) and for an entrance aperture of 4mm!!!
Also FTS do not need second and third order
rejection filters on the detector which causes spectral distortions and
absorptions.
Check pdf file below that demonstrates the
advantages of having a high throughput spectrometer compared to a standard grating
spectrometer:
 |
DOWNLOAD pdf
comparison
between the ArcspectroHT and a conventional grating
spectrometer |
Another important advantage the arcspectro-HT
is the simplicity of the optical setup: The user can directly illuminate
the 4mm entrance window
with the light to be
spectrally analyzed.
There is no need for cumbersome and expensive optics for coupling the light into
a small optical fiber as it is the case for conventional grating spectrometers.
Also, if necessary, the light
can be
directly injected in the
arcspectro-HT
via a thick
light guide that
is connected to the entrance.
|
Features |
ARCspectro HT |
|
Spectral range |
400
nm – 1100 nm |
|
Signal-to-Noise (single
measurement full detector dynamic used, Ratio between
the peak value and bottom value of HeNe Spectrum) |
500:1 (Multiplex advantage) |
|
Spectral Resolution |
< 1 nm @
l
= 550 nm |
|
Detector type |
Silicium
CCD front illuminated detector array |
|
Full-well detector capacity |
30'000 e- |
|
Dark noise |
0.5% |
|
Detector sensitivity |
~15 photons
per count |
|
Relative wavelength
fluctuation (measured with HeNe over 1 hour) |
< 0.01 nm |
|
Absolute
Wavelength Accuracy |
< 0.5 nm |
|
Operating Temperature |
10°C – 50°C |
|
Wavelength Drift with
temperature |
0.001nm per °C |
|
Measurement time |
1 ms to "infinite" |
|
Operating Voltage |
USB powered |
|
Light guide core diameter (optional) |
4 mm |
|
Entrance aperture |
4 mm (Diam.) |
|
Communication Interface |
USB 2.0 |
|
Software Interface |
Windows XP,
Labview |
|
CCD Readout Sampling rate |
0.5 MHz |
|
A/D converter |
10-16 bits |
|
Product Dimensions (including
electronics) |
15cm x 10cm
x10cm |
|
Product Weight |
300 g |
Software
The
ARCspectro HT series is delivered with a free windows XP,98,2000, compatible
program.
The software recognize automatically the spectrometer (USB plug and play system)
and
is able as other conventional spectrometer software to:
- Display
real time spectral measurement results
- Configure
measurement parameters (integration time, averaging).
- Choose
Transmission or Reflection mode
- Usual
features such as save, open, zoom, rescale...
- Some
specific features related to Fourier transform spectrometry:
choose apodization (automatic recognition option), look and
save the interferograms.
On demand application specific
features can be implemented in the program within a few weeks.
Visit our custom software page.
Also free Labview Vi's
for driving the spectrometer are available on demand.
Accessories:
The
ARCspectro HT is available with
four different "light inputs" possibilities depending of the application and the
type of light source to be analyzed:
- Glass
window: The spectrometer module can directly be placed in
front of an extended diffusing source or for a point source.
This solution presents minimal losses when looking with
diffusing sources
- Diffusing
window: One can directly shine onto the diffusing plate. This
solution is ideal for collimated sources
- Single
branch light guide: Ideal when the source is not directly
accessible.
- Dual
branch light guide: Ideal for reflection measurements
How does it works?
The
ARCspectro HT series is
static (so no moving scanning parts)
FTS based on a
so-called common path polarization interferometer. The hart of Arcspectro HT is
a monolithic bloc constituted of high-end crystal prisms and polarizers that are
transparent over a very large spectral band (UV-VIS-NIR). The spectral dependent
intensity pattern (interference pattern) created at the output of the bloc is recorded
with a CCD detector array and the spectrum is calculated by the computer via a
Fourier transform algorithm and calibration tables.
The diffusing light (over
a diameter of 4mm) can directly enter the device and so it does not need
to pass trough a narrow entrance
slit (generally of 25mm for an equivalent resolution
and comparable acceptance angles) as for the conventional commercially available
grating spectrometers. This explains the tremendous throughput advantage
(between 50 and 100x more!) of the ARCSpectro-HT.
Notice also that fiber and collimation optics are not absolutely necessary,
this may be an advantage for certain applications where cumbersome and lossy
optics are not desired.
Throughput Advantage:
A FTS does not use a slit (or glass fiber) to limit the individual
frequency reaching the sample and detector as a grating
spectrometer does. Overall, more energy reaches the sample and
hence the detector in an FTS than in a dispersive
spectrometer. This means, for a comparable source and
integration time, that the signal-to-noise
ratio of a spectrum measured on an FTS
is higher than the signal-to-noise ratio attained on a grating
spectrometer .
Multiplex advantage:
A Static Fourier transform
spectrometer basically measure an interferogram on a CCD array and calculates
its Fourier transform to find the spectrum. Every pixel of the CCD that measure
the interferogram contains information of each wavelength of the light being
measured. In contrast to a dispersive (or grating spectrometer) where a pixel
contains only (and the whole) information of a single wavelength. So for a small
band spectrum (laser line) only one or two pixels will contribute to the
spectrum in a grating spectrum. In a
FTS every pixel
of the CCD (interferogram) will contribute to the final spectrum and we will
theoretically get a better signal to noise ratio equal to the root mean square
of the number of pixels off the CCD that records the interferogram.
Notice that this
advantage is not valid anymore if broadband spectra without emission or
absorption lines are considered.
Precision Advantage:
For similar reasons
mentioned for the multiplex advantage, the FTS is
capable to determined the position of a peak (absorption or emission line) with
much more precision than a grating spectrometer. Indeed, in the dispersive the
precision is limited by the covered spectral divided by the number of pixels. In
a FTS information of the emission or absorption line is spread
over all the pixels and mathematical Fourier transform methods permits to
determine the peak or dip position with much more accuracy.
Some application examples:
-
Raman spectroscopy
-
fluorescence detection
- Diffuse Reflection
-
Dynamic
processes analysis
|
- Reflectance measurement
- Colorimetry
- Gas detection
- Diffusing sources
|
