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Copyright © Multichannel Instruments AB 0602-1 / 1
Promis Electro Optics
 Voor verdere informatie betreffende deze instrumenten kunt u
contact opnemen met:
 Ing. Frank Godschalk
 Sales manager
 Promis-Electro-Optics B.V.
Bezoekadres: Kraanvogelstraat 2, 6601 DH Wijchen.
Postadres:
Postbus 194, 6600 AD Wijchen.
Tel:
+31 (0) 24 648 8688
Fax:
+31 (0) 24 366 1984
[email protected]
www.promis-electro-optics.com
Copyright © Multichannel Instruments AB 0602-1 / 2
Short history
 The optics concept of using Echelle gratings with an order sorter
was made at the Royal Institute of Technology in Stockholm 1989.
Patents granted. Company started in 1991.
 This company was bought out in 1993 by an electronic
consultancy company, acting also as a subcontractor for the
sensors and all electronics. Company became NOW Optics.
 Multichannel Instruments was founded in 1997 with a new
manufacturing philosophy, called the Mechelle®. Design can be
integrated with any commercial camera on the market.
 In July 2001 Multichannel Instruments introduced a new line of
products, aimed at the telecom market, called Raptelle™.
Copyright © Multichannel Instruments AB 0602-1 / 3
Product range
Copyright © Multichannel Instruments AB 0602-1 / 4
Technical
Presentation
Copyright © Multichannel Instruments AB 0602-1 / 5
Mechelle Technical Overview
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Wavelength range required is spread across many orders.
Orders are positioned one above each other.
Each order contains a portion of the whole spectrum.
Focussed onto a two dimensional camera detector.
Software reconstructs complete spectrum.
 Standard Echelle gratings used with high efficiency.
 The unique part of the Mechelle is the order sorter.
 Ensures orders cover area of sensor uniformly
 can fit more – higher resolution
 Larger wavelength range.
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Provides a flat field image.
Coma and astigmatism compensated.
Allows larger aperture = more light throughput. Sensitivity!
Less cross-talk
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Echelle
Blazed reflectance grating
q
a
b
= incidence angle
= diffraction angle
q
= blaze angle
d
= grating constant
(d 5 - 30 mm)
W
= width of grating
N
= total number of grooves W/d
f
= focal length
m
= diffraction order (m  50)
q
= Blaze angle  60

a
a
q
b

b0
d
GRATING EQUATION
ml = d (sina + sin b)  mlm = k  lm overlap
b > 0 when incident and diffracted rays on the same side of grating normal.
Max. intensity for wavelengths satisfying the grating equation at angles a + b0 = 2q
 mlm0= d (sina + sinb0).
Special case a = b0 = q = condition for auto-collimation
Resolution:
Reciprocal linear dispersion:
l
2W sin q
 Nm 
l
l
(
dl 1 1 db 1
)  ( )
dl
f dl
Angular dispersion:
db
m

dl d cos b

2tgq
l
for a  b  q
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Schematic description of echelle grating
order-sorter combination
Cross dispersion order-sorter
Echelle grating
Separated order spectra
Diffraction many orders overlap
Copyright © Multichannel Instruments AB 0602-1 / 8
Complete Mechelle optical layout
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1024 pixels
Echelle image of Xe flash
1024 pixels
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512 pixels
Segmented echelle spectral image
768 pixels
1
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Intensity distribution in each order
•
For echelle gratings the intensity distribution in one order m is given by:
  0 (
•
sin 

)2
First minimum at:
where

m
( l  l0 )
l
    l  l0  
ml0  d (sina  sin(2q  a ))
l
m
0
0.410
l0 
l
l0 
m
l
2m
•
To get spectral continuity, the optimal range
•
At the wavelength:
l0 
l
2m
l0 
l0
l0 
l
2m
 l0 
l
2m
l
2m
l0 
l
m
of each order is needed.
2
  ( ) 2  0  0.41 0

• The efficiency in the whole spectral range is thus better than 40% of the efficiency at the
blaze wavelength, when the optimal part of each spectral order is used.
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Calculated echelle spectrum on CCD
max
l
Segments =
spectral orders
min
l
m-1
max
=
l
max
l
m
m
min
l
m
min
l
Central blaze wavelength
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Fitting order correction
120000
100000
Counts
80000
60000
40000
20000
0
550
600
650
700
750
800
850
Wavelength (nm )
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Spectral continuity
Change of orders
 b

1
lm
min
m 1
1
lm
max
1
lm
0
m 1
m
lm
0
lm
min
• At
 b

m
lm
max
lm
max in order m read-off is continued in order m - 1
• Spectral continuity if:
l
m
max
l
l
m1
min
m
max
l
m 1
min

lm
0
m
• Optimal blaze efficiency if:
(
sin 

) 2l lm  (
max
sin 

) 2l lm1
min
 
d cos( q )
(sin( q  a )  sin(q  b ))
l
Copyright © Multichannel Instruments AB 0602-1 / 15
New optical design
The distance LT between two adjacent order-spectra is given by
f
dbT l0m
db
LT  f 


 T  (l0m ) 2
dl m 2  d  sin(q )  cos(q  a ) dl
valid for large m. The quantity dbT / dl is the angular dispersion of the order-sorter.
Approximately constant order separation, if
dbT
1
 2
dl
l
implying dispersive properties for a prism order-sorter that no optical material can
meet, especially in a range including both the UV and the NIR wavelength regions.
New optical design eliminates this, by nature given drawback, giving
 A virtually uniform order distribution for the whole wavelength range
 Both stigmatic and coma compensated imaging
 Flat image field
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Distribution of orders

Large wavelength range and max. transmission, if spectral orders are uniformly
distributed on detector surface.

Distance between orders is:

For LT to be constant on must have:
db T
 ( l0m ) 2
2  d  sin(q )  cos( ) dl
f
LT 
db T
1
 2
dl
l
Grating
order-sorter
d b T
d l

= 2 constant
1
l
LT  l
Prism
order-sorter
d b T
d l

1
l=2 more steep than
1/l
N ew M e c he l l e
o r d e r- so rt e r s yst e m
( p at en t e d)
Ap p r . c o n s t a n t o r d e r s e p a r a t i o n
2
2

(which no dispersive
component can give)
Orders close at low l
Orders close at high l
L a r ge w av e le n g t h c o v e r ag e
( 200 - 1100 nm )
Copyright © Multichannel Instruments AB 0602-1 / 17
Constant spectral resolution - CSR
Example
Suppose a Mechelle system has a spectral resolution of 1000, which through the
entrance aperture width and the dispersion has been related to 3 pixels FWHM
in the focal plane (pixel size 20 mm2)
Then
 The resolution is 1 nm at 1000 nm and 0.2 nm at 200 nm
 One pixel corresponds to 1/3000 of the wavelength or to 0.33 nm at 1000
nm and to 0.067 nm at 200 nm
All relevant data for the spectrograph follow from specifying one single figure,
such as the spectral resolution, and its corresponding distance in the focal plane.
Copyright © Multichannel Instruments AB 0602-1 / 18
Implications of CSR
LINEAR WAVELENGTH SCALE
l
l
 l contains more channels at low
wavelengths - lines appear narrower
LOGARITHMIC WAVELENGTH SCALE
(logl)
(logl)
  (logl) ~ l/l = constant, contains about the
same number of spectral channels anywhere
in the spectrum
Mechelle spectrum makes possible full utilisation of the whole wavelength range
1
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Wavelength calibration
l
CCD - chip
y
Calibration lines
Optics, ray-tracing
Spectral order = m
xcycm
x
Design co-ordinates (mm)
Xp = Ax + BxXc + CxYc + DxXc2 + ExXcYc + FxYc2
Yp = Ay + ByYc + CyXc + DyYc2 + EyXcYc + FyXc2
Displ.
xpyp
Magn.
Rot.
Distortion (normally not needed)
Pixel co-ordinates (pixels)
Copyright © Multichannel Instruments AB 0602-1 / 20
Mechelle Software
Compilation of spectra
l
m
max
l
m
min
central pixel
of channel
2
1 spectral channel
= sum of 2n + 1 pixel intensities

The co-ordinates of the central pixel (xcp ycp) and its wavelength (lcp) are calculated (ray-tracing
parameters, calibration constants) initially and stored for each channel.

After recording, the channel intensity is calculated as the sum of 2n + 1 vertical pixel intensities.
The channel intensity and the central pixel wavelength is stored for each channel.

The individual segments (orders) are connected (and corrected for the blaze efficiency etc.) to
form a linear Mechelle spectrum.
Copyright © Multichannel Instruments AB 0602-1 / 21
Mechelle 900
Mechelle 7500
Cameras, Software,
accessories &
Custom models
Copyright © Multichannel Instruments AB 0602-1 / 24
Image intensified CCD (ICCD)
MCP
Gating electrode
(Micro-Channel
Plate)
Phosphor

Electrons
LIGHT

Electrons

Photocathode
PROVIDES:
CCD
LIGHT

FO - plate
RESTRICTS:
1. Gain of image
A. Wavelength range (up to about 850 nm)
2. Gateability.
B. Resolution
C. Dynamic range
Copyright © Multichannel Instruments AB 0602-1 / 25
Shuttered CCD detector systems
For time-resolved studies
CCD - camera system integrated with a fast electronic shutter
Or a fast mechanical shutter:
Electronic shutter
(3 versions available-all from PCO right now)
- Fast Shutter
- Long Exposure
- Double Shutter
Mechanical shutter
- gate and delay time 100 ns to 1 ms
- 2 ms to 1000 s
- 2 gated images of 100ns at 200 ns
interval
‘UniBlitz’ can be fitted to any Mechelle.
- Exposure time can be set from 2ms upwards.
Implementation of new cameras to the Mechelle spectrographs are constantly being made
Copyright © Multichannel Instruments AB 0602-1 / 26
Intensified CCD

Electronic Shuttered CCD
Advantages
Advantages
ICCD
Gated CCD camera
1. High sensitivity (in UV)
1. High resolution (6.7 x 6.7 mm2 pixels)
2. Low gate time
2. Sensitive in NIR up to 1100 nm
3. Excellent ON/OFF ratio
3. Antiblooming
4. No external pulse electronics required
5. Reasonable price
Drawbacks
Drawbacks

Low resolution degraded by the image
intensifier

Gate time restricted to 100 ns
(at present)

Upper wavelength range restricted by the
sensitivity of the photocathode to about
850 nm.

ON/OFF ratio 2000:1
1. The ICCD cameras are very expensive
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CMOS Cameras - (Not standard yet)
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Easier to fabricate = Cheaper
Each pixel has built in Amplifier
Each pixel can be read out individually
Pixels generate voltage instead of charge
Pixels can be read out during integration
Can group any number of regions together
 Higher background noise – but can be compensated
 Less efficient at converting light to signal.
Copyright © Multichannel Instruments AB 0602-1 / 28
Software
 Overview
 Mechelle SDK, LabVIEW, GRAMS, FindELMO.
 Camera Imaging software
 New software
 Functions
 Mechelle SDK
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Starting
Calibration
Taking standard spectra
Taking time-resolved spectra
Radiometric spectra
 GRAMS
 Importing spectra
 Importing multiple spectra
 Viewing options
 FindELMO
 How to install
 How to use
Copyright © Multichannel Instruments AB 0602-1 / 29
Accessories
 Collectors/Collimators
 Specially designed for full spectrum
 Integrating spheres.
 Spectrum intensity adjuster
 Selectable filter
 Normalises intensity of spectrum
 Prevents saturation
 Other accessories can be supplied
 Fibre multiplexer
 Microscope interfaces
Copyright © Multichannel Instruments AB 0602-1 / 30
Custom Models
 Sub ranges of the spectrum can be selected
 Gives higher resolution
 Final spectrum achieved depends on gratings used.
 OEM models welcomed. Mechanics and Optics set for
integration. Detector incorporated or can be separate.
 Custom designs include splitting UV and VIS regions into
two areas on the detector. Gives very high resolution.
 Miniature and vacuum enclosed designs.
Copyright © Multichannel Instruments AB 0602-1 / 31
Selling the Mechelle
Copyright © Multichannel Instruments AB 0602-1 / 32
The Mechelle concept
GRAMS
Mechelle
(from Galactic Industries, Corp.)
Mechelle Software
Copyright © Multichannel Instruments AB 0602-1 / 33
Applications
Copyright © Multichannel Instruments AB 0602-1 / 34
Time-resolved system set-up
PULSE
GENERATOR
(DG 535)
TRIG
TRIG
POWER
SUPPLY
XE-FLASH
Duration of Xe-flash
Trig
Delay
Gate
Gate and delay controlled
by the Mechelle Software
Copyright © Multichannel Instruments AB 0602-1 / 35
Time-resolved spectra of Xe - lamp
Log (Counts)
6
1000
1500
2000
2500
3000
3500
4000
4500
5000
3
200
320
440
560
680
800
920
1040
Wavelength (nm)
Copyright © Multichannel Instruments AB 0602-1 / 36
Mechelle application
LIBS - Laser Induced Breakdown Spectroscopy
GRAMS
Sample
Mechelle
PULSED LASER
Time-resolved spectra
containing signatures from
sample elements
Copyright © Multichannel Instruments AB 0602-1 / 37
Laser induced breakdown spectra of glass
Counts
12000
1600
1800
2000
2200
2400
2600
2800
0
200
320
440
560
680
800
920
1040
Wavelength (nm)
Copyright © Multichannel Instruments AB 0602-1 / 38
Mechelle 7500 / AP8 system
>18 000 spectral channels / recording
N2 and N2+
NO g band
N2
(Gaydons Green)
Herman IR bands?
Copyright © Multichannel Instruments AB 0602-1 / 39