Prepared by CI Systems Ltd. Feb 2008€¦ · 2.1. Basic Radiometry Concepts Table 1 Definitions and...

Prepared by CI Systems Ltd.

Feb 2008

The following products were added during 2007:

A full line of rugged and cost effective spectral imagers for field and airborne use

A Solar Blind UV (SBUV) imaging radiometer system

Spectral Target Projector

New Products

Proprietary Information Notice:

The information contained in this document is proprietary to CI Systems and may not be reproduced, used or disclosed to others without its prior written consent.

1. Introduction .........................................................................................................................................5

2. BackgroundandTheory ................................................................................................................6

2.1. Basic Radiometry Concepts .............................................................................................6

2.2. Noise ........................................................................................................................................10

3. SR-5000Spectraradiometer..................................................................................................... 12

3.1. Some applications of the SR-5000 ............................................................................12

3.2. Features ...................................................................................................................................13

3.3. Models .....................................................................................................................................14

Field of view ..........................................................................................................................14

Internal blackbody .............................................................................................................15

SR-5000 detectors .............................................................................................................16

Circular variable filters (CVF’s) .....................................................................................16

3.4. Basic Software description ............................................................................................17

Main features ........................................................................................................................17

3.5. Specifications (Basic SR-5000 and SR-5000WNV) .............................................18

3.6. Ordering information .......................................................................................................20

4. SingleandMulti-ChannelRadiometers ........................................................................... 23

4.1. TeleRad....................................................................................................................................23

4.2. MiniRad ...................................................................................................................................25

4.3. ColoRad ..................................................................................................................................27

4.4. MultiRad ..................................................................................................................................29

CATALOG CONTENTS

5. SpectralImagingSystems......................................................................................................... 31

Theory and design ..........................................................................................................................31

5.1. SD 300 Visible-NIR Spectral Imager .........................................................................32

Background on SD-300 ...................................................................................................32

Purpose of SD-300 ............................................................................................................32

Additional design issues .................................................................................................33

Performance .........................................................................................................................33

5.2. cI Systems ..............................................................................................................................35

SI-900 Specifications ........................................................................................................40

SI-2500 Specifications ......................................................................................................40

SI-5000 Specifications ......................................................................................................41

SI-12000 Specifications ...................................................................................................42

6. BDR(BackgroundDiscriminationRadiometer) .......................................................... 43

6.1. Introduction ..........................................................................................................................43

6.2. Specifications .......................................................................................................................43

6.3. Performance .........................................................................................................................43

7. SBUVImagingRadiometer ...................................................................................................... 44

Features ................................................................................................................................................44

Options .................................................................................................................................................45

Specification .......................................................................................................................................45

CATALOG CONTENTS

1Introduction

1. Introduction

CI Systems has been supplying instrumentation for the remote sensing market for over 25 years. Many of these systems were initially developed as customized systems according to customer requests.

CI Systems is a world known manufacturer of specialized E-O equipment and is known for its high quality of engineering and innovative designs.

This catalog presents CI Systems current line of products for the remote sensing market. Some of these products, such as the SR-5000, have been on the market for many years, and others are newcomers, such as the MCR-8 and the SI hyperspectral imager series.

CI Systems is committed to continue its development of innovative remote sensing products. Also, we will be happy to provide customized solutions for individual customers.

2. Background and TheoryThe following is a brief review of the theory and concepts involved in remote sensing measurements:

2.1. Basic Radiometry Concepts

Table 1 Definitions and Symbols

Quantity Symbol Definition Units

Energy Q Joules

Flux (Power) Φ

CI SYSTEMS CI Systems proprietary

- 6 -

2. Background and Theory The following is a brief review of the theory and concepts involved in remote sensing measurements:


Table Definitions and Symbols


Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A

Power reflected from or emitted by a body 2cmWatt

Intensity I

W

srWatt

Irradiance E

A

Power incident on a body 2cmWatt

Radiance L

AW

Power emitted by a body 2cmsrWatt

Where A is the area and W is the solid angle.

Watt

Radiant Exitance M


- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW




- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW



Intensity I


- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW




- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW



Irradiance E


- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW




- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW



Radiance L


- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW




- 6 -





Energy Q Joules

Flux (Power) Φ

dtdQ Watt

Radiant Exitance M

A


Intensity I

W

srWatt

Irradiance E

A


Radiance L

AW


Where A is the area and W is the solid angle. Where A is the area and W is the solid angle.

Solid Angle Definition:

22,

,

rA

rA

==Ω


- 7 -


22,

,

rA

rA

Lambertian Surface:

Defined as a surface for which:

cos0 II

Where I0 is the energy emitted (or reflected) by the source at perpendicular angle. For a Lambertian surface the integral over the hemisphere is π.

AA’r’

r

Unit of : steradians (sr)A = Arear = distance

Background and Theory

Lambertian Surface:



- 7 -


22,

,

rA

rA

Lambertian Surface:


cos0 II


AA’r’

r

Unit of : steradians (sr)A = Arear = distance


Conservation of Energy


- 8 -

Conservation of Energy

The total power remains constant and this holds true for each wavelength separately. For bodies of irregular shape, the reflected radiation must include the scattered one

Ideal cases:

• Perfect transmitter: τ = 1, α + ρ = 0

• Perfect reflector: ρ = 1, α + τ = 0

• Perfect absorber: α = 1, ρ + τ = 0

If the above equalities are true for a whole wavelength region, they are true for every wavelength λ separately, because τ, ρ and α can never be >1

Kirchoff’s Law

It can be shown that any object emits as much radiation as it is capable to absorb:

Absorptivity = emissivity, α(λ) = ε (λ)

A perfect radiator is called a “Blackbody”: α (λ) = ε (λ) =1

Emissivity is defined as the ratio of the object’s emitted radiation to that of a blackbody at the same temperature

It () = Ii

Ii() Ir () = Ii

Ia () = Ii ()

1)()()(

where:= reflectivity= absorptivity = transmissivity

tari IIII

The total power remains constant and this holds true for each wavelength separately. For bodies of irregular shape, the reflected radiation must include the scattered one

Ideal cases:

Perfect transmitter: τ = 1, α + ρ = 0

Perfect reflector: ρ = 1, α + τ = 0

Perfect absorber: α = 1, ρ + τ = 0

If the above equalities are true for a whole wavelength region, they are true for every wavelength λ separately, because τ, ρ and α can never be >1

Kirchoff’s Law

It can be shown that any object emits as much radiation as it is capable to absorb:Absorptivity = emissivity, α(λ) = ε (λ)A perfect radiator is called a “Blackbody”: α (λ) = ε (λ) =1

Emissivity is defined as the ratio of the object’s emitted radiation to that of a blackbody at the same temperature

Background and TheoryBackground and Theory

Planck Law

The fundamental relation between emitted radiation, temperature and wavelength. A useful form of this equation is:


- 9 -

Planck Law


)(104388.1

)/(107415.3

)()1(

),(

042

2441

25

12

KmCcmmWattC

mcmWatt

e

CTLT

C

In the above form of the Planck function λ is in micrometers and T is in degrees Kelvin.

In cases where the emitting surface is Lambertian, divide the Planck equation by π to get the spectral radiance in

units of mcmsr

Watt 2

The partial derivative of the Planck function, with respect to temperature is also useful in many cases:

251

22

12

2

TC

TC

e

eCT

CTL


In cases where the emitting surface is Lambertian, divide the Planck equation by π to get the spectral radiance in units of


- 9 -

Planck Law


)(104388.1

)/(107415.3

)()1(

),(

042

2441

25

12

KmCcmmWattC

mcmWatt

e

CTLT

C



units of mcmsr

Watt 2


251

22

12

2

TC

TC

e

eCT

CTL



- 9 -

Planck Law


)(104388.1

)/(107415.3

)()1(

),(

042

2441

25

12

KmCcmmWattC

mcmWatt

e

CTLT

C



units of mcmsr

Watt 2


251

22

12

2

TC

TC

e

eCT

CTL

Stefan-Boltzmann Law

The relation between the total emitted radiation and temperature as an integral on the entire wavelength range:


- 10 -

Some examples of Planck functions:

Stefan-Boltzmann Law

The relation between the total emitted radiation and temperature as an integral on the entire wavelength range:

)/(1067033.5

)/(),(

4212

2

0

4

KcmW

cmWTdTW


Some examples of Planck functions:


Wavelength (mm)

Blackbody curves, 100 to 1000 K.

Spec

tral R

adia

nt E

xita

nce

(W c

m-2

mm-1

)

Wien’s Law

The relation between the location of the maxima of the Planck function and the temperature:


- 11 -

Wien’s Law


KmTMax 2898

With λ in μm and temeprture in degrees Kelvin.

Signal collection

The ability of an optical system to collect signal is known as the “Etendue” or throughput.

The units of this property are str*cm2. This means that given a source with Radiance, in units of Watt/cm2/str, multiplying by the Etendue of the system will give the power (units of Watts) that will enter the system.

The Etendue can be expressed as:

2det

fAA Opticsector

And for systems with circular field of view (FOV) may be written as:

2

4FOVAOptics

Where:

Adetector is the detector area (cm2)AOptics is the collecting optics area (cm2)f is the focal length of the system FOV is the field of view of the system (Rad).


Signal collection





- 11 -

Wien’s Law


KmTMax 2898


Signal collection




2det

fAA Opticsector


2

4FOVAOptics

Where:




- 11 -

Wien’s Law


KmTMax 2898


Signal collection




2det

fAA Opticsector


2

4FOVAOptics

Where:


Where:

Adetector is the detector area (cm2) AOptics is the collecting optics area (cm2) f is the focal length of the system FOV is the field of view of the system (Rad).


10

2.2. Noise

There are a number of ways to measure noise. The NEP is a general method while for the IR spectral band NETD is preferred in many cases

The following is an expression for the noise equivalent power (NEP), at the entrance of an optical system:


- 12 -

2.2. Noise



*

.4

. D

BWdNEPinstr

Where:

d is the detector diameter BW is the bandwidth D* is the detector figure of merit is the transmittance of the instrument

The following is an expression for the noise equivalent temperature difference (NETD or NEΔT):

o

TTTTA

TLD

BWd

sTLD

BWdFTNE

mm ,

*22

,

*

2

4

)4

(

4#

In this equation:

NET is the Noise Equivalent temperature difference of the spectroradiometer, when measuring a blackbody at temperature Tm,F# is the f number of the spectroradiometer collection optics d is the detector diameter D* is the spectral detectivity of the detector in units of cmHz.Watt-1, normalized to detector area and electronic bandwidth: this is measured and given by the detector manufacturer is the wavelength at which the measurement is done is the wavelength full width half maximum bandpass of the spectroradiometer monochromator (in this case a CVF or Circular Variable Filter), at the measurement wavelength L is the blackbody spectral radiance at temperature Tm and wavelength L/T is the partial derivative of L with respect to temperature s is the diameter of the field stop defining the field of view of the spectroradiometer is the solid angle field of view of the spectroradiometer Ao is the area of the collection optics,

Where:

d is the detector diameter BW is the bandwidth D* is the detector figure of merit τ is the transmittance of the instrument



- 12 -

2.2. Noise



*

.4

. D

BWdNEPinstr

Where:

d is the detector diameter BW is the bandwidth D* is the detector figure of merit is the transmittance of the instrument


o

TTTTA

TLD

BWd

sTLD

BWdFTNE

mm ,

*22

,

*

2

4

)4

(

4#

In this equation:

NET is the Noise Equivalent temperature difference of the spectroradiometer, when measuring a blackbody at temperature Tm,F# is the f number of the spectroradiometer collection optics d is the detector diameter D* is the spectral detectivity of the detector in units of cmHz.Watt-1, normalized to detector area and electronic bandwidth: this is measured and given by the detector manufacturer is the wavelength at which the measurement is done is the wavelength full width half maximum bandpass of the spectroradiometer monochromator (in this case a CVF or Circular Variable Filter), at the measurement wavelength L is the blackbody spectral radiance at temperature Tm and wavelength L/T is the partial derivative of L with respect to temperature s is the diameter of the field stop defining the field of view of the spectroradiometer is the solid angle field of view of the spectroradiometer Ao is the area of the collection optics,

In this equation:

NE∆T is the Noise Equivalent temperature difference of the spectroradiometer, when measuring a blackbody at temperature Tm, F# is the f number of the spectroradiometer collection optics d is the detector diameter D*λ is the spectral detectivity of the detector in units of cm√Hz.Watt-1, normalized to detector area and electronic bandwidth: this is measured and given by the detector manufacturer λ is the wavelength at which the measurement is done ∆λ is the wavelength full width half maximum bandpass of the spectroradiometer monochromator (in this case a CVF or Circular Variable Filter), at the measurement wavelength L is the blackbody spectral radiance at temperature Tm and wavelength λ, ∂L/∂T is the partial derivative of L with respect to temperature s is the diameter of the field stop defining the field of view of the spectroradiometer Ω is the solid angle field of view of the spectroradiometer Ao is the area of the collection optics, τλ is the monochromator t

ransmittance at wavelength λ BW is the electronic bandwidth of the measurement.


11

The factors √(π/4) in the numerator and (π/4)2 in the denominator of equation (1) result from assuming circular optics, circular detector and circular field of view (FOV).

Further assumptions in the NE∆T equation are:

1. The electronics noise contribution is negligible,

2. Equation (1) here is more general than Equation 1.42 of reference 3, because here the field stop area π/4s2 is not necessarily equal to the detector area π/4d2, but the detector is large enough to receive all radiation entering the field of view of the instrument through the field stop.

3. The NE∆T measurement will be done with an electronic bandwidth BW of 1 Hz.

In practice, NE∆T is measured by recording the two signals S1 and S2 corresponding to two different blackbody temperatures in the vicinity of the temperature range of most measurements (filling the field of view of the instrument), recording the peak to peak noise npp, and calculating:


- 13 -

is the monochromator transmittance at wavelength BW is the electronic bandwidth of the measurement.

The factors (/4) in the numerator and (/4)2 in the denominator of equation (1) result from assuming circular optics, circular detector and circular field of view (FOV).

Further assumptions in the NET equation are: 1. The electronics noise contribution is negligible,

2. Equation (1) here is more general than Equation 1.42 of reference 3, because here the field stop area /4s2 is not necessarily equal to the detector area /4d2, but the detector is large enough to receive all radiation entering the field of view of the instrument through the field stop.

3. The NET measurement will be done with an electronic bandwidth BW of 1 Hz.

In practice, NET is measured by recording the two signals S1 and S2 corresponding to two different blackbody temperatures in the vicinity of the temperature range of most measurements (filling the field of view of the instrument), recording the peak to peak noise npp, and calculating:

TSS

nTNE pp

measured

122

1

T in the above equation is the difference between the two measured temperatures (in units of degrees C). The factor 1/2 is needed to properly take into account the fact that npp is random noise, while NET is defined in this field as root mean square noise.

∆T in the above equation is the difference between the two measured temperatures (in units of degrees C). The factor 1/2π is needed to properly take into account the fact that npp is random noise, while NE∆T is defined in this field as root mean square noise.


1

33. SR-5000 Spectraradiometer

3.1. Some applications of the SR-5000

The SR-5000 Computerized Spectraradiometer can be used for both spectral (intensity versus wavelength over time) or radiometric (intensity versus time) measurements.

Some specific applications of the SR-5000 include:

Radiometric temperature measurement and monitoring

Radiometric calibration of blackbody sources and electro-optical test systems

Countermeasures analysis

Decoy systems development and testing

Atmospheric transmissometry studies

Generalized transmittance and reflectance measurements

Camouflage materials development and testing

SR-5000Spectraradiometer

1

Signatures of military objects

Signatures of jet plumes and afterburners

Spectral emittance of sky, ground, horizon, sea and clouds

Remote sensing of objects

Emissivity measurements

Process control and development

3.2. Features

The SR-5000 has many outstanding features, which are described in this catalog. Some of the key features of the system are:

Extremely high sensitivity to detect faint signals

Extremely high stability and repeatability for accurate measurements

Uniform and symmetric field of view performance for distant targets which do not fill the FOV

All mirror optics (UV to Far-IR) for maximal optical performance

Advanced state-of-the-art software

High versatility in measurement setup for a wide range of measurement types

Display of spectra in radiance units

Real-time data analysis and display

Automatic calibration and reference to an internal floating blackbody source for maximum accuracy

Modular, rugged and field tested design

Customized options as required by specific users

3SR-5000Spectraradiometer

1

3.3. Models

The SR5000 models differ in the f/# of the optics and in the filed of view (FOV) sizes. The basic model is called an SR5000 and consists of a 500mm f/4 on-axis Newtonian telescope with a primary spherical mirror of 5”. The largest FOV available with the primary telescope unit (optical options for increasing the FOV are available) is 6 milirad.

Another new model called the SR5000WNV uses a 250 mm focal length telescope with a primary parabolic mirror. The WNV model is intended specifically for measurements requiring high sensitivity and small FOV’s (less than 2 milirad). The maximal FOV of the SR5000WNV model is 10 milirad.

Field of view

The SR-5000, with its wide range of available fields of view (FOV), is suitable for both small and large objects to cover most applications of radiometry. The system can be configured for narrow fields of view between 0.3 and 6 milliradians. A medium field of view (of up to 5.7 degrees) or a wide field of view (of 14 degrees) can be ordered, as an option.

In addition, the SR-5000’s FOV is exceptionally uniform and symmetric. This very smooth uniformity and symmetry allow for repeatable results when very small, non-uniform or moving targets are measured.

The flatness or uniformity of response is defined by the ratio:

1

21

2SSSf −

=

Where S1 and S2 are defined in Figure 1.

The symmetry of the field of view in the horizontal and vertical directions is defined as:

Avg

VerHor

FOVFOVFOV

S×

−=

2

Where FOVHOR and FOVVER are the horizontal and vertical fields of view measured at 10% of the maximum signal. FOVAvg is the average value of FOVHOR and FOVVER (see Figure 1).

The parameters f and S are specified to be better than ±10% and ±5% (respectively) for the SR-5000 (typically, the values are much better than these values).


1

Figure 1 FOV flatness and symmetry

Internal blackbody

The internal blackbody is at ambient temperature, and it provides a known radiation spectrum, which is used as a reference by the SR-5000. Its temperature is monitored continuously by the computer and is used to adjust the data in case of changes in the ambient temperature drifts after calibration.

An ambient temperature blackbody has distinct advantages over a temperature-controlled blackbody since very small temperature gradients, which occur inside the optical head, do not affect a room temperature source as much as it would affect a temperature controlled source. When errors due to the emissivity of the chopper and internal blackbody are accounted for, a controlled source can cause sensitivity inaccuracies of up to 5% compared to an ambient source with inaccuracies of less than 0.5%.

Figure 4 horizontal scannig of fov

Rela

tive

resp

onse


1

SR-5000 detectors

CI offers a wide range of detector packages that are suitable for the SR-5000. These packages are complete units that are interchangeable in the field. Complete wavelength regions can be changed in less than five minutes, without realignment.

All liquid nitrogen cooled detectors are supplied with 77K dewars. (Joule - Thompson and Stirling coolers are also available.) The preamplifier is attached directly to the dewar, thereby eliminating an important source of electronic and vibration noise. These dewars have a holding time of above 8 hours, which allows a day’s worth of measurements without refilling. They are also rugged and re-pumpable. A one-way, blow-off valve prevents seepage of moisture to the inner vessel. An example of a detector subassembly is pictured in Figure 2.

Figure 2 LN2 cooled detector subassembly

Circular variable filters (CVF’s)

A Circular Variable Filter (CVF) is a monochromator, which allows monochromatic light with a specific wavelength bandpass to pass through to the detector. This is a medium resolution component, typically 2% of wavelength at Full Width Half Max (FWHM).

In the SR-5000, the CVF module is an optically encoded, motorized subassembly, which, combined with supplied calibration data, constantly monitors the central waveband the CVF allows to pass through.

A number of CVFs and filter wheel subassemblies are available which, when matched to the correct detector, give spectral data covering the entire CVF wavelength range.

Table 2 includes the currently supplied CVF configurations. In addition to CVF’s, a discrete six or twelve position filter wheel may also be purchased.


1

Table 2 CI CVF’s

CVF NUMBER Spectral Range (mm) Spectral Resolution (%) Recommended Detector

CVF 4N 1.2 - 6.5 <2 InSb

CVF 6N 2.3 - 14.2 <2 InSb/MCT Sandwich

CVF 7N 0.4 - 2.5 <5 Si/InGaAs Sandwich

3.4. Basic Software description

Main features

Runs under Microsoft Windows XP thus supporting currently sold PC’s, including laptops

User-friendly “wizard style” user interface (UI) with online tips, explanations and help

User-programmable capabilities (macro style operation) in analyzing results

Fully integrated advanced data-base with filters, archiving, backup and export capabilities

A “smart-setup” system for aiding the user in selecting the right parameters for the experiment, thus preventing erroneous setups.

Integration of a CCD, boresighted with LOS, to allow the user to capture snapshots of the object during measurement (synchronously with spectral scans or with radiometric measurement)

Integration of a cross-hairs layer on-top of the CCD image

Import of external files to be used with system acquired data (such as files created by Excel or Modtran).

User-friendly analysis interface.

Advanced measurement and results display

Support for 10 scans/sec as the default and capable of supporting 30 scans/sec

Backwards compatible with older format files (DAS/DAR formats)


1

3.5. Specifications (Basic SR-5000 and SR-5000WNV)

Table 3 Optical specifications

Parameter SR-5000 SR-5000WNV

Optics5” diameter entrance aperture, all reflective Newtonian telescope, F# = 4

5” diameter entrance aperture, all reflective Newtonian telescope, F# = 2

Standard FOV 6 milirad ± 10% 10 milirad ± 10%

Motorized FOV (option) 0.3 to 6 milirad ± 10% (in 8 steps) 0.6 to 10 milirad ± 10% (in 8 steps)

Wide FOV (option) 5.7° ± 15% (Variable if motorized option is included) Not available

UV-Wide FOV (option) 4.8° ± 15% (Variable if motorized option is included) Not available

Very Wide FOV (option) Up to 14 degrees Not available

Focusing Range: 2.5 meters to infinity for std. FOV (measured from front panel)

1.25 meters to infinity for std. FOV (measured from front panel)

Table 4 Other specifications

Parameter Value Remarks

Spectral Range with CVF’s 0.24-14.2 mm with various CVF’s or filter wheels

Radiometric spectral range 0.4-30 mm UV enhancement option extends spectral region down to 0.2 mm

Spectral Scan Rates 0.015 to 10 scans/sec Optionally up to 30 scans/sec

Aiming and Focusing On-line, non-parallax Reflex sight with Focus Lock

Optional CCD and riflescope alignment aids available. WNV model offers motorized focus

Uniformity of FOV ±10% in both horizontal and vertical directions across 70% of the standard FOV

±15% for wide FOV option and

Symmetry of FOV ±5% when measured at 10% of the maximum response in the horizontal and vertical directions

For standard optics

Internal Blackbody accuracyAmbient with minimum drift and gradient. Continuous monitoring and display of temperature with better than 0.1°C


1


Chopping Frequency 100 to 1800 Hz by as small as 50 Hz steps. External chopper input or stop open/closed.

Power110 VAC, 60 Hz or 220 VAC, 50 Hz.

Less than 100 Watt

Electronic Bandwidth in spectral mode

Automatically selected by the computer to match data rate in spectral mode. (function of CVF scan rate and resolution).

Electronic Bandwidth in Radiometric mode

50 Hz to 900 Hz sampling rate using synchronous detection measurement 1500 Hz - 60 000 Hz sampling rate for non - synchronous detection (transient measurement).

Dynamic Range 1:500,000 and larger depending on detector dynamic range can be increased by using

variable FOV’s or attenuators

A/D

Spectral Measurement: 14 bitRadiometric Measurement 1 Hz - 300 Hz Bandwidth: 14 bit 500 Hz - 20 KHz Bandwidth: 8 bit

Noise Performance

Spectral Measurement: 14 bitRadiometric Measurement 1 Hz - 300 Hz Bandwidth: 14 bit 500 Hz - 20 KHz Bandwidth: 8 bit

Noise Performance

Dependent upon detector; for InSb without filter, typically 5.4 microwatt on the detector or an equivalent radiance of a 1000°C blackbody with 0.095” aperture diameter (2.4 mm) at 3 m distance

See detectors list for noise performance

Size 18.5 x 35.5 x 69 cm

Weight 25 Kg Standard Tripod Mount: 3/8”


0

3.6. Ordering informationTable 5 SR5000 Basic system options

P/N Description Remarks

A430-100-2000 SR5000 optical head final assembly including reports, packing, cables, software and manuals A PC option (desktop or laptop) must be added.

A430-480-0090 220 VAC option Standard is 110 VAC

A430-480-2070 Desktop computer kit Brand-name, Windows XP Pro

A430-480-2050 Laptop computer kit Brand-name, Windows XP Pro

Table 6 SR5000 optical options


A430-480-0261 FOV scan option

A430-480-2010 Sideview integrated CCD option To be ordered in systems that include only the basic optics (up to 6 mrad)

A430-480-2020 Boresight CCD option (B&W) To be ordered in systems that include FOV options

A430-480-1990 Boresight CCD option (color) To be ordered in systems that include FOV options

A430-480-0120 A430-480-0380 A430-480-0310

100 mrad (5.7 degree) FOV option 100 mrad (5.7 degree) FOV option 88 mrad (4.8 degree) FOV option

To be ordered if FOV scan option is selected To be ordered if UV coating option is selected

A430-480-0370 14 degree FOV option

A430-480-0130 Window option For use in cases where the optical system is N2 purged (high humidity)

A430-480-0300 UV window Is the widow to be used if UV coating was selected

A430-480-0080 Boresight riflescope option

A430-480-2140 A430-480-2150 A430-480-0140

Attenuator set (OD1, OD2 and OD3) Attenuator set (OD1, OD2 and OD3) Attenuator set (OD1, OD2 and OD3)

For spectral range 0.2÷2.5μm (fits CVF7N) For spectral range 1.0÷14.5μm (fits CVF6N) Includes both of the above sets

A430-480-0180 UV coating option Extends the optics reflectivity down to 0.2μm

A430-480-0300 UV window This is the widow to be used if UV coating was selected


1

Table 7 SR5000 CVF options


A430-413-1180 CVF4N (1.2÷6.0 μm)

A430-413-1170 CVF7N (0.4÷2.5 μm)

A430-413-1160 CVF6N (2.3÷14.2 μm)

A430-480-0160 12 position filter wheel Holds ½” filters

A430-480-0170 6 position filter wheel Holds 1” filters

A430-480-2130 11 filter set covering 300 to 400 nm with 10 nm FWHM filters every 10 nm

Table 8 SR5000 detector options

P/N Detector Material

Cooling Method

Spectral Range (μm)

NETD [mdeg C0] Conditions of measurement

A430-473-0150 Si None 0.2÷1.1 Max: 1.0 Measured with a CVF at λMAX 1Hz electronic-bandwidth, 900°C Blackbody cavity and filled 6mrad FOV.

A430-473-0190 Pbs TEC 0.7÷3.0 Max: 5.0 Measured with a CVF at λMAX 1Hz electronic bandwidth, 500°C Blackbody and filled 6mrad FOV

A430-473-0160 PbSe TEC 1.0÷4.7 Max: 40 Measured with a CVF at λMAX 1Hz electronic bandwidth, 500°C Blackbody and filled 6 mrad FOV.

A430-473-0110 InSbLN2

Stirling1.2÷5.5 Typical: 2.5,

Max: 5.0

Measured with CVF at λMAX 1Hz electronic bandwidth, 100°C Blackbody and filled 6mrad FOV.

A430-473-0120 MCTLN2

Stirling5.0÷14.5 Typical: 0.3,

Max: 2.0Measured without a CVF, 1Hz electronic bandwidth, 100°C Blackbody and filled 6mrad FOV


P/N Detector Material

Cooling Method

Spectral Range (μm)

NETD [mdeg C0] Conditions of measurement

A430-473-0180 Pyro None * Maximum: 10

Measured without a CVF, 1Hz electronic bandwidth, 900°C Blackbody and filled 6mrad FOV

A430-413-0820 Si/InGaAs

None/TEC 0.4÷2.5 Max: 2/5

A430-413-0140 Si/PbS None/TEC 0.4÷5.0 Max: 2/10

A430-413-0170 Si/PbSe None/TEC 0.4÷4.7 Max: 2/80

A430-473-0130 InSb/MCT

LN2

Stirling

JT

1.2÷14.2Max: 5/2

* Pyro detectors come in different spectral ranges (the spectral range is a function of the window material). Available windows include Ge, Si, KRS-5, CaF2, Quartz, and Sapphire.Table 9 Other SR5000 options


A430-480-2110 15 meter cable extension option

A430-480-0271 Chopper to increase spectral scan rate to 30 Hz Includes SR60 chopper controller and optical chopper

385-0100 150 lb rated tripod for SR5000

A430-480-2060 Training at CI Systems facilities 3-day training

A430-480-2080 Training at customer site 3-day trainingSR800 7A extended area blackbody calibration source

Advised for SR5000 calibration in applications of IR optical systems calibrations

SR20 cavity blackbody (1000 or 1200 degrees)

Advised for SR5000 calibration in applications of IR field measurements of flares, plumes and other hot sources

Integration sphere 4” with 1” port and single color temperature calibration

Advised for SR5000 calibration in applications of VIS-SWIR (when using CVF7N) measurements

A430-486-2030 IRIG-B timing device

A430-486-2010 PCModWin software Atmospheric calculation software


4. Single and Multi-Channel RadiometersThis line offers radiometers for a wide variety of applications. These radiometers are developed by CI Systems in cooperation with the Institute of Advanced Research and Design (IARD).

Four platforms are offered in this line named TeleRad, MiniRad, ColoRad and MultiRad.

The basic concept for these systems is that the user has the flexibility to select a platform and for each platform define the engines combination (an engine is an assembly including detector, pre-amplifier and optics) he/she would like to use.

All of these radiometers share many components (including detectors, electronics and software) and are designed for field use. CI Systems would be most willing to assist users in selecting the radiometer of choice for specific requirements.

4.1. TeleRad

The TeleRad is a large aperture radiometer optimal for applications demanding narrow FOV (4-8 mrad available) and high sensitivity. It supports 1-2 spectral channels (using the same telescope)

Single andMulti-Channel Radiometers

Table 10 Telerad specifications


Channels 1-2 channels

Optics aperture 6” (150mm CA)

FOV 4 – 8 mrad 0.23°, 0.46°

Spectral Range 0.4-12µm Wide choice of spectral ranges

Detectors Si, PbSe, InGaAs, InSb, MCT See Table 11

Filters 1 Spectral band and 1 ND filter per channel User changeable per channel

Operational Mode Fast transient mode (DIR) Lock In Amplifier mode (LIA)

<20µs rise time For high sensitivity applications

Chopper 100-600Hz Variable, SW controllable

Lock In amplifiers 1 per channel Included in optical head

Data Acquisition Up to 16 bit 200Ks/s per channel Included in optical head UB2.0 interface to PC

FOV Viewer Video overlaid with sight pattern FOV limits and cross sight

Table 11 Telerad engine options

Spectral Range Detector Material Cooling FOV

mrad /°NEI DIR [W/cm²]

NEI LIA [W/cm²] P/N

0.4 - 1.0µm Si None 4 / 0.23° 8 / 0.46° 1∙10-8 1∙10-10 SIN-N150

SIN-W150

Photopic Si None 80 / 4.6° 5 ∙10-8 5∙10-11 SIN-W150Phot

1.0- 2.4µm InGaAs TEC 4 / 0.23° 8 / 0.46° 1∙10-10 2∙10-12 IGT-N150

IGT-W150

2.0 – 5.0 µm PbSe TEC 4 / 0.23° 8 / 0.46° 5∙10-8 5∙10-10 PBT-N150

PBT-W150

1.0- 5.0µm InSb LNC 4 / 0.23° 8 / 0.46° 5∙10-11 2∙10-12 INL-N150

INL-W150

1.0 – 5.0µm PV-MCT TEC 40 / 2.3° 5∙10-10 1∙10-11 MCT-N150

8.0 – 12.0µm MCT LNC 4 / 0.23° 8 / 0.46° 2∙10-11 5∙10-14 MCL-N150

MCL-W150Cooling: TEC=TE Cooled, LNC=Liquid N2 Cooled


NEI DIR – NEI for fast transient mode BW=50KHz, NEI LIA – for lock in mode TC=30msec; Both NEI values are typical. Actual performance depends on the spectral band pass of the channel.

4.2. MiniRad

The MiniRad is a simple and compact single channel radiometer. It operates in AC and DC modes (with or without chopper and LIA) .

Figure 3 Minirad attached to an IRTS unit

The MiniRad shown above is connected to a CI Systems threat simulator and provides a comprehensive solution for measuring the jam beam produced by the DIRCM of an airborne system after the threat simulator “shoots” a missile profile at the airborne platform.


Table 12 Minirad specifications


Channels 1 channel

Optics aperture 1”(23mm CA) or 2” (48mm CA)

FOV 40 or 80 mrad

Spectral Range 0.4-12µm Wide choice of spectral ranges

Detectors Si, PbSe, InGaAs, InSb, MCT, Pyroelelctric See Table 14

Filters 1 Spectral band and 1 ND filter per channel User changeable per channel

Operational Modes Fast transient mode (DIR) Lock In Amplifier mode (LIA) <20µs rise time

Chopper 100-600Hz Variable, SW controllable

Lock In amplifiers 1 channel Included in optical head

Data Acquisition Up to 16 bit 200Ks/s Included in optical head USB2.0 interface to PC

FOV Viewer Video overlaid with sight pattern FOV limits and cross sight


4.3. ColoRadThe ColoRad is designed to measure radiant intensity in 2-4 spectral bands simultaneously. Offering a wide selection of detectors (spectral bands) including Liquid Nitrogen (LN2) cooled detectors; The ColoRad with its lightweight and compact design is an ideal tool for field measurements of countermeasures, signatures and fast transient events.

Figure 4 Colorad system

Table 13 ColoRad specifications:

Parameter Value RemarksSpectral Channels 2 - 4 channelsOptics aperture 1” (23mm CA) or 2” (48mm CA)FOV 40 or 80 mrad Additional X2 FOV expanders availableSpectral Range 0.4-12µm Wide choice of spectral rangesFilters 1 Spectral band and 1 ND filter per channel User changeable per channel



Chopper 100-600Hz Variable, SW controllableLock In amplifiers 1 per channel Included in optical head

Data Acquisition Up to 16 bit 200Ks/s per channel Included in optical head USB2.0 interface to PC

FOV Viewer Video overlaid with sight pattern FOV limits and cross sightDimensions 255 (H) x 255 (W) x 600 (L) Weight <25Kg


Table 14 ColoRad/MiniRad engine options

Spectral Range Detector Material Cooling FOV

mrad /°Optics CA [mm]

NEI DIR [W/cm²]

NEI LIA [W/cm²] P/N

0.4 - 1.0µm Si None40 / 2.3° 80 / 4.6°

23 48 23 48

5∙10-7 2∙10-7 5∙10-7 2∙10-7

5∙10-9 2∙10-9 5∙10-9 2∙10-9

SIN-N25 SIN-N50 SIN-W25 SIN-W50

Photopic Si None 80 / 4.6° 23 5 ∙10-8 1∙10-9 SIN-W25Phot

1.0- 2.4µm InGaAs TEC40 / 2.3° 80 / 4.6°

23 48 23 48

3∙10-9 1∙10-9 3∙10-9 1∙10-9

5∙10-11 1∙10-11 5∙10-11 1∙10-11

IGT-N25 IGT-N50 IGT-W25 IGT-W50

2.0 – 5.0 µm PbSe TEC 40 / 2.3° 80 / 4.6°

23 23 1∙10-6 1∙10-8 PBT-N25

PBT-W25

1.0- 5.0µm InSb LNC40 / 2.3° 80 / 4.6°

23 48 23 48

3∙10-9 1∙10-9 3∙10-9 1∙10-9

5∙10-11 1∙10-11 5∙10-11 1∙10-11

INL-N25 INL-N50 INL-W25 INL-W50

1.0 – 5.0µm MCT TEC 40 / 2.3° 23 1∙10-8 2∙10-10 MCT-N25

8.0 – 12.0µm MCT LNC40 / 2.3° 80 / 4.6°

23 48 23 48

1∙10-9 5∙10-10 1∙10-9 5∙10-10

2∙10-11 1∙10-11 2∙10-11 1∙10-11

MCL-N25 MCL-N50 MCL-W25 MCL-W50

8 – 12.0µm Pyroelectric None40 / 2.3° 80 / 4.6°

23 48 23 48

Not Available

<5∙10-6 <1∙10-6 <5∙10-6 <1∙10-6

PYN-N25 PYN-N50 PYN-W25 PYN-W50

Cooling: TEC=TE Cooled, LNC=Liquid N2 Cooled



4.4. MultiRad

The MultiRad measures radiant intensity in 5-8 spectral channels. It was designed and built to measure fast transients that have a medium (and high) radiant intensity in the UV-VIS-IR spectral regions. In this way, it satisfies the requirements of flare developers to allow them to compare their signatures to those of the platforms the flares were designed to protect.

The MultiRad is a fully integrated system that contains the optics, chopper detectors and electronics all built into a compact unit.

The radiometric output of the MCR is logged into the system computer. User-friendly analysis software processes the data of the measured signals.

Each optical channel is composed of optics, detector and electronics. The optics, detector and its corresponding electronics are customized according to the customer’s needs. The optics and detectors options are described in Table 16.

Table 15 MultiRad specifications

Spectral Channels 5 - 8 channelsOptics aperture 1” (23mm CA)FOV 40 or 80 mradSpectral Range 0.4-12µm Wide choice of spectral ranges

Detectors Si, PbSe, InGaAs, MCT, Pyroelelctric See Table 16

Filters 1 Spectral band 1 ND filter per channel

User defined per channel, factory set (not user-replacable)



Chopper 100-600Hz Variable, SW controllableLock In amplifiers 1 per channel Included in optical head

Data Acquisition Up to 16 bit 200Ks/s per channel Included in optical head USB2.0 interface to PC

FOV Viewer Video overlaid with sight pattern FOV limits and cross sightDimensions 255 (H) x 255 (W) x 650 (L)Weight <25Kg


0

Table 16 MultiRad engine options

Spectral Range Detector Material Cooling FOV mrad /°

Optics CA [mm]

NEI DIR [W/cm²]

NEI LIA [W/cm²] Code

0.4 - 1.0µm Si None 40 / 2.3° 80 / 4.6° 23 5∙10-7 5∙10-9 SIN-N25

SIN-W25

Photopic Si None 80 / 4.6° 23 5 ∙10-8 1∙10-9 SIN-W25Phot

1.0- 2.4µm InGaAs TEC 40 / 2.3° 80 / 4.6° 23 3∙10-9 5∙10-11 IGT-N25

IGT-W25

2.0 – 5.0 µm PbSe TEC 40 / 2.3° 80 / 4.6° 23 1∙10-6 1∙10-8 PBT-N25

PBT-W25

1.0 – 5.0µm PV-MCT TEC 40 / 2.3° 23 1∙10-8 2∙10-10 MCT-N25

8 – 12.0µm Pyroelectric None 40 / 2.3° 80 / 4.6° 23 Not Available <5∙10-6 PYN-N25

PYN-W25Cooling: TEC=TE Cooled



1

5. Spectral Imaging SystemsCI Systems was one of the pioneers in the field of hyperspectral imagers based on the Sagnac interferometer. The first commercial hyperspectral imagers based on this unique technology were presented to the market in the early 90’s (the SD200 and SD300 models), with a current install base of hundreds of units, and CI Systems has been pursuing the technology ever since.

Theory and designThe new SI line of instruments is based on two technologies. The systems for the VIS and SWIR spectral band are based on grating technology while the MWIR and LWIR systems are based on a Sagnac interferometer technology.

Grating technology is a mature technology for the VIS and SWIR spectral bands with superb spectral resolution and imaging performance. The major problem with grating technology is that for implementation in the thermal IR spectral bands the entire spectrograph needs to be cooled down to very low temperatures for eliminating parasitic radiation. FTIR technology does not suffer from the parasitic radiation and therefore results in a much smaller and cost effective system while maintaining high performance.

Sagnac interferometers belong to a class of interferometers known as “common-path interferometers”. This means that the transmitted and reflected beams in the interferometer use the same optical elements. As a result, this class of interferometers is inherently stable and less given to drifts.

For measuring spectra with an interferometer, one needs to create an interferogram. An interferogram is a recording of the intensity as a function of optical path difference (OPD) within the interferometer.

Figure 5 Interferogram (double sided)

Spectral Imaging Systems

The SD 300 model performs a two-sided interferogram, meaning that it scans from –OPDmax to +OPDmax. The other SI5000 (MWIR) and SI12000 (LWIR) models, of the SI line, perform one-sided interferograms

Following the measurement of the interferogram, Fast Fourier Transform (FFT) is applied to transform the interferogram to spectrum (intensity as a function of wavelength).

In a hyperspectral imager, one needs to measure the spectral content of each pixel. In a Sagnac based system, this means that first we have to produce a complete interferogram for each pixel. In the SD-300, this is achieved by rotating the interferometer at an angle θ. The OPD is C* θ, where C is a constant of the interferometer arising from the angle of the beam-splitter relative to the incoming radiation. In the other SI line systems the interferogram is created by scanning the scene with the optical head (in what is known as push-broom imaging).

With grating based systems a 2D image is produced at the output of the spectrograph where each row consists of the spectral contents of a single image pixel. The spectrograph used is an X1 magnification system and it disperses the spectral information into 6 mm on the FPA plane.

Figure 6 Interferometer design of SD-300

5.1. SD 300 Visible-NIR Spectral ImagerBackground on SD-300

The SD-300 is a third generation in the CI hyper-spectral imager line. It was preceded by the SD-100 (launched 1993) and SD-200 (launched 1995). The SD-300 was released in 1999 and hundreds of units have been sold since, mainly to the medical market where these units are attached to research fluorescent microscopes for performing a unique diagnosis known as spectral-karyotyping. The SD-300 is a laboratory spectral imager especially designed as a microscope add-on attachment but it also lends itself to remote sensing work.

Purpose of SD-300

The SD-300 is designed for measuring moderate and low light level spectral images in the VIS-NIR range of stable scenes. Small foot-print and weight, low maintenance requirements and high stability are its main features.


Figure 7 SD-300 optical head

The SD-300 has the following design issues implemented:

Software-controlled rotation of the disk, on which the interferometer is assembled, allows for “direct imaging”. This means that the user has the ability to view the scene not obstructed by the interferometer and acquire a high spatial resolution grayscale image of the scene. If needed, the software may acquire the grayscale image immediately prior to the spectral image scan.

The beam-splitter angle can be changed easily in the field in a simple process.

The SD-300 includes a filter holder allowing for the quick insertion of a user-selected filters into the optical path for instances where a part of the spectrum is to be cut off or enhanced.

Semi-automatic spectral calibration is performed in a quick and easy manner by inserting a specially designed filter into the optical path and measuring it.

The SD-300 is an f#4 system and interfaces the fore-optics through a “C-mount”. It also includes a “C to F-mount” converter for an even wider lens selection.

Additional design issues

The SD-300 has low-power consumption so that it is powered directly by the PC without the need of an additional power supply.

Performance

Major performance issues of the SD-300 are reviewed below.

5.1.1.1. Spectral resolutionThe spectral resolution of the SD-300 is user-selectable through both hardware and software.

By changing the angle of the beam-splitter, relative to the incoming rays, fringe density can be increased or decreased.

Increasing fringe density means that a higher optical path difference (OPD) is generated per an angle rotation of the interferometer which leads to a greater total OPD thus increasing the resolution (resolution = 1/OPDmax). The limit to the fringe density is that there must be enough (2 at least) sampling points per cycle for Fourier transform (Nyquist condition).

In the software, the user selects the total scan angle to be performed in the measurement thus defining the total OPD i.e. the resolution.

The type of signal that the instrument measures also influences the spectral resolution. The interferometer measures all wavelengths at once. This is an advantage when sensitivity is considered, but it has the drawback that the shot noise of the system also contributes to the entire signal. The practical outcome is that, for a set OPD scan, monochromatic or quasi-monochromatic type spectra are measured in highest resolution while broad or absorption line type spectra feature reduced spectral resolution.


Figure ‎5‑8 Maximal Spectral Resolution of SD‑300 for a monochrome signal:

5.1.1.2. Spatial resolutionThe detector array is a high-quality, low noise, front illuminated, 1280x1024 pixels, 6.7 μm pitch, 2/3” format, 12 bit digital CCD. 2x2 hardware binning is available, through software control, for improving the signal to noise ratio (SNR) and lowering the file size at the cost of reducing spatial resolution.

5.1.1.3. Spectral responseThe dominant contributors to the systems’ response are the detector QE, beam-splitter performance and optical throughput:

Figure 9 Detector typical Quantum Efficiency (QE)

The beam-splitter response is relatively flat across most of the 400-1000 nm range, as is the lenses throughput. Therefore, the total spectral response behaves similar to the detector QE.

It is possible to measure the lower response parts of the spectrum by using a cut-on or cut-off filter to enhance the part of the spectrum one needs to measure.


5.1.1.4. Acquisition timeThe acquisition time is a function of the resolution and of the SNR one needs. Typically, a few seconds will be required for a complete acquisition. The scene is required to stay stable during this period. If it is not, the interferogram will be distorted and will produce an inaccurate spectrum.

5.1.1.5 Radiometric calibrationThe SD-300 measures in arbitrary units. There are two valid ways of performing radiometric calibration to the data. The best method is to have a known source included in some part of the acquired image. With this method, the user is sure to eliminate all effects on the measured spectrum by dividing all image pixels by a user-selected pixel (the one that contains the known reference). In this way, the user knows the measurement is calibrated.

The second method is to measure a known source, using the same measurement setup, and then calibrating.

Both of these methods are supported by the SD-300 software.

5.1.1.6. NoiseAs previously stated, the system is dominated by shot noise. It should be noted that in an interferometer system, the same noise is distributed across the entire spectral range. As a result, the SNR distribution is approximately the inverse of the spectral intensity. In other words, the noise is constant at all wavelengths and so the SNR is high where the signal is high and low where the signal is low.

As the detector allows for long exposure times while maintaining low dark noise (approximately 100 counts), we can assume that for most conditions, high detector well-fill is achieved by the measured signal.

5.1.1.7. Operation softwareIntuitive control software is used to operate the SD-300. This software makes it easy for the user to set up the measurement by including an intelligent parameter set-up algorithm.

5.1.1.8. Additional softwareThe SD-300 includes, apart from the operation package, two additional software packages:

A database for storing measurements with tools for data filtering, backup and archiving, report generating, security system and more. This database can work in a client-server configuration as well.

Analysis package with advanced tools for creating spectral libraries, classification, linear components analysis, statistical analysis and many more.


5.2 CI SystemsCI Systems new line of spectral imagers is an evolution of the SD300 model and is specially designed for compactness, simplicity and rugged operation in the field as ground and airborne hyperspectral sensors.

The spectral imaging systems described here lend themselves to perform aerial spectral imaging using the pushbroom method (with the addition of stabilized mount, GPS/IMU unit and software).

Airborne implementation of grating technology is a widely excepted technology and will not be discussed in length here. The spectrographs which are the basis to the SI900 (VIS) and SI2500 (SWIR) models are high performance imaging spectrographs with exceptionally high and flat efficiency throughout the spectral band, high spectral resolution and low stray light. The Keystone and smile aberrations are reduced to sub-pixel levels and the sensitivity to polarization is very low.

The principle of operation of the thermal IR models (SI5000 and SI12000) is described:

By placing an interferometer between the FPA and the scene, a superposition of the fringe pattern and the image is created on the FPA (see Figure 10).

Figure 10 Scene image with fringes superimposed

For implementing a spectral imager, based on an interferometer, some scanning mechanism is required.

The method implemented in CI’s SpectraCube (SD300) systems involves changes to the optical path difference (OPD) within the interferometer (in a Michelson interferometer one of the arms is moved, in a Sagnac the interferometer is rotated). Figure 11 demonstrates such a case. The two images (a and b) present the same image with the fringes moving (which is the result of rotating the Sagnac interferometer).

This occurs while the spectral imager is fixed on a certain area of the scene and is referred to as “Stare mode” (the fringes “move” across a fixed image).

Figure 11 Scanning in “Stare Mode”

Recent development in FPA technology now allows a new implementation of an interferometer based spectral imager. The increase in FPA sizes and decrease in cost has made it possible to create a simple and robust system that has all the advantages of an interferometer in regards to signal collection and avoids the difficulties arising from stability issues of these systems.

If the position of the interferometer does not change relative to the FPA, each column of the FPA remains at a set and different OPD. By scanning the image through all the OPD’s one is able to construct the interferogram of each scene element and to later convert the interferogram into the spectra of each scene element to create a spectral image.

Figure 12 presents such a case. Notice that in figures a and b the position of the fringes relative to the image (i.e. the OPD of each column) remains constant while the whole scene is scanned (the image “moves” and the fringes remain stationary on the FPA). This scanning method is referred to as “pushbroom”.


Figure 12 Scanning in “Pushbroom Mode”

All of the described spectral imaging systems are based on a solid Sagnac interferometer rigidly situated in front of an FPA where the scan operation is performed for the entire optical head.

All of the described spectral imagers are field and airborne usable and so operate on 12 or 24 VDC, are light-weight and maintain calibration throughout long periods of operation in the field.

Spectral Reso an Interferometer

The spectral resolution of an interferometer equals 1/OPDmax OPDmax is a linear function of the number of FPA columns and the fringe density, the larger the FPA the higher the spectral resolution of this type of spectral imager is.

As an example consider an FPA with 320 columns, with a minimal working wavelength of 3μm; Assume the fringe density of the system is adjusted to 4 pixels/cycle. In this case we have available ~75 cycles on the FPA (320/4 with a few columns on the other side of OPDzero). OPDmax is then found to be 75 x 3E-4 cm (75 cycles at 3 μm) equaling 0.0225 cm. The resolution is then found to be 1/OPDmax≈ 44 cm-1 (wavenumber). The resolution in wavelength is given by


- 49 -

21 MaxOPD

The graphical displays of the resolution as a function of wavelength, for each model, are provided in the specifications section.

Scan

For a full image at full spectral resolution the system needs to acquire frames twice the number of FPA columns. As an example consider an FPA with 320 columns and an exposure time of 10 msec per frame. The total scan time is then equal to 640 x 10 msec ≈ 6.5 seconds for an image of 320 x 240 pixels. Since the system works in a pushbroom method the acquisition is not limited in the horizontal axis and panoramic images (up to 350 degrees) are supported.

Data

The amount of data produced by the spectral imager is substantial and should not be over-looked. A 320x240 spectral image will result in a spectral vector of 256 points for each pixel. Each vector value is 2 byte (Imagers are 12, 14 or 16 bit) and therefore the total file size is: 320x240x256x2≈40 Mbyte

Cooling

The MWIR and LWIR models incorporate cryogenically cooled detectors (InSb and MCT). No additional cooling of the system enclosure is required.

The graphical displays of the resolution as a function of wavelength, for each model, are provided in the specifications section.


Scan

For a full image at full spectral resolution the system needs to acquire frames twice the number of FPA columns. As an example consider an FPA with 320 columns and an exposure time of 10 msec per frame. The total scan time is then equal to 640 x 10 msec ≈ 6.5 seconds for an image of 320 x 240 pixels. Since the system works in a pushbroom method the acquisition is not limited in the horizontal axis and panoramic images (up to 350 degrees) are supported.

Data

The amount of data produced by the spectral imager is substantial and should not be over-looked. A 320x240 spectral image will result in a spectral vector of 256 points for each pixel. Each vector value is 2 byte (Imagers are 12, 14 or 16 bit) and therefore the total file size is: 320x240x256x2≈40 Mbyte

Cooling

The MWIR and LWIR models incorporate cryogenically cooled detectors (InSb and MCT). No additional cooling of the system enclosure is required.

5.2.1.1. Optical ModuleThe FPA modules are wavelength specific and are optimized for best performance.

The VIS system (SI 900) uses a Silicon FPA

The SWIR system (SI 2500) uses a 320x240 PV-MCT FPA with thermo-electric cooling (TEC)

The MWIR system (SI 5000) uses a 320x240 InSb FPA with Stirling cycle cryogenic cooling

The LWIR system (SI 12000) uses a 320x240 MCT FPA with Stirling cycle cryogenic cooling

5.2.1.2. Base unitThe base unit provides the scanning required for the acquisition of a spectral image when operated as a ground system. This unit is a 2-axis motorized (pan/tilt) that allows the user to aim the spectral imager at the target and to perform the scan operation required for an acquisition. The acquisition is a continuous horizontal scan between two user defined endpoints. Unattended operation is also supported.

5.2.1.3. Calibration Sources:For calibrating spectral images into units of radiance a calibration process is required. For the VIS and SWIR modules the recommended calibration source is an integration sphere. For the MWIR and LWIR units CI Systems provides an extended area blackbody as the calibration source.


5.2.1.4. SoftwareThe software that runs the spectral imagers is common to all models. Software is Windows XP Pro based and contains an acquisition module and a database module. The analysis suite is ENVI software by Research Systems. A schematic data flow is presented in the following flow chart.

Figure 13 Data Flow Chart

BuildAcquisition

Raw

Data File

Spectral Data File

File Header

Data Expor

t

AnalysisSoftwareENVI

Database

Raw Data File

5.2.1.5. AcquisitionThe acquisition software allows the user to set the start and end points for the scan. It supports an unattended mode for acquiring spectral images at user-defined intervals. The acquisition mode implements automatic exposure control so as to ensure that saturation is avoided during the scan or can be adjusted manually. The output of the acquisition is a file containing the un-processed data (a set of images along with the corresponding angle at which each image was acquired). The created file is stored into the measurement database

5.2.1.6. BuildThe build software module performs a few mathematical operations. The first operation is to construct the intensity data vector for each image pixel and to create what is known as an interferogram (intensity as a function of OPD). The second operation is to handle the interferogram by re-sampling, zero-filling and windowing. The third step is to convert the output interferogram into a spectral data vector by means of an FFT.

This application runs automatically after the acquisition and requires a few seconds for completion (~2 seconds for a 320x240 pixel image). It produces the raw data file and a file header. The created file is stored into the measurement database


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5.2.1.7. DatabaseThe database stores data in a two-level hierarchy. It includes tools for data filtering, data backup/archive and holds all acquisition parameters.

5.2.1.8. Analysis The analysis software is ENVI by Research Systems. This is a proven and widely-used high-level, open-code software with many built-in tools specifically written for analysis of hyperspectral datacubes. For more information refer to www.rsinc.com

SI-900 Specifications

No. Parameter Value

1 Spectral range (nm) 400÷1000

2 Spectral resolution (nm) 2

3 Spatial resolution (pixels) 1K in swath direction

4 Detector type Silicon FPA

5 IFOV 0.6 mrad (Other IFOV available on demand)

6 Data format 12 bit

7 Keystone and smile (%) <0.1


No. Parameter Value

1 Spectral range (nm) 1200÷2500

2 Spectral resolution (nm) <13 throughout the spectral range

3 Spatial resolution (pixels) At least 320 in swath direction

4 Detector type PV-MCT FPA 4 stage TEC cooled with digital output or InSb Stirling cycle

5 IFOV 0.6 mrad (Other IFOV available on demand)


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No. Parameter Value Remarks

1 Spectral range (μm) 3÷5

2 Spectral resolution (maximal) <50 cm-1 (see Figure 14)

3 Spatial resolution (maximal) At least 320 x 240 computer controlled windowing and binning

4 Detector type InSb FPA Stirling-cycle cooled 14 bit readout with real-time NUC and BPR

5 Interferometer Type Common path Sagnac interferometer in block design

6 IFOV 0.5 mrad Other IFOV sizes available upon request

7 Data rate <1 sec for a 64x64 pixel image at resolution of 50 cm-1

8NESR

Wattcm2 x sr x cm-1 2.5 x 10-9 @ 4.8 µm and uniform source over the

field of view

9 Weight <15 Kg for the optical module 6.5 Kg for scanning stage

Figure 14 Spectral resolution of SI 5000:

40

50

60

70

80

90

100

110

120

130

3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5

Wavelength, microns

Res

olut

ion,

nm



No. Parameter Value

1 Spectral range (μm) 8÷11.5

2 Spectral resolution (maximal) <17 cm-1 (see Figure 15)

3 Spatial resolution (maximal) 320 x 240

4 Detector type MCT FPA Stirling-cycle cooled

5 Interferometer Type Common path Sagnac interferometer in block design

6 IFOV 0.5 mrad

7NESR

Wattcm2 x sr x cm-1

<25 E-9 @ 10 µm and uniform source over the field of view

8 Weight <15 Kg for the optical module 6.5 Kg for scanning stage

Figure 15 Spectral resolution of SI 12000:

100

120

140

160

180

200

220

240

260

8 8.5 9 9.5 10 10.5 11 11.5 12

Wavelength, microns

Res

olut

ion,

nm


6. BDR (Background Discrimination Radiometer)

6.1. Introduction

Infrared contrast measurement of a moving target with respect to its background is currently achieved by one of two methods:

Measuring the background with and without the target in succession and subtracting one measurement from the other. This technique is difficult to perform and relies on a relatively stationary background.

Measuring with an imaging system equipped with a small number of constantly rotating filters and then using background pixels, within each image, for background characterization. This method has low sensitivity (as a result of the small pixel size) and involves huge amounts of data.

CI’s SR 5100 is a unique real-time BDR that eliminates all background and surrounding radiation to provide clear IR contrast of moving targets in Air-to-Air, Ground-to-Air and Air-to-Sea scenarios.

The SR 5100 operates in multiple spectral bands has a wide field of view, ideal for moving target tracking missions, with exceptional flatness of field and sensitivity.

6.2. Specifications

Filter Wheel Motorized-settable rotation rate between zero and 2 rev/sec. Provision is made for fitting 12 filters.

Sighting On-line nonparallex boresighting telescope

Focusing Single focus on infinity

Chopping Rate 25÷300 Hz

6.3 Performance

System Dynamic Range >105 (with InSb detector)

Frequency ResponseDC coupled: 1÷100 Hz (synchronous detection mode)AC coupled: up to 20 KHz in transient mode (1 Hz AC coupled)

Minimal detectable Irradiance Difference (MDID) <2x10-10 Watts/Cm2

FOV (instantaneous) 25 milirad

BackgroundDiscrimination Radiometer

7. SBUV Imaging Radiometer

CI’s new SBUV imaging radiometer is the perfect tool for quantitatively measuring SBUV sources in the field. It measures SBUV phenomena in a very large dynamic range, high frame rates and high spatial resolution with excellent wavelength specificity. The imager is supplied with calibration curves that allow the user to accurately calibrate measurements, advanced measurement and analysis software and a rifle-scope for aid in aiming.

FEATURES:

Operates in the SBUV waveband with no signal, above background, when pointed directly at the sun.

Very high sensitivity,

Very high dynamic range

Choice of collecting optics

Frame rate as high as 200 Hz

Comes complete with a set of 7 ND filters, 105 mm lenses, rifle-scope, lunchbox PC, calibration data and software.

Interfaces a standard tripod

SBUV Imaging Radiometer

OPTIONS:

- 28mm or 78mm lenses

SPECIFICATION:

Item Value Remarks

Wavelength range 245÷285 nm

Out of band rejection No signal when directly viewing the sun

Spatial resolution 512x512 Pixels, measured resolution of <90 lp/mm with 105 mm lenses

Frame rate 17 Hz at full resolution and up to 200 Hz See table

Lenses 105 mm f/4 Focus range from a few meters to infinity

Sensitivity Will clearly measure a 30Watt D2 lamp from 3 Km See image, with Ozone level of 28 ppb

Field of view 9.8 degrees For 105 mm focal length

ND filters set 0.1, 0.3, 0.5, 1.0, 2.0, 3.0, 4.0 OD Included with system

IMAGER SPATIAL RESOLUTION vs. FRAME RATE:

Binning 512 x 512 200 x 200 100 x 100

1 x 1 17 42 77

2 x 2 35 77 143

4 x 4 65 143 200


IMAGE OF 30 WATT D2 SOURCE AT 3Km DISTANCE:


Prepared by CI Systems Ltd. Feb 2008€¦ · 2.1. Basic Radiometry Concepts Table 1 Definitions and...

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Transcript of Prepared by CI Systems Ltd. Feb 2008€¦ · 2.1. Basic Radiometry Concepts Table 1 Definitions and...