irdc theory and practice of building instruments for diffuse reflectance measurements
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IDRC-2016
The theory and practice of building
instruments for DR measurements
Jerome Workman
Unity Scientific and National University
IDRC-2016
Outline
• Light Interaction with Matter
• Sampling Accessories
• Illumination/Measurement Geometries
• The Integrating Sphere and Integrating Sphere Type Measurements
• Reflectance Theory: Review
• Instrument Parameters Affecting Spectra
• Problem Highlighted: Distance to Detector
Light Interaction with Matter
Light interaction with solid materials. Ray tracing indicates the possible outcomes for
individual photons from the incoming beam.
Specular Reflection
Diffuse Reflection
Absorption
Transmittance
Interaction
Scattering
Rayleigh Scattering
Color/Electronic Absorption
Am
plit
ud
e
Wavelength (nm)
Effective Pathlength
Absorptivity
200 1150 2500
Light Interaction in Transmittance
Sample Attenuates the
Light
Sample Layer
I0 I
hν
100% Initial Light
% Attenuated or Absorbed
Light
I0 Sample Beam Sample Detector Optics
Detector
I
None
Cuvet
Large Lens
Small Lens
Beam Geometries of Various Transmission Measurements
Light Interaction with Particles in Diffuse Transmittance
Sample Attenuates the
Light
Sample Layer
I0 I
hν
Particles cause Scattering
Losses
Particles cause Scattering
Losses
100% Initial Light
% Attenuated or Absorbed
Light
Light as Specular Reflection (Elastic Collision)
Reflective Surface
Specular Viewing Angle
I0 Elastic
Collision with no light
Interaction with Sample
Normal Angle (0°)
~I θ θ
Light as Diffuse Reflection (Inelastic Collision)
Diffuse Surface
Sample Layer
I0 Inelastic
Collision with light
Interaction with Sample
Normal Incidence Angle (o°)
I Θ = 45°
Angular Distribution of Reflected Light
Diffuse Surface Sample Layer
Lambertian Reflection
B S0 cos α
B cos ϑ
α
ϑ
From G. Kortum, Reflectance Spectroscopy
Illustration of Terms for Angular Distribution of Reflected Light
Sample Layer
Lambertian Reflection
α
ϑ dϑ
dω
df
I0 I
From G. Kortum, Reflectance Spectroscopy
Angular Reflected Energy Distribution
Diffuse Surface Sample Layer
Lambertian Angular
Distribution
B S0 cos α
B cos ϑ
α
ϑ
Seeliger Angular
Distribution
From G. Kortum, Reflectance Spectroscopy
Sampling Accessories
Locking powder cup – optical view
Top View
Powder Cup
I0 I
Side View
Reflective Back
Window
Fine ground sample
Sample
Transflectance
I0
Diffuse Reflective Back
Sample
Optical Window
I I0 I
Physical Pathlength
Optical Pathlength
Liquid transflectance cell
Liquid Transflectance Cell
Top View
I0
I
Side View
Physical Pathlength is physical distance where photon passes through, e.g. 0.3 mm nominal
Effective Pathlength is optical distance where photon passes
through: ~ 0.3 mm x 2.5 = 0.75 mm
Diffuse Reflective back
Optical Window
Liquid Sample
Locking powder cup – optical view
Top View
Powder Cup
I0 I
Side View
Liquid cuvet and powder cell types
Top View
Powder Cup
I0 I
Side View
Powder Cup (Top and Bottom Sections)
External Reflectance Regimes
Specular surface
θ1 θ2
Θ1 = Θ2
Specular external reflectance
I0 I
θ1 θ2 Reflection/absorption or Transflectance
I
Θ1 ‡ Θ2
I0
Reflective Surface
Sample absorptive surface
Elastic photon collision
Inelastic photon collision
Illumination/Measurement Geometries
0°/45° Measurement Geometry
Detector
I0 I
Θ = 45°
Horizontal Surface
Incident Energy at
Normal Angle
(0°)
Sample
45°/0° Measurement Geometry
Detector
I0 I
Θ2 = 45°
Horizontal Surface
Incident Energy at
(45°)
Sample
Θ1 = 45°
Θ3 = 45° Measure at
(0°)
d/8° Color Measurement Geometry
Detector
I0
I
Θ2 = 82°
Horizontal Surface
Normal Angle to Sample
(0°)
Sample
Θ1 = 8°
22.5°/22.5° Specular/Color Measurement Geometry
Detector
I0 I
Θ2 = 45°
Horizontal Surface
Incident Energy at
(22.5°)
Sample
Θ1 = 22.5°
Measure at
(0°)
Θ3 = 22.5°
Basic Configurations for Variable Measurement Geometry
I0
I
Horizontal Surface Sample
DIFFUSE REFLECTION
I SPECULAR
TRANSMISSION I DIFFUSE
TRANSMISSION
Incident Energy at Normal Angle (0°)
I SPECULAR
REFLECTION
Θ = 5°
Θ = 5°
Θ = 45°
Θ = 135°
Diffuse Reflection Color Measurement Geometry
I0
I
Θ = 45°
Horizontal Surface Sample
DIFFUSE REFLECTION
Incident Energy at Normal Angle (0°)
Diffuse Transmission Color Measurement Geometry
I0
Horizontal Surface Sample
I DIFFUSE
TRANSMISSION
Incident Energy at Normal Angle (0°)
Θ = 135°
Specular Reflection Color Measurement Geometry
I0
Horizontal Surface Sample
Incident Energy at Normal Angle (0°)
I SPECULAR
REFLECTION
Θ = 5°
Specular Transmission Color Measurement Geometry
I0
Horizontal Surface Sample
I SPECULAR
TRANSMISSION
Incident Energy at Normal Angle (0°)
Θ = 5°
Transmitted, Remitted, and Absorbed Energy: Small Area Detection
I
I0
Sample
MEASURED TRANSMITTED
Incident Energy at Normal Angle (0°)
I MEASURED REMITTED
UNMEASURED ABSORBED
Unmeasured Remittance
Unmeasured Transmittance
Unmeasured Transmittance
Remitted, and Absorbed Energy: Hemispherical Detection
I0
Detector I
Light Shield Cylinder
Sample in Reflection
Port
Remitted Reflection
Energy
ABSORBED ENERGY IS NOT
MEASURED DIRECTLY
Transmitted and Absorbed Energy: Hemispherical Detection
I0
Detector I
Light Shield Cylinder
Sample in Transmission
Port
Transmitted Energy
ABSORBED ENERGY IS NOT
MEASURED DIRECTLY
Light Reflector in Sample Port
Integrating Sphere: Late 1970s Type
I0
Sphere Detector Port
I
Light Shield Cylinder
Sphere Entrance Port
Two Position Mirror
(Sample and Reference)
Monochromatic Light
Sphere Sample Port
0°/45° Measurement Geometry: Type I
Sample
Window
Detectors
Light Energy – Post-dispersive
0°/45° Measurement Geometry: Type II
Sample Window
Detectors
Light Energy – Post-dispersive Front surface Diagonal mirror
Pre-Dispersive, Grating Single Monochromator Design
Exit Slit
Diffraction Grating
Normal Angle Entrance Slit
Sample
Collimating Optics
Collimating Optics
Shutter
Source
Detector 1
Detector 2
0°/ 45° Reflectance
Exit Slit
Diffraction Grating
Normal Angle Entrance Slit
Detector
Sample
Collimating Optics
Collimating Optics
Shutter
Source(s)
Analog Amplifier and A to D Converter
Controller Board
Computer Board
Power Supply
Electronics
//
//
Post-Dispersive, Grating Single Monochromator Design
45°/0° Illumination
Grating and DLP DMD with Single Element Detector Design Pre-Dispersive Optics
Fixed Diffraction Grating
Normal Angle
Detector
Collimating Optics
DLP DMD
Entrance Slit
Collimating Optics
Shutter
Source(s)
45°/0° Illumination
Digital light processing (DLP)—Digital micromirror device (DMD) spectrometer
Grating and Fixed Array Detector Design Pre-Dispersive Optics
Fixed Diffraction Grating
Normal Angle
Fixed Array Detector
Analog Amplifier and A to D Converter
Controller Board
Computer Board
Power Supply
Electronics
//
//
Entrance Slit
Collimating Optics
Shutter
Source(s)
45°/0° Illumination
Optical Schematic
Moving mirror
Scanning Michelson Interferometer
Light Source
IR-Source
Light Pipe
Integrating Chamber
J-Stop
Beam Splitter
Fixed mirror
Fixed Mirror
Detector Optics
Michelson Interferometer Design (FT-NIR) - Optics
Detectors
Sample
0°/ 45° Reflectance
The Integrating Sphere
Beam Geometry for Diffuse Transmittance/Transmission Measurements
I0
Sample Beam
Detector I
Optical Sample
Light Shield Cylinder
Photometric Port or
Window
Inner Reflective Surface of Integrating
Sphere Diffuse
Transmission Energy
I0
Detector I
Optical Sample
Light Shield Cylinder
Sample Port or Window
Inner Reflective Surface of Integrating
Sphere
Diffuse Reflection
Energy
Beam Geometry for Diffuse Reflectance/Reflection Measurements
Figure showing the distance from the exit port entrance plane to the detector window (δ).
Detector
Detector Port
Integrating Sphere Wall
δ
Integrating Sphere Type
Measurements
Integrating Sphere – Single Beam Reflectance: 0%
I0
Detector I
Light Shield Cylinder
No Sample in Sample Port
Entrance Port
Integrating Sphere – Double Beam Reflectance: 0%
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I REFERENCE SAMPLE
PORT (100% REFLECTOR)
TEST PORT (NO SAMPLE
PRESENT)
Entrance Port
Integrating Sphere – Single Beam Reflectance: 100%
I0
Detector I
Light Shield Cylinder
100% Reflectance Material in Sample
Port
Entrance Port
Integrating Sphere – Double Beam Reflectance: 100%
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I REFERENCE SAMPLE
PORT (100% REFLECTOR)
TEST PORT (100% REFLECTOR)
Entrance Port
Integrating Sphere – Single Beam Reflectance: Test Sample
I0
Detector I
Light Shield Cylinder
Test Sample Material in Sample Port
Entrance Port
Integrating Sphere – Double Beam Reflectance: Test Sample
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I
REFERENCE SAMPLE PORT (STANDARD
REFERENCE MATERIAL)
TEST PORT (TEST SAMPLE
MATERIAL)
Entrance Port
Integrating Sphere – Single Beam Transmittance: 0%
I0
Detector I
Light Shield Cylinder
100% Reflector in Sample Port
Transmittance Port Blocked
Integrating Sphere – Double Beam Transmittance: 0%
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I REFERENCE SAMPLE
PORT (100% REFLECTOR)
Transmittance Port Blocked 100%
Reflector in Sample Port
Integrating Sphere – Single Beam Transmittance: 100%
I0
Detector I
Light Shield Cylinder
100% Reflectance Material in Sample
Port
Transmittance Port
Integrating Sphere – Double Beam Transmittance: 100%
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I REFERENCE SAMPLE
PORT (100% REFLECTOR)
TEST PORT (100% REFLECTOR)
Transmittance Port
Integrating Sphere – Single Beam Transmittance: Test Sample
I0
Detector I
Light Shield Cylinder
100 % Reflector Material in Sample
Port
Transmittance Port with Test
Sample
Integrating Sphere – Double Beam Transmittance: Test Sample
I0
Detector
I
TEST SAMPLE BEAM I0
REFERENCE BEAM
I REFERENCE SAMPLE
PORT (100% REFLECTOR)
TEST PORT (100% REFLECTOR)
Transmittance Port with Test
Sample
Angular Reflected Energy Distribution
Diffuse Surface Sample Layer
Lambertian Angular
Distribution
B S0 cos α
B cos ϑ
α
ϑ
Seeliger Angular
Distribution
Sample Layer
Lambertian Reflection
α
ϑ dϑ
dω
df
I0 I
From G. Kortum, Reflectance Spectroscopy
Instrument Parameters Affecting DR Spectra
1. Wavelength accuracy
2. Wavelength repeatability
3. Wavelength linearity
4. Wavelength reproducibility
5. Photometric accuracy
6. Photometric repeatability
7. Photometric reproducibility
8. Photometric linearity
9. Photometric noise
10.Photometric drift
11.Signal averaging integrity (systematic noise component)
12.Instrument line shape
13.Detector response
14.Source color temperature
15.Instrument temperature (thermistor)
16.Sample temperature (thermistor)
17. Technology difference artifacts (FT-DA-M-LVF-DLP-Other)
Readily Measurable Instrument Parameters Affecting Spectra
Detector Response using Dual Channel Ultra-cooled InGaAs
1E+09
1E+10
1E+11
1E+12
900 1100 1300 1500 1700 1900 2100 2300 2500 2700 2900
D*
in c
m H
z1/2
/W
Wavelength (nm)
D* Spectral Response
InGaAs (-30C)
InGaAs (-50C)
PbS (-10C)
PbS(-20C)
Specific Detectivity (D*)
Detector Response time Dual Channel Ultra-cooled InGaAs
0
200
400
600
800
1000
1200
-30C 27C
Detector response Times (μs)
InGaAs PbS
0.01 0.1
-30 °C 27 °C
Measurement issues affecting reflectance spectra
1. Reflectance and transmittance of window from sample cup 2. Sample thickness, packing density, particle size, refractive
index, crystalline form, surface characteristics 3. Sample scattering coefficient (s) 4. Sample absorption coefficient (k) 5. Measurement geometry 6. Number of detectors (response speed and linearity/dynamic
range) 7. Wavelength of light 8. Polarization effects: s- and p-polarization from beam 9. Beam size and beam angle with respect to sample 10. Sample distance from detector
1. Reflectance and transmittance of window from sample cup
2. Sample thickness and background material
3. Sample scattering coefficient (s) 4. Sample absorption coefficient (k) 5. Measurement geometry 6. Number of detectors (response
speed and linearity/dynamic range) 7. Wavelength of light 8. Polarization effects: s and p-
polarization from beam 9. Beam size, uniformity, and beam
angle with respect to sample 10. Sample distance from detector
1 2, 3, 4
5 5
Illustration
6 6
7, 8
9
10
0°/45° Measurement Geometry: Type II
Sample Thickness and Background Material
Side View
Powder Cup
I0 I
Reflective Back
Window
Sample
2
Change in Percent Reflectance for plane (Rs) and perpendicularly (Rp) polarized
light as a function of the angle of incidence.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 50 100
Ref
lect
ion
Angle of Incidence (Degrees)
Rs
Rp
Φ1 Φ1
Φ2
8
Beam Shape
9
Beam Size vs. Sample Size
1.5 “
9
Main Variability Problem Highlighted:
Distance to Detector
Distance effect: major changes in slope and
offset for each detector in optical path
0°/45° Measurement Geometry: Type II
Sample Window
Detectors
Light Energy – Post-dispersive Front surface Diagonal mirror
Issues Affecting Distance
Sample Layer
Lambertian Reflection
B
S0 cos α B cos ϑ
α
ϑ
Sample Holding Device
Sample Window
Angular Distribution of Reflected Light
Sample
0 = Ideal height for maximum reflectance signal amplitude Si
gnal
Am
plit
ud
e
-2 -1 0 +1 +2
Sample Distance from Highest Signal
Sample
+1 (0.0125” or 0.32 mm) Si
gnal
Am
plit
ud
e
-2 -1 0 +1 +2
Sample Distance from Highest Signal
Sample
+2 (0.0250” or 0.64 mm)
Sign
al A
mp
litu
de
-2 -1 0 +1 +2
Sample Distance from Highest Signal
Sample
-1 Si
gnal
Am
plit
ud
e
-2 -1 0 +1 +2
Sample Distance from Highest Signal
-1 (0.0125” or 0.32 mm)
-2
Sample
Sign
al A
mp
litu
de
-2 -1 0 +1 +2
Sample Distance from Highest Signal
-2 (0.0250” or 0.64 mm)
SN3 Platter
SN2 Platter
Sample in glass cell
Sample only
Instrument #1 With R99
Cup + window = 0.116”
+0.048”
+0.065”
(2.9 mm)
(0 mm)
(1.2 mm)
(1.65 mm)
Sample only
Instrument # 2 With R99
cell = 0.116”Sample in glass cell
(0 mm)
(1.65 mm)
1000 1500 2000 2500
Nanometers
3
4
5
6
Ab
sorb
an
ce
Dark Standard (A~3.2)
Dark Standard (A~3.2) – Diff
1000 1500 2000 2500
Nanometers
-1
0
1
Ab
sorb
an
ce
1000 1500 2000 2500
Nanometers
1.0
1.1
1.2
1.3
Ab
sorb
an
ce
R10 (A~1.0)
0.0 mm
0.32 mm
0.64 mm
R10 (A~1.0) - Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.35
0.40
0.45
0.50
0.55
Ab
sorb
an
ce
R50 (A~0.301)
0.0 mm
0.32 mm
0.64 mm
R50 (A~0.301) - Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
R99 (A~0.0044)
0.0 mm
0.32 mm
0.64 mm
R99 (A~0.0044) – Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.1
0.2
0.3
0.4
0.5
Ab
sorb
an
ce
1920a (A~0.314)
0.0 mm
0.32 mm
0.64 mm
1920a (A~0.314) - Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.2
0.4
0.6
0.8
Ab
sorb
an
ce
Grd. Wheat
0.0 mm
0.32 mm
0.64 mm
Grd. Wheat – Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.2
0.4
0.6
0.8
Ab
sorb
an
ce
Flour
0.0 mm
0.32 mm
0.64 mm
Flour – Diff
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Ab
sorb
an
ce
Forage - Hay
0.0 mm
0.32 mm
0.64 mm
Forage – Hay – Diff.
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
1000 1500 2000 2500
Nanometers
0.03
0.04
0.05
0.06
0.07
Ab
sorb
an
ce
Flour – Wheat – Forage – Diff (1= 0.32 mm)
Flour
Wheat
Forage
Flour – Wheat – Forage – Diff (2= 0.64 mm)
1000 1500 2000 2500
Nanometers
0.12
0.14
0.16
0.18
0.20
0.22
Ab
sorb
an
ce
Flour
Wheat
Forage
R10 – R50 – R99 – Diff (1=0.32 mm)
1000 1500 2000 2500
Nanometers
0.03
0.04
0.05
0.06
Ab
sorb
an
ce
R10 – R50 – R99 – Diff (2=0.64 mm)
1000 1500 2000 2500
Nanometers
0.12
0.14
0.16
0.18
0.20
0.22
Ab
sorb
an
ce
Compare offset distance to Forage multiplied 1.1 and 1.5
1000 1500 2000 2500
Nanometers
0.2
0.4
0.6
0.8
Ab
sorb
an
ce
Superimpose (Normalize) Mode: Compare Forage multiplied 1.1 and 1.5
1000 1500 2000 2500
Nanometers
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
0.25
Ab
sorb
an
ce
Compare offset distance to Forage multiplied 1.1 and 1.5 - Diff
1 Der – 11 pt smooth : Compare Forage multiplied 1.1 and 1.5
1000 1500 2000 2500
Nanometers
-0.015
-0.010
-0.005
0.000
0.005
Abs
orba
nce
1200 1400 1600 1800 2000 2200 2400
Nanometers
0.000
0.002
0.004
0.006
Abs
orba
nce
1 Der – 11 pt smooth : Compare Forage multiplied 1.1 and 1.5
Close-up
1 Der – 11 pt smooth : Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
-0.010
-0.005
0.000
Abs
orba
nce
1 Der – 11 pt smooth : Compare Forage Height Differences
1200 1400 1600 1800 2000 2200 2400
Nanometers
-0.001
0.000
0.001
0.002
0.003
0.004
Abs
orba
nce
Close-up
2 Der – 21 pt smooth: Compare Forage multiplied 1.1 and 1.5
Close-up
1200 1400 1600 1800 2000 2200 2400
Nanometers
-0.00010
-0.00005
-0.00000
0.00005
0.00010
Abs
orba
nce
1400 1600 1800 2000 2200 2400
Nanometers
-0.00010
-0.00005
-0.00000
0.00005
0.00010
Abs
orba
nce
1 Der – 11 pt smooth : Compare Forage multiplied 1.1 and 1.5
Close-up
2 Der – 21 pt smooth: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
-0.0006
-0.0004
-0.0002
0.0000
0.0002
Abs
orba
nce
1000 1200 1400 1600 1800 2000 2200 2400
Nanometers
-0.00010
-0.00005
-0.00000
0.00005
0.00010
Abs
orba
nce
2 Der – 21 pt smooth : Compare Forage Height Differences
Close-up
Normalize and set minimum to 0 offset: Height and Multiplicative
1000 1500 2000 2500
Nanometers
0.0
0.2
0.4
0.6
Ab
sorb
an
ce
Set mean to zero and then offset min to zero
Normalize and set minimum to 0 offset: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
Set minimum to 0 offset: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
Set minimum to 0 offset: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Ab
sorb
an
ce
Set minimum to 0 offset: Compare Forage Height Differences
1st order poly min to zero
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Ab
sorb
an
ce
Set minimum to 0 offset: Compare Forage Height Differences
2nd order poly (quadratic) min to zero
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
Set minimum to 0 offset: Compare Forage Height Differences
3rd order poly (quintic) min to zero
1000 1500 2000 2500
Nanometers
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
Ab
sorb
an
ce
Kramers-Kronig: Compare Forage Height Differences
Abs: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Ab
sorb
an
ce
Refl: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Re
fle
cta
nc
e
0.0 mm
0.32 mm
0.64 mm
Kubelka-Munk: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.0
0.5
1.0
1.5
Ku
be
lka
-Mu
nk
0.0 mm
0.32 mm
0.64 mm
Dahm Eq.: Compare Forage Height Differences
0
0.5
1
1.5
2
2.5
3
3.5
4
700 900 1100 1300 1500 1700 1900 2100 2300 2500 2700
0.0 mm
0.32 mm
0.64 mm
Dahm Eq. w offset: Compare Forage Height Differences
0
0.5
1
1.5
2
2.5
3
700 900 1100 1300 1500 1700 1900 2100 2300 2500 2700
0.0 mm
0.32 mm
0.64 mm
Offset min set to zero: Compare Forage Height Differences
1000 1500 2000 2500
Nanometers
0.0
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
Precise Detector Height Alignment Process
Wheat Sample: Five aligned instruments
1000 1500 2000 2500
Nanometers
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Ab
sorb
an
ce
Wheat Sample: Five aligned instruments - Diff
1000 1500 2000 2500
Nanometers
-0.01
0.00
0.01
Ab
sorb
an
ce
Wheat Sample: Five aligned instruments Diff vs height Diff for 1 instrument
1000 1500 2000 2500
Nanometers
0.00
0.05
0.10
0.15
0.20
Ab
sorb
an
ce
0.0 mm
0.32 mm
0.64 mm
Five Instruments
1 instrument
R99-Polystyrene: Five aligned instruments
1000 1500 2000 2500
Nanometers
0.5
1.0
1.5
2.0
2.5
Ab
sorb
an
ce
R99-Polystyrene: Five aligned instruments - Diff
800 1000 1200 1400 1600 1800 2000
Nanometers
-0.02
0.00
0.02
0.04
Ab
sorb
an
ce
SRM1920a: Five aligned instruments
1100 1200 1300 1400
Nanometers
0.1
0.2
0.3
0.4
Ab
sorb
an
ce
Acknowledgments
• John Glaberson, Designs Work Group
• Barry Lavine, Oklahoma State University
• Art Springsteen, Avian Technologies
• Ken Galer, IELLC
• Chris Ubaldi, Unity Scientific
• Bob Schumann, Unity Scientific
• Some of you!
Thank you!
jworkman@unityscientific.com
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