Download - Optical-Sensors. Wavelength nm Visible Light Near Infrared 4505506507508509501050 0.250.50 % Reflectance

Optical-SensorsOptical-Sensors

Wavelength nmWavelength nm

Visible LightVisible LightVisible LightVisible LightNear InfraredNear Infrared

450450 550550 650650 750750 850850 950950 10501050

0.250.25

0.500.50%

Ref

lect

ance

% R

efle

ctan

ce

Irradiance Sensing StrategiesIrradiance Sensing Strategies

Inir

Rnir

Ired

R red

Spectral shift in illuminationSpectral shift in illuminationprevents use ofprevents use ofsimple irradiance sensingsimple irradiance sensing

Example Index:Example Index:RRredred / / RRnirnir

Inir

Rnir

Ired

R redRed Red Reflectance:Reflectance:r = Rr = Rredred / I / Iredred

Reflectance is primarilyReflectance is primarilya function of targeta function of target

Reflectance Sensing StrategiesReflectance Sensing Strategies

nm670nm6780

nm670nm6780

dReNIR

dReNIRNDVI

Normalized Difference Normalized Difference Vegetative Index (NDVI)Vegetative Index (NDVI)

Incident

flectedRe

Inicident

flectedRe

Incident

flectedRe

Inicident

flectedRe

cetanflecRe

NIR

dRe

NIR

NIR

NIR

dRe

NIR

NIR

NDIV

Reflectance NDVIReflectance NDVI

Natural LightingNatural Lighting

• Light source is free.Light source is free.• Much of the effect of Much of the effect of

spectral shift can be spectral shift can be corrected by measuring corrected by measuring incident and reflected. incident and reflected. light and calculating light and calculating reflectance.reflectance.

• Spectral shifts occur as Spectral shifts occur as sun angle changes.sun angle changes.

• Cloud cover affects Cloud cover affects intensity.intensity.

• Moisture and dust cause Moisture and dust cause differences in refraction differences in refraction and absorbence across and absorbence across the spectra.the spectra.

• Can’t be operated at Can’t be operated at night. night.

AdvantagesAdvantages LimitationsLimitations

Photo-Detector

Target

Optical Filters

Fiber OpticLight Guides

GlassCover

Collimation

Sensor/AmplifierIntegrated Circuit

OSU Reflectance SensorOSU Reflectance Sensor

Artificial Lighting Artificial Lighting

• Patchen high frequency Patchen high frequency pulsed narrow spectra pulsed narrow spectra lightinglighting

• Broad spectra lighting with Broad spectra lighting with filters filters – ConstantConstant

or or – PulsedPulsed

Artificial LightingArtificial Lighting

• Removes the effect of Removes the effect of changing background changing background illumination.illumination.

• Can be operated 24 Can be operated 24 hours/day.hours/day.

• Can produce an Can produce an absolutely calibrated absolutely calibrated signal.signal.

• Choice of spectral bands Choice of spectral bands are limited when pulsed are limited when pulsed solid state lighting solid state lighting sources (LED’s or lasers) sources (LED’s or lasers) are used.are used.

• Broadband lighting Broadband lighting requires high power .requires high power .

• Cost of the Cost of the sensor/lighting systems sensor/lighting systems are higher than those are higher than those using natural lighting.using natural lighting.

Turf Target

NIR and REDModulated

Illumination

Direction

Patchen WeedseekerPatchen WeedseekerOptical SensorOptical Sensor

Patchen Sensing TechniquePatchen Sensing Technique

PhotodiodeDetector

Reflected Light

NIR+Red+Sun NIR+Red+Sun

Voltage Voltage

High PassFilter

NIR+Red

Patchen Sensing TechniquePatchen Sensing Technique

90o

RedNIR

NIR+Red

a

RNIR

RNIRa

a NDVI

Patchen Sensor NDVI CalibrationPatchen Sensor NDVI Calibration

y = 0.7711x - 1.0618

0.4

0.5

0.6

0.7

0.8

0.9

1

1.9 2.1 2.3 2.5 2.7

Patchen DET_OUT Voltage (x/6420)Patchen DET_OUT Voltage (x/6420)

OS

U N

DV

IO

SU

ND

VI

Good calibration to Good calibration to NDVI after filteringNDVI after filtering

11500

12500

13500

14500

40 60 80 100 120

Temperature (F)

DE

T_O

UT

* 6

420

Unit 3385

Unit 3386

Unit 3388

Unit 3493

Unit 3387

Temperature driftTemperature driftunacceptable for unacceptable for absolute measurementsabsolute measurements

Patchen Temperature Patchen Temperature CalibrationCalibration

y = 0.68x - 0.78y = 0.71x - 0.90y = 0.70x - 0.91y = 0.77x - 1.06y = 0.82x - 1.25

0.4

0.5

0.6

0.7

0.8

0.9

1

1.9 2.1 2.3 2.5 2.7

Patchen DET_OUT Voltage (x/6420)

OS

U N

DV

I

33873386338834933385

Sensor to sensorSensor to sensorvariability largevariability large

Patchen - NDVI CalibrationPatchen - NDVI Calibration

Field of View Issues -Field of View Issues - Fixed Detection ThresholdFixed Detection Threshold

Background affects Background affects weed detection errorweed detection error

0

10

20

30

40

50

0.0 2.0 4.0 6.0 8.0

Bindweed Coverage (%)

Err

or

at T

hre

sho

ld (

%)

All Data

Dry Soil

Moist Soil

1% detection error, requires 26% plant coverage5% detection error, requires 12 % plant coverage

Weed Detection Error When the Threshold Weed Detection Error When the Threshold is Adjusted for Changing Soil Backgroundis Adjusted for Changing Soil Background

WWeeeedd CCoovveerr((%% FFiieelldd--ooff--VViieeww))

DDeetteeccttiioonn EErrrroorr((%%))

66..00 00

33..00 00

22..00 22

11..00 00

00..88 00

00..55 00

Methods for Compensating for Methods for Compensating for Changing BackgroundChanging Background

• Periodic, manual Periodic, manual recalibration (current recalibration (current Patchen strategy).Patchen strategy).

• Reduce field-of-view to the Reduce field-of-view to the size where it will always size where it will always distinguish weeds from soil distinguish weeds from soil (fixed threshold).(fixed threshold).

• Build automatic adaptive Build automatic adaptive thresholding into the sensor.thresholding into the sensor.

OSU/NTech SensorOSU/NTech Sensor

Target

NIR and REDModulated

Illumination

Direction

Detection ofReflected

NIR and RED+Sun

GreenSeeker SensorGreenSeeker Sensor

• NDVI is independent of ambient temperatureNDVI is independent of ambient temperature• Sensor can operate 32 to 48 inches above the Sensor can operate 32 to 48 inches above the

targettarget• Sensor can control 3 or more valvesSensor can control 3 or more valves• Calibration curves can be downloaded to the Calibration curves can be downloaded to the

sensor.sensor.• The sensor can transmit NDVI readings and valve The sensor can transmit NDVI readings and valve

settings through the CAN network to a central settings through the CAN network to a central computercomputer

OSU/NTech OSU/NTech GGREENREENSSEEKEREEKERTMTM ApplicatorApplicator

• Sense and treat each 2 ft by 2 ft areaSense and treat each 2 ft by 2 ft area• Apply one of seven fertilizer rates Apply one of seven fertilizer rates

based on the crops yield potentialbased on the crops yield potential• Accomplish this while driving 15 Accomplish this while driving 15

mphmph• Operate day or nightOperate day or night• Provide the capability to detect and Provide the capability to detect and

treat other plant problemstreat other plant problems• Record and georeference sensor Record and georeference sensor

data for GIS analysisdata for GIS analysis• Sense and spot spray weeds (current Sense and spot spray weeds (current

Patchen technology)Patchen technology)

Sensor ElectronicsSensor Electronics

Oscillator(40 kHz)

CurrentDriver

Red LEDlight

production

CurrentDriver

NIR LEDlight

production

LED lightdetector

Reflectedlight

detector

MultiplexerBand-pass

filterand Amp

A/Dconversion

Micro-Micro-processorprocessor

CAN CAN NetworkNetwork

Valve Control Valve Control ModuleModule

UserInterfaceUI-ECU

PressureControlPC-ECU

Plant SensorSEN_ECU1

8


7


6


0





5

NozzleAngleECU

BoomHeightECU

DiagnosticConnector

Terminator

HeightSensor #1

Terminator

Terminator

Terminator

VCM

VCM

VCM

VCM

VCM

VCM

VCM

VCM

UserInterfaceUI-ECU

PressureControl

PC-ECU









DiagnosticConnector

Terminator

Terminator

Terminator

RADAR

GPS

ValveControlModule

ValveControlModule

ValveControlModule

ValveControlModule

ValveControlModule

ValveControlModule

ValveControlModule

ValveControlModule

Joystick

Valves Available for Precision Valves Available for Precision ApplicationApplication

• Several different kindsSeveral different kinds– Solenoid/Diaphragm controlled valves (Capstan, Solenoid/Diaphragm controlled valves (Capstan,

Patchen, etc.).Patchen, etc.).– Pneumatic/Solenoid controlled valves (OSU).Pneumatic/Solenoid controlled valves (OSU).– Pintle and valve seat in spray solution (Detect Spray).Pintle and valve seat in spray solution (Detect Spray).

1. 1. All valves can only be operated on or off.All valves can only be operated on or off.

2. Both valve types can be pulse width modulated to2. Both valve types can be pulse width modulated to vary application rate without affecting distribution. vary application rate without affecting distribution.

3. There are no valves available the can be3. There are no valves available the can be continuously varied without affecting distribution. continuously varied without affecting distribution.

Tri-valve Set for Varying RateTri-valve Set for Varying Rate

• Stepped rates -Stepped rates -1x, 2x, 3x, 4x, 5x, 1x, 2x, 3x, 4x, 5x, 6x, 7x and off6x, 7x and off

• Can treat 0.6 by Can treat 0.6 by 0.6 m area 0.6 m area applying the target applying the target rate on 85% of that rate on 85% of that areaarea

BOOM PLUMBING LAYOUTBOOM PLUMBING LAYOUT

Units are in inches.

Forward directionForward direction

Farmer CheckNon-N Limiting

RI = 0.7/0.5 = 1.46RI = 0.7/0.5 = 1.46

In-Season Response Index (RINDVI)

ratefield

itingNnonNDVI NDVI

NDVIRI lim

Non-N-Limiting and Field Rate StripsNon-N-Limiting and Field Rate Strips7

10

5

20

3

30

1

39

9

49

7

59

5

69

3

79

1

88

9

98

7

10

85

11

83

12

81

13

79

14

77

15

75

1

15

29

43

57

Distance, ft

0.9-1

0.8-0.9

0.7-0.8

0.6-0.7

0.5-0.6

0.4-0.5

0.3-0.4

0.2-0.3

0.1-0.2

0-0.1

OSU/GreenSeeker Unit 1OSU/GreenSeeker Unit 1 N-Fertilizer Applicator N-Fertilizer Applicator

Download - Optical-Sensors. Wavelength nm Visible Light Near Infrared 4505506507508509501050 0.250.50 % Reflectance

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