emva 1288 ite 2008 m. wäny cmos image sensors clear definitions for a clear vision emva 1288...

EMVA 1288 ITE 2008 M. Wäny www.awaiba.com CMOS IMAGE SENSORS

Clear definitions for a

clear VISION

EMVA 1288 Standard for Measurement and Presentation of Specifications for Machine Vision Sensors and Cameras

CMOS IMAGE SENSORS


o Why we need EMVA 1288 Standardo EMVA 1288 Standard organizationo Measurement setupo 1288 Module 1 “in 12 Slides”

o Interpretation of the standard for the user

Agenda

Example DR-4k-7


Motivationo Existing Standards for cameras are not suitable for MVo Each Sensor and Camera Manufacturer has it’s own definitionso The Customer is left guessing with datasheets

Today cameras and sensor are digital but manufacturers specify V/lux s ?!

Lux is a unit adapted vor human vision not for wider spectral band

LcurveQuantum Efficiency

0

10

20

30

40

50

60

70

80

350 450 550 650 750 850 950 1050

Wavelength [nm]Q

uant

um E

ficie

ncy

[%]

QE-SensorIllumination

= 0 Lux!!

= ?

max

min

max

min

d,

d,683

.

.

0

TEL

TE

TL

rel

rel


The EMVA 1288 Working Group (logos status 2007)

The EMVA 1288 Working group is open! Contact [email protected]


Current status

o Standard Release 2.0 Covers Sensitivity Spatial and Temporal Noise;

LinearityAdapted by many companies in Europe and World wide

for internal use and on customer request.Published data on www.standard1288.org from

• AWAIBA• BASLER• PCO

Supported world wide by agreement between JIIA, AIA & EMVA on G3 standardization frame work


o Illumination Setup from Module 1Homogenous illuminationWithout lensF-number 8Definition of temperature

measurements

temperature sensor

Standard requirements

Standard 1288 Module 11) Measurement Setup


Integrating sphere

Illuminator < 50nm FWHM

Integrating sphere

LED ArrayCollimator Diffusor

Tint

DN

Module 1 measurement

Possible realizations of set up


Outlook measurement setup variation for Color module

Integrating sphere

Illuminator

Integrating sphere

Recommended Setup:(Preliminary)

Diffuser

<10nm FWHM


Camera

Mathematical ModelParameters

ParameterIdentification

Standard 1288 Module 12) Mathematical Model

! The standard will only produce sense full results for cameras / sensors that follow the mathematical model !

Current module covers only linear integrating sensors

More sensor types to follow


Standard 1288 Module 13) Basic Information

This section delivers general information and information regarding the operation point at which data is acquired.

o Vendor name o Model nameo Type of data presented: Typical; Guaranteed; Guaranteed over life time[1]o Sensor type (CCD; CMOS; CID etc...)o Sensor diagonal in [mm]; Indication of lens category to be used [inch]o Resolution; Pixel size (width x height in [µm])o Readout type (CCD only) ; Transfer type (CCD only); o Shutter type (CMOS only); Global; Rolling o Overlap capabilities; (readout of frame n and exposure of frame n+1 can

happen at the same time). o Maximum frame rate at the given operation point. (no change of settings

permitted) o Others (Interface Type etc..)


EXAMPLE DR-4k-7AVAILABLE under www.awaiba.com/en/products

Vendor Name AWAIBA Lda

Model Name DR-4k-7

Sensor Type CMOS Digital Line Scan Sensor

Sensor diagonal in mm 28.67mm

Indication lens category (inch) --

Resolution ( width x height) 4096 x 1

Pixel size 7um x 7um

Readout type 4 Tap 40MHz 12bit parallel

Shutter type ( Rolling/ Global) Global Shutter

Overlap capabilities (Integration overlaps Readout) Interleaved integration & Readout

Maximum frame rate at given operation point 9765 lines / second (40k lines / sec @ maximum operation point)

Type of presented data (typical /guaranteed/ guaranteed over live time)

typical

Definition of "typical" (number of samples etc..) 1 random sample

Other relevant information (interface type etc...) 12 bit digital parallel

Photodiode type (see QE plot) Standard diode


Standard 1288 Module 14) Operation Point

o This section describes exactly in what configuration the camera / Sensor is operated. I.e. all gain & register settings and environmental conditions.

o Unless for the scans of the integration time, the camera / sensor has to be in the same operation point for all EMVA1288 measurements.


EXAMPLE DR-4k7AVAILABLE under www.awaiba.com/en/products

Main Clock Frequency 40MHz

Line Period 205 us

ADC End Range Register 0x84

Illumination Wavelength 625nm

On chip ADC offset subtraction Enabled

Config. Register 1 00100001

Config. Register 2 00110000

ADC Gain 0x20h


Standard 1288 Module 15) Measurement Scans

Acquire 2 series of images with increasing Exposure time. One series in dark, one with a constant illumination. Compute the mean value of The images, report the mean versus the integration time and the number of photons Collected in each pixel.

From 2 images at the same integration time, compute the square difference image. The mean of the squared difference image is the Variance. Report the variance for the series in dark and for the series with light versus integration time and number of photons. Saturation exposure is defined as the exposure where the variance is maximal

[p~]

[DN]

[s]

[p~]

[DN2]

[s]

Saturation



Photoresponse Plot

0.00E+000

5.00E+002

1.00E+003

1.50E+003

2.00E+003

2.50E+003

3.00E+003

3.50E+003

4.00E+003

4.50E+003

0.00E+000 5.00E+004 1.00E+005

Nbr Photons

DN

[12

b]

0.00E+000 5.00E-005 1.00E-004 1.50E-004

Integration Time [s]

Variance Plot

0.00E+000

5.00E+001

1.00E+002

1.50E+002

2.00E+002

2.50E+002

3.00E+002

3.50E+002

4.00E+002

4.50E+002

0.00E+000 5.00E+004 1.00E+005

Nbr Photons

Var

ain

ce

[DN

² / 1

2b

it]

0.00E+000 5.00E-005 1.00E-004 1.50E-004

Integration Time [s]


Standard 1288 Module 16) Photon Transfer Method

oSubtract the mean dark values from the mean values with illumination.oSubtract the dark variance values form the bright variance values.oReport the dark corrected variance versus the dark corrected mean values. oFit a line going through the origin through the data points until saturationoThe slope of this line gives the conversion gain in DN/e- or K

[DN2]

[DN]

Used data for fit

Saturation



Photon Transfer Plot

0

50

100

150

200

250

300

350

400

450

0.00E+000 1.00E+003 2.00E+003 3.00E+003 4.00E+003

Dark corr Signal [DN]

Var

ain

ce [

DN

² /

12b

it]

Dark corr Variance

Linear Fit


Standard 1288 Module 17) Derived Quantities

Quantity Value : Total quantum efficiency in [%] at measurement wavelength

0d : Standard deviation of the temporal dark noise referenced to electrons for exposure time zero in [e-].

30dN : Dark current for a housing temperature of 30°C in [e-/s].

K

1 : Inverse of overall system gain in [e-/DN].

sate. : Saturation capacity referenced to electrons in [e-]. min.p : Absolute sensitivity threshold in [p~] at the measurement

wavelength

pySNR : Signal to noise ratio at saturation

outin DYNDYN : Dynamic range in [1] DSNU1288 PRNU1288 o : Standard deviation of the spatial offset noise referenced to

electrons in [e-]

gS : Standard deviation of the spatial gain noise in [%].



Parameter Value

Conversion Gain [DN/e-] 0.0886

QE* 49.58%

Saturation capacity [e-] 47’737

Responsivity [DN/nJ/cm2]** 67.9

Temporal dark noise [DN] 1.1

Temporal dark noise [e-] 12.9

Absolute sensitivity threshold [p/pix] 26

SNR emva1288 193

SNR emva1288[dB] 46

DYN (standard SNR) 1972

DYN [dB] (standard SNR in dB) 65.9

DSNU 1288 [e-] 13.4

DSNU [DN] (standard deviation of mean dark image) 1.4

PRNU 1288 1.9%

Dark Current 30C [e-/ms] 3

Dark current doubling temperature [C] 11.5


Standard 1288 Module 18) SNR Plot

oPlot the SNR values resulting from each integration time versus the number of photons impinging on a pixel during this integration time.oUse Logarithmic scale (dB or bit (base log2)oPlot values from lowest chosen integration time til saturation.

[SNR]

[Nbr Photons]

Saturation

Shot noise limited

Readnoise limited

Theoretical limit



DYN = 66dB

Theoretical limitof SNR based onphoton shot noiseOf incoming signal

Maximum SNR

SNR EMVA1288 DR-4k-7

1

10

100

100 1´000 10´000 100´000

Photons/pixel

SN

R [

dB

]


Standard 1288 Module 19) Quantum Efficiency Plot

oFrom the conversion gain and the light intensity used during exposure compute the total QE. oReport the QE versus measurement wavelengths.

oNote for EMVA1288 data given per unit: When clearly stated this measurement can be based on typical data even for production data, however the curve should be scaled to the QE measured at the specific measurement wavelength of sample.

QE [ % e-/ph]

Wavelength [nm]



Total QE DR-4k-7 Lot P21676.2

0%

10%

20%

30%

40%

50%

60%

70%

375 425 475 525 575 625 675 725 775 825 875 925

Wavelength[nm]

QE

[%

]


Standard 1288 Module 110) Dark Current

oAcquire series of dark images versus increasing integration times at different housing temperatures. (Measurement not applicable for cooled cameras)oReport the increased signal values versus integration time.oReport the increase of variance versus integration time.

oSubtract from each series the mean signal value and the variance value of the shortest integration time from each measurements point.oFrom the increase in variance compute the dark current in [e-/s] and the dark current doubling temperature [K]

Image mean[DN]

[s]

T1

T2

T3 Variance[DN2]

[s]

T1

T2

T3



Idark DR-4k-7 C log

1

10

100

300,00 310,00 320,00 330,00 340,00 350,00 360,00 370,00 380,00

T [K]

Ida

rk [e

-/m

s]

Dark current doubling temperature 11.2K

Dark current at ambient 3e-/ms


Standard 1288 Module 111) Spectrogram

oFrom each row compute the DFFToAverage the FFT values along each column of the FFT result matrixoPlot the resulting spectrogram for Dark; 50% Saturation; 90% Saturation

Idea: describe DSNU & PRNU effects in from of a spectral amplitude plot toShow high frequency (E.g. odd even mismatch) and low frequency (E.g. over all gradients) parts of spatial and temporal noise separately

DFFT


Standard 1288 Module 112) Interpretation of Spectrogram

Interpretation:

0 1/2 N columns

Low frequencygradients

Zero orderset 0 by Offsetsubtraction

¼ column mismatch

Odd even mismatch



DR-4k-7 Spectrogram Total noise(Spatial & temporal noise)

0

10

20

30

40

50

60

70

80

90

100

0 512 1024 1536 2048

AmplitudeDark [DN]

Amplitude50% Sat[DN]Amplitude90% [DN]


User Benefit 1288 Compare different Settings Objectively

Physical shot noise limit

DR-4k-7 gain x4DR-4k-7 gain x1 Dgain1 & Dgain x4

Analogue CMOS

CCD 2

CCD 1


Optimize performance based on real values rather than visual impression!Raw sample image DR-4k-7 at previously described operation point

SPECIMEN


Thank you for your attention

In God we trust, all other we measure

o Current standard draftwww.emva.org or www.standard1288.org

Contact EMVA:

[email protected]

Contact me:

[email protected]

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