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EMVA Standard 1288
Standard for Characterization of Image
Sensors and Cameras
Release 3.0
November 29, 2010
Issued by
European Machine Vision Association
www.emva.org
Contents
1 Introduction and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Sensitivity, Linearity, and Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Linear Signal Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Noise Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Signal-to-Noise Ratio (SNR) . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Signal Saturation and Absolute Sensitivity Threshold . . . . . . . . . . . . 7
3 Dark Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1 Mean and Variance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Temperature Dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4 Spatial Nonuniformity and Defect Pixels . . . . . . . . . . . . . . . . . . . . . . 8
4.1 Spatial Variances, DSNU, and PRNU . . . . . . . . . . . . . . . . . . . . . 9
4.2 Types of Nonuniformities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Defect Pixels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3.1 Logarithmic Histograms. . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3.2 Accumulated Histograms. . . . . . . . . . . . . . . . . . . . . . . . . 11
4.4 Highpass Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5 Overview Measurement Setup and Methods . . . . . . . . . . . . . . . . . . . . 12
6 Methods for Sensitivity, Linearity, and Noise . . . . . . . . . . . . . . . . . . . . 12
6.1 Geometry of Homogeneous Light Source . . . . . . . . . . . . . . . . . . . . 12
6.2 Spectral Properties of Light Source . . . . . . . . . . . . . . . . . . . . . . . 13
6.3 Variation of Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.4 Calibration of Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.5 Measurement Conditions for Linearity and Sensitivity . . . . . . . . . . . . 15
6.6 Evaluation of the Measurements according to the Photon Transfer Method 15
Standard for Characterization
of Image Sensors and Cameras
Release 3.0, Nov. 29, 2010
6.7 Evaluation of Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7 Methods for Dark Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1 Evaluation of Dark Current at One Temperature . . . . . . . . . . . . . . . 19
7.2 Evaluation of Dark Current with Temperatures . . . . . . . . . . . . . . . . 19
8 Methods for Spatial Nonuniformity and Defect Pixels . . . . . . . . . . . . . . . 21
8.1 Spatial Standard Deviation, DSNU, PRNU . . . . . . . . . . . . . . . . . . 21
8.2 Horizontal and Vertical Spectrograms . . . . . . . . . . . . . . . . . . . . . 24
8.3 Defect Pixel Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9 Methods for Spectral Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.1 Spectral Light Source Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.2 Measuring Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.4 Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10 Publishing the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.1 Basic Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.2 The EMVA 1288 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.3 The EMVA 1288 Datasheet . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.4 Template Datasheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
A Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
B Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
C Changes to Release A2.01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
C.1 Added Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
C.2 Extension of Methods to Vary Irradiation . . . . . . . . . . . . . . . . . . . 33
C.3 Modifications in Conditions and Procedures . . . . . . . . . . . . . . . . . . 33
C.4 Limit for Minimal Temporal Standard Deviation; Introduction of Quantiza-
tion Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
C.5 Highpass Filtering with Nonuniformity Measurements . . . . . . . . . . . . 35
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c
Copyright EMVA, 2010
Standard for Characterization
of Image Sensors and Cameras
Release 3.0, Nov. 29, 2010
Acknowledgements
Please refer to www.standard1288.org for the list of contributors to the Standard.
EMVA 1288 is an initiative driven by the industry and living from the personal initiative
of the supporting companies and institutions delegates as well as from the support of these
organizations. Thanks to this generosity the presented document can be provided free of
charge to the users of this standard. EMVA thanks those contributors in the name of the
whole vision community.
Rights and Trademarks
The European Machine Vision Association owns the ”EMVA, standard 1288 compliant” logo.
Any company can obtain a license to use the ”EMVA standard 1288 compliant” logo, free
of charge, with product specifications measured and presented according to the definitions
in EMVA standard 1288. The licensee guarantees that he meets the terms of use in the
relevant release of EMVA standard 1288. Licensed users will self-certify compliance of their
measurement setup, computation and representation with which the ”EMVA standard 1288
compliant” logo is used. The licensee has to check regularly compliance with the relevant
release of EMVA standard 1288, at least once a year. When displayed on line the logo has
to be featured with a link to EMVA standardization web page. EMVA will not be liable
for specifications not compliant with the standard and damage resulting there from. EMVA
keeps the right to withdraw the granted license any time and without giving reasons.
About this Standard
EMVA has started the initiative to define a unified method to measure, compute and present
specification parameters and characterization data for cameras and image sensors used for
machine vision applications. The standard does not define what nature of data should be
disclosed. It is up to the component manufacturer to decide if he wishes to publish typical
data, data of an individual component, guaranteed data, or even guaranteed performance
over life time of the component. However the component manufacturer shall clearly indicate
what the nature of the presented data is. The standard is organized in different sections,
each addressing a group of specification parameters, assuming a certain physical behavior
of the sensor or camera under certain boundary conditions. Additional sections covering
more parameters and a wider range of sensor and camera products will be added succes-
sively. There are compulsory sections, of which all measurements must be made and of
which all required data and graphics must be included in a datasheet using the EMVA1288
logo. Further there are optional sections which may be skipped for a component where the
respective data is not relevant or the mathematical model is not applicable. Each datasheet
shall clearly indicate which sections of the EMVA1288 standard are enclosed.
It may be necessary for the manufacturer to indicate additional, component specific
information, not defined in the standard, to fully describe the performance of image sensor
or camera products, or to describe physical behavior not covered by the mathematical models
of the standard. It is possible in accordance with the EMVA1288 standard to include such
data in the same datasheet. However the data obtained by procedures not described in the
current release of the EMVA1288 standard must be clearly designated and grouped in a
separate section. It is not permitted to use parameter designations defined in any of the
EMVA1288 modules for such additional information not acquired or presented according
the EMVA1288 procedures.
The standard is intended to provide a concise definition and clear description of the
measurement process and to benefit the Automated Vision Industry by providing fast, com-
prehensive and consistent access to specification information for cameras and sensors. It will
be particularly beneficial for those who wish to compare cameras or who wish to calculate
system performance based on the performance specifications of an image sensor or a camera.
c
Copyright EMVA, 2010 3 of 36
Standard for Characterization
of Image Sensors and Cameras
Release 3.0, Nov. 29, 2010
1 Introduction and Scope
This release of the standard covers monochrome and color digital cameras with linear photo
response characteristics. It is valid for area scan and line scan cameras. Analog cameras
can be described according to this standard in conjunction with a frame grabber; similarly,
image sensors can be described as part of a camera. If not specified otherwise, the term
camera is used for all these items.
The standard text is parted into four sections describing the mathematical model and
parameters that characterize cameras and sensors with respect to
• Section 2: linearity, sensitivity, and noise for monochrome and color cameras,
• Section 3: dark current,
• Section 4: sensor array nonuniformities and defect pixels characterization,
a section with an overview of the required measuring setup (Section 5), and five sections
that detail the requirements for the measuring setup and the evaluation methods for
• Section 6: linearity, sensitivity, and noise,
• Section 7: dark current,
• Section 8: sensor array nonuniformities and defect pixels characterization,
• Section 9: spectral sensitivity,
The detailed setup is not regulated in order not to hinder progress and the ingenuity of
the implementers. It is, however, mandatory that the measuring setups meet the properties
specified by the standard. Section 10 finally describes how to produce the EMVA 1288
datasheets. Appendix B describes the notation and Appendix C details the changes to
release 2
It is important to note that the standard can only be applied if the camera under test can
actually be described by the mathematical model on which the standard is based. If these
conditions are not fulfilled, the computed parameters are meaningless with respect to the
camera under test and thus the standard cannot be applied. Currently, electron multiplying
cameras (EM CCD, [1, 2]) and cameras that are sensitive in the deep ultraviolet, where more
than one electron per absorbed photon is generated [5], are not covered by the standard.
The general assumptions include
1. The amount of photons collected by a pixel depends on the product of irradiance E
(units W/m
2
) and exposure time t
exp
(units s), i. e., the radiative energy density Et
exp
at the sensor plane.
2. The sensor is linear, i. e., the digital signal y increases linear with the number of photons
received.
3. All noise sources are wide-sense stationary and white with respect to time and space.
The parameters describing the noise are invariant with respect to time and space.
4. Only the total quantum efficiency is wavelength dependent. The effects caused by light
of different wavelengths can be linearly superimposed.
5. Only the dark current is temperature dependent.
These assumptions describe the properties of an ideal camera or sensor. A real sensor will
depart more or less from an ideal sensor. As long as the deviation is small, the description is
still valid and it is one of the tasks of the standard to describe the degree of deviation from
an ideal behavior. However, if the deviation is too large, the parameters derived may be too
uncertain or may even render meaningless. Then the camera cannot be characterized using
this standard. The standard can also not be used for cameras that clearly deviate from one
of these assumptions. For example, a camera with a logarithmic instead of a linear response
curve cannot be described with the present release of the standard.
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Copyright EMVA, 2010
Standard for Characterization
of Image Sensors and Cameras
Release 3.0, Nov. 29, 2010
a
42
A number of
photons
...
... hitting the
pixel area
during exposure time ...
... creating a number of
electrons
...
... forming a
charge
which is converted
by a
capacitor
to a
voltage
...
... being
amplified
...
... and
digitized
...
... resulting in the
digital gray value
.
b
p
e
K
y
η
n
n
d
n
quantum
efficiency
system
gain
number of
photons
number of
electrons
digital
grey value
dark noise
quantization noise
q
σ
Figure 1: a Physical model of the camera and b Mathematical model of a single pixel.
2 Sensitivity, Linearity, and Noise
This section describes how to characterize the sensitivity, linearity, and temporal noise of
an image sensor or camera [3, 4, 6, 8].
2.1 Linear Signal Model
As illustrated in Fig. 1, a digital image sensor essentially converts photons hitting the pixel
area during the exposure time by a sequence of steps finally into a digital number. During
the exposure time on average µ
p
photons hit the whole area A of a single pixel. A fraction
η(λ) =
µ
e
µ
p
(1)
of them, the total quantum efficiency, is absorbed and accumulates µ
e
charge units.
1
The
total quantum efficiency as defined here refers to the total area occupied by a single sensor
elementpixel not only the light sensitive area. Consequently, this definition includes the
effects of fill factor and microlenses. As expressed in Eq. (1), the quantum efficiency depends
on the wavelength of the photons irradiating the pixel.
The mean number of photons that hit a pixel with the area A during the exposure time
t
exp
can be computed from the irradiance E on the sensor surface in W/m
2
by
µ
p
=
AEt
exp
hν
=
AEt
exp
hc/λ
, (2)
using the well-known quantization of the energy of electromagnetic radiation in units of
hν. With the values for the speed of light c = 2.99792458 · 10
8
m/s and Planck’s constant
h = 6.6260755 · 10
−34
Js, the photon irradiance is given by
µ
p
[photons] = 5.034 · 10
24
· A[m
2
] · t
exp
[s] · λ[m] · E
W
m
2
, (3)
or in more handy units for image sensors
µ
p
[photons] = 50.34 · A[µm
2
] · t
exp
[ms] · λ[µm] · E
µW
cm
2
. (4)
These equations are used to convert the irradiance calibrated by radiometers in units of
W/cm
2
into photon fluxes required to characterize imaging sensors.
1
The actual mechanism is different for CMOS sensors, however, the mathematical model for CMOS is
the same as for CCD sensors
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Copyright EMVA, 2010 5 of 36
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