ISO 18221:2016

INTERNATIONAL ISO
STANDARD 18221
First edition
2016-07-01
Microscopes — Microscopes
with digital imaging displays —
Information provided to the user
regarding imaging performance
Microscopes — Microscopes avec écrans d’affichage numérique —
Informations fournies à l’utilisateur concernant la performance
d’affichage
Reference number
ISO 18221:2016(E)
©
ISO 2016

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ISO 18221:2016(E)

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© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

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ISO 18221:2016(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Magnification . 3
5.1 Optical magnification, M .
TOT PROJ 3
5.2 Display magnification, M .
DIS 3
5.3 Visual display magnification, M .
DIS VIS 3
6 Resolving power limit. 3
6.1 Optical resolving power limit, RL .
OPT 3
6.2 Sensor resolving power limit, RL .
SEN 4
6.3 Display resolving power limit, RL .
DIS 4
6.4 System resolving power limit, RL .
SYS 4
7 Useful range of magnification . 5
7.1 Useful range of viewing distance . 5
7.2 Useful range of visual magnification . 5
7.3 Empty magnification . 6
8 Object field . 6
8.1 Object field limited by the sensor . 6
8.2 Object field limited by the display . 6
8.3 Object field of the microscopy system . 7
9 Depth of field . 7
10 Information to be provided to the user by manufacturers . 8
10.1 General information . 8
10.2 Imaging performance data . 8
Annex A (informative) Examples for information to be provided to the user .9
Bibliography .13
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ISO 18221:2016(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 172, Optics and photonics, Subcommittee SC 5,
Microscopes and endoscopes.
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INTERNATIONAL STANDARD ISO 18221:2016(E)
Microscopes — Microscopes with digital imaging displays
— Information provided to the user regarding imaging
performance
1 Scope
This International Standard specifies the minimum information to be provided to the user by the
manufacturers of microscopes with digital displays regarding imaging performance.
It further specifies terms and definitions for describing the optical performance of the digital imaging
path of microscopy systems including the observation of the image on digital displays.
NOTE Terms and definitions for the direct visual observation with eyepieces are specified in ISO 8039 and
ISO 10934-1.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 10934-1, Optics and optical instruments — Vocabulary for microscopy — Part 1: Light microscopy
ISO 10934-2, Optics and optical instruments — Vocabulary for microscopy — Part 2: Advanced techniques
in light microscopy
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 10934-1, ISO 10934-2 and the
following apply.
NOTE Terms shown in italics within a definition or a note are defined elsewhere within this International
Standard or in ISO 10934.
3.1
digital microscopy system
instrument consisting of an objective, an image sensor (3.2) and a digital display (3.3) to make visible
minute details that are not seen with unaided eye
Note 1 to entry: The system might include means for image enhancement, image analysis, archiving, etc.
3.2
image sensor
device to transform an optical image into a digital image
3.3
digital display
output device for the visual presentation of a digital image and other information
3.4
resolving power limit
maximum spatial frequency distinguishable in object space, expressed in lp/mm
Note 1 to entry: The resolving power actually achieved will always be lower than the resolving power limit due to
reduced contrast, moiré patterns, etc. In addition, it depends on sensor type, object structure, illumination, etc.
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ISO 18221:2016(E)

3.5
pixel pitch
distance between the centres of adjacent pixels (picture elements) in an image sensor (3.2) or a digital
display (3.3)
3.6
line pair
one line and one space between the lines of a spatial grid with equal line thickness and space width
between lines
3.7
viewing distance
distance between the digital display (3.3) and the observer’s eye
4 Symbols and abbreviated terms
c coefficient related to the operation mode of the image sensor
1
d depth of field for observation of the image presented on the digital display
AX SYS
d actual viewing distance
VIEW
d useful range of viewing distance
VIEW USEF
h height of the object field limited by the image area in the display
LIM DIS
h height of the object field limited by the sensor
LIM SEN
h height of the object field of the microscopy system
SYS
λ wavelength
M display lateral magnification
DIS
M visual display magnification
DIS VIS
M useful range of the perceived visual display magnification
DIS VIS USEF
M lateral magnification at the image projected onto the sensor
TOT PROJ
M total visual magnification of the virtual microscope image formed by the eyepiece
TOT VIS
NA numerical aperture
N number of image pixels in the display in x-direction
x DIS
N number of active sensor pixels in x-direction
x SEN
N number of image pixels in the display in y-direction
y DIS
N number of active sensor pixels in y-direction
y SEN
n refractive index of the object or of the immersion media
pp pixel pitch of the digital display
DIS
pp pixel pitch of the image sensor
SEN
RL display resolving power limit in object space
DIS
RL optical resolving power limit in object space
OPT
RL sensor resolving power limit in object space
SEN
RL system resolving power limit in object space
SYS
w width of the object field limited by the image area in the display
LIM DIS
w width of the object field limited by the sensor
LIM SEN
w width of the object field of the microscopy system
SYS
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ISO 18221:2016(E)

5 Magnification
5.1 Optical magnification, M
TOT PROJ
M is the lateral magnification at the image projected onto the image sensor. It should be
TOT PROJ
expressed in proportional form, e.g. 10:1.
5.2 Display magnification, M
DIS
M is the lateral magnification at the digital image presented on the digital display or monitor. It
DIS
should be expressed in proportional form, e.g. 100:1.
NOTE The display magnification, M , is the ratio of a given distance in the image presented on the monitor
DIS
to the corresponding distance in the object.
5.3 Visual display magnification, M
DIS VIS
M is the display lateral magnification by observing the digital image presented on the digital
DIS VIS
display. It should be expressed in numerical form with the multiplication sign, e.g. 50×.
The visual display magnification is given by:
M ⋅250
DIS
M = (1)
DISVIS
d
VIEW
where
M is the visual display magnification;
DIS VIS
M is the display lateral magnification;
DIS
250 is the reference viewing distance in mm;
d is the actual viewing distance in mm.
VIEW
NOTE The value of M is comparable with the value of M of light microscopes with eyepieces.
DIS VIS TOT VIS
6 Resolving power limit
6.1 Optical resolving power limit, RL
OPT
RL is the lateral resolving power limit in object space that is limited by the optical system. It should
OPT
be expressed in line pairs per millimetre, e.g. 200 lp/mm. It is given by:
6
21⋅⋅NA 0
RL = (2)
OPT
λ
where
RL is the optical resolving power limit in object space in line pairs per millimetre;
OPT
NA is the effective numerical aperture at object side of the optical system projecting the
image onto the sensor;
λ is the wavelength in nm.
NOTE 1 The formula for RL does not apply for super-resolution.
OPT
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ISO 18221:2016(E)

NOTE 2 In consideration of consistency with the definition of resolving limit of electric equipment, the optical
resolving limit defined in this International Standard is based on the cut-off frequency of an optical system.
6.2 Sensor resolving power limit, RL
SEN
RL is the lateral resolving power limit in object space that is limited by the image sensor. It should be
SEN
expressed in line pairs per millimetre, e.g. 100 lp/mm. It is given by:
500⋅M
TOT PROJ
RL = (3)
SEN
cp⋅ p
1 SEN
where
RL is the sensor resolving power limit in object space in line pairs per millimetre;
SEN
M is the lateral magnification at the image projected onto the sensor;
TOT PROJ
c is a coefficient related to the operation mode of the image sensor;
1
pp is the pixel pitch of the image sensor in μm.
SEN
EXAMPLES for c
1
1 corresponds to a standard or full frame mode;
2 corresponds to a 2 × 2 binning mode;
3 corresponds to a 3 × 3 binning mode;
0,5 corresponds to a pixel shift mode with a lateral movement of the image sensor of 0,5 pp .
SEN
6.3 Display resolving power limit, RL
DIS
RL is the lateral resolving power limit in object space that is limited by the digital display. It should
DIS
be expressed in line pairs per millimetre, e.g. 50 lp/mm. It is given by:
M
DIS
RL = (4)
DIS
2⋅pp
DIS
where
RL is the display resolving power limit in object space in line pairs per millimetre;
DIS
M is the display lateral magnification;
DIS
pp is the pixel pitch of the digital display in mm.
DIS
6.4 System resolving power limit, RL
SYS
RL is the lateral resolving power limit in object space of the microscopy system. It should be
SYS
expressed in line pairs per millimetre, e.g. 50 lp/mm. Its value corresponds to the smallest value of
either the optical resolving power limit or the sensor resolving power limit
...