SIST EN ISO 14880-2:2025

SLOVENSKI STANDARD
01-januar-2025
Nadomešča:
SIST EN ISO 14880-2:2007
Optika in fotonska tehnologija - Vrste mikroleč - 2. del: Preskusne metode za
ugotavljanje odstopanja valovne fronte (ISO 14880-2:2024)
Optics and photonics - Microlens arrays - Part 2: Test methods for wavefront aberrations
(ISO 14880-2:2024)
Optik und Photonik - Mikrolinsenarrays - Teil 2: Prüfverfahren für
Wellenfrontaberrationen (ISO 14880-2:2024)
Optique et photonique - Réseaux de microlentilles - Partie 2: Méthodes d'essai pour les
aberrations du front d'onde (ISO 14880-2:2024)
Ta slovenski standard je istoveten z: EN ISO 14880-2:2024
ICS:
31.260 Optoelektronika, laserska Optoelectronics. Laser
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 14880-2
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2024
EUROPÄISCHE NORM
ICS 31.260 Supersedes EN ISO 14880-2:2006
English Version
Optics and photonics - Microlens arrays - Part 2: Test
methods for wavefront aberrations (ISO 14880-2:2024)
Optique et photonique - Réseaux de microlentilles - Optik und Photonik-Mikrolinsenarrays-Teil
Partie 2: Méthodes d'essai pour les aberrations du 2:Prüfverfahren für Wellenfrontaberrationen (ISO
front d'onde (ISO 14880-2:2024) 14880-2:2024)
This European Standard was approved by CEN on 23 November 2024.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14880-2:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 14880-2:2024) has been prepared by Technical Committee ISO/TC 172 “Optics
and photonics” in collaboration with Technical Committee CEN/TC 123 “Lasers and photonics” the
secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2025, and conflicting national standards shall be
withdrawn at the latest by May 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 14880-2:2006.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 14880-2:2024 has been approved by CEN as EN ISO 14880-2:2024 without any
modification.
International
Standard
ISO 14880-2
Second edition
Optics and photonics — Microlens
2024-11
arrays —
Part 2:
Test methods for wavefront
aberrations
Optique et photonique — Réseaux de microlentilles —
Partie 2: Méthodes d'essai pour les aberrations du front d'onde
Reference number
ISO 14880-2:2024(en) © ISO 2024

ISO 14880-2:2024(en)
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 14880-2:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions .1
3.2 Symbols and abbreviated terms .1
4 Apparatus . 2
5 Test principle . 3
6 Measurement arrangements . 3
6.1 Measurement arrangement for single microlenses .3
6.2 Measurement arrangements for microlens arrays .3
6.3 Geometrical alignment of the sample .4
6.4 Preparation .4
7 Procedure . 4
8 Evaluation . 4
9 Uncertainty of measurement . 4
10 Test report . 5
Annex A (informative) Measurement requirements for test methods for microlenses . 6
Annex B (informative) Microlens test Methods 1 and 2 using Mach-Zehnder interferometer
systems . 8
Annex C (informative) Microlens test Methods 3 and 4 using a lateral shearing interferometer
system. 14
Annex D (informative) Microlens test Method 5 using a Shack-Hartmann sensor system .18
Annex E (informative) Microlens array test Method 1 using a Twyman-Green interferometer
system.20
Annex F (informative) Measurement of uniformity of microlens array using test Method 2 .22
Bibliography .25

iii
ISO 14880-2:2024(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 172, Optics and Photonics, Subcommittee SC 9,
Laser and electro-optical systems, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 123, Lasers and photonics, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 14880-2:2006), which has been technically
revised.
The main changes are as follows:
— text for Annex E was revised;
— Figure E.1 was replaced;
— references and numbering confirmed.
A list of all parts in the ISO 14880 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 14880-2:2024(en)
Introduction
Examples of applications of microlens arrays include three-dimensional displays, coupling optics associated
with arrayed optical radiation sources and photo-detectors, enhanced optics for liquid crystal displays, and
optical parallel processor elements.
The market in microlens arrays has generated a need for agreement on basic terminology and test methods
for defining microlens arrays. Standard terminology and clear definitions are needed not only to promote
applications but also to encourage scientists and engineers to exchange ideas and new concepts based on
common understanding.
Microlenses are used as single lenses and also in arrays of two or more lenses. The characteristics of the
lenses are fundamentally evaluated with a single lens. Therefore, it is important that the basic characteristic
of a single lens can be evaluated. However, if a large number of lenses is formed on a single substrate, the
measurement of the whole array will incur a lot of time and cost. Furthermore, methods for measuring lens
shapes are essential as a production tool.
Characteristic parameters are defined and examples of applications given in ISO 14880-1. It has been
completed by a set of three other International Standards, i.e. ISO 14880-2, ISO 14880-3 and ISO 14880-4.
This document specifies methods for measuring wavefront quality. Wavefront quality is the basic
performance characteristic of a microlens. Characteristics other than wavefront aberrations are specified in
ISO 14880-3, ISO 14880-4 .
ISO/TR 14880-5 guides the user in selecting the appropriate measurement method from the ISO 14880
series of standards.
v
International Standard ISO 14880-2:2024(en)
Optics and photonics — Microlens arrays —
Part 2:
Test methods for wavefront aberrations
1 Scope
This document specifies methods for testing wavefront aberrations for microlenses within microlens arrays.
It is applicable to microlens arrays with very small lenses formed inside or on one or more surfaces of a
common substrate.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 14880-1, Optics and photonics — Microlens arrays — Part 1: Vocabulary
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14880-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.2 Symbols and abbreviated terms
Table 1 lists associated symbols, abbreviated terms and units of measurement used in this document.
Table 1 — Symbols, abbreviated terms and units of measure
Symbol Unit Term
Φ µm wavefront aberration
Φ µm peak-to-valley value of wavefront aberration
P-V
Φ µm root-mean-square value of wavefront aberration
rms
λ µm wavelength
Θ degree (°) acceptance angle
NA none numerical aperture
NOTE The wavefront aberration, peak-to-valley values of wavefront aberration and root-mean-square values
of wavefront aberration are often expressed in units of ”λ” based on the results of interferometer measurements.
Wavefront aberration is expressed in multiples of ”λ” (wavelength (μm)) of the laser light source used in the
interferometer.
ISO 14880-2:2024(en)
4 Apparatus
The test system consists of a source of optical radiation, a collimator lens, a method of limiting the
measurement aperture, a sample holding apparatus, imaging optics, an image sensor and a system for
[4][5][7][8][12][15][25]
analysing interference patterns .
4.1 Standard optical radiation source.
A source of optical radiation shall be used, which is suitable for the testing of wavefront aberrations of
microlenses. The aberrations of the wavefront incident on the test equipment shall have a rms deviation less
than or equal to λ/20, at the wavelength of operation, over an area corresponding to the effective aperture
of the microlens to be tested. For information on calculating rms values refer to ISO 14999-4:2015, 3.1.3.
Properties of the source to be specified include centre wavelength, half-width of the spectrum, the type
of optical radiation source, states of polarization (randomly polarized optical radiation, linearly polarized
optical radiation, circularly polarized optical radiation, etc.), radiance angle (in mrad), spot size or beam
waist parameters. Otherwise, the specification of the radiation source shall be described in the test report.
[11]
ISO 12005 deals with a method for determining the polarization state of a laser beam .
NOTE 1 He-Ne gas lasers are sometimes used. Other gas lasers, solid-state lasers, semiconductor lasers (LD), and
light emitting diodes (LED) are also used.
NOTE 2 LDs and LEDs are used with beam-shaping optics where necessary.
4.2 Standard lens (reference lens).
Where a standard lens is used as a reference or for generating an ideal spherical wave, the wavefront
aberrations of the standard lens shall be smaller by at least one order of magnitude compared to that of the
lens to be tested or shall be less than λ/20 rms deviation.
The objective lens of an optical microscope used as the standard lens shall be specified with the effective
numerical aperture. The following shall be given:
— effective aperture;
— focal length at the wavelength of operation.
The test geometry for the measurement of wavefront aberrations is restricted to the case with lens
conjugates ∞/f.
4.3 Collimator.
The collimator optics shall have a numerical aperture greater than the maximum numerical aperture of
the test sample sufficient to avoid effects due to diffraction. The wavefront aberrations should be less
than the Maréchal criterion value and/or the Strehl definition value (both λ/14: 0,07λ rms). It is however
recommended that they are less than λ/20 at the operational wavelength.
Otherwise the specification used should be described in the test report.
4.4 Beam reduction optical system.
A telescopic system consisting of two positive lenses in an afocal arrangement is used to adapt the beam
cross-section to the array detector. The ratio of the focal lengths gives the reduction factor. It is recommended
that the wavefront aberrations are less than λ/20 at the operational wavelength.
NOTE The diameter of the lens area to be evaluated can be selected with an effective aperture defined by software
to avoid additional diffraction at a physical aperture.

ISO 14880-2:2024(en)
4.5 Aperture stop.
A physical stop is placed in the optical radiation beam of the test equipment to limit the diameter of the
optical radiation beam incident on the lens to be tested. Alternatively, the stop may be defined by truncation
software during evaluation.
5 Test principle
The wavefront aberrations of the test microlens shall be determined with an interferometer or another
wavefront test device as described in the Annexes. When small-diameter Gaussian beams are used, care
should be taken because geometrical optical theory does not apply to the propagation of such beams. The
detector surface shall be conjugate with the entrance or exit pupil of the test microlens. An aperture is used
[13][14][16][17][18]
to analyse the data for the wave aberrations .
The test method shall be chosen to suit the application. Single-pass applications require testing using single-
[13]
pass interferometers .
NOTE Interferometers often use laser sources for the interferometric test. Dielectric boundaries between
lenses contribute to unwanted reflections, stray light and spurious fringe patterns. This can cause severe problems
if a double-pass arrangement using reflected optical radiation is chosen, such as when Fizeau or Twyman-Green
interferometers are used.
Arrangements using transmitted optical radiation are less affected by spurious fringes than reflection type
interferometers. It is preferable to use interferometers of the Mach-Zehnder or lateral shearing type or
Shack-Hartmann arrangements in transmitted optical radiation. For the measurement of wave aberrations
a single-pass geometry in transmitted optical radiation will often be the first choice for reducing spurious
reflections.
6 Measurement arrangements
6.1 Measurement arrangement for single microlenses
Interferometers or wavefront detectors shall be used to measure the transmitted wavefront of the
microlens under test. Single-path interferometers such as Mach-Zehnder, lateral shearing or double-pass
interferometers such as Fizeau, Twyman-Green, and Shack-Hartmann wavefront detectors can be used for
testing as shown in Annexes B to D.
The requirements for the measurement shall be defined. Typical criteria for choosing a specific method are
— required uncertainty of measurement,
— required properties to be measured,
— flexibility of the measurement,
— costs, and
— spot test on one lens or complete measurement.
For more details see ISO/TR 14999-2.
6.2 Measurement arrangements for microlens arrays
Interferometers or wavefront detectors shall be used to measure simultaneously whole arrays or parts of
them in the transmitted radiation. Typical test arrangements are described in Annexes E and F.
NOTE While the testing of single lenses selected from an array can be carried out by illuminating with a spherical
wave this is in general not possible with array tests. In that case, illuminating with plane wave is more suitable or
[13]
special provisions using diffractive array wavefront shaping elements have to be used .

ISO 14880-2:2024(en)
6.3 Geometrical alignment of the sample
Usually the microlens being tested and its coupling optics shall be set or adjusted into coaxial alignment
with the wavefront measuring instruments. Optical alignment instruments and/or devices are commercially
available for this purpose.
The sample can be mounted on a stage such as an air-chuck, which has two or three directions of freedom
for adjustment.
6.4 Preparation
The test equipment shall be maintained in a temperature-controlled environment and not exposed to
vibration so as to obtain consistent results. The use of an optical table is recommended.
The optical surfaces to be tested shall be clean. Uncoated glass surfaces may be safely cleaned with alcohol
and cotton wool. The cotton wool should be soaked in a very small amount of solvent before touching the
surface and wiped only once across it before being discarded. This minimizes the chances of scratching the
surface. Dust may be removed using a clean camel-hair brush or filtered compressed air.
Coated optical surfaces such as antireflection surfaces should be treated with great care and not cleaned
unless absolutely necessary. They may be dusted using filtered compressed air.
Guidance should be sought on the correct use of solvents, cotton wool or other wiping materials.
7 Procedure
Measurement requirements and typical methods for measuring the wavefront aberration of individual
lenses are described in the Annexes A to D.
Examples for measurements of wavefront aberrations of microlens arrays are described in the Annexes E and F.
8 Evaluation
[12][16]
The wavefront aberration can be calculated from the interferogram or from other wavefront
measuring systems described in Annexes A to F. From the wavefront aberrations of spherical lenses with
circular apertures primary Zernike coefficients can be derived with a prescribed software aperture.
NOTE 1 Typical wavefront aberrations described by Zernike coefficients are
— spherical aberration,
— astigmatism, and
— coma.
NOTE 2 For other lens aperture shapes (such as rectangular), see ISO/TR 14999-2.
The measured wavefront aberrations of samples shall be evaluated and quoted, for example, as peak-to-valley
or root-mean-square values. ISO 14999-4 gives definitions of these terms relating to optical measurements.
Care should be taken to interpret peak-to-valley values because they are influenced by spurious values. It is
recommended to use multiple times (at least three times) the rms figure instead.
9 Uncertainty of measurement
The wavefront aberrations of a sample are measured by a wavefront test system, which may introduce
some aberration of its own. The uncertainty of measurement can be improved by subtracting the system
[9][10]
aberrations .
ISO 14880-2:2024(en)
10 Test report
The test results shall be recorded and shall include the following information if applicable:
a) general information:
1) test has been performed in accordance with ISO 14880-2:2024;
2) date of test;
3) name and address of test organization;
4) name of individual performing the test;
b) information concerning the tested lens:
1) lens type;
2) manufacturer;
3) manufacturer’s model;
4) serial number;
c) test conditions (environmental conditions):
1) temperature;
2) relative humidity;
d) information concerning testing and evaluation:
1) test method used;
2) optical system used;
3) irradiation:
i) source type,
ii) wavelength,
iii) FWHM (full width at half maximum) of optical radiation spectrum,
iv) polarization status,
v) irradiance angle,
vi) spot size;
4) detector;
5) aperture;
e) test results:
1) peak-to-valley value of wavefront aberration Φ ;
P-V
2) root-mean-square value of wavefront aberration Φ ;
rms
3) Zernike polynomials or other polynomial coefficients.

ISO 14880-2:2024(en)
Annex A
(informative)
Measurement requirements for test methods for microlenses
The test for wave aberrations of microlenses shall be performed in transmitted optical radiation and
in a single-pass arrangement, an interferometer like a Mach-Zehnder interferometer, a lateral shearing
interferometer, or a Shack-Hartmann wavefront sensor. A single-pass test arrangement is required for
sharp imaging of the lens aperture onto the detector or sensor array and to avoid the strong disturbances
due to spurious reflections. Such reflections can occur in a double-pass arrangement like a Fizeau or a
Twyman-Green interferometer. In a double-pass geometry the lens under test will deliver two images of
the lens aperture one being out of focus causing diffraction effects like edge ringing in the rim region of
the lens under test. Such effects can be avoided by using a single-pass arrangement because all reflections
from lens surfaces in the auxiliary optical system in the forward direction are negligible, being reflected
twice at antireflection coated surfaces. In addition, due to sharp imaging of the lens aperture, there are no
ambiguities concerning the definition of the wave aberrations.
The test device shall not introduce aberrations of its own. In a Mach-Zehnder geometry, where the test
sample is put into one arm of the interferometer and the reference arm delivers a plane wavefront, the beam
splitting/combining optical elements are traversed by plane waves only. Spherical waves would produce
spherical aberration or other aberrations for non-symmetric beam splitters. Similar requirements are also
applicable for a Shack-Hartmann sensor although no beam splitters are used in this case.
In the case of lateral shearing interferometers, it is necessary to keep the design of the shearing device
symmetric and as simple as possible (see for example the shearing interferometer based on two-phase
gratings in a series arrangement [array tests]) in order to avoid additional measurement errors.
Since microlens diameters range from a few micrometres to a few millimetres, it is necessary to provide a
means for changing the magnification by at least two orders of magnitude. This is in order to fill the aperture
of the array photo-detector, typically a CCD-or CMOS array, to obtain sufficient lateral resolution so that
strongly deformed wavefronts can also be tested without violating the sampling theorem. Due to the great
span of magnifications in combination with the requirement of a plane wave interferometer, the imaging
microscope shall be incorporated into the test arm for high magnification ratios commonly obtained with
short working distances of the imaging microscope objective. If the imaging objective is to be used outside
the interferometer structure, special objective designs are necessary to enable high magnification ratios
in combination with long working distances. Two alternative solutions will be discussed in some detail
to demonstrate Mach-Zehnder interferometers for the testing of wavefront aberrations. The imaging
microscope will preferably be of the telescopic type in order to maintain in the test arm plane waves at the
beam combiner.
The change of magnification requires special measures to adapt the beam splitting ratio between the two
arms of the interferometer to obtain sufficient contrast in the interference fringes. A good choice for this is
a polarizing splitting unit consisting of a polarizing beam splitter in combination with two quarter-wave
plates (QWP), one in each arm of the interferometer and a half-wave plate (HWP) in front of the beam
splitting uni
...