Laser displays - Part 5-6: Measuring methods for optical performance of projection screens

IEC 62906-5-6:2020 (E) specifies the standard measurement conditions and measuring methods for determining the optical performance of a projection screen in terms of its photometric characteristics, including screen gain and speckle contrast, from different viewing directions. These methods are only applied for the case in which the projection screen and a laser projector are integrated and used with a fixed configuration as a set to create a real image. Both front and rear projection screens, with a flat surface, are included. This document excludes projection screens which are classified as optically see-through screens, including head-up displays.

General Information

Status
Published
Publication Date
27-Apr-2020
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
28-Apr-2020
Ref Project

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IEC 62906-5-6
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
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Laser displays –
Part 5-6: Measuring methods for optical performance of projection screens
IEC 62906-5-6:2020-04(en)
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IEC 62906-5-6
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
colour
inside
Laser displays –
Part 5-6: Measuring methods for optical performance of projection screens
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.260 ISBN 978-2-8322-8233-5

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
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– 2 – IEC 62906-5-6:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms, definitions, and abbreviated terms ....................................................................... 6

3.1 Terms and definitions .............................................................................................. 6

3.2 Abbreviated terms ................................................................................................... 7

4 Standard measuring conditions ........................................................................................ 7

4.1 General ................................................................................................................... 7

4.2 Environmental conditions ........................................................................................ 7

4.3 Power supply .......................................................................................................... 7

4.4 Warm-up time ......................................................................................................... 7

4.5 Measurement coordinate system ............................................................................. 8

4.6 Darkroom conditions ............................................................................................... 8

4.7 Measuring facilities ................................................................................................. 8

5 Installation and adjustment of the DUT ............................................................................ 9

5.1 Placement of the projector and the screen .............................................................. 9

5.2 Focusing of the projector ........................................................................................ 9

5.3 Standard projector setup conditions ...................................................................... 10

5.4 Standard image measurement locations ................................................................ 10

6 Signal patterns .............................................................................................................. 11

7 Measuring methods ....................................................................................................... 12

7.1 Screen gain .......................................................................................................... 12

7.1.1 Purpose ......................................................................................................... 12

7.1.2 Measuring equipment and conditions ............................................................. 12

7.1.3 Measuring methods ....................................................................................... 13

7.2 Screen gain directivity and half-gain angle ............................................................ 13

7.2.1 Purpose ......................................................................................................... 13

7.2.2 Measuring conditions ..................................................................................... 14

7.2.3 Measuring methods ....................................................................................... 14

7.3 Screen gain uniformity .......................................................................................... 14

7.3.1 Purpose ......................................................................................................... 14

7.3.2 Measuring conditions ..................................................................................... 15

7.3.3 Measuring methods ....................................................................................... 15

7.4 Angular characteristics of speckle contrast ........................................................... 15

7.4.1 Purpose ......................................................................................................... 15

7.4.2 Measuring conditions ..................................................................................... 15

7.4.3 Measuring methods ....................................................................................... 16

Annex A (informative) Screen colour shift ............................................................................ 17

A.1 Purpose ................................................................................................................ 17

A.2 Measuring conditions ............................................................................................ 17

A.3 Measuring methods ............................................................................................... 17

Annex B (informative) Screen directivity using a Fresnel lens .............................................. 18

Annex C (informative) Angular characteristics of speckle contrast with different

screens ................................................................................................................................. 20

Bibliography .......................................................................................................................... 22

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IEC 62906-5-6:2020 © IEC 2020 – 3 –

Figure 1 – Coordinate system for projection direction and viewing direction ............................ 8

Figure 2 – Example of image pattern with horizontal size H and vertical size V used for

alignment .............................................................................................................................. 10

Figure 3 – Standard measurement locations on the screen (nine measurement points) ......... 11

Figure 4 – Example of DUT setup ......................................................................................... 11

Figure 5 – Full screen patterns ............................................................................................. 11

Figure 6 – Measuring geometry of screen gain ...................................................................... 13

Figure 7 – Viewing direction measurement in both horizontal and vertical directions ............. 14

Figure 8 – Measuring geometry of speckle contrast with changing viewing direction ............. 16

Figure B.1 – Directivity of the screen under different setups ................................................. 18

Figure C.1 – Optical configuration for speckle contrast measurement with different

viewing directions ................................................................................................................. 20

Figure C.2 – Angular characteristics of speckle contrast obtained from different screen

and different de-speckle conditions ....................................................................................... 20

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– 4 – IEC 62906-5-6:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LASER DISPLAYS –
Part 5-6: Measuring methods for optical
performance of projection screens
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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International Standard IEC 62906-5-6 has been prepared by IEC technical committee 110:

Electronic displays.
The text of this International Standard is based on the following documents:
FDIS Report on voting
10/1187/FDIS 110/1198/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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IEC 62906-5-6:2020 © IEC 2020 – 5 –

A list of all parts in the IEC 62906 series, published under the general title Laser displays, can

be found on the IEC website.

Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.

The committee has decided that the contents of this document will remain unchanged until the

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• reconfirmed,
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– 6 – IEC 62906-5-6:2020 © IEC 2020
LASER DISPLAYS –
Part 5-6: Measuring methods for optical
performance of projection screens
1 Scope

This part of IEC 62906 specifies the standard measurement conditions and measuring

methods for determining the optical performance of a projection screen in terms of its

photometric characteristics, including screen gain and speckle contrast, from different viewing

directions. These methods are only applied for the case in which the projection screen and a

laser projector are integrated and used with a fixed configuration as a set to create a real

image. Both front and rear projection screens, with a flat surface, are included. This document

excludes projection screens which are classified as optically see-through screens, including

head-up displays.
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.

IEC 60050-845, International Electrotechnical Vocabulary (IEV) – Part 845: Lighting (available

at www.electropedia.org)

IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements

IEC 62906-1-2, Laser display devices – Part 1-2: Terminology and letter symbols

IEC 62906-5-2, Laser display devices – Part 5-2: Optical measuring methods of speckle

contrast

IEC 62471-5, Photobiological safety of lamps and lamp systems – Part 5: Image projectors

CIE S 014-1, Colorimetry – Part 1: Standard Colorimetric Observers
3 Terms, definitions, and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-845,

IEC 62906-1-2 and CIE S 014-1 apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
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IEC 62906-5-6:2020 © IEC 2020 – 7 –
3.1.1
screen gain
relative deviation from Lambertian distribution of light from the screen
3.1.2
peak gain
maximum screen gain of the screen
3.1.3
half-gain angle

viewing angle from normal at which the screen gain drops to half of the peak gain

3.1.4
screen colour shift

chromaticity difference between images projected on the screen and a reference reflectance

or transmittance target
3.2 Abbreviated terms
DUT Device under test
LMD Light measuring device
LPD Laser projection display
NOTE DUT in this document means the combination of the LPD and the screen.
4 Standard measuring conditions
4.1 General

Unless stated otherwise, the following conditions shall be applied. During the measurement,

optical radiation safety shall be implemented in accordance with IEC 60825-1 for the products

classified above Class 2M, and/or IEC 62471-5 for RG2 and RG3.
4.2 Environmental conditions
Measurements shall be carried out under the standard environmental conditions:
– temperature: 25 ºC ± 3 °C,
– relative humidity: 25 % to 85 % RH,
– atmospheric pressure: 86 kPa to 106 kPa.

When different environmental conditions are used, they shall be noted in the measurement

report.
4.3 Power supply

The power supply for driving the LPD in the DUT shall be adjusted to the rated voltage within

±0,5 %, and the frequency shall be supplied at the rated frequency within ±0,2 %.

4.4 Warm-up time

The measurements shall be carried out after the light output is sufficiently stable. The warm-

up time is defined as the time elapsed from when the supply source is switched on, and a full

level of input signal is applied to the LPD in the DUT, until the repeated measurements show

a variation in illuminance of no more than ±5 %. The illuminance shall not vary by more than ±

5 % over the entire measurement.
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– 8 – IEC 62906-5-6:2020 © IEC 2020
4.5 Measurement coordinate system

The viewing direction is the direction under which the observer looks at the point of interest

on the DUT surface (screen surface). During the measurement, the LMD simulates the

observer, by aiming the LMD at the point of interest on the DUT from the viewing direction.

The viewing direction is defined by two angles: the angle of inclination θ (relative to the

surface normal of the DUT) and the angle of rotation Φ (also called azimuth angle) as

illustrated in Figure 1. Although the azimuth angle is measured in the counter-clockwise

direction, it is related to the directions on a clock face as follows: Φ = 0° is the 3-o'clock

direction ("right"), Φ = 90° the 12-o'clock direction ("top"), Φ = 180° the 9-o'clock direction

("left") and Φ = 270° the 6-o'clock direction ("bottom").
Figure 1 – Coordinate system for projection direction and viewing direction
4.6 Darkroom conditions

The luminance contribution from the background illumination reflected off the screen shall be

less than 1/20 of the lowest black level of the display. If these conditions are not satisfied, then

background subtraction is required and it shall be noted in the report. The average reflectance

of the inner walls of the measurement room shall be lower than 3 %.
4.7 Measuring facilities

The configuration and operating conditions of the measuring equipment shall comply with the

structures specified in each item. The sensitivity and the dynamic range of each measuring

equipment shall be checked if it is suitable for the required task. To ensure repeatable

measurements, the following requirements shall be applied.

a) Luminance meter: Filtered luminance meters are generally considered not to be accurate

enough for laser projector measurements. Spectral measurement instruments are

preferred for these narrow bandwidth light sources. Filtered luminance meters shall only

be used if they are calibrated with a precision spectral radiance meter. However, it is

noted that this calibration is valid only for a given spectral distribution of the light source

(e.g. red, green, blue primaries, in addition to white and black), and the luminance meter

will need a unique calibration factor for every different spectral distribution.
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IEC 62906-5-6:2020 © IEC 2020 – 9 –

b) Illuminance meter: Filtered illuminance meters are generally considered not to be accurate

enough for laser projec
...

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