COMMISSIONINTERNATIONALEDELECLAIRAGE INTERNATIONALCOMMISSIONONILLUMINATION INTERNATIONALE BELEUCHTUNGSKOMMISSION NUMBER 74 June 2005 VISION AND LIGHTING IN MESOPIC CONDITIONS E ro possibl mes decrea large n h g ano by V( e ver since the CIE defined the photopic spectral luminous efficiency curve, V(λ), in 1924, researchers have been grappling with the difficult question of how to deal with the fact that the performance of the human eye changes depending on the level of illumination to which it is exposed. The photopic curve applies only at "high" light levels (daylight, lit interiors etc.), where the ds are less active and cones dominate our vision, and colour discrimination and the ability to resolve detail in the visual field are both good. At "low" levels (e.g. moonlight), only the rods are active, visual acuity is poor, and it is not e to distinguish colours; in this condition, the scotopic spectral luminous efficiency curve, V(λ), applies. The intermediate region, the so-called opic, has proved an intractable problem so far. Here the eyes sensitivity changes rapidly depending on the characteristics (level and spectral distribution) of the lighting used, shifting towards the blue as the level ses. No agreed system of photometry presently exists for this mesopic region. Of course this raises the question, "Is there a need for measurements of lighting in the mesopic?" The answer is a definite "Yes!" The reason is that a umber of safety critical applications, such as night time driving, fall in the mesopic region. Under the current system of photometry, lamps which emit a large proportion of their power around the peak of the V(λ) curve (such as high pressure sodium lamps) are rated as having a high luminous efficacy and are thus the lamp of choice in many situations. Under mesopic conditions, owever, a lamp with a higher blue content (e.g. metal halide) will have a reater visual effectiveness and may therefore be a better choice. The difficulty is that without an agreed system for mesopic photometry, it is not possible to make meaningful comparisons between one lamp type and ther, with the result that the optimum lamps are generally not specified. A major limitation in research to date has been the fact that there are 2 key response channels in the human visual system. One, the luminance channel, is achromatic and additive; the other, the chromatic channel, provides colour information and is non-additive. The relative contribution from each channel depends on the light level and the task being undertaken. Flicker photometry, for example, is dominated by the luminance channel and is the basis for the V(λ) function. Heterochromatic brightness matching, on the other hand, is dominated by the chromatic channel and is not well-described λ). As a result, researchers have developed many different models by which to describe the performance of the eye in the mesopic, the characteristics of which have varied significantly depending on the xperimental conditions under which they were developed. CIE Australia Inc. * ComitØ National Belge de lEclairage * CIE - Brazil * Bulgarian National Committee on Illumination * Canadian National Committee of the CIE * Chinese National Committee CIE * Croatian National Committee of the CIE * Czech National Committee of the CIE * National Illuminating Committee of Denmark * Deutsches Nationales Komitee der CIE * ComitØ Espaæol de Iluminacin * National Illumination Committee of Finland * ComitØ National Franais de lEclairage * CIE UK * Hellenic Illumination Committee (HIC) * CIE ( Hong Kong) Limited * CIE Hungary * CIE India * Israel National Committee on Illumination * Comitato Nazionale Italiano della CIE * Japanese National Committee of CIE * Korean National Committee of CIE * Nederlands Nationaal ComitØ van de CIE * CIE New Zealand * Norsk Lysteknisk KomitØ * sterreichisches National- komitee der CIE * Polski Komitet Oswietleniowy * Comitatul National Roman de Iluminat * Russian National Committee of the CIE * Slovenski nacionalni komite pri CIE * South African National Committee of CIE * Svenska NationalkommittØn av CIE * Schweizerisches Nationalkomitee der CIE * Thai National Committee of CIE * Aydinlatma Türk Milli Komitesi * CIE- USA * CIE National Committee of Yugoslavia IN THIS ISSUE Vision and Lighting in Mesopic Conditions News from the Divisions CIE Midterm Meeting - New Publications CIE Symposia Instrument Systems In Memoriam - From the Lighting Journals For your Diary
Transcript
COMMISSION INTERNATIONALE DE L�ECLAIRAGE INTERNATIONAL COMMISSION ON ILLUMINATION INTERNATIONALE BELEUCHTUNGSKOMMISSION
NUMBER 74
June 2005
VISION AND LIGHTING IN MESOPIC CONDITIONS
E
ro
possibl
mes
decrea
large n
hg
ano
by V(
e
ver since the CIE defined the photopic spectral luminous efficiency curve, V(λ), in 1924, researchers have been grappling with the difficult question of how to deal with the fact that the performance of the human eye changes depending on the level of illumination to which it is exposed. The photopic curve applies only at "high" light levels (daylight, lit interiors etc.), where the
ds are less active and cones dominate our vision, and colour discrimination and the ability to resolve detail in the visual field are both good. At "low" levels (e.g. moonlight), only the rods are active, visual acuity is poor, and it is not
e to distinguish colours; in this condition, the scotopic spectral luminous efficiency curve, V�(λ), applies. The intermediate region, the so-called
opic, has proved an intractable problem so far. Here the eye�s sensitivity changes rapidly depending on the characteristics (level and spectral distribution) of the lighting used, shifting towards the blue as the level
ses. No agreed system of photometry presently exists for this mesopic region.
Of course this raises the question, "Is there a need for measurements of lighting in the mesopic?" The answer is a definite "Yes!" The reason is that a
umber of safety critical applications, such as night time driving, fall in the mesopic region. Under the current system of photometry, lamps which emit a large proportion of their power around the peak of the V(λ) curve (such as high pressure sodium lamps) are rated as having a high luminous efficacy and are thus the lamp of choice in many situations. Under mesopic conditions,
owever, a lamp with a higher blue content (e.g. metal halide) will have a reater visual effectiveness and may therefore be a better choice. The
difficulty is that without an agreed system for mesopic photometry, it is not possible to make meaningful comparisons between one lamp type and
ther, with the result that the optimum lamps are generally not specified.
A major limitation in research to date has been the fact that there are 2 key response channels in the human visual system. One, the luminance channel, is achromatic and additive; the other, the chromatic channel, provides colour information and is non-additive. The relative contribution from each channel depends on the light level and the task being undertaken. Flicker photometry, for example, is dominated by the luminance channel and is the basis for the V(λ) function. Heterochromatic brightness matching, on the other hand, is dominated by the chromatic channel and is not well-described
λ). As a result, researchers have developed many different models by which to describe the performance of the eye in the mesopic, the characteristics of which have varied significantly depending on the
xperimental conditions under which they were developed.
CIE Australia Inc. * Comité National Belge de l�Eclairage * CIE - Brazil * Bulgarian National Committee on Illumination * Canadian National Committee of the CIE * Chinese National Committee � CIE * Croatian National Committee of the CIE * Czech National Committee of the CIE * National Illuminating Committee of Denmark * Deutsches Nationales Komitee der CIE * Comité Español de Iluminación * National Illumination Committee of Finland * Comité National Français de l�Eclairage * CIE � UK * Hellenic Illumination Committee (HIC) * CIE (Hong Kong) Limited * CIE � Hungary * CIE India * Israel National Committee on Illumination * Comitato Nazionale Italiano della CIE * Japanese National Committee of CIE * Korean National Committee of CIE * Nederlands Nationaal Comité van de CIE * CIE � New Zealand * Norsk Lysteknisk Komité * Österreichisches National-komitee der CIE * Polski Komitet Oswietleniowy * Comitatul National Roman de Iluminat * Russian National Committee of the CIE * Slovenski nacionalni komite pri CIE * South African National Committee of CIE * Svenska Nationalkommittén av CIE * Schweizerisches Nationalkomitee der CIE * Thai National Committee of CIE * Aydinlatma Türk Milli Komitesi * CIE-USA * CIE National Committee of Yugoslavia
IN THIS ISSUE
Vision and Lighting in Mesopic Conditions � News from the Divisions � CIE Midterm Meeting - New Publications � CIE Symposia � Instrument Systems � In Memoriam - From the Lighting Journals � For your Diary
Recently, research has shifted towards a new approach to this problem. Instead of trying to describe the detailed performance of the eye under a given set of conditions, the emphasis has been on developing a system which can be readily implemented in practice, but which may not provide a precise description of visual performance. This places two important constraints on the model:
• It must be additive
• It must tend to V(λ) at the upper end of the mesopic region and to V�(λ) a the lower end
The results of this research were presented at the recent CIE Expert Symposium, "Vision and Lighting in Mesopic Conditions 2005". At the discussion session following the symposium, a clear distinction was drawn between the two approaches to mesopic photometry and it was proposed that 2 systems should be developed. The first, the so-called "practical" or "luminance" system, should focus on an additive system to provide a bridge between the V(λ) and V�(λ) curves and would be used for specification of lighting installations etc. Although this system would not provide a precise prediction of the performance of any particular visual task, in this respect it would be no worse than the present photometric system in the photopic. The second, the so-called "brightness system", should incorporate the influence of the chromatic channel and would link with work on brightness matching in the photopic region.
The work presented at the symposium, and elsewhere, is now sufficiently advanced to form a basis for the practical system. The model takes the form x V(λ)+(1-x) V�(λ), with x being a function of the level of illumination. It was agreed during the discussion that those involved in the development of the practical system should, over the next year, refine the model based on existing experimental data, with the aim of having a trial system ready by June 2006 for field-testing by the road lighting and road safety industries in particular. This work will be carried out under the auspices of TC 1-58. In parallel, work will continue in TC 1-37 and TC 1-46 to develop a system for brightness evaluations.
It is truly encouraging that, after more than 7 decades of research, we are now close to establishing a practical system for mesopic photometry. The potential implications for road safety and improved energy efficiency alone make this a major break through for the CIE. We would encourage everyone with an interest in lighting to watch for further developments over the next year or so, and to become active in the work of the relevant TCs in order to take this forward as quickly as possible.
Teresa Goodman, Director, CIE Division 2
János Schanda, Secretary of the CIE
! News from the Divisions
Division 1 - Vision and Colour http://www.bio.im.hiroshima-cu.ac.jp/~cie1
A Division Meeting was held on 16 May in León/Spain. Minutes will soon be available on the Divisional website.
Division 1 has established the following new reportership:
"Concept and application of equivalent luminance" (Reporter: Y. Nakano, Japan)
The next Division meeting will take place in Ottawa, Canada, 17-19 May 2006. On 16/17 May, a CIE Expert Symposium on the 1931 Standard Colorimetric Observer will be organized in conjunction with this meeting.
A CIE Expert Symposium on Visual Appearance is planned for September 2006 in Paris.
Division 2 - Physical Measurement of Light and Radiation http://cie2.nist.gov
A Division Meeting was held on 17 May in León/Spain. Minutes will soon be available on the Divisional website.
Division 2 has established the following new reporterships:
"Measurement requirements for solid state light souces" (Reporter: G. Heidel, Germany) "Industrial lighting requirements for a D65 illuminant" (Reporter: E. Pierson, Belgium)
The Division meeting 2006 will be held in Braunschweig/Germany, 14-17 June 2006. The 2nd CIE Expert Symposium on Uncertainty Evaluation will be organized on 12-13 June 2006 in Braunschweig.
Division 3 - Interior Environment and Lighting Design http://www.ciediv3.entpe.fr
The draft report of TC 3-33 "Test cases to assess the accuracy of lighting computer programs" was circulated for Division and Board ballot. Deadline for vote is: 2005-09-23.
The next meeting of Division 3 will take place on 22-23 September 2005 in Berlin.
In 2006, the Division meeting will be held in Ottawa/Canada in September.
The 2nd CIE Expert Symposium on Light and Health will be organized jointly by Division 3 and Division 6 in Ottawa, Canada, in September 2006.
2 � CIE NEWS 74
Division 4 - Lighting and Signalling for Transport http://www.tut.fi/cie4/
The draft report of TC 4-10 "Requirements for light beam pattern of front fog lamps" was circulated for Division and Board ballot. Deadline for vote is: 2005-07-26.
A Division Meeting was held on 16 May in León/Spain. Minutes are already available on the Divisional website.
Division 4 has established the following new reportership:
"Collection of research programs" (Reporter: Dick Stark, USA)
The next Division 4 meeting will take place in Greece, 18-21 September 2006, in conjunction with the conference "Urban Nightscape" (21-24 September) in Delphi.
CIE Midterm Meeting
May 2005, León, Spain
From 12-17 May, the CIE Board of Administration, its different subcommittees, the CIE General Assembly as well as CIE Divisions 1, 2, 4, 5 and several TCs met in León, Spain.
Major decision taken were:
The General Assembly elected the Officers for the next quadrennium (2007-2011): President-Elect 2005-2007 Franz Hengstberger (South Africa) and President 2007-2011: Past-President: Wout van Bommel (The Netherlands) Vice-President Technical: János Schanda (Hungary) Vice-President Publications: Teresa Goodman (Great Britain) Vice-President Standards: Michael Seidl (Germany) Vice-President Marketing: Todd Newman (USA) Vice-President: Lily Chang Wai Ling (China) Vice-President. Ramani Venkataramani (India) Vice-President: Gennady Shakhparunyants (Russian Fed.) Vice-President: Marc Fontoynont (France) Secretary: Ken Sagawa (Japan) Treasurer: Peter Gradl (Austria)
The General Assembly approved the 2006-2007 budgets.
The following persons received a CIE Award: John Shaw Australia Gueorgui Dikanarov Bulgaria Veneta Stefanova Bulgaria Dai Deci China C.M. H. Driscoll UK Gyula Dézsi Hungary József Horváth Hungary G.J. van den Beld The Netherlands Alie Rommers-Jong The Netherlands
Heartiest congratulations to the recipients of the awards. The Central Bureau would like to thank them for their contribution to the CIE work and would like to wish them good health and much success in their future activities. May we rely also in the future on their expertise!
The next CIE Session will be held from 4 to 11 July 2007 in Beijing, China. The Call for Papers will be circulated by end October 2005.
3 � CIE NEWS 74
Division 5 � Exterior and Other Lighting Applications http://www.cie.co.at/div5/
The draft report of TC 5-11 "Practical design guidelines for the lighting of sport events for colour television and filming" was circulated for Division and Board ballot. Deadline for vote is: 2005-07-15.
A Division Meeting was held on 17 May in León/Spain. Minutes are already available on the Divisional website.
Division 5 has established the following new reportership:
"To review CIE Publication 94: Guide for Floodlighting" (Reporter: J. Horváth, Hungary)
The next Division 5 meeting will take place in Greece, September 2006, in conjunction with the conference "Urban Nightscape" (21-24 September) in Delphi.
Division 6 - Photobiology and Photochemistry http://physics.nist.gov/cie6/
The Draft Standard of CIE TC 6-32: CIE DS 019.2/E:2005 "Photocarcinogenesis action spectrum (non-melanoma skin cancers)" was circulated to NCs for comments. Deadline: 2005-10-26.
The following new TC was established: TC 6-59 "UVC photocarcinogenesis risks from germicidal lamps" (Chair: Richard Vincent, US)
Terms of Reference: To prepare a technical report on the potential carcinogenic risk of low-pressure mercury discharge lamps used for ultraviolet germicidal irradiation (UVGI).
The new chairman of TC 6-20 "Phototoxicity in domestic and industrial environments" is Neil Gibbs, UK.
The next Division 6 meeting will be held in Aix-les-Bains/France, in September 2005, in conjunction with the European Society for Photobiology meeting.
In 2006, the Division meeting will be held in Ottawa/Canada in September.
The 2nd CIE Expert Symposium on Light and Health will be organized jointly by Division 3 and Division 6 in Ottawa, Canada, in September 2006.
" New CIE Publications At the time you receive this NEWS issue, the CIE webshop announced in CIE News 73 will already be operative. You can reach it via a link from the CIE
main website (http://www.cie.co.at) or you can go directly to http://www.techstreet.com/cgi-bin/joint.cgi/cie
Hollow Light Guide Technology and Applications
CIE 164:2004 ISBN 3 901 906 38 X
CIE initiated a Technical Committee "Hollow Light Guides" for the purpose of developing new terminology and dissemination of information in the field of illumination with hollow light guides. This report is a first step in that direction, representing the state of the art at the time of its substantial completion in 1999.
It includes a brief history of the field of hollow light guides, reviews the different solutions and describes the basic physics behind them. The pros and cons of each of the solutions are summarized and the terminology is given. System design and the photometry of hollow light guides are detailed. Finally, a review of four example projects is given.
The report consists of 37 pages with 13 figures and 6 tables.
CIE 10 Degree Photopic Photometric Observer
CIE 165:2004 ISBN 3 901 906 39 8
The V(λ) function accepted in 1924 is valid for photopic vision. It was long recognized that for para-foveal vision this function does not describe luminance perception correctly. In 1964 the CIE accepted a large field colorimetric observer, but this system had no photometric counterpart. Subsequent research has shown that )(10 λy function can be used as the spectral luminous efficiency function of a 10° photometric observer. The present report provides guidance when and how this large field photometric observer could be used, especially if luminance has to be determined para-foveally.
Based on the detailed evaluation of the available literature data TC 1-59 came to the conclusion that the adoption of a 10° photopic photometric observer [V10(λ)] can be recommended to the CIE and that this system should be based - according to the original recommendations of the CIE Colorimetric Committee - on the )(10 λy function of the CIE 1964 standard colorimetric observer.
The report is consists of 23 pages with 3 tables.
4 � CIE NEWS 74
Cognitive Colour CIE 166:2005 ISBN 3 901 906 40 1
This report surveys cognitive aspects of colour in terms of behavioural, neuropsychological, and neurophysiological data. Colour is usually defined as a colour stimulus or as perceived colour. In this report the concept of cognitive colour has been discussed in relation to colour categorization, colour coding, colour naming, the Stroop effect, spatial organization of coloured visual objects, visual search, and colour memory.
The results show that there are aspects of colour that the CIE definitions of psychophysical and perceived colour do not cover, although it gives notes to some of them. These phenomena could be referred to as "cognitive colour" and they point to the need for a new formal definition of colour in the CIE terminology.
Cognitive colour is very important in certain specific tasks. A common property of these tasks is the importance of the economy of cognition of the human brain. It means that perceived colours are represented and stored in a compressed form i.e. as "cognitive colours". This accelerates complex tasks like visual attention, visual search, figural organization, figural segregation, etc. For these tasks, colour appearance models alone, including the calculations recommended for assessing colour appearance and colour differences, may be limited for predicting how an observer will behave in these complex tasks. We must define cognitive colours by the boundaries of a continuous perceived colour set, or by a "representative item" of this set, and assign a name to the cognitive colour.
The final report from the CIE Reportership "Cognitive Aspects of Colour" was published with the title "Cognitive Color" in Color Research and Application, 29(1), pp. 7-19, 2004 and has been reprinted with the kind permission of John Wiley and Sons, Inc.
The report consists of 24 pages with 14 coloured figures.
Recommended Practice for Tabulating Spectral Data for Use in
Colour Computations CIE 167:2005 ISBN 3 901 906 41 X
This technical report describes several difficulties resulting from incompatibility of tables of spectral data used for computations, such as colour computations, with automatic digital computers, and provides guidance in tabulating spectral data to facilitate such applications. The recommended practices, with regard to spectral ranges, spectral
intervals, etc., are based on the experience of members of the committee, who were experts in the field of colour measurement and computation.
The report consists of 21 pages with 3 figures and 12 tables.
CIE Draft Standard DS 019.2/E:2005 Photocarcinogenesis Action Spectrum
(Non-Melanoma Skin Cancers) Solar ultraviolet radiation is recognized as a major cause of non-melanoma skin cancer in man. Skin cancer occurs most frequently in the most heavily exposed areas and correlates with degree of outdoor exposure. Describing the relationship of exposure (dose) to risk (skin cancer) requires the availability of a biological hazard function or action spectrum for photocarcinogenesis. This standard proposes the adoption of an action spectrum (weighting function) derived from experimental laboratory data and modified to estimate the non-melanoma tumor response in human skin. The experimental data are sufficient for estimating effectiveness down to about 250 nm, but experimental data are not sufficient for specifying effectiveness above 400 nm.
The draft standard has been sent to CIE National Committees for comments and sales to interested parties. It is still subject to changes and may not yet be referred to as a CIE Standard. When approved by the CIE National Committees, it will be published as a CIE Standard and later on eventually as a joint standard with ISO.
CIE Standard S 015/E:2005 Lighting of Outdoor Work Places
To enable people to perform visual tasks efficiently and accurately, especially during the night, adequate and appropriate lighting has to be provided. The degree of visibility and comfort required in a wide range of outdoor work places is governed by the type and duration of activity.
This standard specifies requirements for lighting of tasks in most outdoor work places and their associated areas in terms of quantity and quality of illumination. In addition recommendations are given for good lighting practice. All usual visual tasks are considered.
After the definitions of terms, the standard gives detailed information on lighting design criteria. Fifteen tables specify the lighting requirements for various areas, tasks and activities, and a short chapter recommends verification procedures. Following a bibliography, an extensive index of areas, tasks and activities facilitates consultation of the tables of the standard.
5 � CIE NEWS 74
A further CIE Standard giving the specific requirements for safety and security in outdoor work places is to follow as CIE S 016/E:2005.
This standard has been prepared by a joint Technical Committee of the CIE Division 5 and CEN/TC 169 �Light and lighting� and approved by CIE National Committees. French and German versions are under preparation.
CIE Standard S 016/E:2005 Lighting of Outdoor Work Places �
Lighting Requirements for Safety and Security
To enable people to perform visual tasks efficiently and accurately, especially during the night, adequate and appropriate lighting has to be provided. The degree of visibility and comfort required in a wide range of outdoor work places is governed by the type and duration of activity.
This standard specifies the lighting requirements that will contribute to the visual needs for safety and security within outdoor work places.
This standard has been prepared by CIE Division 5 and should be read in conjunction with CIE S 015/E:2005 "Lighting of Outdoor Work Places". It has been approved by CIE National Committees. French and German versions are under preparation.
" New Publications in the Field of Light and Lighting
IESNA Guide for Testing the Calibration of Locking-Type
Photoelectric Control Devices used in Outdoor Applications
LM-48-01 IESNA, 2001
ISBN 0-87995-181-8
This Guide describes a procedure and a test equipment by which photoelectric control devices used in outdoor applications can be tested. These devices are generally used to close or open a switch to turn on or off the electric power to a lighting installation in response to changing light level. Since the colour of the daylight from sunset to dark or from sunrise to daytime changes considerably the test is carried out - as a compromise - under simulated conditions at a constant correlated colour temperature, using halogen lamp in combination with an infrared blocking and a colour correction filter.
The test equipment has to provide ways for the fast setting of the illuminance level, controlled by an illuminance meter traceable to standard laboratories, and for the changing of operating voltage and temperature of the device to test it even at the extreme points. Together with the description of the testing procedure precise requirements on the setting of these parameters are given. The different handling of CdS and Si detector based photo controls are described.
The appendix describes a possible realization of the test equipment consisting of the halogen lamp, filters, a rotating shutter, two opal glasses and mounts for the photo control and the illuminance meter. Even detailed mechanical drawings are given that enable the replication of the set-up. Uniform illumination level is claimed but unfortunately, no test results of the realized set-up are provided on the uniformity of the illuminance in the test plane at the different relative positions of the shutter.
J. M.
Metrics for High-Quality Specular Surfaces
Lionel R. Baker
SPIE PRESS, 2004 ISBN 0-8194-5576-8
The quality of specular or mirrorlike surfaces is of interest to scientists and engineers from the optics, electronics, semiconductor, precision mechanical, etc. industries. Optical components, with which this book is mostly concerned, usually require a degree of surface quality unsurpassed by most manufactured products. Traditionally, the quality of a specular surface has been carried out subjectively by looking at the surface. This inspection process can achieve a high level of sensitivity in some respects but lacks precision and accuracy. This book provides a basic working knowledge of the definition, measurement, and standardization of a number of different metrics used to characterize high-quality specular surfaces.
Chapter 1 defines the basic metrics influencing the quality of an optical surface, i.e form, roughness, waviness, imperfections (scratch and dig). Errors in the shape or form of a surface have a direct effect on the shape of a wavefront passing through an optical system. As little as a quarter of a wavelength of light deformation of a wavefront shape can transfer approximately 20% of power out from the center of the PSF to its edges. This broadens the PSF and gives rise to a reduction in the capability of the system to resolve extended images. Although optical system resolution may not be much affected by residual surface finish, an image could suffer reduced contrast and the presence of imperfections will degrade the cosmetic quality and therefore the
6 � CIE NEWS 74
value of the component. Imperfections cause additional problems with laser optics and low-light-level imaging systems, where a scratch can produce a disturbing line of light across an image plane. Imperfections can also give rise to radiation absorption and high field concentrations that may trigger surface damage in the presence of high-power/energy laser beams.
Chapter 2 details the methods for measuring surface form either mechanically or optically. Mechanical methods rely on contacting the surface with some form of lightly loaded stylus or probe. This is scanned over the surface to precisely known coordinate positions, and changes in its height from the surface are recorded. Possible damage to the surface can be avoided, by the use of noncontacting optical methods in this case Twyman-Green or laser Fizeau interferometers.
Chapter 3 deals with the most common methods for the measurement of surface roughness. The effect of roughness is to scatter image-forming rays and produce an unwanted haze over the image plane. This reduces contrast and limits the dynamic range of image intensity. The cause of roughness is usually imperfect polish. Scatter of light can also arise from optical coatings employed to change reflectance values, or from contamination. The metric most widely used to measure roughness is the RMS value obtained from surface height variations with stated lower and upper limits. Surface roughness specifications are applicable to matte and ground surfaces as well as to specular ones. The most popular instrument used for optical surface topographical analysis is the computer-aided microinterferometer.
Surface waviness is described in Chapter 4, it is the periodic component of surface texture, arising most frequently from induced vibrations of a single-point surface generator, and when surface profiles are Fourier analyzed it usually occupies a spatial frequency band between those of surface form and roughness. The periodic nature of such a surface results in diffraction of a reflected or transmitted beam, giving rise to multiple images rather than a single image when the beam is brought into a focus. A surface generated by the more common process involving area contact between the lap and the work surface is unlikely to suffer in this way. Very small periodic surface height variations of less than a nanometer can be measured by a microscope interferometer even in the presence of residual roughness.
The next chapter introduces the two types of surface imperfections: scratches and digs. The effect of imperfections on system performance is significant when the field of view is restricted to a point, as is the case with laser optics and spectrographs. The increasing use of very small lenses, as in microengineering, where the area of the lens becomes comparable with the area of the imperfection, will result in much closer tolerances on imperfections. The
chapter concludes with the enumeration of the different standards on imperfections in a variety of countries.
The rest of the chapters are devoted to the different types of measurement techniques to define the measure of imperfections and their details in national or international standards. First the obscuration technique then the microscope image comparators and finally the laser scanning methods are detailed. The inspection and measurement of imperfections on a single optical component are difficult enough using conventional dark-field techniques, but the task is practically impossible when the component is within an assembled system. Although imperfections and contamination may be visible when a system is held up to the light, the task of measurement through other optical components with power is problematic, in the microscope image comparator the calibration lines need to experience the same power conditions.
J. M. A Guide to the Use and Calibration of
Detector Array Equipment Gordon R. Hopkinson, Teresa M. Goodman,
Stuart R. Prince
SPIE PRESS in cooperation with Sira Technology Ltd. and NPL (UK), 2004
ISBN 0-8194-5532-6
Solid state imaging arrays became very popular in the last two decades. They provide many advantages over single element detectors, like fine resolution in imaging or spectrometry, reduction in measurement time, but on the other hand the complex structure of these detectors present a challenge for both users and equipment manufacturers in the measurement and calibration.
Chapter 1 introduces the different types of detector arrays. Since silicon arrays are the most widely used detectors, their structures are discussed in detail, the practical combinations of the two types of detectors (photodiode and MOS capacitors) and the two types of readout systems (CCD and X-Y addressed) are given. Infrared arrays are only briefly introduced, for further studies references are given. Then the key parameters and their measurements are described following the definitions and methods adopted by the European Space Agency. It is emphasized that the parameters of the array detectors depend strongly on the operational conditions (temperature, clock rate, irradiation, etc.), therefore care should be taken in case of any comparison of measurement or calibration results. Separate sub clauses are dedicated to the definitions and measurement methods of the following parameters: offset level, dark signal, non-uniformity of dark signal, fixed pattern noise, photo-response non-uniformity, conversion gain, temporal noise, linearity, saturation level, charge transfer efficiency,
7 � CIE NEWS 74
modulation transfer function, (spectral) responsivity, quantum efficiency, lag, crosstalk and geometry.
Chapter 2 considers applications of detector arrays in equipments and their calibration requirements. Having different requirements the two main applications requiring calibrations: imaging and spectrometry are separately discussed. The influence of the array parameters on the instrument calibration is described in Chapter 3. The variations of array parameters due to the change in operational conditions are discussed for the parameters defined in Chapter 1. Changes in temperature causes change in the dark signal, in the band gap and absorption coefficient (consequently quantum efficiency, spectral responsivity), in offset voltage, or the change of the irradiation may cause changes in linearity, response non-uniformity, etc.
Chapter 4 concentrates on the calibration techniques for instruments. Usually, a complete instrument should be calibrated preferably under similar conditions as the instrument is used. It is emphasized that any change in the pre-optics, even if only the aperture or the focus was altered, or in the electronics will necessitate new calibration. First the techniques and artifacts for imagers, including thermal imagers are shortly described then the instruments for spectrometry are analyzed. The latter equipments cover a broad range of instruments and techniques, but they generally fall into the categories of spectroradiometry and spectrophotometry. The potential sources of errors, transfer standards and recommended methods for calibration of key aspects of the performance of array-based spectrometers are detailed. Many of the examples refer to linear arrays, but the principles can be applied also to 2D arrays. The most detailed part of this guide deals with the wavelength calibration, responsivity, stray light, linearity and dark reading of the instrument. First these parameters are explained then calibration methods and examples are given.
Chapter 5 is dedicated to the calibration equipments, mainly sources of continuous and spectral line radiation as well as filters. The many factors that need to be considered when selecting a calibration source and the way of operation of these sources are detailed. The last chapter compares international standards and describes the Photometry Key Comparison carried out by BIPM.
Finally, three appendices survey calibration services and contacts, definitions of terms and recommended calibration procedures.
Most parts of this book do not provide long explanations and deep derivations of the key parameters of array detectors and the errors caused by them, it is intended to be a guide that provides rules of thumb for the calibration procedures, drawing the attention to the effect of the different factors. Ample references are listed for further research in the field.
J. M.
# CIE Symposia
2nd CIE Expert Symposium on Light and Health
The Symposium will be organized jointly by CIE Divisions 3 and 6, and will take place in Ottawa, Canada, in September 2006. Details are being clarified at the time this NEWS issue is printed, thus may we ask you to check the CIE website (www.cie.co.at) for further news.
2nd CIE Expert Symposium on Measurement Uncertainty:
Methods and models for analysis of uncertainties in optical radiation
measurement 12 - 13 June 2006, Braunschweig, Germany
This symposium will be held in conjunction with the CIE Division 2 Meeting (14-17 June).
The goals of the symposium are to: • provide guidance on techniques for the
evaluation of uncertainties associated to values of photometric and radiometric quantities;
• present the latest developments relating to methods for assessment of uncertainties for values of quantities which are derived from spectral measurements;
• provide a forum for discussion of related effects such as correlation of data.
The meeting will be split into 2 parts; the first part (12 June) will include tutorial presentations with Invited Papers, while the second part (13 June) will be a Workshop with Contributed Papers.
The Tutorial Sessions will cover fundamentals for uncertainty evaluation, particularly for photometry and radiometry:
• Fundamentals of uncertainty analysis, including evaluation of standard uncertainty for both repeated measurements and other knowledge, degrees of freedom and expanded uncertainty;
• Modelling of measurements especially the development of measurement equations under the consideration of correlations and their use in uncertainty evaluation;
• Introduction to the work of CIE TC 2-43.
The Workshop Sessions will cover recent work related to uncertainty evaluation for optical radiation measurements.
A Call for Papers will be published within short (check the Symposium website www.ptb.de/en/org/4/41/412/cie/cie.htm or contact [email protected]).
8 � CIE NEWS 74
Information from CIE Supportive Member: Instrument Systems
High Power LEDs � Measurement Solutions for Solid State Lighting The semiconductor light of LEDs has long been deployed in many areas of daily life. Examples include applications such as backlighting for displays and panel graphics on mobile phones and instrument clusters in cars. The new High Power LEDs now on the market enable LED light to be used for applications in traditional illumination as well.
This is good news, but High Power LEDs also present new challenges for optical metrology. Test and measurement systems for individual LEDs have been technically refined with highly developed and fast spectroradiometers, but when it comes to lighting applications, it is necessary to deploy systems from conventional photometry such as goniophotometers and large integrating spheres. These test systems generally use photometer measurement heads that are not accurate enough for LED spectra. One solution is to combine modern spectroradiometer technology with the systems of classical photometry. Instrument Systems, based in Munich, has addressed this problem and launched appropriate measuring systems.
High Power also means High Temperature Today, modern spectroradiometers are able to record accurately all the optical parameters of LEDs, such as luminous intensity, luminous flux, chromaticity and spatial radiation pattern. However, the new High Power LEDs with luminous flux values in excess of 100 lumens require proper thermal management. Some of these LEDs cannot be operated without heat dissipation. Their optical properties are also significantly influenced by temperature. The light output, for example, can degrade by some 10 percent if the temperature increases by 40 K, and the colour temperature of white LEDs changes to the point where it is clearly visible to the human eye. It is therefore necessary to consider the thermal behavior of LEDs adequately during optical analysis.
To this end, Instrument Systems has developed special test adapters for High Power LEDs. They combine with integrated passive or active cooling to create stable temperature conditions and permit measurement of the temperature at the LED slug.
From the single LED to the LED module Despite the impressive light power, a single LED is far from adequate for applications such as headlights in cars or interior illumination. Entire clusters and modules of LEDs are required for these applications. This is why the analysis of photometric parameters for modules is becoming increasingly important alongside the measurement of single LEDs. A goniophotometer can be used to analyze the spatial radiation pattern of an LED module. Using a spectroradiometer as a detector allows the distribution curve for luminous intensity and colour to be determined. A feature that is particularly important for white LEDs since there can be major changes in colour coordinates for different viewing angles. This is because there is a lower proportion of the broadband phosphor radiation present in the lateral radiation of the LED by comparison with the primary radiation of the blue LED chip. LED luminous flux measurement using integrating spheres Integrating spheres are used to determine the luminous flux (total flux of light emitted). These comprise a hollow sphere, the interior of which is coated with a material that is an almost perfect diffuse reflector. This ensures that the total flux of light is integrated. The quality of the measurements is largely dependent on the homogeneity of the reflection properties within the sphere. It is important to keep sources of errors such as openings and adapters in the sphere to a minimum. The self-absorption of the test specimen is a key factor during analysis of LED modules and should be taken into account when measurements are taken.
Figure 1: cross-section of an integrating sphere for measuring LED modules
There is a trend toward larger integrating spheres in order to minimize the defect area as a proportion of the interior area of the sphere. Whereas sphere diameters of 75 mm to 150 mm were adequate for conventional single LEDs, diameters of 250 to 500 mm are now recommended for High Power LEDs and LED clusters.
Instrument Systems GmbH www.instrumentsystems.de
9 � CIE NEWS 74
$ In Memoriam
A. M. Marsden $
We regret to report the death on 15 May 2005 at the age of 76 of Dr A M (Mike) Marsden. He had been ill for some time, and finally succumbed to pneumonia after recurrent other infections after a short period in hospital.
Mike Marsden was President of CIE from 1985 to 1987.
Mike was the fourth President of CIBS, in 1979-80, and the first and so far the only President from a lighting background.
Educated at Rounday School, Leeds, and Manchester University, he took up a position as a lecturer at the Royal Military College of Science before moving in 1958 to Nottingham University where he also studied for an MSc and later a PhD. In 1969 for a short time he took up a post as Visiting Professor at the State University of Virginia. Although alongside his extensive involvement with lighting, Mike also had an interest in building acoustics, his major contributions were in lighting, though over a very wide range of topics .
In 1970 he moved to Thorn Lighting as Manager of lighting research and development, also becoming manager of the Jules Thorn Lighting Laboratories at Enfield.
His MSc thesis on visual performance and lighting codes and his PhD thesis on the relationship between brightness and luminance were a firm foundation for his work in the Illuminating Engineering Society, CIBSE, the Association of Public Lighting Engineers (now the ILE) and the International Commission on Illumination where he rose to a place on the action committee and took over the Presidency half way through a quadrennial period in 1985 on the death in office of Gunther Wyszecki.
He published numerous papers on both lighting and acoustics covering a wide range of topics, and was co-editor of the second and subsequent editions of the standard work �Lamps and Lighting�.
Eventually, Mike decided that he wished to return to academia, and moved to Hong Kong for a number of years as a university lecturer. Following his eventual retirement and return to the UK, he joined Joe Lynes and Bill Burt in the development of Hyperlight, an innovative software product which was combination of a teaching package and codified guidance material.
In his private life Mike was a keen musician and a keen mountain climber. Two results of the latter were the ascent of Buckden Pike which formed the formal start of the 1979 CIBSE conference in Harrogate, and formation of a completely unofficial CIE committee on "high level matters".
A memorial service was held at St. Michael's Linton (near Grassington, N Yorks) on Friday 20 May, at which CIBSE was represented by Alan Wilson, a past Chairman of the CIBSE Lighting Division.
He is succeeded by his wife Anne, three sons and a daughter.
(provided by CIE-UK) % From the Lighting Journals
Journal of Light & Visual Environment (www.soc.nii.ac.jp/ieij/) Volume 29, Number 1, 2005 Novel electrical modeling of arc discharges of fluorescent lamps
Y. Tamida, S. Funayama, A. Iwata Finite-element stress analysis and strength evaluation of super high pressure mercury lamp bulbs under internal pressure
M. Kase,Y. Iwama, T. Sawa Sky glow caused by the spill light from office buildings
N. Oba, K. Kawakami, T. Iwata, T. Uozumi, S. Kohko
Visual impression of lighting from a window and a ceiling: the effect of their compound ratio
S. Han, T. Ishida, W. Iwai An electronic ballast using back-boost converter
I. Yokozeki, Y. Kato, T. Kuratani, Y. Okamura, M. Ohkita, N. Takahashi
Study of the halogen volume on the tungsten halogen lamps
K. Shimogaki, H. Yoshiike The influence of dimming in road lighting on the visibility of drivers
A. Bacelar
10 � CIE NEWS 74
Light & Engineering (www.lta.ru) Volume 13, Number 1, 2005 Effect of optical characteristics of the discharge tube envelope on HPS lamp radiation
S.P. Reshenov Color and color distribution of signal lamps with LEDs
R. Rattunde Explosion-proof light fittings
B. Weis Radiation spectra of high power white LEDs and their application for lighting
Influence of various road coatings on road lighting power inputs
U. Carraro, J. Stromeier Investigations of visual perception conditions on pedestrian crossings
J. Zahr
Lighting Research & Technology (www.lrtjournal.com) Volume 37, Number 2, 2005 Lighting quality research using rendered images of offices
G.R. Newsham, C. Richardson, C. Blanchet, J.A. Veitch
A comparison of visual objectives used in side-by-side matching tests
S. Fotios, T. Gado
Potential recommendations for illuminance reductions by load-shedding
Y. Akashi, J. Neches Mesopic models - from brightness matching to visual performance in night-time driving: a review
M. Eloholma, M. Viikari, L. Halonen, H. Walkey, T. Goodman, J. Alferdinck, A. Freiding, P. Bodrogi, G. Várady
Lighting Design + Application (www.iesna.com) March 2005: Light in Motion April 2005: Museum & Exhibit Lighting May 2005: Hospitality
The Lighting Journal (www.ile.co.uk) Volume 70, Number 2, March/April 2005 The principle of light beam image splitting
P. Zsohár Bringing highway lighting management into the 21st century
M. Burrows The power demand of discharge lamps used in public lighting
S. Fotios, P. Boyce, R. Forster A short guide to lighting column structural safety
D. Coatham, S. Hobbs Street lighting and street clutter: an alternative solution?
H. Crossman
Volume 70, Number 3, May/June 2005 Office lighting - why all the fuss?
D. Burton Making light work of the office
N. Jones The lighting of the historic bridge at S. Ives, Cambridgeshire
P. Lummis All you need to know about seasonal decorative lighting
P. Harrison Two hundred years of gas lighting
G. White The importance of unity power factor
S. Hobbs
% For your Diary Date Title of Meeting Organizer Place of Meeting 2005 Sep. CIE Division 6 Meeting CIE Division 6 Aix-les-Bains, FranceSep. 9-14 Light India International 2005 ISLE, [email protected]
