1、BS ISO18921:2008ICS 35.220.30; 37.040.99NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDImaging materials Compact discs (CD-ROM) Method forestimating the lifeexpectancy basedon the effects oftemperature andrelative humidityThis British Standard was published und
2、er theauthority of the StandardsPolicy and StrategyCommittee on 30 November2008 BSI 2008ISBN 978 0 580 63274 7Amendments/corrigenda issued since publicationDate CommentsBS ISO 18921:2008National forewordThis British Standard is the UK implementation of ISO 18921:2008. Itsupersedes BS ISO 18921:2002
3、which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CPW/42, Photography.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract.
4、Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 18921:2008Reference numberISO 18921:2008(E)ISO 2008INTERNATIONAL STANDARD ISO18921Second edition2008-10-15Imaging materials Compact discs (CD-ROM) Method for estim
5、ating the life expectancy based on the effects of temperature and relative humidity Matriaux pour limage Disques compacts (CD-ROM) Mthode destimation de lesprance de vie base sur les effets de la temprature et de lhumidit relative BS ISO 18921:2008ISO 18921:2008(E) PDF disclaimer This PDF file may c
6、ontain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the respons
7、ibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
8、parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 Al
9、l rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country
10、of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedBS ISO 18921:2008ISO 18921:2008(E) ISO 2008 All rights reserved iiiContents Page Forew
11、ord iv 1 Scope1 2 Normative references1 3 Terms and definitions .1 4 Purpose and assumptions3 4.1 Purpose 3 4.2 Assumptions3 5 Measurements .3 5.1 Block error rate (BLER).3 5.2 Test equipment 3 5.3 Test specimen4 6 Accelerated stress test plan.4 6.1 General .4 6.2 Stress conditions 5 6.3 Accelerated
12、 test cell specimen population.7 6.4 Time intervals 8 6.5 Test plan.8 6.6 Measurement conditions 8 7 Data evaluation 8 7.1 Eyring acceleration model8 7.2 Failure distribution model 9 7.3 Acceleration factors 9 7.4 Survivor analysis.10 8 Disclaimer 10 Annex A (informative) Step analysis outline 11 An
13、nex B (informative) Example of test plan and data analysis12 Bibliography19 BS ISO 18921:2008ISO 18921:2008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prep
14、aring 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
15、liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task
16、of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention
17、is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 18921 was prepared by Technical Committee ISO/TC 42, Photography. This second edition cancels and replaces
18、the first edition (ISO 18921:2002), of which it constitutes a minor revision. The following changes have been made to the first edition: modification of definition 3.8 (life expectancy); modification of 5.1 on block error rate; correction of Equations (1) and (2) in 7.1; updating of normative and bi
19、bliographical references; removal of the original Annex A. BS ISO 18921:2008INTERNATIONAL STANDARD ISO 18921:2008(E) ISO 2008 All rights reserved 1Imaging materials Compact discs (CD-ROM) Method for estimating the life expectancy based on the effects of temperature and relative humidity 1 Scope This
20、 International Standard specifies a test method for estimating the life expectancy (LE) of information stored on compact disc (CD-ROM) media, including CD audio, but excluding recordable media. Only the effects of temperature and relative humidity on the media are considered. 2 Normative references
21、The following referenced documents are indispensable for the application 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/IEC 101491), Information technology Data inte
22、rchange on read-only 120 mm optical data disks (CD-ROM) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 cumulative distribution function F(t) probability that a random unit drawn from the population fails by time t, or the fraction of all uni
23、ts in the population which fails by time t 3.2 survivor function R(t) probability that a unit drawn from the population will survive at least time t, or the fraction of units in the population that will survive at least time t NOTE () 1 ()R tFt= . 3.3 baseline condition representing the disc at time
24、 of manufacture NOTE This is customarily the initial parameter measurement taken prior to any application of stress. The designation is usually t = 0 for a stress time equal to zero hours. 1) Equivalent to ECMA 130. BS ISO 18921:2008ISO 18921:2008(E) 2 ISO 2008 All rights reserved3.4 block error rat
25、e BLER ratio of erroneous blocks to total blocks measured at the input of the first (C1) decoder (before any error correction is applied) NOTE The more commonly reported value for BLER is the number of erroneous blocks per second measured at the input of the C1-decoder during playback at the standar
26、d (1X) data rate. IEC 60908:1999 3.5 CD-ROM compact disc-read only medium 3.6 end-of-life occurrence of any loss of information 3.7 information signal or image recorded using the system 3.8 life expectancy LE length of time that information is predicted to be retrieved in a system at 23 C and 50 % r
27、elative humidity (RH) 3.8.1 standard life expectancy SLE minimum life span, predicted with 95 % confidence, of 95 % of the product stored at a temperature not exceeding 25 C and a relative humidity (RH) not exceeding 50 % RH 3.9 retrievability ability to access information as recorded 3.10 stress ex
28、perimental variable to which the specimen is exposed for the duration of the test interval NOTE In this International Standard, the stress variables are confined to temperature and relative humidity. 3.11 system combination of recording medium, hardware, software and documentation necessary to retri
29、eve information 3.12 test cell device that controls the stress to which the specimen is exposed 3.13 test pattern distribution of the characters l and 0 within a block and the block-to-block variation BS ISO 18921:2008ISO 18921:2008(E) ISO 2008 All rights reserved 34 Purpose and assumptions 4.1 Purp
30、ose The purpose of this International Standard is to establish a methodology for estimating the life expectancy of information stored on CD-ROMs. This methodology provides a technically and statistically sound procedure for obtaining and evaluating accelerated test data. 4.2 Assumptions The validity
31、 of the procedure defined by this International Standard relies on three assumptions: the dominant failure mechanism acting at the usage condition is the same as at the accelerated conditions; the dominant failure mechanism is appropriately modelled by an Eyring acceleration model; life expectancy i
32、s appropriately modelled by the two parameter Weibull distribution (see 1 in the Bibliography). The shape parameter of the Weibull distribution is assumed to be independent of the stress level. 5 Measurements 5.1 Block error rate (BLER) The objective of measuring the block error rate (BLER) is to es
33、tablish a practical estimation of the systems ability to read the pre-recorded bits using a standard drive. This International Standard considers BLER to be a high level estimate of the performance of the system. A change in BLER in response to the time at an elevated temperature and humidity is the
34、 principal quality parameter. IEC 60908 states that the BLER averaged over any 10 s shall be less than 3 102. At the standard (1X) data rate, the total number of blocks per second entering the C1-decoder is 7 350. Thus, an equivalent limit on BLER is 220 blocks per second. For the purposes of this I
35、nternational Standard, recorded data are considered to have reached end-of-life when the BLER, measured as erroneous blocks per second, exceeds 220 anywhere on the disc, i.e. when the maximum BLER exceeds 220. It is recognized that the correlation between actual loss of information and maximum BLER
36、is very system dependent. A BLER of 220 is an arbitrary level chosen as a predictor of the onset of uncorrectable errors and thereby end-of-life. 5.2 Test equipment 5.2.1 Compact disc test system Any compact disc test system (tester) that is in accordance with ISO/IEC 10149 may be used. The make, mo
37、del and version of the test equipment (including software) shall be reported with the test results. 5.2.2 Calibration and repeatability Calibration according to the tester manufacturers procedure shall be performed prior to any measurement data being collected. A calibration disc shall be available
38、from the tester manufacturer. BS ISO 18921:2008ISO 18921:2008(E) 4 ISO 2008 All rights reservedIn addition to the calibration disc, one control disc shall be maintained at ambient conditions and its maximum BLER measured before and after each data collection interval. A control chart shall be mainta
39、ined for this control disc with 3 action limits. The mean and standard deviation of the control disc shall be established by collecting at least five measurements. Should any individual maximum BLER reading exceed the action limit, the problem shall be corrected and all data collected since the last
40、 valid control point shall be remeasured. If it becomes necessary to replace the tester, a method shall be followed for correlating tester outputs (see 2 in the Bibliography). 5.3 Test specimen A test specimen is any disc that meets ISO/IEC 10149 specifications and contains representative data exten
41、ding to within 2 mm of the maximum recording diameter. 6 Accelerated stress test plan 6.1 General A CD-ROM of good manufacture should last several years or even decades. Consequently, it is necessary to conduct accelerated ageing studies in order to develop a life expectancy estimate. The key is con
42、ducting and evaluating a test plan that will provide the information necessary to satisfactorily evaluate the particular product. Many accelerated life test plans follow a rather traditional approach in sampling, experimentation and data evaluation. These “traditional plans” share the following char
43、acteristics: a) the total number of specimens is evenly divided amongst all the accelerated stresses; b) each stress is evaluated at the same time increments; c) the Arrhenius relationship is used as the acceleration model; d) the least squares method is used for all regressions; e) the calculated l
44、ife expectancy is for the mean or median life rather than for the first few failure percentiles. On the other hand, “optimum test plans” have been proposed which differ in significant aspects from traditional plans. These plans have the following characteristics: two and only two acceleration levels
45、 for each stress; a large number of specimens distributed mostly in the lowest stress levels; the need to know the failure distribution, a priori, in order to develop the plan. The maximum effectiveness of a plan can either be estimated before the test starts or determined after the results have bee
46、n obtained. As each CD-ROM system has different characteristics, a specific, detailed optimum plan is impossible to forecast. This test plan borrows from the optimum plan, the traditional plan, previous experience with the systems, test equipment and accelerated test stresses to put together a “comp
47、romise test plan”. Modifications of this plan will be required to design the best plan for other applications. The methodology shall be applicable to all CD-ROM media assessments. BS ISO 18921:2008ISO 18921:2008(E) ISO 2008 All rights reserved 56.2 Stress conditions 6.2.1 Levels As mentioned in 6.1,
48、 an optimum test plan utilizes only two stress levels for each parameter evaluated, since in an ideal case the relationship between changes in the parameter investigated and changes in stress is known. The compromise test plan documented in this International Standard does not make such an assumptio
49、n; therefore, three different stress levels per parameter shall be used so that the linearity of the parameter function versus the stress level may be demonstrated. The test plan shall have the majority of test specimens placed at the lowest stress condition. This minimizes the estimation error at this condition and results in the best estimate of the degradation rate at a level close to the usage condition. The greater number of specimens at the lower stress also tends to equalize the
