BS AU 170-1979 Methods for measurement of reflectance of rear view mirrors《后视镜反射率的测量方法》.pdf

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1、BRITISH STANDARD AUTOMOBILE SERIES CONFIRMED DECEMBER1987 BS AU 170:1979 Methods for Measurement of reflectance of rear view mirrors UDC 629.113.0181:535.346.1BSAU170:1979 This BritishStandard, having been prepared under the directionof the Automobile Standards Committee, was published under the aut

2、hority ofthe Executive Board on 28February1979 BSI 03-2000 The following BSI references relate to the work on this standard: Committee reference AUE/- Draft for comment77/73276 DC ISBN 0 580 10695 0 Foreword This BritishStandard, which has been prepared under the direction of the Automobile Standard

3、s Committee, is based on ISO5740 “Road vehicles Rearview mirrors Test method for determining reflectivity”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British S

4、tandard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to6 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indi

5、cated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBSAU170:1979 BSI 03-2000 i Contents Page Foreword Inside front cover 1 Scope and field of application 1 2 References 1 3 Definitions 1 4 Apparatus 1 5 Procedures 2 Appendix A Sp

6、ectral tristimulus values for CIE1931 standard colorimetricobserver 4 Figure 1 Generalized reflectometer showing geometriesfor thetwocalibrationmethods 5 Figure 2 Generalized reflectometer incorporating an integrating sphere 6ii blankBSAU170:1979 BSI 03-2000 1 1 Scope and field of application This B

7、ritishStandard specifies a test method for determining the reflectance of rear-view mirrors for road vehicles. It applies to flat and convex surface mirrors intended for internal and external mounting. 2 References The following publications are referred to in this standard. BS354, Recommendations f

8、or photometric integrators. BS667, Portable photoelectric photometers. BS4727, Glossary of electrotechnical, power, telecommunications, electronics, lighting and colour terms Part4: Terms particular to lighting and colour Group01: Radiation and photometry Group02: Vision and colour terminology. 3 De

9、finitions For the purposes of this BritishStandard, the following definitions apply. 3.1 CIE standard illuminant A (as defined in term number4022031 of BS4727-4:Group02:1971) colorimetric illuminant, representing the full radiator at T 68 =2855.5K 3.2 CIE standard source A (as defined in term number

10、4022032 of BS4727-4:Group02:1971) gas-filled tungsten filament lamp operating at a correlated colour temperature of T 68 =2855.5K 3.3 CIE1931 standard colorimetric observer (asdefined in term number4022011 of BS4727-4:Group02:1971) receptor of radiation whose colorimetric characteristics correspond

11、to the spectral tristimulus values , , adopted by the International Commission on Illumination in1931 (See3.4 and Appendix A.) 3.4 CIE spectral tristimulus values (as defined in term number4022008 of BS4727-4: Group02:1971) tristimulus values of the spectral components of an equienergy spectrum in t

12、he CIE (XYZ) system NOTE 1Formerly CIE-distribution coefficients. NOTE 2In the CIE1931 standard colorimetric system, applicable to observing fields of angular subtense between1and4 (0.017 and0.07 rad), these tristimulus values, , are so chosen that the values of areidentical with the spectral lumino

13、us efficiencies V (2). (SeeAppendix A.) 3.5 photopic vision (as defined in term number4021111 of BS4727-4:Group02:1971) vision by the normal eye when it is adapted to levels of luminance of at least several candelas per square metre NOTEThe cone receptors of the retina are considered to be the princ

14、ipal active elements under these conditions and the spectrum appears coloured. 3.6 reflectance (as defined in term number4013008 of BS4727-4:Group01:1971) the ratio of reflected luminous flux to the incident luminous flux ( ) NOTEWhere mixed reflection occurs, the total reflectance may be divided in

15、to two parts, specular reflectance ( r ) and diffuse reflectance ( d ). Total reflectance may be expressed by the following equation: = r + d 4 Apparatus 4.1 General. The apparatus shall consist of a light source, a holder for the test sample, a reflectometer with a photodetector and an indicating m

16、eter (seeFigure 1), and a means of eliminating the effects of extraneous light. The reflectometer in Figure 1 measures the specular component of reflectance. The reflectometer may incorporate a light-integrating sphere to facilitate measuring the reflectance of non-flat (convex) mirrors (seeFigure 2

17、). In this case the reflectometer measures the total reflectance, i.e.the sum of the specular and diffuse components. The required characteristics of the components of the apparatus are described in BS354 and in BS667. 4.2 Spectral characteristics of light source and reflectometer. The light source

18、shall consist of a CIE standard source A and associated optics to provide a near-collimated light beam. A voltage stabilizer is recommended to maintain a fixed lamp voltage during instrument operation. x () y () z () x () y () z () y ()BSAU170:1979 2 BSI 03-2000 The reflectometer shall have a photod

19、etector with a spectral response proportional to the photopic luminosity function of the CIE (1931) standard colorimetric observer (SeeAppendix A.) Any other combination of illuminant-filter-receptor giving the overall equivalent of CIE standard illuminant A and photopic vision may be used. When an

20、integrating sphere is used in the reflectometer, the interior surface of the sphere shall be coated with a matt (diffusive) spectrally non-selective white coating. 4.3 Geometric conditions. The angle of the incident beam ( i ) should preferably be0.44 0.09 rad (25 5 ) from the perpendicular to the t

21、est surface and shall not exceed the upper limit of the tolerance (i.e.0.53 rad or30 ). The axis of the receptor shall make an angle ( r ) with this perpendicular equal to that of the incident beam (seeFigure 1). The incident beam upon arrival at the test surface shall have a diameter of not less th

22、an19mm (0.75in). The reflected beam shall be narrower than the sensitive area of the photodetector, shall cover not less than50% of such area, and as nearly as possible shall cover the same area segment as used during instrument calibration. NOTEIf the beam width is the same as the sensitive area, p

23、roblems with vignetting may occur. When an integrating sphere is used in the reflectometer, the sphere shall have a minimum diameter of127mm (5in). The sample and incident beam apertures in the sphere wall shall be of such a size as to admit the entire incident and reflected light beams. The photode

24、tector shall be located so as not to receive direct light from either the incident or the reflected beams, and should be screened from any scattered light which might pass directly from the sample (seeFigure 2). 4.4 Electrical characteristics of the photodetector-indicator unit. The photodetector ou

25、tput as read on the indicating meter shall be a linear function of the light intensity on the photo-sensitive area. Means (electrical and/or optical) shall be provided to facilitate zeroing and calibration adjustments. Such means shall not affect the linearity or the spectral characteristics of the

26、instrument. The accuracy of the receptor-indicator unit shall be within2% of full scale, or 10% of the magnitude of the reading, whichever is the smaller. 4.5 Sample holder. The mechanism shall be capable of locating the test sample so that the axes of the source arm and receptor arm intersect at th

27、e principle reflecting surface. The reflecting surface may lie within or at either face of the mirror sample, depending on whether it is a first-surface, second-surface, or prismatic “flip” type mirror. 5 Procedures 5.1 General. Four procedures, for use with different kinds of measuring instruments,

28、 are given below. (See5.2 to5.6.) 5.2 Direct calibration method. In the direct calibration method, the incident flux is used as the reference standard. This method is applicable to those instruments which are so constructed as to permit calibration at the100% point by swinging the receiver to a posi

29、tion directly on the axis of the light source (seeFigure 1). It may be desirable in some cases (such as when measuring low-reflectance surfaces) to use an intermediate calibration point (between0 and100% on the scale) with this method. In these cases, a neutral density filter of known transmittance

30、shall be inserted in the optical path, and the calibration control can then be adjusted until the meter reads the percentage transmission of the neutral density filter. This filter shall be removed before making measurements on the sample. NOTETo expand the scale when dealing with low-reflectance sa

31、mples, it may be desirable to set a full-scale reading with the calibrated filter and multiply the apparent measured reflectance by the transmittance of the filter. 5.3 Indirect calibration method. The indirect calibration method is applicable to those instruments with fixed source and receiver geom

32、etry. A properly calibrated and maintained reflectance standard is required. This reference standard should preferably be a flat mirror with a reflectance value as near as possible to that of the test samples. 5.4 Flat mirror measurement. The reflectance of flat mirror samples can be measured on ins

33、truments employing either the direct or indirect calibration method. The reflectance value is read directly from the indicating meter. 5.5 Non-flat (convex) mirror measurement. The measurement of the reflectance of non-flat (convex) mirrors require requires the use of instruments which incorporate a

34、n integrating sphere (seeFigure 2). If the instrument indicating meter indicates n Edivisions with a reference standard mirror of E % reflectance, then, with a mirror of unknown reflectance, n Xdivisions will correspond to a reflectance of X %, given by the formula where the symbols are as given abo

35、ve.BSAU170:1979 BSI 03-2000 3 5.6 Measurement of diffuse component of reflectance. The reflectometer shown in Figure 2 may also be used to measure the diffuse components of reflectance separately. In this case a gloss trap shall be used which covers the geometrical optical cross section of the regul

36、arly reflected beam from the sample, allowing for any curvature of the sample. The gloss trap may consist of a blackened cap covering an additional port hole, or a blackened cavity held behind this additional port hole. When this additional port hole exists in the reflectometer, it should be covered

37、 by a whitened cap whose coating is as similar to the sphere walls and coating as possible.BSAU170:1979 4 BSI 03-2000 Appendix A Spectral tristimulus values for the CIE1931 standard colorimetric observer NOTEThis table, which is extracted from IEC Publication50(45) (1970), has been abridged. The val

38、ues of=V (2) are rounded to four decimal places. 2 mm 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550 560 570 580 590 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 780 0.0014 0.0042 0.0143 0.0435 0.1344 0.2839 0.3483 0.3362 0.2908 0.1954 0.0956 0.032

39、0 0.0049 0.0093 0.0633 0.1655 0.2904 0.4334 0.5945 0.7621 0.9163 1.0263 1.0622 1.0026 0.8544 0.6424 0.4479 0.2835 0.1649 0.0874 0.0468 0.0227 0.0114 0.0058 0.0029 0.0014 0.0007 0.0003 0.0002 0.0001 0.0000 0.0000 0.0001 0.0004 0.0012 0.0040 0.0116 0.0230 0.0380 0.0600 0.091 0 0.1390 0.2080 0.3230 0.5

40、030 0.7100 0.8620 0.9540 0.9950 0.9950 0.9520 0.8700 0.7570 0.6310 0.5030 0.3810 0.2650 0.1750 0.1070 0.0610 0.0320 0.0170 0.0082 0.0041 0.0021 0.0010 0.0005 0.0002 a 0.0001 0.0001 0.0000 0.0000 0.0065 0.0201 0.0679 0.2074 0.6456 1.3856 1.7471 1.7721 1.6692 1.2876 0.8130 0.4652 0.2720 0.1582 0.0782

41、0.0422 0.0203 0.0087 0.0039 0.0021 0.0017 0.0011 0.0008 0.0003 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 a In1966 this value was altered from0.0003 to0.0002. y () x () y () z ()BSAU170:1979 BSI 03-2000 5 Figure 1 Generalize

42、d reflectometer showing geometries for the two calibration methodsBSAU170:1979 6 BSI 03-2000 Figure 2 Generalized reflectometer incorporating an integrating sphereblankBS AU 170:1979 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsi

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