FORD FLTM EU-BO 022-1-2000 TEST METHOD FOR LUMINOUS REFLECTANCE OF MIRRORS.pdf

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1、 FORD LABORATORY TEST METHOD EU-BO 022-01 Date Action Revisions 2000 12 01 Revised Editorial no technical change A. Cockman 1994 02 28 Printed copies are uncontrolled Page 1 of 6 Copyright 2000, Ford Global Technologies, Inc. TEST METHOD FOR LUMINOUS REFLECTANCE OF MIRRORS Application This procedure

2、 describes the basis for measurement of the absolute luminous (visual) specular reflectance of automotive rear view mirrors to C.I.E. (Commission International d Eclairage) standard illuminant “A“ (tungsten light). Apparatus Required The device employed shall consist of a light source, mirror sample

3、 holder, photoelectric receptor, indicating meter and associated light shields, circuitry, etc. This device shall be capable of proper calibration and zero adjustments for the required sample measurements and be within the following specific limitations. General guidelines for such systems are descr

4、ibed in ASTM (American Society for Testing and Materials) Designation E 179T, “Selection of Geometric Conditions for Measurement of Reflectance and Transmittance“ (see 1965 edition, Book of ASTM Standards, Part 30, Page 1383 - 1390). A similar procedure is also described in the 1967 SAE Handbook; SA

5、E J964. Light Source A tungsten lamp is required with associated light shields and/or other optics necessary to provide a near collimated standard C.I.E. illuminant “A“ (i.e. a tungsten light beam having a colour temperature of approx 2854 K or equivalent). Lamp voltage shall be fixed and sufficient

6、ly stable to permit instrument calibration and zeroing, then sample measurement, within the accuracy specified. Receptor A photoelectric cell is required with associated light shields and/or other optics as necessary to adequately receive that light specularly reflected from the sample mirror. The s

7、pectral response of the photoreceptor shall be equivalent to that of the normal observer (i.e., the C.I.E. standard observer). Photometric accuracy of the receptor-indicator circuit shall be within +/- 2 % of the full scale, or +/- 10 % of the magnitude of the reading whichever is smaller. The angle

8、 of the incident beam ( ) shall not J exceed 30 deg from the perpendicular to the test surface, and the axis of the receptor shall make an angle () with this perpendicular equal to that J of the incident beam (Figure 1). The incident beam upon arrival at the test surface shall have a diameter of 18

9、mm or larger, and shall not exceed the sample test area. The reflected beam, upon arrival at the photoreceptor, shall not be larger than the photosensitive area and shall not cover less than 50 % of such area, and should strike that area of the photoreceptor used for calibration. FORD LABORATORY TES

10、T METHOD EU-BO 022-01 Page 2 of 6 Copyright 2000, Ford Global Technologies, Inc. Instrument Calibration System The instrument shall have means by which calibration can be achieved by projecting the light beam directly onto the receptor unit at a calibration position distance equivalent to the total

11、test position distance. Such a calibration technique is referred to as “Direct Calibration“ and is illustrated in Figure 1. In this figure the receptor is shown in the “measure“ position by the solid line drawing and in the “calibrate“ position by the dashed line drawing. Equivalent “Indirect Calibr

12、ation“ technique employing a properly calibrated and maintained secondary standard and a fixed instrument geometry are acceptable. In the case of indirect calibrating instruments, the secondary standard is used in the same position as the mirror sample and the receptor is generally fixed in the “tes

13、t“ position (see Figure 1). Calibration adjustments shall be achieved through the use of a properly designed photocell shunt, optical iris, or equivalent means not affecting the linearity of the reflectance measuring system. (Note: Calibration by variation of the light source voltage is not an accep

14、table means.) It may be desired in some cases (such as when measuring low reflective surfaces) to use an intermediate calibration point (between 0 and 100 % on the scale) with this method. In such a case, a neutral density filter of known transmission value may be inserted in the optical path, and t

15、he calibrate control will then be adjusted until the meter reads the percent transmission of the neutral density filter. This filter must be removed before making any reflectivity measurement. Instrument Zeroing System The instrument shall include means by which the meter can be adjusted to read zer

16、o as required in the “Procedure“ section of this test method. This is generally achieved by a potentiometer controlled back-bias battery on the measuring photocell. Another method uses a second photocell located adjacent to the light source. The power generated by this second photocell is controlled

17、 by a potentiometer and connected electrically in opposition to the measuring photocell as a back-bias. This second back-bias photocell should be electrically and optically equivalent to the measuring photocell if used. Equivalent means are acceptable. However, any means employed shall provide a suf

18、ficiently constant meter zero to permit proper calibration and subsequent sample reflectance measurements. Mirror Sample Holder The mechanism for holding the sample mirror in position shall be such that the reflecting surface of the sample mirror is in the plane or reflectance of the instrument. In

19、other words, when testing a second surface mirror, for example, (such as a “silvered“ mirror or a lead-sulfide mirror) the back, or second, glass surface shall be in the plane of reflectance; or when testing a first surface mirror (such as a first surface chrome mirror), the front, or first, glass s

20、urface shall be in the plane of reflectance. Wedge (or “flip“) type day/night mirrors require a special fixture to accommodate the small angle between the glass surfaces. Other special mirrors require other special fixtures. FORD LABORATORY TEST METHOD EU-BO 022-01 Page 3 of 6 Copyright 2000, Ford G

21、lobal Technologies, Inc. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specifi

22、ed. Procedure Calibration and Zero Adjustments 1. Direct Calibration Method The direct calibration method is for those mirror reflectometers which are constructed so as to permit calibration at the 100 % point by swinging the measuring photoelectric receptor to a position directly on the axis of the

23、 light source, then to an angle of 60 to this axis for the 30 specular reflectance measurement. Direct calibration procedures follow (see Figure 1). (a) Allow the instrument to warm up according to instructions of the instrument manufacturer or designer. (b) Obstruct the light beam with an opaque ob

24、ject at an aperture or area between the light source and sample area. Adjust the “zero“ control until the meter reads “0 %“. (c) Remove the light obstruction and adjust the “calibrate“ control until the meter reads “100 %“. (d) Repeat Steps (b) and (c) above at least twice until no further adjustmen

25、ts of the “zero“ and “calibrate“ controls are necessary before proceeding with the reflectance measurements. 2. Indirect Calibration Method The indirect calibration method is for those mirror reflectometers which are of fixed geometry with the measuring photoelectric receptor axis oriented at 60 to

26、the light source axis. Since direct calibrations are impossible with these instruments, they require the indirect calibration method using a secondary reflectance standard. Indirect calibration procedures follow (see Figure 1). (a) Allow the instrument to warm up according to the instructions of the

27、 instrument manufacturer or designer. (b) Obstruct the light beam with an opaque object at an aperture or area between the light source and sample area. Adjust the “zero“ control until the meter reads “0 %“. FORD LABORATORY TEST METHOD EU-BO 022-01 Page 4 of 6 Copyright 2000, Ford Global Technologie

28、s, Inc. (c) Remove the light obstruction and mount the reflectance standard in the mirror sample holder. Adjust the “calibrate“ control until the meter reads the percent reflectance value assigned to this standard. Note: See para 1 below, including special “note“ for mounting of reflectance standard

29、. (d) Repeat Steps (b) and (c) above at least twice until no further adjustment of the “zero“ and “calibrate“ controls are necessary before proceeding with the reflectance measurements. Reflectance Measurements 1. Mount mirror to be tested in sample holder according to instrument instructions. Note:

30、 Follow any special instrument instructions if special sample holders or attachments are required when testing; for example, two-position “flip“ (or wedge) type day/night mirrors or other special mirrors. 2. Read percent reflectance from meter. 3. Repeat calibration and zero checks periodically to d

31、etermine the frequency with which such adjustments should be made to maintain accuracy. Report 1. Instrument manufacturer, type and serial number. 2. Instrument (or special measurement) geometry if other than specular 30. 3. Method of instrument calibration i.e., “direct“ or “indirect“. If “indirect

32、“ state: (a) Serial number or other identification of indirect reflectance standard. (b) Source or method of calibration of standard. (c) Percent reflectance of standard. FORD LABORATORY TEST METHOD EU-BO 022-01 Page 5 of 6 Copyright 2000, Ford Global Technologies, Inc. 4. Sample identification and

33、test results. (a) Sample number, source and manufacturer. (b) Mirror sample type (i.e. first surface mirror, second surface mirror, two-position day/night mirror, etc.). (c) Percent reflectance for each sample. Note: If sample is a day/night or other multi-position mirror, report percent reflectance

34、 for each position. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD EU-BO 022-01 Page 6 of 6 Copyright 2000, Ford Global Technologies, Inc. TEST METHOD FOR LUMINOUS REFLECTANCE OF MIRRORS GENERALIZED REFLECTOMETER Geometries for the Two Calibration Methods.