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1、International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION*MEYHAPOHAR OPrAHH3AUMR fl0 CTAHAPTAMCJRGANISATION INTERNATIONALE DE NORMALISATION Personal eye-protectors - Optical test methods Protectem individuels de l cail - M alter- natively, the protector may be displaced relative to the s
2、ingle telescope and target, these remaining fixed. The distance be- tween ocular and telescope shall be reduced to a minimum. In the event that the telescope, a large-aperture instrument, shows a doubling of the image or other aberration, the ocular to be tested shall be examined with a 5 mm apertur
3、e instrument to locate and quantify the area or areas of aberration in the total area of 20 mm diameter. A focometer may be used for this operation. 3.2.1.3 Double target, conforming to the design shown in figure 3, or single target, as the case may be, on which the reading is made. The target is br
4、ightly illuminated and placed 4,6 f 0,l m from the telescope(s). 3.2.2 Procedure Place the protector to be tested on the support (3.2,l.l). Using both telescopes, one for each ocular in the case of spectacles (the arms of those must be horizontal) and two-piece goggles, or at each visual centre in t
5、he case of face-shields and one- piece goggles, measure the horizontal and vertical prismatic powers by counting the number of circles across which the ver- tical and horizontal cross-wires of the graticule are displaced and by interpolating between two circles if necessary. Since each circle repres
6、ents 0,05 cm/m, the reading may be made to the nearest f. 0,025 cm/m. Deviations measured for each ocular or each visual centre are added when they are in opposite directions and subtracted when they are in the same direction. Measure the refractive power for each ocular or each visual centre by ope
7、ning the telescope diaphragm to 20 mm. Deter- mine the astigmatism by the difference of refractive powers measured by resolving 2 circular arcs on the target. Spherical effect is the average of refractive powers measured by resolving 2 circular arcs on the target. In this way a value for the horizon
8、tal prismatic power and a value for the vertical prismatic power are obtained, es well as values for the spherical effect and astigmatism. These values shall be within the limits defined in table 3 of sub-clause 7.1.2.1.2 of IS0 484% Two other optional methods for prismatic power measurement are pre
9、sented in annexes B and C. 2 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 4854-1981(E) D
10、imensions in millimetres 3 I -_ - - n -m r= q-+-E Figure 2 - Standard support for spectacles 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or netw
11、orking permitted without license from IHS -,-,- IS0 4854-1981(E) Dimensions in millimetres Figure 3 - Double target 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDT
12、No reproduction or networking permitted without license from IHS -,-,- IS0 4854-1981 (El 4 Diffusion test The test method described in 4.3 is given as a reference method. Alternative methods for filters having a transmittance value (7,) in excess of 10 % may be used, as for example a hazemeter or vi
13、sual inspection, provided that correlation has been established for the material under test. 4.1 Basic notions 4.1.1 Reduced luminance factor The degree of diffusion of light produced by a filter is propor- tional to the illuminance E. Luminance is a measure of the dif- fusion of light by the filter
14、, and the value L, is proportional to the illuminance E of the filter. The proportionality factor is the luminance factor 1 = LJE, which is expressed in candelas per lux per square metre cd . m-2. 1x-11. To obtain a factor I* which does not depend upon the transparency of the filter, the luminance f
15、actor is divided by T, thus producing : p = =A 5 ET This quantity is known as the reduced luminance factor and is expressed in the same units as luminance factor. NOTE - Variation of diffusion with observation direction : Most oculars have diffusion properties which are symmetrical about the op- tic
16、al axis. For these oculars, the mean value of the reduced luminance facfor is constant within an angle limited by the two cones shown in figure 4. This mean value depends upon values a and Aa. 4.1.2 Fluorescence The luminance facfor also includes fluorescent light caused by any ultraviolet radiation
17、; therefore, the spectral distribution of the source used during measurement shall be similar to that of the source to which the filter is exposed in practice. Filter Diffused light Optical axis Figure 4 - Variation of diffusion with observation direction Copyright International Organization for Sta
18、ndardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 4854-1981 (El 4,2 Apparatus Figure 5 illustrates the assembly of the apparatus. Figure
19、5 - Assembly of apparatus for diffusion test L Very pure silica-glass high-pressure xenon lamp (for example XBO 150 W - 4 or CS X 150 W - 4) Hi Spherical concave mirror : focal length 150 mm; diameter 40 mm H2 Spherical concave mirror : focal length 300 mm; diameter 40 mm H3 Spherical concave mirror
20、 : focal length 300 mm; diameter 70 mm A Achromatic lens : focal length 200 mm; diameter 30 mm Ut, U2 Flat mirrors h Annular diaphragm : diameter of outer circle 21,00 mm; diameter of inner circle 15,75 mm BL Circular diaphragm : diameter of aperture 7,5 mm M Photomultiplier corrected according to c
21、urve V (1) with diffusing screen MS 4 Iris-diaphragm to adjust diameter of field of observation 1% Iris-diaphragm to eliminate edge effects from 1st LB Circular diaphragm, diameter of aperture 0,4 mm P, P Positions of test sample Copyright International Organization for Standardization Provided by I
22、HS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 4854-1981 (E) Spherical mirror H, forms an image of light source L at diaphragm LB of the same dimensions as L. T
23、he concave mirror H3 forms an image of diaphragm LB in the plane of diaphragms BL and Ba. The achromatic lens A is positioned im- mediately behind the diaphragm so that a reduced image of the test sample in position P appears on diffusing screen MS. The image of iris-diaphragm IBt is simultaneously
24、formed on IB2. This assembly collects all the light originating from the filter benveen angles a = 1,5O and LY t da = 2O in relation to the optical axis. The angular area is important in the case of welding, where a point in the immediate proximity of the weld spot has to be observed. It is, however
25、, possible to measure scattered light in other angular areas if use is made of an annular diaphragm with suitably modified dimensions. 4.3 Procedure w is the solid angle defined by the annular diaphragm. Test oculars shall meet the optical requirements of sub-clause 7.1.2.1 of IS0 4849. Position the
26、 test sample in the beam parallel to position P, then set diaphragm BL in place. The flux IL falling onto the photomultiplier corresponds to the undiffused light transmitted by the sample and is in proportion to Es. Then replace diaphragm BL by annular diaphragm Ba; flux ,a falling onto the photomul
27、tiplier corresponds to the total diffused light originating from the filter and from the apparatus. Then arrange the test sample at position P . Flux ze falling onto the photomultiplier corresponds to the diffused light coming from the apparatus only. Lamp 1 30 - /- Adjustable opaque dull black mask
28、 b( P i t - Difference (PIa - Q2n is a measure of the light diffused by the filter, and is proportional to wL,. The proportionality factor is the same in both cases. The reduced mean luminance factor i*m for the solid angle w is calculated from the preceding fluxes by means of the formula : 1 I* m=-
29、X %I - 2R 0 lL where tR, Q2a are the luminous fluxes with the annular diaphragm; tL is the luminous flux with the circular diaphragm; Dimensions in millimetres 5 Test for quality of material and surface The apparatus (recommended means of examination) used for this test is shown in figure 6. The bri
30、ghtness of the lamp shall be related to the optical den- sity of the filter. This subjective examination requires ex- perience and is made at the limit “clear-dark” and without op- tical magnifying means. /Dull black background (200 X 360) L I I s 400 Near vision distance (about 300) e Figure 6 - Ap
31、paratus-for test for quality of material and surface Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS
32、-,-,- Is0 4 v is the distance between the points of the refracted rays in the measuring plane (figure 7). For the prismatic power, the following formula applies : . (4) 9 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards
33、 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 4854-1981 (E) The astigmatic power is equal to the difference between the refractive powers in the two principal directions. -Measuring plane Test ocular /I Figure 7 - Dete
34、rmination of the distancef of the focal plane from the test ocular by means of two parallel rays 1 and 2 u = distance between the parallel rays 1 and 2; V = distance between the refracted rays 1 and 2 in the measuring plane; w = distance between the test ocular and measuring plane; 6 = angle of defl
35、ection of the central ray 1; v. = deflection of the central ray from the optical axis in the measuring plane. A.3 Experimental mounting The measuring device is composed of the following main elements (see figure 81 : a) a laser supplying a parallel light beam as narrow as possible; b) a carriage mov
36、ing the test sample support on a spiral path; c1 a position-sensing photodiode, the photocurrent of which is recorded on an XY-recorder. The light source is a He-Ne laser of adequate performance (2 mW1, supplying monochromatic continuous light. Two lenses with a diaphragm at the common focal point e
37、nlarge the laser beam to a diameter of 5 mm, to match the mean size of the eye pupil. This arrangement also provides a homogeneously illuminated spot. The carriage moves the test ocular continuously on a spiral path in a plane perpendicular to the direction of the laser beam. During the measurement,
38、 the test ocular shall not turn in rela- tion to the photodiode, so that the light is directed in a fixed direction. To achieve this, the carriage runs on two guides perpendicular to each other, maintaining the directions of the axes of the carriage and the test ocular constant during the measuremen
39、t. A pivot guided by a spiral transmits the corresponding move- ment to the carriage (see figure 81. Figure 8 - Experimental mounting for measuring small refractive and astigmatic powers He-Ne = He-Ne laser Lt, Lz = lenses B = 20 urn diaphragm S, S2 = deflection mirrors SP = spiral Sch = carriage F,
40、 F, = guiding in x and y directions A = test sample Ph = photodetector v = pre-amplifier X-Y = XY recorder The pitch of the spiral is I,08 mm. The 5 mm diameter laser beam continuously scans the whole surface of the test ocular. By appropriate markings, the position of the light beam on the filter a
41、nd its deflection can be noted simultaneously. The deflection of the laser beam is recorded by a position- sensing photodiode (see figure 9). On this photodiode (PIN SC-251 a rectangular system of co-ordinates is established by the five connections. When the centre, 5, is illuminated, the photocurre
42、nt of the remaining four connections is equal. When the light spot is moved over the sensitive surface, the photocur- rent of connections 1 to 4 changes according to the position of the light spot in relation to the centre. The photocurrent of con- nection 5 remains constant and is directly proporti
43、onal to the radiant flux. Because of the variation of the photocurrent between the con- nections, the potential difference between the connections of one axis is proportional to the displacement on this axis (see figure 91 as well as to the radiant flux. 10 Copyright International Organization for S
44、tandardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 01:19:56 MDTNo reproduction or networking permitted without license from IHS -,-,- Y-axis IS0 4954-1981 (E) A.4 Measurements -+ t t 3 -4 x4 X-axis 0 = electrical connection
45、s from 1 to 5 XY-recorder XY-recorder XY-recorder 3k b) Connections Figure 9 - Position-sensing photodiode The radiation receiver has an active sensitive surface of 1,9 cm x 1,9 cm. In this experimental mounting, it can be positioned at distances between 90 and 250 cm from the test ocular as require
46、d, so that, at a scanned area of 30 mm diameter, a refractive quantity up to a maximum of 2 m-1 can be measured. The sensitivity of this experimental mounting corresponds to approximately 10 -5 m - 1. A.4.1 Interpretation of various measuring results When making measurements, the test ocular is scan
47、ned on a spiral path. The undeflected laser beam always points to the centre of the photodiode and only the test ocular is moved. This allows the distance (U - VI (equation 3) to be measured directly in the plane of the receiver. ) Since directions X.and Y are read in an equivalent way by the photoe
48、lectric cell and by the recorder, the spiral path, depen- ding on the refractive quantity of the test ocular, is presented on the recorder either enlarged or reduced. With a plane test ocular, the direction of the light beam is in- dependent of its position on the test ocular, because it does not change when passing through the test ocular. As a first approx- imation, the image on the recorder is, therefore, a point. With a curved fest ocular without refractive power, i.e. a meniscus, the point may be slightl