SIST EN ISO 8598:2000

SLOVENSKI STANDARD
SIST EN ISO 8598:2000
01-januar-2000
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Optics and optical instruments - Focimeters (ISO 8598:1996)
Optik und optische Instrumente - Scheitelbrechwert-Meßgeräte (ISO 8598:1996)
Optique et instruments d'optique - Frontofocometres (ISO 8598:1996)
Ta slovenski standard je istoveten z: EN ISO 8598:1998
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
SIST EN ISO 8598:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 8598:2000

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SIST EN ISO 8598:2000

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SIST EN ISO 8598:2000

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SIST EN ISO 8598:2000

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SIST EN ISO 8598:2000

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SIST EN ISO 8598:2000
INTERNATIONAL Is0
STANDARD 8598
First edition
1996-08-o 1
Optics and optical instruments -
Focimeters
Op tique et instruments d ‘op tique - Fron tofocom8 tres
Reference number
IS0 8598: 1996(E)

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SIST EN ISO 8598:2000
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be rep-
resented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 8598 was prepared by Technical Committee
lSO/TC 172, Optics and optical instruments, Subcommittee SC 7, Oph-
thalmic, endoscopic, metrological instruments and test methods.
0 IS0 1996
All 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 the publisher.
International Orga nization for Standardization
Case postale 56 l CH-121 1 Geneve 20 l Switzerland
Printed in Switzerland
ii

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SIST EN ISO 8598:2000
IS0 8598: 1996(E)
INTERNATIONAL STANDARD 0 IS0
Focimeters
Optics and optical instruments -
3 Definitions
1 Scope
For the purposes of this International Standard, the
This International Standard specifies requirements for
focimeters and digitally following definitions apply.
continuously indicating
rounding focimeters with which the vertex powers
and prismatic powers of spherical and astigmatic
3.1 focimeter: Instrument that is used to measure
lenses, including lenses mounted in frames and
vertex powers and prismatic effects of spectacle and
contact lenses, can be measured and with which
contact lenses, to orientate and mark uncut lenses,
lenses can be orientated and marked.
and to verify the correct mounting of lenses in spec-
tacles frames.
NOTE 1 For the measurement of vertex powers of contact
lenses, see IS0 9337:- 1), Optics and optical instruments~
3.2 continuously indicating focimeter: Focimeter
- Contact lenses - Determination of back vertex power.
with a continuous scale.
3.3 digitally rounding focimeter: Focimeter which
2 Normative references
displays measured values rounded to the nearest
incremental value.
The following standards contain provisions which,
through reference in this text, constitute provisions of
3.4 lens support: Aperture on the instrument
this International Standard. At the time of publication,
against which the lens or the contact lens is placed
the editions indicated were valid. All standards are
for measurement.
subject to revision, and parties to agreements based
NOTE 2 The focimeter measures the vertex power rela-
on this International Standard are encouraged to
tive to the surface placed against the lens support.
investigate the possibility of applying the most recent
editions of the standards indicated below. Members
of IEC and IS0 maintain registers of currently valid
3.5 adjusting rail: Movable rail or bar used as the
International Standards.
reference axis for spectacles during measurement,
which is aligned perpendicularly to the optical axis of
IS0 7944:-z), Optics and optical instruments - the focimeter and parallel to the axis direction O” to
Reference wavelengths. 1 80°.
NOTE 3 Also called the lens table or frame rest.
IS0 8429:1986, Optics and optical instruments -
Ophthalmology - Graduated dial scale.
3.6 principal meridians: The two meridians of an
astigmatic power lens (see 3.10) containing the optical
-I), Optics and optical instruments - Test
IS0 9342:
axis; one of the meridians has maximum refractive
lenses for the calibration of focimeters.
1) To be published.
2) To be published. (Revision of IS0 7944:1984)

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SIST EN ISO 8598:2000
power, the other meridian has minimum refractive The instrument shall be capable of measuring the axis
power. direction (see IS0 8429) of cylindrical lenses between
O” and 180”. For prisms it shall be possible to deter-
meridians are mutu-
NOTE 4 In general, the two principal
mine the direction of the base setting between O” and
r astigmatism).
ally perpendicular to each other (regula
360°.
powers of
37 vertex power: There are two vertex
4.2 For continuously indicating focimeters, the
aie ns.
dioptre scale shall have a scale interval not greater
than 0,25 D and shall be readable to the accuracy
3.7.1 back vertex power: Reciprocal of the paraxial given in tables 1 and 2. For axis directions (see
value of the back vertex focal length measured in IS0 84291, the scale interval shall not exceed 5” and
metres. shall permit interpolations to be made to the nearest
degree.
3.7.2 front vertex power: Reciprocal of the paraxial
For prismatic power readings the interval shall not
value of the front vertex focal length measured in
exceed 1 A.
metres.
NOTES
4.3 For digitally rounding focimeters in the range
from +I 0 D to -10 D, each increment of the digital
5 Conventionally the back vertex power is specified as the
display shall be not more than 0,125 D. In the range
” power” of a spectacle lens, although the front vertex
outside +I0 D, each increment shall be not more than
power is required for certain purposes, for example in the
0,25 D. The display shall show at least two decimal
measurement of some multifocal lenses.
digits.
6 The unit for expressing vertex power is the reciprocal
metre (m-l). The name for this unit is the “dioptre” for
For axis directions, the increment of the digital display
which the symbol is ‘ID”.
shall be 1 O.
3.8 prismatic power: Deviation of a ray of light
The increment for the prismatic power shall be not
through a specified point on a lens.
greater than 0,25 A.
NOTE 7 The unit for expressing prismatic power is the
4.4 The instruments shall be designed so that it is
centimetre per metre (cm/m). The name for this unit is the
“prism dioptre” for which the symbol is “A”. possible to measure lenses with a diameter of at least
80 mm and a thickness of at least 20 mm. Trans-
lational movements of the lenses on the lens support
3.9 spherical power lens: Lens bringing a paraxial
of not less than 30 mm in a direction perpendicular to
pencil of parallel rays to a single point focus.
the optical axis and to the adjusting rail shall be poss-
NOTE 8 This definition could also apply to single-vision ible, starting from more than 10 mm below the optical
aspheric lenses.
axis of the instrument (see figure 1).
3.10 astigmatic power lens: Lens bringing a par-
Dimensions
axial pencil of parallel rays to two separate line foci
mutually at right angles and hence, unlike a spherical
lens, having two principal powers.
b)
NOTE 9 One of these powers may be zero, with the
\
corresponding focal line at infinity. Lenses referred to as
toric lenses, sphero-cylindrical lenses, and cylinder lenses
are all astigmatic lenses.
3.11 centration error of the instrum ent: Residual
Al
pnsma tic error of the instru men t with no lens in place.
4 Design requirements and
recommendations for general purpose
focimeters aILens support
b) Adjusting rail
4.1 The measuring range shall include vertex pow-
...