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GB 17341-1998 PDF in English

GB 17341-1998 (GB17341-1998) PDF English
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GB 17341-1998: PDF in English

GB 17341-1998
ICS 17.180.30
N 34
neq ISO 8598:1996
Optics and optical instruments - Focimeters
ISSUED ON: MAY 05, 1998
Issued by: State Bureau of Quality Technical Supervision
This standard changed into recommended
standard, from March 23, 2017. Its number
was changed into GB/T 17341-1998.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Definition ... 4 
4 Categories... 6 
5 Basic parameters ... 6 
6 Technical requirements ... 7 
7 Inspection items and inspection methods ... 9 
8 Inspection rules ... 11 
9 Marking, packaging, transportation, storage ... 12 
Appendix A (Informative) Measurement of vertex power after corneal contact
lens ... 14 
Optics and optical instruments - Focimeters
1 Scope
This standard specifies the general specifications for focimeters.
This standard applies to continuously indicating focimeter and digitally rounding
2 Normative references
The provisions contained in the following standards constitute the provisions of
this standard through quotation in this standard. At the time of publication, the
editions indicated were valid. All standards will be revised, and all parties using
this standard shall explore the possibility of using the latest version of the
following standards.
GB 2828-87 Sampling procedures and tables for lot-by-lot inspection by
attributes (Apply to inspection of successive lots or batches)
GB 10050-88 Optics and optical instruments - Reference wavelengths
GB/T 15464-1995 General-purpose specification for the packaging of
instrumentation products
ZBY 002-81 Basic environmental conditions and test methods for
transportation and storage of instruments and meters
JJG 580-96 Verification regulation of focimeters
JJG 866-94 Verification regulation of standard lenses of vertex power
3 Definition
This standard uses the following definition.
An instrument, which is mainly used to measure the vertex power (D) and
prismatic power (Δ) of spectacle lenses (including corneal contact lenses);
determine the cylinder axis direction of the cylindrical lens; print marks on
the uncut lens; check whether the lens is installed correctly in the frame.
Spherical power
The back vertex power of the spherical lens is called the spherical power.
Spherical lenses are lenses, which make paraxial parallel light rays
converge at one focal point. This definition also applies to single visual
distance aspheric lenses.
Astigmatic power
The difference between the two main vertex powers in the cylindrical lens.
Cylindrical lenses are lenses, which make paraxial parallel rays converge on
two separate and orthogonal focal lines. Unlike spherical lenses, they
contain two main vertex powers. One of the main vertex powers can be zero;
the corresponding focal line is at infinity. The toric lens, combined spherical
and cylindrical lenses, and cylindrical lenses are all cylindrical lenses.
Cylindrical lenses are also called astigmatism lenses.
4 Categories
According to the display mode, the focimeter is divided into two types:
continuous indicating type and digital rounding type.
According to the working principle, focimeters are divided into two types:
focimeters based on the principle of focusing and imaging AND focimeters
based on the principle of autofocus.
According to the different observation methods, the focimeter based on the
principle of focusing and imaging is further divided into two types: visual type
and projection type.
The visual focimeter uses a reading telephoto system for observation; whilst
the projection type focimeter uses a projection objective lens and a projection
screen for observation.
5 Basic parameters
5.1 Reference wavelength
The reference wavelength, which is used to display the vertex power and
Use a piece of white paper instead of the inspected lens, to adjust the focus of
the eyepiece crosshairs clearly. Then remove the white paper. Focus the
measurement target image of the instrument clearly. Inspection of parallax-elimination
Adjust the focus of the crosshairs and the target image, according to
Then it may check whether the parallax has been eliminated. The observer
moves his gaze back and forth above the eyepiece; there shall be no obvious
shift between the crosshairs and the target image.
7.2.2 Visually check whether the instrument meets the requirements of 6.5.
7.3 Inspection of vertex power indication
Use one group of spherical standard lens (it shall comply with the requirements
of JJG 866-94), to check whether the indication error of vertex power meets the
requirements of Table 1.
7.3.1 When the lens is not placed, the indication of vertex power of the
instrument shall meet the requirements of 6.6.1.
7.3.2 Measure the spherical standard lenses one by one. The indication of
vertex power of the instrument shall meet the requirements of 6.6.2.
7.4 Inspection of indication of prismatic power
Use a set of prismatic standard lenses (it shall meet the requirements of JJG
866-94), to check whether the indication error of the prismatic power meets the
requirements of Table 2.
7.4.1 When checking the prismatic power, it shall first make the vertex power of
the instrument become zero.
7.4.2 Measure the prismatic standard lenses in sequence; the indication of
prismatic power of the instrument shall meet the requirements of 6.7.
7.5 Inspection of the deviation BETWEEN the axis mark of the optical center of
the lens AND the optical axis of the focimeter
Use a +15D spherical standard lens (it shall comply with the requirements of
JJG 866-94). First align the center, so that the prismatic power is zero. Then
mark the center axis's position. Then rotate the spherical standard lens by 180°.
Center it again. Mark the center axis's position again.
The half of the distance, between the axis marks of the center point, which are
made for the first time and the second time, shall not be greater than 0.4 mm.
8.2.2 The items of the exit-factory inspection are 6.1 ~ 6.10 of this standard.
8.3 Type inspection
8.3.1 Type inspection shall be carried out in one of the following situations:
a) When the new product is subject to type-finalization identification, OR the
old product is subject to prototype test after trans-plant production;
b) After normal production, if there are major changes in structure, material,
process, which may affect product performance;
c) During normal production, inspections shall be carried out periodically or
after accumulating a certain output;
d) When production resumes after a long-term suspension of production;
e) When there is a big difference BETWEEN the exit-factory inspection result
AND the last type inspection;
f) When the national quality supervision agency puts forward a requirement
for type inspection.
8.3.2 The type inspection shall include all the items, which are specified in this
standard. The samples for the type inspection shall be taken from the qualified
products of the exit-factory inspection.
8.3.3 Sampling for type inspection: At least three samples shall be taken for
each type of product; if one of the samples is unqualified, the product of this
type shall be deemed unqualified.
9 Marking, packaging, transportation, storage
9.1 Marking
9.1.1 Product mark
a) The name or trademark of the manufacturer;
b) Product name;
c) Product model;
d) Exit-factory number.
9.1.2 Packaging mark
The packaging mark of the instrument shall meet the requirements of GB/T
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.