GB/T 7962.2-2010 PDF in English
GB/T 7962.2-2010 (GB/T7962.2-2010, GBT 7962.2-2010, GBT7962.2-2010)
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| GB/T 7962.2-2010 | English | 125 |
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Test methods of colourless optical glass -- Part 2: Optical homogeneity -- Fizeau plano-interferometry
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| GB/T 7962.2-1987 | English | 199 |
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Colourless optical glass test methods--Test method by collimator for optical homogeneity
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Standards related to (historical): GB/T 7962.2-2010
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GB/T 7962.2-2010: PDF in English (GBT 7962.2-2010) GB/T 7962.2-2010
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 81.040.01
N 05
Replacing GB/T 7962.2-1987, GB/T 7962.4-1987
Test methods of colorless optical glass - Part 2: Optical
homogeneity - Fizeau plano-interferometry
ISSUED ON: JANUARY 14, 2011
IMPLEMENTED ON: MAY 01, 2011
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions... 5
4 Principles ... 6
5 Instruments ... 6
6 Samples ... 7
7 Test conditions ... 8
8 Measurement steps ... 8
9 Data processing ... 9
Test methods of colorless optical glass - Part 2: Optical
homogeneity - Fizeau plano-interferometry
1 Scope
This Part of GB/T 7962 specifies the test methods, test procedures, data processing for
the optical homogeneity of colorless optical glass.
This Part applies to the test of the optical homogeneity of colorless optical glass, whose
diameter or side length is greater than 100 mm AND thickness is not less than 40 mm.
2 Normative references
The provisions in following documents become the provisions of this Part through
reference in this Part of GB/T 7962. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this Part; however,
parties who reach an agreement based on this Part are encouraged to study if the latest
versions of these documents are applicable. For undated references, the latest edition of
the referenced document applies.
GB/T 903 Colorless optical glass
3 Terms and definitions
The following terms and definitions apply to this Part.
3.1
Optical homogeneity
The maximum positive and negative deviations of the refractive index of each point,
in the same piece of glass, as relative to the average refractive index of the glass,
which are represented by the symbols Δn+ and Δn-, respectively.
3.2
Fizeau plano-interferometry
A certain inclination is formed between the standard plane and the plane to be
inspected; when the orientation and size of the air wedge between them are changed,
the optical path difference of the two coherent beams gradually changes, along the
direction of the main section of the air wedge, thereby forming equal-thickness
interference streaks. This kind of interference is called Fizeau plano-interferometry.
3.3
Peak value and valley value (P value and V value)
Peak and valley values of the transmitted wavefront.
Taking the best ideal transmission wavefront as the "zero plane", (the average plane
of data statistics), within the test aperture range, the wave peak value P of the glass
transmission wavefront is specified as a positive value, whilst the valley value V is
a negative value.
3.4
Peak-valley value (PV value)
Within the test aperture range, the peak-valley value of the transmitted wavefront;
when it is represented by the symbol PV, then PV = P - V .
4 Principles
This Part uses a Fizeau plano-interferometer to measure the optical homogeneity of
colorless optical glass. The sample is placed vertically, in the initial test optical path of
the interferometer. When the refractive index distribution of the sample is not uniform,
the wavefront of the light wave, which is reflected back through the sample twice, is no
longer a strict plane, BUT becomes a curved surface. The transmitted wavefront's P
value, V value and PV value is measured. Calculate the refractive index deviation Δn,
Δn+, Δn- of the tested glass, by formula (1), formula (2), formula (3), respectively.
5 Instruments
5.1 The principle of optical system for measuring optical homogeneity by Fizeau plano-
interferometry is as shown in Figure 1.
AND meets the requirements of 6.4, the sample can be directly placed vertically into
the test optical path for testing, without the attaching plate.
8.3 Perform sampling measurement and data processing, on the interference streaks,
which are generated in the test area, to obtain the P value, V value, PV value of the
transmitted wavefront.
8.4 For the glass whose aperture is larger than the aperture of the attaching plate or the
instrument, use the zoning measurement method, to make measurement. Repeat steps
8.2 ~ 8.3, to measure P1, V1; P2, V2; P3, V3…, (PV)1, (PV)2, (PV)3… of each area,
respectively. Select the maximum PV value from them, as the measurement result.
8.5 Use a thickness measuring instrument, to measure the clear thickness L of the
sample; record the result.
9 Data processing
9.1 Substitute PV value, P value, V value, L value, λ value into the formula (1), formula
(2), formula (3), formula (4), to calculate Δn+, Δn-, Δn, respectively.
Where:
Δn - The maximum deviation of the absolute value of the refractive index, at each
point of the glass under test, within the range of the test aperture;
L - The clear thickness of the sample under test, in millimeters (mm);
PV - The peak-valley value of the transmitted wavefront;
λ - The wavelength of the light wave used for the test, in nanometers (nm).
Where:
Δn+ - The maximum positive deviation of the refractive index, at each point in the
glass, as relative to the average refractive index of the glass, within the test aperture
range;
P - The peak value of the transmitted wavefront;
L - The clear thickness of the sample under test, in millimeters (mm).
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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