ASTM D637-90

Test Method for Surface Irregularities of Flat Transparent Plastic Sheets (Withdrawn 1995)

General Information

• Status: Withdrawn
• Withdrawal Date: 09-Nov-1995
• ICS: 83.140.10 - Films and sheets
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.40 - Optical Properties

Standards Content (Sample)

AMERICAN SOCIETY FOR TESTINO AND MATERIALS
4ITb Designation: D 637 - 90
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Standard Test Method for
Surface Irregularities of Flat Transparent Plastic Sheets'
This standard is issued under the fixed designation D 637; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (E) indicates an editorial change since the last revision or reapproval.
This standard has been approvedjor use by agencies of the Deparlment of Definse Consult the DoD Index of Spec$cations and
Siandards fir the speci/ic year of issue which has been adopted by the Deparlment of Definse.
1. Scope 4. Significance and Use
1.1 This test method covers the measurement of the 4.1 This test method profides empirical results useful for
surface irregularities of flat transparent plasfic sheets that are control purposes and for correlation with service applica-
ordinarily used to cover openings through which visual and tions. The accuracy is much greater than required for most
_-
instrumental observations are made. applications, but it is not expected to measure microscopic
1.2 This test method measures the distortion and the defects or the optical perfection of surfaces in terms of wave
deviation of line of sight through flat sheets of transparent length of light.
plastics. The test method makes use of the prismatic or
5. Apparatus
optical wedge deflection of a beam of light as it passes
through a distortion spot or wave in the body of or on the
5.~1 Projector-A good quality lantern slide projector or
surface of the material being inspected,
similar assembly of light source and lenses that is capable of
1.3 The values stated in SI units are to be regarde.d as the
producing a sharply defined image on a screen at a distance
standard.
of 7.62 m (25 fi). The objective lens of this system shall have
1.4 This standard does not purport to address the safity
an aperture approximately 50.8 mm (2 in.) in diameter and a
problems associated with its use, It is the responsibility of the
focal length of approximately 12 in.
user of this standard to establish appropriate safity and
5.2 Slide-A transparent slide on which have been ruled
health practices and determine the applicability of regulatory
two very fine black lines crossing at right angles at the center
limitations prior to use.
of the slide. This slide may be prepared by photographing a
drawing-or by directly ruling fine lines on some suitable
transparent medium.
2. Referenced Document
5.3 Screen-A square white screen measuring about 1.5
m (5 ft) on a side. This screen shali have a symmetrical cross
2.1 ASTM Standard:
ruled on it consisting of seven horizontai parallel fine lines
D 6 18 Methods of Conditioning Plastics and Electrical
spaced 12.7 mm (0.5 in.) apart and seven vertical parallel
Insulating Materials for Testing
fine lines spaced 12.7 mm (0.5 in.) apart, These lines shall be
D 883 Definitions of Terms Relating to Plastics2 .
as fine as it is possible to make them and still have them
distinctly visible at a distance of 7.62 m (25 ft). A width of
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3. Terminology about 1.6 mm ('/I6 in.) is suggested,
3.1 Description of Terms SpeciJic to This Standard:. NOTE 1-An alternative form of target may be preferred, consisting
of concentric circles having radii increasing by 25.4 mm (I in.) from a
3.1.1 displacement factor-displacement factor is the
25.4-mm (I-in.) radius for the innermost circle, ruled in the center of a
maximum movement (in inches) of the image of the cross,
piece of white cardboard 0.3 m (1 fi) square. It is suggested that the first
divided by the distance (in feet) from the projector to the
circle be ruled with a line thickness of 3.2 mm (y8 in.), the second with a
screen, multiplied by 1000.
line thickness of 1.6 mm (Ih6 in.), the third with a line thickness of 3.2
3.1.2 frequency of image movement-frequency of image
mm(% in.), and so on.
movement shali be described as (I) irregular or wavy, (2)
5.4 Supports-A suitable means of rigidly supporting the
frequent, or (3) single shift.
projector and the screen,
3.1.3 pattern distance-pattern distance is the maximum
5.5 Dark Room-A slightly darkened or dark room of
distance (in integer multiples of 127 mm (5 in,)) from the
sufficient Iéngth to accommodate the test setup, It has been
screen at which the specimen can be held without producing
found that an illumination level of not over 10 footcandles in
a sharply defined pattern of its minor surface irregularities.
the room will be satisfactorily dark when an ordinary lantern
3.1.4 General-Definitions of terms applying to this test
slide projector is being used,
method appear
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