ASTM F1181-96(2003)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:F1181–96 (Reapproved 2003)
Standard Test Method for
Measuring Binocular Disparity in Transparent Parts
This standard is issued under the fixed designation F 1181; 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.
1. Scope milliradians. Since it is an angular measurement, the amount of
displacement increases with distance.
1.1 This test method covers the amount of binocular dispar-
3.1.2 binocular disparity—the difference between the two
ity that is induced by transparent parts such as aircraft
images on the retina resulting from the lateral separation
windscreens, canopies, HUD combining glasses, visors, or
between the two eyes when viewing an object at a fixation
goggles. This test method may be applied to parts of any size,
point or due to the fact that an object is either nearer or farther
shape, or thickness, individually or in combination, so as to
than the fixation point. A certain amount of disparity is
determine the contribution of each transparent part to the
beneficial and natural, leading to the perception of depth.
overall binocular disparity present in the total “viewing sys-
However, when the disparity exceeds the limits for binocular
tem” being used by a human operator.
fusion, doubling of vision, eye fatigue, and headaches occur as
1.2 This test method represents one of several techniques
the eyes strain to merge the disparate images.
that are available for measuring binocular disparity, but is the
3.1.3 diplopia—the doubling of images of an object due to
onlytechniquethatyieldsaquantitativefigureofmeritthatcan
the fact that the object is either nearer or farther than the point
be related to operator visual performance.
of fixation or due to the fact that the lines of regard of the eyes
1.3 This test method employs apparatus currently being
do not intersect at the point of fixation.
used in the measurement of optical angular deviation under
3.1.4 Panum’s area—the area on the retina in which the
Method F 801.
eyes are able to fuse disparate images so that single vision
1.4 The values stated in inch-pound units are the preferred
occurs.
units. The values in parentheses are for information only.
1.5 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 Using an optoelectronic system (consisting of a trans-
responsibility of the user of this standard to establish appro-
mitter and a receiver) and with the part held in its installed
priate safety and health practices and determine the applica-
angle, two sets of angular deviation measurements are made at
bility of regulatory limitations prior to use.
several intervals (for example, 2°) in both azimuth and eleva-
2. Referenced Documents tion. The extent of the area to be measured is dependent on the
2 type of part being measured, for example, windscreen, visor,
2.1 ASTM Standards:
and so forth.The first set of measures is taken from the left eye
F 801 Test Method for Measuring Optical Angular Devia-
position, the second from the right eye position.The separation
tion of Transparent Parts
between the two eye positions is 2.5 in. (6.35 cm), a distance
3. Terminology equivalent to the interpupillary distance between the human
eyes. The measurements taken from the left eye position are
3.1 Definitions:
subtracted from that taken from the right eye position to
3.1.1 angular deviation—the angular displacement of a
determine binocular disparity.
light ray as it passes through a transparent part, expressed as an
angular measurement, for example, degree, minutes of arc,
5. Significance of Use
5.1 Diplopia or doubling of vision occurs when there is
This test method is under the jurisdiction of ASTM Committee F07 on
sufficient binocular disparity present so that the bounds of
Aerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 on
Panum’s area (the area of single vision) is exceeded. This
Transparent Enclosures and Materials.
condition arises whenever one object is significantly closer (or
Current edition approved Oct. 1, 2003. Published October 2003. Originally
approved in1 988. Last previous edition approved in 1996 as F 1181 – 96.
farther)thananothersothatlookingatonewillcausetheimage
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
of the other to appear double. This can be easily demonstrated:
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Close one eye and look at a clock (or other object) on a distant
Standards volume information, refer to the standard’s Document Summary page on
wall. Now place your thumb to one side of the image of the
the ASTM website.
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F1181–96 (2003)
clock. Now open both eyes. If you look at the clock, you position). To obtain the position corresponding to the left
should see two thumbs. If you look at your thumb, you should (right) eye position, move the transparency 1.25 in. (31.7 mm)
see two clocks. to the right (left) of the design eye position.
5.2 Complaints from pilots flying aircraft equipped with
8.3 Locate and firmly mount the receiver external to the part
wide field of view HUDs such as the LANTIRN HUD
to be measured and at a distance from the transmitter that is
indicated that they were experiencing discomfort (eye fatigue,
commensurate with the part being measured. For example, 4.9
headaches, and so forth.) or seeing either two targets or two
ft (1.5 m) if the part is an aircraft windscreen.
pippers when using the HUD. Subsequent investigations re-
8.4 Establish a baseline or zero determination without a
vealed that the problem arose from the fact that the transpar-
transparency in the optical path. Record the number as dis-
ency and the HUD significantly changed the optical distances
played on the digital readout under this condition.
of the target and the HUD imagery so that binocular disparity
8.5 Locatethetransparencypartbetweenthetransmitterand
which exceeded Panum’s area was induced. Use of this test
receiver. Take the readings from the left (right) eye position
methodprovidesaprocedurebywhichtheamountofbinocular
over area of interest as specified by using activity. Record
disparity being experienced by a human operator due to the
readingsforeachpoint(azimuth,elevation)ofthetransparency
presence of a transparent part in his field of view may be easily
thatismeasured.Determinedifferencesbetweenthesereadings
and precisely measured.
and readings (8.4) made without the transparency in place.
8.6 Repeat 8.5, taking readings with the transmitter located
6. Apparatus
and firmly mounted at right (left) eye position or as appropri-
6.1 Transmitter capable of projecting collimated light ra
...