ANNEX F
ASCC
ADV PUB 61/113/12
30 APRIL 1996
FORMERLY
ADV PUB 61/98
ADVISORY PUBLICATION 61/113/12
Aircrew Spectacles
ASCC
AIR STANDARDIZATION COORDINATING COMMITTEE
ADV PUB 61/113/12
30 APRIL 1996
ADVISORY PUBLICATION RECORD OF CHANGE
1.
ADV PUB 61/113/12 (formerly draft 61/113P and proposed 61/98) is an initial
publication dealing with minimum desirable material and optical requirements for design and
manufacturing consideration of aircrew spectacles as agreed at the 32nd Meeting of WP 61.
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PROTECTION OF PROPRIETARY RIGHTS. Release of technical information included in this
ADV PUB, for any purpose whatsoever, should be accompanied by the following statement:
PROPRIETARY RIGHTS
The receipt of the present information does not in any way constitute a licence to utilize
proprietary technical information that might be disclosed herein.
Claims to proprietary rights included in this information and known to the originating
government are as follows:
Subject
Claimant
______________
______________
______________
______________
Document Currency:
1.
Confirmation of this document's currency can be found on the ASCC Home Page at
http://www.airstandards.com/, which lists the latest edition dates.
Notes:
1.
The indications given in the above list do not exempt all those who would be led to use
the present information from the obligation of verifying the completeness of this list. It is the
responsibility of such users to ensure that no other proprietary rights apply to the present
information and complete with third parties (whether governments or individuals) any
agreements which may be necessary in respect of the use of the information.
2.
The restrictions concerning the above stated proprietary rights in respect of the technical
information herein contained should be clearly indicated by all national and international
authorities or any individuals on releasing the whole or part of the information for any purpose
whatsoever. (To this end, the present statement under the title "Proprietary Rights" should be
attached to every release of the technical information herein contained).
3.
Proprietary rights are to be understood in the broadest sense as covering rights in "knowhow" as well as rights in inventions not yet patented and rights in patents, design, trademarks,
utility models and copyrights.
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TERMS OF AGREEMENT
1.
Objective. This publication recommends and defines minimum desirable material and
optical requirements for design and manufacturing consideration of aircrew spectacles. It will
include both lens and frame elements.
2.
References.
a.
Related ASCC AIR STDs/ADV PUBs/INFO PUBs. AIR STD 61/113/14 (Latest
Edition).
b.
Other Standardization Agreements. Nil.
c.
Other Relevant Documents:
(1)
Australian Standard 1067-1990.
(2)
British Standards 2092-1991, 3521-1991, 2724-1987.
(3)
New Zealand Standard (AS 1067-1990).
(4)
US Standards MIL-C-83409, MIL-S-25948G, MIL-V-43511C (1990),
MIL-STD-662, ASTM D-1003, ASTM D-3935.
(5)
ANSI Z-87.1, ANSI Z-80. and
(6)
AGARD Conference Proceedings No. 492.
3.
Agreement. Nations have agreed to the publication of this document and have agreed that
the national content will be kept current by nations providing the Management Committee with
appropriate and timely advice of changes, through the Working Party meeting reports and out of
session correspondence.
4.
Subscription Status. The Services which have subscribed to this ADV PUB are shown in
the following table:
NATION
AIR FORCE
NAVY
ARMY
Australia
X
X
X
Canada
X
X
X
New Zealand
X
X
X
United Kingdom
X
X
X
United States of America * USAF
X
A
X
X - Confirmed
R - Confirmed with Reservation detailed below
N - Not Confirmed
 - Custodian
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5.
National Amplifying Notes.
USN: This document is yet to be confirmed by the USN.
By Authority of:
Chief of Staff, USAF
Chief of Naval Operations, USN
Chief of the Defence Staff, CF
Chief of the Air Staff, RAF
Chief of the Air Staff, RAAF
Chief of the Air Staff, RNZAF
For The Air Standardization Coordinating Committee
Washington, DC, 30 April 1996
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32nd Meeting WP 61
ADV PUB 61/113/12
30 APRIL 1996
DETAILS OF AGREEMENT
General Requirements
6.
The purpose of this publication is to recommend to member nations the optimal design
and material factors to be considered in the development of an ideal aircrew spectacle frame and
lens combination. Although individual member nation requirements may vary, this publication
will highlight those state-of-the-art features that should serve as the existing standard model to
reference in the development of new aircrew spectacles. This report represents a compilation of
input from all member nations as well as a review of current aspects pertaining to aircrew
spectacles.
7.
The standard terms used throughout this ADV PUB are listed in paragraph 12.
Frame
8.
Materials.
a.
General. Frames should be constructed of corrosion resistant, strong, light,
durable, hypoallergenic nationally approved materials. Any design must consider
compatibility with current and future flying equipment, ejection, comfort,
durability, field of view and a range of optical and safety issues. Style and cost
should be of secondary importance. Materials selected should not degrade with
environmental extremes or chemical contamination. Metal should be used to
minimize thickness of components and maximize strength.
b.
Bridge/Temple. Titanium, Stainless steel, gold, nickel-silver or phosphor-bronze
are recommended but not restricted. Malleability to facilitate facial contouring
and integration with personal flying equipment is desirable in any frame
formulation.
c.
Eyewire. Titanium, stainless steel, or monel are recommended but not restricted.
Material selected should be strong and capable of being manufactured into
existing safety standards. The potential for rearward displacement of the lens
element following impact must be minimized. Material selected should ensure
positional stability of the lens elements. There should be a minimum 3 mm bezel
depth to firmly anchor the lens element and to discourage retrodisplacement.
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Table 1: Spectacle Frame Component Materials
NICKEL-SILVER:
TITANIUM:
65% Copper
18% Nickel
17% Zinc
Soldering Performance:
Corrosion Resistance:
Elasticity:
(Component materials and percentages
are proprietarily protected.)
Very High
Moderate
Moderate
Soldering Performance:
Corrosion Resistance:
Elasticity:
Poor
Very High
Very Good
STAINLESS STEEL:
MONEL:
69% Iron
18% Nickel
10% Chromium
03% Others
Soldering Performance:
Corrosion Resistance:
Elasticity:
68% Nickel
30% Copper
01% Iron
01% Magnesium
Average to
Poor
Very High
Good
Soldering Performance:
Corrosion Resistance:
Elasticity:
PHOSPHOR BRONZE:
Good
Very High
Good
GOLD:
94% Copper
06% Tin
Soldering Performance:
Corrosion Resistance:
Elasticity:
9.
Good
Moderate
High
Soldering Performance:
Corrosion Resistance:
Elasticity:
Very Good
Very High
Very Good
Design Features.
a.
Temples. Temples should be narrow and positioned appropriately to maximize
field of view. They should be anatomically contoured to facilitate one-handed
doffing and donning while wearing personal flying equipment. Either a spatula,
bayonette or hockey-stick configuration is ideal for helmet wearers with the
additional prospect of a "c loop" or comfort cable in those cases when a helmet is
not used. The design should be comfortable beneath headsets and not disrupt ear
seals with subsequent disruption of sound attenuation. There should be no sharp
projections or edges. Appropriate anthropometric data should be consulted with
respect to host nation's population but at least three lengths should be available
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(135/140/145 mm) if a spatula contour is not selected. Temples should interface
with eyewire above horizontal meridian at 1000 and 0200 hours to minimize a
lateral field frame scotoma in a preferred gaze position.
b.
Bridge/Nosepads. Either a saddle bridge or adjustable individual nosepads can be
selected. Nosepads should be silicone for comfort, minimal skin interaction and
to reduce slippage. Pad arms should be mounted on the posterior eyewire and be
of a boxmount design or equal alternative. Any design should minimize risk of
separation of pad from pad arm during direct impact or ejection. The frame
should adhere to current bridge strength test standards. Several bridge sizes as
appropriate for the national population can be selected; i.e., 16 and 18 mm.
c.
Eyewire. Should conform to all appropriate safety frame standards currently
employed. This should include incorporation of a safety bezel and posterior
eyewire lip as well as the mono-block type hinge or equivalent. The mono-block
hinge should have minimal lateral projection to maximize lens size held and
integration with flying equipment. The hinge should project posteriorly. The
lenses should be held securely with a pantoscopic tilt limit of 12-15°. Metal will
ensure width and thickness will be minimized. Material composition should be
malleable to allow individual adjustment for facial contouring within acceptable
non-prism induction range and to facilitate helmet/visor fitting. A modified tearshaped or similar lens shape that allows room for sufficient presbyopic correction
is recommended. Multiple frame sizes from 52-60 mm may be required in
individual anthropometric populations. Filamentous suspensions or similar
eyewires should not be allowed because of their inherent weakness.
d.
Color/Finish. Reflections onto helmet visors, posterior lens surfaces and into the
eyes from external lighting or potential laser threats must be attenuated or
eliminated. A flat matte black finish is ideal but certain dull coated or brushed
metal may be an acceptable alternative.
e.
Eye Relief. The frame should be optimally fit to minimize lateral and forward
displacement. This will ensure a higher proportion of compatible frame/personal
equipment fittings. Eye relief should be set at the shortest possible distance that
avoids eyelash/lens contact and does not compromise airflow to the point of
resultant condensation on the posterior lens surface.
f.
Bezel. Bezel or groove depth should be sufficient to maintain stable fixation of
the lens elements. This should conform to existing safety frame standards. The
depth range recommended is 3.0-3.2 mm. Filamentous suspensions or bezelless
designs should not be utilized.
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Lenses
10.
Materials.
a.
General. Any lens material selected should be fabricated from material of the
highest optical quality. The material should possess an index of refraction high
enough (greater than 1.45) to provide optimal refractive capability within a
reasonable material thickness. The material should be light weight, possess
superior optical characteristics, durable, and be resistant to light induced
degradation (especially ultra-violet). It should not degrade in environmental
extremes and with chemical contamination. It ideally should possess superior
ballistic impact resistance. It should meet accepted national impact resistance
standards. It should possess inherent scratch resistance or be capable of accepting
lens coatings that will render it scratch resistant. Any material utilized should not
demonstrate any defects in material, such as, pits, blisters, inclusions, streaks,
ripples, or other defects that would impair vision under normal conditions. The
material should be capable of transmitting light with little reduction of total
transmission. A total transmission of 95-96% should be anticipated with a
minimum of 90%. Induced spectral dispersion as a function of the lens material
should be minimized.
b.
Glass. Glass (i.e., crown glass has a refractive index 1.528) possesses superior
optical characteristics. Tinted material is least likely to introduce optical density
variations. Glass however is heavy and possesses inferior impact resistance when
compared to certain plastic materials. Weight is a lesser factor in minimal
refractive errors. It represents the most economical material with respect to raw
material and lens fabrication costs. Higher refractive errors; i.e., greater than ±
5.00D induce significant weight penalties and increasing difficulties for a frame to
hold these lenses properly. In addition, glass offers the poorest UV-A protection
amongst lens fabrication materials currently available unless it is tinted.
c.
CR-39. Columbia Resin-39 (refractive index 1.499) offers excellent optical
qualities albeit at slighter greater thicknesses than glass or PC. The impact
resistance is better than glass but inferior to PC. However, it is more scratch
resistant than uncoated PC. Recommended minimal safety thickness is 3.0 mm.
It possesses inherently better UV protection than glass but worse IR protection.
d.
Polycarbonate Allyl (PC). Polycarbonate (refractive index 1.586) is a high index
lightweight plastic material with superior impact resistance. Consequently, thin,
lightweight lenses can be manufactured albeit material cost and processing
expenses are higher. Care must be undertaken to ensure raw material is free of
impurities and that heat distortion is not induced in the lens grinding process. The
recommended minimal thickness is 3.0 mm. PC is inherently a soft plastic and is
subsequently prone to scratch, inducing considerable glare and haze. Anti-scratch
coatings would be advisable to avoid this phenomenon. The lower "V" or Abbe
factor of PC can result in the dispersion of white light into spectral elements that
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will contribute to edge blur in powers greater than ± 3.00 diopters. The material
has inherently better UV protection than glass. This can also be further enhanced
with additional coatings; however, this can have a negative impact on the impact
resistance of PC. The overall transmission of PC is lower than glass or CR-39
because of a higher reflective value (10%). Anti-reflection coatings can be utilized
to improve the overall light transmission and thus reduce glare and veil.
11.
e.
Hi-Index Plastics. This represents a selection of continually evolving various
plastic base materials. Any material selected should conform to general
requirements. Scratchability in general and a reduced impact resistance (when
compared to PC) may be limiting factors. Future material development will
warrant continued monitoring for suitable alternatives. Processing costs are less
expensive than PC material.
f.
Hi-Index Glass. This represents a selection of evolving base materials. Any
material should conform to general requirements. Because of higher than crown
glass index of refractions, thinner and lighter materials are available. However,
these materials are more fragile even if safety treated.
Design Features.
a.
Lens Shape/Size. A modified tear drop or similar shape is ideal. The lower nasal
corner of the lens should be maximally extended in order to accept the largest
possible near add in presbyopic aircrew members. The largest lens possible
should be used to avoid visual field defects from the frame or optical aberrations
by the lens periphery. A 52 mm width should be considered the minimum, 58-60
mm ideal. The upper limits are dictated by anthropometric and personal flying
equipment constraints. Weight concerns dictate that the lightest appropriate
materials be considered.
b.
Lens Thickness. Center lens thickness should comply with existing safety
standards. The minimum safety thickness of the lens regardless of material should
be 3.0 mm. It is recommended that the thinnest lens possible be used to maximize
lens/eyewire stability, to reduce weight, and to avoid potential optical
consequences. The final lens configuration must adhere to appropriate impact
resistance standards.
c.
Impact Resistance. All lenses should meet the accepted standards for that
particular base material. National standards may be substituted appropriately
when they meet or exceed these standards. High mass impact and high velocity
impact standards both must be met or exceeded. Caution must be exercised with
respect to the potential effect of coating materials on the impact resistance of a
particular base material.
d.
Prescription Tolerances. Final prescription results should adhere to the
established standard tolerances for that particular base material.
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e.
f.
Coatings.
(1)
General. Coatings applied should not degrade the optical performance or
impact resistance of the base material in either the short or long term.
Applied coatings should be neutral in color and not degrade the spectral
transmission of the visible portion of the spectrum. Applied coatings
should not result in a specular reflectance at near normal incidence in
excess of 4%. Coatings should be durable and not require reapplication in
time.
(2)
Anti-scratch. Anti-scratch coatings are not necessary for glass. However,
they should be applied to all plastic materials especially polycarbonate.
When possible they should be incorporated into the production of the base
material as done for example with CR-39. Application to the finished
product is required with PC. These coatings should not result in an
increase in reflections beyond acceptable standards.
(3)
Anti-reflection. Anti-reflection (AR) multi-coatings should be considered
on plastic materials and to a lesser extent on glass. These coatings should
comply with the comments regarding coatings in general given above and
appropriate standards. They are of benefit in reducing reflection,
enhancing contrast and improving overall light transmission of the base
material.
(4)
Anti-ultraviolet. UV coatings can improve the overall UV blocking effect
of glass which as a class possesses the least blocking ability of UV-A
relative to the other base materials. These coatings have not been shown
to compromise the glass base material. However, UV coatings have been
shown to have a negative and unpredictable effect on plastic material,
especially PC when applied to both inner and outer lens surfaces.
Applications to only one lens surface appears to minimize this effect. This
is an area that will need to be monitored. Fortunately CR-39, PC and
some of the hi-index plastics have superior UV-A blocking ability.
However, increasing transmission begins above 380 mm and rapidly
increases over the 380-420 nm range. Therefore, some UV-A and the
blue-light threat remain partially unattenuated in the base material form.
Total Luminance Transmission. The overall transmission of visible light should
be maximized but be greater than 90% (non-coated PC). The visible spectrum
440-780 nm should be transmitted neutrally without influence so as not to impair
color discrimination. Filtering UV up to 440 nm should be considered. Filtration
of the near and far infrared ranges greater than 800 nm is desirable. Specific
wavelength filtration recommendations are available for an aircrew sunglass under
ASCC Air Standard 61/53 (61/113J). Prescription sunglasses for use in aircrew
should comply with those standards.
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g.
Haze. This should not exceed 0.5% of the transmitted value when measure with
an acceptable hazemeter and illuminant.
h.
Resolution. Any optical distortion which might degrade vision shall be within
national standards as determined by a Military Standard test target, New LondonAnn Arbor test apparatus, ISO laser test, laser interferometer or other approved
test methods.
i.
Presbyopic Correction.
(1)
General. The use of presbyopic correction or add is required in older
aviators who demonstrate inability to resolve clearly and comfortably
appropriate targets at near or intermediate distances. Various bifocal
segment types and configurations are available. Good clinical judgment
dictates that properly prescribed multifocal spectacles should conform to
the individual's requirements with a strong optical consideration given to
the particular aircraft being flown. A pilot who flies several aircraft may
benefit from a different pair of spectacles adjusted to each aircraft. It is
recommended that the height of the bifocal segment be set just above the
highest instrument on the aircraft's instrument panel and below the glare
shield. Oxygen masks and helmets will affect spectacle fitting and it is
essential that this equipment be available during fitting sessions. An
operational fit within the cockpit may prove necessary to reach the proper
compromise between fit, instruments and required reading material
capability without over-correcting and thus eliminating all residual
accommodative tone or ability in a presbyope. An F-16 pilot, because of
the 30 degree seat recline, is more likely to require a weaker and lower
bifocal segment than when in an aircraft requiring a more traditional erect
sitting position.
(2)
Progressive Adds. These lenses are characterized by a transitional,
increasing progressive add power within a zone of fixation on inferior
gaze. There is no obvious line of demarcation visible and a range of
power is theoretically available. The lens requires a meticulous fit and has
a lower acceptance rate. In addition, lateral inferior fields of gaze are
optically compromised, the user being relegated to only a useful more
central zone. They are expensive and require a high motivation for
ultimate acceptance. Although this is an appealing concept further
monitoring and investigation are warranted but their use in the cockpit is
not recommended at this time.
(3)
Hybrids. Other variations and evolving technology regarding correcting
the presbyope or pre-presbyopic aviator exist. Difficulties in fitting,
adaptation, optical compromises, and lower acceptability warrant further
monitoring and investigation but presently these should not be used in
aircrew.
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j.
Diopter Power Consideration. Materials with low Abbe factors, particularly
polycarbonate, have the potential to introduce an additional compromise of
resolution through the dispersion of white light into its spectral components. This
does not seem to be significant in powers less than ± 3.00 diopters. However, the
spectacles of an aviator who exceeds this range should probably be made in CR39 or other hi-index plastic to avoid this complication.
k.
Personal Flying Equipment. It is essential that all spectacle wearing aircrew have
their spectacles properly fitted. This is especially important as it relates to
integration with helmet, mask, NBC, and other flying equipment. It is therefore
recommended that aviators have their helmets, NBC equipment, oxygen masks
and/or headphones available during any spectacle fitting session. This will
facilitate any adjustments before and after the prescription is fabricated and
maximize the integration of the flyer's spectacles with his personal equipment
under the best possible conditions in order to reach the optimal compromise of
comfort, optical correction, and function.
Glossary of Terms
12.
The following terms are used throughout this ADV PUB.
a.
Eyewire - that part of a spectacle frame that wraps around and secures the lens
element.
b.
Eyewire tube - the section screwed together when securing a lens in an eyewire.
c.
Temple - the extended earpiece of a spectacle frame that is mounted to the
spectacle front eyewire usually with a three-, five-, or seven-barrel hinge. Also
called "sidepiece" or "leg."
d.
Bevel - the crown on a lens that allows it to match the inside groove or bezel of an
eyewire.
e.
Bezel - the groove in the eyewire that anchors the lens element within the frame.
f.
Monoblock hinge - high-quality, safety hinge characterized by the bottom eyewire
tube endpiece section fitting into the top endpiece section. Incorporates endpiece
barrel hinge for the temple mount. Adds enhanced stability and lens retention
capability to a frame. Temple hinge soldered separately to temple.
g.
Non-monoblock hinge - tube endpieces are secured along a flat plane without
burying or insertion into each other. Inferior stability compared to monoblock.
h.
Index of refraction - the ratio of the group velocity of light of a given wavelength
in air to that in a given medium. It defines the ability of a material to bend or
refract light of a given wavelength. The higher the index, the greater the bending
or refracting power. Reference wavelength used is the helium d-line at 587.56
nanometers.
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i.
Single vision - a lens that provides correction at a single viewing distance.
j.
Multifocal - a lens designed to provide correction at 2 or more viewing distances.
k.
Add - Also called the segment or "seg"; provides the additional plus power to
provide a second closer viewing distance. It forms a part of a multifocal lens.
l.
Presbyope - an individual who is losing accommodative power as a normal
function of aging who at some point in time will require corrective power for
closer viewing distances.
m.
Abbe Factor - also called "V" factor; an indication of a material's ability to
disperse white light into its individual spectral elements or wavelengths. The
lower the Abbe Factor, the greater the tendency to disperse white light and the
thinner the material's thickness necessary to cause this effect. This results in the
potential of edge blur as individual colour wavelengths are brought to a point
focus at different distances.
n.
Myopia - A refractive condition of the eye in which images are focussed in front
of the retina and require minus lenses to correct.
o.
Hyperopia - A refractive condition of the eye in which images are focussed behind
the retina and require plus lenses to correct.
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