Interpretation ID: 1982-3.30
TYPE: INTERPRETATION-NHTSA
DATE: 12/08/82
FROM: AUTHOR UNAVAILABLE; Frank Berndt; NHTSA
TO: Lucas Industries Inc.
TITLE: FMVSS INTERPRETATION
TEXT: This is in reply to your letter of November 1, 1982, regarding an interpretation of the "lens area requirements of FMVSS No. 108" as applied to the high contrast lamp whose design you enclosed.
We understand that your design applies to rear lamps. The measurement for the illuminated area of a rear lamp as specified in SAE J585e, "Tail Lamps (Rear Position Lamps)," for example, is stated in part as follows:
. . . "To be considered visible, the lamp must provide an unobstructed projected illuminated area of outer lens surface. . . ."
This applies to the installation requirements, i.e., the device as used on a vehicle. It is not part of the laboratory test procedure.
Further, with regard to photometric requirements of a lamp, no measurement for the illuminated area of a rear lamp is specified in SAE test procedures.
In summary, Standard No. 108 does not prohibit Lucas from manufacturing the lamp in question, but the vehicle manufacturer must be careful to insure that the lamp, when installed, conforms to the standard's requirements for visibility of lens area.
SINCERELY,
NOVEMBER 1, 1982
Office of Chief Counsel, Room 5219 National Highway Traffic Safety Administration
Dear Sir
Subject: Federal Motor Vehicle Safety Standard 108
Our sister company, Lucas Electrical Limited, of Birmingham, England, has developed a "high contrast" lamp design for multifunction rear lamps on motor vehicles. The purpose of this letter is to seek your confirmation of our interpretation of the lens area requirements of FMVSS 108 as applicable to this design.
The Lucas high contrast design uses a conventional rear lamp bulb and reflector to direct light on to convex cylindrical lensing which is colored red, yellow or white according to the function. An opaque screen of any color having slits running in the same direction and parallel to the flutes of the lens is positioned between the inner and an outer lens. The outer lens has fluting at right angles to that of the inner lens and can be clear, tinted or of neutral density. A copy of U.S. Patent 4,241,388 is attached for more explicit information.
In operation, light from the bulb is directed as parallel rays onto the inner cylindrical lensing which focuses it through the slits in the opaque screen. After passing through the slits in the screen, the rays of light diverge and then strike the outer lens where they are refracted in a plane at right angles to the slits. To an observer, the light emitted by the lamp will be the color of the inner lens and will be in contrast to the appearance of the unilluminated lamp.
It is our interpretation that with such a lamp the projected luminous and illuminated areas requirements of FMVSS 108 are those of the outer lens rather than those of the slits behind it. We hope you will confirm this opinion.
LUCAS INDUSTRIES INC
A J Burgess Vice President (Technical)
United States Patent [19] Green
[11] 4,241,388 [45] Dec. 23, 1980
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FIG.6.
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