Re: [math-fun] New lighting technology breakthrough?
(Full disclosure: my father worked for Ford Motor Co., Edsel Division(!), in the 1950's.) The "Federal Motor Vehicle Safety Standard 108" is online (referenced from Wikipedia), and is a perfect example of too much detail embedding obsolete technology into law. For example, headlights are restricted to 55-70 watts at 12.8 volts. Elsewhere, the brightness is limited in candela. There is a very detailed specification of the abrasion resistance of the headlamp cover, including the size of the abrading grains, or the coarseness of the steel wool. In the 1940's, Edwin Land, the inventor of the Polaroid instant photography, tried unsuccessfully to polarize headlights and windshields in orthogonal axes; he finally gave up in 1947. I estimate that his invention could likely have saved ~10^6 lives during the past 70 years. Billings, B.H. and Land, E.H. "A comparative survey of some possible systems of polarized headlights". J. Optical Soc. of America, 38(10), 819-829, Oct. 1948. The 1948 Tucker had steerable headlights. Steerable headlights were subsequently banned, and precluded the importation of the innovative Citroen SM into the US until its steerable headlights (& many other features) could be disabled. The US auto lighting regulations also discouraged "non sealed beam" headlights, which completely stalled vehicle lighting innovation for 30-40 years. These obsolete regulations were used (successfully) by the U.S. auto manufacturers to keep out foreign cars and protect domestic manufacturers. --- Here are the specifications for the vehicle light colors, referencing the CIE color chart: Red. Red is not acceptable if it is less saturated (paler), yellower, or bluer than the limit standards. Yellow (Amber). Yellow is not acceptable if it is less saturated (paler), greener, or redder than the limit standards. White. White is not acceptable if its color differs "materially" from that of CIE Source A. Red. The color of light emitted must fall within the following boundaries: y = 0.33 (yellow boundary) y = 0.98 - x (purple boundary) Yellow (Amber). The color of light emitted must fall within the following boundaries: y = 0.39 (red boundary) y = 0.79 - 0.67 x (white boundary) y = x - 0.12 (green boundary) White (achromatic). The color of light emitted must fall within the following boundaries: x = 0.31 (blue boundary) y = 0.44 (green boundary) x = 0.50 (yellow boundary) y = 0.15 + 0.64x (green boundary) y = 0.38 (red boundary) y = 0.05 + 0.75x (purple boundary) --- There must be a chart showing these regions on the CIE diagram, but I couldn't easily find such a chart. There is a way to convert these specifications into wavelengths, but it's a bit complicated, because the specifications are specified with tristimulus coordinates. At 11:21 PM 12/3/2012, Bill Gosper wrote:
[Not math, but hopefully fun] Automotive lights: Besides the traditional yellowish white headlights, we're seeing cold white, and pale green, blue, pink, and lavender. Plus those annoying prismatic things. But crawling down I280 tonight, I was struck by the uniformity of the red in the miles of taillights stretching out before me. Both LED and conventional. Is there some strict spectral standard? Or does my color discrimination roll off fast at the red end?
On 12/4/2012 5:47 AM, Henry Baker wrote:
(Full disclosure: my father worked for Ford Motor Co., Edsel Division(!), in the 1950's.)
The "Federal Motor Vehicle Safety Standard 108" is online (referenced from Wikipedia), and is a perfect example of too much detail embedding obsolete technology into law. For example, headlights are restricted to 55-70 watts at 12.8 volts. Elsewhere, the brightness is limited in candela. There is a very detailed specification of the abrasion resistance of the headlamp cover, including the size of the abrading grains, or the coarseness of the steel wool.
In the 1940's, Edwin Land, the inventor of the Polaroid instant photography, tried unsuccessfully to polarize headlights and windshields in orthogonal axes; he finally gave up in 1947. I estimate that his invention could likely have saved ~10^6 lives during the past 70 years.
Billings, B.H. and Land, E.H. "A comparative survey of some possible systems of polarized headlights". J. Optical Soc. of America, 38(10), 819-829, Oct. 1948.
The 1948 Tucker had steerable headlights. Steerable headlights were subsequently banned, and precluded the importation of the innovative Citroen SM into the US until its steerable headlights (& many other features) could be disabled.
Very hi-tech and complicated - but innovative? No other manufacturer adopted steerable headlights (which were used earlier by Tatra) or air-over-oil suspension, and even Citroen didn't continue with those technologies.
The US auto lighting regulations also discouraged "non sealed beam" headlights, which completely stalled vehicle lighting innovation for 30-40 years.
I don't think so. The standard was adopted to get rid of the bulb and unsealed reflector lights which were common before WW2. Their problem was that the reflector would get dirty from condensation and even corrode. Motorcycle headlights were never required to be sealed beams (because it's easy to carry a spare bulb, but not a whole headlight) but there was no great innovation or superiority in motorcycle lights. Brent
These obsolete regulations were used (successfully) by the U.S. auto manufacturers to keep out foreign cars and protect domestic manufacturers. ---
Here are the specifications for the vehicle light colors, referencing the CIE color chart:
Red. Red is not acceptable if it is less saturated (paler), yellower, or bluer than the limit standards.
Yellow (Amber). Yellow is not acceptable if it is less saturated (paler), greener, or redder than the limit standards.
White. White is not acceptable if its color differs "materially" from that of CIE Source A.
Red. The color of light emitted must fall within the following boundaries:
y = 0.33 (yellow boundary) y = 0.98 - x (purple boundary)
Yellow (Amber). The color of light emitted must fall within the following boundaries:
y = 0.39 (red boundary) y = 0.79 - 0.67 x (white boundary) y = x - 0.12 (green boundary)
White (achromatic). The color of light emitted must fall within the following boundaries:
x = 0.31 (blue boundary) y = 0.44 (green boundary) x = 0.50 (yellow boundary) y = 0.15 + 0.64x (green boundary) y = 0.38 (red boundary) y = 0.05 + 0.75x (purple boundary) --- There must be a chart showing these regions on the CIE diagram, but I couldn't easily find such a chart.
There is a way to convert these specifications into wavelengths, but it's a bit complicated, because the specifications are specified with tristimulus coordinates.
At 11:21 PM 12/3/2012, Bill Gosper wrote:
[Not math, but hopefully fun] Automotive lights: Besides the traditional yellowish white headlights, we're seeing cold white, and pale green, blue, pink, and lavender. Plus those annoying prismatic things. But crawling down I280 tonight, I was struck by the uniformity of the red in the miles of taillights stretching out before me. Both LED and conventional. Is there some strict spectral standard? Or does my color discrimination roll off fast at the red end?
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At 10:19 AM 12/4/2012, meekerdb wrote:
The US auto lighting regulations also discouraged "non sealed beam" headlights, which completely stalled vehicle lighting innovation for 30-40 years.
I don't think so. The standard was adopted to get rid of the bulb and unsealed reflector lights which were common before WW2. Their problem was that the reflector would get dirty from condensation and even corrode. Motorcycle headlights were never required to be sealed beams (because it's easy to carry a spare bulb, but not a whole headlight) but there was no great innovation or superiority in motorcycle lights.
I don't want to start a flame war, but in the 1970's the US car companies were getting their lunch eaten by the foreign car companies. Honda embarrassed the c**p out of GM in the early 1971 by showing US Congress a Chevy Vega whose cylinder heads had been replaced with Honda's CVCC technology, and thereby met 1975 smog standards at very low cost. Congress retaliated with increased trade barriers (including some of these headlight issues), as well as a several year delay in the 1976 smog standards. The following U.S. report to Congress was basically a "Pearl Harbor" moment for the US auto companies. 1973. Report by the Committee on Motor Vehicle Emissions. Board on Environmental Studies and Toxicology. "3.9.3. ... In February 1971, emissions data with this [Honda CVCC] system on engine dynamometer tests indicated the [CVCC] engine could meet 1975 standards; the first successful car test that met the standards was in Spring 1972. In addition to developing a 2-liter, 4-cylinder engine for their own vehicle, Honda has applied the same techniques to modify two Chevrolet Vega 4-cylinder engines. ... All these cars met the 1975 standards without EGR or exhaust [e.g., catalytic converter] treatment, and Honda has expressed confidence that larger engines using the CVCC approach could also be made to meet 1975 standards without a catalyst. ..." "The effects on vehicle performance of the CVCC system are small. ... Fuel economy is essentially unchanged. There are no driveability problems." See also Table 3-11 which compared the Honda cars with 1 original Vega and 2 modified Vegas. --- The dirty/corroded headlight reflector problem had certainly been a problem in the 1940's, but by the 1970's, replaceable bulb headlights were in extensive use around the world outside the U.S. European headlight systems has to be _downgraded_ in the 1970's in order for European cars to be imported into the US. Ask any German who drove the Autobahns in the 1970's and 1980's, and who had also driven US cars on US freeways.
"HB" == Henry Baker <hbaker1@pipeline.com> writes:
HB> European headlight systems has to be _downgraded_ in the 1970's in HB> order for European cars to be imported into the US. When I got my euro-built '97, I found that the rules had just been updated in '96 or so to allow owners to import and use euro headlights, but manufacturers still couldn't sell cars with them installed. (They did still require lower-wattage bulbs than used in europe -- 80W high and ~50W low, IIRC -- but were *vastly* better than the DOT version.) -JimC -- James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6
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