Re: Lights

["Smith, Kirby A" <kirby.a.smith@lmco.com>]

Al Powell comments, in part:

	Ron Wood appropriately comments that it's not the wattage that 
	makes all the difference with lights, it's the LENS.

	<some useful anecdotal evidence snipped>

	I might also suspect that the reflectors are an issue - but I'm not 
	sure.  It is worth noting that the ZX uses round lights which should

	be easier to design for a perfect focus of light.  The Audi
euro-lights 
	are slightly rectangular, which might affect focus a bit.  however, 
	they are freshly re-plated, so they're as good as they get.

In the theory of optimal non-imaging concentrators, recently  (last 30
years) developed by Winston, et. al., the source shape (filament in our
case), reflector, and lens (where used) are all important.  If the theory is
applied to auto lamps, the main limitation to good beam control is allowable
depth for the assembly, which the use of a lens can reduce.  The exit
aperture times the exit beam solid angle need only equal or exceed the
filament area times its radiant solid angle.  Rectangular reflector
apertures are needed if the horizontal and vertical divergences are intended
to differ using optimal concentrators.   However, it is not clear to me that
any automotive lighting applications are utilizing this theory at this time.

At the other extreme, the filament can be projected using just a lens or
just a parabolic reflector with the filament shape determining the
divergences and the built-in lens/reflector distortions providing fill and
side scatter.  I suspect most automotive lighting optics designs are
determined by trial and error (using optics programs I hope) to find a best
compromise among the applicable requirements, driven by cost and styling.

                .... Kirby   (Kirby A. Smith)
                              2 x 1988 90q
                          New Hampshire USA