With the intent of controlling the direction of the non reflected light emanating from
a light using a reflector, I floated an optic element within the reflector's cavity:
A half ball acrylic lens is glued on to a .040" rod of tungsten. The rod passes through the
center of the lexan lens of this 3" turbo head. The LED light source is a 5 Watt Luxeon
"High Dome". The rod will slide in and out of the flat lens and allow for various lens/ LED
placements. The 1/2 ball lens can be positioned such that the LED can not be viewed at any
off angle from the front. In this position, all light is either contacting the reflector or the 1/2 ball.
Some beams shots below start with the LED in a reflector without the 1/2 ball and then progress
with the ball closest to the flat lens and then moving in, closer to the LED. The first set was done
with the same manual exposure and the second set is a copy of the first which was lightened up
in PhotoShop to show more detail in the flood portion of the beam.
Unfortunately in removing the lexan lens from the turbo head, the AR coating crazed and a spider web of
this is visible on the lens. This condition likely effects the light transmission ability of the lens significantly.
It may in fact in validate the comparison with another reflector having no 1/2 ball lens addition (image at
left). I took some lux readings of the same LED module in the other turbo head with a good lens and then
readings of the system with the 1/2 ball lens. The readings were taken at approximately 39". The light was
clamped in place as the different reflectors and reflector/lens positions were measured.
No 1/2 ball {image at left} - 5550 lux
ball close to LED (Flood) {image at far right} - 490 lux
Optimal setting {near 4th image from the left} - 5480 lux
1/2 ball next to flat lens {2nd image from left} - 4750 lux
This combination of lens and reflector seems to point to further considerations for optical control. Various
lenses and reflectors might be combined in such a manner to control not only the primary beam angle of the
spot but the beam angle and intensity of the flood portion as well.
In a proto McLux T head, a SF M3 reflector and 1/2 ball:
I turned my own 1/2 ball lens and left a pedistal stem on it for mounting to the flat lens:
In the beam shot below, a rounded square beam of refracted light can be seen outside of the reflected center
spot beam. There is a third level of considerably lower light in a perimiter beam outside of these.
This is light that has likely feflected off of the lens elements and come out the front end.
Below is a Before (no lens) and After (1/2 ball added) beam shot with same distance, exposure and LED:
Below, the image has been lightened and then darkened to show relative light saturation:
A 1 watt low dome in a Pelican M6 provides a very tight beam. Adding a 1/2 ball lens to the optic
package increased the lux reading from 620 to 820 (relative comparison only) as well as increasing
the center beam size.
In the beam shot below, the reflector/ lens combo is on the right:
