Recently, in one of my Courui build threads, I was asked if sitting the reflector directly on the MCPCB gave the best focus result. My main goal for getting the reflector nice & low was to overcome the shrouding of the LED, which results in output loss, & beam artifacts, etc.
I knew that getting the reflector down lower resulted in better output, & a better beam pattern, but how close was it to the "perfect focus"? Did the LED need to go further in? Was it in too far?
I had to know....was it focused?
Last weekend, I finished two Courui builds for friends; One used an XPL HI, whilst the other used a domed XPL. I took the opportunity to measure the throw of both lights, using a selection of shims placed under the reflectors.
Both lights used identical FET drivers, & tests were done using Samsung 25r's. Lux readings were taken at 10 meters.
I also noted the cell voltage after (almost) each measurement, as obviously that would have a bearing on the results, with it not being a regulated driver.
This is my first attempt of graphing results, maybe the graphs could have been presented differently/better, but the data is there, which is the main object here! :)
I sorted the graph data so the Lux measurement (shown in red) went from lowest to highest.
The reflector height (shown in blue) was measured in thousandths of an Inch, with "0.000" being the lowest point, where the reflector was sitting flush on the MCPCB.
The cell voltage, taken shortly after each test, is noted along the bottom of the graph.
First test was the XPL HI "V2 1A", purchased from FT on 9th November 2015.
The starting height was 0.029". Note that in all but the last three data points, the cells were not fully charged, thus the low readings, & sudden spike at the end of the graph.
The optimum reflector height using the XPL HI works out at 0.021".
Next was the domed XPL "V5 2A", purchased from FT on 6th October 2015;
As I suspected, the domed LED was not as picky as the HI, however, the optimal height was slightly lower, at 0.018".
As far as Lux improvements went, the HI saw a 24k increase from the "base" height, whilst the domed emitter only saw a 3k improvement.
None of the reflector heights I tested got high enough for the LED to be shrouded, but as is apparent in the last graph, the output starts to drop off significantly even when the reflector is slightly too high from the focus point.
Hopefully, this info is of some help to people, as I know there must be a lot of Courui's out there.
So what are you waiting for, scrounge up that 0.020" spacer, & make it happen! :beer:
--------------------
Update 13th December;
I upgraded my own D01 with a de-domed XP-G2 S4 2B, & set about taking focus measurements.
This was my first hot de-dome (I usually use petrol), & it turned out rather well, apart from the smallest amount of phosphor that came off one edge.
I started out with the stock reflector, then swapped it out for the KD 86mm reflector for the second set of tests.
I figured that the focus point would be the same as the first two XPL tests, & it was;
I noticed the smaller die is a lot more sensitive to slight changes in height, but the ideal focal point remained the same. I saw a maximum reading of 443K (@4.16volts), which is the highest number I have seen from the D01, & this was with the stock lens.
The cells went in for a top-up, & I re-installed the KD 86mm reflector on the D01.
This reflector is very sensitive to miss-alignment with the small XP-G2 die. I ended up having to make another centering ring, as the one I had was a loose fit, & was causing inconsistent readings.
There's no "base" to this reflector, so the LED sits up pretty high to begin with. Going on the previous tests, I was sure I'd have to raise it a little, but by how much?
I had high hopes for some big numbers, & I wasn't disappointed. I saw a maximum reading of 804k (@ 4.11 volts), when the reflector was set to 0.0295".
:beer:
