This is an interesting discussion. My brother studied electronics in the mid 80s, so I inherited a beat-up electronics tool box with a few vintage parts and some other scavenged thingamajigs over the years. Some old red led or two lying around (they're quite dim).
However, what is the aim of this? Unless it is possible to get a reliable source of whatever parts, and test them of course. I mean, I think a nice point would be to make a list of parts for a DIY build which anyone could build and use.
Forum members who can do spectral power distribution and other specialized led tests are maukka and djozz. Send them a private message if you will.
If someone already has a C01R could make some measurements please?
If possible measure the current draw in the 3 modes.
If possible measure the diameter of the beam against a flat wall or fixed surface from a distance of 6 cm (2-1/4 inches) and also at 10 cm (4 inches). From this we can calculate an approximate radiant power assuming all the energy is reflected and magnified by the lens and sent out the end. This might be a worst case to determine how much diffusion paper is required to cut the beam down to a safe level.
Or if someone has a radiometer can take measurements at these distances and modes, then we have it for comparison.
It would be much simpler to just know the Lumen output of the light used for the study (including the diffuser), and then the lumen outputs of the C01R
from there it would be pretty easy to calculate the distance at which the two sources would have similar LUX on target, or to compare the output of the C01R with whatever diffusion is applied.
I find a couple of layers of scotch tape an effective diffuser…
I also find it relatively simple to move a light closer or farther away, to reduce or increase the visible brightness on target.
I feel I can pretty easily judge, what a dim level looks like. There is no need for excess brightness, the mitochondria dont need a specific dose… dim is plenty.
Photo red and beyond leds rarely list lumen output, Cree ones certainly don’t. There are tables somewhere to convert between mW and lumens for different wavelengths, like this one .
Edit:
If such data is accurate (I doubt lux meters/integration spheres are very accurate outside ranges typically measured in lumens ) then we have W = lm / 41.663:
0.5 / 41.663 = 12 mW
9 / 41.663 = 216 mW
36 / 41.663 = 864 mW
That would be valid if the the 660nm was pure like a laser, for a 650nm-670nm distribution I think the 650nm will contribute a bit more to visible output so I expect the lm/W convertion factor to be somewhat higher, but not much higher.
That’s what dedicated threads are for
Mode currents:
(the currents listed in this post are taken from:)
Spectography:
And and with my C01R approximately 150cm away from the wall the hotspot is approximately 65cm wide, at approx 75cm wide it’s approx 33cm, and at approx 37.5cm it’s approx 17cm.
Difficult to measure as there’s a small, smooth transition into spill but the measurements seem fairly linear.
I lightly sanded the front of my optic which worked perfectly for me, now it has a TIR style transition from centre to edges.
(I bought a couple extra C01Rs for gifting, the measurements in the above post were taken with an unmolested one :D)
As for dim, i figured a ceiling bounce with no other lights on would work (especially for the Theodore41!), or just looking at the beam projected onto a white wall.
137 lm/W is nonsense for 660nm, they probably copied the value for 620nm LEDs. The table I linked shows 73.081 lm/W for (monochromatic) 650nm, 41.663 lm/W for 660nm, that’s with 100% electrical to light conversion efficiency. Does the manufacturer datasheet lists the 137 lm/W value?
Edit: You would need to integrate over the 600nm-700nm range to get an accurate conversion factor, but I don’t think you can reach 137lm/W even counting the lower wavelengths. Anyway 620nm and such don’t contribute to the desired effects.
The most accurate way would be measuring it directly, with proper equipment that nobody here owns . Assuming some driver efficiency like 80%, I think estimation from current is more likely to obtain a meaningful value than starting from lumen outputs that normally aren’t used for 660nm.
Medium mode inputs 105mA * 1.33V (NiMH) = 140 mW, assuming 40% total efficiency (60% led * 60% driver+optics) that’s 56 mW output power OTF, 40 mW/cm^2 in 1.4cm^2 area, but that’s a very inaccurate calculation, light distribution is not uniform.
But getting from total output to mW/cm^2 precisly would be too difficult, you need to consider the optics characteristics, that’s why integration spheres are used in the first place. Someone with a lux meter could attempt to calibrate it for 660nm, using a led with similar area and the same optic.
i don’t have my FL yet to see how bright it feels, but here’s my estimate based upon this data.
Using the beam shot diameter over distance we find that the beam has a solid angle of about 24 degrees, so we can use that to find the area needed to match the 40mW/cm^2.
To hit both eyes at the same time with this angle requires the light to be about 24cm or 10” out in front of your face, and this results in an area of illumination of about 78cm^2.
To hit that area with 40mW/cm2 would require 40 x 78 = 3120 mW, yikes that surely seems too high!
The radiant power in the datasheet was about 440mW @ 350mA. Medium mode @ 105mA => 132mW Radiant, and Low mode = 19mW. This is in close agreement with ggf’s calculation of 140mW.
Medium mode at 10” from your face gives 132mW/78cm2 = 1.7mW/cm2.
If the 40mW/cm2 is the power at the face/eyelid/pupil, then for a 5mm pupil this would imply about 8mW into the eye—this seems awfully high to me. A 5mW laser will cause eye damage. This led is not a laser but definitely concentrated over a tight band.
Could the radiant power of the study have been in units of microWatts?
From this it looks like the power was measured right at the 9 x 5mmLed flashlight. Area is 3.8 cm2 for these lights, so the radiant power out the tube was 152mW.
This is another point towards the medium mode of the C01R. Use a diffuser, hold it 10” away and close your eyes.
@Hank, this is from CREE’s site (lamp = LED):
Vision Advisory
WARNING: Do not look at an exposed lamp in operation. Eye injury can result.
Im sitting here waving a 10 lumens red LED at my closed eyes. The light is at arms length (28” away), and it has a double layer of scotch tape for diffusion.
It is WAY brighter than necessary for me to see the light Through my closed Eyelids.
I then turn the light down to 1 lumen, and can still easily see the light through closed lids, still at arms length.
I would not dream of aiming 9 lumens at my open eyeball for 3 minutes… that defies my common sense
Average solar irradiance at Earth surface on direct sun is 1050 W/m^2 = 1,050,000mW/10,000cm^2 = 105 mW/cm^2 according to Wikipedia, so indeed 40mW/cm^2 looks like a large value, of course that doesn’t include the eye focusing effects that make seeing the sun on the sky mostly safe, but looking directly to the sun a terrible idea.
. Assuming some driver efficiency like 80%, I think estimation from current is more likely to obtain a meaningful value than starting from lumen outputs that normally aren’t used for 660nm.