Integrating sphere #4 (the fast and cheap one)

Good tips, thanks mate :beer:

In this design it is better to align the face of the light with the top level of the entrance hole, in that position there is no direct light going from the flashlight to the area where the sensor is, which should give better integration.

But it is insightful to compare the readings of both positions, if the ratio of both positions is the same for a flooder and a thrower, it is apparently not so critical what the best position is (but as Garry said, decide on a consistent position).

Great idea and even better ease of making it. Kudos to you Djozz for the guide.

Planing on making one with a 200mm ball, with wall thickness of 23mm. Now as my biggest lights are Convoy L6 and Couroi D01, i would need a 76-77mm hole to be able to measure them and similar sized lights.
Will i get away with a 77-80mm hole on the ball im planing on using, or there is just no way and i should try and find a ball with bigger diameter?

Waking up some sleeping beauty but this cheap integrating sphere is really something nice and as i am making one (well ... actually several as i found a source for 20cm and 30cm polystyren balls not far from where i live) i have some questions about possible upgrades.

Do you think that adding some kind of diffusion layer (frosted glass, dc-fix, ...) inside the ball at the entrance hole would help reduce the reflectivity variation from one flashlight to the other ?

Of course it won't be perfect because some of the light will be reflected from the diffusing thing back to the flashlight where it will be reflected again and it will reduce the light entering the sphere too but i am wondering if the overall result could be better

Has someone already tried that ? what to expect ?

Mmmm maybe the only way to know for sure would be to add a ref light and once you have one installed you don't need that much to reduce the reflectivity variations ;-)

I was watching a doku about LED light (danger of the blue part. . . .and other effects on the body ). When this nice integrating sphere came up.
And i was thinking the 40cm sphere i was planing is bulky :smiley:

I have 50cm at the office, it’s just enough for torches :frowning:

When I’ll have a load of money and a big house I’ll buy this one :

:sunglasses:

We should chip in a few dollars each and buy this for djozz. I’m sure he’d fit it into his unit somewhere. :stuck_out_tongue:

We’re not using the bath very often, I can break it out and place the sphere there, squeezing ourselves past it to reach the shower. But we can’t afford to shower anyway after I bought that thing.

Best integrating bathroom in the world.

Too much information, but I do the ceiling bounce test in the bathroom quite often at night, so it makes sense to me.

If we can get him a even bigger one the space problem goes away because he could move directly into it.
A bit cold in the winter but during the day he could use the calibration quartz tungsten halogen lamp to heat it. :sunglasses:

Preventing my son sticking his dirty fingerprints on the wall will be a daytime job. “Get your f#lthy fingers off my wall, you’re ruining my multiplier”

Here’s mine, 20cm in diameter :

I made the entry aperture the size of a C8 bezel and coated it with some black electrical tape.
I have some quite good measurements, but I don’t have many stock flashlights unfortunately… I tend to mod any new light that comes in my collection :innocent:

Anyway, I average my multiplier with a dozen stock lights, and then apply it to my measurements.
I’m glad to have tested it, but now I kind of regret to not have bought the 30cm version (11€ vs 5€…)
Well, I guess I’ll buy it to measure some bigger lights.

Here is a spreadsheet I made to compile my results.

Looks good X3 !

Your calibration leans on the published numbers of Olight, I’m not sure how they compare to real lumens. But the multiplier at least does not show enormous deviations so that looks trustworthy.

What bother me is my Eagletac D25A 219C… I have a multiplier of about 4 with this one :frowning:

EDIT : I don’t know how Olight round up their numbers, but I do know that they own an integrating sphere (maybe 1m in diameter) as can be seen on the office/factory tour that Marshall did a few years ago

Made from 4 inch , schedule 80 PVC “P” trap and 90’s and with a .05 (or 1/2 of actual reading on meter) comes in about 3% under what the Maukka calibration lights show.

The cut out on the side of the top opening , is so that headlamps or other 90 degree lights can be centered for testing. Also have different sized foam cut outs , from 3/4 inch opening up to almost 4 inch to block any light from escaping the opening.

Below are the pictures of the light tube and under those , the Readings Muakka had on his integrating sphere and my actual readings from my light tube set up with those same lights.





Hi Guys! I read all comments on this beautiful thread. I got curious and I registered, so I am new here!
Is there a welcome cake or something? =D

I was wondering what power could such integrating spheres sustain. what if I plug in a 10W halogen lamp?

Cheers!
Lorenzo

Welcome to BLF lelea!

We have no cake but we do have Milla, if the Raccoon chimes in that is.

Not sure about the halogen inside a styrofoam sphere, 10W sounds still ok for a single measurement but do not do a runtime experiment with that. I have coated a few spheres with latex paint mixed with bariumsulphate, I think those can handle some more heat than bare styrofoam.

Thank you Djozz =)

did they end up collecting money for a larger bathroom with a larger integrating sphere for you?

Unfortunately I have to run long measurements and it has to last “forever”. The point is also to be able to change the lamp when it dies without messing with alignement.
I will think about painting with latex. maybe it’s worth doing a test! In that case is it even necessary to have the foam sphere? I could paint any other material, right?

How should I think about efficiency of integrating spheres in terms of input-output power? If my lamp is 10W how much should I expect to have as output?
Right now I use a lens to collect some of the light, thus I lose most of the source power. To calculate how much I can just compare angle of illumination with size of the lens, but what about the integrating sphere?

Thanks again,
Lorenzo

There is zero chance that I will have a larger bathroom, it implies moving house inside Amsterdam which is virtually impossible with the current crazy housing market. And even if it came true, it will be my girlfriend’s domain, not mine, my hobby is doomed to be restricted to the dark corner behind the cupboard. :cowboy_hat_face:

Painting with latex may make a styrofoam sphere a bit more heat-resistent. I experimented with a PVA-bariumsulphate mixture too (PVA=polyvinylalcohol), that handles a bit better even and should give a better (more constant reflectivity over all visible wavelengths) coating too.

But there is no other reason to start with a styrofoam ball than easy availability, if you can find a sphere from any other material and give it a flat white coating on the inside, you are good. I hope to find an affordable nice metal sphere at some point, that should handle any output power.

It is a misconception that input-output efficiency plays a direct role in integrating spheres. It does not matter if the sensor picks up only a tiny fraction of the input power (which indeed it only does), it can be any fraction as long as that fraction is the same for all colours and output directions of the light source. Your multiplication factor then takes care of the correct calibration. The only reason that you want high reflectance on the inside of your sphere is indirect: high reflectance causes more reflections before the light is finally lost or reached the sensor, and more reflections equals better integration.

(As a side note: I suspect that most people on BLF have no idea what light integration is, and even if they have a clue, why it is an important feature of your device in order to measure light output. I hoped that my threads on integrating spheres would help a bit but it does not seem so.)

I see your point about integration. Maybe I should have pointed out I am most interested about power output than most people. I am considering using a sphere to “save” energy from a halogen lamp that I need illuminating an optical setup. The setup only takes few mm rays, thus now most of the light is lost shining elsewhere. An integrating sphere with a homemade output slit will give me the ability to change lamp without realigning the setup while using somehow all the light from the lamp, even tho I have no clue what would be the efficiency I get out.
Maybe a new thread is due for me =)