Fluorescent light sources 2

[Chemicalguy]

I am currently setting up fluorescent light sources (F15/F17) tubes inside a cell culture incubator (a regular chamber with CO2 gas in it). The lights are setup inside the chamber at the top. I am trying to get uniform light distribution at the bottom of the chamber, but I am not able to do so. There is always some variation spatially at the bottom. The sources are linear long tubes of fluorescent lights. How do I ensure perrfectly uniform distribution over an area of 19" X 19".
Thanks
Ganesh

 

[IRstuff]

How "perfectly" uniform do you need it? And how much are you willing to pay?

A frosted glass diffuser will give pretty good results, but you'd lose quite a lot of energy. An integrating sphere would be even better, but it would be HUGE to cover the area you want and losses of light are even higher.

TTFN

 

[Chemicalguy]

Thanks for letting me know about the glass diffusers.I was thinking about engineered diffusers too. As you have correctly mentioned, I cannot afford to lose more than 20% of the light.
The light source is essentially a bank of three linear fluorescent tubes evenly spaced out at a distance of 5 inches from each other.
I am trying a get a uniform distribution of light(in terms of lux and mW/cm2) on a tray positioned below the sources at a vertical distance of 16 inches. The tray is 19inches X 19 inches.
The whole light assembly is kept inside a temperature controlled Incubator.
I can get a higher wattage fluorescent tube to compensate for the losses from the diffuser.
I am not sure about the cost, please give me a ballpark estimate.
Thanks
Ganesh

 

[IRstuff]

The absolute simplest thing is to put more tubes in. Since the tubes are spaced about 5 inches apart, you can get at least two more tubes into the array. you might actually be able to squeeze in 4 additional tubes.

another possibly cheap thing is to put parabolic reflectors behind each tube. This will tend to bring the light going upward to reflect downward and may smooth things out a bit.

TTFN

 

[Chemicalguy]

Sure,The biggest drawback is that the temperature of the incubator shoots up by adding more tubes.I have to maintain this chamber at 37 deg C at all times for living cells to survive. This incubator does not cool, so the lowest temp it can go to is room temp.
I tried a cheap solution by circulating water thro' a pump and coiled tubes inside the chamber.
In fact I mounted the ballasts for these sources remotely away from the incubator to avoid the heat generated by them.
Yes, thes easiest and most convenient way is what you have suggested-placing more tubes, but I need a better way to control temp.Each tube (even without the ballast) produces atleast a deg C of heat.
Thanks again
Ganesh

 

[IRstuff]

one possibility is to use a heat reflective glass below tubes to keep the heat in and run a big cooling fan to cool the tubes.

TTFN

 

[Chemicalguy]

Great. If the heat reflective glass itself functions as a diffuser,then I can solve two issues right there.
Thanks for your valuable inputs
Ganesh

 

[cev]

I don't think that a heat reflective filter is going to help your temperature problem very much. These filters reflect IR light beyond 750 nm and transmit visible light. Your fluorescent tubes do not emit very much light in the IR.

Rosco is a good source for cheap films. You can get a variety of diffuser films (cinegel line), heat-reflecting films and UV reflecting films (protective filters).

http://www.rosco.com/

You can use fans in the space between the lights and the filters to get rid of some heat.

CV

 

[kyphil]

Hello Chemicalguy from kyphil:

Have you considered a white LED light panel of sufficent size to give you the coverage you need? Depending on the footcandle level you need, the LED's could be placed on a grid pattern on the board. They operate around 12 volts and could be dimmable, to tune the level precisely. One big issue-they produce very little heat compared to filament sources like incandescent or fluorescent even with remote ballasts. There are several companies that could fabricate one for your need. I don't know what the IR or UV spectral energy is, but the UV could be filtered out pretty easily with an overlay. You can find info on the theory and application of LED sources at:

http://hyperphysics.phy-astr.gsu.edu/HBASE/electronic/leds.html

A company that specializes in commercial LED sources is

http://www.luxeonstar.com/

or

http://www.sunled.com/products/spec/XKL4SBWH383WSMD.pdf

or you might even try investigating fiber optic lights-with the right lens, remote light source, etc. you can get very wide, even dispersion of a very pure white source. Try this company:

http://www.luciferlighting.com/fo_fiberops.htm

Good Luck! Let us know how it turns out.

Phil