Diffusing LED Light

[Michael]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

 

[Martin Griffith]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

Check out lenses for the Luxeon range of LEDs, there may be something
suitable


martin

 

[jusme]

Sand the acrylic tube

 

[Paul Mathews]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

A) try wider angle LEDs, which may be sufficient

B) diffusing, when necessary, is generally done in 1 of 3 ways:
1) milky diffusing scattering media has high losses, since usuall less
than 50% of emitted light is transmitted, and angular coverage is
generally 180 degrees, which is often too wide
2) prismatic forward scattering uses transparent (not milky) material
to scatter light and disorganize the LED chip image....usually the
best option if you must diffuse...look for thin sheets of material
with tiny pyramids on 1 or both surfaces
3) secondary condenser lens forms collimated beam with almost uniform
brightness...highest performance alternative if you want relatively
narrow angular coverage
Paul Mathews

 

[Phil Hobbs]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

I suggest experimenting with the degree of diffusion you want, first.
You can get artist's matte spray, which might be enough all by itself,
but then again it might not, and then you have to get it off your
plastic tube. Maybe try putting some Saran wrap over top before
trying stuff.

Cheers,

Phil Hobbs

 

[DJ Delorie]

On the HomeBrew list, someone suggested sanding off the lenses of the
LEDs to diffuse them.

 

[GregS]

Sand the acrylic tube

Sanding is what worked for me. I sanded clear led's. I first cut one flat, but
that was not needed.

greg

 

[Ecnerwal]

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Try sanding the ends of the LEDs. Perhaps start by experimenting with
one, rather than messing with your whole array. By altering the shape
and surface polish of the epoxy "lens" you can do all sorts of things to
the pattern of the light out.

Any diffuser (such as matte drafting film, which would be a good choice
among that type of material) will cut down the light output as well as
diffusing it, so if you can get a good result without doing that, you'll
be better off.

 

[whit3rd]

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots.

If it's a thickwall tube (or maybe you can convert to a rod?) you can
cement the LEDs to the ends and drive it as a light pipe.

Any flaw in the tube surface will glow; just apply sandpaper to
get a uniform light output. You could also apply a milky
paint coating to the tube's (inner or outer) surface.

 

[Jim Yanik]

[email protected] (GregS) wrote in

Sanding is what worked for me. I sanded clear led's. I first cut one
flat, but that was not needed.

greg

I'd use a rubbing compound,not sandpaper;
you want just a translucent finish.

Maybe that 8000 grit SiC wet/dry paper would work,with water lube.

Inside the tube,you could push a swab coated with compound thru it,then
rinse out.
you could use the cleaning rod and swabs from a rifle cleaning kit.

 

[René]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

Use SMD LEDs instead. They do not have any "lens" projection effect,
usually just the led chip in a sort of miniature bowl.

1/10" square experimenter PCB is very convenient to hand solder smt
leds and / or resistors (0805 works best).

RGB SMD leds are getting cheaper too - mix the color to suit your mood

 

[Robert Baer]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

I have attemted to use the white semi-opaque plastic shheting that
also has a rough surface and still had that problem.
I wound up using that only putting a reflector on thesubject-side
surface and used the light from the edges - "useable" is the best i can
say for that idea.
Probably steal an idea from photography and shine the light to a
white umbrella (parabola or close approx) that reflects light to the
object of interest.

 

[Robert Baer]

Sand the acrylic tube

Insufficent.

 

[Robert Baer]

On the HomeBrew list, someone suggested sanding off the lenses of the
LEDs to diffuse them.

Insufficent.

 

[Robert Baer]

Sanding is what worked for me. I sanded clear led's. I first cut one flat, but
that was not needed.

greg

It helps some, but the light is still "spotty" (brighter in front of
each LED even at a few feet).

 

[Robert Baer]

If it's a thickwall tube (or maybe you can convert to a rod?) you can
cement the LEDs to the ends and drive it as a light pipe.

Any flaw in the tube surface will glow; just apply sandpaper to
get a uniform light output. You could also apply a milky
paint coating to the tube's (inner or outer) surface.

*That* is a much superior idea.

 

[David L. Jones]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead of
the 'neon type glow' I'm trying to acheive I'm getting spots. I tried to use
the widest angle lights I could find but I'm still having this problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of spray
paint that I can coat the outside with?

Thanks in advance,

Michael

Perhaps turn the LEDs around so they point out the back and have the
light reflect off the back of the tube, plus add your diffuser of
choice if needed.

Dave.

 

[Robbo]

Hi,

Vaguely on topic......I have a 2m row of LEDs contained within an acrylic
tube that are projecting light onto a surface 300mm away however instead
of the 'neon type glow' I'm trying to acheive I'm getting spots. I tried
to use the widest angle lights I could find but I'm still having this
problem.

Can anyone suggest a good method to diffuse the light? I was thinking of
something along the lines of greaseproof/tracing paper but I'd prefer
something that was easier to apply inside the tube or maybe a form of
spray paint that I can coat the outside with?

Thanks in advance,

Michael

I saw some one do this with "holographic diffusion film" - don't know who
makes it or where it came from. Look at the LED line generator in an old fax
machine - maybe some ideas there?

 

[Martin Griffith]

Perhaps turn the LEDs around so they point out the back and have the
light reflect off the back of the tube, plus add your diffuser of
choice if needed.

Dave.

Maybe use edge lights like this
http://www.omc-uk.com/leds/led_backlights.htm


martin

 

[John Popelish]

I saw some one do this with "holographic diffusion film" - don't know who
makes it or where it came from. Look at the LED line generator in an old fax
machine - maybe some ideas there?

These are available at:
http://www.edmundoptics.com/