LED Viewing Angle

[biferi]

I am looking at this LED and it is rated at 11,000 mcd.
https://www.jameco.com/webapp/wcs/s...oductId=2205333&catalogId=10001&CID=PDF142CAT

But the Viewing Angle is 20
and yes I know this just meens you will see it Head on but you can only go 20 Degrees to the side and see it.

But this will not be a Pin Whole Light just in the front?

 

[ronv]

Depends on how far away from it you are. Very close - very small - very far - pretty wide.

 

[audioguru]

They take a cheap dim LED and put it in a package that focusses the beam to be only 20 degrees so it appears very bright with the very high intensity number when measured on-axis.
When I need light I use a flood light with a wide angle, not one of those spotlights.

 

[biferi]

Well if I have the front of it right on say Papper will it make a 1 inch round area?

 

[audioguru]

I lost my protractor about 60 years ago. If an LED has a viewing angle of 20 degrees then at only 10 degrees off axis the brightness is half. The beam is very narrow.

What is "Papper"? Do you mean paper? It depends on the distance.

 

[MrAl]

Hi,

The sine of 10 degrees is about 0.1736 so twice that is about 0.347 or roughly 0.35, so if you hold the LED about 10 inches away from a flat object and the LED has a circular pattern then the circle you see lit will be roughly 0.35 times 10 or 3.5 inches in diameter. This is just approximate though but gives you some idea what to expect.
Sometimes there is also what they call "splash light" which is a little more light that shoots off to the sides but is much less bright.

The tight angle white LED's are used for various lighting purposes like flashlights. The fact that they have such a tight angle means sometimes we dont need a focusing lens.
Many of the high power LEDs have a much wider beam pattern and require some sort of focusing mechanism to get most of the light directed forward in a narrow beam. They make a lot of different lenses for this purpose that match with the model of the LED so that it fits right over the plastic of the LED. They typically take a 120 degree beam and turn it into a 20 to 40 degree beam with relatively good efficiency.

 

[biferi]

I need to be able to place the LED right on a Flat Paper and have it make a round area.
And if I have to move the LED away from the Paper then I can only move it Half an inch away.

 

[audioguru]

I need to be able to place the LED right on a Flat Paper and have it make a round area.
And if I have to move the LED away from the Paper then I can only move it Half an inch away.

Then you need a wide viewing angle.
I have some Philips Lumileds Luxeon SuperFlux LEDs in a 4-pins package. Some have a viewing angle of 90 degrees. Their max current is 50mA but then they are hot. Use 40mA.

 

[MrAl]

I need to be able to place the LED right on a Flat Paper and have it make a round area.
And if I have to move the LED away from the Paper then I can only move it Half an inch away.

Hi,

What is the size of the round area you need to 'make', the diameter of the circle ?

The formula i gave was for longer distances, if the distance is short then you need to add the diameter of the LED too.
You might have to diffuse the light output a little unless you can get a different LED.