Reflecting Infared Energy - Curved or Angled Surface

Can you explain the set-up a bit better, please? Are the mirrors inside the tube - or is the inner surface of the tube used as the reflector? What are the approximate dimensions of your apparatus? What is your light source?

Any chance of posting a sketch or two?

The tube is made of glass is one inch inside dia and the inside is coated with 24K gold. the lenght is 13 inches and in the shap of a "U". One end has a detector and the other end has an infared generator with a timer (or chopper motor to generate an on/ off on/off cycle). We have tried two different "U" end sections; one curved and one with 45 degree angles. The setup with 45 degree angles looses energy, we assume it is due to the "sharp" angles vs curved "U" section.

In other words say you have a mirror at a 45 degree angle and aim a laser at the mirror it reflect at the same angle if incedience without much loss of energy.

Why, when we do the same with an infared energy source there is a large loss of infared energy at a 45 degree angle?

Thank You in advance.

Gas Man

My guess is your 45° tube reflects more light back toward the direction from which it came.

The reflective properties are dependent on:

Wavelength;

Reflective material;

Angle of incidence;

Polarity of light source.

Gold is a good IR reflector, Beryllium is also.

No longer my field. More information is needed to give you a better answer.

Laser info: Wave length; beam size; beam conditioning; beam polarity; wattage of beam.

Glass light guide ID(u shaped glass tube), Mirror size, Curvature of mirrors, mirror cooling, distance from laser or any beam conditioning optics to mirror to light guide.

My guess is your beam quality need for your light guide was improved by the curved mirror. Much more info would be need to know why for sure. A good ray trace program would tell a lot but after 15 years I'm far from up to date.

Brad

Hi,

infrared is doing the same as light,

but may be your infrared light source is different from what you expect.

Gold is a better reflector in the IR as in visible light.

In usual imaging optical systems you would need an intermediate optical element.

This is designed to image your light source onto your target/detector/focal-plane.

I suppose that with the 45°mirror you lost a lot of light because of beam divergence not meeting mirror size.

So if you replace the 45° mirror by a concave mirror this will work.

Focal length shall be equal to distance from mirror to reflector if the beam is coming from (maybe virtual) infinity.

Focal length shall be half of this distance if beam source to mirror equals mirror to detector.

Why on Earth do you need this arrangement?

Very often two imaging mirrors are used in 180° beam deflection.

This is for example used in spectroscopes for imaging one (entrance) slit onto the other one (exit).

If not working then please send drawing. Will work. Look at your infrared source with a CCD camera if it is near IR. This is visible for the camera. Maybe a visible blocking filter is needed. Scan your beam with a detector to be clear about beam size and divergence if far IR.

RHABE

i can help with this, but would need to make certain that it is no way a competitiion to the company i work for,

please email me so that i can understand the application , and we will see how it goes.

mudbilly@yahoo.com

Make sure that the glass is not absorbing the energy. I don't know about IR but UV is absorbed by glass but not (much) by quartz. A glass mirror doesn't work well with UV but a quartz one will work well if the backing metal does not absorb the wavelength.

Perhaps your IR source rays diverge too much, so that a small portion of the energy reaches the first reflector, even less reaches the next, and very little reaches the sensor. The curved mirrors would help converge the rays. The ultimate solution, though, would be to provide a collimated IR source.