Projecting a dot in hi temp atmosphere

[RobC]

Hi all,

I'm upgrading a machine at work and I need to accomplish the following:

I need to project a visible red dot onto a piece of steel inside a hot chamber inside machine. The dot is to help the operator align parts when when he puts them into the machine. The chamber is 320 deg. F. I have limited space to mount everything, but for alignment purposes, the 'source' of the light has to be inside the chamber, so it has to withstand those temps 24/7.

I can put the light generator outside the chamber, if I can 'pipe' the light in via a fiber optic cable. So I have a small (4x6) junction box mounted just outside the chamber for mounting the diode assembly.

The dot needs to be visible to the machine operator when the chamber opens, a maximum distance of 14"

I've gone through several light sources and a couple different cables, but so far I am unable to project a dot that is visible more than an inch or two away.

Oh, and I have the following voltages available inside the cabinet of the machine: 5 or 24v DC and 120 or 480vac.

Right now the parts I have on hand are:
diodes:
10 PCS 3V 650nm 6mm 5mW Mini Tube Laser Dot Diode Module Copper Head WL Red | eBay
and
http://www.jameco.com/Jameco/Products/ProdDS/2231515.pdf

and I have this cable:

https://www.automationdirect.com/ad...rs/OPT_Fiber_Sensors/OPT_Glass_Fibers/OPT2084

and I have this lens:

E51KFH1 - Cutler Hammer, Div of Eaton Corp - Sensor | Galco Industrial Electronics

right now have a machined aluminum block to hold the laser diode directly in front of the end of the fiber optic cable, but I question how effective a coupling that is, since I can see a significant difference between the amount of light coming out of the diode versus what comes out the end of the cable. Is there any specific hardware or lens that has to go between the diode and the cable to improve efficiency?

Any help with this would be greatly appreciated!!!

 

[CurtisOliver]

First off, you are going to have to put the laser outside the chamber as no diode or dpss will withstand those temperatures without incurring damage. However the fibre cable probably wont get damaged and long as it is silicon based.
On a more technical note, would it be better to use a green dot. As it is the only part of the spectrum that isn't masked by the changing colour temperature of the metal depending on how hot you are heating up the metal.

 

[RobC]

Hi Curtis, thanks for your reply.

The metal only gets to 320F so there are no issues with discoloration, and the red dot provides the most visible as that color gives the greatest contrast to the environment.

I have already provided for the diode to be placed outside the heated atmosphere. The problem I'm having is getting the light from the laser diode to the other side of the fiber optic cable.

What is needed between the diode and the cable end to ensure efficient light transfer?

Secondly, what is needed at the delivery end of the cable to reform the light back into a tight collimated beam?

Thanks

 

[CurtisOliver]

Ok, I thought that was the air temp inside the enclosure. You would need to focus the laser output with a lens into the fibre and then get a fibre collimator. A ball lens is often used to focus the laser into the fibre to start with. And fibre collimators can be found from several suppliers.