Schlieren Photography With Laser Illumination

As the title says I have decided to give lasers a try with my Schlieren Photography experiments. Mostly because lasers are neat but also because I didn't have anything else better to do this weekend! OK Kidding I thought that the monochrome light of a laser and the 'pin point' light source that they are would work good. I think that all in all it turned out pretty well.

  

I didn't have a lot of time this week to set this up properly so it was more of a hack than anything else. The laser that I am using is a red high power solid state laser and it's in place of the LED that I have been using. HERE is a post I did awhile back showing the setup with the LED and it's almost the same as what I am using now. The exception of course is that I am using a laser and some lenses and the Sony video camera so maybe it's not even close! HERE is a summary of everything that I have done in this field up to this point for anyone interested.

  

Candle photographed with laser illumination

Above is a picture of the results and below after the jump link is a video. The point of this is the laser and not the candle and my hand of course. I think that I am getting close to having a setup that I can rely on to get good images. I just need to take the 'hack' out of it and build some reliable and repeatable fixtures to hold everything. Send me an email at ottobelden@yahoo.com or leave a comment if you have any questions about all this.

You can see in the above picture the red concentric rings of the laser light being reflected back from the mirror. On the right side you can see part of the mirror isn't fully illuminated. That is because the laser moved a little in the process of setting everything up and I didn't notice because it was really dark in the room at the time! The laser is round and I had a tie wrap around it that was being help by one of those springy paper clamps to a dial indicator base. The clamp didn't grab the tie wrap too well and the tie wrap didn't grab the laser too good. Add that all up and it's a mess to keep it shining where I wanted it to.

  

Schlieren Setup With The laser and Yellow Filter

The laser is supposed to be running at 5 volts but with it at full power like that it completely over exposed the camera. I turned the voltage down to 2.4 volts and there didn't appear to be any light coming from the laser but the camera was able to photograph just fine. The laser has a couple of lenses in front of it to make the bean diverge into a field the size of the 8" mirror. The lenses just like the laser mount was a unstable hack for this test and I had trouble keeping the spot sized right. More tinkering will fix that. I used a yellow filter as a 'Schlieren stop' in front of the camera. That provided bright yellow highlights where the light was refracting.

  

Schlieren Setup, candle and mirror are in the distance

As I mentioned I like the results that I got with the laser and I think it's the way to go for the photography that I am doing. There is one more thing that I want to try now that I have a camera that zooms well and I know what to do about mounting the laser in a secure but adjustable manner. The only improvement that i think i might try is using a beam splitter (image splitter) to make the laser light and the camera image path coaxial. I have read that it is a tricky thing to do but I think because the laser is turned down so low it will work. We'll see...

Another neat picture

To summarize the laser seems to work really well as a light source for Schlieren photography if you have an adjustable power supply and a solid way to mount it and adjust it's position. You also have to have the correct lenses to get the laser into the right spot size to fully illuminate the mirror.

  

I'm going to build an adjustable mount for the laser, find a way to focus the lenses I'm using to get the spot size and try an image splitter. Once I have all that done I'll be ready to do photograph some more interesting subject matter (no more candles!).