Hi everyone,
I'm working on the interferometric laser imaging for droplet sizing and sometimes I see some concentric circular pattern in the main interferometric pattern, especially when the light intensity increases! (I've put one of the photos below).
Does anybody know about the reason for forming these concentric patterns?
Thanks in advance
Hi Daniel J. Förster and thanks for replying.
In my setup laser beam directly hits a droplet and then the scattered light collected by the lens and camera. When the light comes out from the laser, only passes the droplet. Do you think the scattered light has such power to heat the transmissive optics of the lens to lead focal shift?
Yours sincerely.
hi,
I would agree with Daniel J. Förster for high power lasers only! but it may be happening due to some type of non uniform coating on the optics. This is the thin film interference phenomenon regularly observed if the light is reflected from two surface separated by a very small thin gap. If that is not the case, one peculiar observation of the image shows us another circular pattern of the same type but of small radius near the left upper corner on the peripheral region of the large pattern. This type usually is seen when laser is scattered off from very small particles (probably dust)!!. It would be safe to assume that either of the two phenomenon is happening at image plane.
You could try one thing is to collect the image on a plane white surface and observe with a naked eye (With eye protection). If you get the same effect, atleast you will be sure that it is not happening due to camera optics. Likewise improve the approach while going through all the optical path.
Regards
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