Recent content by ppoonamk

Yes! I see rings only after the iris. But my beam after the spatial filter isn't a gaussian. There are other orders along with it. I clip the pattern to allow only the bright order through. The spatial filter setup alone does not clean the beam. I am using a 40X, .6 NA objective with a 10 um...

HI, Thank you for your suggestion. I don't have a single mode optical fiber. Seems like a very good way to get a Gaussian. Are there other ways to do it?

Hi, You are right! So I am quite sure these rings appear due to the iris I have in my setup. The rings get smaller as the diameter of the iris is reduced. Is there an alternative arrangement to the spatial filter + iris setup?

Thank you for all the answers. Using the tube length in my calculations worked. Thanks :)

Hi, I have a very simple test bench set up with a HeNe laser, followed by a spatial filter, then an Iris and then a couple of lenses. I can observe many fresnel rings on my image plane. Changing the size of the iris, and its distance changes the number of of rings. I would like to know why...

Hi, I am using an objective lens to illuminate my object by a collimated beam. The magnification and NA is available on the objective. How can I calculate the focal length from this information? The objective is not infinity corrected. Thank you

Hi all, Are there any good softwares for drawings schematics like this? I need to make and insert such images in my thesis report.

Hi Andy, Thank you for your response. I understand how the Kohler illumination reduces speckle. So I am writing this program to model an imaging system. So my problem is with the modelling of the illumination on the object. With a He-Ne laser, is the illuminating beam a coherent sum of plane...

Hi everyone, I understand that in Kohler illumination, each point at the source is converted into a plane wave illuminating the object. From what I understand, the total illumination at the object is the incoherent sum of the plane waves. Suppose my source is an ideal coherent laser i.e He-Ne...

Hi everyone, I have an optical test bench. The aim of this test bench is to get a 2 beam interference of the diffracted orders on the image plane. The optical test bench on the whole has a magnification factor of 12.5. 1) I wanted to know how the magnification affects the irradiance. I feel...

You could observe the same effects at the edge of a sharp razor blade. You will need a positive lens to covert your laser beam into a converging cone of light that passes through the exit pupil. Diffraction at the exit pupil causes Fresnel rings near the focus, which get smaller as the camera...

Hi, Thank you for your idea. I made a lookup table to convert it to power readings and found the average calibration factor for a specific exposure time. Thank you so much for the help

Hi, I have an experiment set up to get two beam interference fringes. I would like to know how I could measure the actual amplitude of the irradiance from the experiment. I have with me a power meter and a CMOS camera. How can I go about this? Thank you

H(ξ)=exp{jϕ(ξ)} Yes you are right. Sorry about having so many errors. This was the first time I was using latex. A gentle bounce. Can anyone help me?

The dominant mode in a circular waveguide is TE11