How to merge several gray scale images to increase signal to noise ratio?

Images from X-ray microscope were realigned and have the same resolution. I am trying to come up with a code for intensity image merging to increase SNR. Could someone refer me to a reliable source of information to start me off. Thank you.

Answer 1

[Image Analyst]

If they're all from the same scene, just add them all together (after casting to single or double) and then divide by the number of images. The mean image is the max likelihood answer.