So far, so good?…way wrong because the image of the circular illumination contains dots, circles and spots which are rather bothersome on the test cardboard and so also on the film, the master-hologram (called H1) and also on the reflex-hologram (called H2). These would be transmitted as a bothersome interference pattern. The cause lies in the micro-fine dust particles found in the air which then settle on the lens thereby preventing an optically clean image.
These can be avoided by putting a tiny pin hole in the hologram exactly at the focal point of the lens, centered a few micrometers in front of it. It then absorbs all of the bothersome aberrations. The pin hole is so small that it is hardly visible to the naked eye. To “clean” the beam after the microscope lens I use a pin hole of 25µm, 0,025mm, about the size of toner particles.
Placing a pin hole exactly at the focal point of a microscope lens can be done with the help of an XYZ adjustment instrument. With this the tiny hole can be adjusted up, right, left or towards the front or back. The adjustment itself requires maximum finger sensitivity. This may take up to two hours depending on your own form that day. When finished, you will be rewarded with a wonderfully clear, red spot on the test cardboard. The desire to create a hologram just as “pure” has been awakened