Britannica Sources used in this answer

Why do twin images interfere with one another in Gabor’s original holography method?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

hologram graphic — holography Figure 1: Gabor's original method for creating holograms.

In Dennis Gabor’s original holography method, the hologram is created using a collinear background, meaning the reference beam and the light diffracted by the object travel along the same axis.1

When this hologram is illuminated to reconstruct the image, it produces two distinct images: a real (conjugate) image and a virtual (primary) image. Because the light associated with both images propagates in the same direction, they overlap spatially. Consequently, when viewing one image, the light from the other appears as an out-of-focus component, causing the two images to interfere with one another and degrade the clarity of the reconstruction. This issue is characteristic of in-line Fresnel holograms, whereas modern off-axis holography avoids this interference by introducing the reference beam at an angle, which separates the paths of the two images.1