In-line Gabor Holograms

The modern field of wavefront reconstruction began in 1948 with Dennis Gabor’s development of the in-line hologram. Created to improve electron microscope resolutions, Gabor’s single-axis optical setup laid the groundwork for modern holographic optics.

Unlike modern dual-beam systems, a Gabor hologram uses a single coherent beam that acts as both reference and target beam. Part of the light passes cleanly through a semi-transparent object, while the remaining rays scatter off its structures, interfering directly on a photographic plate.

While Gabor’s setup is simple, it suffers from the "twin-image problem." This optical limitation overlaps the virtual and real reconstructed fields, causing visual shadowing. This challenge was subsequently solved by Leith and Upatnieks’ off-axis dual-beam system, paving the way for the three-dimensional holograms we use today.