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How is a holographic image reconstructed from a hologram?
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holography
Figure 1: Gabor's original method for creating holograms.
To reconstruct a holographic image, the developed hologramâwhich contains a complex pattern of interference fringesâis illuminated with a coherent laser beam.12
The fine-detailed fringes on the hologram act as a diffraction grating, bending the light to reverse the original conditions of the coherent waves that created the record. This process typically produces two distinct images:12
- Virtual Image: Formed on the light source side of the hologram, this image is visible to the eye and exhibits three-dimensional characteristics, including parallax.12
- Real Image: Formed on the opposite side of the hologram, this image can be captured by a camera or microscope at a selected depth.13
Because the hologram stores both amplitude and phase information, the reconstructed images possess a three-dimensional character that ordinary photography cannot replicate. In off-axis holography, the image-forming beams are separated during reconstruction, preventing the overlap of the real and virtual images.142