Object and reference beam must be able to produce interference patterns, that is made in the stability of the holographic record time. To do this, they must have the same frequency and the same relative stage of this period of time, that is, they must be mutually consistent. Many laser beam satisfy this condition, and the laser has been used to do, because they invented the hologram, although the first use Gabor hologram “quasi-color” light. In principle, two independent light sources can be used, if the coherence of the conditions can be met, but in practice, always use single-beam laser.
In addition, the stripe pattern for the recording media must be able to solve this problem, and for the following are some of the more common media. The fringe spacing depends on the angle between the object and reference beams. For example, if the angle is 45 °, the wavelength of 0.5 microns, 0.7 microns or fringe spacing of about 1400 lines / mm. Hologram of a job can be, if not all of the edges are resolved, but the image resolution is reduced as the recording medium reduces the resolution. These are discussed in the following section.
Mechanical stability is also important when the hologram. If a light beam changes in the other due to vibration or air flow moving across the stage of vision stripes. If the edge of space by one or more of the fringe shift, the light intensity is the average, and are not holographic. A half-wavelength shift from a relative path to the edge of the interference pattern. Therefore, the stability requirements are very strict.
In general, the decision in the light of the coherence length in the interests of the hologram can record the maximum depth of field. A good holographic laser usually has a coherence length of several meters, enough for deep hologram. Some pen laser pointer has been used to make small holograms. The hologram is not limiting the size of the laser pointer (which can be more than a few meters), coherence length, but less than 5 mW low power.
The object, forming a scene to be in normal circumstances, the light has a rough surface, so that they spread out over a wide range of light angles. A mirror reflection (or shiny) surface it is generally reflected in only one direction at each point on the surface light source, light and are unlikely event in the recording medium. Object from a rough surface in the form of an objective speckle pattern of scattered light with random amplitude and phase.
Plane wave reference beam is generally not before, it is usually a divergent wave front is placed in the path of the laser beam lens composition.
Hologram Labels
