ZP_Salon

Though there are only a few photographers are taking “artistic” zone plate photographs, in scientific and engineering fields the zone plate is utilized extensively and new types of zone plates such as a fractal zone plate are also being developed and studied. In this page we summarize the features of the zone plate photography over again which are important for discussing applications.

No material on a path of a light: The most important feature of lensless optical systems such as a pinhole or a zone plate is that no material is necessary on a path of a light for diffraction or reflection. Because of this feature lensless optical components can be used for the shortwave ultraviolet, X-ray, gamma ray and so on, and, therefore, they are conveniently utilized in the fields of nuclear physics, solid state physics and so on.

Chromatic aberration: As described in the page of “Taking a photograph by a zone plate” if the focal length is given the sizes of zones should be determined according to the wavelength of the light. In other words for the same zone plate the focal length is different in accordance with the color (wavelength) of the light. This means that the chromatic aberration is unavoidable. Generally this feature seems unfavorable from the standpoint of a photographer but for a special purpose concerning a spectroscopic analysis or compensation of the chromatic aberration itself it may be useful.

High resolution but low contrast: The other important features of the zone plate photography is a fog due to a background light. If the background light is not appropriately suppressed the contrast of the resulting photograph becomes very weak and gives a blurred impression. Moreover, there is a large chromatic aberration and only a light with a very narrow wavelength range can be made in focus. These features cooperatively make the zone plate photography, sometimes, attractive in an artistic viewpoint. These are unfavorable in the scientific and engineering fields and various methods to cope with them are considered. For example, if the spectral width of the light wavelength is small, for a small photogenic object with high luminosity the resolving power increases with increasing the number of zones. That is, in this case a photograph with high resolution but low contrast can be taken. As for the chromatic aberration a fractal zone plate seems promising and it is studied by many researchers. Other types of zone plates are also being developed.

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