Atelier Bonryu(E)

zone plate photography

 
 

Laboratory: Zone Plate Photography

Theory of Zone Plate Photography

- Rectilinear Propagation of Light -

A zone plate as a solution of the above problem: A zone plate (ZP) is just an optical component which solves the above problem.  By the way, though there are two kinds of zone plates, i.e., a Fresnel zone plate (FZP, also called as a binary zone plate) which consists of clearly distinguished transparent and opaque zones and a Gabor zone plate (GZP, also called as a sinusoidal zone plate) in which the transparency changes gradually along the radius, in this page we describe mainly the Fresnel zone plate.  Radii of boundaries of zones are determined from the frequency of the light (usually we use the central frequency of the visible lights, i.e., 550 nm) and the focal length.  If we consider to take a photograph by a zone plate camera of a size of a usual commercial camera the diameter of the outermost zone is around several millimeters.  The diameter of the central circular zone is the same as the diameter of the corresponding pinhole plate, and generally the diameter of the outermost zone is about several to several ten times as large as this pinhole size. 


In principle the number of zones can be increased indefinitely and with increase of the number of zones the size of the zone plate increases and consequently the resolution and brightness are improved.   However, with increasing the number of zones the width of the outermost zone becomes narrower and narrower, which imposes a technical limit on the maximum number of zones from the viewpoint of working accuracy.  Moreover, the product of the wavelength, the focal length, and the number of zones is constant for zone plates with the same pattern even if each of these variables is different.   Therefore, with increasing the number of zones the focal depth and the width of the permissible frequency range of the zone plate decrease.  These features will be described later in detail.  Incidentally, I started zone plate photography by using zone plates with the focal length of 55 mm and 29 zones, and the focal length of 90 mm and 15 zones.

Light propagates rectilinearly: The principle of imaging by a pinhole camera is that “light propagates rectilinearly.”  Light rays from a surface of a photogenic object go straight through a small hole (pinhole) and form an inverted image similar to the object on an image plane, i.e., a film or a sensor of a digital camera.  However, because only a small part of the light rays which are radiated from the surface of the object in all directions and pass through a small pinhole reaches the image plane, the most difficult problem is that the image is inevitably very dark.  The easiest way to make the image brighter is to use a lens instead of a pinhole.  Therefore, most present cameras use lenses or a reflex type interchangeable lens which utilizes a concave mirror as used for an astronomical reflector telescope.  Then, are there no methods to get a brighter image without using lenses or mirrors?

An example of a pattern of a zone plate

   White zones are transparent.  There is also a zone plate where the central circle is opaque.

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 The following e-books (Amazon Kindle Book) have been published.

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ピンホール写真(Pinhole Photography: Japanese Edition)
ゾーンプレート写真(Zoneplate Photography: Japanese Edition)

Soft Light and Shadow (English Edition)
--Zone Plate Photo Album (1) --http://www.amazon.co.jp/dp/B00IWJIZIUhttp://www.amazon.co.jp/dp/B00M1AWVC2http://www.amazon.co.jp/gp/product/B00WKWZDP8?*Version*=1&*entries*=0http://www.amazon.co.jp/gp/product/B00WKWZDP8?*Version*=1&*entries*=0http://apple.excite.co.jp/shapeimage_4_link_0shapeimage_4_link_1shapeimage_4_link_2shapeimage_4_link_3

(English Edition)

Soft Light and Shadow

(Japanese Edition)

Lensless Photography

by Rings of Light

(Volume of Stones)

Lensless Photography

by Rings of Light

(Volume of Birds)

Lensless Photography

by Rings of Light

(Volume of Flowers)

Complete Guide to

ZonePlate Photography

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