One finds a comprehensive summary for the invention, history and technical advancement with wikipedia.de. In the technical and mathematical function mode of the Camera Obscura will follow described.
The function mode of the Camera Obscura:
Similarly a small hole on a projektionsflaeche produces an image of illuminated articles for an optical lens. The small diameter of the screen limits the bundles to a small opening angle and prevents the complete lap of the rays of light. Jets of the upper range of an article fall on the lower edge of the projektionsflaeche, jets of the lower range are upward passed on.
The picture the result of a folding from ideal illustration of the article with the screen surface is mathematically expressed. The distance of the projektionsflaeche to the opening determines the focal length (f). The quotient (f/D) defines, as with an objective, the blendenzahl. The smaller it is, the more brightly is the objective. The smaller the hole diameter (D) is, the smaller is the luminous beams, the more sharply appears the illustration. The limit value for D is reached, if the hole reaches the order of magnitude of the radiation wavelength. The diffraction features set with light with approx.. 0.5É m.
Pivtures taken by wikipedia
Formeltuerei:
The hole size determines the sharpness of the illustration. From jet geometry follows (B: Dimension of picture area of one point of object; f: Image intercept (focal length); g: Article width; D: Hole diameter):
Diffraction features at the lochblende set limits to the classical viewpoint. To diffraction of light applies simplified (with C = const = 1 µm):
After the radiate-optical view the dimension of picture area of a light spot decreases linear with the screen size. The diffraction of light shows a reverse behavior. The dimension of picture area behaves in reverse proportionally to the hole diameter. The optimal diameter D(f) is the value, for which the equations (1) and (2) supply the smallest value. The extreme value search supplies:
(für g>>f)
for D in millimeters, if f in meters
