Optical: systems and elements – Lens – With viewed object support
Patent
1996-02-05
1997-12-02
Ben, Loha
Optical: systems and elements
Lens
With viewed object support
359803, G02B 2702
Patent
active
056942567
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an optical reading device having a rod-shaped lens body.
So-called reading rods, or line-reading magnifying lenses, are known in different embodiments, for example from the publications U.S. Pat. No. 2,420,021, U.S. Pat. No. 2,151,573 and U.S. Pat. No. 2,057,807 and European Patent Application 0 107 256 and German Utility Model G 82 32 211. They typically serve as a magnifying aid in reading an item, for example in reading lines of print. The essential feature of these known reading rods lies in the cylindrical shape of their lens bodies or surfaces. Typically, only the view-through surface of the top side is cylindrical, whereas the surface to be placed onto the item to be read, namely the underside, is planar.
Reading rods of this type only magnify in one direction. If the direction of the rod is identical to the direction of the line, the line is only magnified in height, and hence only perpendicular to the item to be read. Moreover, only slight enlargements, for example of 1.8 times, can be attained.
Reading magnifying lenses having a rectangular contour shape are also known, wherein at least one curved surface of the lens body is configured to be convex in the directions of both the length and the width of the rod, with the lens body having two plane-parallel side surfaces extending transversely to the longitudinal direction of the rod.
But such lenses have the drawback that only a single magnification is available to the user. If a different magnification is desired, a second lens having the desired magnification must be made available. It would also be conceivable to provide a reading device of the type in question with several lenses of different magnification. But this would increase the weight of such a device and impair its ease of handling.
SUMMARY OF THE INVENTION
On this basis, it is the object of the invention to create a reading device which is simple in its construction and easy to handle and which has at least two different degrees of magnification.
This object is solved by providing an optical reading device that comprises a rod-shaped lens body having a first and a second pair of side surfaces extending in the longitudinal direction of the rod and, in pairs, disposed opposite of one another. At least the one side surface of the first pair of side surfaces is configured as a curved surface which is curved convexly in the directions of both the length and the width of the rod. At least one of the side surfaces of the second pair of side surfaces is provided with an additional curved surface. Thus it is possible in a very simple manner to change over from the one view formed by the first pair of side surfaces to a second view having a different magnification formed by the second pair of side surfaces, namely by pivoting the optical reading device around its longitudinal axis.
The convex configuration of the surface of the lens body in two dimensions, i.e. in the directions of the height and length of the line to be read, results in a segment-like lens body shape having the same degree of effective magnification in both dimensions. This segment-like lens body shape leads to a considerable reduction in volume with the viewing field being particularly wide at the same time.
The surface curves can be spherical or aspherical. It is preferable to provide spherical curves in the center region of the lens body, in both the x and y directions, which change over to aspherical curves in the edge regions. This compensates for edge distortions which would otherwise be present due to image distortions. This aspect of edge distortion is significant, because a wide viewing field is created which cannot typically be produced by commercially-available round lenses due to the large magnifying lens diameter.
In an advisable embodiment, both side surfaces of the first pair of side surfaces are configured as curved surfaces which are curved to the same extent. That is, the top side or view-through surface as well as the underside facing the line to be rea
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Ben Loha
Eschenbach Optik GmbH & Co.
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