Patent Application
20120079853
To increase the brilliance of a faceted cut gemstone, diverse types of cuts have been developed over time, which, on the one hand, differ by the number of facets and, on the other hand, by the mutual geometric relationships of the facet positions.
The so-called brilliant cut has been found to be especially esthetic in particular for diamonds since this cut critically impacts the so-called “fire” of the diamond, which fire is based on numerous internal light reflections. These light reflections occur at the individual facets which have special angular relations with one another characterizing the particular cut. Consequently, the cut of a gemstone, especially that of a diamond, is decisive for the generated fire.
Further parameters characteristic of the esthetics of a gemstone, that are dependent on the particular cut, are the scintillation describing the sparkle of a moved gemstone and the brilliance describing the brightness and the contrast of the light exiting from a gemstone. A diamond with a brilliant cut is generally also referred to as a brilliant.
A gemstone with brilliant cut includes a crown, also referred to as the top part, with at least 32 facets and a table, as well as a pavilion, also referred to as the bottom part, with at least 24 facets. The end opposite the table of the gemstone can be formed as a point or as a rounded-off point in the form of a so-called culet. Between top and bottom part is disposed the so-called rondiste or girdle. The gemstone is cut symmetrically.
The invention addresses the problem of further improving the esthetic impression of a gemstone with brilliant cut, for example providing increased luminous efficiency or increased luminance or brightness.
This is resolved in a gemstone with the features of claim 1.
Thereby that the gemstone has a brilliant cut in which the crown angle is between 32.8° and 33°, an especially high luminous efficiency was unexpectedly obtained, whereby the fire, the scintillation and the brilliance of the gemstone are being brought out especially well.
The crown angle is that angle which, in a side view of the gemstone, is formed between the lateral boundary line of the crown and the girdle plane, wherein this boundary line results by orthogonal projection of a crown facet onto a plane containing the longitudinal axis of the gemstone.
The girdle plane is that plane which is located parallel to the table and in which the gemstone has its greatest cross-sectional dimension. The girdle plane is oriented perpendicularly to the longitudinal direction of the gemstone.
To measure the luminous efficiency or brightness of the gemstone, which efficiency corresponds to a reflected light fraction, measurements are carried out using an illumination arrangement and measuring specifications developed by the Gemological Institute of America (GIA). The corresponding measuring specifications are found in the magazine “Gems & Gemology”, Fall 2004, pp. 202-228, in which, in particular on page 219, a measuring arrangement for measuring the brightness of a gemstone is depicted. Instead of an actual measurement, the measurement can also be computationally simulated based on the geometry of the gemstone. The measurement or the results of the simulation yield values for several characteristic light- or radiation-specific parameters of the gemstone, in particular brightness and/or luminous efficiency.
The gemstone located in the center of the base circle is illuminated using a hemispherical illumination arrangement with directed irradiation normal to the surface. The illumination arrangement generates a Lambert beam distribution with sufficiently large sectional angle such that lateral facets of the gemstone are also illuminated. The quantity of light reflected by the gemstone represents a mean value over nearly all possible illumination configurations and consequently provides a quantitative measure of the luminous efficiency or the brightness of the gemstone. The higher the fraction of the reflected or backscattered light, the higher is the light efficiency and the brightness and the better is the reflection behavior of the gemstone, which is accompanied by esthetic perceptions of higher value.
To measure the reflected or backscattered light serves a photo-current detector at a very large distance, relative to the dimensions of the gemstone, with a narrow measuring field.
Further advantageous embodiments of the invention are defined in the dependent claims.
In a preferred embodiment the pavilion angle is between 41.7° and 41.9°.
The pavilion angle is that angle formed, in a side view of the gemstone, between the lateral boundary line of the pavilion and the girdle plane, wherein this boundary line is obtained by orthogonal projection of a pavilion facet onto a plane including the longitudinal axis of the gemstone.
Although the gemstone according to the invention can be produced of any desired natural or synthetic precious or semiprecious stone, a gemstone of glass or synthetic material with the brilliant cut according to the invention is also feasible.
It was herein unexpectedly found that an especially high luminous efficiency is realizable at a crown angle between 32.8° and 33° and/or at a pavilion angle between 41.7° and 41.9° if the gemstone is comprised at least to a large extent, preferably entirely, of cubic zirconia.
The pavilion, also known as bottom part, has at least 24 pavilion facets, which come together at the end opposite the table in the form of a point or a culet. In one embodiment eight pavilion facets have a point located in the direction toward the girdle, while 16 pavilion facets have a broadside bordering on the girdle. The end located opposite the broadside of these pavilion facets forms a point and is directed away from the girdle. The orthogonal projection of the last-cited pavilion facets yields the pavilion angle.
In one embodiment of the invention the angle between the girdle plane and those pavilion facets that have a point bordering on the girdle or located in the direction toward the girdle, is between 41.7° and 41.9°. Additionally or alternatively, it can be provided that the angle between the girdle plane and those pavilion facets that have a broadside bordering on the girdle is between 42.8° and 43.0°.
The crown of the gemstone, also known as the top part, includes a table which is bordered by eight crown facets with one broadside each. In one embodiment of the invention these crown facets form with the girdle plane an angle between 20.2° and 20.4°.
The crown includes furthermore sixteen crown facets which have a point bordering on the girdle. In one embodiment of the invention these crown facets form with the girdle plane an angle between 39.3° and 39.5°.
The crown includes furthermore eight additional crown facets, each of which borders with a broadside on the girdle. In one embodiment of the invention the angle between these crown facets and the girdle plane is between 32.8° and 33.0°. The orthogonal projection of the last cited crown facets forms the crown angle.
Further details and advantages of the present invention will be explained in further detail in conjunction with the description of the figures with reference to the drawing. Therein depict:
a to 1c a side view, a top view as well as a view from below onto a gemstone according to the invention,
a and 3b a comparison of a gemstone of prior art with a gemstone according to the invention using a schematic depiction of paths of rays,
a shows a gemstone 1 according to the invention in a side view. Evident is the girdle 4, which separates the crown 2, also referred to as the top part, from the pavilion 3, also referred to as the bottom part. The girdle 4 is the region of the greatest cross-sectional dimension of the gemstone 1. Schematically shown is furthermore the axis of symmetry of the gemstone in the longitudinal direction which corresponds to the longitudinal axis of the gemstone.
The pavilion 3 has two types of pavilion facets 8, 9. Herein sixteen pavilion facets 9 include a broadside with which these facets border on the girdle 4. At the opposite end the pavilion facets 9 come together in the form of a point in the direction toward the culet 6. The remaining pavilion facets 8 include a point, each of which borders on the girdle 4.
The crown 2 comprises 32 facets 10, 11, 12 as well as a table 5 oriented parallel to the girdle plane 7.
Sixteen crown facets 12 border with one broadside on the girdle 4 and have a point directed in the direction of the table 5. Eight further crown facets 10 border with one broadside each on the table 5. The remaining eight crown facets 11 have each a total of four points, of which one point borders on the table 5, while another point borders on the girdle 4.
Evident is also the lateral boundary line 16 of crown 2, which is formed as the orthogonal projection of the crown facets 12, and the lateral boundary line 17 of the pavilion 3 formed as the orthogonal projection of the pavilion facets 9.
In one embodiment example of the invention the gemstone 1 is comprised of cubic zirconia and has a crown angle α between the lateral boundary line 16 and the girdle plane 7 of 32.9° and a pavilion angle β between the lateral boundary line 17 and the girdle plane 7 of 41.8°. The angle between the girdle plane 7 and the crown facets 12, which border with their broadside on the girdle 4, is 39.4°. The angle between the girdle plane 7 and those crown facets 10 which border with their broadside on the table 5, is 20.3°. The angle between the girdle plane 7 and the remaining crown facets 11 is 32.9°. The angle between the girdle plane 7 and the pavilion facets 9, which border with their broadside on the girdle 4, is 42.9°. The angle between the girdle plane 7 and the remaining pavilion facets 8 is 41.8°.
b depicts a top view onto the crown 2 of the gemstone 1. The schematically shown rectangular coordinates on table 5 make evident the symmetry of the gemstone 1.
c depicts a view from below onto the pavilion 3 of the gemstone 1. On the culet 6 formed by the pavilion facets 8 bordering on one another, is symbolically depicted a further rectangular coordinate system to illustrate the symmetry of the gemstone 1.
a shows a gemstone 1′ with brilliant cut according to prior art. The light rays 13 entering the gemstone are only partially reflected on pavilion 3′ due to the angles at which the different pavilion facets are cut, in particular due to the crown angle and to the pavilion angle. A fraction of the rays exits from the pavilion 3′ in the form of refracted rays 14. The ratio of the light rays 15 exiting from the crown 2′ to the light rays 13 entering into the crown 2′ defines the luminous efficiency.
b shows the same depiction but of a gemstone 1 according to the invention. The luminous efficiency is markedly improved due to the specific geometric configurations of the different facets and of the crown angle aα and of the pavilion angle β3, since the majority of the rays is totally internally reflected in the region of pavilion 3 such that nearly the entire fraction of light rays 13 entering the crown 2, after possibly multiple reflections, is reflected back to the viewer in the form of light rays 15 exiting from the crown 2.
The quantity of light reflected by the gemstone 1 represents a mean value over nearly all possible illumination configurations and consequently yields a quantitative measure of the luminous efficiency or the brightness of the gemstone 1. The reflections occur herein on distinct facets such that light is directly reflected back to the recess upon the first impingement onto the gemstone, however also after several internal reflections.
