(19) Japan Patent Office
`(12) Unexamined Patent Application Publication (A)
`(11) Unexamined Patent Application Publication No.
` S57-199944
`(43) Publication Date: December 8, 1982
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`ID Code:
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`Internal File No.:
`6539-2G
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`(51) Intl. Classification3:
` G 01 N 21/87
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`Number of Inventions: 1 Examination Requested: No (5 Pages Total)
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`(54) METHOD FOR GRADING CUT OF
`(72) Inventor: Akira KOJIMA
`DIAMOND
`
`4-47-3 Kugayama, Suminami-ku,
`
`Tokyo
`(21) Patent Application No. S56-84738
`(71) Applicant: Akira KOJIMA
`(22) Filing Date: June 2, 1981
`
`4-47-3 Kugayama, Suminami-ku,
`Tokyo
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`which the dimension ratio of each portion is not
`ideal, as illustrated in FIGS. 2 and 3, light passes
`through the bottom, and the brilliance of the
`diamond as a gemstone is diminished. In other
`words, the objective of the brilliant cut is that all
`light pouring down from above is returned upward
`to maximize brilliance as a gemstone.
`At present, the method generally used to grade a
`cut is as follows.
`Using precision measurement devices such as a
`gemstone microscope and gemstone scale, each
`portion (girdle diameter, table dimensions, total
`height, crown height, girdle thickness, pavilion
`depth, angle between girdle plane and upper main
`facet, angle between girdle plane and lower main
`facet, and size regularity of facets, girdle, and culet)
`of the diamond is measured, and the cut is judged
`and graded based on the magnitude of the
`differences between those dimension ratios and the
`ideal dimension ratios. Finally, if the weight of the
`diamond subject to grading is taken as a carats and
`the weight of the largest ideally cut diamond (4)
`that could be created by recutting it is taken as b
`carats, the portion of a minus b carats indicated by
`hash marks in FIG. 4 is the excess portion, and
`therefore a deduction is made for this portion and
`the grade of the cut is b carats. The cut is graded by
`conversion to a weight grade.
`This weight deduction method does not associate
`the degree of brilliance and the quality of the cut of
`a diamond as a gemstone, and does not result in a
`
`Specification
`1. Title of Invention
`Method for grading cut of diamond
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`2. Claims
`A method for grading a cut of a diamond wherein
`a simulation is performed, said simulation
`consisting of making simulated light beams incident
`on an upper portion from a girdle of a cross-
`sectional shape of a diamond, and after the
`simulated light beams are refracted by an inner
`portion of the diamond, simulating from which
`portion of the diamond the simulated light beams
`exit, and the cut of the diamond is graded from the
`results thereof.
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`3. Detailed Description of the Invention
`The value of a diamond as a gemstone is
`determined by the so-called “four Cs” of carat (unit
`of weight), color, clarity (grade that expresses the
`presence of inclusions), and cut (dimension ratio of
`each portion).
`Among these, carat, color, and clarity are definite
`grading criteria, but cut is not determined in such a
`rational manner.
`At present, the most common diamond shape is a
`brilliant cut, and the present invention relates to a
`method for grading it.
`The characteristic of an ideal brilliant cut diamond
`is that light pouring down from above is reflected
`by the interior of the diamond and returned upward,
`as illustrated in FIG. 1. Conversely, in a diamond in
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`GIA EXHIBIT 1002
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`grade that is based on the original objective of the
`brilliant cut.
`In consideration of the objective of the brilliant
`cut, the present invention is a method for grading
`the quality of a cut based on the degree of brilliance
`of a diamond. The following two methods are
`considered as such a method.
`Method 1: Light beams are made to enter the
`diamond, and the degree of brilliance is measured
`by actually measuring the paths of those light beams.
`Method 2: The cross-sectional shape of the
`diamond is measured, and using the law of
`refraction when light beams are incident on the
`diamond and the law of reflection inside the
`diamond, how the incident light beams advance is
`theoretically simulated.
`Method 1 is difficult to implement in the
`following respects.
`FIG. 5 illustrates the case where a diamond
`subject to grading (3) is set on a pedestal (5), and
`light beams from above ((6)-e, (6)-f, (6)-g, (6)-h,
`(6)-i) are made to enter it, and after refraction and
`reflection on the interior, whether or not the light
`beams return upward from the girdle (7) is
`measured by means of a hemisphere (8) in which
`photoelectric elements are placed on the entire inner
`surface.
`(a) Because diamonds are generally small, they
`are difficult to set precisely on a pedestal.
`(b) Contamination on the surface of the diamond
`affects measurement.
`(c) Inclusions characteristic of the diamond may
`block light beams.
`(d) Precision equipment is required to accurately
`measure light beams exiting the diamond.
`Therefore, the present invention achieves its
`objective via method 2.
`One method for measuring the cross-sectional
`shape of a diamond is to overlay an X-Y coordinate
`scale on the screen of a proportion scope
`(equipment that magnifies and projects a diamond
`on a screen), and determine the coordinates of five
`points 1, m, n, o, and p. As illustrated in FIG. 6, by
`adjusting the zoom lens of the proportion scope, m
`is measured at the origin (0, 0) of the X-Y
`coordinate system, and o is measured so as to lay
`over the point (N+1, 0) on the X axis. The X axis
`lays over the girdle of the diamond. Furthermore, l,
`n, and p are taken as points (X1, Y1), (Xn, Yn), and
`(Xp, Yp), respectively. Here, m and o are given the
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`conditions described above for ease of explanation,
`but in actual measurement, simulation can be
`performed by measuring in any quadrant.
`When the line segment mo is divided into N equal
`parts and simulated light beams L1, L2, … Lq, …,
`LN are set above the diamond perpendicular to line
`segment mo (parallel to the Y axis) so as to pass
`through each of the equally-spaced points, the
`equation of Lq is represented by x = q (the range is
`up to the point of incidence on the diamond). Lq
`advances downward and intersects any of line
`segments lm, op, and pl, where it is refracted and
`enters the interior of the diamond. The equation of
`the path after refraction can be determined by (e),
`(f), and (g) below.
`(e) Equation x = q of simulated light beam up to
`before incidence
`(f) Coordinates of l, m, n, o, p
`(g) Snell’s law, which expresses the relationship
`between the angle of incidence r and the angle of
`refraction s
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`sin r/sin s = index of refraction (≈ 2.42)
`The simulated light beam after incidence
`intersects with any of line segments lm, mn, no, op,
`and pl, but if the angle of intersection is greater than
`a critical angle (≈ 24°26'), it results in total
`reflection (angle of incidence = angle of reflection).
`The equation for the path after total reflection can
`be determined by (h), (i), and (j) below.
`(h) Equation of path of simulated light beam
`immediately before total reflection
`(i) Coordinates of l, m, n, o, p
`(j) Rule that angle of incidence = angle of
`reflection
`If the totally reflected simulated light beam is also
`totally reflected inside the diamond, the equation of
`its light path can be determined by the above (h), (i),
`and (j).
`On the other hand, if the angle of intersection is
`smaller than the critical angle, the simulated light
`beam exits to outside the diamond. The equation of
`the light path after exiting can be determined from
`(k), (l), and (m) below.
`(k) Equation of path of simulated light beam
`immediately before exiting
`(l) Coordinates of l, m, n, o, p
`(m) Snell’s law (item (g) above)
`In the method described above, the simulated light
`beam x = q is theoretically calculated from when it
`advances into the interior of the diamond until it
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`exits to the outside. If the line segment that it
`intersects with when it exits to the outside is any of
`lm, op, or pl, this simulated light beam returns
`upward and thus results in brilliance. Conversely, if
`it exits to the outside from mn or no, it passes
`through downward, and therefore does not result in
`brilliance.
`Simulation is performed for each of the simulated
`light beams L1, …, LN, and if N' rays among the N
`simulated light beams result in brilliance, N'/N is
`used as the grade of the cut. Considering the case
`where total reflection is repeated and the simulated
`light beams never exit to outside the diamond, the
`limit of the number of times of total reflection is set,
`and if that limit is exceeded, it is not deemed as
`brilliance.
`Since a diamond has rotational symmetry, a more
`rational result can be obtained if several cross-
`sections are measured and simulated and the
`respective results are judged comprehensively.
`Furthermore, to achieve better precision and to
`know which direction of light will result in the most
`efficient brilliance when setting a diamond for
`ornamentation, a method of simulation that adds
`one or several of the following items according to
`objective may be used.
`I. Regarding cross-sectional shape measurement
`(FIG. 7)
`A. Considering girdle thickness, measure m and o
`by separating into m-1, m-2, o-1, and o-2.
`B. Similarly, measure the culet as n-1 and n-2.
`In this case, if a simulated light beam exits to the
`outside from the girdle portion or the culet portion,
`it is not deemed as brilliance. Further, since the
`girdle portion is not normally polished, total
`reflection does not occur, and therefore, light beams
`that advance in it do not result in brilliance.
`II. Regarding setup of simulated light beams
`A. Light beams perpendicular to line segments lm,
`op, and pl are set up, and simulation is performed.
`(FIG. 8)
`B. Incidence points are set up by dividing the
`aforementioned three line segments at equal
`intervals. (FIG. 9)
`C. Simulation is performed using parallel light
`beams from a certain specified direction. (FIG. 10)
`D. Simulation is performed using light beams
`from all directions. (FIG. 11)
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`E. Light is made incident while restricting the
`incidence point to the portion of the table of line
`segment pl. (FIG. 12)
`III. Regarding judgment of brilliance
`A. Among the light beams that exited from any of
`the line segments lm, op, or pl, only those light
`beams having certain directions after exiting are
`considered brilliance. For example, when a light
`beam exits to the outside from the line segment op,
`if the slope of the equation calculated by the
`aforementioned (k), (l), and (m) is negative, the
`light beam is directed downward, and therefore is
`not considered brilliance. (FIG. 13)
`B. Only light beams that exited from line segment
`lm, op, or pl are considered brilliance. (FIG. 14)
`Grades such as proportion (normally expressed by
`the five points l, m, n, o, p while ignoring girdle
`thickness and the culet portion) and symmetry are
`gleaned from the above judgments, but for grading
`of the cut, there are cases where various exterior
`features such as exterior damage are also included.
`In such cases, they should be added into the results
`obtained by the grading method of the present
`invention.
`Furthermore, since it takes time to perform the
`aforementioned calculations in this procedure, it can
`be implemented easily if a computer is used or a
`special calculator programmed with the
`aforementioned logic is used.
`Additionally, since a brilliant cut is used for the
`purpose of ornamentation, it is appropriate to use
`the index of refraction of visible light beams in air,
`but brilliance using infrared rays in water, for
`example, may also be simulated.
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`4. Brief Description of the Drawings
`FIGS. 1, 2, and 3 are plan views illustrating the
`direction of advancement of light beams on the
`interior of a diamond.
`FIG. 4 is a plan view illustrating the excluded
`portion of the grading method that is generally
`performed at present.
`FIG. 5 is a plan view of an embodiment of a
`device for grading a cut using actual light beams.
`FIG. 6 is a plan view illustrating a diamond
`measured on an X-Y coordinate system.
`FIG. 7 is a plan view illustrating the cross-
`sectional shape of a diamond.
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`FIGS. 8, 9, 10, 11, and 12 are plan views
`illustrating embodiments of the setup of simulated
`light beams.
`FIG. 13 is a plan view of a diamond on an X-Y
`coordinate system, illustrating an embodiment of
`the exit direction of simulated light beams.
`FIG. 14 is a plan view of a diamond illustrating an
`embodiment of the exit range of simulated light
`beams.
`(1): Advancement direction of light inside ideally
`cut diamond. (2): Advancement direction inside a
`diamond that is not ideally cut. (3): Diamond
`subject to grading. (4): Largest ideally cut diamond
`that could be created by recutting. (5): Pedestal. (6):
`Light beam. (7): Girdle. (8): Hemisphere with
`photoelectric elements on entire inner surface. (9)
`Incident simulated light beams. (10): Simulated
`light beams exiting from diamond.
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`Patent Applicant: Akira KOJIMA
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`FIG. 3
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`FIG. 2
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`FIG. 1
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`FIG. 4
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`FIG. 5
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`FIG. 8
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`FIG. 6
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`FIG. 7
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`FIG. 9
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`FIG. 10
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`FIG. 11
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`FIG. 12
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`FIG. 14
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`FIG. 13
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`Park IP Translations
`
`
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`October 2nd, 2015
`
`Certification
`
`
`
`This is to certify that the attached translation is, to the best of my knowledge and
`belief, a true and accurate translation from Japanese
`into English of:
`JP57199944_A.
`
`
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`15 W. 37th Street 8th Floor
`New York, NY 10018
`212.581.8870
`ParkIP.com
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`Katie Shallow
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`Project Manager
`Project Number: PAHAS_1509_004
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`Page 8 of 8