From: Doug Miller Subject: Re: optics of diamond jewlry Date: Mon, 25 Sep 2000 18:38:08 GMT Newsgroups: sci.optics,sci.physics,alt.lasers,sci.math Tom, One starting point is an article entitled "Modeling the Appearance of the Round Brilliant Cut Diamond: An Analyisis of Brilliance", T. Scott Hemphill, Ilene M. Reinetz, Mary L. Johnson,and James E. Shigley, Gems & Gemology, Volume 34, Number 3, fall 1998, pages 158 - 183. This is an interesting article. The authors were gemologists with little understanding of ray tracing. They used a very brute force method to investigate the optical performance of diamonds in round brilliant cut. Although not very elegant, their results were quite interesting. There is an inexpensive DOS software package that would allow you to investigate the round brilliant cut. The package is called GemCad and is used by amateur gemcutters (called faceters) to develop gem designs. The software does not allow you to model refractive index as a function of wavelength, so dispersion has to be modeled with multiple independent analsyses. GemCad is available for downloading for free at several WEB sites including: http://www.gemcutter.com/pioneer.htm A manual for the software (definitely needed) can be obtained from the author of the software for a nominal fee. As for optical engineering information, the original Tolkowsky patent can probably be found at: http://www.patents.ibm.com/ However, the essential properties of the Tolkowsky design are also included in the above mentioned article. The crystal axes of diamond are irrelevant to the optical modeling. Diamond is cubic and therefore isotropic with no birefringence. The parameters for the Sellmeier equation for the room temperature index of refraction of diamond is given in table 22, section 33.62 (Optical and Physical Properties of Crystals and Glasses), in the Handbook of Optics, page 33.62. The parameters are: A = 1.0000 B = 4.3356 C = 0.1060 D = 0.3306 E = 0.1750 Any optical analyisis package with nonsequential surfaces that allows you to model a multi-faceted polygon should work. ZEMAX has this capability and I suspect that others do as well. I am however, not familiar enough with other packages to comment on them. Regards, Doug Miller Tom Hubin wrote: > Hello, > > I am looking for detailed info on the optics of diamond jewels. In > particular the "round brilliant" cut that is popular in rings. > > I know that the index is 2.38 and that there are 58 facets and some of > the facet shapes and orientations. I got the facet info at > www.bluenile.com, a diamond vendor. > > What I really need is optical engineering info. Enough data to do a > computer simulation. Including crystal axes. The description from the > mathematician Marcel Tolkowsky or the patent on this cut might be > helpful. I think the patent was early 1900s. > > Are there any ray tracing packages that will allow me to create and > trace into and through a flawless 58 facet "round brilliant" cut > diamond? Non sequential surfaces preferred. > > I am also looking for optical characteristics of fine, polished, and > bruted (rough) finishes on the diamond girdle. > > Tom Hubin > thubin@clark.net ============================================================================== From: Uncle Al Subject: Re: optics of diamond jewlry Date: Mon, 25 Sep 2000 17:08:59 GMT Newsgroups: sci.optics,sci.physics,alt.lasers,sci.math [quote of original message deleted --djr] Optical analysis of the best cut (maximum fire and brilliance) for white diamonds is remarkably difficult given the seemingly simple optically isotropic substrate. The first workable treatise was published in 1919 by mathematician Marcel Tolkowsky for the ideal cut round brilliant (first proposed in the mid-17th century by Vincent Peruzzi). Note that Tolkowsky's analysis results in the loss of about 60% of the stone's original weight. (Argyle's Leo Smans published the benchmark transformation of rough to cut for a magnificent purplish red octahedron. 7.48 carats rough became 3.16 carats cut, a loss of 57.8% in weight.) Almost all diamonds available to the general public are "swindle cut" to increase weight rentention. They are horribly overpiced crap. Fancy (colored) stones' cuts maximize color retention through the analysis of Gabi Tolkowsky (1986). Basil Watermeyer introduced the 1971 "Barion cut" for fancies in recangular shapes. The 1976 "Radiant cut" was introduced by Henry Grossbard. Also see the five-pointed "D1amond Stars" developed and patented by the Fancoldi Registered Trust (1992). http://www.google.com/ "Marcel Tolkowsky" 167 hits "Gabi Tolkowsky" 61 hits "Basil Watermeyer" 26 hits "Henry Grossbard" 7 hits -- Uncle Al http://www.mazepath.com/uncleal/ http://www.ultra.net.au/~wisby/uncleal/ (Toxic URLs! Unsafe for children and most mammals) "Quis custodiet ipsos custodes?" The Net! ============================================================================== From: Uncle Al Subject: Re: Marcel Tolkowsky, diamond math, 1919 Date: Mon, 25 Sep 2000 18:19:55 GMT Newsgroups: sci.optics,sci.math,sci.physics,alt.lasers Summary: [missing] Tom Hubin wrote: > > Hello, > > I have read that in 1919 the mathematician Marcel Tolkowsky designed the > 58 facet "round brilliant" diamond cut popular in jewelry today. > Possibly patented it somewhere. > > I would like to read whatever he wrote about this. In English if > possible, any technical publications, patents, notes, whatever. On the > web would be convenient. > > Some biographical info would also be of interest. Christ. http://www.gemology.ru/cut/english/tolkow/tolk1.htm http://www.niceice.com/tolkowsky.htm Learn how to use a search engine. "Gems and Gemology" Visit a library, read through a few years' back issues. Tolkowsky's analysis is incomplete given real world observation. -- Uncle Al http://www.mazepath.com/uncleal/ http://www.ultra.net.au/~wisby/uncleal/ (Toxic URLs! Unsafe for children and most mammals) "Quis custodiet ipsos custodes?" The Net! ============================================================================== From: bph@primenet.com (Blair P. Houghton) Subject: Re: Marcel Tolkowsky, diamond math, 1919 Date: 26 Sep 2000 07:26:47 GMT Newsgroups: sci.optics,sci.math,sci.physics,alt.lasers Uncle Al wrote: [quote of previous message deleted --djr] Off the top of my head: www.gia.org. --Blair "I wonder if they have an email address, too..." ==============================================================================