Method and apparatus for analyzing gems

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METHOD AND APPARATUS FOR ANALYZING GEMS in 7i2N ητ’73Ν7 ipnm runty

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METHOD AND APPARATUS FOR ANALYZING GEMS 5

Teohnloal Field

The Invention relates generally to apparatus for analyzing gems and ia specifically directed to a digital gem analyzer 10 aapable of distinguishing between natural and synthetic gems as welli as quantitatively analyzing gems within a particular origin group*

Background ι of the Invention A variety of prooesses have been perfeoted which allow 15 the synthesis of crystalline specimens in the laboratory which, with reference to their mode of application or use, are for all practical purposes indistinguishable from their natural counterparts. It ia important to note that suoh synthetic and natural speoimens are members of the same species, and are aeoord- 20 ingly identical in their gross physloal, chemloal and structural properties. The term "synthetic" in the aontext of this invention therefore does not apply to speoimens that are simulants, look-alikes, faoslmlles or imitations.

Differentiation between gems of different speoles or 25 between a gem specimen and a look-alike is.readily done. For example, it is relatively easy to distinguish between an authentlo ruby gemstone and a similarly out and colored representative of the so-called garnet or spinel family. There are clear phyaioal and ohemical differences that produce maorosaoplo property dlf- 30 ferences that oan be measured by oommon laboratory techniques and instruments suoh as refraotometers (measurement of the refractive index), spectrometers, or density determinations and hardness measurements.

Strict Identification (distinguishing between epeoles) 35 Cf gemstones is accomplished relatively easy sinoe members of a species have rather identloal nonvarying ohemical composition and crystal structures. Sinoe ohemical composition and struoture determine the physloal properties, measurements of such gross phy sloal properties yield the means for Identification.

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However, differentiation of gemstones of the same species, which differ from each other in origin (i.e., natural from synthetlo) but not in gross physioal, chemical or structural characteristics, poses a significant problem of a higher order. 5 The finite differences that do exist are submloroscoplo in character and occur at a level where atomic and eleotronio pro** ? cesses find their origin. Only In rare oases will such minor differences readily express themselves externally.

The more closely a growth environment of synthetlo. 10 gemstones is related to that from whioh the natural speoimens originated, and the closer the prooess is controlled chemically, physlaally and thermodynamically, the more readily synthetlo specimens will be produoed whioh are virtually impossible' to differentiate from the best of their natural counterparts. For 15 example, the best synthetic rubies are for all practloal purposes indistinguishable from the best of natural rubies suoh as those from the Magok area of Burma or other fine speoimens from Ceylon or Thailand. « A quality gemstone should be sufficiently beautiful to 20 serve the purpose of personal adornment, and also should be durable to make its display lasting and enduring. This functionality of a gem is of oourse equally well served by a natural specimen as it is by a synthetlo representative of equal beauty. However, there are other charaoteristios that set the natural 25 specimen apart from the synthetlo in the area of rarety, precious ness, authenticity, specific origin, value as an Investment commodity and specific cost. In partloular, the last two categories make it imperative that instrumented means exist to distinguish between naturals and synthetlos. The best of natural stones may 30 fetoh prizes up to a thousand times that paid for synthetlo speoimens.

Synthetlo stones have found their way into the ohannels of trade of natural stones. Exaot duplicates of natural stones have been out from synthetic raw material and have taken the place 35 of previously certified natural materials. Similar exohanges occur with gems in mountings and settings. -3*

At.least four different growth processes—flame fusion, fluxed melt growth, hydrothermal techniques and solution growth— are capable of produolng gem quality ruby and sapphire stones, and several processes are also known to yield high-quality emeralds, 5 The number of manufacturers using these processes is Increasing,

Further, the value of colored stones as a trading and Investment commodity is growing by leaps and bounds.

With thousands of gems of this type being traded eaoh year, there is a olear need for Instrumentation to quickly and 10 efficiently differentiate between the products made by nature and by man.

Standard techniques and devices presently exist for distinguishing between natural and synthetic gemstones. Some of these techniques may be found in textbooks on the transmission of 15 electromagnetic energy, as well as soanning eleotromiorosoopy and light microscopy. These techniques make use of the known fact that synthetic gemstones approaoh perfection in atomic structure to a far greater extent than their natural counterparts. Several forms of radiation have also been used to direotly or indireotly 20 determine structural perfection of materials, lnoludlng gamma rays, X-rays ultraviolet radiation, electron beams and radiation in the visible part of the electromagnetlo energy spectrum. However, all of these approaches Involve highly specialized and expensive equipment that require highly specialized training, pose 25 availability problems, are limited by range of applicability and often require destruotive specimen preparation. In addition, there are often size, orientation and surface quality requirements of the specimen which cannot be readily met by the produot available in the trade. 30 There is to date no available apparatus which will, in one measurement, differentiate between natural and synthetic gemstones of the same speoies without regard to their size, shape, clarity, brilliance, morphology, color, out or degree of finish, and whioh will do so without recourse to reference books, addl- 35 tional or supplemental measurements, and relianoe on individual expertise and experience* -4-

Summary of the Invention

The analyzing apparatus according to the invention la based on the disoovery that the total intensity of radiation from a gem speoimen, as detected In a predetermined narrow spectrum, 5 resulting from Interaction of the gem speoimen with a source of electromagnetic energy over a very broad speotrum, will differ significantly between natural and synthetlo specimens of the same species. "Interaction’' in this regal'd contemplates the combined processes of transmission and absorption of eleotromagnetlo energy 10 through and by the gem specimen, the reflection (dlffraotlon) of energy Internally of the speoimen (which is to be distinguished from refleotanoe from a planar gem surfaoe), and the emission of eleotromagnetlo energy from the gem whlah results from internal excitation (e.g., fluoresoence). 15 The intensity differences are primarily the result of differences in structure and bonding at the atomic level, whlah relate to structural perfection and quality. The degree of transmission, absorption, internal reflection and emission of radiation can, as compared to that in a hypothetical perfeot 20 crystalline speoimen, be signifioantly reduced by a variety of oharacteristios directly related to the growth process, whether natural or synthetlo. All suoh characteristics constitute a departure from order or perfeotlon in the orystal and will directly or indireotly form barriers to the various electronic! 25 processes Involved in transmission, absorption, Internal reflec tion or emission of radiation.

Synthetlo gems have a much higher degree of struotural perfeotlon or atomio order, and X have found that the intensity of radiation resulting from the«full interaction of a broad speotrum 30 of eleotromagnetlo energy with gem specimens will be several orders of magnitude greater for synthetic gems than for their natural counterparts. It is this discovery that permits simple and accurate analysis by discrimination and quantifloatlon.

Analog signals representative of intensity of output 35 radiation from the gem specimen can be electronically processed to determine the origin of the speoimen as well as to provide a quantitative output by which the specimen may be compared with others even in the same origin group.

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In the inventive gem analyzing apparatus,;a source of electromagnetic radiation lnteraots with a specimen, and the integrated response of suoh interaction energizes an appropriate detector, the output signal of whioh Is processed through eleotro- 5 nlo olrouitry, characterizing the stone as falling into broad quantified categories and thus determining origin. Operation of the instrument is not based on the measurement of any one physloal property suoh as the value of the thermal oonductivity, the reflective index, its dispersion, hardness, eleotrloal 10 conductivity, or the like, but rather on the speoifio generation, interpretation, processing and display of an integrated signal resulting from the interaction Of the source of radiated energy and the sample.

The signal type (frequency and frequency distribution) 15 and signal strength will be determined by several factors In two categories;;viz., the lntrinslo atomic structural character and characteristics of the apparatus Itself.

The nature of the response due to its lntrinslo character will depend on many physical properties of the specimen 20 such as refleotive index, dispersion, optical character, absorp tion coefficient and such features as alarlty, inclusions, crystallinity and surface structure of the gem.

The parameters of the apparatus Include the nature of the souroe of radiation, Its Intensity, the size of the aperture 25 through which radiation is exposed to the gem specimen, detector characteristics and the like, all Of whioh oan in any one evaluation be kept fixed so as to provide a common base line. Since the total energy of interaction will be different from speoimen to specimen, and sinoe analysis is not dependent on the accurate 30 determination of any one physical property, operation of the instrument is greatly simplified. Few, if any, restrictions are put on the nature of the speoimen itself which otherwise would be required if measurement of a.singular physical property were needed. As such, the apparatus does not specifically require a 35 monochromatic source, special filtering, accurate foouslng or manipulation of the beam, placement of a sample in a prescribed • &lt; · · ' Τγ&lt;·«*&lt;Ι .ο -6- geometrlo arrangement, position or orientation, or the determination of nature and strength of the source of radiation. For these reasons, the inventive apparatus will accurately perform its analyzing function for speolmens that are large or email, odd or 5 regularly shaped or have varioue degrees of olarity or ranges of color, and operation is accomplished without the need for speolflo orientation, or cut or degree of finish of the specimen.

The analog signal may also be processed through an analog to digital converter to display a unitless, arbitrary number. 10 Thus the Inventive apparatus :not only ls oapable of distinguishing between natural and synthetlo gems, but also is oapable of accurately and quantitatively relating speolmens in a single origin group, enabling further differentiation in terms of other evaluation parameters such as brllllanoe, beauty, fire, quality or 15 speolflo value. These unique features permit unlimited applica tions in other areas suah as.quality oontrol, produot reproduction, gem aertifioatlon and "finger printing" of a particular gem.

The preferred embodiment is speolfloally directed to the 20 selective discrimination and quantification of ruby and emerald gemstones, and is capable of two selective modes of operation.

Because of similarities in molecular structure, a single souroe of radiation may be used for both gens, while different reference values as determined by the eleotronlo olrouitry are 25 selectively used based on the desired mode of operation. In the preferred embodiment, the source of radiation Is a quartz envelope meroury dlsoharge lamp whioh emits radiation in a broad speotrum of electromagnetic energy, the wavelength of whioh ranges at the low end from approximately 1800 Angstroms in the:far-ultraviolet 30 region through the visible region and into the near-infrared region. This partloular lamp peaks at several individual wavelengths, the principal of which ia 2550 Angstroms. Both natural and synthetic rubies undergo internal excitation (fluorescence), whioh produoes a frequenoy shift and results in 35 the emission of electromagnetic energy at approximately 6500

Angstroms. The deteotor used in connection with this -7- partloular lamp is a photocell (photooonductive 01* photoresistant cell) that senses electromagnetic energy in the narrow region around 6500 Angstroms.

The Inventive apparatus does not require the use of arty 5 filters to isolate specific frequencies from the discharge spectrum of the radiation souroe. The presence of well-defined spectral intensities at frequencies aoross the emission speotrum enhances the process of discrimination according to the Invention since differences in attenuation and specific frequencies add 10 cumulatively to the level of the integrated signal. Stated otherwise, the photocell deteotor measures the cumulative effect produced by transmission, internal refleotanoe and Internal excitation in the narrow range of 6500 Angstroms, the result of whioh is an analog signal whioh is directly proportional to the inten- .15 sity of electromagnetic energy to whioh the photooell is exposed.

It is to be emphasized that the desired gem analysis could for any one species be accomplished by different sets of souroe-detector combinations. The eleotromagnetic energy source may, for example, generate accelerated electrons or other 20 particles, X-rays, ultraviolet radiation, visible and Infrared (heat) rays and radiation spanning the electromagnetic speotrum frcm the energy of gamma rays to that of the microwave region.

The specific choioe of a radiation source-detector pair will of course depend on the nature and extent of the differences in the 25 basio characteristics intrinsic to eaoh specimen for whioh discri mination is desired. A Judicious choioe will be influenced by other considerations euch as cost, geometry, safety and other operational parameters. Since the prinolple on whioh the invention is based does not require that a specimen be specifically 30 prepared, oriented, finished or have other geometrlo characteristics, there is no preference for any one souroe having a particular wavelength characteristic.

Preferably, optical filters are used between the gem and deteotor to mask the radiation from the gem except in the narrow 35 detector wavelength range.

Also in the preferred embodiment, the gem specimen is supported on a holder that is fully opaque to the entire spectrum ♦uh -8- of source emission with the exception of an aperture which is sized to effectively limit energy throughput to an area equal to or smaller than the specimen in a direction perpendicular to the plane of the aperture. This is an Important relationship to 5 Insure that whatever energy is detected by the photocell is emitted from the gem.

As suggested above, the detector is ohosen so that its detectability and sensitivity are highest in the frequency range of radiation resulting from the souroe-speoimen interaction as 10 modified by the filters. In the preferred embodiment,: this is a photoconductive (photoreslstant) device or photocell that generates an analog signal directly proportional to the Intensity of detected energy. Other detectors, such as phototransistors (photodiodes), scintillation counters, Faraday cups and photo- 15 multipliers may be used with other radiation sources or other gem specimens.

Because the radiation from a mercury discharge lamp is potentially dangerous to human eyes and skin, it is.neoessary for the inventive apparatus to be optically sealed during all phases 20 of operation to preolude radiation leakage. In the preferred . embodiment, this Is uniquely accomplished by disposing a slidable speaimen drawer between the mercury discharge lamp and the photocell deteotor, and providing a mechanical shutter meohanlsm between the drawer and lamp and between the drawer and photocell. 25 The shutter mechanism is actuated only when the drawer Is fully closed and latohed, at whioh time registration of the several apertures included in the shutter meohanlsm are disposed In registration.

This provision for optical sealing also permits the mer- 30 cury discharge lamp to operate continuously during the analysis of a number of specimens. This is advantageous sinoe the meroury disoharge lamps, and other appropriate disoharge souroes, require a signifioant period of wannup before stabilized operation occurs, and turning it off after each analysis would slow the analysis of 35 a number of speoimens considerably. In addition, repeated on-off operation reduces the life of the disoharge lamp. A gem analyzing apparatus made in accordance with the invention is easily operated by persons without specific

I 10 15 20 30 -9- knowledge, experience or expertise. The user niay quickly and accurately utilize the apparatus to distinguish natural specimens from synthetic specimens for a particular species, to quantify a plurality of gem specimens with any particular origin group, to "fingerprint” a gem of a particular species, and to deteot whether a particular specimen Is or is not within a particular species.

It is also possible to substitute other radiation sources for the mercury discharge lamp of the preferred embodiment to provide all of the foregoing functions for gems other than rubles and emeralds.

Brief Description of the Drawings Figure 1 Is a view in side elevation of the inventive gem discriminating apparatus;

Figure 2 Is a view In top plan' of the gem discriminating apparatus;

Figure 3 is a view In rear elevation of the inventive apparatus;

Figure M is a view in front elevation of the inventive apparatus;

Figure 5 is a seotional view of the apparatus taken along the line 5-5 of Figure 2; 25

Figure 6 is a seotional view taken along the line 6-6 of Figure 5} Figure 7 Is a sectional view taken along the i l ine 7-7 of Figure 5; Figure 8 Is a seotional view taken along the:line 8-8 of

Figure 5 J

Figure 9 is an enlarged fragmentary seotional view similar to portions of Figure 5;

Figure 10 is an enlarged fragmentary perspective view of a holder for the gem speoimen to be analyzed and the support from which it may be moved;

Figure 11 Is a blook diagram of the eleotrloal and eleotronlo signal processing aspects of the apparatus;

Figure 12 is a sohematic diagram of the power supply for the eleotrloal and electronic circuitry of the apparatus; 35 -10-

Figure 13 Is a schematic diagram of the electrical and electronic circuitry relating to the electromagnetic, discharge aouroe;

Figure 14 is a schematic diagram of a portion of the 5 electronic cirouitry including the photocell deteotor, an analog output, an analog to digital converter and a display;

Figure 15 is a schematic diagram of the electrical and electronic comparator circuitry that quantifies the analog output from the photocell and generates appropriate signals; 10 Figure 16 is a schematic diagram of loglo components that receive and process signals from the comparator alroultry and operate the. display;

Figure 17 Is a graphic representation of the display or readout;: and 15 Figures 18A-18F are individual representations of the control and display panel of the apparatus showing various output displays.

Detailed Description of the Invention ,

With initial referenoe to Figures 1-4, a digital gem 20 analyzer is represented generally by the numeral 11. In the pre ferred embodiment, the gem analyzer 11 comprises a cabinet 12 formed from metal stamping and having a top 13» bottom 14, left and right sides 15, 16, respectively, a front 17 and back 18. A single plate member defines the top 13, and front 17, the top 25 defining an upper horizontal seotlon 13a, an intermediate, inclined display seotlon 13b and a lower horizontal section I3o.

The front 17 is formed with a rootangular opening 17a (Figure 4) to accommodate a drawer 19 (shown in phantom in Figures 1 and 2), ln which a gem speoimen is placed for analyzing. As 30 will become apparent below, the inside 6f the cabinet 12 is opti cally sealed with the drawer 19 in both open and olosed positions, with analysis taking plaoe with the drawer closed.

As shown in Figure 5, a single plate member formsιthe sides 15, 16, the bottom 14 and back 18, and this member:receives 35 and supports tabs at each end of the plate member defining the top 13 and front 17 through the use of screws 20*

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With referenoe to Figures 5 and 6, a large reotangular opening 14a ie formed in the bottom 14 toward the front of oabinet 12 to serve as an access opening to a souroe of eleotromagnetio radiation. In the preferred embodiment, the souroe is an 5 unfiltered quartz meroury discharge tube lamp 21 that generates radiation over a broad spectrum of eleotromagnetio energy, the wavelength of whloh ranges from approximately 1800 Angstroms in the far-ultraviolet region at the low end through the visible region and into the near-infrared region* Discharge tube lamp 21 10 is replaceably mounted in a manner described in detail below,

Reotangular opening 14a is normally closed by a slightly larger oover plate 22 that is secured to the bottom 14 by screws 23. A pair of mounting studs 24 are secured to the oover plate . 22, projecting internally to carry a parabolio reflector 25 for 15 the lamp 21. Lamp holders 26 are suitably mounted to eaoh end of the reflector 25 to support the lamp 21 thereabove in a position in which radiated energy will be openly reflected in an upward direction.

Voltage is applied to the lamp 21 throughia ballast 20 transformer 27 that is mounted in spaoed relation along the inner top surface of back 18 by braokets 28 (Figures 5 and 6). The eleetrioal circuitry oonneoting the power supply, lamp 21 and ballast transformer 27 is shown in detail in Figures 12 and 13.

The conductors have been deleted from the structural figures for 25 purposes of.clarity. However, the eleetrioal oirouitry also includes a microswitch 28 (Figures 5 and 6) that is secured to an elongated, L-shaped bracket 29 mounted to the top surfaoe of bottom 14 and extending over a substantial portion of its width. The microswitch 28 is disposed in overlying, engageable relation to 30 one of the mounting screws 23 (reference numeral 23a) for the cover plate 22. The microswitch 28 is normally biased to an electrloally open position, and urged dosed by the sorew 23a, so that withdrawal of the mounting screw 23a for. purposes' of removing the cover plate 22 causes an open condition in the power supply to 35 lamp 21.

As constructed, removal of the oover plate 22 Interrupts power to the lamp 21, the radiation from whloh ia potentially

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-12- dangerous to human eyesight and skin. Because the reflector 25 and lamp holders 26 are mounted to the cover plate 22, its removal also permits easy replacement of the source lamp 21 in. case of failure or when a different type of souroe emission Is required. 5 Rubber feet 31 (Figures 1, 3 and 5) are.seoured to the undersurfaoe of bottom 14 at eaoh corner.

As best shown in Figure 6, the elongated mounting bracket 29 is also used to support a pair of gronmets 32 for guidably retaining internal electrical conductors, a circuit fuse 10 33 and a switch 34 that diverts the applied circuit voltage bet ween 110 volts and 220 volts, depending on the available souroe. The fuse 33 and swltoh 34 are discussed below in connection with the eleotrlcal circuit diagram of Figure 12.

With continued reference to Figures 5 and 6, a pair of 15 transformers 35, 36 are mounted internally of the aablnet 12 on the bottom 14 generally below the ballast 27· The transformer 35 serves to reduce a standard supply of 110 volts to a 12 volt supply to the oontrol circuitry. The transformer 36.1s used in conjunction with the swltoh 34 to provide a supply of 110 volts to 20 the apparatus where the input voltage is 220 volts. The transfor mers 35, 36 are operationally described in conjunction with Figure 12. A plurality of vent holes 37 are formed in the baok 18 rearwardly of the ballast transformer 27, as shown in Figure 3. 25 Two sets of vent holes 38 are formed in the bottom 14 behind the transformers 35» 36, as shown in Figures 5 and 6. The vent holes 37, 3θ are positioned so that they are masked by Internal components to prevent the leakage of radiation, while at the same time permitting ventilation of heat generating Internal 30 components.

With reference to Figure 6, a pair Of internal side support walls 41, 42 are mounted in spaced relation to the respeotlve side walla 15, 16. These support walls are mirror images and a description of the walls 41 will be exemplary of both.: Wall 41 35 Includes a pair of angled tab feet 41a, 41b that are secured to the upper surfaoe of bottom 14 to hold the wall in its1 rigid upstanding position. The front edge of the wall 41 is'bent outwardly to define a spaoer flange 41c.

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The support walls 41, 42 together serve as the foundation for a number of internal frame members and supports. These Include a pair of elongated brackets 43, 44 that extend crosswise of the walls 41, 42 and are disposed below the lnollned sections 5 13b of top 13. Each of the brackets 43, 44 lnoludes a flat sec tion (Figure 5) that extends over a substantial portion of the distance between the support walls, and whioh is disposed in parallel relation to the lnollned seotion 13b. These two seotions, whioh bear the reference numerals 43a, 44a, are coplanar 10 and together offer support to a printed elrcultboard 45 that carries a portion of the eleotronlo oontrol circuitry,iincluding a liquid crystal display 46, The display 46 is viewed through a reotangular opening 13d formed in the inclined section!13b.

With reference to Figure 7, also secured to and 15 extending between the support walls 41, 42 are a pair Of horizon tal support plates 47, 48 that are mounted immediately:above and below the drawer 19, respectively. As best seen in Figure 7, a pair of ball bearing drawer guides 49, 50 are secured to the support walls 41, 42 between the support plates 47, 48, extending 20 rearwardly along eaoh side. The drawer 19 is seoured to the movable portion of each guide 49, 50, permitting it to move freely between open and olosed positions. As shown in Figure 5, a rubberized drawer stop 51 is disposed at the extreme inner end of the guide 50 to cushion the drawer 19 as it reaches the closed 25 position. Guide 49 lnoludes a similar stop which is not shown.

With reference to Figures 5, 7 and 9, drawer 19 is also formed from thin metal plate, and comprises a front 52, back 53, lefthand side 54 (Figure 7 only) and righthand side 55. The bottom is oompound, including upper, middle and lower bottom plates 30 56-58, respectively. For constructional purposes, the middle bot tom plate 57 Is integrally formed with the drawer back.53* and the lower plate 58 is integrally formed with the drawer front 52. All three of the bottom plates 56-58 are reotangular In shape, but plate 58 also lnoludes a rearwardly projecting tongue 59 (see also 1 35 Figure 8).

Centrally disposed, coaxial apertures of different size are formed in eaoh of the plates 56-58. The uppermost aperture, which bears the referenoe numeral 56a, is of intermediate size and

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-14- loosely receives a specimen holder 61 having an axially extending aperture 61a formed therethrough (see also Figure 10). The middle plate 57 hae an aperture 57a into which a disc 62 is placed. The diso 62 is made from material that la fully transparent to the 5 entire frequency range of the radiation source 21 to insure that the gem speolmen is fully exposed to the entire range. For mercury discharge ultraviolet sources, the diso 62 is made from high transparency quartz. The function of disc 62 is to prevent the accidental dropping of a gem specimen or other artiole into the 10 internal portions of the cabinet 12 when the specimen holder 61 is removed, as well as to reduce the entry of dust and other particulate matter into the cabinet 12.

The lower plate 58 is formed with the smallest aperture 58a. 15 With continued referenoe to Figure 9, the lower plate 48 is also formed with an aperture 48a that is disposed immediately above the ultraviolet lamp 21. Further, and as additionally shown in Figure 5, the drawer is constructed and disposed so;that the apertures 58a, disc 62, speoimen holder 61 and aperture 6la 20 direotly overlie the aperture 48a when the drawer 19 is in the closed and latohed position. As suoh, radiation from the lamp 21 is exposed directly to a gem resting on the specimen holder 61. However, for all other positions of the drawer 19, either the tongue 59 or the main portion of the plate 58 directly;overlies 25 the lamp 21, precluding exposure of radiation to the gem speoimen.

With referenoe to Figures 4 and 9, drawer 19 includes a drawer front 63 which takes the general form of a rectangular, forwardly facing open box and houses a latch assembly 64. This latoh assembly comprises a vertically movable handle 65 to which a 30 vertically projecting latch element 66 (Figure 9 only) is oonneoted. As best shown in Figure 4, the handle 65 comprises a symmetrically formed metal strip generally taking the form of a W, and Includes two valleys or recesses permitting the user to depress the handle 65 with two fingers. 35 The latch element 66 is slidably retained within a bushing or guide 67, which also houses a coil spring (not shown) that normally urges the latch, element 66 and handle 65 into the position shown in Figure 9. Downward movement of the handle.65, -15- as shown In Figure 4, οausea the latoh element to withdraw Into the guide 67 In a position that Is flush with the top surface of the drawer front 63.

As shown In Figure 9, the upper support plate 47 has an 5 aperture 47a centrally disposed along Its front edge for registra tion with the latoh element 66. Both the latoh element 66 and aperture 47a are circular In configuration, and the outer cylindrical surface of latch element 66 is vertically disposed. Consequently, the drawer 19 oan only be completely closed by' 10 depressing the handle 65 and pushing it to the fully olosed position., Release of the handle 65 at this time will enable the latoh element 66 to project into the aperture 47a to look the drawer 19 in the closed position. This position la shown in Figure 5. 15 With oontlnued reference to Figure 9, the upper support

plate 47 has a second olroular aperture 47b which Is centrally disposed in ooaxlal relationship with the aperture 48a. Mounted immediately above the aperture 47b are two optical filters 68, 69 and a photoeel?, 71, all of whioh are disposed in a position M 20 receive radiated energy from the lamp 21 with the drawer 19 in olosed position.

With reference to Figures 8 and 9, a rectangular metal plate 72 is slidably mounted on the undersurfaoe of upper support plate 47, extending longitudinally rearward from a point Just 25 behind the aperture 47a. Plate 72 is oapable of limited longitudinal sliding movement by reason of its mounting, whioh includes three nut and bolt assemblies 73 projecting through three elongated slots 74-76 formed in the upper support plate 47. A small transverse strap 77 extends between the assemblies 73 aaso- 30 dated with slots 75, 76 and inoludes a rearwardly projecting finger 77a. A coil spring 78 is mounted in compression between the finger 77a and a forwardly projecting screw 79 that is mounted in an upstanding flange 47o formed on the rear edge of the upper support plate 47. As aonstruoted, the ooll spring 78 urges the 35 strap 77 and rectangular plate 72 forward into the position shown in Figure 9 when the drawer 19 is open.

Rectangular plate 72 also includes a olroular aperture 72a capable of registering with the aperture 47b when the drawer &gt; -, .·4χ·ι4·./ ,/-&gt;· -16- 19 la closed (Figure 5). This rearward sliding movement of the plate 72 against the bias of spring 78 occurs when the drawer front 52 strikes the front edge of the plate 72 when the drawer 19 is being closed. A shallow rectangular recess or slot 53a (Figure 5 9) is formed in the upper central edge of the drawer back 53 to prevent engagement by the baok 53 with the plate 72 as: the drawer 19 is being dosed.

The aperture 72a is positioned within the plate 72 so that registration with the aperture 47b is accomplished when the 10 drawer 19 reaches, its fully dosed position. As discussed above, registration is simultaneously accomplished with the lower group of apertures 48a, 58a, the quartz diso 62 andaperture 61a. This aperture registration system whioh acts as a mechanical shutter, is designed to optioally seal the cabinet 12 during all phases of 15 operation of the apparatus, and regardless of the position of the drawer 19. This not only constitutes a safety feature, eliminating the possibility of leakage of potentially harmful radiation, but also permits the mereury discharge lamp 21 to operate continuously. Lamps of this type generally do not reach a 20 level of, stable operation for several minutes, and it is highly inefficient if the lamp must be turned off after analysis of eaoh gem speolmen.

Optical sealing of the oabinet is also enhanced by the use of sealing tape strips 81 that are disposed between the front 25 17 and eaoh of the front edges of the support plates 47, 48 (Figure 9) between the front 17 and eaoh of the sides.15, 16 (Figures 1 and 6) and between the top 13 and the upper edge of eaoh of the sides 15, 16 (Figure 1).

With reference to Figures 8 and 9, a seoond: printed 30 elroult board 82 is mounted in spaoed relation between the top 13 and upper support plate 47 by three spaoers 83 that surround the aperture 47b, filters 68, 69 and photocell 71. The photocell 71 is mounted on the bottom side of printed olrouit board 82, and the filters 68, 69 are friotlonally held againet the upper surface of 35 support plate 47. A multiple connector strip 45a establishes the appropriate eleotrioal connections between the rear edge of printed circuit board 82 and the leading edge of printed olrouit board 45. •Λ»··?» : : t ο -17-

The inclined or readout seotlon 13b of the top 13 also serves as a mount for a pair of rocker switohes 84, 85,' the former of whioh serves to turn the apparatus on and off, ahd the latter of which permits mode selection as desoribed in further detail 5 below. Also mounted within the display aeotion 13b are a'calibra tion potentiometer 86 and a light emitting diode 87 indicating "aouroe on".

The calibration potentiometer 86 is used in conjunction with a calibration gem specimen 88 (Figure 5), which is per- 10 manently secured to a calibration specimen holder 89 disposed in a dosed box 90 having a hinged top 91. The box 90 is removably disposed in one corner of the drawer 19. The oalibhation operation ia desoribed more fully below.

Figures 11-16 disolose the eleotronio circuitry for ana- 15 lyzer 11. Figure 11 is a block-diagram disclosing the meroury discharge lamp 21, a gem specimen G, red and blue glass optloal filters 68, 69, respectively and the photocell deteotor 71. Lamp 21 radiatesιa broad speotrum of electromagnetic energy as shown at El. E2 represents the electromagnetic radiation from the gem spe- 20 oimen G, whioh is a function of the total interaction of the gem specimen G with the energy El. This takes into aooount the electromagnetic energy transmitted through and absorbed by the gem G, the Internal reflection of energy within the gem G and the electromagnetic energy emitted from the gem G by flouresoenoe 25 and/or other internal excitation.

The electromagnetic energy E2 passes through the filters 68, 69, and electromagnetic energy S3 falls upon the photocell deteotor 71. Deteotor 71, whioh oomprises a photodell and voltage divider, generates an analog voltage signal that is transmitted 30 through a conductor 91 to an analog to digital converter 92. The 3ame analog voltage signal is transmitted through a conductor 93 to a comparator 94.

The analog to digital converter 92 converts the analog voltage from deteotor 71 into a digital binary added signal which 35 is in turn:transmitted through a oonduotor 95 to a liquid crystal display (LCD) 96. The eleotronio oirouits of comparator 94 analyze the analog voltage input from deteotor 71 and generate one of several signals through a plurality of conductors represented •r\ -18- generally by the numeral 97· These conductors 97 lead tologio circuitry 98, whioh analyzes the several signals from comparator 94 and generates appropriate display signals through a plurality of conductors represented generally by the numeral 99 leading to 5 the display 96. Thus, display 96 causes the display of a unltlese, arbitrary deoimal number (preferably three seven-segment digits) in response to the input from the analog to digital converter 92, and also displays one or more of six annunciator symbols or indicators in response to the signals from loglo circuitry 10 98, as will be discussed in further detail below.

Figure 12 is a schematic representation of the power supply which provides regulated PC voltages to the various analog and digital circuits of the apparatus. Booker switoh 84 leade from a standard plug 101, which is oonneoted either to a 120 volt, 15 60 Hz source, or to a 220 volt, 50 Hz souroe. Switoh 31* seleots the appropriate voltage, either providing the 110 volt, 60 Hz supply directly to the fuse 33 to transformer 35, or stepping down the 220 volt, 50 Hz supply to the 110 volt level through the transformer 36. The interlook microswitoh 28 for oover plate 22 20 is oonneoted between relay 34 and fuse 33 so that lamp 21 may be energized only when the cover plate 22 is properly in plaoe; as discussed above. Transformer 35 steps the 110 volt supply down . to 28 volts rms, and this output is 0enter tapped and[delivered to a voltage regulator 102, to deliver +12 volts to the aystern analog 25 cirouits through a conduotor 104. Conduotor 106 serves as a ground.

The output of transformer 35 is also oonneoted to the transformer 107, whioh in turn delivers 14 volts rms to a voltage regulator 108 to produce a +9 volts digital loglo supply voltage 30 on conduotor 109. A conduotor 110 serves as a ground;oonduotor for this supply olrouit. Voltage regulators 102 and 108 are both LM317 three-terminal adjustable regulators available from National Semiconductor Corporation, 2900 Semiconductor Drive, Santa Clara, California 95051. 35 The oirouitry associated with the mercury discharge lamp 21 is.shown in Figure 13· Conductors 111, 112 (see also Figure 12) lead from the fused,supply of 110 volts AC to the lamp 21 through the serially oonneoted ballast transformer 27. Lamp • t · . ·. -.-'.ο·· :-19- start-up circuitry 113 provides a 5 second warmup stimulus to lamp 21 through a relay 114 when the apparatus is supplied with power. The "lamp on" indioator 87 is a light emitting diode (LED)i which is driven.through the relay 105 whenever the ballast voltage g corresponding to an energized lamp condition is developed across ballast transformer 27. Conductor 116 originates in Figure 1*1 and provides ground potential to circuitry 113·

Figure 14 discloses the circuitry associated with photocell detector 71 and the three digital deoimal display portion of 10 display 96, whioh bears the reference numeral 96a. Also shown in

Figure 14 but not directly related to this olrouitry is an optical isolating transistor 115» whioh works in oooperation with'the logic circuitry shown in Figure 16 to indicate proper DC power supply operation. The emitter of isolating transistor 115 is tied 15 to a ground conductor 116 with the colleotor conneoted to a con ductor 117- As shown in Figure.15, conductor 117 is conneoted to the +9 volt supply through a pullup resistor 120, and also to a oonduotor 150 described below.

One side of the photocell detector 71 is connected to 20 the +12 volt conductor 104 fromiFigure 12. The other side of deteotor 71 is conneoted to conductors 118 and 119. Conductor 119 is connected to the calibration potentiometer 86 (Figure 2) and also to the input (pin 31) of the analog to digital converter 92 through a resistor 121 having a very high resistance value. 25 Analog to digital converter 92 is a ICL7106 31 Digit Single Chip A/D Converter manufactured by Intersil, Inc., Cupertino, California. The calibration potentiometer 86 provides adjustment or calibration of the photocell 71 output signal as disoussed below. The other side of calibration potentiometer 86 is con- 30 neoted to the ground conductor 106.

The external components to the analog to digital con verter 92 are represented generally by the numeral 122. These components provide reference voltages, readings/seoond eontrol, auto zero capaoltance and integration circuitry to the converter 35 92. The output of analog to digital oonverter 92 is encoded with a three digit deoimal number and is formatted to drive the three seven-segment displays of the display 96 through conductors 93· ο ο -20-

Figure 15 discloses the oirouitry associated with the upper and lower limit voltage comparator fupotions which determine gem classification in the analyzer 11. A voltage divider network 123 is powered by +12 volts (reference numeral 104) to provide 5 reference voltages at conductors 124-127· The oircuit.includes four operational amplifiers 128—131. The oonduotora 124 and 126 are oonneoted to the inverting input of operational amplifiers 128, 130, respectively, and the conductors 125 arid 127 are oonneoted to the noninverting inputs of operational amplifiers 129, 10 131, respectively. The conductor 118, whioh leads from the photo*· oell detector 71 (Figure 14) and oarries the Integrated analog signal, is oonneoted to the noninverting Inputs of operational amplifiers 128 and 130, and to the inverting inputs of operational amplifiers 129 and 131. 15 A voltage dividing network 132 provides three reference voltages at conductors 133-135, Three operational amplifiers 136-138 are: connected to this network, the conductors 133 and 135 being connected to the inverting input of operational amplifiers 136 and 138, respectively, and the oonduotor 134 being oonneoted 20 to the noninverting input of operational amplifier 137« Conductor 118 extends beyond the operational amplifiers 128-131 as shown, and is connected to the noninverting input of operational amplifiers 136 and 138, and to the inverting input of operational amplifier 137· 25 The outputs of the operational amplifiers 128-131 are multiplexed through.a pair of double pole-single throw relays 1391 140, into the respective upper two Inputs.of a level shifting inverter network 142. A double pole, single throw!relay 141, whioh is ganged with relays 139 and 140, selectively connects 30 +12 volts through a oonduotor 143 to either one of:the two lower inputs to level shifting inverter network 142.

Operational amplifiers 128, 129 represent a first pair and operational amplifiers 130, 131 represent a seoond pair, either pair of whioh may be.selectively operated by the rocker 35 swltoh 85 (see also Figure 2), which is eleotromagnetically con nected to the ganged relays 139 and 140. This permits operation of the apparatus 11 in "mode 1" or "mode 2". With the swltoh 85 ....... ο -21- open as shown in Figure 15, the amplifiers 128, 129 :are operational,&lt; and olosing of the switch 85 oauses the amplifiers 130i 131 to become operational.

Bach of these pairs of amplifiers compares the analog 5 voltage signal appearing on oonduotor 118 with the reference voltages on conductors 124, 125 to operate in a desired manner.

In the preferred embodiment, if.the voltage on conductor 118 is less than a predetermined low reference voltage, amplifier 128 turns "on*, and the resulting signal is transmitted through the 10 level shifting network 142 to the logio olrouitry shown in Figure 16. If the voltage level on oonduotor 118 is greater than a predetermined high reference voltage, amplifier 129 turns, "on"t and its output is transmitted through the level shifting network 142 to the logic network of Figure 16,. If the voltage level on con- 15 duotor 118 falls between the low and high reference voltages, neither of the amplifiers 128, 129 turns "on” and this condition may be logioally sensed by the logio olrouitry of Figure 16.

Selection of the amplifiers 130, 131 results in operation in "mode 2", whioh results in comparison of the voltage level 20 on conductor 118 with the reference voltages appearing on conduc tors 126, 127. "Mode 2" operation is similar to that of ’’mode 1” in that amplifier 130 turns on if the signal voltage on oonduotor 118 is less than a predetermined low reference voltage on oonduotor 126, and amplifier 131 turns on if the signal voltage on oon- 25 duotor 118 is greater than a predetermined high reference voltage on oonduotor 127. Neither of the amplifiers 130, 131iturns on if the signal voltage on oonduotor 118 falls between the'low and high reference voltagee on oonduotors 126, 127.

In either mode of operation, a plurality of output 30 signals are transmitted through a plurality of conductors 145-148 to the logio olrouitry of Figure 16. The signals appearing on oonduotors 145-148 are derived from the voltage level on oonduotor 118 and operational condition of the amplifier pairs 128, 129 or 130, 131. Conductor 150 is conneoted direotly to oonduotor 117, 35 whioh io conneoted to the collector of transistor 115, Figure 14.

Operational amplifiers 136-133 act as a comparator In much the same way as the amplifiers 128-131, generating output ; -22- signals through a level shifting inverter network 151 to output oonduotors 152-154. While the operational amplifiers 128-131 are intended to analyze the signal on conduotor 118 to determine the nature and quality of the gem spealmen G, the amplifiers 135“138 5 are specifically intended to generate an output indicative of a spurious or abnormal condition, as evidenoed by the voltage level on oonduotor 118.

More specifically, the voltage level on conductor 118 will be at a spurious level if there, is no gem specimen G on the 10 gem holder 61, or abnormally low if the radiated energy is blooked for any reason before it reaches the photocell deteotor 71· For the latter case, amplifier 136 turns off if the voltage level on conduotor 118 is less than a predetermined low reference voltage.

For the ease where there ls no gem specimen overlying 15 the test aperture 61a, the referenoe voltages at oonduotors 134 and 135 are set to define a very narrow range corresponding to the spurious voltage level mentioned above. If the voltage level on oonduotor 118 falls within this narrow "window", both amplifiers 137 and 1381 turn on to generate appropriate signals on the output 20 conductors 153 and 154 as dlsoussed In further detail below.

With reference to Figure 16, the oonduotors 145-148 and 152-154 are input to a plurality of logic elements I62a-l62q connected to generate desired outputs on oonduotors 155-162 (described in detail below), all of whioh lead to the display 96b. 25 The displays 96a, 96b are Integrated into a single display 96, the format of whioh is shown in Figure 17.

Figure 17 disoloses the entire display format bf the liquid orystal display 96» whioh is represented generally by the referenoe letter D. In the display D, the unitless, Arbitrary 30 decimal number comprises three seven-segment digits and is repre sented by the reference numeral N. Display D also includes six annunolator symbols S1-S6 that are selectively displayed depending on the status and mode of operation of the apparatus and the nature of the gem speolmen. 35 Symbol S1 comprises a gem in a rectangular frame and is displayed on the display D when the rooker switoh 84 is actuated to the "power on" position and power is received by the logic circuit of Figure 16. --’ΤΡ'ΓΙΙι'ΙΙ^Ι^ΜΜΒΜ -23-

Symbols S2 and S3 respectively represent the selection of "mode 1" or "mode .2", as determined by the position of rocker switch 85.

The symbol S4 in the display D consists of crossed 5 mining hammers and represents the analysis of a "natural” gemstone. In addition, the symbol S4 includes a gemstone that flashes intermittently to better evidenob the analysis of a "natural" gemstone.

Symbol S5 on the display D oomprlses a balance beam sym-10 bol and indicates an. abnormal condition to the user, one of whloh is a gem specimen that is not within the species corresponding to the selected mode.

Symbol S6 on the display D is a mortar and pestle, representing a laboratory or synthetic process for the gem speoi- 15 men under analysis.

The arbitrary, unitless number N comprises three seven-segment decimal digits ranging from 0-999 and constitutes a numerical readout that is directly proportional to the magnitude of the analog signal from the photocell detector 71. The 20 arbitrary numerioal range for "natural" gem specimens in ithe pre ferred embodiment of the Inventive apparatus is 10-80. The "transition" range runs from 61-90, and the range for "synthetic" specimens runs from 91-999.

Figures 18A-18F disclose the entire inclined section 25 13b, including the rocker swltohes 84, 85, the calibration poten tiometer 86, the "source on" LED 87, and the display D of the liquid orystal display 96. With reference to Figure 18a, the presence of the single symbol S1 indicates that the rocker switch 84 is actuated to the "power on" position and power is received by 30 the logia oireuit of Figure 16. Also, the LED 87 is shown to be in the "on" position, which means that the discharge source lamp 21 is properly operating in a stable condition. The LED 67 is shown in the "discharge source on" condition in all of the Figures 18A-18F. 35 With reference to Figure 18B, the symbol S2 represents selection of "mode 1" as determined by the position of rooker switch 85. In Figure 18C, the symbol S3 shows the symbol S3 indi-

-.Jwr'nriM^nOMI o, -24- cative of the selection of "mode 2" by the rocker switoh 85. The seleotion of "mode 1” in the preferred embodiment is for analysis of the ruby species, and "mode 2" is ohoaen to analyzeithe emerald speoies. 5 In both Figures 18B and 18C, the deoimal number N is "000”, which indicates ooolusion of the test aperture 61a or some other obstruction.which precludes radiation from reaohing the photocell 71, or an open test aperture 61a (e.g., absence of a gem speoimen), 10 With reference to Figure 18D, the display D includes the symbol 31 indicating "logio on", the symbol S2 showing seleotion of "mode 1" and the symbol S6, representing a laboratory or synthetic process for the gem specimen under analysis. The digital readout N is 750, which falls within· the synthetio range as 15 described above.

In Figure 18E, symbol S1 displays "logic on"' and symbol S2 is again selected for ruby analysis. The balance beam symbol 35 indicates an abnormal condition to the user, as does the digital readout N, which has a value of 65. This falls within the 20 "transition" range as described above, and indicates to the user one of several possibilities, including improper operation or analysis ofi a gem specimen that is not a ruby.

In Figure 18F, symbol 31 shows a "logic on" status, symbol S2 shows that "mode 1" has again been selected for ruby 25 analysis, and the symbol 34 indloates analysis of a "natural" gemstone. The additional gemstone eymbol flashes to further evidence this analysis. The digital readout N is at 25,Iwhich falls within the arbitrary range for "natural" gem specimens as set forth above. 30 The operation of the deteotor, analog to digital converter, comparator, logio, and display circuits will now be explained. Referring to Figure 14, radiation filling on photocell 71 produces a corresponding voltage on conductor 119· i The voltage on conductor 119 is fed through conductor 118 to the comparator 35 olrcuits of Figure 15 and further applied to the input (pin 31) of analog to digital converter 92 through resistor 121. Converter 92 periodically digitizes the analog current appearing at its input -25- through resistor 121 and outputs through a plurality of conductors 93, the signals of which are encoded for driving the three seven-segment displays of display 96a. Accordingly, a three+plaoe decimal number directly proportional to the radiation falling on 5 photocell 71 is displayed. : Referring to Figure 15, aonduotor 118 carried the generated analog voltage to one input of each of comparators 128, 129, 130 and 131. As desoribed above, oomparators 128 and 129 work in oooperation to define a ’’window" in the analog voltage 10 range associated with the particular family of gems under, test.

Therefore, the analog voltage associated with any partioular gem under test may fall in one of three ranges: (1) below the lower limit of the window; (2) above the upper, limit of the window; or (3) inside the window range. When operational amplifiers 128 and 15 129 are switohed through relays 139 and 140 to level shifting inverter 142, outputs 145 and 146 will produce a two bit digital code corresponding tq the position of the analog voltage on oon-duator 118 with respect to the window defined by potentiometers 124 and 125 of network 123. If, for example, the voltage 20 appearing on conductor 118 is below the.window, the output of com parator 128 will be low and a corresponding logic 1 voltage will appear on conduotor 145, while the output of operational amplifier 129 will be high with a corresponding logic 0 voltage on output 146. If the voltage on oonduotor 118 is within the window, the 25 outputs of both comparators 128 and 129 will be high With corresponding logio-0 voltages on conductors 445 and 146.

Finally, if the voltage on oonduotor 118 is above theiwindow the output of operational amplifier 129 will be low with a corresponding logic 1 voltage on output 146. The output of opera- 30 . tional amplifier 128 will be high with a corresponding logio 0 voltage on conduotor 145. In this manner, one of the three logio conditions .1-0, 0-0, or 0-1'will be present on conductors 145 and 146 of level shifting inverter 142 when a gem Is under test.

Comparators 130 and 131 operate in the same manner only 35 with a different window defined through potentiometers 126 and 127 for a different family of gems. The outputs generated on conductors ,147 and 148 indicate the position of rocker switch 85, and relays 139 and 140. Depending on the position of rocker switch —26— 85» one of outputs 147 and 148 ia aotivated, with the other output in a complementary state.

The comparator network defined by comparators 136, 137 and 138 and oonnected to level shifting inverter network 151 is 5 also oonnected to conductor 118. Like comparators 128and 129 or 130 and 131, and as desoribed above comparators 137 and 138 also define a window voltage range. Comparator 136 defines a lower limit voltage for deteotlng occlusions in the gem test aperture 61a. Accordingly, whenever the voltage appearing on conductor 118 10 is below the lower limit voltage, the output of operational amplifier 136 is low produolng a corresponding logio 1 output on conductor 152. Similarly, a voltage on oonduotor 118 failing within the window defined by.operational amplifiers 137 and 138 will produce a logio 1-1 at conductors 153 and 154. The window 15 voltage is carefully defined to Olosely frame the voltage corresponding to an open test aperture 61a that Is where the radiation falling on photocell 71 is direct from lamp 21..

In the preferred embodiment, the low reference voltage for the operational amplifier 136 is the lowest reference voltage, 20 and may be on the order of 1 millivolt. The referenoe voltage for operational amplifier 128 Is on the order of 6 millivolts in the preferred embodiment, and the referenoe voltage for operational amplifier 129 is 9 millivolts. Thus, any analog signal from the photocell 71 whioh falls between 1 millivolt and 6 millivolts 25 falls in the "natural" gem range, subjeot to the exception defined below. Any analog signal from photocell 71 that exceeds 9 millivolts is in the "synthetic" range. Any analog,signal below T millivolt is treated as a spurious signal and is processed in a manner that precludes a readout. 30 The "window voltage range" defined by the operational amplifiers &gt;137 and 138 is between 3&gt;5 millivolts ahd 4.5 millivolts in the preferred embodiment,, and constitutes !the exception mentioned immediately above. It will be appreciated that this narrow range falls within the range indicative Of "natural" gems. 35 However, this range is ohosen based on the faot that natural gemstones such as rubies will not produce an analog voltage in

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'&lt; .1... ο -27- this particular range (given the other parameters of the electro nio oirouitry). The reason for this ia that son» natural ι gemstones within a particular speoies will undergo Internal excitation (e.g., fluorescence), whereas others do not. Thus, with the 5 parameters of the preferred embodiment, a natural ruby whioh does not emit fluorescence will produce an analog voltage In the range of 1 to 3.5 millivolts. A natural ruby that emits fluorescence will produce an analog signal between the range of 4.5 millivolts and 9 millivolts. It has been found as a practical 10 matter that natural rubies will not produce a signal between 3-5 millivolts and 4,5 millivolts in the preferred embodiment.

However, the eleotronio circuitry is designed so that radiation exposed to the photocell 71 through an open test aperture 61a will fall within the range of 3.5-4.5 millivolts, 15 It will be appreciated that the millivolts reference values described above are mentioned for guidanoe only., and are chosen In the preferred embodiment only for particular olrouit parameters and gem species. These voltage levels may be adjusted for the same or different species to produce different reference 20 values, whion would in turn give rise bu different unitlesc, arbitrary decimal numbers and different ranges of operation.

The interpretation of the logio signals generated on outputs 145-148 and 152-154 is performed by the logio oircuitry shown in Figure 16. Additionally, the logic of Figure 16 gates 25 the applied signals to produce the square waves neoessary for driving the symbols of liquid crystal display 96b.

In the operation of the liquid orystai display 96b a square wave is generated on oonductor 116b by analog to digital oonverter 92. The aquare wave is input to one input of eaoh of. 30 the exclusive-or gates 162a, 162b, 162ο, 162d, l62e and l62h. It is further input to the baok plane connection of LCD 96b. The outputs of gates 162b, l62e, I62d, l62e and l62h are connected to the various liquid crystal symbols 51-53 and 55-57 which represent "logic on" "mode 1", "mode 2", "synthetio", "transition"! and 35 "natural". The "gem" symbol assooiated with the "natural gem" symbol SI is gated through oscillator 1621 so that it appears flashing on the display. When a natural gem is detected by comparator logic 94 a logic 1 or high voltage appears on conductor ..... •^-j.^rinurfwtieww -28- 145. It ia applied to one input of eaoh and-gate 162J and 162k.

The signal propagates through each of these gates and is applied to the respective gates 162L and 162a. The application of a logio 1 voltage to the upper input of gate 162a oauses its output square 5 wave to shift out of phase with the square wave appearing on con ductor 116b and consequently excites the "crossed mining hammer” portion of symbol S4 on LCD 96b. The flashing gem portion of the symbol S4 is driven through gates 162m, 162L and gate 162J.

As mentioned above, the output of operational amplifiers 10 136, 137 and 138 provide spurious condition information to the logio. Outputs 152, 153 and 154 from level shifting inverter 151 are input to the corresponding conductors shown in the lower lefthand comer of Figure 16, In the oase where the voltage level appearing on conductor 118 is less than the defined lower limit, a 15 logio 1 voltage appears on conductor 152 and is passed through or- gate 162η and inverter l62o, disabling and-gates 162k and 162J.

The gates thus disabled, neither symbol associated with the natural gem appears on LCD 96b. Further, when the voltage on conductor 118 falls within the window defined by comparators 137 and 20 138 a logic 1 condition appears on conductors 153 and 154 and thus produoes a logic 1 output on and-gate l62p, consequently disabling the "natural” symbols through or-gate 162n in a similar fashion.

When the gem under test falls in the "transition" window the inputs on conductors 145 and 146 are both logic 0’s. 25 Consequently, neither square wave output from gated 162a or 162b is phase shifted, and their corresponding symbols are not energized. Instead, the logio 0 signals appearing on conduotors 145 and 146 are fed into or-gate l62f to produce a 0 output voltage for input to the upper input of or gate l62g. Given a 30 logio 0 on the output of or-gate l62n, a logio 1 appears on the output of gate l62g and is input to the lower input of exclusive or-gate. 162h. As a result, the square wave output of gate l62h is phase shifted with respect to the baok plane square wave of 116b and the "transition" symbol is energized on LCD 96b. 35 When the gem under test falls in the "synthetic" range, comparator,'oirouits 94 produoe a logio 0-1 oode on the respective conductors^145 and 146. Thus, the output square wave of exoluslve

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........... 1 -29- or-gate 162b ia phase shifted and delivered through oonduotor 156 to energize the "synthetlo" symbol on LCD 96b. The "logic on" symbol is driven through gate 162a, whioh is driven by inverter l62q, As pointed out earlier, the input to gate l62q is derived 5 from the collector transistor 115 (Figure 14). The "mode 1Mand "mode 2" symbols are driven by the respeotive outputs of gates 162c and 162d through the respeotive conductors 157 and 158. The phase shifting inputs to gates 1:62o and l62d are derived from conductors 147 and 148 whioh are oonneoted to level shifting inverter 10 142. Depending on the mode in which the.apparatus is operating, a logic 1 condition will appear on one of the two conduotors 147 and 14B and consequently shift the corresponding square wave to exolte the respeotive mode symbol.

In understanding operation of the apparatus 11, it must 15 also be emphasized that the discharge source 21 and photocell detector 71 are uniquely related to eaoh other and to the species of gems to be analyzed. More specifically, and as pointed out above, the quartz tube meroury discharge lamp 21 emits radiation in a broad spectrum of electromagnetic energy, the wave length of 20 which ranges from approximately 1800 Angstroms in the far- ultraviolet region at the low end through the visible region and into the near-infrared region. This particular lamp peaks at several individual wavelengths, the principal of whioh is 2550 Angstroms. 25 Both natural and synthetic rubles undergo Internal exci tation or fluorescence whioh produces a frequency shift, resulting in the emission of eleotromagnetlc energy at approximately 6500 Angstroms. The photodeteotor 71 is specifically ohosen because it senses electromagnetic energy in the narrow region around 6500 30 Angstroms.

It is the total interaction of the electromagnetic energy from the lamp 21 with the gem speoimen whioh permits quantification in discrete ranges. This interaction includes the transmission of eleotromagnetlc energy through the gem speoimen, 35 whioh is the complement of absorption. Energy is transmitted through the gem and emits from the gem at the same wavelength at which it enters. Only the intensity, as evidenoed by the degree of absorption, is affected.

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I -30-

Interaction also Includes internal reflectance, whioh is largely a, function of atomic imperfections and inclusions (e.g., random iron moleoules or structural imperfections in natural ruby). The internal reflectance alters only the intensity of 5 electromagnetic energy emitted from the gem, and not its frequency and wavelength.

Lastly, interaction of the eleotroniagnetlo source iiith the gem involves internal excitation, a principal form of which is fluorescence. As pointed out above, this causes a frequency 10 shift, and the resulting electromagnetic energy emitted from the gem falls within a speotrura of wavelength entirely different than the exdtation wavelength.

The total interaction gives rise to output radiation from the gem which represents a highly complex wave form if the 15 entire spectrum is taken into consideration. However, the red and blue glass filters 68, 69 mask this speotrun, focusing on the specific region of radiation at around 6500 Angstroms. This takes advantage of the frequency shift from the 2500 angstrom peak caused by fluoresoence, as discussed above. However, the photo- 20 oell detector 71 not only measures the intensity of electromagne tic energy caused by fluoresoenoe, but also the cumulative effeot produced by transmitted, nonabsorbed eleotromagnetlo energy In the detected,range as well as the radiation produced by Internal reflection. It is to be emphasized that it is the cumulative 25 effect of interaction of lamp radiation with the gem that is sensed by the detector in the range of around 6500 Angstroms, suoh cumulative effeot being sensed as intensity of the eleotromagnetlo energy in the deteoted 6500 Angstrom range.

Operation of the apparatus 11 from the standpoint of the 30 user is simple and efficient. The unit must be connected to a source of 110 volt or 220 volt power with internal switch 34 first actuated to the corresponding voltage position. The apparatus 11 may then be turned on through use of the rocker switch 84. When the lamp 21 reaches a stabilized voltage level of operation, the 35 light emitting diode 87 on the inclined panel 13b will light up, indicating that the unit is ready for use.

The mode is then selected with rocker switch 85.

Assuming that "mode 1" is chosen, the drawer 19 is opened by use

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· r&gt; -31- of the latoh 64, and the gem specimen in question is placed on the speoimen holder 6l in a position to completely overlie the test aperture 61a. The size of aperture 61a is ohosen to be smaller than the vast majority of potential gem speolmens, thus: insuring 5 that all of the radiation from the gem will be the produot of its

Interaction with the souroe of radiation from lamp 21.

With the gem speoimen properly placed, the drawer 19 is olosed and the latch 64 aotuated to look the drawer. As discussed above, this causes all of the apertures between the lamp 10 21 and photocell 71 to be ln registration, permitting interaction to occur between the specimen and the eleotromagnetio energy radiated by lamp 21.

As an instantaneous: result, an analog signal is generated by the photooell 71 whioh is directly proportional to 15 the intensity of eleotromagnetio energy to which the photooell 71 is exposed. As described above, this analog signal can be processed by the eleotronio cirouitry to qulokly and automatically provide a readout as to whether the gem is natural or synthetic, as well as an indication of its quality as evldenoed by the 20 numerical digital readout. If an oooluslon of the test aperture 61a appears, or if the aperture 61a is open for any reason, the numerioal digital readout is ”000". If the gem speoimen analyzed is not within the species expected, the "balance beam" ι symbol 36 will appear and the numerioal digital readout will fall in the 25 "transition” range.

It is advisable to calibrate the apparatus 11 periodi cally to compensate for operational shifts such as aging of the eleotronio or eleotrioal components. This is easily accomplished by removing·the loosely held specimen holder 61 from the drawer 19 30 and replacing it with the speoimen holder 89 and calibration spe oimen 88, whioh has a known value expressed as a three digit number. With the oalibratlon specimen in place and the drawer 19 olosed, the calibration potentiometer 86 is adjusted until the numerioal digital readout symbol S4 corresponds to :the known digl- 35 tai number of the oalibratlon speoimen 88. The apparatus 11 is then calibrated for further use.