Patent Publication Number: US-6222620-B1

Title: Apparatus and method for measuring optical characteristics of an object

Description:
This application is a continuation of U.S. patent application Ser. No. 09/263,919 which was filed on Mar. 5, 1999, now abandoned, which was a continuation of U.S. patent application Ser. No. 08/886,564 filed Jul. 1, 1997, now U.S. Pat. No. 5,880,826. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to devices and methods for measuring optical characteristics such as color spectrums, translucence, gloss, and other characteristics of objects such as teeth, and more particularly to devices and methods for measuring the color and other optical characteristics of teeth or other objects or surfaces with a hand-held probe that presents minimal problems with height or angular dependencies. 
     BACKGROUND OF THE INVENTION 
     A need has been recognized for devices and methods of measuring the color or other optical characteristics of teeth and other objects in the field of dentistry. Various color measuring devices such as spectrophotometers and colorimeters are known in the art. To understand the limitations of such conventional devices, it is helpful to understand certain principles relating to color. Without being bound by theory, Applicants provide the following discussion. In the discussion herein, reference is made to an “object,” “material,” “surface,” etc., and it should be understood that in general such discussion may include teeth as the “object,” “material,” “surface,” etc. 
     The color of an object determines the manner in which light is reflected from the object. When light is incident upon an object, the reflected light will vary in intensity and wavelength dependent upon the color of the object. Thus, a red object will reflect red light with a greater intensity than a blue or a green object, and correspondingly a green object will reflect green light with a greater intensity than a red or blue object. 
     The optical properties of an object are also affected by the manner in which light is reflected from the surface. Glossy objects, those that reflect light specularly such as mirrors or other highly polished surfaces, reflect light differently than diffuse objects or those that reflect light in all directions, such as the reflection from a rough or otherwise non-polished surface. Although both objects may have the same color and exhibit the same reflectance or absorption optical spectral responses, their appearances differ because of the manner in which they reflect light. 
     Additionally, many objects may be translucent or have semi-translucent surfaces or thin layers covering their surfaces. Examples of such materials are teeth, which have a complicated structure consisting of an outer enamel layer and an inner dentin layer. The outer enamel layer is semitranslucent. The inner layers are also translucent to a greater or lesser degree. Such materials and objects also appear different from objects that are opaque, even though they may be the same color because of the manner in which they can propagate light in the translucent layer and emit the light ray displaced from its point of entry. 
     One method of quantifying the color of an object is to illuminate it with broad band spectrum or “white” light, and measure the spectral properties of the reflected light over the entire visible spectrum and compare the reflected spectrum with the incident light spectrum. Such instruments typically require a broad band spectrophotometer, which generally are expensive, bulky and relatively cumbersome to operate, thereby limiting the practical application of such instruments. 
     For certain applications, the broad band data provided by a spectrophotometer is unnecessary. For such applications, devices have been produced or proposed that quantify color in terms of a numerical value or relatively small set of values representative of the color of the object. 
     It is known that the color of an object can be represented by three values. For example, the color of an object can be represented by red, green and blue values, an intensity value and color difference values, by a CIE value, or by what are known as “tristimulus values” or numerous other orthogonal combinations. For most tristimulus systems, the three values are orthogonal; i.e., any combination of two elements in the set cannot be included in the third element. 
     One such method of quantifying the color of an object is to illuminate an object with broad band “white” light and measure the intensity of the reflected light after it has been passed through narrow band filters. Typically three filters (such as red, green and blue) are used to provide tristimulus light values representative of the color of the surface. Yet another method is to illuminate an object with three monochromatic light sources or narrow band light sources (such as red, green and blue) one at a time and then measure the intensity of the reflected light with a single light sensor. The three measurements are then converted to a tristimulus value representative of the color of the surface. Such color measurement techniques can be utilized to produce equivalent tristimulus values representative of the color of the surface. Generally, it does not matter if a “white” light source is used with a plurality of color sensors (or a continuum in the case of a spectrophotometer), or if a plurality of colored light sources are utilized with a single light sensor. 
     There are, however, difficulties with the conventional techniques. When light is incident upon a surface and reflected to a light receiver, the height of the light sensor and the angle of the sensor relative to the surface and to the light source also affect the intensity of the received light. Since the color determination is being made by measuring and quantifying the intensity of the received light for different colors, it is important that the height and angular dependency of the light receiver be eliminated or accounted for in some manner. 
     One method for eliminating the height and angular dependency of the light source and receiver is to provide a fixed mounting arrangement where the light source and receiver are stationary and the object is always positioned and measured at a preset height and angle. The fixed mounting arrangement greatly limits the applicability of such a method. Another method is to add mounting feet to the light source and receiver probe and to touch the object with the probe to maintain a constant height and angle. The feet in such an apparatus must be wide enough apart to insure that a constant angle (usually perpendicular) is maintained relative to the object. Such an apparatus tends to be very difficult to utilize on small objects or on objects that are hard to reach, and in general does not work satisfactorily in measuring objects with curved surfaces. Such devices are particularly difficult to implement in the field of dentistry. 
     The use of color measuring devices in the field of dentistry has been proposed. In modern dentistry, the color of teeth typically are quantified by manually comparing a patient&#39;s teeth with a set of “shade guides.” There are numerous shade guides available for dentists in order to properly select the desired color of dental prosthesis. Such shade guides have been utilized for decades and the color determination is made subjectively by the dentist by holding a set of shade guides next to a patient&#39;s teeth and attempting to find the best match. Unfortunately, however, the best match often is affected by the ambient light color in the dental operatory and the surrounding color of the patient&#39;s makeup or clothing and by the fatigue level of the dentist. In addition, such pseudo trial and error methods based on subjective matching with existing industry shade guides for forming dental prostheses, fillings and the like often result in unacceptable color matching, with the result that the prosthesis needs to be remade, leading to increased costs and inconvenience to the patient, dental professional and/or prosthesis manufacturer. 
     Similar subjective color quantification also is made in the paint industry by comparing the color of an object with a paint reference guide. There are numerous paint guides available in the industry and the color determination also often is affected by ambient light color, user fatigue and the color sensitivity of the user. Many individuals are color insensitive (color blind) to certain colors, further complicating color determination. 
     While a need has been recognized in the field of dentistry, however, the limitations of conventional color/optical measuring techniques typically restrict the utility of such techniques. For example, the high cost and bulkiness of typical broad band spectrometers, and the fixed mounting arrangements or feet required to address the height and angular dependency, often limit the applicability of such conventional techniques. 
     Moreover, another limitation of such conventional methods and devices are that the resolution of the height and angular dependency problems typically require contact with the object being measured. In certain applications, it may be desirable to measure and quantify the color of an object with a small probe that does not require contact with the surface of the object. In certain applications, for example, hygienic considerations make such contact undesirable. In the other applications, contact with the object can mar the surface (such as if the object is coated in some manner) or otherwise cause undesirable effects. 
     In summary, there is a need for a low cost, hand-held probe of small size that can reliably measure and quantify the color and other optical characteristics of an object without requiring physical contact with the object, and also a need for methods based on such a device in the field of dentistry and other applications. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, devices and methods are provided for measuring the color and other optical characteristics of objects such as teeth, reliably and with minimal problems of height and angular dependence. A handheld probe is utilized in the present invention, with the handheld probe containing a number of fiber optics in certain preferred embodiments. Light is directed from one (or more) light source(s) towards the object/tooth to be measured, which in certain preferred embodiments is a central light source fiber optic (other light sources and light source arrangements also may be utilized). Light reflected from the object is detected by a number of light receivers. Included in the light receivers (which may be light receiver fiber optics) are a plurality of perimeter and/or broadband or other receivers (which may be light receiver fiber optics, etc.). In certain preferred embodiments, a number of groups of perimeter fiber optics are utilized in order to take measurements at a desired, and predetermined height and angle, thereby minimizing height and angular dependency problems found in conventional methods, and to quantify other optical characteristics such as gloss. In certain embodiments, the present invention also may measure gloss, translucence and fluorescence characteristics of the object/tooth being measured, as well as surface texture and/or other optical or surface characteristics. In certain embodiments, the present invention may distinguish the surface spectral reflectance response and also a bulk spectral response. 
     The present invention may include constituent elements of a broad band spectrophotometer, or, alternatively, may include constituent elements of a tristimulus type colorimeter. The present invention may employ a variety of color measuring devices in order to measure color and other optical characteristics in a practical, reliable and efficient manner, and in certain preferred embodiments includes a color filter array and a plurality of color sensors. A microprocessor is included for control and calculation purposes. A temperature sensor is included to measure temperature in order to detect abnormal conditions and/or to compensate for temperature effects of the filters or other components of the system. In addition, the present invention may include audio feedback to guide the operator in making color/optical measurements, as well as one or more display devices for displaying control, status or other information. 
     With the present invention, color/optical measurements of teeth or the like may be made with a handheld probe in a practical and reliable manner, essentially free of height and angular dependency problems, without resorting to fixtures, feet or other undesirable mechanical arrangements for fixing the height and angle of the probe with respect to the object/tooth. In addition, the present invention includes methods of using such color measurement data to implement processes for forming dental prostheses and the like, as well as methods for keeping such color and/or other data as part of a patient record database. 
     Accordingly, it is an object of the present invention to address limitations of conventional color/optical measuring techniques. 
     It is another object of the present invention to provide a method and device useful in measuring the color or other optical characteristics of teeth or other objects or surfaces with a hand-held probe of practical size that may advantageously utilize, but does not necessarily require, contact with the object or surface. 
     It is a further object of the present invention to provide a color/optical measurement probe and method that does not require fixed position mechanical mounting, feet or other mechanical impediments. 
     It is yet another object of the present invention to provide a probe and method useful for measuring color and/or other optical characteristics that may be utilized with a probe simply placed near the surface to be measured. 
     It is a still further object of the present invention to provide a probe and method that are capable of determining translucency characteristics of the object being measured. 
     It is a still further object of the present invention to provide a probe and method that are capable of determining translucency characteristics of the object being measured by making measurements from one side of the object. 
     It is a further object of the present invention to provide a probe and method that are capable of determining surface texture characteristics of the object/tooth being measured. 
     It is a still further object of the present invention to provide a probe and method that are capable of determining fluorescence characteristics of the object/tooth being measured. 
     It is yet a further object of the present invention to provide a probe and method that are capable of determining gloss (or degree of specular reflectance) characteristics of the object/tooth being measured. 
     It is another object of the present invention to provide a probe and method that can measure the area of a small spot singularly, or that also can measure the color of irregular shapes by moving the probe over an area and integrating the color of the entire area. 
     It is a further object of the present invention to provide a method of measuring the color of teeth and preparing dental prostheses, dentures, intraoral tooth-colored fillings or other materials. 
     It is yet another object of the present invention to provide a method and apparatus that minimizes contamination problems, while providing a reliable and expedient manner in which to measure teeth and prepare dental prostheses, dentures, intraoral tooth-colored fillings or other materials. 
     It is an object of the present invention to provide methods of using measured data to implement processes for forming dental prostheses and the like, as well as methods for keeping such measurement and/or other data as part of a patient record database. 
     It also is an object of the present invention to provide probes and methods for measuring optical characteristics with a probe that is held substantially stationary with respect to the object or tooth being measured. 
     Finally, it is an object of the present invention to provide probes and methods for measuring optical characteristics with a probe that may have a removable tip or shield that may be removed for cleaning, disposed after use or the like 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be more fully understood by a description of certain preferred embodiments in conjunction with the attached drawings in which: 
     FIG. 1 is a diagram illustrating a preferred embodiment of the present invention; 
     FIG. 2 is a diagram illustrating a cross section of a probe that may be used in accordance with certain embodiments of the present invention; 
     FIG. 3 is a diagram illustrating an illustrative arrangement of fiber optic receivers and sensors utilized with certain embodiments; 
     FIGS. 4A to  4 C illustrate certain geometric considerations of fiber optics; 
     FIGS. 5A and 5B illustrate the light amplitude received by fiber optic light receivers as the receivers are moved towards and away from an object; 
     FIG. 6 is a flow chart illustrating a color measuring method in accordance with an embodiment of the present invention; 
     FIGS. 7A and 7B illustrate a protective cap that may be used with certain embodiments of the present invention; 
     FIGS. 8A and 8B illustrate removable probe tips that may be used with certain embodiments of the present invention; 
     FIG. 9 illustrates a fiber optic bundle in accordance with another embodiment, which may serve to further the understanding of preferred embodiments of the present invention; 
     FIGS. 10A,  10 B,  10 C and  10 D illustrate and describe other fiber optic bundle configurations and principles, which may serve to further the understanding of preferred embodiments of the present invention; 
     FIG. 11 illustrates a linear optical sensor array that may be used in certain embodiments of the present invention; 
     FIG. 12 illustrates a matrix optical sensor array that may be used in certain embodiments of the present invention; 
     FIGS. 13A and 13B illustrate certain optical properties of a filter array that may be used in certain embodiments of the present invention; 
     FIGS. 14A and 14B illustrate examples of received light intensities of receivers used in certain embodiments of the present invention; 
     FIG. 15 is a flow chart illustrating audio tones that may be used in certain preferred embodiments of the present invention; 
     FIGS. 16A and 16B are flow charts illustrating dental prosthesis manufacturing methods in accordance with certain preferred embodiments of the present invention; 
     FIGS. 17A and 17B illustrate a positioning implement used in certain embodiments of the present invention; 
     FIG. 18 is a flow chart illustrating a patient database method in accordance with certain embodiments of the present invention; 
     FIG. 19 illustrates an integrated unit in accordance with the present invention that includes a measuring device and other implements; 
     FIG. 20 illustrates an embodiment, which utilizes a plurality of rings of light receivers that may be utilized to take measurements with the probe held substantially stationary with respect to the object being measured, which may serve to further the understanding of preferred embodiments of the present invention; 
     FIGS. 21 and 22 illustrate an embodiment, which utilizes a mechanical movement and also may be utilized to take measurements with the probe held substantially stationary with respect to the object being measured, which may serve to further the understanding of preferred embodiments of the present invention; 
     FIGS. 23A to  23 C illustrate embodiments of the present invention in which coherent light conduits may serve as removable probe tips; 
     FIGS. 24,  25  and  26  illustrate further embodiments of the present invention utilizing intraoral reflectometers, intraoral cameras and/or color calibration charts in accordance with the present invention; 
     FIG. 27 illustrates an embodiment of the present invention in which an interoral camera and/or other instruments in accordance with the present invention may be adapted for use with a dental chair; 
     FIGS. 28A and 28B illustrate cross sections of probes that may be used in accordance with preferred embodiments of the present invention; 
     FIGS. 29 and 30A and  30 B illustrate certain geometric and other properties of fiber optics for purposes of understanding certain preferred embodiments; 
     FIGS. 31A and 31B illustrate probes for measuring “specular-excluded” type spectrums in accordance with the present invention; 
     FIGS. 32,  33  and  34  illustrate embodiments in which intra oral cameras and reflectometer type instruments in accordance with the present invention are integrated; 
     FIGS. 35 and 36 illustrate certain handheld embodiments of the present invention; and 
     FIGS. 37A and 37B illustrate a tooth dental object in cross section, illustrating how embodiments of the present invention may be used to assess subsurface characteristics of various types of objects 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in greater detail with reference to certain preferred embodiments and certain other embodiments, which may serve to further the understanding of preferred embodiments of the present invention. At various places herein, reference is made to an “object,” “material,” “surface,” etc., for example. It should be understood that an exemplary use of the present invention is in the field of dentistry, and thus the object typically should be understood to include teeth, dentures or other prosthesis or restorations, dental-type cements or the like or other dental objects, although for discussion purposes in certain instances reference is only made to the “object.” As described elsewhere herein, various refinements and substitutions of the various embodiments are possible based on the principles and teachings herein. 
     With reference to FIG. 1, an exemplary preferred embodiment of a color/optical characteristic measuring system and method in accordance with the present invention will be described. It should be noted that, at various places herein, such a color measuring system is sometimes referred to as an intraoral reflectometer, etc. 
     Probe tip  1  encloses a plurality of fiber optics, each of which may constitute one or more fiber optic fibers. In a preferred embodiment, the fiber optics contained within probe tip  1  includes a single light source fiber optic and a number of groups of light receiver fiber optics. The use of such fiber optics to measure the color or other optical characteristics of an object will be described later herein. Probe tip  1  is attached to probe body  2 , on which is fixed switch  17 . Switch  17  communicates with microprocessor  10  through wire  18  and provides, for example, a mechanism by which an operator may activate the device in order to make a color/optical measurement. Fiber optics within probe tip  1  terminate at the forward end thereof (i.e., the end away from probe body  2 ). The forward end of probe tip  1  is directed towards the surface of the object to be measured as described more fully below. The fiber optics within probe tip  1  optically extend through probe body  2  and through fiber optic cable  3  to light sensors  8 , which are coupled to microprocessor  10 . 
     It should be noted that microprocessor  10  includes conventional associated components, such as memory (programmable memory, such as PROM, EPROM or EEPROM; working memory such as DRAMs or SRAMs; and/or other types of memory such as non-volatile memory, such as FLASH), peripheral circuits, clocks and power supplies, although for clarity such components are not explicitly shown. Other types of computing devices (such as other microprocessor systems, programmable logic arrays or the like) are used in other embodiments of the present invention. 
     In the embodiment of FIG. 1, the fiber optics from fiber optic cable  3  end at splicing connector  4 . From splicing connector  4 , each or some of the receiver fiber optics used in this embodiment is/are spliced into a number of smaller fiber optics (generally denoted as fibers  7 ), which in this embodiment are fibers of equal diameter, but which in other preferred embodiments may be of unequal diameter and/or numeric aperture (NA) (including, for example, larger or smaller “height/angle” or perimeter fibers, as more fully described herein). One of the fibers of each group of fibers may pass to light sensors  8  through a neutral density filter (as more fully described with reference to FIG.  3 ), and collectively such neutrally filtered fibers may be utilized for purposes of height/angle determination, translucency determination and gloss determination (and also may be utilized to measure other surface characteristics, as more fully described herein). Remaining fibers of each group of fibers may pass to light sensors  8  through color filters and may be used to make color/optical measurements. In still other embodiments, splicing connector  4  is not used, and fiber bundles of, for example, five or more fibers each extend from light sensors  8  to the forward end of probe tip  1 . In certain embodiments, unused fibers or other materials may be included as part of a bundle of fibers for purposes of, for example, easing the manufacturing process for the fiber bundle. What should be noted is that, for purposes of the present invention, a plurality of light receiver fiber optics or elements (such as fibers  7 ) are presented to light sensors  8 , with the light from the light receiver fiber optics/elements representing light reflected from object  20 . While the various embodiments described herein present tradeoffs and benefits that may not have been apparent prior to the present invention (and thus may be independently novel), what is important for the present discussion is that light from fiber optics/elements at the forward end of probe tip  1  is presented to sensors  8  for color/optical measurements and angle/height determination, etc. In particular, fiber optic configurations of certain preferred embodiments will be explained in more detail hereinafter. 
     Light source  11  in the preferred embodiment is a halogen light source (of, for example, 5-100 watts, with the particular wattage chosen for the particular application), which may be under the control of microprocessor  10 . The light from light source  11  reflects from cold mirror  6  and into source fiber optic  5 . Source fiber optic  5  passes through to the forward end of probe tip  1  and provides the light stimulus used for purposes of making the measurements described herein. Cold mirror  6  reflects visible light and passes infra-red light, and is used to reduce the amount of infra-red light produced by light source  11  before the light is introduced into source fiber optic  5 . Such infra-red light reduction of the light from a halogen source such as light source  11  can help prevent saturation of the receiving light sensors, which can reduce overall system sensitivity. Fiber  15  receives light directly from light source  11  and passes through to light sensors  8  (which may be through a neutral density filter). Microprocessor  10  monitors the light output of light source  11  through fiber  15 , and thus may monitor and, if necessary compensate for, drift of the output of light source  11 . In certain embodiments, microprocessor  10  also may sound an alarm (such as through speaker  16 ) or otherwise provide some indication if abnormal or other undesired performance of light source  11  is detected. 
     The data output from light sensors  8  pass to microprocessor  10 . Microprocessor  10  processes the data from light sensors  8  to produce a measurement of color and/or other characteristics. Microprocessor  10  also is coupled to key pad switches  12 , which serve as an input device. Through key pad switches  12 , the operator may input control information or commands, or information relating to the object being measured or the like. In general, key pad switches  12 , or other suitable data input devices (such as push button, toggle, membrane or other switches or the like), serve as a mechanism to input desired information to microprocessor  10 . 
     Microprocessor  10  also communicates with UART  13 , which enables microprocessor  10  to be coupled to an external device such as computer  13 A. In such embodiments, data provided by microprocessor  10  may be processed as desired for the particular application, such as for averaging, format conversion or for various display or print options, etc. In the preferred embodiment, UART  13  is configured so as to provide what is known as a RS232 interface, such as is commonly found in personal computers. 
     Microprocessor  10  also communicates with LCD  14  for purposes of displaying status, control or other information as desired for the particular application. For example, color bars, charts or other graphic representations of the color or other collected data and/or the measured object or tooth may be displayed. In other embodiments, other display devices are used, such as CRTs, matrix-type LEDs, lights or other mechanisms for producing a visible indicia of system status or the like. Upon system initialization, for example, LCD  14  may provide an indication hat the system is stable, ready and available for taking color measurements. 
     Also coupled to microprocessor  10  is speaker  16 . Speaker  16 , in a preferred embodiment as discussed more fully below, serves to provide audio feedback to the operator, which may serve to guide the operator in the use of the device. Speaker  16  also may serve to provide status or other information alerting the operator of the condition of the system, including an audio tone, beeps or other audible indication (i.e., voice) that the system is initialized and available for taking measurements. Speaker  16  also may present audio information indicative of the measured data, shade guide or reference values corresponding to the measured data, or an indication of the status of the color/optical measurements. 
     Microprocessor  10  also receives an input from temperature sensor  9 . Given that many types of filters (and perhaps light sources or other components) may operate reliably only in a given temperature range, temperature sensor  9  serves to provide temperature information to microprocessor  10 . In particular, color filters, such as may be included in light sensors  8 , may be sensitive to temperature, and may operate reliably only over a certain temperature range. In certain embodiments, if the temperature is within a usable range, microprocessor  10  may compensate for temperature variations of the color filters. In such embodiments, the color filters are characterized as to filtering characteristics as a function of temperature, either by data provided by the filter manufacturer, or through measurement as a function of temperature. Such filter temperature compensation data may be stored in the form of a look-up table in memory, or may be stored as a set of polynomial coefficients from which the temperature characteristics of the filters may be computed by microprocessor  10 . 
     In general, under control of microprocessor  10 , which may be in response to operator activation (through, for example, key pad switches  12  or switch  17 ), light is directed from light source  11 , and reflected from cold mirror  6  through source fiber optic  5  (and through fiber optic cable  3 , probe body  2  and probe tip  1 ) or through some other suitable light source element and is directed onto object  20 . Light reflected from object  20  passes through the receiver fiber optics/elements in probe tip  1  to light sensors  8  (through probe body  2 , fiber optic cable  3  and fibers  7 ). Based on the information produced by light sensors  8 , microprocessor  10  produces a color/optical measurement result or other information to the operator. Color measurement or other data produced by microprocessor  10  may be displayed on display  14 , passed through UART  13  to computer  13 A, or used to generate audio information that is presented to speaker  16 . Other operational aspects of the preferred embodiment illustrated in FIG. 1 will be explained hereinafter. 
     With reference to FIG. 2, an embodiment of a fiber optic arrangement presented at the forward end of probe tip  1  will now be described, which may serve to further the understanding of preferred embodiments of the present invention. As illustrated in FIG. 2, this embodiment utilizes a single central light source fiber optic, denoted as light source fiber optic S, and a plurality of perimeter light receiver fiber optics, denoted as light receivers R 1 , R 2  and R 3 . As is illustrated, this embodiment utilizes three perimeter fiber optics, although in other embodiments two, four or some other number of receiver fiber optics are utilized. As more fully described herein, the perimeter light receiver fiber optics serve not only to provide reflected light for purposes of making the color/optical measurement, but such perimeter fibers also serve to provide information regarding the angle and height of probe tip  1  with respect to the surface of the object that is being measured, and also may provide information regarding the surface characteristics of the object that is being measured. 
     In the illustrated embodiment, receiver fiber optics R 1  to R 3  are positioned symmetrically around source fiber optic S, with a spacing of about 120 degrees from each other. It should be noted that spacing t is provided between receiver fiber optics R 1  to R 3  and source fiber optic S. While the precise angular placement of the receiver fiber optics around the perimeter of the fiber bundle in general is not critical, it has been determined that three receiver fiber optics positioned 120 degrees apart generally may give acceptable results. As discussed above, in certain embodiments light receiver fiber optics R 1  to R 3  each constitute a single fiber, which is divided at splicing connector  4  (refer again to FIG.  1 ), or, in alternate embodiments, light receiver fiber optics R 1  to R 3  each constitute a bundle of fibers, numbering, for example, at least five fibers per bundle. It has been determined that, with available fibers of uniform size, a bundle of, for example, seven fibers may be readily produced (although as will be apparent to one of skill in the art, the precise number of fibers may be determined in view of the desired number of receiver fiber optics, manufacturing considerations, etc.). The use of light receiver fiber optics R 1  to R 3  to produce color/optical measurements is further described elsewhere herein, although it may be noted here that receiver fiber optics R 1  to R 3  may serve to detect whether, for example, the angle of probe tip  1  with respect to the surface of the object being measured is at 90 degrees, or if the surface of the object being measured contains surface texture and/or spectral irregularities. In the case where probe tip  1  is perpendicular to the surface of the object being measured and the surface of the object being measured is a diffuse reflector (i.e., a matte-type reflector, as compared to a glossy or spectral or shiny-type reflector which may have “hot spots”), then the light intensity input into the perimeter fibers should be approximately equal. It also should be noted that spacing t serves to adjust the optimal height at which color/optical measurements should be made (as more fully described below). Preferred embodiments, as described hereinafter, may enable the quantification of the gloss or degree of spectral reflection of the object being measured. 
     In one particular aspect useful with embodiments of the present invention, area between the fiber optics on probe tip  1  may be wholly or partially filled with a non-reflective material and/or surface (which may be a black mat, contoured or other non-reflective surface). Having such exposed area of probe tip  1  non-reflective helps to reduce undesired reflections, thereby helping to increase the accuracy and reliability. 
     With reference to FIG. 3, a partial arrangement of light receiver fiber optics and sensors that may be used in a preferred embodiment of the present invention will now be described. Fibers  7  represent light receiving fiber optics, which transmit light reflected from the object being measured to light sensors  8 . In an exemplary embodiment, sixteen sensors (two sets of eight) are utilized, although for ease of discussion only 8 are illustrated in FIG. 3 (in this preferred embodiment, the circuitry of FIG. 3 is duplicated, for example, in order to result in sixteen sensors). In other embodiments, other numbers of sensors are utilized in accordance with the present invention. 
     Light from fibers  7  is presented to sensors  8 , which in a preferred embodiment pass through filters  22  to sensing elements  24 . In this preferred embodiment, sensing elements  24  include light-to-frequency converters, manufactured by Texas Instruments and sold under the part number TSL230. Such converters constitute, in general, photo diode arrays that integrate the light received from fibers  7  and output an AC signal with a frequency proportional to the intensity (not frequency) of the incident light. Without being bound by theory, the basic principle of such devices is that, as the intensity increases, the integrator output voltage rises more quickly, and the shorter the integrator rise time, the greater the output frequency. The outputs of the TSL230 sensors are TTL compatible digital signals, which may be coupled to various digital logic devices. 
     The outputs of sensing elements  24  are, in this embodiment, asynchronous signals of frequencies depending upon the light intensity presented to the particular sensing elements, which are presented to processor  26 . In a preferred embodiment, processor  26  is a Microchip PIC16C55 or PIC16C57 microprocessor, which as described more fully herein implements an algorithm to measure the frequencies of the signals output by sensing elements  24 . In other embodiments, a more integrated microprocessor/microcontroller, such as Hitachi&#39;s SH RISC microcontrollers, is utilized to provide further system integration or the like. 
     As previously described, processor  26  measures the frequencies of the signals output from sensing elements  24 . In a preferred embodiment, processor  26  implements a software timing loop, and at periodic intervals processor  26  reads the states of the outputs of sensing elements  24 . An internal counter is incremented each pass through the software timing loop. The accuracy of the timing loop generally is determined by the crystal oscillator time base (not shown in FIG. 3) coupled to processor  26  (such oscillators typically are quite stable). After reading the outputs of sensing elements  24 , processor  26  performs an exclusive OR (“XOR”) operation with the last data read (in a preferred embodiment such data is read in byte length). If any bit has changed, the XOR operation will produce a 1, and, if no bits have changed, the XOR operation will produce a 0. If the result is non-zero, the input byte is saved along with the value of the internal counter (that is incremented each pass through the software timing loop). If the result is zero, the systems waits (e.g., executes no operation instructions) the same amount of time as if the data had to be saved, and the looping operation continues. The process continues until all eight inputs have changed at least twice, which enables measurement of a full ½ period of each input. Upon conclusion of the looping process, processor  26  analyzes the stored input bytes and internal counter states. There should be 2 to 16 saved inputs (for the 8 total sensors of FIG. 3) and counter states (if two or more inputs change at the same time, they are saved simultaneously). As will be understood by one of skill in the art, the stored values of the internal counter contains information determinative of the period of the signals received from sensing elements  24 . By proper subtraction of internal counter values at times when an input bit has changed, the period may be calculated. Such periods calculated for each of the outputs of sensing elements is provided by processor  26  to microprocessor  10  (see, e.g., FIG.  1 ). From such calculated periods, a measure of the received light intensities may be calculated. In alternate embodiments, the frequency of the outputs of the TSL230 sensors is measured directly by a similar software loop as the one described above. The outputs are monitored by the RISC processor in a software timing loop and are XORed with the previous input as described above. If a transition occurs for a particular TSL230 input, a counter register for the particular TSL230 input is incremented. The software loop is executed for a pre-determined period of time and the frequency of the input is calculated by dividing the number of transitions by the pre-determined time and scaling the result. It will also be apparent to one skilled in the art that more sophisticated measurement schemes can also be implemented whereby both the frequency and period are simultaneously measured by high speed RISC processors such as those of the Hitachi SH family. 
     It should be noted that the sensing circuitry and methodology illustrated in FIG. 3 have been determined to provide a practical and expedient manner in which to measure the light intensities received by sensing elements  24 . In other embodiments, other circuits and methodologies are employed (such other exemplary sensing schemes are described elsewhere herein). 
     As discussed above with reference to FIG. 1, one or more of fibers  7  measures light source  11 , which may be through a neutral density filter, which serves to reduce the intensity of the received light in order to maintain the intensity roughly in the range of the other received light intensities. A number of fibers  7  also are from perimeter receiver fiber optics R 1  to R 3  (see, e.g., FIG. 2) and also may pass through neutral density filters. Such receiving fibers  7  serve to provide data from which angle/height information and/or surface characteristics may be determined. 
     The remaining twelve fibers (of the illustrated embodiment&#39;s total of 16 fibers) of fibers  7  pass through color filters and are used to produce the color measurement. In an embodiment, the color filters are Kodak Sharp Cutting Wratten Gelatin Filters, which pass light with wavelengths greater than the cut-off value of the filter (i.e., redish values), and absorb light with wavelengths less than the cut-off value of the filter (i.e., bluish values). “Sharp Cutting” filters are available in a wide variety of cut-off frequencies/wavelengths, and the cut-off values generally may be selected by proper selection of the desired cut-off filter. In an embodiment, the filter cut-off values are chosen to cover the entire visible spectrum and, in general, to have band spacings of approximately the visible band range (or other desired range) divided by the number of receivers/filters. As an example, 700 nanometers minus 400 nanometers, divided by 11 bands (produced by twelve color receivers/sensors), is roughly 30 nanometer band spacing. 
     With an array of cut-off filters as described above, and without being bound by theory or the specific embodiments described herein, the received optical spectrum may be measured/calculated by subtracting the light intensities of “adjacent” color receivers. For example, band  1  (400 nm to 430 nm)=(intensity of receiver  12 ) minus (intensity of receiver  11 ), and so on for the remaining bands. Such an array of cut-off filters, and the intensity values that may result from filtering with such an array, are more fully described in connection with FIGS. 13A to  14 B. 
     It should be noted here that in alternate embodiments other color filter arrangements are utilized. For example, “notch” or bandpass filters may be utilized, such as may be developed using Schott glass-type filters (whether constructed from separate longpass/shortpass filters or otherwise) or notch interference filters such as those manufactured by Corion, etc. 
     In a preferred embodiment of the present invention, the specific characteristics of the light source, filters, sensors and fiber optics, etc., are normalized/calibrated by directing the probe towards, and measuring, a known color standard. Such normalization/calibration may be performed by placing the probe in a suitable fixture, with the probe directed from a predetermined position (i.e., height and angle) from the known color standard. Such measured normalization/calibration data may be stored, for example, in a look-up table, and used by microprocessor  10  to normalize or correct measured color or other data. Such procedures may be conducted at start-up, at regular periodic intervals, or by operator command, etc. In particular embodiments, a large number of measurements may be taken on materials of particular characteristics and processed and/or statistically analyzed or the like, with data representing or derived from such measurements stored in memory (such as a look-up table or polynomial or other coefficients, etc.). Thereafter, based upon measurements of an object taken in accordance with the present invention, comparisons may be made with the stored data and assessments of the measured object made or predicted. In one illustrative example, an assessment or prediction may be made of whether the object is wet or dry (having water or other liquid on its surface, wet paint, etc.) based on measurements in accordance with the present invention. In yet another illustrative example, an assessment or prediction of the characteristics of an underlying material, such as the pulpal tissue within a tooth may be made. Such capabilities may be further enhanced by comparisons with measurements taken of the object at an earlier time, such as data taken of the tooth or other object at one or more earlier points in time. Such comparisons based on such historical data and/or stored data may allow highly useful assessments or predictions of the current or projected condition or status of the tooth, tissue or other object, etc. Many other industrial uses of such surface and subsurface assessment/prediction capabilities are possible. 
     What should be noted from the above description is that the receiving and sensing fiber optics and circuitry illustrated in FIG. 3 provide a practical and expedient way to determine the color and other optical or other characteristics by measuring the intensity of the light reflected from the surface of the object being measured. 
     It also should be noted that such a system measures the spectral band of the reflected light from the object, and once measured such spectral data may be utilized in a variety of ways. For example, such spectral data may be displayed directly as intensity-wavelength band values. In addition, tristimulus type values may be readily computed (through, for example, conventional matrix math), as may any other desired color values. In one particular embodiment useful in dental applications (such as for dental prostheses), the color data is output in the form of a closest match or matches of dental shade guide value(s). In a preferred embodiment, various existing shade guides (such as the shade guides produced by Vita Zahnfabrik) are characterized and stored in a look-up table, or in the graphics art industry Pantone color references, and the color measurement data are used to select the closest shade guide value or values, which may be accompanied by a confidence level or other suitable factor indicating the degree of closeness of the match or matches, including, for example, what are known as ΔE values or ranges of ΔE values, or criteria based on standard deviations, such as standard deviation minimization. In still other embodiments, the color measurement data are used (such as with look-up tables) to select materials for the composition of paint or ceramics such as for prosthetic teeth. There are many other uses of such spectral data measured in accordance with the present invention. 
     It is known that certain objects such as human teeth may fluoresce, and such optical characteristics also may be measured in accordance with the present invention. A light source with an ultraviolet component may be used to produce more accurate color/optical data with respect to such objects. Such data may be utilized to adjust the amounts and or proportions or types of dental fluorescing materials in dental restorations or prosthesis. In certain embodiments, a tungsten/halogen source (such as used in a preferred embodiment) may be combined with a UV light source (such as a mercury vapor, xenon or other fluorescent light source, etc.) to produce a light output capable of causing the object to fluoresce. Alternately, a separate UV light source, combined with a visible-light-blocking filter, may be used to illuminate the object. Such a UV light source may be combined with light from a red LED (for example) in order to provide a visual indication of when the UV light is on and also to serve as an aid for the directional positioning of the probe operating with such a light source. A second measurement may be taken using the UV light source in a manner analogous to that described earlier, with the band of the red LED or other supplemental light source being ignored. The second measurement may thus be used to produce an indication of the fluorescence of the tooth or other object being measured. With such a UV light source, a silica fiber optic (or other suitable material) typically would be required to transmit the light to the object (standard fiber optic materials such as glass and plastic in general do not propagate UV light in a desired manner, etc.). 
     As described earlier, in certain preferred embodiments the present invention utilizes a plurality of perimeter receiver fiber optics spaced apart from and around a central source fiber optic to measure color and determine information regarding the height and angle of the probe with respect to the surface of the object being measured, which may include other surface characteristic information, etc. Without being bound by theory, certain principles underlying certain aspects of the present invention will now be described with reference to FIGS. 4A to  4 C. 
     FIG. 4A illustrates a typical step index fiber optic consisting of a core and a cladding. For this discussion, it is assumed that the core has an index of refraction of n 0  and the cladding has an index of refraction of n 1 . Although the following discussion is directed to “step index” fibers, it will be appreciated by those of skill in the art that such discussion generally is applicable for gradient index fibers as well. 
     In order to propagate light without loss, the light must be incident within the core of the fiber optic at an angle greater than the critical angle, which may be represented as Sin  −1 {n 1 /n 0 }, where n 0  is the index of refraction of the core and n 1  is the index of refraction of the cladding. Thus, all light must enter the fiber at an acceptance angle equal to or less than phi, with phi=2×Sin −1 {(n 0   2 −n 1   2 )}, or it will not be propagated in a desired manner. 
     For light entering a fiber optic, it must enter within the acceptance angle phi. Similarly, when the light exits a fiber optic, it will exit the fiber optic within a cone of angle phi as illustrated in FIG.  4 A. The value (n 0   2 −n 1   2 ) is referred to as the aperture of the fiber optic. For example, a typical fiber optic may have an aperture of 0.5, and an acceptance angle of 60°. 
     Consider using a fiber optic as a light source. One end is illuminated by a light source (such as light source  11  of FIG.  1 ), and the other is held near a surface. The fiber optic will emit a cone of light as illustrated in FIG.  4 A. If the fiber optic is held perpendicular to a surface it will create a circular light pattern on the surface. As the fiber optic is raised, the radius r of the circle will increase. As the fiber optic is lowered, the radius of the light pattern will decrease. Thus, the intensity of the light (light energy per unit area) in the illuminated circular area will increase as the fiber optic is lowered and will decrease as the fiber optic is raised. 
     The same principle generally is true for a fiber optic being utilized as a receiver. Consider mounting a light sensor on one end of a fiber optic and holding the other end near an illuminated surface. The fiber optic can only propagate light without loss when the light entering the fiber optic is incident on the end of the fiber optic near the surface if the light enters the fiber optic within its acceptance angle phi. A fiber optic utilized as a light receiver near a surface will only accept and propagate light from the circular area of radius r on the surface. As the fiber optic is raised from the surface, the area increases. As the fiber optic is lowered to the surface, the area decreases. 
     Consider two fiber optics parallel to each other as illustrated in FIG.  4 B. For simplicity of discussion, the two fiber optics illustrated are identical in size and aperture. The following discussion, however, generally would be applicable for fiber optics that differ in size and aperture. One fiber optic is a source fiber optic, the other fiber optic is a receiver fiber optic. As the two fiber optics are held perpendicular to a surface, the source fiber optic emits a cone of light that illuminates a circular area of radius r. The receiver fiber optic can only accept light that is within its acceptance angle phi, or only light that is received within a cone of angle phi. If the only light available is that emitted by the source fiber optic, then the only light that can be accepted by the receiver fiber optic is the light that strikes the surface at the intersection of the two circles as illustrated in FIG.  4 C. As the two fiber optics are lifted from the surface, the proportion of the intersection of the two circular areas relative to the circular area of the source fiber optic increases. As they near the surface, the proportion of the intersection of the two circular areas to the circular area of the source fiber optic decreases. If the fiber optics are held too close to the surface (i.e., at or below a “critical height” h c ), the circular areas will no longer intersect and no light emitted from the source fiber optic will be received by the receiver fiber optic. 
     As discussed earlier, the intensity of the light in the circular area illuminated by the source fiber increases as the fiber is lowered to the surface. The intersection of the two cones, however, decreases as the fiber optic pair is lowered. Thus, as the fiber optic pair is lowered to a surface, the total intensity of light received by the receiver fiber optic increases to a maximal value, and then decreases sharply as the fiber optic pair is lowered still further to the surface. Eventually, the intensity will decrease essentially to zero at or below the critical height h c  (assuming the object being measured is not translucent, as described more fully herein), and will remain essentially zero until the fiber optic pair is in contact with the surface. Thus, as a source-receiver pair of fiber optics as described above are positioned near a surface and as their height is varied, the intensity of light received by the receiver fiber optic reaches a maximal value at a peaking or “peaking height” h p . 
     Again without being bound by theory, an interesting property of the peaking height h p  has been observed. The peaking height h p  is a function primarily of the geometry of fixed parameters, such as fiber apertures, fiber diameters and fiber spacing. Since the receiver fiber optic in the illustrated arrangement is only detecting a maximum value and not attempting to quantify the value, its maximum in general is independent of the surface color. It is only necessary that the surface reflect sufficient light from the intersecting area of the source and receiver fiber optics to be within the detection range of the receiver fiber optic light sensor. Thus, in general red or green or blue or any color surface will all exhibit a maximum at the same peaking height h p . 
     Although the above discussion has focused on two fiber optics perpendicular to a surface, similar analysis is applicable for fiber optic pairs at other angles. When a fiber optic is not perpendicular to a surface, it generally illuminates an elliptical area. Similarly, the acceptance area of a receiver fiber optic generally becomes elliptical. As the fiber optic pair is moved closer to the surface, the receiver fiber optic also will detect a maximal value at a peaking height independent of the surface color or characteristics. The maximal intensity value measured when the fiber optic pair is not perpendicular to the surface, however, will be less than the maximal intensity value measured when the fiber optic pair is perpendicular to the surface. 
     Referring now to FIGS. 5A and 5B, the intensity of light received as a fiber optic source-receiver pair is moved to and from a surface will now be described. FIG. 5A illustrates the intensity of the received light as a function of time. Corresponding FIG. 5B illustrates the height of the fiber optic pair from the surface of the object being measured. FIGS. 5A and 5B illustrate (for ease of discussion) a relatively uniform rate of motion of the fiber optic pair to and from the surface of the object being measured (although similar illustrations/analysis would be applicable for non-uniform rates as well). 
     FIG. 5A illustrates the intensity of received light as the fiber optic pair is moved to and then from a surface. While FIG. 5A illustrates the intensity relationship for a single receiver fiber optic, similar intensity relationships would be expected to be observed for other receiver fiber optics, such as, for example, the multiple receiver fiber optics of FIGS. 1 and 2. In general with the preferred embodiment described above, all fifteen fiber optic receivers (of fibers  7 ) will exhibit curves similar to that illustrated in FIG.  5 A. 
     FIG. 5A illustrates five regions. In region  1 , the probe is moved towards the surface of the object being measured, which causes the received light intensity to increase. In region  2 , the probe is moved past the peaking height, and the received light intensity peaks and then falls off sharply. In region  3 , the probe essentially is in contact with the surface of the object being measured. As illustrated, the received intensity in region  3  will vary depending upon the translucence of the object being measured. If the object is opaque, the received light intensity will be very low, or almost zero (perhaps out of range of the sensing circuitry). If the object is translucent, however, the light intensity will be quite high, but in general should be less than the peak value. In region  4 , the probe is lifted and the light intensity rises sharply to a maximum value. In region  5 , the probe is lifted further away from the object, and the light intensity decreases again. 
     As illustrated, two peak intensity values (discussed as P 1  and P 2  below) should be detected as the fiber optic pair moves to and from the object at the peaking height h p . If peaks P 1  and P 2  produced by a receiver fiber optic are the same value, this generally is an indication that the probe has been moved to and from the surface of the object to be measured in a consistent manner. If peaks P 1  and P 2  are of different values, then these may be an indication that the probe was not moved to and from the surface of the object in a desired manner, or that the surface is curved or textured, as described more fully herein. In such a case, the data may be considered suspect and rejected. In addition, peaks P 1  and P 2  for each of the perimeter fiber optics (see, e.g., FIG. 2) should occur at the same height (assuming the geometric attributes of the perimeter fiber optics, such as aperture, diameter and spacing from the source fiber optic, etc.). Thus, the perimeter fiber optics of a probe moved in a consistent, perpendicular manner to and from the surface of the object being measured should have peaks P 1  and P 2  that occur at the same height. Monitoring receiver fibers from the perimeter receiver fiber optics and looking for simultaneous (or near simultaneous, e.g., within a predetermined range) peaks P 1  and P 2  provides a mechanism for determining if the probe is held at a desired perpendicular angle with respect to the object being measured. 
     In addition, the relative intensity level in region  3  serves as an indication of the level of translucency of the object being measured. Again, such principles generally are applicable to the totality of receiver fiber optics in the probe (see, e.g., fibers  7  of FIGS.  1  and  3 ). Based on such principles, measurement techniques that may be applicable with respect to embodiments disclosed herein will now be described. 
     FIG. 6 is a flow chart illustrating a general measuring technique that may be used in accordance with certain embodiments of the present invention. Step  49  indicates the start or beginning of a color/optical measurement. During step  49 , any equipment initialization, diagnostic or setup procedures may be performed. Audio or visual information or other indicia may be given to the operator to inform the operator that the system is available and ready to take a measurement. Initiation of the color/optical measurement commences by the operator moving the probe towards the object to be measured, and may be accompanied by, for example, activation of switch  17  (see FIG.  1 ). 
     In step  50 , the system on a continuing basis monitors the intensity levels for the receiver fiber optics (see, e.g., fibers  7  of FIG.  1 ). If the intensity is rising, step  50  is repeated until a peak is detected. If a peak is detected, the process proceeds to step  52 . In step  52 , measured peak intensity P 1 , and the time at which such peak occurred, are stored in memory (such as in memory included as a part of microprocessor  10 ), and the process proceeds to step  54 . In step  54 , the system continues to monitor the intensity levels of the receiver fiber optics. If the intensity is falling, step  54  is repeated. If a “valley” or plateau is detected (i.e., the intensity is no longer falling, which generally indicates contact or near contact with the object), then the process proceeds to step  56 . In step  56 , the measured surface intensity (IS) is stored in memory, and the process proceeds to step  58 . In step  58 , the system continues to monitor the intensity levels of the receiver fibers. If the intensity is rising, step  58  is repeated until a peak is detected. If a peak is detected, the process proceeds to step  60 . In step  60 , measured peak intensity P 2 , and the time at which such peak occurred, are stored in memory, and the process proceeds to step  62 . In step  62 , the system continues to monitor the intensity levels of the receiver fiber optics. Once the received intensity levels begin to fall from peak P 2 , the system perceives that region  5  has been entered (see, e.g., FIG.  5 A), and the process proceeds to step  64 . 
     In step  64 , the system, under control of microprocessor  10 , may analyze the collected data taken by the sensing circuitry for the various receiver fiber optics. In step  64 , peaks P 1  and P 2  of one or more of the various fiber optics may be compared. If any of peaks P 1  and P 2  for any of the various receiver fiber optics have unequal peak values, then the data may be rejected, and the entire color measuring process repeated. Again, unequal values of peaks P 1  and P 2  may be indicative, for example, that the probe was moved in a non-perpendicular or otherwise unstable manner (i.e., angular or lateral movement), and, for example, peak P 1  may be representative of a first point on the object, while peak P 2  may be representative of a second point on the object. As the data is suspect, in a preferred embodiment of the present invention, data taken in such circumstances are rejected in step  64 . 
     If the data are not rejected in step  64 , the process proceeds to step  66 . In step  66 , the system analyzes the data taken from the neutral-density-filtered receivers from each of the perimeter fiber optics (e.g., R 1  to R 3  of FIG.  2 ). If the peaks of the perimeter fiber optics did not occur at or about the same point in time, this may be indicative, for example, that the probe was not held perpendicular to the surface of the object being measured. As non-perpendicular alignment of the probe with the surface of the object being measured may cause suspect results, in a preferred embodiment of the present invention, data taken in such circumstances are rejected in step  66 . In one preferred embodiment, detection of simultaneous or near simultaneous peaking (peaking within a predetermined range of time) serves as an acceptance criterion for the data, as perpendicular alignment generally is indicated by simultaneous or near simultaneous peaking of the perimeter fiber optics. In other embodiments, step  66  includes an analysis of peak values P 1  and P 2  of the perimeter fiber optics. In such embodiments, the system seeks to determine if the peak values of the perimeter fiber optics (perhaps normalized with any initial calibration data) are equal within a defined range. If the peak values of the perimeter fiber optics are within the defined range, the data may be accepted, and if not, the data may be rejected. In still other embodiments, a combination of simultaneous peaking and equal value detection are used as acceptance/rejection criteria for the data, and/or the operator may have the ability (such as through key pad switches  12 ) to control one or more of the acceptance criteria ranges. With such capability, the sensitivity of the system may be controllably altered by the operator depending upon the particular application and operative environment, etc. 
     If the data are not rejected in step  66 , the process proceeds to step  68 . In step  68 , the color data may be processed in a desired manner to produce output color/optical measurement data. For example, such data may be normalized in some manner, or adjusted based on temperature compensation, or translucency data, or gloss data or surface texture data or non-perpendicular angle data other data detected by the system. The data also may be converted to different display or other formats, depending on the intended use of the data. In addition, the data indicative of the translucence of the object and/or glossiness of the object also may be quantified and/or displayed in step  68 . After step  68 , the process may proceed to starting step  49 , or the process may be terminated, etc. As indicated previously, such data also may be compared with previously-stored data for purposes of making assessments or predictions, etc., of a current or future condition or status. 
     In accordance with the process illustrated in FIG. 6, three light intensity values (P 1 , P 2  and IS) are stored per receiver fiber optic to make color and translucency, etc., measurements. If stored peak values P 1  and P 2  are not equal (for some or all of the receivers), this is an indication that the probe was not held steady over one area, and the data may be rejected (in other embodiments, the data may not be rejected, although the resulting data may be used to produce an average of the measured data). In addition, peak values P 1  and P 2  for the three neutral density perimeter fiber optics should be equal or approximately equal; if this is not the case, then this is an indication that the probe was not held perpendicular or a curved surface is being measured. In other embodiments, the system attempts to compensate for curved surfaces and/or non-perpendicular angles. In any event, if the system cannot make a color/optical measurement, or if the data is rejected because peak values P 1  and P 2  are unequal to an unacceptable degree or for some other reason, then the operator is notified so that another measurement or other action may be taken (such as adjust the sensitivity). 
     With a system constructed and operating as described above, color/optical measurements may be taken of an object, with accepted data having height and angular dependencies removed. Data not taken at the peaking height, or data not taken with the probe perpendicular to the surface of the object being measured, etc., are rejected in certain embodiments. In other embodiments, data received from the perimeter fiber optics may be used to calculate the angle of the probe with respect to the surface of the object being measured, and in such embodiments non-perpendicular or curved surface data may be compensated instead of rejected. It also should be noted that peak values P 1  and P 2  for the neutral density perimeter fiber optics provide a measurement of the luminance (gray value) of the surface of the object being measured, and also may serve to quantify the color value. 
     The translucency of the object being measured may be quantified as a ratio or percentage, such as, for example, (IS/P 1 )×100%. In other embodiments, other methods of quantifying translucency data provided in accordance with the present invention are utilized, such as some other arithmetic function utilizing IS and P 1  or P 2 , etc. Translucence information, as would be known to those in the art, could be used to quantify and/or adjust the output color data, etc. 
     In another particular aspect of the present invention, data generated in accordance with the present invention may be used to implement an automated material mixing/generation machine and/or method. Certain objects/materials, such as dental prostheses or fillings, are made from porcelain or other powders/resins/materials or tissue substitutes that may be combined in the correct ratios or modified with additives to form the desired color of the object/prosthesis. Certain powders often contain pigments that generally obey Beer&#39;s law and/or act in accordance with Kubelka-Munk equations and/or Saunderson equations (if needed) when mixed in a recipe. Color and other data taken from a measurement in accordance with the present invention may be used to determine or predict desired quantities of pigment or other materials for the recipe. Porcelain powders and other materials are available in different colors, opacities, etc. Certain objects, such as dental prostheses, may be layered to simulate the degree of translucency of the desired object (such as to simulate a human tooth). Data generated in accordance with the present invention also may be used to determine the thickness and position of the porcelain or other material layers to more closely produce the desired color, translucency, surface characteristics, etc. In addition, based on fluorescence data for the desired object, the material recipe may be adjusted to include a desired quantity of fluorescing-type material. In yet other embodiments, surface characteristics (such as texture) information (as more fully described herein) may be used to add a texturing material to the recipe, all of which may be carried out in accordance with the present invention. In yet other embodiments, the degree of surface polish to the prosthesis may be monitored or adjusted, based on gloss data derived in accordance with the present invention. 
     For more information regarding such pigment-material recipe type technology, reference may be made to: “The Measurement of Appearance,” Second Edition, edited by Hunter and Harold, copyright 1987; “Principles of Color Technology,” by Billmeyer and Saltzman, copyright 1981; and “Pigment Handbook,” edited by Lewis, copyright 1988. All of the foregoing are believed to have been published by John Wiley &amp; Sons, Inc., New York, N.Y., and all of which are hereby incorporated by reference. 
     In certain operative environments, such as dental applications, contamination of the probe is of concern. In certain embodiments of the present invention, implements to reduce such contamination are provided. 
     FIGS. 7A and 7B illustrate a protective cap that may be used to fit over the end of probe tip  1 . Such a protective cap consists of body  80 , the end of which is covered by optical window  82 , which in a preferred embodiment consists of a structure having a thin sapphire window. In a preferred embodiment, body  80  consists of stainless steel. Body  80  fits over the end of probe tip  1  and may be held into place by, for example, indentations formed in body  80 , which fit with ribs  84  (which may be a spring clip or other retainer) formed on probe tip  1 . In other embodiments, other methods of affixing such a protective cap to probe tip  1  are utilized. The protective cap may be removed from probe tip  1  and sterilized in a typical autoclave, hot steam, chemiclave or other sterilizing system. 
     The thickness of the sapphire window should be less than the peaking height of the probe in order to preserve the ability to detect peaking in accordance with the present invention, and preferably has a thickness less than the critical height at which the source/receiver cones overlap (see FIGS.  4 B and  4 C). It also is believed that sapphire windows may be manufactured in a reproducible manner, and thus any light attenuation from one cap to another may be reproducible. In addition, any distortion of the color/optical measurements produced by the sapphire window may be calibrated out by microprocessor  10 . 
     Similarly, in other embodiments body  80  has a cap with a hole in the center (as opposed to a sapphire window), with the hole positioned over the fiber optic source/receivers The cap with the hole serves to prevent the probe from coming into contact with the surface, thereby reducing the risk of contamination. It should be noted that, with such embodiments, the hole is positioned so that the light from/to the light source/receiver elements of the probe tip is not adversely affected by the cap. 
     FIGS. 8A and 8B illustrate another embodiment of a removable probe tip that may be used to reduce contamination in accordance with the present invention. As illustrated in FIG. 8A, probe tip  88  is removable, and includes four (or a different number, depending upon the application) fiber optic connectors  90 , which are positioned within optical guard  92  coupled to connector  94 . Optical guard  92  serves to prevent “cross talk” between adjacent fiber optics. As illustrated in FIG. 8B, in this embodiment removable tip  88  is secured in probe tip housing  93  by way of spring clip  96  (other removable retaining implements are utilized in other embodiments). Probe tip housing  93  may be secured to base connector  95  by a screw or other conventional fitting. It should be noted that, with this embodiment, different size tips may be provided for different applications, and that an initial step of the process may be to install the properly-sized (or fitted tip) for the particular application. Removable tip  88  also may be sterilized in a typical autoclave, hot steam, chemiclave or other sterilizing system, or disposed of. In addition, the entire probe tip assembly is constructed so that it may be readily disassembled for cleaning or repair. In certain embodiments the light source/receiver elements of the removable tip are constructed of glass, silica or similar materials, thereby making them particularly suitable for autoclave or similar high temperature/pressure cleaning methods, which in certain other embodiments the light source/receiver elements of the removable tip are constructed of plastic or other similar materials, which may be of lower cost, thereby making them particularly suitable for disposable-type removable tips, etc. 
     In still other embodiments, a plastic, paper or other type shield (which may be disposable, cleanable/reusable or the like) may be used in order to address any contamination concerns that may exist in the particular application. In such embodiments, the methodology may include positioning such a shield over the probe tip prior to taking color/optical measurements, and may include removing and disposing/cleaning the shield after taking color/optical measurements, etc. 
     A further embodiment of the present invention utilizing an alternate removable probe tip will now be described with reference to FIGS. 23A-23C. As illustrated in FIG. 23A, this embodiment utilizes removable, coherent light conduit  340  as a removable tip. Light conduit  340  is a short segment of a light conduit that preferably may be a fused bundle of small fiber optics, in which the fibers are held essentially parallel to each other, and the ends of which are highly polished. Cross-section  350  of light conduit  340  is illustrated in FIG.  23 B. Light conduits similar to light conduit  340  have been utilized in what are known as borescopes, and also have been utilized in medical applications such as endoscopes. 
     Light conduit  340  in this embodiment serves to conduct light from the light source to the surface of the object being measured, and also to receive reflected light from the surface and conduct it to light receiver fiber optics  346  in probe handle  344 . Light conduit  340  is held in position with respect to fiber optics  346  by way or compression jaws  342  or other suitable fitting or coupled that reliably positions light conduit  340  so as to couple light effectively to/from fiber optics  346 . Fiber optics  346  may be separated into separate fibers/light conduits  348 , which may be coupled to appropriate light sensors, etc., as with previously described embodiments. 
     In general, the aperture of the fiber optics used in light conduit  340  may be chosen to match the aperture of the fiber optics for the light source and the light receivers or alternately the light conduit aperture could be greater than or equal to the largest source or receiver aperture. Thus, the central part of the light conduit may conduct light from the light source and illuminate the surface as if it constituted a single fiber within a bundle of fibers. Similarly, the outer portion of the light conduit may receive reflected light and conduct it to light receiver fiber optics as if it constituted single fibers. Light conduit  340  has ends that preferably are highly polished and cut perpendicular, particularly the end coupling light to fiber optics  346 . Similarly, the end of fiber optics  346  abutting light conduit  340  also is highly polished and cut perpendicular to a high degree of accuracy in order to minimize light reflection and cross talk between the light source fiber optic and the light receiver fiber optics and between adjacent receiver fiber optics. Light conduit  340  offers significant advantages including in the manufacture and installation of such a removable tip. For example, the probe tip need not be particularly aligned with the probe tip holder; rather, it only needs to be held against the probe tip holder such as with a compression mechanism (such as with compression jaws  342 ) so as to couple light effectively to/from fiber optics  346 . Thus, such a removable tip mechanism may be implemented without alignment tabs or the like, thereby facilitating easy installation of the removable probe tip. Such an easy installable probe tip may thus be removed and cleaned prior to installation, thereby facilitating use of the color/optical measuring apparatus by dentists, medical professions or others working in an environment in which contamination may be a concern. Light conduit  340  also may be implemented, for example, as a small section of light conduit, which may facilitate easy and low cost mass production and the like. 
     A further embodiment of such a light conduit probe tip is illustrated as light conduit  352  in FIG.  23 C. Light conduit  352  is a light conduit that is narrower on one end (end  354 ) than the other end (end  356 ). Contoured/tapered light conduits such as light conduit  352  may be fabricated by heating and stretching a bundle of small fiber optics as part of the fusing process. Such light conduits have an additional interesting property of magnification or reduction. Such phenomena result because there are the same number of fibers in both ends. Thus, light entering narrow end  354  is conducted to wider end  356 , and since wider end  356  covers a larger area, it has a magnifying affect. 
     Light conduit  352  of FIG. 23C may be utilized in a manner similar to light conduit  340  (which in general may be cylindrical) of FIG.  23 A. Light conduit  352 , however, measures smaller areas because of its reduced size at end  354 . Thus, a relatively larger probe body may be manufactured where the source fiber optic is spaced widely from the receiver fiber optics, which may provide an advantage in reduced light reflection and cross talk at the junction, while still maintaining a small probe measuring area. Additionally, the relative sizes of narrow end  354  of light conduit  352  may be varied. This enables the operator to select the size/characteristic of the removable probe tip according to the conditions in the particular application. Such ability to select sizes of probe tips provides a further advantage in making optical characteristics measurements in a variety of applications and operative environments. 
     As should be apparent to those skilled in the art in view of the disclosures herein, light conduits  340  and  356  of FIGS. 23A and 23C need not necessarily be cylindrical/tapered as illustrated, but may be curved such as for specialty applications, in which a curved probe tip may be advantageously employed (such as in a confined or hard-to-reach place). It also should be apparent that light conduit  352  of FIG. 23C may be reversed (with narrow end  354  coupling light into fiber optics  346 , etc., and wide end  356  positioned in order to take measurements) in order to cover larger areas. 
     With reference to FIG. 9, a tristimulus embodiment will now be described, which may aid in the understanding of, or may be used in conjunction with, certain embodiments disclosed herein. In general, the overall system depicted in FIG.  1  and discussed in detail elsewhere herein may be used with this embodiment. FIG. 9 illustrates a cross section of the probe tip fiber optics used in this embodiment. 
     Probe tip  100  includes central source fiber optic  106 , surrounded by (and spaced apart from) three perimeter receiver fiber optics  104  and three color receiver fiber optics  102 . Three perimeter receiver fiber optics  104  are optically coupled to neutral density filters and serve as height/angle sensors in a manner analogous to the embodiment describe above. Three color receiver fiber optics are optically coupled to suitable tristimulus filters, such as red, green and blue filters. With this embodiment, a measurement may be made of tristimulus color values of the object, and the process described with reference to FIG. 6 generally is applicable to this embodiment. In particular, perimeter fiber optics  104  may be used to detect simultaneous peaking or otherwise whether the probe is perpendicular to the object being measured. 
     FIG. 10A illustrates another such embodiment, similar to the embodiment discussed with reference to FIG.  9 . Probe tip  100  includes central source fiber optic  106 , surrounded by (and spaced apart from) three perimeter receiver fiber optics  104  and a plurality of color receiver fiber optics  102 . The number of color receiver fiber optics  102 , and the filters associated with such receiver fiber optics  102 , may be chosen based upon the particular application. As with the embodiment of FIG. 9, the process described with reference to FIG. 6 generally is applicable to this embodiment. 
     FIG. 10B illustrates another such embodiment in which there are a plurality of receiver fiber optics that surround central source fiber optic  240 . The receiver fiber optics are arranged in rings surrounding the central source fiber optic. FIG. 10B illustrates three rings of receiver fiber optics (consisting of fiber optics  242 ,  244  and  246 , respectively), in which there are six receiver fiber optics per ring. The rings may be arranged in successive larger circles as illustrated to cover the entire area of the end of the probe, with the distance from each receiver fiber optic within a given ring to the central fiber optic being equal (or approximately so). Central fiber optic  240  is utilized as the light source fiber optic and is connected to the light source in a manner similar to light source fiber optic  5  illustrated in FIG.  1 . 
     The plurality of receiver fiber optics are each coupled to two or more fiber optics in a manner similar to the arrangement illustrated in FIG. 1 for splicing connector  4 . One fiber optic from such a splicing connector for each receiver fiber optic passes through a neutral density filter and then to light sensor circuitry similar to the light sensor circuitry illustrated in FIG. 3. A second fiber optic from the splicing connector per receiver fiber optic passes through a Sharp Cutting Wrattan Gelatin Filter (or notch filter as previously described) and then to light sensor circuitry as discussed elsewhere herein. Thus, each of the receiver fiber optics in the probe tip includes both color measuring elements and neutral light measuring or “perimeter” elements. 
     FIG. 10D illustrates the geometry of probe  260  (such as described above) illuminating an area on flat diffuse surface  272 . Prob reflected light that is incident upon the receiving elements in the probe will be equal (or nearly equal) for all elements if the probe is perpendicular to the surface as described above herein. 
     FIG. 10C illustrates a probe illuminating rough surface  268  or a surface that reflects light unevenly. The reflected light will exhibit hot spots or regions  266  where the reflected light intensity is considerably greater than it is on other areas  264 . The reflected light pattern will be uneven when compared to a smooth surface as illustrate in FIG.  10 D. 
     Since a probe as illustrated in FIG. 10B has a plurality of receiver fiber optics arranged over a large surface area, the probe may be utilized to determine the surface texture of the surface as well as being able to measure the color and translucency, etc., of the surface as described earlier herein. If the light intensity received by the receiver fiber optics is equal for all fiber optics within a given ring of receiver fiber optics, then generally the surface is smooth. If, however, the light intensity of receiver fibers in a ring varies with respect to each other, then generally the surface is rough. By comparing the light intensities measured within receiver fiber optics in a given ring and from ring to ring, the texture and other characteristics of the surface may be quantified. 
     FIG. 11 illustrates an embodiment of the present invention in which linear optical sensors and a color gradient filter are utilized instead of light sensors  8  (and filters  22 , etc.). Receiver fiber optics  7 , which may be optically coupled to probe tip  1  as with the embodiment of FIG. 1, are optically coupled to linear optical sensor  112  through color gradient filter  110 . In this embodiment, color gradient filter  110  may consist of series of narrow strips of cut-off type filters on a transparent or open substrate, which are constructed so as to positionally correspond to the sensor areas of linear optical sensor  112 . An example of a commercially available linear optical sensor  112  is Texas Instruments part number TSL213, which has 61 photo diodes in a linear array. Light receiver fiber optics  7  are arranged correspondingly in a line over linear optical sensor  112 . The number of receiver fiber optics may be chosen for the particular application, so long as enough are included to more or less evenly cover the full length of color gradient filter  110 . With this embodiment, the light is received and output from receiver fiber optics  7 , and the light received by linear optical sensor  112  is integrated for a short period of time (determined by the light intensity, filter characteristics and desired accuracy). The output of linear array sensor  112  is digitized by ADC  114  and output to microprocessor  116  (which may the same processor as microprocessor  10  or another processor). 
     In general, with the embodiment of FIG. 11, perimeter receiver fiber optics may be used as with the embodiment of FIG. 1, and in general the process described with reference to FIG. 6 is applicable to this embodiment. 
     FIG. 12 illustrates an embodiment of the present invention in which a matrix optical sensor and a color filter grid are utilized instead of light sensors  8  (and filters  22 , etc.). Receiver fiber optics  7 , which may be optically coupled to probe tip  1  as with the embodiment of FIG. 1, are optically coupled to matrix optical sensor  122  through filter grid  120 . Filter grid  120  is a filter array consisting of a number of small colored spot filters that pass narrow bands of visible light. Light from receiver fiber optics  7  pass through corresponding filter spots to corresponding points on matrix optical sensor  122 . In this embodiment, matrix optical sensor  122  may be a monochrome optical sensor array, such as CCD-type or other type of light sensor element such as may be used in a video camera. The output of matrix optical sensor  122  is digitized by ADC  124  and output to microprocessor  126  (which may the same processor as microprocessor  10  or another processor). Under control of microprocessor  126 , matrix optical sensor  126  collects data from receiver fiber optics  7  through color filter grid  120 . 
     In general, with the embodiment of FIG. 12, perimeter receiver fiber optics may be used as with the embodiment of FIG. 1, and in general the process described with reference to FIG. 6 also is applicable to this embodiment. 
     In general with the embodiments of FIGS. 11 and 12, the color filter grid may consist of sharp cut off filters as described earlier or it may consist of notch filters. As will be apparent to one skilled in the art, they may also be constructed of a diffraction grating and focusing mirrors such as those utilized in conventional monochromators. 
     As will be clear from the foregoing description, with the present invention a variety of types of spectral color/optical photometers (or tristimulus-type colorimeters) may be constructed, with perimeter receiver fiber optics used to collect color/optical data essentially free from height and angular deviations. In addition, in certain embodiments, the present invention enables color/optical measurements to be taken at a peaking height from the surface of the object being measured, and thus color/optical data may be taken without physical contact with the object being measured (in such embodiments, the color/optical data is taken only by passing the probe through region  1  and into region  2 , but without necessarily going into region  3  of FIGS.  5 A and  5 B). Such embodiments may be utilized if contact with the surface is undesirable in a particular application. In the embodiments described earlier, however, physical contact (or near physical contact) of the probe with the object may allow all five regions of FIGS. 5A and 5B to be utilized, thereby enabling measurements to be taken such that translucency information also may be obtained. Both types of embodiments generally are within the scope of the invention described herein. 
     Additional description will now be provided with respect to cut-off filters of the type described in connection with the preferred embodiment(s) of FIGS. 1 and 3 (such as filters  22  of FIG.  3 ). FIG. 13A illustrates the properties of a single Kodak Sharp Cutting Wratten Gelatin Filter discussed in connection with FIG.  3 . Such a cut-off filter passes light below a cut-off frequency (i.e., above a cut-off wavelength). Such filters may be manufactured to have a wide range of cut-off frequencies/wavelengths. FIG. 13B illustrates a number of such filters, twelve in a preferred embodiment, with cut-off frequencies/wavelengths chosen so that essentially the entire visible band is covered by the collection of cut-off filters. 
     FIGS. 14A and 14B illustrate exemplary intensity measurements using a cut-off filter arrangement such as illustrated in FIG. 13B, first in the case of a white surface being measured (FIG.  14 A), and also in the case of a blue surface being measured (FIG.  14 B). As illustrated in FIG. 14A, in the case of a white surface, the neutrally filtered perimeter fiber optics, which are used to detect height and angle, etc., generally will produce the highest intensity (although this depends at least in part upon the characteristics of the neutral density filters). As a result of the stepped cut-off filtering provided by filters having the characteristics illustrated in FIG. 13B, the remaining intensities will gradually decrease in value as illustrated in FIG.  14 A. In the case of a blue surface, the intensities will decrease in value generally as illustrated in FIG.  14 B. Regardless of the surface, however, the intensities out of the filters will always decrease in value as illustrated, with the greatest intensity value being the output of the filter having the lowest wavelength cut-off value (i.e., passes all visible light up to blue), and the lowest intensity value being the output of the filter having the highest wavelength cut-off (i.e., passes only red visible light). As will be understood from the foregoing description, any color data detected that does not fit the decreasing intensity profiles of FIGS. 14A and 14B may be detected as an abnormality, and in certain embodiments detection of such a condition results in data rejection, generation of an error message or initiation of a diagnostic routine, etc. 
     Reference should be made to the FIGS. 1 and 3 and the related description for a detailed discussion of how such a cut-off filter arrangement may be utilized in accordance with the present invention. 
     FIG. 15 is a flow chart illustrating audio tones that may be used in certain preferred embodiments of the present invention. It has been discovered that audio tones (such as tones, beeps, voice or the like such as will be described) present a particularly useful and instructive means to guide an operator in the proper use of a color measuring system of the type described herein. 
     The operator may initiate a color/optical measurement by activation of a switch (such as switch  17  of FIG. 1) at step  150 . Thereafter, if the system is ready (set-up, initialized, calibrated, etc.), a lower-the-probe tone is emitted (such as through speaker  16  of FIG. 1) at step  152 . The system attempts to detect peak intensity P 1  at step  154 . If a peak is detected, at step  156  a determination is made whether the measured peak P 1  meets the applicable criteria (such as discussed above in connection with FIGS. 5A,  5 B and  6 ). If the measured peak P 1  is accepted, a first peak acceptance tone is generated at step  160 . If the measured peak P 1  is not accepted, an unsuccessful tone is generated at step  158 , and the system may await the operator to initiate a further color/optical measurement. Assuming that the first peak was accepted, the system attempts to detect peak intensity P 2  at step  162 . If a second peak is detected, at step  164  a determination is made whether the measured peak P 2  meets the applicable criteria. If the measured peak P 2  is accepted the process proceeds to color calculation step  166  (in other embodiments, a second peak acceptance tone also is generated at step  166 ). If the measured peak P 2  is not accepted, an unsuccessful tone is generated at step  158 , and the system may await the operator to initiate a further color/optical measurement. Assuming that the second peak was accepted, a color/optical calculation is made at step  166  (such as, for example, microprocessor  10  of FIG. 1 processing the data output from light sensors  8 , etc.). At step  168 , a determination is made whether the color calculation meets the applicable criteria. If the color calculation is accepted, a successful tone is generated at step  170 . If the color calculation is not accepted, an unsuccessful tone is generated at step  158 , and the system may await the operator to initiate a further color/optical measurement. 
     With unique audio tones presented to an operator in accordance with the particular operating state of the system, the operator&#39;s use of the system may be greatly facilitated. Such audio information also tends to increase operator satisfaction and skill level, as, for example, acceptance tones provide positive and encouraging feedback when the system is operated in a desired manner. 
     The color/optical measuring systems and methods in accordance with the present invention may be applied to particular advantage in the field of dentistry, as will be more fully explained hereinafter. In particular the present invention includes the use of such systems and methods to measure the color and other attributes of a tooth in order to prepare a dental prosthesis or intraoral tooth-colored fillings, or to select denture teeth or to determine a suitable cement color for porcelain/resin prostheses. The present invention also provides methods for storing and organizing measured data such as in the form of a patient database. 
     FIG. 16A is a flow chart illustrating a general dental application process flow for use of the color/optical measuring systems and methods in accordance with the present invention. At step  200 , the color/optical measuring system may be powered-up and stabilized, with any required initialization or other setup routines performed. At step  200 , an indication of the system status may be provided to the operator, such as through LCD  14  or speaker  16  of FIG.  1 . Also at step  200 , the probe tip may be shielded or a clean probe tip may be inserted in order to reduce the likelihood of contamination (see, e.g., FIGS. 7A to  8 B and related description). In other embodiments, a plastic or other shield may also be used (which may be disposable, cleanable/reusable, etc., as previously described), so long as it is constructed and/or positioned so as to not adversely affect the measurement process. 
     At step  202 , the patient and the tooth to be measured are prepared. Any required cleaning or other tooth preparation would be performed at step  202 . Any required patient consultation about the type of prosthesis or area of a tooth to be matched would be performed at (or before) step  202 . In certain embodiments, a positioning device is prepared at step  202 , such as is illustrated in FIGS. 17A and 17B. In such embodiments, for example, a black or other suitably-colored material  282 , which may adhere to tooth  280  (such as with a suitable adhesive), is formed to have opening  281  larger than the diameter of the measuring probe, with opening  281  centered on the area of tooth  280  to be measured. The material of positioning device  282  is formed in a manner to fit on/over tooth  280  (such as over the incisal edge of tooth  280  and/or over one or more adjacent teeth) so that it may be placed on/over tooth  280  in a repeatable manner. Such a positioning device may serve to ensure that the desired area of tooth  280  is measured, and also allows for repeat measurements of the same area for purposes of confirmation, fluorescence measurement, or other optical measurement, or the like. Any other pre-measurement activities may be performed at (or before) step  202 . 
     At step  204 , the operator (typically a dentist or other dental professional) moves the probe towards the area of the tooth to be measured. This process preferably is conducted in accordance with the methodology described with reference to FIGS. 5A,  5 B and  6 , and preferably is accompanied by audio tones such as described with reference to FIG.  15 . With the present invention, the operator may obtain color and translucency data, etc., for example, from a desired area of the tooth to be measured. During step  204 , an accepted color/optical measurement is made, or some indication is given to the operator that the measurement step needs to be repeated or some other action taken. After an accepted color/optical measurement is made at step  204 , for example, the dentist may operate on the desired tooth or teeth or take other action. Before or after such action, additional measurements may be taken as needed (see, e.g., FIG.  18  and related description). 
     Upon successful completion of one or more measurements taken at step  204 , the process proceeds to step  206 . At step  206 , any data conversion or processing of data collected at step  204  may be performed. For example, in the embodiment of FIG. 1, detailed color spectrum and translucency information may be generated. In a particular dental application, however, it may be that a dental lab, for example, requires that the color be presented in Munsell format (i.e., chroma, hue and value), RGB values, XYZ coordinates, CIELAB values, Hunter values, or some other color data format. With the spectral/color information produced by the present invention, data may be converted to such formats through conventional math, for example. Such math may be performed by microprocessor  10  or computer  13 A of FIG. 1, or in some other manner. It also should be noted that, in certain embodiments, the data produced at step  204  in accordance with the present invention may be used directly without data conversion. In such embodiments, step  206  may be omitted. In other embodiments, step  206  consists of data formatting, such as preparing the data for reproduction in hard copy, pictorial or other form, or for transmission as facsimile or modem data. Finally, in certain embodiments a translucency factor is computed in a format suitable for the particular application. In yet other embodiments, a surface texture or detail factor is computed in a format suitable for the particular application. In yet other embodiments, a surface gloss factor is computed in a format suitable for the particular application. 
     At step  208 , a matching is optionally attempted between the data produced at steps  204  and  206  (if performed) and a desired color (in other embodiments, the process may proceed from  204  directly to  210 , or alternatively steps  206  and  208  may be combined). For example, a number of “shade guides” are available in the market, some of which are known in the industry as Vita shade guides, Bioform shade guides or other color matching standards, guides or references or custom shade guides. In certain preferred embodiments, a lookup table is prepared and loaded into memory (such as memory associated with microprocessor  10  or computer  13 A of FIG.  1 ), and an attempt is made to the closest match or matches of the collected data with the known shade guides, custom shade guides or reference values. In certain embodiments, a translucency factor and/or gloss factor and/or a surface texture or detail factor also is used in an effort to select the best possible match. 
     In a particular aspect of certain embodiments of the present invention, at step  208  a material correlation lookup table is accessed. Based on the color and translucency data obtained at step  204 , a proposed recipe of materials, pigments or other instruction information is prepared for a prosthesis or filling, etc., of the desired color and translucency, etc. With the detailed color and other information made available in accordance with the present invention, a direct correlation with the relevant constituent materials may be made. In still other embodiments, such information is made available to an automated mixing or manufacturing machine for preparation of prosthesis or material of the desired color and translucency, etc., as more fully described elsewhere herein. 
     At step  210 , based on the results of the preceding steps, the prosthesis, denture, intraoral tooth-colored filling material or other items are prepared. This step may be performed at a dental lab, or, in certain embodiments, at or near the dental operatory. For remote preparation, relevant data produced at steps  204 ,  206  and/or  208  may be sent to the remote lab or facility by hardcopy, facsimile or modem or other transmission. What should be understood from the foregoing is that, based on data collected at step  204 , a prosthesis may be prepared of a desirable color and/or other optical characteristic at step  210 . 
     At step  212 , the prosthesis or other material prepared at step  210  may be measured for confirmation purposes, again preferably conducted in accordance with the methodology described with reference to FIGS. 5A,  5 B and  6 , and preferably accompanied by audio tones such as described with reference to FIG. 15. A re-measure of the tooth in the patient&#39;s mouth, etc. also may be made at this step for confirmation purposes. If the confirmation process gives satisfactory results, the prosthesis, denture, composite filling or other material may be preliminarily installed or applied in the patient at step  214 . At step  216 , a re-measure of the prosthesis, denture, composite filling or other materials optionally may be made. If the results of step  216  are acceptable, then the prosthesis may be more permanently installed or applied in the patient at step  218 . If the results of step  216  are not acceptable, the prosthesis may be modified and/or other of the steps repeated as necessary in the particular situation. 
     With reference to FIG. 16B, a further embodiment of the present invention will be explained. With this embodiment, an instrument and method such as previously described may be advantageously utilized to prepare a tooth to receive a prosthesis. 
     A dental prosthesis such as a crown or a laminate has optical properties that are determined by a number of factors. Determining factors include the material of the prosthesis, along with the cement utilized to bond the prosthesis to the tooth and the underlying optical properties of the tooth itself. For example, in the preparation of a tooth for a laminate, the thickness of the laminate combined with the bonding cement and the color of the underlying prepared tooth all contribute to the final optical properties of the prosthesis. In order to prepare an optimum prosthesis such as from an esthetic standpoint, the dentist may need to prepare the tooth for the laminate by removing material from the tooth. The final desired esthetic color, shape and contours of the tooth determines the amount of material needed to be removed from the tooth, which determines the final thickness of the laminate, and in significant part may determine whether or not the final restoration will have a desired and esthetically pleasing result as compared to neighboring teeth. By measuring the color of the neighboring teeth, and by measuring the color of the underlying tooth being prepared for the laminate, the amount of tooth material to be removed, or the range of material that should be removed, may be determined and reported to the dentist as the tooth is being prepared. 
     At step  201 , the process is commenced. Any initial calibration or other preparatory steps may be undertaken. At step  203 , the dentist may measure the optical properties including color of one or more neighboring teeth. At step  205 , the dentist may measure the optical properties including color of the tooth receiving the prosthesis. At step  207 , a first amount of material to be removed is calculated or estimated (such as by microprocessor  10 , computer  13 A or other suitable computing device). The first amount is determined based on known color properties of the available laminates, the estimated thickness of the laminate, and the color of the tooth to receive the laminate. If, for example, the tooth to receive the laminate is dark to the degree that an esthetically pleasing laminate likely cannot be produced (based on the range of color/optical characteristics of the known available laminates), then an estimate is made of how much material should be removed such that a thicker laminate will result in a desired and esthetically pleasing result. At step  209  the dentist removes the first amount of material (or approximately such amount) from the tooth (using known removal techniques, etc.). At step  211 , the dentist may again measure the optical properties including color of the tooth receiving the prosthesis. At step  213 , a calculation or estimation is made (in a manner analogous to step  207 ) of whether additional material should be removed, and, if so, how much. At step  215 , if needed, additional material is removed, with steps  211 ,  213  and  215  repeated as necessary. In preferred embodiments, based on known/measured/empirical data analysis of color/optical properties of teeth, at steps such as steps  205  and  211 , a comparison or assessment may be made of whether the tooth being prepared is getting too near the pulp (such as by detection of a pink color, for example). Based on such threshold or other type criteria, the dentist may be alerted that further material should not be removed in order to minimize exposure of the pulp and damage of the tooth. At step  217 , if it is determined at step  213  that a desirable and esthetically pleasing laminate may be produced, such laminate preparation steps are conducted. 
     Similar steps could be taken in other industrial endeavors, such as painting or other finishes, etc. 
     In another particular aspect of the present invention, for example, data processing such as illustrated in FIG. 18 may be taken in conjunction with the processes of FIGS.  16 A and/or  16 B. At step  286 , client database software is run on a computing device, such as computer  13 A of FIG.  1 . Such software may include data records for each patient, including fields storing the history of dental services performed on the patient, information regarding the status or condition of the patient&#39;s teeth, billing, address and other information. Such software may enter a mode by which it is in condition to accept color or other data taken in accordance with the present invention. 
     At step  288 , for example, the dentist or other dental professional may select parameters for a particular tooth of the patient to be measured. Depending on the size and condition of the tooth (such as color gradient or the like), the dentist may sector the tooth into one or more regions, such as a grid. Thus, for example, in the case of tooth for which it is decided to take four measurements, the tooth may be sectored into four regions. Such parameters, which may include a pictorial representation on the computer of the tooth sectored into four regions (such as by grid lines), along with tooth identification and patient information may be entered into the computer at this time. 
     At step  290 , one or more measurements of the tooth may be taken, such as with a system and method as described in connection with FIGS. 1,  5 A,  5 B and/or  6 . The number of such measurements preferably is associated with the parameters entered at step  288 . Thereafter, at step  292 , the data collected from the measurement(s) may be sent to the computer for subsequent processing. As an illustrative example, four color/optical measurements may be taken (for the four regions of the tooth in the above example) and sent to the computer, with the data for the four color/optical measurements (such as RGB or other values) associated with the four regions in accordance with the entered parameters. Also, as an example, the displayed pictorial representation of the tooth may have overlaid thereof data indicative of the color/optical measurement(s). At step  294 , such as after completion of color/optical measurements on the particular patient, the data collected during the process may be associatively stored as a part of the patient&#39;s dental records in the data base. In embodiments accompanied by use of an intraoral camera, for example (see, e.g., FIG.  19  and related description), captured images of one or more of the patient&#39;s teeth also may be associatively stored as part of the patient&#39;s dental records. In certain embodiments, a picture captured by the intraoral camera is overlaid with grid or sector lines (such as may be defined in step  288 ), with color or other data measured as described herein also overlaid over the captured image. In such a manner, the color or other data may be electronically and visually associated with a picture of the particular measured tooth, thereby facilitating the use of the system and the understanding of the collected data. In still other embodiments, all such captured image and color measurement records include a time and/or date, so that a record of the particular history of a particular tooth of a particular patient may be maintained. See FIGS. 24 to  26  and  32  to  34  and related description for additional embodiments utilizing an intraoral camera, etc., in accordance with the present invention. 
     In yet another particular aspect of the present invention, a measuring device and method (such as described elsewhere herein) may be combined with an intraoral camera and other implements. As illustrated in FIG. 19, control unit  300  contains conventional electronics and circuitry, such as power supplies, control electronics, light sources and the like. Coupled to control unit  300  is intraoral camera  301  (for viewing, and capturing images of, a patient&#39;s tooth or mouth, etc.), curing light  302  (such as for curing light-cured intraoral filling material), measuring device  304  (such as described elsewhere herein), and visible light  306  (which may be an auxiliary light for intraoral examinations and the like). With such embodiments, color, translucency, fluorescence, gloss, surface texture and/or other data collected for a particular tooth from measuring device  304  may be combined with images captured by intraoral camera  301 , with the overall examination and processing of the patient facilitated by having measuring device  304 , intraoral camera  301 , curing light  302  and visible light  306  integrated into a single unit. Such integration serves to provide synergistic benefits in the use of the instruments, while also reducing costs and saving physical space. In another particular aspect of such embodiments, the light source for measuring device  304  and intraoral camera  301  are shared, thereby resulting in additional benefits. 
     Further embodiments of the present invention will now be described with reference to FIGS. 20 to  23 . The previously described embodiments generally rely on movement of the probe with respect to the object/tooth being measured. While such embodiments provide great utility in many applications, in certain applications, such as robotics, industrial control, automated manufacturing, etc. (such as positioning the object and/or the probe to be in proximity to each other, detecting color/optical properties of the object, and then directing the object, e.g., sorting, based on the detected color/optical properties, for further industrial processing, packaging, etc.) it may be desired to have the measurement made with the probe held or positioned substantially stationary above the surface of the object to be measured (in such embodiments, the positioned probe may not be handheld as with certain other embodiments). Such embodiments also may have applicability in the field of dentistry (in such applications, “object” generally refers to a tooth, etc.). 
     FIG. 20 illustrates such a further embodiment. The probe of this embodiment includes a plurality of perimeter sensors and a plurality of color sensors coupled to receivers  312 - 320 . The color sensors and related components, etc., may be constructed to operate in a manner analogous to previously described embodiments. For example, fiber optic cables or the like may couple light from source  310  that is received by receivers  312 - 320  to sharp cut-off filters or to notch filters, with the received light measured over precisely defined wavelengths (see, e.g., FIGS. 1,  3  and  11 - 14  and related description). Color/optical characteristics of the object may be determined from the plurality of color sensor measurements, which may include three such sensors in the case of a tristimulus instrument, or 8, 12, 15 or more color sensors for a more full bandwidth system (the precise number may be determined by the desired color resolution, etc.). 
     With this embodiment, a relatively greater number of perimeter sensors are utilized (as opposed, for example, to the three perimeter sensors used in certain preferred embodiments of the present invention). As illustrated in FIG. 20, a plurality of triads of receivers  312 - 320  coupled to perimeter sensors are utilized, where each triad in the preferred implementation consists of three fiber optics positioned equal distance from light source  310 , which in the preferred embodiment is a central light source fiber optic. The triads of perimeter receivers/sensors may be configured as concentric rings of sensors around the central light source fiber optic. In FIG. 20, ten such triad rings are illustrated, although in other embodiments a lesser or greater number of triad rings may be utilized, depending upon the desired accuracy and range of operation, as well as cost considerations and the like. 
     The probe illustrated in FIG. 20 may operate within a range of heights (i.e., distances from the object being measured). As with earlier embodiments, such height characteristics are determined primarily by the geometry and constituent materials of the probe, with the spacing of the minimal ring of perimeter sensors determining the minimal height, and the spacing of the maximal ring of perimeter sensors determining the maximum height, etc. It therefore is possible to construct probes of various height ranges and accuracy, etc., by varying the number of perimeter sensor rings and the range of ring distances from the central source fiber optic. It should be noted that such embodiments may be particularly suitable when measuring similar types of materials, etc. 
     As described earlier, the light receiver elements for the plurality of receivers/perimeter sensors may be individual elements such as Texas Instruments TSL230 light-to-frequency converters, or may be constructed with rectangular array elements or the like such as may be found in a CCD camera. Other broadband-type of light measuring elements are utilized in other embodiments. Given the large number of perimeter sensors used in such embodiments (such as 30 for the embodiment of FIG.  16 ), an array such as CCD camera-type sensing elements may be desirable. It should be noted that the absolute intensity levels of light measured by the perimeter sensors is not as critical to such embodiments of the present invention; in such embodiments differences between the triads of perimeter light sensors are advantageously utilized in order to obtain optical measurements. 
     Optical measurements may be made with such a probe by holding/positioning the probe near the surface of the object being measured (i.e., within the range of acceptable heights of the particular probe). The light source providing light to light source  310  is turned on and the reflected light received by receivers  312 - 320  (coupled to the perimeter sensors) is measured. The light intensity of the rings of triad sensors is compared. Generally, if the probe is perpendicular to the surface and if the surface is flat, the light intensity of the three sensors of each triad should be approximately will be equal. If the probe is not perpendicular to the surface or if the surface is not flat, the light intensity of the three sensors within a triad will not be equal. It is thus possible to determine if the probe is perpendicular to the surface being measured, etc. It also is possible to compensate for non-perpendicular surfaces by mathematically adjusting the light intensity measurements of the color sensors with the variance in measurements of the triads of perimeters sensors. 
     Since the three sensors forming triads of sensors are at different distances (radii) from central light source  310 , it is expected that the light intensities measured by light receivers  312 - 320  and the perimeter sensors will vary. For any given triad of sensors, as the probe is moved closer to the surface, the received light intensity will increase to a maximum and then sharply decrease as the probe is moved closer to the surface. As with previously-described embodiments, the intensity decreases rapidly as the probe is moved less than the peaking height and decreases rapidly to zero or almost zero for opaque objects. The value of the peaking height depends principally upon the distance of the particular receiver from light source  310 . Thus, the triads of sensors will peak at different peaking heights. By analyzing the variation in light values received by the triads of sensors, the height of the probe can be determined. Again, this is particularly true when measuring similar types of materials. As discussed earlier, comparisons with previously-stored data also may be utilized to made such determinations or assessments, etc. 
     The system initially is calibrated against a neutral background (e.g., a gray background), and the calibration values are stored in non-volatile memory (see, e.g., processor  10  of FIG.  1 ). For any given color or intensity, the intensity for the receivers/perimeter sensors (independent of distance from the central source fiber optic) in general should vary equally. Hence, a white surface should produce the highest intensities for the perimeter sensors, and a black surface will produce the lowest intensities. Although the color of the surface will affect the measured light intensities of the perimeter sensors, it should affect them substantially equally. The height of the probe from the surface of the object, however, will affect the triads of sensors differently. At the minimal height range of the probe, the triad of sensors in the smallest ring (those closest to the source fiber optic) will be at or about their maximal value. The rest of the rings of triads will be measuring light at intensities lower than their maximal values. As the probe is raised/positioned from the minimal height, the intensity of the smallest ring of sensors will decrease and the intensity of the next ring of sensors will increase to a maximal value and will then decrease in intensity as the probe is raised/positioned still further. Similarly for the third ring, fourth ring and so on. Thus, the pattern of intensities measured by the rings of triads will be height dependent. In such embodiments, characteristics of this pattern may be measured and stored in non-volatile RAM look-up tables (or the like) for the probe by calibrating it in a fixture using a neutral color surface. Again, the actual intensity of light is not as important in such embodiments, but the degree of variance from one ring of perimeter sensors to another is. 
     To determine a measure of the height of the probe from the surface being measured, the intensities of the perimeter sensors (coupled to receivers  312 - 320 ) is measured. The variance in light intensity from the inner ring of perimeter sensors to the next ring and so on is analyzed and compared to the values in the look-up table to determine the height of the probe. The determined height of the probe with respect to the surface thus may be utilized by the system processor to compensate for the light intensities measured by the color sensors in order to obtain reflectivity readings that are in general independent of height. As with previously described embodiments, the reflectivity measurements may then be used to determine optical characteristics of the object being measured, etc. 
     It should be noted that audio tones, such as previously described, may be advantageously employed when such an embodiment is used in a handheld configuration. For example, audio tones of varying pulses, frequencies and/or intensities may be employed to indicate the operational status of the instrument, when the instrument is positioned within an acceptable range for color measurements, when valid or invalid color measurements have been taken, etc. In general, audio tones as previously described may be adapted for advantageous use with such further embodiments. 
     FIG. 21 illustrates a further such embodiment of the present invention. The preferred implementation of this embodiment consists of a central light source  310  (which in the preferred implementation is a central light source fiber optic), surrounded by a plurality of light receivers  322  (which in the preferred implementation consists of three perimeter light receiver fiber optics). The three perimeter light receiver fiber optics, as with earlier described embodiments, may be each spliced into additional fiber optics that pass to light intensity receivers/sensors, which may be implemented with Texas Instruments TSL230 light to frequency converters as described previously. One fiber of each perimeter receiver is coupled to a sensor and measured full band width (or over substantially the same bandwidth) such as via a neutral density filter, and other of the fibers of the perimeter receivers are coupled to sensors so that the light passes through sharp cut off or notch filters to measure the light intensity over distinct frequency ranges of light (again, as with earlier described embodiments). Thus, there are color light sensors and neutral “perimeter” sensors as with previously described embodiments. The color sensors are utilized to determine the color or other optical characteristics of the object, and the perimeter sensors are utilized to determine if the probe is perpendicular to the surface and/or are utilized to compensate for non-perpendicular angles within certain angular ranges. 
     In the embodiment of FIG. 21, the angle of the perimeter sensor fiber optics is mechanically varied with respect to the central source fiber optic. The angle of the perimeter receivers/sensors with respect to the central source fiber optic is measured and utilized as described hereinafter. An exemplary mechanical mechanism, the details of which are not critical so long as desired, control movement of the perimeter receivers with respect to the light source is obtained, is described with reference to FIG.  22 . 
     The probe is held within the useful range of the instrument (determined by the particular configuration and construction, etc.), and a color measurement is initiated. The angle of the perimeter receivers/sensors with respect to the central light source is varied from parallel to pointing towards the central source fiber optic. While the angle is being varied, the intensities of the light sensors for the perimeter sensors (e.g., neutral sensors) and the color sensors is measured and saved along with the angle of the sensors at the time of the light measurement. The light intensities are measured over a range of angles. As the angle is increased the light intensity will increase to a maximum value and will then decrease as the angle is further increased. The angle where the light values is a maximum is utilized to determine the height of the probe from the surface. As will be apparent to those skilled in the art based on the teachings provided herein, with suitable calibration data, simple geometry or other math, etc., may be utilized to calculate the height based on the data measured during variation of the angle. The height measurement may then be utilized to compensate for the intensity of the color/optical measurements and/or utilized to normalize color values, etc. 
     FIG. 22 illustrates an exemplary embodiment of a mechanical arrangement to adjust and measure the angle of the perimeter sensors. Each perimeter receiver/sensor  322  is mounted with pivot arm  326  on probe frame  328 . Pivot arm  326  engages central ring  332  in a manner to form a cam mechanism. Central ring  332  includes a groove that holds a portion of pivot arm  326  to form the cam mechanism. Central ring  332  may be moved perpendicular with respect to probe frame  328  via linear actuator  324  and threaded spindle  330 . The position of central ring  332  with respect to linear actuator  324  determines the angle of perimeter receivers/sensors  322  with respect to light source  310 . Such angular position data vis-à-vis the position of linear actuator  324  may be calibrated in advance and stored in non-volatile memory, and later used to produce color/optical characteristic measurement data as previously described. 
     Referring now to FIG. 24, a further embodiment of the present invention will be explained. 
     Intraoral reflectometer  380 , which may be constructed as described above, includes probe  381 . Data output from reflectometer  380  is coupled to computer  384  over bus  390  (which may be a standard serial or parallel bus, etc.). Computer  384  includes a video freeze frame capability and preferably a modem. Intraoral camera  382  includes handpiece  383  and couples video data to computer  384  over bus  392 . Computer  384  is coupled to remote computer  386  over telecommunication channel  388 , which may be a standard telephone line, ISDN line, a LAN or WAN connection, etc. With such an embodiment, video measurements may be taken of one or more teeth by intraoral camera  382 , along with optical measurements taken by intraoral reflectometer  380 . Computer  384  may store still picture images taken from the output of intraoral camera  382 . 
     Teeth are known to have variations in color from tooth to tooth, and teeth are known to have variations in color over the area of one tooth. Intraoral cameras are known to be useful for showing the details of teeth. Intraoral cameras, however, in general have poor color reproducibility. This is due to variations in the camera sensing elements (from camera to camera and over time etc.), in computer monitors, printers, etc. As a result of such variations, it presently is not possible to accurately quantify the color of a tooth with an intraoral camera. With the present embodiment, measuring and quantifying the color or other optical properties of teeth may be simplified through the use of an intraoral reflectometer in accordance with the present invention, along with an intraoral camera. 
     In accordance with this embodiment, the dentist may capture a still picture of a tooth and its adjacent teeth using the freeze frame feature of computer  384 . Computer  384 , under appropriate software and operator control, may then “postureize” the image of the tooth and its adjacent teeth, such as by limiting the number of gray levels of the luminance signal, which can result in a color image that shows contours of adjacent color boundaries. As illustrated in FIG. 25, such a postureization process may result in teeth  396  being divided into regions  398 , which follow color contours of teeth  396 . As illustrated, in general the boundaries will be irregular in shape and follow the various color variations found on particular teeth. 
     With teeth postureized as illustrated in FIG. 25, computer  384  may then highlight (such as with a colored border, shading, highlight or the like) a particular color region on a tooth to be measured, and then the dentist may then measure the highlighted region with intraoral reflectometer  380 . The output of intraoral reflectometer  380  is input to computer  384  over bus  390 , and computer  384  may store in memory or on a hard disk or other storage medium the color/optical data associated with the highlighted region. Computer  384  may then highlight another region and continue the process until color/optical data associated with all desired highlighted regions have been stored in computer  384 . Such color/optical data may then be stored in a suitable data base, along with the video image and postureized video image of the particular teeth, etc. 
     Computer  384  may then assess if the measured value of a particular color region is consistent with color measurements for adjacent color regions. If, for example, a color/optical measurement for one region indicates a darker region as compared to an adjacent region, but the postureized image indicates that the reverse should be true, then computer  384  may notify the dentist (such as with an audio tone) that one or more regions should be re-measured with intraoral reflectometer  380 . Computer  384  may make such relative color determinations (even though the color values stored in computer  384  from the freeze frame process are not true color values) because the variations from region to region should follow the same pattern as the color/optical measurements taken by intraoral reflectometer  380 . Thus, if one region is darker than its neighbors, then computer  384  will expect that the color measurement data from intraoral reflectometer  380  for the one region also will be darker relative to color measurement data for the neighboring regions, etc. 
     As with the optical characteristics measurement data and captured images discussed previously, the postureized image of the teeth, along with the color/optical measurement data for the various regions of the teeth, may be conveniently stored, maintained and accessed as part of the patient dental records. Such stored data may be utilized advantageously in creating dental prosthesis that more correctly match the colors/regions of adjacent teeth. Additionally, in certain embodiments, such data images are used in conjunction with smile analysis software to further aid in the prosthesis preparation. 
     In a further refinement to the foregoing embodiment, computer  384  preferably has included therein, or coupled thereto, a modem. With such a modem capability (which may be hardware or software), computer  384  may couple data to remote computer  386  over telecommunication channel  388 . For example, remote computer  386  may be located at a dental laboratory remotely located. Video images captured using intraoral camera  382  and color/optical data collected using intraoral reflectometer may be transmitted to a dental technician (for example) at the remote location, who may use such images and data to construct dental prosthesis. Additionally, computer  384  and remote computer  386  may be equipped with an internal or external video teleconference capability, thereby enabling a dentist and a dental technician or ceramist, etc., to have a live video or audio teleconference while viewing such images and/or data. 
     For example, a live teleconference could take place, whereby the dental technician or ceramist views video images captured using intraoral camera  383 , and after viewing images of the patient&#39;s teeth and facial features and complexion, etc., instruct the dentist as to which areas of the patient&#39;s teeth are recommended for measurement using intraoral reflectometer  380 . Such interaction between the dentist and dental technician or ceramist may occur with or without postureization as previously described. Such interaction may be especially desirable at, for example, a try-in phase of a dental prosthesis, when minor changes or subtle characterizations may be needed in order to modify the prosthesis for optimum esthetic results. 
     A still further refinement may be understood with reference to FIG.  26 . As illustrated in FIG. 26, color calibration chart  404  could be utilized in combination with various elements of the previously described embodiments, including intraoral camera  382 . Color calibration chart  404  may provide a chart of known color values, which may be employed, for example, in the video image to further enhance correct skin tones of patient  402  in the displayed video image. As the patient&#39;s gingival tissue, complexion and facial features, etc., may influence the final esthetic results of a dental prosthesis, such a color calibration chart may be desirably utilized to provide better esthetic results. 
     As an additional example, such a color calibration chart may be utilized by computer  384  and/or  386  to “calibrate” the color data within a captured image to true or known color values. For example, color calibration chart  404  may include one or more orientation markings  406 , which may enable computers  384  and/or  386  to find and position color calibration chart  404  within a video frame. Thereafter, computers  384  and/or  386  may then compare “known” color data values from color calibration chart (data indicative of the colors within color calibration chart  404  and their position relative to orientation mark or markings  406  are stored within computers  384  and/or  386 , such as in a lookup table, etc.) with the colors captured within the video image at positions corresponding to the various colors of color calibration chart  404 . Based on such comparisons, computers  384  and/or  386  may color adjust the video image in order to bring about a closer correspondence between the colors of the video image and known or true colors from color calibration chart  404 . 
     In certain embodiments, such color adjusted video data may be used in the prosthesis preparation process, such as to color adjust the video image (whether or not postureized) in conjunction with color/optical data collected using intraoral reflectometer  380  (for example, as described above or using data from intraoral reflectometer  380  to further color adjust portions of the video image), or to add subtle characterizations or modifications to a dental prosthesis, or to even prepare a dental prosthesis, etc. While not believed to be as accurate, etc. as color/optical data collected using intraoral reflectometer  380 , such color adjusted video data may be adequate in certain applications, environments, situations, etc., and such color adjusted video data may be utilized in a similar manner to color data taken by a device such as intraoral reflectometer  380 , including, for example, prosthesis preparation, patient data collection and storage, materials preparation, such as described elsewhere herein. 
     It should be further noted that color calibration chart  404  may be specifically adapted (size, form and constituent materials, etc.) to be positioned inside of the patient&#39;s mouth to be placed near the tooth or teeth being examined, so as to be subject to the same or nearly the same ambient lighting and environmental conditions, etc., as is the tooth or teeth being examined. It also should further be noted that the utilization of color calibration chart  404  to color correct video image data with a computer as provided herein also may be adapted to be used in other fields, such as medical, industrial, etc., although its novel and advantageous use in the field of dentistry as described herein is of particular note and emphasis herein. 
     FIG. 27 illustrates a further embodiment of the present invention, in which an intraoral reflectometer in accordance with the present invention may be adapted to be mounted on, or removably affixed to, a dental chair. An exemplary dental chair arrangement in accordance with the present invention includes dental chair  410  is mounted on base  412 , and may include typical accompaniments for such chairs, such as foot control  414 , hose(s)  416  (for suction or water, etc.), cuspidor and water supply  420  and light  418 . A preferably movable arm  422  extends out from support  428  in order to provide a conveniently locatable support  430  on which various dental instruments  424  are mounted or affixed in a removable manner. Bracket table  426  also may be included, on which a dentist may position other instruments or materials. In accordance with this embodiment, however, instruments  424  include an intraoral reflectometer in accordance with the present invention, which is conveniently positioned and removably mounted/affixed on support  430 , so that color/optical measurements, data collection and storage and prosthesis preparation may be conveniently carried out by the dentist. As opposed to large and bulky prior art instruments, the present invention enables an intraoral reflectometer for collecting color/optical data, in some embodiments combined or utilized with an intraoral camera as described elsewhere herein, which may be readily adapted to be positioned in a convenient location on a dental chair. Such a dental chair also may be readily adapted to hold other instruments, such as intraoral cameras, combined intraoral camera/reflectors, drills, lights, etc. 
     With the foregoing as background, various additional preferred embodiments utilizing variable aperture receivers in order to measure, for example, the degree of gloss of the surface will now be described with references to FIGS. 28A to  30 B. Various of the electronics and spectrophotometer/reflectometer implements described above will be applicable to such preferred embodiments. 
     Referring to FIG. 28A, a probe utilizing variable aperture receivers will now be described. In FIG. 28A, source A  452  represents a source fiber optic of a small numerical aperture NA, 0.25 for example; receivers B  454  represent receiver fiber optics of a wider numerical aperture, 0.5 for example; receivers C  456  represent receiver fiber optics of the same numerical aperture as source A but is shown with a smaller core diameter; and receivers D  458  represent receiver fiber optics of a wider numerical aperture, 0.5 for example. 
     One or more of receiver(s) B  454  (in certain embodiments one receiver B may be utilized, while in other embodiments a plurality of receivers B are utilized, which may be circularly arranged around source A, such as 6 or 8 such receivers B) pass to a spectrometer (see, e.g., FIGS. 1,  3 ,  11 ,  12 , configured as appropriate for such preferred embodiments). Receiver(s) B  454  are used to measure the spectrum of the reflected light. Receivers C  456  and D  458  pass to broad band (wavelength) optical receivers and are used to correct the measurement made by receiver(s) B. Receivers C  456  and D  458  are used to correct for and to detect whether or not the probe is perpendicular to the surface and to measure/assess the degree of specular versus diffuse reflection (the coefficient of specular reflection, etc.) and to measure the translucency of the material/object. 
     FIG. 28B illustrates a refinement of the embodiment of FIG. 28A, in which receivers B  454  are replaced by a cylindrical arrangement of closely packed, fine optical fibers  454 A, which generally surround light source  452  as illustrated. The fibers forming the cylindrical arrangement for receivers B  454 , are divided into smaller groups of fibers and are presented, for example, to light sensors  8  shown in FIG.  1 . The number of groups of fibers is determined by the number of light sensors. Alternately, the entire bundle of receiver fibers B  454  is presented to a spectrometer such as a diffraction grating spectrometer of conventional design. As previously described, receivers C  456  and D  458  may be arranged on the periphery thereof. In certain embodiments, receivers C and D may also consist of bundles of closely packed, fine optical fibers. In other embodiments they consist of single fiber optics. 
     The assessment of translucency in accordance with embodiments of the present invention have already been described. It should be noted, however, that in accordance with the preferred embodiment both the light reflected from the surface of the material/object (i.e., the peaking intensity) and its associated spectrum and the spectrum of the light when it is in contact with the surface of the material/object may be measured/assessed. The two spectrums typically will differ in amplitude (the intensity or luminance typically will be greater above the surface than in contact with the surface) and the spectrums for certain materials may differ in chrominance (i.e., the structure of the spectrum) as well. 
     When a probe in accordance with such embodiments measures the peaking intensity, it in general is measuring both the light reflected from the surface and light that penetrates the surface, gets bulk scattered within the material and re-emerges from the material (e.g., the result of translucency). When the probe is in contact with the surface (e.g., less than the critical height), no light reflecting from the surface can be detected by the receiver fiber optics, and thus any light detected by the receivers is a result of the translucency of the material and its spectrum is the result of scattering within the bulk of the material. The “reflected spectrum” and the “bulk spectrum” in general may be different for different materials, and assessments of such reflected and bulk spectrum provide additional parameters for measuring, assessing and/or characterizing materials, surfaces, objects, teeth, etc., and provide new mechanisms to distinguish translucent and other types of materials. 
     In accordance with preferred embodiments of the present invention, an assessment or measurement of the degree of gloss (or specular reflection) may be made. For understanding thereof, reference is made to FIGS. 29 to  30 B. 
     Referring to FIG. 29, consider two fiber optics, source fiber optic  460  and receiver fiber optic  462 , arranged perpendicular to a specular surface as illustrated. The light reflecting from a purely specular surface will be reflected in the form of a cone. As long as the numerical aperture of the receiver fiber optic is greater than or equal to the numerical aperture of the source fiber optic, all the light reflected from the surface that strikes the receiver fiber optic will be within the receiver fiber optic&#39;s acceptance cone and will be detected. In general, it does not matter what the numerical aperture of the receiver fiber optic is, so long as it is greater than or equal to the numerical aperture of the source fiber optic. When the fiber optic pair is far from the surface, receiver fiber optic  462  is fully illuminated. Eventually, as the pair approaches surface  464 , receiver fiber optic  462  is only partially illuminated. Eventually, at heights less than or equal to the critical height h c  receiver fiber optic  462  will not be illuminated. In general, such as for purely specular surfaces, it should be noted that the critical height is a function of the numerical aperture of source fiber optic  460 , and is not a function of the numerical aperture of the receiver. 
     Referring now to FIGS. 30A and 30B, consider two fiber optics (source  460  and receiver  462 ) perpendicular to diffuse surface  464 A as illustrated in FIG. 30A (FIG. 30B depicts mixed specular/diffuse surface  464 B and area of intersection  466 B). Source fiber optic  460  illuminates circular area  466 A on surface  464 A, and the light is reflected from surface  464 A. The light, however, will be reflected at all angles, unlike a specular surface where the light will only be reflected in the form of a cone. Receiver fiber optic  462  in general is always illuminated at all heights, although it can only propagate and detect light that strikes its surface at an angle less than or equal to its acceptance angle. Thus, when the fiber optic pair is less than the critical height, receiver fiber optic  462  detects no light. As the height increases above the critical height, receiver fiber optic  462  starts to detect light that originates from the area of intersection of the source and receiver cones as illustrated. Although light may be incident upon receiver fiber optic  462  from other areas of the illuminated circle, it is not detected because it is greater than the acceptance angle of the receiver fiber. 
     As the numerical aperture of receiver fiber optic  462  increases, the intensity detected by receiver fiber optic  462  will increase for diffuse surfaces, unlike a specular surface where the received intensity is not a function of receiver fiber optic numerical aperture. Thus, for a probe constructed with a plurality of receiver fiber optics with different numerical apertures, as in preferred embodiments of the present invention, if the surface is a highly glossy surface, both receivers (see, e.g., receivers  456  and  458  of FIG. 28A, will measure the same light intensity. As the surface becomes increasingly diffuse, however receiver D  458  will have a greater intensity than receiver C  456 . The ratio of the two intensities from receivers C/D is a measure of, or correlates to, the degree of specular reflection of the material, and may be directly or indirectly used to quantify the “glossiness” of the surface. Additionally, it should be noted that generally receiver C  456  (preferably having the same numerical aperture as source fiber optic A  452 ) measures principally the specular reflected component. Receiver D  458 , on the other hand, generally measures both diffuse and specular components. As will be appreciated by those skilled in the art, such probes and methods utilizing receivers of different/varying numerical apertures may be advantageously utilized, with or without additional optical characteristic determinations as described elsewhere herein, to further quantify materials such as teeth or other objects. 
     Referring now to FIG. 31A, additional preferred embodiments will be described. The embodiment of FIG. 31A utilizes very narrow numerical aperture, non-parallel fiber optic receivers  472  and very narrow numerical aperture source fiber optic  470  or utilizes other optical elements to create collimated or nearly collimated source and receiver elements. Central source fiber optic  470  is a narrow numerical aperture fiber optic and receiver fiber optics  472  as illustrated (preferably more than two such receivers are utilized in such embodiments) are also narrow fiber optics. Other receiver fiber optics may be wide numerical aperture fiber optics (e.g., receivers such as receivers  458  of FIG.  28 A). As illustrated, receiver fiber optics  472  of such embodiments are at an angle with respect to source fiber optic  470 , with the numerical aperture of the receiver fiber optics selected such that, when the received intensity peaks as the probe is lowered to the surface, the receiver fiber optics&#39; acceptance cones intersect with the entire circular area illuminated by the source fiber optic, or at least with a substantial portion of the area illuminated by the source. Thus, the receivers generally are measuring the same central spot illuminated by the source fiber optic. 
     A particular aspect of such embodiments is that a specular excluded probe/measurement technique may be provided. In general, the spectrally reflected light is not incident upon the receiver fiber optics, and thus the probe is only sensitive to diffuse light. Such embodiments may be useful for coupling reflected light to a multi-band spectrometer (such as described previously) or to more wide band sensors. Additionally, such embodiments may be useful as a part of a probe/measurement technique utilizing both specular included and specular excluded sensors. An illustrative arrangement utilizing such an arrangement is shown in FIG.  31 B. In FIG. 31B, element  470  may consist of a source fiber optic, or alternatively may consist of all or part of the elements shown in cross-section in FIG. 28A or  28 B. Still alternatively, non-parallel receiver fiber optics  472  may be parallel along their length but have a machined, polished, or other finished or other bent surface on the end thereof in order to exclude all, or a substantial or significant portion, of the specularly reflected light. In other embodiments, receiver fiber optics  472  may contain optical elements which exclude specularly reflected light. An additional aspect of embodiments of the present invention is that they may be more fully integrated with an intraoral camera. 
     Referring now to FIGS. 32 to  34 , various of such embodiments will be described for illustrative purposes. In such embodiments, optical characteristic measurement implements such as previously described may be more closely integrated with an intraoral camera, including common chassis  480 , common cord or cable  482 , and common probe  484 . In one such alternative preferred embodiment, camera optics  486  are positioned adjacent to spectrometer optics  488  near the end of probe  484 , such as illustrated in FIG.  33 . Spectrometer optics  488  may incorporate, for example, elements of color and other optical characteristics measuring embodiments described elsewhere herein, such as shown in FIGS. 1-3,  9 - 10 B,  11 - 12 ,  20 - 21 ,  28 A,  28 B and  31 A and  31 B. In another embodiment, camera optics and lamp/light source  490  is positioned near the end of probe  484 , around which are positioned a plurality of light receivers  492 . Camera optics and lamp/light source  490  provide illumination and optics for the camera sensing element and a light source for making color/optical characteristics in accordance with techniques described elsewhere herein. It should be noted that light receivers  492  are shown as a single ring for illustrative purposes, although in other embodiments light receivers such as described elsewhere herein (such as in the above-listed embodiments including multiple rings/groups, etc.) may be utilized in an analogous manner. Principles of such camera optics generally are known in the borescope or endoscopes fields. 
     With respect to such embodiments, one instrument may be utilized for both intraoral camera uses and for quantifying the optical properties of teeth. The intraoral camera may be utilized for showing patients the general state of the tooth, teeth or other dental health, or for measuring certain properties of teeth or dental structure such as size and esthetics or for color postureization as previously described. The optical characteristic measuring implement may then measure the optical properties of the teeth such as previously described herein. In certain embodiments, such as illustrated in FIGS. 33 and 34, a protective shield is placed over the camera for intraoral use in a conventional manner, and the protective shield is removed and a specialized tip is inserted into spectrometer optics  488  or over camera optics and lamp/light source  490  and light receivers  492  (such tips may be as discussed in connection with FIGS. 23A-23C, with a suitable securing mechanism) for infection control, thereby facilitating measuring and quantifying the optical properties. In other embodiments a common protective shield (preferably thin and tightly fitted, and optically transparent, such as are known for intraoral cameras) that covers both the camera portion and spectrometer portion are utilized. 
     Based on the foregoing embodiments, with which translucency and gloss may be measured or assessed, further aspects of the present invention will be described. As previously discussed, when light strikes an object, it may be reflected from the surface, absorbed by the bulk of the material, or it may penetrate into the material and either be emitted from the surface or pass entirely through the material (i.e., the result of translucency). Light reflected from the surface may be either reflected specularly (i.e., the angle of reflection equals the angle of incidence), or it may be reflected diffusely (i.e., light may be reflected at any angle). When light is reflected from a specular surface, the reflected light tends to be concentrated. When it is reflected from a diffuse surface, the light tends to be distributed over an entire solid hemisphere (assuming the surface is planar) (see, e.g., FIGS.  29 - 30 B). Accordingly, if the receivers of such embodiments measure only diffusely reflected light, the light spectrum (integrated spectrum or gray scale) will be less than an instrument that measures both the specular and diffusely reflected light. Instruments that measure both the specular and diffuse components may be referred to as “specular included” instruments, while those that measure only the diffuse component may be referred to as “specular excluded.” 
     An instrument that can distinguish and quantify the degree of gloss or the ratio of specular to diffusely reflected light, such as with embodiments previously described, may be utilized in accordance with the present invention to correct and/or normalize a measured color spectrum to that of a standardized surface of the same color, such as a purely diffuse or Lambertian surface. As will be apparent to one of skill in the art, this may be done, for example, by utilizing the gloss measurement to reduce the value or luminance of the color spectrum (the overall intensity of the spectrum) to that of the perfectly diffuse material. 
     A material that is translucent, on the other hand, tends to lower the intensity of the color spectrum of light reflected from the surface of the material. Thus, when measuring the color of a translucent material, the measured spectrum may appear darker than a similar colored material that is opaque. With translucency measurements made as previously described, such translucency measurements may be used to adjust the measured color spectrum to that of a similar colored material that is opaque. As will be understood, in accordance with the present invention the measured color spectrum may be adjusted, corrected or normalized based on such gloss and/or translucency data, with the resulting data utilized, for example, for prosthesis preparation or other industrial utilization as described elsewhere herein. 
     Additional aspects of the present invention relating to the output of optical properties to a dental laboratory for prosthesis preparation will now be described. There are many methods for quantifying color, including CIELab notation, Munsell notation, shade tab values, etc. Typically, the color of a tooth is reported by a dentist to the lab in the form of a shade tab value. The nomenclature of the shade tab or its value is an arbitrary number assigned to a particular standardized shade guide. Dentists typically obtain the shade tabs from shade tab suppliers. The labs utilize the shade tabs values in porcelain recipes to obtain the final color of the dental prosthesis. 
     Unfortunately, however, there are variances in the color of shade tabs, and there are variances in the color of batches of dental prosthesis ceramics or other materials. Thus, there are variances in the ceramics/material recipes to obtain a final color of a tooth resulting in a prosthesis that does not match the neighboring teeth. 
     In accordance with the present invention, such problems may be addressed as follows. A dental lab may receive a new batch of ceramic materials and produce a test batch of materials covering desired color, translucency and/or gloss range(s). The test materials may then be measured, with values assigned to the test materials. The values and associated color, translucency and gloss and other optical properties may then be saved and stored, including into the dental instruments that the lab services (such as by modem download). Thereafter, when a dentist measures the optical properties of a patient&#39;s tooth, the output values for the optical properties may be reported to the lab in a formula that is directly related, or more desirably correlated, to the materials that the lab will utilize in order to prepare the prosthesis. Additionally, such functionality may enable the use of “virtual shade guides” or other data for customizing or configuring the instrument for the particular application. 
     Still other aspects of the present invention will be described with reference to FIGS. 35 and 36, which illustrate a cordless embodiment of the present invention. Cordless unit  500  includes a housing on which is mounted display  502  for display of color/optical property data or status or other information. Keypad  504  is provided to input various commands or information. Unit  500  also may be provided with control switch  510  for initiating measurements or the like, along with speaker  512  for audio feedback (such as previously described), wireless infrared serial transceiver for wireless data transmission such as to an intelligent charging stand (as hereinafter described) and/or to a host computer or the like, battery compartment  516 , serial port socket  518  (for conventional serial communications to an intelligent charging stand and/or host computer, and/or battery recharging port  520 . Unit  500  includes probe  506 , which in preferred embodiments may include removable tip  508  (such as previously described). Of course, unit  500  may contain elements of the various embodiments as previously described herein. 
     Charging stand  526  preferably includes socket/holder  532  for holding unit  500  while it is being recharged, and preferably includes a socket to connect to wired serial port  518 , wireless IR serial transceiver  530 , wired serial port  524  (such as an RS232 port) for connection to a host computer (such as previously described), power cable  522  for providing external power to the system, and lamps  528  showing the charging state of the battery and/or other status information or the like. 
     The system battery may be charged in charging stand  526  in a conventional manner. A charging indicator (such as lamps  528 ) may be used to provide an indication of the state of the internal battery. Unit  500  may be removed from the stand, and an optical measurement may be made by the dentist. If the dentist chooses, the optical measurement may be read from display  502 , and a prescription may be handwritten or otherwise prepared by the dentist. Alternately, the color/optical characteristics data may be transmitted by wireless IR transceiver  514  (or other cordless system such as RF) to a wireless transceiver, such as transceiver  530  of charging stand  526 . The prescription may then be electronically created based upon the color/optical characteristics data. The electronic prescription may be sent from serial port  524  to a computer or modem or other communications channel to the dental laboratory. 
     With reference to FIGS. 37A and 37B, additional aspects of the present invention will be discussed. 
     As is known, human teeth consist of an inner, generally opaque, dentin layer, and an outer, generally translucent, enamel layer. As previously discussed, light that is incident on a tooth generally can be affected by the tooth in three ways. First, the light can be reflected from the outer surface of the tooth, either diffusely or specularly. Second, the light can be internally scattered and absorbed by the tooth structures. Third, the light can be internally scattered and transmitted through the tooth structures and re-emerge from the surface of the tooth. Traditionally, it was difficult, if not impossible, to distinguish light reflected from the surface of the tooth, whether specularly or diffusely, from light that has penetrated the tooth, been scattered internally and re-emitted from the tooth. In accordance with the present invention, however, a differentiation may be made between light that is reflected from the surface of the tooth and light that is internally scattered and re-emitted from the tooth. 
     As previously described, a critical height h c  occurs when a pair of fiber optics serve to illuminate a surface or object and receive light reflected from the surface or object. When the probe&#39;s distance from the tooth&#39;s surface is greater than the critical height h c  the receiver fiber optic is receiving light that is both reflected from the tooth&#39;s surface and light that is internally scattered and re-emitted by the tooth. When the distance of the probe is less than the critical height h c , light that is reflected from the surface of the tooth no longer can be received by the received fiber optic. In general, the only light that can be accepted by the receiver fiber optic is light that has penetrated enamel layer  540  and is re-emitted by the tooth (in cases where the object is a tooth). 
     Most of the internal light reflection and absorption within a tooth occurs at enamel-dentin interface or junction (DEJ)  542 , which in general separates enamel layer  540  from dentin  544 . In accordance with the present invention, an apparatus and method may be provided for quantifying optical properties of such sub-surface structures, such as the color of DEJ  542 , with or without comparison with data previously taken in order to facilitate the assessment or prediction of such structures. 
     Critical height h c  of the fiber optic probe such as previously described is a function of the fiber&#39;s numerical aperture and the separation between the fibers. Thus, the critical height h c  of the probe can be optimized based on the particular application. In addition, a probe may be constructed with multiple rings of receive fiber optics and/or with multiple numerical aperture receiving fiber optics, thereby facilitating assessment, etc., of enamel thickness, surface gloss, tooth morphology etc. 
     It is widely known that the thickness of the enamel layer of a tooth varies from the incisal edge to the cervical portion of the tooth crown, and from the middle of the tooth to the mesial and distal edges of the tooth (see FIGS. 37A and 37B, etc.). By utilizing multiple rings of receiver fiber optics, a measurement of the approximate thickness of the enamel layer may be made based on a comparison of the peak intensity above the tooth surface and a measurement in contact with the tooth surface. A probe with multiple critical heights will give different intensity levels when in contact with the tooth surface, thereby producing data that may be indicative of the degree of internal scattering and enamel thickness or tooth morphology at the point of contact, etc. 
     Accordingly, in accordance with the present invention, the color or other optical characteristics of a sub-surface structure, such as DEJ  542  of a tooth, may be assessed or quantified in a manner that is in general independent of the optical characteristics of the surface of the tooth, and do so non-invasively, and do so in a manner that may also assess the thickness of the outer layer, such as enamel layer  540 . 
     Additionally, and to emphasize the wide utility and variability of various of the inventive concepts and techniques disclosed herein, it should be apparent to those skilled in the art in view of the disclosures herein that the apparatus and methodology may be utilized to measure the optical properties of objects/teeth using other optical focusing and gathering elements, in addition to the fiber optics employed in preferred embodiments herein. For example, lenses or mirrors or other optical elements may also be utilized to construct both the light source element and the light receiver element. A flashlight or other commonly available light source, as particular examples, may be utilized as the light source element, and a common telescope with a photoreceiver may be utilized as the receiver element in a large scale embodiment of the invention. Such refinements utilizing teachings provided herein are expressly within the scope of the present invention. 
     As will be apparent to those skilled in the art, certain refinements may be made in accordance with the present invention. For example, a central light source fiber optic is utilized in certain preferred embodiments, but other light source arrangements (such as a plurality of light source fibers, etc.). In addition, lookup tables are utilized for various aspects of the present invention, but polynomial type calculations could similarly be employed. Thus, although various preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and/or substitutions are possible without departing from the scope and spirit of the present invention as disclosed in the claims. In addition, while various embodiments utilize light principally in the visible light spectrum, the present invention is not necessarily limited to all or part of such visible light spectrum, and may include radiant energy not within such visible light spectrum. 
     Reference is made to copending application filed on even date herewith for Apparatus and Method for Measuring Optical Characteristics of an Object, and for Method and Apparatus for Detecting and Preventing Counterfeiting, both by the inventors hereof, which is hereby incorporated by reference.