APPLICATION OF VISBREAKER ANALYSIS TOOLS TO OPTIMIZE PERFORMANCE CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the priority benefit of U.S. Patent Application Serial No. 11/178,846 filed July 11, 2005 and U.S. Continuation-In-Part Patent Application Serial No. 11/456,128 filed July 7, 2006. FIELD OP THE INVENTION [0002] The present invention relates to systems and methods for characterizing and quantifying a dispersive medium; specifically, measuring the concentration of particles or the tendency toward forming a dispersed phase within a fluid sample. The present invention also provides a program which uses these measurements of concentration to monitor and control operation of a visbreaker unit to improve the yield of light streams. BACKGROUND OF THE INVENTION [0003] Thermal conversion is a process hi which, by the application of heat, large hydrocarbon molecules are broken into smaller molecules with a lower boiling point. These operations are carried out k the industry of crude oil refining by plants such as a visbreaker, coker, and.hydrocracker for obtaining intermediate or light cuts of higher value, from heavy residues of lower commercial value. The thermal cracking applied in the visbreaker process will also reduce the viscosity and pour point of the heavy residues. [0004] It is well known that the fouling potential of a fluid can be estimated and characterized by the concentration of the dispersed phase, particularly by the concentration of the dispersed phase present in a specific size range. In hydrocarbon systems hi particular, it has been recognized that the concentration of asphalteries (i.e., carbon particles or opaque species) with linear dimension greater than about 2 microns in visbroken tars is a good indication of the fouling potential of the material. [0005] The VSB process was developed some years ago with the intention of obtaining a viscosity decrease in heavy products hi order to reduce the amount of higher valued flux to meet the viscosity specification of the finished heavy fuel product. Today, however, it is managed with substantially different objects, namely with the aim of obtaining a maximum transformation into middle and light distillates to meet the market requirements. [0006] The controlling factor in obtaining a high conversion is the need to obtain a stable residue. In fact an increase of the cracking temperature certainly would involve a higher conversion in light and middle distillates, but it would produce a much more mstable tar which would produce a final product outside the required stability specifications. [0007] An increase of the light streams is achieved by increasing the cracking severity through an increase of the outlet furnace temperature of the Visbreaker furnace. While increasing this temperature arbitrarily will serve to drive the conversion rate higher, it also comes at the cost of producing a highly unstable tar as a precipitate in the process, with a high concentration of asphaltene particulates. This particulate matter constitutes a severe fouling threat to the energy recovery devices (i.e. furnace and heat exchangers) in the process. As such, in order to maximize the profitability a Visbreaker unit, it is desirable to optimize the outlet furnace temperature while maintaining the stability of the produced tar. While it is known that high temperature dispersants and anti-foulants can be introduced into the system to reduce the tendancy and rate of fouling, prior art systems have not been entirely satisfactory in providing an automated system for determining an optimum type and/or quantity of chemical dispersants and anti-foulants to be introduced into the visbreaker unit hi order to maximize plant profitability. The present teachings will show that if the fouling potential of the tar can be quantified, then the precise level of chemical inhibitor can be dosed to maximize the plant profitability,. [0008] Therefore, in one aspect the present invention provides a simplified, automated system and method that can easily be used to carry out optical analysis of visbroken tars and other fluid samples in order to characterize and quantify the concentration of particles within the fluid sample with high accuracy and reproducibility. In another aspect, the present invention utilizes these concentration measurements to determine the fouling potential of the visbroken tars, and regulates the introduction of chemical inhibitors into the visbreaker unit to improve the yielij of light streams. In yet another or further aspect, a sequence of aliquots are prepared from the same sample at different dilutions to drive phase separation, producing a sequence of concentration measurements correlated to a classical measurement of peptization value (PV), a qualitative measure of the product quality. These and other aspects of the present invention will become apparent to those skilled in the art upon review of the following disclosure. SUMMARY OF THE INVENTION [0009] In one aspect, the present invention provides a system and method for estimating a concentration of inhomogeneities contained within a tar byproduct of visbreaker operations. The invention does so by measuring the modulation of transmitted light through a fluid sample. The system uses a strongly convergent optical lens system to focus light onto a prepared sample. In one exemplary embodiment, the optics of a conventional optical microscope are .used. A 3-dimensional translation stage is installed downstream of the focusing optics so that the sample can be scanned over a large region, and at a specific focal plane. A photo detector is placed on the opposite side of the stage from the focusing optics to measure the transmitted light through the sample. The photpdetector is read-out by an analog-to-digital converter (ADC) in order to provide a digital (i.e., quantitative) measure, of the transmitted light intensity. The translation stages are then moved in a pattern, such that the intensity of the transmitted light is measured over a representative path across the sample. When an opacity, scatterer or opaque particle of a threshold size is encountered in the sample, the intensity of the transmitted light is strongly attenuated. Such change of light intensity is then correlated with the detection of an opaque particle in order to characterize and quantify the concentration of particles within the fluid sample with high accuracy and reproducibility. Data processing algorithms are implemented to determine the background noise level associated with the acquired data and to set a threshold level. As such, a specific signal-to-noise ratio can be specified to define when a detection event is registered. Size discrimination may be achieved according to the physical dimensions of the beam waist of the focused light beam. [0010] In another aspect, the present "invention utilizes the concentration measurement data to estimate the fouling potential of visbroken tars hi a visbreaker unit in order to regulate introduction of chemical inhibitors into the visbreaker unit and improve the yield of light streams. The invention provides an automated program which allows the user to maximize the production of light streams by modeling the correlation between operational parameters such as feed quality, cracking severity, conversion rate, run length, and fouling rate of the subject exchanger or furnace in order to regulate introduction of chemical inhibitors into the visbreaker unit in accordance with customer specifications and/or production requirements. BRIEF DESCRIPTION OF THE DRAWINGS [0011] Fig. 1 is a view of the scanning apparatus of the present invention, showing the schematic relationship of the various elements; [0012] Fig. 2 illustrates an example of a computer screen displaying a data acquisition interface in accordance with the present invention; [0013] Fig. 3 is a diagram illustrating optics used to convergently focus a light beam to a narrow beam waist; [0014] Fig. 4 illustrates a plurality of spaced apart linear scans compared with a solid block representing an equivalent effective surface area; [0015] Fig. 5 is a graph illustrating raw light transmission data obtained over a single line scan; [0016] Fig. 6 is a graph illustrating the raw data of Fig. 5 after the data has been filtered to remove line noise and gross intensity variations; [0017] Fig. 7 is a graph illustrating decreasing statistical error as a function of overall scan length; [0018] Fig 8 is a graph showing the correlation of sample inhomogeneity, as measured by the instrument to samples with a varying degree of dilution from a fuUy cracked (i.e., high asphaltene particle density) sample; [0019] Fig 9 is a schematic of the mechanics of the chemical effect of the dispersants; [0020] Fig 10 is a graph of the relation of PV to the Furnace Outlet Temperature (FOT) with and without chemical treatment; [0021] Fig. 11 illustrates tar stability and conversion as asphaltenes are disbursed in the continuous phase through the peptizing action of aromatics and resins; [0022] Fig. 12 is a graph illustrating raw data obtained from a visbreaker conversion trial; [0023] Figs. 13-16 are graphs illustrating raw data obtained from a conversion enhancement application; [0024] Fig. 17 is a graph illustrating VFM data versus corr. skin temperature; [0025] Fig. 18 is a schematic diagram illustrating exemplary visbreaker process types; and [0026] Figs. 19A, 19B illustrate Pv measurement with a measurement system of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0027] Exemplary embodiments and examples describing the present invention will be described below with reference to the accompanying drawings. As shown in Fig. 1, this invention uses an optical system as generally indicated by the number 10, which in the present exemplary embodiment comprises a convergent lens, a light source 12, and a multi-axis translation stage 14. The light source 12 may be implemented, for example, in the form of a solid state visible laser. An infra-red (IR) laser may also be used, and is in some cases preferable owing to the fact that HC solutions are typically much more transparent to IR light, than visible light. The translation stage 14 may be moved horizontally in the x and y directions in response to control signals generated by an associated computer 20 to direct the light beam along a plurality of paths through the sample. The third axis moves the stage vertically, towards and away from the focusing lens. This permits selection of a focal plane within the sample. In another exemplary embodiment, the present invention contemplates providing means for moving the light source 12 with respect to the sample, thereby allowing the light beam to be directed through the sample to achieve the same results. Moreover, the present invention also contemplates usage of a flow cell to receive a flow of sample fluid, wherein the sample fluid flows through the flow cell while the light beam is directed through a portion of the flowing sample. Also implemented is a photodetector 16, for example, .a PIN photodiode, located on the opposite side of the stage 14 to detect light 13 being transmitted through the sample volume, which is located on the translation stage. The photodetector 16, in turn, is connected by a connector and cable 17, for example, a twisted pair with BNC connector, to an analog-to-digital (A/D) converter 18 to quantify the transmitted light intensity. As described below, this is done to sample or detect the occurrence of inhomogeneities hi light transmission which may be caused by mineral and other inclusions, and agglomerating or stable localized dark matter of various types. [0028] In one exemplary embodiment of the invention, a colloidal fluid sample material of thick viscous tar sampled from a Visbreaker is placed on the translation stage 14. Depending on the conditions in the Visbreaker unit, the sample may or may not contain asphaltene (or carbon based) particles. The asphaltene particles within the tar medium are opaque to visible light. The tar medium is also opaque to visible light when the path length through the medium typically exceeds a linear dimension of about 1 cm. A sample volume is dispensed on a slide, or flow cell 15 such that a typical sample thickness of 10-20 microns is produced. As such, the thickness of sample medium should be made thin enough so as to provide a differential transparency between the viscous tar medium and the asphaltene particles in question. In this exemplary embodiment, in order to optimize light transmission from a low power light source, a solid state laser that produces radiation at about 633 nm is chosen. This provides adequate power at a suitable region in the EM (electromagnetic) spectrum to provide transmission through a thin layer of tar, while the carbide particles remain opaque. [0029] In order to have sensitivity to the specific sized inhomogeneities, appropriate optics should be used to focus the laser light onto the sample. The choice of a monochromatic light source allows the design of the optics to be optimized. As shown in Fig. 3, a highly convergent lens system-200 is" used to focus the light beam 100 down to a beam waist of approximately 1 micron. The size of the beam waist determines the minimum cross-dimension an inhomogeneity must have to fully attenuate the laser light. If an inhomogeneity is smaller than 1 micron, it will still allow the transmission of light. As such, the focusing optics define, in part, a threshold size for inhomogeneity detection. An equation for calculating the beam waist is as follows: W = 0.61X/d Where W = beam waist (1/e) width X = wavelength of light d = numerical aperture For example, if X= 633 nm and d =• 0.56, then W = 0.7 /im. Since we are interested in inhomogeneities larger than 1 micron (and smaller than ~20 microns), we do not use an IR laser, even though the HC solutions are more transparent to IR radiation because the beam waist would increase in size for the given optics. As such, we would reduce the sensitivity of the instrument. Preferably, the wavelength and beam waist are also chosen to minimize interference artifacts that may arise as the concentration of dispersed phase increases or the sample thickness varies (e.g., under a cover slide.) [0030] The fluid sample 120 thickness is chosen to be about 10 microns. The beam 100 is focused on the slide 104, below a cover slip 102, or a flow cell in the sample volume. The depth and width of focus are constrained by the optical system and the selected light wavelength. In one exemplary embodiment, both dimensions are selected to be approximately 1 micron. [0031] Fig. 2 illustrates an example of a screen display presented by the software of the present invention. The screen display illustrated hi Fig. 2 represents a data acquisition interface allowing the operator to specify a variety of scanning acquisition, analysis parameters, operating conditions of the instrument, and results of the measurement. The methods by which the operator selects items, inputs data, and otherwise interacts with the data acquisition interface are conventional, and further discussions of these operations are not provided herein. In an exemplary embodiment of the invention, data acquisition software was implemented via Visual Basic® in Excel® with analysis and signal processing code being implemented in GNU Octave, although those skilled in the art of software programming will appreciate that many other software programming means may be used to achieve the same results. [0032] A testing plan was designed and implemented to validate and measure the scanning performance of an exemplary embodiment of the present invention. In particular, measurement repeatability is validated by analyzing the variation between identical measurements. Reproducibility of the data is examined by analyzing the effects of scanning different regions in the sample. This is complicated by the effects of sample inhomogeneity. Accuracy of the system is tested by comparing the scanning data with visual images and PV (PV = peptization value) of the sample. Precision of results is analyzed for statistical uncertainty with path length and by optimizing sample area, as discussed hi more detail below. [0033] Fig. 4 illustrates an example of how the scanning system samples a large region of the sample. The array of linear scans (shown on the right side of Fig. 4) represent the same effective surface area as the small box illustrated on the left side of Fig. 4. For example, an array of 20 linear scans of 15 mm length with a 1 micron wide laser beam effectively samples the same area-as does the smaller 0.48 mm x 0.64 mm box. However, by arranging the sampling path to extend over a larger region of the sample, the effects of sample inhomogeneity, local fluctuations hi the sample, and sample variation are reduced drastically. As such, the statistical results are much more accurate and reproducible. [0034] To demonstrate the repeatability of our scanning results, five identical 15 mm scans from a same sample, each covering a 0.015 mm2 effective area were measured. The measurement showed that the number of counts per 15 mm line scan were identical within 95% confidence limits. Increasing the sampling region to 20-15 mm scan paths, the same systematic effects were seen. After applying statistical analysis to the results, it was observed that the single line scan measurements are normally distributed, with a standard deviation (