WO2019141201A1

WO2019141201A1 - Colour grading process and system for jade

Info

Publication number: WO2019141201A1
Application number: PCT/CN2019/072079
Authority: WO
Inventors: Ka Wing CHENG; Kin Wing WONG; Kong Chan; Juan CHENG; Wing Chi Tang; Koon Chung Hui
Original assignee: Master Dynamic Limited
Priority date: 2018-01-17
Filing date: 2019-01-17
Publication date: 2019-07-25
Also published as: CN111886492A; CN111886492B

Abstract

A process operable using a computerized system (100) for grading the colour of a jade article (260), wherein the article is at least partially transparent and wherein the colour of the jade article (260) is correlated with the colour from a set of standardized reference colour data, the computerized system (100) including an optical image acquisition device (110, 225), a processor module (120, 220) and an output module (140, 240) operably interconnected together. The process includes the steps of (i) acquiring a background image of the environment; (ii) acquiring a mask image, wherein the mask image is acquired with the jade article (260) disposed between two linear polarizers (250a, 250b); (iii) removing the background and correcting the article image and comparing data derived from the article image with a set of standardized reference colour data; responsive to a predetermined threshold of correlation between the pixel colour values of a region of the article with data derived from input of the first optical image and assigning a colour to region of the article, an output signal is provided indicative of the colour of region of the article.

Description

COLOUR GRADING PROCESS AND SYSTEM FOR JADE

Technical Field

The present invention relates to a system and a process for analyzing the visual characteristics of jade. More particularly, the present invention provides a system and a process for colour grading of jade.

Background of the Invention

Jades, consist of nephrite jades and jadeite jades, are gemstone or material often forming luxury goods as well as are utilized in jewellery, and jade can have a very high value.

The value of a jade highly depends on the on colour or colours, or different distribution on colour or colours. Therefore, the colour judgement is a very important process for jade grading.

For the classification of colour of a jade, within the industry the method is subjective judgement and is performed by humans. The jade is placed on a white background with a day-light equivalent reflected light source illumination. Few standards were ever set on the measurement conditions for determining the colour of jade.

As such, the colour classification of jade can be easily affected by environmental issues pertaining to the environment in which the grading or classification is performed.

Even under a white environment light matching with the day-light with white background, light intensity variations can also significantly affect human judgement in relation colours of jade. If these light conditions are non-uniform, the testing environment can be much more complex.

Colour recognition is a complex parameter for humans, and it is common to have misjudgment of colour, both between difference people and as well when a same person is performing an assessment and, and such inconsistency can cause conflict can cause misclassification.

When providing colour grading, standard data sets in the form of colour cards or charts are utilized, for visual comparison with the jade.

In such cases, repetitive training of colour graders is required, with a view so that different graders can reproduce the same assessment results, with a view to providing uniformity and consistency between colour grading personnel.

However and regardless, when humans are grading jade, different graders can provide a different or varying colour assessment. Further, same graders can also provide inconsistent results for the same jade, and such inconsistencies can cause incorrect grading which can adversely impact upon the value of jade, as well as cause other commercially unacceptable consequences.

Object of the Invention

It is an object of the present invention to provide a system and a process for analyzing the visual characteristics of jade, in particular colour, which overcomes or at least partly ameliorates at least some deficiencies as associated with the prior art.

Summary of the Invention

In a first aspect, the present invention provides a process operable using a computerized system for grading the colour of a jade article, wherein the colour of the jade article is correlated with the colour from a set of standardized reference colour data, the computerized system including an optical image acquisition device, a processor module and an output module operably interconnected together, said process including the steps of (i) acquiring via an optical image acquisition device a background image of the environment in which an image of the jade article is to be acquired and acquiring an article image of the jade article in said environment, wherein said environment has a predetermined constant light level; (ii) acquiring via the optical image acquisition device a mask image, wherein the mask image is an optical image of the jade article including the background against which said image of the jade article is acquired, wherein said mask image is acquired with the jade article disposed between a first linear polarizer and a second linear polarizer, wherein said first linear polarizer and said second linear polarizer are disposed between the optical image acquisition device and a first light source, the first linear polarizer being disposed proximal to the first light source and the second linear polarizer being disposed distal to the first light source and adjacent the optical image acquisition device, wherein said first linear polarizer and said second linear polarizer are operably oriented in crossed orientations to each other such that light emitted from the first light source is substantially prevented from being received by the optical image acquisition device; and wherein the jade article alters the polarization of light polarized by the first linear polarizer such that the jade article is optically detectable by the image acquisition device, and such that the mask image is acquirable by the image acquisition device comprising the article which contrasted from background against which an image of the article is acquired; (iii) in a processor module (a) removing the background from the article image utilising the acquired mask image and correcting the article image by way of flat-field correction using said background image, and (b) comparing data derived from acquisition of the article image having been corrected with data from the with a set of standardized reference colour data; and (iv) from an output module, responsive to a predetermined threshold of correlation between the pixel colour values of a region of the article with data derived from input of the first optical image and assigning a colour to said region of the article, an output signal is provided indicative of the colour of said region of the article.

Preferably, the HSL (Hue, Saturation, Lightness) colour model is used for the pixel colour value. Alternatively, the pixel colour values of the article are referenced to a colour definition include those of the group RGB, HSV, CIE, CMYK, YIQ and the like.

The flatfield correction may be provided using computer programming languages including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R or the like.

The background removal process may be effected by computer programming languages including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R, or the like.

The counting of pixels of the image of jade may be effected by computer programming languages, including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R or the like.

In a second aspect, the present invention provides an image acquisition system for acquiring an image of a jade article, said system including an optical image acquisition device for acquiring an image of a jade article; a first light source for transmitting light through said jade article; a first linear polarizer and a second linear polarizer, wherein said first linear polarizer and said second linear polarizer are disposed between the optical image acquisition device and the first light source, the first linear polarizer being disposed proximal to the first light source and the second linear polarizer being disposed distal to the first light source and adjacent the optical image acquisition device; an an article support member disposed between the first linear polarizer and a second linear polarizer for supporting the article, wherein the article support member is optically transparent; wherein said first linear polarizer and said second linear polarizer are operably oriented in crossed orientations to each other such that light emitted from the first light source is substantially prevented from being received by the optical image acquisition device; and wherein upon the jade article being supported by the article support member, the jade article alters the polarization of light polarized by the first linear polarizer such that the article is optically detectable by the image acquisition device, and such that an image is acquirable by the image acquisition device comprising the jade article which contrasted from background against which an image of the jade article is acquired.

The system may further comprise a second light source disposed between the first linear polarizer and the second liner polarizer for illuminating the article such that upon removal of the polarizers and optical image of the article is acquirable by the optical acquisition device for indicative of the colour of the article.

The first light source and the second light source preferably provide light of a constant colour and intensity so as to provide uniform lighting conditions.

The first light source and the second light source may be selected from the group including such as LED light source, a Xeon lamp light source, a halogen lamp light source, a deuterium lamp light source, an incandescent light bulb light source, a fluorescent lamp light source, a solar simulator light source or the like.

The system may include an integrating sphere system, comprising two spheres interconnected at an aperture providing communication therebetween, wherein the first light source is in communication with a first sphere and the second light source is in communication with a second sphere, and wherein the optical image acquisition device is directed from the periphery of the second sphere towards the aperture, wherein the first linear polarizer occludes the aperture between the two spheres and the second linear polarizer occludes the optical image acquisition device, and wherein the article support member is disposed adjacent the first linear polarizer.

The first linear polarizer and the second linear polarizer are preferably moveable so as to allow for acquisition of an image of the article in the absence of polarized light.

Preferably, the optical image acquisition device is in communication with a processor for analyzing the colour of the article. The processor is preferably in communication with a data store and wherein the data store includes standardized reference data indicative of a range of colours, and wherein the processor quantitatively correlates the pixel colour values of an image of the article acquired by the optical image acquisition device with the standardized reference data.

Brief Description of the Drawings

In order that a more precise understanding of the above-recited invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. The drawings presented herein may not be drawn to scale and any reference to dimensions in the drawings or the following description is specific to the embodiments disclosed.

Figure 1 a shows a schematic represent of a first embodiment of a system according to the present invention;

Figure 1b shows a flow chart of the process according to the present invention;

Figure 2 shows a schematic representation of an embodiment of a system in accordance with the present invention;

Figures 3a and 3b are examples of the raw object image and camera flat-field corrected image with background removal respectively;

Figures 3c and 3d show examples of classified colours with their distribution on an article;

Figure 4 depicts that the colour intensity can be empirically quantified and defined by the colour regions spanned by saturation and lightness values at the boundaries; and

Figure 5 shows finite saturation and lightness data points for each hue, following interpolation for different hues as forming a three-dimensional HSL volume with surface boundaries.

Detailed Description of the Drawings

Background on Colour

For a coloured object or article, human judgement and interpretation of colour is affected heavily by the lighting conditions in which the object or article is viewed. One important condition is the colour of the surrounding light. The colour of light can be precisely described by the light spectrum.

In practice for simplicity, the colour of light can be described by its colour temperature, which demonstrates the light spectrum emitted by an ideal black-body radiator at a particular temperature.

For white light, the light spectrum is similar to that of the solar light spectrum, with a colour temperature at 6,500 K. Under lighting conditions with different colours, such as yellow light (such as incandescent lamps with light temperature at 3,000 K) and white light (sun light with light temperature at 6,500 K) , the colours of an object as observed by the human eye can be completely different.

Another important light condition is light intensity. Even under light with the same colour, for example white light, light intensity variations can also significantly affect human judgements on colours of an object or article. If the lighting conditions are non-uniform, the testing or observation environment can be much more complex. Accordingly, for the assessment of colour by human, a standard environment is needed for repeatable and reliable results.

Problems with Colnur Judgement or Assessment

Further, misconception or misinterpretation may also occur between different people in human colour judgement and interpretation. For example, for a same cloth, some people may classify it as being “blue” , whilst some may classify or consider it as being “green” , which means that the human “reference table” for two people can be different for a colour.

Therefore, human judgement of colour must be done with the same basis and terminology. A reference master set with varying colour may be used for this purpose. The reference master sets are each required to have high accuracy and repeatability between different master sets.

Each reference master must be homogenously saturated with the specific standard colour in order that a best comparison may be made between an object or article to be graded and the reference master set.

For colour grading assessment of jade, the accuracy and usability of master stones as reference sets are not only applicable to different sets of reference master sets but also the same sets of reference master at different points in time when assessment is made, as it has been found that the colour of reference stones in master sets may vary with time.

As such, the colour of the reference master sets must be permanent without any changes over time, otherwise it is necessary to provide useable or serviceable lifetimes to the reference master sets. After the expiration of the usable or serviceable lifespan of a reference master, there is no guarantee that the colour will remain stable and consequently no guarantee as to the accuracy and repeatability of colour grading assessment.

Furthermore, even under well controlled conditions, such as constant light colour, intensity, uniform illumination and good master reference sets, the use human eyes for determining colour can still be an issue to the correct colour judgement of an object or article.

Because of human′s vision tiredness, different colour judgements on the same object or article at different time may have different results. The person looking on the object after looking on many other different coloured objects or articles, can give a different colour assessment than under a different viewing history.

What increases variation in human judgement on colour is a common psychological effect, for colour perception. Variation in colour perception is particularly serious if the object or article has a matrix of assorted colours or is multi-coloured. Humans can also easily misjudge a colour under the present of a background colour.

Therefore, during the process of colour judgement, the object or article should be placed on a background having uniform colour, such as white colour, so as to minimize variance in colour perception. However, for an object or article with a matrix of different colours, the colour perception cannot be eliminated. These physio-psychological issues make repeatable and reliable colour judgements by human eyes impossible.

Thus, for a system capable of transforming light to the “colour” information, which includes an image acquisition device such as a camera, need to take some handling also requires some processing basis on this reason as it not directly output the wavelength of the light.

Identified Disadvantages of the Prior Art

The present inventors have identified shortcomings in the manner in which colour of jade is assessed, and upon identification of the problems with the prior art, have provided a system and process which overcomes the problems of the prior art, and provides a system and process which is more consistent and reliable.

Problems identified by the present inventors include:

(i) intrinsic factors as recited above including the requirement for colour to be precise, saturated and consistent between master sets, which may be master stones of reference cards or charts;

(ii) extrinsic factors including the environment in which a colour judgement assessment is made, including lighting conditions and background; and

(iii) extrinsic factors pertaining to human judgement, including judgement error due to environment, human perception, human consistency, tiredness and distraction, as well as inherent human error.

Present Invention

In order to address the above shortcomings including repeatability and reliability difficulties, the present invention provides a process and a system to determine and analyse the colours of jade.

The system provides well controlled lighting conditions throughout the time, and machine or electronic vision without vision without the inherent deficiencies and inconsistencies of human vision tiredness.

Such a process and system provide advantages over those of the prior art, and provides high repeatability for the analysis of colours of jade or an article formed from jade.

Referring to Figure 1a, there is shown a schematic represent of a first embodiment of a system 100 according to the present invention. The system 100 includes an optical image acquisition device 110 in communication 112 with a processor module including processor 120, which is in

communication

122, 132 with a data store 130. An output device 140 is provided, which is in communication 124 with the processor 120.

The optical image acquisition device 110 is a digital camera device, which allows for acquisition of an optical image of jade or an article formed from jade.

The system 100 may be provided as a single unit and with the integers of the system 100 being provided as an integral device. Alternatively, the integers of the system 100 can be provided separately, and the processor 120 being provided either in an adjacent location to the touch sensitive input device and visual display unit or provided at a remote location and in communication with the touch sensitive input device and visual display unit by way of a telecommunications network.

Further, the data store 130 may be located adjacent the processor 120 or located at a remote location and in communication with the processor 120 by way of a telecommunications network.

Referring to Figure 1b, there is shown a flow chart of a process 150 according to the present invention.

The process 150 is operable using a computerized system for grading the colour of a jade article, wherein the colour of the jade article is correlated with the colour from a set of standardized reference colour data, the computerized system including an optical image acquisition device, a processor module and an output module operably interconnected together such as is shown in Figure 1a or Figure 2.

The process includes the steps of:

(i) 160 acquiring via an optical image acquisition device a background image of the environment in which an image of the jade article is to be acquired and acquiring an article image of the jade article in said environment, wherein said environment has a predetermined constant light level;

(ii) 170 acquiring via the optical image acquisition device a mask image, wherein the mask image is an optical image of the jade article including the background against which said image of the jade article is acquired, wherein said mask image is acquired with the jade article disposed between a first linear polarizer and a second linear polarizer, wherein said first linear polarizer and said second linear polarizer are disposed between the optical image acquisition device and a first light source, the first linear polarizer being disposed proximal to the first light source and the second linear polarizer being disposed distal to the first light source and adjacent the optical image acquisition device, wherein said first linear polarizer and said second linear polarizer are operably oriented in crossed orientations to each other such that light emitted from the first light source is substantially prevented from being received by the optical image acquisition device; and wherein the jade article alters the polarization of light polarized by the first linear polarizer such that the jade article is optically detectable by the image acquisition device, and such that the mask image is acquirable by the image acquisition device comprising the article which contrasted from background against which an image of the article is acquired;

(iii) 180 in a processor module (a) removing the background from the article image utilising the acquired mask image and correcting the article image by way of flat-field correction using said background image, and (b) comparing data derived from acquisition of the article image having been corrected with data from the with a set of standardized reference colour data; and

(iv) 190 from an output module, responsive to a predetermined threshold of correlation between the pixel colour values of a region of the article with data derived from input of the first optical image and assigning a colour to said region of the article, an output signal is provided indicative of the colour of said region of the article.

Referring to Figure 2, there is shown a schematic representation of an embodiment of system 200 in accordance with the present invention which is applicable for implementation of the process as described above with reference to Figure 1a.

The system 200 includes an optical image acquisition device provided as digital camera 225 in communication 212 with a processor module including processor 220, which is in

communication

222, 232 with a data store 230 which holds standardized colour data sets. An output device 240 is provided, which is in communication 224 with the processor 220.

The system 200 includes two integrating spheres, an upper sphere 210a and a lower sphere 210b which are interconnected at the common aperture 211. The internal coating of each integrating

sphere

210a, 210b is diffusive white paint, allowing for homogenous diffusive reflections of light inside the

spheres

210a, 210b.

Accordingly, the dual integrating sphere structure can provide a controllable uniform illumination both above and below a jade article 260 of which an optical image thereof is to be acquired.

For the upper sphere 210a, there are provided an aperture 212 at the most upper portion, referred to as the north pole, and an aperture 213a at the lateral side of the sphere 210a.

In communication with the aperture 212, there is provided the image acquisition device as a camera 225 with a removable linear polariser 250a distal of the camera 225.

For the lower sphere 210b, there is provided an aperture 213b.

The

apertures

213a and 213b connected and in communication with

light sources

230a and 230b respectively, allow entry and delivery of light into the system 200.

Baffles 231a and 231b are provided and positioned adjacent the

apertures

213a and 213b respectively so as to prevent direct illumination from the

light sources

230a and 230b to the jade article 260.

A transparent plate 241 is located at the aperture 211 which provides as a transparent platform for the support and removable of a lower linear polariser 250b.

Polarisers

250a and 250b are operably configured in crossing orientation at 90 degrees to each other, which obstructs passage of light. Extending over the transparent plate 241 and the polariser 250b, there is provided a transparent sample platform 242 for placing the jade article 260 of which an optical image is to be captured thereof.

In accordance with the process of the invention, when an optical image of the jade article 260 is to be acquired, the jade article 260 and

polarisers

250a and 250b will be initially removed.

An empty background image is first acquired via the camera 225, in this case a digital camera, and subsequently a second optical image is acquired with the jade article 260 placed on the sample platform 242.

The second acquired optical image can be flat-field corrected with the empty background image acquired. Flat-field correction, as is known as a term of art, is a method to remove the non-uniformity among different pixels of the image. This difference consists of two sources. One source is the sensitivity variations among different pixels on the detector of the camera, and the other is the contribution of optical distortions, such as the optical distortions of lens. After flat-field correction of the image, the image can achieve a high quality.

In order to contrast the jade article 260 from the background, the present invention utilizes linear polarisers 250a and 250b inserted above and below the jade article can be captured.

The two

polarisers

250a, 250b, are arranged in crossed orientations to each other at 90 degrees. In the absence of the jade article, the two crossed

polarisers

250a, 250b, cut out all the light entering the camera 225.

In accordance with the present invention, in the presence of a jade article 260 with refractive properties, the jade article 260 changes the polarisation of light passing through it.

Only the light passing through the jade article 260 can reach an optical image acquisition device proved as a camera 225 while the light passing through the background is mostly cut out.

This process of the present invention, physically enhances the image contrast between the jade article 260 and the background, and is used to produce a mask to assist the background removal.

The present inventors have identified that by use of the actual physical shape and geometry of a jade article 260 which is at least partially optically transparent, obviates the necessity for utilisation of complex computational algorithms for background removal.

The present inventors have utilized the diffractive properties of the jade article, which fully correspond to the periphery of the article, so as to create an efficient mask for utilization in background removal.

The present inventors have found that a very precise periphery of the article can be determined based on light and physical effects, without the necessity for complex algorithms, and the present invention has proven particularly useful for optical characteristics of jade articles, in particular colour determination of jade or articles of jade.

For jade requiring colour assessment whereby the colour of the article varies including at the periphery, and whereby the article may be of a white colour, it is often difficult to delineate between background and the article, and image analysis software which typically utilizes interpolation between optical parameters to determine peripheries, cannot readily distinguish accurately between background and an article when colours are similar.

By contrast, the system and process of the present invention is immune from such colour differentiation errors, as regardless of even if the article has the same colour at is periphery as the background, the diffractive properties of the article allow the article to be seen via the camera whilst blocking out the background due to the implementation of the two 90-degree offset polarisers.

In order to ascertain whether the system of the present invention can provide the correct colour and provide stable performance without drift, standard colour references are used. Standard colour references are spectrally calibrated by the issuing institutes so their colour values are truly related to the pixel colour values in the image taken by the system. This is particularly important for consistent and accurate colour determination, as different optical acquisition devices, such as cameras, as different brands of camera can have different imaging performance.

Referring now to Figures 3a, 3b, 3c and 3d. the three images, (i) the background image without the article, (ii) the article image and (iii) the mask image are subsequently by a processor for camera fiatfield correction and background removal.

Figures 3a and 3b are examples of the raw jade image and camera flatfield corrected image with background removal respectively.

The colour data can be extracted from the pixel’s colour values of the camera flatfield corrected image with background removal. Figures 3c and 3d are the examples of classified colours with their distribution on a jade. Counting of the pixels having colour values falling into the colour types can be done to analyse the colour composition of the jade 160. In the process of data analysis and colour classification of jade in the present invention, HSL (Hue, Saturation, Lightness) colour model is used in preference to the original RGB (Red, Green, Blue) colour model of the pixel.

It has been found that the HSL colour model can provide enhanced assessment on some perceptual colour properties.

The hue H, expressed in 360 degrees, is defined by the red, green, blue pixel values r, g, b as

M = max (R, G, B)

m = min (R, G, B)

H = 60° × H′.

The lightness L with value from 0 to 1 is defined by:

The saturation S with value from 0 to 1 is defined by:

For the definitions of HSL values to colours, these are required toto be correlated to a relevant market standard.

As will be appreciated, as Since jades are historically and predominantly more popular in the Chinese culture, the definitions of colour from HSL values have been taken with reference to the grading scales as used by the largest jade trader in the Greater China.

The value of hue gives the perception of colour. In order to classify different colour in jade, several colours have been defined according to the hue ranges in Table 1 below

Table 1

As green coloured jades always have a greater value, more focus has been placed on this aspect. Within the green colour (Hue = 95 - 144) of a jade, there are also different “colour intensities” ( 「顔色質量」 ) . The classification of colour intensities is listed in Table 2a (English) and 2b (Chinese) below.

The definition of colour intensity is less trivial than colour. This is due to the more subjective nature of colour intensity. Nonetheless, the colour intensity can be empirically quantified and defined by the colour regions spanned by saturation and lightness values at the boundaries as shown and demonstrated in Figure 4.

As there are only finite saturation and lightness data points for each hue, they are then interpolated for different hues as illustrated in Figure 5, forming a three-dimensional HSL volume with surface boundaries.

However, as human sensitivity to saturation and lightness of different hues is non-linear, interpolation is required using non-linear fitting.

The equation to fit the surface boundaries is:

L = a ₁H ² + a ₂HS + a ₃S ² + a ₄H + a ₅S + a ₆,

where a ₁ -a ₆ are the fitting coefficients.

Determination of whether the colour intensity in the hue range 95-144:

If the hue value of the pixel falls into the range of from 95 to 144, it will undergo the following process to determine it is white or black or green with its colour intensity:

1. If its S < 0.2, then it will be considered as black if L < 0.4 and will be considered as white otherwise.

2. Otherwise, it will be compared with the surface boundaries to see which region it is located to.

The system will check from the lowest surface (L is lowest, starting from #black) , if the surface of that colour intensity lower boundary is higher than the L of the pixel, the pixel is will fall into the last colour intensity region.

E.g. if L < lower boundary of the colour intensity #3, it falls into #2 colour intensity. And it will be white if L is higher than all colour intensity surface

The colour grading process and system as provided by the present invention overcomes numerous disadvantage of the prior art, including:

(i) removal of inherent intrinsic factors and extrinsic factors including environmental aspects;

(ii) removal of variants due to human error or misjudgements; and

(iii) removal of subjectivity in colour assessment.

Accordingly, the present invention provides a process and system for providing repeatable and consistent with reference to an industry-accepted colour grading system.

The present inventors have further found that the models for colour utilized and the processes used in the present invention, further provide good correlation and meaningful and useful colour gradings and correlation to accepted industry standards of jade colour grading.

Claims

A process operable using a computerized system for grading the colour of a jade article, wherein the colour of the jade article is correlated with the colour from a set of standardized reference colour data, the computerized system including an optical image acquisition device, a processor module and an output module operably interconnected together, said process including the steps of:

(i) acquiring via an optical image acquisition device a background image of the environment in which an image of the jade article is to be acquired and acquiring an article image of the jade article in said environment, wherein said environment has a predetermined constant light level;

(ii) acquiring via the optical image acquisition device a mask image, wherein the mask image is an optical image of the jade article including the background against which said image of the jade article is acquired, wherein said mask image is acquired with the jade article disposed between a first linear polarizer and a second linear polarizer, wherein said first linear polarizer and said second linear polarizer are disposed between the optical image acquisition device and a first light source, the first linear polarizer being disposed proximal to the first light source and the second linear polarizer being disposed distal to the first light source and adjacent the optical image acquisition device, wherein said first linear polarizer and said second linear polarizer are operably oriented in crossed orientations to each other such that light emitted from the first light source is substantially prevented from being received by the optical image acquisition device; and wherein the jade article alters the polarization of light polarized by the first linear polarizer such that the jade article is optically detectable by the image acquisition device, and such that the mask image is acquirable by the image acquisition device comprising the article which contrasted from background against which an image of the article is acquired;

(iii) in a processor module (a) removing the background from the article image utilising the acquired mask image and correcting the article image by way of flat-field correction using said background image, and (b) comparing data derived from acquisition of the article image having been corrected with data from the with a set of standardized reference colour data; and

(iv) from an output module, responsive to a predetermined threshold of correlation between the pixel colour values of a region of the article with data derived from input of the first optical image and assigning a colour to said region of the article, an output signal is provided indicative of the colour of said region of the article.
A process according to claim 1, wherein the HSL (Hue, Saturation, Lightness) colour model is used for the pixel colour value.
A process according to claim 1, wherein pixel colour values of the article are referenced to a colour definition include those of the group RGB, HSV, CIE, CMYK, YIQ and the like.
A process according to any of the preceding claims, wherein the flatfield correction is provided using computer programming languages including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R or the like.
A process according to any of the preceding claims, wherein the background removal process is effected by computer programming languages including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R, or the like.
A process according to any one of the preceding claims, wherein the counting of pixels of the image of jade is effected by computer programming languages, including MATLAB, Octave, Python, C, C++, C#, Fortran, Mathematica, R or the like.
An image acquisition system for acquiring an image of a jade article, said system including:

an optical image acquisition device for acquiring an image of a jade article,

a first light source for transmitting light through said jade article;

a first linear polarizer and a second linear polarizer, wherein said first linear polarizer and said second linear polarizer are disposed between the optical image acquisition device and the first light source, the first linear polarizer being disposed proximal to the first light source and the second linear polarizer being disposed distal to the first light source and adjacent the optical image acquisition device; and

an article support member disposed between the first linear polarizer and a second linear polarizer for supporting the article, wherein the article support member is optically transparent;

wherein said first linear polarizer and said second linear polarizer are operably oriented in crossed orientations to each other such that light emitted from the first light source is substantially prevented from being received by the optical image acquisition device; and

wherein upon the jade article being supported by the article support member, the jade article alters the polarization of light polarized by the first linear polarizer such that the article is optically detectable by the image acquisition device, and such that an image is acquirable by the image acquisition device comprising the jade article which contrasted from background against which an image of the jade article is acquired.
A system according to claim 7, wherein the system further comprises a second light source disposed between the first linear polarizer and the second liner polarizer for illuminating the article such that upon removal of the polarizers and optical image of the article is acquirable by the optical acquisition device for indicative of the colour of the article.
A system according to claim 8, wherein the first light source and the second light source provide light of a constant colour and intensity so as to provide uniform lighting conditions.
A system according to claim 8 or claim 9, wherein the first light source and the second light source are selected from the group including such as LED light source, a Xeon lamp light source, a halogen lamp light source, a deuterium lamp light source, an incandescent light bulb light source, a fluorescent lamp light source, a solar simulator light source or the like.
A system according to any one of claims 8 to 10, wherein the system includes an integrating sphere system, comprising two spheres interconnected at an aperture providing communication therebetween, wherein the first light source is in communication with a first sphere and the second light source is in communication with a second sphere, and wherein the optical image acquisition device is directed from the periphery of the second sphere towards the aperture, wherein the first linear polarizer occludes the aperture between the two spheres and the second linear polarizer occludes the optical image acquisition device, and wherein the article support member is disposed adjacent the first linear polarizer.
A system according to any one of claim 7 to 11, wherein the first linear polarizer and the second linear polarizer are moveable so as to allow for acquisition of an image of the article in the absence of polarized light.
A system according to any one of claims 7 to 12, wherein the optical image acquisition device is in communication with a processor for analyzing the colour of the article.
A system according to claim 13, wherein the processor is in communication with a data store and wherein the data store includes standardized reference data indicative of a range of colours, and wherein the processor quantitatively correlates the pixel colour values of an image of the article acquired by the optical image acquisition device with the standardized reference data.