WO2006051319A1

WO2006051319A1 - Forensic spectral microscope

Info

Publication number: WO2006051319A1
Application number: PCT/GB2005/004368
Authority: WO
Inventors: Christopher Hunter
Original assignee: Smcs Limited
Priority date: 2004-11-12
Filing date: 2005-11-11
Publication date: 2006-05-18
Also published as: EP1810006A1; GB2426326B; GB0523017D0; GB2426326A; GB0425114D0

Abstract

There is disclosed a colour assessment apparatus comprising a sample carrier, magnifying optics to capture light from defined locations of a sample located on the sample carrier, means for analyzing the light captured by the magnifying optics to measuring colour values of the defined locations of the sample, means for automatically displacing the optical means relative to the sample carrier in order to the apparatus to scan a succession of locations of the sample and to measure colour values of the sample for each location, memory means for storing a table of location information correlated with colour value information, means for inputting a colour value of a reference sample, and means for analyzing the table so as to determine locations of any colour values from the sample that match the colour value of the reference sample.

Description

COLOUR ASSESSMENT APPARATUS

BACKGROUND

The present invention relates to colour assessment apparatus having applications in a wide variety of fields from biological material assessment to textile assessment with particular applications in the field of forensics.

In forensics, a transparent tape is used at various suspect locations to collect fibres or other material for assessment in order, for example, to identify whether a particular fibre is present on a particular tape and to establish a match between, for example, the garment of a suspect and a particular scene of a crime. The tape is typically placed beneath binocular magnifying lenses in order to identify, for example, the colour of a garment in question. The operator will manually displace the transparent tape beneath the binoculars until a particular fibre is identified. Once it is identified by the naked eye, he will circle around the fibre to mark the location on the tape for further investigation. Once the location and fibre is appropriately marked, the operator cuts out the portion of the tape bearing the fibre and applies the fibre to a clean tape before submitting the fibre to further analysis in a spectrometer, for example, in order to verify the initial eye assessment. This method of assessment is very time consuming involving hours of direct eye observation for an operator, which causes tiredness but also excessive levels of stress due to the critical nature of the assessment. Furthermore, if the fibre is dropped after removal from the tape and prior to spectrometer analysis, vital evidence may be lost. It is also not unusual for the search criteria to change during or after an ' initial assessment of the sample tape, for example, from an initial investigation for a blue fibre to an investigation for a red fibre. In these circumstances, the operator is required to assess the entire tape again. Due to the laborious nature of the current forensic sample assessment method, it is usually only reserved for high profile cases whilst petty crimes do not benefit from this kind of evidence gathering since it is regarded as too time consuming and therefore costly.

Many of the constituents of the present invention are already known in the art such as magnifying optical lenses and sample carriers. Spectrometers, which are the preferred means for assessing colour values, are also not new as of themselves. For example, various colour measurement systems are disclosed in EP0570003, US4464677, US4414635, EP0453830, US4534470, US4505589, EP0497747 and US5149960, some of these including optical lenses and sample carriers adapted for translational and rotational movement.

However, none of these prior art systems specifically addresses the problems encountered in analysing and processing forensic data.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect of the present invention, there is provided a colour assessment apparatus comprising a sample carrier, magnifying optics to capture light from defined locations of a sample located on the sample carrier, means for analyzing the light captured by the magnifying optics to measuring colour values of the defined locations of the sample, means for automatically displacing the optical means relative to the sample carrier in order to the apparatus to scan a succession of locations of the sample and to measure colour values of the sample for each location, memory means for storing a table of location information correlated with colour value information, means for inputting a colour value of a reference sample, and means for analysing the table so as to determine locations of any colour values from the sample that match the colour value of the reference sample.

According to a second aspect, the invention provides a colour assessment apparatus, comprising magnifying optics; a sample carrier located in sufficient proximity to the magnifying optics for the magnifying optics to capture light from defined locations of a sample; means for receiving light from said defined locations and assessing colour values such as spectral values of the light received; and means for displaying colour values; wherein means automatically displace the sample carrier relative to the magnifying lens in order for the apparatus to scan a succession of locations of a sample and means are provided to assess colour values of a succession of locations of a sample.

According to a third aspect of the present invention, there is provided a method of forensic analysis of an adhesive tape bearing fibres collected from a crime scene, the method comprising the steps of: i) using a colour assessment apparatus to scan colour values for a succession of locations on the adhesive tape;

ii) storing the scanned colour values in computer memory means in the form of a table of scanned colour values correlated with location information;

iii) providing a colour value of a reference sample;

iv) using computer means to search the table for colour values that match the reference colour value and to return location information for the colour values that match the reference colour value.

This combination of features is particularly advantageous in forensics where it will allow the assessment of a complete sample tape very rapidly without tiring the operator's eyes through direct observation. It will also allow an operator to gather information over the entire sample rather than manually filtering out fibres which are not of interest at a given point in time. It also does away with the prior art requirement of assessing first the contour of the fibres, since shape is not necessarily taken into consideration in this configuration. It will allow, due to its greater efficiency and greater completeness, the assessment to be carried out for what may be regarded as petty crimes, as well as for more serious crimes. It would even not necessarily require an operator to be present throughout the assessment.

Embodiments of the apparatus may display the colour values in an appropriate format for interpretation by a user.

The colour values may include absorbance values and/or spectral values.

The magnifying optics enable a high resolution colour value scan to be performed across a sample. This is of particular importance in forensic analysis of fibres.

Embodiments of the apparatus may further comprise means to plot a map of absorbance values for an area of the sample. Plotting a map may have a number of beneficial consequences in the forensics context. It may, for example, be sufficient to have a stored map to record the location of a particular fibre of interest on a sample without having to manually mark the location. It may also allow operators to rapidly identify particular areas of interest without having to re-scan the entire sample.

In a further subsidiary aspect, the system displays colour values without necessarily displaying the contour of sample elements. This marks a radical departure from the prior art thinking of first displaying the fibres and then assessing the colours. Assessing colours directly on a pixel level is all that is required in order to identify whether a particular colour is present on a sample or not.

In a further subsidiary aspect, means are provided to compare and display the obtained colour values from the sample with colour values of the reference sample in order to establish whether the sample's colour matches the reference sample's colour. This will allow matches to be rapidly identified. It will also identify whether further investigation of a particular location of the sample is necessary in order to more precisely compare reference sample colour values and obtained colour values.

In a further subsidiary aspect, means are provided for positioning a sample region of interest at a marking station allowing an operator to accurately mark the sample. This ' will improve the manner in which samples are marked. This approach will also reduce - the stress and tiredness imposed on an operator.

In a further subsidiary aspect, means are provided to automatically mark the sample in order to identify a specific region of the sample. This will do away with any need for an operator to mark with precision the location of a fibre of interest. This will create an altogether more efficient system.

In a further subsidiary aspect, the apparatus further comprises processing means which discriminate between sample substrate points and sample element points, whereby when the sample contains an array of element points of interest interspersed between substrate points which are of no interest, a detailed analysis is triggered only for the points of interest. This filtering stage also contributes to an altogether more efficient system of analysis.

In a further subsidiary aspect, the apparatus comprises a camera integrated to the apparatus allowing an operator to visually identify individual elements and direct the analysis of the sample towards identified individual elements without having to move the sample from a visual identification station to a colour analysis station. This would allow an operator to have a form of interaction with the apparatus being able to see a succession of fibres or other sample elements and then directing precise analysis of sample points of interest without having to change work station in the process.

Embodiments of the present invention may use visible light for measurement of colour values, and may additionally or alternatively make use of ultraviolet or other non-visible parts of the spectrum to make fluorescence or other measurements. Use of fluorescence techniques can be useful in determining the material from which a particular fibre is made.

Embodiments of the present invention may be used to provide a first, preliminary scan so as to determine whether there are any potential fibres in the sample that match a particular reference fibre, followed by a second, more detailed scan of the potential fibres so as to determine whether or not they are an exact match with the reference fibre.

A^~ 3D spectral graph may be generated by embodiments of the present invention so as to provide a record of spectral data at all points on a given sample- tape. Furthermore, a real to life image of the surface of the tape may also be recorded and superimposed with or shown together with the 3D spectral graph. The real to life image and the spectral data may be viewed in high resolution and facilities provided to zoom in on areas of interest.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how it may be carried into effect, reference shall now be made by way of example to the accompanying drawings, in which:

FIGURE 1 shows, in schematic form, the colour assessment apparatus in accordance with a first embodiment of the invention;

FIGURE 2 shows a general fibre scan illustrative image;

FIGURE 3 shows a detailed illustrative fibre scan image;

FIGURE 4 shows an absorbance graph of a reference alongside a sample fibre;

FIGURE 5 shows an example of the process used for assessing samples;

FIGURES 6a and 6b show a manual marking station (Figure 6a) and an automatic marking station (Figure 6b).

DETAILED DESCRIPTION

Figure 1 generally shows a colour assessment apparatus 1 with magnifying optics 2. The magnifying optics operate in conjunction with a spectrometer 3. A fibre 4 transfers the light captured by the magnifying optics 2 to the spectrometer, which records the spectral values of the light it receives.

The magnifying optics alternatively use two different objectives respectively referenced 5 and 6. Objective 5 may be an x10 objective whilst the objective 6 may be an x40 objective. The objectives may be located on a carousel so that the objectives may be rotated from a position of use to an idle position. A scanning plate 7 is envisaged and will be equipped with means to hold a sample such as a translucent tape to which are attached a number of fibres for analysis. (The sample tape is not illustrated in the figure for simplicity). The scanning plate is configured to allow the displacement of a sample at a fixed speed if necessary under the microscope objective. The sample may be illuminated from above or beneath using known techniques. The spectrometer may be triggered to acquire spectra during a stage movement. The microscope may acquire light at specific step sizes. For a 1cm x 1cm scan, a step size of 100μm may be employed whilst the stage moves continuously over a 1cm line and the spectrometer may be triggered to acquire 10 spectra, one after every 100μm of stage movement. The stage speed may be adaptable depending upon the number of spectra to be acquired in a specific distance.

Each stage movement typically involves a period of acceleration and deceleration. In order to acquire properly spaced spectra, the scanning process may be adapted to acquire spectra only when travelling at a constant speed, i.e. after acceleration and before deceleration. To allow for this, the stage may be moved a certain amount of millimetres away from the position where data, is acquired and the scan may also be adapted to pursue scanning several millimetres after the scanning line end point. Thus, for a 1cm x 1cm scan, the stage may be set to move 1.-8cm for each line. The scan can be carried out in a raster pattern or a snake pattern as appropriate. The data acquired may be stored in the spectrometer during each line of acquisition. The data may then be read from the spectrometer as the stage moves back to the start of the next scan line. It is also possible to set the spectrometer so that data is read continuously during acquisition. It is also envisaged that absorbance calculations, which may be performed from the data acquired by the spectrometer, are performed by a remote personal computer (PC) instead of being performed directly by the spectrometer. It is therefore particularly advantageous for the spectrometer to be set to read all data but for the calculation of absorbance values to be carried out by a PC.

The PC screen 8 is illustrated in Figure 1 which shows an absorbance variation for a particular location scanned.

The scanning process described above may plot an overall map of a defined area of a sample such as a 1cm x 1cm area. Such a map may have the form as shown in Figure 2. Differences in colour values may be identified overall in this map. Using greater magnifying objectives, a closer view of a particular fibre may be obtained such as that illustrated in Figure 3.

Storage means such as those provided in a PC may include a database of reference absorbance values for particular fibres. A comparison of reference absorbance values with sample absorbance values may be carried out in order to determine whether there exists a match. Further investigation of a match is then possible if required to verify the results obtained through this automatic scanning process.

A number of algorithms may be used for the comparison of spectra. These include: Euclidean Distance, Absolute, Least Squares, Correlation, First Derivative Absolute, First Derivative Least Squares and First Derivative Correlation.

The scanning process may be adaptable. The user may define the number of points to be assessed for a given sample. Acquisition parameters such as the integration time may also be user defined. Preferably parameters will be chosen to give as short a scan time as possible while allowing an accurate separation of points. In a commercial product, security means may be installed to prevent the user to modify such criteria.

The system will be able to adapt to different background spectra. Once all the scan parameters are determined and the dark and background spectra are determined, the system will scan the entire sample taking spectra at each scan point.

In a subsequent step, the system will discriminate fibre points of interest from the substrate or other points which are of no interest. This may be achieved by calculating the integral of each spectrum. High values will indicate a point of interest, while low values will indicate that only the substrate is seen. This separation threshold is set either manually or automatically by calculating a histogram of integral values and setting an appropriate threshold.

Interaction with a user is then envisaged so that a quality assessment takes place. If the quality is sufficient then full analysis may then take place, if the quality is not deemed to be sufficient, certain points or areas or an entire sample may be re-scanned with a higher level of magnifying optics or different integrating techniques if necessary. Samples of interest will then be compared as on Figure 4 to identify potential matches. If the results are definitive, the results are stored and the sample is marked if appropriate and the next sample is readied for analysis.

Figure 5 is a flow chart showing the assessment process of one embodiment of the present invention.

The actual sample is often required to be marked at points of interest, and the scan table may therefore be adapted to incorporate means to displace a sample plate such as that referenced 9 in Figure 6a towards a marking station 10. The marking station 10 may be a plate with a hole under which sample 9 may be displaced with precision for marking. Precision displacement techniques using motors or piezoelectric elements, as is known in the art, may be employed. When at the marking station, the user may apply a dot of ink or circle a particular point of interest using the hole of the plate 10.

Figure 6b shows a further marking station with a sample 11 located underneath a marking arm 12 which, once the sample is placed accurately beneath the marking point 13 of marking arm 12, the arm may be triggered to displace and draw a circle around the ^" point of interest.

The invention also envisages that each sample may incorporate a barcode which, when scanned, will identify the particular sample - thus avoiding the operator to have to manually mark samples.

It is also envisaged that the scanning table and the magnifying lens or lenses be equipped with means to keep the sample in focus as the Z distance between the two is automatically adjusted.

Claims

CLAIMS:

1. A colour assessment apparatus comprising a sample carrier, magnifying optics to capture light from defined locations of a sample located on the sample carrier, means for analyzing the light captured by the magnifying optics to measuring colour values of the defined locations of the sample, means for automatically displacing the optical means relative to the sample carrier in order to the apparatus to scan a succession of locations of the sample and to measure colour values of the sample for each location, memory means for storing a table of location information correlated with colour value information, means for inputting a colour value of a reference sample, and means for analysing the table so as to determine locations of any colour values from the sample that match the colour value of the reference sample.

2. An apparatus as claimed in claim 1 , wherein means are provided to plot a map of absorbance values for an area of the sample.

3. An apparatus as claimed in any preceding claim; further comprising a display for displaying measured colour values. - -

4. An apparatus as claimed in claim 3, wherein the display displays colour values without necessarily displaying the contour of sample elements.

5. An apparatus as claimed in claim 3 or 4, wherein the display displays the measured colour values from the sample together with colour values of the reference sample.

6. An apparatus as claimed in any preceding claim, wherein means are provided for positioning a sample region of interest at a marking station allowing an operator to accurately mark the sample.

7. An apparatus as claimed in any preceding claim, wherein means are provided automatically to mark the sample in order to identify a specific region of the sample.

8. An apparatus as claimed in any preceding claim, further comprising processing means which discriminate between sample substrate points and sample element points, whereby when the sample contains an array of element points of interest interspersed between substrate points which are of no interest, a detailed analysis is triggered only for the points of interest.

9. An apparatus as claimed in any preceding claim, further comprising a camera integrated with the apparatus allowing an operator to identify visually individual elements and direct the analysis of the sample towards identified individual elements without having to move the sample from a visual identification station to a colour analysis station.

10. Colour assessment apparatus, comprising magnifying optics; a sample carrier located in sufficient proximity to the magnifying optics for the magnifying optics to capture light from defined locations of a sample; means for receiving light from said defined locations and assessing colour values such as spectral values of the light received; and means for displaying colour values; wherein means automatically displace the sample carrier relative to the magnifying optics in order for the apparatus to scan a succession of locations of a sample and means are provided to assess colour values of a succession of locations of a sample. . ..

11. A method of forensic analysis of an adhesive tape bearing fibres collected from a crime scene, the method comprising the steps of:

i) using a colour assessment apparatus to scan colour values for a succession of locations on the adhesive tape;

iii) providing a colour value of a reference sample;

12. A method according to claim 11, wherein a map of absorbance values is plotted for an area of the sample.

13. A method according to claim 11 or 12, wherein measured colour values are displayed on a display.

14. A method according to claim 13, wherein the colour values are displayed without necessarily displaying the contour of sample elements.

15. A method according to claim 13 or 14, wherein the measured colour values from the sample are displayed together with colour values of the reference sample.

16. A method according to any one of claims 11 to 15, wherein a sample region of interest is positioned at a marking station to allow the sample region to be marked by an operator.

17. A method according to any one of claims 11 to 16, wherein the sample is automatically marked in order to identify a specific region of the sample.

18. A method according to any one of claims 11 to 17, wherein each sample is provided with an individual barcode to allow automatic recognition of the sample.

19. A method according to any one of claims 11 to 18, wherein processing means discriminate between sample substrate points and sample element points, such that when the sample contains an array of element points of interest interspersed between substrate points which are of no interest, a detailed analysis is triggered only for the points of interest.

20. A method according to any one of claims 11 to 19, wherein a camera integrated with the apparatus is used to identify visually individual elements and direct the analysis of the sample towards identified individual elements without having to move the sample from a visual identification station to a colour analysis station.

21. An apparatus substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and/or figures.

22. A method substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and/or figures.