GB2473230A

GB2473230A - Automated cigarette production line inspection apparatus using a contact image sensor to examine a rotating smoking article

Info

Publication number: GB2473230A
Application number: GB0915394A
Authority: GB
Inventors: Ian Francis Tindall; James Hugh Vincent; Dharmesh Mistry
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 2009-09-03
Filing date: 2009-09-03
Publication date: 2011-03-09
Anticipated expiration: 2029-09-03
Also published as: GB2473230B; GB0915394D0

Abstract

Rod imaging apparatus comprising a contact image sensor 6 that images the rod 2 as they rotate. The rod support may be a plurality of rollers 4 which may double as the rotation means. The rod axis is parallel to the image sensor and the separation distance is adjustable 24. A processor 12 identifies optically recognisable features in the rod to determine when rotation occurs. The outer circumferential surface of the rod/cylinder, or the inner surface of a tube, is imaged. A light source 8 illuminates the rod for front 8c, side 8b or back lighting 8a in infrared or ultra-violet wavelengths. The sensor captures multiple axial portions of the rotating rod, forming a stitched composite image. The rod may pass or fail the inspection based the detected features. The system is designed for the quality control of cigarettes, cigars and cigarillos to detect defects, along the entire length of the rod, such as wrapping paper spots, stains, creases and tears and the presence or absence of printed text.

Description

Apparatus for Imaging Features of a Rod The present invention relates to imaging apparatus for measuring attributes of a rod-shaped article, and a method of operating the apparatus.

Smoking articles such as cigars, cigarettes, and cigarillos are typically manufactured in bulk. As part of a quality control process, a single smoking article may be selected from a mass flow or completed package and its properties may be measured at a testing station. Processes such as these are important for ensuring that smoking articles conform to certain standards.

A testing station may be arranged to measure attributes of a smoking article such as its length, diameter and weight using well known methods. A testing station may also detect features or defects in a smoking article by visual inspection.

Examples of features or defects that may be detected include spots, stains, creases, and tears in the smoking article wrapping paper as well as the presence or absence of printed text of sufficient definition and uniformity.

One simple method for analysing features or defects in smoking articles involves human visual inspection. This approach is undesirable due to high costs, subjectivity in measurement, and inconsistencies due to fatigue.

Automated methods for analysing features or defects may involve the use of CCD cameras. CCD cameras typically create an image of a smoking article and forward it to a processor so that features can be detected and analysed using image processing algorithms.

In some systems CCD cameras are arranged to image the ends of smoking articles. While these systems enable the identification of defects in the ends of smoking articles, they are unable to identify defects in the middle portion of the smoking articles andlor defects that face radially outwards.

In other systems CCD cameras are arranged to image the circumferential surfaces of smoking articles at several rotated positions. The CCD cameras in these systems are generally remote from the smoking article so that the entirety of the smoking article can fill the field of view of the camera. A disadvantage of this arrangement is that there is a fairly low spatial resolution, meaning that microscopic features may not be detected.

Finally, in other systems CCD cameras are arranged to image a portion of the circumferential surface of smoking articles. In these systems optical arrangements are often provided to compensate for distortion. A disadvantage of these systems is that the entirety of a smoking article cannot be imaged by a single CCD camera. In addition, the system may be inflexible to deal with changes in the length of smoking article rods and the optical arrangements provided to compensate for distortion may be susceptible to contamination by dust and tobacco shreds.

There is, therefore, a need for a low cost, small sized system that can identify microscopic defects in smoking articles quickly and accurately over the entire length of a rod. The present invention is intended to address this problem.

According to one aspect of the present invention there is provided imaging apparatus comprising: a contact image sensor; a support for a rod to be imaged; and means for rotating the rod and the contact image sensor relative to one another such that the contact image sensor can image the rod as they rotate relative to one another.

In this way, the contact image sensor may be able to image a rod circumferentially. The contact image sensor may take a plurality of sequential images of adjacent axial strips of the rod, and these sequential images may be stitched together to form a composite image of a circumferential surface.

Generally a contact image sensor comprises a single linear array of image sensors.

A contact image sensor may be able to build an image of an object when the object is scanned past the sensor in a direction that is perpendicular to the linear array. By using a contact image sensor a rod can be imaged at close proximity to the sensor along its entire length. This may allow imaging with a high spatial resolution which may improve the detection of features in a rod when compared to traditional imaging methods. Thus, the contact image sensor may be arranged to take images of axial portions of the rod, or successive images of axial strips of the rod.

The contact image sensor may be provided in near direct contact with the rod, in use. Preferably the separation of the rod and the contact image sensor in use is less than 50mm, and preferably still the separation is less than 20mm.

Contact image sensors are generally highly power efficient, and can often be powered via a USB connection with a computer. Also, contact image sensors are often modularised by including all of the necessary optical elements in a compact module. Thus, a contact image sensor can generally be made smaller and lighter than a CCD line sensor.

In one example, the contact image sensor may be directed towards an outer circumferential surface of the rod as they rotate relatively. Thus, an image of the outward-facing circumferential surface of the rod may be assembled based on the measurements of the contact image sensor.

In another example the contact image sensor may be directed towards an inner circumferential surface of a tube-like rod. Thus, an image of the inward-facing circumferential surface of the rod may be assembled.

Preferably the support for the rod comprises means for rotating the rod. In this way, the contact image sensor may be held stationary while the rod is rotated so that the contact image sensor can take sequential images of axial strips of the rod.

Of course, in an alternative arrangement it would be possible for the rod to be fixed in position while the contact image sensor is rotated.

The support for the rod may include a plurality of rollers. Thus, the rod may be supported against gravity by rollers. Preferably there are at least two rollers so that the rod can rest against the rollers and be supported in a gap therebetween.

By rotating the rollers it may be possible to rotate the rod with respect to the contact image sensor.

Preferably the support is arranged such that a rod is supported with its main axis substantially aligned with the main axis of the contact image sensor. Thus, a plane defined by the contact image sensor may divide the rod in half along its main axis. By aligning the contact image sensor with the main axis of the rod it may be possible to avoid any edge effects that may be obtained by off-axis imaging.

The separation of the contact image sensor and a rod supported by the support may be adjustable. Preferably the positions of the rod and the contact image sensor are controlled so that the separation between the two is maintained substantially constant. Thus, when the rod is replaced by a new rod with different dimensions the relative positions of the new rod and the contact image sensor may be adjusted to provide a predetermined separation. In this way the contact image sensor may be able to image all types of rod with the same accuracy, independent of dimensions of the rod such as its diameter.

One mechanism for adjusting the separation of the rod and the contact image sensor may be to adjust the separation of two rollers that support the rod. A servo mechanism may also be used for adjusting the position of the contact image sensor.

Preferably the imaging apparatus further comprises a processor for identifying at least one optically recognisable feature in a rod in order to determine that a particular rotation of the rod has occurred relative to the contact image sensor.

In this way it may be possible to determine that the contact image sensor has imaged the rod through 3600. This may be achieved by establishing that a full rotation of the rod has occurred between two instances of detection of a single optically recognisable feature. Where the rod is a smoking article the optically recognisable feature may be printed text on the smoking article wrapping paper.

Alternatively it may be the overwrap that is present in the wrapping paper.

The rod may comprise a plurality of evenly spaced optically recognisable features which can be detected by the processor in order to establish that a particular rotation has occurred. For instance, a plurality of optically recognisable features may be spaced by a predetermined angular separation.

The contact image sensor and support may be arranged such that the contact image sensor is directed towards an outer circumferential surface of a rod. Thus, the contact image sensor may be able to image the outer circumferential surface of the rod andlor features of the rod that are below the outer circumferential surface.

In an alternative arrangement the contact image sensor and the support may be arranged such that the contact image sensor is directed towards an inner circumferential surface of a rod. Thus, the contact image sensor may be of a small size such that it can fit inside a tube-shaped rod. By rotating the tube ancllor the contact image sensor it may be possible to allow internal inspection of the tube with high resolution. This may be of use for the internal inspection of tubes used for packaging of cosmetics or healthcare products.

The contact image sensor may be able to image the inner circumferential surface of the rod. The contact image sensor may also may able to image internal features of the rod that are on the other side of the inner circumferential surface from the perspective of the contact image sensor.

Preferably the apparatus further includes a light source for illuminating the rod.

The light source may be particularly useful for highlighting internal features of the rod.

The light source may be arranged for front lighting, side lighting and/or back lighting the rod from the perspective of the contact image sensor. Side lighting may be used to enhance topographical features such as creases in a smoking article wrapping paper. Back lighting may be useful for illuminating smoking articles in order to identify problems in the adhesion in the lap, segment length in a filter, and voids in tobacco fill.

Preferably the light source is substantially coaxial with the contact image sensor.

This may ensure even illumination of the rod along the length of the contact image sensor.

The light source and the contact image sensor may be arranged so that the rod can be imaged in a selected wavelength range. This may be achieved by using filters in order to change the wavelengths of light that are directed towards the rod and/or to change the wavelengths of light that are received by the contact image sensor. It may also be achieved by using a light source with particular wavelength characteristics or by using a contact image sensor that is sensitive over a particular wavelength range.

A plurality of light sources may be provided, each with different wavelength characteristics. One of the light sources may be selected so that the rod can be imaged in a selected wavelength range.

By imaging a rod in a selected wavelength range it may be possible to enhance contrast around features in the rod. This may make features or defects more visible than they had been using polychromatic light or monochromatic light in a different wavelength range. One example of this may be mineral oil contamination of smoking article wrapping paper, the contrast of which may be enhanced by imaging in yellow light.

The light source and the contact image sensor may be arranged so tl1at the rod can be imaged in visible and/or invisible wavelength ranges. The use of ultraviolet or infra-red may allow the identification of chemicals such as menthol (which is invisible to the human eye) on a rod.

A plurality of light sources may be provided, and each light source may have a different operational wavelength. Light sources may also be positioned in order to illuminate a smoking article from different perspectives.

Preferably the contact image sensor is arranged to capture a plurality of images of axial portions of the rod or axial strips of the rod as they rotate relative to one another. The imaging apparatus may further comprise a processor for building a composite image of the rod by stitching together the images of axial portions of the rod.

The apparatus may further include a data storage unit arranged to store feature detection rules, and the processor may be arranged to detect features in the image according to the feature detection rules stored in the data storage unit.

Preferably there is a specific algorithm for the detection of each feature according to the feature detection rules. When the rod is a smoking article the relevant features that are detectable may include crumbs in the seam, poor seam adherence, print non-uniformity, spots, stains, creases, ragged end cuts, perforation defects, angled tipping paper placement, and tears. These features may be classed as defects.

The processor may be arranged to determine a pass or fail for a rod based on the detected features. The processor may be arranged to build a scoring matrix based on the detected features. The pass-fail criteria may be stored in the data storage unit so that rods with unacceptable features are determined as a fail by the processor. A pass or fail is preferably indicated visually on a display, but in alternative embodiments different indicators may be used such as an audible indicator for a fail result.

The apparatus may include a rod supported by the support. Preferably the rod is an elongate object with a regular cross-sectional profile. For example, the rod may be a cylindrical object such as a smoking article. The rod may also be a hollow object such as a tube.

There may be differences in the gain of pixels along the length of the contact image sensor. Thus, even when the contact image sensor is evenly illuminated it may falsely indicate a variation in illumination along its length. The rod may be arranged to reflect, transmit and/or radiate radiation evenly along its axis. By using a test rod that is specially designed to illuminate the contact image sensor evenly it may be possible to calibrate the contact image sensor so that a compensation factor can be applied to images produced subsequently. The compensation factor may be calculated by the processor and stored in the data storage unit.

It may be difficult to provide a scale for images created by the contact image sensor. Thus, while the contact image sensor may be able to image a rod around its full circumference, the physical dimensions of the circumference may be uncertain. The rod may comprise features with known physical dimensions; in particular the circumferential separation of certain features may be predetermined.

In this way the apparatus may be calibrated by rotating the contact image sensor and the test rod relative to one another while the test rod is imaged. By building an image of the test rod with known dimensions it may be possible to provide a scale for the images of subsequent rods.

The test rod may comprise a grid structure or a spiral structure of known physical dimensions so that these structures can be imaged and their properties can be related to the properties of other rods.

According to another aspect of the present invention there is provided an imaging apparatus comprising: an image sensor; a support for a rod to be imaged, wherein the image sensor and the support are arranged such that the image sensor can image an axial portion of the rod; means for rotating the rod and the image sensor relative to one another such that the image sensor can image a plurality of axial portions of the rod as they rotate relative to one another; and a processor arranged to receive the plurality of images of axial portions of the rod from the contact image sensor, and to build a composite image of the rod from the plurality of images.

The image sensor may be capable of imaging sequential adjacent strips of the rod so that these can be stitched together into an overall image of the rod.

According to yet another aspect of the present invention there is provided a method of operating an imaging apparatus as previously defined comprising the step of rotating the rod and the contact image sensor relative to one another such that the contact image sensor can image the rod as they rotate relative to one another.

Any apparatus feature may be provided as a method feature and vice-versa.

In order that the invention may be more readily understood, reference will now be made, by way of example, to drawings, in which: Figure 1 is a schematic drawing of a computer controlled apparatus for imaging a rod in an embodiment of the invention; Figure 2 shows the functional blocks of a computer for controlling an apparatus in an embodiment of the invention; Figure 3 is a flow diagram showing the operational steps undertaken in an embodiment of the invention; Figure 4 is a schematic diagram of a rod being imaged by a contact image sensor, and the resultant image produced in an embodiment of the invention; and Figure 5 is a schematic view of a content image sensor arranged to image a tube-shaped rod in an embodiment of the invention.

Detailed Description of Embodiments of the Invention Figure 1 is a schematic diagram of a computer controlled imaging system. A smoking article 2 is supported by two rollers 4, and a contact image sensor 6 is directed towards the smoking article 2.

As the name implies, the contact image sensor 6 is in near direct contact with the smoking article 2, in use. In fact the gap between the contact image sensor 6 and the smoking article 2 in use is approximately 17mm. The depth of field of the contact image sensor 6 can be considerable; for instance, it may be in the region of 4mm. This means that the separation of the contact image sensor 6 and the smoking article 2 does not need to be precisely 9mm in order to achieve a sharp focus.

The contact image sensor 6 comprises a linear array of detectors covered by a focusing lens. Red, green and blue LEDs may flank the array of detectors for illumination of the smoking article 2. The contact image sensor 6 is longer than the rod 2 and is therefore capable of imaging rods of many different lengths.

The contact image sensor 6 is coaxial with the smoking article 2 and is directed towards the main axis of the smoking article. The contact image sensor 6 is connected to a computer 10 so that it can be controlled and so that its images can be analysed.

Lamps 8a,b,c are provided for lighting the smoking article 2. The lamps are located in a number of positions in order to provide different information about the rod under examination. For example the lamp 8a is positioned on the opposite side of the smoking article 2 from the perspective of the contact image sensor 6, with the lamp 8a coaxial with the smoking article 2 to provide a backlit or through image of the smoking article. The lamp 8b is placed at an oblique angle to the smoking article to provide contrast and shadows for surface defects such as raised or sunken portions of the smoking article. A further lamp 8c is placed adjacent to and co-axial with the contact image sensor 6 in order to provide conventional bright field illumination of the smoking article. The lamps 8a, 8b and 8c may be capable of emitting light in selected wavelength ranges. For example, the lamp 8a may emit light only in infra-red wavelength ranges, or the lamp 8c may emit yellow light only or of a specific wavelength in the ultraviolet wavelength ranges.

A combination of lamps of different wavelengths in one position can be used to create images of pseudo colour using a conventional red, green blue combination of images. The lamps 8a,b,c are connected to the computer 10 so that their operation can be controlled.

A motor 20 is connected to the contact image sensor 6. The motor 20 is arranged to control the position of the contact image sensor 6 with respect to the rod 2 by raising or lowering it. Motors 22 are also provided for rotational control of the rollers 4. A further motor 24 is arranged to connect the axes of rotation of the rollers 4 so that their separation can be controlled. By controlling the separation of the rollers 4 it is possible to control the vertical position of the rod 2 relative to the contact image sensor 6. The motors 20, 22, 24 are arranged for control by the computer 10.

The computer 10 comprises a hub 12, a keyboard 16, a pointing device such as a mouse 18, and a display 14. Figure 2 is a schematic view of the functional blocks of the computer 10, representative of the interaction of the computer 10 with the components shown in Figure 1.

A central controller 30 is connected to a frame grabbing module 34 which in turn is connected to the contact image sensor 6. The central controller 30 also comprises respective connections to a light control module 32 and a motor control module 36; in turn, these are connected respectively to the lamps 8a,b,c and the motors 20, 22, 24.

The central controller 30 comprises connections to a data storage unit 42, a feature detection module 40, a scoring engine 44, and an image stitching module 38. The data storage unit 42 is connected to the feature detection module 40 which in turn comprises a connection to the image stitching module 38.

Figure 3 shows a flow diagram showing the operational steps that are undertaken with the apparatus in an embodiment of the invention.

A rod 2 is placed on the rollers 4, and the position of the contact image sensor 6, and the rollers 4, is controlled at step 50. In particular, the central controller 30 receives information about the separation of the rod 2 and the central image sensor 6, and it instructs the motor control module 36 to operate the motors 20, 24 such that a desirable separation of around 17mm is achieved.

The rollers 4 are rotated clockwise by the motors 22 under control of the motor control module 36 at step 52. This causes the rod 2 to rotate counter clockwise relative to the contact image sensor 6.

In one possible embodiment the rotating rod 2 is imaged at step 54 by the contact image sensor 6. The number of line images taken per second by the contact image sensor 6 is based upon the rate of rotation of the support motors 22 so that the peripheral velocity of the support rollers 4 is known. In this way it is possible to achieve uniform and undistorted pixel images at the contact image sensor 6 such that each sensor pixel has the same spatial dimension in both x and y directions e.g. the x dimension equates to 63 microns on the sample surface as does the y dimension of the pixel. The frame grabbing module 34 is arranged to receive information from the contact image sensor 6 and by setting the capture rate of the sensor based on the peripheral velocity of the support rollers 4 no additional scaling is required of the image.

The frame grabber module 34 receives each line image from the contact image sensor 6. The line images are then stitched together by the image stitching module 38 at step 56 in order to create a single image; this may occur within the computer 10 or internally within the contact image sensor 6.

Of course, the frame grabbing module 34 and the image stitching module 38 may be provided within the contact image sensor 6 and a complete reformed image can be delivered over a high speed communications link such as gigabit Ethernet, or similar high speed protocol, directly to the computer 10.

The stitched image is analysed by the feature detection module 40 at step 58 in order to search for characteristic features. In particular, the feature detection module 40 is arranged to monitor the stitched image for a feature that is indicative of a particular angular rotation of the rod 2. For example, if the rod 2 is a smoking article, there is generally a single wrapping paper seam or overwrap. Sequential detections of an overwrap may be indicative of a 360° rotation of the rod 2.

The feature detection module 40 is arranged to analyse a complete image of the rod 2 at step 60 in order to identify a particular defect, according to rules stored in the data storage unit 42. For example, the feature detection module 40 may be arranged to detect non-uniformity in printed text according to an algorithm stored in the data storage unit 42. If any non-uniformity is detected then this is recorded in the data storage unit 42.

The feature detection module 40 is arranged to detect a plurality of different types of defect in turn. For instance, after detecting non-uniformity in printed text the feature detection module 40 may search for spots in the wrapping paper, and then creases in the wrapping paper according to algorithms in the data storage unit 42.

All detected defects are recorded in the data storage unit 42.

Once the feature detection module 40 has detected all defects in the image of the rod 2, the central controller 30 can change the lamp 8a,b,c selected for illumination, or the settings of individual lamps 8a,b,c, via the lamp control module 32. In particular, a different wavelength range may be selected for the lamps 8a,b,c. This may be desirable in order to increase the contrast of particular defects in the rod 2. For example, mineral oil contamination of smoking article wrapping paper may have its contrast enhanced when the selected lamp 8a,b,c emits yellow light only. Therefore, by creating a new image of the rod at step 54 with the rod bathed in yellow light, the feature detection module 40 may be better able to identify any mineral oil contamination. A number of lamps 8a,b,c may be selected with differing properties by the central controller at step 62 in order to identify different features. The images of the rod achieved in different lighting conditions may even be assembled together by the central controller 30 to create a pseudo colour image of the rod.

The scoring engine 44 is arranged to retrieve all defects that have been detected in the rod 2 from the data storage unit 42 at step 64. The scoring engine 44 creates a scoring matrix of defects to classify the number of defects, their intensity, and size.

The scoring engine 44 sends its scoring matrix to the central controller 30 so that a pass/fail decision can be made at step 66 for the rod under analysis. The central controller 30 makes a pass/fail decision depending on the type of defects detected on the basis of rules stored in the data storage unit 42. For example, if a spot is detected that is less than 1mm in diameter, the central controller 30 may issue a pass result. However, if more than three spots of less than 1mm in diameter are detected, or a single spot of greater than 1mm in diameter is detected, the central controller 13 may issue a fail result. Greater complexity may be added so that a fail result can be issued if a single spot of less than 1mm in diameter is detected together with another defect such as non-uniformity of printed text. The pass/fail result for each rod may be displayed on the display 14 at output step 67.

The pass/fail rules stored in the data storage unit 42 may be established based on the results of testing using trained human scorers. In this way the results achieved with human quality control may be mimicked automatically in a repeatable fashion.

The defects listed in the scoring matrix may be indicative of a particular flaw in the manufacturing process. The central controller 30 is arranged to recognise such flaws based on rules stored in the data storage unit 42. Advice to the operator on how to correct the manufacturing process may then be displayed on the display 14 at output step 67 based on data pre-stored in the data storage unit 42.

Figure 4 is a schematic diagram of a smoking article 68 being imaged by a contact image sensor 6. The result of the imaging process is an image 70 produced by the image stitching module 38. The image 70 is a view of the outer circumferential surface of the smoking article 68. Thus, the size of the image depends on the circumference of the rod under analysis and the speed of rotation (and not on the number of pixels in a CCD array as may be the case in certain prior art systems).

The image 70 shows a seam 72 in the smoking article at both edges, printed matter 74, spots 76, and a hole in the paper 78. The spots 76, hole 78 and the non-uniformity of the printed text 74 are defects that are detectable by the feature detection module 40. In some embodiments the image 70 of the rod may be displayed on the display 14 at the output step 67.

It is generally desirable to calibrate the apparatus of the present invention so that each pixel in the contact image sensor 6 provides the same response to the same lighting conditions. This may be important because of a possible variation in the gain of pixels along the length of the contact image sensor 6. Calibration is performed by placing a test rod on the rollers 4. The test rod is specially designed to provide a known illumination along its length. Thus, the test rod may be imaged by the contact image sensor 6 and a compensation factor may be calculated by the central controller 30 and stored in the data storage unit 42.

Images captured by the contact image sensor 6 may provide a true indication of the features of a rod when the compensation factor is applied. Separate compensation factors may also be stored in the data storage unit 42 to compensate for any variations in the different illumination sources used 8a,b,c.

The apparatus can also be calibrated to ensure that the physical dimensions measured are accurate. In one calibration arrangement, a test rod having a grid-like structure on its outer circumferential surface is placed on the rollers 4. The grid-like structure has known dimensions, so that when the rollers 4 are rotated and the rod is imaged by the contact image sensor 6, the known separation of features on the rod can be compared with those that are measured by the contact image sensor 6. In this way, the physical size of features on rods measured by the contact image sensor 6 can be determined with accuracy.

Figure 5 is a schematic drawing of a further embodiment of the present invention.

In this embodiment the rod is provided as a tube 80, and the contact image sensor 6 is supported at a pivot point 82 which is coincident with the main axis of the tube 80. In this way, the contact image sensor 6 may be rotated relative to the tube so that it can image the inner circumferential surface of the tube 80.

Claims

Claims 1. Imaging apparatus comprising: a contact image sensor; a support for a rod to be imaged; and means for rotating the rod and the contact image sensor relative to one another such that the contact image sensor can image the rod as they rotate relative to one another.
2. An imaging apparatus as claimed in claim 1 wherein the support for the rod comprises means for rotating the rod.
3. An imaging apparatus as claimed in claim 1 or claim 2 wherein the support for the rod is a plurality of rollers.
4. An imaging apparatus as claimed in any of the preceding claims wherein the support is arranged such that a rod is supported with its main axis substantially aligned with the main axis of the contact image sensor.
5. An imaging apparatus as claimed in any of the preceding claims wherein the separation of the contact image sensor and a rod supported by the support isadjustable.
6. An imaging apparatus as claimed in any of the preceding claims further comprising a processor for identifying at least one optically recognisable feature in a rod in order to determine that a particular rotation of the rod has occurred relative to the contact image sensor.
7. An imaging apparatus as claimed in any of the preceding claims wherein the contact image sensor and support are arranged such that the contact image sensor is directed towards an outer circumferential surface of a rod.
8. An imaging apparatus as claimed in any of claims 1 to 6 wherein the contact image sensor and the support are arranged such that the contact image sensor is directed towards an inner circumferential surface of a rod.
9. An imaging apparatus as claimed in any of the preceding claims further comprising a light source for illuminating the rod.
10. An imaging apparatus as claimed in claim 9 wherein the light source is arranged for front lighting, side lighting and/or back lighting the rod from the perspective of the contact image sensor.
11. An imaging apparatus as claimed in claim 9 or claim 10 wherein the light source is substantially coaxial with the contact image sensor.
12. An imaging apparatus as claimed in any of claims 9 to 11 wherein the light source and the contact image sensor are arranged so that the rod can be imaged in a selected wavelength range.
13. An imaging apparatus as claimed in any of the preceding claims wherein the contact image sensor is arranged to capture a plurality of images of axial portions of the rod as they rotate relative to one another.
14. An imaging apparatus as claimed in claim 13 further comprising a processor for receiving the plurality of images from the contact image sensor and building a composite image of the rod.
15. An imaging apparatus as claimed in claim 14 further comprising a data storage unit arranged to store feature detection rules, wherein the processor is arranged to detect features in the image according to the feature detection rules stored in the data storage unit.
16. An imaging apparatus as claimed in claim 15 wherein the processor is further arranged to determine a pass or fail for a rod based on the detected features.
17. An imaging apparatus as claimed in any of the preceding claims further comprising a rod supported by the support.
18. An imaging apparatus as claimed in claim 17 wherein the rod is arranged to reflect, transmit andlor radiate radiation evenly along its axis.
19. An imaging apparatus as claimed in claim 17 or claim 18 wherein the rod comprises features with known physical dimensions.
20. Imaging apparatus comprising: an image sensor; a support for a rod to be imaged, wherein the image sensor and the support are arranged such that the image sensor can image an axial portion of the rod; means for rotating the rod and the image sensor relative to one another such that the image sensor can image a plurality of axial portions of the rod as they rotate relative to one another; and a processor arranged to receive the plurality of images of axial portions of the rod from the contact image sensor, and to build a composite image of the rod from the plurality of images.
21. An imaging apparatus as claimed in claim 20 wherein the image sensor comprises a single line of sensors for imaging an axial portion of the rod.
22. A method of operating an imaging apparatus as claimed in any of the preceding claims comprising the step of rotating the rod and the contact image sensor relative to one another such that the contact image sensor can image the rod as they rotate relative to one another.
23. An apparatus substantially as herein described with reference to and/or as illustrated in the accompanying drawings.
24. A method substantially as herein described with reference to the accompanying drawings.