OPTICAL SORTING APPARATUS

Abstract: Optical sorting apparatus for sorting individual objects such as beans, nuts, seeds or other agricultural products. The sorting apparatus comprises means for detecting light from the objects and background means locatable behind the stream relative to the light detecting means. The apparatus is charac­ terized in that the background means is dynamically variable to provide an adjustable reference for the light detecting means. A method for sorting objects by optical means also is disclosed.

Description: The present invention relates to optical sorting apparatus for sorting individual objects such as beans, nuts, seeds and other agricultural products. Apparatus of the above kind is adapted to receive a plurality of objects to be sorted. The apparatus generally includes a viewing zone or viewing head for analysing objects inter alia on the basis of colour and/or brightness. The products are delivered individually to the viewing zone or head for optical analysis. The apparatus includes means for rejecting or diverting products which do not meet predetermined analysis criteria. There presently exist various systems for carrying out optical sorting. These systems are similar in that they include a feeding zone which separates the products into individual streams. The individual streams pass into respective viewing zones where they are illuminated and the reflected light is collected by one or more viewing assemblies and associated detectors. Where analysis is based on colour at least two detectors are typically provided. Each detector is made responsive to a different part in the light frequency spectrum. The detectors produce electrical signals which are related to the light which they detect. The electrical signals are processed via an electronic circuit which then determines whether a given product falls within an acceptable range. The electronic circuit may activate a rejection mechanism in the event that an object falls outside of an acceptable range. One type of optical sorting apparatus performs the required analysis by comparing the light reflected from the objects with the light coming from a suitably coloured background. The background may be provided by screens painted the required colour, or by screens illuminated with light of the required colour. Current viewing heads use painted backgrounds as colour references or standards. The colour references are critical requiring colour compatibility within 1 - 1.5% of an acceptable colour range. The backgrounds must be replaced for each colour change. In some apparatus these backgrounds may be changed remotely. Nevertheless, most apparatus requires a large number of backgrounds to be kept. To change from one product to another, e.g. peanuts to coffee beans, requires replacement of two filters and one background for each light detector. There may be up to nine or more light detectors in any given apparatus. Even a change from one grade of coffee bean to another grade usually requires a change of backgrounds. Sometimes the light frequencies are unique and must be determined in a laboratory. Dust and colour deterioration of the backgrounds also give rise to problems. Because of these problems associated with painted backgrounds, there have been proposals to provide backgrounds illuminated by light of the required colour and means for varying the illuminating light to facilitate calibration of the apparatus to suit it for sorting different products. One such proposal is EP-A-O 146 299 that discloses the use of backgrounds illuminated by differently coloured light from sources having means to adjust the individual intensities of light output by the respective sources. In other types of optical sorting apparatus the light reflected by the objects is analysed by reference to stored data as to the spectral analysis of light reflected by an acceptable object. US-A-4 057 146 is illustrative of apparatus of this type, disclosing a proposal to recover light reflected from an object by means of a bundle of optical fibres having their ends distributed around the path of the objects and divided into two groups to feed the light to two detectors having different response characteristics. Another proposal involving spectral analysis of the light reflected by an object is contained in GB-A- 1 604 745, that discloses apparatus in which objects are viewed against polarised light backgrounds that can thus be distinguished from the light reflected by an object, the apparatus comprising beam splitter means including a dichroic mirror to divide the light reflected by an object into two beams of different spectral content, the intensities of the two beams being detected by photodetectors. Current viewing heads use a number of spaced viewing assemblies surrounding the travel stream of products to be sorted. The viewing assemblies are typically located in a single plane perpendicular to the line of travel of the products. This ensures that each viewing assembly views the products at the same time. Odd numbers of viewing assemblies (3, 4, 7, 9) predominate in apparatus of the type using coloured backgrounds or colour references because each viewing assembly is located opposite an associated background or reference. However, such coplanar arrangements of viewing assemblies give rise to blind spots particularly in regions close to the streams of the products. Prior art viewing heads are relatively bulky for the viewing area they provide, e.g. 30 cm outside diameter for a 5 cm product viewing area. This is due to the need to accomodate several illuminating lamps (incandescent or fluorescent), spherical lenses having relatively long image and source focal lengths and a plurality of viewing assemblies, photo-detectors, filters, etc., and associated reference backgrounds. The lamps generate heat which affects response characteristics of the photo-detectors. Heat also accelerates the above-mentioned colour deterioration of painted backgrounds. Cooling is desirable to alleviate colour deterioration and avoid drifting of photo-detectors from their cool response characteristics. Prior art viewing heads are deliberately made larger to assist cooling. One disadvantage of bulky viewing heads is that it limits the number of processing channels which a machine of a given size can simultaneously handle. Also because photo-detectors in the viewing head send relatively small currents to processing circuits via long cables these long cables give rise to electrical interference. Electrical interference may be from external sources and from cables carrying relatively high currents to the lamps (due inter alia to capacitance effects). Existing apparatus generally uses different detectors for each viewing assembly. This gives rise to a response imbalance between the detectors because in practice every detecting filter has different characteristics. Prior art viewing assemblies generally utilize common geometry spherical lenses to focus an image of the product onto respective photo-detectors. This requires a lens which is larger in diameter than the area to be viewed. It also requires the image and source focal lengths to be long. Divergent and convergent beam angles also give rise to timing errors in the rejecting mechanism due to beam width increasing with distance from the focal points, (particularly when defects occur on the heel or toe of a product) sometimes causing good products to be rejected. Additionally, lenses are dependant upon and must be selected according to diameter of the viewing area (i.e. approximate size of product) and focal length. The problem of rejection of good products is compounded because existing sorting apparatus does not register acceptable products, i.e. it cannot distinguish a good product from no product. The rejecting mechanism ideally should be able to cope with defects located at the heel or toe of a product. However, random location of defects causes some good products to be rejected when a good product is conveyed too close to a defect on another product. This problem is particularly apparent if a product has defects at both ends (i.e. the middle portion is good) causing the apparatus to register two defective products. Precise alignment of prior art viewing heads and assemblies is required to obtain correct operation. Alignment is generally done in two stages. Firstly, the viewing head is aligned with respect to the product stream. This may need to be done on a regular basis particularly where the apparatus is used to sort a wide range of products. Secondly, each viewing asssembly is separately adjusted with respect to the viewing head and product stream. The viewing assemblies ideally are adjusted to form a flat circle around the product stream. This ensures that all views are synchronized in time. If a defect is detected then the rejecting mechanism will be actuated substantially at the same time irrespective of which viewing assembly 'saw' the defect. It is an object of the present invention to at least alleviate the above-mentioned disadvantages of the prior art apparatus of the type utilising background or colour references for comparative analysis of light reflected by the objects. Thus the invention is applicable to optical sorting apparatus for sorting objects moving in a stream through a viewing zone, of the kind comprising means for illuminating objects in said viewing zone; detecting means for detecting light reflected by an object in said viewing zone; background means disposed opposite said detecting means to be behind an object, relatively to the detecting means, in said viewing zone, said background means being illuminated by differently coloured light from sources having means to adjust the individual intensities of light output by the respective sources. In accordance with the invention, such an apparatus is characterised in that the background means comprise at least one bundle of optical fibres having a first terminal end providing a background in said viewing zone and a second terminal end remote from the viewing zone; and means for combining the light outputs of said sources and for illuminating said second terminal end of said optical fibre bundle by said combined light outputs, whereby all fibres in said bundle carry light of a colour determined by the respective light outputs of said sources. In preferred embodiments of the invention, the apparatus is further characterised in that the detecting means comprise at least one bundle of optical fibres having a first terminal end providing a light receiver in said viewing zone and a second terminal end remote from the viewing zone; beam splitter means positioned to receive light transmitted by said optical fibres from the viewing zone and adapted to divide said light into two beams; and at least one pair of photo-detectors associated respectively with individual different filters, arranged for one of said pair to receive one said beam and the other of said pair to receive the other said beam. The apparatus of the present invention includes at least two sources of light for said background(s), each light source being adjustable in intensity as seen by the background(s). Each light source may comprise white light, e.g. a quartz halogen incandescent lamp. The intensity of each light source may be adjustable by any suitable means. In one form, each light source may be adjustable via a respective ′dimmer′ control circuit. Each dimmer circuit may include at least one solid state switching element such as a thyristor. The dimmer control circuits may be constructed in any suitable manner as is known in the art. Alternatively, intensities of the light sources may be adjustable by means of polarizing filters or other means which reduce illumination of the background(s) by a source. The light sources may be adapted to provide at the background(s) illumination of substantially mutually exclusive spectral content. The light spectrum may be split at any frequency which falls between the light frequencies of interest. For example, where the light frequencies of interest are say, 530 nm and 660 nm respectively, the light spectrum may be split at say, 650 nm. One light source may be adapted to provide spectral content below 650 nm (green). The other light source may be adapted to provide spectral content above 650 nm (red). For this purpose the apparatus may include filter means adapted to pass light having required specific spectral contents. For instance the filter means may include a first filter adapted to pass from one source a first component of light, the spectral content of which is centered at 530 nm and a second filter adapted to pass from the other source a second component of light, the spectral content of which is centered at 660 nm. In accordance with the first aspect of the invention, the light from the sources is combined to provide a composite beam of light to be transmitted to the or each background by a bundle of optical fibres. The light from the sources may be combined in any suitable manner. In one form, the light may be combined by means of a half silvered mirror, the light sources sending individual beams oriented in paths substantially 45° to the plane of the half-silvered mirror and at right angles to each other. It will be appreciated that by independently adjusting the intensities of the light sources, e.g. by adjusting the voltage to each lamp, a desired mix of light content above and below 650 nm may be achieved. In a preferred embodiment of the present invention, the filter function and combining function is provided in a single device such as a dichroic mirror. A dichroic mirror transmits light above a given threshold frequency and reflects light below the threshold frequency. The dichroic mirror may be chosen to split light at a desired frequency, e.g. 650 nm. In another possible arrangement, white light sources and filters are replaced by substantially monochromatic light sources such as L.E.D. arrays selected to provide outputs having any convenient frequency of light (colour). These may be selected to be similar to filters associated with the detecting means. According to the first aspect of the present invention, the light sources are located remote from the viewing zone, light being conducted from the sources to the viewing zone via one or more suitable optical fibre bundles. The optical fibres may comprise glass or plastics and be formed into bundles or cables having any suitable length and cross section. Preferably, the bundles are rectangular in cross section at least in the region of the viewing zone. Rectangular bundles are preferred because it has been found that they minimize occurrence of blind spots when compared to circular bundles. In accordance with the second aspect of the invention, and in preferred embodiments thereof, the detecting means include at least two photo-detectors such as photo-cells located remotely from the viewing zone of the apparatus and receiving light therefrom via at least one bundle of optical fibres. This remote location of detectors (and light sources) is desirable because it minimizes interference. This is so because respective electrical connecting leads may be kept as short as possible and separate from each other. Thus photo-detectors may be placed adjacent their respective processing circuits and light sources may be located adjacent their power supply to minimize cable lengths. The optical fibre bundle(s) associated with the detecting means may have any suitable cross section, but are preferably rectangular in cross section at least in the region of the viewing zone, because they minimize occurrence of blind spots and assist a scanning action as an object moves through the viewing zone. In one form, the or each detecting fibre bundle may be substantially 2 mm high and 13 mm wide in cross section. The dimensions of the or each bundle of optical fibres may be increased or decreased as required. The light receiving end of the or each bundle of optical fibres is preferably directed at a background located opposite thereto in the viewing zone. The light receiving ends of the optical fibres may be focussed in any suitable manner such as by means of lenses. Focussing may be performed by means of micro lenses. Micro lenses manufactured by Nippon Sheet Glass and sold under the trade mark "Selfoc" may be used. Micro lenses are more compact than conventional lenses having similar focal length. A typical micro lens may be 4 mm long and 1.8 mm in diameter. Micro lenses perform the same function as standard spherical lenses with the added feature that the end surfaces are flat. Micro lenses sold under the trade mark "Selfoc" exhibit an index of refraction which varies parabolically across its surface with radial distance from its axis. The micro lenses may be arranged in arrays. Each array may comprise a stack of micro lenses. The stacks preferably are sufficiently high and wide to cover the area of an associated optic fibre bundle. The micro lenses may be staggered in the array like ′bricks′ to minimize occurrence of blind spots. One micro lens array may be placed adjacent the light collecting end face of each bundle of optical fibres. The micro lenses preferably are spaced from the end faces such that they focus at infinity. In one form, each micro lens may be spaced just 0.2 mm from an associated end face. The detecting means further includes a beam splitter such as a half silvered mirror. The beam splitter is adapted to separate light received from the detecting optical fibre bundle(s) into two beams. The two beams may be passed through seprate detecting filters to respective photo-detectors. The detecting filters preferably pass only selected light frequencies. For example, one filter may be adapted to pass a narrow band of light frequencies centered at 530 nm. The other filter may be adapted to pass a narrow band of frequencies centered at 660 nm. The photo-detectors may be adapted to produce electric signals which are related to the amount of light they receive. A suitable electronic circuit may be associated with the photo-detectors to provide an output signal indicative of the relative content of the two bands of frequencies, (i.e. 660 nm and 530 nm in the example given) present in the light which is detected. A plurality of backgrounds and associated detectors may be used to surround the viewing zone, each detector being adapted to receive light from an oppositely located background. When dealing with relatively large or small objects, more or fewer backgrounds and detectors may be employed. For example with five backgrounds and detectors, the backgrounds may be located substantially 72° apart. In general, sufficient backgrounds and detectors are required to cover substantially the whole of the surface area of the object being sorted. Where an even number of backgrounds is used the "background" optical fibre bundles and "detecting" optical fibre bundles may be produced as inetgrated assemblies. Each integrated assembly may include one bundle of "background" optical fibres and one bundle of "detecting" optical fibres and associated lenses. The integrated assemblies may be fitted to any size viewing head. According to a preferred embodiment of the present invention, all detecting optical fibre bundles of the apparatus may be associated with a common light detecting means. That is, the "detector" ends of the bundles of detecting optical fibres may be brought together so that light from the bundles may pass through a common beam splitter and detecting filters. An advantage of the latter arrangement is that light from each detecting bundle may be processed similarly thereby eliminating response differences. Each bundle of detecting optical fibres preferably is termintated with a suitable lens such as a plano convex lens. The plano convex lenses may be adapted to collimate the beams to enable them to pass through the same beam splitter and detecting filters. The apparatus of the present invention preferably includes means for sensing the presence and/or location of an object in the viewing zone. The sensing means may include means for transmitting one or more sensing beams, preferably of electromagnetic energy such as infra-red, in at least one path to intercept the object stream in the viewing zone. The sensing beams preferably cross the object stream substantially at right angles thereto. In one form, the sensing means may comprise at least one infra-red generator and associated receiver. The or each infra-red generator and associated receiver preferably are located remote from the viewing zone. Infra-red beams may be conveyed to and from the viewing zone via suitable conduits such as optical fibres. Transmitting fibres may be used to convey infra-red sensing beams from the or each infra-red generator to the viewing zone. Receiving fibres may be used to convey the sensing beams from the viewing zone to the (or each) associated infra-red receiver. The receiving and transmitting fibres may be located on opposite sides of the object stream. Preferably, the object sensing means utilise a plurality of infra-red beams. In one form, six beams may be used. The six beams preferably are substantially coplanar. The six beams may be arranged in two sets of three beams each. The beams of one set may be perpendicular to the beams of the other set. The three beams of each set preferably are parallel and equally spaced. Signals from the receivers of all six beams may be applied to logic means such as an OR gate. The output of the OR gate will switch if one or more of the beams is intercepted by an object. The infra-red beams preferably are located so that the intersection of the middle of each set of three beams lies substantially along the line of travel of the objects. The object sensing means may be adapted to provide accurate timing control to the rejecting mechanism. In one form, the object sensing means may be adapted to generate an enable pulse having a predetermined dwell time to the rejecting mechanism. Dwell time of the enable pulse also maybe controlled by the object sensing means. The enable pulse may enable the rejecting mechanism for the duration of the enable pulse. It will be appreciated that larger objects will intercept the sensing beam(s) for longer periods. Accordingly, the enable pulse dwell time may be dependent on object size (traversing length). Because timing information may be provided to the rejecting mechanism by the object sensing means, the various backgrounds and associated detectors do not have to be synchronized. Hence the "viewing assemblies" (backgrounds and associated detecting cables) do not have to be in a common plane but may be placed at oblique angles to the object stream. This reduces the number of blind spots on the object. It also enables more viewing assemblies to be placed into a given space. The object sensing means may be used inter alia for alignment purposes. As previously noted, the viewing head should be aligned accurately for optimum results. Prior art alignment procedures rely on physical sighting of the product sensing means may be used to align the viewing head relative to the object stream. The sensing beams described above may be used to determine which beams are being intercepted by the stream of objects. The outputs of the receivers of the beams may be processed by a suitable electronic circuit to determine which beam or beams are being intercepted with most frequency. The viewing head may be adjusted until only the middle beams of each set are intercepted by the object stream. This would indicate that the object stream is in the centre of the viewing zone. Any number of beams may be used, for example 4 or 5 beams for each set, particularly where variation in product size is relatively large. The apparatus according to the present invention may not require alignment of individual viewing assemblies. The actual position of the detecting cables and lenses may be made dependent on the original machining of the viewing head and hence may not alter significantly in use. Because lenses are focussed at infinity focussing of lenses may be obviated when changing from one product size to another. Furthermore, because individual detecting cables may transmit light into a common beam splitter and detecting filters, inaccuracies in this section of the apparatus affect all viewing assemblies in the same way. The apparatus of the present invention preferably includes product illumination means. The illumination means preferably is arranged such that reflected and stray light within the object viewing zone is kept to a minimum. Illumination of an object preferably is limited to an area which is substantially the same as the viewed area of the object. The illuminating light may be directed into the viewing area in a substantially rectangular format. Illuminating light may be provided in any suitable manner and by any suitable means. In one form illuminating light may be provided from a remote light source and conveyed to the viewing zone. Light preferably is conveyed to the viewing zone by means of one or more optic fibres. The optic fibres may be formed into bundles or cables as previously described. Illuminating light may also be conveyed to the object viewing zone by means of lens arrays, lenses, mirrors etc. It is preferable to illuminate only that portion of an object which is scanned by the detecting means. In other words the illuminated area and the viewing area of the detecting means preferably correspond on the product. The illuminated area preferably comprises a rectangle with its long edge across the product stream. Other patterns of illumination could be used eg. circular. In one form the receiving end of the optic cable associated with the detecting means and the transmitting end of the cable associated with the illumination means may be arranged side by side. The cables may be arranged such that the illuminated area and detecting means viewing area coincide substantially on the product. A still better result may be obtained by randomly inter-mixing the receiving ends of the detecting optical fibres and the transmitting ends of the illuminating fibres to form a combined illuminating|detecting cable. The opposite end of the combined illuminating|detecting cable is bifurcated with the illuminating fibres being directed to the illuminating light source and the detecting fibres to their respective photo-detector. Reflection from lenses associated with the illuminating|detecting cable may be reduced by applying anti-reflecting coatings to the lenses. The present invention preferably includes means for automatically setting the backgrounds. The background setting means may be provided in any suitable manner. The background setting means may include means for comparing the output from the detecting means when a good product is in view with the output from the detecting means when no product is in view, i.e. when the detecting means only sees the backgrounds. The background setting means may include means for adjusting the intensity of light sources which provide light to the optical cables which make up the backgrounds. The light sources for each channel (i.e. above 650 nm and below 650 nm in the example given) may be adjusted separately. The intensity of the lamps preferably are adjusted so that the output of the comparing means is a minimum. In other words, the backgrounds are compared to a good product and adjusted such that their spectral content (at least in the critical area) is substantially the same as that of the good product. This is in contrast to prior art apparatus in which backgrounds are selected from fixed standards and products are compared to the standards. A preferred embodiment of the present invention will now be described with reference to the accompanying drawing. The apparatus shown in the drawing includes a viewing head 1. The viewing head 1 surrounds an object viewing zone 2. Objects to be viewed move through the viewing zone 2 in a direction substantially perpendicular to the page. Mounted around the viewing head 1 is a plurality of background assemblies B1-B4 and a corresponding plurality of viewing assemblies V1-V4. Viewing assemblies V1-V4 are located opposite respective background assemblies B1-B4. Background assembly B1 includes an optic cable 3 and lens array 4. Similarly background assemblies B2-B4 include respective optic cables 5, 6, 7 and lens arrays 8, 9, 10. Each cable 3, 5, 6, 7 comprises a plurality of optic fibres. Backgrounds B1-B4 are supplied with sources of light from the assembly shown generally at 50. The assembly 50 includes light sources 11, 12. Light sources 11, 12 feed into the free ends of optic cables 5, 3, 7, 6 via respective lenses 13, 14 and dichroic mirror 15. Alternatively light sources 11, 12 may be prefocussed obviating lenses 13, 14. Dichroic mirror 15 passes light above 650 nm from light source 11 and light below 650 nm from light source 12. Light sources 11, 12 are controlled via respective dimmer control circuits 16, 17. Viewing assembly VI includes a bifurcated optic cable 18 and lens array 19. Similarly viewing assemblies V2-V4 include respective bifurcated optic cables 20, 21, 22 and lens arrays 23, 24, 25. Each cable 20, 21, 22 comprises a plurality of optic fibres. One free end of each bifurcated optic cable 21, 22, 18, 20 feeds into a detecting arrangement shown generally at 51. Detecting arrangement 51 includes a plurality of lenses 26 and a half-silvered mirror 27. Half-silvered mirror 27 passes light collected from optic cables 21, 22, 18, 20, to respective photo-detectors 28a-28d via filter 29 and to respective photo-detectors 30a-30d via filter 31 Signals from photo-detectors 28a-28d, 30-30d are received by background setting means 32. Background setting means 32 includes amplifier means and comparator means. Background setting means 32 adjusts dimmer control circuits 16, 17 such that when a product of good quality is dropped through viewing zone 2, the differences in signals from photo-detectors 28a, 30a with product in view|product out of view is a minimum. Background setting means 32 additionally receives signals from object sensing means 35. The other free end of each optic cable 21, 22, 18, 20 is supllied with a source of illuminating light from wide band light source 33 and lens 34. Object sensing means 35 processes signals from a plurality of infra-red detectors 36-41. Detectors 36-41 receive infra-red beams via respective optic fibres 42-47 and lenses 48-53. The product sensing means includes a plurality of transmitting lenses 54-59 and a corresponding plurality of receiving lenses 60-65. Receiving lenses 60-65 and/or lenses 48-53 may be doped with filter material. The filter material may be adapted to transmit infra-red light only thus reducing errors due to stray light etc. Additionally or alternativley infra-red filter material may be placed over infra-red detectors 36-41 for this purpose. Transmitting lenses 54-59 receive infra-red light from infra-red generator.66 via lens 67 and optic fibres 68-73. Lens 67 may be doped to transmit infra-red light only in which case generator 66 may be wide band. Transmitting lenses 54-59 are adapted to send infra-red beams to respective receiving lenses 60-65. Infra-red transmitting lenses 54-59 and receiving lenses 60-65 although shown separately are located inside viewing head 1. Sensing means 35, infra-red detectors 36-41 and lenses 48-53 are located remote from viewing head 1. The transmitting and receiving lenses are oriented in viewing head 1 such that the infra-red beams are intercepted when a product is being viewed by the viewing assemblies. The intersection of control beams for transmitting lenses 55 and 58 preferably lie substantially along the direction of product flow. When backgrounds have been set product sensing means 46 enables rejecting means 74 whenever the product rejecting means detects that the components of light received by photo-detectors 28a-28d, 30a-30d are not compatible with an acceptable product. It will be appreciated that the arrangement of the present invention enables backgrounds to be matched quickly to any product even when the background values for the product are unique or unknown. To change from one product to another, say peanuts to coffee, requires replacement of a total of two filters only for the whole apparatus and does not require replacement of any backgrounds. to change from one coffee bean to another requires no change of parts. The operator merely selects ′adjust nulls′ on the apparatus and then drops a good product into the viewing area. The good product is scanned by each viewing assembly and detected by the infra-red beams. During the nulls adjustment stage light sources 16, 17 are adjusted so that the light components received by photo-detectors 28a, 30a are the same (or as close as possible) when a product of good quality is in view as when no product is in view. When light sources 16, 17 have been adjusted the apparatus may indicate to the operator that the backgrounds are set and ready to run. When the apparatus is sorting one type of product only (95% of machines do in practice) the apparatus of the present invention requires no change of parts. The background adjustment described herein is possible because two controlled light sources are used for independently adjusting the two light frequencies of interest, e.g. 530 nm and 660 nm. This is in contrast to current technology which uses a fixed white light from incandescent lamps. The present invention allows a particularly compact viewing head to be constructed. This allows more processing channels to be included in a sorting apparatus per given floor space. For example, for an 8 cm viewing area the viewing head may be approximately 13-15 cm in outside diameter. Several features of the present invention contribute to the compact dimensions of the viewing head including: 1) light sources may be located remote from viewing head 2) light detectors may be located remote from viewing head 3) product sensing means may be located remote from viewing head 4) each background and viewing assembly may be combined into one integrated assembly 5) minimum heat generated hence cooling is not required 6) lenses having short focal lengths may be used. The apparatus of the present invention may be adapted to operate in mono-chromatic or bi-chromatic configuration with the same viewing head. This requires one background light source only and one receiving channel, i.e one light source may be turned off or eliminated.

Claims: 1. Optical sorting apparatus for sorting objects moving in a stream through a viewing zone (1), comprising means (33) for illuminating objects in said viewing zone; detecting means (V1-V4) for detecting light reflected by an object in said viewing zone; background means (B1-B4) disposed opposite said detecting means to be behind an object, relatively to the detecting means, in said viewing zone, said background means being illuminated by differently coloured light from sources (11, 12) having means to adjust the individual intensities of light output by the respective sources, characterised in that the said background means comprise at least one bundle of optical fibres having a first terminal end (B1-B4) providing a background in said viewing zone (1) and a second terminal end remote from the viewing zone; and means (15) for combining the light outputs of said sources (11, 12) and for illuminating said second terminal end of said optical fibre bundle by said combined light outputs, whereby all fibres in said bundle carry light of a colour determined by the respective light outputs of said sources. 2. Optical sorting apparatus according to claim 1, further characterised in that said detecting means comprise at least one bundle (18, 20, 21, 22) of optical fibres having a first terminal end (V1-V4) providing a light receiver in said viewing zone (1) and a second terminal end remote from the viewing zone; beam splitter means (27) positioned to receive light transmitted by said optical fibres from the viewing zone and adapted to divide said light into two beams; and at least one pair of photo-detectors (28, 30) associated respectively with individual different filters (29, 31) arranged for one of said pair to receive one said beam and the other of said pair to receive the other said beam. 3. Apparatus according to claim 2, further characterised in that said means (15) for combining the outputs of said sources comprises a dichroic mirror. 4. Apparatus according to claim 3, further characterised in that said dichroic mirror transmits light above 650 nm and reflects light below 650 nm. 5. Apparatus according to any one claims 1 to 4, further characterised by means for automatically adjusting said background means by control of said coloured light sources in response to detection of a correctly coloured object. 6. Apparatus according to any preceding claim, further characterised in that the optical fibres of the first terminal end of a bundle (3, 5, 6, 7) providing a background in said viewing zone are integrated with the optical fibres of the first terminal end of a bundle (18, 20, 21, 22) providing a light receiver. 7. Apparatus according to any preceding claim, further characterised by rejecting means (74) adapted to divert objects from said stream under the control of the detecting means (V1-V4). 8. Apparatus according to any preceding claim, further characterised by means (35) for sensing the presence of an object in said viewing zone (1). 9. Apparatus according to claim 8, further characterised in that said sensing means comprises means (54- 59) for transmitting infra-red light in at least one path to intercept the object stream in the viewing zone (1), and infra-red detecting means (36-41). 10. Apparatus according to claim 7, and claim 8 or 9, further characterised in that the rejecting means (74) is enabled under the control of said sensing means (35). 11. Apparatus according to any preceding claim, further characterised in that said background means provide a plurality of backgrounds and said detecting means provide a corresponding plurality of light receivers, said backgrounds and light receivers being distributed around the path of the stream of objects in the viewing zone. 12. Apparatus according to any preceding claim, further characterised in that said illuminating means (33) are arranged to illuminate only a portion of an object in the viewing zone. 13. Apparatus according to any preceding claim, further characterised in that said illuminating means (33) comprise a light source remote from the viewing zone (1) and optical fibre means to convey light from said source to the viewing zone. 14. Apparatus according to claim 13, further characterised in that said optical fibre means comprise optical fibres interspersed with the optical fibres of the or each bundle of optical fibres (19, 20, 21, 22) of the detecting means (V1-V4).

Inventors: BAILEY, ROGER FREDERICK
Applicants: BAILEY, ROGER FREDERICK
Application year: 1986
Main classification: B07C5
IPC codes: B07C5