AU599931B2

AU599931B2 - Optical sorting apparatus

Info

Publication number: AU599931B2
Application number: AU64223/86A
Authority: AU
Inventors: Roger Frederick Bailey
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-10-29
Filing date: 1986-10-20
Publication date: 1990-08-02
Anticipated expiration: 2006-10-20
Also published as: AU6422386A

Description

AUSTRALIA 93 Patents Act COMLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: 6 2 3 L-odged: Com~iete Specification Lodged: Accepled: Published: Priority Related Art: AP1PLTCANT'3 REF.: CAP of PH3159 Name(s) of Applicant(s): ROGER FREDERICK BAILEY Address(es) of Applicant(s): Lot 252, Shaw Street, MOAMA. N.S.W. 2739.

Actual Inventor(s): ROGER FREDERICK BAILEY Address for Service is: -t PHiLL1PS, ORMOND6ANl? ATZPATRICC Patent and Trade Mark Attorneys.

367 Collins Street t*~t\MebQurne, Australia, Complete Specification for the invention entitled: "OPTICAL SORTING APPARATUS" The following statement is a Puil description of this invention, including the best method of pierforming it known to applicant(s): P19/3 84 lj 13 an object which is scanned by the detecting means. In ofhez tine~ t--p f11uminatad area and the viewing area of the iihr~ ru* r~ i i- ie iu^iw I r; OPTICAL SORTING APPARATUS o 4 o 44 04 o @I oor 4 oo 4 4444 4 4.

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 tone which separates the products into individual streams. The individual streamjs 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 zeptable range. The electronic circuit may activate a rejection mechanism in the event that an object falls outside of an acceptable range. However, a number of problems and disadvantages exist with presently existing sorting apparatus of the above kind, including the following.

Current viewing heads use painted backgrounds as colour references or standards. The color 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 f 4444 4 4 '430 aD PI-~ -i 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.

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 5, 7, 9) predominate 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.

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Prior art viewing heads are relatively bulky for the viewing area they provide, e.g. 30cm outside diameter for a 5cm 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 affect response characteristics of the photo-detectors. Heat also accelerates the abovementioned color deterioration of backgrounds. Cooling is desirable to alleviate color deterioration and avoid drifting of photocell 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 simultan-Lously handle. Also because photo-detectors in the viewing head send relatively small currents to processing

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4 circuits via long cables these long cables give rise to electrical interference. Electrical interference may be from external sources and fromi cables carrying relatively high currents to the lamps (du- inter alia to capacitance effects).

Existing apparatus generally use 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 Swith distance from the focal points, (particularly when defects occur on the heel cr toe of a product) sometimes 0 causing good products to be rejected. Additionally, lenses 0 are dependant upon and must be selected according to diameter ;2O of the viewing area 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 4 i 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 1 particularly apparent if a product has defects at both ends 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 Qf products. Secondly, each viewing assembly is separately adjusted with respect to the viewing 5 1 head and product stream. The viewing assemblies ideally are 2 adjusted to form a flat circle around the product stream.

3 This ensures that all views are synchronized in time. If a 4 defect is detected then the rejecting mechanism will be actuated substantially at the same time irrespective of 6 which viewing assembly 'law' the defect.

7 It is an object of the present invention to at least 8 alleviate one or more of the above-mentioned disadvantages 9 of the prior art. The present invention provides apparatus of the aforementioned kind and comprises a significant 11 departure from currently existing technology.

12 According to the present invention there is provided an o 13 optical sorting apparatus for sorting objects moving in a 14 stream along a substantially predetermined path, said 15 apparatus comprising: °o 0, 16 at least one background means comprising means to .o00 17 provide light; 18 at least one detecting means, being located on a 19 different side of said path from said background means so that said detecting means can detect light from objects in 21 said stream and light provided by said background means; o' 22 a light source, and a plurality of optical fibres for ato 23 conducting light from said light source to said background 24 means, said light source providing light having at least aS 25 first and second frequencies or frequency ranges; and 26 control means for controlling the intensity of the 27 light from said light source having said first frequency or i 28 frequency range, and for controlling the intensity of the I 29 light from said light source having said second frequency or frequency range, said intensities being independently 31 controllable such that both the colour and the intensity of 32 the light provided by the background means can be adjusted.

33 According to a further aspect of the present invention 34 there is provided a method of sorting objects moving in a stream by optical means, said method comprising the steps 36 of: S 37 providing means for detecting light from sa, objects; 38 9OQ024.eidapft.t0,ba' I I- i Ir 1 2 3 4 6 7 8 9 11 12 13 0 4 S 14 o 16 o 16 17 a° 18 19 21 22 23 24 0 o 26 27 S 28 4 2 P 31 32 33 34 36 7 i- p r.

providing background means behind said stream relative to said detecting means, wherein said background means is variable to provide an adjustable reference for said detecting means, by conducting light of more than one frequency or frequency range from a remote light source to said background means, by means of a plurality of optical fibres, the intensity of the light at each frequency or over each frequency range being independently variable.

The apparatus of the present invention may include at least one source of light (mono-chromatic) for said background(s). The light source preferably is adjustable in intensity. Multi-chromatic apparatus bi-chromatic) may include two or more light sources. Each light source may comprise white light, e.g. a quartz halogen incandescent lamp. Each light source preferably is separately adjustable in intensity. The intensity of the or each light source may be adjustable by any suitable means. In one form, the or each 900524,eldspe.005.ballay,6 i -6- .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 intensity of the light source may be adjustable by means of polarizing filters or other means which reduces intensity of light.

Bi-chromatic apparatus preferably includes means adapted to provide a pair of light sources having substantially mutualy 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, 530nm and 660nm respectively, the light spectrum may be split at say, 650nm. One light source may be adapted to provide spectral content below 650nm S(green). The other light source may be adapted to provide spectral content above 650nm (red). The apparatus preferably S includes filter means. The filter means may be adapted to *,pass light having specific spect, 1 content. The filter means may include a first filter adapted to pass a first component Sof light, the spectral content of which is centered at 530nr.

The filter means may include a second iilter adapted to pass a second component of light, the spectral content of which is S4 1 centered at 660nm.

o; ,The light sources may be combined to provide a composite beam of light. The light sources may be combined in S any suitable manner. In one form, the light sources may be combined by means of a half silvered mirror. The light sources to be combined preferably are oriented in paths j .0 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 650nm may be achieved.

According to a preferred embodiment of the present invention, the filter function and comnbining function may be provided in a single device such as a dichroic mirror. A dichroic mirror transmits light above a given threshold -7frequency and reflects light below the threshold frequency.

The dichroic mirror may be chosen to split light at a desired frequency, e.g. 650nm.

According to a further embodiment each white light source and filter may be replaced by a substantially mono-chromatic light source such as an L.ED. array. The L.E.D. array may be selected to provide an output having any convenient frequency of light (color). These may be selected to be similar to filters associated with the detecting means.

Mixing also may be performed by means of optic fibres. For example, a bundle of optic fibres may be formed into a cable which is bifurcated at one end. The cable may be formed such that alternate fibres in the bundle are accessed by one light source whilst the remaining fibres are accessed by the other light source. This increases the cost of the optic cables but eliminates the need for a dichroic mirror to combine the two light sources.

0 40 According to the present invention, the light I sources preferably are located remote from the viewing head.

020: Light may be conducted from the sources to the viewing area via one or more suitable conduits such as optic fibres. The optic fibres may comprise glass or plastics. The optic fibres may be formed into bundles or cables having any suitable 0 a 4 length and cross section. Preferably, the bundles are rectangular in cross section at leastin the region of the viewing area. Rectangular bundles are preferred because it has been found that they minimize occurrence of blind spots when compared to circular bundles.

h Each active background for the sorting apparatus of the present invention may be provided by an optic cable comprising one or more optic fibres. One terminal end of the optic cable may define each background surface. The relative spectral content of light being conducted along the optic cables may be dynamically adjusted by means of the abovementioned dimmer circuits thereby adjusting the spectral content of the reference backgrounds. The above arrangement lends itself readily to automatic control. Relative spectral content of the backgrounds may be adjusted automatically by adjusting the dimmer circuits. This may be done via a -8suitable electronic circuit.

The detecting means of the present invention may include at least one photo-detector such as a photo-cell. The or each photo-detector preferably is located remotely from the viewing head of the apparatus.

Remote location of detectors (and light sources) is desirable because it minimizes interference. This is so oecause 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 length.

The detecting means may receive light from the objects being sorted via suitable conduits such as optic fibres. The optic fibres associated with the detecting means .o may be formed into cables having any suitable cross section.

0 o Preferably, the detecting cables are rectangular in cross 0 section at least in the region of the viewing area.

Rectangular cables are preferred because they minimize 201 1 occurrence of blind spots and assist a scanning action as an So° object moves through the viewing area of the detecting means.

oo4 In one form, the deLecting cables may comprise a bundle of fibres substantially 2mm high and 13mm wide in cross section.

The dimensions of each bundle of optic fibres may be increased "o or decreased as required. The light receiving end of each cable of optic fibres preferably is directed at a background located opposite. The light receiving ends of the optic o .4 fibres may be focussed in any suitable manner such as my means of lenses.

3 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 4mm long and 1.8mm 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.

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-9- 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 osoociated 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 optic 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 0.2mm from an associated end face.

The detecting means may include a beam splitter such as a half silvered mirror. The beam splitter may be adapted to separate light received from the detecting cables into two o o,4 beams. The two beams may be passed through separate detecting filters to respective photo-cell detectors. The detecting filters preferably pass only selected light frequencies. For *4 example, one filter may be adapted to pass a narrow band of o" light frequencies centered at 530nm. The other filter may be adapted to pass a narrow band of frequencies centered at 660nm.

The photo-cell detectors may be adapted to produce electric signals which are related to the amount of light they 0. receive. A suitable electronic circuit may be associated with the photo-cell detectors to provide an output signal indicative of the relative content of the two bands of 0oc frequencies, 660nm 530nm in the example given) present in the light which is detected.

o° A plurality of backgrounds and associated detectors may be used to surround the product viewing area. Each detector is adapted to receive light from the 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 720 apart. in general, sufficient backgrounds and detectors are required to cover substantially the whole of the surface area of the object being sorted.

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9a Where an even number of backgrounds is used the "background" optic cables and "detecting" optic cables may be produced as integrated assemblies. Each integrated assembly may include one bundle of "background" optic fibres and one bundle of "detecting" optic fibres and associated lenses. The integrated assemblies may be fitted to any size viewing head having any even number of view.

According to a preferred embodiment of the present invention all detecting cables of the apparatus may be 0 1 t 4 0 G4

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associated with a common light detecting means. That is the "detector" ends of the bundles of detecting optical fibres maybe brought together so that light from the bundles may pass through a common beam splitter and detecting filters. An advantage of the latter arrangemen is that light from each detecting cable may be processed similarly thereby eliminating response differences. Each bundle of detecting optical fibres preferably is terminated with a suitable lens such as piano convex lens. The piano convex lenses may he adapted to collimate the beams to enable them to pass through the same beam splitter and detecting filters, The apparatus of the present invention includes object sensing means. The sensing means may be adapted to sense presence and/or location of an object relative to the Sviewing head. The sensing means may i,iclude one or more S° sensing beams, The sensing beams preferably comprise °o electrogmagnetic energy such as infra-red. The sensing beams preferably are located in the object viewing zone such that 0 Q4 they cross the object stream, The sensing beams preferably o6. cross the object stream substantially at right angles thereto.

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O 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 °o located cemote from '.he viewing zone, Infra-red beams may be conveyed to and from the viewing zone via suitable conduits such as optic fibres. Transmitting fibres may be used to a0 convey infra-red sensing beams from the or each infra-red generator to the viewing zone. Receiving fibres may be used oo" to convey the sensing beams from the viewing zone to the (or 3Q" each) associated infra-red receiver. The receiving and S transmitting fibres may be located on opposite sides of the object stream, The transmitting and receiving fibres preferably are located such that the or each infra-red beam crosses the object path substantially at right angles thereto, The or each infra-red beam may be adapted to intercept objects passing through the viewing area.

The object sensing means may comprise a plurality of infra-red beams, In one form, six beams may be used. The six beams preferably are suostantially coplanar. The six beams -11may 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 liessubstantially 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 may Sbe 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 C Ot intercept the sensing beam(s) for longer periods.

020, Accordingly, the enable pulse dwell time may be dependent on 0 0 t object size (traversing length).

Beauase timing information may be provided to the Q" rejecting mechanism by the object sensing means, the various ati S 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.

o* It Ulso 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 auove may we i,

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12 determine which beams are being intercepted by the stream of oojects. The outputs of the receivers of the beams may be Srocessed by a suitable electronic circuit to determine which :eam or beams are being intercepted with most frequency.

The viewing head may be- adjusted until only the "iddle beams of each set are intercepted by the object stream.

This would indicate that the object stream is in the centre u: 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 Sfocussed at infinity focussing of lenses may be obviated when changing from one product size to another. Furthermore, o because individual detecting cables may transmit light into a common beam splitter and detecting filters, inaccuracies in o, this section of the apparatus affect all viewing assemblies 0 0 0 in the same way.

The apparatus of the present invention preferably includes product illumination means. The illumination means o oo 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 Swhich 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 :ource and conveyed to the viewing zone. Light preferably 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 conveyed to the object viewing zone by means of lens arrays, lenses, mirrors etc, It is preferable to illuminate only that portion of

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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 oi 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 deteuLing optical fibres and the transmitting ends of the illuminating fibres to form a combined illuminating I detecting cable. The opposite end of the combined illuminating detecting cable is bifurcated o* with the illuminating fibres being directed to the illuminating light source and the detecting fibres to their respective photo-detector. Reflection from lenses associated o 1 4 with the illuminating detecting cable may be reduced by applying anti-reflecting coatings to the lenses.

The present invention preferably includes means for t 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, 0, i.e. when the detecting means only sees the backgrounds.

SO 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 above 650nm and below 650nm 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.

i i' k LI SC Li_ i 14 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 r.)w 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 Bl-B4.

Background assembly Bl includes an optic cable 3 and lens array 4. Similarly background assemblies B2-B4 include 0 respective optic cables 5, 6, 7 and lens arrays 8, 9, C"o Each cable 3, 5, 6, 7 comprises a plurality of optic fibres.

o0 Backgrounds B1-B4 are supplied with sources of light from the assembly shown generally at 50. The assembly 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 "o 11, 12 may be prefocussed obviating lenses 13, 14. Dichroic Oo mirror 15 passes light above 650nm from light source 11 and light below 650nm from light source 12. Light sources 11, 12 are controlled via respective dimmer control circuits 16, 17.

Viewing assembly Vl 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

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15 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 viewiproduct out of view is a minimum. Background setting means 32 additionally receives signals from object sensing maans 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.

op 1 0 9 0 I 0 9; .94~ 0 4 049 9; 0 099 ol 4~ 041 The product sensing means includes a plurality of transmitting lenses 54-59 and a corresponding plurality 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

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1 -16means 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 t-he 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, \I 0 a During the nulls adjustment stage light sources,11, 12b- are adjusted so that the light components received by o4 photo-detectors 28a, 30a are the same (or as close as possible) when a product of good quality is in view as when no 0.20 product is in view, it CL o:f When light sources%2 117?' 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 9 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. 530nm and 660nm. This is in contrast to current 9. 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 8cm viewing area the viewing head may be approximately 13-15cm in outside diameter. Several features of the present invention contribute to the compact dimensions of the viewing head including:

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-17- 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 :emote from viewing head 4) each background and viewing assembly may be combined into one integrated assembly 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 oo background light source only and one receiving channel, i.e.

0 0 :i one light source may be turned off or eliminated.

o It will be appreciated that various modifications Sand/or alterations may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the present invention.

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Claims

7. Optical sorting apparatus according to claim 5 wherein 11 said dichroic mirror transmits light having a wavelength 12 greater than 650mm and reflects light having a wavelength 0 a 13 less than 650mm. 00 0 00 14 14 o o 0 15 8. Optical sorting appara+:us according to claims 2 anr' 4, I 16 wherein said plurality of optical fibres is divided, a first I ,0o 17 portion of said fibres, in use, conducting light from one of 18 said pair of light emitters, and a second portion of said 19 fibres, in use, conducting light from the other of saLd pair of light emitters, to said background means. 00 21 22 9. Optical sorting apparatus according to claim 8 wherein 23 fibres from said first and second portions alternate in S. 24 spatial distribution in relation to said background means such that the light conducted by the plurality of fibres to 26 the background means is evenly distributed with respect to 27 light from each of said pair of light emitters. 28 29 10. Optical sorting apparatus according to any one of the preceding claims comprising a plurality of said background 31 means, and a plurality of said detecting means, each 32 detecting means being located on a different side of said 33 path from a respective one of said background means so as to 34 detect light from objects in said stream and from said respective one of said background means. 36 37 11. Optical sorting apparatus according to claim 10 wherein 38 900524,eldspe.005,bailey,8 1 said pluralities of background and detecting means are 2 arranged in adjacent pairs, each pair comprising a 3 background means and a detecting means. 4
12. Optical sorting apparatus according to any one of the 6 preceding claims, comprising feedback means between said 7 detecting means and said control means, for automatic 8 adjustment of the light from the light source by the control 9 means in response to changes in the output of said detecting means. 11 o 12 13. Optical sorting apparatus according to any one of the 13 preceding claims wherein said light source is remote from S 14 said path. o0" 0b 14. Optical sorting apparatus according to any one of the °o 17 preceding claims wherein said at least one background means, 18 or each of said background means, comprises a surface 19 provided at least in part by end faces of said plurality of optical fibres. 21 22 15. Optical sorting apparatus according to any one of the o 23 preceding claims wherein said detecting means includes at S 24 least one detecting optical cable, a terminal end of said detecting cable defining a detecting surface which is 26 located for detecting light from said objects. 27 o° 28 16. Apparatus accordinxg to claim 15 wherein said detecting 29 means includes at least one photo-detector, said photo- detectnr being arranged to receive light from the other 31 terminal end of said detecting optic cable. 32 33 17. Apparatus according to claim 16 wherein said detecting 34 means includes at least one pair of photo-detectors, a pair of filters and a beam splitter, one photo-detector of the or 36 each pair being arranged to receive light passing from said 37 beam splitter and one filter, the other photo-detector of S38 900524,eldspe.005,bailey,9 21 1 the or each pair being arranged to receive light passing 2 from said beam splitter and the other filter, said beam 3 .itter being arranged to receive light from said other 4 terminal end of said detecting optic cable. 6 18. Optical sorting apparatus according to any one of 7 claims 15 to 17 incorporating a plurality of such detecting 8 surfaces spaced about said stream. 9
19. Optical sorting apparatus according to any one of the 11 preceding claims including sensing means for sensing o a 12 presence of said objects. 0 0 4 o 1 13 14 20. Optical sorting apparatus according to claim 19 wherein °o 15 said sensing means includes a plurality of infra red beams S 16 intercepting said path. o 0 17 18 21. Optical sorting apparatus according to claim 20 wherein 19 said beams lie substantially perpendicular to said path and are oriented such that they intercept said path as said 21 detecting means is detecting light from said objects. 22 23 22. Optical sorting apparatus according to any one of the n n" 24 preceding claims including rejecting means adapted to divert objects from said stream in accordar 3 with the output of 26 said detecting means. 27 o"0 28 23. Optical sorting apparatus according to claim 22 when 29 appended to claim 18 wherein said rejecting means is enabled under control of said sensing means. 31 32 24. Optical sorting apparatus according to any one of the 33 preceding claims including means for illuminating said 34 objects, said illmuniating means being adpated to limit illumination substantially to that portion of an object 36 which is being detected by said detecting means. 37 38 900524,ldspeo00,bailey,10 Lme A 22 C-1- A method of sorting objects moving in a stream by optical means, said method comprising the steps of: providing means for detecting light from said objects; providing background means behind said stream relative to said detecting means, wherein said background means is variable to provide an adjustable reference for said detecting means, by conducting light of more than one frequency or frequency range from a remote light source to said background means, by means of a plurality of optical fibres, the intensity of the light at each frequency or over each frequency range being independently variable. 0 a 12 0 0 o 13 S 14 0 o 16 17 18 19 21 S 22 23 0 0 0 0 24 26 S 27 I 28 29 31 32 33 34 36 37 38
26. Optical sorting apparatus substantially as described with reference to the accompanying drawing. herein
27. A method of sorting objects by optical means substantially as herein described with reference to the accompanying drawing. DATED 24th May, 1990. ROGER FREDERICK BAILEY By His Patents DAVIES COLLISON ATTORNEYS FOR: ROGER FREDERICK BAILEY, 4, 900524 eld1pe1OOSbail ey. tt