WO2013117769A1 - Illumination and detection system - Google Patents

Illumination and detection system Download PDF

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Publication number
WO2013117769A1
WO2013117769A1 PCT/EP2013/052705 EP2013052705W WO2013117769A1 WO 2013117769 A1 WO2013117769 A1 WO 2013117769A1 EP 2013052705 W EP2013052705 W EP 2013052705W WO 2013117769 A1 WO2013117769 A1 WO 2013117769A1
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WO
WIPO (PCT)
Prior art keywords
objects
detector
illumination
radiation
adjacent
Prior art date
Application number
PCT/EP2013/052705
Other languages
French (fr)
Inventor
Benedict Deefholts
Robert James Neil Mclean
Original Assignee
Buhler Sortex Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Buhler Sortex Ltd filed Critical Buhler Sortex Ltd
Publication of WO2013117769A1 publication Critical patent/WO2013117769A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
    • B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
    • B07C5/34—Sorting according to other particular properties
    • B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour
    • B07C5/3425—Sorting according to other particular properties according to optical properties, e.g. colour of granular material, e.g. ore particles, grain
    • B07C5/3427—Sorting according to other particular properties according to optical properties, e.g. colour of granular material, e.g. ore particles, grain by changing or intensifying the optical properties prior to scanning, e.g. by inducing fluorescence under UV or x-radiation, subjecting the material to a chemical reaction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
    • B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
    • B07C5/36—Sorting apparatus characterised by the means used for distribution
    • B07C5/363—Sorting apparatus characterised by the means used for distribution by means of air
    • B07C5/367—Sorting apparatus characterised by the means used for distribution by means of air using a plurality of separation means
    • B07C5/368—Sorting apparatus characterised by the means used for distribution by means of air using a plurality of separation means actuated independently
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features
    • G01N2021/8845—Multiple wavelengths of illumination or detection

Definitions

  • the present invention relates to a detection system for and a method of detecting objects, including translucent objects, within an object flow, and a monitoring or sorting apparatus and method which incorporates such a detection system or method, in particular for use in grading particles in a flowing stream.
  • Certain apparatus utilize diffuse illumination which illuminates a particulate stream, and differentiate objects in dependence upon the radiation scattered from the objects, typically in different wavelength ranges, with the illumination being provided by fluorescent lamp or LED light sources. Examples of such apparatus are disclosed by GB-A-993063 and WO-A- 2011/007117.
  • Various other apparatus utilize point source illumination which is scanned over a particulate stream, and differentiate objects in dependence upon the radiation scattered from the objects, being reflected and diffuse radiation, typically in different wavelength ranges.
  • diffuse light referred to as a "halo”
  • US-A-3786266 One example of such apparatus is disclosed by US-A-3786266.
  • a laser beam is typically used as the point source illumination, and a spinning polygonal mirror is used to target both the laser beam at the objects to be examined and the radiation from the object back to an optical sub-system.
  • Such apparatus use comparatively-expensive optics to achieve targeting and detection, and it is an aim of the present invention to provide an improved optical system and method for detecting objects, from the perspective of cost and efficiency in relation to flows of objects, and a related monitoring or sorting apparatus and method which incorporates such a detection system or method.
  • the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises a plurality of line detector elements for detecting radiation received from the objects, wherein one detector element detects reflected radiation from an illuminated region of the objects, and at least one other detector element detects diffuse radiation from sub-surface diffusion at at least one region adjacent the illuminated region in the objects.
  • the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises at least one line detector element for detecting radiation received from the objects; wherein the optical axes of the at least one illumination unit and the detector are substantially coaxial.
  • the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises at least one line detector element for detecting illumination received from the objects; wherein the elongate illumination beam and the detector element are substantially co-planar.
  • the present invention also extends to a sorting apparatus for sorting a flow of objects incorporating the above-described detection system.
  • the present invention further extends to a monitoring apparatus for monitoring a flow of objects incorporating the above-described detection system.
  • the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising a plurality of line detector elements, wherein one detector element detects reflected radiation from an illuminated region of the objects, and at least one other detector element detects diffuse radiation from at least one region adjacent the illuminated region in the objects.
  • the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising at least one line detector element; wherein the optical axes of the at least one illumination unit and the detector are substantially co-axial, and the detector element detects reflected radiation from an illuminated region of the objects and/or diffuse radiation from a region adjacent an illuminated region of the object.
  • the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising at least one line detector element; wherein the elongate illumination beam and the detector element are substantially co-planar, and the detector element detects reflected radiation from an illuminated region of the objects and/or diffuse radiation from a region adjacent an illuminated region of the object.
  • Figure 1 illustrates a sorting apparatus in accordance with a first embodiment of the present invention
  • Figure 2 illustrates a sorting apparatus in accordance with a second embodiment of the present invention
  • Figures 3(a) and (b) illustrate the detector elements of the detector of the detecting system of the sorting apparatus of Figure 2;
  • Figure 3(c) illustrates images acquired using a laser line generator operating at a wavelength of 880 nm as the illumination unit of the sorting apparatus of Figure 2;
  • Figure 4 illustrates a sorting apparatus in accordance with a third embodiment of the present invention
  • Figure 5 illustrates the beam splitter of the detecting system of Figure 4.
  • Figure 6 illustrates a sorting apparatus in accordance with a fourth embodiment of the present invention
  • Figure 7 illustrates the beam splitter of the detecting system of Figure 6
  • Figure 8 illustrates a sorting apparatus in accordance with a fifth embodiment of the present invention .
  • Figure 9 illustrates a sorting apparatus in accordance with a sixth embodiment of the present invention
  • Figure 10 illustrates a sorting apparatus in accordance with a seventh embodiment of the present invention
  • FIG. 11 illustrates a sorting apparatus in accordance with an eighth embodiment of the present invention.
  • Figure 12 illustrates a modified detector arrangement
  • Figure 1 illustrates a sorting apparatus in accordance with a first embodiment of the present invention.
  • the sorting apparatus comprises a delivery device 3 for delivering a flow F of objects O, here a particulate material, such as foodstuffs or other particulate commodities.
  • the delivery device 3 comprises a vibrating chute 5, which is fed from a hopper 7, and from which is delivered the object flow F.
  • the delivery device 3 could comprise any delivery system which delivers an object flow F, including a stationary feed chute, a feed belt or pneumatic transport.
  • the sorting apparatus further comprises a detection system 11 for detecting objects O within the object flow F.
  • the detection system 11 comprises an illumination unit 14, in this embodiment comprising an illumination source 15 and illumination optics 17, here providing an elongate illumination beam B, which illuminates a narrow, elongate line across a width of the object flow F.
  • the illumination source 15 provides visible light, but could provide any of X-rays, including near X-rays, UV, or infrared, including near infrared, microwave or terahertz radiation .
  • the illumination source 15 comprises a laser, which provides a laser beam
  • the illumination optics 17 comprise one or more lenses which provide a fixed elongate line of illumination.
  • the illumination optics 17 comprise a Powell lens, which provides a fixed elongate line of illumination of substantially uniform intensity.
  • the illumination unit 14 could omit the illumination optics 17, and instead the illumination source 15 would provide a pre-shaped illumination beam.
  • the detection system 11 further comprises a detector 21, in this embodiment comprising a line scan camera 22, and detection optics 25 which relay the radiation from the object O to the camera 22.
  • the line scan camera 22 is a single line scan camera which directly detects reflected radiation or diffuse radiation, generated by sub-surface diffusion, from objects 0 within the object flow F.
  • the line scan camera 22 is substantially co-planar with the elongate illumination beam B, optionally with the illumination unit 14 and the detector 21 being in close, side-by-side relation, such that the optical axes of the illumination unit 14 and the detector 21 have a relatively-small angular spacing.
  • Figure 1 illustrates the illumination unit 14 out of plane with the line scan camera 22.
  • the detector 21 detects reflected or diffuse radiation, in dependence on set-up, from the objects 0 which pass through the elongate illumination beam B, allowing for characterization of the objects O based on this reflected or diffuse radiation.
  • This configuration is particularly suited to sorting the objects O by shape, where the objects O intersect the elongate illumination beam B and appear in contrast relative to the background of the illumination beam B, which may be bright or dark.
  • the sorting apparatus further comprises an ejector 41, in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
  • an ejector 41 in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
  • FIGS. 2 and 3 illustrate a sorting apparatus in accordance with a second embodiment of the present invention.
  • the sorting apparatus comprises a delivery device 3 for delivering a flow F of objects O, here a particulate material, such as foodstuffs or other particulate commodities.
  • the delivery device 3 comprises a vibrating chute 5, which is fed from a hopper 7, and from which is delivered the object flow F.
  • the delivery device 3 could comprise any delivery system which delivers an object flow F, including a stationary feed chute, a feed belt or pneumatic transport.
  • the sorting apparatus further comprises a detection system 11 for detecting objects O within the object flow F.
  • the detection system 11 comprises an illumination unit 14, in this embodiment comprising an illumination source 15 and illumination optics 17, here providing an elongate illumination beam B, which illuminates a narrow, elongate line across a width of the object flow F.
  • the illumination source 15 provides visible light, but could provide any of X-rays, including near X-rays, UV, or infrared, including near infrared, microwave or terahertz radiation.
  • the illumination source 15 comprises a laser, which provides a laser beam
  • the illumination optics 17 comprise one or more lenses which provide a fixed elongate line of illumination.
  • the illumination optics 17 comprise a Powell lens, which provides a fixed elongate line of illumination of substantially uniform intensity.
  • the illumination unit 14 could omit the illumination optics 17, and instead the illumination source 15 would provide a pre-shaped illumination beam.
  • the line of illumination causes the generation of a bright diffuse regions Rl, R2 within the object O, which extend to the adjacent sides of the line of illumination; the bright regions Rl, R2 being generated by sub-surface diffusion within the object O.
  • the detection system 11 further comprises a detector 21, in this embodiment comprising a multiple line scan camera 22, which comprises a plurality of line array detector elements 23, and detection optics 25 which relay the radiation from the object 0 to the camera 22.
  • the optical axis of the detector 21 is substantially coaxial with the optical axis of the illumination unit 14, and thus the elongate illumination beam B generated thereby.
  • the illumination unit 14 and the camera 22 are illustrated off-axis.
  • the camera 22 comprises a tri-linear array, which comprises three adjacent line array detector elements 23a, 23b, 23c for detecting the reflected radiation from the objects O which pass the detector 21 and the diffuse radiation from the adjacent regions Rl, R2 in objects 0 which pass the detector 21.
  • the central, of the detector elements 23a detects reflected radiation from objects O which pass the detector 21, and the other detector elements 23b, 23c detect diffuse radiation generated by subsurface diffusion, the "halo", and emitted from each side region Rl, R2 of the line of illumination.
  • the other detector elements 23b, 23c which detect diffuse radiation from the adjacent regions Rl, R2, have a width greater than the width of the one detector element 23a, which detects radiation reflected from the object O. With this arrangement, greater sensitivity to the diffuse radiation is achieved.
  • the detector 21 could comprise a bi-linear array, which comprises two adjacent line array detector elements 23a, 23c for detecting reflected radiation from the objects O which pass the detector 21 and diffuse radiation from the one adjacent region Rl in objects O which pass the detector 21.
  • one detector element 23a detects reflected radiation from objects O which pass the detector 21, and the other detector element 23c detects diffuse radiation generated by sub-surface diffusion to one adjacent side region Rl of the line of illumination.
  • the other detector element 23c which detects diffuse radiation from the adjacent side region Rl, has a width greater than the width of the one detector element 23a, which detects reflected radiation from the object O. With this arrangement, greater sensitivity to the diffuse radiation is achieved.
  • the detector 21 can be configured to have a higher gain on the one or two other, outer line detector elements 23b, 23c than the one, center line detector element 23a. In this way, the detector 21 accommodates the lower intensity of the diffuse radiation as detected by the or two other, outer line detector elements 23b, 23c.
  • the objects O which pass the elongate illumination beam B can be characterized based on reflectance, which is particularly suited to characterizing the shape of the objects O, and translucency, which is particularly suited to characterizing the material of objects O.
  • Figure 3(c) illustrates images acquired using a laser line generator operating at a wavelength of 880 nm as the illumination unit 14.
  • the almond shell can be distinguished from almond meat.
  • the detection system 11 can comprise a beam splitter 31 to which the illumination unit 14 and the detector 21 are optically coupled, such that the radiation delivered to and received from the object O is co-linear.
  • the illumination unit 14 is provided to the side leg of the beam splitter 31.
  • the beam splitter 31 includes a narrow, silvered mirror or reflective line 35 which extends only on the center line.
  • the radiation from the illumination unit 14 is reflected by the reflective line 35 onto the flow of objects O, and the reflective line 35 acts as an aperture stop for the component of the reflected radiation from the objects O corresponding to the width of the reflective line 35, thereby providing that the reflected radiation as received by the camera 22 has a reduced intensity, with the remainder of the reflected radiation from the objects O and the diffuse radiation from the adjacent regions Rl, R2 of the object O passing through the beam splitter 31 adjacent the respective edges of the reflective line 35.
  • the detector 21 can be provided to the side leg of the beam splitter 31.
  • the beam splitter 31 includes a narrow, non-silvered or reduced-reflectivity line 37 on the center line and silvered mirror or reflective regions 39 juxtaposed the reduced-reflectivity line 37.
  • the illumination beam B from the illumination unit 14 is able to pass through the aperture provided by the reduced-reflectivity line 37, and the reflected radiation from the objects 0 is received at the beam splitter 31, with the component of the reflected radiation corresponding to the width of the reduced-reflectivity line 37 passing at least partially therethrough, thereby providing that the reflected radiation as received by the camera 22 has a reduced intensity, and the remainder of the reflected radiation from the objects O and the diffuse radiation from the adjacent regions Rl, R2 of the objects O being reflected by the respective reflective regions 39 to the camera 22.
  • the reflective regions 39 comprise elongate areas or wide lines.
  • the sorting apparatus further comprises an ejector 41, in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
  • an ejector 41 in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
  • FIG. 8 illustrates a sorting apparatus in accordance with a further embodiment of the present invention. This embodiment is very similar to the second-described embodiment, and thus, in order to avoid unnecessary duplication of description, only the differences will be described in detail, with like parts being designated by like reference signs.
  • This embodiment differs from the second-described embodiment in comprising a plurality of, in this embodiment first and second illumination units 14a, b, and a plurality of, in this embodiment first and second beam splitters 31a, b which are associated with the respective illumination units 14a, b, such as to provide for the illumination of the flow of objects O on the common center line of the camera 22.
  • the beam splitters 31a, b are located in spaced relation on the optical axis of the camera 22, such that the illumination units 14a, b are provided to the side legs thereof.
  • further illumination units 14a, b can be incorporated by use of further beam splitters 31a, b.
  • the objects O can be illuminated with radiation of a plurality of wavelengths or ranges of wavelengths, for example, red and green laser light or red, green and blue laser light.
  • the camera 22 is a monochromatic camera, and the illumination units 14a, b are modulated to allow for the selective illumination by the respective illumination units 14a, b.
  • the camera 22 is a multichromatic camera, such as an area scan camera, typically a CCD, and respective lines of the camera 22 detect radiation of different wavelength corresponding to the respective wavelengths of the illumination units 14a, b.
  • the camera 22 could be a bichromatic camera, which has a first set of first lines which detect red light and a second set of lines which detect green light.
  • the camera 22 could be a trichromatic camera, which has a first set of first lines which detect red light, a second set of lines which detect green light and a third set of lines which detect blue light.
  • Figure 9 illustrates a sorting apparatus in accordance with a yet further embodiment of the present invention.
  • This embodiment differs from the second-described embodiment in comprising a plurality of, in this embodiment first and second illumination units 14a, b, and a plurality of, in this embodiment first and second beam splitters 31a, b, which provide for the illumination of the flow of objects O on the common center line of the camera 22.
  • first beam splitter 31a is located on the optical axis of the ca mera 22, such as to receive illumination from one, here the side, leg thereof, and the other, second beam splitter 31b receives illumination from the illumination units 14a, b to the respective input legs thereof and delivers a single illumination beam, formed of illumination of the wavelengths or ranges of wavelengths of each of the illumination units 14a, b, to the one, side leg of the first beam splitter 31a .
  • further illumination units 14a, b can be incorporated by use of further beam splitters 31a, b.
  • the objects O can be illuminated with radiation of a plurality of wavelengths or ranges of wavelengths, for example, red and green laser light or red, green and blue laser light.
  • the camera 22 is a monochromatic camera, and the illumination units 14a, b are modulated to allow for the selective illumination by the respective illumination units 14a, b.
  • the camera 22 is a multichromatic camera, such as an area scan camera, typically a CCD, and respective lines of the camera 22 detect radiation of different wavelength corresponding to the respective wavelengths of the illumination units 14a, b.
  • the camera 22 could be a bichromatic camera, which has a first set of first lines which detect red light and a second set of lines which detect green light.
  • the camera 22 could be a trichromatic camera, which has a first set of first lines which detect red light, a second set of lines which detect green light and a third set of lines which detect blue light.
  • the detector 21 could comprise a plurality of, here first and second monochromatic cameras 22a-c and a wavelength splitter 45, here a dichroic prism, for separating the received radiation into a plurality of wavelength components, here first and second wavelength components, such as red and green.
  • the detector 21 could comprise first, second and third monochromatic cameras 22a, b, c and the wavelength splitter 45 could comprise a trichroic prism, for separating the received radiation into first, second and third wavelength components, such as red, green and blue.
  • the detector 21 could be an area scan camera, such as a CCD, having a plurality of detector lines 51, with groups of the detector lines 51, each comprising one or more of the detector lines 51, here a plurality of detector lines 51, providing adjacent line array detector elements 23a, 23b, 23c for detecting the reflected radiation from the objects O which pass the detector 21 and the diffuse radiation the adjacent regions Rl, R2 in objects 0 which pass the detector 21.
  • an area scan camera such as a CCD
  • groups of the detector lines 51 each comprising one or more of the detector lines 51, here a plurality of detector lines 51, providing adjacent line array detector elements 23a, 23b, 23c for detecting the reflected radiation from the objects O which pass the detector 21 and the diffuse radiation the adjacent regions Rl, R2 in objects 0 which pass the detector 21.
  • the signals from the detector lines 51 of each detector element 23a, 23b, 23c can be processed individually in characterizing detected objects O.
  • the signals from one or more sub-groups of detector lines 51 of each detector element 23a, 23b, 23c can be combined, in order to improve the signal-to-noise ratio in signal processing.
  • the present invention has application in any inspection environment for the inspection of a stream of particles, for, example, in checking quality, such as for statistical analysis or for machine/plant control .

Abstract

A detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises a plurality of line detector elements for detecting radiation received from the objects, wherein one detector element detects reflected radiation from an illuminated region of the objects, and at least one other detector element detects diffuse radiation from sub-surface diffusion at at least one region adjacent the illuminated region in the objects.

Description

ILLUMINATION AND DETECTION SYSTEM
The present invention relates to a detection system for and a method of detecting objects, including translucent objects, within an object flow, and a monitoring or sorting apparatus and method which incorporates such a detection system or method, in particular for use in grading particles in a flowing stream.
Various sorting apparatus exist which allow for the characterization of particulate material.
Certain apparatus utilize diffuse illumination which illuminates a particulate stream, and differentiate objects in dependence upon the radiation scattered from the objects, typically in different wavelength ranges, with the illumination being provided by fluorescent lamp or LED light sources. Examples of such apparatus are disclosed by GB-A-993063 and WO-A- 2011/007117.
Various other apparatus utilize point source illumination which is scanned over a particulate stream, and differentiate objects in dependence upon the radiation scattered from the objects, being reflected and diffuse radiation, typically in different wavelength ranges. By applying concentrated or focussed illumination to objects, diffuse light, referred to as a "halo", is generated around the irradiated spot, which is caused by sub-surface diffusion. One example of such apparatus is disclosed by US-A-3786266.
In such apparatus, a laser beam is typically used as the point source illumination, and a spinning polygonal mirror is used to target both the laser beam at the objects to be examined and the radiation from the object back to an optical sub-system.
Such apparatus use comparatively-expensive optics to achieve targeting and detection, and it is an aim of the present invention to provide an improved optical system and method for detecting objects, from the perspective of cost and efficiency in relation to flows of objects, and a related monitoring or sorting apparatus and method which incorporates such a detection system or method.
In one aspect the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises a plurality of line detector elements for detecting radiation received from the objects, wherein one detector element detects reflected radiation from an illuminated region of the objects, and at least one other detector element detects diffuse radiation from sub-surface diffusion at at least one region adjacent the illuminated region in the objects.
In another aspect the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises at least one line detector element for detecting radiation received from the objects; wherein the optical axes of the at least one illumination unit and the detector are substantially coaxial.
In a further aspect the present invention provides a detection system for detecting a flow of objects, the system comprising : at least one illumination unit for providing an elongate illumination beam across a width of a flow of objects; and a detector which comprises at least one line detector element for detecting illumination received from the objects; wherein the elongate illumination beam and the detector element are substantially co-planar.
The present invention also extends to a sorting apparatus for sorting a flow of objects incorporating the above-described detection system. The present invention further extends to a monitoring apparatus for monitoring a flow of objects incorporating the above-described detection system.
In a still further aspect the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising a plurality of line detector elements, wherein one detector element detects reflected radiation from an illuminated region of the objects, and at least one other detector element detects diffuse radiation from at least one region adjacent the illuminated region in the objects.
In a yet further aspect the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising at least one line detector element; wherein the optical axes of the at least one illumination unit and the detector are substantially co-axial, and the detector element detects reflected radiation from an illuminated region of the objects and/or diffuse radiation from a region adjacent an illuminated region of the object.
In a yet still further aspect the present invention provides a method of detecting a flow of objects, comprising the steps of: providing an elongate illumination beam of at least one wavelength across a width of a flow of objects; and detecting radiation received from the objects using a detector comprising at least one line detector element; wherein the elongate illumination beam and the detector element are substantially co-planar, and the detector element detects reflected radiation from an illuminated region of the objects and/or diffuse radiation from a region adjacent an illuminated region of the object. Preferred embodiments of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which ;
Figure 1 illustrates a sorting apparatus in accordance with a first embodiment of the present invention;
Figure 2 illustrates a sorting apparatus in accordance with a second embodiment of the present invention ;
Figures 3(a) and (b) illustrate the detector elements of the detector of the detecting system of the sorting apparatus of Figure 2;
Figure 3(c) illustrates images acquired using a laser line generator operating at a wavelength of 880 nm as the illumination unit of the sorting apparatus of Figure 2;
Figure 4 illustrates a sorting apparatus in accordance with a third embodiment of the present invention;
Figure 5 illustrates the beam splitter of the detecting system of Figure 4;
Figure 6 illustrates a sorting apparatus in accordance with a fourth embodiment of the present invention;
Figure 7 illustrates the beam splitter of the detecting system of Figure 6;
Figure 8 illustrates a sorting apparatus in accordance with a fifth embodiment of the present invention ;
Figure 9 illustrates a sorting apparatus in accordance with a sixth embodiment of the present invention ; Figure 10 illustrates a sorting apparatus in accordance with a seventh embodiment of the present invention;
Figure 11 illustrates a sorting apparatus in accordance with an eighth embodiment of the present invention; and
Figure 12 illustrates a modified detector arrangement.
Figure 1 illustrates a sorting apparatus in accordance with a first embodiment of the present invention.
The sorting apparatus comprises a delivery device 3 for delivering a flow F of objects O, here a particulate material, such as foodstuffs or other particulate commodities.
In this embodiment the delivery device 3 comprises a vibrating chute 5, which is fed from a hopper 7, and from which is delivered the object flow F.
In other embodiments the delivery device 3 could comprise any delivery system which delivers an object flow F, including a stationary feed chute, a feed belt or pneumatic transport.
The sorting apparatus further comprises a detection system 11 for detecting objects O within the object flow F.
The detection system 11 comprises an illumination unit 14, in this embodiment comprising an illumination source 15 and illumination optics 17, here providing an elongate illumination beam B, which illuminates a narrow, elongate line across a width of the object flow F.
In this embodiment the illumination source 15 provides visible light, but could provide any of X-rays, including near X-rays, UV, or infrared, including near infrared, microwave or terahertz radiation . In this embodiment the illumination source 15 comprises a laser, which provides a laser beam, and the illumination optics 17 comprise one or more lenses which provide a fixed elongate line of illumination.
In one embodiment the illumination optics 17 comprise a Powell lens, which provides a fixed elongate line of illumination of substantially uniform intensity.
In an alternative embodiment the illumination unit 14 could omit the illumination optics 17, and instead the illumination source 15 would provide a pre-shaped illumination beam.
The detection system 11 further comprises a detector 21, in this embodiment comprising a line scan camera 22, and detection optics 25 which relay the radiation from the object O to the camera 22.
In one embodiment the line scan camera 22 is a single line scan camera which directly detects reflected radiation or diffuse radiation, generated by sub-surface diffusion, from objects 0 within the object flow F.
In this embodiment the line scan camera 22 is substantially co-planar with the elongate illumination beam B, optionally with the illumination unit 14 and the detector 21 being in close, side-by-side relation, such that the optical axes of the illumination unit 14 and the detector 21 have a relatively-small angular spacing. For purposes of illustration, Figure 1 illustrates the illumination unit 14 out of plane with the line scan camera 22.
With this configuration, the detector 21 detects reflected or diffuse radiation, in dependence on set-up, from the objects 0 which pass through the elongate illumination beam B, allowing for characterization of the objects O based on this reflected or diffuse radiation. This configuration is particularly suited to sorting the objects O by shape, where the objects O intersect the elongate illumination beam B and appear in contrast relative to the background of the illumination beam B, which may be bright or dark.
The sorting apparatus further comprises an ejector 41, in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
Figures 2 and 3 illustrate a sorting apparatus in accordance with a second embodiment of the present invention.
The sorting apparatus comprises a delivery device 3 for delivering a flow F of objects O, here a particulate material, such as foodstuffs or other particulate commodities.
In this embodiment the delivery device 3 comprises a vibrating chute 5, which is fed from a hopper 7, and from which is delivered the object flow F.
In other embodiments the delivery device 3 could comprise any delivery system which delivers an object flow F, including a stationary feed chute, a feed belt or pneumatic transport.
The sorting apparatus further comprises a detection system 11 for detecting objects O within the object flow F.
The detection system 11 comprises an illumination unit 14, in this embodiment comprising an illumination source 15 and illumination optics 17, here providing an elongate illumination beam B, which illuminates a narrow, elongate line across a width of the object flow F. In this embodiment the illumination source 15 provides visible light, but could provide any of X-rays, including near X-rays, UV, or infrared, including near infrared, microwave or terahertz radiation.
In this embodiment the illumination source 15 comprises a laser, which provides a laser beam, and the illumination optics 17 comprise one or more lenses which provide a fixed elongate line of illumination.
In one embodiment the illumination optics 17 comprise a Powell lens, which provides a fixed elongate line of illumination of substantially uniform intensity.
In an alternative embodiment the illumination unit 14 could omit the illumination optics 17, and instead the illumination source 15 would provide a pre-shaped illumination beam.
As illustrated, the line of illumination causes the generation of a bright diffuse regions Rl, R2 within the object O, which extend to the adjacent sides of the line of illumination; the bright regions Rl, R2 being generated by sub-surface diffusion within the object O.
The detection system 11 further comprises a detector 21, in this embodiment comprising a multiple line scan camera 22, which comprises a plurality of line array detector elements 23, and detection optics 25 which relay the radiation from the object 0 to the camera 22.
In this embodiment the optical axis of the detector 21 is substantially coaxial with the optical axis of the illumination unit 14, and thus the elongate illumination beam B generated thereby. For purposes of illustration, the illumination unit 14 and the camera 22 are illustrated off-axis.
In this embodiment, as illustrated in Figures 3(a) and (b), the camera 22 comprises a tri-linear array, which comprises three adjacent line array detector elements 23a, 23b, 23c for detecting the reflected radiation from the objects O which pass the detector 21 and the diffuse radiation from the adjacent regions Rl, R2 in objects 0 which pass the detector 21.
In this embodiment one, the central, of the detector elements 23a detects reflected radiation from objects O which pass the detector 21, and the other detector elements 23b, 23c detect diffuse radiation generated by subsurface diffusion, the "halo", and emitted from each side region Rl, R2 of the line of illumination.
In one embodiment, as in this embodiment, the other detector elements 23b, 23c, which detect diffuse radiation from the adjacent regions Rl, R2, have a width greater than the width of the one detector element 23a, which detects radiation reflected from the object O. With this arrangement, greater sensitivity to the diffuse radiation is achieved.
In an alternative embodiment the detector 21 could comprise a bi-linear array, which comprises two adjacent line array detector elements 23a, 23c for detecting reflected radiation from the objects O which pass the detector 21 and diffuse radiation from the one adjacent region Rl in objects O which pass the detector 21.
In this embodiment one detector element 23a detects reflected radiation from objects O which pass the detector 21, and the other detector element 23c detects diffuse radiation generated by sub-surface diffusion to one adjacent side region Rl of the line of illumination.
In one embodiment the other detector element 23c, which detects diffuse radiation from the adjacent side region Rl, has a width greater than the width of the one detector element 23a, which detects reflected radiation from the object O. With this arrangement, greater sensitivity to the diffuse radiation is achieved. In one embodiment the detector 21 can be configured to have a higher gain on the one or two other, outer line detector elements 23b, 23c than the one, center line detector element 23a. In this way, the detector 21 accommodates the lower intensity of the diffuse radiation as detected by the or two other, outer line detector elements 23b, 23c.
With this configuration, the objects O which pass the elongate illumination beam B can be characterized based on reflectance, which is particularly suited to characterizing the shape of the objects O, and translucency, which is particularly suited to characterizing the material of objects O.
Example
By way of example, Figure 3(c) illustrates images acquired using a laser line generator operating at a wavelength of 880 nm as the illumination unit 14. As is clearly evident, the almond shell can be distinguished from almond meat.
In alternative embodiments, as illustrated in Figures 4 to 7, the detection system 11 can comprise a beam splitter 31 to which the illumination unit 14 and the detector 21 are optically coupled, such that the radiation delivered to and received from the object O is co-linear.
In one embodiment, as illustrated in Figures 4 and 5, the illumination unit 14 is provided to the side leg of the beam splitter 31.
In this embodiment the beam splitter 31 includes a narrow, silvered mirror or reflective line 35 which extends only on the center line. In this way, the radiation from the illumination unit 14 is reflected by the reflective line 35 onto the flow of objects O, and the reflective line 35 acts as an aperture stop for the component of the reflected radiation from the objects O corresponding to the width of the reflective line 35, thereby providing that the reflected radiation as received by the camera 22 has a reduced intensity, with the remainder of the reflected radiation from the objects O and the diffuse radiation from the adjacent regions Rl, R2 of the object O passing through the beam splitter 31 adjacent the respective edges of the reflective line 35.
In another embodiment, as illustrated in Figures 6 and 7, the detector 21 can be provided to the side leg of the beam splitter 31.
In this embodiment the beam splitter 31 includes a narrow, non-silvered or reduced-reflectivity line 37 on the center line and silvered mirror or reflective regions 39 juxtaposed the reduced-reflectivity line 37. In this way, the illumination beam B from the illumination unit 14 is able to pass through the aperture provided by the reduced-reflectivity line 37, and the reflected radiation from the objects 0 is received at the beam splitter 31, with the component of the reflected radiation corresponding to the width of the reduced-reflectivity line 37 passing at least partially therethrough, thereby providing that the reflected radiation as received by the camera 22 has a reduced intensity, and the remainder of the reflected radiation from the objects O and the diffuse radiation from the adjacent regions Rl, R2 of the objects O being reflected by the respective reflective regions 39 to the camera 22.
In this embodiment the reflective regions 39 comprise elongate areas or wide lines.
The sorting apparatus further comprises an ejector 41, in this embodiment comprising an array of ejector nozzles 43, which is operable to provide air pulses in response to one or more characteristics detected by the detection system 11, such to eject objects O from the object flow F into a separate object flow F', which is typically a waste flow.
Figure 8 illustrates a sorting apparatus in accordance with a further embodiment of the present invention. This embodiment is very similar to the second-described embodiment, and thus, in order to avoid unnecessary duplication of description, only the differences will be described in detail, with like parts being designated by like reference signs.
This embodiment differs from the second-described embodiment in comprising a plurality of, in this embodiment first and second illumination units 14a, b, and a plurality of, in this embodiment first and second beam splitters 31a, b which are associated with the respective illumination units 14a, b, such as to provide for the illumination of the flow of objects O on the common center line of the camera 22.
In this embodiment the beam splitters 31a, b are located in spaced relation on the optical axis of the camera 22, such that the illumination units 14a, b are provided to the side legs thereof.
In other embodiments further illumination units 14a, b can be incorporated by use of further beam splitters 31a, b.
With this configuration, the objects O can be illuminated with radiation of a plurality of wavelengths or ranges of wavelengths, for example, red and green laser light or red, green and blue laser light.
In one embodiment the camera 22 is a monochromatic camera, and the illumination units 14a, b are modulated to allow for the selective illumination by the respective illumination units 14a, b.
In another embodiment the camera 22 is a multichromatic camera, such as an area scan camera, typically a CCD, and respective lines of the camera 22 detect radiation of different wavelength corresponding to the respective wavelengths of the illumination units 14a, b. In one embodiment, where the illumination units 14a, b are red and green lasers, the camera 22 could be a bichromatic camera, which has a first set of first lines which detect red light and a second set of lines which detect green light.
In another embodiment, where the illumination units 14a, b are red, green and blue lasers, the camera 22 could be a trichromatic camera, which has a first set of first lines which detect red light, a second set of lines which detect green light and a third set of lines which detect blue light.
Figure 9 illustrates a sorting apparatus in accordance with a yet further embodiment of the present invention.
This embodiment is very similar to the second-described embodiment, and thus, in order to avoid unnecessary duplication of description, only the differences will be described in detail, with like parts being designated by like reference signs.
This embodiment differs from the second-described embodiment in comprising a plurality of, in this embodiment first and second illumination units 14a, b, and a plurality of, in this embodiment first and second beam splitters 31a, b, which provide for the illumination of the flow of objects O on the common center line of the camera 22.
In this embodiment one, first beam splitter 31a is located on the optical axis of the ca mera 22, such as to receive illumination from one, here the side, leg thereof, and the other, second beam splitter 31b receives illumination from the illumination units 14a, b to the respective input legs thereof and delivers a single illumination beam, formed of illumination of the wavelengths or ranges of wavelengths of each of the illumination units 14a, b, to the one, side leg of the first beam splitter 31a . In other embodiments further illumination units 14a, b can be incorporated by use of further beam splitters 31a, b.
With this configuration, the objects O can be illuminated with radiation of a plurality of wavelengths or ranges of wavelengths, for example, red and green laser light or red, green and blue laser light.
In one embodiment the camera 22 is a monochromatic camera, and the illumination units 14a, b are modulated to allow for the selective illumination by the respective illumination units 14a, b.
In another embodiment the camera 22 is a multichromatic camera, such as an area scan camera, typically a CCD, and respective lines of the camera 22 detect radiation of different wavelength corresponding to the respective wavelengths of the illumination units 14a, b.
In one embodiment, where the illumination units 14a, b are red and green lasers, the camera 22 could be a bichromatic camera, which has a first set of first lines which detect red light and a second set of lines which detect green light.
In another embodiment, where the illumination units 14a, b are red, green and blue lasers, the camera 22 could be a trichromatic camera, which has a first set of first lines which detect red light, a second set of lines which detect green light and a third set of lines which detect blue light.
In a further embodiment, as illustrated in Figure 10, the detector 21 could comprise a plurality of, here first and second monochromatic cameras 22a-c and a wavelength splitter 45, here a dichroic prism, for separating the received radiation into a plurality of wavelength components, here first and second wavelength components, such as red and green. In an alternative embodiment, as illustrated in Figure 11, the detector 21 could comprise first, second and third monochromatic cameras 22a, b, c and the wavelength splitter 45 could comprise a trichroic prism, for separating the received radiation into first, second and third wavelength components, such as red, green and blue.
Finally, it will be understood that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.
In one modification, as illustrated in Figure 12, the detector 21 could be an area scan camera, such as a CCD, having a plurality of detector lines 51, with groups of the detector lines 51, each comprising one or more of the detector lines 51, here a plurality of detector lines 51, providing adjacent line array detector elements 23a, 23b, 23c for detecting the reflected radiation from the objects O which pass the detector 21 and the diffuse radiation the adjacent regions Rl, R2 in objects 0 which pass the detector 21.
In one embodiment the signals from the detector lines 51 of each detector element 23a, 23b, 23c can be processed individually in characterizing detected objects O.
In an alternative embodiment the signals from one or more sub-groups of detector lines 51 of each detector element 23a, 23b, 23c can be combined, in order to improve the signal-to-noise ratio in signal processing.
In addition, although the above-described embodiment have been described in relation to a sorting apparatus, the present invention has application in any inspection environment for the inspection of a stream of particles, for, example, in checking quality, such as for statistical analysis or for machine/plant control .

Claims

1. A detection system for detecting a flow (F) of objects (O), the system comprising :
at least one illumination unit ( 14; 14a, b) for providing an elongate illumination beam (B) across a width of a flow (F) of objects (0) to illuminate an elongate region thereof; and
a detector (21) which comprises a plurality of line detector elements (23a-c; 23a, c) for detecting radiation received from the objects (0), wherein one detector element (23a) detects reflected radiation from the illuminated region of the objects (0), and at least one other detector element (23b, c; 23c) detects diffuse radiation from subsurface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O).
2. A detection system for detecting a flow (F) of objects (O), the system comprising :
at least one illumination unit ( 14; 14a, b) for providing an elongate illumination beam (B) across a width of a flow (F) of objects (O) to illuminate an elongate region thereof; and
a detector (21) which comprises at least one line detector element (23a-c; 23a, c) for detecting radiation received from the objects (O); wherein (I) optical axes of the illumination beam (B) and the detector (21 ), and optionally of the radiation received from the objects (O), are substantially co-axial and/or (II) the illumination beam (B) and the detector (21) are substantially co-planar.
3. The system of claim 1 or 2, wherein the detector (21) comprises (I) at least one detector element (23a) which detects reflected radiation from the illuminated region of the objects (O), (II) at least one detector element (23b, c; 23c) which detects diffuse radiation from at least one region (Rl, R2) adjacent the illuminated region of the objects (O), or (III) a plurality of line detector elements (23a-c; 23a, c) for detecting radiation received from the objects (O), wherein one detector element (23a) detects reflected radiation from the illuminated region of the objects (O), and at least one other detector element (23a-c; 23a, c) detects diffuse radiation from sub-surface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O), optionally the radiation delivered to or received from the objects (O) is substantially co-axial, co-planar and/or parallel, optionally the detector elements (23a-c; 23a, c) detect substantially one of or substantially only one of reflected or diffuse radiation from the objects (O), optionally the diffuse radiation is detected at a distance of from about 0.5 mm to about 5 mm, from about 0.5 mm to about 4 mm, from about 1 mm to about 4 mm, from about 1 mm to about 3mm or from about 2 mm to about 3 mm from the illuminated region of the objects (O).
4. The system of any of claims 1 to 3, wherein the detector (21) comprises (I) a tri-linear camera array (22) having three adjacent line detector elements (23a-c), with one, the central, of the detector elements (23a) detecting reflected radiation from the illuminated region of the objects (O), and the other detector elements (23b, c) detecting diffuse radiation from sub-surface diffusion at regions (Rl, R2) of the objects (O) adjacent the illuminated region of the objects (O), or (II) a bi-linear camera array (22) having two adjacent line detector elements (23a, c), with one of the detector elements (23a) detecting reflected radiation from the illuminated region of the objects (O), and the other detector element (23c) detecting diffuse radiation from sub-surface diffusion at a region (Rl ) of the objects (O) adjacent the illuminated region of the objects (O), optionally the one or more other detector elements (23b, c; 23c) have a length in the direction of flow (F) of the objects (O) which is greater than a length of the one detector element (23a) in the direction of flow (F) of the objects (0), optionally the detector (21) has a higher gain on the one or more other detector elements (23b, c; 23c) than the one detector element (23a).
5. The system of any of claims 1 to 4, wherein the at least one illumination unit (14; 14a, b) comprises an illumination source ( 15) which comprises (I) a laser which provides a laser point beam, and illumination optics (17) which provide an elongate illumination beam (B), optionally the illumination optics (17) comprise a Powell lens, or (II) the at least one illumination unit (14; 14a, b) comprises an illumination source ( 15) which comprises a laser which provides a pre-shaped elongate iilumination beam (B),
6. The system of any of claims 1 to 5, further comprising :
at least one beam splitter (31 ; 31a, b) to which the at least one illumination unit (14; 14a, b) and the detector (21) are optically coupled, whereby radiation delivered to and received from the objects (O) is co-axial, optionally (I) the at least one illumination unit ( 14; 14a, b) is provided to a side leg of the at least one beam splitter (31 ; 31a, b), whereby the at least one illumination unit ( 14; 14a, b) is off-axis and the detector (21) is on-axis, preferably the at least one beam splitter (31 ; 31a, b) includes a reflective line or zone (35) which extends on a center line thereof, whereby the illumination beam (B) from the at least one iilumination unit ( 14; 14a, b) is reflected by the reflective zone (35) onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (0) passes through the reflective zone (35) to the detector (21) and diffuse radiation from the one or more adjacent regions (Rl, R2) of the objects (O) pass through the at least one beam splitter (31 ; 31a, b) adjacent the respective edges of the reflective zone (35) to the detector (21), or (II) the detector (22; 22a, b) is provided to a side leg of the at least one beam splitter (31 ; 31a, b), whereby the detector (22; 22a, b) is off-axis and the at least one illumination unit ( 14) is on-axis, preferably the at least one beam splitter (31 ; 31a, b) includes (i) a reduced-reflectivity line or zone (37) which extends on a center line thereof and at least one reflective zone (39) adjacent the reduced-reflectivity zone (37), whereby the illumination beam (B) from the at least one illumination unit (14; 14a, b) passes through the reduced-reflectivity zone (37) and onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (O) is reflected by the reduced-reflectivity zone (37) to the detector (22; 22a, b) and diffuse radiation from the one or more adjacent regions (Rl, R2) of the objects (O) is reflected by the at least one reflective zone (39) to the detector (22; 22a, b), or (ii) a reduced- reflectivity line or zone (37) which extends on a center line thereof and first and second reflective zones (39) adjacent the reduced- reflectivity zone (37), whereby the illumination beam (B) from the at least one illumination unit ( 14; 14a, b) passes through the reduced- reflectivity zone (37) and onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (O) is reflected by the reduced-reflectivity zone (37) to the detector (22; 22a, b) and diffuse radiation from the adjacent regions (Rl, R2) of the objects (O) is reflected by the respective reflective zones (39) to the detector (22; 22a, b).
7. The system of claim 6, comprising :
a plurality of illumination units ( 14a, b) for providing illumination of different wavelength ; and
a plurality of beam splitters (31a, b) which are arranged to render coaxial the illumination of the illumination units ( 14a, b) to provide the illumination beam (B) ;
optionally the detector (21) includes (I) a monochromatic camera (22), and the illumination units ( 14a, b) are modulated to allow for selective illumination by the respective illumination units ( 14a, b) and detection by the camera (22), (II) a multichromatic camera (22) and respective lines (51 ) of the camera (22) detect radiation of different wavelength corresponding to the respective wavelengths of the illumination units (14a, b), or (III) a plurality of monochromatic cameras (22a, b; 22a-c) and a wavelength splitter (45) for separating the received radiation into a plurality of components, each being detected by a respective one of the cameras (22a, b; 22a-c).
8. The system of any of claims 1 to 7, wherein the detector (21) is an area scan camera having a plurality of detector lines (51), with groups of the detector lines (51), each comprising one or more of the detector lines, providing adjacent line detector elements (23a-c; 23a, c), optionally the detector lines of each line detector element (23a-c; 23a, c) are processed individually in characterizing detected objects (O) or signals from one or more sub-groups of detector lines (51) of each line detector element (23a-c; 23a, b) are combined in characterizing detected objects (O).
9. A sorting or monitoring apparatus for sorting a flow (F) of objects (O) incorporating the detection system of any of claims 1 to 8, optionally the objects (O) comprise a particulate material, such as foodstuffs or other particulate commodities.
10. A method of detecting, sorting or monitoring a flow (F) of objects (O), comprising the steps of:
providing an elongate illumination beam (B) of at least one wavelength across a width of a flow (F) of objects (O) to illuminate an elongate region thereof; and
detecting radiation received from the objects (O) using a detector (21) comprising a plurality of line detector elements (23a-c; 23a, c), wherein one detector element (23a) detects reflected radiation from the illuminated region of the objects (O), and at least one other detector element (23b, c; 23c) detects diffuse radiation from subsurface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O).
11. A method of detecting, sorting or monitoring a flow (F) of objects
(0) , comprising the steps of:
providing an elongate illumination beam (B) of at least one wavelength across a width of a flow (F) of objects (O) to illuminate an elongate region thereof; and
detecting radiation received from the objects (O) using a detector (21) comprising at least one line detector element (23a-c; 23a, c); wherein (I) optica! axes of the illumination beam (B) and the detector (21) are substantially co-axial, and optionally of the radiation received from the objects (O), and the detector (21) detects reflected radiation from the illuminated region of the objects (O) and/or diffuse radiation from sub-surface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O), or (II) the illumination beam (B) and the detector (21) are substantially co- planar, and the detector (21) detects reflected radiation from the illuminated region of the objects (O) and/or diffuse radiation from sub-surface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O).
12. The method of claim 10 or 11, wherein the detector (21) comprises
(1) at least one detector element (23a) which detects reflected radiation from the illuminated region of the objects (O), (II) at least one detector element (23b, c; 23c) which detects diffuse radiation from at least one region (Rl, R2) adjacent the illuminated region of the objects (O), or (III) a plurality of detector elements (23a-c; 23a, c) which detect radiation received from the objects (O), wherein one detector element (23a) detects reflected radiation from the illuminated region of the objects (O), and at least one other detector element (23b, c; 23c) detects diffuse radiation from sub-surface diffusion at at least one region (Rl, R2) adjacent the illuminated region of the objects (O), optionally the radiation delivered to or received from the objects (O) is substantially co-axial, co-planar and/or parallel, optionally the detector elements (23a-c; 23a, c) detect substantially one of or substantially only one of reflected or diffuse radiation from the objects (0), optionally the diffuse radiation is detected at a distance of from about 0.5 mm to about 5 mm, from about 0.5 mm to about 4 mm, from about 1 mm to about 4 mm, from about 1 mm to about 3mm or from about 2 mm to about 3 mm from the illuminated region of the objects (O).
13. The method of any of claims 10 to 12, wherein the detector (21) comprises (I) a tri-linear camera array (22) having three adjacent line detector elements (23a-c), with one, the central, of the detector elements (23a) detecting reflected radiation from the illuminated region of the objects (O), and the other detector elements (23b, c; 23c) detecting diffuse radiation from sub-surface diffusion at regions (Rl, R2) of the objects (O) adjacent the illuminated region of the objects (O), or (II) a bi-linear camera array (22) having two adjacent line detector elements (23a, c), with one of the detector elements (23a) detecting reflected radiation from the illuminated region of the objects (O), and the other detector element (23c) detecting diffuse radiation from sub-surface diffusion at a region (Rl) of the objects (O) adjacent the illuminated region of the objects (O), optionally the one or more other detector elements (23b, c; 23c) have a length in the direction of flow (F) of the objects (O) which is greater than a length of the one detector element (23a) in the direction of flow (F) of the objects (O), optionally the detector (21) has a higher gain on the one or more other detector elements (23b, c; 23c) than the one detector element (23a).
14. The method of any of claims 10 to 1 3, wherein the illumination beam (B) is provided by at least one illumination unit ( 14; 14a, b) comprising (I) an illumination source ( 15) which comprises a laser which provides a laser point beam, and illumination optics ( 17) which provide an elongate illumination beam (B), optionally the illumination optics ( 17) comprise a Powell lens, or (II) an illumination source ( 15) which comprises a laser which provides a pre-shaped elongate illumination beam (B), and/or the detector (21) is an area scan camera having a plurality of detector lines (51), with groups of the detector lines (51), each comprising one or more of the detector lines (51), providing adjacent line detector elements (23a-c; 23b, c), optionally the detector lines (51) of each line detector element (23a- c; 23b, c) are processed individually in characterizing detected objects (O) or signals from one or more sub-groups of detector lines (51) of each line detector element (23a-c; 23b, c) are combined in characterizing detected objects (O).
The method of any of claims 10 to 14, wherein the illumination beam (B) and the detector (21) are optically coupled by at least one beam splitter (31; 31a, b), whereby radiation delivered to and received from the objects (O) is co-axiai, optionally (I) the illumination beam (B) is provided to a side leg of the at least one beam splitter (31 ; 31a, b), whereby the illumination beam (B) is off-axis and the detector (21 ) is on-axis, preferably the at least one beam splitter (31 ; 31a, b) includes a reflective line or zone (35) which extends on a center line thereof, whereby the illumination beam (B) is reflected by the reflective zone (35) onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (O) passes through the reflective zone (35) to the detector (21) and diffuse radiation from the one or more adjacent regions (Rl, R2) of the objects (O) passes through the at least one beam splitter (31 ; 31a, b) adjacent the respective edges of the reflective zone (35) to the detector (21), or (II) the detector (21) is provided to a side leg of the at least one beam splitter (31 ; 31a, b), whereby the detector (21) is off-axis and the at least one illumination beam (B) is on-axis, preferably the at least one beam splitter (31 ; 31a, b) includes (i) a reduced-reflectivity line or zone (37) which extends on a center line thereof and at least one reflective zone (39) adjacent the reduced- reflectivity zone (37), whereby the at least one illumination beam (B) passes through the reduced-reflectivity zone (37) and onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (O) is reflected by the reduced-reflectivity zone (37) to the detector (21) and diffuse radiation from the one or more adjacent regions (Rl, R2) of the objects (O) is reflected by the at least one reflective zone (39) to the detector (21), or (ii) a reduced-reflectivity line or zone (37) which extends on a center line thereof and first and second reflective zones (39) adjacent the reduced-reflectivity zone (37), whereby the illumination beam (B) passes through the reduced- reflectivity line (37) and onto the flow (F) of objects (O), and reflected radiation from the illuminated region of the objects (O) is reflected by the reduced-reflectivity zone (37) to the detector (21) and diffuse radiation from the adjacent regions (Rl, R2) of the objects (O) is reflected by the respective reflective zones (39) to the detector (21), optionally the method provides illumination at a plurality of different wavelengths and the illumination is rendered coaxial by a plurality of beam splitters (31 ; 31a, b), optionally the detector (21) includes (I) a monochromatic camera (22), and the illumination of different wavelength is modulated to allow for selective illumination by the respective illumination and detection by the camera (22), (II) a multichromatic camera (22) and respective lines of the camera (22) detect radiation of different wavelength corresponding to the respective wavelengths of the illumination of different wavelength, or (III) a plurality of monochromatic cameras (22a, b) and a wavelength splitter (45) which separates the received radiation into a plurality of components, each being detected by a respective one of the cameras (22a, b) .
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