Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/02—Viewing or reading apparatus
  • G02B27/022—Viewing apparatus
  • G02B27/024—Viewing apparatus comprising a light source, e.g. for viewing photographic slides, X-ray transparancies
• • 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
  • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
  • G01N21/952—Inspecting the exterior surface of cylindrical bodies or wires

Definitions

• the present invention relates to viewing apparatus.
• CCD focal plane array charge-coupled device
• the surface of the object under investigation is essentially three-dimensional in form (as compared to the surface of a fabric, for example, which is essentially two- dimensional)
• a minimum of two cameras will be required to view the whole surface and, in practice, three are usually employed. This incurs considerable expense and. in addition, a relatively sophisticated computer program will be required to enable the computer to correlate the information it receives from the three different cameras and to take account of the fact that some of this information may be in part duplicated, owing to the fact that some regions of the object surface will be seen by more than one camera.
• a further drawback is that the high cost of some cameras dictates that economical usage limits the number of viewpoints to 2 or 3 to view the entire object.
• Each of these cameras will be accepting light over a relatively large included angle so that the intensity of at least some of the incident light will almost certainly have been augmented by specular reflectance at the object surface due to the position of direct light sources. This will tend to result in the occurrence of spurious "bright spots" at the associated camera.
• This problem is exacerbated when in addition to being three-dimensional, the object surfaces are also significantly non-uniform, as will be the case with many agricultural products for example.
• the present invention comprises viewing apparatus operative to transpose the views of an object or object surface seen from two or more different viewpoints into a single two-dimensional representation.
• viewing apparatus operative to transpose the views of an object or object surface seen from two or more different viewpoints into a single two-dimensional representation.
• the apparatus includes a circumferential arrangement of reflecting surfaces disposed to present said different views side-by-side in said two-dimensional representation.
• the principal advantage of taking multiple viewpoints around an object is that the distonion when transferring a viewed object to a single plane is reduced as the number of radial viewpoints increases. This is important as a minimum feature on the surface of the subject may otherwise not be resolved to its full extent. For example, if one considers the three viewpoint systems of the prior art systems mutually positioned at 120° to each other, then it is possible, when viewing an object of circular cross section, to transfer an area, say a rectangular area on the curved surface with length twice the breadth, to a square on the transferred plane.
• the distortion maximum with a ten viewpoint system is a maximum of 1.07 as a fraction of length/breadth.
• the viewing apparatus of the present invention also includes an array of reflecting surfaces disposed to present the different views side-by-side in said two- dimensional plane.
• the reflecting surfaces of the circumferential arrangement are disposed to present said side-by-side views in the same sequence as occurs in the object or object surface viewed.
• the reflecting surfaces of the circumferential arrangement are disposed to present each of said side-by-side views with the same reversed or non-reversed and the same inverted or no-inverted format as one another when compared with the object or object surface viewed.
• the apparatus includes a viewing point for direct observation by a manual operator.
• the apparatus of the present invention also includes a convener which responds to the visual information in said two dimensional representation to produce and feed a corresponding electric signal into a computer or like monitoring device e.g. a microprocessor.
• the monitoring device is operative to monitor said side-by-side views in the same sequence as occurs in the object or object surface viewed and/or to correct for any differences in format as regards reversal/non-reversal or inversion/non-inversion of the side-by-side views so as in effect to monitor the side-by-side views as though they had the same reversed or non-reversed and the same inverted or non-inverted format as one another when compared with the object or object surface viewed.
• the invention comprises a quality control system comprising apparatus as claimed in any preceding claim operative to actuate a selector to divide objects leaving the apparatus into objects which satisfy predetermined criteria and objects which fail to satisfy said criteria.
• Figure 2 is a perspective view of a test object to be viewed in the apparatus
• Figure 3 is a side view of a ten viewpoint central mirror system used in said first embodiment, the path of the light through that system being also indicated in the Figure:
• Figures 4A, 4B and 4C. collectively referred to as Figure 4, are perspective views illustrating one of the two side mirror systems used in the first embodiment, the path of the light through that system being also indicated in Figure 4A;
• Figure 5 shows the two side mirror systems as they will appear when viewing the apparatus in plan view, the paths of the light through those systems being also indicated in the Figure:
• Figure 6 shows the two dimensional representation of the test object as it would be seen by the human eye when the test object is in place in the apparatus of Figure 1 :
• Figures 7A. 7B. 7C and 7D are side views of four different designs of eight viewpoint central mirror systems for use in the first embodiment of the invention, the path of the light through the system being also indicated in the Figure:
• Figures 8 and 9 are side views of a twelve viewpoint and twenty viewpoint central mirror system respectively, the path of the light through that system being indicated in each case:
• Figures 10A, 10B and IOC. collectively referred to as Figure 10. are respective side, plan and end views of a horizontal feed system for use with the apparatus of Figure 1 :
• Figure 1 1 is a side view of a gravity feed system for use with the apparatus of
• Figure 12 is a side view of Figure 3 modified to produce viewing axis which converge to allow complete imaging of the views by a lens system, in place of the parallel viewing axis shown in Figure 3;
• Figure 13 illustrates a multi-spectral sensor unit for "waveband imaging" of objects within the viewing apparatus
• Figures 14A and 14B collectively referred to as Figure 14. show a schematic of a conversion unit operative to convert optical information received from the multispectral sensor unit into an electric signal output to a processing unit:
• Figure 15 shows a quality control system incorporating the viewing apparatus of Figure 1. the multispectral sensor unit of Figure 13 and the conversion unit of Figure 12;
• Figures 16A and 16B collectively referred to as Figure 16. show the operating characteristics and spectral sensitivity of two types of camera used in a preferred embodiment of the invention namely typical characteristics for an electron-tube camera (Figure 16A) and typical sensor characteristics for a CCD sensor ( Figure 16B); and
• FIG 17 illustrates a narrow-width ten viewpoint central mirror system according to vet another embodiment of the invention.
• a viewer 12 according to the present invention comprises a box 14 to the floor of which are secured a central support structure 16 for a central mirror system 18 ( Figure 3) and the respective side support structures 20.21 for the two side mirror systems 23.24 ( Figure 5).
• Four "light- folding" mirrors 26.27,28,29 are secured in the box 14 as shown to span the width of the three support structures 16,20.21.
• the walls of these latter are apertured. as are the side walls of box 12. to provide a feed passage or viewing chamber 31 extending from one side of the apparatus to the other.
• a transparent cylindrical tube may be secured within the apertures to protect the mirror system from any dust or dirt falling off the objects under examination.
• a suitable material for the feed tube would be polycarbonate flexible sheeting, for example or toughened glass, provided the transmission characteristics of the chosen material was compatible with the wavebands imaged in the multi-spectral sensor unit.
• Figure 2 shows a test object 35 which may be used in checking that the various mirrors in systems 18.23 and 24 are all at the required setting. This same object will also be referred to in explaining the manner in which the mirror systems operate.
• the test object shown in Figure 2 comprises a decagon core section 37 with a right-angled prism 39,40 either end.
• the core section facets of the object 35 are sequentially numbered from “1 " to “ 10" with the “bottom” of each facet number adjacent to the "top” of the following facet number.
• the upright faces of the end prisms 39,40 bear upright numbers “1 “. “2” (prism 39) and "3”.”4" (prism 40).
• Figure 3 shows a side view of a ten-viewpoint central mirror system with the test object in place in the viewing chamber. It will be noted that the top and bottom facets of the object are reflected seven times before viewing at the viewing port 42 while those of the middle facets, for example, are reflected ten times. It will be noted that the image of the numbers on the longitudinal faces of the test object is reversed (left to right and vice versa ) on each reflection. Inversion (top to bottom and vice versa) occurs after reflections in mirrors which are convergent in the vertical plane ( as is the case with mirrors 26 and 27. say) but not when the mirrors are parallel in that plane (as is the case with mirrors 28 and 29, say).
• the optical path length from the viewing point to the surface for each facet of the test object does vary, so it is desirable to set a long viewing distance such that the error in focus for a viewing sensor is minimal. This is done by increasing the overall path length in the system which is at the same time kept reasonably compact by "folding" the light path in the way shown in Figure 3. This allows direct viewing by an observer or camera system at a point adjacent to the viewing apparatus.
• the reflecting elements preferably have the reflective coating applied to their front surfaces, thereby minimising light attenuation through the glass substrates as in common mirror type systems.
• Figure 4A shows the mirror arrangement in the more remote mirror system 23 of the two side systems 23.24. This Figure also illustrates how the light from the furthest end (40) of the test object is reflected around that system.
• Both the side mirror systems 23.24 are shown in the plan view of Figure 5. In both these systems, the final beam of light is discharged horizontally from the system towards
• mirror pairs 46.48 and 47.49 have vertical reflecting surfaces inclined at 45° to the axis of the feed passage 31.
• the reflecting surfaces of mirrors 51,52 lie parallel to the feed passage axis but inclined at 45° to the vertical
• the reflecting surfaces of mirrors (54,55 lie at 45° to the axis of feed passage axis and at 45° to the vertical.
• the test object of Figure 2 might, for example, have a body portion in the form of a decagon with pre-defined facet dimensions of 25 mm x 160 mm and four facets of size 57 mm x 80 mm disposed at forty-five degrees to the viewing axis at each end of the decagon.
• Objects which are significantly under this size will, when viewed, show commensurate overlap in each segment of surface features seen from a particular viewpoint. For example, objects which have a maximum dimension less than one half of the maximum described will only require one half of the available viewpoint (alternate viewpoints) to fully view the surface.
• Reference numerals 57 in this (and subsequent) Figures indicate tungsten-halogen lamps mounted adjacent to the feed path 31 on the internal faces of support constructions (20.21) for evenly illuminating the object under investigation while it moves through the feed passage. Similar lamps will also be mounted in a similar fashion between the reflected beams in the arrangement of Figure 3 to give a total often in all but these lamps have been omitted from Figure 3 for clarity.
• Figure 7B shows another eight-viewpoint design of central mirror system in which two of the beams are split by split-mirrors 59,60 and are either recombined again in the middle of the single plane representation (left hand vertical face of the test object) or are disposed at opposite ends of the representation (right hand vertical face of the test object).
• the image numbers of the faces run sequentially but. once again, some are inverted and reversed while others are neither..
• Figure 7C shows yet another eight viewpoint design in which the image numbers can be made to run sequentially by means of an appropriate mirror arrangement 62,63,64 in place of the beam-splitter 59 and mirror 66 etc. in place of beam-splitter 60.
• Figure 7D shows a modification of the Figure 7C embodiment in which mirrors 62 and 63 in the Figure 7C embodiment have been replaced by mirrors 62A. 62B. 62C and 63A. 63B respectively in the Figure 7D embodiment. Since the image of vertical facet number "3" is now reflected by an odd number of mirrors and the vertical orientation of the mirrors is such as to produce image inversion, it follows that the image of facet number "3" will now be inverted and reversed in the single plane representation in the same way as those of object facets " 1 ",”2”,”4"",5",”6” and “8". A similar optical system (not shown) can be used to reverse and invert the image of facet "7".
• Figures 8 and 9 show the light paths for 12-viewpoint and 20-viewpoint systems, respectively.
• the various images will not run sequentially and some of them will have different reversal/non-reversal and inversion/non-inversion characteristics to others.
• the objects to be scanned may be placed one by one within the viewing chamber with the object in a preferred longitudinal orientation and its longitudinal axis preferentially coincident with the centre axis of the chamber, in the more sophisticated versions, a convenient transport means may be employed for passing objects sequentially through the chamber.
• Figure 10 shows a convenient form of horizontal feeder for this purpose comprising an array of differently tensioned horizontal wires 68. Each of these wires has a horizontal run which passes through the transparent cylindrical tube 33 secured within the apertured walls of item 14.16.20,21 to define the viewing chamber in this embodiment.
• the resiliently sprung tension adjusters 70 have been set so that the tensions of the wires are graduated to produce a tension "profile" with the tension of the wires increasing as one passes from the most highly tensioned outer wires of the array to the least tensioned middle wire.
• this difference in tension controls the degree of sagging in such a way as to keep that object fairly centrally located within the tube 33 as is best seen from Figure IOC where reference numeral 72 indicates an irregular object, such as a potato, being transported through the system.
• the loading of objects on to the feeder wires prior to their passage through the apparatus may be accomplished using any suitable means, for example, using the flighted conveyor 74 shown in Figure 10A.
• the viewing apparatus is re ⁇ orientated to have a vertical viewing chamber and the objects to be viewed, such as potato 76. are dropped into the upper end of tube 33 using a pair of horizontal transporter belts 78.79 disposed relative to one another in a V-formation.
• a snapshot of the object as represented in the single plane composite representation produced by the apparatus can then be taken by an appropriately activated camera as each object passes a predetermined point in the viewing chamber e.g. as detected by sensor 81 in Figure 1 1.
• the invention includes the combination of a viewing/scaru ⁇ ng apparatus with a conversion unit adapted to change the information displayed in the single plane composite representation from an optical format into a corresponding series of electrical signals e.g. for processing by a dedicated computer or microprocessor.
• a viewing/scaru ⁇ ng apparatus with a conversion unit adapted to change the information displayed in the single plane composite representation from an optical format into a corresponding series of electrical signals e.g. for processing by a dedicated computer or microprocessor.
• FIG 15A where the image acquisition unit (100) and processing unit (101 ) are linked to the multispectral sensor (85).
• reference numerals 104.105.106 and 107 respectively indicate a signal timing extraction unit (104).
• an analogue to digital conversion unit (105) an image pre-processing unit ( 106) and a memory unit (107).
• the invention comprises a quality control system including the optical viewing/scanning apparatus, a conversion unit, a computer comparing the signal received from the conversion unit with a predetermined standard indicative of an object in acceptable condition and an actuator responsive to a signal from the computer to activate a reject mechanism which will remove from any objects leaving the viewing apparatus, those which have been shown not to satisfy the predetermined criteria required.
• a quality control system including the optical viewing/scanning apparatus, a conversion unit, a computer comparing the signal received from the conversion unit with a predetermined standard indicative of an object in acceptable condition and an actuator responsive to a signal from the computer to activate a reject mechanism which will remove from any objects leaving the viewing apparatus, those which have been shown not to satisfy the predetermined criteria required.
• a quality control system including the optical viewing/scanning apparatus, a conversion unit, a computer comparing the signal received from the conversion unit with a predetermined standard indicative of an object in acceptable condition and an actuator responsive to a signal from the computer to activate a reject mechanism which will remove from any objects leaving the viewing apparatus,
• the field of view issuing at the viewing port 42 will, in a commercial automatic viewing system, be fitted with a converging lens system to focus the light on the objective lens of a camera system or the like which will convert the optical input into an electric signal output e.g. for feeding into a computer.
• a converging lens system to focus the light on the objective lens of a camera system or the like which will convert the optical input into an electric signal output e.g. for feeding into a computer.
• viewing apparatus in accordance with the present invention may be used as an aid to direct observation by a manual operator, with the viewing position optimised for the human eye. Observations of the whole of the surface of an object can be made.
• a staggered mirror system identical to system 83 can once again be employed to converge the light, but this time on to the imaging objective lens of a multi-spectral sensor analyser.
• the basic requirements of the multi-spectral sensor show that eight wavebands are required. These view a common field-of-view by the use of beam-splitters (special coatings applied to a glass substrate which allow some radiation to be transmitted and some reflected). Narrow-bandpass filters are situated adjacent to the cameras which restrict the incident radiation to the wavebands desired.
• One such sensor is shown in more detail in Figure 13 and comprises an objective lens 87, filters (as indicated by way of example at 89), CCD (charge coupled device) silicon based cameras (as indicated by way of example at 91 ), eyepiece lenses (as indicated by way of example at 93), beam-splitters (as indicated by way of example at 95) and a special infra-red camera 97.
• an objective lens 87 filters (as indicated by way of example at 89), CCD (charge coupled device) silicon based cameras (as indicated by way of example at 91 ), eyepiece lenses (as indicated by way of example at 93), beam-splitters (as indicated by way of example at 95) and a special infra-red camera 97.
• filters as indicated by way of example at 89
• CCD charge coupled device silicon based cameras
• eyepiece lenses as indicated by way of example at 93
• beam-splitters as indicated by way of example at 95
• the multi-spectral sensor has to include both the CCD silicon based cameras as well as a special infra-red camera because although most of the required wavebands for the application of disease/defect detection occur below 1 100 nanometres, the operating limit for CCD cameras, one waveband occurs at around 1660 nanometres, which requires a sensor to be sensitive to that part of the spectrum.
• An infra-red vidicon tube camera is conveniently used in this case for camera 97 but there are alterative solid-state cameras that may perform the function equally well. Details on the operating characteristics and spectral sensitivity of the CCD and infra ⁇ red cameras are reproduced in Figures 16A and 16B, respectively. From the above description in relation to Figure 13.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Analytical Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Optics & Photonics (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

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• 1995
  • 1995-02-03 GB GB9502197A patent/GB2297628A/en not_active Withdrawn
• 1996
  • 1996-01-15 WO PCT/GB1996/000071 patent/WO1996024084A1/en not_active Application Discontinuation
  • 1996-01-15 PL PL96321629A patent/PL321629A1/xx unknown
  • 1996-01-15 EP EP96900353A patent/EP0807275A1/de not_active Ceased
  • 1996-01-15 CA CA002209905A patent/CA2209905A1/en not_active Abandoned

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