WO2005088366A2 - Light guide assembly - Google Patents

Light guide assembly Download PDF

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Publication number
WO2005088366A2
WO2005088366A2 PCT/GB2005/000956 GB2005000956W WO2005088366A2 WO 2005088366 A2 WO2005088366 A2 WO 2005088366A2 GB 2005000956 W GB2005000956 W GB 2005000956W WO 2005088366 A2 WO2005088366 A2 WO 2005088366A2
Authority
WO
WIPO (PCT)
Prior art keywords
assembly according
light
enclosure
axis
mirrors
Prior art date
Application number
PCT/GB2005/000956
Other languages
French (fr)
Other versions
WO2005088366A3 (en
Inventor
Robert James Neil Mclean
Original Assignee
Sortex Limited
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 Sortex Limited filed Critical Sortex Limited
Publication of WO2005088366A2 publication Critical patent/WO2005088366A2/en
Publication of WO2005088366A3 publication Critical patent/WO2005088366A3/en

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0055—Reflecting element, sheet or layer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00—Reflectors for light sources
    • F21V7/0025—Combination of two or more reflectors for a single light source

Definitions

  • This invention relates to light guide assemblies, and particularly such assemblies for use in sorting and inspection apparatus in which light is provided for a viewing station where a product is examined.
  • background light and sometimes foreground illumination can be provided in the form of an elongate strip.
  • the present invention is directed particularly, but not exclusively at an assembly which enables the generation of a strip of light longer than the corresponding dimension of the light source.
  • a strip of light can be created using a fluorescent tube.
  • a fluorescent tube does not produce uniform radiance along its length, as the radiance reduces towards either end. Uniformity of radiance along the length of a strip can be improved by using a tube longer than the length of the strip.
  • the present invention seeks to address this problem and by doing so also reduce the space requirements in one dimension which can be significant.
  • a light guide assembly comprises two spaced plates, each having a reflective surface and arranged with their reflective surfaces in juxtaposition to define an enclosure with a light source side and a display side.
  • An array of mirrors is arranged between the plates, normally symmetrically on either side of an axis extending generally between the source and display sides of the enclosure, with mirrored surfaces facing outward relative to and inclined to the axis to divert light admitted at the source side outwardly relative to the axis towards the display side of the enclosure.
  • the mirrors will preferably have mirrored surfaces on both sides.
  • This arrangement and orientation of mirrors in the enclosure enables a fluorescent tube of predetermined length to be used as the light source and located adjacent the light source side of the enclosure, and generate a strip of light of longer length at the display side. It can also be used to improve the uniformity of a strip of light generated by a tube in a strip of the same length as the tube.
  • the invention has particular application in sorting and inspection apparatus, where the assemblies may be used to create either or both of a background light and foreground illumination.
  • the mirrors between the reflective surfaces will normally extend to the display side of the enclosure to define a display surface.
  • the display surface will normally be planar, but there may be circumstances in which is will be desirable to have it curved in one or sometimes two dimensions.
  • the mirrored surfaces of the mirrors are normally flat, but there may be circumstances in which some curvature, normally concave, might be of value.
  • the inclination of the mirrors relative to the axis extending between the source and display sides of the enclosure in the assembly of the invention can be same on either side of the axis identified above, but will normally increase in proportion to the lateral distance from the axis.
  • the precise angles and indeed any curvature of the mirrored surfaces will be selected according to the result desired, and of course having regard to the dimensions of the light source itself with which the assembly is to be used.
  • the strip of background light has been created at the display side of an assembly according to the invention, it can of course be redirected if it is required at a different location. This can be easily accomplished by the use of a mirror at the display surface.
  • a fold mirror may be used to redirect the light onto a white diffuse plate which can then be rotated to vary the radiance of a complete background assembly at the viewing station.
  • the light guide or mirror box assembly shown in the drawing has two elongate plates 4, reinforced by stiffening ribs 6.
  • a plurality of mirrors 8 are shown mounted on the lower plate 4, but when the plates 2 and 4 are brought together to create an enclosure, the upper edges of the mirrors 8 will abut against the respective lower face of the plate 2.
  • the ends of the enclosure are defined by respective end plates 10.
  • a fold mirror is fitted to direct light transmitted through the enclosure from the side adjacent the rear edge 14 to a desired location in a sorting apparatus.
  • the juxtaposed faces of the upper and lower plates 2 and 4 are formed with reflective surfaces which may be for example polished aluminium.
  • the inner faces of the end plates will also normally be reflective.
  • Each of the mirrors 8 will have its reflective surface facing outwards, and the mirrors themselves are arranged symmetrically on either side of an axis extending perpendicularly between the edges 12 and 14 of the lower plate 4.
  • the mirrors are inclined relative to that axis, and the inclination will normally be greater the further the respective mirror is located from the axis.
  • Both sides of each mirror 8 have reflective surfaces, with the consequence that a battery of light boxes is effectively created between the plates 4.
  • the plates 2, 4 and 10 will define an enclosure having a light source side adjacent the edge 14 of the lower plate 4, and a display side adjacent the fold mirror 12.
  • a fluorescent tube for example will be disposed at or adjacent the light source side, and light emanating from the tube will be at least partially diverted outwardly by the mirrors 8.
  • a fluorescent tube shorter than the length of the light source side of the box can be used to generate at the display side, a strip of light of greater length.
  • a light guide assembly according to the invention can be used to create an effective background light in optical sorting apparatus. It can also be used to create foreground illumination. Particularly, the invention facilitates the matching of background light and foreground illumination with reflected light being of the same order of brightness as the background light in a given region of the sorting zone. It offers similar benefits in inspection apparatus, and in such apparatus where only foreground illumination is required.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
  • Illuminated Signs And Luminous Advertising (AREA)

Abstract

A light guide assembly directs light from a source to form an elongate strip. The assembly has two spaced plates (2,4) arranged with reflective surfaces in juxtaposition to define an enclosure with a light source side and a display side. An array of mirrors (8) is arranged between the plates (2,4) on either side of an axis extending between the sides of the enclosure, with mirrored surfaces facing outward relative thereto. The surfaces are inclined relative to the axis to divert light admitted at the source side outwardly relative to the axis towards the display side of the enclosure.

Description

LIGHT GUIDE ASSEMBLY
This invention relates to light guide assemblies, and particularly such assemblies for use in sorting and inspection apparatus in which light is provided for a viewing station where a product is examined. In such apparatus background light and sometimes foreground illumination, can be provided in the form of an elongate strip. The present invention is directed particularly, but not exclusively at an assembly which enables the generation of a strip of light longer than the corresponding dimension of the light source.
A strip of light can be created using a fluorescent tube. However,' a fluorescent tube does not produce uniform radiance along its length, as the radiance reduces towards either end. Uniformity of radiance along the length of a strip can be improved by using a tube longer than the length of the strip. The present invention seeks to address this problem and by doing so also reduce the space requirements in one dimension which can be significant.
A light guide assembly according to the present invention comprises two spaced plates, each having a reflective surface and arranged with their reflective surfaces in juxtaposition to define an enclosure with a light source side and a display side. An array of mirrors is arranged between the plates, normally symmetrically on either side of an axis extending generally between the source and display sides of the enclosure, with mirrored surfaces facing outward relative to and inclined to the axis to divert light admitted at the source side outwardly relative to the axis towards the display side of the enclosure. The mirrors will preferably have mirrored surfaces on both sides. This arrangement and orientation of mirrors in the enclosure enables a fluorescent tube of predetermined length to be used as the light source and located adjacent the light source side of the enclosure, and generate a strip of light of longer length at the display side. It can also be used to improve the uniformity of a strip of light generated by a tube in a strip of the same length as the tube. As noted above, the invention has particular application in sorting and inspection apparatus, where the assemblies may be used to create either or both of a background light and foreground illumination.
In a light guide assembly according to the invention the mirrors between the reflective surfaces will normally extend to the display side of the enclosure to define a display surface. The display surface will normally be planar, but there may be circumstances in which is will be desirable to have it curved in one or sometimes two dimensions. Similarly, the mirrored surfaces of the mirrors are normally flat, but there may be circumstances in which some curvature, normally concave, might be of value.
The inclination of the mirrors relative to the axis extending between the source and display sides of the enclosure in the assembly of the invention can be same on either side of the axis identified above, but will normally increase in proportion to the lateral distance from the axis. The precise angles and indeed any curvature of the mirrored surfaces will be selected according to the result desired, and of course having regard to the dimensions of the light source itself with which the assembly is to be used.
Once the strip of background light has been created at the display side of an assembly according to the invention, it can of course be redirected if it is required at a different location. This can be easily accomplished by the use of a mirror at the display surface. In sorting apparatus a fold mirror may be used to redirect the light onto a white diffuse plate which can then be rotated to vary the radiance of a complete background assembly at the viewing station.
An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing which shows an exploded view thereof. The light guide or mirror box assembly shown in the drawing has two elongate plates 4, reinforced by stiffening ribs 6. A plurality of mirrors 8 are shown mounted on the lower plate 4, but when the plates 2 and 4 are brought together to create an enclosure, the upper edges of the mirrors 8 will abut against the respective lower face of the plate 2. The ends of the enclosure are defined by respective end plates 10. At the front edge of the lower plate 4 a fold mirror is fitted to direct light transmitted through the enclosure from the side adjacent the rear edge 14 to a desired location in a sorting apparatus.
The juxtaposed faces of the upper and lower plates 2 and 4 are formed with reflective surfaces which may be for example polished aluminium. The inner faces of the end plates will also normally be reflective. Each of the mirrors 8 will have its reflective surface facing outwards, and the mirrors themselves are arranged symmetrically on either side of an axis extending perpendicularly between the edges 12 and 14 of the lower plate 4. The mirrors are inclined relative to that axis, and the inclination will normally be greater the further the respective mirror is located from the axis. Both sides of each mirror 8 have reflective surfaces, with the consequence that a battery of light boxes is effectively created between the plates 4.
Once assembled, the plates 2, 4 and 10 will define an enclosure having a light source side adjacent the edge 14 of the lower plate 4, and a display side adjacent the fold mirror 12. In use, a fluorescent tube for example will be disposed at or adjacent the light source side, and light emanating from the tube will be at least partially diverted outwardly by the mirrors 8. As a consequence, a fluorescent tube shorter than the length of the light source side of the box can be used to generate at the display side, a strip of light of greater length. Additionally, as the radiance of light from a fluorescent tube falls off towards either end, by diverting light lengthwise from the centre of the tube, more uniform radiance can be accomplished at the display side than is created at the light source side even if the length of the light source is the same as the length of the light guide assembly.
As noted above, a light guide assembly according to the invention can be used to create an effective background light in optical sorting apparatus. It can also be used to create foreground illumination. Particularly, the invention facilitates the matching of background light and foreground illumination with reflected light being of the same order of brightness as the background light in a given region of the sorting zone. It offers similar benefits in inspection apparatus, and in such apparatus where only foreground illumination is required.

Claims

1. A light guide assembly for providing an elongate strip of light in optical sorting apparatus, which assembly comprises two spaced plates each having a reflective surface and arranged with their reflective surfaces in juxtaposition to define an enclosure with a light source side and a display side; and an array of mirrors arranged between the plates on either side of an axis extending between the sides of the enclosure, with mirrored surfaces facing outward relative to and are inclined to the axis to divert light admitted at the source side outwardly relative to the axis toward the display side of the enclosure.
2. An assembly according to Claim 1 wherein the mirrors extend to the display side of the enclosure to define a display surface.
3. An assembly according to Claim 1 or Claim 2 wherein the display side of the enclosure defines a planar surface.
4. An assembly according to Claim 1 or Claim 2 wherein the display side of the enclosure defines a surface curved in one dimension.
5. An assembly according to Claim 1 or Claim 2 wherein the display side of the enclosure defines a surface curved in two dimensions.
6. An assembly according to any preceding Claim wherein the mirrored surfaces of the mirrors are flat.
7. An assembly according to any preceding Claim wherein the mirrors have reflective surfaces on their sides facing inwards as well as outward relative to said axis.
8. An assembly according to any preceding Claim wherein the inclination of the mirrors relative to the axis increases in relation to its spacing from the axis.
9. An assembly according to any preceding Claim wherein the mirrors are arranged symmetrically on either side of said axis
10. An assembly according to any preceding Claim including a mirror at the display surface for redirecting displayed light to generate a background strip of light.
11. Optical sorting apparatus having a viewing station through which passes product to be sorted, and including a light guide assembly according to any preceding Claim for providing a strip of background light in the viewing station.
12. Optical sorting apparatus having a viewing station through which passes product to be sorted, and including a light guide assembly according to any of Claims 1 to 10 for providing foreground illumination in the viewing station.
PCT/GB2005/000956 2004-03-11 2005-03-11 Light guide assembly WO2005088366A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0405525.7 2004-03-11
GB0405525A GB2411947B (en) 2004-03-11 2004-03-11 Light guide assembly

Publications (2)

Publication Number Publication Date
WO2005088366A2 true WO2005088366A2 (en) 2005-09-22
WO2005088366A3 WO2005088366A3 (en) 2008-12-31

Family

ID=32117497

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2005/000956 WO2005088366A2 (en) 2004-03-11 2005-03-11 Light guide assembly

Country Status (2)

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GB (1) GB2411947B (en)
WO (1) WO2005088366A2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010043873A1 (en) * 2008-10-17 2010-04-22 Buhler Sortex Ltd Light guide and illumination assembly incorporating the same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3263233A1 (en) 2016-06-28 2018-01-03 Buhler Sortex Ltd. Illumination devices

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB308669A (en) * 1927-11-24 1929-03-25 William Albert Burns Improvements in the illumination and working of advertising signs
US4621309A (en) * 1984-03-31 1986-11-04 Trilux-Lenze Gmbh + Co. Kg Elongated luminaire
EP1143193A2 (en) * 2000-04-07 2001-10-10 Glättli Hansheinrich Lighting device

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5117342A (en) * 1990-10-16 1992-05-26 Vlah John A Universal fit longeron supported louver system
US5961198A (en) * 1996-02-02 1999-10-05 Hitachi, Ltd. Liquid crystal display device and method of manufacturing backlighting light guide panel therefor
JPH11284803A (en) * 1998-03-27 1999-10-15 Citizen Electronics Co Ltd Linear light source unit
PL343963A1 (en) * 2000-11-16 2002-05-20 Grzegorz Drozdowski Edge-illuminated optical device
JP2003045214A (en) * 2001-07-27 2003-02-14 Airesu Denshi Kogyo Kk Light-emitting device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB308669A (en) * 1927-11-24 1929-03-25 William Albert Burns Improvements in the illumination and working of advertising signs
US4621309A (en) * 1984-03-31 1986-11-04 Trilux-Lenze Gmbh + Co. Kg Elongated luminaire
EP1143193A2 (en) * 2000-04-07 2001-10-10 Glättli Hansheinrich Lighting device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 01, 31 January 2000 (2000-01-31) -& JP 11 284803 A (CITIZEN ELECTRONICS CO LTD), 15 October 1999 (1999-10-15) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010043873A1 (en) * 2008-10-17 2010-04-22 Buhler Sortex Ltd Light guide and illumination assembly incorporating the same
US9074756B2 (en) 2008-10-17 2015-07-07 Buhler Sortex Ltd Light guide and illumination assembly incorporating the same

Also Published As

Publication number Publication date
GB0405525D0 (en) 2004-04-21
WO2005088366A3 (en) 2008-12-31
GB2411947B (en) 2007-07-11
GB2411947A (en) 2005-09-14

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