CA1076679A - Method and apparatus for testing a flat, reflecting surface for imperfections - Google Patents
Method and apparatus for testing a flat, reflecting surface for imperfectionsInfo
- Publication number
- CA1076679A CA1076679A CA221,612A CA221612A CA1076679A CA 1076679 A CA1076679 A CA 1076679A CA 221612 A CA221612 A CA 221612A CA 1076679 A CA1076679 A CA 1076679A
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- set forth
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- section
- scanning
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- 239000000463 material Substances 0.000 claims abstract description 10
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- 238000010998 test method Methods 0.000 claims description 2
- 230000007547 defect Effects 0.000 abstract description 14
- 230000033001 locomotion Effects 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000009924 canning Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- IVQOFBKHQCTVQV-UHFFFAOYSA-N 2-hydroxy-2,2-diphenylacetic acid 2-(diethylamino)ethyl ester Chemical compound C=1C=CC=CC=1C(O)(C(=O)OCCN(CC)CC)C1=CC=CC=C1 IVQOFBKHQCTVQV-UHFFFAOYSA-N 0.000 description 1
- 208000019300 CLIPPERS Diseases 0.000 description 1
- 241000896693 Disa Species 0.000 description 1
- 241001669679 Eleotris Species 0.000 description 1
- PBAYDYUZOSNJGU-UHFFFAOYSA-N chelidonic acid Natural products OC(=O)C1=CC(=O)C=C(C(O)=O)O1 PBAYDYUZOSNJGU-UHFFFAOYSA-N 0.000 description 1
- 208000021930 chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids Diseases 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 239000005357 flat glass Substances 0.000 description 1
- 239000005338 frosted glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
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- 235000012976 tarts Nutrition 0.000 description 1
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Classifications
-
- 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
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
- G01N21/8901—Optical details; Scanning details
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- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The reflecting surface of an object to be tested for imperfections is scanned by the light beam of a laser, and the specularly reflected portion of the beam is converted to dif-fuse light by a sheet of translucent material before it im-pinges on a photo-multiplier tube. The output signal of the tube gives an indication of surface defects. When pinholes may be disregarded, but hairline cracks of equal width are ob-jectionable, the scanning beam is passed through a diverging cylinder lens to give it an elongated cross section.
The reflecting surface of an object to be tested for imperfections is scanned by the light beam of a laser, and the specularly reflected portion of the beam is converted to dif-fuse light by a sheet of translucent material before it im-pinges on a photo-multiplier tube. The output signal of the tube gives an indication of surface defects. When pinholes may be disregarded, but hairline cracks of equal width are ob-jectionable, the scanning beam is passed through a diverging cylinder lens to give it an elongated cross section.
Description
10';'6f~'~9 This invention relates to a method of testing a flat reflecting surface of an object for optically aYcertainable Lmperfections and to apparatus for performing the method.
In its more specific aspect~, this invention is con-cerned with an improvement in the apparatus di~clo~ed in the commonly owned United States Patent No. 3,023,9000 In th~
known apparatu~, primarily intended ~or detecting imperfect-ions in sheets or continuous web~ of paper, a surface of the tested material i scanned by a light beam, and the keam is diffusely reflected by the surface to a photomultiplier tube.
The output signal of the tube controls a defect indicator or equipment for sorting the tested materialO
The known apparatus, while very successful in the ap-plication for which it was de~ ed, is unsuited for detect-ing imperfection~ in ob~ects having specularly reflecting, flat ~urfaces, such a~ flat g~ass with or without a mirror coating, mirror-finished metal foil~, and the like. In the absence of a defect, tho photomultiplier tube receive~ sub-stantialy the entire beam of the light source. When a defect i~scanned, the magnitude of the reflected light i8 ~uddenly reduced to practically zero. The range of light contra~t i~
too great to be enaompas~ed by a very sensitive photomulti-plier tube or other photoelectric tran~ducer of similar pro-pertie~, and a less sen~itive tran~ducer would not detect minor flaws, such as scrat¢hes or roller trac~s in a planar glas~ surface. The ~me difficultie~ would be encountered if it were attempted to reduce the output of the light 60urce.
Thi~ prbblem wa~ recognized prior to thls ~nvention, but its solution heretofore required complex apparatus aostly to build and to maintain, as exempli~ied by that disclo~ed in ~ .
.
~- .
107~79 the published German application ~o. 2,152,510.
The object of the invention i~ a modification of the apparatus of the afore-mentioned United State~ Patent whlch permits the apparatu~ to be u~ed in a methsd of detectLng ~in-or and major imperfections ln a surface from which light i8 reflected mainly by spe¢ular reflection.
With this object and other~ in view, a~ will hereinaf-ter become apparent, the invention provldes a method in which the ~urface to be te~ted i8 scanned with a narrow light beam of high inten~ity, whereby a portion of tho beam i~ specu-larly reflected. The roflected beam portion i~ intercepted by a diffuser and thereby converted to diffuse light. An elec-tria signal indicative of changes in the inten~ity of the dif-fuse light i9 then generated a~ an indication of the quality of the te~ted surface.
The apparatus of the invention which i~ preferably em-ployed for performing the above method includes a support for the object to be tested, a 30ur¢e of a narrow light bea~ of high inten~ity, and a refle¢ting device in the path of the beam and movable for scanning the surface of the testod ob-je¢t with the reflected light of the beam. A diffuser i~ in-terposed betwoen the tested surface and a photoelectric trans-ducer for rece~ving the portion of the light beam spocularly reflected from the surface, and for tran~mitting the receiv-ed beam port~on to the transducer as diffuse light, the tr~n~-ducor being adapted to produce an eleotri¢ ~ignal in response to the tran~mitted light.
Other features and many of the attendant advantages of this invention will readily be appreciated aQ the same be-o~me~ better understood by reference to the following detailed 107~679 description of a preferred embodiment when considered in con-nection with the appended drawing in which:
FIG. 1 dhows testing apparatus of the invention in frag-mentary, side-elevational sect~on; and FIG. 2 is a fragmentary, perspective front view of the apparatu~ of FIG. 1.
The drawing shows only a~ much of the basic elements of the apparatus disclosed in the earller United State~ pa-tent as i~ necessary for an understanding of this inventionO
The optical and electrical elements of the testing app~-r~tus are mounted ln a casing 1. They include a laser 2 as a ~ght source productng a n~rrow, inten~e beam 4 of parallel light rays. The beam 4 impingefi on a multi-faceted mirror 3 which is rotated at high speed by an electric motor 31 dur-ing operatlon of the apparatu~. The beam 4' reflected by the mirror 3 falls on plate gla~ 5 coated with a second re-flecting surface of silver. The plate glas~ is moved con-tinuou~ly by a supporting ¢onveyor of whiGh only one roller 51 i~ indicated in FIG. 1. The angle of incidence of the beam 4' is approximately 15 in the position of the mirror 3 in which the beam 4' is parallel to the plane of FIGo 1~ It ~hould generally not be greater than 45 nor smaller than 5, and preferably not greater than 15.
Very little light is scattered by the mirror plate 5, and mo~t of the incident light is specularly reflectea a~ a beam 4a aga~nst the lower one of the two parallel surface of a frosted glass plate 60 ~he incident beam 4' forms a bright spot on the mirror 5, and an image ~f the ~pot i~ formed on the fro~ted glass plate 6. Its light i8 transmitted d~f-fusea~ from the upper surface of the plate 6 into the inte-1~7fGjl~79 rior of a housing lOo The plate 6 clos~s th~ bottom openingof a housing 10 which i8 otherwise made of material ~mper-meable to light, but internally covered with a reflectin~ coat-ing 9 which directs light from the housing walls to two photo-multiplier tubes 8. The output ~ignal of the s~rie~-Qonnected photomultipller tube~ is fed to a defect indicator 81 in a manner more fully descri~ed in ~he earlier patentO
An apertured disc 21and a diverging cylinder lens 22 are interposed between the la3er 2 and the mirror 3 in the path of the beam 4, as is shown only in FIG. 1, to control the cros~ section of the bright spot formed on the Jurface of the tested mirror 5. The aperture in the disc 21 is square, and the square beam leaving the aperture i8 lengthened in the plane of FI~. 1 by the lens 22 80 that the bright spot on the mlrror 5 i8 a Jharply defined rectangleO
The diffuser plate 6 i~ covered with a ~lot diaphragm 7. The ~lot in the diaphragm, not illu~trated ~n detail, i8 bounded by two convex,circular arcs in ~uch a manner that the ~lot, elongated at right angle~ to the plane of FIG. 1, tapers from one longitudinal end to its center and there-after again diverges toward tho other end. The diaphragm 7 may be replaced by other diaphragms having slots of similar shap4, but d~fferent dimensionJ to match the te3ted material and reduce~ the amount of light reaching the diffu~er plate 6 and the photomultiplier tubes 8 when the bea~ 4a is in the cent~r of it~ scanning qtroke aJ aompared to the amount of light transmitted from the edge portions 11 of the mirror plate 50 Two photoelectri¢ transducers 14, of which only one i8 ~hown in each of FIGS. 1 and 2, are mounted ln the ~asing 1 above the edge portions 11 of the mirror plate 5, and may be adjusted transversely to the ~rection of mirror plate move-ment as more specifically described in the earlier U.S. patent.
They are arranged behind an optically flat sheet 12 of trans-parent gla88 obliquely inclined relative to the beam 4' most of which passes through the sheet 12 without change in direct-ion. A small portion 13 of the beam 4' 18 reflected toward a tran~ducer 14 when the beam 4' enters the right edge portion 11 during it~ ~canning movement. The transducers 1~ are elec-trically connected to the defect indicator 81 in a manner not specifically illustrated, but known in itself.
The apparatus describea above ~perates as follows~--While the mirror 3 turns andthe la~er 2 i8 energized, a rectangular light spot travels acros~ the mirror plate S
from the left to the right, a~ viewed in FIG. 1, and ~ts ~pe-cularly reflected portion 4a i~ intercepted by the diffu~er plate 6. In the ab~ence of an imperfection ln the gla~ or in the reflecting ba¢k coating of the mirror plate 5, the out-put ~ignal generated by the ~eries-connected photomultiplier tubes 8 in respon~e to the diffu~e light transm~tted by the plate 6 is oubstantially constant, and the defect dete¢tor 81 includeq a clipper circuit which prevents a defect indicat-ion in response to the minor variatione of signal ~trength which are due to the geometry of the apparatu~ and are held to a minimum by the slot diaphragm.
When the scanning beam reaches the right edge portion 11, as shown in FIGo 2~ the illustrated tran~ducer 14 receives a portion 13 of the beam and tran~mits a signal to the defect indicator 81 whi~h inactivates the indicator and prevents the indication of a defect when the beam travels beyond the la-teral edge of the mirror plate 50 During further rotation of . . .
1~'7~i~79 the mirror 3, the next facet of the mirror ~tarts a new sweep of the beam 4' from the left edge 11 of the mirror plate 5 so that the non-illustrated second tran~ducer 14 emit~ a ~ig-nal which re-a¢tivate~ the defect detector 81.
The dimensions of the aperture in the disa 21 and the curvature of the len3 22 are cho~en to match the dimensions of the imperfection~ that it i8 de~ired ~o detect. Generally, the width of the bright spot on the mirror sheet 5 in the direction of ~canning beam movement ~hould be betwsen 0.1 and 1 m~llimeter, and tho longth of the ~pot in the direction of conveyor movement botwoen 1 millimeter and 100 millimete~ , and greater than the width. Those dimeneion~ are praatically identical with those of the boam cros~ ~ection at the preferred angles of incidence, the angle being defined in the usual manner by the incident b-am and a line perpendicular to the reflecting surface.
As not specifically illu~trated, but known from the earlier patent, the suitably amplified output ~ignal of the photomultiplier tubes 8 may be fed from the indicator 81 to automatlc device~ which remove defective material from a production run or which sort indiv~dual sheets according to their quality.
The apparatus has been found u~eful not only for in-spocting glass mirror plates, but al~o uncoated plate glass, polished or otherwise, reflecting metal ~heets and foil~, and paper provided with a glossy coating. When the apparatu~
is u~ed for in~pe¢ting ~heet~ of finite length, the gaps between successive sheets may be prevented from causing a defect signal in the manner described in the earli-r UOS.
patentO
la ~ g A la~er i8 the best source of a narrow light beam of high intensity that is commercially available at thiB t~me for the apparatu~ of the invention, but other~ may be e~ployed for detecting relatively gros~ defect~. A rotat~ng multi-faceted mirror is commonly u~od in this art to produce the scanning mot~on of a light beam which is much more rapid than the speed at which the te~ted materlal i8 conveyed at right angles to the ~canning motion, but other device~ have be~n employed for the ~ame purpose and are equally applicable hereO
Frostod glass is merely one of the many translucent dif-fuser materials which may ~onstitute the plato 6. Actually, ths diffuser may be opaque and refleat incident parallel light rays in a diffuse manner. The reflecting wali aoating 9 may be replaced by a p~rabolic m~rror and fluorosaent mato-rial in the hou~ing 10 may ~hift tho wa~olength of the dif-fuJe light to a range in which the ~en~itivity of the photo-multiplier tube~ 8 i8 at its peakO The lens 22, the aper-tured disc 21, or both, may be omitted if the shape of the defects is not predominantly elong-tedO Other varlations in the apparatus doscribed and illustrated will readily sug-gest themselve~ to those skilled in the art.
It should be understood, therefore, that tho fore-going diw losure relates only to a preferred embodiment of the invention, and that it i8 intended to cover all change~
and modifications in the example of the invention herein chosen for the puxpose of the disclosure which do not cnn-stitute departures from the spirit and scope of the invent-ion set forth in the appended claims.
In its more specific aspect~, this invention is con-cerned with an improvement in the apparatus di~clo~ed in the commonly owned United States Patent No. 3,023,9000 In th~
known apparatu~, primarily intended ~or detecting imperfect-ions in sheets or continuous web~ of paper, a surface of the tested material i scanned by a light beam, and the keam is diffusely reflected by the surface to a photomultiplier tube.
The output signal of the tube controls a defect indicator or equipment for sorting the tested materialO
The known apparatus, while very successful in the ap-plication for which it was de~ ed, is unsuited for detect-ing imperfection~ in ob~ects having specularly reflecting, flat ~urfaces, such a~ flat g~ass with or without a mirror coating, mirror-finished metal foil~, and the like. In the absence of a defect, tho photomultiplier tube receive~ sub-stantialy the entire beam of the light source. When a defect i~scanned, the magnitude of the reflected light i8 ~uddenly reduced to practically zero. The range of light contra~t i~
too great to be enaompas~ed by a very sensitive photomulti-plier tube or other photoelectric tran~ducer of similar pro-pertie~, and a less sen~itive tran~ducer would not detect minor flaws, such as scrat¢hes or roller trac~s in a planar glas~ surface. The ~me difficultie~ would be encountered if it were attempted to reduce the output of the light 60urce.
Thi~ prbblem wa~ recognized prior to thls ~nvention, but its solution heretofore required complex apparatus aostly to build and to maintain, as exempli~ied by that disclo~ed in ~ .
.
~- .
107~79 the published German application ~o. 2,152,510.
The object of the invention i~ a modification of the apparatus of the afore-mentioned United State~ Patent whlch permits the apparatu~ to be u~ed in a methsd of detectLng ~in-or and major imperfections ln a surface from which light i8 reflected mainly by spe¢ular reflection.
With this object and other~ in view, a~ will hereinaf-ter become apparent, the invention provldes a method in which the ~urface to be te~ted i8 scanned with a narrow light beam of high inten~ity, whereby a portion of tho beam i~ specu-larly reflected. The roflected beam portion i~ intercepted by a diffuser and thereby converted to diffuse light. An elec-tria signal indicative of changes in the inten~ity of the dif-fuse light i9 then generated a~ an indication of the quality of the te~ted surface.
The apparatus of the invention which i~ preferably em-ployed for performing the above method includes a support for the object to be tested, a 30ur¢e of a narrow light bea~ of high inten~ity, and a refle¢ting device in the path of the beam and movable for scanning the surface of the testod ob-je¢t with the reflected light of the beam. A diffuser i~ in-terposed betwoen the tested surface and a photoelectric trans-ducer for rece~ving the portion of the light beam spocularly reflected from the surface, and for tran~mitting the receiv-ed beam port~on to the transducer as diffuse light, the tr~n~-ducor being adapted to produce an eleotri¢ ~ignal in response to the tran~mitted light.
Other features and many of the attendant advantages of this invention will readily be appreciated aQ the same be-o~me~ better understood by reference to the following detailed 107~679 description of a preferred embodiment when considered in con-nection with the appended drawing in which:
FIG. 1 dhows testing apparatus of the invention in frag-mentary, side-elevational sect~on; and FIG. 2 is a fragmentary, perspective front view of the apparatu~ of FIG. 1.
The drawing shows only a~ much of the basic elements of the apparatus disclosed in the earller United State~ pa-tent as i~ necessary for an understanding of this inventionO
The optical and electrical elements of the testing app~-r~tus are mounted ln a casing 1. They include a laser 2 as a ~ght source productng a n~rrow, inten~e beam 4 of parallel light rays. The beam 4 impingefi on a multi-faceted mirror 3 which is rotated at high speed by an electric motor 31 dur-ing operatlon of the apparatu~. The beam 4' reflected by the mirror 3 falls on plate gla~ 5 coated with a second re-flecting surface of silver. The plate glas~ is moved con-tinuou~ly by a supporting ¢onveyor of whiGh only one roller 51 i~ indicated in FIG. 1. The angle of incidence of the beam 4' is approximately 15 in the position of the mirror 3 in which the beam 4' is parallel to the plane of FIGo 1~ It ~hould generally not be greater than 45 nor smaller than 5, and preferably not greater than 15.
Very little light is scattered by the mirror plate 5, and mo~t of the incident light is specularly reflectea a~ a beam 4a aga~nst the lower one of the two parallel surface of a frosted glass plate 60 ~he incident beam 4' forms a bright spot on the mirror 5, and an image ~f the ~pot i~ formed on the fro~ted glass plate 6. Its light i8 transmitted d~f-fusea~ from the upper surface of the plate 6 into the inte-1~7fGjl~79 rior of a housing lOo The plate 6 clos~s th~ bottom openingof a housing 10 which i8 otherwise made of material ~mper-meable to light, but internally covered with a reflectin~ coat-ing 9 which directs light from the housing walls to two photo-multiplier tubes 8. The output ~ignal of the s~rie~-Qonnected photomultipller tube~ is fed to a defect indicator 81 in a manner more fully descri~ed in ~he earlier patentO
An apertured disc 21and a diverging cylinder lens 22 are interposed between the la3er 2 and the mirror 3 in the path of the beam 4, as is shown only in FIG. 1, to control the cros~ section of the bright spot formed on the Jurface of the tested mirror 5. The aperture in the disc 21 is square, and the square beam leaving the aperture i8 lengthened in the plane of FI~. 1 by the lens 22 80 that the bright spot on the mlrror 5 i8 a Jharply defined rectangleO
The diffuser plate 6 i~ covered with a ~lot diaphragm 7. The ~lot in the diaphragm, not illu~trated ~n detail, i8 bounded by two convex,circular arcs in ~uch a manner that the ~lot, elongated at right angle~ to the plane of FIG. 1, tapers from one longitudinal end to its center and there-after again diverges toward tho other end. The diaphragm 7 may be replaced by other diaphragms having slots of similar shap4, but d~fferent dimensionJ to match the te3ted material and reduce~ the amount of light reaching the diffu~er plate 6 and the photomultiplier tubes 8 when the bea~ 4a is in the cent~r of it~ scanning qtroke aJ aompared to the amount of light transmitted from the edge portions 11 of the mirror plate 50 Two photoelectri¢ transducers 14, of which only one i8 ~hown in each of FIGS. 1 and 2, are mounted ln the ~asing 1 above the edge portions 11 of the mirror plate 5, and may be adjusted transversely to the ~rection of mirror plate move-ment as more specifically described in the earlier U.S. patent.
They are arranged behind an optically flat sheet 12 of trans-parent gla88 obliquely inclined relative to the beam 4' most of which passes through the sheet 12 without change in direct-ion. A small portion 13 of the beam 4' 18 reflected toward a tran~ducer 14 when the beam 4' enters the right edge portion 11 during it~ ~canning movement. The transducers 1~ are elec-trically connected to the defect indicator 81 in a manner not specifically illustrated, but known in itself.
The apparatus describea above ~perates as follows~--While the mirror 3 turns andthe la~er 2 i8 energized, a rectangular light spot travels acros~ the mirror plate S
from the left to the right, a~ viewed in FIG. 1, and ~ts ~pe-cularly reflected portion 4a i~ intercepted by the diffu~er plate 6. In the ab~ence of an imperfection ln the gla~ or in the reflecting ba¢k coating of the mirror plate 5, the out-put ~ignal generated by the ~eries-connected photomultiplier tubes 8 in respon~e to the diffu~e light transm~tted by the plate 6 is oubstantially constant, and the defect dete¢tor 81 includeq a clipper circuit which prevents a defect indicat-ion in response to the minor variatione of signal ~trength which are due to the geometry of the apparatu~ and are held to a minimum by the slot diaphragm.
When the scanning beam reaches the right edge portion 11, as shown in FIGo 2~ the illustrated tran~ducer 14 receives a portion 13 of the beam and tran~mits a signal to the defect indicator 81 whi~h inactivates the indicator and prevents the indication of a defect when the beam travels beyond the la-teral edge of the mirror plate 50 During further rotation of . . .
1~'7~i~79 the mirror 3, the next facet of the mirror ~tarts a new sweep of the beam 4' from the left edge 11 of the mirror plate 5 so that the non-illustrated second tran~ducer 14 emit~ a ~ig-nal which re-a¢tivate~ the defect detector 81.
The dimensions of the aperture in the disa 21 and the curvature of the len3 22 are cho~en to match the dimensions of the imperfection~ that it i8 de~ired ~o detect. Generally, the width of the bright spot on the mirror sheet 5 in the direction of ~canning beam movement ~hould be betwsen 0.1 and 1 m~llimeter, and tho longth of the ~pot in the direction of conveyor movement botwoen 1 millimeter and 100 millimete~ , and greater than the width. Those dimeneion~ are praatically identical with those of the boam cros~ ~ection at the preferred angles of incidence, the angle being defined in the usual manner by the incident b-am and a line perpendicular to the reflecting surface.
As not specifically illu~trated, but known from the earlier patent, the suitably amplified output ~ignal of the photomultiplier tubes 8 may be fed from the indicator 81 to automatlc device~ which remove defective material from a production run or which sort indiv~dual sheets according to their quality.
The apparatus has been found u~eful not only for in-spocting glass mirror plates, but al~o uncoated plate glass, polished or otherwise, reflecting metal ~heets and foil~, and paper provided with a glossy coating. When the apparatu~
is u~ed for in~pe¢ting ~heet~ of finite length, the gaps between successive sheets may be prevented from causing a defect signal in the manner described in the earli-r UOS.
patentO
la ~ g A la~er i8 the best source of a narrow light beam of high intensity that is commercially available at thiB t~me for the apparatu~ of the invention, but other~ may be e~ployed for detecting relatively gros~ defect~. A rotat~ng multi-faceted mirror is commonly u~od in this art to produce the scanning mot~on of a light beam which is much more rapid than the speed at which the te~ted materlal i8 conveyed at right angles to the ~canning motion, but other device~ have be~n employed for the ~ame purpose and are equally applicable hereO
Frostod glass is merely one of the many translucent dif-fuser materials which may ~onstitute the plato 6. Actually, ths diffuser may be opaque and refleat incident parallel light rays in a diffuse manner. The reflecting wali aoating 9 may be replaced by a p~rabolic m~rror and fluorosaent mato-rial in the hou~ing 10 may ~hift tho wa~olength of the dif-fuJe light to a range in which the ~en~itivity of the photo-multiplier tube~ 8 i8 at its peakO The lens 22, the aper-tured disc 21, or both, may be omitted if the shape of the defects is not predominantly elong-tedO Other varlations in the apparatus doscribed and illustrated will readily sug-gest themselve~ to those skilled in the art.
It should be understood, therefore, that tho fore-going diw losure relates only to a preferred embodiment of the invention, and that it i8 intended to cover all change~
and modifications in the example of the invention herein chosen for the puxpose of the disclosure which do not cnn-stitute departures from the spirit and scope of the invent-ion set forth in the appended claims.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of testing a flat, reflecting surface of a specularly reflecting object, wherein said object is being moved in a first direction, for optically ascertainable imperfections, which comprises the steps of:
(a) scanning the surface to be tested with a narrow light beam of high intensity, said light beam being moved during said scanning in a second direction transverse to said first direction, the cross section of said beam being elongated in said first direction, whereby a portion of said beam is specularly reflected;
(b) intercepting the specularly reflected beam portion by a diffusing plate and thereby converting said beam portion to diffuse light; and (c) generating an electric signal indicative of changes in the intensity of said diffuse light as an indication of an imperfection in said surface.
(a) scanning the surface to be tested with a narrow light beam of high intensity, said light beam being moved during said scanning in a second direction transverse to said first direction, the cross section of said beam being elongated in said first direction, whereby a portion of said beam is specularly reflected;
(b) intercepting the specularly reflected beam portion by a diffusing plate and thereby converting said beam portion to diffuse light; and (c) generating an electric signal indicative of changes in the intensity of said diffuse light as an indication of an imperfection in said surface.
2. A method as set forth in claim 1, wherein the angle of incidence of said light beam on said surface is between 5° and 45°.
3. A method as set forth in claim 1, wherein the width of said cross section in said direction is 0.1 to 1 millimeter, and the length of said cross section in said first direction is 1 millimeter to 100 millimeters.
4. Apparatus for testing a flat specularly reflecting sur-face of an object for optically ascertainable imperfections, said apparatus comprising:
(a) a support for the object to be tested;
(b) a source of a narrow light beam of high intensity;
(c) reflector means in the path of said beam and movable for scanning a reflecting surface of said object on said support with the light of said beam, whereby a portion of said beam is specularly reflected by said object;
(d) a photoelectric transducer;
(e) a diffusing plate operatively interposed between said surface and said transducer for receiving said specularly reflected portion, and for transmitting the received portion of said beam to said transducer as diffuse light, said transducer being adapted to produce an electric signal in response to the transmitted diffuse light; and (f) a diverging cylinder lens interposed between said source and said reflector means in said path for lengthening the cross section of said beam.
(a) a support for the object to be tested;
(b) a source of a narrow light beam of high intensity;
(c) reflector means in the path of said beam and movable for scanning a reflecting surface of said object on said support with the light of said beam, whereby a portion of said beam is specularly reflected by said object;
(d) a photoelectric transducer;
(e) a diffusing plate operatively interposed between said surface and said transducer for receiving said specularly reflected portion, and for transmitting the received portion of said beam to said transducer as diffuse light, said transducer being adapted to produce an electric signal in response to the transmitted diffuse light; and (f) a diverging cylinder lens interposed between said source and said reflector means in said path for lengthening the cross section of said beam.
5. Apparatus as set forth in claim 4, wherein said reflector means include a multi-faceted mirror and a motor driving said mirror for sequential exposure of the facets thereof to said beam, and said photoelectric transducer includes a photomultiplier tube.
6. Apparatus as set forth in claim 4, wherein said diffusing plate is a sheet of translucent material, said sheet having two parallel, planar surfaces respectively facing toward said surface and toward said transducer.
7. Apparatus as set forth in claim 6, further comprising a housing of material impermeable to light and formed with an opening, said housing enclosing said transducer, and said sheet covering said opening.
8. Apparatus as set forth in claim 7, further comprising a reflecting material covering a portion of said impermeable material in said housing and directing light to said trans-ducer.
9. Apparatus as set forth in claim 4, wherein said source is a laser.
10. Apparatus as set forth in claim 4, wherein said reflector means when moving scan the surface of said object in a pre-determined direction, the apparatus further comprising a diaphragm formed with a slot elongated in said predetermined direction and interposed between said reflector means and said surface, the width of said slot increasing from a central position of said slot toward the longitudinal end portions of said slot.
11. Apparatus as set forth in claim 4, further comprising an apertured disc interposed between said source and said lens in said path for limiting said cross section to ap-proximately equal length and width prior to said lengthening.
12. Apparatus as set forth in claim 4, wherein said support includes means for conveying said object in a first direction during said scanning, said reflector means scanning the sur-face of said object in a second direction transverse to said first direction, and said cross section of the beam incident on said surface being elongated in said first direction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19742411407 DE2411407C3 (en) | 1974-03-09 | Device for testing reflective surfaces | |
| DE19742460077 DE2460077C3 (en) | 1974-12-19 | Device for testing flat, highly reflective surfaces |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076679A true CA1076679A (en) | 1980-04-29 |
Family
ID=25766762
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA221,612A Expired CA1076679A (en) | 1974-03-09 | 1975-03-07 | Method and apparatus for testing a flat, reflecting surface for imperfections |
Country Status (5)
| Country | Link |
|---|---|
| JP (2) | JPS50141390A (en) |
| CA (1) | CA1076679A (en) |
| FR (1) | FR2263509B1 (en) |
| GB (1) | GB1507548A (en) |
| SE (1) | SE7502440L (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52159683U (en) * | 1976-05-28 | 1977-12-03 | ||
| JPS6036013B2 (en) * | 1977-09-30 | 1985-08-17 | 動力炉・核燃料開発事業団 | Metal surface defect inspection method |
| CS241114B2 (en) * | 1981-07-29 | 1986-03-13 | Feldmuehle Ag | Method of materials' transparent bands quality testing and device for its performance |
| DE3338802A1 (en) * | 1983-10-26 | 1985-05-09 | Feldmühle AG, 4000 Düsseldorf | DEVICE AND METHOD FOR TESTING MATERIAL LEVELS |
| GB2159271B (en) * | 1984-04-27 | 1988-05-18 | Nissan Motor | Surface flaw detecting method and apparatus |
| DE3806385A1 (en) * | 1988-02-29 | 1989-09-07 | Feldmuehle Ag | METHOD AND DEVICE FOR TESTING TRANSPARENT RAILS |
| CN117346694B (en) * | 2023-12-04 | 2024-02-23 | 常州微亿智造科技有限公司 | Detection method and detection system for composite surface type sample |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1062594B (en) * | 1955-11-24 | 1959-07-30 | Rudolf Reiser | Double-acting drive and switch motor for rail-bound and non-rail-bound toys, in particular driving, swimming and flying toys with remote control |
| US3385971A (en) * | 1965-08-06 | 1968-05-28 | Appalachian Electric Instr Inc | Radiation sensitive fabric flaw detecting systems |
| GB1376135A (en) * | 1971-02-26 | 1974-12-04 | Ferranti Ltd | Detection of blemishes in surfaces |
| GB1389444A (en) * | 1971-03-09 | 1975-04-03 | Sira Institute | Apparatus for automatic inspection of materials |
| GB1407409A (en) * | 1971-10-27 | 1975-09-24 | Ferranti Ltd | Detection of blemishes in a surface |
| GB1439129A (en) * | 1972-09-21 | 1976-06-09 | Ferranti Ltd | Detection of blemishes in surfaces |
-
1975
- 1975-03-05 SE SE7502440A patent/SE7502440L/ not_active Application Discontinuation
- 1975-03-05 FR FR7506910A patent/FR2263509B1/fr not_active Expired
- 1975-03-07 CA CA221,612A patent/CA1076679A/en not_active Expired
- 1975-03-10 JP JP50028915A patent/JPS50141390A/ja active Pending
- 1975-03-10 GB GB9944/75A patent/GB1507548A/en not_active Expired
-
1985
- 1985-06-14 JP JP1985089036U patent/JPS6117656U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1507548A (en) | 1978-04-19 |
| JPS50141390A (en) | 1975-11-13 |
| SE7502440L (en) | 1975-09-10 |
| FR2263509B1 (en) | 1981-04-10 |
| FR2263509A1 (en) | 1975-10-03 |
| JPS6117656U (en) | 1986-02-01 |
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