Event scanning

• US 4,623,797 A
• Filed: 06/27/1983
• Issued: 11/18/1986
• Est. Priority Date: 06/27/1983
• Status: Expired due to Fees

• Current Assignee: MTS Systems Corporation (Illinois Tool Works Inc.)
• Original Assignee: MTS Vektronics Corporation
• Inventors: Eaton, Homer L., Schmidt, Joe
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Gatto, James G.
• Application Number:
  US06/507,925
• Time in Patent Office: 1,240 Days
• Field of Search: 250/563, 250/572, 250/202, 250/560, 250/235, 318/577, 356/376, 356/377, 356/384, 356/385, 356/386, 356/387
• US Class Current: 250/559.36
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques

Abstract

A scanning laser beam is directed in a circular scanning pattern, perpendicular to the surface of a part that moves across the scan pattern. Reflected light received solely from part edges or other surface discontinuities is compared with a number of preselected threshold levels. When reflection intensity attains any one of the selected threshold levels, an event is triggered, and the beam position at the time of the event, together with the intensity level triggering the event, are recorded, so as to provide information limited to the part edges and other surface discontinuities.

Claims

1. The method of scanning surface characteristics of an object to selectively obtain data representing only portions of the surface having selected characteristics comprising

moving a scanning energy beam in a scan pattern across the object so that beam energy reflected from discrete positions on the object is detectable,

relatively moving the object and scan pattern to cause the beam to illuminate areas on the surface of the object in scan paths that repetitively cross the object,

generating position signals representing the position of the beam in said scan paths, in reference to discrete positions on the object,

detecting energy of said beam reflected from said object at such discrete positions,

employing the magnitude of detected energy to select certain of the position signals, each corresponding to a selected discrete position, based upon the occurrence of a detected energy magnitude at one of a plurality of different magnitudes of detected energy, and

employing the selected position signals and the magnitude associated with each such selected position signal to define details of the surface characteristics of only those portions of the object having the selected characteristics of the object.

2. The method of claim 1 including the step of establishing said predetermined magnitudes at a value between the magnitudes of energy reflected from said object and from the background of the object.

3. The method of scanning surface characteristics of an object to obtain detailed data representing points within a discontinuity of the object along a line transverse to the discontinuity comprising

moving a scanning energy beam in a scan pattern across the object so that beam energy reflected from discrete positions within a discontinuity of the object along a line transverse to the discontinuity is detectable,

relatively moving the object and scan pattern to cause the beam to illuminate areas on the surface of the object in scan paths that repetitively cross the object,

generating position signals representing the position of the beam in said scan paths in reference to discrete positions including a plurality of portions within a discontinuity along a line transverse to the discontinuity on the object,

detecting energy of said beam reflected from said object at such discrete positions,

employing the magnitude of detected energy to select certain of the position signals each corresponding to a selected discrete position within a discontinuity, based upon the occurrence of a detected energy magnitude at one of a plurality of different magnitudes of detected energy,

said step of selecting position signals comprising generating an event signal when detected beam energy reflected from the object attains any one of a number of mutually different predetermined magnitudes, and selecting only those position signals that represent position of the beam when an event signal occurs.

10. The method of claim 3 wherein said step of indicating positions comprises generating position signals representing the positions of the beam throughout at least a portion of its scan that traverses the part, generating an event signal when the level of reflected energy received from the part is equal to any one of a group of said intermediate levels of reflected energy, selecting only those position signals that occur together with said event signals, and indicating with the selected position signals the level of intensity of reflected beam energy upon occurrence of each said event signal.

4. The method of scanning a part for surface discontinuities comprising the steps of

moving an energy beam over an object in a scan path so as to cause energy to be reflected from the object and its background,

receiving energy of the beam reflected from the object and its background,

comparing the level of a parameter of received reflected beam energy with each one of a group of reference levels of such parameter,

signaling occurrence of an event when the compared level of the parameter of the received reflected energy has a predetermined relation to at least one of said reference levels, and

indicating the position of the beam upon occurrence of said signaled event.

5. The method of claim 4 wherein said parameter is intensity of reflected energy, wherein said event is signaled whenever the level of received reflected energy is the same as one of said reference levels of reflected energy intensity, and including the step of indicating that one of the reference levels at which the event is signaled, in conjunction with the indicating of position of the beam upon occurrence of said signaled event, to thereby indicate the beam position and reflection intensity level at which each event occurs.

6. The method of claim 5 including the step of indicating the sense of variation of received reflected energy at each signaled event, to thereby indicate sense of a transition.

7. The method of determining configuration of a part comprising

scanning an energy beam across said part in a fixed direction,

receiving energy reflected from the part and its background in a direction opposite the fixed direction whereby the received energy at different times in the scan has been reflected from respective different areas of the part, and the intensity of the reflected energy varies according to, at least, the contour of the part in relation to the fixed direction as the beam traverses the part,

selecting a plurality of levels of intensity of reflected beam energy intermediate of the maximum level of energy reflected from the part and the level of energy reflecte from its background, and

indicating positions of the beam only at the times that the reflected energy has a predetermined relation to one of the selected levels.

8. The method of claim 7 including receiving said reflected energy in a direction parallel to the fixed direction of the scanning beam, and wherein said beam position is indicated in two dimensions with respect to said part, said part having a portion with points thereof at different angles relative to said direction parallel to the fixed direction, whereby intensity of received reflected energy varies with the angle of the point within the portion at which energy is reflected, and whereby indicated positions of the beam occur for all points within the portion having one of a plurality of different angles.

9. The method of claim 7 wherein said step of indicating positions comprises indicating positions of the beam when the level of reflected energy equals a selected level.

11. Scanning apparatus for providing data representing details of a surface discontinuity comprising

carrier means for supporting an object to be scanned, said object having surface discontinuities which reflect energy with different intensities at different points within the discontinuity along a scan that traverses the discontinuity,

a scanning device comprising means for generating an energy beam in a fixed direction moving in a scan pattern across an object supported by the carrier means,

means for effecting relative motion of said carrier means and said scanning device to thereby move said scan pattern over said object in a plurality of paths that repetitively traverse the object, its surface discontinuities, and said carrier means,

means for receiving energy of said beam reflected from said object and carrier means in a direction opposite the fixed direction, the magnitude of said reflected energy varying between a first value when reflected from the carrier means and a second value when reflected from parts of the object generally perpendicular to the fixed direction, as the beam moves across the object, and varying between said values when reflected from different points within the discontinuity along a line transverse to the discontinuity,

event means responsive to said reflected energy receiving means for detecting occurrence of a predetermined relation of the magnitude of said reflected energy to any one of a plurality of preselected discrete magnitudes between said first and second values, and

means responsive to said event means for indicating position of said beam in a coordinate system fixed to said part upon detection of said predetermined relation, thereby to indicate positions of a plurality of different points within the discontinuity along a scan that traverses a discontinuity, which points reflect with different intensities.

12. The apparatus of claim 11 wherein said event means comprises means for detecting a change of magnitude of reflected energy to said preselected magnitude.

13. The apparatus of claim 11 wherein said event means comprises an electrical comparator, means for establishing a reference level in said comparator, and means responsive to said receiving means for transmitting to said comparator an electrical signal having a magnitude indicative of the magnitude of energy received by the receiver.

14. The apparatus of claim 11 wherein said event means comprises a plurality of electrical comparator means responsive to said energy receiving means for producing an event signal when received reflected energy attains the respective comparator reference level, means for establishing a different reference level for each said comparator, and means for transmitting to said comparators an electrical signal representing received reflected energy, said means for indicating position comprising means for generating beam position signals indicating postiion of said beam upon occurrence of each said event signal.

15. The apparatus of claim 14 including means for indicating the individual reference level for each indicated beam position signal at which the corresponding event signal occurred.

16. The apparatus of claim 14 including means for generating threshold level signals each paired with a respective one of said beam position signals, said threshold level signals each indicating a reference level of one of said comparators.

17. The apparatus of claim 11 including means for indicating the sense of the variation of the magnitude of said reflected energy.

18. The apparatus of claim 11 wherein said event means comprises a plurality of threshold detector circuits, each having a different preselected reference level, means responsive to the energy receiving means for transmitting to each said threshold detector circuit a signal representing magnitude of reflected energy, each said threshold detector circuit including means for generating an up event signal when said reflection intensity signal from the energy receiving means rises to the reference level of the individual comparator, and including means for generating a down event signal when said reflection intensity signal falls to the reference level of the individual comparator, said means responsive to said event means for indicating position including means for indicating beam position upon occurrence of an output from one of said comparators, and indicating, together with such indication of beam position, an identification of the individual comparator providing such output and whether such output is an up or down event signal.

19. The apparatus of claim 18 wherein each threshold detector circuit comprises a differential amplifier having a reference level established at a first input thereof and having a second input thereof connected to receive a reflection intensity signal from said reflected energy receiving means, a first inverter having an input connected to the output of said amplifier and having an output, an up threshold interrupt flip-flop connected to be triggered from the output of said first inverter, a second inverter having an input connected to the output of said first inverter and having an output, and a down threshold interrupt flip-flop connected to be triggered from the output of said second inverter.

20. The apparatus of claim 19 wherein said means for indicating position comprises scan counter means for generating scan count signals representative of position of the beam in the course of its scan, length counter means for generating length count signals representative of position of the carrier means relative to said scanning device, event data control word assembly means for generating threshold interrupt signals representing the reference level at which each event signal occurs, and storage means for said threshold interrupt signals together with the length and scan count signals corresponding to an individual event.

21. Scanning apparatus comprising

a carrier for supporting an object to be scanned,

a scanning laser projecting a light beam in a fixed direction and in a scan pattern across the object and carrier,

means for moving the carrier relative to the scan pattern to cause said scan pattern to repetitively cross the surface of said object,

a detector receiving light of said beam reflected from points of the object surface crossed by said scan pattern and having an output representating intensity of reflected light in a direction opposite the fixed direction,

a plurality of comparators responsive to said detector output, said comparators each having a different reference level and each having an output representing coincidence of said detector output and a respective one of said reference levels, and

means for indicating the respective position of said light beam upon occurrence of any one of said comparator outputs.

22. The scanning apparatus of claim 21 wherein at least one of said comparators comprises first direction sensitive means for generating said output when said detector output rises to said reference level and second direction sensitive means for generating a second comparator output when said detector output falls to said reference level, and means responsive to said direction sensitive means for identifying said comparator outputs.

23. Scanning apparatus comprising

a carrier for supporting an object to be scanned,

a scanning laser projecting a relatively small area light beam, having an axis of columnation, in a fixed direction and in a scan pattern across the object and carrier,

means for moving the carrier relative to the scan pattern to cause said scan pattern to repetitively cross the surface of said object,

a detector receiving light of said beam reflected in a direction opposite the fixed direction from points of the object surface crossed by said scan pattern and having an output representing intensity of reflected light,

a comparator responsive to said detector output, said comparator having a reference level and having an output representing coincidence of said detector output and said reference level,

means for indicating position of said axis of columnation of said light beam upon occurrence of said comparator output, and

a plurality of additional comparators responsive to said detector output, each having an unique reference level and having an output representing coincidence of said detector output and the reference level of the respective comparator,

said means for indicating position including means for indicating position of said axis of columnation of said light beam upon occurrence of the output of each of said comparators and indicating the individual comparator producing such output together with the position indication to thereby indicate beam position relative to the object when reflected light has each one of a number of different intensities.

24. The apparatus of claim 23 wherein each said comparator includes direction sensitive means for generating a first comparator output when the detector output increases to a value above the comparator reference level and for producing a second comparator output when the detector output decreases below the comparator reference level, said first and second outputs respectively indicating transition of the scanning light beam from areas of lower to areas of higher reflection intensity and from areas of higher to areas of lower reflection intensity to thereby denote arrival of the scanning beam at the object to be scanned and departure of the beam from the object.

25. The method of scanning an object to provide enhanced resolution contour data for regions of the object having contours, said method comprising

sweeping a relatively small area energy beam in a fixed direction across the object in a plurality of scan paths to illuminate points of the object lying in said paths and to cause beam energy to be reflected from the object with intensity that varies along said paths, said object having at least a portion with different points within said portion extending at different angles with respect to a plane perpendicular to said fixed direction, said different angles causing the beam energy to be reflected with intensity that varies from point to point within said portion,

selecting a number of different reference levels of reflection intensity,

comparing intensities of reflected beam energy with said reference levels to detect the occurrence of a reflected beam energy having a predetermined relation to a respective one of said reference levels, and

indicating location of the point at which reflected beam energy has such predetermined relation, to thereby provide data indicating the locations of points of said portion that reflect beam energy at said predetermined relation to any of the respective reference levels.

26. For use with a scanning apparatus in which a relatively small area columnated laser beam, having an axis of columnation, and emanating in a fixed direction is moved in a scan pattern across an object transported past the scan pattern by a carrier so that light of the scanning beam is reflected from the object and the carrier along a line opposite from the fixed direction, event data means comprising

detector means responsive to reflected light energy for generating a signal representing the intensity of the reflected light energy,

means for generating a length signal representing position of the carrier and object transported thereby relative to the laser scan pattern,

scan counter means for generating a scan position signal representing position of the scanning beam in its scan pattern,

a plurality of threshold detector circuits having mutually different reference levels, each circuit receiving said reflected light energy intensity signal from said detector means, and each including means for generating an event output signal when the reflected light energy intensity signal attains the reference level of the individual detector circuit,

intensity identification means responsive to said threshold detector circuits for producing an event data signal identifying which of the threshold detector circuits produces an event output signal, and

storage means, operable upon occurrence of an event output signal, for storing each event data signal together with the length signal and scan position signal occurring together with said event output signal.

27. The apparatus of claim 26 wherein each said threshold detector circuit includes means for generating an up/down signal representing either rise or fall of the reflection intensity signal, and wherein said event data signals include said up/down signal.

28. The method of scanning an object to detect selected surface characteristics and to provide high resolution data regarding detected surface characteristics without providing high resolution data over the entire scan, said method comprising the steps of

moving a small area scanning energy beam across the object so that beam energy is reflected from the object at successive points on a scan across a selected surface characteristic,

said selected surface characteristic reflecting said scanning energy beam with intensity that varies from one point to another on said scan across said selected surface characteristic, whereby variation of intensity of energy reflected from successive points represents variation of said selected characteristic,

detecting energy of said scanning energy beam reflected from said object, preselecting a plurality of reference magnitudes respectively corresponding to magnitudes of energy reflected at different selected magnitudes from within all of the possible different magnitudes of energy reflected from each of the possible points on a scan across a selected surface characteristic, and

selecting only those positions of said scanning energy beam at which occur reflected energy having any one of said reference magnitudes, thereby to enable high resolution display of detail of a selected surface characteristic.

29. The method of claim 28 wherein said surface characteristic is a surface discontinuity, wherein said scanning energy beam is projected in paths parallel to itself and substantially perpendicular to at least some portions of said object in a scan pattern that crosses the object, said surface discontinuity having

contoured portions thereon having contours which are not substantially perpendicular with respect to scanning energy beam, whereby said selecting of positions provides data representing position of said beam only at points of said contoured portions of said surface having discretely different contour properties to thereby provide data representing a plurality of points on a scan across said surface discontinuity and the variance of the contour property at each such point from the portions of the object substantially perpendicular to the energy beam direction.

30. A method of determining the configuration of a part moving relative to a scanning station containing a source of columnated light, having an axis of columnation and emanating in a first direction and wherein the part has portions which are generally flat and generally perpendicular to the first direction and is positioned on a background which is substantially less reflective than the part, and positioned in an XY coordinate system in a plane generally perpendicular to the first direction, comprising the steps of

moving the light source relative to the part to scan the part in a manner to impinge the column of light upon substantially all of the part during the scanning process, due to the relative movement of the columnated light and the part,

detecting the magnitude of the light energy reflected from the part and the background along a path generally aligned with the axis of columnation of the beam and detecting the position of the axis of columnation within the X-Y coordinate system,

employing the magnitude of the detected reflected light energy to select certain positions of the axis of columnation within the X-Y coordinate system based upon the occurrence of the reflected light at such selected position equaling one of a plurality of selected magnitudes,

storing the position in the X-Y coordinate system of the axis of columnation along with the magnitude of the reflected light energy at such position, and

generating a map of the part contours based upon the stored values for the X-Y coordinate system beam positions and the associated reflected energy magnitude for such positions.

31. The method of claim 30 wherein the plurality of selected reflected energy magnitudes are selected to be intermediate the reflected energy from the background and the reflected energy from the generally flat portions of the part which are generally perpendicular to the first direction.

32. An apparatus for determining the configuration of a part moving relative to a scanning station, containing a source of columnated light, having an axis of columnation and emanating in a first direction wherein the part is positioned on a background substantially less reflective than the part and positioned in an X-Y coordinate system in a plane generally perpendicular to the first direction, and the part has portions of the part which are generally flat and generally perpendicular to the first direction, comprising

transport means for moving the part and the source of columnated light relative to each other such that after completion of the relative movement the columnated light has impinged upon substantially all of the part due to the relative movement of the part and the source of columnated light,

reflection detection means for detecting the magnitude of the light energy reflected from the part or its background along an axis generally aligned with the axis of columnation,

position detection means for detecting the position of the axis of columnation in the X-Y coordinate system,

selection means for selecting certain positions of the axis of columnation within the X-Y plane upon the occurrence of the magnitude of the reflected energy equalling one of a plurality of selected magnitudes, and

storage means for storing data representative of the selected position of the axis of columnation and the magnitude of the reflected energy at such selected positions for each such selected position at which one of the selected magnitude occurs.

33. The apparatus of claim 32 wherein the plurality of selected reflected energy magnitudes utilized by the selection means are magnitudes intermediate the magnitude of the energy reflected by the background and the magnitude of the energy reflected by the portions of the part which are generally flat and generally perpendicular to the first direction.

34. A method of scanning a part to obtain data defining surface characteristics of a discontinuity on a portion of the surface of the part, said data including a plurality of data points dispersed within the portion of the surface containing the discontinuity and along a line that crosses the discontinuity, to thereby provide an output representative of details of the position of the portion of the part containing the discontinuity in relation to the entire part and variations of the discontinuity within the portion containing the discontinuity and along a line that crosses the discontinuity, comprising the steps of

causing an energy beam to successively impinge upon a plurality of small adjacent areas of the part positioned along a line that crosses the discontinuity in an X-Y coordinate system within which the part is referenced,

receiving reflected energy from the part,

selecting some but not all of the small adjacent area locations within the X-Y coordinate system, based upon the occurrence of the reflected energy attaining one of a plurality of different selected threshold levels, and

storing the respective locations within the X-Y coordinate system at which there occurs the reflected energy attaining one of the plurality of selected threshold levels and the particular threshold level occurring at each such location, whereby there are stored data points for a plurality of locations on the discontinuity along a line that crosses the dicontinuity.

35. The mthod of claim 34 wherein the part is positioned on a background which is less reflective than any portion of the part, and has portions which are generally free of any discontinuity and thereby reflect the energy beam from such portions at a maximum level, and the plurality of different selected threshold levels are selected to be between the maximum level reflected from the part and the level reflected from the background.

36. An apparatus for scanning a part to obtain data defining surface characteristics of a discontinuity on a portion of the surface of the part, said data including a plurality of data points dispersed within the portion of the surface containing the discontinuity, to thereby provide an output representative of details of the position of the portion of the surface having the discontinuity in relation to the entier part and variations within the portion containing the discontinuity, comprising

scanning means for scanning an energy beam to cause the beam to impinge upon a plurality of small adjacent areas of the part positioned in an X-Y coordinate system in which the part is referenced,

receiving means for receiving energy reflected from the part,

selection means for selecting some but not all of the small adjacent area locations within the X-Y coordinate system, based upon the occurrence of the reflected energy attaining one of a plurality of different selected threshold levels, and

storage means for storing the respective locations within the X-Y coordinate system at which there occurs the reflected energy attaining one of the plurality of selected threshold levels and the particular threshold level occurring at each such location.

37. The apparatus of claim 36 wherein the part is positioned on a background which is less reflective than any portion of the part, and has portions which are generally free of any discontinuity and thereby reflect the energy beam from such portions at a maximum level, and the plurality of different selected threshold levels are selected to be between the maximum level reflected from the part and the level reflected from the background.

38. The method of determining configuration of a part comprising scanning an energy beam across the surface of said part, receiving energy reflected from the part and its background in receiving directions parallel to a fixed direction, whereby the received energy at different times in the scan is reflected from respective different areas of the surface of the part, and the intensity of the received energy, reflected in said receiving directions, varies according to the inclination of the surface of the part at respective ones of said areas relative to the fixed direction as the beam traverses the part,

selecting a plurality of levels of intensity of reflected beam energy intermediate the maximum level of energy reflected from the part and the level of energy reflected from its background, and

indicating positions of the beam only at the times that the reflected energy received in a receiving direction has a predetermined relation to one of the selected levels, whereby data is selected to denote relative inclinations of different areas of the surface of said part to thereby provide an indication of profile of a portion of said part in a plane parallel to said fixed direction.

39. The method of claim 38 including the step of directing the scanning beam toward the object in a projection direction perpendicular to the object and receiving said reflected energy in directions parallel to the projection direction of the scanning beam, said projection direction being parallel to said fixed direction, and wherein said beam position is indicated in two dimensions with respect to said part, said part having a surface portion with points thereof at different inclinations relative to said fixed direction, whereby intensity of received reflected energy varies with the inclination of the area on the surface portion at which energy is reflected.