Optical tracking device

• US 4,636,612 A
• Filed: 04/06/1984
• Issued: 01/13/1987
• Est. Priority Date: 04/19/1983
• Status: Expired due to Fees

• Current Assignee: Powcon Corporation
• Original Assignee: Cyclomatic Industries Incorporated
• Inventors: Cullen, Richard A.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US06/597,460
• Time in Patent Office: 1,012 Days
• Field of Search: 219/124.34, 219/124.03, 219/124.31, 219/136, 318/577, 350/96.25, 250/202, 356/376, 356/377
• US Class Current: 219/124.34
• CPC Class Codes: B23Q 35/128 Sensing by using optical means

Abstract

The optical tracker of this invention is for tracking a boundary on an illuminated surface where the reflectivity of the surface changes at the boundary. In the preferred embodiment the optical tracker includes an optic foot which rides on the surface to be tracked. The optic foot comprises a housing with two channels for receiving a transmitter optical fiber and the receiver optical fiber. The two channels converge to form an opening in the housing which faces the surface to be tracked. Light supplied by the transmitter optical fiber illuminates the portion of the surface underneath the opening and the reflected light from such portion of the surface enters the receiver optical fiber which transmits the light to a detecting means for locating and tracking the boundary on the surface. In the preferred embodiment the receiver optical fiber is oriented substantially normal to the surface and the transmitter optical fiber substantially at 60 degrees thereto to reduce dynamic range. In the preferred embodiment the optic foot rides on two ruby or sapphire half spheres to accommodate uneven surfaces to be tracked. If the boundary to be tracked is an edge or lap joint, the portion of the joint at an angle to the surface is illuminated by a source located away from the vertical plane containing the joint for improved illumination. The light reflected from the surface is focused by a lens system onto the receiver optical fiber. The distance between the surface and the receiver optical fiber is adjustable by the addition or removal of shims. Where it is desirable for the tracker not to touch the surface, an arc voltage control system is employed in the tracker to sense the distance between the surface and an instrument for performing work on the surface.

Claims

1. An apparatus for tracking a boundary on a surface wherein the boundary and the portion of the surface adjacent to the boundary are illuminated, and wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

a light sensor means;

an optical fiber for transmitting light reflected from the surface to the light sensor means;

a housing adapted to ride on the surface, said housing having a channel passing therethrough, said channel having a first end facing the surface to receive light reflected from the surface when the housing is riding on the surface, and a second end adapted to receive the optical fiber;

a lens system in the channel and connected to the housing for focusing the reflected light onto one end of the optical fiber;

annular shims defining apertures therein, said shims fitting onto the housing with their apertures aligned with the second end of the channel to allow passage of the reflected light therethrough; and

means connecting the shims and the optical fiber to the housing so that the distance between the lens system and said end of the optical fiber is adjustable by selecting the shims with the appropriate thickness.

2. The apparatus of claim 1, wherein said connecting means comprises an annular flange.

3. The apparatus of claim 1, wherein said connecting means comprises a second housing for the optical fiber, said second housing having an annular flange for connecting the second housing to the shims and the first housing.

4. The apparatus of claim 3, wherein said annular flange defines therein a plurality of holes for connecting the flange to the shims and the first housing, said holes being unevenly spaced about the flange so that the flange can be connected with only one orientation with respect to the shims and the first housing to prevent twisting the optical fiber.

5. An apparatus for tracking a boundary on a surface wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

a housing defining therein a first and a second channel converging and meeting to form an opening in the housing, said housing adapted to be placed with its opening adjacent to and facing the boundary and the surface;

a transmitter optical fiber having two ends with its first end adapted to fit into and engage the first channel of the housing and its second end adapted to receive light from a light source, so that the light so received will emerge at the other end to illuminate the boundary and the surface through the opening in the housing;

a coherent receiver optical fiber having two ends with its first end adapted to fit into and engage the second channel of the housing so that the first end receives light reflected by the boundary and the surface through the opening in the housing, said receiver optical fiber transmitting the light received to a light sensor means for sensing the location of the boundary on the surface; and

said housing being such that it is riding on the surface, the housing and the two channels therein are so located that the first channel is substantially at 60°

to the surface and the second channel is substantially normal to the surface, whereby when the sensing means is moved over the surface, the dynamic range of light reflected by the boundary and surface and received by the receiver optical fiber is minimized.

6. An apparatus for tracking a boundary on a surface wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

light sensing means for sensing light reflected from the surface to detect the location of the boundary on the surface for tracking the boundary;

means for transmitting light reflected from the surface to the light sensing means;

housing connected to the transmitting means, said housing defining an opening facing the surface for receiving light so that the light reflected from the portion of the surface facing said opening passes through said opening to reach the transmitting means for transmission to the light sensing means, said housing having two round protruding portions on each side of the opening defining two riding feet for riding on the surface to closely track surfaces with depressions or elevations.

7. The apparatus of claim 6, wherein the two round protruding portions are half-spheres.

8. The apparatus of claim 6, wherein the two round protruding portions are made of sapphire or ruby.

9. The apparatus of claim 6, wherein the two round protruding portions are made of an electrically insulating and wear resistant material.

10. An apparatus for tracking a boundary on a surface wherein the boundary and the portion of the surface adjacent to the boundary are illuminated, and wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

means for sensing the light reflected from an elongated portion of the surface defining a window so that when the sensing means is moved over the surface, said sensing means will receive consecutively light reflected from a sequence of windows it passes over, said sensing means generating a set of electrical signals indicative of the intensity of light reflected from locations along the length of the window, so that when a portion of the boundary is in the window, the set of electrical signals will indicate the difference in light reflectivity at the boundary and the locations in the window where the changes in reflectivity occur;

processing and control means for deriving secondary sets of signals from sets of signals provided by the sensing means indicative of optically detectable characteristics of the boundary, wherein said processing and control means is capable of recording a secondary set of signals as a template when the window includes and intersects a selected portion of the boundary, and is capable of comparing the template set of signals to a sequence of secondary sets of signals derived from signals provided by the sensing means when it is moved over the surface to determine whether the window intersects the boundary during such movement of the sensing means; and

means for sensing the distance between the sensing means and the surface and for controlling such distance.

11. An apparatus for tracking a boundary on a surface where work is to be performed using an instrument wherein the boundary and the portion of the surface adjacent to the boundary are illuminated, and wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

means for sensing the light reflected from an elongated portion of the surface defining a window so that when the sensing means is moved over the surface, said sensing means will receive consecutively light reflected from a sequence of windows it passes over, said sensing means generating a set of electrical signals indicative of the intensity of light reflected from locations along the length of the window, so that when a portion of the boundary is in the window, the set of electrical signals will indicate the difference in light reflectivity at the boundary and the locations in the window where the changes in reflectivity occur, said sensing means connected to the instrument for guiding the instrument;

processing and control means for deriving secondary sets of signals from sets of signals provided by the sensing means indicative of optically detectable characteristics of the boundary, wherein said processing and control means is capable of recording a secondary set of signals as a template when the window includes and intersects a selected portion of the boundary, and is capable of comparing the template set of signals to a sequence of secondary sets of signals derived from signals provided by the sensing means when it is moved over the surface to determine whether the window intersects the boundary during such movement of the sensing means; and

means for sensing the distance between the instrument and the surface and for controlling such distance.

12. The apparatus of claim 11, wherein the distance sensing and controlling means is an arc voltage control system.

13. The apparatus of claim 11, wherein the boundary is a seam and wherein the template set of signals indicates the width of the seam and the magnitudes of the change in light reflectivities at the edges of the seam.

14. The apparatus of claim 13, further comprising means for altering a work related parameter as a function of the seam width to improve the quality of the work performed by the work instrument.

15. The apparatus of claim 14, further comprising means for moving the sensing means and the work instrument over the surface, wherein said parameter is the travel speed of the sensing means and of the work instrument.

16. The apparatus of claim 11, wherein the boundary is an edge and wherein the template set of signals indicates the magnitude of the change in light reflectivity at the edge.

17. The apparatus of claim 11 further comprising:

means for moving the sensing means over the surface, said moving means responsive to control signals from the processing and control means for controlling the movement of the sensing means.

18. The apparatus of claim 17, further comprising input control means for selecting among a plurality of operating modes of the apparatus including a teach mode wherein a template set of signals is recorded and a search mode for finding the boundary, said input control means being connected to the processing and control means such that, when a search mode is selected, the processing and control means causes the moving means to move the sensing means in a selected direction towards the boundary and such that when the processing and control means detects a boundary whose secondary set of signals are within predetermined ranges of the template set of values, said processing and control means will cause the moving means to stop the motion of the sensing means, so that the sensing means will stop at a location substantially above the boundary.

19. An apparatus for tracking a boundary on a surface wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

a housing having a first and a second portion rotatably connected to each other, said first portion defining therein a first channel and the second portion defining therein a second channel converging and meeting to form an opening in the housing, said housing adapted to be placed with its opening adjacent to and facing the boundary and the surface;

a transmitter optical fiber having two ends with its first end adapted to fit into and engage the first channel of the housing and its second end adapted to receive light from a light source, so that the light so received will emerge at the other end to illuminate the boundary and the surface through the opening in the housing;

a coherent receiver optical fiber having two ends with its first end adapted to fit into and engage the second channel of the housing so that the first end receives light reflected by the boundary and the surface through the opening in the housing, said receiver optical fiber transmitting the light received to a light sensor means for sensing the location of the boundary on the surface, said two portions of the housing being rotatably connected to each other so that when the first portion is rotated relative to the second portion, the transmitter optical fiber is transverse to the plane of the boundary and the receiver optical fiber for improved illumination of the boundary.

20. The apparatus of claim 19, wherein the boundary is an edge or a lap joint, said edge or lap joint having a high side and a low side on said surface, wherein the first portion of the housing is rotated relative to the second portion such that light transmitted by the transmitter optical fiber shines from the high side of the joint or edge to the low side for improved illumination of the boundary for tracking purposes.

21. The apparatus of claim 19, wherein a plane normal to the surface at the opening defines a vertical plane, and wherein the first portion of the housing is rotated relative to the second portion so that the transmitter optical fiber is transverse to the vertical plane containing the boundary facing the opening, and the receiver optical fiber is substantially in such vertical plane for improved tracking of the boundary.

22. An apparatus for tracking a boundary on a surface where work is to be performed by an instrument wherein the boundary and the portion of the surface adjacent to the boundary are illuminated, and wherein the reflectivity of the surface changes at the boundary, said apparatus comprising:

means for sensing the light reflected from an elongated portion of the surface defining a window so that when the sensing means is moved over the surface, said sensing means will receive consecutively light reflected from a sequence of windows it passes over, said sensing means generating a set of electrical signals indicative of the intensity of light reflected from locations along the length of the window, wherein said sensing means is connected to the instrument for performing work at the boundary;

processing and control means for determining the position of the center of the boundary in the window, said control means generating, from the set of signals provided by the sensing means, a control signal indicative of the position of the center of the boundary relative to the center of the window;

moving means for moving the sensing means in a predetermined direction, said direction being adjustable to substantially coincide with the direction of the boundary, said moving means responsive to the control signal for moving the sensing means in a direction transverse to the predetermined direction so that the center of the boundary will substantially coincide with the center of the window;

means for sensing the distance between the instrument and the surface and for controlling such distance; and

means for determining the magnitudes of the changes in reflectivity between adjacent positions in the window, said determining means also adapted to generate a second control signal to indicate that the boundary is not in the window when said magnitudes do not exceed a predetermined value.

23. The apparatus of claim 22, wherein said moving means will move the sensing means along the direction of motion of the sensing means immediately before the generation of the second control signal for a time period set in advance and will stop the motion of the sensing means when no boundary is detected by the sensing means within said time period.