SINGLE INTERFEROMETER MULTIPLE AXIS LASER MEASURING SYSTEM

• US 3,661,463 A
• Filed: 03/05/1970
• Issued: 05/09/1972
• Est. Priority Date: 03/05/1970
• Status: Expired due to Term

• Current Assignee: Charles B. Sipek, Wallace E. Brainard
• Original Assignee: Charles B. Sipek, Wallace E. Brainard
• Inventors: Brainard, Wallace E., Sipek, Charles B.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Clark, Conrad
• Application Number:
  US05/016,848
• Time in Patent Office: 796 Days
• Field of Search: 356/106
• US Class Current: 356/500
• CPC Class Codes: B23Q 17/2495 using interferometers
• CPC Class Codes: G01B 9/02021 contacting different faces of object, e.g. opposite faces
• CPC Class Codes: G01B 9/02081 simultaneous quadrature detection, e.g. by spatial phase shifting
• CPC Class Codes: G05B 19/21 using an incremental digital measuring device

Abstract

This invention relates to an extremely accurate measuring system comprising a single laser interferometer and associated single counting apparatus responsive to a multiple axis laser beam reflectively connected to measure one of a plurality of different movements in a multiple axis machine tool. Preferably, the measuring apparatus is incorporated in a machine tool having a frame provided with a worktable movable along an X axis relative to an upright column mounted on the frame for transverse movement along a Z axis. The upright is disposed to carry a spindle head for movement along a vertical or Y axis to effect selective movement of a cutter relative to an associated workpiece mounted on the worktable in the usual manner.

Claims

1. In a rectilinear positioning mechanism comprising a frame;

a plurality of members movably carried by said frame for selective independent rectilinear movement relative to one another and including first and second terminal members transversely movable relative to one another;

a stationary angular reflector secured to said frame in fixed relationship between said terminal members;

an interferometer secured to said first terminal member including a light source and a beam splitter operative to provide a fixed length reference light beam and a variable length measuring light beam comprising an output light beam directed along a path parallel to the path of movement of said first member and toward said angular reflector secured to said frame;

a return reflector carried by said second terminal member operative to receive the reflectively directed output light beam from said angular reflector and reflectively return a spaced apart parallel measuring light beam toward said angular reflector and parallel to the path of movement of said second terminal member for continued return transmission along a reflectively directed return path to said interferometer carried by said first terminal member in parallel relationship to the output light beam therefrom;

means for moving a predetermined one of said terminal members a selected distance; and

, light beam combining means in said interferometer being operative to combine said reference beam with said reflectively returned measuring beam to produce interference fringes indicating a change in length of said measuring light beam proportional to the rectilinear movement of said members.

2. In a positioning mechanism according to claim 1 including a laser light source carried in position to direct a laser light beam toward said beam splitter in said interferometer for division into a fixed length internal reference beam and an externally directed variable length measuring beam;

a transparent phase differentiating plate partially interposed in the path of the continuous measuring beam angularly interreflected along different axes between said first and second terminal members to provide separate phase differentiated bidirectional signals in the returned beam; and

, said light beam combining means in said interferometer being operative to combine separate reference beam signals in said internal laser reference beam with said separate reflectively returned laser measuring beam signals to produce separate bidirectional interference fringe signals indicating both a change in length and direction of change of said measuring light beam proportional to the rectilinear movement and direction of one of said members.

3. In a positioning mechanism according to claim 1 including an intermediate third member movably carried for transverse movement by one of said terminal members for transverse movement relative thereto;

a beam interrupting roof prism fixedly carried by said member that is disposed to carry said third member, said roof prism being positioned to interrupt one of the reflectively returned beams and direct that beam toward said third member and along a path parallel to the path of movement of said third member; and

, a retroreflector carried by said third member adapted to receive the beam from said roof prism and return thereto another reflectively returned beam along a parallel path, said roof prism being adapted to, in turn, receive the retroreflectively returned beam and reflectively direct it at right angles onwardly toward said terminal member.

4. In a positioning mechanism according to claim 3;

light sensitive means actuated by interference fringes from said beam combining means;

anD, counting means connected to be actuated by said light sensitive means for indicating the extent of movement of a selected member.

5. In a positioning mechanism for a machine tool having a frame;

a pair of members movably carried by said frame for selective relative movement along different axes;

light beam generating interference means secured to the first of said members for relative movement therewith, said interference means including a source of a light beam and light beam dividing means positioned to divide the beam into an internal reference beam and an external variable measuring beam directed outwardly along a path parallel to the axis of movement of said first member;

a stationary angular reflector secured to said frame adapted to receive the variable measuring beam from said interference means and direct a continuous unbroken measuring beam to said second member along an axis parallel to the axis of movement thereof;

angular reflecting means secured to said second member adapted to receive and delimit the extent of an output measuring beam relative to said frame reflector, said angular reflecting means adapted to direct a return measuring beam along an axis parallel to the axis of movement of said second member;

said stationary angular reflector being adapted to receive the reflectively returned measuring beam from said angular reflecting means carried by said second member and reflectively redirecting a continuous return measuring beam to said interference means along a spaced apart axis parallel to the axis of the output measuring beam therefrom; and

, beam combining means in said interference means operative to combine said reflectively returned continuous variable length measuring beam with said fixed length reference beam to produce interference fringes indicating a change in length of said measuring beam due to a rectilinear change in position of said members.

6. First and second members movably carried for rectilinear relative movement along different angularly disposed axes by support means;

interferometer means including a light beam projector carried by said first member and beam dividing means positioned to divide a light beam from said projector into an internal fixed beam and an external variable length output measuring beam;

a relatively fixed angular reflector secured to said support means positioned to receive the output beam from said interferometer means and angularly reflect a continuous output beam to said second member;

beam reflecting means affixed to said second member adapted to receive the output beam reflected from said fixed angular reflector and retroreflect a continuous return measuring beam thereto for continuous angular return reflection to said interferometer means;

phase differentiating means interposed in the path of the continuous returned measuring beam adapted to provide phase differentiated signals in the beam returned to said interferometer means; and

, beam combining means in said interferometer means operative to combine the phase-differentiated signals in the continuous returned measuring beam with separate signal components in said fixed length reference beam to produce phase-differentiated interference fringes indicating a change in the length and direction of the continuous measuring beam.

7. In a positioning mechanism according to claim 6 including a laser light source in said interferometer means adapted to operate as a light beam projector.

8. In a positioning mechanism according to claim 6 including an intermediate third member movably carried for relative transverse movement by said movable first member;

angular beam interrupting means carried by said first member in a position to interrupt one of the continuous beams directed between said interferometer means and said fixed angular reflector secured to said support means and to angularly reflect the interrupted beam toward said third member;

retroreflective means fixedly carried by saiD third member in position to receive the angularly directed interrupted beam and reflectively return the continuously received beam toward said angular beam interrupting means for completing the transmission of the interrupted beam between said interferometer means and said fixed angular reflector secured to said support means.

9. In a positioning mechanism comprising support means;

a pair of members carried by said support means for relative movement along different axes;

an interferometer including light beam producing and beam dividing means fixedly carried by one of said members for producing fixed length reference beam and a variable length measuring beam;

an angular reflector affixed to said support means adapted to reflect the variable beam along an angular path toward said other member;

reflecting means affixed to said other member adapted to receive the variable beam from said frame reflector and return thereto a continuous variable beam for return angular reflection to said interferometer; and

, combining means in said interferometer adapted to combine the continuous reflectively returned variable length beam with the fixed length reference beam to produce interference fringes indicating a change in length of the continuous variable length measuring beam.

10. In a rectilinear positioning mechanism comprising a frame;

a plurality of relatively movable members movably carried by said frame for selective independent rectilinear movement relative to one another, two of said members comprising first and second terminal members transversely movable relative to one another;

a stationary angular reflector secured to said frame in fixed relationship between said terminal members;

a light beam dividing interferometer carried by said first terminal member operative to project an internal fixed beam and a rectilinear measuring output beam toward said angular reflector for reflection along an output path parallel to the path of movement of said second terminal member;

a return reflector carried by said second terminal member operative to receive the output beam from said angular reflector and return a spaced apart parallel return beam toward said fixed angular reflector for continued return transmission along a return path to said interferometer in said first terminal member and in parallel relationship to the output beam therefrom, said interferometer including beam combining means for combining said internal fixed beam with said reflectively returned variable length output beam to provide interference fringes;

power operable means connected to move a preselected one of said terminal members; and

counting means actuated by interference fringes from said interferometer for measuring the change in length of the continuous output beam during movement of one of said terminal members.

11. In a positioning mechanism according to claim 10 including a beam dividing laser interferometer carried by said first terminal member and operative to supply two divided beams including an internal fixed length reference beam and a variable length output beam directed to said rectilinear beam projector;

and, means to combine the variable length reflectively returned beam with the fixed length reference beam to provide interference fringes indicating a change in distance between one of said terminal members and said stationary angular frame reflector.

12. In a positioning mechanism according to claim 10 including an intermediate third member movably carried for transverse movement by one of said terminal members for transverse movement relative thereto;

a beam interrupting roof prism carried by said terminal member mounting for said third member operative to interrupt one of the return beams therefrom and direct the beam upwardly;

a retroreflector carried by said third member operative to return the received beam from said roof prism and reflectively return thereto a continuous return beam along a parallel path; and

said roof prism being operative to receive the return beam from said retroreflector and continue the returned beam onwardly to said terminal member.

13. In a positioning mechanism according to claim 12 including a laser projecting interferometer operative to provide a divided beam including an internal fixed length reference beam and direct a variable length measuring beam to said light projector carried by said terminal member;

phase differentiating means operative to combine the reflectively return beam with the reference beam to provide interference fringes; and

, light sensitive means actuated by the interference fringes and being operatively connected to actuate said counting means.

14. In a machine tool having a frame;

a plurality of relatively movable members carried by said frame including two terminal members respectively mounted for transverse movement on said frame;

another of said members being mounted on one of said frame mounted terminal members for transverse relative movement thereto;

light beam dividing interference means including a source of light carried by one of said terminal members for movement therewith and adapted to provide an internal reference beam and an outward projected measuring beam;

a return retroreflector carried by the other of said terminal members for movement therewith;

said movable members being each mounted for relative individual movement on an associated relatively stationary member;

angular reflective means mounted on alternate ones of said relatively stationary and said individually movable members between said spaced apart terminal members, aid angular reflective means being operative to transmit an output beam in one direction between said interference means and said retroreflector and to reflectively return the continuous output beam in a reverse direction from said retroreflector to said interference means on said output terminal member in a manner that the output beam from said interference means is one continuous measuring beam comprising a plurality of reflectively connected output beam segments together with a plurality of reflectively interconnected reverse output beam segments, combining means in said interference means operative to combine the reference beam with the continuous output measuring beam to provide interference fringes connected to indicate the distance moved by a selected one of said members and corresponding to a change in length of the single continuous interreflected output measuring beam.

15. In a machine tool having a frame according to claim 14 having a presettable counting apparatus connected to be selectively actuated in response to actuation of said sensitive means actuated by said interferometer;

and, power drive means connected to effect selective independent power driven movement of one of said members.

16. In a machine tool having a frame according to claim 14 including a laser operative to project a beam of light for said interference means carried by one of said terminal members, said interference means comprising a laser interferometer operative to provide two divided laser light beams including a fixed length internal reference beam and a continuous variable length output measuring beam, said laser interferometer being operatively disposed to combine said continuous variable length measuring beam with said fixed length internal reference beam to provide interference fringes indicating the change in length of said continuous reflectively interconnected measuring beam;

and, light sensitive means actuated by light fringes from said interferometer.

17. In a measuring apparatus including a frame;

first and second members movably carried by said frame for selective transverse movement;

a light beam projector and light beam interference means carried by said first member including beam dividing means operative to provide divided beams including a reference beam and a variable continuous output measuring beAm;

an angular reflector carried by said frame for receiving the output beam from said interference means and transmitting it along a continuous path to said second member;

a return reflector carried by said second member operative to receive the continuous output beam from said angular frame reflector and return thereto a continuous output beam, said angular frame reflector being operative to receive the continuous output beam from said second reflector and reflectively transmit a continuous output beam to said interference means carried by said first member;

transparent phase differentiating means operatively interposed in the return path of the continuous beam reflectively transmitted between said angular frame reflector and said interference means to provide phase differentiated signals; and

, beam combining means associated with said interference means operative to combine like components in said reference beam with phase differentiated signals in said returned measuring beam to produce phase differentiated interference fringes to measure a change in length and direction of the reflectively interconnected continuous output beam for indicating the extent of movement of one of said members.

18. A measuring apparatus for a machine having a frame according to claim 17 and having an intermediate third member normally carried by said second member for transverse rectilinear movement thereto;

a reflective roof prism carried by said second member in such position as to be interposed in the return path of the continuous measuring beam from said angular frame reflector for reflecting the continuous beam therefrom upwardly along the transverse path of movement of said third member; and

, a retroreflector carried by said third member for position controlling movement therewith and in position to receive the upwardly reflected continuous output beam from said roof prism, said retroreflector being operative to reflectively return a continuous output beam to said roof prism for continuous transmission therefrom through said phase differentiating means and to said beam interference means secured to said first member. 19. A machine tool having a frame;

first and second support members slidably carried by said frame for relative transverse movement;

a third member slidably carried by said second member for transverse movement relative to the rectilinear direction of movement thereof;

a laser interferometer secured to said first member including a beam splitter operative to provide a fixed length reference beam and being operative to direct an output measuring beam parallel to the path of movement;

a first mirror affixed to said frame in position to receive the output beam from said first member in a manner to direct a continuous beam at a right angle along a path parallel to the transverse path of movement of said second member;

a second mirror affixed to said second member operative to receive the beam from said first mirror and in turn reflect a continuous beam at a right angle along a path parallel to the rectilinear path of said third member;

a retroreflective prism carried by said third member operative to receive the output beam from said second prism and to return thereto a continuous reflected measuring beam;

said second mirror being operative to reflectively redirect the returned beam toward said first mirror and said first mirror being in turn operative to continue the returned beam at right angles to said interferometer carried by said first member; and

, beam combining means in said interferometer being operative to combine said reference beam with said reflectively returned reference beam to produce interference fringes indicating a change in length of said beam due to a change in the position of a single one of said members.

20. A machine tool according to claim 19 including power drive means connected to selectively move one of said members;

light sensitive means connected to be actuated by Interference fringes in said interferometer; and

, counting means actuated by said light sensitive means connected to indicate the extent of movement of said member.

21. In a measuring apparatus for a machine having a frame;

first and second terminal members movably carried by said frame for selective transverse rectilinear movement;

an intermediate third member carried by said second terminal member for transverse rectilineal movement relative thereto;

a beam dividing interferometer carried by said first terminal member operative to provide a divided fixed length internal reference beam and to project a variable length output measuring beam parallel to the path of movement of said first terminal member;

an angular reflector fixedly carried by said frame for receiving the output beam from said first terminal member and transmitting it along a continuous output path parallel to the path of movement of said second member;

a first retroreflector carried by said second terminal member operative to receive the output beam from said angular frame reflector and return thereto a continuous and parallel return beam;

said angular frame reflector being operative to receive the return beam from said second member and to reflectively transmit a continuous return beam in the direction of said first terminal member and along a path parallel to the continuous output beam from said first terminal member;

first angular reflective means carried by said second terminal member disposed to reflect the return beam from said angular frame reflector vertically upward along the rectilinear path of movement of said third member;

a second retroreflector carried by said third member for movement therewith in a manner to receive the upwardly directed beam from said first reflective means and operative to return thereto a spaced apart beam along a parallel path toward said second terminal member;

second angular reflective means carried by said second terminal member in position to receive the parallel return beam from said second retroreflector and reflectively continue the return beam along a parallel path toward said first terminal member and to said interferometer carried thereby;

prismatic means associated with said interferometer disposed to combine the reflectively returned beam with the reference beam to provide interference fringes;

light responsive means in said first terminal member actuated by the light fringes from said prismatic means; and

, a counter actuated by operation of said light responsive means connected to indicate a change in length of said continuous output and return beams for indicating the rectilineal extent of movement of a single one of said three selectively movable machine members.