Machine tool position measurement employing multiple laser distance measurements

A method of measuring position of a tool carried by a movable tool support member that is driven to a plurality of positions within a predetermined work area, said method comprising:

• mounting a retro-reflector on said member,
• projecting an energy beam from a fixed position in a scanning sweep through said work area as said member is driven, and
• employing said energy beam to measure the distance between said retro-reflector and said reference position when said tool support member is at one of said positions,
• said step of mounting a retro-reflector comprising mounting three retro-reflectors at predetermined positions on said movable tool support member, said step of projecting an energy beam comprising projecting three separate energy beams from three separate fixed reference positions in three separate scanning sweeps through the target areas that include respective ones of said retro-reflectors as said member is driven within said work area, and wherein said step of employing said energy beam to measure distance comprises the step of employing each of said three energy beams to measure the distance from respective ones of said retro-reflectors to respective ones of said fixed reference positions.

Apparatus for measuring position of a tool comprising:

• a support,
• a tool support member movably mounted on said support,
• means for driving the tool support member relative to the support to a plurality of positions within a predetermined work area,
• a plurality of retro-reflectors mounted on said member at known mutually spaced positions,
• a plurality of energy beam scanning devices mounted on said fixed support, each said scanning device including means for projecting an energy beam from a fixed reference position on said scanning support in a scanning sweep through a target area that includes an individual one of said retro-reflector positions as said member is driven within said work area, and
• means in each said scanning device for measuring the distance from such scanning device to an individual one of said retro-reflectors.

Position measuring apparatus for a machine tool having a tool support member movably mounted for travel over a fixed support through a predetermined work area, said positioning apparatus comprising:

• first, second and third retro-reflectors mounted on said tool support member in predetermined fixed positions relative to said member,
• first distance measuring means for measuring a first distance to said first retro-reflector, said first measuring means comprising:
• a first scanning sweep mirror mounted at a first known reference position on said fixed support,
• a first motor connected to drive said mirror through an angular oscillation sweep,
• means for projecting a first laser beam along a first optical path to said first mirror,
• a first interferometer mounted in said first optical path for transmitting said first laser beam to said first mirror and for receiving reflected light from said first mirror,
• a first sweep control circuit for controlling said first motor to control said first mirror, and
• a first receiver responsive to an output of said first interferometer for providing an output signal indicative of the distance between said first mirror and said first retro-reflector,
• second distance measuring means for measuring a second distance to said second retro-reflector, said second distance measuring means comprising:
• a second scanning sweep mirror mounted at a second known reference position on said fixed support,
• a second motor connected to drive said second mirror through a second angular oscillation sweep,
• means for projecting a second laser beam along a second optical path to said second mirror,
• a second interferometer mounted in said second optical path for transmitting said second laser beam to said second mirror and for receiving reflected light from said second mirror,
• a second sweep control circuit for controlling said second motor to control said second mirror, and
• a second receiver responsive to an output of said second interferometer for providing an output signal indicative of the distance between said second mirror and said second retro-reflector, and
• third distance measuring means for measuring a third distance to said third retro-reflector, said third distance measuring means comprising:
• a third scanning sweep mirror mounted at a third known reference position on said fixed support,
• a third motor connected to drive said third mirror through a third angular oscillating sweep,
• means for projecting a third laser beam along a third optical path to said third mirror,
• a third interferometer mounted in said third optical path for transmitting said third laser beam to said third mirror and for receiving reflected light from said third mirror,
• a third sweep control circuit for controlling said third motor to control said third mirror, and
• a third receiver responsive to an output of said third interferometer for providing an output signal indicative of the distance between said third mirror and said third retro-reflector.

Tool positioning apparatus for positioning a tool in a positioning plane comprising:

• a tool support table having a flat surface parallel to said positioning plane,
• a tool carriage that is unguided in said plane,
• means for exerting first and second forces in mutually opposite directions on said carriage and at an angle to said plane for movably supporting said carriage on said surface for unguided motion over said table,
• means on said carriage for carrying a tool, and
• drive means for driving said carriage over said flat surface to a controlled position and orientation, said drive means comprising three extensible actuators connected between said carriage and said support table.

Tool positioning apparatus for positioning a tool in a plane comprising:

• a tool support table,
• a guide structure extending parallel to and spaced from said tool support table,
• means for mounting said guide structure to said tool support table for rotation about an axis perpendicular to said tool support table,
• a platform mounted on said guide structure for motion along the guide structure,
• means for rotating said guide structure and driving said platform along said guide structure, and
• means for measuring distance from first and second points fixed with respect to one another and with respect to said tool support table and each of third and fourth points fixed with respect to said platform.