Method and apparatus for positioner calibration system

Claim 2

Apparatus for calibrating a positioner which positions an article at a selected position between first and second known positions along at least one axis of a reference frame, said calibration apparatus comprising: a. means for producing a measurable output which positionally relates the article and the frame, said output varying as said article moves along said axis in one direction between said first and second known positions and which varies more slowly with article movement outside the range of positions between said first and second known positions; b. means for measuring and storing the values of the outputs of said measurable output producing means when said article is positioned at points beyond and on opposite sides of said known positions; and c. means for establishing an intermediate value between the stored values which, as a percentage between said stored values, is the same as the percentage between said first and second known positions of the location of said selected position along the axis.

Claim 3

The apparatus of claim 1 further comprising means for driving said article to points beyond and on opposite sides of the range of positions between said known positions to allow measuring and storing of the output values of said measurable output producing means at said points.

Claim 4

varying said first signal at a second slower rate when said article is not between said known positions to define two plateaus in said first signal;

Claim 5

varying said first signal at a second slower rate when said article is not between said known positions to define two plateaus in said first signal;

Claim 6

measuring and storing the values of said first signal at points in both plateaus in said first signal; and,

Claim 7

measuring and storing the values of said first signal at points in both plateaus in said first signal; and,

Claim 8

The apparatus of claim 1 further comprising drive means for positioning said article at a position where said intermediate value and the output value of said measurable output producing means each have a predetermined value.

Claim 9

The apparatus of claim 3 further characterized by said drive means being further adapted to: a. first position said article along said axis at an initial position between said known positions; and then b. drive said article along said axis to points beyond and on opposite sides said known positions to allow measuring and sToring of the output values of said measurable output producing means at said points.

Claim 10

generating from said stored plateau values a second electrical signal having a value which as a percentage between said stored plateau values, is the same as the selected percentage of the distance between said known positions of said selected position along the axis.

Claim 11

generating from said stored plateau values a second electrical signal having a value which as a percentage between said stored plateau values, is the same as the selected percentage of the distance between said known positions of said selected position along the axis.

Claim 12

The apparatus of claim 4 further characterized by the subsequent drive motions of said article from said initial position being a motion a fixed distance along said axis in a first direction to a first point followed by a motion of twice said fixed distance along said axis in an opposite direction to a second point, said fixed distance being at least equal to the distance between said known positions.

Claim 13

Apparatus for calibrating a positioner which positions an article at a selected position between first and second known positions along at least one axis of a reference frame, said calibration apparatus comprising: a. sensor means for producing an output representing a sensed quantity which positionally relates the article and the frame, said sensor means receiving the quantity along a path having a transmission of said quantity which progressively changes as said article moves along said axis in one direction between said first and second known positions and which varies more slowly with article movement outside the range of positions between said first and second known positions; b. means for measuring and storing the values of the outputs of said sensor means when said article is positioned at points beyond and on opposite sides of said known positions; and, c. means for establishing an intermediate value between the stored values which, as a percentage between said stored values, is the same as the percentage between said first and second known positions of the location of said selected position along the axis.

Claim 14

Apparatus for calibrating a positioner which positions an article at a selected position between first and second known positions along at least one axis of a reference frame, said calibration apparatus comprising: a. sensor means for producing an output representing a sensed quantity which positionally relates the article and the frame, said sensor means receiving the quantity along a path having a transmission of said quantity which progressively changes as said article moves along said axis in one direction between said first and second known positions and which varies more slowly with article movement outside the range of positions between said first and second known positions; b. means for measuring and storing the values of the outputs of said sensor means when said article is positioned at points beyond and on opposite sides of said known positions; and, c. means for establishing an intermediate value between the stored values which, as a percentage between said stored values, is the same as the percentage between said first and second known positions of the location of said selected position along the axis.

Claim 15

The apparatus of claim 6 wherein: a. said quantity positionally relating said article and said frame is light; and, b. said sensor means includes photodetector means for receiving light reflected off two optically contrasting portions of said article through at least one aperture in said frame, the light transmission of said path varying with the amount of each portion of said article which reflects light through said aperture and being non-varying when only one portion is positioned to reflect light through said aperture.

Claim 16

The apparatus of claim 7 further characterized by said sensor means further including: a. at least two photodetectors each receiving a separate quantity which positionally relates the article and frame along a separate path; and, b. means for combining the outputs of said photodetectors, the combined outputs becoming the output of said sensor means.

Claim 17

The apparatus of claim 6 characterized by the transmission of said path being constant to produce plateaus in the output of said sensor means outside the range of positions for said article between said known positions.

Claim 18

A calibration system for use in a positioner of the type having: a. means for moving a first element relative to a second element along an axis in a direction depending upon the sign of the difference between a first and second signal; b. sensor means for outputting as said first signal a signal which varies with the position of said first element relative to said second element, said first signal having at least two plateaus of slower variation in said first signal with movement of said first element relative to said second element, said plateaus commencing at first and second known positions along said axis of first element with respect to said second element, said known positions having therebetween a selected position for said first element, said calibration system comprising: a. sampling means for recording the values of said first signal at points in its plateaus; b. means for generating as said second signal a reference value between the recorded plateau values, which, as a percentage between said recorded plateau values, is the same as the percentage between said first and second known positions of the location of said selected first element position along said axis; c. sequEncer means for commanding said moving means to position said first element at a point where said first signal is in one plateau and then to position said first element at another point where said first signal is in the other plateau to allow said sampling means to record the values of the output of said sensor means at said plateaus.

Claim 19

A calibration system for use in a positioner of the type having: a. means for moving a first element relative to a second element along an axis in a direction depending upon the sign of the difference between a first and second signal; b. sensor means for outputting as said first signal a signal which varies with the position of said first element relative to said second element, said first signal having at least two plateaus of slower variation in said first signal with movement of said first element relative to said second element, said plateaus commencing at first and second known positions along said axis of first element with respect to said second element, said known positions having therebetween a selected position for said first element, said calibration system comprising: a. sampling means for recording the values of said first signal at points in its plateaus; b. means for generating as said second signal a reference value between the recorded plateau values, which, as a percentage between said recorded plateau values, is the same as the percentage between said first and second known positions of the location of said selected first element position along said axis; c. sequEncer means for commanding said moving means to position said first element at a point where said first signal is in one plateau and then to position said first element at another point where said first signal is in the other plateau to allow said sampling means to record the values of the output of said sensor means at said plateaus.

Claim 20

The calibration system of claim 10 wherein said sequencer means in commanding said motion means to position said first element is further adapted to cause: a. first motion of said first element to a position where the output of said sensor means is between said plateaus; b. second motion of said first element for a fixed distance at least equal to the distance between said known positions to allow the output of said sensor means to be in one plateau; c. third motion of said first element for a distance twice said fixed distance in a direction opposite to said second motion to allow the the output of said sensor means to be in the other plateau; and, d. fourth motion of said first element to a point where said first and second signals each have a predetermined value.

Claim 21

The calibration system of claim 11 wherein said sequencer is further adapted to cause at least one repetition of said second, third and fourth motions with a new reference value being established during each repetition.

Claim 22

The calibration system of claim 11 further characterized by said sensor means sensing a quantity which positionally relates said first and second elements and receiving said quantity along a path having a transmission of said quantity which progressively diminshes as said first element moves in one direction relative to said second element between said known positions and with said plateaus being defined by a reduction in the rate of variation of said path''s transmission beyond said known positions.

Claim 23

The calibration system of claim 13 characterized by the transmission of said path being constant to produce constant value plateaus in the output of said sensor means outside the range of positions for said first element relative to said second element between said known positions.

Claim 24

The calibration system of claim 13 wherein: a. said first element is a semiconductor wafer having at least one straight edged target region of different light reflectivity from said wafer; b. said second element is a mask having at least one straight sided aperture therethrough; c. said sensor means further comprises at least one photodetector receiving light reflected from the regions of different reflectivity of said wafer through said mask aperture; and, d. said first and second known positions are the positions where the straight edge of the target region is aligned with the opposite straight sides of said aperture.

Claim 25

The calibration system of claim 15 further characterized by: a. there being at least two photodetectors in said sensor means receiving light through separate apertures; and, b. said sensor means further including means for combining the outputs of said photodetectors, the combined outputs forming the output of said sensor means.

Claim 28

The method of claim 17 further comprising the step of positioning said article along said axis to a point where said first and second electrical signals each have a predetermined value.