Digital interpolator

Claim 2

In a digital interpolator for successively deriving from information defining a curve to be followed up, the coordinates of the actual followup points for said curve being defined by an equation f(x, y) 0 (where xand y are variables), said curve being replaceable with at least one replacement segment with sufficient precision, said segment being one of a circular arc and a straight line segment, said followup point being selected from at least the two next possible followup points existing near the present followup point, the improvement which comprises: means responsive to data defining said replacement segment for deriving a least deviation signal determined by the least one of the absolute values of f(x, y) with the variables being substituted with the coordinates of said possible followup points, and means responsive to said least deviation signal for successively deriving said coordinates of said actual followup points.

Claim 3

The interpolator according to claim 1, wherein said data consists of information defining the kind of said replacement segment and the sense of followup, and the information representing the coordinates of the start and end points of followup.

Claim 4

The interpolator according to claim 1, wherein said coordinates are quantized coordinates, and wherein at least two of said possible followup points for said reference followup point each have coordinates differing by one quantization unit from the corresponding one of the coordinates of said reference followup point.

Claim 5

The interpolator according to claim 1, wherein said least deviation-signal-deriving means comprises means responsive to said data for deriving sense signals representative of the permissible directions into which the next subsequent step of followup should proceed, and means responsive to said data and said sense signals for producing said least deviation signal.

Claim 6

The interpolator according to claim 4, wherein said coordinate deriving means comprises means responsive to said least deviation signal and said sense signals for producing an incremental signal representative of an increment which, when algebraically added to the coordinates of said reference followup point, provides the coordinates of the next actual followup point.

Claim 7

A digital interpolator for a curve to be traced, said curve being defined by an equation f(x, y) 0 where x and y are variables, said interpolator comprising means for storing first information defining the kind of said curve the curve followup direction, and the start and end points having quantized coordinates and second information corResponding to a reference followup point, means coupled to said storing means for determining the permissible directions of a plurality of possible followup points adjacent to said reference followup point, means coupled to said storing means and said determining means for comparing the absolute values of f(x, y) with the variables being substituted with the coordinates of said possible followup points, means coupled to said storing means, said determining means, and said comparing means for converting said second information into information corresponding to that one of said possible followup points for which the absolute value is a minimum, and an output device coupled to said determining means and said comparing means for deriving information indicating changes in the position of said one of said followup points.

Claim 8

A digital interpolator for a curve to be traced, said curve being defined by an equation f(x, y) 0 where x and y are variables, said interpolator comprising means for storing first information defining the kind of said curve the curve followup direction, and the start and end points having quantized coordinates and second information corResponding to a reference followup point, means coupled to said storing means for determining the permissible directions of a plurality of possible followup points adjacent to said reference followup point, means coupled to said storing means and said determining means for comparing the absolute values of f(x, y) with the variables being substituted with the coordinates of said possible followup points, means coupled to said storing means, said determining means, and said comparing means for converting said second information into information corresponding to that one of said possible followup points for which the absolute value is a minimum, and an output device coupled to said determining means and said comparing means for deriving information indicating changes in the position of said one of said followup points.

Claim 9

In a digital interpolator for successively deriving the coordinates of actual followup points for a curve to be followed up from a small amount of information defining said curve, said curve being defined by the equation f(x, y) where x and y are variables, said curve being replaceable with at least one replacement segment with sufficient precision, said segment being one of a circular arc and a straight line segment, each of said followup points being selected from at least the two next possible followup points located near the present followup point, the improvement which comprises: first means responsive to the data defining said replacement segment for deriving a sign signal representative of the sign of f(x1, y1) 2- f(x2, y2) 2, where (x1, y1) and (x2, y2) are the coordinates of two of the possible followup points for the present followup point, and second means responsive to said sign signal for deriving an incremental signal representative of an increment which provides the actual direction of the next subsequent followup and which, when algebraically added to the coordinates of the present followup point, provides the coordinates of the next actual followup point.

Claim 10

In a digital interpolator for successively deriving the coordinates of actual followup points for a curve to be followed up from a small amount of information defining said curve, said curve being defined by the equation f(x, y) where x and y are variables, said curve being replaceable with at least one replacement segment with sufficient precision, said segment being one of a circular arc and a straight line segment, each of said followup points being selected from at least the two next possible followup points located near the present followup point, the improvement which comprises: first means responsive to the data defining said replacement segment for deriving a sign signal representative of the sign of f(x1, y1) 2- f(x2, y2) 2, where (x1, y1) and (x2, y2) are the coordinates of two of the possible followup points for the present followup point, and second means responsive to said sign signal for deriving an incremental signal representative of an increment which provides the actual direction of the next subsequent followup and which, when algebraically added to the coordinates of the present followup point, provides the coordinates of the next actual followup point.

Claim 11

The interpolator according to claim 7, wherein said first means comprises first and second accumulator means responsive to said data and said sign signal for storing the x and y coordinates of the present followup point, and for producing the x and y signals representative of said x and y coordinates, respectively, third means responsive to said data and said x and y signals for producing sense signals representative of the senses of the x and y coordinate axes in which the next subsequent step of followup should proceed, third accumulator means responsive to said data, said sign signal, the x and y signals, and said sense signals for storing the algebraic sum of the present store plus the x and y signals when said actual direction is in the y and x directions, respectively, and for deriving a second sign signal representative of the sign of the store, and fourth means responsive to said data, said sense signals, and said second sign signal for deriving said first-mentioned sign signal.

Claim 12

The interpolator according to claim 7, wherein said first deriving means comprises third means responsive to said data for deriving the sense signals representative of two of the permissible directions, said two directions being parallel with the coordinate axes, except for the senses, said permissible directions consisting of said two directions and a third direction extending along the diagonal determined by said two directions, one of said permissible directions giving the direction in which the next subsequent step of followup should proceed, fourth means responsive to the derivation of the incremental signal for producing a first command signal, and fifth means responsive to said data, said sense signals, and said command signal for deriviNg a first sign signal representative of the sign of f(x1, y2) 2- f(x2, y2) 2, where (x1, y1) and (y1, y2) are the coordinates of two of the possible followup points, said two possible followup points being spaced from the present followup point in said two permissible directions, respectively, and wherein said second deriving means comprises sixth means responsive to said sense signals and said first sign signal for producing a first incremental signal, and seventh means responsive to said incremental signal for temporarily storing the same, said fourth means being further responsive to said second sign signal for producing a second command signal, said fifth means being further responsive to said second command signal for deriving a zero signal when the sign of the differences f(x3, y3) 2- f(x1, y1) 2 and f(x3, y3) 2- f(x2, y2) 2 are both positive, where (x3, y3) is the coordinates of a third possible followup point spaced from the present followup points said two possible followup points being spaced from the present followup point in said two permissible directions, respectively, said second means comprising sixth means responsive to said sense signals and said first sign signal for producing a first incremental signal, and seventh means responsive to said incremental signal for temporarily storing said incremental signal, said fourth means being responsive to said second sign signal for producing a second command signal, said fifth means being responsive to said second command signal, for deriving a zero signal when the signs of the differences f(x3, y3) 2- f(x1, 1) 2 and f(x3, y3) 2- f(x2, y2) 2 are both positive, where (x3, y3) is the coordinates of a third possible followup point spaced from the present followup point.