Electrographic system and method

• US 4,650,926 A
• Filed: 06/07/1985
• Issued: 03/17/1987
• Est. Priority Date: 10/26/1984
• Status: Expired due to Term

• Current Assignee: Frances B. Cuniberti, Scriptel Corporation, Walter T. Krumm
• Original Assignee: Scriptel Corporation
• Inventors: Nakamura, Shoichiro, Kable, Robert G.
• Primary Examiner(s): SCHREYER, STAFFORD
• Application Number:
  US06/742,733
• Time in Patent Office: 648 Days
• Field of Search: 178/18, 178/19, 178/20, 340/709, 340/707, 340/711, 364/515, 364/561, 364/520, 364/571
• US Class Current: 178/18.02
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An electrographic system and method having a control which carries out correction for graphic surface non-linearities. The control employs a procedure wherein a correction look-up table is developed as part of the manufacture of the device wherein output readings are taken along a physical domain rectangular grid array of predetermined dimension and these output readings are adjusted in their signal domain to establish a regularly incremented sequence of address values within that signal domain. Physical domain coordinate values then are derived and placed in the table for each address value. The control then accesses this memory for each of a given locator or tracer position on the graphic surface and carries out an interpolative weighting to derive acceptably accurate coordinate pair signals which are outputted to a host computer or the like.

Claims

1. An electrographic system comprising:

means defining a graphics surface;

locator means movable in adjacency about said surface for select interaction therewith to effect the derivation of position signals;

circuit means responsive to said position signals for deriving digital position signals;

memory means for retaining computed physical domain coordinate values derived as values corresponding with select said digital position signals of a signal domain and established for each position within a predetermined grid array of pre-established positions of said physical domain, adjusted to establish a regularly incremented sequence of address values within said signal domain; and

control means responsive to each given said digital position signal received thereby for deriving a said address value corresponding therewith, for accessing said memory means at said address value to retrieve computed physical domain coordinate values corresponding therewith and for adjusting the values of said computed physical domain coordinate value by select-dimensional interpolative weighting thereof in correspondence with said received digital position signal to derive corrected coordinate pair output signals.

2. The electrographic system of claim 1 in which each said memory means address value corresponds with a rectangle of said signal domain bounded at the corners thereof by four said computed physical domain coordinate values.

3. The electrographic system of claim 1 in which said memory means address values comprise select high order bits of said digital position signals generated by said locator means interactions.

4. The electrographic system of claim 1 in which:

said memory means address values comprise select high order bits of said digital position signals generated by said locator means interactions; and

said control means select-dimensional interpolative weighting is carried out with select lower order bits of said given digital position signals generated by said locator means interactions.

5. The electrographic system of claim 1 in which:

each said memory means address value corresponds with a rectangle of said signal domain bounded at the corners thereof by four said computed physical domain coordinate values;

said control means is responsive to said given digital signal for deriving four discrete weighting factors corresponding with said four computed physical domain values, for applying a select said weighting factor to each to derive a weighted coordinate pair value and for summing said weighted coordinate pair values to derive said corrected coordinate pair output signals.

6. The electrographic system of claim 4 in which:

said memory means address values comprise select high order bits of said digital position signals generated by said locator means interactions; and

said control means select-dimensional interpolative weighting is carried out with select lower order bits of said given digital position signals generated by said locator means interactions.

7. The electrographic system of claim 6 in which said control means derives an initial said weighting factor in accordance with the expression, (1-x) (1-y) where x and y are said select low order bits.

17. The electrographic system of claim 1 in which said control means is configured to effect a two-dimensional said interpolative weighting in correspondence with said received digital position signal to derive said corrected coordinate pair output signals.

8. In an electrographic system wherein a surface is selectively accessed to develop electrical signals which are treated to provide outputs corresponding with the accessed position, the method of correcting the value of given said outputs, comprising:

providing a memory for retaining computed physical domain coordinate values derived as values corresponding with select said outputs of a signal domain and established for each position within a predetermined grid array of pre-established positions of said physical domain, adjusted to establish a regularly incremented sequence of address values within said signal domain;

deriving a said address value from a said given output;

accessing said memory at said address value to provide a computed physical domain coordinate value corresponding therewith;

adjusting the value of said accessed computed physical domain coordinate value by a two dimensional interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate information representing said accessed position at said surface.

9. The method of claim 8 in which said address value is derived from select high order bits of a digital signal generated as said given output.

10. The method of claim 9 in which said adjustment of the value of said accessed computed physical domain coordinate value by interpolative weighting is carried out with weighting factors derived from said given output and applied to said accessed computed physical domain coordinate value.

11. The method of claim 10 in which:

each said memory address value corresponds with a rectangle of said signal domain, the corners of which are defined by four successive said computed physical domain values; and

said interpolative weighting is carried out by four discrete weighting factors, each applied to a select said computed physical domain value corresponding with one said corner.

18. The method of claim 8 in which said step of adjusting the value of said access computed physical domain coordinate value is caried out by a two-dimensional interpolative weighting thereof in correspondence with a given output.

12. In an electrographic system wherein a surface of known geometric configuration is selectively accessed to develop electrical signals which are treated to provide outputs corresponding with the accessed physical position, the method of correcting the value of given said outputs with respect to variations of said surface comprising the steps of:

determining, within a physical domain, a grid array of physically locatable positions over said surface;

deriving, within a signal domain, said electrical signals and corresponding outputs with respect to each said array position of said physical domain;

deriving, within said signal domain, a regularly incremented sequence of address values;

determining physical domain coordinate values corresponding with each of said address values;

recording said physical domain coordinate values in conjunction with corresponding said address values;

deriving a correction said address value from a said given output;

accessing said memory at said correction address value for said physical domain coordinate values corresponding therewith;

adjusting the value of said physical domain coordinate values by select dimensional interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate pair information representing said locator physical position.

13. The method of claim 12 in which said adjustment of the value of said physical domain coordinate values is carried out by a two-dimensional interpolative weighting.

14. The method of claim 12 wherein:

said grid array is a rectangular array of grid lines the sections of which define said positions; and

said memory address corresponds with a discrete region of said signal domain incorporating a select number of adjacent said physical domain coordinate values.

15. The method of claim 14 in which said correction memory address value for said discrete region is provided as select high order bits of a corresponding said given output.

16. The method of claim 12 in which:

each said given output is derived as a given digital signal; and

said correction address value is derived as select high order bits of said given digital signal.

19. The method of claim 12 in which said step of adjusting the value of said physical domain coordinate values is carried out by two-dimensional interpolative weighting thereof in correspondence with said given output.

20. In a system wherein a resistive surface is positionally accessed to evolve position outputs in a signal domain with respect to a predetermined array of grid locations within the physical domain of said surface, the method for correcting said position outputs comprising the steps of:

providing a memory for retaining computed physical domain coordinate values derived as values corresponding with select said outputs of said signal domain and established for each position within a predetermined grid array of pre-established positions of said physical domain, adjusted to establish a regularly incremented sequence of address values within said signal domain;

deriving a said address value from said given output;

accessing said memory at said address value to provide a computed physical domain coordinate value corresponding therewith;

adjusting the value of said accessed computed physical domain coordinate value by a selectively dimensional interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate information representing the location of said positional access of said surface.

21. The method for generating a memory retained look-up table for use in interpolatively correcting the position outputs in a signal domain corresponding to accessed locations within the physical domain of a resistive surface, comprising the steps of:

collecting an input data set from said surface representing physical and signal domain characteristics of said surface;

determining the bounds of said input data set as maximum and minimum signal domain values for first and second coordinate directions;

deriving first and second sets of regularly incremented address locatable values extending between said maximum and minimum signal domain values corresponding, respectively, with said first and second coordinate directions;

providing a first estimate of the physical domain coordinate location values on said surface corresponding with said address locatable values for each said first and second coordinate directions;

deriving from said first estimate and adjacent values of said input data set interpolated said physical domain coordinate location values for each said first and second coordinate directions; and

positioning said interpolated physical domain coordinate location values in said memory in combination with corresponding said signal domain address locatable values.

22. The method of claim 21 including the step of testing said interpolated physical domain coordinate location values with respect to a predetermined error level variation from the immediately subsequently derived said interpolated physical domain coordinate location value prior to said memory positioning thereof.

23. The method of claim 21 wherein said input data set corresponds with a set of predetermined coordinate aligned grid locations in said physical domain.

24. The method of claim 23 wherein said step of collecting said input data set is carried out by accessing said resistive surface with readout means at a predetermined number of coordinate aligned regularly spaced grid point locations to derive column and row voltage level readouts at each said grid point location, and converting said voltage level readouts to corresponding digital values constituting said input data set.

25. The method of claim 21 wherein said step of deriving said first and second sets of regularly incremented address locatable values is carried out employing a predetermined numer of increments which is greater in number than said predetermined number of said input data set grid point locations.

26. The method of claim 21 wherein said interpolated physical domain coordinate location values are derived employing a Newtonian interpolation technique.

27. The method of claim 21 in which:

said step deriving said interpolated physical domain coordinate location values includes the steps of interpolatively determining adjustment values, and summing said adjustment values with said first estimates of said physical domain coordinate location values to derive second estimates thereof.

28. The method of claim 26 including the step of testing said interpolated physical domain coordinate location values by comparison of said adjustment values with predetermined tolerance criteria.

29. The method of claim 21 in which said first estimate of said physical domain coordinate location values is provided as the next preceding interpolated value thereof.

30. In an electrographic system wherein a surface of known geometric configuration is selectively accessed to develop electrical signals which are treated to provide outputs corresponding with the accessed physical position, the method of correcting the value of given said outputs with respect to variations of said surface comprising the steps of:

collecting an input data set from said surface representing physical and signal domain characteristics of said surface;

determining the bounds of said input data set as maximum and minimum signal domain values for first and second coordinate directions;

deriving first and second sets of regularly incremented address locatable values extending between said maximum and minimum signal domain values corresponding, respectively, with said first and second coordinate directions;

providing a first estimate of the physical domain coordinate location values on said surface corresponding with said address locatable values for each said first and second coordinate directions;

deriving from said first estimate and adjacent values of said input data set interpolated said physical domain coordinate location values for each said first and second coordinate directions;

positioning said interpolated physical domain coordinate location values in memory in combination with corresponding said signal domain address locatable values;

deriving a correction address locatable value from a said given output;

accessing said memory at said correction address locatable value for said physical domain coordinate location values corresponing therewith;

adjusting the value of said physical domain coordinate location values by select dimensional interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate pair information representing said locator physical position.