Digital vector generation with velocity correction by tabulation of counter control signals
AssigneeTektronix, Inc.
InventorJohn C. Dalrymple
Life of this patent
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Abstract
Method and apparatus for drawing vectors on limited precision display devices in amounts of time approximately proportional to the vector's geometric length. Vectors are drawn by a series of strokes. Each stroke is a series of counter control signals, each signal representing a vertical, horizontal, or diagonal movement of the CRT electron beam between adjacent addressable screen points. The counter control signals making up the strokes are stored on a look-up table.
Claims7
A method of generating a vector having an X component and a Y component, on a random-scanned cathode ray tube defining an X and a Y axis, the method comprising the steps of:
- dividing the vector into segments, each segment having a geometric length;
- and
- drawing each segment by a stroke, each stroke comprising a sequence of pumps, and each sequence of pumps having a number of pumps wherein said number is a function of the geometric length and the angle with respect to the X axis of the segment to which said sequence of pumps and the stroke of which they are a part corresponds, with each stroke being drawn in an amount of time that is proportional to the geometric length of its corresponding segment.
An apparatus for generating a vector having an X component and a Y component, on a random-scanned cathode ray tube, the cathode ray tube having a phosphor screen and an electron beam, the apparatus comprising:
- shift normalizing means for forming a first number and a second number, each having a significant part and a fractional part, and the first number corresponding to the X component and the second number corresponding to the Y component of the vector;
- adding means for adding the fractional part of the first number to a first sum having a fractional part and a carry bit, and adding the fractional part of the second number to a second sum having a fractional part and a carry bit, wherein the initial first and second sums are said fractional parts of said first number and said second number respectively, and thereafter the first and second sums are the respective accumulations of previous such additions;
- a look-up table for generating sequences of pumps whenever the significant parts of the first number and the second number and the carry bits of the first sum and the second sum are received as input signals, the number of pumps in each said sequence being proportional to the geometric length of the vector;
- and
- means for directing the electron beam in accordance with the sequence of pumps generated by the look-up table.
Dependencies are inferred from the claim text.