Overview
ISO 1073-1:1976 defines the OCR-A alphanumeric character set - the shapes and dimensions of printed images intended for optical character recognition (OCR). This International Standard specifies centrelines, nominal stroke widths and printing-frame dimensions for the OCR‑A repertoire in three sizes, supplies radii and corner guidance, and gives rules for vertical and horizontal placement of characters. It is intended to promote reliable machine and human reading of printed alphanumeric characters and graphics compatible with ISO 646:1973.
Key topics and technical requirements
- Character repertoire and scope: OCR‑A comprises 69 characters (including digits, capital letters and selected graphics); a numeric sub‑set of 14 digits is also identified for numeric‑only applications.
- Three print sizes: Dimensions for three standard printing frames (height H, width W), nominal stroke width T, and minimum length L for the long vertical mark are specified; values are given in both millimetres and inches (metric and inch units should not be intermixed).
- Nominal printed image: Each character is defined by its centreline and nominal strokewidth; tabled values (height, width, stroke dimensions) are provided for all characters.
- Radii and corners: All edges should be blended with rounded corners; specific centreline radii (r1…r6) and formulae are supplied. The standard recognizes production limits and states corner radii need not be smaller than 0.08 mm for OCR purposes.
- Placement rules: Definitions and rules for the base line, base‑line displacement, vertical position, and horizontal reference line (constant pitch printing) ensure consistent alignment for OCR scanning.
- Print process considerations: The standard is written for a wide range of printing technologies (typewriters, cash registers, numbering machines, high‑speed printers, credit card imprinters, letterpress, offset, non‑impact imprinters).
Applications and who uses it
ISO 1073-1:1976 is used by:
- Printer and type‑face manufacturers to design OCR‑A type and molds that meet machine‑readable specifications.
- Equipment makers of scanners, OCR readers and document processing hardware for reliable recognition.
- Document and form designers in banking, transportation, billing and archival systems that require standardized OCR fonts for automated reading.
- Software developers implementing OCR engines who need precise printed‑image constraints for training, recognition thresholds and test data.
- Standards bodies and quality assurance teams seeking interchangeability of OCR documents across organizations and printing processes.
Related standards
- ISO 1073-2 (OCR‑B character set - shapes and dimensions) - complementary part for OCR‑B.
- ISO 646:1973 - the 7‑bit coded character set referenced for graphics and national letters.
- ISO 1073 (combined) replaces earlier ISO Recommendation R 1073-1969.
Keywords: ISO 1073-1:1976, OCR‑A, optical character recognition, alphanumeric character sets, printed image shapes and dimensions, OCR standard, ISO 646.
Open preview (PDF)Alphanumeric character sets for optical recognition — Part 1: Character set OCR-A — Shapes and dimensions of the printed image