Overview
ISO 1831:1980 - "Printing specifications for optical character recognition" defines optical and dimensional requirements for media used in Optical Character Recognition (OCR). The standard establishes measurable parameters, tolerance limits and test methods for OCR paper and print to support reliable document interchange and system interoperability. It covers paper optical properties, ink/character image characteristics, and basic rules for character positioning.
Key topics and technical requirements
- Optical properties of paper
- Luminous reflectance factor (R): measured relative to a perfect reflecting diffuser. Typical requirements: R > 60% in 425–500 nm and R > 70% in 500–700 nm; R ≥ 70% at 900 nm if near-IR is relevant.
- Paper opacity (paper backing): measured per ISO 2471; opacity and reflectance variation requirements span specified spectral bands.
- Dirt/contaminants: two evaluation methods - a quick grid assay (Method A) and a particle count (Method B). Example limits: grid counts not to exceed 200 squares with dirt per 6 m²; Method B thresholds for particle size and counts are given for representative samples.
- Spectral measurement and bands
- Defines reference spectral bands (B425 … B900) for measuring instruments (light source + filter + detector). Instruments must produce smooth response curves; illumination energy below 490 nm should not exceed 5% of the band energy.
- Printed image and character parameters
- Optical and dimensional properties of ink patterns forming OCR characters, print quality tolerance ranges, and character outline limits. Measurement procedures and sampling approaches are specified.
- Character positioning
- Requirements for document reference edges, character boundaries, skew, line separation, margins, fields and alignment to ensure consistent OCR reading.
- Measurement methodology
- Detailed test methods, sampling plans, and annexes that include paper measurements, printed image characteristics, a computer-aided method (CAM) for print-quality measurement, and character positioning guidance.
Practical applications and users
ISO 1831:1980 is used by:
- Printer and paper manufacturers to produce OCR-optimized media and supplies.
- OCR system vendors and integrators for establishing input tolerances and test criteria.
- Quality assurance teams in banking, postal services, government forms, data capture and archival digitization to ensure reliable OCR throughput.
- Document designers and systems engineers specifying document layouts and character placement for machine readability.
The standard helps reduce OCR errors (rejections/substitutions) by defining measurable media characteristics and mutually agreed sampling/acceptance criteria between printing-system and recognition-system suppliers.
Related standards
Key cross-references include: ISO 216, ISO 1073-1, ISO 1073-2, ISO 2469, ISO 2471, and CIE Publication 15 (1971) - all cited for sizing, character shapes, reflectance and colorimetry measurement methods.
