EAN-13 traceability: lighting and quiet zones

Purpose and operating boundary

Keep the printed symbol, its quiet zones and source coordinate mapping intact when comparing illumination or tightening a reader ROI.

This tutorial defines an engineering evaluation, not a ready-to-run product certification. The current Deyi Vision public PC example covers an EAN-13 workflow on confirmed sample images. Native OCR and detection work in the engineering code must be checked against the installed runtime, bound models and job before use. A browser template does not prove browser execution: the planned OpenCV.js backend needs separate verification. Cloud recognition requires explicit approval of the image scope, provider, model and cost. A review archive is not an executable release package. Camera, firmware and driver compatibility require their own check. All worksheet values below are hypothetical; they are not Deyi Vision measurements or customer results.

Prepare the evidence

Prepare black bars on real label stock with film glare and damaged edges. Identify the symbol boundary independently of any successful decoded payload. Repeat the selected condition after restoring the fixture, not merely while leaving everything untouched. This reveals whether the recipe can be reproduced during changeover. Record ambient-light state and the time since illumination was enabled when these affect the image. Do not compare measurements taken from different masks or different bit-depth conversions as though only lighting changed. Keep the rejected optical condition in the record, including its image and the reason for rejection. A visually attractive image is not automatically the best inspection image: the selected condition must preserve the relevant feature and its separation from acceptable variation over the full agreed sample range. Keep decoding, identity validation, print verification and unit tracking as separate records. The EAN-13 value identifies a trade item and is normally shared by multiple physical units; it is not a per-frame sequence number or a unique serial. A successful decode does not prove print-quality compliance, correct product master data or successful downstream rejection. This series uses EAN-13 as its bounded example because that is the confirmed public PC evaluation scope. Other symbologies, QR, direct-part marks and reader hardware require their own confirmed integration. The original source image must retain bars, spaces and quiet zones; a cropped display or cleaned binary image alone is insufficient failure evidence. Specify how a missing frame and an unreadable code differ in the traceability database. Build a controlled optical comparison before moving the threshold. Mark the fixture, working distance, light angle and focus so that each condition can be restored. Change only the selected lighting or region variable while holding the camera settings and sample identity fixed. Retain the entire source frame beside every crop or mask, with the transform back to source coordinates. Capture both acceptable variation and a known problematic sample, including the edge of the allowed placement range. Inspect the region overlay on the original image before interpreting a numeric result. A smaller region can hide a failure rather than improve inspection, so excluded areas need an explicit engineering reason.

Procedure

1. Compare diffuse and directional light at fixed exposure; inspect white background clipping and dark-bar visibility.
2. Map the ink boundary to source pixels and retain surrounding blank areas rather than drawing a box around bars alone.
3. Inspect the ROI at permitted rotation and displacement; a rectangular crop must contain the entire transformed symbol.
4. Save original, ROI and lighting revision together; investigate no-read cases without extending the crop into a neighboring label.

Interpret the trial

The hypothetical ink spans x = 120 to 380 in a 640 px-wide frame. An ROI from x = 80 to 420 leaves 40 px on either side. This is an engineering margin example, not a claim that the GS1 quiet-zone requirement is satisfied; actual requirements depend on symbol dimensions.

Recording worksheet

left = 120 - 80 = 40 px
right = 420 - 380 = 40 px

Two engineering views

Failure diagnosis

• A decoder reading under glare does not prove bar contrast or print quality.
• A neighboring symbol appearing after ROI expansion must be associated with its own item, not silently substituted.

Acceptance and handover

Accept the ROI only if the whole symbol and required blank areas remain source-linked across the declared pose range. Keep independent print verification separate from this lighting comparison.

Keep the source images, the expected decision, the exact revision and the complete result record together. Freeze the evaluation set before selecting the final parameters. If those answers are later used to tune the workflow, mark that set as development data and obtain a new independent acceptance set. Keep Review, NoResult, execution error and missing acquisition visible in the denominator; do not turn them into passes by filtering rows. Save a reproducible failure alongside the successful sample. The handover should identify who may change the recipe, how a prior approved revision is restored and which device output remains inhibited until acceptance. A software result alone does not establish that a moving physical part reached the correct destination.