QR Codes trên bề mặt cong

QR Codes on Curved Surfaces

Bottles, cans, tubes, and other cylindrical packaging present unique challenges for QR code placement and scanning.

The Distortion Problem

On a curved surface, modules at the edges of the QR code are compressed when viewed from a perpendicular position. This geometric distortion can exceed the correction capabilities of alignment patterns, causing scan failure.

Guidelines for Curved Surface QR Codes

Keep the QR code small relative to the circumference: The QR code should subtend no more than 60-90 degrees of the cylinder's circumference. Beyond this, edge distortion becomes severe.

Use lower versions: Fewer modules mean each module is larger relative to the curvature, reducing the distortion impact. Shorten URLs to use Version 2-5.

Increase error correction: Use EC Level Q or H to compensate for distortion-induced misreads at the edges.

Position on the flattest area: For bottles, the flattest area is typically the centre of the label. For cans, position on the least curved section.

Cylinder Radius Guidelines

Material-Specific Tips

Glass bottles: Print on the label, not directly on glass. Ensure the label lies flat (no wrinkles or bubbles over the QR code area).

Aluminium cans: Direct printing or sleeve printing. High-quality print reproduction is typically excellent on cans.

Plastic tubes: Flexible tubes deform during handling. Use EC Level H and larger modules.

Shrink-wrap sleeves: Pre-distortion compensation may be needed — the QR code is printed flat but distorts when the sleeve shrinks around the container.

Key Takeaways

• Limit QR code angular coverage to 60-90 degrees of the cylinder
• Lower versions (fewer modules) handle curvature better
• EC Level Q or H compensates for distortion-induced errors
• Position the QR code on the flattest available area
• Shrink-wrap sleeves may need pre-distortion compensation