QR Code hiển thị trên màn hình: TV, màn hình và máy chiếu

QR Codes for Screen Display: TVs, Monitors, and Projectors

Displaying QR codes on screens has unique challenges: pixel grids, refresh rates, viewing angles, and the awkward phone-to-screen scanning ergonomics.

Resolution Requirements

QR code modules must align cleanly with screen pixels. When the module size is not an exact multiple of pixels, subpixel rendering causes blurry edges that impair scanning.

Rule: Each module should be at least 4x4 screen pixels for reliable scanning. For a Version 5 QR code (37 modules), that means at least 148x148 pixels on screen.

Moire Patterns

When the QR code's module grid frequency closely matches the screen's pixel grid frequency, Moire interference patterns appear. These wavy patterns confuse scanners.

Mitigation: - Ensure module sizes are at least 4 pixels wide (avoids frequency matching) - Use exact pixel multiples (do not scale QR codes to arbitrary sizes) - On projectors, increase the QR code size to reduce the pattern frequency

Screen-Specific Considerations

TV screens: Place the QR code in a corner, leaving it on screen for at least 10 seconds. Viewers need time to locate the code, unlock their phone, and scan. Keep the QR code at a low version for scan distance.

Computer monitors: Most common for 2FA setup. The phone is held at 15-30 cm from the monitor. Standard-sized QR codes (150-300 pixels) work well.

Projectors: Low resolution and ambient light reduce contrast. Use large QR codes (at least 20% of screen width) with maximum contrast (black on white).

Digital signage: Similar to poster placement. Account for viewing distance and ambient lighting. Use dynamic QR codes to update content without changing the display file.

Brightness and Contrast

• Set screen brightness to maximum when displaying a QR code
• Use black-on-white (not inverted) for maximum compatibility
• Avoid placing QR codes on video backgrounds or animations
• Do not overlay QR codes on moving content

Key Takeaways

• Each module should be at least 4x4 screen pixels to avoid blur
• Moire patterns occur when module size matches pixel grid frequency
• TV QR codes should stay on screen for at least 10 seconds
• Maximise screen brightness and contrast when displaying QR codes
• Use static, non-animated backgrounds behind screen QR codes