Reading Barcodes Behind Tempered Glass

Tempered glass is widely used in self-service kiosks, parcel lockers, EV charging stations, visitor terminals, and access control equipment because it protects internal components from dust, water, vandalism, and accidental impact.

However, many OEM manufacturers discover that barcode reading performance changes after the scanner is installed behind the front glass panel, even though the same scanner worked perfectly during bench testing.

In most cases, the scanner is not the problem—the optical path has changed.

The Challenge: The Glass Is Only Part of the Problem

Many engineers focus on the thickness of the tempered glass.

While glass thickness does matter, the distance between the scanner and the glass is often a much bigger factor.

If the scanner is mounted too far behind the front panel, the barcode must pass through:

• An air gap

• The tempered glass

• Additional reflections created by both surfaces

Each interface slightly changes the light reaching the image sensor.

For printed labels, the impact may be small.

For mobile phone QR codes, especially on bright screens, these additional reflections can reduce image contrast and increase the chance of failed first-pass reads.

Why Increasing Scanner Brightness Doesn't Solve It

When scanning becomes inconsistent, some designers try increasing illumination.

This usually treats the symptom rather than the cause.

More illumination may also produce stronger reflections between the phone screen and the glass panel.

Instead of improving image quality, the scanner may receive even more reflected light.

Successful barcode reading behind tempered glass depends on the entire optical design, not just scanner brightness.

Engineering Considerations

When designing equipment with a protective glass panel, OEM manufacturers should consider the following:

• Keep the scanner as close to the glass as practical to reduce the air gap

• Avoid unnecessarily thick front panels

• Reduce direct reflections by selecting an appropriate installation angle

• Keep the glass surface clean to prevent fingerprints and dust from affecting image quality

• Validate the design using actual mobile phone screens rather than printed test codes only

Small mechanical changes often produce a much larger improvement than replacing the scanner itself.

Recommended Barcode Scanner

For self-service equipment that requires barcode reading behind a tempered glass panel, the XTIOT XT206H3 is designed for OEM integration.

Key features include:

• Built-in acrylic front window for enclosed panel installations

• 1280 x 800 CMOS image sensor for high-resolution barcode capture

• Reliable reading of printed barcodes and mobile phone QR codes

• Compact embedded design for kiosks and unattended terminals

• Supports USB, TTL, and RS232 communication interfaces

• Suitable for parcel lockers, self-service kiosks, EV charging stations, visitor management systems, ticketing machines, and access control equipment

When combined with proper glass selection, minimized installation distance, and optimized optical alignment, the XT206H3 helps OEM manufacturers achieve more reliable barcode reading behind protective panels without redesigning the entire terminal.