The uniformity of barcode paper thickness is a core element ensuring accurate focusing by scanning equipment, and its mechanism permeates the entire process of optical signal acquisition, reflection path control, and image resolution. When there is a thickness deviation in the barcode paper, the optical system of the scanning equipment will experience focusing misalignment due to differences in object distance, resulting in blurred edges of the barcode symbol, reduced contrast, and ultimately decoding errors. This impact is particularly significant in high-speed scanning or long-distance recognition scenarios, making thickness uniformity a key indicator of barcode paper quality.
From an optical perspective, the focusing mechanism of a scanning equipment relies on a constant distance between the barcode surface and the optical center of the lens. When the barcode paper thickness is uneven, the barcode symbol in different areas will be located at different object distance planes, creating a "local defocus" phenomenon. For example, areas with excessive thickness will cause the barcode symbol to move away from the ideal focusing plane of the lens, resulting in diffused light spots on the sensor; while areas with insufficient thickness may cause the barcode symbol to fall outside the depth of field, causing signal attenuation. This difference in object distance directly disrupts the geometric integrity of the barcode symbol, causing the originally uniformly wide bar and space structure to exhibit non-linear deformation in the image.
The impact of thickness uniformity on the reflected light path is reflected in the consistent control of signal intensity. Scanning devices interpret information by detecting changes in the intensity of reflected light from barcode symbols, and this intensity is closely related to the surface roughness of the barcode paper and the transmittance of the coating. When thickness fluctuates, even with the same coating formulation, the surface microstructure of different thickness areas will differ: thicker areas may have a smoother surface due to coating compression, resulting in increased reflectivity; thinner areas may have increased surface roughness due to coating stretching, resulting in decreased reflectivity. This uneven distribution of reflectivity weakens the contrast of the barcode symbol, making it difficult for the scanning device to accurately identify bar/space boundaries.
In high-speed scanning scenarios, thickness uniformity is crucial for the stability of dynamic focusing. Modern scanning devices mostly employ autofocus technology, compensating for changes in object distance by adjusting the lens position in real time; however, this compensation has a response delay. When the frequency of barcode paper thickness fluctuations exceeds the focusing adjustment speed of the scanning device, some barcode symbols will be captured in an incompletely focused state, resulting in "motion blur." Furthermore, uneven thickness can lead to an imbalance in the energy distribution of the scanning spot, causing information loss at the edges of the barcode symbol due to insufficient illumination, further reducing the decoding success rate.
Thickness uniformity has a decisive impact on the scanning reliability of curved surfaces. When attaching barcodes to cylindrical containers or curved surfaces, the paper's flexibility must be precisely matched to the radius of curvature. If the thickness is uneven, thicker areas will have gaps with the curved surface due to their strong bending resistance, forming a "hollow" phenomenon; thinner areas may deform the barcode symbol due to excessive stretching. This localized poor attachment will change the flatness of the barcode symbol, causing a phase difference in the reflected signal received by the scanning device, leading to decoding errors. Therefore, barcode paper used for curved surfaces needs to ensure the uniformity of overall flexibility through thickness gradient control.
Material processing is the foundation for ensuring thickness uniformity. High-quality barcode paper uses high-precision coating technology, controlling the viscosity, leveling properties, and drying rate of the coating liquid to form a uniform thin film on the substrate surface. Meanwhile, the flatness of the substrate is also crucial. Supercalendering eliminates fiber voids within the paper, significantly improving thickness uniformity. Furthermore, multi-layered composite barcode paper requires interlayer tension matching to avoid thickness fluctuations during lamination, ensuring tight adhesion and controllable thickness across all layers.
The thickness uniformity of barcode paper provides the foundation for accurate decoding by scanning equipment, controlling object distance stability, reflective signal consistency, and dynamic focusing reliability. From optical design to material processing, thickness control at every stage directly impacts the final barcode recognition result. With the widespread adoption of automatic identification technology, the requirements for barcode paper thickness uniformity will become increasingly stringent. This necessitates collaborative optimization between material suppliers and equipment manufacturers to jointly improve the reliability of barcode recognition technology.
