Many printed products (currency, tickets, commercial publications, newspaper packaging, pharmaceuticals and food, etc.) require 100% print inspection (usually in color) as part of the quality control process; multiple inspections are required during production.

For conventional automated label inspection systems, we are familiar with a frontal camera system for labels on flat box surfaces, or using multiple cameras to capture different angles for round bottle surfaces. So have you ever wondered how to conveniently inspect the labels on the bottom of trays for products with labels on both the top and bottom, most of which run on conveyor systems?

Labels on both sides of tray-type products

The answer is that the vision system uses a high-resolution linear scanning camera, a special type of camera that acts as a scanner, it can record a single line of the framed area, and then completely reproduce the image of the label as soon as the trays are passed through the capture system.

It is thanks to this working feature that it is possible to install a scanning camera system, the lighting is located under the conveyor plane, respectively at the conveyor junction position.

System configuration for label capture under the conveyor belt

Why use a line scan camera?

Line scan technology involves building an image, one line at a time, using a line sensor (linear array), which follows a linear motion across an object or where the object follows a linear motion below the sensor.

Most basic CCD technology is suitable for area scan cameras, although there are subtle and complex differences to line scan photography that often make it a more specialized subject. Line scan technology has been around for many years, and the most common applications include photocopiers and PC flatbed scanners, which typically feature large linear arrays, the same size as the scan width.

Although linear arrays have similar pixel sizes to area scan sensors, the line length can be much larger. Instead of the maximum 1-2k width common to most mega-pixel area scan sensors, a line scan sensor can have up to 12K pixels. Therefore, for a given field of view (FOV), a line scan setup can provide much superior spatial resolution.

Line scan technology allows for the capture of wide objects in a single scan. Using area scan techniques, a series of images are captured in succession and then ‘stitched’ together.

Common line scan cameras use linear array sensors that are typically available in widths ranging from 512 to 16K elements (pixels). The process of constructing a high fidelity image from individual lines requires a very high degree of precision.

System alignment and timing are critical to the fidelity and geometry of the resulting image and therefore line scan systems are more complex to implement than area scan systems. It should also be noted that line scan cameras also require higher illumination levels than area scan cameras, due to the shorter exposure times.

From paper to cardboard, plastic or metal, in various shapes, print inspection applications are well suited to line scanning systems. Line scanning provides unlimited pixel count in the direction of image movement without blurring even at high speeds, higher dynamic range, higher processing performance.

Line scan systems provide higher resolution with fewer cameras and 100% inspection of the moving surface without blurring or the need for frame overlap.

An ideal automated label inspection system for ensuring label quality related to accurate positioning, matching, integrity, verification/reading of part (front-back), opaque and part transparent labels. The configurations used vary depending on the type of label and the level of accuracy required to meet the specific needs of the plant.

Features:

- Using Machine Vision Technology, Artificial Intelligence

- System can be configured with 1 or 2 cameras

- Specific lighting for maximum visibility of defects

- Can be installed without modifying the line

- Can be integrated inside the labeling machine

Advantages

Increase productivity:

- Reduce the number of rejected products in case of labeling machine failure thanks to the ability to control the types of rejected products in succession

- Optimize the adjustment and maintenance of the labeling machine

Increase quality:

- Eliminate market complaints related to incorrect labeling

- Guarantee the correct label

- Guarantee the integrity, correspondence, clear printing of the code on the label

- Guarantee the quality of the product

Functions, results:

The system allows to detect:

- Presence of the label

- Label positioning (vertical, horizontal, rotation)

- Integrity of label

- Check presence/integrity of lot code

- Read barcode, Datamatrix or QR - Code

- Read text