Linear image scanning inferior as an auto ID solution? Think again.
Guest blog from MHI member SICK
Restoring the reputation of linear image scanning systems by busting myths about using the system for your auto ID needs
If you are wanting to detect products reliably and efficiently, one of the best options is auto ID technology. There are many different auto ID options that work for a variety of applications. However, you may be lead astray from the solution that best fits the application with myths circulating in the industry. We found the truth about five of these myths so that you are given the facts about your options for auto ID technology.
Myth 1: Decoding in Real Time
The first myth is that linear image scanning technology must build the entire object image before decoding, causing packages to travel longer distances past the scan point before data transmission. In contrast, it is said that a camera-based barcode reading system can decipher 1D and 2D codes much faster which reduces the distance between the reader and divert point. This is a myth. In fact, linear image scanning systems can use a method of decoding called progressive scan.
Progressive scan works to decode in real time. First, the decoder always has single strip sections available, and does not wait until the whole image is captured. The strip is then examined in parallel on several cores for features and, based on the results, the strip is decompressed into areas of interest. If the current strip is used to segment one or more new regions, a new decode is attempted. If several regions are created in a single new strip, then the decoding process is distributed over several cores. This method works at high frequencies and does not cause a significant time delay when compared to other auto ID technology. Furthermore, some camera-based systems require stitching of multiple images, which need to see a certain number of pixels and overlap between strips. This can lead to gaps when working at higher speeds.
Myth 2 – Read Rate
The second myth is about the read rate of a linear image scanning system. This myth falsely states that these systems acquire images 1-pixel row at a time, meaning that any dust or debris on the scanner can block vital code information and lead to no reads. However, it is said that a camera-based system captures more information in an image and has higher read rates.
This is a myth because dust and debris are not a significant problem for linear image scanning systems. The systems do not work 1-pixel row at a time as assumed. They use a quad-line imager which allows the system to make an average result from four-pixel lines. Additionally, the camera for the system is installed below the belt, but directly under the belt gap. The mirrors for the system are installed directly under the gap. This means that the camera is not in focus at the position to the mirror. The blurred focus causes single dirt parts to not be visible, so an under-belt system can function without dirt influencing performance.
Myth 3 – Performance with Vibration
The third myth supposes that the natural motion and vibration from the conveyor can create artifacts in the acquired image and cause no reads. It states that other systems are less vulnerable to box movement than a linear image scanning system.
The fact is that box movement is never an issue for a bottom reading system. This is because the cameras from below are working with a fix focus mode. Some linear image scanning systems, such as ones from SICK, use time delay and integration technology in the systems to provide greater responsiveness at higher speeds. This system can take images above the gap when objects move across it, even with existing vibration and box movement above the conveyor. Therefore, movement causes no influence on performance.
Myth 4 – Installation
The fourth myth concerns installation. Some people think that linear image scanning systems can take up to double the amount of time to set up as other systems. Additionally, they think that installing and maintaining linear image scanning systems in space-constrained facilities is challenging.
However, the truth is that there is a new SICK ICR stand-alone solution that reduces the installation and maintenance costs. This is successful because an ICR camera takes over the task of a system controller, meaning the system controller is no longer needed. This can save up to 30 minutes during commissioning per system. Additionally, there is a new ICR device that can be used for smaller reading distances and this device reduces installation space.
Myth 5 – Maintenance
Finally, the last myth is about the maintenance of linear image scanning technology. This myth suggests that linear image scanning technology requires reaching under the conveyor to clean the system. Other systems, in comparison, have a removable cover and mirror for cleaning and sometimes an available air knife accessory to reduce dust and dirt build up. However, there is more to this than meets the eye.
As previously stated, the camera should not be located in the belt gap, so it can be better protected against dust or any liquids that could damage the system. The deflection mirror in SICKs ICR imager has a robust vaporized metal surface with chrome coating that has a high abrasion and scratch resistance. This coating can be cleaned more frequently and easily. The mirrors use a skew angle of 15 degrees which allows the dust to be more easily blown away from an integrated blower unit. Maintaining this blower unit can be done easily by cleaning the surface of the fan housing and changing the air filter mat. Additionally, the deflector mirror is mounted underneath the conveying surface and can easily be replaced due to the separation of the base support and mirror holder. This allows the mirror to be pulled out to the side for cleaning or replacing.
The Final Verdict
Some companies have tried to create linear image scanning solutions but were unsuccessful. Because of this, myths arose that incorrectly portrayed the technology as ineffective. Now that linear image scanning technology has been accurately portrayed as a valuable player in the auto ID space, you can be confident that you know the truth. If linear image scanning technology seems to be the best solution for your application, know that it is both a reliable and efficient option that has the potential to optimize your processes.
