Spectrum Ultrasonic Multifeed Detection
Ultrasonic multifeed detection is the best way to prevent multiple documents feeding through the scanner at the same time. "Multifeeds” occur when information on the bottom page is lost because only the top page is scanned.
How Does it Work?
Ultrasonic multifeed detection from Böwe Bell + Howell consists of two sensors: a transmitter below the paper transport and a receiving sensor above. The transmitter emits an ultrasonic wave through the document. Normally, only one document is being fed through at a time, causing this wave to pass through the paper and directly into the top sensor. See the illustration below.
Ultrasonic Multifeed Detection During Normal Scanning
If multiple documents feed through, small gaps of air get trapped between the pages. When the ultrasonic wave hits the combination of the air gap and additional paper, the signal falls below a certain threshold and the receiver interprets this as a multifeed. The scanner transport then stops and the user is notified that a multifeed has occurred so that it can be quickly resolved as soon as it happens. Thus, ultrasonic multifeed detection from Böwe Bell + Howell ensures that no data is lost if multiple documents feed through simultaneously. See the illustration below.
Ultrasonic Multifeed Detection During a Doublefeed
Never Scan the Entire Batch Again Because of a Multifeed
Just detecting multifeeds is important, but users need a fast and efficient way to resolve them. Some scanners can tell you if a multifeed occurred but leave you with no way of solving the problem other than to have you scan the entire batch again, which is not only unproductive but may also cause more significant problems if imprinting or endorsing is required. Ultrasonic multifeed from Böwe Bell + Howell actually works in conjunction with our hardware implementation of Kofax VirtualReScan™ (VRS). So when a user encounters a multifeed, a VRS message pops up on the user’s PC indicating that a multifeed has occurred. The scanner then pauses so that you can immediately remove the documents that multifeed. All you need to do is place the documents back into the feeder (so that they don’t multifeed again) and then press the CLEAR button on the scanner. Feeding then starts automatically and VRS automatically deletes the bad image (one document scanned on top of another) and keep all good images in the proper order.
Old School vs. New School
Some claim that you should never stop scanning under any circumstances, including when the scanner detects a multifeed. We at Böwe Bell + Howell believe that the best way to resolve a multifeed is to isolate it and resolve it immediately rather than to go through unnecessary effort of scanning batches multiple times and manually deleting bad images. Yes, this method may slow down throughput initially, but is sure to save you a lot of time on the back end. However, users that do not want their Spectrum scanner to stop on a multifeed can easily set the scanner to notify when a multifeed is detected (the scanner beeps and keeps scanning) or to ignore multifeeds altogether.
Ignore by Size
Exclusively from Böwe Bell + Howell is the ultrasonic multifeed “Ignore by Size” functionality. This added intelligence allows you to scan items that other scanners may interpret as a multifeed, quickly and seamlessly without stopping.
Such formerly troublesome items include:
- Photographs – background sometimes separate from the image, creating an air gap
- Envelopes – often slit open so that contents can be removed; front, back and folds create air gaps
- Labels and Sticky Notes – are not usually affixed 100% to whatever placed upon, creating an air gap
The best way to set ignore by size, is to enter the maximum length of photograph, envelope or label that will be scanned and set the ignore length to a size a half inch or 10 mm higher. This is not an exact science, so you will not need to spend a lot of time estimating; if you enter a setting that doesn’t catch everything, the scanner will simply stop, you can change the ignore by size setting and quickly reefed the document.
One vs. Many
The angled orientation of the Böwe Bell + Howell ultrasonic transmitter and receiver allows for coverage of the majority of the feeder’s width. Some ultrasonic sensors on other scanners are oriented directly opposite each other. This can significantly reduce the width of coverage and necessitate the use of multiple ultrasonic sensor pairs oriented in this way to have the same coverage as a single, angled ultrasonic transmitter and receiver.
Ultrasonic vs. Length-Width and Infrared Detection
Other multifeed detect technologies exist but can easily be fooled. One such example is length and width multifeed detect. This methodology is flawed because users typically have multiple documents of the same size (length x width) in any given batch, even if they have many other different sizes. As a result, it is inevitable that two documents of the same size will feed through simultaneously, with one directly on top of the other such as when documents are taped together, stapled together, or stuck together because of static electricity. This type of multifeed will be missed with length and width detect.
Another multifeed technology is infrared detection, which detects doublefeeds when a manual thickness parameter is exceeded. This method requires users to guess the maximum thickness of documents being scanned. The theory is that when two documents feed through, the maximum thickness parameter will be exceeded and the scanner will signal a multifeed. This methodology breaks down when users scan batches having mixed document thicknesses, such as when one scans invoices or NCR paper (very thin) along with normal office paper (thicker bond paper) or cardstock. In these batches, the maximum thickness setting a user enters may be thicker than that of the combined thickness of an invoice and a piece of bond paper that feed simultaneously, resulting in a missed multifeed. Alternatively, users may set their infrared thickness setting lower, which could then trigger false multifeeds when individual sheets of thicker paper feed through.
A Limitation
It is important to know that there is an ultrasonic multifeed limitation: with the scanner’s feeder guides all the way open (to allow for documents up to 11.7” or 297 mm in width), there is a possibility that a document less than 3” or 76 mm in width, such as a check or receipt, may not be detected if fed all the way to the left or right side of the feeder input tray. However, from our experience, these occurrences tend to be rare in most production scanning environments. Additionally, users can minimize the risk of this limitation occurring by making sure all documents are centered prior to scanning.
How to Buy
All new Böwe Bell + Howell scanners are available for sale through our superb network of specially trained VARs (value added resellers) and authorized distributors. If you are looking to buy a scanner for your organization, please contact the Böwe Bell + Howell Regional Sales Manager or International Sales Team member in your area and they will put you in touch with one of our channel partners. If you are looking to resell our scanners, please contact the Böwe Bell + Howell authorized distributor serving your area. Thank you.
