Moire – One Reason Scans may have Lines and Dots

Back when we were testing scanners, the clue that led me to discover the low scanning resolution of one particular scanner was what I later learned was something called moire. Some images scanned just fine, but scanning an image containing a brick wall brought out a moire pattern. The pattern exacerbated the scanning pattern.

moire_brick_wall

Sample of moire on scanned image

Instead of re-explaining what others have done, I’m sharing the following two websites which I found extremely helpful in explaining the problem and providing tips for avoiding and fixing moire patterns.

Voyager 1202g Wireless Scanner

This Voyager 1202g barcode scanner has been great for our inventory project! I’ve had some questions from my co-workers about how much this scanner can really do in batch mode. Well I finally found something that says the scanner can hold 14,000 twelve digit numbers in it’s memory. Even though our barcodes are 14 digits long, I think my colleagues can rest easy…the biggest file students have scanned so far is only 321 barcodes. That’s still a lot of books to manually scan in one sitting, but our scanner can handle it.

Lessons learned: Scanner Purchasing

Several months ago, a colleague got a grant to purchase a large format (and preferably an overhead) high resolution scanner for a project related to our archives. This process did not go as smoothly as hoped. Essentially, we were misled to believe that the Book-2-Net Spirit scanner would scan at 600 dpi and it doesn’t. The images actually scan at 200 dpi despite the scanners settings that list 600 dpi as an option.  So while the scans are crisp, moire becomes a real problem with anything that already has a pattern.

So here’s what I learned:

  • Never trust the vendor at their word.
  • Never trust other library websites and insist on seeing the specs from the vendor. (There are other libraries advertising that this scanner scans at 600 dpi. It doesn’t. And at the time we originally purchased the scanner there were no specs from vendors on the internet.) I have since found a great description on another vendor’s site: http://bdm-technology.com/product/book2net-a3-spirit-overhead-scanner/
  • Document everything in writing (a lesson that goes for lots of stuff.)
  • Even if it’s not your project, but you’re the “tech” go-to person, take the extra time to research scanners yourself, ask questions about what the user really wants to use the scanner for, and create a comparison chart containing all the important specs/details.
  • Most Important! Look at the file details and properties of the output image, not just the resulting picture. This will tell you if you are really getting the scan you want.

 

Book Scan Station – Error: Disk Full

I’ve gotten several complaints that our Book Scan Station won’t scan and displays an error essentially saying the disk is full. At first I thought the users had very full usb drives, but the error was occurring after a scan but before a user chose to save the document. Looking quickly through the folders on the Book Scan Station’s computer, it didn’t look like anything was being saved to the computer. The problem persisted so I took a more detailed look. The computer said it had 130+ GB of storage but only MB’s remained as free space. So I sought to track down where all the GB’s were getting used. I found the folder of massiveness but no visible folder or document within accounted for the insane size. So I found the option to show hidden folders and presto! There was 123 GB of scan preview images stashed in Documents and Settings\Administration\Local Settings\Temp. I deleted over 30,000 files and emptied the recycle bin. Problem solved!

BookScan Station

Just a quick tidbit. There are only a few scanners that work with the BookScan station. Unfortunately, if yours breaks (like ours did) you will need to get a replacement scanner that is the same model (or perhaps a more recent model) as the one that broke.

Because the scanner is used heavily, I wanted to offer a temporary solution while the library looked into getting a new one. So, I unsuccessfully tried to attach another scanner we had in the library  to the computer.  I just got an error: “Error Code 129, Can not find the scanner” even though the scanner was properly hooked up  and installed on the computer. I suppose it’s a good sign that the scanning station gets so much use that the scanner wore out.