Scanner Buying Guide

Benefits of a Scanner (back to top)

In today's computer-driven world, it is a dream of every organization, burdened by decades of piling files and rooms full of heaps of documents, to have a truly 'paperless office'. Would it not be a great idea to have the contents of all the documents stored digitally on a computer where retrieval is fast and simple? This would serve a double advantage of freeing up a lot of space in the office and also avoiding the risk of important documents being exposed to the elements or getting destroyed in the event of a fire. The invention of a versatile gadget like the scanner has resolved this long pending issue. Now amongst its many users, every document in the office could be scanned and saved on disc for future use.

Even for personal use at home, the scanner has become an indispensable accessory on most computer workstations, alongside the printer. There are numerous occasions when people have wanted to share photographs shot on analog cameras with friends and relatives. Before, this task required the usage of the negative to develop another copy of the photo which would then have to be mailed to the recipient. Scanners now allow one to scan and save the photo as an image file on the computer, which could then be emailed, no negatives required!

With scanner accessories such as transparency adaptors (XPA), even negative images can be scanned to generate the positive output. Not to mention an Automatic Document Feeder (ADF) and an Automatic Photo feeder (ADF) attachment allow scanning of a number of individual documents or photos continuously without any user intervention.

1. How Scanners Function (back to top)

For exploration of how a scanner works, we will consider the flatbed scanner for purposes of this Buying Guide. The flatbed scanner is an ideal model as this is the type of scanner most used across the world and the technology used in this scanner is the same as that used in most all other scanners. The flatbed scanner consists of a transparent glass forming the upper surface of a shallow box. This glass can be covered by a hinged cover, the undersurface of which is coated with a white plastic sheet. The document to be scanned is placed face down on the glass and then covered by lid. The clear white face of the cover enables the scanner sensor to detect the color variations on the document to get correct image. A lamp which passes beneath the glass illuminates the document to be scanned in specific miniscule increments. This lamp can be either a cold cathode fluorescent lamp or a xenon lamp.

The actual electronic capture of the data is carried out by the Charge-Couple Device (CCD), which is an array of photosensitive diodes, having the power to convert light energy into electricity. An apparatus consisting of precisely angled mirrors, lens, a filter, and the CCD make up the scan head. The scan head moves across the document pulled by a belt powered by a stepper motor. The successive images of the parts of the document exposed to the scan head are reflected by the mirrors onto a lens, which in turn focuses the image through the filter onto the CCD.

Before focusing the image on the CCD, the lens splits the image into three smaller replicas, each replica passing through a color filter that separates the red, green, and blue colors. Each colors data falls on a distinct part of the CCD. Information from all the three portions of the CCD is superimposed to form a single full color image. Depending on the light intensities, a varying electric charge is generated, which results in a replication of the original image.

Basically, the scanner is an ingenious device that uses the CCD technology to electronically 'read' images and text on a paper sheet inserted into the scanner, convert this data into digital format and allow the user to save this image on the computer as either an image file or a text file. Scanners can be connected to a computer through a USB port or a Parallel port, this connectivity acting as the mode for data transfer between the scanner and the computer. Given below are a few distinguishing features of the main types of scanners:

• Flatbed Scanners: These are the most commonly used scanners, also called desktop scanners. They have a glass surface with a cover over it. The sheet to be scanned is placed face down on the glass face and scanning takes place after the cover is closed. The detailed description of this process is provided further below in this guide. These scanners support scanning of A4 and legal size documents.

 

• Handheld Scanners: Using the same technology as flatbed scanners, these scanners are not as large and cannot scan large documents as the scanning heads are just around 4-5 inches wide. An example of a handheld scanner is the scanner used at payment counters of departmental stores to read information from bar codes.

 

• Sheetfed Scanners: In this type of scanner, unlike the method used in flat bed scanners, the document to be scanned is actually moved over the scanning head, which remains stationary. Such scanners are smaller than flatbed scanners.

 

• Slide Scanners: This type of scanner, also called a negative or transparency scanner, creates positive images from negatives, slides, or transparencies.

 

• Drum Scanner: These scanners, used mostly in the publishing industry, work using a Photomultiplier Tube (PMT). The document to be scanned rolls around a glass cylinder having a photo sensor at the center that separates light reflecting from the document into three distinct beams. After passing through a color filter, each beam is converted into an electrical signal in the PMT.

2. Purchasing Criteria (back to top)

Buying a scanner is can be a tricky proposition considering the numerous technological innovations. Below we have listed a few parameters you may want to consider when buying a scanner:

• Resolution: The quality of the scanned image depends on the resolution offered by the gadget, which is a measure of the number of pixels contained within an image. Resolution is measured in pixels per inch. Scanners normally have two resolutions: optical and interpolated. While optical resolution affects the image quality directly, interpolated resolution offers an advantage only during image magnification.

 

• Bit-Depth: This is a count of the number of bits per pixel. Higher the bit-depth better is the image quality. A scanner should have a bit depth of at least 24.

 

• Speed: For high volume scanning the speed of the scanner is very important. The speed depends on the sensitivity of the CCD and the movement and stability of the stepper motor.

 

• Optical Character Recognition (OCR): This is a feature of the scanner to be able to recognize characters in a text document and scan the same to a word processing application such as MS Word, which can then be edited. This is a very useful feature and most scanners today offer this feature.

 

• Automatic Document Feeder (ADF): The ADF is an appendage to the lid of the scanner which enables a sheaf of A4 sized or legal sized documents to be placed at together with each paper rolling into the mechanism and getting scanned successively.

 

• Automatic Photo Feeder: This accessory is similar to the ADF except that it is smaller sized to fit only photos.

 

• Transparency Adaptor: This is an ingenious contraption that uses a unique software program to generate the positive image of a negative, slide, or transparency.

3. Making the Decision (back to top)

Following a thorough understanding of your requirements and preferences with regards to the various features mentioned above, you should compare the different scanners available in the market that match those requirements offered by leading brands at a comparison shopping site such as www.smarter.com.

A scanner is a very useful machine that blends an innovative hardware with a multipurpose software application. When buying a scanner, we recommend that you analyze the pros and cons of a particular scanner from different manufacturers and also consult with present scanner owners if you know any. It would be a good idea to check the scanner you purchase for the parameters mentioned above, with the OCR, XPA, and APF being the 'must-have' functionalities.

All scanner manufacturers offer warranties. Since the internal parts of a scanner are delicate and can be damaged through rough handling, it would make sense to confirm what the warranty covers prior to purchase. Also, we recommend that you ask the dealer about the after sales service facilities and technical support. Be assured that with proper maintenance, the scanner will live up to its reputation of being one of the most important computer accessories.

Buying a good scanner requires investment of a reasonable amount of time in researching and evaluating the various contenders. The trick is to strike the perfect balance between price and functionality; and the best way to begin is to find out exactly what your needs are. Hopefully, you now have more information to help make your purchasing decision more informed, now go find a great scanner!