A document scanner is an input device that converts text documents or images into softcopy that can be manipulated into the computer. They scan hardcopy of either text or images to convert them mostly into digital images. They use a light sensor to do the scanning.
The main document scanners are hand-held, flat-bed, drum, sheet-fed, and smartphone scanners. They scan documents by passing a sensing mechanism over the document which is then converted to a digital image.
Types of document scanners
In this article, we will discuss 5 types of document scanners which include:
- Handheld scanners
The user holds the scanner and passes it along to the document or image that they are scanning. It should be moved slowly to capture all the details and to get the best quality.
They are portable, cheaper than flatbeds and they are mostly met for home use or scanning of small documents. They are used in retail shops to scan barcodes for stock record management.
- Flatbed scanners
With a flatbed scanner instead of the user holding the document in their hand, the document is placed onto the scanner just like a photocopier then the scanner moves the light along the document to scan. They are bigger than handheld and more expensive but they can scan a larger document and the user is less involved.
- Drum scanners
These are big scanners that are used to capture large images and more details. This means they are large in size and expensive. They are mostly used by professionals. While other types of scanners cannot scan transparent documents drum can achieve that. They offer the best resolution and clarity of output.
- Sheet-Fed Scanners
It is a type of scanner that papers are fed to enable it to scan. Only used when dealing with loose papers. It cannot scan items such as books or other bound multi-page documents.
- Smartphone application scanner
The latest technology is where the smartphone digital camera is converted into a handheld scanner. With applications like Adobe Scan, you can comfortably scan your document using a smartphone. They are more convenient since you have your smartphone anywhere you go. However, the quality of the scan is not good.
How a document scanner works
First, the user put the document to be scanned in the right place on the scanner. The scanner passes light over the document like in a photocopier machine. The light is then passed to a light sensor which determines how much light is reflected from each point.
Blank spaces are brighter than those with content which means they reflect more light back. The sensor converts this into light electrical signals which are then converted into digital for computer processing. If the scanner is to capture a colored document the signals are passed to the color filter to get the appropriate colors. Read more about how they work
Parts of a document scanner and their functions
- Charge-coupled device (CCD) array: this is an IC circuit that has sensors and is used for imaging to capture the document that is being scanned. It ensures the document is converted to a digital image.
- Lamp: This is used to illuminate the document so that it can be clear. It ensures all document content is captured with clarity.
- Mirrors: they are used to reflect the elements in the documents and focus them where they can be recorded.
- Cover: this is the out cover that protects the document from external light when scanning. It is always recommended to cover the document when scanning for quality output.
- Scan head: this moves from one side of the scanner as it scans the document. It moves together with other scanning parts such as the lamp and CCD.
- Connectors: there are 2 types of connectors in a scanner. Power supply connector to power the device. Data connectors are mostly USBs that transfer scanned data. In some scanners USB act as a power and data connector.
Factor to consider when buying a document scanner
- Type of scanner: Depending on the work you intend to do with the scanner you should choose one that will meet your needs. If you intend to scan large documents frequently then flatbed,sheet-fed or drum will be the best.
- Quality of scan: Different scanners come with different numbers of pixels that they can be able to capture. For a clear scan select one with high resolution, one that can capture more pixels per inch. Again flatbed is more likely to give a good quality scan than a handheld for the ordinary user. For professional users, the drum will be worth the investment. High quality means it requires more storage space on the hard disk and is more expensive.
- Cost: You cannot buy what you cannot afford, so check your budget before going for a scanner. Remember not to compromise the quality by going for something that is cheap and may not meet your needs.
- Portability: If your work involves moving around them it would be appropriate to get a handheld because it is easier to carry around.
- Colored or black and white: Depending on what you want to scan, you can consider getting a scanner that can give you black and white only or one that can give you colored images. Most of the scanners are colored scanners.
Advantages of a document scanner
- They are used to digitalize documents that can be edited and shared.
- They are very convenient for document sharing. With smartphone scanners, users can scan the document anywhere at any time.
- They are very simple to use. Most of the scanners a plug-and-play and even a novice user can operate them.
Disadvantages of a document scanner
- Depending on the quality of the scanner will determine the quality of the output document.
- Drum scanners can be expensive for the ordinary user.
- The scanned document mostly will require some after-scan editing to improve its quality. The scanned image also takes up a big storage capacity.
- Drum and sheet-fed scanners can take up a big office space.
- They will require maintenance to ensure they work optimally.