What Is A Scanner?

Date First Published: 9th July 2023

Topic: Computer Systems

Subtopic: Computer Hardware

Article Type: Computer Terms & Definitions

Difficulty: Easy

Difficulty Level: 3/10

CONTENTS

How Do Scanners Work?
Types Of Scanners
Scan Quality

Learn about what a scanner is in this article.

A scanner is an input device that scans hard-copy documents and converts them into a digital format. This creates an electronic version of a document that can be stored, viewed and edited on a computer system. For example, hard copies of photos can be scanned so that they can be edited and shared online. Scanners most commonly connect to computers by a USB cable and come with scanning software programs, which import data from the scanner.

Scanners vary in terms of scanning speed, resolution, compatibility, and sheet capacity. This is why it is important to look at these factors carefully before deciding to buy a certain scanner.

How Do Scanners Work?

Scanners work by capturing images, printed text, and handwriting and then converting it into digital information. This process is done by a scanning head, which uses sensors to capture the text and images as light or electrical charges. Depending on the type of scanner, the scanner moves the physical document or the scanning head. Scanners save users from having to manually type up text stored on a hard copy or taking pictures of it.

Types Of Scanners

Different types of scanners include:

Flatbed scanners - The most common type of scanner. Flatbed scanners can scan documents of different sizes, including newspaper articles, book chapters, and photographs. Flatbed scanners look like mini printers and the document is placed on a flat surface for scanning, as suggested in the word 'flatbed'. These have a cover that lifts up so that documents and photographs can be scanned. Some flatbed scanners are integrated into multifunctional printers.
Sheetfed scanners - These are smaller and more portable than flatbed scanners. Documents are placed into the automatic feeder and can be fed in bunches rather than placed one at a time on top of the platen. One page can be scanned at a time unless it is an automatic document feeder.
Handheld scanners - Also known as portable scanners, these scanners are smaller than flatbed scanners, making them more suitable for scanning whilst travelling. However, they are not as suitable for scanning photographs when high quality is needed as they do not give high-resolution scans.
Photo scanners - These are scanners specifically designed for photos. Although most scanners are capable of scanning photos, these include built-in technology to scan at higher resolutions, which is useful when sending professional photos for assessment so that they pass the quality test.
3D scanners - These are different from traditional scanners in that they collect data on the three-dimensional shape and appearance of an object and convert them into a virtual 3D object that can be stored on a computer system.

Scan Quality

Below are four important measurements of scan quality.

Resolution - The number of pixels captured by the sensor of the scanner. The higher the resolution, the more detail captured. Resolution is measured in dots per inch (DPI).
Density range - The higher the density range, the better the scanner's ability to record shadow details, tones, and brightness details in one scan.
Purity - A measure of colour quality. This measures the extent the main colour contains other colours. A decline in purity can be caused by scanner noise, optical flare, scratches, dust, and poor analogue to digital conversion.
Colour depth - The number of bits used to indicate the colour of a single pixel. The more bits per channel (bpc), the more shades of colour that can be displayed without dithering (altering) when scanning. For example, a scanner with an 8-bit colour depth can only create images in greyscale. The colour depth depends on the scanning array characteristics and is usually at least 24 bits. High quality models have 36-48 bits of color depth.