Key information Section 3

Input devices such as scanners and cameras allow you to capture and copy images into a computer.

A scanneris a peripheral that reads images and converts them into electronic codes which can be understood by a computer. An optical scanner uses light-sensing equipment to convert images such as a picture or text into a digital data that can be manipulated by a computer. For example, a photo can be

scanned into a computer and then included in a text document created on that computer.

There are different types.

A flatbed (desktop) scanner is built like a photocopier and is for use on a desktop; it can capture text, colour images and even small 3D objects. A flatbed scanner is usually composed of a glass pane (or platen), under which there is a bright light which illuminates the pane. Images to be scanned are placed face down on the glass, an opaque cover is lowered over

it to exclude ambient light, and the sensor array and light source move across the pane, reading the entire area. An image is therefore visible to the detector only because of the light it reflects.

	A film scanner is used to scan film negatives or 35 mm slides - pictures on photographic film, mounted in a frame.
Hand held scanners are small manual devices that are passed manually across the surface of the image to be scanned. Scanning in this manner requires a steady hand, as an uneven scanning rate would produce distorted images. The use of hand held scanners remains popular for many applications, including industrial design,
reverse engineering, inspection & analysis, digital manufacturing and medical applications.
	Barcode scanners read barcodes on the products sold in shops and send the price to the computer in the cash register. Barcodes consist of a series of black and white stripes used to give products a unique identification number. They are used to identify items for stock control and pricing.
	A pen scanner looks like a pen; you can scan text, figures, barcodes and handwritten numbers.

The resolution of a scanner is measured in dpi or dots per inch. For example, a 1,200 dpi scanner gives clearer, more detailed images than a 300 dpi scanner.

Most scanners come with Optical Character Recognition software. OCR allows you to scan pages of text and save them into your word processor; they can then be edited.

A digital camera doesn't use film. Photos are stored as digital data (bits made up of 1s and 0s), usually on a tiny storage device known as a flash memory card. You can connect the camera or memory card to a PC and then alter the images using a program like Adobe Photoshop, or you can

view the images on a TV set. Many printers have a special socket so that you can print images directly from a memory card or camera.

A camcorder(camera+recorder), or digital video camera, records moving pictures and converts them into digital data that can be stored and edited by a computer with special video editing software. Digital video cameras are used by home users to create their own movies, or by professionals in computer art and video conferencing.

Webcams (short for Web cameras) let you send and receive live video pictures through the Internet. They're primarily used for video conferences - video calls - but they can be used to record photos and video onto your hard disk.

The resolution of webcams is expressed in megapixels (million pixels). Webcams connect to the PC via a USB (universal serial bus)or FireWire port; they display video at 24 to 30 frames (pictures) per second. Some include a headset witha microphone and earpiece.

Дата добавления: 2014-12-27