Optical Input Devices

For a long time, futurists and computer scientists have had the goal of enabling computers to "see." may never see in the same way that humans do, but optical technologies allow computers to use light as a source of input. These tools fall into the category of optical devices.

Bar Code Readers

Bar code readers are one of the most widely used input devices. The most common type of bar code reader is the flatbed model, which is commonly found in supermarkets and department stores (see Figure 2B.7). Workers for delivery services, such as F dEx also use handheld bar code readers in the field to identify packages (see Figure 2B.8). These devices read bar codes, which are patterns of printed bars that appear on product packages. The bar codes identify the product. The bar code reader emits a beam of light-frequently a laser beam--that is reflected by the bar code image. A light-sensitive detector identifies the bar code image by recognizing special bars at both ends of the image. These special bars are different, so the reader can tell whether the bar code has been read right-side-up or upside down. After the detector has identified the bar code, the individual bar patterns into numeric digits- code the computer can understand. The reader then feeds the data into the computer, as though the number had been raped on a keyboard.

Image Scanners and Optical

Character Recognition (OCR) The bar code reader is a special type of image scanner. Image scanners (also called scanners) convert any printed image into electronic form by shining light onto the image and sensing the intensity of the light's reflection at every point. 

Color: scanners use filters to separate the components of color into the primary additive colors (red, green, and blue) at each point. Red, green, and blue are known as primary additive colors because they can be combined to create any other color. Processes that describe color in this manner are said to use RGB color. 

The image scanner is useful because it translates printed images into an electronic format that can be stored in a computer's memory. Then you can use software to organize or manipulate the electronic image. For example, if you a photo, you can use a graphics program such as Adobe Photoshop to increase the contrast or adjust the colors. If you have scanned a text document, you mean want to use optical character recognition (OCR) software to translate the image into te. you can edit. 

When the scanner first creates an image from a page, the image is stored in the computer's memory as a bitmap. A bitmap is a grid of den each dot represented by one or more bits. The job of OCR software is to translate that array of dots into text that the computer can interpret as letters and numbers that array numbers.

To translate bitmaps into text, the OCR software looks at each character and tries to match the character with its own assumptions about how the letters should look. Because it is difficult to make a computer recognize an unlimited number of typefaces and fonts, OCR software is extremely complex and not always 100 percent reliable. 

Despite the complexity of the task, OCR software has become quite advanced. Today, many programs can decipher a page of text received by a fax machine. In fact, computers with fax modems can use OCR software to convert faxes directly into text that can be edited with a word processor. Scanners come in a range of sizes from handheld models to flatbed scanners that sit on a desktop. Handheld scanners are more portable but typically require multiple passes to scan a single page because they are not as wide as letter-size paper. Flatbed scanners offer higher-quality reproduction than do handheld scanners and can scan a page in a single pass. (Multiple scans are sometimes required for color images, however. ) To use a flatbed scanner, you place the printed image on a piece of glass similar to the way you place a page on a photocopier. In some medium-sized scanners, you feed the sheet to be scanned through the scanner, similar to the way you feed a page through a fax machine.