Scanners: Components and Functionality

• External components include input devices like trackballs, light pens, mice, keyboards, and scanners.

Scanners

• Scanners convert physical objects into digital images or documents and serve as input devices.
• Scanners send information to a computer but can't receive information back.
• The main components include the CCD, optics, and the interface.
• CCD (charge-coupled device) is a light-sensitive element that captures the image.
• Optics focus the light onto the CCD.
• The interface transfers image data to a computer.
• CCD sensors are collections of light-sensitive diodes converting light into an electrical charge.
• CCD sensors are the most common technology for image capture in scanners.
• Optics are a series of lenses and mirrors focusing the light beam on the document.
• The scan head contains sensors and detectors and converts reflected light from the document into digital data.
• The light source, a cold cathode fluorescent lamp (CCFL) or light-emitting diode (LED), shines light on the document.
• Scanners use a light source and a sensor to capture an image.
• The sensor converts light patterns into digital information.
• The scanner processes the image and produces a digital file, which can be stored, modified, or distributed.

Types of Scanners

• Flatbed scanners are the most common type, where the document is placed on a flat surface for scanning.
• Flatbed scanners can scan various sizes of documents and are more versatile than sheetfed scanners.
• Sheetfed scanners are designed to scan documents fed into the scanner one at a time.
• Scanners with automatic document feeders are smaller and more portable and often used in home offices or small businesses.
• Handheld scanners are portable and smaller than flatbed scanners and are designed for scanning documents on the go.

Keyboards

• A keyboard is an input device used to enter characters and functions into a computer system by pressing keys.
• It is the primary device used to enter text and typically contains keys for letters, numbers, and special characters.
• Parts include keycaps, switches, case, gaskets, plate, printed circuit board (PCB), stabilizers, and power cable.

Mouse

• A computer mouse is a small, hand-held device that controls the cursor on a computer screen.
• Used to select items, activate programs, and perform other tasks.
• Parts include right and left buttons, a scroll wheel, a USB cable, and a printed circuit board.

Light Pen

• Light pens are light-sensitive input devices that allow users to interact with a computer screen.
• Light pens are a form of light-sensitive wand used with computers' cathode ray tube (CRT) displays.
• Light pens were commonly used in the 1960s and 1980s but are no longer used due to touchscreens.
• Light pens have a light sensor that detects changes in brightness on a CRT display. When pointed at a pixel, the light sensor generates a signal.
• The advantages of light pens include more positional accuracy than touchscreens and can be used to draw text and diagrams.
• A disadvantage is that light pens can sometimes give false readings due to background lighting, requiring special implementation.

Trackball Features

• Trackballs are an alternative pointing device and are important with the rise of graphically oriented operating systems.
• The ball rests on support rollers connected to encoders which track the movement.
• The circuit board processes this data along with button inputs and converts all signals into standard mouse-type signals.
• Trackballs can be positioned away from the user's body, requiring less space to operate.
• Some trackballs have limited compatibility with certain types of software and gaming applications.