Tutorial 2- Flatbed Input Devices CE406 – Computer Peripherals Workshop16BCE059Qasim Burhan BhatiaAbstractThis report briefly summarises the presentation given by 16BCE048 and 16BCE056 on Flatbed Input Devices and a few other topics they may have left out.IntroductionFlatbed Input Devices are scanners which are used to scan documents. Documents can be scanned without moving the document and everything in the document is retrieved. The technology behind scanning is divided into four types:Charged Coupled Device (CCD)Contact Image Sensor (CIS)Hand ScannersSmartphone Camera ScannerModern scanners can use the TCP/IP protocol suite to communicate in a network and hence a single scanner can be shared throughout the network. They can scan large documents and are more reliable than Handheld scannersFunctioning of ScannersAll scanners work on the same process, Light is shone onto the document, the light which is reflected is directed to a image sensor to be decoded. This image information is processed and stitched together to form the document in digital form. The interface between the device and computer is handled by a device driver which the manufacturer provides either embedded in the device or on a separate disk. Additional software may be bundled with the scanner which is used improve the quality of scanned documents and export the file into various file formats. The most common of them are JPG(for Images) and PDF(for Documents). Now we discuss the four technologies in brief.Charged Coupled Device ScannerThe CCD scanner uses a image sensor and a lens to focus the reflected light on to it. The document is placed on the glass surface, a moving light source shines a light onto document. The light is then focused onto the sensor using mirrors and lenses.The diagram shows the working of a typical CCD Scanner. Advantage of CCD scanners is their High SNR, whereas their large form factor, fragile design, and low optical resolution (Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.)Contact Image Sensor ScannerThe CIS scanner employes an array of sensors which are in almost direct contact with the document. Due to the small size of the sensors, it consumes small amount of power and are smaller than CCD scanners. This fact also causes lower image quality and lack of depth, so they are not useful if the document is not perfectly flat.The following diagram shows the working of a generic CIS Scanner, as the scan head moves, it acquires the document and forwards it for processing. Its attractive due to its low cost and portable design.Hand ScannerA hand scanner is handheld and requires a steady hand to operate. The document is laid flat and and the scanner is moved slowly over the document to scan it. It can cause bad scans if users don’t have a steady hand or move through the document too fast. Software enhancements may be used to fix such errors.Smartphone Camera ScannersModern Smartphones have powerful cameras and processing power to take images of documents and turn them into professional looking scanned documents. Many apps are available of the Google Play Store TM and Apple Store ™ that produce amazing scanned documents and provide further tools such as mailing documents and uploading files to cloud storage services. I too use such an app to scan and save exam papers for future reference.