SCANNER
A scanner can be defined as a device that is responsible for analyzing an image (or) on an object and later connecting it to digital content. The flatbed scanner is the basis of all the scanners that are used currently. Therefore, the workings of a scanner can be better understood by learning the workings of a flatbed scanner.
History of Flatbed Scanner
In this Modern era, scanners are considered the successors of early telephotography and fax input devices. The Pantelegraph was an early form of the facsimile machine transmitting over normal telegraph lines developed by Giovanni Caselli, used commercially in the 1860s, that was the first such device to enter practical service.
It used electromagnets to drive and synchronize the movement of pendulums at the source and the distant location, to scan and reproduce images. It can transmit handwriting and signatures within an area of up to 150 × 100 mm.
They send a linear analog AM signal through the standard telephone voice lines to receptors, which synchronously print the proportional intensity on special paper. Color photos were sent as three separate RGB-filtered images consecutively, but only for special events due to transmission costs.
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Working of Flatbed Scanner
A flatbed scanner is one of the most commonly used input devices for scanning documents. It is similar to a Xerox machine. It is a box that consists of a transparent glass plate at the top and a covering lid. In a flatbed scanner, a document can be scanned by placing it onto the glass plate and closing the lid.
This document is then enlightened by using a lamp (i.e., Cold Cathode Fluorescent Lamp (CCFL) is mostly preferred).
And after this, the scan head is moved parallelly onto the document. A scan head (or scanner head) consists of mirrors, lens, CCD (Charge Coupled Device), and filters. The scan head functions through a stepper motor which is tied with a belt and a stabilizer bar is attached to it for ensure that there is no deviation in the past (i.e., Completing the single scan of the entire document).
As the head is moving slowly, the document’s image is reflected back through mirrors. These mirrors are placed in such a way that the reflected image strikes the smaller surface. The number of mirrors can be 2 or 3 (i.e., 2-way mirrors or 3-way mirrors) depending on the design of the device.
The mirror that receives the image at the last will reflect the image onto the lens which then passes it through a filter and focuses on the CCD array. The CCD array is a set of small light-sensitive diodes (photosites) that is used for the conversion of light to electrical charges T hight with high intensity strikes the photosite then a huge amount of electrical charges will get accumulate at that particular location.
Basically, scanners make use of three pass-scanning methods. In this method, every individual pass uses a color filter (i.e., red or green or blue). These colors are used among the lens and CCD array. Upon completion of three passes, the software of the scanner unites three filtered images into one fully colored image. But, today scanners make use of the single-pass method.
In this method, the image gets split into three smaller segments. Every individual segment is passed through a color filter (i.e., red or green or blue) across the different CCD array sections Then the scanner unites these three segments of data into one fully colored image. Thus, the obtained resultant image is forwarded to the system
