How do Photo Scanners Work

Scanners over the years have become an essential machine at any home or office. While the multipurpose scanners have made significant inroads to our premises, the recent years have seen a steady rise in demand of dedicated scanners for merely scanning images.

One of the most essential reasons for the rise has been the clarity and advanced features these dedicated scanners come with. They are pretty similar to the traditional scanners being it the multipurpose or standalone scanners but are available with additional features. The following articles puts some light on the manner in which these photo scanners work based on their types.

Types of Photo Scanners

Flatbed photo scanners are mostly the preferred and widely sold option across the globe. They are versatile and are preferred due to ease of usage. The sheet-fed scanners do the task conveniently but function completely different than the flatbed variants. In the flatbed scanners, the photos scanned remains immobile while the sheet-fed scanners move the images from top to bottom while scanning.

Another variant that has emerged as a popular alternative recently are the handheld photo scanners. These are essentially popular due to the convenience and portability.

They can be easily carried from a place to the other and is powered by batteries. However, the quality of scanning is still debatable when compared to the output delivered by the other alternatives. One of the other less known variants particularly used by the publishing industry is the drum scanners that are expensive and capable of capturing detailed images.

The technology used here is termed as photomultiplier tube where the photo that is used is mounted on the glass cylinder that has a sensor at the center. The sensor splits the light that bounces from the image in three different beams. Consequently, each beam is sent through the color filter inside the photomultiplier tube that changes the light into electrical signals.

The Principle of Scanning

The basic premise of a photo scanner is to analyze the image and process it in the desired way. The concept of optical character recognition or OCR captures image and text that allows a person to save information on the computer. The recent technology allows the users to edit, enhance, and print high-quality images after scanning.

Core Component

Control circuitry or CCD is the common technology that is used for capturing images using image scanners. The CCD powered machines collect tiny light-sensitive diodes that convert light (photons) into electrical charge (electrons). Also known as Photosites, these diodes are sensitive towards light and the brighter the light hits the photo site, the better is the electrical charge that accumulates at the site.

Process of Scanning

The following are the steps that a photo scanner goes through while the process of scanning is performed.

Stage1

The photo has to be placed over the glass plate, and cover of the scanner is closed. Usually, the covers are white, but some of the recent products have also come in black. These covers offer a uniform background to facilitate the scanner software to use them as a reference point to determine the size of the image.

Stage 2

After the button for scanning or the option of scanning through the software is clicked, a lamp lights up illuminating the image. The lamps in the new scanners use either a xenon lamp or a cathode fluorescent lamp (CCFL). The older variants had been using standard fluorescent lamps.

Stage 3

The scan head that comprises of mirrors, lens, filter and CCD array moves slowly across the entire image through the belt that is fitted with a stepper motor. The scan head is also attached to the stabilizer bar for ensuring that during the process of scanning there is no deviation. Referred to as pass, it signifies that the scan head has completed the scanning of the image from top to bottom.

Stage 4

In this stage, the photo gets reflected through an angled mirror on to another mirror. Most scanners come with two mirrors while some are fitted with three. Each mirror is position in a curved angle that focuses on the image that is reflected by a smaller surface. The last mirror is used to reflect the image on the lens which later focuses on the image through the filter over the CCD array.

Stage 5

The scanner further uses a filter and lens arrangement that varies from one type to the other. Some scanners use three pass scanning approach wherein each pass utilizes different color filters in between the lens and the CCD array. Once the three passes get completed, the scanner software assembles the filtered images in a single full-colored image.

However, the scanners available today adopt a single pass method where the lens splits the photo into three small versions. Each of these versions passes through the color filter which may be green, red or blue on the discrete section of the CCD array. The photo scanner later combines the data from these three parts in a single full colored image.

Latest Development in the Imaging Array Technology

One of the recent imaging array technology that has gained popularity due affordability is the contact image sensor. The CIS technology replaces the CCD array, filters, mirrors, lenses, and lamps with the rows of red, green and blue LEDs.

This image sensor mechanism comprises of 300 to 600 sensors that span over the entire width of the scanned area. While the image gets scanned, the fitted LEDs combine to offer white light.

The row of sensors captures the illuminated image. CIS scanners are cost-effective, light in weight and much thinner as compared to the previously launched technologies. However, the quality of resolution found in these printers is comparatively lower when compared to the CCD scanners.

Concluding Remarks

The most important role of using a dedicated photo scanner is to scan physical images and preserve them to be used in a digitized form. Different technologies power these scanners and advancement in technology has made the output better with every release. The photo scanners are capable of editing, modifying and even correcting damaged images in a digitized form.

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