COURSE 1 DIGITAL LIBRARIES – INTRODUCTION

UNIT 3 D.L. FUNCTIONALCOMPONENTS - HARDWARE

Introduction

• Digital libraries born out of computing and network technologies• D.L. require several infrastructure facilities –

• Hardware, software, middleware, human ware• Hardware – physical artifacts of technology for storage and speed

Functional components- hardware

• Digitization devices• Storage devices• Client side devices

Digitization devices - scanners

• Scanners- peripheral devices• Optically scans images, printed text, handwritings, or an object, and

converts it to a digital image.• Typically connect via Universal Serial Bus (USB) • Software provided by the manufacturer or the operating system to

scan documents, photos or other items to the computer

Scanners- important aspects

• Capability and suitability to the material to be scanned• Should be capable to produce requisite quality of material• Image quality – resolution measured in dpi, bit depth, size and

compression• Categorized – contact and non-contact

Scanner - contact

• Contact scanners gather the spatial data of an object by physically probing it. • Contact scanners are used in the manufacturing process to probe

smaller objects for one of two purposes: • to produce replicas of a certain object or • to further refine the dimensions of an object that exists in model form.

Scanner – non contact

• Non-contact scanners do not probe their subject matter • Generally used to record the spatial data of larger objects, including

buildings, building systems, sculptures, terrains and specific spaces.• Companies and organizations that use non-contact scanning services

use either a time-of-flight 3D laser scanner or a triangulation 3D laser scanner.

Scanner – types - flatbed

• most common piece of equipment available• compatible for scanning with any personal computer.• Flatbed scanner has a glass plate on to which the source document is

laid facedown. • They have increased speed and economical to use. • They allow bi-tonal, grey scale and colour scanning. • Most of them offer resolution of 600 dpi and it is available in 24 bit

or 36 bit colour. • They are often bundled with their own scanning software Optical

Character Recognition (OCR). • Disadvantage - it relies on contact scanning and is thus unsuitable for

rare and fragile material.

Flatbed scanner

HardwareComputersNetworks / Internet ConnectivityWeb serversStorage media: Hard disk tower and CDsBack up storage CD /DVD/ writersScanners Digital cameraVideo digitizerMultimedia interfacesConvertersUPS back up

Scanners-types -drum

• The drum scanner gets its name from the clear acrylic cylinder, the drum. • It allows very high resolution. This rotates and the image read one

line at a time through photomultiplier tube technology (not CCD).• Possible to mount originals up to 11"x17"(but maximum size varies)

used for relatively big size of documents. • It offers highest resolution up to 12,500 dpi with colour gradation

and value structure• Recommended when a scanned image is going to be enlarged.• Disadvantage - extremely expensive compared to flatbed.

Drum scanner

Scanners- types – sheet feed

• Sheet fed scanner - useful for large collection of loose leaf documents and transparent material• To convert the light and dark areas into corresponding image data,

the scanner typically illuminates the sheet with a light source. • Benefit - remarkable speed and one can leave it churning through

the documents unattended up to 100 pages. • Photocopying the sheets from the bound volumes will be a better

option to use the sheet feed. • Disadvantage - unable to deal with fragile or brittle items, oversized

documents (usually size restricted to A 4).

Sheet feed scanner

Scanners- types -book

• Book scanners are usually a high quality digital camera with light sources on either side of the camera mounted on some sort of frame to provide easy access for a person or machine to flip the pages of the book. • Some models involved are V-shaped book cradles, which provide

support for book spines and also center book position automatically.• The advantage of this type of scanner is that it is very fast, compared

to the productivity of overhead scanners. • Compared with traditional overhead scanners whose prices normally

high, this type of digital camera-based book scanner is much more cost-effective.

Book scanner

Scanner – types -microfilm

• There may be separate film and fiche scanners• Automatically detect each frame and scan the image. • Necessary to see whether they accommodate 16 mm / 35 mm films

to cope with positive and negative images. • Fiche scanners are similar to sheet feeders and can take a stack of

50-100 microfiches at a time. • At higher speed it processes 200 dpi and at lower speed 600 dpi. • The flatbed scanners also provide the facility to scan microforms

using film/ strip holders.

DIGITAL CAMERA

• Sensors - the primary component of digital cameras - made out of silicon. • A digital camera takes light and focuses it via the lens onto a sensor.• The sensors are a grid of tiny photosites that are sensitive to light. • Each photosite is usually called a pixel and millions of these individual

pixels are there in the sensor of a digital camera or otherwise known as single-lens reflex camera (DSLR). • There are high level DSLRs with extreme sharpness, excellent image

quality, high density and fast image processing with anti-flicker and crop shooting features. • HDSLR is a DSLR camera with the capability for HD video recording.

DIGITAL CAMERAS (Contd.)

• The digital camera useful in case of fragile or brittle • High level digital cameras that provide 300-600 dpi and 24 bit colour. • 300 DPI is the minimum quality for an image to be digitized. But that

is just the absolute minimum for an 8 x 10. • Depending on the image size to be digitized requirements will vary

from 300-600 dpi.• 600 DPI with extra room to crop out a high quality 8”x10” without re-

sample and lower the original quality is perfect.

DIGITAL CAMERAS (Contd.)

• Bit depth - indicates the quantity of colours that are available in an image in terms of 0s and 1s or bits.• Images with higher bit depths can encode more shades or colours as

there are more combination of 0s and 1s are available. • Every colour pixel in a digital image is created through a combination

of three primary colours or colour channels – red, gree and blue.• Each colour channel have its own intensity specified by bit depth i.e.

bit per channel. • Bits per pixel bpp – is the sum of the bits in three primary colours

and represents the total colours available at each pixel.

DIGITAL CAMERA

STORAGE DEVICES

• Digital library requires huge storage space with multiple hard disks.• DL in distributed client server environment consists of hardware and

software at client as well as server side. • Server hosts databases, digital objects and search interfaces. • Clients are the machines that are used for accessing DL by users.

• Server consists of –• Adequate memory• Large space for data / file storage• Good communication capabilities• Scalability for additional storage and processing

BACK UP STORAGE SERVERS

• File server is a computer attached to a network that has the primary purpose of providing a location for shared disk access• It is designed primarily to enable the storage and retrieval of data • Storage servers are normally individual units built into a 4 U rack

mount or consist of two boxes.• They come with a host of specialized services like storage

management, configuration and extra network connections. . • The time tested file server technologies are Network Attached

Storage (NAS), Storage area networks (SAN) etc.

STORAGE SERVER

NETWORK ATTACHED STORAGE

• NAS system consists of a dedicated data storage unit connected directly to a computer network • It is like any other PC or a server, but stores only files which can be

shared by any network member. • The server comes with pre-installed operating system and a file

management system (FMS).• NAS uses 2 types of storage technologies

• Stripped-down operating system or Thin OS: The operating system if loaded on a chip of the mother board• Redundant Array of Independent/Inexpensive Disks (RAIDS): The NAS server

usually consists of multiple hard disks configured as RAID

STORAGE AREAS NETWORKS

• SAN is a network designed to attach computer storage devices such as disk array controllers and tape libraries to servers.• A SAN allows a machine to connect to remote targets such as disks

and tape drives on a network. • SAN support disk mirroring, backup and restore, archival and

retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network. • SANs can incorporate sub-networks with network-attached storage

(NAS) systems.

CLIENT SIDE HARDWARE

• In a networked environment, client is often a Web browser running on a computer that connects the end user to the network server. • Obviously, computers with more memory, hard drive space, and

processors tend to make better servers.• The clients have to be provided with devices like PCs, laptops,

tablets, mobile devices to get access. • The device should meet certain technical requirements -client side

operating system (Windows or Mac), client side browser (Internet Explorer, Google Chrome, Safari).

CLIENT SERVER

SUMMARY

• Digitization activity depends on obtaining a qualitative facsimile of the original. • This can be accomplished with a combination of software and

hardware imaging tools. • Hardware tools include storage devices, scanning devices and

computing devices at server end and client end. • There are different varieties of hardware available and there is

emerging new equipment. • The library professional has to choose the hardware suitable to the

project on hand. • Advice from computer professionals will be an added advantage.