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5,401 | Some microphones are intended for testing speakers, measuring noise levels and otherwise quantifying an acoustic experience. These are calibrated transducers and are usually supplied with a calibration certificate that states absolute sensitivity against frequency. The quality of measurement microphones is often referr... |
5,402 | Measurement microphones are generally scalar sensors of pressure; they exhibit an omnidirectional response, limited only by the scattering profile of their physical dimensions. Sound intensity or sound power measurements require pressure-gradient measurements, which are typically made using arrays of at least two micro... |
5,403 | To take a scientific measurement with a microphone, its precise sensitivity must be known . Since this may change over the lifetime of the device, it is necessary to regularly calibrate measurement microphones. This service is offered by some microphone manufacturers and by independent certified testing labs. All micro... |
5,404 | Depending on the application, measurement microphones must be tested periodically and after any potentially damaging event, such as being dropped or exposed to sounds beyond the acceptable level. |
5,405 | A microphone array is any number of microphones operating in tandem. There are many applications: |
5,406 | Typically, an array is made up of omnidirectional microphones distributed about the perimeter of a space, linked to a computer that records and interprets the results into a coherent form. |
5,407 | Windscreens provide a method of reducing the effect of wind on microphones. While pop-screens give protection from unidirectional blasts, foam "hats" shield wind into the grille from all directions, and blimps, zeppelins, and baskets entirely enclose the microphone and protect its body as well. The latter is important... |
5,408 | The shielding material used – wire gauze, fabric or foam – is designed to have a significant acoustic impedance. The relatively low particle-velocity air pressure changes that constitute sound waves can pass through with minimal attenuation, but higher particle-velocity wind is impeded to a far greater extent. Increasi... |
5,409 | Since all wind noise is generated at the first surface the air hits, the greater the spacing between the shield periphery and microphone capsule, the greater the noise attenuation. For an approximately spherical shield, attenuation increases by the cube of that distance. With full basket windshields there is an additi... |
5,410 | Since turbulence at a surface is the source of wind noise, reducing gross turbulence can add to noise reduction. Both aerodynamically smooth surfaces, and ones that prevent powerful vortices being generated, have been used successfully. Historically, artificial fur has proved very useful for this purpose since the fibe... |
5,411 | Modern scanners typically use a charge-coupled device or a contact image sensor as the image sensor, whereas drum scanners, developed earlier and still used for the highest possible image quality, use a photomultiplier tube as the image sensor. A rotary scanner, used for high-speed document scanning, is a type of dr... |
5,412 | Digital cameras can be used for the same purposes as dedicated scanners. When compared to a true scanner, a camera image is subject to a degree of distortion, reflections, shadows, low contrast, and blur due to camera shake . Resolution is sufficient for less demanding applications. Digital cameras offer the advantages... |
5,413 | Scans are usually downloaded by a computer the unit is attached to. Some scanners are able to store scans on standalone flash media . |
5,414 | In the biomedical research area, detection devices for DNA microarrays are called scanners as well. These scanners are high-resolution systems , similar to microscopes. The detection is done via CCD or photomultiplier tubes. |
5,415 | Modern scanners are considered the successors of early telephotography and fax input devices. |
5,416 | The pantelegraph was an early form of 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 dist... |
5,417 | Édouard Belin's Belinograph of 1913, scanned using a photocell and transmitted over ordinary phone lines, formed the basis for the AT&T Wirephoto service. In Europe, services similar to a wirephoto were called a Belino. It was used by news agencies from the 1920s to the mid-1990s and consisted of a rotating drum with a... |
5,418 | Drum scanners capture image information with photomultiplier tubes , rather than the charge-coupled device arrays found in flatbed scanners and inexpensive film scanners. "Reflective and transmissive originals are mounted on an acrylic cylinder, the scanner drum, which rotates at high speed while it passes the object ... |
5,419 | The drum scanner gets its name from the clear acrylic cylinder, the drum, on which the original artwork is mounted for scanning. Depending on size, it is possible to mount originals up to 20 by 28 inches , but the maximum size varies by manufacturer. "One of the unique features of drum scanners is the ability to contro... |
5,420 | While drum scanners are capable of scanning both reflective and transmissive artwork, a good-quality flatbed scanner can produce good scans from reflective artwork. As a result, drum scanners are rarely used to scan prints now that high-quality, inexpensive flatbed scanners are readily available. Film, however, is wher... |
5,421 | The situation as of 2014 was that only a few companies continued to manufacture and service drum scanners. While prices of both new and used units dropped from the start of the 21st century, they were still much more costly than CCD flatbed and film scanners. Image quality produced by flatbed scanners had improved to t... |
5,422 | This type of scanner is sometimes called a reflective scanner because it works by shining white light onto the object to be scanned and reading the intensity and color of light that is reflected from it, usually a line at a time. They are designed for scanning prints or other flat, opaque materials but some have availa... |
5,423 | "A flatbed scanner is usually composed of a glass pane , under which there is a bright light which illuminates the pane, and a moving optical array in CCD scanning. CCD-type scanners typically contain three rows of sensors with red, green, and blue filters." |
5,424 | Contact image sensor scanning consists of a moving set of red, green, and blue LEDs strobed for illumination and a connected monochromatic photodiode array under a rod lens array for light collection. "Images to be scanned are placed face down on the glass, an opaque cover is lowered over it to exclude ambient light, ... |
5,425 | Sheetfed scanners do not have a scanning bed, have a mechanism to feed paper through the scanner, and some are capable of scanning several sheets at once using an ADF. A printer cartridge, the Canon IS-22, was released that could be used to convert an inkjet printer into a sheetfed scanner. |
5,426 | These scanners have an overhead scanning mechanism that moves a beam of light, or have a fixed camera, and a scanning area defined by a mat to easily scan books. |
5,427 | This type of scanner is sometimes called a slide or transparency scanner and it works by passing a narrowly focused beam of light through the film and reading the intensity and color of the light that emerges. "Usually, uncut film strips of up to six frames, or four mounted slides, are inserted in a carrier, which is m... |
5,428 | Scanners are available that pull a flat sheet over the scanning element between rotating rollers. They can only handle single sheets up to a specified width, typically 8.5 inches to accommodate both US letter and standard A4 sizes, but can be very compact, just requiring a pair of narrow rollers between which the docu... |
5,429 | A roller scanner may be embedded inside a computer keyboard, with a footprint no larger than a computer keyboard. |
5,430 | Some roller scanners are portable, powered by batteries and with their own storage, eventually transferring stored scans to a computer over a USB or other interface. |
5,431 | 3D scanners collect data on the three-dimensional shape and appearance of an object. |
5,432 | Planetary scanners scan a delicate object without physical contact. |
5,433 | Hand scanners are moved over the subject to be imaged by hand. There are two different types: document and 3D scanners. |
5,434 | Hand-held document scanners are manual devices that are dragged across the surface of the image to be scanned by hand. Scanning documents in this manner requires a steady hand, as an uneven scanning rate produces distorted images; an indicator light on the scanner indicates if motion is too fast. They typically have a ... |
5,435 | Inexpensive portable battery-powered or USB-powered "glide-over" hand or pen scanners, typically capable of scanning an area as wide as a normal letter and much longer remain available as of 2014. Some computer mice can also scan documents. |
5,436 | Handheld 3D scanners are used in industrial design, reverse engineering, inspection and analysis, digital manufacturing, and medical applications. "To compensate for the uneven motion of the human hand, most 3D scanning systems rely on the placement of reference markers, typically adhesive reflective tabs that the scan... |
5,437 | Image scanners are usually used in conjunction with a computer which controls the scanner and stores scans. Small portable scanners, either roller-fed or "glide-over" hand-operated, operated by batteries and with storage capability, are available for use away from a computer; stored scans can be transferred later. Many... |
5,438 | The higher-resolution cameras fitted to some smartphones can produce reasonable quality document scans by taking a photograph with the phone's camera and post-processing it with a scanning app, a range of which are available for most phone operating systems, to whiten the background of a page, correct perspective disto... |
5,439 | Smartphone scanner apps can be broadly divided into three categories: |
5,440 | Document scanning apps primarily designed to handle documents and output PDF, and sometimes JPEG, files |
5,441 | Photo scanning apps that output JPEG files, and have editing functions useful for photo rather than document editing; |
5,442 | Barcode-like QR code scanning apps that then search the internet for information associated with the code. |
5,443 | Color scanners typically read RGB data from the array. This data is then processed with some proprietary algorithm to correct for different exposure conditions, and sent to the computer via the device's input/output interface . |
5,444 | Color depth varies depending on the scanning array characteristics, but is usually at least 24 bits. High-quality models have 36-48 bits of color depth. |
5,445 | Another qualifying parameter for a scanner is its resolution, measured in pixels per inch , sometimes more accurately referred to as Samples per inch . Instead of using the scanner's true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher ... |
5,446 | "Effective resolution" is the true resolution of a scanner, and is determined by using a resolution test chart. The effective resolution of most all consumer flatbed scanners is considerably lower than the manufactures' given optical resolution. Example is the Epson V750 Pro with an optical resolution given by manufa... |
5,447 | Manufacturers often claim interpolated resolutions as high as 19,200 ppi; but such numbers carry little meaningful value because the number of possible interpolated pixels is unlimited, and doing so does not increase the level of captured detail. |
5,448 | The size of the file created increases with the square of the resolution; doubling the resolution quadruples the file size. A resolution must be chosen that is within the capabilities of the equipment, preserves sufficient detail, and does not produce a file of excessive size. The file size can be reduced for a given r... |
5,449 | Purity can be diminished by scanner noise, optical flare, poor analog to digital conversion, scratches, dust, Newton's rings, out-of-focus sensors, improper scanner operation, and poor software. Drum scanners are said to produce the purest digital representations of the film, followed by high-end film scanners that use... |
5,450 | The third important parameter for a scanner is its density range or Drange . A high-density range means that the scanner is able to record shadow details and brightness details in one scan. Density of film is measured on a base 10 log scale and varies between 0.0 and 5.0, about 16 stops. Density range is the space t... |
5,451 | Consumer-level flatbed photo scanners have a dynamic range in the 2.0–3.0 range, which can be inadequate for scanning all types of photographic film, as Dmax can be and often is between 3.0d and 4.0d with traditional black-and-white film. Color film compresses its 12 stops of a possible 16 stops into just 2.0d of spac... |
5,452 | By combining full-color imagery with 3D models, modern hand-held scanners are able to completely reproduce objects electronically. The addition of 3D color printers enables accurate miniaturization of these objects, with applications across many industries and professions. |
5,453 | For scanner apps, the scan quality is highly dependent on the quality of the phone camera and on the framing chosen by the user of the app. |
5,454 | Scans must virtually always be transferred from the scanner to a computer or information storage system for further processing or storage. There are two basic issues: how the scanner is physically connected to the computer and how the application retrieves the information from the scanner. |
5,455 | The file size of a scan can be up to about 100 megabytes for a 600 DPI 23 x 28 cm uncompressed 24-bit image. Scanned files must be transferred and stored. Scanners can generate this volume of data in a matter of seconds, making a fast connection desirable. |
5,456 | Scanners communicate to their host computer using one of the following physical interfaces, listing roughly from slow to fast: |
5,457 | During the early 1990s professional flatbed scanners were available over a local computer network. This proved useful to publishers, print shops, etc. This functionality largely fell out of use as the cost of flatbed scanners reduced enough to make sharing unnecessary. |
5,458 | From 2000 all-in-one multi-purpose devices became available which were suitable for both small offices and consumers, with printing, scanning, copying, and fax capability in a single apparatus that can be made available to all members of a workgroup. |
5,459 | Battery-powered portable scanners store scans on internal memory; they can later be transferred to a computer either by direct connection, typically USB, or in some cases a memory card may be removed from the scanner and plugged into the computer. |
5,460 | A paint application such as GIMP or Adobe Photoshop must communicate with the scanner. There are many different scanners, and many of those scanners use different protocols. In order to simplify applications programming, some Applications programming interfaces were developed. The API presents a uniform interface to t... |
5,461 | In practice, there are often problems with an application communicating with a scanner. Either the application or the scanner manufacturer may have faults in their implementation of the API. |
5,462 | Typically, the API is implemented as a dynamically linked library. Each scanner manufacturer provides software that translates the API procedure calls into primitive commands that are issued to a hardware controller . The manufacturer's part of the API is commonly called a device driver, but that designation is not str... |
5,463 | Common scanner software API: |
5,464 | SANE is a free/open-source API for accessing scanners. Originally developed for Unix and Linux operating systems, it has been ported to OS/2, Mac OS X, and Microsoft Windows. Unlike TWAIN, SANE does not handle the user interface. This allows batch scans and transparent network access without any special support from t... |
5,465 | TWAIN is used by most scanners. Originally used for low-end and home-use equipment, it is now widely used for large-volume scanning. |
5,466 | ISIS created by Pixel Translations, which still uses SCSI-II for performance reasons, is used by large, departmental-scale, machines. |
5,467 | WIA is an API provided by Microsoft for use on Microsoft Windows. |
5,468 | Although no software beyond a scanning utility is a feature of any scanner, many scanners come bundled with software. Typically, in addition to the scanning utility, some type of image-editing application , and optical character recognition software are supplied. OCR software converts graphical images of text into sta... |
5,469 | Some scanners, especially those designed for scanning printed documents, only work in black-and-white but most modern scanners work in color. For the latter, the scanned result is a non-compressed RGB image, which can be transferred to a computer's memory. The color output of different scanners is not the same due to t... |
5,470 | Images are usually stored on a hard disk. Pictures are normally stored in image formats such as uncompressed Bitmap, "non-lossy" compressed TIFF and PNG, and "lossy" compressed JPEG. Documents are best stored in TIFF or PDF format; JPEG is particularly unsuitable for text. Optical character recognition software allow... |
5,471 | Document imaging requirements differ from those of image scanning. These requirements include scanning speed, automated paper feed, and the ability to automatically scan both the front and the back of a document. On the other hand, image scanning typically requires the ability to handle fragile and or three-dimensional... |
5,472 | Document scanners have document feeders, usually larger than those sometimes found on copiers or all-purpose scanners. Scans are made at high speed, from 20 up to 280 or 420 pages per minute, often in grayscale, although many scanners support color. Many scanners can scan both sides of double-sided originals . Sophisti... |
5,473 | The resolution used is usually from 150 to 300 dpi, although the hardware may be capable of 600 or higher resolution; this produces images of text good enough to read and for optical character recognition , without the higher demands on storage space required by higher-resolution images. |
5,474 | Document scans are often processed using OCR technology to create editable and searchable files. Most scanners use ISIS or TWAIN device drivers to scan documents into TIFF format so that the scanned pages can be fed into a document management system that will handle the archiving and retrieval of the scanned pages. Los... |
5,475 | While paper feeding and scanning can be done automatically and quickly, preparation and indexing are necessary and require much work by humans. Preparation involves manually inspecting the papers to be scanned and making sure that they are in order, unfolded, without staples or anything else that might jam the scanner.... |
5,476 | Indexing involves associating relevant keywords to files so that they can be retrieved by content. This process can sometimes be automated to some extent, but it often requires manual labour performed by data-entry clerks. One common practice is the use of barcode-recognition technology: during preparation, barcode she... |
5,477 | A specialized form of document scanning is book scanning. Technical difficulties arise from the books usually being bound and sometimes fragile and irreplaceable, but some manufacturers have developed specialized machinery to deal with this. Often special robotic mechanisms are used to automate the page-turning and sca... |
5,478 | Another category of document scanner is the document camera. Capturing images on document cameras differs from that of flatbed and Automatic document feeder scanners in that there are no moving parts required to scan the object. Conventionally either the illumination/reflector rod inside the scanner must be moved over... |
5,479 | It is not required that the documents or objects being scanned make contact with the document camera, therefore increasing flexibility of the types of documents which are able to be scanned. Objects that have previously been difficult to scan on conventional scanners are now able to be done so with one device. This inc... |
5,480 | Increased reaction time whilst scanning also has benefits in the realm of context-scanning. ADF scanners, whilst very fast and very good at batch scanning, also require pre- and post-processing of the documents. Document cameras can be integrated directly into a Workflow or process, for example, a teller at a bank. The... |
5,481 | Whilst scanning with document cameras may have a quick reaction time, large amounts of batch scanning of even, unstapled documents is more efficient with an ADF scanner. There are challenges that face this kind of technology regarding external factors which may have influence on the scan results. The way in which thes... |
5,482 | Infrared cleaning is a technique used to remove the effects of dust and scratches on images scanned from film; many modern scanners incorporate this feature. It works by scanning the film with infrared light; the dyes in typical color film emulsions are transparent to infrared light, but dust and scratches are not, and... |
5,483 | Scanner manufacturers usually have their own names attached to this technique. For example, Epson, Minolta, Nikon, Konica Minolta, Microtek, and others use Digital ICE, while Canon uses its own system FARE . Plustek uses LaserSoft Imaging iSRD. Some independent software developers design infrared cleaning tools. |
5,484 | Flatbed scanners have been used as digital backs for large-format cameras to create high-resolution digital images of static subjects. A modified flatbed scanner has been used for documentation and quantification of thin layer chromatograms detected by fluorescence quenching on silica gel layers containing an ultraviol... |
5,485 | The device consists of a rough surface upon which the user may "draw" or trace an image using the attached stylus, a pen-like drawing apparatus. The image is shown on the computer monitor, though some graphic tablets now also incorporate an LCD screen for more realistic or natural experience and usability. |
5,486 | Some tablets are intended as a replacement for the computer mouse as the primary pointing and navigation device for desktop computers. |
5,487 | The first electronic handwriting device was the Telautograph, patented by Elisha Gray in 1888. |
5,488 | The first graphic tablet resembling contemporary tablets and used for handwriting recognition by a computer was the Stylator in 1957. Better known is the RAND Tablet also known as the Grafacon , introduced in 1964. The RAND Tablet employed a grid of wires under the surface of the pad that encoded horizontal and vertic... |
5,489 | The acoustic tablet, or spark tablet, used a stylus that generated clicks with a spark plug. The clicks were then triangulated by a series of microphones to locate the pen in space. The system was fairly complex and expensive, and the sensors were susceptible to interference by external noise. |
5,490 | Digitizers were popularized in the mid-1970s and early 1980s by the commercial success of the ID and BitPad manufactured by the Summagraphics Corp. The Summagraphics digitizers were sold under the company's name but were also private labeled for HP, Tektronix, Apple, Evans and Sutherland and several other graphic syst... |
5,491 | In 1981, musician Todd Rundgren created the first color graphic tablet software for personal computers, which was licensed to Apple as the Utopia Graphic Tablet System. |
5,492 | In 1981, the Quantel Paintbox color graphic workstation was released; This model was equipped with the first pressure sensitive tablet. |
5,493 | The first home computer graphic tablet was the KoalaPad, released in 1983. Though originally designed for the Apple II, the Koala eventually broadened its applicability to practically all home computers with graphic support, examples of which include the TRS-80 Color Computer, Commodore 64, and Atari 8-bit family. Comp... |
5,494 | In the 1980s, several vendors of graphic tablets began to include additional functions, such as handwriting recognition and on-tablet menus. |
5,495 | Typically tablets are characterized by size of the device, drawing area, its resolution size , pressure sensitivity , number of buttons and types and number of interfaces: Bluetooth, USB; etc. The actual drawing accuracy is restricted to pen's nib size. |
5,496 | There have been many attempts to categorize the technologies that have been used for graphic tablets: |
5,497 | For all these technologies, the tablet can use the received signal to also determine the distance of the stylus from the surface of the tablet, the tilt of the stylus, and other information in addition to the horizontal and vertical positions, such as clicking buttons of the stylus or the rotation of the stylus. |
5,498 | Compared to touchscreens, a graphic tablet generally offers much higher precision, the ability to track an object which is not touching the tablet, and can gather much more information about the stylus, but is typically more expensive, and can only be used with the special stylus or other accessories. |
5,499 | Some tablets, especially inexpensive ones aimed at young children, come with a corded stylus, using technology similar to older RAND tablets. |
5,500 | After styluses, pucks are the most commonly used tablet accessory. A puck is a mouse-like device that can detect its absolute position and rotation. This is opposed to a mouse, which can only sense its relative velocity on a surface . Pucks range in size and shape; some are externally indistinguishable from a mouse, wh... |
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