What is an optical scanner and how does it work?

3d scanner large objects image

huzaifai

Answer
in computing, a scanner is a device that analyzes an image (such as a photograph, printed text, or handwriting) or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner The flatbed scanner is the most common in offices. Hand-held scanners, where the device is moved by hand, were briefly popular but are now not used due to the difficulty of obtaining a high-quality image. Both these types of scanners use charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor.

Another category of scanner is a rotary scanner used for high-speed document scanning. This is another kind of drum scanner, but it uses a CCD array instead of a photomultiplier.

Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects.



Scanners typically read red-green-blue color (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 (usually SCSI or USB, or LPT in machines pre-dating the USB standard). Color depth varies depending on the scanning array characteristics, but is usually at least 24 bits. High quality models have 48 bits or more color depth. The other qualifying parameter for a scanner is its resolution, measured in pixels per inch (ppi), sometimes more accurately referred to as samples per inch (spi). 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 thanks to software interpolation. As of 2004, a good flatbed scanner has an optical resolution of 1600â3200 ppi, high-end flatbed scanners can scan up to 5400 ppi, and a good drum scanner has an optical resolution of 8000â14,000 ppi.

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. The higher the resolution, the larger the file. In most cases, there is a trade-off between manageable file size and level of detail. Resolutions higher than 1200dpi are overkill for colour printers and monitors.

The third important parameter for a scanner is its density range. A high density range means that the scanner is able to reproduce shadow details and brightness details in one scan.

Does anyone know of a site that I can get a PICTURE if the apparatus used in both the CAT scan and the MRI?

Wizard of

I have had BOTH of these, but my sister is going for an MRI and, for the life of me, I cannot remember which is which! I need PICTURES to show her what to expect! HELP!!
I cannot remember which one is the "quickie" and which one takes 1/2 hour

Answer
Images of MRI machine

http://images.google.co.in/imgres?imgurl=http://www.asahi-net.or.jp/~YS2K-SIK/00kseike/2003/0406jmcf/mri-150.jpg&imgrefurl=http://ghettodriveby.com/mri/&h=443&w=592&sz=25&hl=en&start=1&tbnid=BH5RbxSM1MCWXM:&tbnh=101&tbnw=135&prev=/images%3Fq%3DMRI%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG
http://images.google.co.in/imgres?imgurl=http://nobelprize.org/nobel_prizes/medicine/laureates/2003/mri_press1.jpg&imgrefurl=http://nobelprize.org/nobel_prizes/medicine/laureates/2003/press.html&h=237&w=300&sz=21&hl=en&start=6&tbnid=9rM1MrQ5neDpWM:&tbnh=92&tbnw=116&prev=/images%3Fq%3DMRI%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG


CAT machine

http://images.google.co.in/imgres?imgurl=http://www.karlloren.com/images/139.gif&imgrefurl=http://www.karlloren.com/ultrasound/index.htm&h=300&w=240&sz=25&hl=en&start=2&tbnid=nPAEJg9Rd67jKM:&tbnh=116&tbnw=93&prev=/images%3Fq%3DCAT%2Bscan%2Bmachine%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG
http://images.google.co.in/imgres?imgurl=http://www.karlloren.com/ultrasound/images/catsca9.gif&imgrefurl=http://www.karlloren.com/ultrasound/p44.htm&h=344&w=391&sz=72&hl=en&start=1&tbnid=_1Dw6chPI9rnLM:&tbnh=108&tbnw=123&prev=/images%3Fq%3DCAT%2Bscan%2Bmachine%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

Computed tomography (CT), originally known as computed axial tomography (CAT or CT scan) and body section roentgenography, is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The word "tomography" is derived from the Greek tomos (slice) and graphein (to write). CT produces a volume of data which can be manipulated, through a process known as windowing, in order to demonstrate various structures based on their ability to block the X-ray beam. Although historically (see below) the images generated were in the axial or transverse plane (orthogonal to the long axis of the body), modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures.

MRI is short for Magnetic Resonance Imaging. (If your doctor has sent you for an MRA [Magnetic Resonance Angiography], this is also a kind of MRI.) MRI is an advanced technology that lets your doctor see internal organs, blood vessels, muscles, joints, tumors, areas of infection, and more -- without x-rays, surgery, or pain. MRI is very safe; in fact, it makes use of natural forces and has no known harmful effects. It's important to know that MRI will not expose you to any radiation.


MRI take half hr to one hr to complete

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