They have stable and precisely known internal geometries and verylow lens distortions.The principal distance is constant, which means, that the lenscannot be sharpened when taking photographs.The image coordinate system is defined by (mostly) four fiducialmarks, which are mounted on the frame of the camera.Aerial metric cameras are built into aero planes mostly lookingstraight downwards.The elements of interior orientation are known i.e the focal lengthand location of the centre of the photograph.
The overlapping area of the two photographs (which are called astereo pair) can be seen in 3D, simulating mans stereoscopic vision.In practice, a stereo pair can be produced with a single camera fromtwo positions or using a stereo metric camera.A stereo metric camera in principle consists of two metric camerasmounted at both ends of a bar, which has a precisely measuredlength (mostly 40 or 120 cm).Both cameras have the same geometric properties. Since they areadjusted to the normal case, stereo pairs are created easily.
3) AMATEUR CAMERASThese cameras are used when the internal geometry is not stableand unknown like normal commercially available camera.They can only be used for purposes, where no high accuracy isdemanded.The precision will never reach that of metric cameras.
SCANNERS:Scanners allow information such as a photo or text to be input intoa computer.Various scanners are:1) ROTATING DRUM SCANNER2) FLAT BED SCANNER3) STRUCTURED LIGHT SCANNER4) ARM AND LINE SCANNER
It got its name from the clear acrylic cylinder, the drum, on which theoriginal artwork is mounted for scanning.They capture image information with photomultipliertubes (PMT), rather than the charge-coupled device (CCD) arrays. It has the ability to control sample area and aperture sizeindependently. The ability to control aperture and sample size separatelyis particularly useful for smoothing film grain when scanning black-andwhite and color negative originals.They are superior in resolution, color gradation, and value structurealso capable of resolutions up to 24,000 PPI. They are used when ascanned image is going to be enlarged.
This type of scanner is sometimes called a reflective scanner.They are designed for scanning prints or other flat, opaquematerials.These scanners work by shining white light onto the object andreading the intensity and color of the light that is reflected from it.Some flatbed scanners have available transparency scanningadapters but these are not suited to scanning film as a dedicatedfilm scanner.
MEASUREMENT PRINCIPLE:A structured light scanner uses a projector and two calibratedcameras to generate a 3D point cloud.The projector projects a structured pattern onto the object. Thispattern is observed by the two cameras.This generates the necessary data for the software to calculate the3D position of every point on the lines of the pattern.When scanning an object, the scanner will be oriented in differentpositions and each scan will be aligned by the use of referencemarkers or best fit algorithms.
RANGE AND ACCURACY:Range: objects from the size of a coin to full cars can be measured.Typical accuracy: depends on the size of the object, the accuracyranges from 10µm for very small objects (the size of a key) to 0.1mm for larger objects (the size of a car).ADVANTAGES:Measurements can be done on site.Can be used for objects of nearly any size.
MEASUREMENT PRINCIPLE:It consists of 4 main segments: the base, two arm segments and themain handle. Each of those is connected with one or more hinges, 7 intotal.This allows the main handle to be positioned in virtually everypossible direction hence angle of every hinge is measured. With this information the software can calculate the absolutecoordinate of the probe at the end of the main handle.With a laser scanner attached to the arm it becomes a scanninginstrument. The arm is used to measure the position of the laserscanner.The laser scanner itself is then used to scan a geometric object.
RANGE AND ACCURACY:Range: Both arms offer a total range of 2.4 m. Bigger objects canbe measured by using jump points for different positions.Typical accuracy for laser scanning: 0.1-0.2 mm.ADVANTAGES:Portable and easy to use.Ability to measure in tight spaces and difficult geometries.Easy combination of single point measurements and scanned pointclouds.
MOUSE1) SPACE MOUSE2)STEALTH 3D MOUSE3) TRACKBALL
Space Mouse is a professional 3D controller specificallydesigned for manipulating objects in a 3D environment.It permits the simultaneous control of all six degrees offreedom (translation , rotation or combination).Drawing time is reduced by 20%-30% increasing overallproductivity.Going back and forth to the menu is eliminated.Natural hand position (resting on table) eliminates fatigue.
2)STEALTH 3D MOUSEThe Stealth 3D Mouse provides an two-handed 3D input formapping. The mouse has an optical XY motion sensor, a high-resolution Z wheel and 10 buttons. The standard Stealth 3D Mousehas two thumb buttons above the Z-wheel. The connection of theStealth 3D Mouse requires a single USB port.
3)TRACKBALL The trackball is an upside-down mouse, with the ball located ontop. A trackball has three sensors. In this the fingers are rolledover the trackball, and internal rollers sense the motion which istransmitted to the computer. advantage is that the trackballremains stationary on the desk, so less room is required to use thetrackball.
INFRARED EMITTER:An infrared emitter is usually an electrically-powered device that isused to emit light wavelengths in the infrared spectrum, which areinvisible to the naked eye .These emitters produce a red type of light invisible to the human eyewith a wavelength of around 880 nanometers.
OUTPUT DEVICESOutput is the result of processes that are done on the computer which canread or another machine can read.An output device receives information from the computer and translatesit from machine language to a form that humans understand .The variousoutput devices are:1) 3D GLASSES2) PLOTTERS3)DISPLAY DEVICES4)GRAPHICS CARD
3D GLASSESTypes Of 3D Glasses:-1) Anaglyph glasses2) Pulfrich glasses3) Polarized glasses4) LCD Shutter glasses
Anaglyph 3D is the name given to the stereoscopic 3D effectachieved by means of encoding each eyes image using filters ofdifferent (usually chromatically opposite) colors, typically red and blue.The purpose of 3D glasses is to filter a separate image into eacheye.The red image goes in the red lens and the blue image goes in theblue lens(color separation ).
The Pulfrich effect is a psycho-optical phenomenon wherein lateralmotion by an object in the field of view is interpreted by the brainas having a depth component, due to differences in processingspeed between images from the two eyes. The effect is generallycreated by covering one eye with a really dark filter.These glasses use the concept of one dark and one light lens toform 3D images.The image through the dark lens reaches the brain slightly after theimage that went through the clear lens, creating a 3D illusion.
Polarized lenses are both a gray color and unlikeanaglyph glasses allows color pass through.The lenses are specially cut at opposing 45 degrees.Two images are projected on the screen and each one hasa different polarization. The polarized glasses allow only one of the images intoeach eye because each lens has a different polarization.
LCD shutter glasses are a type of electronic 3D glasses.They are used to view 3D images on a computer screenFirst, two images are displayed on a screen, each image fora specific eye.The images are shown rapidly.While the image for the left eye is shown, the right eye isblocked by the glasses, and vice versa for the right eye.Each lens can be turned off separately .This happens extremely fast ( 60 flashes per second)Thelenses turn off and on so quickly that the brain just sees one3D image that is the two images combined.
PLOTTERSPlotters are used to obtain a graphic or pictorial presentation of thefinal result (output).Plotters are used for variety of applicationswhich include drawing graphs, making maps and detailing ofhouses or cars.A plotter is a hard copy output device that reproduces graphicimages on paper using a pen that is attached to a movable arm.These are slow devices. The graphics they produce are uniform andof very good quality.
Types of plotters:On the basis of no. of pens used:- 1)SINGLE PEN PLOTTERS 2)MULTIPLE PEN PLOTTERSOn the basis of pen interaction methods:- 1)DRUM PLOTTERS 2)FLAT BED PLOTTERS
1)SINGLE PEN PLOTTERThe single pen plotter contains a single pen into penholder whichcan be changed manually. The single pen plotter will consumemore time and method used by it maybe mare frustrating ascompared to multiple pen plotter.
2)MULTIPLE PEN PLOTTERThe multiple pen plotter contains a main pen holder and a pen changingassembly. The pen that is drawing is holded by the main pen holder andrest pens lie in the assembly. The main holder collects different pensfrom the pen assembly as they are needed automatically. For this, thecomputer supplies instructions to the main pen holder.
3)DRUM PLOTTERS In a drum plotter the paper is placed between a drum and a platenwhich holds the paper. The paper moves up and down verticallyand the pen moves left and right horizontally. Any required shapedgraph or image can be plotted on paper using these movements .For plotting a picture image the paper moves up and down multipletimes in a drum plotter and this reduces over all accuracy of theplotter.The size of the graph is therefore limited only by the width of thedrum and can be of any length.
4) FLAT BED PLOTTERSFlat bed plotters are rectangle shaped open box type instruments. Theyare made bigger than the largest sized paper . It contains a penassembly in which additional pens are arranged. The holder bar, movesback and forth along X-axis and the pen holder moves back and forthalong Y-axis to plot an image . The paper remains fixed at its place .They can plot any sized images, smaller as well as larger with sameaccuracy. The accuracy of flat bed plotter is more than .001 inch. Thusfor higher size images the drum plotter is a better option . The penspeed of these plotter is 15 to30 inches per second and they are slowfor complex graphical images like CAD applications.
5) ELECTROSTATIC PLOTTERSThis plotter can handle large formats up to 90 cm and 120 cm in widthwith effectively no limitations in length and generate map images atmoderate resolutions (300 dpi) .The colour electrostatic plotter includecompeting single pass and multiple pass technologies for generatingcolour hard copy on both film and paper. They are useful to generate,edit plots , colour proofs and those maps required in smallnumbers(i.e. requiring small runs )for plots. An Electrostatic Plotterproduces a raster image by charging the paper with a high voltage.This voltage attracts toner which is then melted into the paper withheat .This type of plotter is fast, but the quality is generally consideredto be poor when compared to pen plotters.
6) INKJET PLOTTERInkjet plotter is a type of computer plotter that creates a digitalimage by propelling droplets of ink onto paper. These printers createimage by spraying jet of ink on the paper surface and hence the name.The speed of these printers is measured in pages per minute(PPM). Itproduce very high quality printouts on any surface. It can be used to getmulticolor print outs. It provides a resolution of 300 dots per inch.Per page printing cost of these printers is very high. They cannot beused to take multiple carbon copies. Since it require smaller mechanicalparts, it is popular as portable printers. It provides an inexpensive wayto print full color documents.
7)THERMAL PLOTTERThese plotters use a linear thermal writing head covering the wholewidth of the sheet of heat sensitive paper or film.This head sweepsacross the sheet and plots out only in monochrome at reasonableresolutions (400 dpi).Recently bi colour media have been introducedallowing the generation of both black and red.These are used forshowing up revision detail on large scale maps.
Laser plotter utilizes a laser beam to produce an image and hence thename. It is also called page printers.Laser plotter are expensive. Speed is measured in Pages Per Minuteor PPM. It produce very high quality print and print in unlimitedvariety of fonts. It cannot be used to take multiple carbon printouts. The laser light produces the image on a drum. The laser light altersthe electrical charge on a drum whenever it hits. The drum is rolledthrough a reservoir of toner, which is picked by the charged portionsof the drum. Finally the toner is transferred to the paper through acombination of heat and pressure.
1)CRT MONIT0R The CRT monitor contains a large cathode ray tube that uses anelectron beam of varying strength to “paint” a picture onto the colorphosphorescent dots on the inside of the screen. Monitor screensize is measured diagonally across the screen, in inches.The resolution of the monitor is 800 x 600, or 1024 x 768, or 1600x 1200). The spacing of the screen’s tiny phosphor dots is calledthe dot pitch (dp), typically .28 or .26 (measured in millimeters). Ascreen with a smaller dot pitch produces sharper images.
2) FLAT PANEL MONITOR A flat panel display usually uses an LCD (Liquid Crystal Display)screen to display output from the computer. The LCD consists ofseveral thin layers that polarize the light passing through them. Thepolarization of one layer, containing long thin molecules calledliquid crystals, can be controlled electronically at each pixel,blocking varying amounts of the light to make a pixel lighter ordarker.
A Plasma display is composed of two parallel sheets of glass, whichenclose a mixture of discharged inert gases (like helium, neon, argon).Groups of electrodes placed at right angles between thepanes, forming rectangular compartments, or cells, between the glasssheets. Phosphors embedded within each cell individually emit red, greenor blue light and collectively create a singlecolor pixel when excited. Applied voltages to the electrodes causes themto generate a discharge in the panel’s dielectric layerand on its protective surface. This generates ultraviolet light that excitesthe phosphors, stimulating them to emit light.
3)HEAD MOUNTED DISPLAY Head mounted display is usually a helmet like device where thereis two separate displays installed. Using two displays and someoptics it is possible to make very realistic 3D graphics. In HMDdevices we can turn our head and feel that we are inside the 3Dworld.
Street Mapper uses laser scanning technology to capture theposition of up to 600,000 3D point measurements per second whilein motion. The typical positional accuracy is better than 2cm andthe point-to-point accuracy within the data is 1cm.Street Mapper offers a 360-degree field of view, a measurementrange of 300m and a scanning speed of 300kHz persensor, delivering high precision performance and coverageAn integrated high-resolution digital camera can be used to captureeither still or video images.