Chapter2Laparoscopic Imaging SystemsIt is well known that laparoscopy is the consequence ofadvances made in the field of medical engineering. Eachsurgical specialty has different requirement of instruments.Laparoscopy was initially criticized owing to the cost ofspecialized instruments and possible complications due tothese sharp long instruments. Also, it necessitated difficulthand eye coordination. Gradually, the technique gainedrecognition and respect from the medical fraternity since itdrastically reduced many of the complications of the openprocedure. Minimal access surgery has developed rapidlyonly after grand success of laparoscopic cholecystectomy.Computer aided designing of laparoscopic instruments isan important branch of medical engineering. It is nowpossible to control the access through microprocessorcontrolled laparoscopic instruments. New procedures andinstruments are innovated regularly which makes it importantfor the surgeon to be familiar with the developments.Laparoscopy is a technologically dependent surgery and itis expected every surgeon should have reasonably goodknowledge of these instruments.IMAGING SYSTEMS Light sourceLight cableTelescopeLaparoscopic cameraLaparoscopic video monitor.The imaging system is a chain of equipments that arelink together in place perfectly and functioning well toproduce an excellent laparoscopic image. The break in thisLAPAROSCOPIC TROLLEYThe mobile laparoscopic video cart is equipped with lockingbrakes and has four anti-static rollers. The trolley has adrawer and three shelves (Fig. 2.1).The upper shelves have a tilt adjustment and used forsupporting the video monitor unit. Included on the trolley isan electrical supply terminal strip, mounted on the rear ofthe second shelf (from the top). Recently, ceiling mountedtrolleys are launched by many companies which areergonomically better and consume less space in operationtheater.Fig. 2.1: Laparoscopic trolley

10Section 1: Essentials of Laparoscopysequential pass of links of the chain will be rendered ourimaging system impotent.The classic imaging chain starts with a light source, andends in the monitor, requiring seven pieces of equipment,known as the Magnificent Seven: light source, fiber-opticlight cable, laparoscope, camera head, video signalprocessor, video cable, and monitor (Fig. 2.2). This imagingchain is often supported by a cast of VCRs, photo printers,or digital capture devices. The surgeon and the operatingroom team must work together to ensure optimal equipmentfunction through careful handling of the equipment in theoperating room and during the sterilization process. Yet,when the image is poor, many operating teams becomeparalyzed, unable to function without the aid of a medicalengineer. “Understanding can overcome any situation,however, mysterious or insurmountable, it may appear tobe.” Accordingly, understanding the ( imaging) video systemwill allow the operating surgeon to do the basictroubleshooting for his or her system and not be totallydependent on nursing or technical staff, especially at nightwhen experienced personnel may not be available. Theadvent of integrated operating suites has not changed theprinciples of this basic idea.THE LIGHT SOURCEIt is clear and easy to say that, life, recently, is impossiblewithout light, and simply: no light, no laparoscopy. The lightsource is the often-overlooked soldier of the videolaparoscopic system.High-intensity light is created with bulbs of halogen gas,xenon gas or mercury vapor. The bulbs are available indifferent wattages” 150 and 300 Watt”and should be chosenbased on the type of procedure being performed. Becauselight is absorbed by blood, any procedure in which bleedingis encountered may require more light. We use the strongerlight sources for all advanced laparoscopy. Availability oflight is a challenge in many bariatric procedures where theabdominal cavity is large.A good laparoscopic light source should emit light asmuch as possible near the natural sun light.Three types of light source are in use today:1. Halogen light source2. Xenon light source3. Metal halide light sourceThe output from the light sources is conducted to thetelescope by light cables that contain either glass fiberbundles or special fluid.The halogen light source is used in the medical fieldsince last 20 years, but the spectral temperature of theselights is 3200 Kelvin which makes it too different and toolow from natural sunlight. The midday sunlight hasapproximately 5600 Kelvin color temperature. In practice,the yellow light of the halogen bulb is compensated for inthe video camera system by white balancing.A more suitable light source for laparoscopic camerasinvolves the creation of an electrical arc in a metal halidesystem or in xenon. This electrical arc is produced in sameway as in flash of photographic camera.Xenon has a more natural color spectrum and a smallerspot size than halogen. The xenon light source emits aspectral temperature of color of approximately 6000 Kelvinon average for a power of 300 W (Fig. 2.3).Arc generated lamps have a spectral temperature thatgradually decreases with use and white balance is requiredbefore each use. The bulb needs replacing after 250 to 500hours of usage, depending on the type of lamp.One of the main advantages of the laparoscopy is thatof obtaining a virtually microsurgical view compared to thatobtained by laparotomy. Quality of the image obtained verymuch depends on the quantity of light available at eachstep of optical and electronic system.The Interface of the laparoscopic team work with aStandard Light Source:It is essential for the laparoscopic team, particularly thesurgeons, to know about all the switch and function of thelight source. All essential details of the equipment and allthe action required on the part can be found on the operatingmanual of the product.Many light sources record and display the hours of serviceand alert the biomedical medical engineer (or the wellinformed surgeon) when it is time to make a change. WhenFig. 2.2: The “Magnificent Seven” of the basic imaging chainFig. 2.3: Spectrum of light

Chapter 2: Laparoscopic Imaging Systemsthe lifetime rating of the bulb has been exceeded, thesubsequent performance of the light source becomesunpredictable, often slowly dwindling until the surgeon justcan not produce a well-lit scene despite the fact that a brightlight seems to emanate from the laparoscope (Fig. 2.4).A typical light source consists of: A lamp (bulb) A heat filter A condensing lens Manual or automatic intensity control circuit (shutter).Lamp (Bulb)Lamp or bulb is the most important part of the light source.When the bulb fails, the entire system is out ofcommission until either the bulb is replaced or a new light isbrought to bear. Many light sources record and display thehours of service and alert the biomedical medical engineer(or the well-informed surgeon) when it is time to make achange. When the lifetime rating of the bulb has beenexceeded, the subsequent performance of the light sourcebecomes unpredictable, often slowly dwindling until thesurgeon just can not produce a well-lit scene despite the factthat a bright light seems to emanate from the laparoscope.The quality of light depends on the lamp used. Severalmodern types of light sources are currently available (Fig.2.5). These light sources mainly differ on the type of bulbused.Three types of lamp are used more recently:1. Quartz halogen Incandescent lamp2. Xenon lamp3. Metal halide vapor arc lamp.I-Halogen Bulbs (150-watt) or Tungsten-halogen BulbIt is an incandescent lamp with a transparent quartz bulband a compressed gas filling that includes a halogen. Quartzis used instead of glass to permit higher temperatures, highercurrents, and therefore greater light output. The lamp givesbrilliant light. The halogen combines with the tungstenevaporated from the hot filament to form a compound thatis attracted back to the filament, thus extending the filament’slife. The halogen gas is also prevents the evaporated tungstenfrom condensing on the bulb and darkening it, an effectthat reduces the light output of ordinary incandescent lamps.First used in the late 1960s in motion-picture production,halogen lamps are now also used in automobile headlights,underwater photography, and residential lighting.Incandescent (to begin to glow): It is so hot to the pointof glowing or emitting intense light rays, as an incandescentlight bulb.Quartz, one of the commonest of all rock-formingminerals and one of the most important constituents of theFig 2.4: Xenon light source: bulb-life display is shownFig. 2.5: New generation light source bulbearth’s crust. Chemically, it is silicon dioxide, SiO2. It occursin crystals of the hexagonal system, commonly having theform of a six-sided prism terminating in a six-sided pyramid;the crystals are often distorted and twins are common. Quartzmay be transparent, translucent, or opaque; it may becolorless or colored.The halogen lamp takes its name from the halogensincluded in the gas within its tungsten-filament bulb, addedto prolong filament life and increase brightness.Halogen: Any of the elements of the halogen family,consisting of fluorine, chlorine, bromine, iodine, and astatine.They are all monovalent and readily form negative ions.Halogen bulbs provide highly efficient crisp white lightsource with excellent color rendering. Electrodes in halogenlamps are made of tungsten filament. This is the only metalwith a sufficiently high melting temperature and sufficientvapor pressure at elevated temperatures. They use a halogen11

12Section 1: Essentials of Laparoscopygas that allows bulbs to burn( light) more intensely. Halogenbulbs use low voltages and have an average life of 2,000hours. The color temperature of halogen lamp is around(5000–5600 K). These lamps are economical and can beused for laparoscopic surgery if low budget setup is required.II-Xenon Lamps (300-watt)Xenon (Symbol Xe): A colorless, odorless, highly unreactivegaseous nonmetallic element found in minute quantities inthe atmosphere and extracted commercially from liquefiedair. Atomic number is 54. The radioactive isotope 133Xe,having a half-life of 5.3 days, is used for diagnostic imagingin assessment of pulmonary function, lung imaging, andcerebral blood flow studies.Xenon lamps consist of a spherical or ellipsoidal envelopemade of quartz glass, which can withstand high thermal loadsand high internal pressure. For ultimate image quality, onlythe highest-grade clear fused silica quartz is used. It istypically doped, although not visible to the human eye, toabsorb harmful UV radiation generated during operation.The color temperature of xenon lamp is about 6000 to 6400K. The operating pressures are tens of atmospheres at times,with surface temperatures exceeding 600 C.The smaller, pointed electrode is called the cathode,which supplies the current to the lamp and facilitates theemission of electrons. To supply a sufficient amount ofelectrons, the cathode material is doped with thorium. Theoptimum operating temperature of the cathode tip isapproximately 2000 C. To obtain this precise operatingtemperature, the cathode tip is pointed and in many caseshas a groove on the pointed tip to act as a heat choke. Thisheat choke causes the tip to run at a higher temperature.This configuration of the cathode tip allows for a very highconcentration of light from the cathode tip and a very stablearc.The anode, the larger electrode, receives electronsemitted by the cathode. Once the electrons penetrate theanode face, the resulting energy is converted to heat, mostof which radiates away. The large, cylindrical shape of theanode helps to keep the temperature low by radiating theheat from the anode surface.The advantage of xenon bulb is that, it used a twoelectrodes (cathode and anode) and there is no filament asin halogen bulb, so it has somewhat a fixed lifetime with anaverage of 1500 hours.The two most frequently used types of lamps arehalogen and xenon. The main difference between them isin the colors obtained. The xenon lamp has a slightly bluishtint. The light emitted by xenon lamp is more naturalcompared to halogen lamp. However, most of the camerasat present analyze and compensate these variations bymeans of automatic “equalization of whites” (2100–10,000 K),which allows the same image to be obtained with bothlight sources.A proper white balancing before start of the operation isessential for obtaining a natural color. The white light iscomposed of equal proportion of red, blue and green color.At the time of white balancing, the camera sets its digitalcoding for these primary colors to equal proportion,assuming that the target is white. If at the time of whitebalancing, the telescope is not seeing a perfectly white object,the setup of the camera will be incorrect and the colorperception will be poor.The newer light source of xenon is defined as a coollight but practically it is not completely heat free and it shouldbe cared for ignition hazard.III-Metal Halide Vapor Arc Lamp (250-watt)Halide: A halide is a binary compound, of which one part isa halogen atom and the other part is an element or radicalthat is less electronegative (or more electropositive) thanthe halogen, to make afluoride, chloride, bromide, iodideor astatide compound. Many salts are halides. All group 1metals form halide compounds which are white solids atroom temperature.A halide ion is a halogen atom bearing a negative charge.The halide ions are fluoride (F–), chloride (Cl–), bromide(Br–), iodide (I–) and astatide (At–). Such ions are presentin all ionic halide salts.Metal halides are used in high-intensity discharge lampscalled metal halide lamps, such as those used in modernstreet lights. These are more energy-efficient than mercuryvapor lamps, and have much better color rendition thanorange high-pressure sodium lamps. Metal halide lamps arealso commonly used in greenhouses or in rainy climates tosupplement natural sunlight.Examples of halide compounds are: sodium chloride(NaCl), potassium chloride (KCl), potassium iodide (KI),lithium chloride (LiCl), copper (II) chloride(CuCl2), silverchloride (AgCl), and chlorine fluoride (ClF).Metal halide lamps, a member of the high-intensitydischarge (HID) family of lamps, produce high light outputfor their size, making them a compact, powerful, and efficientlight source. By adding rare earth metal salts to the mercuryvapor lamp, improved luminous efficacy and light color isobtained. Originally created in the late 1960s for industrialuse, metal halide lamps are now available in numerous sizesand configurations for commercial and residentialapplications (Figs 2.6 to 2.8).Like most HID lamps, metal halide lamps operate underhigh pressure and temperature, and require special fixturesto operate safely.

Chapter 2: Laparoscopic Imaging SystemsFig. 2.6: A metal halide gas discharge lighting system providesillumination for a college baseball game. Note the various colors ofthe lights as they warm upIn metal halide lamp, a mixture of compounds(comprising mostly salts of rare earths and halides as wellas the mercury which provides the conduction path) iscarefully chosen to produce an output which approximatesto ‘white’ light as perceived by the human eye (Fig. 2.9).There are two type of metal halide lamp generally used.They are iron iodide lamp and gallium iodide lamp. Ironiodide is a broad emitter and enhances the spectral outputof the lamp in the 380 nm. Gallium iodide has the effect ofintroducing spectral lines at 403 nm and 417 nm of theelectromagnetic spectrum (Fig. 2.10).The intensity of the light delivered by any lamp alsodepends on the power supply of the source. However,increasing the power poses a real problem as it generatesmore heat. At present, the improvements made to thecameras means that it is possible to return to reasonableFig. 2.7: A low-bay light fixture using a high wattage metal halidelamp, of the type used in factories and warehousesFig. 2.9: Metal halide bulbFig. 2.8: A linear/tubular metal halide lamp lit up at half powerFig. 2.10: Internal structure of metal halide tube13

14Section 1: Essentials of Laparoscopypower levels of 250 W. However, 400 W units are preferablein order to obtain sufficient illumination of the abdomeneven when bleeding causes strong light absorption. It isimportant to remember that a three chip camera requiremore light than single chip camera so a 400 W light sourceis recommended for 3 chips camera.Metal Halide LampHeat FilterFor 100 percent of energy consumed, a normal light source(a light bulb) converts approximately two percent to lightand 98 percent as heat. This heat is mainly due to the infraredspectrum of light and due to obstruction in the pathway oflight. If infrared travels through the light cable, the cable willbecome hot. A heat filter is introduced to filter this infraredin fiberoptic cable. A cool light source lowers this ratio bycreating more light, but does not reduce the heat producedto zero. This implies a significant dissipation of heat, whichincreases as the power rating increases. A cold light is lightemitted at low temperatures from a source that is notincandescent, such as fluorescence or phosphorescence.Incandescence is the emission of light (visible electromagneticradiation) from a hot body as a result of its temperature.The sources are protected against transmitting too muchheat at present. The heat is essentially dissipated in transport,along the cable, in the connection with the endoscope andalong the endoscope.While it is remarkable how little heat is delivered to thetip of the laparoscope, the effects are cumulative. A lightedlaparoscope or fiber-optic bundle in direct contact with paperdrapes or the patient’s skin will cause a burn after 20 or 30seconds and must be avoided.Some accidents have been reported due to burningcaused by the heat of the optics system. It is thereforeimportant to test the equipment, particularly if assembliesof different brands are used.Condensing LensThe purpose of condensing lens is to converge the lightemitted by lamp to the area of light cable input. In most ofthe light source it is used for increasing the light intensityper square cm of area.Manual or Automatic Intensity Control Circuit (Shutter)Manual adjustment allows the light source to be adjusted toa power level defined by the surgeon. In video cameras,close-up viewing is hampered in too much light, whereasmore distant view is too dark. To address this, the luminosityof most of the current light sources is adjustable.The advanced light source system is based on the automaticintensity adjustment technology. The video camera transformsthe signal into an electronic signal. This electronic signal is codedin order to be transported. The coding dissociates the luminanceand chrominance of the image. The luminance is the quantityof light of the signal (black and white) that dictates the qualityof the final image. When there is too much light for the image(when the endoscope is near to the tissue), the luminance signalof the oscilloscope increases. On the other hand, when theluminosity is low (distant view or red surroundings), theluminance is low and the electronic signal is much weaker. Agood quality luminance signal is calibrated to one millivolt.Overexposed images make the electronic signal pass aboveone millivolt, whereas underexposed images make the signaldrop below one millivolt. Light sources equipped withadjustment analyze the luminance. If the signal is significantlyhigher than one millivolt, they lower the power and bring thesignal back within the standards. Conversely, if the signal istoo weak, they increase their intensity.These systems are extremely valuable, permitting workto be performed at different distances from the target ingood viewing conditions. However, the cameras currentlyavailable are often equipped with a regulation system, whichis capable of automatic gain control in poor light conditionand the purchase of a light source with adjustment associatedwith a camera equipped with an adjustment system, is adouble purchase that is unnecessary.Troubleshooting of Laparoscopic Light Source:Troubleshooting for inadequate lighting is shown inTable 2.1.A laparoscopic surgeon should be technically wellacknowledged of the principle of the instrument they areusing. The purchase of a costly instrument is not an answerfor achieving a good task, ability to handle them is equallyimportant.Light CableMinimal access surgery depends on the artificial lightavailable in closed body cavity, and before the discovery ofTable 2.1: Troubleshooting of light sourceProbable causeLoose connection at sourceor scopeLight is on “manual-minimum”Bulb is burned outFiberoptics are damagedAutomatic iris adjusting to brightReflection from instrumentRemedyAdjust connectorGo to “automatic”Replace bulbReplace light cableDim room lightsRe-position instruments,or switch to “manual”

Chapter 2: Laparoscopic Imaging Systemslight source and light cable; mirrors were used to reflect thelight onto the subject where direct light access was notpossible.In 1954, a major breakthrough in technology occurredin the development of fiberoptic cables (Fig. 2.11). Theprinciple of fiberoptic cable was based on the total internalreflection of light. Light can be conducted along a curvedglass rod due to multiple total internal reflections. Light wouldenter at one end of the fiber and emerge at the other endafter numerous internal reflections with virtually all of itsintensity.Total Internal ReflectionAn effect that combines both refraction and reflection is totalinternal reflection (Fig. 2.12). Consider light coming from adense medium like water into a less dense medium like air.When the light coming from the water strikes the surface,part will be reflected and part will be refracted. Measuredwith respect to the normal line perpendicular to the surface,the reflected light comes off at an angle equal to that atwhich it entered at, while that for the refracted light is largerthan the incident angle. In fact the greater the incident angle,the more the refracted light bends away from the normal.Thus, increasing the angle of incidence from path “1” to“2” will eventually reach a point where the refracted angleis 90o, at which point the light appears to emerge along thesurface between the water and air. If the angle of incidenceis increased further, the refracted light cannot leave the water.It gets completely reflected. The interesting thing about totalinternal reflection is that it really is total. That is 100 percentof the light gets reflected back into the more dense medium,as long as the angle at which it is incident to the surface islarge enough.Fiberoptics uses this property of light to keep light beamsfocussed without significant loss (Fig. 2.13).The light enters the glass cable, and as long as thebending is not too sudden, will be totally internally reflectedwhen it hits the sides, and thus is guided along the cable.This is used in telephone and TV cables to carry the signals.Light as an information carrier is much faster and moreefficient than electrons in an electric current. Also, sincelight rays do not interact with each other (whereas electronsinteract via their electric charge), it is possible to pack alarge number of different light signals into the samefiberoptics cable without distortion. You are probably mostfamiliar with fiber optics cables in novelty items consistingof thin, multi-colored strands of glass which carry lightbeams.Nowadays, there are two types of light cable available:1. Fiberoptic cable2. Liquid crystal gel cable.Fig. 2.11: Fiberoptic light cableFig. 2.12: Refraction of light from water into airFig. 2.13: Fiberoptic cable, total internal reflection15

16Section 1: Essentials of LaparoscopyFiberoptic CableFiberoptics is the science or technology of light transmissionthrough (a bundle of optical fibers) very fine, flexible glassor plastic fibers.Fiberoptic cables are made up of a bundle of optical fiberglass thread swaged at both ends. The fiber size used is usually20 to 150 micron in diameter. A good fiberoptic cable willtransmit all the spectrum of light without loss (Fig. 2.14). Theyhave a very high quality of optical transmission, but are fragile.The light inside these fibers travels on the principle oftotal internal reflection without losing much of its intensity.The multimode fiber maintains the intensity of light and thelight can be passed in a curved path of light cable (Fig. 2.15).Fig. 2.14: Internal structure of fiberoptic cableFig. 2.15: Multimode fiber

Chapter 2: Laparoscopic Imaging SystemsAs the light cables are used progressively, some opticalfibers break (Fig. 2.16). The loss of optical fibers may beseen when one end of the cable is viewed in daylight. Thebroken fibers are seen as black spots. To avoid the breakageof these fibers, the curvature radius of light cable should berespected and in any circumstances it should not be lessthan 15 cm in radius.If the heat filter or cooling system of light source doesnot work properly, the fibers of these light cable is burnt(melt) and it will decrease the intensity of light dramatically(Fig. 2.17). If poor quality fibers are used, it might burn justwithin a few months of use.Liquid Crystal Gel CableThese cables are made up of a sheath that is filled with aclear optical gel (Liquid crystal).Crystal (a clear, transparent mineral or glass resemblingice) is a piece of solid substance, such as quartz, with a regularshape in which plane faces intersect at definite angles, due tothe regular internal structure of its atoms, ions, or molecules.Within a crystal, many identical paralleled-piped unit cells,each containing a group of atoms, are packed together to fillall space (see illustration). In scientific nomenclature, the termcrystal is usually short for single crystal, a single periodicarrangement of atoms. Most gems are single crystals.However, many materials are polycrystalline, consisting ofmany small grains, each of which is a single crystal. Forexample, most metals are polycrystalline (Fig. 2.18).Fig. 2.16: Broken fibers showing significant loss of lightFig. 2.17: Burnt fiber causes significant reduction inintensity of lightLiquid CrystalSubstance that flows like a liquid but maintains some of theordered structure characteristic of a crystal. Some organicsubstances do not melt directly when heated but insteadturn from a crystalline solid to a liquid crystalline state. Whenheated further, a true liquid is formed. Liquid crystals haveunique properties. The structures are easily affected bychanges in mechanical stress, electromagnetic fields,temperature, and chemical environment.Liquid Crystal Gel Cables are capable of transmitting upto 30 percent more light than optic fibers. Due to lighter andbetter color temperature transmission, this cable isrecommended in those circumstances, where documentation(movie, photography or TV) is performed.The quartz swaging at the ends is extremely fragile,especially when the cable is hot. The slightest shock, on abench for example, can cause the quartz end to crack andthus cause a loss in the transmission of the light.Gel cables transmit more heat than optical fiber cables.These cables are made more rigid by a metal sheath, whichmakes them more difficult to maintain and to store. Inconclusion, even though the choice is a difficult one, weFig. 2.18: Structure of a simple crystal17

18Section 1: Essentials of Laparoscopyuse optical fiber cables, which are as fragile as the gel cablesbut their flexibility makes them much easier to maintain.Attachment of the Light Cable to the Light Sourcetelescope provides a total field of view of 152 degreescompared with the 0-degree telescope, which only providesa field of view of 76 degrees (Fig. 2.21). The 30 forwardoblique angle permits far greater latitude for viewingConventional attachment has at right angle connection forlight source and camera. Recently, new attachment for lightcable is available known as DCI interface (Display controlinterface) (Fig. 2.19). The benefit of this is that it maintainsupright orientation regardless of angle of viewing, using autorotation system. It also provides single handed control ofthe entire endoscope camera system.Maintenance of Light CableThe following points should be followed for the maintenanceof light cable: Handle them carefully. Avoid twisting them. After the operation has been completed, the cable shouldpreferably be first disconnected from the endoscope andthen disconnected from the light source. In fact, most ofthe sources currently available have a plug for holdingthe cable until it cools down. The end of the crystal of cable should be periodicallycleaned with a cotton swab moistened with alcohol. The outer plastic covering of the cable should be cleanedwith a mild cleaning agent or disinfectant. Distal end of fiberoptic cable should never be placed onor under drapes, or next to the patient, when connectedto an illuminated light source. The heat generated fromthe intensity of light may cause burns to the patient orignite the drapes (Fig. 2.20). The intensity of light source is so high that there is chanceof retinal damage if the light will fall directly on eye.Never try to look directly on light source when it is lighted.Fig. 2.19: DCI attachment of light cableTelescopeThere are two type of telescope, rigid and flexible.The rigid laparoscopic and thoracoscopic telescopes comein a variety of shapes and sizes, and offering several differentangles of view. The standard laparoscope consists of a metalshaft between 24 to 33 cm in length.There are three important structural differences intelescope available in the market: No. of the rod lens: From 6 to 18 rod lens system telescopes The Angle of view: Between 0 degree to 120 telescopes The Diameter: 1.5 to 15 mm of telescopes.Fig. 2.20: Negligence with light cable can

This electrical arc is produced in same way as in flash of photographic camera. Xenon has a more natural color spectrum and a smaller spot size than halogen. The xenon light source emits a spectral temperature of color of approximately 6000 Kelvin on average for a power of 300 W (Fig. 2.3). Arc generated lamps have a spectral temperature that