LIGHT SOURCES 



The life of the lamp varies inversely with the number of starts to which it is 

 subjected, but with normal use a life of 500 hours can be expected, by which 

 time the hght output will have dropped to 80 per cent of its initial value. 



Molybdenum 

 foil seal 



Starting 

 winding 



Tungsten 

 electrode 



Auxiliary, 

 electrode 



Auxiliary/' 

 electrode seal 



Starting/ ' 

 resistance 



Outer glass envelope 

 filled with inert gas 



Heat shield 

 Quartz bulb 

 Heat shield 



Pre-focus cap 



Figure 28.10 Construction of Mazda type ME compact source lamp 



2Q000 



Across arc 

 plane AB 



10 



«/) 



I 1QpOO 



m 



Arc length 375mm 

 Voltage drop 70V 

 Lamp wattage 250W 



<SI 



E 

 o 

 in 

 0) 



c 



't_ 



m 





 8Q000r 



2 10 1 



Distance across arc 



2 



mm 



Along 

 arc 

 6Q0O0- plane 



^QDOO- 

 20,000 



2 10 12 



Distance along arc mm 



Figure 28.11 Brightness distribution of arc of 250W type ME lamp 



The luminance varies from point to point on the arc {Figure 28.11). 

 Most of the arc area has a luminance of 20,000 cd/cm^, but there are two 

 small areas, near the electrodes, which reach a luminance of 80,000 cd/cm^ 



345 



