Light source apparatus using electric lamp as light source

A light source apparatus including a discharge lamp, said discharge lamp being subject to progressive degradation during use so that its output light intensity achievable with a given level of electrical input gradually decreases through its lifetime, said apparatus comprising:

• an output light intensity control for controlling electrical input to said discharge lamp in order to maintain output light intensity of said discharge lamp at a substantially fixed, desired intensity level, said output light intensity control comprising:
• a) an output light intensity detector for detecting output light intensity of said discharge lamp and providing an intensity detection signal indicative of a detected level of output light intensity of said discharge lamp;
• b) a reference signal generator for generating a reference signal indicative of a reference level corresponding to said desired intensity level of output light of said discharge lamp;
• c) a differential generator connected to receive said intensity detection signal and said reference signal so as to produce an output signal indicative of a difference in level between said detection signal and said reference signal;
• d) a control signal generator for responding to said output signal from said differential generator by generating a control signal;
• and
• e) a current control element for controlling input current to said discharge lamp in response to said control signal;
• a detector for detecting an electrical parameter relating to electrical input to said discharge lamp, said electrical parameter having a tendency that its level for achieving a given level of output light intensity of said discharge lamp gradually and monotonically varies through the lifetime of said discharge lamp;
• and
• an indicator for determining when a level of said electrical parameter detected by said detector has reached a threshold level and providing an indication when said indicator determines so.

A light source apparatus including a discharge lamp, said discharge lamp being subject to progressive degradation during use so that its output light intensity achievable with a given level of electrical input gradually decreases through its lifetime, said apparatus comprising:

• an output light intensity control for controlling electrical input to said discharge lamp in order to maintain output light intensity of said discharge lamp at a substantially fixed, desired intensity level;
• a detector for detecting an electrical parameter relating to electrical input to said discharge lamp, said electrical parameter having a tendency that its level for achieving a given level of output light intensity of said discharge lamp gradually and monotonically varies through the lifetime of said discharge lamp, wherein said detector provides a detection signal indicative of a detected level of said electrical parameter;
• and
• an indicator for determining when the level of said electrical parameter detected by said detector has reached a threshold level and providing an indication when said indicator determines so, said indicator comprising:
• a threshold signal generator for generating a threshold signal indicative of said threshold level;
• a comparator connected to receive said detection signal and said threshold signal so as to produce an output signal indicative of comparison between said detection signal and said threshold signal;
• and
• an alarm generator for responding to said output signal from said comparator by selectively generating an alarm indication.

A light source apparatus for a video endoscope system including an endoscope with an image sensor for sensing an image under illumination provided by said light source apparatus, said light source apparatus comprising:

• a discharge lamp;
• a power supply for said discharge lamp;
• an output light intensity detector for detecting an intensity level of output light of said discharge lamp to be supplied to said endoscope;
• an electrical input control for controlling electrical input to said discharge lamp in order to maintain output light intensity of said discharge lamp as detected by said output light intensity detector at a substantially fixed, desired intensity level;
• an electrical input detector for detecting electrical input to said discharge lamp;
• and
• an indicator for determining when a level of electrical input to said lamp, as detected by said electrical input detector, has reached a threshold level and providing an indication when said indicator determines so;
• and
• said desired intensity level being selected such that said discharge lamp will produce output light at said desired intensity level when it is supplied with electrical input at a level below a rated electrical input level of said discharge lamp.