Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
  • H05B41/02—Details
  • H05B41/04—Starting switches
  • H05B41/048—Starting switches using electromagnetic relays

Definitions

• the invention relates to image transmission technology, in particular to document scanning using DC-operated discharge lamps.
• the filling of these lamps consists of a heavy gas, usually mercury vapor, which, when excited by the discharge, emits radiation predominantly in the ultraviolet range. This in turn strikes a coating applied to the inner wall of the discharge tube, which has the property of emitting light in the visible range when exposed to UV radiation.
• a depletion of mercury occurs in the vicinity of the anode, because the mercury atoms ionized by impact ionization by so-called Cataphoresis are moved to the cathode and accumulate there. The result is that the number of non-excited mercury atoms in the anode environment and thus the likelihood of impact ionization is reduced.
• the UV radiation generated and therefore the excitation of the phosphor is therefore less there.
• the tube darkens at the anode end and can no longer meet the requirement for uniform illumination of an image line for scanning.
• the described effect is time-dependent and occurs quite suddenly after a few hours of constant luminance.
• Polarity reversal circuits that are manually operated by the operator after a certain time are not suitable for image scanning devices because their operation is often forgotten. Even a simple polarity reversal by means of a time switch is not usable for image scanning because the probability that this changeover takes place in the middle of a transmission is too great. Because the lamp during polarity reversal - even if only briefly extinguishes completely - the transmission would be disturbed.
• the object of the invention is to provide a circuit which automatically reverses the polarity before the luminance distribution along the tube becomes uneven by cataphoresis, which ensures that the polarity reversal never takes place during an ongoing transmission and which thus ensures that the lamp, viewed over its entire life, is operated in half in both polarities.
• the invention achieves this in that the
• Lamp burn time is measured and stored in a first polarity during a first image transfer, the polarity is changed before the start of a second image transfer, the lamp burn time is also measured and stored in the second polarity, so that the difference between the first and second burn duration is formed and stored and that in this way, for all further transmissions, a transmission of the total burning time taking into account the polarity is formed, which, compared to the burning time of the last transmission, only then the lamp voltage before the following transmission reversed polarity if the last burn time was longer than the saved carry.
• the invention is based on the
• Fig. 1 Basic circuit
• Fig. 2 flow chart
• a microcomputer 2 e.g. Intel 8748
• the microcomputer also ignites the fluorescent lamp 3, which is used for line-by-line illumination in the case of electron-optical scanning.
• the fluorescent lamp 3 is switched on by means of a corresponding output signal of the microcomputer 2 at the output 4 via a transistor 5.
• the fluorescent lamp 3 is operated with direct current for the reasons mentioned above.
• the ignition takes place in the usual way a starter 6 and an upstream choke 7.
• a current-limiting resistor 8 is inserted into the circuit.
• the counting process starts again and is stopped with this transfer.
• the microcomputer 2 compares this last burning time with the stored difference and derives a criterion as to whether the polarity reversal relay 11 is excited via the output 9 and the driver stage 10 or not.
• the polarity reversal relay always reverses the lamp voltage if the last burning time is longer was the stored burn time difference of the previous samples. For all further transmissions, these processes take place in a similar manner, the last burning time always being compared with the stored transmission of the previous total burning time, taking into account the polarity.
• the polarity reversal takes place through the relay contacts 12 and 13. Although the transmission times can be very different, the described manner results in a halve distribution of the two polarities over the life of the lamp and thus an increase in the lamp life under the specified operating conditions.
• a corresponding circuit can also be constructed with conventional counter and memory modules, but the use of microcomputers can already be regarded as state of the art today.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mixers Of The Rotary Stirring Type (AREA)
• Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
• Control Of Indicators Other Than Cathode Ray Tubes (AREA)
• Circuit Arrangement For Electric Light Sources In General (AREA)
• Lasers (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6711786

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (1)

Citations (2)

Family Cites Families (3)

• 1980
  • 1980-11-22 EP EP80902230A patent/EP0064493B1/de not_active Expired
  • 1980-11-22 JP JP56500013A patent/JPS6047720B2/ja not_active Expired
  • 1980-11-22 WO PCT/DE1980/000174 patent/WO1982001802A1/de not_active Ceased
• 1982
  • 1982-06-25 NO NO82822148A patent/NO159690C/no unknown
  • 1982-07-19 DK DK321982A patent/DK321982A/da not_active Application Discontinuation

Patent Citations (2)

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