Flash lamp

Abstract

A flash lamp (1) is provided with: a lamp housing (2) in which an inert gas is introduced and sealed; a cathode (20) and an anode (30) that generate arc discharge; a trigger electrode (40) that performs preliminary discharge prior to the arc discharge; and a plurality of sparkers (60, 70) that promote ionization for starting the arc discharge. The plurality of sparkers (60, 70) are arranged at a distance from each other. At least one of the plurality of sparkers (60, 70) can be placed in the vicinity of the cathode (20). The trigger electrode (40) can be provided in a plurality.

Description

flash lamp

[0001] The present invention relates to a flash lamp.

[0002] In recent years, flash lamps, which use xenon gas as the inert gas, have been used as light sources for spectroscopic analysis because they can emit a strong emission spectrum across a wide range from ultraviolet to infrared. Applications include water quality testing equipment, automobile exhaust gas monitors, and nitrogen oxide monitors. Because light emission is achieved through an arc discharge caused by the discharge of a charged capacitor, these lamps offer higher light output, less heat generation, and a longer lifespan than light sources such as deuterium lamps. Their energy-saving and maintenance-free nature make them popular light sources.

[0003] However, conventional flash lamps have drawbacks such as flash misses, where no light is emitted, fluctuations in light emission intensity with each light emission, or a decrease in the absolute value of light emission intensity as the number of discharges accumulates, and various methods have been attempted to improve these. For example, if a metal material containing a large amount of barium on a tungsten base with a lower work function is used as the cathode material to facilitate electron emission, the electrode will wear out rapidly and its life will be shortened. In addition, sputtering caused by arc discharge is likely to cause the glass panel through which the emitted light passes to become cloudy, and the light emission intensity will decrease as the number of discharges accumulates.

[0004] One possible solution to this problem is to reduce the amount of barium to reduce spatter. However, even when the spatial distance between the cathode and anode for arc discharge is short, the arc discharge may not initiate in the early stages due to the accumulation of discharges, resulting in no light emission. Therefore, measures are taken to compensate for the difficulty in discharging from the electrodes by providing multiple trigger electrodes. However, even with this method, there are cases where a flash miss occurs, in which the arc discharge does not initiate and no light emission occurs. On the other hand, even if this flash miss phenomenon is avoided, the path of the arc discharge may vary slightly from discharge to discharge. In optical systems where the light emitted from the flash lamp passes through a narrow slit, problems such as an increase in aperture dipping, in which the amount of light passing through the slit appears to fluctuate, can occur.

[0005] Patent Document 1 describes a technology that reduces variations in the discharge path for each pulse emission and improves the stability of the light output. A cathode and an anode that generate an arc discharge are arranged opposite each other in a lamp housing filled with inert gas, and multiple needle-shaped trigger electrodes that generate a preliminary discharge prior to the arc discharge are arranged between the cathode and anode.

[0006] US Patent No. 5,949,999 describes a technique that reduces the labor, cost, and operational variability associated with flash lamps and associated sparkers. The sparker is integrated directly into the hermetic feedthrough header of the flash lamp.

[0007] Patent No. 4575012 Patent No. 6097437

[0008] The flash lamps of Patent Documents 1 and 2 have improved light output stability, but what is desired is a xenon flash lamp that further minimizes fluctuations in light emission intensity for each light emission and eliminates the characteristic in which the absolute value of light emission intensity decreases with the accumulation of discharges.

[0009] Furthermore, a xenon flash lamp having the above characteristics is desirable, even for flash lamps with a long arc discharge distance between the cathode and anode. Furthermore, a xenon flash lamp is desired that can reduce the number of leads embedded in and leading out of the flash lamp, ensure a sufficient creepage distance between pads when connecting the flash lamp to a pattern on a printed circuit board, make creepage discharge less likely, and reduce the temperature rise of the cathode.

[0010] In view of the above problems, an object of the present invention is to provide a flash lamp that can obtain a stable light output and can prevent the light emission intensity from decreasing due to the accumulation of the number of discharges.

[0011] To solve the above problems, a flash lamp according to a first aspect of the present invention comprises a lamp housing filled with an inert gas and sealed, a cathode and an anode for generating an arc discharge, a trigger electrode for generating a preliminary discharge prior to the arc discharge, and a plurality of sparkers for promoting ionization for starting the arc discharge, the plurality of sparkers being spaced apart from one another. The cathode and anode for generating an arc discharge and the trigger electrode for generating a preliminary discharge prior to the arc discharge are disposed within the lamp housing filled with an inert gas, and the plurality of sparkers for promoting ionization for starting the arc discharge are disposed spaced apart from one another. This allows for a wider ionization area due to ultraviolet light generated when the sparkers emit light, facilitating the emission of electrons from the cathode, anode, or trigger electrode into the plasma. In the flash lamp, at least one of the plurality of sparkers may be disposed near the cathode. Since at least one of the plurality of sparkers for promoting ionization for starting the arc discharge is disposed near the cathode, the emission of electrons from the cathode, which is the starting point of light emission, into the plasma is facilitated, more reliably, and stably. The flash lamp may also comprise a plurality of trigger electrodes. A plurality of trigger electrodes are arranged near the arc discharge path between the cathode and anode so that the tip of each trigger electrode is positioned approximately on a line connecting the small spherical portions on the opposing end faces of the cathode and anode, thereby achieving stable light emission even when the arc discharge distance between the cathode and anode is long. The cathode, anode, trigger electrode, and multiple sparklers of the flash lamp are arranged above the stem within the lamp housing, and leads supplying electricity to the anode, trigger electrode, and multiple sparklers are embedded and electrically insulated from the stem and extend to the outer surface of the lamp housing. The stem may include a metal exhaust pipe, which is connected to the cathode and serves as a power supply terminal. Since the metal exhaust pipe is connected to the cathode within the lamp housing, the cathode lead can be eliminated, and the reduced number of leads allows for a smaller flash lamp. Furthermore, the increased creepage distance between the patterns to which the leads are attached when connecting to a printed circuit board pattern also allows for a smaller printed circuit board.Furthermore, heat generated by the cathode due to light emission can be dissipated by a metal exhaust pipe, thereby reducing the temperature rise of the flash lamp and the amount of spatter due to arc discharge. The cathode, anode, trigger electrode, and multiple sparkers of the flash lamp are disposed above a stem within the lamp housing, and leads for supplying electricity to the cathode, trigger electrode, and multiple sparkers are embedded and electrically insulated from the stem and led to the outer surface of the lamp housing, and the stem is provided with a metal exhaust pipe, which serves as a terminal for connecting to the anode to supply power. This provides the same effect as when the exhaust pipe is connected to the cathode to supply power. A flash lamp according to a second aspect of the present invention comprises a lamp housing filled with an inert gas and sealed, a cathode and an anode for generating an arc discharge, a trigger electrode for performing a preliminary discharge prior to the arc discharge, and a sparker for promoting ionization for starting the arc discharge, wherein the cathode, the anode, the trigger electrode, and the sparker are disposed above a metal stem within the lamp housing, leads for supplying electricity to the anode, the trigger electrode, and the sparker are embedded and electrically insulated from the stem and extend to the outer surface of the lamp housing, the stem is connected to the cathode, and the sparker comprises a sparker pin and a conductive plate surrounding the sparker pin with an insulator interposed therebetween and extending in a direction away from the sparker pin, the conductive plate being connected to the stem. This allows for greater freedom in sparker placement, and even in the case of a single sparker, the flash lamp can be made even simpler and more compact. The stem of the flash lamp may include a metal exhaust pipe, and the exhaust pipe may be connected to the cathode and used as a terminal for supplying power. The flash lamp may further include a metal cap that covers the cathode, the anode, the trigger electrode, and the sparker, and the stem and the cap may be electrically connected. This allows the cathode to be located close to the cap.More specifically, problems that occur when the cap is not electrically connected to the cathode, such as a discharge occurring between the cathode and the cap when the cathode is brought close to the cap, causing a stray current to flow and causing the flash lamp to malfunction, can be avoided.

[0012] The flash lamp of the present invention can provide a stable light output and can prevent the light emission intensity from decreasing due to the accumulation of the number of discharges.

[0013] 11 is a partially cutaway perspective view of a flash lamp according to a first embodiment of the present invention; FIG. 12 is a partially cutaway side view of the flash lamp of FIG. 1; FIG. 13 is a plan view showing the arrangement of a cathode, an anode, a trigger electrode, and a sparker in a state where the transmission glass and cap of the flash lamp of FIG. 1 have been removed; FIG. 14 is a plan sectional view of a sparker of the flash lamp of FIG. 1; FIG. 15 is a side sectional view of a sparker of the flash lamp of FIG. 1; FIG. 16 is a plan view showing an arrangement of a cathode, an anode, a trigger electrode, and a sparker that is different from that of FIG. 3; FIG. 17 is a plan view showing an arrangement of a cathode, an anode, a trigger electrode, and a sparker that is different from that of FIG. 3; FIG. 18 is a plan view showing an arrangement of a cathode, an anode, a trigger electrode, and a sparker in a state where the transmission glass and cap of a flash lamp according to a second embodiment of the present invention have been removed; FIG. 19 is a plan view showing an arrangement of a cathode, an anode, a trigger electrode, and a sparker that is different from that of FIG. 9; FIG. 19 is a partially cutaway perspective view of a flash lamp according to a third embodiment of the present invention; FIG. 11 is a rear view of the flash lamp of FIG. 11 with the transmission glass and cap removed; Fig. 12 is a plan view showing the arrangement of the cathode, anode, trigger electrode, and sparker in the state where the transmission glass and cap of the flash lamp of Fig. 11 are removed. Fig. 13 is a block circuit diagram of a lighting device that lights a flash lamp according to embodiment 1 or 3 of the present invention. Fig. 14 is a partial block circuit diagram of a lighting device that lights a flash lamp according to embodiment 2 of the present invention.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, common parts are assigned the same reference numerals, and duplicate explanations of parts with the same reference numerals will be omitted. Note that in the following embodiments, an example will be described in which two sparkers (a first sparker 60 and a second sparker 70) are provided as the multiple sparkers, but the present invention is not limited to this and can be applied to flash lamps provided with three or more sparkers.

[0015] (Embodiment 1) The configuration of a flash lamp 1 according to this embodiment 1 will be described with reference to Figures 1 to 8. As shown in Figure 1, the flash lamp 1 comprises a lamp housing sealed and filled with an inert gas, a cathode 20 and an anode 30 for generating an arc discharge, a trigger electrode 40 for performing a preliminary discharge prior to the arc discharge, and a plurality of sparkers (a first sparker 60 and a second sparker 70) for promoting ionization for starting the arc discharge. The first sparker 60 and the second sparker 70 are spaced apart so that when they discharge, the sparks spark without mixing or interfering with each other. The enclosed inert gas may be, for example, xenon gas.

[0016] The opposing ends of the cathode 20 and the anode 30 have a generally conical shape with a small spherical tip to generate an arc discharge along a stable path. Lead rods 21 and 31 made of molybdenum or the like are press-fitted into the other ends of the cathode 20 and the anode 30, respectively, and the lead rods 21 and 31 are further fixed to leads 22 and 32 by spot welding or the like. The cathode 20 and the anode 30 use an electron-emitting material with a small work function, such as a tungsten base containing barium oxide, aluminum oxide, calcium oxide, or the like.

[0017] 2 and 3 , the lead 32 electrically connected to the anode 30 is embedded in the metal, disk-shaped stem 3 so as to penetrate the stem 3 via a glass, hemispherical insulator 33 that ensures a long creepage distance. The cathode 20 can also be configured in the same manner as the anode 30, but in this embodiment, the lead 22 electrically connected to the cathode 20 is fixed by welding to the surface of the metal stem 3. In other words, the stem 3 is electrically connected to the cathode 20.

[0018] The lamp housing 2 includes a stem 3, a metal cap 4, and a transmission glass 5. The cathode 20, the anode 30, the trigger electrode 40, and the sparklers 60 and 70 are disposed above the stem 3 in the lamp housing 2, and the metal cap 4 is disposed to cover the cathode 20, the anode 30, the trigger electrode 40, and the sparklers 60 and 70. One end of the cap 4 is fitted onto the outer circumferential portion of the metal stem 3, and the fitting portion is welded and sealed. Meanwhile, the other end of the cap 4 has a flange to which transmission glass 5 made of a material such as quartz glass or borosilicate glass is fused, allowing arc discharge light from the cathode 20 and the anode 30 to pass. The metal stem 3 and the metal cap 4 are connected by welding, so that the cap 4 is also electrically connected to the cathode 20. This allows the cathode 20 to be positioned close to the cap 4. More specifically, problems such as discharge occurring between the cathode 20 and the cap 4 due to bringing the cathode 20 close to the cap 4, which occurs when the cap 4 is not electrically connected to the cathode 20, can be avoided.

[0019] A metal exhaust pipe 6 is welded to the center of the stem 3. An inert gas such as xenon gas is injected through the exhaust pipe 6, and the exhaust pipe 6 is then sealed to hermetically seal the lamp housing 2. As described above, in this embodiment, the lead 22 connected to the cathode 20 is welded to the surface of the stem 3, so that the exhaust pipe 6 extending outside the lamp housing 2 can be electrically connected to serve as a heat dissipation path for the cathode 20. That is, the exhaust pipe 6 can be connected to the cathode 20 and used as a terminal for supplying power. This is the configuration used in this embodiment. Note that the electrical connection with the stem 3 is not limited to this embodiment; a configuration in which the anode 30 is connected to the stem 3 is also possible. The exhaust pipe 6 can also be connected to the anode 30 and used as a terminal for supplying power. In this case, the lead 22 electrically connected to the cathode 20 is embedded (not shown) in the disk-shaped metal stem 3, penetrating a hemispherical glass insulator with a long creepage distance.

[0020] The trigger electrode 40 is made of tungsten or the like. As shown in FIG. 3 , the tip of the trigger electrode 40 is positioned slightly closer to the cathode 20 on a line connecting the small spherical portions of the opposing end faces of the cathode 20 and the anode 30. A lead 42 is fixed to the trigger electrode 40 by spot welding or the like, and, like the anode 30, penetrates the stem 3 via a glass insulator 43 and extends to the outside of the lamp housing 2. In this embodiment, the leads 22, 32, 42, 62, 72, the stem 3, the cap 4, and the exhaust pipe 6 are made of metal, such as Kovar metal. Although the stem 3, the cap 4, and the exhaust pipe 6 are made of metal in this embodiment, the materials are not limited to metal and may be glass or the like.

[0021] As shown in the cross-sectional views of Figures 4 and 5, the first sparker 60 has a structure in which a sparker pin 61 made of tungsten or the like is inserted into a cylindrical insulator 64 made of alumina or the like with sufficient tracking resistance, and is surrounded by a conductive plate 65 serving as a cathode. That is, the sparker pin 61 is surrounded by the conductive plate 65 via the insulator 64. The conductive plate 65 is, for example, a nickel plate, and extends in a direction away from the sparker pin 61. The end of the conductive plate 65 opposite the sparker pin 61 is welded to the stem 3. One end of the sparker pin 61 is extended to the outside of the lamp housing 2 via a lead 62 that is embedded in the stem 3 and passes through a glass insulator 63. At the other end of the sparker pin 61, as shown in Figure 4, the end faces of the sparker pin 61, insulator 64, and conductive plate 65 are arranged approximately flush with each other, and creeping or space discharge occurs between the sparker pin 61 and the conductive plate 65. Similar to the first sparker 60, the second sparker 70 is also composed of a glassy insulator 73, a cylindrical insulator 74 made of alumina or the like, a conductive plate 75 made of nickel or the like, a lead 72, and a sparker pin 71. In this way, by configuring the conductive plates 65, 75 of the first sparker 60 and the second sparker 70 to be fixed by welding to the stem 3 electrically connected to the cathode 20, it is possible to increase the degree of freedom in the arrangement of the first sparker 60 and the second sparker 70.

[0022] As shown in Figures 1 and 3, in this embodiment, the first sparker 60 and the second sparker 70 are arranged near the cathode 20. The arrangement of the first sparker 60 and the second sparker 70 is not limited to the arrangement shown in Figure 3; only one of them may be arranged near the cathode 20, or neither may be arranged near the cathode 20. As described above, the first sparker 60 and the second sparker 70 are arranged at a distance from each other. If they are arranged too close to each other, a malfunction occurs in which the respective discharges mix and interfere with each other, so it is preferable to avoid them being too close. Furthermore, if the first sparker 60 and the second sparker 70 are arranged too close to the cathode 20 or the anode 30, a similar malfunction occurs, so they are arranged at a distance that does not cause spatial discharge.

[0023] In the flash lamp 1 configured as described above, the main discharge capacitor (107 in FIG. 14) connected in parallel between the cathode 20 and anode 30 that generate the arc discharge is charged to approximately 300 V to 1000 V, with the cathode 20 at a negative potential and the anode 30 at a positive potential. In this charged state, a steep spike voltage of approximately 4000 V of negative potential is applied between the cathode 20, the sparker pin 61 of the first sparker 60, the sparker pin 71 of the second sparker 70, the trigger electrode 40, and the anode 30, with the cathode 20 at the reference potential.

[0024] When the steep spike voltage reaches a spike voltage value of about 500 V to 2500 V after a few hundred nanoseconds while rising toward about 4000 V, preliminary discharges start at different spike voltage values ​​between the cathode 20 and the trigger electrode 40, between the conductive plate 65 electrically connected to the cathode 20 and the sparker pin 61, and between the conductive plate 75 and the sparker pin 71, and ionization for starting the arc discharge progresses. After that, about 1 microsecond later, the space filled with inert gas between the cathode 20 and the anode 30 breaks, causing an arc discharge and light emission.

[0025] In this embodiment, the first sparker 60 and the second sparker 70, which perform preliminary discharge prior to arc discharge, are located near the cathode 20, so that ionization for starting arc discharge is evenly performed over a wide area. This facilitates electron emission from the cathode 20 toward the anode 30 into the plasma atmosphere, reliably avoiding, for example, the problem of arc discharge not starting even when a steep spike voltage is applied. Furthermore, because the cathode 20 or the anode 30 is formed from a conductive material with a high tungsten content, electron emission is at a normal level, but electrode wear is minimal, resulting in stable light output and preventing a decrease in light emission intensity due to the accumulation of discharges.

[0026] Furthermore, comparing the present embodiment with the prior art, which uses multiple trigger electrodes 40 for preliminary discharge prior to arc discharge, the prior art has the drawback that, because the tips of the multiple trigger electrodes 40 are positioned near the arc discharge path between the cathode 20 and the anode 30, the shadow of the trigger electrodes 40 may be reflected in the slit depending on the arc discharge path if the slit width of the optical system is short. On the other hand, the first sparker 60 and the second sparker 70 of the present embodiment discharge between the lead 62 and the conductive plate 65 in the first sparker 60, and between the lead 72 and the conductive plate 75 in the second sparker 70, so that the discharge path is self-contained. Therefore, there is a high degree of freedom in the installation location of the first sparker 60 and the second sparker 70, and they do not need to be installed on or near the arc discharge path between the cathode 20 and the anode 30, so the above-mentioned drawback does not occur. The same applies to the case where three or more sparkers are provided.

[0027] Furthermore, in this embodiment, the metal exhaust pipe 6 welded to the center of the stem 3 is used as a terminal for supplying power to the cathode 20 extending outside the flash lamp 1. This reduces the number of leads extending from the flash lamp 1 and the projected area of ​​the flash lamp 1. This increases the creepage distance between the patterns to which the leads of the flash lamp 1 are attached when connecting the leads to the patterns on a printed circuit board. This increases the creepage discharge inception voltage between the patterns on the printed circuit board, eliminating or simplifying the need for insulation treatment of the printed circuit board surface. Furthermore, the heat generated by the cathode 20 due to light emission can be dissipated by the metal exhaust pipe, suppressing the temperature rise of the flash lamp 1 and reducing the amount of spatter associated with arc discharge. Using the metal exhaust pipe 6 as a terminal for supplying power to the cathode 20 is particularly useful for flash lamps with a small outer diameter of the lamp housing 2. Similar effects can be achieved when the metal exhaust pipe 6 is used as a terminal for supplying power to the anode 30 extending outside the flash lamp 1. Furthermore, even in the case of a single sparker, the metal exhaust pipe 6 can be used as a terminal for supplying power to the cathode 20 or anode 30 extending outside the flash lamp 1, which makes it possible to further simplify and miniaturize the flash lamp 1.

[0028] (Variation 1) Next, several variations will be described which have arrangements different from that shown in Fig. 3. Figs. 6 to 8 are plan views showing the cathode 20, anode 30, trigger electrode 40, first sparker 60, and second sparker 70 in an arrangement different from that shown in Fig. 3. In the variation shown in Fig. 6, the first sparker 60 is arranged near the cathode 20, and the second sparker 70 is arranged near the anode 30, both of which are arranged on the trigger electrode 40 side. This arrangement also provides the same effect as the previous embodiment (the arrangement of Fig. 3).

[0029] 7, the first sparker 60 is disposed near the cathode 20, and the second sparker 70 is disposed near the anode 30, both of which are disposed on the side opposite the trigger electrode 40. This not only achieves the effects of the previous embodiment, but also makes it easier to assemble the electrodes and to provide insulation within the lamp housing 2 or between the leads 32, 42, 62, and 72.

[0030] 8, the first sparker 60 is disposed near the cathode 20, and the second sparker 70 is disposed near the anode 30, with the first sparker 60 on the trigger electrode 40 side and the second sparker 70 on the side opposite the trigger electrode 40. In this way, in addition to the effects of the previous embodiment, the first sparker 60 and the second sparker 70 are disposed at positions apart from each other, which makes assembly of the first sparker 60 and the second sparker 70 easier, and improves the ease of assembly of the entire flash lamp 1.

[0031] 9 and 10 are plan views showing the arrangement of the cathode 20, anode 30, first trigger electrode 40, second trigger electrode 50, first sparker 60, and second sparker 70 of a flash lamp 100 according to a second embodiment of the present invention, with the transmission glass 5 and cap 4 removed. The configurations of the lamp housing 2, cathode 20, anode 30, first trigger electrode 40, second trigger electrode 50, first sparker 60, and second sparker 70 constituting the flash lamp 100 are the same as those of the first embodiment, and therefore description thereof will be omitted. The difference between the first embodiment and the second embodiment is that multiple trigger electrodes are provided. FIGS. 9 and 10 illustrate a flash lamp 100 in which the distance between the tips of the cathode 20 and the anode 30 (electrode spacing) is wider than that of the first embodiment. In the case of a flash lamp 100 with such a wide electrode spacing, providing two trigger electrodes can facilitate arc discharge. 9 and 10, two trigger electrodes are provided, but three or more may be provided. The two trigger electrodes in this embodiment are referred to as a first trigger electrode 40 (the trigger electrode 40 in FIGS. 3 to 8) and a second trigger electrode 50, respectively.

[0032] In the example shown in FIG. 9 , the second trigger electrode 50 has the same configuration and structure as the first trigger electrode 40, and its tip is positioned approximately on the line connecting the small spherical portions on the opposing end faces of the cathode 20 and the anode 30. Like the first trigger electrode 40, a lead 52 is fixed to the second trigger electrode 50 by spot welding or the like, penetrates the stem 3 via a glass insulator 53, and is extended to the outside of the lamp housing 2. By positioning the tips of the first trigger electrode 40 and the second trigger electrode 50 near the arc discharge path between the cathode 20 and the anode 30, stable light emission can be achieved even when the arc discharge distance between the cathode 20 and the anode 30 is long. FIG. 9 shows an example in which the first sparker 60 is positioned near the cathode 20 and the second sparker 70 is positioned near the anode 30. The effect of providing two sparkers in the second embodiment is similar to that in the first embodiment.

[0033] The example shown in Fig. 10 has the same configuration as the example shown in Fig. 9 in which a second trigger electrode 50 is newly provided, but is mainly devised in terms of the arrangement of the first trigger electrode 40 and the second trigger electrode 50. Specifically, the implanted leads 42 and 52 are assembled so that the tips of the first trigger electrode 40 and the second trigger electrode 50 are positioned approximately on a line connecting the small spherical portions on the opposing end faces of the cathode 20 and the anode 30, while the shapes of the implanted leads 42 and 52 remain approximately linear. As shown in Fig. 10, the first sparker 60 and the second sparker 70 are provided near the cathode 20, facing each other with the cathode 20 in between. The flash lamp 100 of the example shown in Fig. 10 can obtain the same effects as the example shown in Fig. 9, and is also easy to assemble.

[0034] (Embodiment 3) Fig. 11 is a partially cutaway perspective view of a flash lamp 200 according to Embodiment 3 of the present invention. Fig. 12 is a rear view of the flash lamp 200 with the transmission glass 5 and cap 4 removed, and Fig. 13 is a plan view of the flash lamp 200 with the transmission glass 5 and cap 4 removed, showing the arrangement of the cathode 20, anode 30, trigger electrode 40, first sparker 60, and second sparker 70. Embodiment 3 differs from Embodiment 1 in that the stem 3 and cap 4 are formed of glass rather than a metal such as Kovar. Accordingly, the lead 22 fused to the cathode 20 is embedded in and penetrates the stem 3, and the conductive plates 65, 75 of the first sparker 60 and second sparker 70, respectively, are electrically connected to the lead 22 of the cathode 20. The remaining configuration is the same as in Embodiment 1, and therefore a description thereof will be omitted.

[0035] If the stem 3 and the cap 4 are made of glass, the lead rods 21, 31 of the cathode 20 and the anode 30, the trigger electrode 40, etc. can be prevented from approaching the stem 3 or the cap 4 and discharging with them, which is effective when the flash lamp 200 has a small diameter.

[0036] In the third embodiment, the effect of providing two sparkers is the same as in the first embodiment. The effect of the present invention can be achieved whether the material of the exhaust pipe 6 is metal or glass. Furthermore, even when the arc discharge distance between the cathode 20 and the anode 30 is long, stable light emission can be obtained by providing two trigger electrodes as in the second embodiment.

[0037] [Block Circuit Diagram of Lighting Device] Next, block circuit diagrams of lighting devices that light the flash lamps of embodiments 1 to 3 will be described with reference to Fig. 14 and Fig. 15. Fig. 14 is a block circuit diagram of a lighting device that lights the flash lamp of embodiment 1 or embodiment 3. Fig. 15 is a partial block circuit diagram of a lighting device that lights the flash lamp of embodiment 2.

[0038] First, the configuration of the block circuit diagram in Figure 14 will be described. Terminal A is a power input terminal, and terminal B is a GND terminal for power terminal A, through which DC power is supplied. The supply voltage typically ranges from the 3.3V system used by USB to the 24V system used in FA control. Terminal C is an input terminal for a pulse voltage signal that lights up the flash lamp 1.

[0039] One end of the primary winding of flyback transformer 102 is connected to terminal A, the other end is connected to the drain of MOSFET 111, and the source of MOSFET 111 is connected to terminal B. By switching MOSFET 111 on and off, main discharge capacitor 107 is charged to a predetermined voltage between 300 V and 1000 V in this case from the secondary winding of flyback transformer 102 via reverse blocking diode 103. Both ends of main discharge capacitor 107 are connected to anode 30 and cathode 20 of flash lamp 1 to form an arc discharge circuit.

[0040] A charging circuit for pulse-generating capacitor 109 is formed from the intermediate winding of the secondary winding of flyback transformer 102 via reverse-blocking diode 104 to the primary side of trigger transformer 110, and a regulator 106 is provided midway along the circuit to keep the charging voltage of pulse-generating capacitor 109 constant at a point between approximately 100 V and 200 V. IGBT 108 discharges the charge stored in pulse-generating capacitor 109 to the primary side of trigger transformer 110.

[0041] A high-voltage pulse voltage of approximately 4000 V is output from the secondary winding of trigger transformer 110, and DC blocking capacitors 81 to 84 have one end connected to the secondary winding of trigger transformer 110 and the other end connected to the anode 30, trigger electrode 40, first sparker 60, and second sparker 70 of flash lamp 1, respectively, as shown in Figure 14. High-resistance discharge resistors 91 to 94 are connected in parallel to capacitors 81 to 84, respectively.

[0042] In the partial block circuit diagram of Fig. 15, parts with the same functions as those in Fig. 14 are assigned the same numbers. In the partial block circuit diagram of Fig. 15, a DC blocking capacitor 85 and high resistance discharge resistors 95 and 96 have been added for the second trigger electrode 50 for the same purposes as those described above.

[0043] Of the inputs to controller 101, the P terminal is connected to the A terminal, the G terminal is connected to the B terminal, and the IN2 terminal receives a reference input of the charging voltage of main discharge capacitor 107. Of the outputs of controller 101, the O1 terminal is connected to the gate of MOSFET 111, and the O2 terminal is connected to the base of IGBT 108. The IN1 terminal is a terminal to which a pulsed trigger signal for emitting light from flash lamp 1 connected to the C terminal is input, and controller 101 is configured to emit light once in response to the input of one trigger signal.

[0044] 14 and 15. Until immediately before a pulsed trigger signal is input from the IN1 terminal, the controller 101 references the charging voltage of the main discharge capacitor 107 from the IN2 terminal and outputs a pulse width control signal from the O1 terminal to the MOSFET 111 so that the charging voltage coincides with a predetermined target charging voltage.

[0045] When MOSFET 111 is turned on, the primary winding of flyback transformer 102 is excited, and when the excitation of the primary winding is stopped by turning MOSFET 111 off, the magnetic energy stored in flyback transformer 102 charges main discharge capacitor 107 and pulse generating capacitor 109, which are connected from the secondary winding via diodes 103 and 104, respectively.

[0046] When a trigger signal is input from the IN1 terminal while the main discharge capacitor 107 and the pulse-generating capacitor 109 are charged to a predetermined voltage, the controller 101 stops outputting the pulse width control signal from the O1 terminal for approximately 500 microseconds. This stops charging the main discharge capacitor 107 and the pulse-generating capacitor 109 for 500 microseconds. Simultaneously with this operation, the controller 101 outputs a pulse signal, lasting approximately 20 microseconds in this case, from the O2 terminal to the IGBT 108. This turns the IGBT 108 ON, and the charge stored in the pulse-generating capacitor 109 excites the primary winding of the trigger transformer 110. A high-voltage, steep, negative spike voltage of approximately 4000 V is applied from the secondary winding to capacitors 81 to 84. In FIG. 15 , this voltage is also applied to capacitor 85.

[0047] By applying this spike voltage, with the cathode 20 as the reference potential, spike voltages simultaneously appear between the cathode 20 and the sparker pin 61 of the first sparker 60, between the cathode 20 and the sparker pin 71 of the second sparker 70, between the cathode 20 and the trigger electrode 40, and between the cathode 20 and the anode 30, initiating a preliminary discharge. In Figure 15, a spike voltage also appears between the cathode 20 and the second trigger electrode 50, initiating a preliminary discharge. As a result, an arc discharge occurs between the anode 30 and the cathode 20 by the mechanism described above, and the flash lamp 1 emits light for several microseconds.

[0048] During the 500 microseconds that elapse, the inert gas inside flash lamp 1 returns from the ionized state at the time of light emission to its original inactive state. After this, controller 101 resumes outputting a pulse width control signal from terminal O1 to MOSFET 111, and then, while referencing the charging voltage of main discharge capacitor 107 from terminal IN2, outputs a pulse width control signal from terminal O1 to MOSFET 111 so that the charging voltage coincides with a target charging voltage that is a predetermined value. Then, main discharge capacitor 107 and pulse generating capacitor 109 are charged to a predetermined voltage in several milliseconds, and an operation is performed to prepare for the next light emission operation of flash lamp 1.

[0049] After this, when a trigger signal is input from the IN1 terminal, the flash lamp 1 emits light in the same operational sequence as described above, and then the main discharge capacitor 107 and the pulse generating capacitor 109 are charged to a predetermined voltage in a few milliseconds, and this operation is repeated.

[0050] As described above, the flash lamp and its circuit of the present invention are configured so that the flash lamp of the present invention can provide a stable light output and can prevent a decrease in light emission intensity due to the accumulation of the number of discharges.

[0051] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of equivalent disclosures are considered to be within the scope of the present disclosure.

[0052] This application is based on Japanese Patent Application No. 2023-220778, filed on December 27, 2023. The entire specification, claims, and drawings of Japanese Patent Application No. 2023-220778 are incorporated herein by reference.

[0053] REFERENCE SIGNS LIST 1, 100, 200... flash lamp, 2... lamp housing, 3... stem, 4... cap, 5... transmission glass, 6... exhaust pipe, 20... cathode, 21, 31... lead rod, 22, 32, 42, 52, 62, 72... leads, 23, 33, 43, 53, 63, 73... insulator, 30... anode, 40... (first) trigger electrode, 50... second trigger electrode, 60... first sparker, 61, 71... sparker pin, 64, 74... insulator, 65, 75 ...Conductive plate, 70...Second sparker, 81-85...Capacitors, 91-96...Resistors, 101...Controller, 102...Flyback transformer, 103-105...Diodes, 106...Regulator, 107...Main discharge capacitor, 108...IGBT, 109...Pulse generating capacitor, 110...Trigger transformer, 111...MOSFET, A...Power supply terminal (positive), B...Power supply terminal (negative), C...Pulse voltage signal input terminal.

Claims

1. A flash lamp comprising a lamp housing filled with an inert gas and sealed, a cathode and an anode for generating an arc discharge, a trigger electrode for performing a preliminary discharge prior to the arc discharge, and a plurality of sparkers for promoting ionization for starting the arc discharge, wherein the plurality of sparkers are arranged separately from each other.

2. The flash lamp according to claim 1, wherein at least one of the plurality of sparkers is arranged in the vicinity of the cathode.

3. The flash lamp according to claim 1 or 2, characterized by comprising a plurality of the trigger electrodes.

4. The cathode, the anode, the trigger electrode, and the plurality of sparkers are arranged above a stem in the lamp housing, leads for supplying electricity to each of the anode, the trigger electrode, and the plurality of sparkers are electrically insulated from the stem and implanted and led out to the outer surface of the lamp housing, the stem includes a metal exhaust pipe, and the exhaust pipe is connected to the cathode and serves as a terminal for supplying power. The flash lamp according to any one of claims 1 to 3.

5. The cathode, the anode, the trigger electrode, and the plurality of sparkers are arranged above a stem in the lamp housing, leads for supplying electricity to each of the cathode, the trigger electrode, and the plurality of sparkers are electrically insulated from the stem and implanted and led out to the outer surface of the lamp housing, the stem includes a metal exhaust pipe, and the exhaust pipe is connected to the anode and serves as a terminal for supplying power. The flash lamp according to any one of claims 1 to 3.

6. A lamp housing filled and sealed with an inert gas, a cathode and an anode for generating an arc discharge, a trigger electrode for performing a preliminary discharge prior to the arc discharge, and a sparker for promoting ionization for starting the arc discharge, wherein the cathode, the anode, the trigger electrode, and the sparker are disposed above a metal stem within the lamp housing, and leads for supplying electricity to each of the anode, the trigger electrode, and the sparker are electrically insulated from the stem and implanted and led out to the outer surface of the lamp housing, the stem is connected to the cathode, the sparker includes a sparker pin and a conductive plate surrounding the sparker pin via an insulator and extending in a direction away from the sparker pin, and the conductive plate is connected to the stem. A flash lamp characterized by this.

7. The flash lamp according to claim 6, wherein the stem includes a metal exhaust pipe, and the exhaust pipe is used as a terminal for connecting to and supplying power to the cathode.

8. The flash lamp according to claim 6 or 7, further comprising a metal cap covering the cathode, the anode, the trigger electrode, and the sparker, and the stem and the cap are electrically connected.

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