JP2012234828A - Light source device, projector, and discharge lamp driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain an electrode on a sub-reflex mirror side from rapidly degrading under the influence of the sub-reflex mirror, while restricting lopsided wear of an electrode or the growth of a needle crystal when a high luminance discharge lamp is lighted.SOLUTION: The duty ratio of an AC current supplied between first and second electrodes 15 and 16 is changed according to a prescribed pattern by which the duty ratio is increased and decreased stepwise in certain cycles. This helps prevent individual electrodes from lopsidedly wearing, as well as restrict the growth of a needle crystal into an electrode core rod. Furthermore, since the maximum value D2 of the duty ratio at a second electrode 16 when acting as an anode is made smaller than the maximum value D1 of the duty ratio at a first electrode 15 when acting as an anode, a temperature rise of the second electrode 16 can be restricted, even when the second electrode 16 is affected by a sub-mirror 3. Therefore, damage from which the second electrode 16 suffers can relatively be reduced, making it possible to prevent the second electrode 16 from degrading earlier than the others. Thus, the luminous intensity of illumination light from an arc tube 1 can be maintained.

Description

  The present invention relates to a light source device including a discharge lamp having a pair of electrodes, a driving method thereof, and a projector incorporating such a discharge lamp.

  Conventionally, a single drive waveform has been used as a lighting method for a high-intensity discharge lamp. However, if lighting with a single driving waveform is continued for a long time, the electrodes are maintained for a long time with a constant temperature distribution, so the asymmetry of the electrodes caused by the state change over time is further promoted with time. Head in the direction As a result, there is a problem in that a plurality of irregularities are generated in the vicinity of the pole tip, and flicker occurs. As a lighting method of the high-intensity discharge lamp for improving this, there is a method of making the absolute value of the AC lamp current supplied to the high-intensity discharge lamp substantially constant and modulating the AC lamp current by pulse width (see Patent Document 1). Specifically, the pulse width modulation of the pulse width ratio between the pulse width of the positive pulse and the pulse width of the negative pulse is performed at a frequency lower than the lighting frequency.

JP-T-2004-525496

However, even when the AC lamp current is subjected to pulse width modulation as in the above-mentioned Patent Document 1, in a light source provided with a secondary mirror in order to efficiently capture the light emitted forward, the deterioration of the electrode on the secondary mirror side proceeds excessively. However, there is a bias in the progress of deterioration of the left and right electrodes.
Therefore, the present invention can suppress a relative temperature increase and early deterioration of the electrode on the secondary mirror side, and can prevent uneven wear of the electrode and uneven deposition of the electrode material, and this An object is to provide a projector or the like used.

  In order to solve the above-described problems, a light source device according to the present invention includes (a) an arc tube having a first electrode and a second electrode that emit light by discharge between each other, and (b) disposed on the first electrode side. A main reflecting mirror that reflects the light beam generated by the discharge between the first electrode and the second electrode and emits it to the illuminated area; and (c) is disposed on the second electrode side so as to face the main reflecting mirror. A sub-reflector that reflects a light beam from the inter-electrode space of the electrode and the second electrode toward the inter-electrode space; and (d) a steady operation of supplying an alternating current to the first and second electrodes. The alternating current duty ratio supplied between the second electrode and the second electrode is changed in a predetermined pattern, and the ratio of the time during which the first electrode operates as an anode in one cycle (hereinafter, this ratio is also referred to as the first anode duty ratio). The second electrode is the anode in one cycle than the maximum value of Percentage of time that the operation (hereinafter this percentage also referred to as a second anode duty ratio) and a current driver to reduce the maximum value of. Here, the steady operation means an operation of causing the arc tube to emit light steadily after starting lighting.

  In the light source device, the current driving device changes the alternating current duty ratio supplied between the first electrode and the second electrode in a predetermined pattern in a steady operation, and the first electrode operates as an anode in one cycle. Since the maximum value of the second anode duty ratio corresponding to the ratio of the time during which the second electrode operates as the anode in one cycle is smaller than the maximum value of the first anode duty ratio corresponding to the ratio of the time to Since the phenomenon that the second electrode on the reflecting mirror side becomes higher in temperature than the first electrode on the main reflecting mirror side can be prevented, the phenomenon that only the second electrode deteriorates early can be suppressed. Thereby, while the illumination intensity of the illumination light from a light source device can be maintained, a lifetime of a light source device can be extended. As described above, the reason why the second electrode on the side of the sub-reflecting mirror becomes relatively high is that the second electrode is closer to the sub-reflecting mirror and easily exposed to radiant heat from the sub-reflecting mirror. It is conceivable that the cooling air flowing around the arc tube is blocked by the sub-reflecting mirror and is covered with the sub-reflecting mirror, that is, the cooling efficiency is lowered on the hemisphere side housing the second electrode.

  Further, in a specific aspect of the present invention, the current driving device changes the current value of the polarity at which the time ratio is at least 50% among the positive and negative polarities per AC driving cycle. In this case, flicker is suppressed in the electrode operating as the cathode, and the melting amount of the tip is increased in the electrode operating as the anode. Thereby, it is possible to stabilize the discharge and maintain the electrode shape.

  In yet another aspect of the present invention, the current driving device outputs a current value having a polarity with a time ratio of 50% or more among positive and negative polarities per cycle of AC driving at the end of the anode period. Change so that the current value is maximized. In this case, it is possible to effectively suppress flicker and maintain the shape by melting the tip of the electrode.

  In still another aspect of the present invention, the current driving device increases the current value of the polarity at which the time ratio is at least 50% of the positive and negative polarities per cycle of AC driving with time. In this case, flicker is suppressed in the electrode operating as the cathode, and the melting amount of the tip is increased in the electrode operating as the anode. Thereby, it is possible to stabilize the discharge and maintain the electrode shape.

  In the light source device, the predetermined pattern is divided into a first divided period and a second divided period having a different alternating current duty following the first divided period as a divided period in which the alternating current duty ratio is maintained at a constant value. And the difference between the AC current duty ratio in the first segment period and the AC current duty ratio in the second segment period may be larger than a predetermined value. When the duty ratio difference (amount of change) is larger than a predetermined value in this way, the tip of the consumed electrode grows toward the opposing electrode. Therefore, it becomes easier to maintain the electrode shape.

  In this case, the AC current duty ratio in the first segment period and the AC current duty ratio in the second segment period cross over a reference duty ratio that is determined in advance based on the median value of the change range of the AC current duty ratio. You may make it change as follows. By changing the alternating current duty ratio so as to cross the reference duty ratio, it is possible to restore the two electrodes in a well-balanced manner while ensuring a sufficient amount of change in the anode duty ratio. Further, the amount of change in the alternating current duty ratio can be increased, and the electrode shape can be more easily maintained.

  Furthermore, the length of the first segment period and the length of the second segment period may be different from each other. In general, when the duty ratio is high and the temperature of the electrode is rising, the sputtering amount of the electrode material increases during the period in which the electrode operates as a cathode. This is presumably because, in a state where the anode duty ratio is high, immediately after the polarity of the electrode is reversed from the anode to the cathode, the electrode is at a high temperature and the electrode material is easily detached. Therefore, by making the lengths of the first and second segment periods in which the duty ratio changes greatly different from each other, the time during which the electrode operates as a cathode can be shortened when the temperature of the electrode is rising. Can do. As a result, since the amount of spatter is reduced and blackening is suppressed, deterioration of the arc tube can be suppressed.

  Also, the predetermined pattern is a pattern that changes periodically, and the length of the segment period in which the alternating current duty ratio is higher than the reference duty ratio in a predetermined period within one cycle of the pattern is the reference current duty ratio. Longer than the lower segment period length, and in the remaining period in one cycle of the pattern, the AC current duty ratio is higher than the reference duty ratio. It may be shorter than the length of the lower segment period. In this way, in a predetermined period, the temperature of one electrode becomes higher, so that the shape of the electrode can be more reliably maintained, and sputtering in the one electrode can be suppressed. Further, in the remaining period, the temperature of the other electrode becomes higher, so that the shape of the electrode can be more reliably maintained, and sputtering at the other electrode can be suppressed.

  The projector of the present invention includes (a) the above-described light source device, (b) a light modulation device illuminated by illumination light from the light source device, and (c) a projection optical system that projects an image formed by the light modulation device. With.

  In the projector, since the light source device described above is used, it is possible to prevent any one of the pair of electrodes constituting the light source device from being biased and deteriorating at an early stage. Thereby, the projection luminance of the projector can be maintained over a long period of time.

The light source device driving method according to the present invention includes an arc tube having a first electrode and a second electrode that emits light by discharge between each other, a first electrode, and a discharge between the first electrode and the second electrode. A main reflecting mirror that reflects the generated light beam and emits it to the illuminated area, and is disposed on the second electrode side so as to face the main reflecting mirror, and the light beam from the interelectrode space between the first electrode and the second electrode is disposed between the electrodes. A discharge lamp driving method comprising a sub-reflecting mirror that reflects toward the space side, and in a steady operation of supplying an alternating current for discharge to the first and second electrodes, between the first electrode and the second electrode The alternating current duty ratio supplied to the first electrode is changed in a predetermined pattern, and the second electrode operates as an anode in one cycle than the maximum value of the time ratio in which the first electrode operates as an anode in one cycle. Decrease the maximum value of the time ratio.
In the above driving method, in a steady operation, the alternating current duty ratio supplied between the first electrode and the second electrode is changed in a predetermined pattern, and the ratio of the time during which the first electrode operates as an anode in one cycle is set. Since the maximum value of the second anode duty ratio corresponding to the ratio of the time during which the second electrode operates as an anode in one cycle is made smaller than the corresponding maximum value of the first anode duty ratio, Since the phenomenon that the second electrode is higher in temperature than the first electrode can be prevented, the phenomenon that only the second electrode is deteriorated at an early stage can be suppressed. Thereby, while the illumination intensity of the illumination light from a light source device can be maintained, a lifetime of a light source device can be extended.

It is sectional drawing explaining the light source device of 1st Embodiment of this invention. It is a block diagram which shows the structure of the current drive device integrated in the light source device. It is an expanded sectional view explaining the convection in the discharge space of a main-body part. It is a graph explaining the modulation | alteration of the duty ratio of the alternating current supplied to both electrodes. It is a graph explaining the waveform of the alternating current actually supplied to both electrodes. (A), (B) is a graph explaining the modification of the modulation | alteration shown in FIG. It is a flowchart explaining operation | movement of a light source drive device. It is a figure explaining the projector incorporating a light source device. It is sectional drawing explaining operation | movement of the light source device of 2nd Embodiment. Explanatory drawing which shows the influence which duty ratio variation | change_quantity exerts on an electrode. Explanatory drawing which shows the influence which duty ratio variation | change_quantity exerts on an electrode. Explanatory drawing which shows the influence which duty ratio variation | change_quantity exerts on an electrode. It is sectional drawing explaining operation | movement of the light source device of 3rd Embodiment. It is explanatory drawing which shows the 1st modification of a modulation pattern. It is explanatory drawing which shows the 2nd modification of a modulation pattern.

[First Embodiment]
The light source device according to the first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view conceptually illustrating the structure of the light source device 100. In the light source device 100, the light source unit 10 includes, as a discharge lamp, a discharge light emitting tube 1, a reflector 2 that is an elliptical main reflecting mirror, and a sub mirror 3 that is a spherical sub reflecting mirror. The light source driving device 70 is an electric circuit for supplying an alternating current to the light source unit 10 to emit light in a desired state, details of which will be described later.

  In the light source unit 10, the arc tube 1 is composed of a light-transmitting quartz glass tube having a central portion bulged in a spherical shape, and a main body portion 11 that is a sealed body that emits illumination light. First and second sealing portions 13 and 14 extending along an axis passing through both ends are provided.

  In the discharge space 12 formed in the main body portion 11, the tip portion of the first electrode 15 made of tungsten and the tip portion of the second electrode 16 made of tungsten are similarly spaced apart by a predetermined distance. Gas, which is a discharge medium containing gas, metal halide, and the like, is enclosed. Each of the sealing portions 13 and 14 extending at both ends of the main body portion 11 is a metal made of molybdenum that is electrically connected to the root portions of the first and second electrodes 15 and 16 provided in the main body portion 11 therein. The foils 17a and 17b are hermetically sealed from the outside with a glass material or the like. When AC pulsed power is supplied to the lead wires 18a and 18b connected to the metal foils 17a and 17b by the light source driving device 70, arc discharge occurs between the pair of electrodes 15 and 16, and the main body portion 11 has high brightness. Lights on.

  The sub-mirror 3 closes and covers approximately half of the main body portion 11 of the arc tube 1 on the front side where the second electrode 16 is present. The secondary mirror 3 is an integrally molded product made of quartz glass. The secondary mirror 3a returns the light beam radiated forward from the main body portion 11 of the arc tube 1 to the main body portion 11, and the base portion of the secondary reflecting portion 3a. The support part 3b fixed to the circumference | surroundings of the 2nd sealing part 14 is supported. The support portion 3 b allows the second sealing portion 14 to pass therethrough and holds the sub-reflecting portion 3 a in an aligned state with respect to the main body portion 11.

  The reflector 2 is disposed so as to face approximately half of the main body portion 11 of the arc tube 1 on the rear side where the first electrode 15 is located. The reflector 2 is an integrally molded product made of crystallized glass or quartz glass, and has a neck-shaped portion 2a through which the first sealing portion 13 of the arc tube 1 is inserted, and an elliptically curved surface that extends from the neck-shaped portion 2a. The main reflection part 2b is provided. The neck portion 2 a is inserted through the first sealing portion 13 and holds the main reflection portion 2 b in an aligned state with respect to the main body portion 11.

  The arc tube 1 is disposed along the system optical axis OA corresponding to the rotational symmetry axis or the optical axis of the main reflecting portion 2b, and the emission center O between the first and second electrodes 15 and 16 in the main body portion 11. Are arranged so as to substantially coincide with the position of the first focal point F1 of the elliptical curved surface of the main reflecting portion 2b. When the arc tube 1 is turned on, the light beam emitted from the arc around the emission center O of the main body portion 11 is reflected by the main reflection portion 2b or further reflected by the main reflection portion 2b after being reflected by the sub-reflection portion 3a. Thus, the light beam converges to the position of the second focal point F2 of the elliptical curved surface. In other words, the reflector 2 and the secondary mirror 3 have reflection curved surfaces that are substantially axisymmetric with respect to the system optical axis OA, and the pair of electrodes 15 and 16 have their axial axes that are substantially coincident with the system optical axis OA. It is arranged to let you.

  The arc tube 1 supports, for example, the first and second electrodes 15 and 16 fixed to the tips of the metal foils 17a and 17b in a quartz glass tube, and a quartz glass tube at a portion corresponding to both the sealing portions 13 and 14. It is made by a shrink seal that softens and shrinks by heating with a burner from the surroundings. The arc tube 1 is fixed by injecting, filling, and solidifying the inorganic adhesive C with the first sealing portion 13 inserted into the neck portion 2a of the reflector 2, and is fixed to the support portion 3b of the secondary mirror 3. In the state where the second sealing portion 14 of the arc tube 1 is inserted, the inorganic adhesive C is injected, filled, and solidified.

  FIG. 2 is a block diagram schematically showing a configuration of a light source driving device 70 for lighting the light source unit 10 shown in FIG. 1 in a desired state.

  The light source driving device 70 generates an alternating current for discharging between the pair of electrodes 15 and 16 shown in FIG. 1 and the like, and controls the supply state of the alternating current to both the electrodes 15 and 16. The light source driving device 70 includes a lighting device 70a, a control device 70b, and a DC / DC converter 70c. Here, as an example, a case where the light source driving device 70 uses an external power source will be described. That is, the light source driving device 70 is connected to the AC / DC converter 81, and the AC / DC converter 81 is connected to the commercial power source 90. The AC / DC converter 81 converts an alternating current supplied from the commercial power supply 90 into a direct current.

  The lighting device 70a is a circuit portion that drives the light source unit 10 of FIG. The driving waveform output from the light source driving device 70 is adjusted by the lighting device 70a. Here, the drive waveform has the output current or voltage frequency, amplitude, duty ratio, positive / negative amplitude ratio, waveform characteristics, and the like as elements, and for example, a rectangular wave from the lighting device 70a to the light source unit 10, A drive current having an arbitrary waveform characteristic such as a superimposed wave obtained by superimposing a triangular wave on the rectangular wave is output.

  The control device 70b is, for example, a circuit unit including a microcomputer, a memory, a sensor, an interface, and the like, and is driven by an appropriate drive voltage generated by a DC / DC converter 70c that is a power source. The control device 70b includes a drive control unit 74 that controls the operation state of the lighting device 70a, a determination unit 75 that determines the state of the arc tube 1, and data that stores various information such as the operation mode of the lighting device 70a, that is, power supply conditions. And a storage unit 76.

  The drive control unit 74 is a part that operates according to a program stored in the data storage unit 76 or the like. The drive control unit 74 selects an initial operation power supply condition and a steady operation power supply condition stored in the data storage unit 76 and is suitable for the current state of the arc tube 1, and an initial value according to the selected power supply condition. The lighting device 70a is caused to perform an operation or a steady operation. The drive control unit 74 functions as a current driving device for supplying power to the arc tube 1 to perform a necessary lighting operation in cooperation with the lighting device 70a. In the present embodiment, the operation of supplying steady energy to the first electrode 15 and the second electrode 16 is a steady operation, and the first electrode 15 is an operation different from the steady operation at the start of lighting before performing the steady operation. An operation for supplying energy to the second electrode 16 is an initial operation.

  The determination unit 75 is a part that determines the deterioration stage of the arc tube 1 based on the state of the arc tube 1, that is, the cumulative lighting time of the arc tube 1, the voltage between the electrodes to the arc tube 1, and the like.

  In addition to the operation program for the drive control unit 74, the data storage unit 76 stores a plurality of initial power supply conditions as an initial operation mode of the arc tube 1, and a plurality of constant power supply conditions as a mode of steady operation of the arc tube 1. The normal power supply conditions are stored. Specifically, the data storage unit 76 stores various parameters such as a set value such as a current value and a frequency at start-up and startup included in the initial operation. In addition, the data storage unit 76 stores various parameters relating to current values, frequencies, duty ratios, duty ratio modulation contents, triangular wave jumping rates, etc. in steady operation, that is, rated drive. Here, the modulation content of the duty ratio includes the variable range of the duty ratio, the segment period, and the modulation frequency as parameters. The triangular wave jump rate refers to the ratio of the maximum current value to the average current value in a half cycle of a superimposed wave obtained by superimposing a triangular wave on a rectangular wave.

  FIG. 3 is an enlarged cross-sectional view for explaining convection in the discharge space 12 formed in the main body portion 11 of the arc tube 1 of FIG. In the main body portion 11, the first and second electrodes 15 and 16 include tip portions 15a and 16a, large diameter portions 15b and 16b, and shaft portions 15c and 16c, respectively. In a steady operation in which the arc tube 1 is operated at a rated value, an arc AR is formed by arc discharge between the tip portions 15a and 16a of the pair of electrodes 15 and 16. The arc AR and the vicinity thereof are extremely hot. Therefore, convection AF that flows upward from the arc AR is formed in the discharge space 12. The convection AF hits the top portion 11a of the main body portion 11 and moves along the upper half portion 11b, and descends while being cooled by passing through the shaft portions 15c and 16c of both the electrodes 15 and 16. The convection AF thus lowered further descends along the lower half 11c of the main body portion 11, but rises so as to collide with each other below the arc AR and return to the upper arc AR. That is, convection AF is formed and circulated around the electrodes 15 and 16, but such convection AF includes electrode material melted and evaporated by the arc AR, and therefore, the local portions of the shaft portions 15c and 16c are caused by steady convection. There is a possibility that the electrode material is deposited or segregated and grows in a needle shape, for example, and an unintended discharge occurs toward the upper half 11b. Such unintended discharge deteriorates the inner wall of the main body portion 11 and causes the life of the arc tube 1 to be reduced. In addition, if lighting with a single driving waveform is continued for a long time, the electrode is maintained for a long time with a constant temperature distribution, so that the asymmetry of the electrode caused by the state change over time is further promoted with time. Head in the direction For this reason, the duty ratio of the alternating current supplied between the first and second electrodes 15 and 16 is gradually and periodically changed with a relatively long period, and the temperature distribution of the electrodes 15 and 16 is periodically changed. In this case, the electrode is prevented from being deteriorated unevenly, and the temperature difference of several hundreds K generated in the left and right electrodes 15 and 16 causes a temporal fluctuation in the convection, so that a steady convection AF is formed in the discharge space 12. To prevent. Specifically, the duty ratio (alternating current duty ratio) of the current waveform is cycled with a period sufficiently larger than the period of the current waveform of a constant frequency (lighting frequency) supplied to the pair of electrodes 15 and 16. Change. At this time, as a pattern for periodically changing the duty ratio of the current waveform supplied to both the electrodes 15 and 16 in order to increase the fluctuation of the convection AF, the duty ratio changing period or modulation period is composed of a plurality of divided periods. In each division period, the duty ratio is maintained for a certain period or more. That is, the duty ratio of the current waveform supplied to the electrodes 15 and 16 is changed stepwise and increased or decreased periodically.

  The specific driving conditions will be described. The lighting frequency supplied to both electrodes 15 and 16 is relatively high, for example, about 60 Hz to 500 Hz. Each division period constituting the modulation cycle of the duty ratio is set to, for example, about 1 second or more (in the specific example, 10 seconds), and the duty ratio is maintained at a constant value in each division period. Here, by dividing the duty ratio into, for example, about 10 (16 in the specific example), the modulation cycle of the duty ratio integrating each divided period becomes, for example, 10 seconds or more (160 seconds in the specific example). With such a modulation pattern, the thermal states of the electrodes 15 and 16 and their surroundings can be gradually changed with a long span that affects the convection AF, so that the main body portion 11 of the arc tube 1 can be changed. It is possible to avoid the formation of steady convection AF in the interior. As a result, it is possible to prevent the electrode material from growing in a needle shape at an unintended location of both electrodes 15, 16, and to prevent uneven deterioration of both electrodes 15, 16. In order to avoid the formation of steady convection AF, the length of the segment period is more preferably 1 minute or less.

  In order to evaluate the lower limit of the length of the segment period, an experiment was conducted to evaluate the transient characteristics of the electrode temperature when the duty ratio was changed. In this experiment, the temperature of the electrode 15 was measured by setting the division period to 5 seconds and changing the duty ratio from 20% to 80% in units of 10%. When the duty ratio was increased from 40% to 50%, the temperature of the electrode 15 increased by about 40K. When about 0.5 seconds passed after the duty ratio was changed from 40% to 50%, the temperature of the electrode 15 was stabilized. Prior to this stable period, a metastable period in which the temperature change of the electrode 15 becomes gentle was observed. Assuming that the temperature increase Δt in the transition period in which the temperature change of the electrode 15 is large is the difference between the temperature in the stable period before the duty ratio change and the temperature at which the metastable period starts after the duty ratio change, the temperature difference Δt If there is a time during which a temperature difference of 1/2 of this occurs, the temperature of the electrode 15 can be changed sufficiently. In this experimental result, a temperature difference of ½ of the temperature difference Δt occurred when about 0.1 seconds elapsed from the change of the duty ratio. Therefore, it was found that the length of the segment period is preferably 0.1 seconds or more, and more preferably 0.5 seconds or more.

  Hereinafter, the point that the second electrode 16 on the secondary mirror 3 side is likely to be hotter than the first electrode 15 on the reflector 2 side will be described. First, since the second electrode 16 is disposed closer to the secondary mirror 3 than the first electrode 15, the second electrode 16 is easily exposed to radiant heat from the secondary mirror 3. For this reason, the second electrode 16 is likely to be relatively hotter than the first electrode 15. Further, the light source unit 10 is cooled to an appropriate temperature by cooling air from a cooling device (not shown), but the cooling efficiency is reduced on the hemisphere side covered with the secondary mirror 3 in the main body portion 11 of the arc tube 1. Tend to occur. For this reason, the second electrode 16 is likely to be relatively hotter than the first electrode 15. As described above, the second electrode 16 on the side of the secondary mirror 3 tends to be hotter than the first electrode 15, so that the deterioration of the second electrode 16 is accelerated. For this reason, when the duty ratio of the alternating current supplied between the first and second electrodes 15 and 16 is periodically changed as described above, the duty ratio when the first electrode 15 is the anode (the first anode duty) The maximum value DM2 of the duty ratio (second anode duty ratio) when the second electrode 16 is the anode is smaller than the maximum value DM1 of the ratio), thereby increasing the temperature of the second electrode 16 on the secondary mirror 3 side. suppress. Specifically, the maximum value DM1 of the first anode duty ratio related to the first electrode 15 is set to 70%, for example, and the maximum value DM2 of the second anode duty ratio related to the second electrode 16 is set to 65%, for example. Accordingly, it is possible to prevent uneven wear of the second electrode 16 on the secondary mirror 3 side while maintaining the brightness of the arc AR.

  FIG. 4 is a graph illustrating the modulation of the duty ratio of the alternating current supplied to the pair of electrodes 15 and 16. The horizontal axis represents time, and the vertical axis represents the duty ratio. As indicated by the solid line, the duty ratio of the alternating current supplied to both electrodes 15 and 16 changes at a constant ratio for each division period and periodically increases and decreases at the period Tm. Each cycle Tm includes a first half H1 in which the anode period of the first electrode 15 is relatively long and a second half H2 in which the anode period of the second electrode 16 is relatively long. In addition, the duty ratio is divided into four stages in which the anode period of the first electrode 15 on the reflector 2 side is larger than the anode period of the second electrode 16 in the first half H1, and the second electrode 16 on the secondary mirror 3 side in the second half H2. There are nine stages in total, including four stages in which the anode period is equal to or longer than the anode period of the first electrode 15 and one stage of 50% in which the duty ratios of the electrodes 15 and 16 are equal. However, the maximum value DM1 of the first anode duty ratio in the first half period H1 in which the first electrode 15 is biased toward the anode is 70%, whereas the second anode duty ratio in the second half period H2 in which the second electrode 16 is biased toward the anode. The maximum value DM2 of 65% is 65%. That is, the maximum value DM2 of the second anode duty ratio when the second electrode 16 is the anode is smaller than the maximum value DM1 of the first anode duty ratio when the first electrode 15 is the anode. For reference, a modulation pattern in which the maximum value of the second anode duty ratio when the second electrode 16 is an anode is 70% is indicated by a dotted line. In the case of the modulation pattern indicated by the dotted line, the maximum values of the duty ratio when the electrodes 15 and 16 are anodes are equal to each other.

  FIG. 5 is a graph for explaining the waveform of the alternating current actually supplied to the pair of electrodes 15 and 16. The horizontal axis represents time, and the vertical axis represents the current value. Both electrodes 15 and 16 are supplied with a rectangular wave current having a constant current value A0 at a constant lighting frequency corresponding to the period Ta, and each divided period constituting the first half period H1 in the period Tm of FIG. In each waveform W1, W2, W3 included in P1, P2, P3,..., The alternating current duty ratio is kept constant, and each time the divided periods P1, P2, P3,. The duty ratio changes stepwise. Specifically, when the first and second anode duty ratios of the waveforms W1 of both electrodes 15 and 16 are 50% in the segment period P1, the waveforms of both electrodes 15 and 16 in the next segment period P2. The first and second anode duty ratios of W2 are, for example, 55% and 45%, respectively. In the next segment period P3, the first and second anode duty ratios of the waveforms W3 of both electrodes 15, 16 are, for example, 60%, respectively. 40%. The above is related to the first half H1 in the cycle Tm of FIG. 4, but the current waveform of the second half H2 is also the same except for the duty ratio. That is, when the first and second anode duty ratios of the waveforms W1 of the electrodes 15 and 16 are 50% in the segment period P1 ′, the waveforms W2 of the electrodes 15 and 16 in the next segment period P2 ′. The first and second anode duty ratios are 46.2% and 53.8%, for example, and the first and second anode duty ratios of the waveforms W3 of the electrodes 15 and 16 are, for example, in the next segment period P3 ′. These are 42.5% and 57.5%, respectively. As a result, as shown in FIG. 4, the first anode duty ratio on the first electrode 15 side is a relatively large value DM1 of 70% and a minimum value of 35% at a constant modulation frequency corresponding to the period Tm. The second anode duty ratio on the second electrode 16 side changes periodically in a relatively low modulation range in which the maximum value DM2 is 65% and the minimum value is 30%.

  In addition, in the duty ratio modulation as shown in FIGS. 4 and 5, it is not necessary to keep the lighting frequency and current value of the current supplied to both electrodes 15 and 16 constant, and each divided period P1, P2, P3. Different lighting frequencies and current values can be assigned to each.

  In addition, in the modulation of the duty ratio as shown in FIGS. 4 and 5, the set values such as the lighting frequency, current value, variable range of the duty ratio, segment period, modulation frequency, etc. It can be increased or decreased based on information on the 16 wear levels and other deterioration stages. For example, when the deterioration of both the electrodes 15 and 16 progresses, the shapes of the tip portions 15a and 16a of both the electrodes 15 and 16 can be maintained by temporarily increasing and decreasing the lighting frequency and the current value. Further, by increasing the variable range of the duty ratio, it is possible to reliably melt the electrode that has become difficult to melt due to deterioration over time, and to maintain a good tip shape.

  FIG. 6A is a graph illustrating a modification of the duty ratio modulation shown in FIG. In this case, in each of the division periods P1, P2, P3,... Constituting the first half period H1, the duty ratio of the alternating current is kept constant, and the duty ratio is stepped every time the division periods P1, P2, P3,. 6A, the first electrode 15 in FIG. 6A is at least a polarity in which the time ratio is at least 50% of the positive and negative polarities per cycle of the alternating current. At the time of the anode, a superposed wave in which a triangular wave gradually increasing is superposed on a rectangular wave is supplied. The average current value of the superimposed wave is maintained at A0, but the peak value is A1. Here, assuming that the ratio of the peak value A1 to the average current value A0 is the triangular wave jumping rate of the superimposed wave, the triangular wave jumping rate A1 / A0 is larger than the triangular wave jumping rate 1 of the rectangular wave. By adjusting the triangular wave jumping rate, it is possible to increase the melting amount of the first electrode 15 and suppress flicker of the second electrode 16.

  FIG. 6B corresponds to FIG. 6A, but shows the respective divided periods P1 ', P2', P3 ',... Constituting the second half H2. Also in this case, the duty ratio of the alternating current is kept constant, and the duty ratio changes stepwise every time the divided periods P1 ′, P2 ′, P3 ′,. When the polarity is at least 50% of the positive and negative polarities per cycle of the alternating current, in FIG. 6B, a triangular wave that gradually increases is superimposed on the rectangular wave when the second electrode 16 is the anode. A superposed wave is supplied. The average current value of the superimposed wave is maintained at A0, but the peak value is A1. Here, the triangular wave jumping rate A1 / A0 is higher than the triangular wave jumping rate 1 of the rectangular wave. By adjusting the triangular wave jumping rate, it is possible to suppress flicker of the first electrode 15 and increase the melting amount of the second electrode 16.

  Note that the operations in FIGS. 6A and 6B can be combined, but only the operation in FIG. 6A can be performed. That is, the first half H1 in which the anode period of the first electrode 15 is relatively long is a rectangular wave, and only in the second half H2 in which the anode period of the second electrode 16 is relatively long is shown in FIG. A superimposed wave as shown can also be used.

  Further, in the above-described modification, the current value is obtained by superimposing a gradually increasing triangular wave on the basic rectangular wave when the time ratio is at least 50% of the positive and negative polarities per cycle of the alternating current. Although it is changed, based on the information about the deterioration stages of the electrodes 15 and 16, the waveform in which the current value becomes maximum at the end of the polarity period in which the time ratio is 50% or more, or the basic rectangular wave On the other hand, the current value can be changed by superimposing various waveforms such as a triangular wave, a rectangular wave, and a sine wave that increase in the latter half of the half cycle.

  In addition, in the duty ratio modulation as shown in FIGS. 6A and 6B, the setting value such as the variable range of the duty ratio, the segment period, the modulation frequency, the lighting frequency, and the current value is obtained by the determination unit 75. Furthermore, the increase / decrease can be changed based on the information on the degree of wear of the electrodes 15 and 16 and other deterioration stages.

  FIG. 7 is a flowchart for explaining the operation of the light source driving device 70. The control device 70b reads appropriate initial drive data necessary for starting lighting of the arc tube 1 from the drive control table stored in the data storage unit 76 (step S11).

  Next, the control device 70b controls the lighting device 70a based on the initial power supply condition read out in step S11, and controls the initial operation including the startup operation from the start of the arc tube 1 (step S12).

  Next, the control device 70b reads appropriate steady drive data necessary for maintaining the light emission of the arc tube 1 from the drive control table stored in the data storage unit 76 (step S13). Specifically, set values such as a current value, a lighting frequency, a variable range of a duty ratio, a segment period, a modulation frequency, and a triangular wave jump rate during a steady operation are read out. At this time, based on information on the degree of wear and other deterioration stages of the electrodes 15 and 16 obtained by the determination unit 75, a lighting waveform such as a current value and a lighting frequency, a variable range of a duty ratio, a division period, a modulation frequency, and the like Is selected.

  Next, the control device 70b controls the steady operation of the arc tube 1 of the lighting device 70a based on the steady power supply condition read in step S13 (step S14). Specific operations are illustrated in FIGS.

  Here, the determination unit 75 determines whether or not an interrupt request signal for requesting the end of the lighting operation of the light source unit 10 is input during the steady operation (step S15). When such an interrupt request signal is input, information indicating the current state of the arc tube 1 such as the current cumulative lighting time and the voltage supplied to the current arc tube 1 is recorded in the data storage unit 76. Then, the operation is turned off.

  As is clear from the above description, according to the light source device 100 of the present embodiment, the first and second lighting devices 70a operating under the control of the control device 70b are operated in a steady operation in which the arc tube 1 is operated at a rated value. The duty ratio of the alternating current supplied between the second electrodes 15 and 16 is changed with a predetermined modulation pattern that increases or decreases stepwise at a constant cycle. Furthermore, since the maximum value D2 of the second anode duty ratio when the second electrode 16 is an anode is made smaller than the maximum value D1 of the first anode duty ratio when the first electrode 15 is an anode, the second electrode 16 Even when the thermal influence of the secondary mirror 3 is more strongly affected, such an influence can be offset and the temperature rise of the second electrode 16 can be suppressed. Therefore, the damage which the 2nd electrode 16 receives can be reduced relatively, and the early deterioration only of the 2nd electrode 16 can be suppressed. Thereby, while being able to maintain the illumination intensity of the illumination light from the arc_tube | light_emitting_tube 1, the arc_tube | light_emitting_tube 1, ie, the light source device 100, can prolong the lifetime.

  FIG. 8 is a conceptual diagram for explaining the structure of a projector incorporating the light source device 100 of FIG. The projector 200 includes a light source device 100, an illumination optical system 20, a color separation optical system 30, a light modulation unit 40, a cross dichroic prism 50, and a projection lens 60. Here, the light modulation unit 40 includes three liquid crystal light valves 40a, 40b, and 40c having the same structure.

  In the projector 200, the light source device 100 includes the light source unit 10 shown in FIG. 1 and the light source driving device 70. The light modulation unit 40, that is, the liquid crystal light valves 40a, 40b, and 40c is provided via the illumination optical system 20 and the like. Illumination light for illuminating is generated.

  The illumination optical system 20 includes a collimating lens 22 that collimates the light beam direction of the light source light, first and second fly-eye lenses 23a and 23b that constitute an integrator optical system for dividing and superimposing light, Are provided with a polarization conversion element 24 that aligns the polarization directions, a superimposing lens 25 that superimposes light that has passed through both fly-eye lenses 23a and 23b, and a mirror 26 that bends the optical path of the light. In the illumination optical system 20, the collimating lens 22 converts the luminous flux direction of the illumination light emitted from the light source unit 10 to be substantially parallel. The first and second fly-eye lenses 23a and 23b are each composed of a plurality of element lenses arranged in a matrix, and the light that has passed through the collimating lens 22 is divided by the element lenses that constitute the first fly-eye lens 23a. The light beams are individually condensed, and the divided light beams from the first fly-eye lens 23a are emitted with an appropriate divergence angle by the element lenses constituting the second fly-eye lens 23b. The polarization conversion element 24 is formed of an array having a PBS, a mirror, a retardation plate, etc. as a set of elements, and the polarization direction of each partial light beam divided by the first fly-eye lens 23a is linearly polarized in one direction. It has a role to align. The superimposing lens 25 appropriately converges the illumination light that has passed through the polarization conversion element 24 as a whole, and enables superimposing illumination on the illuminated areas of the liquid crystal light valves 40a, 40b, and 40c, which are light modulators for the respective colors at the subsequent stages. That is, the illumination light that has passed through both the fly-eye lenses 23a and 23b and the superimposing lens 25 passes through the color separation optical system 30 that will be described in detail below, and each color liquid crystal panel 41a, 41b, and 41c provided in the light modulator 40. Is uniformly superimposed.

  The color separation optical system 30 includes first and second dichroic mirrors 31a and 31b, reflection mirrors 32a, 32b, and 32c, and three field lenses 33a, 33b, and 33c, and emits illumination light from the illumination optical system 20. While separating into three colors of red (R), green (G), and blue (B), each color light is guided to the liquid crystal light valves 40a, 40b, and 40c at the subsequent stage. More specifically, first, the first dichroic mirror 31a transmits R light and reflects G light and B light among the three colors of RGB. The second dichroic mirror 31b reflects G light and transmits B light out of the two colors of GB. Next, in the color separation optical system 30, the R light transmitted through the first dichroic mirror 31a enters the field lens 33a for adjusting the incident angle through the reflection mirror 32a. Further, the G light reflected by the first dichroic mirror 31a and further reflected by the second dichroic mirror 31b is incident on the field lens 33b for adjusting the incident angle. Further, the B light that has passed through the second dichroic mirror 31b enters the field lens 33c for adjusting the incident angle via the relay lenses LL1 and LL2 and the reflection mirrors 32b and 32c.

  Each of the liquid crystal light valves 40a, 40b, and 40c constituting the light modulation unit 40 is a non-light-emitting light modulation device that modulates the spatial intensity distribution of incident illumination light. The liquid crystal light valves 40a, 40b, and 40c are incident on the three liquid crystal panels 41a, 41b, and 41c, and the liquid crystal panels 41a, 41b, and 41c that are illuminated corresponding to the respective color lights emitted from the color separation optical system 30. Three first polarizing filters 42a, 42b, and 42c disposed on the respective sides, and three second polarizing filters 43a, 43b, and 43c respectively disposed on the exit sides of the liquid crystal panels 41a, 41b, and 41c. The R light transmitted through the first dichroic mirror 31a enters the liquid crystal light valve 40a via the field lens 33a and the like, and illuminates the liquid crystal panel 41a of the liquid crystal light valve 40a. The G light reflected by both the first and second dichroic mirrors 31a and 31b enters the liquid crystal light valve 40b via the field lens 33b and the like, and illuminates the liquid crystal panel 41b of the liquid crystal light valve 40b. The B light reflected by the first dichroic mirror 31a and transmitted through the second dichroic mirror 31b enters the liquid crystal light valve 40c through the field lens 33c and the like, and illuminates the liquid crystal panel 41c of the liquid crystal light valve 40c. Each of the liquid crystal panels 41a to 41c modulates the spatial intensity distribution in the polarization direction of the incident illumination light, and the three colors of light incident on the liquid crystal panels 41a to 41c are electrically transmitted to the liquid crystal panels 41a to 41c. The polarization state is adjusted in units of pixels in accordance with the drive signal or image signal input as. At this time, the polarization direction of the illumination light incident on the liquid crystal panels 41a to 41c is adjusted by the first polarizing filters 42a to 42c, and the light is emitted from the liquid crystal panels 41a to 41c by the second polarizing filters 43a to 43c. Modulated light having a predetermined polarization direction is extracted from the modulated light. As described above, each liquid crystal light valve 40a, 40b, 40c forms image light of each color corresponding to each.

  The cross dichroic prism 50 combines the image light of each color from the liquid crystal light valves 40a, 40b, and 40c. More specifically, the cross dichroic prism 50 has a substantially square shape in plan view in which four right angle prisms are bonded together, and a pair of dielectric multilayer films intersecting in an X shape at the interface where the right angle prisms are bonded to each other. 51a and 51b are formed. One first dielectric multilayer film 51a reflects R light, and the other second dielectric multilayer film 51b reflects B light. The cross dichroic prism 50 reflects the R light from the liquid crystal light valve 40a by the dielectric multilayer film 51a and emits the G light from the liquid crystal light valve 40b through the dielectric multilayer films 51a and 51b. The B light from the liquid crystal light valve 40c is reflected by the dielectric multilayer film 51b and emitted to the left in the traveling direction. In this way, the R light, the G light, and the B light are combined by the cross dichroic prism 50 to form combined light that is image light based on a color image.

  The projection lens 60 is a projection optical system, and projects the color image on a screen (not shown) by enlarging the image light by the combined light formed through the cross dichroic prism 50 with a desired magnification.

  According to the projector 200 described above, any of the pair of electrodes 15 and 16 constituting the light source device 100 can be prevented from being biased and deteriorated at an early stage, and the projection luminance of the projector 200 can be maintained over a long period of time.

[Second Embodiment]
Hereinafter, the light source device of the second embodiment will be described. Note that the light source device of the second embodiment is a modification of the light source device 100 of the first embodiment, and parts not specifically described are the same as those of the light source device 100 of the first embodiment.

  FIG. 9 is a graph illustrating the modulation of the duty ratio of the alternating current supplied to the pair of electrodes 15 and 16. The horizontal axis represents time, and the vertical axis represents the duty ratio. In this case, as indicated by the solid line, the modulation pattern of the alternating current supplied to both the electrodes 15 and 16 has a divided period in which the first anode duty ratio in which the anode period of the first electrode 15 is relatively long is 50% or more. DP1 and the segment period DP2 in which the first anode duty ratio in which the anode period of the second electrode 16 is relatively long is 50% or less are alternately repeated. As is apparent from the graph, the first anode duty ratio on the first electrode 15 side changes within a relatively high modulation range in which the maximum value DM1 is 70% and the minimum value is 35%. The second anode duty ratio varies within a relatively low modulation range where the maximum value DM2 is 65% and the minimum value is 30%. For reference, a modulation pattern in which the maximum value of the second anode duty ratio when the second electrode 16 is an anode is 70% is indicated by a broken line.

  As shown in FIG. 9, a sufficient change in the anode duty ratio is obtained by alternately repeating the segment period DP1 having the first anode duty ratio of 50% or more and the segment period DP2 having the first anode duty ratio of 50% or less. It is possible to restore the two electrodes in a balanced manner while securing the amount. In addition, it is possible to increase the amount of change in the duty ratio between two consecutive segment periods (hereinafter also simply referred to as “duty ratio change amount”).

  In the modulation pattern shown in FIG. 9, the duty ratio change amount gradually increases in the first half of the modulation cycle Tm and gradually decreases in the second half of the modulation cycle Tm. However, as the modulation pattern, the anode duty ratio of one electrode is a reference duty ratio (in the example of FIG. 9, a category in which the median value of the modulation range of the anode duty ratio is rounded to the 10% digit) or more. Various patterns can be used as long as the pattern alternately repeats the period and the divided period that is equal to or less than the reference duty ratio. For example, a modulation pattern that alternately repeats a segment period in which the first anode duty ratio is 70% and a segment period in which the first anode duty ratio is 40% may be used. However, it is more preferable to change the amount of change in the duty ratio within the modulation period Tm as shown in FIG. 9 in that the localization of the convection AF in the arc tube 1 can be more effectively suppressed. In the example of FIG. 9, the reference duty ratio is a value obtained by rounding the median value of the modulation range (50%), but the reference duty ratio may be the median value of the modulation range itself (52.5%). Generally, the reference duty ratio has only to be determined in advance based on the median value of the modulation range, and is appropriately set according to the characteristics of the arc tube 1, the length of each segment period, the waveform of an alternating current, or the like.

  10 to 12 are explanatory diagrams showing the influence of the duty ratio change amount on the distal end portion 15a of the first electrode 15 where the secondary mirror 3 is not provided. FIGS. 10A, 11A, and 12A show AC current modulation patterns when the duty ratio change ΔD is 5%, 10%, and 20%, respectively. In these graphs, the horizontal axis represents time, and the vertical axis represents the duty ratio of the alternating current. FIGS. 10B, 11B, and 12B show the first case where the modulation patterns shown in FIGS. 10A, 11A, and 12A are used. A state in which the shapes of the tip portion 15a and the large diameter portion 15b of the electrode 15 change is shown. 10B, FIG. 11B, and FIG. 12B, the solid line indicates the electrode shape after driving the arc tube 1 for 65 hours, and the alternate long and short dash line indicates the electrode shape when the arc tube 1 is not used. Is shown.

  When the modulation pattern shown in FIG. 10A is used, that is, when the duty ratio change amount ΔD is 5%, as shown in FIG. 10B, the size of the tip 15a of the electrode surrounded by the broken line is It was almost the same as the unused state (dashed line). When the duty ratio change amount ΔD is 10% (FIG. 11A), as shown in FIG. 11B, the size of the tip portion 15a of the electrode surrounded by the broken line is 5%. It became bigger than the case. Furthermore, when the duty ratio change amount ΔD is 20% (FIG. 12A), the size of the tip 15a of the electrode surrounded by the broken line is larger than that when the duty ratio change amount ΔD is 10%. It was. Thus, the magnitude | size of the front-end | tip part 15a of the 1st electrode 15 after driving the arc tube 1 became large as the duty ratio variation | change_quantity (DELTA) D was enlarged.

  As shown in FIGS. 10 to 12, as the duty ratio change ΔD is increased, the tip portion 15a of the electrode 15 grows larger with energization. From this, the duty ratio change amount ΔD is made larger than a predetermined value (for example, 7.5%), so that the tip portion 15a is grown with energization and the flattening of the tip portion 15a is suppressed. I found it possible. As with the first electrode 15, the second electrode 16 can also grow the tip portion 16 a with energization by increasing the duty ratio change amount ΔD and suppress flattening of the tip portion 16 a. It becomes possible.

  In the second embodiment, the first anode 15 has a relatively long anode period DP1 in which the first anode duty ratio is 50% or more, and the second electrode 16 has a relatively long anode period. The duty ratio change amount is increased by alternately repeating the segment periods DP2 in which the anode duty ratio is 50% or less. Therefore, according to 2nd Embodiment, the front-end | tip parts 15a and 16a can be grown with electricity supply, and deterioration of electrode shapes, such as planarization of the front-end | tip parts 15a and 16a, can be suppressed.

[Third Embodiment]
The light source device according to the third embodiment will be described below. The light source device of the third embodiment is a modification of the light source device 100 of the first embodiment, and parts that are not particularly described are the same as those of the light source device 100 of the first embodiment.

  FIG. 13 is a graph for explaining the modulation of the duty ratio of the alternating current supplied to the pair of electrodes 15 and 16. The horizontal axis represents time, and the vertical axis represents the duty ratio. In this case, as shown by the solid line, the modulation pattern of the alternating current supplied to both electrodes 15 and 16 is the first half period in which the first anode duty ratio in which the anode period of the first electrode 15 is relatively long is 50% or more. H1 and the second half H2 in which the first anode duty ratio in which the anode period of the second electrode 16 is relatively long is 50% or less. Also, the duty ratio does not increase or decrease monotonously as shown in FIG. 4, but the rate of change changes with time. For reference, a modulation pattern in which the maximum value of the second anode duty ratio when the second electrode 16 is an anode is 70% is indicated by a dotted line.

  Also in the third embodiment, both the change amount of the duty ratio between the divided periods P1 and P2 and the change amount of the duty ratio between the divided periods P1 'and P2' are increased. Therefore, similarly to the second embodiment, the tip portions 15a and 16a can be grown with energization, and deterioration of the electrode shape such as flattening of the tip portions 15a and 16a can be suppressed.

[Modification of modulation pattern]
The modulation patterns shown in FIGS. 4, 9, and 13 are merely examples, and convection AF is generated in the arc tube 1 by changing the alternating current supplied to the pair of electrodes 15 and 16 with various modulation patterns. Excessive localization can be prevented. Further, as shown in FIGS. 9 and 13, it is possible to suppress deterioration of the electrode shape by making the duty ratio change amount larger than a predetermined value. For example, the alternating current may be changed with the following modulation pattern.

[First Modification of Modulation Pattern]
FIG. 14 is an explanatory diagram showing a first modification of the modulation pattern. In the modulation pattern of the first modification, a period (low duty ratio period) in which the first anode duty ratio is lower than the reference duty ratio (50%) in the first half of the modulation period Tm is shortened, and the first in the second half of the modulation period Tm. The period during which the anode duty ratio exceeds the reference duty ratio (high duty ratio period) is shortened. The other points are the same as the modulation pattern in the second embodiment shown in FIG.

  When the anode duty ratio of one electrode is high, the temperature of the electrode rises. As described above, when the electrode operates as a cathode in a state where the temperature has risen, the discharge (sputtering) of the electrode material into the discharge space 12 due to the collision of cations (for example, Ar + and Hg +) generated by the discharge is large. Therefore, the inner wall of the discharge space 12 tends to be blackened. Therefore, in the first modification, in the first half of the modulation period Tm in which the temperature of the first electrode 15 is rising, the low duty ratio period is shortened to suppress the occurrence of sputtering, and the temperature of the second electrode 16 is suppressed. In the latter half of the modulation period Tm in which the rise is, the high duty ratio period is shortened to suppress the occurrence of sputtering.

  On the other hand, also in the first modification example, the segment period in which the anode duty ratio of the first electrode 15 in which the anode period of the first electrode 15 is relatively long and the anode duty ratio of the first electrode 15 is 50% or more and the anode period of the second electrode 16 are relative. The amount of change in the duty ratio is increased by alternately repeating the segment period in which the anode duty ratio of the first electrode 15 that is longer than 50% is 50% or less. Therefore, the tip portions 15a and 16a can be grown along with energization, and deterioration of the electrode shape such as flattening of the tip portions 15a and 16a can be suppressed.

[Second Modification of Modulation Pattern]
FIG. 15 is an explanatory diagram illustrating a second modification of the modulation pattern. In the modulation pattern of the second modification, the amount of change in the duty ratio from the high duty ratio period of the first electrode 15 to the low duty ratio period following the high duty ratio period is a constant value (25% in the example of FIG. 15). ) And the duty ratio as a whole changes gently at the modulation period Tm (8 seconds). Also in FIG. 15, the modulation pattern with the maximum value of the second anode duty ratio being 70% is indicated by a broken line. In this case, the amount of change in the duty ratio from the high duty ratio period to the low duty ratio period following the high duty ratio period is set to 30%.

  As shown in FIG. 15, also in the second modification, the amount of change in the duty ratio is sufficiently large, so that the tip portions 15a and 16a grow with energization, and the tip portions 15a and 16a are flattened. Deterioration of the electrode shape is suppressed. In addition, since the thermal states of the electrodes 15 and 16 and their surroundings can be gradually changed with a long span that affects the convection AF, it is steady in the main body portion 11 of the arc tube 1. Formation of convection AF can be avoided.

  The present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

  Various lamps such as a high-pressure mercury lamp and a metal halide lamp are conceivable as the lamp used in the light source unit 10 of the above embodiment.

  Further, in the projector 200 of the above embodiment, a pair of fly-eye lenses 23a and 23b is used to divide the light from the light source device 100 into a plurality of partial light beams. That is, the present invention can be applied to a projector that does not use a lens array. Furthermore, the fly-eye lenses 23a and 23b can be replaced with rod integrators.

  Further, in the projector 200, the polarization conversion element 24 that converts the light from the light source device 100 into a specific direction of polarization is used. However, the present invention is also applicable to a projector that does not use such a polarization conversion element 24. is there.

  In the above embodiment, an example in which the present invention is applied to a transmissive projector has been described. However, the present invention can also be applied to a reflective projector. Here, “transmission type” means that a liquid crystal light valve including a liquid crystal panel transmits light, and “reflection type” means that the liquid crystal light valve reflects light. It means that there is. The light modulation device is not limited to a liquid crystal panel or the like, and may be a light modulation device using a micromirror, for example.

  Further, as the projector, there are a front projector that projects an image from the direction of observing the projection surface and a rear projector that projects an image from the side opposite to the direction of observing the projection surface. The projector configuration shown in FIG. Is applicable to both.

  In the above-described embodiment, only the example of the projector 200 using the three liquid crystal panels 41a to 41c has been described. However, the present invention is a projector using only one liquid crystal panel, a projector using two liquid crystal panels, Or it is applicable also to the projector using four or more liquid crystal panels.

  In the above-described embodiment, light modulation of each color is performed using the color separation optical system 30 and the liquid crystal light valves 40a, 40b, 40c, etc., but instead, for example, by the light source device 100 and the illumination optical system 20 By using a combination of an illuminated color wheel and a device that is configured by pixels of a micromirror and irradiated with light transmitted through the color wheel, color light modulation and synthesis can be performed.

    DESCRIPTION OF SYMBOLS 2 ... Reflector, 3 ... Secondary mirror, 10 ... Light source unit, 11 ... Main part, 12 ... Discharge space, 13, 14 ... Sealing part, 15 ... 1st electrode, 15a, 16a ... Tip part, 15b, 16b ... Large Diameter part 16 ... 2nd electrode 20 ... Illumination optical system 22 ... Parallelizing lens 23a, 23b ... Fly eye lens 24 ... Polarization conversion element 25 ... Superposition lens 30 ... Color separation optical system 31a, 31b ... Dichroic mirror, 40 ... Light modulation unit, 40a, 40b, 40c ... Liquid crystal light valve, 41a, 41b, 41c ... Liquid crystal panel, 42a, 42b, 42c ... Polarization filter, 50 ... Cross dichroic prism, 60 ... Projection lens, 70 DESCRIPTION OF SYMBOLS ... Light source drive device, 70a ... Lighting device, 70b ... Control device, 74 ... Drive control part, 76 ... Data storage part, 1 0 ... light source apparatus, 200 ... projector, AF ... convection, AR ... arc, EG ... inter-electrode space, OA ... system optical axis

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.
One aspect of the present invention is a light source device, an arc tube having a first electrode and a second electrode that emit light by discharge between each other; and disposed on the first electrode side, the first electrode and the first electrode A main reflecting mirror that reflects a light beam generated by a discharge between two electrodes and emits the light to an illuminated area; and is disposed on the second electrode side so as to face the main reflecting mirror, and the first electrode and the second electrode A sub-reflector that reflects a light beam from the inter-electrode space toward the inter-electrode space; in a steady operation of supplying an alternating current to the first and second electrodes, the first electrode and the second electrode The alternating current duty ratio supplied between the electrodes is changed in a predetermined pattern, and the second electrode is an anode in one cycle than the maximum value of the time ratio in which the first electrode operates as an anode in one cycle. The maximum value of the percentage of time to operate as small And the predetermined pattern includes a plurality of segment periods in which the alternating current duty ratio is maintained at the same value for a predetermined time, and the alternating current in each segment period in the plurality of segment periods. The current polarity is inverted multiple times between positive and negative. With such a configuration, the second electrode on the sub-reflecting mirror side prevents the phenomenon of higher temperature than the first electrode on the main reflecting mirror side, and suppresses the phenomenon that only the second electrode deteriorates earlier. be able to. In addition, the present invention can be realized in the following forms.
In order to solve the above-described problems, a light source device according to the present invention includes (a) an arc tube having a first electrode and a second electrode that emit light by discharge between each other, and (b) disposed on the first electrode side. A main reflecting mirror that reflects the light beam generated by the discharge between the first electrode and the second electrode and emits it to the illuminated area; and (c) is disposed on the second electrode side so as to face the main reflecting mirror. A sub-reflector that reflects a light beam from the inter-electrode space of the electrode and the second electrode toward the inter-electrode space; and (d) a steady operation of supplying an alternating current to the first and second electrodes. The alternating current duty ratio supplied between the second electrode and the second electrode is changed in a predetermined pattern, and the ratio of the time during which the first electrode operates as an anode in one cycle (hereinafter, this ratio is also referred to as the first anode duty ratio). The second electrode is the anode in one cycle than the maximum value of Percentage of time that the operation (hereinafter this percentage also referred to as a second anode duty ratio) and a current driver to reduce the maximum value of. Here, the steady operation means an operation of causing the arc tube to emit light steadily after starting lighting.

Claims (10)

An arc tube having a first electrode and a second electrode that emit light by discharge between each other;
A main reflector that is disposed on the first electrode side and reflects a light beam generated by a discharge between the first electrode and the second electrode to be emitted to an illuminated area;
A sub-reflecting mirror disposed on the second electrode side facing the main reflecting mirror and reflecting a light beam from the inter-electrode space of the first electrode and the second electrode toward the inter-electrode space;
In a steady operation of supplying an alternating current to the first and second electrodes, an alternating current duty ratio supplied between the first electrode and the second electrode is changed in a predetermined pattern, and the first electrode is A light source device comprising: a current driving device configured to reduce a maximum value of a ratio of a time during which the second electrode operates as an anode in one period to a maximum value of a ratio of a time during which the second electrode operates as an anode in one period.   2. The light source device according to claim 1, wherein the current driving device changes a current value of a polarity in which at least a time ratio is 50% or more among positive and negative polarities per cycle of AC driving.   The current driving device changes a current value of a polarity at which the time ratio is at least 50% of positive and negative polarities per cycle of AC driving so that the current value becomes maximum at the end of the half cycle. The light source device according to claim 2. The light source device according to claim 3, wherein the current driving device increases a current value of a polarity at which a time ratio is 50% or more among positive and negative polarities per cycle of AC driving with time. The light source device according to any one of claims 1 to 4,
The predetermined pattern includes a first divided period and a second divided period in which the alternating current duty is different from the first divided period as a divided period in which the alternating current duty ratio is maintained at a constant value. And
A light source device, wherein a difference between the alternating current duty ratio in the first segment period and the alternating current duty ratio in the second segment period is greater than a predetermined value. The light source device according to claim 5,
The alternating current duty ratio in the first segment period and the alternating current duty ratio in the second segment period are a reference duty ratio determined in advance based on a median value of the change range of the alternating current duty ratio. A light source device that changes over time. The light source device according to claim 6,
The length of the first segment period and the length of the second segment period are different from each other. The light source device according to claim 7,
The predetermined pattern is a periodically changing pattern;
In a predetermined period within one cycle of the pattern, the length of the segment period in which the alternating current duty ratio is higher than the reference duty ratio is longer than the length of the segment period in which the alternating current duty ratio is lower than the reference duty ratio. Lengthen and
In the remaining period in one cycle of the pattern, the length of the segment period in which the alternating current duty ratio is higher than the reference duty ratio is longer than the length of the segment period in which the alternating current duty ratio is lower than the reference duty ratio. Shortened light source device. The light source device according to any one of claims 1 to 8,
A light modulation device illuminated by illumination light from the light source device;
A projection optical system for projecting an image formed by the light modulation device;
A projector comprising: An arc tube having a first electrode and a second electrode that emits light by discharge between each other and a light beam that is disposed on the first electrode side and that is generated by the discharge between the first electrode and the second electrode is reflected. A main reflecting mirror that exits to the illuminated region; and is disposed on the second electrode side so as to face the main reflecting mirror, and transmits a light beam from the interelectrode space of the first electrode and the second electrode to the interelectrode space side A discharge lamp driving method comprising a sub-reflecting mirror that reflects toward the
In a steady operation of supplying an alternating current for discharge to the first and second electrodes, the alternating current duty ratio supplied between the first electrode and the second electrode is changed in a predetermined pattern, and the first A method for driving a discharge lamp, wherein the maximum value of the ratio of time during which the electrode operates as an anode in one cycle is smaller than the maximum value of the ratio of time during which the second electrode operates as an anode in one period.