JP2013118105A - Light source device, driving method of discharge lamp and projector - Google Patents

Abstract

To provide a light source device, a discharge lamp driving method, and a projector capable of suppressing the blackening of a discharge lamp, maintaining a distance between electrodes at a constant distance, and driving the discharge lamp.
A light source device includes a light emitting container, a discharge lamp having a pair of electrodes, and a drive device that supplies a drive current to the pair of electrodes, the drive device having a first frequency greater than 1 kHz. The first alternating current supply section for supplying the alternating current to the pair of electrodes and the second alternating current having a frequency of 1 kHz or less shorter than the first alternating current supply section and the first alternating current supply section are supplied to the pair of electrodes. And the second alternating current supply section that repeats alternately. When the polarity of the second alternating current is switched from the positive current section to the negative negative current section, At least one of the switching to the current section is provided with an off section in which a current within ± 5% of the amplitude a of the second alternating current is supplied to the pair of electrodes or no current is supplied.
[Selection] Figure 4

Description

  The present invention relates to a light source device, a discharge lamp driving method, and a projector.

As a light source of a projector, a discharge lamp (discharge lamp) such as a high-pressure mercury lamp or a metal halide lamp is used.
Such a discharge lamp is driven by, for example, a driving method that supplies a high-frequency alternating current as a driving current (see, for example, Patent Document 1). According to this driving method, discharge stability can be obtained, blackening and devitrification of the discharge lamp body can be prevented, and a reduction in the life of the discharge lamp can be suppressed.

However, in this driving method, when the discharge lamp is lit, an arc discharge is generated between the pair of electrodes, and the electrodes are at a high temperature. come.
For example, in the application of a projector, in order to improve the light utilization efficiency, it is preferable to maintain a narrow state between the electrodes and reduce the size of light emission. Spreading between the electrodes during lighting is not preferable because it reduces light utilization efficiency.

On the other hand, there is also a driving method in which an alternating current (direct current alternating current) having a rectangular waveform at a low frequency is supplied as a driving current (see, for example, Patent Document 2). According to this driving method, when the discharge lamp is lit, the protrusions are formed at the tip portions of the pair of electrodes, thereby maintaining a narrow state between the electrodes.
However, this driving method has a problem that the discharge lamp main body is blackened, devitrified, and the like, and the life of the discharge lamp is reduced.

Further, in Patent Document 3, a pair of alternating currents having a steady lighting frequency of 60 to 1000 Hz and alternating currents having a frequency lower than the steady lighting frequency and a low frequency of 5 to 200 Hz are alternately paired. There is disclosed a lighting device that supplies a discharge lamp to a discharge lamp.
However, in the lighting device described in Patent Document 3, the frequency of both the alternating current with a steady lighting frequency and the alternating current with a low frequency is too low, resulting in blackening or devitrification of the discharge lamp body, and the life of the discharge lamp. There is a problem that decreases. In addition, when the discharge lamp is lit, a protrusion is formed at the tip of the pair of electrodes, but the electrode is gradually consumed while it is lit for a long time, for example, several hundreds or thousands of hours. As a result, the protrusion cannot be enlarged to a predetermined size.

JP 2007-115534 A JP 2010-1114064 A JP 2010-123478 A

  An object of the present invention is to provide a light source device, a discharge lamp driving method, and a projector capable of suppressing the blackening of a discharge lamp, maintaining a distance between electrodes at a constant distance, and driving the discharge lamp. .

Such an object is achieved by the present invention described below.
In order to solve the above-described problems, a light source device according to the present invention includes a light emitting container including a cavity in which a discharge medium is sealed, and a discharge lamp having a pair of electrodes whose end portions are opposed to each other in the cavity. And a driving device that supplies a driving current to the pair of electrodes, wherein the driving device supplies a first AC current having a frequency higher than 1 kHz to the pair of electrodes. A current supply section and a second alternating current supply section that is shorter than the first alternating current supply section and that supplies a second alternating current having a frequency of 1 kHz or less to the pair of electrodes are alternately repeated. In the second alternating current supply section, when the polarity of the second alternating current is switched from a positive current section in which the polarity is positive to a negative current section in which the polarity is negative, the positive current from the negative current section is configured. At least one of when switching to a section Wherein the pair of electrodes to either deliver power within ± 5% of the amplitude a of the second alternating current, or a current-off interval is not supplied is provided.

According to the light source device of the present invention described above, blackening of the discharge lamp is suppressed in the first AC current supply section, and the blackening of the discharge lamp blackened in the second AC current supply section described later. Can be recovered.
On the other hand, in the second AC current supply section, a protrusion is formed at the tip portion of the pair of electrodes, and the protrusion becomes large, and thereby, between the electrodes of the pair of electrodes spread in the first AC current supply section. The distance can be reduced.

By alternately repeating the first alternating current supply section and the second alternating current supply section, blackening of the discharge lamp is suppressed, and the distance between the electrodes of the pair of electrodes is kept constant. The discharge lamp can be driven.
In addition, since the off section is provided in the second alternating current supply section, in the second alternating current supply section, the distance between the electrodes of the pair of electrodes surely becomes a preset lower limit value. The protrusion can be enlarged. Thereby, a lifetime can be lengthened.

Further, in the light source device of the present invention, in the light source device, the off section is provided when switching from the positive current section to the negative current section and when switching from the negative current section to the positive current section. It is characterized by.
According to the light source device of the present invention as described above, the protrusion can be grown more reliably.
The light source device of the present invention is characterized in that, in the light source device, no current is supplied to the pair of electrodes in the off section.
According to the light source device of the present invention as described above, the protrusion can be grown more reliably.

The light source device of the present invention is characterized in that, in the light source device, the period of the off section is 0.1 μsec or more and 5 ms or less.
According to the light source device of the present invention described above, in the second AC current supply section, it is possible to grow the protrusion while reducing the blackening of the discharge lamp.
In the light source device of the present invention, the light source device further includes detection means for detecting a change amount per unit time of the distance between the electrodes of the pair of electrodes, and the driving device includes the first alternating current. The absolute value | V1 | of the average value of the change amount per unit time of the distance between the electrodes of the pair of electrodes in the supply section is a unit of the distance between the electrodes of the pair of electrodes in the second alternating current supply section. When the absolute value | V2 | of the average value of the amount of change per time becomes larger, the off section is configured to have a longer period.
According to the light source device of the present invention as described above, the protrusion can be more reliably grown in the second AC current supply section while reducing the blackening of the discharge lamp.

In the light source device of the present invention, in the above light source device, when the period of the first alternating current supply section is A and the period of the second alternating current supply section is B, A / B is 2 or more. It is characterized by being set.
According to the light source device of the present invention as described above, the blackening of the discharge lamp can be suppressed more reliably and the distance between the electrodes of the pair of electrodes can be maintained at a constant distance.
Moreover, the light source device of the present invention is characterized in that, in the light source device, the amplitude of the first alternating current is reduced with time in the first alternating current supply section.
According to the light source device of the present invention as described above, fluctuations in the amount of light can be suppressed.

Moreover, the light source device of the present invention is characterized in that, in the light source device, the amplitude of the second alternating current is increased with time in the second alternating current supply section.
According to the light source device of the present invention as described above, fluctuations in the amount of light can be suppressed.
The light source device of the present invention is characterized in that, in the light source device, the waveform of the first alternating current is rectangular.
According to the light source device of the present invention as described above, blackening of the discharge lamp can be suppressed more reliably.

The light source device of the present invention is characterized in that, in the light source device, the waveform of the second alternating current is rectangular.
According to the light source device of the present invention as described above, blackening of the discharge lamp can be suppressed more reliably.
Moreover, the light source device of the present invention is characterized in that in the light source device described above, blackening of the discharge lamp is suppressed by supplying the first alternating current.
According to the light source device of the present invention described above, blackening of the discharge lamp can be suppressed.

The light source device of the present invention is characterized in that, in the light source device, the distance between the electrodes of the pair of electrodes is reduced by supplying the second alternating current.
According to the light source device of the present invention as described above, the distance between the electrodes of the pair of electrodes widened in the first alternating current supply section can be narrowed, and the distance between the electrodes can be kept constant. .

In the light source device according to the present invention, in the light source device, an average value of an amplitude of the first alternating current in the first alternating current supply section and the second in the second alternating current supply section. The average value of the amplitude of the alternating current is the same.
According to the light source device of the present invention as described above, the light amount in the first alternating current supply section and the light amount in the second alternating current supply section can be made the same.

In the light source device according to the present invention, an upper limit value and a lower limit value of the inter-electrode voltage of the pair of electrodes are set in the light source device, and a difference between the upper limit value and the lower limit value is 15 V or less. It is characterized by being.
According to the light source device of the present invention as described above, fluctuations in the amount of light can be suppressed.
In order to solve the above-mentioned problem, a discharge lamp driving method according to the present invention includes a light emitting container including a hollow portion in which a discharge medium is sealed, and a pair of electrodes whose end portions are opposed to each other in the hollow portion. A first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a period of the first alternating current supply section Shorter than the second alternating current supply section for supplying the second alternating current having a frequency of 1 kHz or less to the pair of electrodes, and alternately repeating the second alternating current supply section in the second alternating current supply section. The alternating current of the first electrode is connected to the pair of electrodes at least one of when switching from a positive current section with a positive polarity to a negative current section with a negative polarity and when switching from the negative current section to the positive current section. ± 5 of amplitude a of 2 alternating current Generating a drive current off period is provided is not supplied to or current supplied within the current, and supplying the drive current to the electrodes of the pair.

According to the discharge lamp driving method of the present invention as described above, it is possible to suppress the blackening of the discharge lamp, hold the distance between the electrodes of the pair of electrodes at a constant distance, and drive the discharge lamp.
In addition, since the off section is provided in the second alternating current supply section, in the second alternating current supply section, the distance between the electrodes of the pair of electrodes surely becomes a preset lower limit value. The protrusion can be enlarged. Thereby, a lifetime can be lengthened.

In order to solve the above problems, a projector according to the invention includes the light source device.
According to the projector of the present invention as described above, it is possible to suppress the blackening of the discharge lamp, hold the distance between the electrodes of the pair of electrodes at a constant distance, and drive the discharge lamp, thereby reducing the power consumption. It can be reduced and a stable and good image can be displayed.
In addition, since the off section is provided in the second alternating current supply section, in the second alternating current supply section, the distance between the electrodes of the pair of electrodes surely becomes a preset lower limit value. The protrusion can be enlarged. Thereby, a lifetime can be lengthened.

It is sectional drawing (a block diagram is also included) which shows 1st Embodiment of the light source device of this invention. It is sectional drawing which shows the discharge lamp of the light source device shown in FIG. It is a block diagram which shows the light source device shown in FIG. It is a figure which shows the drive current of the light source device shown in FIG. It is a figure which shows the absolute value of the voltage between electrodes of the light source device shown in FIG. It is a flowchart which shows the control operation of the light source device shown in FIG. It is a flowchart which shows the control action in 2nd Embodiment of the light source device of this invention. It is a figure which shows typically embodiment of the projector of this invention.

Hereinafter, a light source device, a discharge lamp driving method, and a projector of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<First Embodiment>
1 is a cross-sectional view (including a block diagram) showing an embodiment of a light source device of the present invention, FIG. 2 is a cross-sectional view showing a discharge lamp of the light source device shown in FIG. 1, and FIG. 3 is shown in FIG. 4 is a block diagram showing the light source device, FIG. 4 is a diagram showing the drive current of the light source device shown in FIG. 1, FIG. 5 is a diagram showing the absolute value of the interelectrode voltage of the light source device shown in FIG. 1, and FIG. 2 is a flowchart showing a control operation of the light source device shown in FIG. In FIG. 2, the sub-reflecting mirror is not shown.

  As shown in FIGS. 1 and 3, the light source device 1 includes a light source unit 110 having a discharge lamp 500, a discharge lamp driving device (driving device) 200 that drives the discharge lamp 500, and a detector (interelectrode distance detection unit). ) 35 and a cooling device (not shown) for cooling a light emitting vessel 511 described later of the discharge lamp 500. The discharge lamp 500 receives electric power from the discharge lamp driving device 200 to discharge and emit light.

  The light source unit 110 includes a discharge lamp 500, a main reflecting mirror 112 having a concave reflecting surface, and a collimating lens 114 that makes emitted light substantially parallel. The main reflecting mirror 112 is disposed on one end side of the discharge lamp 500, and the collimating lens 114 is disposed on the other end side of the discharge lamp 500. The main reflecting mirror 112 and the discharge lamp 500 are bonded with an inorganic adhesive 116. Further, the main reflecting mirror 112 has a surface (inner surface) on the discharge lamp 500 side as a reflecting surface, and this reflecting surface forms a spheroidal surface in the illustrated configuration.

Note that the shape of the reflecting surface of the main reflecting mirror 112 is not limited to the above shape, and other examples include a rotating paraboloid. Further, when the reflecting surface of the main reflecting mirror 112 is a rotating paraboloid, the collimating lens 114 can be omitted if the light emitting part of the discharge lamp 500 is arranged at the so-called focal point of the rotating paraboloid.
The discharge lamp 500 includes a discharge lamp main body 510 and a sub-reflecting mirror 520 having a concave reflecting surface. The sub-reflecting mirror 520 is disposed on the opposite side of the main reflecting mirror 112 of the discharge lamp main body 510, that is, on the parallelizing lens 114 side, and at a position separated from the outer peripheral surface of the discharge lamp main body 510 by a predetermined distance. The discharge lamp main body 510 and the sub-reflecting mirror 520 are bonded by an inorganic adhesive 522 provided between the discharge lamp main body 510 and the sub-reflecting mirror 520. Further, in the sub-reflecting mirror 520, the surface (inner surface) on the discharge lamp 500 side is a reflecting surface, and this reflecting surface is a spherical surface in the illustrated configuration.

  At the center of the discharge lamp main body 510, a light emitting container 511 including a discharge space (hollow part) 512 hermetically sealed with a discharge medium described later is formed. At least a portion corresponding to the discharge space 512 of the discharge lamp main body 510 has light transmittance. Examples of the constituent material of the discharge lamp main body 510 include glass such as quartz glass and light-transmitting ceramics.

The discharge lamp main body 510 is provided with a pair of electrodes 610 and 710, a pair of conductive connection members 620 and 720, and a pair of electrode terminals 630 and 730. The electrode 610 and the electrode terminal 630 are electrically connected by a connection member 620. Similarly, the electrode 710 and the electrode terminal 730 are electrically connected by a connection member 720.
Each electrode 610, 710 is accommodated in the discharge space 512. In other words, the electrodes 610 and 710 are arranged such that their tip portions are spaced apart from each other by a predetermined distance in the discharge space 512 of the discharge lamp main body 510 and face each other.

The distance between the electrodes, which is the shortest distance between the electrode 610 and the electrode 710, is preferably 1 μm or more and 5 mm or less, and more preferably 0.5 mm or more and 1.5 mm or less.
As shown in FIG. 2, the electrode 610 includes a core rod 612, a coil portion 614, and a main body portion 616. The electrode 610 is formed by winding a wire rod of an electrode material (tungsten or the like) around a core rod 612 to form a coil portion 614 before heating and melting the formed coil portion 614 before being enclosed in the discharge lamp main body 510. It is formed by doing. As a result, a body portion 616 having a large heat capacity is formed on the tip side of the electrode 610. Similarly to the electrode 610, the electrode 710 also includes a core rod 712, a coil portion 714, and a main body portion 716, and is formed in the same manner as the electrode 610.

In the state where the discharge lamp 500 has never been lit, the main body portions 616 and 716 are not formed with protrusions 618 and 718. However, if the discharge lamp 500 is lit even once under the conditions described later, the main body portion Protrusions 618 and 718 are formed at the tips of 616 and 716, respectively. The protrusions 618 and 718 are maintained while the discharge lamp 500 is turned on, and are also maintained after the lamp is turned off.
In addition, as a constituent material of each electrode 610,710, high melting point metal materials, such as tungsten, etc. are mentioned, for example.

Further, a discharge medium is enclosed in the discharge space 512. The discharge medium includes, for example, a discharge start gas, a gas that contributes to light emission, and the like. Further, the discharge medium may contain other gas.
Examples of the discharge starting gas include noble gases such as neon, argon, and xenon. Examples of the gas that contributes to light emission include mercury, vaporized metal halide, and the like. Examples of the other gas include a gas having a function of preventing blackening. Examples of the gas having a function of preventing blackening include a halogen (for example, bromine), a halogen compound (for example, hydrogen bromide), or a vaporized product thereof.
The atmospheric pressure in the discharge lamp main body 510 when the discharge lamp is lit is preferably 0.1 atm or more and 300 atm or less, and more preferably 50 atm or more and 300 atm or less.

  As described above, one electrode terminal 730 of the discharge lamp 500 is led out by being electrically connected to the discharge lamp main body 510 via the electrode 710 and the connection member 720 on the side opposite to the main reflecting mirror 112. ing. Similarly, the other electrode terminal 630 of the discharge lamp 500 is electrically connected to the discharge lamp main body 510 on the side of the main reflecting mirror 112 via the electrode 610 and the connecting member 620, and the back surface of the main reflecting mirror 112. Is led to the side. The electrode terminals 630 and 730 of the discharge lamp 500 are connected to the output terminals of the discharge lamp driving device 200, respectively. The discharge lamp driving device 200 includes a high-frequency alternating current (AC power) in the discharge lamp 500. A drive current (drive power) is supplied. In other words, the discharge lamp driving device 200 supplies power to the discharge lamp 500 by supplying the drive current to the electrodes 610 and 710 via the electrode terminals 630 and 730. When the drive current is supplied to the electrodes 610 and 710, arc discharge (arc AR) is generated between the tips of the pair of electrodes 610 and 710 in the discharge space 512. Light (discharge light) generated by the arc discharge is radiated in all directions from the generation position (discharge position) of the arc AR. As described above, the sub-reflecting mirror 520 is disposed so as to cover the curved surface on the side opposite to the side on which the main reflecting mirror 112 is disposed with respect to the discharge lamp main body 510, and thus in the direction of the one electrode 710. The emitted light is reflected toward the main reflecting mirror 112. In this way, by reflecting the light emitted in the direction of the electrode 710 toward the main reflecting mirror 112, the light emitted in the direction of the electrode 710 can be effectively used. In the present embodiment, the discharge lamp 500 includes the sub-reflecting mirror 520, but the discharge lamp 500 may be configured not to include the sub-reflecting mirror 520.

Next, the discharge lamp driving device 200 and the detector 35 will be described.
As shown in FIG. 3, the discharge lamp driving device 200 includes a direct current generator 31 that generates a direct current, a polarity switch 32 that switches between positive and negative polarities of the direct current output from the direct current generator 31, and a control. Unit (control means) 33, and the polarity switch 32 switches the polarity of the direct current to generate an alternating current having a predetermined frequency (direct current alternating current). The alternating current is used as a drive current for the discharge lamp 500. This is a device that supplies a pair of electrodes 610 and 710. The direct current generator 31, the polarity switch 32, and the control unit 33 constitute a first alternating current supply unit and a second alternating current supply unit.

  The controller 33 controls the overall operation of the discharge lamp driving device 200 such as the direct current generator 31 and the polarity switch 32. The direct current generator 31 can adjust the current value as its output, and the current value of the direct current generator 31 is adjusted under the control of the control unit 33. The timing of switching the polarity of the direct current in the polarity switch 32 is adjusted by the control of the control unit 33.

  Further, a detection result of a detector (interelectrode distance detection unit) 35 described later provided separately on the output side of the discharge lamp driving device 200 (between the electrode terminals 630 and 730 of the discharge lamp 500 and the discharge lamp driving device 200). Is input to the control unit 33. In the present embodiment, the detector 35 is provided separately from the discharge lamp driving device 200, but may be configured to be incorporated in the discharge lamp driving device 200. Further, an amplifier (not shown) may be provided, for example, at a subsequent stage of the polarity switch 32, that is, between the polarity switch 32 and the detector 35.

As shown in FIGS. 4 and 5, the discharge lamp driving device 200 generates a first alternating current (high-frequency alternating current) and supplies the first alternating current to a pair of electrodes 610 and 710. A section 41 and a second alternating current supply section 42 that generates a second alternating current having a frequency lower than that of the first alternating current (a low-frequency alternating current) and supplies the second alternating current to the pair of electrodes 610 and 710. The polarity switch 32 switches the polarity of the direct current generated by the direct current generator 31 so as to be repeated alternately. That is, an alternating current, which is a driving current for driving a discharge lamp, in which the first alternating current supply section 41 and the second alternating current supply section 42 are alternately repeated is generated and output. The drive current output from the discharge lamp driving device 200 is supplied to a pair of electrodes 610 and 710 of the discharge lamp 500.
Thereby, as described above, arc discharge occurs between the tip portions of the pair of electrodes 610 and 710, and the discharge lamp 500 is turned on. In addition, while the discharge lamp 500 is lit, the cooling device operates to cool the light emitting container 511.

  Here, in the light source device 1, the discharge lamp 500 is lit using a driving current under the conditions described later. Therefore, when the discharge lamp 500 is lit, the temperature of the electrodes 610 and 710 varies. The projections 618 and 718 are formed at the tip portions of the electrodes 610 and 710, respectively, so that the projections 618 and 718 can be maintained, the blackening of the discharge lamp 500 can be prevented, and the life can be extended. it can.

  That is, in the second alternating current supply section 42, a second alternating current described later is supplied to the electrodes 610 and 710, so that protrusions 618 and 718 are formed at the tips of the electrodes 610 and 710, and the protrusions 618 and 718. As a result, the distance between the electrodes of the pair of electrodes 610 and 710 widened in the first alternating current supply section 41 described later can be reduced (reduced).

  Specifically, in the second alternating current supply section 42, first, in the positive current section 44 in which the polarity of the second alternating current is positive, the electrodes 610 and 710 are heated to increase the temperature of the electrodes 610 and 710, respectively. A part of the tip portion of 710 is melted, and the melted electrode material gathers at the tip portions of the electrodes 610 and 710 due to surface tension. On the other hand, in the negative current section 45 in which the polarity of the second alternating current is negative, the temperature of the electrodes 610 and 710 decreases, so that the molten electrode material is solidified. The protrusions 618 and 718 grow by repeating such a state in which the molten electrode material is collected at the tip portions of the electrodes 610 and 710 and a state in which the molten electrode material is solidified.

Then, as will be described later, by switching between the first alternating current supply section 41 and the second alternating current supply section 42 and restricting the interelectrode distance within a predetermined range, the interelectrode distance is prevented from spreading. It is possible to maintain a narrow state between the electrodes. Thereby, the discharge lamp 500 can be driven efficiently.
However, in the second AC current supply section 42, the discharge lamp 500 is blackened.

On the other hand, in the first alternating current supply section 41, since a first alternating current described later is supplied to the electrodes 610 and 710, blackening of the discharge lamp 500 is suppressed, and in the second alternating current supply section 42, The blackening of the blackened discharge lamp 500 can be recovered.
However, in the first alternating current supply section 41, the protrusions 618 and 718 formed at the tip portions of the electrodes 610 and 710 in the second alternating current supply section 42 are reduced, thereby increasing the distance between the electrodes.

By alternately repeating the first AC current supply section 41 and the second AC current supply section 42 as described above, blackening of the discharge lamp 500 is suppressed, the distance between the electrodes is maintained at a constant distance, and the discharge is performed. The electric lamp 500 can be driven.
In the second alternating current supply section 42, a current is applied to the pair of electrodes 610 and 710 between the positive current section 44 in which the polarity of the second alternating current is positive and the negative current section 45 in which the polarity is negative. Off sections 46 and 47 that are not supplied are provided. That is, an off section 46 is provided when the positive current section 44 is switched to the negative current section 45, and an off section 47 is provided when the negative current section 45 is switched to the positive current section 44. The reason is as follows.

  First, for a long time, for example, several hundreds or thousands of hours, while the protrusions 618 and 718 are repeatedly increased in the second alternating current supply section 42 or decreased in the first alternating current supply section 41, The electrodes 610 and 710 are gradually consumed, and the protrusions 618 and 718 are enlarged until the distance between the electrodes, that is, the absolute value of the voltage between the electrodes reaches a predetermined value appropriately determined as the lower limit value of the allowable range. It becomes impossible.

Providing the off sections 46 and 47 facilitates the growth of the protrusions 618 and 718, thereby allowing the protrusions 618 and 718 to grow until the absolute value of the interelectrode voltage reaches the lower limit value of the allowable range. it can. Thereby, the lifetime of the light source device 1 can be lengthened. Further, the growth rate of the protrusions 618 and 718 can be increased.
Further, the period t1 of the off section 46 and the period t2 of the off section 47 are not particularly limited, but are preferably 0.1 μsec or more and 5 msec or less, and preferably 0.1 μsec or more and 2 msec or less. More preferably, it is 0.1 μsec or more and 100 μsec or less.

When the periods t1 and t2 are shorter than 0.1 μsec, the protrusions 618 and 718 are difficult to grow depending on other conditions. Further, when the periods t1 and t2 are longer than 5 milliseconds, the discharge lamp 500 is likely to be blackened depending on other conditions.
Note that the period t1 and the period t2 may be the same or different.
Here, the rated power of the discharge lamp 500 is appropriately set depending on the application and the like, and is not particularly limited. However, the rated power is preferably 10 W or more and 5 kW or less, and more preferably 100 W or more and 500 W or less.

  Further, the frequency of the first alternating current is greater than 1 kHz. The frequency of the first alternating current is preferably greater than 1 kHz and 10 GHz or less, preferably greater than 1 kHz and 100 kHz or less, more preferably 3 MHz or more and 10 GHz or less, or 3 kHz or more and 100 kHz or less, or It is more preferably 3 MHz or more and 3 GHz or less, and particularly preferably 5 kHz or more and 100 kHz or less, or 3 MHz or more and 3 GHz or less. Further, the frequency of the first alternating current is preferably 3 kHz or more and 100 kHz or less, and more preferably 5 kHz or more and 100 kHz or less.

  When the electrodes 610 and 710 operate as anodes, the electrode temperature is higher than when the electrodes 610 and 710 operate as cathodes respectively. However, by setting the frequency of the first alternating current to be higher than 1 kHz, the first The fluctuation of the electrode temperature within one cycle of the alternating current can be prevented, the blackening of the discharge lamp 500 is suppressed, and the blackening of the discharge lamp 500 blackened in the second alternating current supply section 42 is suppressed. Can be recovered.

However, if the frequency of the first alternating current is 1 kHz or less, the temperature of the electrodes 610 and 710 varies and the discharge lamp 500 is blackened every cycle of the first alternating current.
In addition, if the frequency of the first alternating current is greater than 10 GHz, the cost is high.
If the frequency of the first alternating current is larger than 100 kHz and smaller than 3 MHz, the discharge becomes unstable due to the acoustic resonance effect depending on other conditions.

The frequency of the second alternating current is 1 kHz or less. The frequency of the second alternating current is preferably 500 Hz or less, more preferably 10 Hz or more and 500 Hz or less, and further preferably 30 Hz or more and 300 Hz or less.
When the frequency of the second alternating current exceeds the upper limit value, the protrusions 618 and 718 are not formed. If the frequency of the second alternating current is smaller than the lower limit value, depending on other conditions, the protrusions 618 and 718 are melted and crushed, and blackening is more likely to occur.

  Further, the period of the first alternating current supply section 41 is set longer than the period of the second alternating current supply section 42. That is, when the period of the first alternating current supply section 41 is A and the period of the second alternating current supply section 42 is B, A / B is set to be larger than 1 and set to 2 or more. Preferably it is. Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably.

A / B is preferably set to be greater than 1 and 50 or less, more preferably 2 or more and 50 or less, and even more preferably 2 or more and 5 or less. Thereby, both suppression of blackening of the discharge lamp 500 and constant electrode distance can be achieved, and in particular, blackening of the discharge lamp 500 can be more reliably suppressed.
The period A is preferably 10 minutes or longer and 3 hours or shorter, and more preferably 10 minutes or longer and 1 hour or shorter. Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably, and the blackening of the discharge lamp 500 blackened in the second alternating current supply section 42 can be recovered.

The period B is preferably 1 minute or more and 60 minutes or less, and more preferably 1 minute or more and 10 minutes or less. Thereby, the inter-electrode distance can be held at a constant distance more reliably.
In the first alternating current supply section 41, the amplitude of the first alternating current is gradually decreased with time. That is, in the first AC current supply section 41, the protrusions 618 and 718 are reduced, the distance between the electrodes is increased, and the voltage between the electrodes (absolute value of the voltage between the electrodes) gradually increases with time. The amplitude of the first alternating current is gradually decreased over time so that the power supplied to 500 becomes constant. Thereby, the light quantity can be made constant.

  Conversely, in the second alternating current supply section 42, the amplitude of the second alternating current is gradually increased over time. That is, in the second AC current supply section 42, the protrusions 618 and 718 are increased, the distance between the electrodes is decreased, and the voltage between the electrodes (absolute value of the voltage between the electrodes) gradually decreases with time. The amplitude of the second alternating current is gradually increased with time so that the power supplied to 500 becomes constant. Thereby, the light quantity can be made constant.

The waveforms of the first alternating current and the first alternating current each have a rectangular shape (rectangular wave). Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably.
Note that the waveforms of the first alternating current and the first alternating current are not limited to rectangular shapes, and may be, for example, wave shapes.
When the period of the first alternating current is b and the period of the section 43 where the polarity of the first alternating current is positive is c, the ratio c / b (duty ratio) between the period b and the period c is 10%. It is preferably 90% or less, more preferably 20% or more and 80% or less, and even more preferably 50%.

Further, when the period of the positive current section 44 of the second alternating current is d and the period of the negative current section 44 is e, the ratio e / d between the period d and the period e is 1/9 or more and 9 or less. Is preferable, it is more preferably 1/4 or more and 4 or less, and even more preferably 1. Accordingly, the protrusions 618 and 718 can be formed on the electrodes 610 and 710 symmetrically to each other.
In addition, when the light amount in the first alternating current supply section 41 and the light amount in the second alternating current supply section 42 are made the same, the magnitude of the first alternating current in the first alternating current supply section 41. And the average value of the magnitude of the second alternating current in the second alternating current supply section 42 are set to the same value.

  In the present embodiment, a voltmeter is used as the detector 35 of the light source device 1. The detector 35 detects the interelectrode voltage of the pair of electrodes 610 and 710 of the discharge lamp 500, and uses the detected interelectrode voltage for driving control of the discharge lamp 500, as will be described later. This interelectrode voltage is a value corresponding to the interelectrode distance. Therefore, the interelectrode distance is obtained indirectly by obtaining the interelectrode voltage. In addition, the distance between electrodes is so long that the voltage between electrodes is large. Moreover, in this embodiment, since the voltage between electrodes is measured with a voltmeter, it is preferable to apply when the frequency of a drive current, ie, the frequency of a 1st alternating current, is less than 1 MHz.

  In the light source device 1, while the discharge lamp 500 is lit, the detector 35 detects the interelectrode voltage of the pair of electrodes 610 and 710, and the detected interelectrode voltage is sent to the control unit 33. . As shown in FIG. 5, the control unit 33 includes a first alternating current supply section 41, a second alternating current supply section 42, and the like according to the detection result of the detector 35, that is, the detected interelectrode voltage. Switch. That is, when the absolute value of the interelectrode voltage reaches the upper limit value of the allowable range, the first AC current supply section 41 is changed to the second AC current supply section 42, and the absolute value of the interelectrode voltage is set to the lower limit value of the allowable range. Then, the second alternating current supply section 42 is changed to the first alternating current supply section 41. Thereby, the distance between electrodes can be limited within a predetermined allowable range.

Further, the upper limit value and the lower limit value of the allowable range of the absolute value of the interelectrode voltage are not particularly limited, and are appropriately set according to various conditions. The difference between the upper limit value and the lower limit value is 15 V or less. It is preferably 1 V or more and 10 V or less, more preferably 1 V or more and 5 V or less. Thereby, the light quantity can be made constant.
Moreover, it is preferable to adjust the upper limit value and the lower limit value of the allowable range of the absolute value of the interelectrode voltage according to the lighting time of the discharge lamp 500, respectively. That is, as the lighting time of the discharge lamp 500 is longer, the protrusions 618 and 718 are less likely to extend. Therefore, as the lighting time of the discharge lamp 500 is longer, the upper limit value and the lower limit value of the allowable range of the absolute value of the interelectrode voltage are increased. Let Thereby, the distance between electrodes can be made more reliable.

Next, a control operation of the discharge lamp driving device 200 of the light source device 1 will be described based on FIG.
First, the drive current is set to the first alternating current supply section 41 that supplies the first alternating current to the pair of electrodes 610 and 710, the first alternating current is supplied to the pair of electrodes 610 and 710, The discharge lamp 500 is turned on (step S101). Accordingly, the protrusions 618 and 718 become smaller, and the voltage between the electrodes gradually increases. As described above, the first alternating current is gradually decreased so that the supplied power becomes constant.

Next, the inter-electrode voltage is detected (step S102), and it is determined whether or not the detected absolute value of the inter-electrode voltage is equal to or larger than a predetermined value (upper limit value) appropriately determined as an upper limit value of the allowable range. (Step S103).
In step S103, when the absolute value of the interelectrode voltage is smaller than the upper limit value (not higher than the upper limit value), the process returns to step S102, and step S102 and subsequent steps are executed again.

  In step S103, when the absolute value of the interelectrode voltage is equal to or greater than the upper limit value (equal to or greater than the upper limit value), the drive current is set to the second AC current and the pair of electrodes 610, 710. Is set in the second AC current supply section 42 to be supplied to the second AC current, and the second AC current is supplied to the pair of electrodes 610 and 710 (step S104). Accordingly, the protrusions 618 and 718 become larger, and the voltage between the electrodes gradually decreases. As described above, the second alternating current is gradually increased so that the supplied power becomes constant.

Next, the inter-electrode voltage is detected (step S105), and it is determined whether or not the detected absolute value of the inter-electrode voltage is equal to or less than a predetermined value (lower limit value) appropriately determined as a lower limit value of the allowable range. (Step S106).
In step S106, when the absolute value of the interelectrode voltage is larger than the lower limit value (not lower than the lower limit value), the process returns to step S105, and step S105 and subsequent steps are executed again.

In step S106, when the absolute value of the interelectrode voltage is equal to or lower than the lower limit value (equal to or lower than the lower limit value), the process returns to step S101, and step S101 and subsequent steps are executed again. As a result, the absolute value of the interelectrode voltage is maintained within the allowable range, and the interelectrode distance is maintained within the allowable range.
As described above, according to the light source device 1, it is possible to suppress the blackening of the discharge lamp 500 and extend the life. Further, the protrusions 618 and 718 are formed on the electrodes 610 and 710, the distance between the electrodes can be maintained at a constant distance, and the discharge lamp 500 can be driven efficiently.

In the off sections 46 and 47, the supply of current to the pair of electrodes 610 and 710 is not stopped, but the amplitude of the second alternating current a is ± 5 to the pair of electrodes 610 and 710, respectively. % Current, that is, current of −5% or more and + 5% or less of the amplitude a may be supplied. The “+” indicates that the polarity of the current is positive, and the “−” indicates that the polarity of the current is negative. In this case, the current value of the current supplied to the pair of electrodes 610 and 710 in the off sections 46 and 47 may be within ± 5% of the amplitude a, but within ± 2.5% of the amplitude a. It is preferable that it is within ± 1% of the amplitude a. As described above, it is further preferable that current is not supplied to the pair of electrodes 610 and 710 in the off sections 46 and 47, respectively.
Further, the off section may be provided only in one of the switching from the positive current section 44 to the negative current section 45 and the switching from the negative current section 45 to the positive current section 44.

Second Embodiment
FIG. 7 is a flowchart showing a control operation in the second embodiment of the light source device of the present invention.
Hereinafter, the second embodiment will be described with a focus on the differences from the first embodiment described above, and the description of the same matters will be omitted.

  In the light source device 1 of the second embodiment, while the discharge lamp 500 is lit, the detector 35 detects the interelectrode voltage of the pair of electrodes 610 and 710 of the discharge lamp 500, and the change per unit time of the interelectrode voltage. An amount is obtained, and the obtained change amount per unit time of the interelectrode voltage is used for driving control of the discharge lamp 500. The amount of change per unit time of the interelectrode voltage is a value corresponding to the amount of change per unit time of the interelectrode distance. Therefore, the amount of change per unit time of the interelectrode distance is indirectly obtained by obtaining the amount of change per unit time of the interelectrode voltage.

  Specifically, the control unit 33 averages the amount of change per unit time of the interelectrode distance in the first alternating current supply section 41 based on the detection result of the detector 35, that is, the detected interelectrode voltage. As an absolute value of the value, the absolute value | V1 | of the average value of the amount of change per unit time of the interelectrode voltage in the first alternating current supply section 41 and the unit of the interelectrode distance in the second alternating current supply section 42 As an absolute value of the average value of the change amount per time, an absolute value | V2 | of the average value of the change amount per unit time of the voltage between the electrodes in the second alternating current supply section 42 is obtained. The control unit 33 and the detector 35 constitute detection means for detecting a change amount per unit time of the interelectrode voltage (interelectrode distance). Further, the control unit 33 constitutes a calculation means for obtaining the amount of change per unit time of the interelectrode voltage (interelectrode distance) based on the detection result of the detector 35.

Then, the control unit 33 compares | V1 | and | V2 |, and if | V1 | becomes larger than | V2 |, the periods t1 and t2 of the off sections 46 and 47 are increased and lengthened, respectively. . The control unit 33 constitutes a determination unit that compares | V1 | and | V2 | to determine whether | V1 | is greater than | V2 |.
Accordingly, the protrusions 618 and 718 can be more reliably grown until the absolute value of the interelectrode voltage reaches the lower limit value of the allowable range.

  Further, the increments (increase periods) of the periods t1 and t2 are not particularly limited, and are appropriately set according to various conditions, but are 1% to 1000% of the initial values of the periods t1 and t2. Or less, more preferably 10% or more and 500% or less. Specifically, the increments of the periods t1 and t2 are each preferably 0.01 μsec or more and 10 μsec or less, and more preferably 0.1 μsec or more and 5 μsec or less.

Note that the increase in the period t1 and the increase in the period t2 may be the same or different.
Also, the detection of | V1 | and | V2 | may be performed periodically while the discharge lamp 500 is lit, or may be performed irregularly.

Next, a control operation of the discharge lamp driving device 200 of the light source device 1 will be described based on FIG.
First, the drive current is set to the first alternating current supply section 41 that supplies the first alternating current to the pair of electrodes 610 and 710, the first alternating current is supplied to the pair of electrodes 610 and 710, The discharge lamp 500 is turned on (step S201). Accordingly, the protrusions 618 and 718 become smaller, and the voltage between the electrodes gradually increases. As described above, the first alternating current is gradually decreased so that the supplied power becomes constant.

Next, the inter-electrode voltage is detected (step S202), and the absolute value | V1 | of the average value of the change amount per unit time of the inter-electrode voltage in the first alternating current supply section 41 is obtained (step S203).
Next, it is determined whether or not the detected absolute value of the inter-electrode voltage is equal to or greater than a predetermined value (upper limit value) determined in advance as an upper limit value of the allowable range (step S204).

In step S204, if the absolute value of the interelectrode voltage is smaller than the upper limit value, the process returns to step S202, and step S202 and subsequent steps are executed again.
In step S204, if the absolute value of the interelectrode voltage is greater than or equal to the upper limit value, the drive current is set to the second AC current supply section 42 that supplies the second AC current to the pair of electrodes 610 and 710. Then, the second alternating current is supplied to the pair of electrodes 610 and 710 (step S205). Accordingly, the protrusions 618 and 718 become larger, and the voltage between the electrodes gradually decreases. As described above, the second alternating current is gradually increased so that the supplied power becomes constant.

Next, the voltage between the electrodes is detected (step S206), and the absolute value | V2 | of the average value of the amount of change per unit time of the voltage between the electrodes in the second alternating current supply section 42 is obtained (step S207).
Next, | V1 | is compared with | V2 |, and it is determined whether | V1 | is greater than | V2 | (step S208).

If | V1 | is equal to or smaller than | V2 | in step S208, the process proceeds to step S210 without changing the periods t1 and t2 of the off sections 46 and 47.
In step S208, if | V1 | is larger than | V2 |, the periods t1 and t2 of the off sections 46 and 47 are increased by one step (step S209), and the process proceeds to step S210.

Next, it is determined whether or not the detected absolute value of the inter-electrode voltage is equal to or less than a predetermined value (lower limit value) determined in advance as a lower limit value of the allowable range (step S210).
If the absolute value of the interelectrode voltage is larger than the lower limit value in step S210, the process returns to step S206, and step S206 and subsequent steps are executed again.
In step S210, if the absolute value of the interelectrode voltage is equal to or lower than the lower limit value, the process returns to step S201, and step S201 and subsequent steps are executed again. As a result, the absolute value of the interelectrode voltage is maintained within the allowable range, and the interelectrode distance is maintained within the allowable range.

According to the light source device 1, the same effect as that of the first embodiment described above can be obtained.
In the light source device 1, the protrusions 618 and 718 can be more reliably grown until the absolute value of the interelectrode voltage reaches the lower limit of the allowable range.
Note that when | V1 | becomes larger than | V2 |, only one of the periods t1 and t2 may be increased.
As mentioned above, although the light source device and the discharge lamp driving method of the present invention have been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is an arbitrary one having the same function. It can be replaced with that of the configuration. In addition, any other component may be added to the present invention.

<Projector>
FIG. 8 is a diagram schematically showing an embodiment of the projector of the present invention.
A projector 300 shown in FIG. 8 includes the light source device 1 described above, an illumination optical system including integrator lenses 302 and 303, a color separation optical system (light guide optical system), and a liquid crystal light corresponding to red (for red). A bulb 84, a liquid crystal light valve 85 corresponding to green (for green), a liquid crystal light valve 86 corresponding to blue (for blue), a dichroic mirror surface 811 reflecting only red light, and reflecting only blue light A dichroic prism (color combining optical system) 81 on which a dichroic mirror surface 812 is formed, and a projection lens (projection optical system) 82.

The color separation optical system includes mirrors 304, 306, and 309, a dichroic mirror 305 that reflects blue light and green light (transmits only red light), a dichroic mirror 307 that reflects only green light, and a dichroic that reflects only blue light. A mirror 308 and condensing lenses 310, 311, 312, 313, and 314 are included.
The liquid crystal light valve 85 includes a liquid crystal panel 16, a first polarizing plate (not shown) disposed on the incident surface side of the liquid crystal panel 16, and a second polarizing plate disposed on the output surface side of the liquid crystal panel 16. (Not shown). The liquid crystal light valves 84 and 86 have the same configuration as the liquid crystal light valve 85. The liquid crystal panels 16 of the liquid crystal light valves 84, 85 and 86 are respectively connected to drive circuits (not shown).

  In the projector 300, the liquid crystal light valves 84, 85, 86 and the drive circuit constitute a main part of a modulation device that modulates the light emitted from the light source device 1 based on image information. The main part of the projection apparatus which projects the light modulated by the modulation apparatus is comprised.

Next, the operation of the projector 300 will be described.
First, white light (white light flux) emitted from the light source device 1 passes through the integrator lenses 302 and 303. The light intensity (luminance distribution) of this white light is made uniform by the integrator lenses 302 and 303.
White light transmitted through the integrator lenses 302 and 303 is reflected to the left side in FIG. 8 by the mirror 304, and blue light (B) and green light (G) of the reflected light are respectively reflected by the dichroic mirror 305 in FIG. The red light (R) is reflected downward and passes through the dichroic mirror 305.

The red light transmitted through the dichroic mirror 305 is reflected downward in FIG. 8 by the mirror 306, and the reflected light is shaped by the condenser lens 310 and enters the liquid crystal light valve 84 for red.
Green light of blue light and green light reflected by the dichroic mirror 305 is reflected to the left in FIG. 8 by the dichroic mirror 307, and the blue light passes through the dichroic mirror 307.
The green light reflected by the dichroic mirror 307 is shaped by the condenser lens 311 and enters the green liquid crystal light valve 85.

Further, the blue light transmitted through the dichroic mirror 307 is reflected to the left side in FIG. 8 by the dichroic mirror 308, and the reflected light is reflected to the upper side in FIG. 8 by the mirror 309. The blue light is shaped by the condenser lenses 312, 313 and 314 and enters the blue liquid crystal light valve 86.
As described above, the white light emitted from the light source device 1 is separated into the three primary colors of red, green, and blue by the color separation optical system, and is guided to the corresponding liquid crystal light valves 84, 85, and 86, respectively, and enters. .

  At this time, each pixel of the liquid crystal panel 16 of the liquid crystal light valve 84 is switching-controlled (on / off) by a drive circuit that operates based on the image signal for red, and the liquid crystal panel 16 of the liquid crystal light valve 85 is controlled. Each pixel is controlled by a drive circuit that operates based on a green image signal, and each pixel of the liquid crystal panel 16 of the liquid crystal light valve 86 is controlled by a drive circuit that operates based on a blue image signal. The switching is controlled.

Thereby, red light, green light, and blue light are modulated for each color by the liquid crystal light valves 84, 85, and 86, respectively, and a red image, a green image, and a blue image are formed.
The red image formed by the liquid crystal light valve 84, that is, the red light from the liquid crystal light valve 84, is incident on the dichroic prism 81 from the incident surface 813, and is reflected by the dichroic mirror surface 811 to the left in FIG. The light passes through the mirror surface 812 and exits from the exit surface 816.

Further, the green image formed by the liquid crystal light valve 85, that is, the green light from the liquid crystal light valve 85, enters the dichroic prism 81 from the incident surface 814, and passes through the dichroic mirror surfaces 811 and 812, respectively. The light exits from the exit surface 816.
Further, the blue image formed by the liquid crystal light valve 86, that is, the blue light from the liquid crystal light valve 86, enters the dichroic prism 81 from the incident surface 815, and is reflected by the dichroic mirror surface 812 to the left in FIG. Then, the light passes through the dichroic mirror surface 811 and exits from the exit surface 816.

Thus, the light of each color from the liquid crystal light valves 84, 85 and 86, that is, the images formed by the liquid crystal light valves 84, 85 and 86 are synthesized by the dichroic prism 81, thereby forming a color image. The This image is projected (enlarged projection) onto the screen 320 installed at a predetermined position by the projection lens 82.
As described above, according to the projector 300, since the light source device 1 described above is included, power consumption can be reduced, and a stable and good image can be displayed.

Next, specific examples of the present invention will be described.
Example 1
As shown in FIG. 1, a light source device having the following configuration was produced.
In this case, in the second alternating current supply section, when switching from the positive current section to the negative current section, an off section (period t1) in which no current is supplied to the pair of electrodes is provided, and the negative current section is changed to the positive current section. When switching, an off section (period t2) in which no current is supplied to the pair of electrodes is provided.

In addition, the absolute value | V1 | of the average value of the change amount per unit time of the interelectrode voltage in the first AC current supply section is the average change amount per unit time of the interelectrode voltage in the second AC current supply section. When the absolute value of the value | V2 | became larger, control was performed to increase the off-periods t1 and t2 by 1 μs.
Discharge lamp body material: Quartz glass Inclusion in the discharge lamp body: Argon, mercury, methyl bromine Atmospheric pressure in the discharge lamp body: 200 atm
Electrode constituent material: Tungsten Electrode distance: 1.1 mm
Rated power: 200W
Frequency of first alternating current (high frequency current): 5 kHz
Duty ratio of first alternating current (c / b): 50%
Waveform of the first alternating current: rectangular shape Frequency of the second alternating current (low frequency current): 135 Hz
Ratio (e / d) of the period d of the positive current section and the period e of the negative current section of the second alternating current: 1
Second AC current waveform: rectangular shape Initial value of off-period period t1: 0.7 μsec Initial value of off-period period t2: 0.7 μsec Drive current: current controlled so that power is 200 W Electrode Lower limit of absolute value of inter-voltage: 68V
Upper limit of absolute value of voltage between electrodes: 78V

(Example 2)
In the second AC current supply section of the drive current, a light source device similar to that in Example 1 was created except that an off section (period t2) for switching from the negative current section to the positive current section was not provided.
(Example 3)
In the second AC current supply section of the drive current, a light source device similar to that in Example 1 was created except that the off section (period t1) for switching from the positive current section to the negative current section was not provided.
(Comparative Example 1)
In the second AC current supply section of the drive current, there are an off section (period t1) when switching from the positive current section to the negative current section and an off section (period t2) when switching from the negative current section to the positive current section. A light source device similar to that in Example 1 was prepared except that the light source device was not provided.

[Evaluation]
Each of the light source devices of Examples 1 to 3 and Comparative Example 1 was used as a light source device of a projector, and the projector was continuously turned on to check the change in illuminance on the screen.
As a result, in Examples 1 to 3, since blackening did not occur from the beginning, devitrification did not occur, and since the electrode was gradually consumed, it was initially until 500 hours after the start of lighting. The inter-electrode distance in the state was maintained.
On the other hand, in Comparative Example 1, since blackening did not occur from the beginning, devitrification did not occur, but the inter-electrode voltage of the pair of electrodes increased as aging progressed. In the first 100 hours after the start of lighting, the initially set distance between the electrodes could not be maintained.

  DESCRIPTION OF SYMBOLS 1 ... Light source device, 31 ... DC current generator, 32 ... Polarity switch, 33 ... Control part, 35 ... Detector, 41 ... 1st alternating current supply area, 42 ... 2nd alternating current supply area, 43 ... Section: 44 ... Positive current section, 45 ... Negative current section, 46, 47 ... Off section, 110 ... Light source unit, 112 ... Main reflector, 114 ... Parallelizing lens, 116 ... Inorganic adhesive, 200 ... Discharge lamp driving device , 500 ... discharge lamp, 510 ... discharge lamp body, 511 ... luminous vessel, 512 ... discharge space, 520 ... sub-reflecting mirror, 522 ... inorganic adhesive, 610, 710 ... electrode, 612, 712 ... core rod, 614, 714 ... Coil part, 616, 716 ... Main part, 618, 718 ... Projection, 620, 720 ... Connection member, 630, 730 ... Electrode terminal, 16 ... Liquid crystal panel, 81 ... Dichroic prism, 811, 812 ... Dyke Ic mirror surface, 813 to 815 ... incident surface, 816 ... exit surface, 82 ... projection lens, 84 to 86 ... liquid crystal light valve, 300 ... projector, 302, 303 ... integrator lens; 307, 308 ... Dichroic mirror, 310-314 ... Condensing lens, 320 ... Screen, S101-S106 ... Step, S201-S210 ... Step

Claims (16)

A discharge lamp having a light emitting container including a cavity portion in which a discharge medium is enclosed, a pair of electrodes whose end portions are arranged to face each other in the cavity portion, and
A driving device for supplying a driving current to the pair of electrodes,
The driving device has a first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes and a period shorter than a period of the first alternating current supply section, and the frequency is 1 kHz. The second alternating current supply section for supplying the following second alternating current to the pair of electrodes is alternately repeated,
In the second alternating current supply section, when the polarity of the second alternating current is switched from a positive current section where the polarity is positive to a negative current section where the polarity is negative, and when the polarity is switched from the negative current section to the positive current section At least one of the pair of electrodes is provided with an off section in which a current within ± 5% of the amplitude a of the second alternating current is supplied to the pair of electrodes, or no current is supplied. apparatus.   2. The light source device according to claim 1, wherein the off section is provided in each of the switching from the positive current section to the negative current section and the switching from the negative current section to the positive current section.   The light source device according to claim 1, wherein no current is supplied to the pair of electrodes in the off period.   4. The light source device according to claim 1, wherein a period of the off section is 0.1 μsec or more and 5 msec or less. Detecting means for detecting a change amount per unit time of the distance between the electrodes of the pair of electrodes;
In the driving device, the absolute value | V1 | of the average value of the amount of change per unit time of the distance between the electrodes of the pair of electrodes in the first alternating current supply section is calculated in the second alternating current supply section. 5. The off-interval period is increased when the absolute value | V2 | of the average value of the amount of change per unit time of the distance between the electrodes of the pair of electrodes becomes larger. The light source device according to any one of the above.   6. A / B is set to 2 or more, where A is a period of the first AC current supply section and B is a period of the second AC current supply section. Light source device.   The light source device according to claim 1, wherein an amplitude of the first alternating current is decreased with time in the first alternating current supply section.   The light source device according to any one of claims 1 to 7, wherein an amplitude of the second alternating current is increased with time in the second alternating current supply section.   The light source device according to claim 1, wherein a waveform of the first alternating current has a rectangular shape.   The light source device according to claim 1, wherein a waveform of the second alternating current is rectangular.   The light source device according to claim 1, wherein blackening of the discharge lamp is suppressed by supplying the first alternating current.   The light source device according to any one of claims 1 to 11, wherein an inter-electrode distance between the pair of electrodes is decreased by supplying the second alternating current.   The average value of the amplitude of the first alternating current in the first alternating current supply section and the average value of the amplitude of the second alternating current in the second alternating current supply section are the same. The light source device according to claim 1.   14. The light source device according to claim 1, wherein an upper limit value and a lower limit value of an inter-electrode voltage of the pair of electrodes are set, and a difference between the upper limit value and the lower limit value is 15 V or less. . A discharge lamp driving method comprising: a light emitting container including a cavity portion in which a discharge medium is sealed; and a pair of electrodes whose end portions are arranged to face each other in the cavity portion,
A first alternating current supply section that supplies a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a second alternating current that is shorter than the first alternating current supply section and has a frequency of 1 kHz or less. The second alternating current supply section for supplying alternating current to the pair of electrodes is alternately repeated, and in the second alternating current supply section, the polarity of the second alternating current is changed from a positive current section. When the polarity is switched to the negative current section and at least one of the switching from the negative current section to the positive current section is within ± 5% of the amplitude a of the second alternating current on the pair of electrodes. To generate a driving current provided with an off period in which current is supplied or current is not supplied,
A method for driving a discharge lamp, wherein the driving current is supplied to the pair of electrodes.   A projector comprising the light source device according to claim 1.

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