JP2013004318A - Light source device, discharge lamp driving method and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device, a discharge lamp driving method and a projector in which a discharge lamp can be restrained from blackening, and widening of the distance between electrodes can be suppressed.SOLUTION: A light source device 1 comprises: a discharge lamp 500 having a light-emitting container including a cavity part 512 in which a discharge medium is sealed, and a pair of electrodes 610 and 710 whose ends are disposed opposite to each other in the cavity part 512; and a discharge lamp driving device 200 which supplies a drive current to the pair of electrodes 610 and 710. The drive current is obtained by performing amplitude modulation of alternating current whose frequency is 1 kHz or more and 10 GHz or less, and the amplitude modulation of the alternating current is performed so that a first section and a second section having the amplitude smaller than that of the first section are alternately repeated. When an average value of the amplitude of the alternating current in the first section is a, and an average value of the amplitude of the alternating current in the second section is b, b/a changes with time in the range of 0% or more and 90% or less.

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. 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, when the discharge lamp is lit, arc discharge is generated between the pair of electrodes, and the electrodes are at a high temperature, so that the electrodes are melted and the space between the electrodes is expanded. For example, in projector applications, 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. The efficiency is lowered, which is not preferable. In addition, the change between the electrodes changes the impedance between the electrodes. Therefore, even if the discharge lamp can be lit efficiently at the beginning of lighting, impedance mismatch occurs over time, and reactive power is generated. There is a problem that the efficiency increases and the efficiency decreases.

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. 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, there is a problem that the discharge lamp main body is blackened, devitrified, etc., and the life of the discharge lamp is reduced.

JP 2007-115534 A

  The objective of this invention is providing the light source device which can suppress blackening of a discharge lamp, and can suppress that the distance between electrodes spreads, the drive method of a discharge lamp, and a projector.

Such an object is achieved by the present invention described below.
A light source device of the present invention includes a light emitting container including a hollow portion in which a discharge medium is sealed, a discharge lamp having a pair of electrodes disposed so that the end portions face each other in the hollow portion, and
A driving device for supplying a driving current to the pair of electrodes,
The driving current is obtained by amplitude-modulating an alternating current having a frequency of 1 kHz or more and 10 GHz or less, and a first section and a second section having a smaller amplitude than the first section are alternately repeated. The AC current is amplitude-modulated as follows,
When the average value of the amplitude of the alternating current in the first section is a and the average value of the amplitude of the alternating current in the second section is b, b / a is in the range of 0% to 90%. It is characterized by changing over time.
Thereby, blackening of the discharge lamp can be suppressed, and the distance between the electrodes can be suppressed from being increased, and the discharge lamp can be driven.

In the light source device of the present invention, it is preferable that the modulation frequency of the amplitude modulation is constant.
Thereby, a protrusion can be more reliably formed on the electrode.
In the light source device of the present invention, it is preferable that B / A is constant, where A is a total period of the first section and the second section and B is a period of the first section.
Thereby, a protrusion can be more reliably formed on the electrode.

In the light source device of the present invention, it is preferable that the amplitude of the alternating current is constant in the first section.
Thereby, a protrusion can be more reliably formed on the electrode.
In the light source device of the present invention, it is preferable that the amplitude of the alternating current is constant in the second section.
Thereby, a protrusion can be more reliably formed on the electrode.

In the light source device of the present invention, the frequency of the alternating current is preferably 1 kHz to 100 kHz, or 3 MHz to 10 GHz.
This can prevent the discharge from becoming unstable due to the acoustic resonance effect.
In the light source device of the present invention, when the discharge lamp is lit by the supply of the driving current, the temperature of the pair of electrodes fluctuates, and a protrusion is formed at the tip of the pair of electrodes. preferable.
Thereby, it is possible to drive the discharge lamp while suppressing an increase in the distance between the electrodes.

A method for driving a discharge lamp according to the present invention is a method for driving a discharge lamp having a light emitting container including a cavity in which a discharge medium is enclosed, and a pair of electrodes whose ends are opposed to each other in the cavity. And
An alternating current having a frequency of 1 kHz to 10 GHz is generated;
The alternating current is amplitude-modulated so that the first interval and the second interval having a smaller amplitude than the first interval are alternately repeated, and an average of the amplitudes of the alternating currents in the first interval When the value is a and the average amplitude of the alternating current in the second interval is b, b / a is changed over time in a range of 0% to 90% to generate a drive current,
The driving current is supplied to the pair of electrodes.
Thereby, blackening of the discharge lamp can be suppressed, and the distance between the electrodes can be suppressed from being increased, and the discharge lamp can be driven.

The projector of the present invention includes a light source device that emits light,
A modulation device that modulates light emitted from the light source device based on image information;
A projection device that projects the light modulated by the modulation device,
The light source device includes a light emitting container including a cavity portion in which a discharge medium is enclosed, a discharge lamp having a pair of electrodes whose end portions are opposed to each other in the cavity portion, and
A driving device for supplying a driving current to the pair of electrodes,
The driving current is obtained by amplitude-modulating an alternating current having a frequency of 1 kHz or more and 10 GHz or less, and a first section and a second section having a smaller amplitude than the first section are alternately repeated. The AC current is amplitude-modulated as follows,
When the average value of the amplitude of the alternating current in the first section is a and the average value of the amplitude of the alternating current in the second section is b, b / a is in the range of 0% to 90%. It is characterized by changing over time.
This suppresses the blackening of the discharge lamp, suppresses the increase in the distance between the electrodes, and can drive the discharge lamp, thereby reducing power consumption and displaying a stable and good image. can do.

It is sectional drawing (block diagram is also included) which shows 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 alternating current and drive current which are produced | generated with the discharge lamp drive device of the light source device shown in FIG. It is a figure which shows the change pattern of the modulation frequency of the drive current produced | generated with the discharge lamp drive device of the light source device shown in FIG. It is a figure which shows the change pattern of the modulation frequency of the drive current produced | generated with the discharge lamp drive device of the light source device shown in FIG. It is a figure which shows the envelope in the structural example of a drive current. It is a figure which shows the envelope in the structural example of a drive current. 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.
<Light source device>
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 alternating current and drive current generated by the discharge lamp driving device of the light source device shown in FIG. 1, and FIGS. 5 and 6 are the discharges of the light source device shown in FIG. It is a figure which shows the change pattern of the modulation frequency of the drive current produced | generated with an electric lamp drive device. In FIG. 2, the sub-reflecting mirror is not shown.

As shown in FIG. 1, the light source device 1 includes a light source unit 110 having a discharge lamp 500 and a discharge lamp driving device (driving device) 200 that drives 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 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 discharge lamp main body 510 and the sub-reflecting mirror 520 are bonded with an inorganic adhesive 522. 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.
A light emitting container including a discharge space (hollow part) 512 hermetically sealed is formed in the center of the discharge lamp main body 510 in which a discharge medium described later is sealed. 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 500 μm 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.

  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 supplies a driving current (driving power) including a high frequency alternating current (alternating current power) to the discharge lamp 500. 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. The sub-reflecting mirror 520 reflects the light emitted in the direction of the one electrode 710 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 will be described.
As shown in FIG. 3, the discharge lamp driving device 200 includes a high-frequency current generator 31 that generates a high-frequency alternating current, an amplitude modulator (amplitude modulation unit) 32, and an amplifier 33. In this device, the alternating current is supplied to the pair of electrodes 610 and 710 of the discharge lamp 500 as a drive current.

In this discharge lamp driving device 200, the alternating current shown in FIG. 4A generated by the high-frequency current generator 31 is obtained from the first section 41 and the first section 41 as shown in FIG. 4B. Amplitude modulation is performed by the amplitude modulator 32 so that the second section 42 having a small drive current amplitude is alternately repeated. Then, the alternating current is amplified by the amplifier 33 to generate and output an alternating current that is a driving current for driving the discharge lamp. 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.

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 protrusions 618 and 718 are formed at the tips of the electrodes 610 and 710, respectively, and the protrusions 618 and 718 can be maintained.
That is, first, in the first section 41 of the drive current, when the temperature of the electrodes 610 and 710 is increased, a part of the tip of the electrodes 610 and 710 is melted, and the melted electrode material is caused by the surface tension. Collects at the tip of the electrodes 610 and 710 On the other hand, in the second section 42, the temperature of the electrodes 610 and 710 is lowered, so that the molten electrode material is solidified. Protrusions 618 and 718 grow by repeating such a state in which the molten electrode material gathers at the tips of the electrodes 610 and 710 and a state in which the molten electrode material is solidified, thereby reducing the distance between the electrodes. Spreading can be suppressed, and a state where the distance between the electrodes is narrow can be maintained. Thereby, the discharge lamp 500 can be driven efficiently.
In addition, since the driving current includes an alternating current having a high frequency, blackening of the discharge lamp 500 can be prevented and a long life can be achieved.

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.
The frequency of the alternating current is 1 kHz to 10 GHz, preferably 1 kHz to 100 kHz, or 3 MHz to 10 GHz, and more preferably 10 kHz to 100 kHz, or 3 MHz to 3 GHz.

When the electrodes 610 and 710 operate as anodes, the electrode temperature is higher than when they operate as cathodes. By setting the frequency of the alternating current to be equal to or higher than the lower limit value, one cycle of the driving current is obtained. The fluctuation of the electrode temperature inside can be prevented.
However, if the frequency of the alternating current is smaller than the lower limit value, the temperature of the electrodes 610 and 710 fluctuates for each cycle of the drive current, which makes it impossible to form and maintain the protrusions 618 and 718. Blackening may occur. Moreover, the thing larger than the said upper limit has the problem that cost becomes high.
If the frequency of the 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 modulation frequency of the amplitude modulation of the drive current is not particularly limited and is appropriately set according to various conditions, but is preferably 10 Hz or more and 1 kHz or less, and more preferably 100 Hz or more and 1 kHz or less. Note that the modulation frequency of the amplitude modulation of the drive current indicates the frequency of the drive current when the waveform of one first section 41 and one second section 42 is defined as one cycle of the drive current. .
If the modulation frequency of the driving current is smaller than the lower limit value, the protrusions 618 and 718 may be excessively extended depending on other conditions. If the modulation frequency of the drive current is higher than the upper limit value, the protrusion 618 may be increased depending on other conditions. , 718 are not formed. Note that the protrusions 618 and 718 extend as the modulation frequency of the drive current is lower.

  The modulation frequency of the drive current is constant, but the modulation frequency of the drive current may be changed with time. By making the modulation frequency of the drive current constant, other conditions can be easily set. In addition, by changing the modulation frequency of the drive current with time, relatively large protrusions 618 and 718 are more reliably formed on the electrodes 610 and 710, and the protrusions 618 and 718 can be maintained. It is possible to suppress the distance between the electrodes from increasing.

In the present embodiment, the amplitude of the alternating current is constant in each of the first section 41 and the second section 42. Thereby, the protrusions 618 and 718 can be more reliably formed on the electrodes 610 and 710.
As shown in FIG. 4, when the average value of the alternating current amplitude in the first section 41 is a and the average value of the alternating current amplitude in the second section 42 is b, the average value a of the amplitude a The ratio b / a between the average value b and the amplitude is not constant (see FIG. 5). That is, b / a is changed over time in the range of 0 to 90%. As a result, relatively large protrusions 618 and 718 are formed on the electrodes 610 and 710, and the protrusions 618 and 718 can be maintained, thereby suppressing an increase in the distance between the electrodes. A configuration example of the drive current in which b / a changes with time will be described in detail later.
Further, b / a is 0 or more and 90% or less.
When b / a is larger than the upper limit, the protrusions 618 and 718 are not formed.
In addition, protrusion 618,718 extends so that b / a is small.

Further, as shown in FIG. 4, when the total period of the first section 41 and the second section 42 is A and the period of the first section 41 is B, the ratio B / A is not particularly limited, and is appropriately set according to various conditions, but is preferably 10% or more and 90% or less, and more preferably 20% or more and 80% or less.
When B / A is smaller than the lower limit value or larger than the upper limit value, the protrusions 618 and 718 are not formed depending on other conditions. As B / A is closer to 50%, the protrusions 618 and 718 extend, and when B / A is 50%, the protrusions 618 and 718 extend most.

  B / A is constant, but B / A may be changed with time. By setting B / A constant, other conditions can be easily set. Further, by changing B / A with time, relatively large protrusions 618 and 718 can be more reliably formed on the electrodes 610 and 710, and the protrusions 618 and 718 can be maintained. An increase in the distance can be suppressed.

Next, a configuration example of the drive current will be described, but the b / a change pattern of the drive current is an example, and the present invention is not limited to this.
As shown in FIG. 5, the drive current, the b / a is the first value alpha ₁ and comprising a first region 51, b / a is the second value alpha ₂ greater than the first value The first region 51 and the second region 52 are alternately repeated. That is, the amplitude modulator 32 amplitude-modulates the alternating current so that the first region 51 and the second region 52 are alternately repeated. At this time, α ₁ and α ₂ are set to values of 0% or more and 90% or less.

When the period of the first region 51 is t ₁ and the period of the second region 52 is t ₂ , t ₁ and t ₂ may be the same or different.
Further, in the illustrated configuration example, b / a changes regularly, but is not limited to this, and may change irregularly.
In the illustrated configuration example, b / a takes two values, but is not limited to this and may take three or more values. Further, the magnitude relationship between the plurality of modulation frequencies is not limited to this, and for example, the value of b / a may be set so that the value of b / a gradually decreases after the value of b / a increases sequentially.

As shown in FIG. 6, as one embodiment thereof, the driving current has a first region 51 where b / a is the first value alpha _1, b / a is the second value alpha ₂ a second region 52, and third region 53 that b / a is the third value alpha _3, and the fourth region 54 b / a is the fourth value alpha _4, b / a is the 5 value alpha ₅ to become the fifth region 55, b / a and the sixth region 56, which is a value alpha ₆ of the sixth, seventh region 57 of b / a is the seventh value alpha ₇ When, the eighth region 58 b / a is the value alpha ₈ eighth, and ninth regions 59 b / a is the value alpha ₉ ninth, the value of b / a is the 10 alpha ₁₀ and a tenth region 60, the eleventh region 61 of b / a is the 11th value alpha _11, the region 62 of the 12 b / a is the twelfth value alpha _12, the b / a There a region 63 of the 13 becomes a value alpha ₁₃ of the 13, b / a is 14 A fourteenth region 64 becomes a value alpha _14, and the 15 regions 65 of b / a is the value alpha ₁₅ of the 15, and a sixteenth area 66 b / a is the value alpha ₁₆ of the 16 Have.
In this case, from the first value alpha ₁ to the ninth value alpha _9, becomes sequentially larger, the value alpha ₉ ninth up, from the ninth value alpha ₉ until the 16 value alpha _16, It becomes small sequentially. The value alpha ₁₆ of the 16 is greater than the first value alpha _1.
Then, drive current, after the first 16 values alpha _16, again, the first value alpha _1, and the subsequent first value alpha ₁ ~ 16 value alpha ₁₆ thereof, the first value alpha ₁ ~ No. 16 values α ₁₆ ,... Are repeated.

Further, the second value α ₂ and the sixteenth value α ₁₆ , the third value α ₃ and the fifteenth value α ₁₅ , the fourth value α ₄ and the fourteenth value α _{14, and} the fifth value α ₅ And a thirteenth value α ₁₃ , a sixth value α ₆ and a twelfth value α ₁₂ , a seventh value α ₇ and an eleventh value α ₁₁ , an eighth value α ₈ and a tenth value α ₁₀ Are the same as each other. The second value α ₂ and the sixteenth value α ₁₆ , the third value α ₃ and the fifteenth value α ₁₅ , the fourth value α ₄ and the fourteenth value α _{14, and} the fifth value α _5. And a thirteenth value α ₁₃ , a sixth value α ₆ and a twelfth value α ₁₂ , a seventh value α ₇ and an eleventh value α ₁₁ , an eighth value α ₈ and a tenth value α ₁₀ Needless to say, they may be different from each other.

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. In addition, the protrusions 618 and 718 are formed on the electrodes 610 and 710, so that the distance between the electrodes can be prevented from being widened, and the discharge lamp 500 can be driven efficiently.
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.

  In the above embodiment, b / a changes with time, and the modulation frequency and B / A of the drive current are constant. However, the present invention is not limited to this, and the modulation frequency of the drive current and B / A Either or both of and may change over time. That is, the modulation frequency of b / a and drive current may change over time, and b / a and B / A may change over time, and b / a and drive current modulation The frequency and B / A may change over time.

  Moreover, in the said embodiment, although the amplitude of alternating current is constant in each of the 1st area 41 and the 2nd area 42, in this invention, either of the 1st area 41 and the 2nd area 42 is used. On the other hand, the amplitude of the alternating current may change over time. In both the first section 41 and the second section 42, the amplitude of the alternating current may change over time.

First, a configuration example of the drive current in which the amplitude of the alternating current is constant in the second section 42 and the amplitude of the alternating current changes over time in the first section 41 will be described.
FIG. 7 is a diagram showing an envelope in the configuration example of the drive current.
In the configuration example illustrated in FIG. 7A, the envelope when the drive current is a positive value among the envelopes of the drive current (hereinafter simply referred to as “envelope”) is as follows: It rises over time (the amplitude of the alternating current gradually increases). That is, the envelope is a straight line with a positive inclination.

In the configuration example shown in FIG. 7B, the envelope decreases with time in the first section 41 (the amplitude of the alternating current gradually decreases). That is, the envelope has a linear shape with a negative slope.
In the configuration example shown in FIG. 7C, the envelope has a curved shape that is curved so as to protrude upward in the first section 41.
In the configuration example illustrated in FIG. 7D, the envelope curve has a curved shape that is curved to protrude downward in the first section 41.

In the configuration example shown in FIG. 7E, the envelope rises stepwise over time in the first section 41.
In the configuration example illustrated in FIG. 7F, the envelope is gradually lowered in the first section 41 over time.
In FIG. 7A to FIG. 7F, the envelope when the drive current is a negative value is the envelope when the drive current is a positive value, and the line where the current value is 0 is the axis of symmetry. As shown in FIG.

Next, a configuration example of a drive current in which the amplitude of the alternating current is constant in the first section 41 and the amplitude of the alternating current changes over time in the second section 42 will be described.
FIG. 8 is a diagram illustrating an envelope in the configuration example of the drive current.
In the configuration example shown in FIG. 8A, the envelope increases with time in the second section 42 (the amplitude of the alternating current gradually increases). That is, the envelope is a straight line with a positive inclination.
In the configuration example shown in FIG. 8B, the envelope decreases with time in the second section 42 (the amplitude of the alternating current gradually decreases). That is, the envelope has a linear shape with a negative slope.

In the configuration example shown in FIG. 8C, the envelope has a curved shape that is curved so as to protrude upward in the second section 42.
In the configuration example shown in FIG. 8D, the envelope curve has a curved shape that is curved to be convex downward in the second section 42.
In the configuration example shown in FIG. 8E, the envelope rises stepwise over time in the second section.
In the configuration example illustrated in FIG. 8F, the envelope decreases stepwise over time in the second section 42.

In FIG. 8A to FIG. 8F, the envelope when the drive current is a negative value is an envelope when the drive current is a positive value. It has a line-symmetric shape folded as a symmetry axis.
Further, although not shown in the drawing, the configuration example of the drive current in which the amplitude of the alternating current changes with time in both the first section 41 and the second section 42 is the first section shown in FIG. The envelope curve in the section 41 and the envelope curve in the second section 42 shown in FIG. 8 can be arbitrarily combined.

<Projector>
FIG. 9 is a diagram schematically showing an embodiment of the projector of the present invention.
A projector 300 shown in FIG. 9 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) bonded to the incident surface side of the liquid crystal panel 16, and a second polarizing plate bonded to 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.
The white light transmitted through the integrator lenses 302 and 303 is reflected to the left in FIG. 9 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. 9 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 side in FIG. 9 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. 9 by the dichroic mirror 308, and the reflected light is reflected to the upper side in FIG. 9 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 by the liquid crystal light valves 84, 85, and 86, respectively, and a red image, a green image, and a blue image are formed, respectively.

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 is incident on the dichroic prism 81 from the incident surface 815, and is reflected to the left side in FIG. 9 by the dichroic mirror surface 812. 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. 6, the drive current b / a changes from the first value to the sixteenth value, returns to the first value again, changes from the first value to the sixteenth value again, and repeats this driving. The light source device shown in FIG. 1 having the following configuration for generating current was produced. In addition, the period of each said area | region was 1 second, respectively.

Material of discharge lamp body: Quartz glass Inclusion in discharge lamp body: Argon, mercury, bromine Pressure at lighting in discharge lamp body: 200 atm
Electrode constituent material: Tungsten Electrode distance: 1.1 mm
Rated power: 200W
AC current frequency: 13.56 MHz
Modulation frequency of amplitude modulation: 300Hz
First value of b / a: 10%
b / a second value: 20%
b / a third value: 30%
4th value of b / a: 40%
b / a fifth value: 50%
6th value of b / a: 60%
7th value of b / a: 70%
8th value of b / a: 80%
9th value of b / a: 90%
10th value of b / a: 80%
11th value of b / a: 70%
12th value of b / a: 60%
13th value of b / a: 50%
14th value of b / a: 40%
15th value of b / a: 30%
16th value of b / a: 20%
B / A: 50%

(Example 2)
The drive current b / a changes from the first value to the sixth value, returns to the first value again, changes from the first value to the sixth value again, generates a drive current that repeats this, and otherwise A light source device similar to that in Example 1 was prepared. The first to sixth values are as follows.
First value of b / a: 80%
b / a second value: 85%
b / a third value: 90%
b / a fourth value: 95%
b / a fifth value: 90%
The sixth value of b / a: 85%

(Comparative Example 1)
A light source device similar to that of Example 1 was prepared except that b / a of the drive current was changed to 50% (a constant value).
(Comparative Example 2)
A light source device similar to that of Example 1 was prepared except that b / a of the drive current was changed to 90% (a constant value).

[Evaluation]
Each evaluation was performed as follows with respect to Examples 1-2 and Comparative Examples 1-2. The results are as shown in Table 1 below.
(Projection)
In each example and comparative example, lighting was performed for 500 hours, and the tip portions of a pair of electrodes in the discharge lamp were observed to evaluate the protrusion state.
The evaluation criteria for protrusions in Table 1 are as follows: ◎ indicates that the initial protrusion shape is well maintained, ○ indicates that there are relatively good protrusions that are different from the initial state, and △ indicates a state that appears to be a protrusion. , X indicates a state in which there is no protrusion shape and the discharge position is not stable.

(Blackening resistance)
In each example and comparative example, lighting was performed for 500 hours, and the inner wall portion constituting the cavity portion of the discharge lamp was observed to evaluate the blackened state.
The evaluation criteria for blackening resistance in Table 1 indicate that ◎ indicates a state where no blackening was observed, and × indicates a state where blackening was observed.

As apparent from Table 1 above, in Examples 1 and 2, protrusions were reliably formed at the tips of the electrodes, and blackening did not occur and good results were obtained.
On the other hand, in Comparative Example 1, although the protrusions were extended, they were slightly extended due to excessive extension. In Comparative Example 2, although the protrusion was formed, it was a thin and unstable protrusion shape. In both Comparative Examples 1 and 2, blackening did not occur.

  DESCRIPTION OF SYMBOLS 1 ... Light source device 31 ... High frequency current generator 32 ... Amplitude modulator 33 ... Amplifier 41 ... 1st area 42 ... 2nd area 51 ... 1st area | region 52 ... 2nd area | region 53 ... 3rd area | region 54 ... Fourth region 55 ... Fifth region 56 ... Sixth region 57 ... Seventh region 58 ... Eighth region 59 ... Ninth region 60 ... Tenth region 61 ... Eleventh region 62 ... Twelfth Area 63 ... 13th area 64 ... 14th area 65 ... 15th area 66 ... 16th area 110 ... Light source unit 112 ... Main reflector 114 ... Parallelizing lens 116 ... Inorganic adhesive 200 ... Discharge lamp drive Device 500 ... Discharge lamp 510 ... Discharge lamp body 512 ... Discharge space 520 ... Sub-reflecting mirror 522 ... Inorganic adhesive 610,710 ... Electrodes 612,712 ... Core rods 614,714 ... Coil portions 616,716 ... Body part 618, 718 ... Protrusion 620, 720 ... Connection member 630, 730 ... Electrode terminal 16 ... Liquid crystal panel 81 ... Dichroic prism 811, 812 ... Dichroic mirror surface 813-815 ... Incident surface 816 ... Output surface 82 ... Projection lens 84 -86 ... Liquid crystal light valve 300 ... Projector 302, 303 ... Integrator lens 304, 306, 309 ... Mirror 305, 307, 308 ... Dichroic mirror 310-314 ... Condensing lens 320 ... Screen

Claims (9)

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 current is obtained by amplitude-modulating an alternating current having a frequency of 1 kHz or more and 10 GHz or less, and a first section and a second section having a smaller amplitude than the first section are alternately repeated. The AC current is amplitude-modulated as follows,
When the average value of the amplitude of the alternating current in the first section is a and the average value of the amplitude of the alternating current in the second section is b, b / a is in the range of 0% to 90%. A light source device that changes over time.   The light source device according to claim 1, wherein a modulation frequency of the amplitude modulation is constant.   3. The light source device according to claim 1, wherein B / A is constant when a total period of the first section and the second section is A and a period of the first section is B. 4.   4. The light source device according to claim 1, wherein an amplitude of the alternating current is constant in the first section. 5.   5. The light source device according to claim 1, wherein an amplitude of the alternating current is constant in the second section.   The light source device according to any one of claims 1 to 5, wherein the frequency of the alternating current is 1 kHz to 100 kHz, or 3 MHz to 10 GHz.   The temperature of the pair of electrodes fluctuates when the discharge lamp is lit by the supply of the drive current, and a protrusion is formed at the tip portion of the pair of electrodes. The light source device described. 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,
An alternating current having a frequency of 1 kHz to 10 GHz is generated;
The alternating current is amplitude-modulated so that the first interval and the second interval having a smaller amplitude than the first interval are alternately repeated, and an average of the amplitudes of the alternating currents in the first interval When the value is a and the average amplitude of the alternating current in the second interval is b, b / a is changed over time in a range of 0% to 90% to generate a drive current,
A method for driving a discharge lamp, wherein the driving current is supplied to the pair of electrodes. A light source device that emits light;
A modulation device that modulates light emitted from the light source device based on image information;
A projection device that projects the light modulated by the modulation device,
The light source device includes a light emitting container including a cavity portion in which a discharge medium is enclosed, a discharge lamp having a pair of electrodes whose end portions are opposed to each other in the cavity portion, and
A driving device for supplying a driving current to the pair of electrodes,
The driving current is obtained by amplitude-modulating an alternating current having a frequency of 1 kHz or more and 10 GHz or less, and a first section and a second section having a smaller amplitude than the first section are alternately repeated. The AC current is amplitude-modulated as follows,
When the average value of the amplitude of the alternating current in the first section is a and the average value of the amplitude of the alternating current in the second section is b, b / a is in the range of 0% to 90%. A projector that changes over time.

Images