JP2007280734A - High pressure discharge lamp lighting device, high pressure discharge lamp device, projection-type image display device, and high pressure discharge lamp lighting method - Google Patents

Abstract

The present invention provides a high pressure discharge lamp lighting device capable of improving life characteristics determined by a decrease in luminance and maintaining stability against color reproduction over a life period and subtle changes in brightness.
An AC current is supplied to a high-pressure mercury lamp having an arc tube in which a pair of electrodes having a halogen substance and xenon enclosed therein and a protrusion formed at the tip are disposed. A high-pressure discharge lamp lighting device comprising: a lighting circuit that is lit; and a frequency control unit that changes the frequency of the alternating current without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. The control means changes the frequency of the alternating current for each cycle between 340 Hz and 85 Hz without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp.
[Selection] Figure 4

Description

  The present invention relates to a lighting device for a high-pressure discharge lamp, a high-pressure discharge lamp device, a projection-type image display device, and a high-pressure discharge lamp lighting method, and more particularly to a high-pressure discharge lamp lighting device that turns on the high-pressure discharge lamp by passing an alternating current.

Among the high-pressure discharge lamps, the high-pressure mercury lamp is used as a light source for a projection-type image display device such as a liquid crystal projector, and has attracted attention in recent years.
In general, a high-pressure mercury lamp has a pair of electrodes opposed to each other in an arc tube in which a halogen substance, a rare gas, and mercury are sealed. In the high pressure discharge lamp lighting device, a predetermined high voltage pulse voltage is applied to the high pressure discharge lamp to break the insulation between the electrodes, and then an alternating current having a predetermined fixed period is supplied to light the lamp.

As the rare gas, argon gas alone is selected as the starting assisting gas.
The lamp life of such a high-pressure mercury lamp is about 2000 to 3000 hours.
JP-A-4-303592

Conventionally, liquid crystal projectors have been mainly used in school classrooms and conference rooms, but in recent years, they are becoming popular.
The liquid crystal projector uses light generated by causing discharge between short electrodes, that is, a point light source, as the light source. For this reason, the stability of the image depends on the stability of the discharge. For this reason, in order to ensure the discharge stability of the discharge lamp, the following lamp configuration and lighting method have been conventionally used.

  In general, high-pressure mercury lamps for liquid crystal projectors currently used contain a halogen substance in addition to mercury as an enclosure. This is to prevent the blackening of the lamp that occurs when tungsten, which is the material of the electrode, evaporates during lighting by using the halogen cycle action of the enclosed halogen substance. This halogen cycle action is very effective in preventing the blackening of the lamp, but at the same time, tungsten transferred to the tip of the electrode is deposited by this action and forms protrusions on the electrode. JP-A-2001-312997 and JP-A-2003-338394 disclose that the growth of this protrusion can be controlled by changing the frequency of the alternating current supplied. In this method, by forming appropriate protrusions, the distance between the electrodes is shortened to make a point light source, so that the light collection efficiency is improved and high luminance is achieved while the luminance is stabilized.

In recent years, the range of use of liquid crystal projectors has come to be used as displays for home theaters and the like that can realize television screens and large screens. For such usage, it is desired to realize a brighter screen, that is, to achieve higher luminance.
Therefore, in order to achieve higher brightness, the distance between the electrodes can be shortened by forming the projections of the electrodes as described above, but in addition to this, the pair of electrodes are simply brought closer to each other to shorten the distance between the electrodes. Is considered effective. However, in that case, the temperature at the tip of the electrode rises excessively, increasing the intensity of tungsten scattering, which is the material of the electrode, and the method described above cannot sufficiently control the growth of protrusions. all right. That is, it has been found that it is difficult to shorten the distance between the electrodes by forming the protrusions of the electrodes.

In addition to these problems, there are the following problems.
In other words, projectors mainly used in school classrooms and conference rooms have many still images, and their usage time is at most several hours a day. On the other hand, when it is used as a television display or a home theater, a moving image display is the center and it is continuously used. For this reason, it is premised on long-time use that cannot be compared with conventional use. Furthermore, television images and images displayed in home theaters are more demanding than color images and subtle changes in brightness compared to computer images. For this reason, the lamp is required to be stable for a long time. As a result, the lifespan of liquid crystal projectors that have been mainly used in classrooms and conference rooms in conventional schools, from 2000 hours to 3000 hours, is insufficient, and a life time several times that of conventional lamps is required. Moreover, extremely stable color reproduction and brightness have been demanded during this long lifetime.

  However, when these conventional lighting methods are used as a display such as a home theater capable of realizing a television screen and a large screen, the above-mentioned long life (for example, 6000 hours) and stable color reproduction and brightness cannot be obtained. As a result of analyzing the cause, the following was clarified. At the electrode tip of the lamp, the growth of the protrusions is noticeable in the early stage of driving. However, in the subsequent 2000 to 3000 hours, the decrease progresses more slowly than the growth of the protrusions, and the electrode interval gradually increases. For this reason, the discharge area is enlarged, and the luminance in the optical device is lowered. In the conventional lamp lighting method, the discharge voltage is detected and control is performed by changing the frequency of the supplied AC current. In this process, the change in the discharge voltage is gradual, and this control method works effectively. do not do. In addition, since the electrical characteristics of the lamp gradually change with the lapse of the driving time, the optimum conditions for controlling the growth and reduction of the protrusions also change. For these reasons, it has been difficult to maintain the electrode shape at the start of lamp use sufficiently in the control method in which control is performed under the same drive frequency conditions in the time period from the initial driving of the lamp to 2000 hours or 3000 hours. .

  Furthermore, there is stability against color reproduction of the displayed image and subtle changes in brightness. As described above, a display such as a home theater capable of realizing a television screen and a large screen requires stability for a long time. As a result of analysis on this problem, it was found that maintaining the shape of the electrode tip is necessary to maintain stability. The light emission center of the light source is located between the electrodes of the lamp. The brightness and color reproduction of the projector depends on the size of the light emission center, and the position is also important in relation to the optical axis of the optical system. As a result, if the shape of the tip of the electrode is maintained, stability against color reproduction of the image and subtle changes in brightness can be maintained.

  The present invention is a high-pressure discharge lamp that can improve the lifetime characteristics determined by a decrease in luminance while maintaining higher stability and maintain stability against color reproduction and subtle changes in brightness over the lifetime. An object is to provide a lighting device, a high-pressure discharge lamp device, a projection-type image display device, and a high-pressure discharge lamp lighting method.

  In order to achieve the above object, a high pressure discharge lamp lighting device according to the present invention is a light emitting device in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip are disposed. A lighting circuit for supplying an alternating current to a high-pressure mercury lamp having a tube and lighting it, and a frequency control for changing the frequency of the alternating current without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. Means.

  Here, the “protrusion” refers to a high-pressure discharge lamp that is formed during the manufacturing process, particularly during the aging of the manufacturing process, and at the beginning of lighting of the finished product (within 100 hours of lighting elapsed time). “Operation data that changes with lighting elapsed time” refers to the voltage value, current value, brightness of the optical device, the distance between the electrodes (arc length), and the temperature of the arc tube (especially light emission that becomes high during lighting). It is measurable operation data that changes as the lighting time of the high-pressure discharge lamp elapses, such as the temperature at the top of the tube.

Further, the frequency control means changes the frequency regularly or irregularly for a certain period of time without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. This is characterized in that the control is continuously repeated as a cycle, or the control is continued intermittently.
Further, the frequency control means alternately repeats a change period in which the frequency is continuously changed without depending on operation data that changes with a lighting elapsed time of the high-pressure mercury lamp, and a fixed period in which the frequency is fixed. Control is performed.

Further, the frequency control means performs control to intermittently switch the frequency to at least two different values.
Furthermore, the frequency control means performs control to constantly change the frequency regularly or irregularly without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp.

  The high pressure discharge lamp lighting device according to the present invention includes a high pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A lighting circuit for supplying an alternating current to the light source, and changing the frequency of the alternating current regularly or irregularly, and repeating this continuously as one cycle, or And high-pressure mercury lamp frequency control means for performing control to continue this intermittently.

  The high pressure discharge lamp lighting device according to the present invention includes a high pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A control circuit that alternately turns on a lighting circuit that supplies an alternating current to the lamp for lighting, a change period in which the frequency of the alternating current is continuously changed according to a predetermined rule, and a fixed period in which the frequency is fixed And a frequency control means for performing the above.

  The high pressure discharge lamp lighting device according to the present invention includes a high pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A lighting circuit for supplying an alternating current to light and a frequency control means for constantly changing the frequency of the alternating current according to a predetermined rule.

The frequency control means continuously changes the frequency during the predetermined period.
The frequency control means may change the frequency by switching the frequency intermittently to at least two or more values during the predetermined period.
Further, the fixed period includes a change period in which the frequency continuously changes and a fixed period in which the frequency is fixed.

Further, the frequency control means changes the frequency between a predetermined maximum frequency and a minimum frequency, and the minimum frequency is 70 Hz or more.
The arc tube is further filled with krypton 85.
The high-pressure discharge lamp device according to the present invention includes a high-pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip are disposed. The high-pressure discharge lamp lighting device for lighting the high-pressure mercury lamp is provided.

In addition, a projection type image display device according to the present invention includes the high-pressure discharge lamp device.
A lighting method for a high-pressure discharge lamp according to the present invention is a high-pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A method for lighting a high-pressure discharge lamp that is supplied with an alternating current to be lit, wherein the frequency of the alternating current is changed without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. And

Further, the frequency is changed regularly or irregularly for a certain period without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury lamp, and this constant period is defined as one cycle. It repeats automatically, or it is characterized by continuing this intermittently.
The frequency is characterized by alternately repeating a change period in which the frequency changes continuously without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp, and a fixed period in which the frequency is fixed. To do.

Furthermore, the frequency is intermittently switched to at least two different values.
In addition, the frequency is always changed regularly or irregularly without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp.
The lighting method of the high-pressure discharge lamp according to the present invention includes a high-pressure mercury having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A method for lighting a high-pressure discharge lamp in which an alternating current is supplied to a lamp for lighting, wherein the frequency of the alternating current is changed regularly or irregularly for a certain period, and the certain period is one cycle. This is characterized by repeating this continuously or intermittently.

  The lighting method of the high-pressure discharge lamp according to the present invention includes a high-pressure mercury having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A method for lighting a high-pressure discharge lamp that supplies an alternating current to a lamp to light the lamp, wherein the alternating current frequency is continuously changed according to a predetermined rule, and a fixed period in which the frequency is fixed. Is alternately repeated.

  The lighting method of the high-pressure discharge lamp according to the present invention includes a high-pressure mercury having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed. A method of lighting a high-pressure discharge lamp that supplies an alternating current to the lamp to light it, wherein the frequency of the alternating current is constantly changed according to a predetermined rule.

  The high pressure discharge lamp lighting method according to the present invention is characterized in that a krypton 85 is further sealed in the arc tube.

According to the present invention, a high pressure discharge lamp capable of improving the lifetime characteristics determined by the decrease in luminance while maintaining high stability and maintaining stability against color reproduction and subtle changes in brightness over the lifetime. It is possible to provide a lighting device, a high-pressure discharge lamp device, a projection-type image display device, and a high-pressure discharge lamp lighting method.
In addition, a change in luminance caused by a change in the shape of the protrusion at the tip of the electrode during steady lighting is suppressed, and a lifetime that cannot be achieved with a conventional lamp can be realized. Accordingly, the lifetime is limited by other factors such as a decrease in light transmittance due to white turbidity of the lamp outer tube or a decrease in light transmittance due to deformation of the lamp outer tube.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1. Configuration of High-Pressure Mercury Lamp The configuration of a high-pressure mercury lamp as an example of a high-pressure discharge lamp will be described.
FIG. 1 is a diagram showing a schematic configuration of a high-pressure mercury lamp 100 (hereinafter simply referred to as “lamp”) having a rated power of 130 W.

As shown in the figure, the arc tube 101 is made of quartz glass as a material for the envelope, and includes a light emitting part 101a and sealing parts 101b and 101c provided at both ends of the light emitting part 101a. Yes.
The light-emitting portion 101a has a substantially spheroid shape, and inside the discharge space (light-emitting space) 108, mercury 109 as a light-emitting substance, a rare gas composed of at least xenon (Xe), and iodine (I ), Halogen substances such as bromine (Br) are enclosed.

  In addition to xenon as a rare gas, it is preferable to enclose krypton 85 (Kr) as described later. Of course, argon may be enclosed here. However, as described later, when xenon is encapsulated, the breakdown voltage tends to increase. In this case, it is considered difficult for argon alone to function as a starting aid gas.

A pair of tungsten (W) electrodes 102 and 103 are disposed substantially opposite to each other inside the light emitting unit 101a.
The enclosed amount of mercury 109 is set in the range of 150 to 650 mg / cm ³ per inner volume of the arc tube 101, and the enclosure pressure during rare gas lamp cooling is set in the range of 0.1 MPa to 1 MPa.

The halogen substance has a function of performing a so-called halogen cycle action in which tungsten evaporated from the electrodes 102 and 103 due to a high temperature during lighting is returned to the electrodes 102 and 103. In order to make the above action function effectively, the bromine encapsulation amount is preferably set in the range of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁴ mol / cm ³ , more preferably 1 × 10 ^−9. mol / cm ³ to 1 × 10 ⁻⁵ mol / cm ³ .

The distance between the tip portions of the electrodes 102 and 103, that is, the interelectrode distance De is set in the range of 0.3 to 2.0 mm. In addition, in the electrodes 102 and 103 of the present embodiment, when the product is completed, a certain amount of protrusions 124 and 134 are formed at the tip portions thereof, so the interelectrode distance De is the distance between the tips of the protrusions 124 and 134. Indicates the interval.
The electrodes 102 and 103 (102a and 103a) are electrically connected to the external molybdenum lead wires 106 and 107 via the molybdenum foils 104 and 105. The external molybdenum lead wires 106 and 107 are connected to the sealing portion 101b. , 101c is led out of the arc tube 101 from the end face.
2. Configuration of Lamp Unit FIG. 2 is a partially cutaway perspective view showing the configuration of the lamp unit (high pressure mercury lamp apparatus) 200.

The lamp unit 200 includes a lamp 100, a lighting device (not shown) for lighting the lamp 100, and a concave reflecting mirror 203 as a reflector (reflecting material) that reflects light emitted from the lamp 100.
A base 201 is attached to one end of the arc tube 101 (see FIG. 1), and the lamp 100 is attached to the concave reflecting mirror 203 via a spacer 202. This attachment is adjusted so that the central axis in the longitudinal direction of the arc tube 101 and the optical axis of the concave reflecting mirror are substantially parallel, and the position of the discharge arc of the lamp 100 is substantially coincident with the focal position of the concave reflecting mirror 203. It is done.

Electric power is supplied to the lead wire 107 (see FIG. 1) on the base 201 side of the lamp 100 via a terminal 204. Electric power is supplied to the other lead wire 106 through a lead wire 205 that passes through a through-hole 206 formed in the concave reflecting mirror 203 and is drawn to the outside.
3. Configuration of Lighting Device FIG. 3 is a block diagram showing a configuration of a lighting device 300 that lights the lamp 100.

As shown in the figure, the lighting device 300 includes a DC power source 302, a DC / DC converter 304, a DC / AC inverter 306, a high voltage generator 308, a control unit 310, a current detector 312, a voltage detector 314, and a programmable oscillator 316. Composed.
The DC power supply 302 includes, for example, a rectifier circuit, and generates a DC voltage from household AC 100V.

The DC / DC converter 304 supplies a direct current having a predetermined magnitude to the DC / AC inverter 306.
The DC / AC inverter 306 generates a rectangular wave alternating current having a predetermined frequency based on the control signal sent from the control unit 310 and sends it to the high voltage generator 308.
The high voltage generator 308 includes, for example, a transformer, generates a high voltage, and applies it to the lamp 100.

The control unit 310 comprehensively controls the DC / DC converter 304, the DC / AC inverter 306, and the like.
The current detector 312 detects the current of the lamp 100, and the voltage detector 314 detects the voltage of the lamp 100.
The programmable oscillator 316 generates a rectangular wave alternating current having a predetermined frequency based on a predetermined program. Control unit 310 refers to this waveform and sends a control signal to DC / AC inverter 306.

By changing the set value of the program, it is possible to change the frequency of the rectangular alternating current in a desired pattern. That is, in the present embodiment, the configuration including the control unit 310 and the programmable oscillator 316 corresponds to a frequency control unit that changes the frequency of the alternating current.
When a lighting switch (not shown) of the lamp 100 is turned on, the lighting device 300 applies a high-pressure pulse to the lamp 100. When the dielectric breakdown occurs between the electrodes of the lamp 100 and an arc discharge current starts flowing between the electrodes, the current detector 312 sends a detection signal to the control unit 310, and the lighting determination circuit in the control unit 310 “lights start”. Judging.

  After “lighting start”, control unit 310 performs constant current control until the voltage increases and reaches the rated power. And after a voltage reaches | attains a predetermined value, it transfers to constant power control. That is, the control unit 310 compares the product of the current value detected by the current detector 312 and the voltage value detected by the voltage detector 314 with the power reference value stored in the internal memory of the control unit 310. The output current of the DC / DC converter 304 is controlled so as to be constant power.

Note that a switch for communicating with a control unit 402 (see FIG. 8) provided outside the lighting device 300 is connected to the control unit 310.
4). Background to the Invention of the Present Invention Since xenon has a higher boiling point than argon, which is the same noble gas, it can be easily sealed in a liquefied state, and the sealing pressure can be set high.

Therefore, the present inventors have found that the voltage value (lamp voltage) at the time of stable lighting can be considerably increased when the xenon in the arc tube 101 is increased to a high sealing pressure. As an example, when xenon is sealed at several atmospheres (a value that could not be achieved when argon was used), the voltage value during lighting could be increased by about 10% or more compared to argon. It was.
Since the lamp 100 is lit by constant power control, the current value (lamp current) can be decreased by increasing the voltage value during stable lighting in this way. If the current value decreases, the temperature of the electrodes 102 and 103 at the time of lighting also decreases. Therefore, even if the pair of electrodes 102 and 103 are simply brought closer to each other and the distance between the electrodes is further shortened, tungsten, which is the material of the electrodes 102 and 103. It can be considered that the scattering of this can be suppressed as compared with the conventional case where argon alone is enclosed.

However, it has been found that the growth of the protrusions formed at the tips of the electrodes 102 and 103 cannot be sufficiently controlled only by applying the conventional method for controlling the protrusion growth. That is, even when the pair of electrodes 102 and 103 are brought close to each other and the distance between the electrodes can be shortened, a problem that the shortening of the distance between the electrodes due to the formation of the protrusions of the electrodes 102 and 103 becomes difficult appears. I understood. The details of the cause are unknown, but this is because, as described above, the high enclosure pressure of xenon reduces the temperature of the electrodes 102 and 103 only by reducing the temperature on average. As the distance between the electrodes is further shortened, the temperature of the local portion, particularly the tip portions of the electrodes 102 and 103, increases considerably excessively, and the intensity of scattering of tungsten, which is the material of the electrodes 102 and 103, increases. It is thought that.
5). Therefore, the present inventors perform the above-mentioned problem by performing specific control on the frequency of the alternating current when the high-pressure mercury lamp is lit in the high-pressure mercury lamp enclosing xenon. It was found that can be solved. The details will be described below.

FIG. 4 shows an example of the rectangular wave alternating current generated by the lamp lighting device according to the present embodiment, the upper graph shows the temporal change of the rectangular wave alternating current, and the lower graph is the upper graph. It corresponds, and shows the temporal change of the frequency of the rectangular wave alternating current.
In the present embodiment, during the steady lighting of the lamp, the frequency of the rectangular wave alternating current is switched stepwise between the frequencies of 340 Hz, 255 Hz, 170 Hz, 128 Hz, and 85 Hz for each period of the rectangular wave.

When the frequency is gradually reduced from 340 Hz, which is the maximum frequency to be switched, to 85 Hz, which is the minimum frequency, the frequency is increased stepwise to 340 Hz, and this frequency switching is repeated.
As shown in FIG. 4, a cycle (cycle) at which frequency switching is repeated is referred to as a variable cycle. During lighting, the frequency switching during the variable period is always repeated. This variable period is about 50.0 ms per period.

Using the lamp lighting method according to the present invention, the following lighting test was performed.
That is, a lighting test was conducted to investigate the change in luminance maintenance rate of the lamp 100 and the lamp voltage over time. In this test, the frequency of the rectangular wave current that flows during steady lighting of the lamp with the lamp 100 having the rated power of 130 W attached to the high-pressure mercury lamp apparatus 200 is shown in FIG.

FIG. 5 shows a graph of the test results. In the figure, a graph of a conventional 170 Hz frequency fixing method is also shown for convenience of comparison. In this test, five lamps are used for each frequency, and the average value for the five lamps is drawn on the graph.
In the graph of FIG. 5, the luminance maintenance rate represents a relative value when the luminance at the beginning of lighting is 100%. This luminance is obtained based on ANSIlm measurement (ancillary measurement: the screen illuminance projected from the optical system is measured at nine points determined on the screen, and the luminous flux is calculated from the average illuminance). It was. Moreover, the graph of FIG. 5 is a semilogarithmic graph, and represents the cumulative lighting time on the horizontal axis logarithmically. The reason why the semi-logarithm is used is to make it easy to grasp the dynamic change in the initial lighting stage. As shown in the graph of FIG. 5 (a), the variable method lighting method according to the present embodiment does not increase in luminance at the initial stage of life unlike the conventional frequency fixing method, and from the start of lighting to 100 hours. Has a substantially constant luminance. In general, the lamp is required to have a constant luminance during its lifetime, but according to the variable method, the luminance during the lifetime can be stabilized more than before.

Then, it can be seen that in the late stage of the lifetime, the brightness has decreased more gradually than before, and a long lifetime of 6000 hours or more has been realized.
As described above, in the lighting method of the present invention, the lifetime can be extended by maintaining the balance between the above-described deposition and evaporation, so that the protrusions 124 at the tips of the electrodes 102 and 103 in the initial state of the start of lamp use. This is probably because the shape of 134 could be maintained for a longer time than before.

  In the conventional frequency-fixed lighting method, the protrusions 124 and 134 of the electrodes 102 and 103 grow excessively and the distance between the electrodes becomes excessively short after several tens of hours after starting lighting at the initial stage of life. In the graph of FIG. 5B, the voltage value is decreasing (the current value is increasing) as a result of shortening the distance between the electrodes. That is, in the conventional lighting method, it is considered that the tip part of the electrodes 102 and 103 excessively increases due to the extreme shortening of the distance between the electrodes, and a large amount of tungsten as the electrode material is scattered. Then, the projections 124 and 134 at the tips of the electrodes 102 and 103 were worn out early, so to speak, due to a large amount of scattering. In the graph of FIG. 5 (b), the inclination of the increase after the voltage value decreases is larger than that in the frequency variable method. The protrusions 124 and 134 are immediately retracted and the electrodes are separated from each other. It is a sign of that.

6 and 7 are tables showing the results of luminance transition and voltage transition in the lighting test described above.
(About changing frequency)
(1) In the present embodiment, the frequency is not directly changed between 340 Hz and 85 Hz, but there are three frequencies of 255 Hz, 170 Hz, and 128 Hz between the frequencies of 340 Hz and 85 Hz, 340 Hz, 255 Hz, It is made to change stepwise with 170 Hz, 128 Hz, and 85 Hz (refer FIG. 4). This is because, due to the characteristics of the lighting circuit, if the frequency is rapidly changed, the rectangular wave may be distorted. In this way, it is possible to suppress the distortion of the rectangular wave by changing the frequency stepwise.

  (2) In the present embodiment, the frequency is changed between 340 Hz and 85 Hz so as to sandwich the frequency of 170 Hz that has the longest lifetime at the fixed frequency. If the frequency is changed across 170 Hz, which is optimal for the lifetime in the fixed frequency, it is considered that the balance between the above-mentioned deposition and evaporation can be maintained as compared with the conventional one, and the lifetime of the lamp can be surely increased. . Here, “optimal in terms of lifetime” means that a luminous flux having no practical problem is obtained at the beginning of the lifetime, and that the luminous flux maintenance factor is unlikely to decrease for a long time.

Which pattern should be used to change the frequency of the rectangular wave alternating current during steady lamp operation depends on the lamp specifications (such as the arc tube volume, the composition of the substance enclosed in the tube, the distance between the electrodes, etc.) and is suitable from experiments. Can determine the correct pattern.
(3) Lower limit of frequency to be changed The minimum frequency when the lamp 100 is driven to be steadily lit can be driven from several Hz. However, when it is driven at 50 Hz or 60 Hz, which is currently used as a commercial frequency, the lighting device blinks and the projector display screen blinks with the phase change, and the display screen blinks. It becomes. In order to avoid such a problem, 60 Hz or more is required as a minimum frequency in order to avoid interference with a commercial frequency. According to the experiment, such a flashing was less noticeable when shifted by 10 Hz. Therefore, considering the margin to the maximum frequency currently used as a commercial frequency, 70 Hz or higher can be selected as a safe frequency. It has been confirmed that the protrusions at the tip of the electrode grow at this frequency.

(4) Upper limit of frequency to be changed It has been confirmed that when the 130 W lamp 100 is driven at 130 W, steady driving is possible at each of fixed frequencies of 300 Hz, 400 Hz, 500 Hz, and 550 Hz. Experiments were also performed for other power conditions, but a fixed frequency of 300 Hz to 500 Hz can be used as the maximum frequency. Even in consideration of the inherent variation of the lamp, the maximum driving frequency capable of steady driving is in the range of 300 Hz to 500 Hz. At this time, the electrode protrusions of the lamp were also evaluated. The electrode protrusions of the lamp do not grow at this frequency, and there is a tendency to decrease. This is also confirmed from the discharge voltage of the lamp. That is, this frequency is a driving frequency at which the growth of the protrusion generated at the electrode tip is the least or the distance between the electrodes is increased.

(5) The maximum frequency to be changed is preferably at least three times the minimum frequency. This is because it is considered that it is easy to maintain the distance between the electrodes appropriately by providing such a difference between the maximum and minimum frequencies.
(6) In the present embodiment, the three frequencies of 340 Hz, 170 Hz, and 85 Hz are switched and changed, but only two frequencies may be switched. In that case, in order to lengthen the period during which the distance between the electrodes is properly maintained, a larger one of the two frequencies is set to a frequency at which the tip of the electrode grows at the initial stage of the life, and The smaller frequency is preferably set to a frequency at which the tip of the electrode recedes at the initial stage of life.

By the way, when xenon is enclosed, there is a possibility that the breakdown voltage, which is a voltage for dielectric breakdown at the time of starting the lamp, is increased. Specifically, the breakdown voltage rises by several kV in a lamp with a rated power of 250 W.
Therefore, it is preferable to enclose krypton 85, which is a radioactive element having the property of beta decay, in addition to xenon. This is because the initial electrons in the discharge space 108 are increased by the beta decay of the krypton 85, so that the breakdown voltage can be lowered.

If such krypton 85 is enclosed, for example, about several kBq, it is possible to cancel the increase in breakdown voltage due to the xenon encapsulation.
To summarize the above, by combining xenon gas and krypton 85 and enclosing them, it is possible to reduce the current value during stable lighting without causing an increase in breakdown voltage.
6). Image Display Device The lamp unit 200 including the lamp lighting device 300 according to the present invention can be applied to a projection type image display device.

FIG. 8 is a schematic diagram showing a configuration of a liquid crystal projector 400 using the above-described lamp unit 200 as an example of a projection type image display apparatus.
As shown in the figure, a transmissive liquid crystal projector 400 includes a power unit 401, a control unit 402, a condenser lens 403, a transmissive color liquid crystal display panel 404, a lens unit 405 incorporating a drive motor, and a cooling unit. Fan device 406 for use.

The power supply unit 401 converts commercial AC input (100 V) into a predetermined DC voltage and supplies it to the control unit 402.
The control unit 402 displays the color image by driving the color liquid crystal display panel 404 based on the image signal input from the outside. In addition, a driving motor in the lens unit 405 is controlled to execute a focusing operation or a zoom operation.

The light emitted from the lamp unit 200 is collected by the condenser lens 403, passes through the color liquid crystal display plate 404 disposed in the middle of the optical path, and is formed on the liquid crystal display plate 404 via the lens unit 405. Is projected onto a screen outside the figure.
By using a lamp unit having a longer life than the conventional lamp unit comprising a high-pressure mercury lamp and a lighting device according to the present invention, a liquid crystal projector having a high commercial value can be provided.

Note that the lamp unit 200 including the lamp lighting device 300 according to the present invention includes a DLP (registered trademark) projector using a DMD (digital micromirror device), and a liquid crystal using other reflective liquid crystal elements. The present invention can also be applied to other projection type image display devices such as a projector.
7). Modifications As described above, the present embodiment has been described. However, the present invention is not limited to the above-described form, and can be appropriately changed without departing from the spirit of the invention.

(1) Various variations of the frequency switching pattern of the rectangular wave alternating current are conceivable. The said modification is shown in FIGS. In any figure, it is the figure made into the expression similar to the graph of the upper part of FIG.
The switching pattern shown in FIG. 9 is the same as in the first embodiment in that when the frequency is decreased stepwise from the maximum frequency to the minimum frequency, the frequency is increased stepwise again to the maximum frequency. The frequency is changed every time. For example, in one variable cycle, the frequency is sequentially switched every half cycle from 340 Hz, 255 Hz, 170 Hz, 128 Hz, 85 Hz, 128 Hz, 170 Hz, and 255 Hz.

In the switching pattern shown in FIG. 10, a cycle in which the frequency is switched stepwise for each cycle of the rectangular wave from the maximum frequency to the minimum frequency is defined as one variable cycle. For example, one variable cycle switches the frequency to 340 Hz, 255 Hz, 170 Hz, 128 Hz, and 85 Hz for each cycle of the rectangular wave.
The switching pattern shown in FIG. 11 switches the frequency every half cycle of the rectangular wave from the maximum frequency to the minimum frequency. For example, in the variable 1 period, the frequency is sequentially switched between 340 Hz, 255 Hz, 170 Hz, 128 Hz, 85 Hz, 128 Hz, 170 Hz, and 255 Hz for each half period of the rectangular wave.

  The switching pattern shown in FIG. 12 is a cycle in which three types of frequencies of fixed periods a, b, and c in which the frequency is fixed every fixed time are sequentially switched as one variable period (one cycle), and this cycle is repeated. For example, the fixed frequency of the fixed period a (first period) is 340 Hz, the fixed frequency of the fixed period b (second period) is 170 Hz, and the fixed frequency of the fixed period c (third period) is 85 Hz.

Further, as shown in FIG. 12, each fixed period a, b, c has a length including a plurality of fixed frequencies, the fixed period a is 7.5 periods, and the fixed period b is 6.5 periods. The fixed period c includes 2.5 cycles.
In the switching pattern shown in FIG. 13, a cycle in which a fixed period in which the frequency is fixed every fixed time and a variable period in which the frequency is changed are alternately switched is one variable cycle. For example, one variable period is composed of two periods, a fixed period in which the fixed frequency is 340 Hz, and a variable period in which the same switching as the frequency switching in the variable period shown in FIG. 10 is performed.

(2) In the present embodiment, the frequency is changed stepwise (jumping), but the frequency may be changed linearly.
A lighting device for realizing a linear change in frequency will be described. FIG. 14 is a block diagram illustrating a configuration of a lighting device 301 according to a modification. Since the lighting device 301 shown in FIG. 14 has basically the same configuration as the lighting device 300 according to the embodiment (see FIG. 3), the differences will be mainly described.

The oscillator a318 generates a modulated signal, and the oscillator b320 generates a modulated signal.
The frequency determination circuit 316 modulates the modulated signal with a modulation signal and generates a modulated rectangular wave.
The control unit 310 sends a predetermined control signal to the DC / AC inverter 306 with reference to the rectangular wave.

According to such a lighting device 301, it is possible to constantly change the frequency of the rectangular wave alternating current supplied to the lamp with a simple circuit configuration, and to finely control the change in frequency.
A known frequency modulation circuit may be used in place of the frequency determination circuit 316 and the oscillators 318 and 320.

(3) Various variations of the frequency change are possible. The said modification is shown in FIGS. The graphs in FIGS. 15 to 18 all show time-dependent changes in frequency, with time (t) on the horizontal axis and frequency (f) on the vertical axis.
(A) Regular change and irregular change The frequency may be changed regularly, that is, according to a fixed interval, or may be changed irregularly. The graph in FIG. 15 conceptually shows regular changes and irregular changes. As shown in the figure, the change in the frequency in the period A ₁ whereas a regular change of the frequency in the period A ₂ is irregular. In the period A2, even if it is an irregular change, the maximum (fmax) and minimum (fmin) of the frequency are determined and changed between the two.

(B) Intermittent change and continuous change The frequency may be changed intermittently, or may be changed continuously, that is, constantly. The graphs in FIGS. 16A and 16B conceptually show intermittent change and continuous change.
In the graph in FIG. 16 (a), after a certain period for changing the frequency, a period for fixing the frequency is continued, and the certain period for changing the frequency is occasionally followed.

On the other hand, in the graph in FIG. 16B, the frequency changes continuously.
(C) Combination of intermittent change and continuous change The period of intermittent change and the period of continuous change described in (B) above may be combined. For example, as shown in the graph in FIG. 17, an intermittent change period and a continuous change period may be alternately repeated.

(D) Grouping of change period and fixed period Although not particularly shown, a period in which both a period in which the frequency is continuously changed and a period in which the frequency is fixed may be grouped may be repeated as one cycle. For example, two periods of a continuously changing period and a subsequent fixed period may be grouped and handled as one cycle, and this may be repeated.

(E) Irregular repetition As shown in the graph in FIG. 18, two periods of continuous change and a fixed frequency period may be prepared, and both periods may be repeated irregularly. That is, the order of both may not be determined in advance, and it may be undefined which period is set after a certain period.

(F) Combination with frequency change depending on operation data (discharge voltage, etc.) In the above (A) to (E), there are a period for changing the frequency without depending on the operation data and a period for fixing the frequency. Although the combination has been described, a period in which the frequency is changed depending on operation data may be used instead of the period in which the frequency is fixed.
8). Others (1) Lamp type In the above embodiment, the high-pressure mercury lamp in which mercury is sealed as the luminescent material has been described as an example. However, the present invention is also applicable to other high-pressure discharge lamps such as a metal halide lamp. be able to.

  Since the high-pressure discharge lamp lighting device according to the present invention has a longer life than before, it can be applied to a liquid crystal display device or the like.

1 is a diagram showing a schematic configuration of a high-pressure mercury lamp 100. FIG. 1 is a partially cutaway perspective view showing a configuration of a lamp unit 200 using a high-pressure mercury lamp 100. FIG. 3 is a block diagram showing a configuration of a lighting device 300. FIG. The upper graph shows the temporal change in the waveform of the rectangular alternating current. The lower graph corresponds to the upper graph and shows the temporal change in the frequency of the rectangular wave alternating current. (A) is a graph which shows the relationship between the cumulative lighting time of the lighting test result using the conventional system, and a luminance maintenance factor.

(B) is a graph showing the relationship between the cumulative lighting time of the lighting test result using the conventional method and the lamp voltage;
It is a table | surface which shows the result of the brightness transition in a lighting test. It is a table | surface which shows the result of the voltage transition in a lighting test. It is a block diagram which shows the structure of a liquid crystal projector. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a block diagram which shows the structure of the lighting device 301 which concerns on a modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 High pressure mercury lamp 101 Light emission tube 101a Light emission part 101b, 101c Sealing part 102,103 Electrode 200 Lamp unit (high pressure discharge lamp apparatus)
300, 301 lighting device 400 liquid crystal display device

Claims (24)

A lighting circuit that supplies an alternating current to a high-pressure mercury lamp that has a light-emitting tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed to light the lamp. When,
A high-pressure discharge lamp lighting device comprising: frequency control means that changes the frequency of the alternating current without depending on operation data that varies with the lighting elapsed time of the high-pressure mercury lamp.   The frequency control means changes the frequency regularly or irregularly without depending on the operation data that changes with the elapsed time of the high-pressure mercury lamp for a certain period, and the certain period is one cycle. 2. The high pressure discharge lamp lighting device according to claim 1, wherein the control is repeated continuously or intermittently.   The frequency control means performs control to alternately repeat a change period in which the frequency is continuously changed without depending on operation data that changes with a lighting elapsed time of the high-pressure mercury lamp and a fixed period in which the frequency is fixed. The high pressure discharge lamp lighting device according to claim 1, which is performed.   2. The high pressure discharge lamp lighting device according to claim 1, wherein the frequency control means performs control to intermittently switch the frequency to at least two different values.   2. The frequency control means performs control to change the frequency regularly or irregularly without depending on operation data that changes with an elapsed lighting time of the high-pressure mercury lamp. The high-pressure discharge lamp lighting device described. A lighting circuit that supplies an alternating current to a high-pressure mercury lamp that has a light-emitting tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed to light the lamp. When,
A high-pressure mercury lamp frequency control means for controlling the frequency of the alternating current to change regularly or irregularly and to repeat this constant period as one cycle or to continue this intermittently. A high-pressure discharge lamp lighting device comprising: A lighting circuit that supplies an alternating current to a high-pressure mercury lamp that has a light-emitting tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed to light the lamp. When,
A high-pressure discharge comprising frequency control means for performing control to alternately repeat a change period in which the frequency of the alternating current is continuously changed according to a predetermined rule and a fixed period in which the frequency is fixed Lamp lighting device. A lighting circuit that supplies an alternating current to a high-pressure mercury lamp that has a light-emitting tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed to light the lamp. When,
A high-pressure discharge lamp lighting device comprising: frequency control means for constantly changing the frequency of the alternating current according to a predetermined rule.   The high-pressure discharge lamp lighting device according to claim 2 or 6, wherein the frequency control means continuously changes the frequency during the predetermined period.   The high-pressure discharge lamp lighting device according to claim 2 or 6, wherein the frequency control means changes the frequency intermittently by switching to at least two values during the certain period.   The high-pressure discharge lamp lighting according to claim 2 or 6, wherein the fixed period includes a change period in which the frequency continuously changes and a fixed period in which the frequency is fixed. apparatus.   The frequency control means changes the frequency between a predetermined maximum frequency and a minimum frequency, and the minimum frequency is 70 Hz or more. The high-pressure discharge lamp lighting device described.   The high-pressure discharge lamp lighting device according to any one of claims 1 to 12, wherein a krypton 85 is further enclosed in the arc tube.   A high pressure mercury lamp having an arc tube in which a pair of electrodes in which a halogen substance and xenon are enclosed and a protrusion is formed at the tip is disposed, and a lamp for lighting the high pressure mercury lamp A high-pressure discharge lamp device comprising the high-pressure discharge lamp lighting device according to any one of claims 1 to 13.   A projection-type image display device comprising the high-pressure discharge lamp device according to claim 14. A high-pressure discharge that supplies an alternating current to a high-pressure mercury lamp that has an arc tube in which a halogen substance and xenon are enclosed, and a pair of electrodes with projections formed at the tip are arranged to supply light. A method of lighting the lamp,
A method for lighting a high-pressure discharge lamp, characterized in that the frequency of the alternating current is changed without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp.   The frequency is changed regularly or irregularly for a certain period without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury lamp, and this constant period is defined as one cycle. The method of lighting a high-pressure discharge lamp according to claim 16, wherein the method is repeated or continued intermittently.   The change period in which the frequency continuously changes without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp and the fixed period in which the frequency is fixed are alternately repeated. Item 17. A high-pressure discharge lamp lighting method according to Item 16.   17. The high pressure discharge lamp lighting method according to claim 16, wherein the frequency is intermittently switched to at least two different values.   The method of lighting a high-pressure discharge lamp according to claim 16, wherein the frequency is changed regularly or irregularly constantly without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. . A high-pressure discharge that supplies an alternating current to a high-pressure mercury lamp that has an arc tube in which a halogen substance and xenon are enclosed, and a pair of electrodes with projections formed at the tip are arranged to supply light. A method of lighting the lamp,
A frequency of the alternating current is changed regularly or irregularly for a certain period, and this constant period is set as one cycle, and this is continuously repeated or intermittently. Lighting method. A high-pressure discharge that supplies an alternating current to a high-pressure mercury lamp that has an arc tube in which a halogen substance and xenon are enclosed, and a pair of electrodes with projections formed at the tip are arranged to supply light. A method of lighting the lamp,
A lighting method for a high-pressure discharge lamp, characterized by alternately repeating a change period in which the frequency of the alternating current is continuously changed according to a predetermined rule and a fixed period in which the frequency is fixed. A high-pressure discharge that supplies an alternating current to a high-pressure mercury lamp that has an arc tube in which a halogen substance and xenon are enclosed, and a pair of electrodes with projections formed at the tip are arranged to supply light. A method of lighting the lamp,
A method for lighting a high-pressure discharge lamp, wherein the frequency of the alternating current is constantly changed according to a predetermined rule.   The lighting method for a high-pressure discharge lamp according to any one of claims 16 to 23, wherein krypton 85 is further enclosed in the arc tube.

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