JPH11133506A - Optical device for short arc metal halide lamp, liquid crystal projector device using the same and method for turning on the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for turning on an optical device for a short arc metal halide lamp and a liquid crystal projector device using the optical device where the compression strain of the light emitting tube of a short arc metal halide lamp, especially, the compression strain or the tensile stress of an anode side electrode sealing part is restrained to reduce the mechanical fatigue of quartz glass caused by the flickering of the lamp. SOLUTION: This device is constituted of the short arc metal halide lamp which is equipped with a pair of electrodes 2a and 2b at both ends of a quartz tube, inside which at least mercury, rare gas and metallic halide are enclosed and where the light emitting tube 1 having single tube structure is arranged so that an arc axis may be horizontal; a concave reflection mirror 8 which is arranged to be combined with the short arc metal halide lamp and whose reflection surface 8 is constituted to be spherical, parabolic or ellipsoidal; and the optical device where the arc axis of the short arc metal halide lamp is positioned on the optical axis of the mirror 8 and which is DC-turned on. After starting up the short arc metal halide lamp, the rush current of the lamp after shifting from glow discharge to arc discharge is set to a value nearly equal to the value of a lamp current at the time when the lighting of the lamp is stable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically efficient light source mainly used for video equipment or optical equipment, which is used by combining an arc tube and a reflector without providing an outer tube. The present invention relates to an improvement in an optical device for a short arc metal halide lamp, and particularly to an improvement in a lighting method thereof.

[0002]

2. Description of the Related Art In recent years, a liquid crystal projector device configured to project an image on a large screen by combining a liquid crystal panel and an optical system such as a lens has become widespread. And, in the liquid crystal projector device, an optical device combining a short arc metal halide lamp and a reflector, which is constituted only by an arc tube without using an outer tube, is easy to use.
It is mainly used in terms of color reproducibility and brightness.

Further, in order to reduce the size and weight of the entire liquid crystal projector device and make it easier to use, a short arc metal halide lamp for direct current lighting is used. This is because a short arc metal halide lamp for DC lighting can be made closer to a point light source and have a shorter arc length. Furthermore, in a projector device using a liquid crystal panel, since the light transmission angle of the liquid crystal panel is limited, control of the light reflection angle by the reflector becomes important from the viewpoint of effective use of light. Therefore, a short arc metal halide lamp for direct current lighting, which is closer to a point light source, has a shorter arc length, and is used so that light is focused at the focal point of the reflector.

[0004]

However, in a short arc metal halide lamp for DC lighting using a quartz arc tube, a very large inrush current is generated when the glow discharge changes to an arc discharge after the lamp is started. And the arc voltage is reduced due to the short arc,
Since the lamp current is larger than that during the AC lighting, the temperature of the anode is high.

[0005] Also, the lamp is hot when turned on,
Usually, the electrode made of tungsten becomes extremely hot due to self-heating by the current, radiant heat from the arc, and even electron collision, and the temperature of the molybdenum foil connected to the electrode, and thus the temperature of the anode-side electrode sealing portion also becomes extremely high. I have. Since the quartz glass of the anode-side electrode sealing portion has a smaller coefficient of thermal expansion than tungsten as the electrode material, compressive strain occurs.

On the other hand, when the light is turned off, a tensile stress acts on the quartz glass of the electrode sealing portion. Therefore, especially when used in a state where the frequency of blinking is high and the large pulse current is periodically superimposed and lit, the electrode mandrel adheres to the electrode mandrel by repeated expansion and contraction due to temperature change. This causes mechanical fatigue in the quartz glass, and the high pressure in the arc tube during lighting causes cracks, particularly in the quartz glass in the anode-side electrode sealing portion, causing problems such as leaks and cracks.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a liquid crystal projector using an optical device for a short arc metal halide lamp. Long-life optical device for short-arc metal halide lamps that suppresses the generation of compressive strain and tensile stress in the anode-side electrode sealing portion and reduces the occurrence of mechanical fatigue of quartz glass due to lamp flickering, and a liquid crystal projector using the same It is an object to provide an apparatus and a lighting method thereof.

[0008]

According to a first aspect of the present invention, there is provided a quartz tube including a pair of electrodes at both ends of a quartz tube, and at least mercury, a rare gas, and a metal halide enclosed therein. A short arc metal halide lamp comprising an arc tube having a single tube structure, a concave reflecting mirror comprising a spherical surface, a parabolic surface, an elliptical surface or the like in which the lamps are arranged in combination, and an arc axis of the lamp. An optical device horizontally disposed so as to be located on the optical axis of the concave reflecting mirror, wherein the short arc metal halide lamp is lit by DC, and after the lamp is started, a transition from a glow discharge to an arc discharge is made. The inrush current of the lamp after the lamp has a value substantially equal to the lamp current when the lamp lighting is stable. That.

A second aspect of the present invention is a liquid crystal projector having the optical device for a short arc metal halide lamp and at least an air cooling device for cooling a lamp in a main body of the device. 3. The liquid crystal projector according to claim 2, wherein the air cooling device stops immediately after the short arc metal halide lamp is turned off.

According to a fourth aspect of the present invention, there is provided a short arc metal halide lamp comprising a quartz tube having a single tube structure and a concave reflecting mirror, and the arc axis of the lamp is positioned on the optical axis of the reflecting mirror. The lamp is used for direct current lighting, and after starting the lamp, the inrush current of the lamp after transition from glow discharge to arc discharge is determined. An optical device for a short arc metal halide lamp, a liquid crystal projector using the same, and a method of lighting the optical device, wherein the optical device is turned on at a value substantially equal to the current. 5. The control according to claim 4, wherein the control is performed from a state where the lamp voltage is substantially equal to the lamp voltage when the lamp lighting is stable. It is a lighting method for mounting a short arc metal Ha Tide lamp optical device and a liquid crystal projector device using the same.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of an optical device for a short arc metal halide lamp according to the present invention. An anode 2a and a cathode 2 are provided at both ends of a quartz glass arc tube 1.
b is embedded and fixed in the sealing portion. The distance between the electrodes of the anode 2a and the cathode 2b, that is, the arc length is 1.5 mm, 3 is an electrode mandrel, 4 is a molybdenum foil connected to the electrode, 5 is an electrode sealing portion, and 6 is a base. I have. An outer surface near the embedded portion of the cathode 2b is coated with a heat-resistant and heat-reflective film 7 made of white alumina silica. Arc tube 1
Is fixed to the bottom of a reflecting mirror 8 with a cold mirror with a cement via a base 6 to constitute an optical device for a short arc metal halide lamp.

[0012] In this way, the maximum outside diameter of the arc tube 1 thus formed is 9.0 mm, inner volume is 0.18 cc, the the arc tube 1, as an inclusion additives, DyI ₃ -NdI ₃ -Cs
0.6 m when I is 8: 2: 5 in weight ratio
g, 33250 Pa of argon for starting, and mercury as a buffer gas.

FIG. 2 shows an embodiment of the present invention in which the inrush current after the transition from the glow discharge to the arc discharge is set to a value substantially equal to the lamp current when the lamp lighting is stable, and the power control is performed so that the lamp voltage is stable. FIG. 9 is a diagram showing lamp current value waveforms of a lighting method performed from a state in which the lamp voltage is substantially equal to the lamp voltage at the time and a conventional lighting method. In the figure, I _L is the lamp current, and A is the time of transition from glow discharge to arc discharge 2 m.
s, and the maximum value of the lamp current at this time is 8A.
B indicates each inrush current value, C indicates a displacement point for each power control, D indicates a current value when lighting is stable, and t indicates a lighting time.

Next, as shown in Table 1, three types of lighting methods for controlling the inrush current value were changed, and each of the five optical devices for the short arc metal halide lamp was formed using a dedicated constant-power electronic ballast. The lamp is lit so that the tube axis is horizontal at a constant DC power of 150 W, and is lit for 15 minutes.
A flash cycle test was performed to turn off the light for a minute. When the lamp is stable, the electric characteristics are as follows: the lamp voltage is 60 V, the lamp current is 2.5 A, and the lamp power becomes 150
W is kept constant. Also, when the lamp voltage rises above the lamp voltage at which the power control works, the lamp current decreases.

[0015]

[Table 1]

The number of blinks 500 times, 1000 times and 2
Table 2 (500 times), Table 3 (1000 times), and Table 4 show the results of observation of the occurrence of compressive strain at the anode-side electrode sealing portion of the arc tube and the degree of cracking and cracking of the quartz glass at the 000th time. (2000 times). In each table, ◎ indicates no compression distortion, ○ indicates slight compression distortion, Δ indicates compression distortion, Δ indicates minute cracks, □ indicates cracks, and × indicates inadequacy due to leak or crack. Is shown.

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

From Tables 2 to 4, it can be seen that the lighting method No. 1 suppresses the compressive strain and the tensile stress generated in the anode-side electrode sealing portion most.

Next, FIGS. 3 and 4 show changes in the temperature of the anode-side electrode sealing portion and the lamp voltage as the lamp lighting time elapses for the above three types of lighting methods. As shown in FIG. 3, the lighting method No. 1 has the gentlest gradient of temperature rise, and can suppress a rapid rise in the temperature of the anode-side electrode sealing portion at the time of startup after lamp lighting. It can be seen that the generated compressive strain and tensile stress can be suppressed, and the phenomenon of cracks, leaks and cracks in the arc tube can be suppressed. Also, it can be seen from FIG. 4 that the lamp voltage is controlled after about 90 S has elapsed.

From the above results, it is only necessary to set the inrush current after the transition from the glow discharge to the arc discharge of the lighting method No. 1 to a value substantially equal to the lamp current when the lamp lighting is stable, and to light the lamp. Is performed from a state in which the lamp voltage is substantially equal to the lamp voltage at the time of stable lamp operation, so that compressive strain and tensile stress generated in the anode-side electrode sealing portion can be suppressed, and cracks and leakage of the arc tube can be suppressed. And the phenomenon of cracking can be suppressed, and the life of the lamp can be prolonged.

The optical device for a short arc metal halide lamp is used as a light source of a liquid crystal projector device. In the projector device main body, an optical system such as a liquid crystal panel and a lens is combined with an air cooling device for cooling. in use. Therefore, the timing of stopping the air-cooling device when the lamp was turned off was examined.

A comparison experiment was conducted between when the cooling fan of the air cooling device was stopped immediately after the lamp was turned off and when the cooling fan was not stopped. FIG. 5 is a characteristic diagram showing a change in the temperature of the anode-side electrode sealing portion of the arc tube with the elapse of the lamp extinguishing time. As is clear from FIG. 5, the temperature of the sealing portion starts to decrease at a stretch when the lamp is turned off in any case. Temperature can be moderated. This means that, similarly to the above embodiment, it is possible to suppress the compressive strain and the tensile stress due to the temperature change, to suppress cracks, leaks and cracks in the arc tube, and to cause the mechanical fatigue of quartz glass due to lamp flickering. Can be reduced, and the life of the lamp can be extended.

Immediately after the lamp is turned off, the cooling fan of the lamp cooling air cooling device reduces the wind speed, adjusts the wind direction so that the cooling wind does not hit the lamp, and coats the lamp with a heat insulating film. The temperature drop of the sealing portion may be moderated, the compressive strain and the tensile stress due to the temperature change may be suppressed, and the occurrence of mechanical fatigue of the quartz glass due to the lamp flickering may be reduced.

The reflecting mirror with a cold mirror includes:
An optical multilayer interference film is applied to the reflection surface, and only visible light is reflected to the front surface. The shape is a concave reflecting mirror such as a spherical surface, a parabolic surface, or an elliptical surface.

[0027]

As described above with reference to the embodiments,
ADVANTAGE OF THE INVENTION According to this invention, the compressive distortion and tensile stress of the arc tube of a short arc metal halide lamp, and especially the generation of the compressive distortion and tensile stress of the anode side electrode sealing part are suppressed, and the mechanical fatigue of quartz glass by lamp flickering is suppressed. It is possible to obtain an optical device for a short-arc metal halide lamp, a liquid crystal projector device using the optical device, and a lighting method thereof, which generate less and have a long life.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an optical device for a short arc metal halide lamp according to the present invention.

FIG. 2 is a diagram showing lamp current value waveforms in a lighting method according to an embodiment of the present invention and a conventional lighting method.

FIG. 3 is a characteristic diagram showing a change in the temperature of an anode-side electrode sealing portion of an arc tube with the lapse of lighting time in lighting methods Nos. 1 to 3;

FIG. 4 is a characteristic diagram showing a change in lamp voltage with a lapse of lighting time in lighting methods Nos. 1 to 3;

FIG. 5 is a characteristic diagram showing a change in temperature of an anode-side electrode sealing portion with a lapse of time of turning off a lamp of a liquid crystal projector device having an air cooling device for cooling a lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2a Anode 2b Cathode 3 Electrode core 4 Molybdenum foil 5 Electrode sealing part 6 Base 7 Heat-resistant and heat-reflective film 8 Reflector

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01J 61/52 H01J 61/52 B 61/86 61/86 61/88 61/88 C H04N 5/74 H04N 5/74 KA

Claims (5)

[Claims] 1. A short-arc metal halide lamp comprising a single-tube luminous tube having a pair of electrodes at both ends of a quartz tube and at least mercury, a rare gas, and a metal halide enclosed therein, and the lamp. And a concave reflecting mirror formed of a spherical surface, a parabolic surface, an elliptical surface, or the like, which is arranged in combination, and the arc axis of the lamp is horizontally disposed such that the arc axis of the lamp is positioned on the optical axis of the concave reflecting mirror. The short arc metal halide lamp comprises an optical device, and the short arc metal halide lamp is lit by direct current. After the lamp is started, the inrush current of the lamp after the transition from the glow discharge to the arc discharge is substantially equal to the lamp current when the lamp lighting is stable. An optical device for a short arc metal halide lamp, characterized in that: 2. A liquid crystal projector device having an optical device for a short arc metal halide lamp and at least an air cooling device for cooling a lamp in a device main body. 3. The liquid crystal projector according to claim 2, wherein the lamp cooling air cooling device stops immediately after the short arc metal halide lamp is turned off. 4. A short arc metal halide lamp comprising a single-tube quartz arc tube and a concave reflector, which are horizontally disposed such that the arc axis of the lamp is positioned on the optical axis of the reflector. The lamp is used for direct current lighting, and after starting the lamp, the inrush current of the lamp after transition from glow discharge to arc discharge is obtained.
An optical device for a short arc metal halide lamp and a method of lighting a liquid crystal projector device using the same, wherein the lamp is lit at a value substantially equal to the lamp current when the lamp lighting is stable. 5. The short arc metal halide lamp according to claim 4, wherein the power control of the short arc metal halide lamp is performed from a state in which the lamp voltage is substantially equal to the lamp voltage when the lamp lighting is stable. An optical device and a lighting method of a liquid crystal projector device using the same.