JPH08273596A - Short-arc metal halide lamp and optical device using same - Google Patents

Abstract

PURPOSE: To provide a screen of good quality and to extend the life of a lamp by suppressing changes in screen luminance distribution which result when an arc is moved as the anode end of a light emitting tube made of quartz is melted and deformed. CONSTITUTION: A light emitting tube 1 made of quartz has an anode 2 sealed at one end and a cathode 3 at the other. The anode 2 comprises a tungsten coil 22 wound into plural turns on the end of a tungsten core 21. Coil portions 23a, 24a serving as cooling portions at both ends of time coil 22 are cut perpendicular to the core 21. Cooling action is effected evenly with respect to the axis of the core 21 so that even if the anode end is melted by lamp current, the starting point of an arc can be set to the axis. Therefore, changes in luminance distribution on a screen can be suppressed, and a screen of good quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an anode electrode when a short arc metal halide lamp having a short distance between both electrodes is used by being lit by direct current, and particularly to an improvement of an optical metal halide lamp used in combination with a reflecting mirror. Regarding

[0002]

2. Description of the Related Art In recent years, liquid crystal projectors configured to project an image on a large screen by combining a liquid crystal panel and an optical system such as a lens have become popular. And
An optical device that combines a short arc metal halide lamp and a parabolic reflector, which is composed only of an arc tube without an outer tube, has become the mainstream in terms of ease of use, color reproducibility, and brightness. There is. In order to reduce the size and weight of the entire liquid crystal projector and make it easier to use, it has been proposed to use a DC lighting lamp. This is because a small and inexpensive DC lighting ballast can be used as a ballast built into the device. In this short arc metal halide lamp for direct current lighting, an anode is sealed at one end of a quartz arc tube and a cathode is sealed at the other end, and a metal halide such as scandium iodide is sealed together with mercury and a rare gas. .

[0003]

Conventionally, the anode of such a lamp has a tungsten core rod 31 placed at the center as shown in FIG.
The ones that are wound are the mainstream. However, due to the design of the ballast, the electric current at the time of starting flows more than the electric current at the time of stabilization, and the tungsten core rod at the tip of the anode is melted. Further, in this type of device, since the number of times of blinking is large, the tip part may be remarkably deformed, and the brightness of the central part on the screen which is initially set may be largely changed depending on the state of dissolution of the anode part.

The above-mentioned lamp whose central illuminance is greatly changed has a bright portion outside the center of the screen,
It can be seen that the arc between both electrodes of the arc tube moved. When the tip of the anode of the lamp was observed, it was confirmed that the tip 33 of the core rod 31 was rounded as shown in FIG. 7, and the shape of the roundness was distorted from the center. Was given. It is considered that this is because the coil wound to perform the cooling function of the anode does not uniformly cool the tip of the core rod located in the center, and is thus unevenly melted.

The present invention has been made in view of the above circumstances, and is caused by the movement of the arc generated by the deformation of the tip portion of the anode used in the DC-lit short arc metal halide lamp due to the lamp current at the time of starting. The present invention provides a long-life short arc metal halide lamp having stable screen characteristics by suppressing changes in the screen illuminance distribution, and an optical device configured by combining this lamp and a reflecting mirror.

[0006]

According to the present invention, an anode and a cathode are sealed at both ends of a quartz arc tube, at least a metal halide is sealed inside, and the arc length between the electrodes is 10 mm or less and DC lighting is performed. The anode is formed by winding a tungsten coil around the tip of a cylindrical tungsten core rod, and at least the coils at both ends of the coil portion, which are cooling portions, are cut so as to be orthogonal to the cylindrical core rod. And configure. Further, a light source device formed by combining the short arc metal halide lamp and a reflecting mirror having a concave surface is used in a liquid crystal projector.

[0007]

With the above structure, when the change of the illuminance distribution on the screen is confirmed by the life test of the optical device, the change of the illuminance distribution is small, and therefore, the cooling of the tungsten coil is approximately approximately uniform, and this change is the initial setting. In contrast, it has become smaller.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. FIG. 1 is a sectional view of an essential part of an optical device configured by combining a concave reflecting mirror and a short arc metal halide lamp to be lit by direct current. In the figure, 1 is a short arc metal halide lamp composed of a quartz arc tube, An anode 2 is sealed at one end of the arc tube and a cathode 3 is sealed at the other end. Further, seal portions 4a and 4b are formed at both ends of the arc tube, and the other end portions of the anode and the cathode are sealed to the seal portions via molybdenum foils 5a and 5b. Further, on the outer peripheral surface of the cathode, which is the outer surface of the arc tube, a reflective and heat retaining film 6 made of a mixture of aluminum oxide and silicon oxide is applied. A base 7 is fixed to the end of the arc tube on the anode side, and a trigger wire made of a heat-resistant metal wire extends from the outer peripheral surface of the anode along the outer surface of the arc tube to the external lead wire on the cathode side. 8 are arranged.

In the figure, reference numeral 11 denotes a parabolic reflector made of borosilicate hard glass, and an inner surface thereof forms a cold mirror 12 having a dielectric multilayer film formed by vacuum vapor deposition. And
The base side of the short arc metal halide lamp 1 is inserted into a mounting hole 13 formed at the bottom of the reflecting mirror and fixed via an inorganic adhesive 14. Further, by connecting the nickel lead wire 16 to the external lead wire on the cathode side via the nickel sleeve 15, and connecting the tip end portion thereof to the metal terminal 18 via the through hole 17 formed in the side portion of the reflecting mirror. Make electrical connection. In this way, the optical device is constructed.

Next, design values of the optical device will be described. In order to utilize the color reproducibility of the liquid crystal projector device and to increase the illuminance, in the lamp, in addition to argon as a starting auxiliary gas and mercury as a buffer gas, dysprosium iodide, neodymium iodide,
0.5 mg of a metal halide containing cesium iodide in a weight ratio of (8: 2: 5) is enclosed. The inner volume of the arc tube of this lamp is about 0.4 cc, and a spheroid having a central part with an outer diameter of 11.5 mm and an inner diameter of 8.2 mm is provided with a reflection and heat insulation film on one end, and the side with the heat insulation film is the cathode. 3 and is fixed so as to be positioned on the opening side with respect to the reflecting mirror. At the other end of the arc tube, as shown in FIG. 2, a cylindrical tungsten core rod 21 having a diameter of 0.8 mm is arranged in the center, and a tungsten coil 22 is wound a plurality of turns around the tip of the core rod. At least the coil portions 23a and 23b on both sides, which are cooling portions during lamp lighting, are cut so as to be orthogonal to the cylinder axis, and the anode 2 protruding by 0.5 mm from the tip thereof is sealed. The distance between the anode and the cathode (arc length) is 5 mm.

The optical device thus constructed is rated at 150
When the lamp was turned on by the W electronic DC ballast, the lamp current at the time of starting was 4 A, the current at the time of stable was 2 A, and the lamp voltage at the time of stable was 75V. Then, when it was mounted on a liquid crystal projector and subjected to a life test, after being lit for 1,000 hours at these lamp currents, the tip of the anode was rounded and deformed as shown in FIG. 4, but a screen projected from the device. There was no significant change in the above illuminance distribution, especially in the central area, and a good quality screen was obtained. Also, it was lit up until the end of its life of 4000 hours, but it did not deform further,
The screen characteristics were also satisfactory.

A similar experiment was conducted on an optical device in which a short arc metal halide lamp for direct current lighting with a lamp power of 250 W and a reflecting mirror were combined.
The effect similar to the above was recognized. As the anode of this lamp, a tungsten core rod having a diameter of 1.0 mm, a tungsten coil having a wire diameter of 0.5 mm and a cylindrical tungsten core rod 25 having a diameter of 0.8 mm are arranged in the center as shown in FIG. A plurality of turns of a tungsten coil 26 are wound around the tip of the core rod, and at least both sides of the coil portions 27a and 27b, which are cooling sections during lamp lighting, are cut so as to be orthogonal to the cylinder axis, and the anode 24 that does not project its tip is formed. It is sealed. The distance between the anode and the cathode (arc length) is 5 mm. Furthermore, the arc tube of this lamp has an internal volume of about 0.8 cc,
The lamp was of a spheroidal shape having an outer diameter of 13 mm and an inner diameter of 10 mm, and was of the same type as the lamp, but was filled with the same amount of additives. Then, an experiment was carried out by lighting with a DC electronic ballast with a lamp voltage of 65 V, a starting current of 7 A, and a stable current of 3.8 A. As a result, there was little change in the illuminance distribution on the screen throughout the life period and the image quality was good. Met. Further, the tip of the anode after lighting for 1000 hours had a shape as shown in FIG.

As described above, in order to prevent the deviation caused by the arc current generated at the center of the anode being melted by the lamp current and the arc tip being melted, the cooling action is evenly performed with respect to the axial center of the anode core rod. By providing the ring-shaped cooling part so that the arc occurs, melting can occur and the arc origin can be centered on the axis, the change in the illuminance distribution on the screen during the life can be suppressed, and a high-quality screen can be obtained. Also, since the end of the tip coil has a long and slender tail, it is good to push it toward the core rod forming a cylinder mechanically, and fix it to the coil surface away from the tip with argon plasma etc. It was good. If the arc length of the short arc metal halide lamp exceeds 10 mm, the lamp current can be designed to be small, and the cooling effect from the coil end is great, so even with a general coil type electrode, the above-mentioned phenomenon occurs until the end of life. Therefore, the present invention has an arc length of 10
It is applicable to short arc metal halide lamps of mm or less.

[0014]

As described above, the short arc metal halide lamp and the optical device using the same according to the present invention emit light in addition to the advantages of a direct-current lighting lamp such as downsizing of a ballast and easy handling. There is no deformation of the anode, which is one of the electrodes of the tube, and the change in the illuminance distribution on the screen due to the instability of the arc is small,
There is an advantage that a high quality screen can be obtained. Further, since a long-life lamp can be obtained, there is an advantage that a video device as an optical device with high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an optical device according to the present invention.

FIG. 2 is a side view and a perspective view of an anode also used in the short arc metal halide lamp.

FIG. 3 is a side view and a perspective view of another anode similarly used in the short arc metal halide lamp.

FIG. 4 is a side view of essential parts showing a change in the anode shown in FIG. 2 after being lit for 1000 hours.

5 is a side view of a main part showing a change of the anode shown in FIG. 3 after being lit for 1000 hours.

FIG. 6 is a side view of an anode used in a conventional short arc metal halide lamp.

7 is a side view of essential parts showing a deformation of the anode shown in FIG. 6 after being lit for 1000 hours.

[Explanation of symbols]

 1 Short arc metal halide lamp 2 Anode 3 Cathode 4a, 4b Seal part 5a, 5b Molybdenum foil 6 Reflective and heat-retaining film 7 Base part 8 Trigger wire 11 Reflector 12 Cold mirror 13 Mounting hole 14 Adhesive 15 Nickel sleeve 16 Nickel lead wire 17 Through hole 18 Metal terminal 21 Tungsten core rod 22 Tungsten coil 23a, 23b Coil part 24 Anode 25 Tungsten core rod 26 Tungsten coil 27a, 27b Coil part

Claims (2)

[Claims] 1. A short arc metal halide in which an anode and a cathode are sealed at both ends of a quartz arc tube and at least a metal halide is sealed inside, and the arc length between the electrodes is 10 mm or less for direct current lighting. In the lamp, the anode is formed by winding a tungsten coil around the tip of a cylindrical tungsten rod, and at least coil portions at both ends of the coil portion, which are cooling portions, are orthogonal to the cylindrical rod. A short arc metal halide lamp composed by cutting. 2. A light source device comprising a combination of the short arc metal halide lamp according to claim 1 and a reflecting mirror having a concave surface, which is used in a liquid crystal projector. Optical device using a short arc metal halide lamp.