JPH07320690A - Metal halide lamp device - Google Patents

Abstract

PURPOSE:To provide a metal halide lamp excellent in optical characteristics by alleviating shade and shallow by lamp constituents at a projecting surface in a liquid crystal projector or high brightness by a hot spot of an arc so as to eliminate color unevenness and luminance unevenness. CONSTITUTION:A light emitting tube 1 is combined with a cup-like reflection mirror. Electrodes 2 are sealed at both ends of the light emitting tube 1, where a distance between the electrodes 2 is smaller than 5mm. Mercury, noble gas and metal halide are enclosed inside of the light emitting tube 1. A wall surface load is set to 40W/cm or higher. The electrodes 2 are disposed on the optical axis of the reflection mirror. In this light emitting tube 1, an exhaust pipe chip-off portion 5 and a glass thick portion are positioned at the opening of the reflection mirror. The tip of the thick portion by the chip-off is formed smaller than the maximum diameter of the light emitting tube 1. Light emitted from the chip-off portion is prevented from being directly emitted into an optical aperture disposed in front of the reflection mirror.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp device which is a light source mainly for video equipment or optical equipment used only in an arc tube without providing an outer tube, and more particularly to improvement of the arc tube shape.

[0002]

2. Description of the Related Art Conventionally, a short arc metal halide lamp, which is used only by an arc tube without using an outer tube, has been used in an overhead projector (OHP), a projector, a liquid crystal projector and the like. This short arc metal halide lamp is used by controlling the light by using a reflecting mirror together depending on its application. In this case, since it is easier to control the light by the reflecting mirror when it is closer to a point light source, the distance between the electrodes at both ends is 5 mm or less.

Further, this lamp is required to have little illuminance, color unevenness, etc. on the screen projected from the above-mentioned applications. For this reason, various improvements have been made to the arc tube. For example, the outer surface of the arc tube is frosted to diffuse the light so as to alleviate the lightness due to the hot spot of the arc between the electrodes, and to eliminate the shadow of the arc tube constituent members and the like.

Further, in order to eliminate the shadow on the screen of the exhaust pipe tip off portion formed on the outer surface of the arc tube for exhausting and enclosing the inside of the arc tube, the tip off portion is flattened. . FIG. 2 shows a conventional example, and 21 is a quartz glass arc tube tare, which is substantially spherical. Reference numeral 22 is an electrode attached by connecting the molybdenum foil 23 at the sealing portions at both ends of the arc tube. Reference numeral 24 is a molybdenum external lead wire connected to the molybdenum foil 23, and 25 is an exhaust pipe tip-off portion. In the arc tube, dysprosium iodide, neodymium iodide, and cesium iodide are enclosed as luminous metals, and a predetermined amount of mercury is enclosed as a buffer gas and argon is enclosed as a starting auxiliary gas.

[0005]

However, when the arc tube is frost-processed, the effective utilization rate of light by the reflecting mirror is reduced, and accordingly the screen illuminance is reduced. Further, when the exhaust pipe tip-off portion is crushed, there is a problem in that it is not possible to completely eliminate color unevenness and illuminance unevenness on the projection screen.

The present invention has been made in view of the above, and is strong due to a shadow of a lamp constituent member on a projection surface or a hot spot of an arc on a projection surface in a metal halide lamp device for a projector which is used only by an arc tube without using an outer tube. An object of the present invention is to provide a metal halide lamp device having excellent optical characteristics by relaxing the lightness and eliminating unevenness in color and unevenness in illuminance.

[0007]

The present invention is constructed by combining an arc tube without an outer tube and a bowl-shaped reflecting mirror, and the arc tube is sealed with at least a main electrode at both ends and the distance between the electrodes is 5 mm.
In a double-mouthed short arc metal halide lamp device, in which a metal halide is enclosed together with mercury and a rare gas at a thickness of mm or less, a wall load is 40 W / cm ² or more, and the reflection mirror is arranged on the optical axis, The exhaust pipe tip-off portion of the arc tube and the glass wall portion due to the tip-off are located on the bowl-shaped reflector opening side, and the light emitted from the tip-off portion passes through the reflector and the front surface of the reflector. It is characterized in that it is formed so as to be displaced toward the reflecting mirror opening side so as not to be directly incident on the aperture of the optical system arranged at. Further, the tip of the thick glass portion due to the tip-off of the exhaust pipe is formed so as to be smaller than the maximum diameter of the arc tube and not to exceed the maximum diameter. Further, the heat insulating film applied to the outer surface of the arc tube on the opening side of the reflecting mirror is applied so as to include at least the chip-off part. The bowl-shaped reflecting mirror used in combination with the arc tube has a spherical surface, a spheroidal surface, or a paraboloid of rotation.

[0008]

With the above structure, the exhaust pipe tip-off portion is located on the reflector opening side, and the light emitted from the tip-off portion is shifted to the reflector opening side so as not to directly enter the aperture. Since there is no shadow on the screen, there is no uneven color. Also, since the glass wall thickness portion of the exhaust pipe tip-off portion is formed smaller than the maximum diameter of the arc tube,
The projection screen characteristics can be improved. Further, even when the exhaust pipe tip-off portion is located at the coldest portion of the arc tube or the like, by applying the heat-retaining film to at least the tip-off portion, the luminous characteristics of the lamp are not significantly deteriorated.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a side view of a metal halide lamp. Reference numeral 1 is a quartz glass arc tube tare which has a substantially spherical shape and has a maximum inner diameter of 9 mm, a maximum outer diameter of 11 mm and an internal volume of about 0.5 cc. Reference numeral 2 denotes an electrode attached by connecting the molybdenum foil 3 at the sealing portions at both ends of the arc tube tare.
The distance between the two is usually set to 5 mm. Reference numeral 4 is an external lead wire made of molybdenum connected to the molybdenum foil 3, and 5 is an exhaust pipe tip-off portion. In the arc tube, dysprosium iodide, neodymium iodide and cesium iodide as light emitting metals are enclosed, and a predetermined amount of mercury as a buffer gas and 200 torr of argon as a starting auxiliary gas are enclosed. This arc tube is constructed as a lamp with a wall load of about 59 W / cm ² without an outer tube, and is AC-lit with a tube input of 150 W using a dedicated electronic ballast. In addition, a reflective film having visible light reflecting, ultraviolet and infrared transmitting properties is vapor-deposited on the reflecting surface of this lamp, and the focal distance f = 13 m.
A reflective parabolic mirror with an aperture of 100 mm and an aperture diameter of 100 mm constitutes a liquid crystal projector with a 3-inch diagonal aperture and a predetermined optical system on its front surface so that the projected light has predetermined screen characteristics. Set.

Next, an experimental example will be described. First, a lamp (lamp No. 1) in which the conventional exhaust pipe tip-off part 25 shown in FIG. 2 is located at the maximum diameter part of the arc tube (center of arc tube).
And a lamp (lamp No. 2) in which the exhaust pipe tip-off part shown in FIG. 3 is displaced 1 mm from the maximum diameter part of the arc tube to the opening side (right side in the drawing) of the rotating parabolic reflector, the same as shown in FIG. 2m
A m-shifted lamp (Lamp No. 3) and a 3 mm-shifted lamp (Lamp No. 4) similar to that shown in FIG. 5 were manufactured, and the type and amount of the enclosed metal halide and the heat insulating film coating area were constant. It was created. The thickness of the heat retaining film is almost the same, and only one side (the right side in each drawing) is applied.

Then, the respective lamps are projected on a 40-inch screen using a specific optical system, and when the average of the illuminances at the center of the screen divided into nine equal parts (average illuminance) is made constant, unevenness in color and illuminance is observed. The average illuminance and the color unevenness were compared for each lamp when the minimum / maximum value (illuminance ratio) of the illuminance at the center divided into 9 equal parts was constant. The results are shown in Tables 1 and 2. In addition, color unevenness is on the screen,
The maximum value of the chromaticity difference between the central chromaticity and each measurement point.

[0012]

[Table 1]

[0013]

[Table 2]

As can be seen from Tables 1 and 2, in the conventional example, the chip-off portion appears as a shadow (a point where the illuminance is low) on a portion of the projection screen. As a result, when the average illuminance is constant, the illuminance ratio is constant. descend. Further, when the illuminance ratio is constant, the average illuminance becomes a low value because the illuminance ratio cannot be earned unless the overall illuminance is reduced in accordance with the shadowed area on the screen. This means that the tip of the exhaust pipe is 1 mm
Even if the lamp is shifted and the lamp is shifted by 2 mm, the portion that appears as a shadow on the screen is reduced, but since the shadow cannot be completely erased, the screen characteristics are deteriorated.

On the other hand, in the lamp in which the exhaust pipe tip-off portion is displaced by 3 mm, even if the light emitted from the tip-off portion is reflected by the reflecting mirror, the light is shielded by the aperture and does not appear as a shadow on the projection screen. Therefore, good characteristics can be obtained without deterioration of the screen characteristics. As for the color unevenness on the screen, it can be seen from the results that the shadows appearing on the projection screen increase the color difference and deteriorate the characteristics.

Next, a second experimental example will be described. A lamp having the same specifications as the lamp (lamp No. 4) in which the exhaust pipe tip-off portion used in Experiment 1 was shifted by 3 mm was prepared, and the size (height) of the glass wall portion of the tip-off portion was changed, A comparative experiment of screen characteristics similar to that of Experiment 1 was conducted. The size of the thick glass portion was set as shown in FIGS. 1, 5 and 6 and 7, and three types of lamps were produced. (A) 1 mm (Figs. 1 and 5, Lamp No. 4) (b) 2 mm (Fig. 6, Lamp No. 5) (c) 3 mm (Fig. 7, Lamp No. 6) The results are shown in Tables 3 and 4. Show.

[0017]

[Table 3]

[0018]

[Table 4]

As is clear from Tables 3 and 4, comparing the screen characteristics by changing the size of the thick portion of the chip-off, the wall thickness increases (the height in the direction perpendicular to the arc tube axis increases. ) Therefore, it can be seen that the characteristics deteriorate. This is because the thick portion becomes larger than the maximum diameter of the arc tube and protrudes beyond the maximum diameter, which obstructs the light emitted from the reflecting mirror and appears as a thin shadow on the projection screen. Further, since the chip portion becomes thicker, the light emitted from the chip-off portion is further refracted and becomes stray light, which causes deterioration of screen characteristics.

Further, a third experimental example will be described. The size of the arc tube was changed to 11 mm and the total length of the light emitting section was 13 mm. An elliptical arc tube was used to create a lamp with an electrode distance of 3 mm, and the position of the tip-off section with good screen characteristics was determined. As shown in FIG. 8, it is on the back side of the electrode coil of the arc tube. The back side of this coil is originally a region that is likely to be the coldest part of the arc tube, and if the chip-off part is formed here, the emission characteristics of the arc tube will be degraded. Therefore, using this lamp, a heat insulating film was applied to the outer surface of the arc tube in order to eliminate the coldest part, and the optimum application range was determined. The application range of the heat insulating film was as follows. (A) No heat insulating film was applied. (Figure 8, Lamp No. 7) (b) The amount of heat insulating film applied is up to half of the tip-off part. (Fig. 9, Lamp No. 8) (c) The amount of heat insulating film applied is up to the entire tip part off part. (FIG. 10, Lamp No. 9) However, the thickness of the heat insulating film and the type and amount of the enclosed metal halide were the same. Then, this evaluation method was performed by the background ratio to the mercury peak at 546 nm from the spectral distribution chart of the arc tube alone. The results are shown in Table 5.

[0021]

[Table 5]

As is clear from Table 5, the temperature of the coldest part is strongly controlled in the lamp not coated with the heat insulating film, and as a result, the mercury peak becomes high, and the emission characteristic is not high in the background and the spectral distribution is poor. Further, by coating the heat insulating film by half or more from the center of the chip-off portion, the mercury peak is lowered, the background is raised, and the lamp has a good spectral distribution.

As is clear from the above experimental results and Tables 1 to 5, the exhaust pipe tip-off portion and the glass wall portion due to the tip-off are located on the reflector opening side and emitted from this tip-off portion. Good projection screen characteristics can be obtained by forming the light so as not to directly enter the aperture on the front surface via the reflecting mirror so as to be shifted toward the opening of the reflecting mirror. Further, if the thick glass portion due to the exhaust pipe tip off is formed smaller than the maximum diameter of the arc tube and is not outside the maximum diameter, the screen characteristics can be further improved. Furthermore,
Even when the exhaust pipe tip-off portion is located at the coldest portion of the arc tube, by applying the heat-retaining film within at least half the range of the tip-off portion, it is possible to prevent the emission distribution from being significantly reduced.

[0024]

As described above, the metal halide lamp device according to the present invention has a relatively simple structure and has optimum lamp characteristics as a light source for video equipment and the like, and is excellent in color unevenness and illuminance unevenness. Excellent screen characteristics can be obtained. Further, there are advantages that not only the projection screen characteristics can be improved, but also the light emission characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a side view showing an arc tube of a metal halide lamp according to the present invention.

FIG. 2 is a side view showing an arc tube of a conventional metal halide lamp.

FIG. 3 is a side view showing an arc tube of the metal halide lamp used in Experimental Example 1.

FIG. 4 is a side view showing an arc tube of the metal halide lamp used in Experimental Example 1.

FIG. 5 is a side view showing an arc tube of a metal halide lamp used in Experimental Examples 1 and 2.

6 is a side view showing an arc tube of a metal halide lamp used in Experimental Example 2. FIG.

7 is a side view showing an arc tube of a metal halide lamp used in Experimental Example 2. FIG.

FIG. 8 is a side view showing an arc tube of a metal halide lamp used in Experimental Example 3.

9 is a side view showing an arc tube of a metal halide lamp used in Experimental Example 3. FIG.

FIG. 10 is a side view showing an arc tube of a metal halide lamp used in Experimental Example 3.

[Explanation of symbols]

 1 Arc tube 2 Electrode 3 Molybdenum foil 4 External lead wire 5 Exhaust tube Chip off part

Claims (4)

[Claims] 1. An arc tube not provided with an outer tube and a bowl-shaped reflector are combined to form at least main electrodes on both ends of the arc tube, the distance between the electrodes is 5 mm or less, and mercury is internally contained. In a double-ended short arc metal halide lamp device, in which a metal halide is enclosed together with a rare gas, a wall load is 40 W / cm ² or more, and the reflecting mirror is arranged on the optical axis, the arc tube is exhausted. The tube tip-off portion and the glass wall portion due to the tip-off are located on the bowl-shaped reflecting mirror opening side, and the light emitted from this tip-off portion is arranged in front of the reflecting mirror through the reflecting mirror. A metal halide lamp device that is formed so as to be displaced toward the opening of the reflecting mirror so that it does not directly enter the aperture of the optical system. 2. The metal halide lamp device according to claim 1, wherein the tip of the thick glass portion due to the tip-off of the exhaust pipe is formed so as to be smaller than the maximum diameter of the arc tube and not to exceed the maximum diameter. . 3. The metal halide lamp device according to claim 1, wherein the heat insulating film applied to the outer surface of the arc tube on the opening side of the reflecting mirror is applied so as to include at least the chip-off part. 4. The metal halide lamp device according to claim 1, wherein the bowl-shaped reflecting mirror used in combination with the arc tube has a spherical surface, a spheroidal surface, or a paraboloid of rotation.