JPH0711942B2 - Image projection device - Google Patents

Description

The present invention relates to an image projection device such as a projector device using a metal halide lamp as a light source.

(Prior Art) As means for enlarging and projecting an image of characters, tables, figures, etc. on a display surface, a projector or a magic lamp has been known for a long time, and recently a projector device has been known.

As shown in FIG. 2, the basic principle of these image projection devices is a light source 1, a light condensing device such as a reflector 2 for condensing light emitted from the light source, and the reflector 2.
And a projection device such as an optical system lens 4 for projecting the light condensed by the projection surface such as the screen 3 in the case of a liquid crystal projector device. Alternatively, an image such as a graphic is enlarged and projected on the screen 3.

In such an image projection device, a halogen light bulb has been conventionally used as a light source because a predetermined light output is required.

However, since the halogen bulb emits light due to the incandescence of the filament, there are problems that the amount of light is small, the luminous efficiency is low, and the life characteristics are inferior.

If a halogen bulb is used to increase the amount of light, the filament must be upsized, and the lamp is upsized, which causes a problem that the entire image projection apparatus is upsized.

For this reason, recently, a metal halide lamp is often used as a light source. The metal halide lamp has high luminous efficiency, long life, and excellent color rendering properties, and has an advantage of greatly contributing to downsizing of the light source.

As shown in FIG. 1, a metal halide lamp has a pair of electrodes 11 and 11 sealed in an arc tube 10 made of quartz glass or the like, and these electrodes 11 and 11 are connected to an external lead wire 13 via a metal foil conductor 12 or 12. Connected to 13. The illustrated metal halide lamp is of a sealed type at both ends, and has sealed portions 14 and 14 formed at both ends in the axial direction of the arc tube 10. The sealed portions 14 and 14 are provided with the metal foil conductors 12 and 12, respectively. Sealed and these sealing parts 1
Mouth 15,1 connected to external lead wires 13,13 above 4,14
I'm wearing 5.

As for the metal halide lamp, there is also a single-sealed lamp in which a sealed portion is formed on only one side and a pair of metal foil conductors is sealed to the sealed portion, in addition to the above-described sealed type. .

In some cases, such an arc tube is surrounded by an outer tube to have a double tube structure, but a single tube structure in which the arc tube is exposed is preferable from the viewpoint of downsizing of the light source.

The arc tube 10 is filled with mercury as a buffer metal, a metal halide as a light emitting metal, and a rare gas such as argon.

Examples of metal halides include sodium Na and lithium Li
Alkali metal halides are known, including dysprosium Dy, holmium Ho, and thulium Tm.
If a halide of a rare earth metal such as is used, the luminous efficiency is further improved and the color temperature is increased, and the correlated color temperature is 50
There is an advantage that it can be over 00K.

The halogen is combined with these metal iodides are iodine I are used, in conjunction with the rare earth metal iodide dysprosium DyI _3, or iodide holmium HoI _3, it is sealed in the form of such iodide thulium TmI ₃ ing.

(Problems to be Solved by the Invention) However, when only the iodine I is used as the halogen as in the above-mentioned conventional technique and the light emitting tube is enclosed in the arc tube in the form of a rare earth metal iodide, the color temperature of the central portion in the discharge arc is Causes a temperature difference that is higher than the surrounding color temperature, and therefore when projected onto the screen 3, the color temperature in the central portion is high and the color temperature in the peripheral portions and corners is low, causing so-called color unevenness. Is recognized.

This means that when iodine is used as halogen and the arc is expanded together with the rare earth metal, the arc tends to swell, and the color temperature of molecular emission generated at the outer edge of the arc tends to further decrease. Become. Therefore,
The color temperature at the center of the screen corresponding to the light emission at the center of the arc and the color temperature at the peripheral portion or the corner of the screen corresponding to the outer edge of the arc are significantly different.

An object of the present invention is to provide an image projection device capable of eliminating a color temperature difference between a central portion and a peripheral portion in an arc and preventing color unevenness on a screen.

[Structure of the Invention] (Means for Solving the Problems) The present invention relates to an image projection apparatus using a metal halide lamp as a light source, wherein the metal halide enclosed in the arc tube of the lamp is metal iodide and iodine. Other than halogenated metal compounds, and the weight ratio of the metal halide other than the above iodine to the metal iodide is 1: 0.2 to
It is characterized by being regulated in the range of 1: 5.

(Function) When the metal halide enclosed in the arc tube is composed of metal iodide and a metal compound of halogen other than iodine,
That is, when a plurality of kinds of halogens are used, the difference in color temperature in the arc is reduced, so that the color unevenness of the light projected on the screen is reduced.

This is because if the weight ratio of metal halide other than iodine to metal iodide is appropriately set and a plurality of kinds of halogens are used, the arc is narrowed, and therefore the part of molecular emission that emits light at the outer edge of the arc. It is presumed that the difference in color temperature from the light emission at the center of the arc is greatly improved.

(Embodiment) Hereinafter, in addition to the drawings described above, the third embodiment of the present invention will be described.
An embodiment will be described with reference to the characteristic diagrams of FIGS.

The overall structure of the projector device is as shown in FIG. 2, and the structure of the metal halide lamp used as the light source is as shown in FIG.

The above metal halide lamp is a 220 W type, and the electrodes 11 and 11 sealed in the arc tube 10 are electrode shafts 16 respectively.
The electrode shaft 16 is made of tungsten W having a wire diameter of 0.8 mm, and the electrode coil portion 17 is also made of tungsten W having a wire diameter of 0.8 mm. It is wound 3 to 4 times around the tip of 16.

The distance between the tips of the electrodes 11, 11, that is, the distance l between the electrodes, is formed to be about 4 to 10 mm. Therefore, this metal halide lamp is extremely small and is configured to approach a point light source.

The arc tube 10 is filled with a predetermined amount of mercury as a buffer metal, a metal halide, and a rare gas such as argon.

In the case of the present embodiment, the metal halide is a rare earth metal halide, and the rare earth metals of dysprosium Dy, holmium Ho, and thulium Tm are enclosed together in the halogens of iodine and bromine.

Therefore, in the arc tube 10, dysprosium iodide Dy
I ₃ , holmium iodide HoI ₃ , thulium iodide TmI ₃ , dysprosium bromide DyBr ₃ , holmium bromide HoBr ₃ , and thulium bromide TmBr ₃ are enclosed.

In this case, the total enclosed amount of rare earth metal halide is 2
-0 mg / cc, and these inclusions have a rare earth metal iodide to rare earth metal bromide weight ratio of 1: 0.5.

The metal halide lamp having such a structure has initial characteristics shown in the following table.

In a projector device using such a lamp 1 as a light source, when the distribution of color temperature on the screen surface 3 was examined, the characteristics shown by the solid line in FIG. 3 were obtained. Comparing this with the characteristic (indicated by the broken line) when only iodine is used as the halogen as in the conventional case, it can be seen that the difference in color temperature is reduced.

This is because the rare earth metal bromide is present in addition to the rare earth metal iodide, so the thickness of the arc generated between the electrodes is narrowed, which causes the molecular emission portion that emits light at the outer edge of the arc and the arc. It is presumed that this is because the difference in color temperature from the light emission in the central portion is significantly reduced. Therefore, the uneven color of the light projected on the screen is eliminated.

Therefore, the present inventors investigated the relationship between the enclosed weight ratio of rare earth metal iodide and rare earth metal bromide and the correlated color temperature difference. The color temperature difference was obtained by measuring the maximum color temperature difference between the four corners on the screen and the central portion, and the results are shown in FIG.

Normally, in an image projection device such as a liquid crystal projector device, it is necessary to visually suppress the color temperature unevenness on the projection surface to less than 1000K. Therefore, according to the result shown in FIG.
It can be seen that the encapsulation weight ratio of metal bromide to metal iodide must be at least 0.2.

On the other hand, when the enclosed weight ratio of metal iodide and metal bromide was variously changed and the luminous flux maintenance factor was examined by experiments,
The results shown in the figure were obtained.

From FIG. 5, it can be seen that the luminous flux maintenance factor tends to decrease as the enclosed weight ratio of metal bromide to metal iodide increases.

In this type of image projection apparatus, it is necessary that the luminous flux maintenance factor is practically at least 60% at a life of 2000 hours, but if the enclosed weight ratio of metal bromide to metal iodide is 5 or less, the above required characteristics are obtained. Can be satisfied.

In addition, in the case where a metal halide of chloride, for example, was enclosed together with the metal iodide instead of the metal bromide, various experiments were conducted, and the same result as that in the case where the above metal bromide was enclosed was obtained. Was given.

From the above results, if the weight ratio of the metal halide other than iodine to the metal iodide is 1: 0.2 to 1: 5,
Color unevenness on the projection surface can be significantly reduced without impairing practicality.

The present invention is not limited to the above embodiment,
For example, tin halide may be added to prevent premature blackening due to electrode wear.

Further, the structure of the arc tube may be a single-sealing type lamp in which a sealing portion is formed only on one side, and further, the arc tube may be surrounded by an outer tube to have a double tube structure, or the light source may be A single-tube structure in which the arc tube is exposed to reduce the size may be used.

Furthermore, the present invention may be a projector, a magic lamp, etc., other than the projector device.

[Effects of the Invention] As described above, according to the present invention, the color temperature difference between the central portion and the peripheral portion in an arc can be reduced, and the uneven color of light projected on the screen can be eliminated.

[Brief description of drawings]

FIGS. 1 and 2 are commonly used to describe one embodiment of the present invention and the background art. FIG. 1 is a diagram of a reflector and a metal halide lamp, FIG. 2 is a principle diagram of a projector device, and FIG. 5 to 5 are characteristic diagrams. 1 ... Metal halide lamp (light source), 2 ... Reflector (light collector), 3 ... Screen (projection surface), 4 ...
Lens (projection device), 5 ... Liquid crystal display surface, 10 ... Arc tube, 11 ... Electrode, 12 ... Metal foil conductor, 13 ... External lead wire, 14 ... Crushing seal part, 15 ... Base , 16 …… Electrode shaft, 17
...... Electrode coil.

Claims (1)

[Claims] 1. A light source, a condenser for condensing light emitted from the light source, and a projector for projecting the light condensed by the condenser on a projection surface, and the metal halide as the light source. This metal halide lamp is used in an image projection apparatus in which mercury, a metal halide containing at least iodine and a rare earth metal, and a rare gas are enclosed in an arc tube having electrodes sealed therein. The metal halide comprises a metal iodide and a metal compound of halogen other than iodine,
An image projection apparatus, characterized in that the weight ratio of the metal halide other than the above iodine to the metal iodide is in the range of 1: 0.2 to 1: 5.