JPH0247598Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a microwave discharge light source device that utilizes microwave discharge.

BACKGROUND ART Recently, light source devices that use high-frequency discharge, particularly microwaves as high-frequency waves, have been attracting attention as light source devices that utilize electric discharge. In conventional light source devices with electrodes, the life of the lamp is determined by the wear and tear of the electrodes, but in light source devices using microwaves, the lamp can be made electrodeless, so the lamp life can be extended.

Furthermore, since there is no heat loss due to electrodes, and the difference in discharge impedance is small between the initial state and the stable state, it is easy to inject power in the initial state even when impedance matching is performed in the stable state. Another characteristic is that the time it takes to reach maximum output is short because the power is concentrated on the lamp tube wall.

FIG. 1 is a longitudinal cross-sectional view showing the configuration of a microwave discharge light source device previously devised by the present inventors that takes advantage of these features, in which 1 is a magnetron, 2 is a magnetron antenna, 3 is a waveguide, and 4 is a A microwave cavity whose inner wall is rotationally symmetrical; 5 is a microwave power feed port provided at the junction of the cavity 4 and the waveguide 3; 6 is a spherical discharge lamp; 7 is a spherical discharge lamp; A fan for cooling the magnetron 1 and the discharge lamp 6; 8 is a vent provided in a part of the waveguide 3;
9 is a mesh plate that covers the front surface of the cavity 4; 10 is a box that covers the magnetron 1, the waveguide 3, the cavity 4, etc.; 1;
1 is a support rod that supports the discharge lamp 6.

Next, the operation will be explained. Microwaves generated by the magnetron 1 are radiated into a waveguide 3 through a magnetron antenna 2.

This microwave propagates through the waveguide 3 and feeds into the feed port 5.
is radiated into the cavity 4 through the microwave, forming a microwave electromagnetic field within the cavity 4. Due to this microwave electromagnetic field, the gas in the discharge lamp 6 is discharged, the inner wall of the discharge lamp is heated, the metal such as mercury in the tube is evaporated and gasified, and the discharge shifts to a discharge of metal gas. At this time, light with a specific emission spectrum depending on the type of metal is generated, and this is used as a light source. In order to effectively utilize the light from the lamp 6, the rear surface of the cavity 4 is used as a reflector, and the front surface is a metal mesh plate 9 that blocks microwaves but transmits light.
It is configured to emit light only in the forward direction. On the other hand, since the magnetron 1 and the discharge lamp 6 need to be cooled during operation, the magnetron 1 is cooled by the cooling fan 7, and this cooling air is guided to the vent 8 by the ventilation hood 12, and the waveguide 3 and the power supply Mouth 5
After the lamp 6 is cooled down, it is exhausted from the mesh plate 9.

Further, FIG. 2 is a longitudinal sectional view showing the structure of another microwave discharge light source device according to the prior invention, in which a vent hole 8 is provided in the cavity 4. In this case as well, the cooling fan 7
Since there is no vent in the box body 10, this cooling air is guided into the cavity 4 through the vent 8, cools the lamp 6, and then is exhausted from the mesh plate 9. Ru.

On the other hand, after the discharge lamp 6 is turned off, the internal pressure remains high because the temperature is high. However, when the gas pressure is high, the discharge starting voltage increases along with the gas pressure.
That is, even if the temperature of the discharge lamp 6 is high after the discharge lamp 6 is turned off, it may not be possible to turn it on. The time until the discharge lamp 6 can be turned on again after being turned off depends on the cooling state of the discharge lamp 6 after being turned off. In the above-mentioned conventional device, cooling air introduced through a waveguide or a mesh-shaped vent 8 formed in a cavity is used to cool the discharge lamp 6. Therefore, the discharge lamp 6
The wind speed of the cooling air was slow on the outer walls of the building, so the cooling capacity was insufficient after the lights were turned off, and it took a long time before the lights could be turned on again.

This idea was made to solve the above-mentioned problem of the long time it takes to relight the lamp.By locally cooling the discharge lamp, it is possible to create a microwave discharge light source device that takes a short time to relight. is intended to provide.

FIG. 3 is a longitudinal sectional view showing the configuration of an embodiment of this invention, in which 71 is a fan for cooling the magnetron and discharge lamp, 14 is a ventilation hood, and 15 is a fan that penetrates a part of the cavity 4. It is a connected metal pipe and also has a microwave shielding effect. A dielectric pipe 16 is inserted, for example, into the metal pipe 15, and its tip is protruded into the cavity 4 and is provided close to the outer wall of the discharge lamp 6.

In this device, the cooling air from the fan 71 first cools the magnetron 1, is guided to the metal pipe 15 by the ventilation hood 14, and is directed to the dielectric pipe 16.
Through the discharge lamp 6, there is a discharge lamp 6 in close proximity to the outer wall of the discharge lamp 6.
It is sprayed in the direction of The discharge lamp 6 is cooled and exhausted from the mesh plate 9. The outlet of the dielectric pipe 16 has a narrow outlet and the cooling air is blown very close to the outer wall of the discharge lamp 6. Compared to conventional devices, the cooling air is blown onto the part of the outer wall of the discharge lamp 6 facing the pipe. , the wind speed is increasing. Therefore,
The discharge lamp 6 is locally well cooled and its temperature drops quickly. On the other hand, the internal pressure of the discharge lamp 6 is determined by the coldest point on the inner wall.

That is, if the temperature of a part of the inner wall is low, vapor such as mercury inside will condense at that part, and the internal pressure will drop. Therefore, after the light is turned off, the time required for the internal pressure to drop to the point where the light can be turned on again becomes shorter. Here, the length of the metal pipe 15 needs to be such that leakage of microwaves in the cavity is below a level (1 mw/cm) that does not pose a safety problem.

When the free space wavelength of the microwave is λcm, the microwave input is Pomatt, and the inner radius of the metal pipe is acm, the power density P of the leakage radio wave is given by the following equation.

P=Po/πa ² exp(−2α) However, Unless a is less than λ/3.41, the microwave will not be attenuated within the metal pipe. From the above formula, to make P<1mw/ ^cm2 or less For example, when Po = 1KW a = 0.4cm λ = 12.24cm, it is sufficient to set it to 1.6cm or more. In this case, the ventilation hood 14 is not limited to metal, and may be made of dielectric material such as resin.

By the way, the reason why a dielectric material is used for the pipe protruding into the cavity 4 to blow cooling air is that
This is in order not to greatly disturb the microwave electromagnetic field within the
Furthermore, if you use a dielectric material with low dielectric loss, such as a quartz glass pipe, it will be difficult to absorb microwaves.
This is good because it is difficult to get heated.

FIG. 4 is a longitudinal sectional view showing the configuration of another embodiment of this invention, in which the outside air sucked in by the discharge lamp cooling fan 13 is radiated as it is through the ventilation hood 141, the metal pipe 15, and the dielectric pipe 16. Since the electric lamp 6 is cooled, the cooling effect is greater. In this case, the magnetron 1 is cooled using cooling air from the fan 7, which is exhausted from the exhaust port 81.

Furthermore, in the apparatuses shown in FIGS. 3 and 4, by narrowing the tip of the dielectric pipe, the wind speed on the outer wall surface of the discharge lamp 6 can be further increased, thereby further increasing the cooling effect.

As described above, according to this invention, in the microwave discharge light source device, the length and the radius of the circle are a,
Powatt microwave input, microwave wavelength λ
When, a＜λ/3.41,＞(10ogPo−20oga+
25)/√1-(3.41) A microwave cavity having a metal pipe having the relationship of ² , a high-pressure discharge lamp disposed inside the cavity, and a microwave cavity having a metal pipe having the relationship of The discharge lamp consists of a fan that blows air into the cavity, and a dielectric pipe that is inserted or connected to a metal pipe and whose tip protrudes close to the high-pressure discharge lamp inside the microwave cavity. The cooling effect is large, and the time required to turn on the light again after the light is turned off is short. In addition, the metal pipe is effective in simultaneously achieving efficient cooling of the high-pressure discharge lamp and shielding from microwaves.

[Brief explanation of drawings]

1 and 2 are longitudinal cross-sectional views showing the configuration of a conventional microwave discharge light source device, FIG. 3 is a longitudinal cross-sectional view of a microwave discharge light source device according to an embodiment of the invention, and FIG. 4 is a longitudinal cross-sectional view of the conventional microwave discharge light source device. FIG. 3 is a longitudinal cross-sectional view of a microwave discharge light source device according to another embodiment of the invention. In the figure, 4 is a microwave cavity, 6 is a discharge lamp, 13 and 71 are fans, 15 is a metal pipe, 1
6 is a dielectric pipe. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of claim for utility model registration] Length, circle radius a, microwave input
Powatt, when the wavelength of microwave is λ, a＜λ/3.41,＞(10ogPo−20oga+
25)/16√1-(3.41) A microwave cavity having a metal pipe having the relationship of ² , a high-pressure discharge lamp disposed within the cavity, and the above-mentioned pipe at least for a predetermined period of time after the high-pressure discharge lamp is turned off. A micrometer comprising a fan that blows air into the cavity, and a dielectric pipe inserted or connected to the metal pipe so that its tip protrudes close to the high-pressure discharge lamp in the microwave cavity. Wave discharge light source device.