JPS61104560A - Microwave electric-discharge light source - Google Patents

Abstract

PURPOSE:To minimize the luminous intensity reduction and the luminous nonuniformity of the electrodeless lamp installed in a microwave cavity resonator by locating the antenna of the magnetron used as an output terminal for microwaves in the cavity resonator. CONSTITUTION:The antenna 16 of a magnetron 11 is directly placed in a cavity resonator 18 through a hole 22 formed in the base 18a of the cavity resonator 18. Microwaves radially discharged from the antenna 16 are directly applied to an electrodeless lamp 23 to produce plasma in an emitter tube 24 in the electrodeless lamp 23. As the electrodeless lamp 23 is located in the focus of the cavity resonator 18, light reflected by its light-reflecting surface 20 is raliably introduced toward an opening 19 thereby efficiently drawing light out from the cavity resonator 18. By thus discharging the microwaves into the cavity resonator 18 without causing them to pass through a waveguide or a similar part, the attenuation and reflection of the microwaves are prevented. Consequently, it is possible to minimize the luminous intensity and the luminous nonuniformity of the electrodeless lamp 23.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a light source device using microwave discharge.

[Technical background of the invention]

Electrodeless light sources that utilize microwave discharge have recently attracted attention for their long lifespan, and attempts have been made to use them, for example, as light sources for drying UV sand-curing inks.

Incidentally, as this type of electrodeless light source, one having a configuration as shown in FIG. 2, for example, is conventionally known.

That is, inside the box-shaped device main body 1, there is a hollow microwave cavity resonator 3 having an opening 2 at one end for extracting light.
and a magnetron 4 are arranged, and this cavity resonator 3
Inside, microwaves emitted from the microwave output section 5 of the magnetron 4 are guided through a waveguide 6 and a feeding lower provided on the circumferential surface of the cavity resonator 3. In this microwave cavity resonator 3, for example, an electrodeless lamp 8 made of a quartz bulb sealed with a discharge medium is installed, and when microwave waves are applied to this electrodeless lamp 8, A discharge occurs in the internal discharge medium,
For example, ultraviolet light of 200 nm or less is generated, and this ultraviolet light is radiated outward through the opening 2.

[Problems with background technology]

By the way, when guiding microwaves to the cavity resonator 3 through the waveguide 6 as described above, the microwaves emitted from the microwave output section 5 are gradually attenuated in the process of passing through the waveguide 6. At the same time, as shown by the imaginary line in FIG. There was a drawback that the light emission intensity of the electrodeless lamp 8 was also reduced.

In addition, a part of the reflected microwave is applied to the electrodeless lamp 8 through the feeding lower part while repeating multiple reflections, but the mode of the microwave is directly from the microwave output section 5 without being reflected. Since this mode is different from the normal mode of the microwave applied to the electrodeless lamp 8, the presence of multiple modes due to this reflection causes uneven light emission in the electrodeless lamp 8.

[Purpose of the invention]

The present invention was made based on these circumstances, and
The purpose of the present invention is to provide a microwave discharge light source device which can reduce microwave attenuation and mode disturbance, and can correspondingly suppress a decrease in emission intensity and uneven emission of an electrodeless lamp.

[Summary of the invention]

That is, in order to achieve the above object, the present invention is characterized in that an antenna, which is the output end of the microwave of a magnetron, is provided directly within a microwave cavity resonator housing an electrodeless lamp.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on FIG.

In the figure, 11 is a magnetron that generates microwaves, and inside the case 12 that houses this magnetron 11,
A cooling fan 13 is provided. In addition, the code 14
15 is a motor for driving the fan, and 15 is a power source for the magnetron 11.

The magnetron 11 is equipped with an antenna 16 that emits microwaves radially, and this antenna 16 is led out through an opening 12a at one end of the case 12.
Its outer periphery is covered with a cover 17 made of quartz glass that is transparent and magnetically permeable to prevent spatter.

A metal microwave cavity resonator 18 (hereinafter referred to as cavity resonator) is connected to one end opening 12 a of the case 12 . The cavity resonator 18 of this embodiment has a peripheral wall shaped like a paraboloid of revolution, and has an opening 19 for extracting light at one end opposite to the apex 18a.
The inner surface of this cavity resonator 18 is finished into a light reflecting surface 20 by, for example, vapor-depositing aluminum.

Such a cavity resonator 18 has a top portion 18a.
is directly connected to the case 12 by overlapping it with the opening 12a at one end of the case 12 via the gasket 21, and at this time, the antenna 16 of the magnetron 11 is connected through the through hole 22 formed in the top 18a of the cavity resonator 18. It is located directly within the cavity resonator 18.

Further, an electrodeless lamp 23 is housed at a focal point within the cavity resonator 18 . This electrodeless lamp 23 has a spherical arc tube 24 made of quartz glass, and inside the arc tube 24, for example, mercury as a discharge medium is contained at a partial pressure of 5 x 10' Torr (operating pressure: 3 Torr). Nitrogen gas is also filled as a starting rare gas to a depth of several to ten Horrors. Then, this electrodeless lamp 23 is connected to the cavity resonator 1 via a support 25° 25.
It is supported at the focal position within 8.

Note that the opening 19 of the cavity resonator 18 is provided with a metal mesh 2 that allows light to pass through but prevents microwave leakage.
6 is posted. In this case, the microwave shielding effect is determined by the size of each mesh of the mesh body 26 and the aperture ratio occupied by the mesh, and according to experiments conducted by the present inventors, although it depends on the thickness of the mesh body 26, It has been confirmed that when the average opening area of the mesh is smaller than 0.2 cM and the ratio of the opening area of the mesh is less than 60%, passage of microwaves is substantially blocked.

Next, the operation of the above configuration will be explained.

First, the magnetron 11 is operated, and its antenna 16 is
emit microwaves from. At this time, since the antenna 16 is present in the cavity resonator 18 in which the electrodeless lamp 23 is housed, the microwaves emitted radially from the antenna 16 are directly incident into the cavity resonator 18, and the electrodeless lamp 23 is placed inside the cavity resonator 18. applied to the lamp 23. As a result, the electrodeless lamp 2
A discharge (plasma) is excited in the arc tube 24 of No. 3, and ultraviolet rays generated by this discharge are radiated into the cavity resonator 18. A part of the ultraviolet rays directly passes through the net 26 of the opening 19 and is irradiated outward, while the rest is reflected by the light reflecting surface 20 and then passes through the net 26 and irradiates outward. is irradiated. At this time, since the electrodeless lamp 23 is installed at the focal point of the cavity resonator 18, the light reflecting surface 23
The reflected light is reliably guided to the opening 19 side, and the light can be extracted efficiently.

According to such an embodiment of the present invention, the antenna 16 is located inside the cavity resonator 18, and the microwave is made to enter the cavity resonator 18 without passing through any waveguide or the like. Attenuation and reflection of this microwave are eliminated. Therefore, a decrease in the luminous intensity and uneven luminescence of the electrodeless lamp 23 can be suppressed accordingly.

In particular, in the case of this embodiment, since the antenna 16 is provided at the top 18a of the cavity resonator 18 having a paraboloid of revolution shape, the intensity distribution of the microwave within the cavity resonator 18 is as shown in FIG. As shown by the imaginary line, it becomes maximum at the focal point of the cavity resonator 18, and it becomes possible to make this microwave closer to a so-called single mode with less noise. Therefore, if the electrodeless lamp 23 is installed at the focal position as in this embodiment, the electrodeless lamp 23
On the other hand, microwaves can be guided almost uniformly from the outer periphery, and uneven light emission can be further improved.

In the present invention, the electrodeless lamp is not limited to a spherical shape, but may be rod-shaped, and the cavity resonator may also be formed in the shape of an elongated gutter.

Further, the discharge medium sealed in the electrodeless lamp is not limited to mercury, but may be changed to, for example, hydrogen, krypton, or xenon gas, or a mixed gas thereof depending on the light to be obtained.

In addition, in the above embodiment, the opening of the cavity resonator is coated with a mesh that prevents microwave leakage, but if the equipment that incorporates this light source device and uses it has a microwave leakage prevention function. , this mesh may be omitted.

〔Effect of the invention〕

According to the present invention described in detail above, the microwave emitted from the antenna is immediately incident on the microwave cavity resonator housing the electrodeless lamp, so that attenuation and reflection of the microwave are eliminated. Therefore, the decrease in the emission intensity of the electrodeless lamp is suppressed to a small level, and the mode of the microwave applied to the electrodeless lamp is almost the same as that when emitted from the antenna, and the disturbance of this microwave is reduced. This has the advantage that uneven light emission can be suppressed to a small level.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional microwave discharge light source device. 11... Magnetron, 16... Antenna, 18.
...Microwave cavity resonator, 19...opening, 23.
・Electrodeless lamp.

Claims (3)

[Claims] (1) A magnetron that generates microwaves, a microwave cavity resonator into which the microwaves are incident and which has an opening for extracting light at one end, and a microwave cavity resonator housed within the microwave cavity, and an electrodeless lamp enclosing a discharge medium that is discharged by the microwave, and an antenna, which is an output end of the microwave of the magnetron, is provided directly within the microwave cavity. Microwave discharge light source device. (2) The microwave cavity resonator has the shape of a paraboloid of revolution, and the antenna is located at the apex thereof, and
Claim 1, characterized in that an opening is located opposite to this apex, and the electrodeless lamp is located at the focal point of the paraboloid of rotation of the microwave cavity resonator.
) The microwave discharge light source device described in item ). (3) The microwave discharge light source device according to claim (2), wherein the electrodeless lamp is spherical.