JPH0158621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a microwave discharge light source device that utilizes light emission by microwave discharge.

FIG. 1 shows a conventional microwave discharge light source device. In the figure, 1 is a microwave oscillator that is a magnetron that generates microwaves, 2 is a magnetron antenna, 3 is a waveguide that transmits microwaves, 4 consists of a spherical part 5 and a cylindrical part 6 following it, and a cavity wall made of aluminum or the like;
is a metal mesh plate attached to the flange portion 10 of the cavity wall 4 with a presser flange 8 and a presser screw 9, which blocks microwaves but transmits light. A wave cavity 11 is configured. 12 is a power supply port provided at the joint between the waveguide 3 and the cavity wall 4; 13 is a spherical discharge lamp disposed near the center of the spherical portion 5; it is made of quartz glass or the like; It contains rare gases such as mercury, metals such as iron, and halogens such as iodine.
14 is a protrusion provided on a part of the outer wall of the discharge lamp 13, and one end of a discharge lamp support 15 made of a low-loss dielectric material such as quartz glass is fitted into a flared discharge lamp support 16. It supports the discharge lamp 13. Reference numeral 17 indicates a discharge lamp support support part provided in a part of the cavity wall 4 into which the other end of the discharge lamp support member 15 is inserted and supports it; reference numeral 18 indicates a light emitted from the metal mesh plate 7 to the outside. This is a lens for condensing the light onto an irradiated surface (not shown).

Next, the operation of the microwave discharge light source device configured as described above will be explained. Microwaves generated by the magnetron 1 are radiated into the waveguide 3 through the magnetron antenna 2, and the microwaves propagate through the waveguide 3 and are radiated into the microwave cavity 11 through the feed port 12. and forms a microwave electromagnetic field in the microwave cavity 11. Due to this microwave electromagnetic field, the rare gas in the discharge lamp 13 is discharged and the inner wall of the discharge lamp 13 is heated, and then,
The mercury, iron, etc. inside the tube become halides and evaporate, and the discharge is mainly a discharge of metal gas, and light with a specific emission spectrum depending on the type of metal enclosed is emitted. At this time, the discharge is from discharge lamp 1
It occurs near the tube wall of No.3. That is, the light emission is spherical. If the spherical portion 5 of the cavity wall 4 is made a light reflecting surface, the discharge lamp 13 will be located near the center of the spherical portion 5, so that the reflected light will pass through the vicinity of the discharge lamp 13 again. This reflected light and the direct light from the discharge lamp 13 are radiated outward through the metal mesh plate 7.
The light emitted outward is condensed onto a necessary irradiated surface by a condenser lens 18 or the like.

However, in the microwave discharge light source device configured in this way, the power supply port 12 is connected to the discharge lamp 13.
The discharge lamp 13 is provided so that the impedance of the microwave cavity 11 matches the impedance of the waveguide 3 when the rare gas inside the discharge lamp 11 is in a stable state. Until the discharge occurred, the impedance matching was poor and the electromagnetic field within the microwave cavity 11 was weak, consisting only of the electromagnetic field leaking from the feed port. Therefore,
There were cases in which the electromagnetic field generated in the discharge lamp 13 was below the level at which the rare gas in the discharge lamp 13 started discharging, and even when microwave power was applied, the discharge lamp 13 sometimes did not start discharging.

This invention has been made in view of the above points, and in a microwave discharge light source device, a mesh plate on the opening side of the microwave cavity wall is movably provided, and this mesh plate is moved at the time of startup to The purpose is to make it easier to start discharge of a discharge lamp by changing the resonant frequency of the wave cavity.

An embodiment of this invention is shown below in Figures 2 and 3.
To explain based on the figure, in the figure, 101 is a movable flange 102 that is provided so as to be movable while contacting the outer wall of the cylindrical part 6 of the cavity wall 4 via a contactor 103, and a presser flange 8 and a presser screw 9 are attached to the movable flange 102. a movable part 10 to which a metal mesh plate 7 is attached;
4 is an arm extending from the movable flange 102, and 19 is a drive device coupled to this arm, which moves the movable portion 101 in the directions of arrows A and B in the figure. P.S.
is the input power supply, S is the power switch, T is the transformer,
Ti is the primary winding of transformer T, TH is the high voltage winding of transformer T, TF is the filament winding of transformer T,
C is a voltage doubler rectifier capacitor, and D is a voltage doubler rectifier diode.

In the microwave discharge light source device configured in this way, the movable part 101 before power is turned on is located at the position indicated by the broken line in FIG. 2, that is, above the opening end of the cavity wall 4. Powered by switch S
When PS is turned on, voltage is applied to the filament and node of magnetron 1 via transformer T, generating microwaves. At the same time,
The power PS is also turned on to the drive device 19. Then, the drive device 19 operates to drive the arm 104 in the direction of arrow B, so that the movable part 101 starts to move downward immediately after the microwave output appears, and after several milliseconds to one second, the metal mesh plate 7 It moves to the open end of the cavity wall 4, that is, to the position indicated by line C in the figure, detects that the metal mesh plate 7 and the open end of the cavity wall 4 come into contact, and stops the drive device 19.
The movement of the movable part 101 is stopped. In this case, if there is poor contact between the movable part 101 and the outer wall of the cylindrical portion 6 of the cavity wall 4, there is a risk of discharge or microwave leakage, so a contactor 103 is provided to avoid a state of poor contact.

In this way, by moving the movable part 101 from above the open end of the cavity wall 4 to the open end, the microwave cavity 1 composed of the cavity wall 4 and the metal mesh plate 7 is moved.
Since the resonant frequency of the microwave cavity 11 changes, there is a time when the resonant frequency of the microwave cavity 11 and the frequency of the microwave, that is, the oscillation frequency of the magnetron 1 match, and the electromagnetic field inside the microwave cavity 11 becomes a resonant electromagnetic field. be. This resonant electromagnetic field has no impedance matching when the discharge lamp 13 is not lit.
It is stronger than the leakage electromagnetic field mentioned above,
Even if the discharge lamp 13 is not lit due to the leakage electromagnetic field alone, the discharge lamp 13 will definitely be lit when the microwave cavity 11 becomes a resonant electromagnetic field. After the discharge lamp 13 is started, the impedance inside the microwave cavity 11 decreases, making it easier for microwave energy to be injected.
The discharge of the discharge lamp 13 is maintained and the state is shifted to a stable lighting state. Note that after the discharge lamp 13 is started, the movable part 101 is located at the open end of the cavity wall 4 (the position shown by line C in the figure), and when the discharge of the discharge lamp 13 is in a stable state, microwave matching is in a good state. It is something that

Next, the improved startability will be explained in more detail.

When a nominally 2450 MHz magnetron is used as the microwave oscillator 1, this magnetron generally has a variation of ±5 to 10 MHz.On the other hand, the microwave cavity 11 is formed by a spherical part 5 consisting of a hemisphere with a diameter of 115 mm and a spherical part 5 with a length of 25 mm. When configured with the cylindrical portion 6, the resonant frequency of the microwave cavity 11 when the discharge lamp 3 is not discharging is 2540MHz. The Q of the resonant state of the microwave cavity 11 is several hundreds, that is, the half-width is several MHz, and the resonant electromagnetic field becomes about one-tenth at a frequency several MHz away from this resonant frequency. Furthermore, this microwave cavity 1
1, the resonance frequency is 2450M when the discharge lamp 13 is lit.
Hz, and microwave energy can be efficiently applied to the discharge lamp 13. In other words, it is possible to achieve good microwave matching. In addition, the Q at this time is several tens, so even if there is variation in the oscillation frequency of the magnetron, it has almost no effect on the microwave matching state. By the way, the resonance frequency of the microwave cavity 11 when the discharge lamp 13 is not discharging changes by about 80 MHz if the length of the cylindrical portion 6 changes by 5 mm. That is, if the length of the cylindrical portion 6 increases by 5 mm, the resonance frequency decreases by 80 MHz, and if the length decreases by 5 mm, the resonance frequency increases by 80 MHz. Therefore, when the metal mesh plate 7 is placed at the position indicated by line C in FIG. If the upper limit of the movable range is set to 7 mm, the metal mesh plate 7 can be moved to a position 7 mm above the line C shown in FIG. 32mm
(25+7), and the resonant frequency of the microwave cavity 11 is approximately 2430MHz (≒2450−80×7/5). Therefore, by moving the metal mesh plate 7 from above to below by the movable part 101, even if the discharge lamp 13 is not lit even after the microwave oscillator 1 is activated, the microwave cavity 1
The resonant frequency of microwave cavity 1 can be changed continuously from approximately 2430MHz to 2540MHz.
When the resonance frequency of 1 and the oscillation frequency of the magnetron match, that is, they are both around 2450MHz,
A resonant electromagnetic field will be generated in the microwave cavity 11, and at this time, the electromagnetic field will be stronger than a simple leakage electromagnetic field, making it easier to start discharging the discharge lamp 13 and increasing the lighting probability. . In addition,
After the discharge lamp 13 is lit, the Q of the microwave cavity 11 decreases, microwave energy is easily injected, the discharge of the discharge lamp 3 is maintained, and the metal mesh 9 is fixed to the line C shown in FIG. Then, discharge lamp 1
When the discharge of 3 becomes stable, the microwave cavity 1
Since the microwave matching between the discharge lamp 1 and the magnetron is good, the discharge lamp 13 continues to be stably lit. After that, when the power supply PS is no longer turned on by the switch S, the discharge stops, and the drive device 19 moves the movable part 102 so that the metal mesh plate 7 returns to the initial position above the open end of the cavity wall 4. is moved in the direction of arrow A in the figure.

In the above embodiment, the metal mesh plate 7 constituting the microwave cavity 11 is movable, but a part of the cavity wall 4 constituting the microwave cavity 11 may be movable.In short, the microwave cavity It is sufficient if at least a part of the microwave oscillator 4 is a movable part so that the resonance frequency of the microwave cavity 11 can be varied immediately after the microwave oscillator 1 is activated.

As described above, the present invention includes a microwave oscillator that generates microwaves, a waveguide that transmits the microwaves generated by the microwave oscillator,
A microwave cavity consisting of a cavity wall connected to this waveguide via a power supply port and a mesh plate that closes the opening of this cavity wall, and an electrodeless structure disposed inside this microwave cavity. In a microwave discharge light source device equipped with an electric lamp, the mesh plate is moved so that the size of the microwave cavity decreases from large to small immediately after the power is turned on to the microwave oscillator, so if the microwave oscillator When the discharge lamp does not discharge even after the discharge lamp is operated, a resonant electromagnetic field can be generated within the microwave cavity, which has the effect of making it easier to start lighting the discharge lamp.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the main parts of a conventional microwave discharge light source device, FIG. 2 is a vertical cross-sectional view showing the main parts of a microwave discharge light source device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the power supply of FIG. 2. FIG. In the figure, 1 is a microwave oscillator, 3 is a waveguide, 4 is a cavity wall, 7 is a metal mesh plate, 11 is a microwave cavity, 13 is a discharge lamp, 101 is a movable part,
19 indicates a drive device. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A microwave oscillator that generates microwaves, a waveguide that transmits the microwaves generated by this microwave oscillator, and a mesh plate that closes the opening in the cavity wall that is connected to this waveguide via a power supply port. In the microwave discharge light source device, the mesh plate is movably provided, and the mesh plate is movable, and the microwave oscillator has a power source. A microwave discharge light source device comprising a drive device for driving the mesh plate so as to change the size of the microwave cavity from large to small immediately after the microwave discharge light source device is turned on.