JP2010232000A - Discharge lamp device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp device capable of detecting accurately at an early stage leakage of a heat conductor from an electrode. <P>SOLUTION: The discharge lamp device consists of a discharge lamp 10 in which a pair of electrodes are arranged oppositely inside an arc tube filled with a light-emitting substance and a measuring means 30 which monitors lighting state of the discharge lamp 10, and at least one of electrodes of the discharge lamp 10 has a heat conductor consisting of a metal having a melting point lower than that of the metal to constitute the electrode, filled in a sealed space inside. The measuring means 30 has a detection means 35 which measures both of power of the discharge lamp 10 and emission light emitted from the light-emitting substance simultaneously in order at fixed intervals, compares in order the latest ratio being a ratio of measured value of the latest power of the discharge lamp and the measured value of the latest emission light and the past ratio of the measured value of the past power of the discharge lamp and the measured value of emission light after a fixed time interval than the time when the latest power and the emission light of the discharge lamp are measured, and detects the changes of the ratio. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a discharge lamp device. In particular, the present invention relates to a discharge lamp apparatus using a short arc type discharge lamp used in an exposure apparatus for liquid crystal and semiconductor wafers.

  Discharge lamps can be classified into several lamps from the viewpoints of luminescent materials, distance between electrodes, and pressure in the arc tube. Among these, luminescent materials are xenon lamps using xenon gas as luminescent materials, mercury lamps using mercury as luminescent materials, mercury It can be classified as a metal halide lamp using a rare earth metal other than the above as a luminescent material. In terms of the distance between the electrodes, it can be classified into a short arc type discharge lamp having a short distance between electrodes and a long arc type discharge lamp having a long distance between electrodes. Furthermore, from the viewpoint of the vapor pressure in the arc tube, it can be classified into a low pressure discharge lamp, a high pressure discharge lamp, and an ultrahigh pressure discharge lamp.

Of these, for the short arc type high-pressure mercury lamp, quartz glass having a high heat resistance temperature is used as the arc tube, and tungsten electrodes are arranged in the inside thereof with a gap of about 2 to 12 mm. Is filled with a rare gas such as mercury or argon having a lighting vapor pressure of 10 ⁵ Pa to 10 ⁷ Pa as a luminescent substance.
This short arc type high-pressure mercury lamp has an advantage that a high brightness can be obtained because the distance between the electrodes is short, so that it has been widely used as a light source for lithography exposure.

  On the other hand, in recent years, it has been attracting attention as a light source for exposure not only for semiconductor wafers but also for liquid crystal substrates, particularly for large area liquid crystal displays, and as a lamp that is a light source from the viewpoint of increasing throughput in the manufacturing process. However, there is a strong demand for higher output.

When the rated power consumption increases due to an increase in the output of the discharge lamp, the value of the current flowing through the discharge lamp increases in most cases, although it depends on the design value of the current voltage.
For this reason, the electrode (especially the anode in direct current lighting) increases the amount of electron impact, leading to a problem that it is easily heated and melted. In addition, in discharge lamps arranged vertically, not limited to the anode, the electrode located on the upper side is susceptible to heat from the arc due to the influence of thermal convection in the arc tube, and similarly the temperature rises. It will be melted by.

In addition, when the electrode, particularly its tip, melts, the arc becomes unstable, and there is a problem that the material constituting the electrode evaporates and adheres to the inner surface of the arc tube to reduce the radiation output. .
Such a phenomenon is not limited to the short arc type high-pressure mercury lamp, but is a problem that generally occurs when the discharge lamp has a large output.

In order to prevent such problems from occurring, it is necessary to suppress the temperature rise of the electrode, and a sealed space with a cavity is formed inside the electrode, and heat transfer such as silver or copper is formed in this space. A structure for enclosing a body has been proposed (Japanese Patent Laid-Open No. 2004-6246).
The heat transfer body is made of a metal having a melting point lower than that of the metal constituting the electrode body. When the lamp is lit, the convection action or boiling transfer action of the heat transfer body that is in a liquid state in the sealed space is used. Thus, the heat at the electrode tip is efficiently transported to the rear part, and in particular, the temperature rise at the electrode tip is suppressed.

However, even if an electrode having a heat transfer body is used inside the electrode body having the above structure, the problem of electrode wear can be solved as compared with an electrode existing before that, but electrode wear can be completely suppressed. However, the evaporation of the materials that make up the electrode cannot be completely suppressed, and the evaporated material from the electrode adheres to the inner surface of the arc tube, and the radiation output gradually decreases as the lamp lights up. To do.
In order to compensate for such a decrease in radiation output, the input power of the discharge lamp is increased as the lamp lighting time elapses, so that a desired radiation output is always obtained.
Such a method controls the illuminance on the surface to be processed, which is the irradiation surface, to be constant, and is called a constant illuminance lighting mode. (Japanese Patent Laid-Open No. 10-294271).

The constant illumination lighting mode will be described in detail.
FIG. 6 is an explanatory diagram of the time at which the emitted light from the discharge lamp is measured.
As shown in FIG. 6, the symbols S1, S2, S3... S598, S599, S600, S601, and S602 represent times when radiated light is measured at regular intervals (1 second intervals).

The conventional method measures the radiated light at the time S1 when a stable elapsed time has elapsed after the lamp is lit, and the measured value of the radiated light, and the reference value that is the measured value of the radiated light to obtain a desired illuminance. Compare. If this measured value is within an allowable range with respect to the reference value, it is determined that the emitted light has not decreased, and the power to the discharge lamp is not changed.
Then, as the lamp lighting time elapses, the radiated light is sequentially measured and compared with the reference value as in the times of S598, S599, and S600.
The measured value of the synchrotron radiation measured at the time of S601 is compared with the reference value, and when the measured value is lower than the allowable range with respect to the reference value, the power to the discharge lamp is increased and the desired illuminance is always obtained. To be.
Next, the measured value of the radiated light measured at the time of S602 is compared with the reference value, and if the measured value is within the allowable range with respect to the reference value, it is determined that the radiated light has not decreased, and the discharge lamp Electricity is not changing.

JP 2004-6246 A JP-A-10-294271

  However, even with an electrode having a heat transfer body inside the electrode body, as described above, electrode wear is not completely suppressed, and if the electrode is worn, the discharge is affected by the wear shape. In the worst case, there was a problem that a hole was opened in the electrode body and the heat transfer body leaked out.

  As an example, in the case of a discharge lamp in which mercury is enclosed in an arc tube and light having an emission line of mercury of 365 nm is used, if a hole is formed in the electrode body and a heat transfer body such as silver or copper leaks, Vaporized when exposed to high temperature, becomes mist-like, fills the inside of the arc tube, and 365 nm light is not transmitted outside the arc tube, and the illuminance at 365 nm on the treatment surface of the object to be treated decreases. It is.

The relationship between the leakage of the heat transfer body, the illuminance and the lamp power will be described in detail.
When a large crack occurs in the electrode body in a moment and a hole is made, almost all of the heat transfer body inside the electrode leaks in an instant. In this case, the illuminance at 365 nm is a leakage of the heat transfer body. At the same time, it decreases.
On the other hand, in the case where the electrode body has a small hole and the heat transfer body inside the electrode gradually leaks out, at the initial stage when the heat transfer body leaks out, the decrease in illuminance at 365 nm is small and gradually takes time. The illuminance at 365 nm decreases.

  If almost all of the heat transfer element inside the electrode leaks in an instant, the 365 nm illuminance suddenly increases at the same time as the heat transfer element leaks. If the power of the discharge lamp is increased for a moment according to the constant illuminance lighting mode, the power cannot be increased beyond the upper limit of the power, so the illuminance at 365 nm cannot be increased, and the heat transfer element leaks. Can be detected instantly.

However, when the heat transfer body inside the electrode gradually leaks out, the amount of the leaked heat transfer body is small in the initial stage, and if the illuminance at 365 nm is measured by the light measuring device, the illuminance at 365 nm is slightly It is a grade which falls to.
When the power of the discharge lamp is increased in the constant illuminance lighting mode with the decrease in illuminance at 365 nm, the illuminance at 365 nm also increases, and there is a problem that leakage of the heat transfer body cannot be detected at an early stage.

That is, when almost all of the heat transfer body inside the electrode leaks in an instant, the illuminance at 365 nm does not increase even if the power is increased in the constant illuminance lighting mode, and leakage of the heat transfer body can be detected.
However, when the heat transfer body inside the electrode gradually leaks, there is a problem that when the power is increased in the constant illumination lighting mode, the illuminance at 365 nm increases, and the leakage of the heat transfer body cannot be detected early. It was.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a discharge lamp device capable of accurately and quickly detecting leakage of a heat transfer body from an electrode. .

  The discharge lamp device according to claim 1 comprises a discharge lamp in which a pair of electrodes are opposed to each other inside an arc tube in which a luminescent material is sealed, and a measuring means for monitoring the lighting state of the discharge lamp. At least one of the electrodes is composed of an electrode body having a sealed space formed therein, and a heat transfer body made of a metal having a melting point lower than the melting point of the metal constituting the electrode enclosed in the sealed space. In the discharge lamp device, the measuring means measures both the electric power of the discharge lamp and the radiated light emitted from the light emitting material at the same time and sequentially, and the latest measured value of the electric power of the discharge lamp and the latest radiated light. The latest ratio, which is the ratio of the measured values of the discharge lamp, and the measured values of the discharge lamp power and the synchrotron radiation measured at a certain time interval from the time when the latest discharge lamp power and synchrotron light were measured. Sequentially compares the past and the ratio is the ratio of, and having a detecting means for detecting a change in the ratio.

  A discharge lamp apparatus according to a second aspect is the discharge lamp apparatus according to the first aspect, wherein the detection means is a ratio detection means for detecting a ratio between the latest ratio and the past ratio.

  The discharge lamp device according to claim 3 is the discharge lamp device according to claim 1 or 2, wherein the electrode body is made of a metal mainly composed of tungsten, and the heat transfer body is And any one of gold, silver and copper.

  In the discharge lamp apparatus of the present invention having a discharge lamp using an electrode having a heat transfer body inside the electrode body and a measuring means for monitoring the lighting state of the discharge lamp, the measuring means is based on the electric power of the discharge lamp and the luminescent material. Measure both the emitted synchrotron radiation at the same time and at the same time in sequence, the latest ratio, which is the ratio of the latest discharge lamp power measurement to the latest synchrotron radiation measurement, and the latest discharge lamp power and radiation. A detection means for detecting a change in the ratio by sequentially comparing the past measured value of the power of the discharge lamp and the past ratio which is the ratio of the measured value of the radiated light at a certain time interval from the time when the light was measured. Therefore, even if the discharge lamp is lit to increase the power in the constant illuminance lighting mode and maintain the predetermined illuminance, the heat transfer body leaks from the electrode due to the change in the discharge lamp power and radiated light. That it was issued Accurately, it can be detected early.

  Furthermore, since the detection means is a ratio detection means for detecting the ratio between the latest ratio and the past ratio, it is possible to detect accurately and early that the heat transfer body has leaked from the electrode due to the change in the ratio. .

  Furthermore, the electrode body is made of a metal mainly composed of tungsten, and the heat transfer body contains any one of gold, silver and copper, and the heat at the tip of the electrode is efficiently transferred to the rear part. It can be transported and temperature rise at the electrode tip can be suppressed.

1 is an overall configuration diagram of a discharge lamp device according to the present invention. 1 shows an overall view of a discharge lamp according to the present invention. 1 shows an electrode of a discharge lamp according to the present invention. It shows the change in illuminance due to the discharge lamp. 2 shows a flowchart of a measuring means according to the present invention. 2 shows a flowchart of a measuring means according to the present invention. It is explanatory drawing of the measurement time which measures synchrotron radiation and electric power.

FIG. 1 is a schematic diagram showing the overall structure of a discharge lamp device according to the present invention.
The discharge lamp device according to the present invention has the discharge lamp 10 and the measuring means 30 for monitoring the lighting state of the discharge lamp 10 as essential components, and further includes a lighting power supply 50 for supplying current to the discharge lamp 10 to light it. The power supply control device 40 that controls the lighting power supply 50 is provided.
The measuring means 30 will be described in detail later.

  FIG. 2 shows an enlarged view of the discharge lamp 10. The arc tube of the discharge lamp 10 is made of quartz glass, and sealing portions 12 are integrally connected to both ends of the substantially spherical arc tube 11. The arc tube 11 has an anode 2 and a cathode 3 facing each other, and each electrode (2, 3) is held by a sealing portion 12, in which an external lead rod is interposed via a metal foil (not shown). 13 and connected to the lighting power source 50 of FIG.

  The arc tube 11 is filled with a predetermined amount of a luminescent substance such as mercury, xenon, or argon, or a starting gas. When electric power is supplied from the lighting power supply 50, the discharge lamp 10 emits light by arc discharge at the anode 2 and the cathode 3. The discharge lamp 10 is a so-called vertical lighting type discharge lamp that is lit with the anode 2 facing up and the cathode 3 facing down, with the tube axis of the arc tube 11 supported in a substantially vertical direction with respect to the ground. .

FIG. 3 shows a cross-sectional structure of the anode 2. The anode 2 has a structure having an electrode body 20 and a heat transfer body M therein.
The electrode body 20 is made of a refractory metal or an alloy containing a refractory metal as a main component, and has a container shape in which a sealed space S (hereinafter also referred to as “internal space”) is formed.
The heat transfer body M is a metal hermetically sealed inside the electrode body 20 and is made of a metal having a melting point lower than that of the metal constituting the electrode body 20.
The electrode body 20 includes a lid part 201, a body part 202, and a tip part 203. The lid part 201 is formed with an insertion hole 2011 into which a lead bar that supports the anode is inserted.

As the metal constituting the electrode body 20, a refractory metal having a melting point of 3000 (K) or higher, such as tungsten, rhenium, or tantalum, is employed. In particular, tungsten is preferable in that it hardly reacts with the internal heat transfer body M, and so-called pure tungsten having a purity of 99.9% or more is preferable.
In addition, as an alloy mainly composed of a refractory metal, for example, a tungsten-rhenium alloy mainly composed of tungsten can be adopted. The resistance to repetitive stress at high temperatures is high, and the life of the electrode can be extended.

  The heat transfer body M is made of a metal having a melting point lower than that of the metal constituting the electrode body 20. Specifically, when tungsten is used as the constituent material of the electrode body 20, gold, silver, copper, or an alloy containing these as a main component can be adopted as the heat transfer body M. Since gold, silver, and copper do not form an alloy with tungsten, these metals are desirable metals in the sense that they stably function as heat transporters. Among these, since gold is expensive, silver and copper are practically preferable materials.

As another specific example, when rhenium is used as the metal constituting the electrode body 20, tungsten can be used as the heat transfer body M.
The advantage of adopting rhenium as the metal constituting the electrode body 20 is that it can prevent corrosion of the electrode in the case of a mercury lamp or a metal halide lamp encapsulating halogen, thereby extending the life of the discharge lamp. is there.

  The electrode body 20 has a substantially container-shaped structure having a sealed space S inside. For this reason, even if the heat transfer body M is heated and melted and a part thereof is vaporized, it does not leak into the light emitting space of the light emitting unit 11.

  The measuring means 30 includes a measuring means control device 31, a light measuring device 32 that measures the emitted light of the discharge lamp 10, a power measuring unit 33 that measures the power of the discharge lamp 10, and the emitted light measured by the light measuring device 32. Storage means 34 for storing the measured value and the measured value of the power measured by the power measuring unit 33, and a detecting means 35 for detecting a change in the measured value. A ratio detecting means for detecting a ratio between the measured value and the measured value of the emitted light is provided.

The light measuring device 32 captures the emitted light of the discharge lamp 10 and is desirably disposed at a position where it can be captured as direct light. However, the light measuring device 32 is obstructive in relation to the original purpose of use of the discharge lamp 10. It is installed in a position where it does not become.
The light measuring device 32 is a wavelength selection filter for transmitting only predetermined light of the radiated light of the discharge lamp 10, and a neutral density filter for adjusting the predetermined light transmitted through the wavelength selection filter to an intensity suitable for processing. And a sensor that receives the predetermined light and converts it into an electrical signal, and an amplifier that amplifies the electrical signal.

For example, a band pass filter or a color glass filter is employed as the wavelength selection filter, an ND filter is employed as the neutral density filter, and a silicon photodiode is employed as the sensor, for example.
In the present embodiment, the light measurement device 32 receives light of the emission line 365 nm of mercury, which is a luminescent material enclosed in the arc tube 11 of the discharge lamp 10, using a wavelength selection filter and a neutral density filter. The light of 365 nm received by the sensor is converted into an electric signal.
The 365-nm light amount received by the sensor is light having a half-value width of 10 nm centered on 365 nm transmitted through the wavelength selection filter.

When the power control unit 40 controls the lighting power source 50, the power measuring unit 33 converts a power signal sent from the power source control device 40 to the lighting power source 50 into an electric signal corresponding to the magnitude of the power, and discharge lamp It measures the power of.
The power signal is a signal synthesized from a voltage signal and a current signal sent to the lighting power supply 50.

  The measurement means control device 31 operates the light measurement device 32 and the power measurement unit 33 at regular intervals. As an example, the measurement means control device 31 transmits a signal every second and operates the light measurement device 32 and the power measurement unit 33 simultaneously. Then, control is performed so that the emitted light from the discharge lamp 10 and the power of the discharge lamp 10 are sequentially measured at intervals of one second.

  The storage unit 34 stores the electrical signal transmitted from the light measurement device 32 and the electrical signal transmitted from the power measurement unit 33, and is transmitted from the light measurement device 32 at regular intervals by the measurement unit control device 31. The electric signal transmitted and the electric signal transmitted from the power measuring unit 33 are individually stored.

The light measuring device 32 measures the light of the luminescent material enclosed in the arc tube 11 of the discharge lamp 10. When the luminescent material is mercury, light of 405 nm or 436 nm which is light other than 365 nm is used. May be measured.
When the luminous material enclosed in the arc tube of the discharge lamp is mercury, when a heat transfer material such as silver or copper leaks out during lighting, light of 365 nm, 405 nm, or 436 nm, which is an emission line of mercury, is emitted from the arc tube. The rate of transmission to the outside is remarkably reduced.

  The detection means 35 has the latest ratio, which is the ratio of the electrical signal corresponding to the latest measured value of the discharge lamp power stored in the storage means 34 and the latest measured value of the emitted light, and the latest The past ratio, which is the ratio of the electrical signal corresponding to the measured value of the discharge lamp and the measured value of the emitted light at a certain time interval from the time when the power of the discharge lamp and the emitted light are measured Are sequentially detected, and a change in the ratio between the latest ratio and the past ratio is detected.

  Furthermore, the detection means 35 has a ratio detection means for detecting the ratio between the latest ratio value and the past ratio value.

  And when the change of the electrical signal corresponding to the ratio change detected by the detection means 35 deviates from the reference value, or when the ratio value detected by the ratio detection means 36 deviates from the reference value, it is in an abnormal state. Is displayed, or an electric signal is sent from the detection means 35 or the ratio detection means 36 to the power supply control device 40 as an abnormal state, thereby operating the power supply control device 40 and stopping the operation from the power supply control device 40 to the lighting power supply 50. A signal is sent to turn off the discharge lamp 10.

Here, a phenomenon in which the discharge becomes unstable due to wear of the anode 2 of the discharge lamp 10, a damage phenomenon due to the electrode main body material, and a phenomenon in which the heat transfer body leaks from the internal space of the electrode main body will be described.
The anode is made of a refractory metal such as tungsten, but as the lighting time elapses, the material constituting the anode evaporates or deforms. In particular, when the arc is locally concentrated on a part of the anode surface or when the arc fluctuates, the wear of the part becomes severe, and finally the electrode body is broken.
In addition, if there are cracks or voids in the electrode body, the strength may decrease locally, leading to damage. In either case, leakage of the heat transfer body occurs due to the passage of the heat transfer body enclosed inside to the discharge space.

FIG. 4 is a data explanatory diagram showing a change in illuminance of the discharge lamp when the heat transfer body leaks from the electrode of the discharge lamp 10.
In FIG. 4, the vertical axis indicates the amount of light detected by the sensor with light having a wavelength of 365 nm as the sensor output voltage (V), and the horizontal axis indicates the elapsed lighting time (minutes).
In the case of FIG. 4, the discharge lamp 10 has the structure shown in FIG. 2, and the arc tube 11 is filled with mercury and xenon, and the electrode body 20 is made of silver as the heat transfer body M. The encapsulated one is taken as an example.

In FIG. 4, on the horizontal axis, the period from −3 to 0 minutes is a time zone in which the discharge lamp 10 is stably lit, and the amount of light detected by the sensor is stable. That is, the illuminance on the processing surface of the workpiece is stable.
Then, at the time of 0 minutes, the silver enclosed inside from the electrode body 20 starts to leak into the arc tube, and at this moment, silver is newly mixed in the arc tube, and the silver is exposed to a high temperature. Vaporizes and fills the arc tube, and 365 nm light is not transmitted outside the arc tube. As a result, the amount of light with a wavelength of 365 nm detected by the sensor starts to decrease.
Further, after 0 minute, the light quantity of the wavelength 365 nm detected by the sensor is gradually decreasing.

Next, a method for measuring the emitted light and power from the discharge lamp 10 will be described with reference to the flowchart of FIG.
In step 1, the lighting power supply 50 is activated to turn on the discharge lamp 10.
Next, in step 2, it is determined whether or not a stable elapsed time for which the discharge lamp 10 is stably lit has elapsed.
If the stable elapsed time has not elapsed, it is determined as N0, and the stable elapsed time is determined again.
If the stable elapsed time has elapsed, it is determined YES and the process proceeds to step 3.
In step 3, the measurement means control device 31 is activated, and the light measurement device 32 and the power measurement unit 33 simultaneously measure the emitted light and power sequentially at a constant interval, and a signal Sa1, corresponding to the measurement value from the light measurement device 32, Sa2, Sa3... Sa (n-2), Sa (n-1), Sa (n), Sa (n + 1) and signals Sb1, Sb2, Sb3 corresponding to the measured values from the power measuring unit 33. Sa (n-2), Sb (n-1), Sb (n), and Sb (n + 1) are individually stored in the storage unit 34.

Next, in step 4, the latest ratio of the signal Sb (n + 1) corresponding to the latest discharge lamp power and the signal Sa (n + 1) corresponding to the latest discharge lamp radiation, and the latest discharge lamp power The past ratio of the signal Sb1 corresponding to the power of the discharge lamp in the past and the signal Sa1 corresponding to the light emitted from the discharge lamp at a certain time interval from the time when the synchrotron light is measured is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... D / E
Latest ratio: D = Sa (n + 1) / Sb (n + 1)
Past ratio: E = Sa1 / Sb1

Next, in step 5, the D / E value and the threshold value T are compared.
If the D / E value is smaller than the threshold value T in step 5, it is determined YES, and an abnormal signal is transmitted from the ratio detection means 26 in step 6.

In step 5, when the value of D / E is larger than the threshold value T, it is determined to be NO, and the process returns to step 3 to measure the power and the radiated light at the same time by the light measurement device 32 and the power measurement unit 33. Sa (n + 2) and Sb (n + 2) are stored in the storage means 34.
In step 4, the latest ratio of the signal Sb (n + 2) corresponding to the latest discharge lamp power and the signal Sa (n + 2) corresponding to the latest discharge lamp radiation, and the latest discharge lamp power and radiation. The past ratio between the signal Sb2 corresponding to the power of the discharge lamp in the past and the signal Sa2 corresponding to the emitted light of the discharge lamp at a certain time interval from the time when the light was measured is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... D / E
Latest ratio: D = Sa (n + 2) / Sb (n + 2)
Past ratio: E = Sa2 / Sb2

Next, in step 5, the D / E value and the threshold T are compared, and a determination of YES or NO is made.
While it is determined NO in step 5, step 3 to step 5 are repeated.

  The abnormal signal in step 6 is sent to the power supply control device 40, an operation stop signal is sent from the power supply control device 40 to the lighting power supply 50, and the discharge lamp 10 is turned off.

  In the above description, in step 3, the signal corresponding to the measurement value from the light measurement device 32 and the signal corresponding to the measurement value from the power measurement unit 33 are individually stored in the storage unit 34. As described above, when the storage capacity of the storage unit 34 is small, the ratio of the measurement value of the radiated light and the measurement value of the power is calculated for each measurement, and then only the ratio value of the calculation result is stored in the storage unit 34. You may let them.

In the above embodiment, it has been described that the ratio of the latest ratio value and the past ratio value is taken in step 4, but the difference between the latest ratio value and the past ratio value may be taken.
With respect to the method for measuring the emitted light and power from the discharge lamp 10, a method for taking the difference between the latest ratio value and the past ratio value will be described with reference to the flowchart of FIG.
Steps 1 to 3 in the flowchart shown in FIG. 6 are the same as those in the flowchart shown in FIG.
In step 4 of FIG. 6, the latest ratio of the signal Sb (n + 1) corresponding to the latest discharge lamp power and the signal Sa (n + 1) corresponding to the latest discharge lamp radiation, and the latest discharge lamp power The past ratio of the signal Sb1 corresponding to the power of the discharge lamp in the past and the signal Sa1 corresponding to the light emitted from the discharge lamp at a certain time interval from the time when the synchrotron light is measured is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... ED
Latest ratio: D = Sa (n + 1) / Sb (n + 1)
Past ratio: E = Sa1 / Sb1

Next, in step 5, the value of E−D is compared with the threshold value T.
In this step 5, when the value of ED is larger than the threshold value T, it is determined YES, and in step 6, an abnormal signal is transmitted from the ratio detection means 26.

In step 5, when the value of ED is smaller than the threshold value T, it is determined as NO, and the process returns to step 3 where the power and the emitted light are simultaneously measured by the light measuring device 32 and the power measuring unit 33, and the latest measured value is obtained. Sa (n + 2) and Sb (n + 2) are stored in the storage means 34.
In step 4, the latest ratio of the signal Sb (n + 2) corresponding to the latest discharge lamp power and the signal Sa (n + 2) corresponding to the latest discharge lamp radiation, and the latest discharge lamp power and radiation. The past ratio between the signal Sb2 corresponding to the power of the discharge lamp in the past and the signal Sa2 corresponding to the emitted light of the discharge lamp at a certain time interval from the time when the light was measured is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... ED
Latest ratio: D = Sa (n + 2) / Sb (n + 2)
Past ratio: E = Sa2 / Sb2

Next, in step 5, the value of ED and the threshold value T are compared, and a determination of YES or NO is made.
While it is determined NO in step 5, step 3 to step 5 are repeated.

The abnormal signal in step 6 is sent to the power supply control device 40, an operation stop signal is sent from the power supply control device 40 to the lighting power supply 50, and the discharge lamp 10 is turned off.

Next, a specific method for measuring emitted light will be described with reference to FIGS.
FIG. 7 is an explanatory diagram of the measurement time. Symbols such as S1 represent times when the radiated light and the power are measured at regular intervals.
In step 2 of FIG. 5, it is determined whether or not a stable elapsed time of 10 minutes for the discharge lamp 10 to stably light has elapsed.
If the stable elapsed time of 10 minutes has elapsed, it is determined YES and the process proceeds to step 3.
In step 3, as shown in FIG. 7, the measurement means control device 31 is operated, and the light measurement device 32 and the power measurement unit 33 are continuously emitted at intervals of 1 second as shown at times such as S1 and S2. Light and power are sequentially measured, and signals Sa1, Sa2, Sa3... Sa598, Sa599, Sa600, Sa601, Sa602 corresponding to the measured values from the light measuring device 32 and the measured values from the power measuring unit 33 are corresponded. The signals Sb1, Sb2, Sb3... Sb598, Sb599, Sb600, Sb601, Sb602 are stored individually in the storage means 34.
Here, S601 means the time 600 seconds after the first measured time S1, and the signal corresponding to the measured value of the radiated light measured at time S601 is Sa601, and at time S601. The signal corresponding to the measured value of the measured power is Sb601.

Next, in step 4, the latest ratio D of the signal Sb601 corresponding to the power of the discharge lamp at the latest time S601 and the signal Sa601 corresponding to the emitted light of the discharge lamp at the latest time S601, and the past time 600 seconds ago. The past ratio E of the signal Sb1 corresponding to the power of the discharge lamp in S1 and the signal Sa1 corresponding to the emitted light of the discharge lamp in the past time S1 is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... D / E
Latest ratio: D = Sa601 / Sb601
Past ratio: E = Sa1 / Sb1

In step 5, a threshold value is determined in advance, and the threshold value is set to 0.8.
In this step 5, the D / E value is compared with the threshold value 0.8. If the D / E value is larger than 0.8, it is determined that silver does not leak from the electrode, and the process returns to step 3. A signal Sb602 corresponding to the power of the discharge lamp at the next time S602 and a signal Sa602 corresponding to the emitted light of the discharge lamp at the time S602 are stored in the storage unit 34.
Here, S602 means a time 600 seconds after the second measured time S2.
In Step 5, when the value of D / E is smaller than 1.0 and larger than 0.8, silver is not leaking from the electrode.
As described above, even if an electrode having a heat transfer body is used inside the electrode body, the evaporation of the material constituting the electrode cannot be completely suppressed. Since the radiation output from the lamp is reduced due to adhesion to the inner surface, the value of the latest ratio D at time S601 is the past 600 seconds ago as a result of increasing the power to the discharge lamp in accordance with the constant illuminance lighting mode. It is smaller than the value of the past ratio E at time S1.

In step 4, the latest ratio D of the signal Sb602 corresponding to the power of the discharge lamp at the latest time S602 and the signal Sa602 corresponding to the emitted light of the discharge lamp at the latest time S602, and the past time S2 600 seconds before. The past ratio E of the signal Sb2 corresponding to the electric power of the discharge lamp at and the signal Sa2 corresponding to the emitted light of the discharge lamp at the past time S2 is compared.
Specifically, the value of Equation 1 below is created from each signal.
Formula 1 ... D / E
Latest ratio: D = Sa602 / Sb602
Past ratio: E = Sa2 / Sb2

In step 5, the value of D / E is compared with the threshold value 0.8. If the value of D / E is smaller than 0.8, it is determined that silver has leaked from the electrode, the process proceeds to step 6, and the ratio is An abnormal signal is transmitted from the detection means 26.
This is because even if silver does not leak from the electrode, as described above, the evaporative substance from the electrode adheres to the inner surface of the arc tube, so that the radiation output from the lamp is reduced and the constant illumination is applied. As a result of increasing the power to the discharge lamp in accordance with the mode, the D / E value decreases. However, when silver leaks from the electrode, the decrease in the D / E value is much larger and exceeds the normal decrease range. Thus, by observing the change in the value of D / E, it is possible to accurately and quickly detect that the heat transfer body has leaked from the electrode.

  In step 5, when the latest ratio D and the past ratio D are expressed in a generalized manner, the latest measured value is compared with the measured value 600 seconds before, so that D = Sa (m + 600) / Sb (m + 600), E = Sam / Sbm, and the D / E value using the D and E values is compared with the threshold value 0.8.

In the present invention, the measurement interval between the power and the emitted light is appropriately set according to the storage capacity of the storage means 33 and is not limited to 1 second, but is shorter than 5 minutes, and preferably shorter than 30 seconds. It is.
In the present invention, the latest measured power value and the measured value of synchrotron radiation are not only the latest measured power value and the measured value of synchrotron radiation but also the measured value measured within 5 minutes from the latest. It is considered as the latest power measurement and synchrotron radiation measurement.
If it is within 5 minutes, it will not be affected by lamp troubles other than a decrease in synchrotron radiation. If there is a limit to the calculation capability or processing speed of the ratio detection means, the latest power and synchrotron radiation will be used. There is no problem even if a value within 5 minutes is used from the measured value.

  Although the constant illuminance lighting mode has been described, if the heat transfer body leaks out from the electrode body even in the constant power lighting mode, the ratio of D / E is similarly reduced, or the ED Since the difference becomes large, the present invention can also be applied in the constant power lighting mode.

DESCRIPTION OF SYMBOLS 10 Discharge lamp 30 Measuring means 31 Measuring means control apparatus 32 Optical measuring apparatus 33 Electric power measurement part 34 Memory | storage means 35 Detection means 36 Ratio detection means

Claims (3)

A discharge lamp in which a pair of electrodes are arranged opposite to each other inside an arc tube in which a luminescent material is sealed, and a measuring means for monitoring the lighting state of the discharge lamp,
At least one of the electrodes of the discharge lamp includes an electrode main body in which a sealed space is formed, and a heat transfer body made of a metal having a melting point lower than that of the metal constituting the electrode enclosed in the sealed space. In the constructed discharge lamp device,
The measuring means sequentially measures both the power of the discharge lamp and the radiated light emitted from the luminescent material at regular intervals, and the ratio of the latest measured value of the discharge lamp power and the latest measured value of the radiated light. And the past ratio that is the ratio of the measured value of the discharge lamp and the measured value of the past discharge lamp at a fixed time interval from the time when the measured power and the emitted light of the latest discharge lamp are measured. A discharge lamp device comprising detecting means for sequentially comparing the two and detecting a change in the ratio.   2. The discharge lamp device according to claim 1, wherein the detecting means is a ratio detecting means for detecting a ratio between a latest ratio and a past ratio. The electrode body is made of a metal whose main component is tungsten,
The discharge lamp device according to claim 1, wherein the heat transfer body includes any one of gold, silver, and copper.

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