JP2014075608A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light source device in which emission can be sustained stably while maintaining high temperature plasma state stably after start of lighting, and shortening of the lighting life due to heating of a luminous tube is minimized.SOLUTION: A pulse-like laser beam from a pulse laser oscillation unit 21 and a laser beam of continuous wave from a continuous wave laser oscillation unit 25 are entered into a luminous tube 1 filled with light-emitting gas, and condensed so that both beams overlap in the luminous tube 1. When lighting is started, a high temperature plasma state is formed by the pulse-like laser beam, a beam of continuous wave having an intensity lower than that of the pulse-like laser beam is superposed at a position where the high temperature plasma state is formed, irradiation of the pulse-like laser beam is stopped after emission, and only the continuous wave laser beam is irradiated. Consequently, the high temperature plasma state can be sustained stably. Furthermore, since the continuous wave beam has a low intensity, the luminous tube is not heated and a long life can be ensured.

Description

  The present invention relates to a light source device that is turned on by a laser beam emitted from a laser device and that is suitable for application to an exposure apparatus or the like.

There is known a light source device that emits light by exciting a gas by irradiating a light emitting tube enclosing a luminescent gas with a laser beam from a laser device (see Patent Document 1).
In the technique disclosed in Patent Document 1, a beam from a laser oscillator that oscillates continuous or pulsed laser light is condensed by a condensing optical system component such as a lens, and a luminescent gas (luminescent element) is enclosed. The light is emitted to the arc tube by exciting the luminescent gas in the arc tube.
In the 16th to 18th lines from the upper right column on page 2 of Patent Document 1, it is described that the laser oscillator oscillates continuous or pulsed laser light having a sufficient intensity for discharge excitation of the sealed gas.

JP-A-61-193358

As described in Patent Document 1, a continuous or pulsed laser beam is conceivable as a laser beam for exciting the luminescent gas sealed in the arc tube. I found out there was a problem.
(A) In the case of pulsed laser light, lighting is started because it “oscillates pulsed laser light with sufficient intensity for discharge excitation of the encapsulated gas”, but as shown in FIG. Since the laser beam is intermittently incident on the gas, the high temperature plasma state may be cut off when the laser beam is cut off, and it is difficult to always maintain the high temperature plasma state. That is, there is a problem that the discharge maintenance is unstable.

(B) In the case of continuous laser light, if the continuous laser light with sufficient intensity to start the discharge of the sealed gas is oscillated, lighting starts, but the high-temperature plasma state is maintained as shown in FIG. When the same energy as that at the start of lighting is input, the tube is heated, and this heat causes distortion and breakage of the tube. That is, there is a problem that the lighting life is short.
Further, the power of the laser beam necessary for starting the discharge is several tens to several hundreds kW, but such a laser device that continuously outputs such a high-power laser beam is large and expensive, and is not practical.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser beam having a large power in a light source device that emits light by irradiating a light-emitting tube enclosing a light-emitting element with a laser beam. A light source device that can stably maintain a high-temperature plasma state after the start of lighting without irradiating light, stably maintain light emission, and can suppress a decrease in lighting life due to heating of the arc tube. It is to be.

Since the pulsed laser beam has a large peak power, it is possible to excite the gas sealed in the arc tube with a relatively small output of the laser device. On the other hand, since a continuous wave laser beam is not cut off like a pulsed laser beam, it is possible to maintain light emission by irradiating the arc tube in a high temperature plasma lighting state with the continuous wave laser beam. .
In view of the above, the present inventor has tried to light an arc tube in which a light emitting element is sealed using both a pulse laser beam and a continuous wave laser beam. As a result, a light emitting tube filled with a light emitting element is irradiated with a pulsed laser beam to start lighting, and at the same time, a continuous wave laser beam is irradiated to maintain lighting, thereby using a relatively low power laser device. It was confirmed that it was possible to start the lighting of the arc tube with certainty and to maintain the lighting stably after the lighting was started.
Here, in order to maintain the light emission, it is necessary that the high energy state region formed by the pulse laser beam and the high energy state region formed by the continuous wave laser beam overlap in the arc tube.
Therefore, if the laser device is arranged so that the optical path of the pulse laser beam and the optical path of the continuous wave laser beam overlap in the entire region of the arc tube, the region in a high energy state formed by the pulse laser beam and the continuous wave laser beam can be obtained. It can be easily and reliably overlapped in the arc tube.
In addition, by using a continuous wave laser beam as excitation light and generating a pulse laser beam, a pulsed laser beam whose optical path overlaps the continuous wave laser beam can be generated with a relatively simple configuration.

Based on the above, the present invention solves the above problems as follows.
(1) The light source device includes an arc tube in which a light emitting element is sealed, a pulse laser oscillation unit that emits a pulse laser beam toward the arc tube, and a continuous wave laser oscillation that emits a continuous wave laser beam toward the arc tube The continuous wave laser beam has a smaller intensity than the pulsed laser beam.
(2) In the above (1), the pulsed laser beam is irradiated only at the start of light emission when causing the arc tube to emit light, and after the light emission, the irradiation of the pulsed laser beam is stopped and the continuous wave laser is emitted. Irradiate only the beam.

In the present invention, the following effects can be obtained.
(1) The light source device includes an arc tube in which a light emitting element is sealed, a pulse laser oscillation unit that emits a pulse laser beam toward the arc tube, and a continuous wave laser oscillation that emits a continuous wave laser beam toward the arc tube Therefore, the high-temperature plasma state can be maintained with the pulsed laser beam, the high-temperature plasma state can be maintained with the continuous beam, the high-temperature plasma state can be prevented from being cut off, and the discharge state can be stabilized.
In addition, the intensity of the continuous wave laser beam may be the intensity necessary to maintain a high temperature plasma state, and a laser oscillation unit having a relatively small power can be used. it can.
In addition, since the pulsed laser beam has a high peak power, it is possible to create a high-temperature plasma state with a laser device having a relatively small average output, and the continuous wave laser oscillation unit also has an oscillation unit with a relatively small output. Since it can be used, the apparatus does not increase in size.
(2) By configuring the optical path of the beam from the pulse laser oscillating unit and the optical path of the beam from the continuous wave laser oscillating unit to overlap at least in the entire region in the arc tube, the pulsed laser is generated inside the arc tube. The region of the high energy state of the beam and the continuous wave laser beam can be reliably superimposed. For this reason, generation | occurrence | production of a high-temperature plasma state and maintenance of a high-temperature plasma state can be performed reliably, a high-temperature plasma state can suppress interruption and can be discharged stably.
(3) The pulse laser oscillating unit is configured to excite a laser crystal in the pulse laser oscillating unit by using a part of the beam from the continuous wave laser oscillating unit as excitation light and to emit a pulse laser beam. Thus, the device configuration can be simplified. Further, the optical paths of the pulsed laser beam and the continuous wave laser beam can be reliably overlapped, and the high temperature plasma state can be generated and the high temperature plasma state can be reliably maintained.
(4) By setting the continuous wave laser beam to an intensity smaller than that of the pulsed laser beam, it is possible to suppress the formed high temperature plasma state from being cut off and maintain the high temperature plasma stably.
Furthermore, by irradiating the pulsed laser beam only at the start of light emission and stopping the irradiation of the pulsed laser beam after light emission, it is possible to prevent the high temperature plasma from being cut off by the shock wave of the pulsed beam. .
(5) Condensing means is provided in the middle of the optical path of the pulse laser beam and the continuous wave laser beam to condense the pulse laser beam and the continuous wave laser beam in the arc tube, and in the middle of at least one optical path of the laser beam. By providing the optical means, the high energy state region formed by the pulsed laser beam and the high energy state region formed by the continuous wave laser beam can be surely overlapped.
Further, by providing the optical means as described above, even if the wavelengths of the pulse laser beam and the continuous wave laser beam are different, the chromatic aberration due to the difference can be corrected, and a high energy state formed by the pulse laser beam. This region can be reliably overlapped with the high energy state region formed by the continuous wave laser beam.

It is a figure which shows the structural example at the time of applying the light source device of this invention to exposure apparatus. It is a figure which shows the 1st Example of the light source device which concerns on this invention. It is a schematic diagram of a pulsed beam and a continuous wave beam inside the arc tube. It is a figure explaining the state of a continuous wave beam and a pulse-shaped beam inside an arc tube. It is a figure which shows the 2nd Example of the light source device which concerns on this invention. It is a figure which shows the 3rd Example of the light source device which concerns on this invention. It is a figure which shows the 4th Example of the light source device which concerns on this invention. It is a figure which shows the 5th Example of the light source device which concerns on this invention. It is a figure which shows the 6th Example of the light source device which concerns on this invention. It is a figure which shows the 7th Example of the light source device which concerns on this invention. It is a figure which shows the 8th Example of the light source device which concerns on this invention. It is a figure which shows the 9th Example of the light source device which concerns on this invention. It is a figure explaining a chromatic aberration. It is a figure which shows the 10th Example of the light source device which concerns on this invention. It is a figure which shows the example of arrangement | positioning of the optical means for suppressing chromatic aberration. It is a figure which shows the 11th Example of the light source device which concerns on this invention. It is a figure explaining the case where a high temperature plasma state is formed in the near side of a condensing point with a pulse-shaped beam. It is a schematic diagram of a pulsed laser beam and a continuous wave laser beam.

FIG. 1 is a diagram showing a configuration example when the light source device according to the present invention is applied to an exposure apparatus which is one example of its use, and FIG. 2 is a diagram showing a first embodiment of the light source device according to the present invention. is there.
First, an exposure apparatus provided with the light source device of the present invention will be described with reference to FIG.
The exposure apparatus includes a light source device 10 that emits light. The light source device 10 will be described in detail with reference to FIG.
The light source device 10 includes a laser oscillating unit 2, a condensing unit 3 that condenses the light from the laser oscillating unit 2, and an arc tube 1 into which the light collected by the condensing unit 3 is incident. . Although only one laser oscillation unit 2 is shown in FIG. 1, as will be described later, the laser oscillation unit 2 includes a pulse laser oscillation unit that outputs a pulsed laser beam and a continuous laser beam that outputs a continuous wave laser beam. It consists of a wave laser oscillator.
A mechanical shutter 7 and a mirror 8 are provided on the optical path of the beam from the laser oscillating unit 2 to the light condensing unit 3, and opening / closing of the shutter 7 controls the emission / non-emission of the beam.
The arc tube 1 is substantially surrounded by a mirror 11a having a spheroid reflecting surface. The mirror 11 a has one through hole 111 for receiving light from the laser oscillation unit 2 and the other through hole 112 for emitting light that has passed through the arc tube 1.

The mirror 11 a and the arc tube 1 are housed in the lamp house 11.
The lamp house 11 is provided with condensing means 3 constituting the light source device 10. The lamp house 11 is also provided with a condensing unit 11b that condenses the light emitted from the other through-hole 112 of the condensing mirror 11a.
A beam damper 12a is disposed outside the lamp house 11 so that light from the light converging means 11b enters, attenuates the incident light, and does not return to the lamp house.
A beam from the laser oscillating unit 2 is incident on the arc tube 1, and the luminescent gas inside the arc tube is excited to generate excitation light. This excitation light is condensed by the mirror 11 a, emitted toward the lower side of the drawing in FIG. 1, and reaches the dichroic mirror 13. The dichroic mirror 13 reflects light having a wavelength necessary for exposure and transmits other light. A beam damper 12b is disposed on the back surface of the dichroic mirror 13, and the light transmitted through the dichroic mirror 13 is condensed and terminated here.

The light reflected by the dichroic mirror 13 is focused by condensing by the condensing mirror 11a, and passes through the aperture portion 14a of the filter 14 disposed at this focal position. At this time, the light is shaped into the shape of the aperture portion 14a.
The light that has passed through the aperture portion 14a is condensed by the condensing means 15a disposed in the middle while spreading and becomes substantially parallel light.
This light enters the integrator lens 16 and is condensed by the condensing means 15b disposed on the exit side. The light emitted from each cell lens of the integrator lens 16 is condensed by the condensing means 15b, so that the light is superimposed at a short distance, and the illuminance is made uniform.
The light emitted from the condensing means 15 b is reflected by the mirror 17 and enters the collimator lens 18 while being superimposed. The light emitted from the collimator lens 18 is converted into parallel light, passes through a mask 19, and irradiates an object W such as a silicon wafer. Thus, the light from the light source device irradiates the object W to be processed.

Next, the light source device according to the first embodiment of the present invention will be described with reference to FIG.
In the first to fourth embodiments described below, the optical path of the beam from the continuous wave laser oscillation unit 25 and the optical path of the beam from the pulse laser oscillation unit 21 are different. The case where the light is collected by being superimposed is shown.
The light source device shown in FIG. 2 which is the first embodiment of the present invention includes an arc tube 1 in which a luminescent gas is sealed, and a diffractive optical element 31 (DOE: Diffractive Optical) that focuses inside the arc tube 1. Element), a pulse laser oscillation unit 21 that makes a pulsed beam incident on the diffractive optical element 31, and a continuous wave laser oscillation unit 25 that makes a continuous wave beam incident on the diffractive optical element 31. In this embodiment, the wavelengths of the laser beams from the laser oscillation units 21 and 25 are the same. Hereinafter, a continuous wave beam is also referred to as a CW beam, and a continuous wave laser oscillation unit is also referred to as a CW laser oscillation unit. A pulsed beam is also called a pulse beam.
The arc tube 1 is composed of a member (for example, quartz glass) that transmits beams from the laser oscillation units 21 and 25 and transmits excitation light of a light emitting element.
The arc tube 1 may have any shape as long as it can enclose a light emitting element. However, when the luminescent element is sealed at a high pressure (atmospheric pressure greater than atmospheric pressure), if the inner surface shape is a spheroidal surface or a spherical surface, the pressure is applied substantially uniformly to the inner surface of the arc tube 1, so that durability is considered. Good.
A luminous element is enclosed in the arc tube 1, and various luminous elements are used depending on the application. For example, mercury is used as a light emitting element as a light source for exposure. For example, as a light source for a projector, xenon gas is used as a light emitting element.

The laser oscillation units 21 and 25 are supplied with power from a power supply device (not shown).
The pulse laser oscillation unit 21 outputs a pulsed beam, and the continuous wave laser oscillation unit 25 outputs a continuous wave beam. Both of these are incident on the diffractive optical element 31 (DOE) at the same angle (parallel in the case of the figure), so that they are overlapped inside the arc tube 1 to be focused after passing. At this time, inside the arc tube 1, as shown in FIG. 3A, the pulsed beam and the continuous wave beam overlap each other.

The light emitting element sealed inside the arc tube 1 requires a large amount of energy in order to form a high temperature plasma state. Since the pulsed beam is intermittent but can form high energy, it is assumed that the light-emitting element is formed in a high-temperature plasma state by this beam.
After forming the high temperature plasma state, the energy required to maintain this state may be smaller than when forming the high temperature plasma state and must be continuously supplied. The continuous beam is superimposed in the arc tube 1 at the position where the pulsed beam is incident, and has a small energy with respect to the pulsed beam (the vertical axis in FIG. 3A indicates relative energy). Value is continuous), so that a high temperature plasma state can be maintained.
Thus, the pulse laser oscillation unit 21 functions as an ignition source for starting a high temperature plasma state, and the continuous wave laser oscillation unit 25 functions as a heating source for heating the high temperature plasma state.

As described above, the light source device of the present invention has the following features (1) and (2).
(1) A pulsed laser beam and a continuous wave laser beam are superposed inside the arc tube 1.
(2) The continuous wave laser beam has a smaller intensity (energy) than the pulsed laser beam.
Thereby, at the start of lighting, a high-temperature plasma state can be formed by a pulsed beam. Furthermore, by superimposing a continuous wave beam with a lower intensity than the pulsed beam at the position where this high temperature plasma state is formed, the high temperature plasma state is prevented from being interrupted and the high temperature plasma state is maintained stably. it can.
In addition, the continuous wave beam is less intense than the pulsed beam, so the energy input into the arc tube is not large, and it can be suppressed that the arc tube is heated and distorted. The service life can be extended.
Further, the continuous wave laser oscillating unit does not need to output so much energy that it can form a high-temperature plasma state, and thus can be realized by using a laser apparatus that is currently in practical use.
Note that a high-temperature plasma state is easily formed by forming a high-density energy region. For this reason, it is preferable to focus so that it may have a focus inside an arc tube.

In order to confirm that the continuous-wave laser beam requires less energy than the pulsed beam, an arc tube (quartz glass) filled with quinocene at 10 atm is prepared, and the pulsed laser beam (527 nm) and the continuous-wave laser beam are prepared. (1070 nm) was collected by optical means (convex lens) and superimposed inside the arc tube, and the emission of the arc tube was examined. As a result, it was confirmed that the arc tube emits light continuously under the following input conditions, for example.
・ Pulse laser beam input condition example Repeat frequency: 1000Hz
Energy: 5mJoule / shot Pulse width: 80ns
Average power: 5W
Peak power: 62.5kW
・ Example of input conditions of continuous wave laser beam Power: 200W
In the above example, the power of the continuous wave laser beam is about 0.03% of the power of the pulsed laser beam. In this way, the arc tube can be lit even if the power of the continuous wave laser beam is smaller than the power of the pulsed laser beam.

The reason why the power of the continuous wave laser beam may be smaller than the power of the pulsed laser beam is considered as follows.
In the arc tube, a high temperature plasma state is formed by inputting high energy into the arc tube at the start of lighting. Once the high temperature plasma is formed, energy is input from the outside, so that the high temperature plasma is excited and emits light.
However, when a pulsed beam with high energy is input from the outside, the formed high-temperature plasma state is blown away by a shock wave when plasma is generated by a pulse laser, and energy is input to the high-temperature plasma state. It can no longer be excited.
Thus, the energy required at the start of lighting is energy for forming a high-temperature plasma state, and the energy required after starting lighting is energy for exciting the high-temperature plasma state. In comparison, the energy for exciting the high-temperature plasma state may be significantly lower.
For this reason, an extremely low energy such as 0.03% is sufficient for the power of the continuous wave beam for exciting the high temperature plasma state as compared with the power of the pulsed beam. Also, if power is input more than necessary, the conventional problem of heating and damaging the arc tube wall will occur, so the power of the continuous wave beam is as low as 0.03%. There is a need.

As mentioned above, a pulsed beam is always necessary at the start of lighting, but if the energy of the continuous beam is sufficient to maintain lighting, high-temperature plasma that has been continuously lit up if the pulse is continued for a long time. May be cut off by a shock wave of a pulsed beam. For this reason, after starting lighting, it is considered preferable to eliminate the input of a pulsed beam as shown in FIG.
As described above, the light source device of the present invention can maintain a high-temperature plasma state and has a long lighting life. Therefore, for example, in the exposure apparatus shown in FIG. The irradiated object can be irradiated for a long time.
The light source device according to the present invention can be used as a light source of the exposure apparatus shown in FIG. 1, and if the light emitting element in the arc tube is changed, the light emitted from the arc tube has various wavelengths. For example, the light source can be used as a light source for a projector that is a visible light source. This is because a light source called a lamp in which a pair of electrodes are opposed to each other inside a conventional arc tube is used in various applications. It can be used as an alternative and can be used in various applications similar to lamps.

Numerical examples and member examples in the first embodiment will be described below.
-Arc tube members: Quartz glass-Arc tube outer diameter: 30mm
・ Inner diameter of arc tube: 26 mm
・ Luminescent element enclosed in arc tube: Xenon Xenon gas enclosure pressure or quantity: 10 atm.
・ Laser crystal of pulse laser oscillation part: YAG crystal ・ Laser crystal of continuous wave laser oscillation part: YAG crystal ・ Conditions of input power to the pulse laser oscillation part:
-Wavelength of the beam from the pulse laser oscillator: 1064 nm
-Wavelength of beam from continuous wave laser oscillator: 1064 nm
-Beam output from pulse laser oscillator: 1 to 100 mJ
Pulse repetition frequency: 0.01 to 10 kHz
-Beam output from continuous wave laser oscillator: 20 to 10 kW

In the present invention, the pulsed beam and the continuous beam are superposed inside the arc tube. The high-temperature plasma state generated inside the arc tube by the pulsed beam is generated when the energy density of the beam is equal to or higher than the threshold value for ionizing the luminescent element, and the ionized luminescent element has a high density.
For this reason, by condensing the beam by the condensing optical system component, the energy density of the beam is increased, and the light emitting element is made to be equal to or higher than the ionization threshold.
At this time, since the energy density of the pulsed beam is larger than the energy density of the continuous beam, the region above the threshold value for ionizing the light emitting element (region in the high energy state) is longer than the continuous beam. End up. Therefore, as shown in FIG. 4, it is desirable that the continuous wave laser beam (CW beam) is irradiated in the vicinity of the center of the region equal to or greater than the threshold lengthened by the pulsed beam. The continuation is performed well, and the lighting performance can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG.
The light source device shown in FIG. 5 uses a convex lens instead of the DOE 31 shown in FIG. 2, and a light emitting tube 1 in which a light emitting gas is sealed and a pulse-like shape inside the light emitting tube 1. It is comprised from the convex lens 32 arrange | positioned so that a beam and a continuous wave beam may focus. In FIG. 5, the beams indicated as “CW or pulse” and “pulse or CW” mean either a continuous wave laser beam or a pulsed laser beam. When one beam is a continuous wave laser beam, the other Is a pulsed laser beam (the same applies to the following examples).
As long as it is an optical means that can focus inside the arc tube, the convex lens 32 can be used as described above. In this case, each beam is incident on the convex lens 32 at the same angle.
Also in the present embodiment, as in the light source device of the first embodiment, the high-temperature plasma state can be stably maintained, and the continuous wave beam is less intense than the pulse beam, so that the arc tube is heated. Generation | occurrence | production of distortion can be suppressed and, thereby, a lighting lifetime can be made long. Further, it can be realized as a continuous wave laser oscillating unit using a laser apparatus that is currently in practical use.

A third embodiment of the present invention will be described with reference to FIG.
In FIG. 6, instead of the DOE 31 and the convex lens 32 shown in FIG. 2 and FIG. 5, a parabolic mirror 33 is disposed at a position that surrounds the arc tube 1 and is focused inside the arc tube 1. Is.
In this case, the optical path (optical axis) of the pulsed beam from the pulse laser oscillation unit and the optical path (optical axis) of the continuous wave beam from the continuous wave laser oscillation unit are parallel to each other, and the reflecting surface of the parabolic mirror 33 Is incident on. At this time, the beam reflected by the reflecting surface is condensed so as to be focused toward the inside of the arc tube.
In this embodiment, similarly to the light source device of the above embodiment, the high-temperature plasma state can be stably maintained, and the continuous wave beam has a lower intensity than the pulsed beam, so that the arc tube is heated and the distortion is caused. Generation | occurrence | production can be suppressed and a lighting lifetime can be made long by this. Further, it can be realized as a continuous wave laser oscillating unit using a laser apparatus that is currently in practical use.

A fourth embodiment of the present invention will be described with reference to FIG.
In FIG. 7, an elliptical mirror 34 is arranged so as to surround the arc tube 1 instead of the parabolic mirror 33 shown in FIG. 6.
The elliptical mirror 34 is arranged so that the first focal point is located inside the arc tube 1 and the second focal point is located outside the arc tube 1.
Each laser oscillation part is arrange | positioned so that each beam may pass a 2nd focus. Condensing means 3 (convex lens or DOE) for condensing at the second focal point is disposed on the optical path of each beam.
Each beam is collected at the second focal point of the elliptical mirror 34 and reflected by the reflecting surface of the elliptical mirror 34. Since the light condensed at the second focal point is also condensed at the first focal point, each beam is condensed inside the arc tube 1 so as to be focused.
Also in this embodiment, as in the light source device of the above embodiment, the high-temperature plasma state can be stably maintained, and the lighting life can be extended. Further, it can be realized as a continuous wave laser oscillating unit using a laser apparatus that is currently in practical use.

In the first to fourth embodiments described above, each beam follows a different optical path, and finally overlaps inside the arc tube. Thus, it is technically difficult to follow different optical paths and overlap at a desired position. For example, even if the optical path of the beam is set so that the light is condensed at the same position in the arc tube and the optical means is arranged, the refractive index changes when the environment changes, for example, when the temperature rises, and the condensing position May shift.
In the fifth to ninth embodiments described below, the optical paths of the beams overlap at least in the entire region in the arc tube. With this configuration, for example, even if the temperature rises and the refractive index changes, the condensing positions of the pulsed beam and the continuous wave beam do not deviate greatly.
A fifth embodiment will be described with reference to FIG.
In the example shown in FIG. 8, the optical path of the pulsed beam and the continuous wave beam is overlapped by using the dichroic mirror 4 and is condensed by the condensing means 3 (convex lens or DOE). Other configurations are the same as those shown in FIG.

In FIG. 8, the wavelengths of the pulse beam and the continuous wave beam are different, so that one of the beams incident on the dichroic mirror 4 is reflected and the other is transmitted.
By utilizing this, in the present embodiment, the optical path of each beam is overlapped between the dichroic mirror 4 and the arc tube 1.
For example, it is assumed that one beam (indicated by a thick line) has a wavelength of 1064 nm and the other beam (indicated by a solid line) has a wavelength of 532 nm.
The dichroic mirror 4 reflects light of 532 nm but transmits light of 1064 nm, so that the transmitted 1064 nm beam can be superimposed on the optical path of the beam of 532 nm reflected by the dichroic mirror 4. That is, the optical path can be positioned on the same axis.
Note that the high-temperature plasma state is easily formed by forming high-density energy. For this reason, as shown in FIG. 8, it is preferable to condense with the condensing means 3 (a convex lens or DOE) so that it may have a focus in the inside of the arc_tube | light_emitting_tube 1. FIG.

Thus, by superimposing the optical paths of the beams along the path to the arc tube 1, both can be superimposed even inside the arc tube, so that the high energy state of each beam is inside the arc tube. Can be reliably overlapped. For this reason, generation | occurrence | production of a high temperature plasma state and maintenance of a high temperature plasma state can be performed reliably, and it can discharge stably.
Further, since the power of the continuous wave laser beam may be small as in the light source device of the above embodiment, it is possible to suppress the arc tube from being heated and distorted, and the lighting life can be extended. In addition, the continuous wave laser oscillating unit can be realized by using a laser apparatus that is currently in practical use.

A sixth embodiment will be described with reference to FIG.
In FIG. 9, a polarizing mirror 5 is arranged in place of the dichroic mirror shown in FIG. 8, and the other configuration is the same as that of FIG.
The polarizing mirror 5 reflects and transmits the polarized light (P-polarized light and S-polarized light) at the same wavelength. By using this, the optical path of each beam overlaps between the polarizing mirror 5 and the arc tube 1. Can be matched.
For example, it is assumed that one beam (shown by a thick line) is P-polarized light having a wavelength of 1064 nm, and the other beam (shown by a solid line) is also S-polarized light having a wavelength of 1064 nm. Suppose that P-polarized light is transmitted and S-polarized light is reflected.
As a result, the transmitted P-polarized beam can be superimposed on the optical path of the S-polarized beam reflected by the polarizing mirror 5. That is, the optical path can be positioned on the same axis.
As described above, by superimposing the optical paths of the respective beams along the path to the arc tube 1, it is possible to reliably overlap the high energy state regions of the respective beams inside the arc tube as in the fifth embodiment. It is possible to reliably generate the high temperature plasma state and maintain the high temperature plasma state.
Further, since the power of the continuous wave laser beam may be small as in the light source device of the above embodiment, it is possible to suppress the arc tube from being heated and distorted, and the lighting life can be extended. In addition, the continuous wave laser oscillating unit can be realized by using a laser apparatus that is currently in practical use.

Next, seventh to ninth embodiments of the present invention in which a part of the beam from the continuous wave laser oscillating unit is used as the seed laser of the pulse laser oscillating unit will be described.
FIG. 10 is a diagram showing a seventh embodiment of the present invention.
In FIG. 10, the pulse laser oscillator 22 is arranged on the optical path of a beam from a continuous wave laser oscillator (not shown), and other configurations are the same as those in the above embodiment.
In this embodiment, the pulse laser oscillation unit 22 excites a laser crystal in the pulse laser oscillation unit 22 by using a part of the continuous wave beam (CW beam) from the continuous wave laser oscillation unit as excitation light.
That is, as shown in FIG. 10, the pulse laser oscillation unit 22 is disposed in the path of the CW beam emitted from the continuous wave laser oscillation unit (not shown). The pulse laser oscillation unit 22 operates using the CW beam as excitation light and outputs a pulsed beam. This pulsed beam is superimposed on the optical path of the CW beam and is condensed in the arc tube 1 through the condensing means 3 (convex lens, DOE, etc.).

With this configuration, the optical path of the beam from the pulse laser oscillator 22 is superimposed on the optical path of the beam of the continuous wave laser, and is also superimposed inside the arc tube 1. In the present embodiment, since the optical paths of the respective beams are overlapped in the path to the arc tube 1, the high energy state regions of the respective beams can be surely overlapped in the arc tube as in the above embodiment. It is possible to reliably generate the high temperature plasma state and maintain the high temperature plasma state.
Further, since the power of the continuous wave laser beam may be small as in the light source device of the above embodiment, it is possible to suppress the arc tube from being heated and distorted, and the lighting life can be extended. In addition, the continuous wave laser oscillating unit can be realized by using a laser apparatus that is currently in practical use.
Further, since the pulse laser oscillation unit 22 uses a beam from a continuous wave laser as excitation light, a part of the laser oscillation part for the pulse laser oscillation unit shown in the first to sixth embodiments may be omitted. Thus, the entire apparatus can be made simple and the entire light source apparatus can be miniaturized.

FIG. 11 is a diagram showing an eighth embodiment of the present invention. As in the seventh embodiment, FIG. 11 shows a configuration example in which a pulse laser oscillation unit is oscillated using CW laser as excitation light.
As shown in FIG. 11, a part of the CW beam emitted from a continuous wave laser oscillating unit (not shown) is reflected by the partial reflection mirror 23 a and is incident on the pulse laser oscillating unit 23. The pulse laser oscillator 23 operates using the CW beam as excitation light and outputs a pulsed beam. This pulsed beam is incident on the dichroic mirror 4 and overlaps the optical path of the CW beam, and is condensed in the arc tube 1 via the condensing means 3 (convex lens, DOE, etc.).
Here, the operation in the pulse laser oscillation unit 23 will be described on the assumption that the wavelength of the continuous wave laser beam is 808 nm and the wavelength of the pulse laser beam is 1064 nm.
The partial reflection mirror 23a reflects a part of the beam having a wavelength of 808 nm and transmits the rest. The partially reflected beam is condensed by the condenser lens 23b and is incident on the total reflection mirror 23c.
The total reflection mirror 23c transmits the beam incident from the back surface and reflects the beam incident from the front surface. For this reason, the beam condensed by the condensing lens 23b is incident from the back side of the total reflection mirror 23c, is transmitted, and is irradiated to the laser crystal 23d. For example, a YAG crystal or Nd glass is used for the laser crystal 23d, and the laser crystal 23d is excited by transmitting light with a wavelength of 808 nm.

In a state in which the Q switch 23e is closed, the laser crystal 23d is excited and stored by continuously irradiating the beam.
When the desired energy is reached, the Q switch 23e is opened, the excitation light from the laser crystal 23d is reflected by the exit mirror 23f, and resonance is caused between the total reflection mirror 23c and the exit mirror 23f. As a result, a pulsed laser beam having a wavelength of 1064 nm is transmitted through the exit mirror 23f and is incident on the dichroic mirror 4 via the mirrors 23g and 23h.
The dichroic mirror 4 reflects a beam having a wavelength of 1064 nm and transmits a beam having a wavelength of 808 nm, so that the pulsed beam having a wavelength of 1064 nm is superimposed on a continuous wave beam having a wavelength of 808 nm. This beam is condensed by the condensing means 3 and travels toward the inside of the arc tube 1. The pulse width and period of the pulsed laser beam are determined by the opening time of the Q switch 23e.
Note that the optical means 6 indicated by a dotted line in FIG. 11 is for suppressing chromatic aberration caused by the difference in wavelength between the pulse beam and the CW beam, and the suppression of chromatic aberration will be described later.
Also in this embodiment, the same effects as those of the seventh embodiment can be obtained, the generation of the high temperature plasma state and the maintenance of the high temperature plasma state can be reliably performed, and the power of the continuous wave laser beam can be obtained. Therefore, the arc tube can be prevented from being heated and distorted, and the lighting life can be extended. In addition, the continuous wave laser oscillating unit can be realized by using a laser apparatus that is currently in practical use.
Further, since the pulse laser oscillation unit 23 uses a beam from a continuous wave laser as excitation light, the laser oscillation part for the seed fire in the pulse laser oscillation unit shown in the first to sixth embodiments may be omitted. Thus, the entire apparatus can be made simple and the entire light source apparatus can be miniaturized.

FIG. 12 is a diagram showing a ninth embodiment of the present invention. As in the seventh embodiment, FIG. 12 shows a configuration example in which a pulse laser oscillation section is oscillated using CW laser as excitation light.
As shown in FIG. 12, a part of the CW beam emitted from a continuous wave laser oscillating unit (not shown) is reflected by a partially reflecting mirror and dichroic mirror 24 d and is incident on the pulse laser oscillating unit 24. The pulse laser oscillation unit 24 operates using the CW beam as excitation light and outputs a pulsed beam. This pulsed beam is superimposed on the optical path of the CW beam and is condensed in the arc tube 1 via the condensing means 3 (convex lens, DOE, etc.).
Here, the operation of the pulse laser oscillation unit 24 will be described assuming that the wavelength of the beam of the continuous wave laser is 808 nm and the wavelength of the beam of the pulse laser is 1064 nm.
As described above, the dichroic mirror 4 reflects a certain wavelength and transmits another wavelength. Here, a beam having a wavelength of 1064 nm is reflected and a beam having a wavelength of 808 nm is transmitted.
A partial reflection mirror and dichroic mirror 24d provided on the output side of the pulse laser oscillation unit 24 reflects a part of a certain wavelength and transmits another wavelength. Here, it is assumed that a part of the 1064 nm beam is reflected and the light of 808 nm is transmitted.
As the laser crystal 24c, for example, a YAG crystal or Nd glass is used, and when a 1064 nm beam is transmitted, a part of the laser crystal 24c is absorbed and excited to oscillate.

In a state where the EO switch 24a functioning as the Q switch is closed, the laser crystal 24c is continuously irradiated with a beam and excited to accumulate energy.
When the desired energy is reached, the EO switch 24a is opened, the excitation light from the laser crystal 24c is reflected by the total reflection mirror 24b, and resonance is caused between the partial reflection mirror and the dichroic mirror 24d. As a result, a pulsed laser beam having a wavelength of 1064 nm is partially transmitted through the partial reflection mirror and the dichroic mirror 24d, and is superimposed on the continuous wave beam. The pulsed beam and the continuous wave beam travel toward the inside of the arc tube 1 through the condensing means 3. The pulse width and period of the pulsed laser beam are determined by the opening time of the EO switch 24a.
Note that the optical means 6 indicated by a dotted line in FIG. 12 is for suppressing chromatic aberration caused by the difference in wavelength between the pulse beam and the CW beam, and the suppression of chromatic aberration will be described later.
Also in this embodiment, the same effect as in the eighth embodiment can be obtained, the generation of the high temperature plasma state and the maintenance of the high temperature plasma state can be reliably performed, and the power of the continuous wave laser beam can be obtained. Therefore, the arc tube can be prevented from being heated and distorted, and the lighting life can be extended. In addition, the continuous wave laser oscillating unit can be realized by using a laser apparatus that is currently in practical use.
Furthermore, since the pulse laser oscillation unit 22 uses a beam from a continuous wave laser as excitation light, the laser oscillation part for the seed fire in the pulse laser oscillation unit shown in the first to sixth embodiments can be omitted. The whole can have a simple structure.

As described above, in order to form a high-temperature plasma state inside the arc tube 1, it is preferable to form a high-density energy. For this reason, the light condensing means 3 has a focal point inside the arc tube 1. It is possible to condense.
When a convex lens or the like is used as the condensing unit 3, the focal point is focused at the same position when the wavelength of each beam is the same, but when the wavelength of each beam is different, the solid line and the dotted line in FIG. As shown, chromatic aberrations that focus at different positions occur.
When this chromatic aberration occurs, the continuous wave beam may not be focused in the high temperature plasma state region formed by the pulsed beam, and the high temperature plasma state may not be maintained by the continuous beam.
Means for suppressing this chromatic aberration will be described below in the tenth and eleventh embodiments.

A tenth embodiment will be described with reference to FIG.
FIG. 14 shows an arrangement in which optical means 6a and 6b for suppressing chromatic aberration are individually arranged in the second embodiment shown in FIG. 5 when the wavelength of the pulsed beam and the continuous wave beam are different. The other configurations are the same as those shown in FIG.
In FIG. 14, optical means 6a and 6b are provided on the optical paths until both beams overlap, and the functions and positions of the optical means are as described in (1) to (3) below. It can be either.
(1) As shown in FIG. 15 (a), one optical means 6a is provided in the optical path of a pulsed laser beam, and the other optical means 6b having a focal length different from the one optical means is continuously provided. It is provided in the middle of the optical path of the wave laser oscillating unit, and the distance from one optical means 6a to the overlapping position of each beam is the same as the distance from the other optical means 6b to the overlapping position of each beam.
(2) As shown in FIG. 15 (b), one optical means 6a is provided in the middle of the optical path of the pulse laser oscillation section, and the other optical means 6b having a focal length different from the one optical means 6a is Provided in the middle of the optical path of the continuous wave laser oscillating unit, the distance from the one optical means 6a to the overlapping position of each beam is made different from the distance from the other optical means 6b to the overlapping position of each beam. (3) As shown in FIG. 15 (c), one optical means 6a is provided in the middle of the optical path of the pulse laser oscillation section, and the other optical means 6b having the same focal length as the one optical means 6a is Provided in the middle of the optical path of the continuous wave laser oscillating unit, the distance from the one optical means 6a to the overlapping position of each beam is made different from the distance from the other optical means 6b to the overlapping position of each beam.

Optical means for eliminating the chromatic aberration of each beam is individually provided on the optical path of each beam, and the chromatic aberration due to the difference in the wavelength of each beam can be suppressed by configuring as in the above (1) to (3). The state can be maintained well.
In the case of (1), chromatic aberration is suppressed by the difference between the focal lengths f1 and f2 of the optical means.
In the case of (2), the chromatic aberration is suppressed by the difference between the focal lengths f1 and f2 of the optical means and the distance from the optical means to the overlapping position.
In the case of (3), chromatic aberration is suppressed by each optical means and the distance to the overlapping position.
FIG. 15 is a schematic diagram. Actually, the optical axes of the beams that have passed through the optical means 6a and 6b coincide with each other before entering the condensing means such as the convex lens 32.

An eleventh embodiment will be described with reference to FIG.
FIG. 16 shows at least an optical means 6 for eliminating the chromatic aberration of each beam in order to suppress chromatic aberration when the wavelength of the pulse beam and the continuous wave beam are different from each other in the fifth embodiment shown in FIG. It is provided on one optical path, and the other configuration is the same as that shown in FIG.
The configuration shown in FIG. 16 is configured such that the optical path of the pulsed beam and the continuous wave beam is overlapped by using the dichroic mirror 4 and is condensed by the condensing means 3. The optical means 6 for suppressing chromatic aberration caused by the difference in the wavelength of the continuous wave beam is arranged on the incident side of the dichroic mirror 4.
Also in this embodiment, chromatic aberration can be suppressed by appropriately selecting the focal length and position of the optical means 6.
Since the problem of chromatic aberration occurs when beams of different wavelengths are collected by a convex lens or the like that is a common condensing unit, it may occur in the above-described FIGS. 5 and 8 to 12. Therefore, the techniques described in the tenth and eleventh embodiments can be used in FIGS. 5 and 8 to 12.
8 to 10, chromatic aberration can be suppressed by providing the above-described optical means until the optical paths of the beams overlap. Further, in FIG. 11, the optical means 6a and / or the optical means 6b are arranged at the position indicated by the dotted line in FIG. 11, and the optical means 6 is provided at the position indicated by the dotted line in FIG. By disposing, chromatic aberration can be suppressed.
Although a convex lens is shown here as an optical means for suppressing chromatic aberration, other optical components can be used as long as the focal length can be changed, for example, a concave lens or DOE can be used.

The chromatic aberration occurs when the wavelength of the pulsed laser beam and the continuous wave laser beam are different. However, when the difference in wavelength is small, it is not necessary to provide a means for suppressing chromatic aberration, which will be described below. As described above, it is desirable to provide a means for correcting chromatic aberration when the wavelength differs approximately twice or more.
For example, the difference in focal position in fused silica when the focal length f = 100 mm is as follows depending on the wavelength.
When the wavelength of the continuous wave laser beam is 1064 nm, the position of the condensing point is 114.5 mm, and when the wavelength of the pulsed laser beam is 532 nm, the position of the condensing point is 111.8 mm. The difference between the focal positions is 2.7 mm.
The region of the high temperature plasma is extremely small, for example, a region having a diameter of 0.5 mm, and if the focal position is separated by 2.7 mm as described above, energy for exciting the high temperature plasma cannot be supplied, and steady lighting can be performed. Can not.
In particular, high-temperature plasma generated by a pulse laser is easily generated on the near side of the focal point due to the large pulse energy, and the position is further shifted to the near side. For this reason, when the wavelengths are different by a factor of 2 as described above, a condensing means for correcting chromatic aberration is required.
Note that the difference in focal position varies depending on the material of the optical means, and the region of the high temperature plasma state may be other than 0.5 mm depending on the input energy, and the above is an example, It is not limited to this.

By the way, in order to form a high-temperature plasma state inside the arc tube 1 as described above, it is preferable to form a high-density energy state region. It is conceivable to collect light so as to have
However, since the high temperature plasma state is formed when the energy density of the laser beam is equal to or higher than the threshold value for ionizing the light emitting element, the position where the high temperature plasma state is formed is not necessarily the focal point of the laser beam. That is, when the energy of the laser beam is large, the energy density exceeds the threshold before reaching the focal point, and in this case, a plasma state is formed before the focal point.

The case where the power of the pulsed beam is larger than the power of the continuous wave beam and a high-temperature plasma state is formed in front of the focal point by the pulsed beam will be described with reference to FIG.
As shown in FIG. 17A, when a convex lens or the like is used as the light condensing means 3, when the wavelengths of the respective beams are the same, the focal point is set at the same position.
Here, when the power of the pulsed beam is large, the energy density becomes high and starts forming a high-temperature plasma state in the middle of being focused by the focusing means 3 as shown in FIG. However, as the focal point is approached, the power of the pulsed beam is used to form the high temperature plasma, and when the focal point is reached, the power is almost lost. That is, the position where the high temperature plasma state A is formed by the pulsed beam is in front of the condensing point as shown in FIG.
On the other hand, since the beam of the continuous wave has a small power, it is condensed by the condensing means 3 to form an energy density that maintains a high-temperature plasma state at the focal position (B in the figure).
Then, as shown in FIG. 17A, a region A (high energy state region) where the pulsed beam forms a high temperature plasma state and a region B (high energy state) where the continuous wave beam maintains the high temperature plasma state. Unlike the state region), the high temperature plasma state may not be maintained with a continuous wave beam.

As the position adjusting means for adjusting the positions of both regions, the optical means 6 described in the means for suppressing chromatic aberration can be used.
For example, as shown in FIG. 16, the optical means 6 is provided on at least one optical path. When the optical means 6 is arranged in this way, the beam incident on the arc tube 1 is condensed by the optical means 6 and incident on the light collecting means 3 as shown in FIG. Focused. Thereby, the region B ′ for maintaining the high-temperature plasma state of the continuous wave beam is focused on the region A ′ where the pulsed beam forms the high-temperature plasma state, and the two overlap each other to maintain the high-temperature plasma state. Can do.
That is, as shown in FIG. 17C, a region where the density to the energy of the pulsed beam (solid line in the figure) exceeds a threshold value (a dashed line in the figure) for forming a high-temperature plasma state, and a continuous wave beam A region where the density (broken line in the figure) exceeds the threshold (two-dot chain line in the figure) that forms a high-temperature plasma state overlaps, and the high-temperature plasma state is reliably maintained.

In the above description, the beam having the same wavelength is collected by the same focusing means. However, even if the wavelengths are different, the problem of chromatic aberration, the region that forms the high temperature plasma state, and the high temperature plasma are described. The problem that the high temperature plasma state cannot be maintained may occur in combination with the problem that the region in which the state is maintained is different.
For this reason, even when the beams having different wavelengths are condensed by the same optical means, the above-mentioned solving means function effectively.

DESCRIPTION OF SYMBOLS 1 Arc tube 2 Laser oscillation part 21, 22, 23, 24 Pulse laser oscillation part 25 Continuous wave laser oscillation part
3 Condensing means 31 Diffractive optical element (DOE)
32 Convex lens 33 Parabolic mirror 34 Elliptical mirror 4 Dichroic mirror 5 Polarizing mirror 6, 6a, 6b Optical means (for suppressing chromatic aberration)
7 Mechanical shutter 8 Mirror 10 Light source device 11 Lamp house 11a Mirror (reflective surface of rotating ellipse)
11b Condensing means 111, 112 Through-holes 12a, 12b Beam damper 13 Dichroic mirror 14 Filter 14a Aperture parts 15a, 15b Condensing means 16 Integrator lens 17 Mirror 18 Collimator lens 19 Mask W Subject to be irradiated

Claims (2)

A light-emitting tube enclosing a light-emitting element, a pulse laser oscillation unit that emits a pulse laser beam toward the light-emitting tube,
A light source device comprising a continuous wave laser oscillating unit that emits a continuous wave laser beam toward the arc tube,
The continuous wave laser beam has a smaller intensity than the pulsed laser beam. 2. The pulsed laser beam is irradiated only at the start of light emission of the arc tube, and after the light emission, the pulsed laser beam stops irradiation and only the continuous wave laser beam is irradiated. Light source device.

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