JP4740908B2 - Lamp device - Google Patents

Description

  The present invention is formed by mounting a high-pressure discharge lamp having a sealing portion for inserting and sealing an electrode assembly at both front and rear ends of a light emitting portion to be mounted on a concave reflecting mirror. The present invention relates to a lamp device used in the above.

  A liquid crystal projector transmits light from a back surface of a liquid crystal panel that generates an image after passing through a light amount distribution uniformizing optical system (homogenizer) such as a rod lens or an array lens that flattens the light amount distribution of light emitted from a light source. The DLP projector is a type of video equipment that uses a reflective optical element called a DMD element (Digital Micromirror Device) instead of a liquid crystal panel to project an image on the front screen. is there.

FIG. 11A shows a basic configuration of a conventional lamp device 51 installed in the apparatus as a light source of such a liquid crystal projector, etc., and shows a high-pressure discharge lamp 52 and an ellipsoidal mirror or a reflector that reflects the light. And a concave reflecting mirror 53 formed of an object mirror.
In the high-pressure discharge lamp 52, a pair of electrode assemblies 57 is inserted from both side sealing portions 55A and 55B into a light emitting tube 56 in which sealing portions 55A and 55B are formed at both ends in the tube axis direction across the light emitting portion 54. ing.
The electrode assembly 57 is formed by welding a tip electrode portion 58 made of tungsten, a molybdenum foil 59 and a molybdenum wire 60 in series, and the tip electrode portion 58 is sealed in a state facing the light emitting portion 54. The portions 55A and 55B are hermetically sealed.

Then, one sealing portion 55A of the high pressure discharge lamp 52 is directed to the opening 53a side of the concave reflecting mirror 53, and the other sealing portion 55B is directed to the bottom 53b side of the concave reflecting mirror 53. 52 the optical axis Z _L of the tube axis Z _P and the concave reflecting mirror 53 is disposed coaxially.
As a result, the light irradiated from the light emitting portion 54 to the periphery thereof in a predetermined angle range in the front-rear direction is reflected by the concave reflecting mirror 53, and the light quantity distribution uniformizing optical system 61 such as a rod lens arranged in front of the lamp. The light condensing area 61in of a predetermined size such as the light incident surface is condensed and irradiated.

In this case, the use of the relatively large size of the reflector 53 as shown in FIG. 12 (a), although it is possible to effectively utilize the most of the light emitted at the angle range theta _21, the size and weight of the device When the concave reflecting mirror 53 is downsized as shown in FIG. 12B, the light use efficiency is inevitably lowered.
That is, when the concave reflecting mirror 53 is downsized, only the light emitted from the light emitting unit 54 at the predetermined angle θ ₂₁ to the rear side at the predetermined angle θ ₂₂ is reflected by the concave reflecting mirror 53 and collected. It reaches the optical area 61In, light emitted at a predetermined angle theta ₂₃ on the front side does not reach the light collection area 61In leaked around, so that not only the utilization efficiency of light is reduced, the light liquid There is a problem that the casing parts and the like in the projector apparatus are irradiated and deteriorated, damaged or deteriorated.
FIG. 13 is a graph showing the light distribution with respect to the light emission direction. The horizontal axis is the direction of the tube axis Z _L of the high pressure discharge lamp 52, and the vertical axis direction perpendicular to the tube axis Z _L through tube axis emission points on Z _L, concentric graduations light in the vertical axis direction 100% The light quantity ratio is shown.
According to this, among the light radiated from the high-pressure discharge lamp 52, only the light radiated at the predetermined angle θ ₂₂ (82 to 145 °) to the rear side is effectively used, and the angle θ ₂₃ ( It can be seen that light of 60 to 100% emitted at 45 to 82 ° is not used at all.

For this reason, as shown in FIG. 14A, the light emitted from the light emitting portion 54 of the high-pressure discharge lamp 52 toward the front opening 53a side of the concave reflecting mirror 53 is reflected toward the center (light emitting point) of the light emitting portion 54. There is also proposed one provided with a sub-reflecting mirror 62 or a reflecting film (not shown) (see Patent Documents 1, 2, 3, and 4).
According to this, the light radiated at the predetermined angle θ ₂₄ to the rear side is reflected by the concave reflecting mirror 53 and reaches the condensing area 61in, and the light radiated to the front side at the predetermined angle θ ₂₅ is sub-reflector 62. And again passes through the center (light emitting point) of the light emitting portion 54 and is reflected by the reflecting mirror 53 on the back side to reach the condensing area 61in. Therefore, the leakage of the light irradiated forward is suppressed and the light use efficiency is high.
JP 2005-309372 A Japanese Patent No. 3184404 Japanese Patent No. 3204733 JP 2005-505909 A

  However, since the sub-reflecting mirror 62 and the reflecting film reflect the light emitted from the light emitting unit 54 to the light emitting unit 54, the electrode disposed in the light emitting unit 54 is overheated by the reflected light, and from the front end portion thereof. The amount of evaporation of the electrode material increases and adheres to the inner surface of the light-emitting portion 54, which may cause early blackening. At the same time, the heat radiated from the tip of the electrode that becomes the highest temperature when the lamp is lit, The inner surface temperature of the light emitting portion 54 on the sealing portion 55A side is significantly increased by heat propagated from the portion, and the light emitting portion 54 may be swollen or ruptured.

Further, as shown in FIG. 14B, the light radiated from the light emitting portion 54 of the high pressure discharge lamp 52 to the front opening 53a side of the concave reflecting mirror 53 is directly reflected forward without being reflected to the light emitting portion 54 side. It is also possible to increase the light utilization efficiency of the high-pressure discharge lamp 51 by providing an auxiliary reflecting mirror 63 that reflects the light (see Patent Document 5).
Also in this case, the light emitted at the predetermined angle θ ₂₆ to the rear side is reflected by the concave reflecting mirror 53 and reaches the condensing area 61 in, and the light emitted at the predetermined angle θ ₂₇ to the front side is transmitted by the auxiliary reflecting mirror 63. It is reflected and reaches the condensing area 61in. Accordingly, leakage of light emitted forward is suppressed, and light utilization efficiency is high.
JP 2001-125197 A

However, the reflecting film formed on the auxiliary reflecting mirror 63 is generally formed by laminating several tens or more dielectric thin films. Therefore, it takes time and effort to manufacture the reflecting film, and the manufacturing cost increases. As a result, the reflective film deteriorates and peels off, causing a problem in durability.
Further, such an auxiliary reflecting mirror 63 must be supported by metal spokes 64. Therefore, when the lamp 52 is turned on, shadows of the spokes 64 are reflected, or the spokes 64 are distorted due to overheating. There were problems such as the light breaking down, oxidation and rusting.

  Therefore, the present invention has a technical problem of improving the light utilization efficiency of the high-pressure discharge lamp without using a sub-reflecting mirror or an auxiliary reflecting mirror even when the reflecting mirror is downsized.

In order to achieve this object, the present invention includes a high-pressure discharge lamp and a concave reflecting mirror that reflects the light, and the high-pressure discharge lamp has sealing portions formed at both front and rear ends in the tube axis direction across the light-emitting portion. The electrode assembly is inserted into the arc tube from both side sealing portions, and the sealing portion is hermetically sealed with the tip electrode portion facing the inside of the light emitting portion, and the tube axis of the concave reflector is A part of the light emitted from the light emitting part in a predetermined angle range in the front-rear direction toward the periphery thereof is reflected by the concave reflecting mirror and reflected to the front of the lamp. In the lamp device for irradiating the formed condensing area of a predetermined size, at least a part of the light emitted from the light emitting unit that is not reflected by the concave reflecting mirror is disposed on the outer peripheral surface of the light emitting unit. Total reflection toward the condensing area Annular prism surface at an angle is characterized by being integrally formed to.

According to the present invention, the annular prism surface is formed on the outer peripheral surface of the light emitting unit, and at least part of the light emitted from the light emitting unit of the lamp that is not reflected by the concave reflecting mirror is formed in front of the lamp. The light is totally reflected toward the condensing area.
Therefore, by reducing the size of the concave reflecting mirror, it is possible to change the direction of the light that is not reflected by the concave reflecting mirror and deviate from the condensing area, and to irradiate the condensing area. Use efficiency improves.

Since a prism is used instead of a reflecting mirror as means for changing the direction of light, it can be formed of the same quartz glass as the arc tube.
Therefore, since it is not necessary to form an expensive reflective film, the manufacturing cost can be reduced correspondingly, and there is no fear of deterioration of the reflective film.
Furthermore, since the prism can be integrally formed with the arc tube or fused, it is not necessary to support the prism with a metal material, so that distortion due to overheating and rust due to metal oxidation do not become a problem.

  In this example, in order to achieve the purpose of improving the light use efficiency of the high-pressure discharge lamp without using a sub-reflecting mirror or an auxiliary reflecting mirror, the light emitted from the light emitting unit is provided on the outer peripheral surface of the light emitting unit. Among them, the annular prism surface was formed at an angle that totally reflected at least a part of the light not reflected by the concave reflecting mirror toward the condensing area.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is an explanatory view showing an example of a lamp device according to the present invention and its light distribution.
FIG. 2 is an explanatory view showing a molding die of the arc tube used for the same,
FIG. 3 is an explanatory view showing the manufacturing process of the arc tube,
FIG. 4 is an explanatory view showing another embodiment and its light distribution.
FIG. 5 is an explanatory view showing a molding die of a prism used for the same,
FIG. 6 is a diagram illustrating still another embodiment and its light distribution.
FIG. 7 is an explanatory view showing a manufacturing process of the arc tube,
8-10 is explanatory drawing which shows the molding die of the prism used for it.

FIG. 1 shows an example of a lamp device according to the present invention. The lamp device 1 includes a high-pressure discharge lamp 2 and a concave reflecting mirror 3 formed of an ellipsoidal mirror or a parabolic mirror for reflecting the light.
For example, light used as a light source of a liquid crystal projector and transmitted through a light amount distribution uniformizing optical system (homogenizer) 11 such as a rod lens or an array lens is transmitted from the back surface of a liquid crystal panel (not shown) serving as an image generation unit. It is arranged to be irradiated.

In the high pressure discharge lamp 2, a pair of electrode assemblies 7 is inserted from both side sealing portions 5 </ b> A and 5 </ b> B into a light emitting tube 6 in which sealing portions 5 </ b> A and 5 </ b> B are formed on both ends in the tube axis direction across the light emitting portion 4. ing.
The electrode assembly 7 is formed by welding a tip electrode portion 8 made of tungsten, a molybdenum foil 9 and a molybdenum wire 10 in series, and the tip electrode portion 8 is sealed in a state facing the light emitting portion 4. The parts 5A and 5B are hermetically sealed.

In the high-pressure discharge lamp 2 and the concave reflecting mirror 3, one sealing portion 5A of the lamp 2 is directed to the opening 3a side of the reflecting mirror 3, and the other sealing portion 5B is directed to the bottom 3b side of the reflecting mirror 3. directed, the optical axis Z _L of the tube axis Z _P and the reflecting mirror 3 of the lamp 2 is fixed so as to be positioned coaxially.
As a result, a part of the light emitted from the light emitting unit 4 toward the periphery in a predetermined angle range in the front-rear direction (mainly light directed backward) is reflected by the concave reflecting mirror 3, and the rod disposed in front of the lamp A light condensing area 11in having a predetermined size such as a light incident surface of a light quantity distribution uniformizing optical system 11 such as a lens is condensed and irradiated.

In addition, on the outer peripheral surface of the light emitting unit 4 on the side of the sealing unit 5A, at least a part of the light emitted from the light emitting unit 4 that is not reflected by the concave reflecting mirror 3 (mainly forward light) is collected. An annular prism surface 12S is formed at an angle for total reflection toward 11in.
In this example, the sealing portion 5A side of the light emitting portion 4 bulges out in an annular shape, and the prism 12 is formed integrally, and the back side of the prism 12 is an annular prism surface 12S.
The annular prism surface 12S, as light is emitted from the light emitting unit 4 is reflected by the prism surface 12S does not diverge out of the light collection area 11in, when cutting the arc tube 6 by a plane including the tube axis Z _P Is formed by a curved surface that bulges outward.
Further, the front side of the prism 12 facing the opening 3a is formed in a substantially flat shape, and the light reflected by the prism surface 12S is irradiated to the front side.

FIG. 2 shows a mold for forming the arc tube 6 of such a high-pressure discharge lamp 2, and FIG. 3 shows the arc tube forming procedure.
Mold 13 is made of a lower mold 14L and the upper mold 14U, the recess 15 of the half shape obtained by cutting the arc tube 6 in a plane including the tube axis Z _P is formed in the lower die 14L, the upper die 14U emission A convex portion 16 that forms a hollow portion in the tube is formed.
When making the arc tube 6, the quartz fine particles are pressure-filled in the recesses 15 of the lower die 14L, and the upper die 14U is joined and tightened to form a half-sintered molded product. and thereby forming along the arc tube 6 to the tube axis Z _P arc tube halves 6h having a shape in halves is formed.

Next, as shown in FIG. 3, when the two arc tube halves 6h are joined together and frit glass or the like is sandwiched between them and heated again, the frit glass melts and the arc tube halves 6h are welded together to emit light. A tube 6 is formed.
In this state, if the electrode assemblies 7 and 7 are inserted from the sealing portions 5A and 5B on both sides and the tip electrode portion 8 is opposed in the light emitting portion 4, the sealing portions 5A and 5B are hermetically sealed. A high-pressure discharge lamp 3 is formed.
If the high-pressure discharge lamp 2 is fixed to the concave reflecting mirror 3 so that the front side of the prism 12 faces the opening 3a side of the reflecting mirror 3, the lamp device 1 is completed.

The above is one configuration example of the present invention, and the operation thereof will be described next.
When the high-pressure discharge lamp 2 is turned on, light is emitted from the light emitting unit 4 in a predetermined angular range in the front-rear direction toward the periphery thereof.
1 (b) is the amount of light in a direction perpendicular to the tube axis Z _P is taken as 100%, the tube axis Z _P front and 0 °, the light distribution with respect to the radial direction of the light when the rear and 180 ° It is a graph which shows distribution. The horizontal axis is a direction perpendicular to the direction of the tube axis Z _L of the high-pressure discharge lamp 2, the vertical axis and the tube axis Z _L through tube axis emission points on Z _L, showing a concentric graduation the light intensity ratio.
The light emitted from the light emitting unit 4 to the periphery thereof has a light amount of 60% or more in the angle range of 45 to 135 °, and the light L ₁ emitted in the angle range θ ₁ (90 to 130 °) on the back side is included. It is reflected by the concave reflecting mirror 3 and reaches the condensing area 11in.
Further, the light L ₂ emitted in the angle range θ ₂ (60 to 88 °) on the front side is reflected by the annular prism surface 12S formed on the outer periphery of the light emitting unit 4 and irradiated to the front side, and the light collecting area. It reaches 11in.

In this case, assuming a high-pressure discharge lamp of a conventional type with no prism 12, the light L ₂₂ emitted by the angular range θ _{22 (82~145} °) is reflected by the concave reflection mirror 3 reaches the light collection area 11in.
On the other hand, in this example, since the prism 12 bulges outside the light emitting unit 4, the light L ₃ in the angle range θ ₃ (130 to 145 °) emitted to the rearmost side is blocked by the prism 12.
However, since the light L ₄ having a light amount of 60 to 100% in the angular range θ ₄ (60 to 82 °) that has been wasted until now is reflected by the prism surface 12S and irradiated onto the light condensing area 11in, the light amount 60%. the following light utilization efficiency even when light L ₃ is blocked is sufficiently improved.

At this time, the light emitted from the light emitting unit 4 and incident on the prism 12 is totally reflected due to the difference in the refractive index generated at the interface between the prism surface 12S and the outside air, so there is no need to form an expensive reflection film. Accordingly, the manufacturing cost can be reduced, and there is no concern about the deterioration of the reflective film.
Further, since the prism 12 is integrally formed with the arc tube 4, metal parts such as spokes for supporting the prism 12 are not required, so that distortion of the metal parts due to overheating and rust due to metal oxidation do not become a problem.

FIG. 4 is an explanatory view showing another embodiment of the present invention. The parts common to FIG.
The lamp device 21 of this example uses a high-pressure discharge lamp 22 molded in advance in a normal process, and an annular prism 24 having an annular prism surface 24S is integrated with the arc tube 23 by retrofitting.

FIG. 5 shows a manufacturing process of the annular prism 24.
In the annular prism 24, quartz fine particles are put into a mold 25 and pressed to form a sintered compact 26. After the mold is separated and taken out, this is sintered to form a prism 24.
As shown in FIG. 5A, the mold 25 includes outer frames 25R and 25L divided into left and right, a base 25B that also serves as a core that forms a hole in the annular prism 24, the outer frames 25R and 25L, It consists of a pressurizer 25P that pressurizes the quartz fine particles 27 filled in the cavity formed by the base 25B.
First, as shown in FIG. 5B, quartz fine particles 27 are filled in a cavity formed by assembling the outer frames 25R and 25L and the base 25B, and the pressurizer 25P is used as shown in FIG. 5C. After pressurizing to form the sintered compact 26, as shown in FIG. 5 (d), the mold is separated and the sintered compact 26 is taken out and sintered to complete the annular prism 24.

If this annular prism 24 is packaged from the side of one sealing portion 5A of the arc tube 23, and the frit glass 28 is inserted into the gap with the light emitting portion 4 and heated again, the prism 24 is attached to the light emitting portion 4 of the high pressure discharge lamp 22. Fused.
Finally, the high-pressure discharge lamp 22 the optical axis Z _L of the tube axis Z _P and the concave reflection mirror 3 is be fixed so as to be positioned coaxially, the lamp device 21 is completed.
Since the outer peripheral surface of the prism 24 is an annular prism surface 24S and the shape thereof is the same as the prism surface 12S of the first embodiment, the behavior of the light emitted from the light emitting unit 4 is also substantially the same as that of the first embodiment of FIG.

FIG. 6 is an explanatory view showing still another embodiment of the present invention, in which parts common to FIG.
The lamp device 31 of this example is the same as that of the second embodiment in that the annular prism 34 is integrated by retrofitting into the arc tube 33 of the high-pressure discharge lamp 32 formed in advance in a normal process. A prism 34 having prism surfaces S _{11 to} S ₁₃ formed in multiple stages is used.

As shown in FIG. 7B, the prism 34 is formed by stacking and sintering the annular sintered compacts F _{11 to} F ₁₃ divided into three as shown in FIG. 7A. After the transparent prism 34 is formed, it is fused to the arc tube 33 of the high-pressure discharge lamp 32 through the frit glass 35 as shown in FIG.

Each of the sintered compacts F _{11 to} F ₁₃ is formed by pressure-molding quartz fine particles 39 with molds 36 to 38 as shown in FIGS.
In the same manner as the mold 25 of the second embodiment, the molds 36 to 38 have outer frames 36R to 38R and 36L to 38L that are divided into left and right, and bases 36B to 38B that also serve as cores that form holes in the annular prism 34. And pressurizers 36P-38P that pressurize the quartz fine particles 39 filled in the cavity formed by the outer frames 36R-38R, 36L-38L and the base 36B.
Then, as shown in FIGS. 8A to 10A, cavities formed by assembling the molds 36 to 38 are filled with quartz fine particles 39 and pressurized with the pressurizers 36P to 38P. 8 (b) ~ FIG 10 (b) the type Balazs to sintered compacts _F 11 _{to F 13} as shown in extraction, which upon sintering overlapped state as shown in FIG. 7 (a) 7 The transparent quartz annular prism 34 is completed as shown in FIG.

If this annular prism 34 is packaged from one sealing part 5A side of the arc tube 33, and the frit glass 35 is put in the gap with the light emitting part 4 and heated again, as shown in FIG. The prism 34 is integrally fused to the 32 light emitting units 4.
Finally, be fixed to the high-pressure discharge lamp 32 so that the optical axis Z _L of the tube axis Z _P and the concave reflection mirror 3 is situated coaxially, the lamp device 31 as shown in FIG. 6 (a) is completed To do.

Here, when the high-pressure discharge lamp 32 is turned on, light is emitted from the light emitting unit 4 toward the periphery thereof in a predetermined angle range in the front-rear direction.
6 (b) is the amount of light in a direction perpendicular to the tube axis Z _P is taken as 100%, the tube axis Z _P front and 0 °, the light distribution with respect to the radial direction of the light when the rear and 180 ° It is a graph which shows distribution. The horizontal axis is a direction perpendicular to the direction of the tube axis Z _L of the high pressure discharge lamp 32, the vertical axis and the tube axis Z _L through tube axis emission points on Z _L, showing a concentric graduation the light intensity ratio.
The light emitted from the light emitting unit 4 to the periphery thereof has a light amount of 60% or more in the angle range of 45 to 135 °, and the light L ₁ emitted in the angle range θ ₁ (90 to 130 °) on the back side is included. It is reflected by the concave reflecting mirror 3 and reaches the condensing area 11in.
The light L ₁₁ emitted in the forward angle range θ ₁₁ (7 to 88 °) is reflected by the annular prism surface S ₁₁ , and the light L ₁₂ emitted in the angle range θ ₁₂ (54 to 75 °) is The light L ₁₃ reflected by the annular prism surface S ₁₂ and emitted in the angle range θ ₁₃ (43 to 51 °) is reflected by the annular prism surface S ₁₃ , and is irradiated to the condensing area 11 in on the front side.

In this case, assuming a high-pressure discharge lamp of a conventional type with no prism 34, the light L ₂₂ emitted by the angular range θ _{22 (82~145} °) is reflected by the concave reflection mirror 3 reaches the light collection area 11in.
In contrast, in this example, since the prism 34 bulges outside the light emitting unit 4, the light L ₃ in the angle range θ ₃ (130 to 145 °) radiated to the rearmost side is blocked by the prism 34.
However, of the light that has been wasted until now, the light L ₁₄ having a light amount of 100% in the angle range θ ₁₄ (77 to 82 °) and the light amount 80 to 100% in the angle range θ ₁₂ (54 to 75 °). a light _{L 12,} and the light _{L 13} of the light amount 50% to 75% range of angle θ ₁₃ (43~51 °) is, so is reflected by the prism 34 reaches the light collection area 11in located in front, the light quantity of 60% or less Even if the light L ₃ is blocked, the light use efficiency is sufficiently improved.

  As described above, the present invention is particularly applicable to uses such as light sources such as liquid crystal projectors and DLP projectors.

Explanatory drawing which shows an example of the lamp device which concerns on this invention, and its light distribution. Explanatory drawing which shows the metal mold | die of the arc tube used for it. Explanatory drawing which shows the manufacturing process of the arc tube. Explanatory drawing which shows another embodiment and its light distribution. Explanatory drawing which shows the molding die of the prism used for it. Furthermore, explanatory drawing which shows other embodiment and its light distribution. Explanatory drawing which shows the manufacturing process of the arc tube. Explanatory drawing which shows the molding die of a prism. Explanatory drawing which shows the molding die of a prism. Explanatory drawing which shows the molding die of a prism. Explanatory drawing which shows a conventional apparatus. Explanatory drawing which shows the relationship between the magnitude | size of a reflective mirror, and light utilization efficiency. Explanatory drawing which shows the light distribution of a conventional apparatus. Explanatory drawing which shows the improved conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lamp apparatus 2 High pressure discharge lamp 3 Concave reflecting mirror 4 Light emission part 5A, 5B Sealing part 6 Arc tube
7 Electrode assembly 3a Opening 3b Bottom Z _P tube axis Z _L Optical axis 11in Condensing area 12 Prism 12S Annular prism surface 21 Lamp device 22 High pressure discharge lamp
23 arc tube
24 Annular prism
24S annular prism surface
31 Lamp device
32 high pressure discharge lamp 33 arc tube 34 annular prism surface S ₁₁ S ₁₂ S ₁₃ annular prism surface

Claims (3)

The high-pressure discharge lamp includes a high-pressure discharge lamp and a concave reflecting mirror that reflects the light. The assembly is inserted, and the sealing portion is hermetically sealed in a state where the tip electrode portion is opposed in the light emitting portion, and the tube axis thereof is arranged to coincide with the optical axis of the concave reflecting mirror. A part of the light emitted from the light emitting portion toward the periphery in a predetermined angle range in the front-rear direction is reflected by the concave reflecting mirror and reflected to the light collecting area of a predetermined size formed in front of the lamp. In the lamp device to irradiate,
An annular prism surface is integrally formed on the outer peripheral surface of the light emitting unit at an angle that causes at least a part of the light emitted from the light emitting unit not reflected by the concave reflecting mirror to be totally reflected toward the light collection area. A lamp device characterized by being formed.   2. The lamp device according to claim 1, wherein the annular prism surface is formed as a curved surface in which a cut surface shape by a plane including a tube axis of the arc tube bulges outward.   2. The lamp device according to claim 1, wherein the annular prism having the annular prism surface is mounted on the arc tube so as to be positioned on the outer peripheral surface of the light emitting portion.

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