Patent Application
20080054776
Hereunder, embodiments of the present invention will be described in detail with reference to the attached drawings.
The lamp 12 is a direct current (DC) type short-arc high pressure discharge lamp, and is provided with an envelope 26 comprising a spherical light-emitting portion 22 and rod-shaped seal portions 24 extending straight from opposite ends of the light-emitting portion 22. Within each of the seal portions 24 of the envelope 26, there are provided an electrode pin 28 having one end protruding inside the light-emitting portion 22, a lead pin 30 having one end protruding outside the seal portion 24, and a molybdenum foil 32 electrically interconnecting the other end of the electrode pin 28 and the other end of the lead pin 30. The one ends of the electrode pins 28 protruding into the light-emitting portion 22 are attached to an anode 34a and a cathode 34b, i.e., a pair of electrodes 34, respectively. Mercury in an amount of 0.15 mg/mm3 is encapsulated within the light-emitting portion 22.
As described above, the lamp 12 shown in
The lamp 12 is provided with the ultraviolet blocking member 14 for passing visible rays included in light emitted from the lamp 12, and for blocking ultraviolet rays included therein to prevent ultraviolet rays from reaching the reflector 16. The ultraviolet blocking member 14 includes an ultraviolet blocking portion 36 and mounting portions 38.
The ultraviolet blocking portion 36 has a tubular shape, and is formed of an ultraviolet blocking glass for passing visible rays and blocking ultraviolet rays. The ultraviolet blocking portion 36 has an inside diameter larger than an outside diameter of the light-emitting portion 22 of the lamp 12. The ultraviolet blocking portion 36 has an axial length larger than a length of the light-emitting portion 22 along a direction that the seal portions 24 extend. One specific example of the ultraviolet blocking glass is a glass formed of SiO2 containing a small amount of zinc oxide power or titanium oxide power.
Preferably, the ultraviolet screen 36 has a wall thickness ranging from 1.0 mm to 1.5 mm. When the wall thickness of the ultraviolet screen 36 is smaller than 1.0 mm, the ultraviolet screen 36 has an insufficient mechanical strength, thereby making it difficult to absorb an impact resulting from explosion of the lamp 12. When the wall thickness of the ultraviolet screen 36 is larger than 1.5 mm, the ultraviolet screen 36 can absorb an impact resulting from explosion of the lamp, but tends to accumulate heat generated from the lamp 12 therein. Such accumulated heat might cause explosion of the lamp 12.
The mounting portions 38 are ring-shaped members for mounting the ultraviolet screen 36 on the lamp 12. An outside diameter of the mounting portions 38 is substantially equal to an inside diameter of the ultraviolet screen 36. The mounting portions 38 have holes at center portions thereof having an inner shape fitted to an outer shape of the seal portion 24 of the lamp 12.
Preferably, the-mounting portions 38 are formed of a ceramic material having both a high thermal conductivity and high heat resistance (alumina or steatite and the like). In the embodiment, the mounting portions 38 are formed of alumina.
The reflector 16 is a bowl-shaped member for forwardly reflecting light produced by the light-emitting portion 22 of the lamp 12. The reflector 16 has an internal surface forming a concave reflecting surface 40. The reflector 16 is provided with a lamp mounting hole 42 at a center portion thereof.
The reflector 16 may be formed of various materials including glass, metal, and the like. In the embodiment, the reflector 16 is formed of a borosilicate glass as an inexpensive material. It should be noted that the borosilicate glass fractures due to a thermal stress when a temperature difference between an inner surface and an outer surface of the reflector 16 becomes larger than 180° C. Accordingly, the reflector 16 preferably has a thickness of larger than 1.8 mm and smaller than 3.5 mm, so that the temperature difference is maintained less than 180° C., thereby maintaining a sufficient substrate strength.
The reflecting surface 40 of the reflector 16 is coated with a visible-ray reflective film 44 for efficiently reflecting visible rays emitted from the lamp 12 forwardly. As shown in
The visible-ray reflective film 44, as a whole, is formed of 38 to 46 layers. In the present embodiment, the visible-ray reflective film 44, as a whole, has 42 layers. The lowermost and uppermost layers of the visible-ray reflective film 44 are the second reflective films 44b.
The second reflective film 44b is formed of a material having a refractive index lower than that of the first reflective film 44a formed of ZnS. For example, the material of the second reflective film 44b includes SiO2, MgF2, CaF2, NaF and the like. In the embodiment, the second reflection film 44b is formed of SiO2.
The lamp holder 18 holds an end portion of one of the seal portions 24 of the lamp 12 as well as a power feed line 46 (see
In assembling the light source device 10, first, the mounting portions 38 are attached to the seal portions 24 located on opposite sides of the lamp 12, respectively. In the present embodiment, the mounting portions 38 are attached to the seal portions 24 at boundary portions thereof between the seal portions 24 and the light-emitting portion 22. The mounting portions 38 are disposed apart from each other according to the length of the ultraviolet screen 36 in the axial direction thereof.
After the seal portions 24 and the mounting portions 38 are cemented together, the ultraviolet blocking portion 36 is mounted on the mounting portions 38 integrated with the lamp 12, so that the mounting portions 38 and the ultraviolet blocking portion 36 are cemented together. Thus, the light-emitting portion 22 of the lamp 12 is surrounded with the ultraviolet blocking member 14 (ultraviolet blocking portion 36).
After the lamp 12 is integrated with the ultraviolet blocking member 14, one of the seal portions 24 of the lamp 12 is inserted into the lamp mounting hole 42 of the reflector 16 from a side of the reflecting surface 40. Afterward, the lamp holder 18 is fitted to an end of the one of the seal portions 24, and the lamp 12 is connected to the lamp holder 18 with cement.
Afterward, the lamp 12 is placed at the center portion of the reflector 16, and the lamp holder 18 and the one of the seal portions 24 are attached to the reflector 16 with the cement 20. The cement 20 may include alumina-silica (Al2O3—SiO2) cement, alumina (Al2O3) cement, and silicon carbide (SiC) cement.
After the light source device 10 fitted in a projector, when the projector is powered on, an ignition voltage is applied to the lamp 12 in order to emit light from the light-emitting portion 22.
As described above, the light-emitting portion 22 is surrounded with the ultraviolet blocking portion 36. Accordingly, ultraviolet rays included in light from the light-emitting portion 22 are blocked with the ultraviolet blocking portion 36, and only visible rays pass through the ultraviolet blocking portion 36.
Accordingly, ultraviolet rays do not reach the visible-ray reflective film 44 (more specifically, the first reflective film 44a formed of ZnS in the visible-ray reflective film 44) formed on the reflecting surface 40 of the reflector 16. Therefore, the first reflective film 44a formed of ZnS is not exposed to ultraviolet, thereby preventing deterioration thereof. As a result, illuminace of the light source device 10 does not lower due to deterioration of the visible-ray reflecting film 44.
In Japanese Patent Publication No. 11-25709, an ultraviolet removing member is provided for preventing ultraviolet rays from leaking outside from a lighting device. According to Japanese Patent Publication No. 11-25709, the ultraviolet removing member may be provided on a front illuminating lens, as far as the ultraviolet removing member can prevent ultraviolet rays from leaking outside. In this case, ultraviolet rays may reach a visible-ray reflective film of a reflector, thereby lowering illuminance of the lighting device. On the other hand, in the embodiment of the present invention, the ultraviolet blocking member 14 is provided for blocking ultraviolet rays from the visible-ray reflective film 44. Accordingly, the ultraviolet blocking member 14 is not the same as the ultraviolet removing member disclosed in Japanese Patent Publication No. 11-25709.
In the present embodiment, the ultraviolet blocking portion 36 with a tubular shape is disposed so as to surround the light-emitting portion 22. For this reason, when inadvertent explosion of the lamp 12 occurs, the ultraviolet screen 36 is capable of absorbing an impact resulting from the explosion of the light-emitting portion 22. That is, the ultraviolet blocking portion 36 functions as a shock-absorbing member upon explosion of the lamp 12. For this reason, even when the reflector 16 is formed of a borosilicate glass having a low mechanical strength, the reflector 16 is hard to break.
As described above, in the embodiment, the ultraviolet blocking portion 36 is the tubular member formed of an ultraviolet screening glass. Alternatively, the ultraviolet blocking portion 36 may be formed of stacked layers of a translucent material layer and an ultraviolet screening material layer. For example, as the ultraviolet blocking member 36, an ultraviolet blocking film may be coated on a surface of a tubular member formed of a regular glass, i.e., a transparent material. In this case, the coating may be formed on an outer peripheral surface or an inner peripheral surface of the tubular member. The ultraviolet blocking film may be formed of fine power of ZnO or Al2O3 coated with an amorphous silica.
As described above, the tubular member may be coated with the ultraviolet blocking film on the inner peripheral surface or the outer peripheral surface thereof. Preferably, the coating is formed on the outer peripheral surface of the tubular member, thereby preventing heat from accumulating within the tubular member, and preventing the lamp 12 from easily braking.
When the tubular ultraviolet blocking portion 36 surrounds the light-emitting portion 22, heat generated by the lamp 12 may accumulate within the ultraviolet blocking portion 36, thereby excessively heating and causing explosion of the lamp 12. In order to prevent heat from accumulating within the ultraviolet screen 36, the mounting portions 38 may be provided with a vent hole. Alternatively, just one of the mounting portions 38 may be provided.
A second embodiment of the present invention will be explained next.
In the present embodiment, the light-emitting portion 22 is coated with the ultraviolet blocking coating 48. Alternatively, the envelope 26 including the seal portions 24 may be coated with the ultraviolet blocking coating 48. It is suffice that the ultraviolet blocking coating 48 is formed on at least the light-emitting portion 22 for obtaining the effect of the ultraviolet blocking member 14.
Similar to the first embodiment, in the second embodiment, it is possible to prevent the first reflective film 44a formed of ZnS from deteriorating due to exposure to ultraviolet rays, whereby preventing illuminance of the light source device 10 from lowering.
Though not shown, the envelope 26 of the lamp 12 may be formed of an ultraviolet blocking glass. In the case, the envelope 26 itself functions as the ultraviolet blocking member 14, thereby preventing the first reflective film 44a formed of ZnS from deteriorating due to ultraviolet rays, and preventing illuminance of the light source device 10 from lowering, i.e., obtaining an effect same as that in the second embodiment.
The disclosure of Japanese Patent Application No. 2006-232163, filed on Aug. 29, 2006, is incorporated herein by reference in its entirety.
While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2006-232163 | Aug 2006 | JP | national |
