JP2006294268A - Lamp unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamp unit capable of suppressing a decrease in light utilization rate even if the ambient temperature of an arc tube becomes higher due to miniaturization or sealing.
In a lamp unit (10) including a high-pressure mercury lamp (12) and a spheroid mirror (14) that reflects and collects light emitted from an arc tube (18) of the high-pressure mercury discharge lamp (12), A reflecting member 16 having a plurality of retroreflective prisms 62 is arranged on the outer periphery of the arc tube 18 with the optical center C interposed therebetween and facing the spheroid mirror 14. The reflecting member 16 is made of the same quartz glass as the arc tube 18.
[Selection] Figure 1

Description

  The present invention relates to a lamp unit, and more particularly to a lamp unit that is a combination of a high-pressure discharge lamp and a reflecting mirror, and is used as a light source unit such as a liquid crystal projector.

A lamp unit used as a light source for a liquid crystal projector or the like has a reflecting mirror in order to increase the utilization factor of light emitted radially from a high-pressure discharge lamp. The reflecting surface of the reflecting mirror is formed in a rotating paraboloid, a rotating ellipsoid, or a hemispherical shape. Almost half of the light emitted from the high-pressure discharge lamp is collected by the reflecting mirror and travels toward the target.
However, of the light emitted from the high-pressure discharge lamp, the remaining half of the light that is not reflected by the reflecting mirror (light that does not go directly to the reflecting mirror) is low and there is room for improvement. Therefore, in Patent Document 1, a second reflecting mirror smaller than the first reflecting mirror is provided close to the light emitting unit at a position facing the reflecting mirror (referred to as the first reflecting mirror). A lamp unit is disclosed. The light emitted from the light emitting unit is reflected by the second reflecting mirror, travels toward the first reflecting mirror, is condensed by the first reflecting mirror, and is effectively used. Note that the second reflecting mirror is configured by forming a multilayer interference film on the concave surface of hard glass having a hemispherical concave surface in order to achieve a high reflectance (about 99%).
Japanese Patent No. 3235357 Japanese Patent No. 3184404

By the way, with the spread of liquid crystal projectors to general households, further downsizing is required while maintaining the brightness on the screen. For this reason, the input electric power to the high-pressure discharge lamp is increased, and as a result, the light emitting part becomes higher in temperature and exceeds 1000 ° C. in some cases. When the temperature of the light emitting unit becomes high, a problem occurs in the second reflecting mirror provided in the vicinity of the light emitting unit, resulting in a situation where the light utilization rate of the entire unit is reduced. The multilayer interference film constituting the second reflecting mirror is formed by alternately laminating two kinds of thin films (for example, TiO ₂ film and SiO ₂ film) made of different materials. This is because, due to the difference, the thin film is cracked or the thin film is peeled off from the hard glass.

  In order to cope with this, it is conceivable to use a kind of thin metal film instead of the multilayer interference film, but there is no general metal material suitable for the above-mentioned environment. For example, when silver is used, the reflectance is about 90%, but at a high temperature as described above, it is oxidized and peeled off from the hard glass. In the case of aluminum, since melting | fusing point is 1000 degrees or less, it cannot employ | adopt. Platinum can be considered as a material that can withstand high temperatures, but the reflectivity is as low as about 80%. In addition, since it is very expensive, it is not realistic as a general household device that requires a low price.

Further, in general household liquid crystal projectors, it is necessary to make the high-pressure discharge lamp a sealed type in which the high-pressure discharge lamp is cut off from the outside air, and this also raises the above-mentioned problems caused by the temperature rise.
An object of the present invention is to provide a lamp unit that can suppress a decrease in the utilization factor of light even when the ambient temperature of the arc tube becomes higher due to downsizing, sealing, or the like. To do.

In order to achieve the above object, a lamp unit according to the present invention includes a high-pressure discharge lamp and a reflecting mirror that has a concave reflection surface and reflects and collects light emitted from the arc tube of the high-pressure discharge lamp. A lamp unit is provided, wherein a reflecting member including a plurality of retroreflective prisms is arranged on the outer periphery of the arc tube so as to face the reflecting mirror.
The reflecting member is formed of a material having at least the same heat resistance as the material forming the arc tube. In this case, the arc tube and the reflecting member may be formed of quartz glass.

  Further, the reflecting member has a hemispherical portion formed in a generally hemispherical shell shape as a whole, and the inner peripheral surface of the hemispherical portion is formed into a smooth substantially spherical surface, and the outer peripheral surface is formed by the prisms. Convex portions are formed, and the reflecting member is arranged so that the inner peripheral surface of the hemispherical portion and the reflecting surface of the reflecting mirror face each other. In this case, the reflecting mirror is arranged so that its focal point substantially coincides with the optical center of the high-pressure discharge lamp, and the reflecting member is arranged so that the center of the hemispherical part substantially coincides with the optical center. It is good as well.

Further, the arc tube has a main tube part that swells in a substantially spherical shape and forms a discharge chamber in which the optical center of the high-pressure discharge lamp exists, and the reflecting member has the hemispherical part that is the main part of the main tube part. It is arrange | positioned so that the substantially half surrounding surface on the opposite side to a reflective mirror may be covered.
Furthermore, each said convex part which comprises each said prism is carrying out the hook shape which has a triangular cross section, and is arrange | positioned along the internal peripheral surface of the said hemisphere part, It is characterized by the above-mentioned. In this case, the plurality of convex portions may be arranged concentrically in parallel with the circular opening of the hemispherical portion. Alternatively, the plurality of convex portions may be arranged radially so as to expand toward the circular opening of the hemispherical portion.

  Further, each of the convex portions constituting each of the prisms has a triangular pyramid shape.

According to the lamp unit having the above configuration, the light emitted from the arc tube is reflected to the reflector by the plurality of retroreflective prisms provided in the reflecting member disposed to face the reflecting mirror. In addition to the light emitted directly from the light toward the reflecting mirror, the light emitted toward the opposite side of the light can be condensed by the reflecting mirror, and the light utilization efficiency can be improved.
Moreover, since the means for reflecting the emitted light to the reflecting mirror is a prism, the means (prism) can be formed of, for example, a glass material similar to that of the arc tube, and the above-described problems caused by the temperature rise are also eliminated. The In other words, even if the ambient temperature of the arc tube becomes higher due to downsizing or sealing, the reflecting member can be made of a material that can withstand the high temperature, so that the reflecting member deteriorates due to the influence of heat. Therefore, it is possible to suppress a decrease in the utilization rate of light.

Hereinafter, embodiments of a lamp unit according to the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a lamp unit 10 according to an embodiment. In all the figures including this figure, the scales between the constituent members are not unified.
The lamp unit 10 includes a high-pressure mercury lamp 12 shown as an example of a high-pressure discharge lamp serving as a light source, a spheroid mirror 14 shown as an example of a reflecting mirror that reflects and collects light emitted from the high-pressure mercury lamp 12, and high-pressure mercury. A reflecting member 16 that reflects a part of the light emitted from the lamp 12 to the spheroid mirror 14 is provided.

The high pressure mercury lamp 12 has an arc tube 18 made of quartz glass. The arc tube 18 swells in a substantially spherical shape and has a main tube portion 22 having a discharge chamber (light emission space) 20 hermetically sealed, and first and first extending from the main tube portion 22 in substantially opposite directions on the same axis. 2 side pipe portions 24 and 26.
Further, the high-pressure mercury lamp 12 has a pair of electrodes 28 and 30 disposed in the discharge chamber 20 with their tip portions facing each other. The first electrode 28 is formed by winding a coil 34 around an electrode shaft 32. Similarly, the second electrode 30 is formed by winding a coil 38 around an electrode shaft 36. The electrode shafts 32 and 36 and the coils 34 and 38 are made of tungsten.

The base ends of the electrode shafts 32 and 36 are supported by the arc tube 18, and the electrode shafts 32 and 36 extend substantially coaxially to the discharge chamber 20, and the coils are disposed at the tip portions thereof. 34 and 38 are wound. Each of the coils 34 and 38 is provided to exhibit an appropriate heat dissipation function and prevent overheating of the electrode when the high-pressure mercury lamp 12 is turned on.
Moreover, a part of the front-end | tip part which the 1st electrode 28 and the 2nd electrode 30 oppose is processed into the substantially hemispherical shape, and the heads 40 and 42 are formed. The reason for processing into a substantially hemispherical shape is to concentrate the discharge at the time of lighting as much as possible at the tip of the head to prevent a so-called arc jump phenomenon in which the arc is displaced randomly. The distance between the tips of both heads 40 and 42 in the tube axis direction of the arc tube 18, that is, the distance between the electrodes is set to about 0.5 to 1.0 mm in order to approach the point light source.

The ends of the electrode shafts 32 and 36 opposite to the heads 40 and 42 are joined to one end of strip-shaped metal foils 44 and 46. Each of the pair of metal foils 44 and 46 is made of molybdenum foil.
One end portion of a first external lead wire 48 is joined to the other end portion of the first metal foil 44, and a second external portion is joined to the other end portion of the second metal foil 46. Lead wire 50 is joined. The first and second lead wires 48 and 50 are both made of molybdenum wires. The end portions of the first and second external leads 48 and 50 opposite to the metal foil 44.46 are exposed from the arc tube 18, and power is supplied from the end portions, whereby high-pressure mercury is supplied. The lamp 12 can be turned on. At this time, the point C located in the middle between both electrodes 28 and 30 (between the tips of both heads 40 and 42) becomes the optical center.

  The discharge chamber 20 is formed by sealing portions of the arc tube 18 corresponding mainly to the metal foils 44 and 46. The discharge chamber 20 is filled with mercury, which is a luminescent material, and a rare gas such as argon, krypton, or xenon as a starting aid, together with a halogen material such as iodine or bromine (all not shown). The halogen substance is said to suppress the blackening of the arc tube by returning tungsten evaporated from the electrodes 28 and 30 to the electrodes 28 and 30 without adhering to the inner surface of the quartz arc tube 18 by a so-called halogen cycle. It is enclosed to fulfill its function.

The high-pressure mercury lamp 12 having the above configuration is fixed to the ellipsoidal mirror 14 with cement 52 at the second side tube portion 26 portion.
The spheroid mirror 14 has a hard glass base 54 having a funnel shape. A multilayer interference film 56 is deposited as a reflective film on the concave surface portion 54 </ b> A formed on the spheroidal surface of the base 54. The opening diameter of the spheroid mirror 14 is 50 mm.

  After the high-pressure mercury lamp 12 is positioned at a predetermined position in the axis A direction of the spheroid mirror 14 by inserting the second side tube portion 26 into the mounting hole 54C provided in the neck portion 54B of the base 54. And fixed with the cement 52. The predetermined position is a position where the first focal point f1 of the spheroid mirror 14 and the optical center C substantially coincide. Specifically, the high-pressure mercury lamp 12 is lit on the test, and in the left-right, up-down, front-back direction (for example, an X, Y, Z orthogonal coordinate system with the axis A as the X axis) toward the paper surface of FIG. When slid in the direction of the three axes), the high-pressure mercury lamp 12 is positioned at a position where the illuminance ahead of the spheroid mirror 14 becomes maximum.

The reflection member 16 is attached to the first side tube portion 24 of the high-pressure mercury lamp 12 so as to face the spheroid mirror 14 with the optical center in between. The reflecting member 16 is made of a material (in this example, quartz glass) having at least the same heat resistance as the material forming the arc tube 18.
2A is a perspective view of the reflecting member 16, and FIG. 2B is a half sectional view of the reflecting member 16. As shown in FIG.

As shown in FIG. 2, the reflecting member 16 includes a mounting portion 58 having a cylindrical shape and a reflecting portion 60 having a substantially hemispherical shell shape as a whole.
The inner peripheral surface of the reflection part 60 is finished into a smooth substantially spherical surface. The radius R1 of the inner peripheral surface is, for example, 5 mm. A plurality of convex portions 62 are formed on the outer peripheral surface of the reflecting portion 60, and each convex portion constitutes a retroreflective prism 62 (hereinafter simply referred to as “prism 62”). Specifically, the convex part of this example has a bowl shape with a triangular cross section, and the convex part is arranged along a virtual spherical surface concentric with the inner peripheral surface to constitute a prism 62. . The plurality of prisms 62 are arranged concentrically in parallel with the circular opening 60 </ b> A of the reflecting portion 60.

  The reflection member 16 is extrapolated to the first side tube portion 24 with the reflection portion 60 side at the top, and is positioned at a predetermined position in the axis A direction of the spheroid mirror 14 (the tube axis direction of the arc tube 18). Thereafter, it is fixed with cement 64 (see FIG. 1). The predetermined position is a position where the center of the spherical surface defined by the radius R1 substantially coincides with the optical center (FIG. 1). Specifically, when the high-pressure mercury lamp 12 is test lit and the reflecting member 16 is slid in the direction of the axis A, the reflecting member 16 is positioned at a position where the illuminance in front of the spheroid mirror 14 becomes maximum. The

Next, a preferred shape of the prism 62 (dimensional relationship of each part) will be described with reference to FIG. FIG. 3 is an enlarged cross section of the prism 62. In FIG. 3, the prism 62 is exaggerated for convenience of explanation.
First, the definition of each part dimension shown in FIG. 3 will be described. The radius of the circle connecting the top 62A of each prism 62A with the optical center C as the center is R2, and the radius of the circle connecting the bottom 62B of each prism 62A is R3. A circle defined by a radius R4 = (R2 + R3) / 2 around the optical center C is defined as a circle E. Two points of the prism 62 intersecting the circle E are 62C and 62D, and the length of the line segment connecting the two points 62C and 62D is P. The apex angle of the prism 62 is α. Here, when the incident angle of the light L from the optical center C at the point 62D of the prism 62 is α ₀ , the relationship is α = 2α ₀ .

Here, if α, P, and R4 satisfy the relationship represented by the following expression, the light from the optical center C is returned (reflected) to the optical center C by the prism 62.
α = 90 ° -tan ⁻¹ {(P / R4) / 2}
In this case, two points 62C, by total reflection at 62D, in order to increase the reflectivity in the prism 62 is preferably a alpha ₀ and less than the critical angle. In this example, quartz glass is used, so the critical angle is 43.3 °. Therefore, α ₀ is set to about 44 °, for example.

A state when the high-pressure mercury lamp 12 is turned on in the lamp unit 10 having the above configuration will be described with reference to FIG. In FIG. 4, in order to avoid complication, only the outline of the high-pressure mercury lamp 12 is represented by a one-dot chain line.
The light emitted from the optical center C and directed directly to the spheroid mirror 14 (shown by a dotted line) is reflected by the multilayer interference film 56 and collected at the second focal point f2 of the spheroid mirror 14. The

Further, the emitted light (indicated by the alternate long and short dash line) emitted from the optical center C and directed to the reflecting portion 60 of the reflecting member 16 is retroreflected by each prism 62 of the reflecting portion 60. The reflected emitted light passes through the optical center C, travels toward the ellipsoidal mirror 14, is reflected by the multilayer interference film 56, and is collected at the second focal point f2.
That is, the emission light emitted from the hemispherical part on the spheroidal mirror 14 side of the main pipe part 22 is directly reflected and condensed by the spheroidal mirror 14 and emitted from the remaining hemispherical part of the main pipe part 22. The emitted light is reflected by the reflecting portion 60 of the reflecting member 16 and then condensed by the spheroid mirror 14. As a result, most of the light emitted from the main pipe section 22 is collected, and the light use efficiency is improved.

  Further, when the spheroid mirror 14 is the first reflecting member and the reflecting member 16 is the second reflecting member, in the present embodiment, the material forming the second reflecting member is the same material as the arc tube 18. Since it is (quartz glass), as long as the arc tube 18 can withstand heat, the second reflecting member (reflecting member 16) can also withstand heat. That is, with respect to heat resistance, the second reflecting member (reflecting member 16) can be used without any problem within the range where the arc tube 18 is actually used.

  Further, when the light reflecting portion of the second reflecting member is configured with a multilayer interference film as in Patent Document 1, the wavelength range of light that can be reflected is limited (about 400 nm to about 700 nm). In the case of the reflecting portion 60 of the reflecting member 16, the light can be reflected over at least the entire wavelength range (300 nm to 1200 nm) of the light emitted from the arc tube 18. This also improves the light utilization rate. At the same time, since the discharge plasma temperature in the discharge chamber 20 (FIG. 1) is raised, the red component of the luminescent color can be increased, so that the color balance is improved.

Next, an example of a manufacturing method of the reflecting member 16 having the above configuration will be described with reference to FIG.
First, as shown in FIG. 5A, the reflecting portion 60 is to be formed while rotating a glass tube 66 (quartz) having one end closed and the other end open around the tube axis. The part is heated from the outer periphery with a burner 68 and softened.

Next, as shown in FIG. 3 (b), a carbon mold 74 that is composed of an upper mold 70 and a lower mold 72 and in which closed cavity portions 70A and 72A having the same shape as the outer periphery of the reflecting section 60 is formed. And sandwich the softened portion.
And as shown in FIG.3 (c), the compressed gas which consists of inert gas is blown in from an open end part, the said softened part is expanded, and the outer periphery of the glass tube 66 is made to follow the inner surface of said cavity part 70A, 72A. Thus, the reflection part 60 is formed. Thereafter, the glass tube 66 is cut at the positions indicated by arrows B1, B2, and B3, and two reflecting members 16 are completed.

  In the above example, the prism portion is formed by molding using a carbon mold. However, the present invention is not limited thereto, and for example, the following may be used. That is, first, the above-described carbon mold 74 having a smooth spherical surface without providing irregularities on the surfaces of the cavity portions 70A and 70B is prepared. Using this carbon mold, the glass tube 66 is processed in the same manner as described above. As a result, a glass tube 66 having a central portion bulged into a substantially spherical shell (the outer surface of the bulged portion is formed into a smooth spherical surface) is produced. Then, the outer surface of the bulging portion is cut by laser processing to form a prism (convex portion).

Subsequently, two modifications of the reflecting member 16 will be described.
(Modification 1)
FIG. 6 shows a schematic configuration of the reflecting member 80 according to the first modification. 6 (a) is a half sectional view of the reflecting member 80, FIG. 6 (b) is a sectional view taken along the line D / D in FIG. 6 (a), and FIG. 6 (c) is a sectional view of FIG. ) In FIG.

  In the reflection member 16 (FIG. 2) described above, the plurality of prisms 62 are arranged concentrically in parallel with the circular opening 60A, whereas in the reflection member 80, the plurality of prisms 82 are shown in FIG. As described above, the reflecting member 16 is different from the reflecting member 16 in that the circular opening 84 (refer to FIG. 6A) is arranged radially. In addition, it is the same as that of the convex part 62 of the reflecting member 16 that each convex part 82 which comprises each prism 82 has the shape of a bowl with a triangular cross section. However, the area of the triangle of the cross section of each of the convex portions 62 in the reflecting member 16 is constant everywhere, whereas the triangle of the cross section of each of the convex portions 82 in the reflecting member 80 is closer to the circular opening 84. large.

(Modification 2)
FIG. 7 shows a schematic configuration of the reflecting member 90 according to the second modification. FIG. 7A is a half sectional view of the reflecting member 90.
In the reflecting member 16 (FIG. 2) and the reflecting member 80 (FIG. 6), each prism (62, 82) is configured in a bowl shape having a triangular cross section. Was configured in a regular triangular pyramid shape as shown in FIG. Other configurations are substantially the same as those of the reflecting member 16 and the reflecting member 80. That is, in the reflecting member 90, a plurality of prisms (convex portions) 92 each having a regular triangular pyramid shape are arranged on a virtual spherical surface having the optical center C as a center and a radius R3 (see also FIG. 3).

As mentioned above, although this invention has been demonstrated based on embodiment, this invention is not restricted to an above-described form, Of course, it can also be set as the following forms, for example.
(1) In the above embodiment, the high-pressure mercury lamp is used as the light source constituting the lamp unit. However, the present invention is not limited to this, and other high-pressure discharge lamps such as a metal halide lamp may be used.
(2) Although the rotating ellipsoidal mirror is used as the reflecting mirror (first reflecting member) in the above embodiment, the present invention is not limited to this, and a rotating parabolic mirror or a concave (spherical) mirror can also be used. .
(3) In the above embodiment, the reflecting member (second reflecting member) and the arc tube are made of the same material (quartz glass), but the materials of both may be different. Any material may be used as long as the material of the reflecting member is translucent and has at least the same heat resistance as the material forming the arc tube. For example, it is also conceivable to use a light-transmitting ceramic instead of quartz glass as the material for forming the reflecting member.
(4) In the above embodiment, the reflecting member (second reflecting member) is fixed to the high-pressure mercury lamp. However, the fixing destination is not limited to this, for example, a spheroidal mirror (first reflecting member). It may be fixed to the member via an appropriate attachment member.
(5) In the above embodiment, there is a slight gap between the inner surface of the reflecting portion of the reflecting member and the outer peripheral surface of the main tube portion of the arc tube (see FIG. 1). The inner surface of the reflecting portion of the reflecting member may be in contact with the outer peripheral surface of the main tube portion of the arc tube.

  The lamp unit according to the present invention can be suitably used as a light source unit used in a projection display device such as a liquid crystal projector, a slide projector, or DLP (trademark).

It is a longitudinal cross-sectional view which shows schematic structure of the lamp unit which concerns on embodiment. (A) is a perspective view of the reflective member which comprises the said lamp unit, (b) is a half cross-sectional view of a reflective member. It is an expanded sectional view of the reflective part in the above-mentioned reflective member. In the said lamp unit, it is a figure for demonstrating the condensing aspect of the emitted light emitted from an optical center. It is a figure for demonstrating an example of the manufacturing method of the said reflection member. (A) is a half cross-sectional view showing a first modification of the reflecting member, and (b) is a cross-sectional view taken along the line D / D in (a). (C) is the figure which looked at the reflective member from the direction of arrow G in (a). (A) is a half sectional view showing a second modification of the reflecting member. (B) is a figure showing the shape of each prism in the said reflection member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lamp unit 12 High pressure mercury lamp 14 Spheroid mirror 16, 80, 90 Reflective member 18 Light emission tube 60 Reflection part 62, 82, 92 Retroreflective prism (convex part)

Claims (10)

A lamp unit comprising a high-pressure discharge lamp and a reflecting mirror that has a concave reflecting surface and reflects and collects light emitted from the arc tube of the high-pressure discharge lamp,
A lamp unit, wherein a reflecting member having a plurality of retroreflective prisms is arranged on the outer periphery of the arc tube so as to face the reflecting mirror.   2. The lamp unit according to claim 1, wherein the reflecting member is made of a material having at least the same heat resistance as the material forming the arc tube.   The lamp unit according to claim 2, wherein the arc tube and the reflection member are made of quartz glass. The reflecting member has a hemispherical portion formed in a generally hemispherical shell shape as a whole, and an inner peripheral surface of the hemispherical portion is formed into a smooth substantially spherical surface, and an outer peripheral surface constitutes each of the prisms. A convex part is formed,
The lamp unit according to any one of claims 1 to 3, wherein the reflecting member is arranged so that the inner peripheral surface of the hemispherical portion and the reflecting surface of the reflecting mirror face each other. . The reflector is arranged so that its focal point substantially coincides with the optical center of the high-pressure discharge lamp,
The lamp unit according to claim 4, wherein the reflecting member is disposed so that a center of the hemispherical portion substantially coincides with the optical center. The arc tube has a main tube portion that swells into a substantially spherical shape and forms a discharge chamber in which the optical center of the high-pressure discharge lamp exists.
6. The lamp unit according to claim 4, wherein the reflecting member is disposed so that the hemispherical portion covers a substantially semicircular surface of the main pipe portion opposite to the reflecting mirror.   Each of the convex portions constituting each prism has a bowl shape having a triangular cross section, and is disposed along an inner peripheral surface of the hemispherical portion. The lamp unit according to claim 6.   The lamp unit according to claim 7, wherein the plurality of convex portions are arranged concentrically in parallel with the circular opening of the hemispherical portion.   The lamp unit according to claim 7, wherein the plurality of convex portions are radially arranged so as to expand toward a circular opening of the hemispherical portion.   The lamp unit according to any one of claims 4 to 6, wherein each of the convex portions constituting each of the prisms has a triangular pyramid shape.

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