JP2007073276A - 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.
A high-pressure discharge lamp 12 having an arc tube 16 in which a discharge chamber 18 is formed, and a reflecting mirror that has a concave reflecting surface and reflects and collects light emitted from the discharge chamber 18. A plurality of convex portions 50 are formed on the outer surface of the light emitting portion 20 forming the discharge chamber 18 in the arc tube 16. The convex portion 50 constitutes a prism that reflects part of the light emitted from the discharge chamber 18, returns it to the discharge chamber 18, and emits the light to the reflection surface.
[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. Most of the light emitted from the discharge chamber of 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 light that is not reflected by the reflecting mirror (light that does not go directly to the reflecting mirror) is lost and there is room for improvement. In particular, when the reflecting mirror is downsized, the loss increases and the light collection efficiency decreases. Therefore, Patent Document 1 discloses a lamp including a high-pressure discharge lamp in which a reflection film is formed on an outer peripheral surface portion of an arc tube portion forming a discharge chamber, which is on the opposite side to the reflecting mirror. A unit is disclosed. The light emitted from the discharge chamber is reflected by the reflection film, passes through the discharge chamber again, travels to the reflection mirror, and is collected by the reflection mirror and used effectively. The reflective film is made of a dielectric multilayer film in order to achieve a high reflectance.
JP 2000-353493 A

By the way, with the spread of liquid crystal projectors to general households, further downsizing is required while maintaining the brightness on the screen. When the reflector is downsized, the light collection efficiency decreases. However, in order to maintain the brightness, the input power to the high-pressure discharge lamp increases, and as a result, the arc tube becomes hotter and may exceed 1000 ° C. Has occurred. When the arc tube becomes high temperature, a defect occurs in the reflection film directly formed on the arc tube, and it is impossible to expect an improvement in light utilization rate by the reflection film. This is because the dielectric multilayer film constituting the reflective film is formed by alternately laminating two kinds of thin films (for example, tantalum oxide (Ta ₂ O ₅ ) film and silica (SiO ₂ ) film) made of different materials. Therefore, due to the difference in thermal expansion coefficient between the two thin films, the thin film is cracked or the thin film is peeled off from the arc tube.

In order to cope with this, instead of the dielectric multilayer film, it may be possible to adopt a thin film of a kind of metal having a high reflectivity, but there is no general metal material suitable for the above temperature environment. For example, silver (melting point: 961 ° C.) and aluminum (melting point: 660 ° C.) are often used as reflecting mirror materials, but both cannot be adopted because the melting point is 1000 ° C. or less.
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 temperature of the arc tube becomes higher due to downsizing, sealing, or the like. .

  In order to achieve the above object, a lamp unit according to the present invention includes a high-pressure discharge lamp having an arc tube in which a discharge chamber is formed, a concave reflecting surface, and emits light emitted from the discharge chamber. A lamp unit including a reflecting mirror that reflects and collects light, and a plurality of convex portions are formed on an outer surface of the light emitting portion forming the discharge chamber of the arc tube, The convex portion constitutes a prism that reflects part of the light emitted from the discharge chamber, returns the light to the discharge chamber, and emits the light to the reflection surface.

Further, the plurality of convex portions are arranged so that a cross section thereof is a triangular bowl shape. In this case, the plurality of convex portions may be arranged in a substantially concentric circle centered on a point on the tube axis of the arc tube. Alternatively, the plurality of convex portions may be arranged radially around a point on the tube axis of the arc tube.
The plurality of convex portions have a triangular pyramid shape and are arranged adjacent to each other.

  According to the lamp unit configured as described above, since the light emitted from the discharge chamber is reflected to the discharge chamber, not only the light emitted directly from the discharge chamber to the reflecting mirror but also the light reflected by the prism (directly) (Emitted light not directed to the reflecting mirror) can also be collected by the reflecting mirror, and the light utilization efficiency can be improved. In addition, since the prism is constituted by a part of the arc tube, the above-described problems caused by the temperature rise are also solved.

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, and 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. The tube axis B of the high-pressure mercury lamp 12 and the optical axis A of the spheroid mirror 14 are substantially on the same axis. The alignment of the high-pressure mercury lamp in the reflecting mirror is performed, for example, by illuminating the screen with light emitted from the reflecting mirror so that the illuminance on the screen is maximized. Therefore, when the parameters of the high-pressure mercury lamp are as designed and the reflecting surface of the reflecting mirror has an ideal shape, the tube axis B of the high-pressure mercury lamp 12 and the optical axis A of the reflecting mirror are perfect. In reality, however, the illuminance may be maximized at a position where the tube axis B and the optical axis A deviate due to processing variations and the like. Therefore, “substantially on the same axis” means including such a case. The positional relationship of the high-pressure mercury lamp in the reflecting mirror is not limited to the case where the tube axis B and the optical axis A are substantially on the same axis, but also when the tube axis B and the optical axis A are substantially orthogonal. Good.

  The high pressure mercury lamp 12 has an arc tube 16 made of quartz glass as an envelope. The arc tube 16 has a light emitting part 20 having a discharge chamber (discharge space) 18 swelled in a substantially spherical shape and hermetically sealed in a central part, and a first light pipe extending from the light emitting part 20 in a substantially coaxial opposite direction. The first and second sealing portions 22 and 24 are included. Note that the basic outer shape of the light emitting unit 20 is not limited to a substantially spherical shape, and may be, for example, a substantially spheroidal shape, but is preferably closer to a spherical shape. Details of the external shape of the light emitting unit 20 will be described later. In addition, the arc tube 16 has a pair of electrodes 26 and 28 that are disposed in the discharge chamber 18 so that their tip portions face each other. Details of the pair of electrodes 26 and 28 will be described later.

In the discharge chamber 18, mercury, which is a luminescent material, and a rare gas such as argon, krypton, and xenon for start-up, and a halogen material such as iodine and bromine (all not shown) are enclosed. Amount of enclosed mercury is, for example, 0.10 mg / mm ³ or more, ^{preferably, 0.15mg / mm 3 ~0.35mg / mm} 3. Further, amount of halogen substances are, for example, ^{1 × 10 -6 μmol / mm 3} ~1 × 10 -6 μmol / mm 3, the filling pressure of the rare gas is 5kPa~40kPa at room temperature. The halogen material is returned to the electrodes 26 and 28 without attaching tungsten evaporated from the electrodes 26 and 28 to the inner surface of the quartz arc tube 16 (light emitting unit 20) by a so-called halogen cycle. It is sealed to fulfill the function of suppressing the blackening of the inner surface.

The first electrode 26 is composed of a coil 32 attached to one end of an electrode shaft 30, and the second electrode 28 is composed of a coil 36 attached to one end of an electrode shaft 34. The electrode shafts 30 and 34 and the coils 32 and 36 are both made of tungsten.
The other end portions of the electrode shafts 30, 34 are supported by the arc tube 16, and the electrode shafts 30, 34 are substantially coaxial, and one end portions thereof extend to the discharge chamber 18.

  Further, a part of the tip portion of the first electrode 26 and the second electrode 28 facing each other is formed with head portions 38 and 40 having convex curved shapes such as substantially hemispherical or substantially spherical. The convex curved surface is processed in this manner in order to prevent arc jump phenomenon in which the arc is randomly displaced by concentrating the arc discharge at the time of lighting as much as possible at the tips of the heads 38 and 40 as much as possible. . The distance between the tips of the heads 38 and 40 in the tube axis direction of the arc tube 16, that is, the interelectrode distance De (see FIG. 3) is about 0.5 to 1.0 mm in order to approach the point light source.

  The other end of each electrode shaft 30, 34 (the end opposite to the heads 38, 40) is interposed via molybdenum foils 42, 44 sealed by the first and second sealing parts 22, 24. The first and second lead wires 46 and 48 made of molybdenum are electrically connected to one end portions, respectively. The other end portions of the first and second external lead wires 46 and 48 are led out from the end portions of the first and second sealing portions 22 and 24, and power is supplied from the other end portions. The high-pressure mercury lamp 12 can be turned on. At this time, the point C located in the middle between the electrodes 26 and 28 (between the tips of both heads 38 and 40) is the optical center.

Next, details of the external shape and the like of the light emitting unit 20 will be described with reference to FIGS. 2 (a) and 2 (b). 2A shows a perspective view of the light emitting section 20 and the vicinity thereof, and FIG. 2B shows a half sectional view thereof. In FIGS. 2A and 2B, the first and second electrodes 26 and 28 and other members are not shown in order to avoid complexity.
The inner surface of the light emitting unit 20 is finished into a smooth substantially spherical surface. A part of the outer surface of the light emitting unit 20 (substantially half in this example) is formed with an uneven surface obtained by directly processing quartz glass, which is a constituent material of the envelope, and a plurality of protrusions forming the uneven surface. Each of the parts 50 constitutes a retroreflective prism 50 (hereinafter simply referred to as “prism 50”). Specifically, the prisms 50 of this example are arranged so that the cross section is a triangular bowl shape, and each is arranged along a virtual spherical surface concentric with the substantially spherical inner surface. Further, the plurality of prisms 50 are arranged in a substantially concentric shape with a point on the tube axis B of the arc tube 16 as the center. Here, in the light emitting unit 20, the outer peripheral surface portion where the plurality of prisms 50 are formed is referred to as a prism reflection lens portion 52, and the smooth surface portion where the prism 50 is not formed is referred to as a transmission portion 54.

Next, a preferred shape of the prism 50 (dimensional relationship of each part) will be described with reference to FIG. FIG. 3 is an enlarged cross section of the prism 50. In FIG. 3, for convenience of explanation, the prism 50 is drawn in a considerably exaggerated manner.
First, the definition of each part dimension shown in FIG. 3 will be described. The radius of the circle connecting the top 50A of each prism 50 around the optical center C is R2, and the radius of the circle connecting the bottom 50B of each prism 50 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 50 intersecting with the circle E are 50C and 50D, and a length of a line segment connecting the two points 50C and 50D is P. The apex angle of the prism 50 is α. Here, when the incident angle of the light L from the optical center C at the point 50D of the prism 50 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 50.
α = 90 ° -tan ⁻¹ {(P / R4) / 2}
In this case, two points 50C, by total reflection at 50D, in order to increase the reflectivity in the prism 50 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.

  When the dimensional relationship of each part of the prism 50 is set as described above, the light reflected at the two points 50C and 50D out of the light from the optical center C returns to the optical center C again. However, although the light from the optical center C is also reflected by the prism portions other than the points 50C and 50D, in this case, the light does not accurately return to the optical center C. Even in this case, it is preferable that the light reflected by the prism 50 be returned between the first and second electrodes 26 and 28 as much as possible. For this purpose, each prism 50 may be as small as possible. Specifically, in the cross section of the prism 50, when the length of the base of an isosceles triangle including two sides including the points 50C and 50D is equal to Dp, Dp ≦ De is preferable, and more preferably, Dp ≦ ( De / 2). In this example, De = 1 mm.

  Next, the formation region of the prism reflection lens portion 52 on the outer periphery of the light emitting portion 20 will be described with reference to FIG. The prism reflection lens portion 52 is basically a plane that includes the optical center C and is orthogonal to the tube axis B of the arc tube 16 in the outer periphery of the light emitting portion 20 that is generally spherical. In this case, the lamp unit 10 is formed in a region of the light emission direction side half (hereinafter referred to as “front side half”).

  Of the half area on the front side, the formation area of the prism reflection lens portion 52 is set as follows. That is, the prism reflection lens portion 52 is formed at least in a region that does not face the reflection surface (multilayer interference film 60) of the spheroid mirror 14. When the prism reflection lens portion is not formed, the objective is to reflect the outgoing light not reflected by the reflection surface (multilayer interference film 60) toward the reflection surface (multilayer interference film 60) by providing the prism reflection lens portion. That's why. Here, the region of the outer surface of the light emitting unit 20 that does not face the reflective surface (multilayer interference film 60) is a case where the optical center C and any part of the reflective surface (multilayer interference film 60) are connected in a straight line. The outer surface portion where the straight lines do not intersect. In the example shown in FIG. 1, a part of the prism reflection lens portion 52 is also formed in a region facing the reflection surface (multilayer interference film 60) of the spheroid mirror 14. This is to provide a margin in the relative positional relationship between the interference 60) and the prism reflection lens portion, and to reduce the emitted light that is not reflected by the reflecting surface as much as possible. In short, it is only necessary that a prism reflection lens portion is formed in at least a region that does not face the reflection surface in the front half region, and a part thereof extends to the region that faces the reflection surface. It does not matter.

Returning to FIG. 1, the high-pressure mercury lamp 12 having the above configuration is fixed to the spheroid mirror 14 with cement 56 at the second sealing portion 24 portion.
The spheroid mirror 14 has a hard glass substrate 58 having a funnel shape. A multilayer interference film 60 is deposited as a reflective film on the concave surface portion 58A formed on the spheroidal surface of the base body 58 to form a concave reflective surface. 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 sealing portion 24 into the mounting hole 58C provided in the neck portion 58B of the base body 58. And fixed with the cement 56. The predetermined position is ideally a position where the designed first focal point f1 of the ellipsoidal mirror 14 and the designed optical center C substantially coincide. However, in practice, there may be a variation in the shape of the reflecting surface of the spheroid mirror 14 or an axial misalignment of the electrode axes 30 and 34. Therefore, specifically, the high-pressure mercury lamp 12 was turned on by test, and the left, right, up, and front and back directions (for example, an XYZ orthogonal coordinate system with the axis A as the X axis) were taken toward the paper surface of FIG. The high-pressure mercury lamp 12 is positioned at a position where the illuminance in front of the spheroid mirror 14 becomes maximum when it is slid in the three-axis direction. Therefore, in the state in which the high-pressure mercury lamp 12 is integrated with the spheroid mirror 14, the first focal point f1 and the optical center C are not always completely coincident with each other.

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 complexity, the high-pressure mercury lamp 12 is represented only by its outline.
The light emitted from the optical center C toward the transmission part 54 and directed directly to the spheroid mirror 14 (shown by a dotted line) is reflected by the multilayer interference film 60 and the second focal point of the spheroid mirror 14. Focused on f2.

Further, the emitted light (indicated by a two-dot chain line) emitted from the optical center C toward the prism reflection lens unit 52 is retroreflected by each prism 50 of the prism reflection lens unit 52. The reflected emitted light again passes through the optical center C, passes through the transmission part 54, travels to the ellipsoidal mirror 14, is reflected by the multilayer interference film 60, and is collected at the second focal point f2.
That is, of the light generated in the discharge chamber 18, the light directly directed to the transmission part 54 (the hemispherical part on the spheroid mirror 14 side) of the light emitting part 20 passes through the transmissive part 54 as it is, and the spheroid mirror 14. The light reflected and collected by the light and directed toward the prism reflection lens unit 52 of the light emitting unit 22 is retroreflected by the prism 50 to the discharge chamber 18, and then passes through the transmission unit 54 and is rotated by the spheroid mirror 14. Reflected and condensed. As a result, most of the light generated in the discharge chamber 18 is collected, and the light use efficiency is improved. In the present application, the term “recursive reflection” means that light is always reflected in the original direction (light source direction) regardless of the incident direction of light. Here, in order to reflect as much as possible all the light generated in the discharge chamber 18 that does not go directly to the transmission part 54 of the light emitting part 20 with the spheroid mirror 14, the prism reflection lens part 52 is used as the light emitting part. In this case, it is most preferable, but of course, if desired, only a part of the light not directed to the transmission part 54 is reflected by the spheroid mirror 14 so as to reflect the light. You may provide the prism reflection lens part 52 in a part of front side half.

Moreover, since the prism 50 which is a reflecting member is formed in a part of the arc tube 16, it is a matter of course that the problem relating to heat resistance that the conventional reflecting film has is related to the present embodiment. It does not occur in the high pressure mercury lamp 12.
Further, when the reflection film formed on the arc tube is configured as 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), but the prism 50 according to the embodiment. In this case, it is possible to reflect radiant energy (300 nm to 1200 nm) in a wider band including at least ultraviolet rays and infrared rays radiated from the discharge chamber 18 (FIG. 1). Thereby, since the discharge plasma temperature in the discharge chamber 18 can be increased, the red component of the emission color can be increased, so that the color balance is improved.

Next, an example of a method for manufacturing the arc tube 16 constituting the high-pressure mercury lamp 12 will be described with reference to FIG.
First, as shown in FIG. 5A, while rotating a glass tube (made of quartz) 62 having one end closed and the other end opened around the tube axis, the light emitting unit 20 (FIG. 1). ) Is heated by the burner 64 and softened.

Next, as shown in FIG. 5 (b), a carbon mold 70 which is composed of an upper mold 66 and a lower mold 68 and in which cavity portions 66A and 68A having the same shape as the outer periphery of the light emitting portion 20 are formed in a closed state. And sandwich the softened portion.
And as shown in FIG.5 (c), the compressed gas which consists of inert gas is blown in from an open end part, the said softening part is expanded, and the outer periphery of the glass tube 62 is made to follow the inner surface of said cavity part 66A, 68A. Thus, the light emitting unit 20 is formed.

  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, in the carbon mold 70 described above, a smooth spherical surface is prepared without making the surfaces of the cavities 66A and 68A uneven. Using this carbon mold, the glass tube 62 is processed in the same manner as described above. As a result, a glass tube 62 whose center portion bulges in a substantially spherical shell shape (having the outer surface of the bulged portion formed into a smooth spherical surface) is completed. Then, the outer surface of the bulging portion is cut by laser processing to form a prism (convex portion).

  Although the prism reflection lens portion 52 can be formed by the manufacturing method described with reference to FIG. 5, the top of each prism 52 and the valley between the prisms 52 are actually sharp angles. It is not round and rounded. In addition, according to the above laser processing, it is possible to sharpen the top part and the valley part, but when considering the mechanical strength of the light emitting part (strength against repeated thermal stress, etc.) It is preferable to have a minimum roundness. However, in any case, if the top part or the valley part is rounded, the reflection efficiency of the entire prism 52 is slightly lower than the ideal value (design value).

Therefore, the inventor of the present application conducted an experiment for confirming the effect of providing the prism reflection lens portion 52.
The inventor of the present application, in addition to the high-pressure mercury lamp 12 (hereinafter also referred to as “example lamp”), a high-pressure mercury lamp that does not form a prism reflection lens (hereinafter referred to as “first comparison lamp”), and A lamp (hereinafter referred to as “second comparison lamp”) having a reflective film formed on the outer surface of the light emitting portion of the first comparison lamp was prepared. In the second comparison lamp, the region where the reflective film is formed is the same as the region where the prism reflection lens portion of the example lamp is formed. The reflective film is a dielectric multilayer film in which 40 layers of SiO ₂ films and TiO ₂ films are alternately laminated, and has a visible range reflectance of 95 to 100%.

And the lamp unit was created for every said lamp | ramp, and the illumination intensity experiment was implemented. Needless to say, in each lamp unit, all components other than the lamp have the same configuration.
FIG. 6 shows a part of the configuration of the evaluation optical system used in the experiment.
The evaluation optical system basically has the same configuration as that of an actual liquid crystal projector, and corresponds to a concave lens 102, integrator lenses 104 and 106, condenser lenses 108 and 110, a mask 112 corresponding to a liquid crystal panel, and an RGB combining prism. It consists of a dummy prism 114, a projection lens 116, and a screen (not shown). The screen is provided at a position 2 m ahead of the projection lens 116. The illuminance was evaluated based on the average value of illuminance measured at 9 points on the screen in accordance with ANSI standards.

For each of the above lamp units, the lamp was turned on at a rated power of 170 W and the illuminance was measured. When the first comparison lamp was used, it was 4310 lux, when the second comparison lamp was used, 5430 lux. When used, it was 5170 lux. The illuminance of the second comparison lamp is a value measured in a state where the reflecting film is not yet damaged.
From this result, when the illuminance of the first comparison lamp is 100%, the illuminance of the second comparison lamp is 126% and the illuminance of the example lamp is 120%, both of which are from the first comparison lamp. It can also be seen that the illuminance can be improved, that is, the light utilization rate can be improved. The lamp according to the embodiment cannot improve the illuminance as much as the second comparison lamp, but the difference is only 6%. When the deterioration / damage of the reflection film under the high temperature of the second comparison lamp is taken into consideration (reflection film) When the lamp is deteriorated or damaged, it is expected that the illuminance is greatly reduced.) The lamp of the example is more advantageous in the comprehensive evaluation.

Subsequently, two modified examples of the prism reflection lens unit (arc tube) will be described.
(Modification 1)
FIG. 7 shows a schematic configuration of the arc tube 80 according to the first modification. 7A is a half sectional view of the light emitting portion 82 of the arc tube 80 and its vicinity, and FIG. 7B is a sectional view taken along the line D / D in FIG. 7A. FIG. 7A is a diagram viewed from the direction of arrow G in FIG. In FIGS. 7A to 7C, the first and second electrodes and other members are not shown in order to avoid complexity.

  In the above-described prism reflection lens unit 52 (FIG. 2), the plurality of prisms 50 are arranged in a substantially concentric circle centered on a point on the tube axis B, whereas in the prism reflection lens unit 84 according to Modification 1, A plurality of prisms (convex portions) 86 are arranged radially around a point on the tube axis B as shown in FIG. That is, it is different from the prism reflection lens unit 52 in that it is arranged so as to be radial when viewed in the direction of the arrow G (in the tube axis B direction). In addition, the point which each convex part 86 which comprises each prism 86 has the shape of a bowl with a triangular cross section is the same as that of the convex part 50 of the prism reflection lens part 52. However, the triangle of the cross section of each convex part 50 in the prism reflection lens part 52 has a constant area everywhere, whereas the triangle of the cross section of each convex part 86 in the prism reflection lens part 84 is the transmission part 88. The closer it is, the bigger.

(Modification 2)
FIG. 8A shows a part of the arc tube 90 according to the second modification. FIG. 8A is a half sectional view of the light emitting portion 92 of the arc tube 90 and its vicinity. In FIG. 8A, the first and second electrodes and other members are not shown in order to avoid complexity.
In the prism reflection lens unit 50 (FIG. 2) and the prism 84 (FIG. 7), each prism (52, 84) is configured in a bowl shape having a triangular cross section, but in the prism reflection lens unit 94, Each prism was configured in a regular triangular pyramid shape as shown in FIG. Other configurations are substantially the same as those of the arc tube 16 (FIG. 2) and the arc tube 80 (FIG. 7). That is, in the prism reflection lens portion 94, a plurality of prisms (convex portions) 96 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). is there.

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 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) Further, the inner surface shape of the light emitting portion is not limited to a substantially spherical shape, and may be the shape shown in FIG. 9 or other known shapes. FIG. 9 is a half sectional view showing the light emitting portion 102 of the arc tube 100 according to Modification 3 and the vicinity thereof, and is a drawing drawn according to FIG. 2B. In FIG. 9, the same reference numerals as those in FIG. 2B are assigned to components that are substantially the same as those of the arc tube 16 according to the embodiment shown in FIG.

  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 which shows the light emission part of the arc tube of the high pressure mercury lamp which comprises the said lamp unit, and its vicinity, (b) is the half sectional view. It is an expanded sectional view of the prism reflection lens part in the said light emission part. 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 arc tube. It is the schematic which shows a part of evaluation optical system of a lamp unit. (A) is a half cross-sectional view showing a first modification of the arc tube (prism reflection lens portion), and (b) is a cross-sectional view taken along line D / D in (a). (C) is the figure which looked at the prism reflection lens part from the direction of arrow G in (a). (A) is a half sectional view showing a second modification of the arc tube (prism reflection lens part), and (b) is a diagram showing the shape of each prism in the prism reflection lens part. It is a half sectional view showing the 3rd modification of an arc tube (prism reflective lens part).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lamp unit 12 High pressure mercury lamp 14 Rotating ellipsoidal mirror 18 Discharge chamber 16,80,90,100 Light emission tube 20,82,92,102 Light emission part 26 1st electrode 28 2nd electrode 60 Multilayer interference film 50,86 , 94 Retroreflective prism (convex)

Claims (5)

A lamp unit comprising a high-pressure discharge lamp having an arc tube in which a discharge chamber is formed, and a reflecting mirror having a concave reflecting surface and reflecting and collecting light emitted from the discharge chamber. And
A plurality of convex portions are formed on the outer surface of the light emitting portion forming the discharge chamber of the arc tube,
The convex portion constitutes a prism that reflects part of light emitted from the discharge chamber, returns the light to the discharge chamber, and emits the light to the reflection surface.   2. The lamp unit according to claim 1, wherein the plurality of convex portions are arranged so that a cross section thereof has a triangular bowl shape.   The lamp unit according to claim 2, wherein the plurality of convex portions are arranged in a substantially concentric shape with a point on a tube axis of the arc tube as a center.   3. The lamp unit according to claim 2, wherein the plurality of convex portions are arranged radially around a point on a tube axis of the arc tube.   The lamp unit according to claim 1, wherein the plurality of convex portions have a triangular pyramid shape and are arranged adjacent to each other.

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