JP5238402B2 - Reflector, lamp unit, and projection-type image display device - Google Patents

Description

  The present invention relates to a reflecting mirror, a lamp unit including the reflecting mirror and a high-pressure discharge lamp as components, and a projection type image display apparatus including the lamp unit, and more particularly to a technique for improving a reflecting surface shape in the reflecting mirror.

  A lamp unit used as a light source of a liquid crystal projector which is one of projection type image display apparatuses has a reflecting mirror in order to increase the utilization factor of light emitted radially from a high-pressure discharge lamp. One of the shapes of the reflecting surface in the reflecting mirror is a spheroid. Here, in the present specification, the simple term “spheroid” means not only a mathematically perfect spheroid (hereinafter referred to as “true spheroid”) but also a little from the true spheroid. It also includes the displaced spheroid. A reflecting mirror having a reflecting surface formed on a spheroid is called a spheroid.

The high-pressure discharge lamp arranged in the spheroid mirror includes a bulb having a main pipe portion whose outer surface shape is, for example, a substantially spherical shape. In the main pipe part (discharge chamber), the tips of a pair of electrodes are arranged substantially opposite to each other, and arc discharge occurs between the electrodes to emit light.
The high-pressure discharge lamp is usually arranged so that the center between the electrodes (hereinafter referred to as “interelectrode center”) is located at the first focal point in the spheroid mirror by design. If the light emitted from the first focal point toward the spheroid mirror passes through the main pipe portion without being refracted and travels straight and is reflected by the reflecting surface, the reflected light is collected at the second focal point. .

  However, the thickness of the main pipe portion usually varies with distance from the center between the electrodes in the facing direction of the pair of electrodes (that is, the central axis direction of the bulb) due to the relationship between the outer surface shape and the inner surface shape. For this reason, the light emitted from the first focal point is refracted and changes the traveling direction when passing through the main pipe portion. As a result, the reflected light travels in a direction shifted from the second focal point because light enters the reflective surface from a direction different from the first focal point. Such a shift causes a reduction in light collection efficiency in the optical system of the entire liquid crystal projector.

In order to cope with this problem, Japanese Patent Application Laid-Open No. H10-228667 considers that the traveling direction changes due to the light emitted from the center between the electrodes being refracted by the main pipe portion, and corrects the true rotation ellipsoid to reflect the reflection surface. Is set to accurately collect the reflected light, which is emitted from the first focal point, passes through the main pipe portion, and is reflected by the reflecting mirror, by the second focal point.
Specifically, δ represents an angle formed by a traveling direction of light emitted from the first focal point and passing through the main pipe part and incident on an arbitrary reflection point of the reflecting mirror and a straight line connecting the first focal point and the reflection point. Then, the inclination of the reflection surface at the reflection point is set to an inclination corrected by (δ / 2) with respect to the inclination in the case of a true spheroid, thereby obtaining a desired reflection surface. .

According to this, the traveling direction of the reflected light emitted from the first focal point and passing through the main pipe part and reflected by the reflection point having the reflection surface is such that the main pipe part does not exist and the reflection surface is a true spheroidal surface. In this case, in the actual lamp unit, the reflected light is more accurately transmitted to the second focal point because it coincides with the traveling direction of the virtual reflected light emitted from the first focal point and reflected by the same reflection point. It will be condensed.
JP 2004-265702 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. For this purpose, further improvement in the light collection efficiency required for the reflecting mirror is desired.
An object of this invention is to provide the reflective mirror which can implement | achieve much higher condensing efficiency in view of an above-described subject. It is another object of the present invention to provide a lamp unit having such a reflecting mirror and a projection type image display apparatus including the lamp unit.

In order to achieve the above object, a reflecting mirror according to the present invention has a corrected spheroid on which the true spheroid is corrected on the reflecting surface, and a pair of electrodes are arranged oppositely in a hermetically sealed bulb. The high-voltage discharge lamp is incorporated into the reflector, and the high-pressure discharge lamp is incorporated in the reflector so that the center point between the electrodes is located at the first focal point in the reflecting surface. In an arbitrary plane including the optical axis of the reflecting mirror, the optical axis is the Z-axis, and the second focal point is an axis perpendicular to the Z-axis, and the light is emitted from one point between the electrodes and reflected. Adopting a ZY orthogonal coordinate system in which the intersection position of the reflected light reflected at one reflection point on the surface with the Y axis is represented by the Y coordinate and the illuminance at the intersection position is represented by the Z coordinate, the opposing direction between the two electrodes , N points (n is 3 The illuminance of the light emitted from the i-th point (i is an arbitrary integer from 1 to n) of the n reflected lights emitted from any one of the same reflection points. And the intersecting position as a point Pi (Zi, Yi) on the ZY orthogonal coordinates, and the Y axis of light emitted from the first and nth points of the n reflected lights Are the points Py ₁ (0, Y1) and Pyn (0, Yn), respectively, the corrected spheroids are points P1 (Z1, Y1),..., Pi (Zi, Yi). ), ..., the point Pn (Zn, Yn), the point Pyn (0, Yn), the point Py ₁ (0, Y1), the point P1 (Z1, Y1) sequentially, the region surrounded by connecting by a line segment, the The area of the portion existing between two reference lines that are equidistant from the Z-axis and parallel to the Z-axis is such that the emitted light from the n points is a true rotation ellipse. It is characterized in that the angle of the reflecting surface at each reflecting point is corrected to an angle that is wider than that assumed when the light is reflected by a circular surface.

Further, when the n is three, the second point is a point located on the center of the between the two electrodes, the first and third points, respectively, the said high-pressure discharge lamp in the arc discharge generated between the electrodes when is lit by incorporating in the reflector, characterized in that a point corresponding to the highest position of the luminance at both side portions of the second point.
Further characterized in that portion present between the reference line of the region surrounded by the line segment is the corrected angle of the reflecting surface at the reflection point of each angle whose maximum.

In order to achieve the above object, a lamp unit according to the present invention includes the above-described reflecting mirror and a high-pressure discharge lamp incorporated in the reflecting mirror.
In order to achieve the above object, a projection type image display apparatus according to the present invention includes the lamp unit as a light source.

According to the reflection mirror having the above structure, the point P1 (Z1, Y1), ... , the point Pi (Zi, Yi), ... , the point Pn (Zn, Yn), the point Pyn (0, Yn), the point Py ₁ ( 0, Y1) and point P1 (Z1, Y1) are connected at the same distance from the Z axis (optical axis) of the area surrounded by the line segment, that is, the area corresponding to the illuminance distribution at the second focal position. The area of the portion existing between two reference lines parallel to the Z-axis is larger than the case where it is assumed that emitted light from n points (n is an integer of 3 or more) is reflected by a true spheroid. The reflection surface is formed by correcting the angle of the reflection surface at each reflection point so that the angle becomes wider. That is, conventionally, the angle of the reflecting surface is corrected only in consideration of the emitted light from one point, whereas in the present invention, the illuminance distribution at the second focal point is considered in consideration of the emitted light from at least three points. Since the angle of the reflecting surface is corrected based on the above, the angle of the reflecting surface can be corrected considering the asymmetry at the second focal position of the illuminance distribution. It is possible.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a schematic configuration of a front type liquid crystal projector 10 shown as an example of a projection type image display apparatus. In all the figures including this figure, the scales between the constituent members are not unified.
The liquid crystal projector 10 drives the liquid crystal panel 24 based on the lamp unit 12, the concave lens 14, the integrator lenses 16 and 18, the condenser lenses 20 and 22, the liquid crystal panel 24, the RGB combining prism 26, the projection lens 28, and the input image signal. The liquid crystal panel driving unit 30 displays an image on the liquid crystal panel 24.

The lamp unit 12 includes a high-pressure mercury lamp 32 shown as an example of a high-pressure discharge lamp serving as a light source, and a spheroid mirror 34 that reflects and collects light emitted from the high-pressure mercury lamp 32.
FIG. 2 is a cross-sectional view of the lamp unit 12 cut along a plane including the optical axis Z of the spheroid mirror 34.
The high-pressure mercury lamp 32 has a quartz glass bulb 36. The bulb 36 has a main body 40 having a discharge chamber (light-emitting space) 38 that is hermetically sealed, for example, and has an outer shape that bulges out in a generally spherical shape. The first and second side pipe portions 42 and 44 are formed. The shape of the main pipe part 40 will be described later.

  Further, the high-pressure mercury lamp 32 has a pair of electrodes 46 and 48 that are disposed in the discharge chamber 38 with their tip portions facing each other. The first electrode 46 is formed by winding a coil 52 around an electrode shaft 50, and similarly, the second electrode 48 is formed by winding a coil 56 around an electrode shaft 54. The electrode shafts 50 and 54 and the coils 52 and 56 are both made of tungsten.

The base ends of the electrode shafts 50 and 54 are supported by the bulb 36, and the electrode shafts 50 and 50 are substantially coaxially extended to the discharge chamber 38, and the respective coils 52 and 56 are provided at the tip portions thereof. Is wound. Each of the coils 52 and 56 is provided to exhibit an appropriate heat dissipation function and prevent overheating of the electrode while the high-pressure mercury lamp 32 is lit.
Moreover, a part of the front-end | tip part which the 1st electrode 46 and the 2nd electrode 48 oppose is processed into the substantially hemispherical shape, and the heads 58 and 60 are formed. The reason for processing into a substantially hemispherical shape is to prevent the so-called arc jump phenomenon in which the arc is displaced randomly by concentrating the discharge during lighting as much as possible at the tip of the head. The distance between the tips of both heads 58 and 60 in the tube axis direction of the bulb 36, that is, the distance between the electrodes is set to 0.5 [mm] to 2.0 [mm], for example, 1.0 [mm].

The end portions of the electrode shafts 50 and 54 opposite to the head portions 58 and 60 are joined to one end portions of strip-shaped metal foils 62 and 64. Each of the pair of metal foils 62 and 64 is made of molybdenum foil.
One end of a first external lead wire 66 is joined to the other end of the first metal foil 62, and a second external part is joined to the other end of the second metal foil 64. Lead wire 68 is joined. The first and second lead wires 66 and 68 are both made of molybdenum wire. The end portions of the first and second external lead wires 66 and 68 opposite to the metal foils 62 and 64 are exposed from the bulb 36, and the end portions are respectively connected to the feeder lines 70 and 70, respectively. 72 is connected. By supplying power from the power supply lines 70 and 72, the high-pressure mercury lamp 32 can be turned on. At this time, a point C located in the middle between the electrodes 46 and 48 (between the tips of both heads 58 and 60) is the arc center (light emission center).

  The discharge chamber 38 is formed by sealing portions corresponding to the metal foils 62 and 64 of the bulb 36. In the discharge chamber 38, mercury, which is a luminescent material, and a rare gas such as argon, krypton, and xenon as a starting aid, and a halogen material such as iodine and bromine (all not shown) are enclosed. The halogen substance is returned to the electrodes 46 and 48 by the so-called halogen cycle without causing tungsten evaporated from the electrodes 46 and 48 to adhere to the inner surface of the quartz bulb 36 (main tube portion 40). It is enclosed in order to fulfill the function of suppressing the formation.

The high-pressure mercury lamp 32 having the above configuration is fixed to the spheroidal mirror 34 with cement 74 at the second side tube portion 44.
The spheroidal mirror 34 has a hard glass base 76 having a funnel shape. A multilayer interference film 78 is deposited as a reflective film on the concave surface portion 76A formed on the spheroidal surface of the base 76, thereby forming a reflective surface 80.

  The high-pressure mercury lamp 32 is positioned at a predetermined position in the optical axis Z direction of the spheroid mirror 34 by inserting the second side tube portion 44 into the mounting hole 76C provided in the neck portion 76B of the base 76. Then, it is fixed with cement 74. The predetermined position is, for example, a position where the first focal point f1 of the spheroid mirror 34 and the arc center C substantially coincide. Specifically, when the high-pressure mercury lamp 32 is lit in a test and slid in the left, right, up, down, and front and rear directions toward the paper surface of FIG. A mercury lamp 32 is positioned. The meaning of the “substantially coincide” is that the arc center C (the center point between the electrodes) and the second electrode are in the state where the high-pressure mercury lamp 32 has been incorporated into the spheroid mirror 34 as can be seen from the positioning method. This means that the focal point f1 does not always coincide completely. On the other hand, since correction to be described later of the true spheroid for determining the shape of the spheroid of the spheroid mirror 34 is performed by design, the arc center C (center point between the electrodes) and It is made under a virtual state where the first focus f1 coincides.

FIG. 3A shows an enlarged cross-sectional view of the main pipe portion 40. The outer surface shape of the main pipe portion 40 is, for example, a substantially spherical shape or a substantially oval shape, and the inner surface shape is similar to the outer surface shape. There is no need, and various designs are made. Therefore, due to the relationship between the outer surface shape and the inner surface shape,
The thickness of the main pipe portion 40 is not constant. In the case of the example shown in FIG. 3A, the thickness of the main pipe portion 40 is maximum T1 in the central portion in the tube axis direction (optical axis Z direction) and decreases as it approaches both ends (T1> T2). . However, as described above, the thickness of the main pipe section 40 also varies depending on the relationship between the outer surface shape and the inner surface shape, but “correction” described later is appropriately corrected according to the change.

Therefore, even the light emitted from the center point (arc center C) between the electrodes 46 and 48 is the inner surface (discharge) of the main pipe portion 40 except for the radiated light passing through the maximum thickness portion (T1). The light is refracted according to Snell's law at the chamber (light emitting space 38 and the boundary between the quartz glass) and the outer surface of the main pipe 40.
FIG. 4 shows a luminance distribution during arc discharge generated between the electrodes 46 and 48 (between both heads 58 and 60) when the high-pressure mercury lamp 32 is lit.

4A is a diagram showing the luminance distribution by contour lines, and FIG. 4B is a cross-sectional view of the contour map of FIG. 4A cut at the center. In FIG. 4B, the luminance distribution is expressed by the relative luminance with the highest luminance being “1”.
As shown in FIG. 4, the arc discharge luminance is not highest at the arc center C, but is highest near the tips of the electrodes 46 and 48. As shown in FIG. 4B, the luminance distribution curve BK exhibits bimodality with the arc center C as a boundary.

  Here, a point corresponding to the arc center C is a point S2, a point having the highest luminance between the point S2 and the electrode 48 is a point S1, and a point having the highest luminance between the point S2 and the electrode 46 is a point. S3 is assumed. That is, the opposing direction between the electrodes 48 and 46, the three points arranged in this order of the point S1, the point S2, and the point S3 are defined as described above. In this example, it is assumed that the points S1 and S3 are equidistant from the point S2.

Returning to FIG. 3, the emitted light emitted from the points S1, S2, and S3 will be described.
If the main pipe portion 40 is not present and there is no refraction, and the reflecting surface is a true spheroidal surface, the radiated light L1 reaching the reflecting point Ra of the reflecting surface from the points S1, S2, and S3. , L2 and L3 take a straight course. The angle α1 formed by L2 and L1 is equal to the angle α2 formed by L2 and L3. Then, the light is reflected at the reflection point Ra, L2 goes to the second focal point f2, and L1 and L3 form angles α1 and α2 with respect to L2, respectively, toward the second focal point F2.

Here, the illuminance at the virtual light receiving surface orthogonal to the optical axis Z at the second focal point f2 is defined as follows.
As shown in FIG. 3B, the second focal point f2 employs a ZY orthogonal coordinate system with the axis perpendicular to the optical axis Z as the Y axis and the second focal point f2 as the origin. And the intersection position with the Y-axis of the reflected light emitted from one point between both electrodes 46 and 48 and reflected by one reflection point of the reflecting surface is represented by the Y coordinate, and the virtual position at the intersection position is represented by the Z coordinate. It represents the illuminance on the light receiving surface.

Then, the intersection of the reflected light L1, L2, and L3 emitted from the points S1, S2, and S3 and reflected by the arbitrary reflection point Ra with the Y axis and the illuminance at the intersection are expressed as Z-Y orthogonal coordinates. The upper point P1 (Z1, Y1), the point P2 (Z2, Y2), and the point P3 (Z3, Y3) are represented.
The intersection position of L1 with the Y axis is represented by a point Py ₁ (0, Y1), and the intersection position of L3 with the Y axis is represented by a point Py ₃ (0, Y3).

Here, as a matter of course, the point P1 (Z1, Y1), the point P2 (Z2, Y2), and the point P3 (Z3, Y3) are illuminance distribution curves on the virtual light receiving surface of the reflected light reflected at the reflection point Ra. Exists on the BS.
Under the above virtual conditions (that is, when the main pipe portion 40 is not present and there is no refraction, and the reflecting surface is a true spheroidal surface), the point P2 is on the Z axis, and the illuminance distribution curve BS Has a symmetric shape with the Z axis as the symmetric axis, and is similar to the luminance distribution curve BK (FIG. 4).

However, in actuality, since the light is refracted by the main pipe section 40, the point P2 deviates from the Z axis (second focal point f2), and the illuminance distribution curve BS becomes asymmetric.
This will be described with reference to FIG. In the following description, regarding the illuminance distribution curve BS, the three points of the point P1 (Z1, Y1), the point P2 (Z2, Y2), and the point P3 (Z3, Y3) are represented as representative points. It will be explained with a simple representation of the connected line segments.

The radiated lights L1, L2, and L3 that reach the reflection point Ra on the reflection surface from the points S1, S2, and S3 are refracted in the main pipe section 40, respectively. For this reason, the radiated light radiated from the point S2 (first focal point f1) is incident on the reflective point Ra from a direction deviating from the straight line connecting the first focal point f1 and the reflective point Ra, and as a result, the reflected light is reflected. Will deviate from the second focus f2.
Further, the angle α1 formed by L2 and L1 and the angle α2 formed by L2 and L3 are different from each other (in this example, α1 <α2). As a result, the illuminance distribution on the virtual light receiving surface at the second focal position becomes asymmetric.

Returning to FIG. 3, in the design of an optical system such as a liquid crystal projector, improving the light condensing property on the virtual light receiving surface at the second focal point f2 position leads to compactness of the optical system and consequently miniaturization of the entire apparatus. It will be.
Here, in the optical system, a region that uses reflected light from the spheroid mirror on the virtual light receiving surface is defined as a use region Q. The use area Q is set to a square or a rectangle. Further, as shown in FIG. 3A, lines QL1 and QL2 indicating the boundaries of the usage region Q in the ZY plane are referred to as reference lines. The reference lines QL1 and QL2 are two lines that are equidistant from the Z axis and are parallel to the Z axis. When the use area Q is a rectangle, the reference lines QL1 and QL2 are straight lines passing through the ends of the long sides of the rectangle.

If the area of the use region Q is constant, it can be said that the more light flux enters the use region Q, the higher the light collecting property (the light utilization rate is high). In other words, the point P1 (Z1, Y1), the point P2 (Z2, Y2), the point P3 (Z3, Y3), the point y ₃ (0, Y3), the point Py ₁ (0, Y1), the point P1 (Z1, A portion (hereinafter referred to as “effective use region”) existing between the reference lines QL1 and QL2 in a region (hereinafter referred to as “basic region”) that is sequentially connected with line segments by Y1) is widened. The wider it is, the higher the light condensing property (the higher the light utilization efficiency).

However, if the reflecting surface is a true spheroidal surface, as described with reference to FIG. 5, the light from the point S2 between the electrodes is deviated from the second focal point f2, and the illuminance distribution is asymmetric. The area becomes narrow, and the light utilization efficiency decreases. This will be further described with reference to FIG.
FIG. 6A is a diagram in which the reference lines QL1 and QL2 are written in the second focal point f2 in FIG. 5 and its peripheral portion.

  In FIG. 6 (a), it can be seen that the effective use area subjected to the lower left hatching is narrower than the basic area subjected to the lower right hatching, and the effective use efficiency of light is low. Hereinafter, in the other drawings as well, as in FIG. 6A, the basic area is hatched downward and the effective use area is hatched downward to make it easy to distinguish the two.

Here, as described above, the technique disclosed in Patent Document 1 is such that the reflected light L2 emitted from the point S2 (FIG. 5) and reflected by the reflection point Ra on the reflection surface passes through the second focal point f2 ( FIG. 6 (b)) corrects the angle of the reflection surface at the reflection point Ra.
As a result, the effective use area is increased and the light use efficiency is improved as shown in FIG. 6B, compared with the result shown in FIG. There are not a few basic areas that protrude from between the reference lines QL1 and QL2, and there is room for improvement.

Therefore, in the present embodiment, the use efficiency of light is further improved by placing the basic region between the reference lines QL1 and QL2.
Specifically, the angle of the reflecting surface at an arbitrary reflecting point Ra is corrected to an angle such that the portion (area) existing between the reference lines QL1 and QL2 in the basic region is substantially maximized (FIG. 6C). It was decided. In the example shown in FIG. 6C, the entire basic area is between the reference lines QL1 and QL2 (that is, all the basic areas are effective use areas), but the Y direction of the basic area Is extended or contracted depending on the position of the reflection point in the optical axis direction (Z-axis coordinates), so that the basic region may protrude from between the reference lines QL1 and QL2. In short, even if it protrudes, it suffices if the portion (area) existing between the reference lines QL1 and QL2 of the basic region is substantially maximized (if the effective use region is substantially maximized).

In the above examples shown in FIGS. 5 and 6, for the sake of convenience, the Z coordinate values (that is, the illuminance) of the points P1 and P3 are drawn to be equal. When the distance in the Y-axis direction from P2 is different, the Z coordinate value (illuminance) at a point far from the point P2 is a relatively smaller value than the Z coordinate value (illuminance) at a near point.
This is shown in FIG. FIG. 8 shows a basic region at the second focal point f2 position after the angle correction of the reflecting surface, and corresponds to FIG. 6C. Incidentally, the L2, and the point Py ₂ the intersection with the Y axis.

  As described above, since the angle α1 and the angle α2 are different, when the distance from the point Py2 to the point Py1 and the distance from the point Py2 to the point Py3 in the Y-axis direction are different, the point Py2-point Py1-point P1- The area of the region surrounded by connecting the point P2-point Py2 with the line segment is equal to the area of the region surrounded by connecting the point Py2-point Py3-point P3-point P2-point Py2 with the line segment sequentially. Therefore, the Z coordinate values (illuminance) of the point P1 and the point P3 are different values. In the example shown in FIG. 8, since the distance from the point Py2 to the point Py1 in the Y-axis direction is longer than the distance from the point Py2 to the point Py3, the Z coordinate value (illuminance) of the point P1 is correspondingly increased to the point P3. The Z coordinate value (illuminance) is relatively small. FIG. 8 shows an example where the basic region protrudes from between the reference lines QL1 and QL2.

Returning to FIG. 6, subsequently, the state shown in FIG. 6A is changed to the state shown in FIG. 6C, that is, the position where the reflected light L1, L2, L3 intersects with the Y axis is A method of obtaining the correction angle Δθ of the reflection surface at the reflection point Pt for moving to the reference point will be described with reference to FIG.
In FIG. 7, for convenience of explanation, only the emitted light L2 from the point S2 between the electrodes is drawn. Of the reflected light, the two-dot chain line indicates the reflected light L2b before the “reflecting surface angle” at any reflecting point Pt on the reflecting surface is corrected.

Here, the “angle of the reflecting surface” is an angle formed by the tangent line drawn at the reflection point with the optical axis Z in the cross section of the reflecting mirror cut along the plane including the optical axis. Since the shape of the reflection surface is a “rotation” ellipse, the shape of the entire reflection surface is determined once the shape of the cross section (ellipse shape) is determined.
Here, as shown in FIG. 7, the first focal point f1 (arc center C, point S2) is the origin, the optical axis Z is the Z axis, and the axis orthogonal to the Z axis is the Z-axis. The Y orthogonal coordinate system shall be adopted.

The coordinate of the intersection Pb of the reflected light L2b with the straight line QL3 (straight line on the virtual light receiving surface) orthogonal to the Z axis at the second focal point f2 is defined as (Zb, Yb). The correction angle Δθ of the reflection surface at the reflection point Pt (Zt, Yt) for moving the intersection Pb upward by ΔY (= Ya−Yb) and changing the intersection to Pa (Zb, Ya) is given by It is obtained by.
Δθ = tan ⁻¹ {(Yt−Yb) / (Zb−Zt)}
-Tan ^-1 {(Yt-Ya) / (Zb-Zt)} (1)
The correction of the angle of the reflecting surface at an arbitrary reflection point is repeated by the correction angle Δθ obtained by the equation (1), and a correction is made over the whole to obtain a desired elliptical shape. By rotating about the center, the target corrected spheroid is obtained.

Specifically, first, the coordinates (Zs, Ys) of the reflection point Ps on the Y axis (Z = 0) not affected by refraction by the main pipe section 40 and the angle θ _S of the reflection surface at the point Ps are determined. Based on this. The point Ps (Zs, Ys) and the angle θ _S coincide with those of the true spheroidal surface.
Then, a point P _{(S + 1)} (Z _{S + 1} , Y _{S + 1} ) obtained by displacing the point Ps by a minute amount in the tangential direction (that is, the angle θ _S direction) of the reflecting surface at the point Ps is determined, and the point P _{(S +} obtain a correction angle [Delta] [theta] in the case where is reflected in _1), set the angle obtained by adding the correction angle [Delta] [theta] in the angle theta _S, the angle _{θ1 [= (θ S + Δθ} )] of the reflecting surface at the point P _{(S + 1)} To do. Next, a point P _{(S + 2)} obtained by displacing the point P _{(S + 1)} by a minute amount in the tangential direction of the reflecting surface at the point P _{(S + 1)} (that is, the direction of the angle θ1 ₎ is determined, and the same as described above. Then, the angle θ2 of the reflecting surface after correction at the point P _{(S + 2)} is set. By repeating such a procedure, the shape of the corrected spheroid (the shape in the range of Z> 0) is set.

On the other hand, the shape of the corrected spheroid in the range of Z <0 is similarly set while being shifted by a minute amount in the tangential direction.
Thus, according to the corrected spheroid according to the embodiment obtained by correcting the true spheroid, the light utilization efficiency is improved by about 5% compared to the case of Patent Document 1. This has been confirmed by computer simulation. Here, the light use efficiency refers to the ratio of the light flux passing through the use region Q (FIG. 3) to the total light flux.

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 correction angle of the reflecting surface is obtained based on the modeled illuminance distribution on the virtual light receiving surface when light is emitted from three points between the electrodes. However, when obtaining the correction angle, the starting point of the light emitted from between the electrodes is not limited to three, and an arbitrary number of four or more points may be set to obtain a modeled illuminance distribution.

  That is, it is also possible to set n points (n is an integer of 3 or more) arranged in the facing direction between the electrodes and in the order of the ordinal numbers from 1 to n to obtain a modeled illuminance distribution. I do not care. At this time, it is emitted from the i-th point (i is an arbitrary integer from 1 to n) out of the n reflected lights that are emitted from the n points and reflected at any same reflection point Ra. When the point on the ZY orthogonal coordinates of the reflected light reflected at the reflection point Ra is a point Pi (Zi, Yi), the basic region is the point P1 (Z1, Y1),. (Zi, Yi),..., A point Pn (Zn, Yn), a point P (0, Yn), a point P (0, Y1), a point P1 (Z1, Y1) are sequentially surrounded by line segments. It becomes.

  When the number n is 5 or more, the tip position of the second electrode 48 (head 60) is the first point, and the tip position of the first electrode 46 (head 58) is the nth. It is preferable to set the n points at equal intervals. In this case, it is preferable to set n to an odd number, that is, to set the middle point to coincide with the first focal position. In any case, it is preferable that the arc discharge generated between the two electrodes is set so as to include a point corresponding to a position where the luminance is substantially maximum.

Alternatively, an illuminance distribution represented by the illuminance distribution curve BS (FIG. 3B) itself may be used instead of the modeled illuminance distribution. The illuminance distribution curve BS is considered to be obtained when an infinite number of light emission starting points between the electrodes is set.
Note that the illuminance distribution represented by the modeled illuminance distribution or illuminance distribution curve BS is obtained by simulation using a computer.
(2) In the above embodiment, an example in which a high-pressure mercury lamp is used as a high-pressure discharge lamp is shown. However, the present invention is not limited to this, and for example, a metal halide lamp can be used.

  The reflector according to the present invention can be suitably used as a reflector constituting a lamp unit used in a projection type image display apparatus such as a liquid crystal projector.

It is a conceptual diagram which shows schematic structure of a liquid crystal projector. It is sectional drawing which cut | disconnected the lamp unit by the plane containing the optical axis of a rotation ellipsoidal mirror. It is a figure for demonstrating the optical path etc. between the main pipe part of a high pressure mercury lamp, the reflective surface of a reflective mirror, and the 2nd focus of a reflective mirror. It is a figure which shows the luminance distribution in the arc discharge of a high pressure mercury lamp. It is a figure which shows a mode that the radiated light from an arc discharge part is refracted | refracted in a main pipe part, and is reflected in a 2nd focus direction with a reflective mirror. It is a figure which shows the arrival position of the Y-axis direction in the 2nd focus of light L1, L2, L3 emitted from three points between the electrodes of a high pressure mercury lamp, (a) is the arrival position before correction | amendment of a reflective surface. (B) is a figure which shows the arrival position at the time of correct | amending a reflective surface by the technique of patent document 1, (c) is a figure which shows the arrival position at the time of correcting a reflective surface by the technique which concerns on embodiment, respectively. It is a figure for demonstrating the correction angle of the reflective surface in a reflective mirror. It is a figure which shows the arrival position of the Y-axis direction in the 2nd focus of light L1, L2, L3 emitted from three points between the electrodes of a high pressure mercury lamp, Comprising: When the reflective surface is correct | amended with the technique which concerns on embodiment It is a figure which shows an example of the arrival position of.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal projector 12 Lamp unit 32 High pressure mercury lamp 34 Spheroid mirror 80 Reflecting surface

Claims (5)

A reflecting mirror in which a high-pressure discharge lamp having a corrected rotating ellipsoid whose true rotating ellipsoid is corrected and having a pair of electrodes facing each other in a hermetically sealed bulb,
In a virtual state in which the high-pressure discharge lamp is incorporated in the reflecting mirror so that the center point between the two electrodes is located at the first focal point in the reflecting surface,
In an arbitrary plane including the optical axis of the reflecting mirror, the optical axis is the Z-axis, and the axis perpendicular to the Z-axis in the second focal point is the Y-axis. Adopting a Z-Y orthogonal coordinate system in which the intersection position with the Y axis of the reflected light reflected by the reflection point is represented by the Y coordinate, and the illuminance at the intersection position is represented by the Z coordinate,
N number of points emitted from n points (n is an integer of 3 or more) arranged in the opposite direction between the two electrodes in the order of the first to nth ordinal numbers and reflected at any same reflection point The illuminance and the intersection position of the light emitted from the i-th point (i is an arbitrary integer from 1 to n) of the reflected light are represented by a point Pi (Zi, Yi) on the ZY orthogonal coordinates. ), And the intersection positions of the light emitted from the first and nth points of the n reflected lights with the Y axis are point Py ₁ (0, Y1) and point Pyn (0, Yn) ,
The corrected spheroid is
Point P1 (Z1, Y1), ... , a point Pi (Zi, Yi), ... , point Pn (Zn, Yn), point Pyn (0, Yn), point Py ₁ (0, Y1), the point P1 (Z1, The area of the region surrounded by two reference lines that are equidistant from the Z-axis and parallel to the Z-axis in the region surrounded by connecting Y1) with the line segments sequentially from the n points A reflecting mirror characterized in that the angle of the reflecting surface at each reflecting point is corrected to an angle that is wider than when the emitted light is assumed to be reflected by a true spheroid. When n is 3,
The second point is a point located on the center of the between the two electrodes,
The first and third points are respectively
Characterized in that the arc discharge for generating the high-pressure discharge lamp between the electrodes when is lit by incorporating in the reflector, a point corresponding to the highest position of the luminance at both side portions of the second point The reflecting mirror according to claim 1. Claim 1 or 2, characterized in that the portion present between the reference line of the region surrounded by the line segment is the corrected angle of the reflecting surface at the reflection point of each angle whose maximum Reflector described in 1. The reflecting mirror according to any one of claims 1 to 3,
A high-pressure discharge lamp incorporated in the reflector;
A lamp unit comprising:   A projection type image display device comprising the lamp unit according to claim 4 as a light source.

Images