Lighting device and projection-type display device using the same including a color-combining prism

A lighting device includes: a phosphor wheel; a color-combining prism including dichroic surfaces, the film surfaces of these dichroic surfaces being disposed to cross a center ray of luminous flux of fluorescence emitted from the phosphor wheel and to be orthogonal to a plane that contains the center ray; a blue laser; a red laser; and excitation light sources. When viewed from the direction perpendicular to the plane, the blue laser, red laser, and excitation light sources are arranged on one side of the center ray of the luminous flux of the fluorescence.

TECHNICAL FIELD

The present invention relates to the lighting device of a projection-type display device.

BACKGROUND ART

Patent Document 1 describes a projector that uses a phosphor as a light source.

The principle parts of the projector described in Patent Document 1 are made up by a light source device, a cooling fan, a display element, and projection-side optics.

The light source device includes a light-emitting device in which the fluorescent color is red, a light-emitting device in which the fluorescent color is green, a light-emitting device in which the fluorescent color is blue, and first and second dichroic mirrors that combine the fluorescent light of each color from these light-emitting devices.

Each light-emitting device includes a cylinder-shaped rotating body in which a phosphor layer is formed on the outer periphery, a drive source that rotates the rotating body, a collimator lens that converts the fluorescent luminous flux emitted from the phosphor layer to parallel luminous flux, an excitation light source, and a mirror that reflects excitation light from the excitation light source in the direction toward the phosphor layer. The excitation light that is reflected by the mirror is irradiated by way of the collimator lens onto the phosphor layer. The fluorescent light that is emitted from the phosphor layer is converted to parallel luminous flux by the collimator lens.

The blue fluorescent light that is emitted from the blue light-emitting device is entered to one surface of the first dichroic mirror and the green fluorescent light that is emitted from the green light-emitting device is entered to the other surface of the first dichroic mirror. The first dichroic mirror has the property of transmitting blue light but reflecting green light and thus combines the incident blue and green fluorescent light.

The fluorescent light (green and blue) that is combined in the first dichroic mirror is entered to one surface of the second dichroic mirror, and red fluorescent light that is emitted from the red light-emitting device is entered to the other surface of the second dichroic mirror. The second dichroic mirror has the property of transmitting blue and green light but reflecting red light and thus combines the incident blue, green, and red fluorescent light.

Each light-emitting device is arranged in a chamber that is supplied with an air current from a cooling fan. Each light-emitting device is cooled by supplying the air current from the cooling fan to each light-emitting device.

In the above-described projector, light from the light source device is irradiated to a display element, and the image formed in this display element is then projected onto a screen by projection-side optics.

In addition to the above-described projector, Patent Document 2 describes a projector that uses light-emitting diodes (LED) as a light source.

The projector described in Patent Document 2 has illumination optics that includes: a red LED array in which a plurality of red LEDs are arranged, a green LED array in which a plurality of green LEDs are arranged, a blue LED array in which a plurality of blue LEDs are arranged, and a cross dichroic prism that combines the luminous flux for each of the colors red, green, and blue from these LED arrays.

In the above-described projector, light from the illumination optics is irradiated into a digital micro-device (DMD) and the image formed by the DMD is projected onto a screen by projection lenses.

LITERATURE OF THE PRIOR ART

Patent Documents

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-197497Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-186110

SUMMARY OF THE INVENTION

The recent advances in the development of compact high-luminance projectors have created demand for lighting devices (the light source device described in Patent Document 1 and the illumination optics described in Patent Document 2) that are more compact and that have greater luminance so that such projectors can be realized.

Because the light sources such as LEDs or excitation light sources (for example, semiconductor lasers) that make up the lighting device give off a large volume of heat, cooling means for cooling these light sources is normally provided inside the projector to limit the effect of heat upon other components. Depending on the configuration of the lighting device (in particular, the arrangement of each light source), the cooling means may become a large-scale structure, resulting in an increase in the size of the projector. As a result, the lighting device must be configured to avoid an increase in the size of the cooling means.

In the projector described in Patent Document 1, the light-emitting device of each color can be cooled by one cooling fan, whereby the increase in the size of the cooling means can be limited. However, in the projector described in Patent Document 1, the light-emitting device employs a phosphor, and the device is therefore larger than a solid-state light source such as a semiconductor laser or LED, and miniaturization of the light source device becomes problematic.

On the other hand, in the projector described in Patent Document 2, since LEDs are used as the light source, it is easier to realize illumination optics (lighting device) having greater compactness compared to the device described in Patent Document 1. However, the projector described in Patent Document 2 suffers from the problems described below.

High-luminance components in the form of green lasers or green LEDs are not yet being mass-produced and, currently, low-luminance components are being used. As a result, LEDs in the projector described in Patent Document 2 achieve high luminance by being arranged in an array.

However, a projection-type display device in which light from the light source is irradiated upon a display element and the image formed in the display element is projected by projection lens is subject to the constraint known as “etendue” that is determined by the area of the light source and the angle of divergence. If the value of the product of the area of the light source and the angle of divergence is not made equal to or less than the value of the product of the area of the display element and the acceptance angle (solid angle) that is determined by the f-number of the projection lens, the light from the light source cannot be used as projection light. Accordingly, even if a multiplicity of LEDs is aligned in an array, brightness cannot be improved beyond the limits of etendue.

In the illumination optics described in Patent Document 2, since the area of the LED semiconductor chip or the number of LEDs is limited due to the above-described limits of etendue, it is difficult to obtain output light whose amount is enough. Thus realizing higher luminance in the illumination optics described in Patent Document 2 is difficult.

Further, in the projector of Patent Document 2, an LED array of each color is arranged to face a different surface of a cross dichroic prism. When providing cooling means for the LED arrays of each color that are arranged in this way, the following two methods can normally be used.

In the first method, cooling means is provided for each LED array. However, in this case, a plurality of cooling means must be provided and this causes an increase in the size of the projector.

In the second method, the air current from a single cooling means is supplied to the LED array of each color by way of air ducts. However, a cooling system that uses such air ducts becomes a large-scale component and therefore causes an increase in the size of the projector.

In the illumination optics described in Patent Document 2 as described hereinabove, limiting an increase in the size of the cooling means is problematic.

It is an object of the present invention to provide a lighting device that is both compact and high-luminance in which the cooling means is not large and a projection-type display device that is equipped with the lighting device.

To achieve the above-described object, the lighting device of the present invention includes:

an excitation light source unit that supplies excitation light;

a phosphor unit that emits fluorescent light by the excitation caused by excitation light supplied from the excitation light source unit;

first and second solid-state light sources for which the color of emitted light differs; and

first to third reflection units each equipped with a dichroic film, the film surfaces of the dichroic films crossing the center ray of luminous flux of fluorescent light emitted from the phosphor unit, and moreover, being orthogonal to the plane that contains the center ray;

the excitation light source unit and the first and second solid-state light sources being arranged on one side of the center ray of the fluorescent luminous flux when viewed from a direction perpendicular to the plane;

the dichroic film of the first reflection unit being provided at the position at which the luminous flux of the excitation light supplied from the excitation light source unit crosses the luminous flux of the fluorescent light emitted from the phosphor unit and both reflecting the excitation light from the excitation light source unit toward the phosphor unit and transmitting the fluorescent light from the phosphor unit;

the dichroic film of the second reflection unit being provided at the position at which the luminous flux of first light supplied from the first light source unit crosses the luminous flux of the fluorescent light from the first reflection unit and both reflecting the first light from the first light source unit toward the third reflection unit and transmitting the fluorescent light from the first reflection unit; and

the dichroic film of the third reflection unit being provided at the position at which the luminous flux of second light supplied from the second light source unit crosses the luminous flux of the fluorescent light and the luminous flux of the first light from the second reflection unit and both transmitting the fluorescent light and the first light from the second reflection unit and reflecting the second light from the second light source unit in a traveling direction of the transmitted light.

The projection-type display device of the present invention includes:

the above-described lighting device;

a cooling fan that supplies an air current to the excitation light source unit and first and second solid-state light sources that make up the lighting device;

a display element that spatially modulates light emitted from the lighting device; and

projection optics that project the image light formed in the display element.

EXPLANATION OF REFERENCE NUMBERS

BEST MODE FOR CARRYING OUT THE INVENTION

Exemplary embodiments of the present invention are next described with reference to the accompanying drawings.

First Exemplary Embodiment

FIG. 1is a schematic view showing the configuration of the lighting device that is the first exemplary embodiment of the present invention.

Referring toFIG. 1, the lighting device is a device that is used in a projection-type display device such as a projector and includes: red laser10, blue laser11, excitation light sources12and13, phosphor wheel14, collimator lenses15-19, color-combining prism20, and light path changing prism22.

InFIG. 1, the light path of red laser light that is supplied from red laser10, the light path of blue laser light that is supplied from blue laser11, the light paths of excitation light that is supplied from excitation light sources12and13, and the light path of green fluorescent light that is emitted from phosphor wheel14are shown by solid lines (heavy lines) with arrows. The white arrow is light in which the red laser light, blue laser light, and green fluorescent light are combined and is the output light of the lighting device of the present exemplary embodiment. All of the light paths of each color are indicated only by the light paths of the center rays and are actually luminous flux composed of a plurality of rays.

Red laser10and blue laser11are solid-state light sources such as semiconductor lasers or LEDs of which laser diodes are representative. Red laser10supplies S-polarized laser light having a peak wavelength in the red wavelength band (hereinbelow indicated as red laser light). Blue laser11supplies S-polarized laser light having a peak wavelength in the blue wavelength band (hereinbelow indicated as blue laser light).

Phosphor wheel14is composed of a wheel on which a phosphor region is formed along the outer periphery of one surface. The center portion of phosphor wheel14is supported by a rotation axis that is linked to an output axis of a motor not shown in the figure (or the output axis), phosphor wheel14receiving the rotational drive realized by the motor and rotating at a fixed speed. The emitted color of the phosphor that is formed in the phosphor region is green, and due to the excitation of the phosphor by the excitation light of a wavelength shorter than that of this green wavelength, green phosphor light is emitted from the phosphor region.

Excitation light sources12and13are light sources that supply S-polarized excitation light of a wavelength that is shorter than the wavelength of green fluorescent light, and are made up of solid-state light sources of which, for example, blue lasers or blue LEDs are representative. The peak wavelength of output light of excitation light sources12and13may be the same as or may differ from blue laser11.

Collimator lens15is a component that converts the green fluorescent light (diverging light) that is emitted from the phosphor region of phosphor wheel14to parallel luminous flux and is made up of two convex lenses15aand15cand one concave lens15c. Collimator lens15is not limited to the lens configuration shown inFIG. 1, and may be of any lens configuration that enables conversion of the green fluorescent light emitted from the phosphor region to parallel luminous flux.

Collimator lens16converts the red laser light (diverging light) supplied from red laser10to parallel luminous flux. Collimator lens17converts the blue laser light (diverging light) that is supplied from blue laser11to parallel luminous flux. Collimator lens18converts the excitation light (diverging light) that is supplied from excitation light source12to parallel luminous flux. Collimator lens19converts the excitation light (diverging light) that is supplied from excitation light source13to parallel luminous flux.

When viewed from a direction perpendicular to the plane that contains the center ray of green fluorescent light from phosphor wheel14, red laser10, blue laser11, and excitation light sources12and13are positioned on one side of the center ray.

Red laser10, blue laser11, and excitation light sources12and13are arranged so as to emit light in the same direction. More specifically, the optical axes of each of red laser10, blue laser11and excitation light sources12and13are mutually parallel. The output light of each of red laser10, blue laser11, and excitation light sources12and13is incident to color-combining prism20from the same side.

Color-combining prism20is a dichroic prism shaped as a rectangular parallelepiped and composed of four prisms20a-20d.

Prisms20aand20dare rectangular prisms, their shape and size being substantially equal.FIG. 2gives a schematic representation of a rectangular prism that is used as these prisms20aand20d.

As shown inFIG. 2, the rectangular prism is a right isosceles triangular prism and has five surfaces P10-P14. InFIG. 2, reference numbers P10-P14are underlined, the reference numbers that are underlined by solid lines indicating visible surfaces and the reference numbers that are underlined by broken lines indicating hidden surfaces.

Surfaces P10and P11are rectangular surfaces that are mutually orthogonal (corresponding to surfaces that make up the two orthogonal sides of a right triangle when viewed from the side). Surface P12is an inclined surface (corresponding to the surface that makes up the hypotenuse of a right triangle when viewed from the side). Surface P13and surface P14are side surfaces that are orthogonal to each of surfaces P10-P12. The angle formed by surface P11and surface P12is θ1.

Prism20bis a trapezoid-shaped prism (square pole).FIG. 3gives a schematic representation of a trapezoid-shaped prism that is used as prism20b.

The trapezoidal prism shown inFIG. 3is a shape obtained by cutting away the apex (the point that forms a right angle) of a right isosceles triangular prism and has six surfaces P20-P25. InFIG. 3, reference numbers P20-P25are underlined, the reference numbers underlined by solid lines indicating visible surfaces and the reference numbers underlined by broken lines indicating hidden surfaces.

Surfaces P20and P21are the opposing inclined surfaces of a trapezoid, and the plane that contains surface P20is orthogonal to the plane that contains surface P21. Surface P25is the surface that constitutes the upper surface of the trapezoid, and surface P22is the surface that forms the bottom surface of the trapezoid. Surface P25and surface P22are parallel. Surface P23and surface P24are side surfaces that are orthogonal to each of surfaces P20-P22. Angle θ2formed by surface P20and surface P22is identical to the angle formed by surface P21and surface P22. Angle θ2is identical to angle θ1formed by surface P11and surface P12shown inFIG. 2.

The shape and size of surface P20of prism20bare substantially identical to the shape and size of surface P12(inclined surface) of prism20a. As shown inFIG. 1, surface P12of prism20aand surface P20of prism20bare bonded together, and dichroic surface (film)21ais formed on this bonded surface.

Prism20cis parallelogram-shaped prism (oblique prism).FIG. 4gives a schematic representation of a parallelogram-shaped prism that is used as prism20c.

As shown inFIG. 4, the parallelogram-shaped prism has six surfaces P30-P35. InFIG. 4, reference numbers P30-P35are underlined, the reference numbers underlined by solid lines indicating visible surfaces and the reference numbers underlined by broken lines indicating hidden surfaces.

Surfaces P30-P33are rectangular surfaces, surface P30and surface P32are arranged facing each other, and surface P31and surface P33are arranged facing each other. The shape and size of surface P30are substantially equal to the shape and size of surface P21of prism20b. The shape and size of surface P32are substantially equal to the shape and size of surface P12(inclined surface) of prism20d.

Surface P34and surface P35are side surfaces that are orthogonal to each of surfaces P30-P33and are shaped as parallelograms. The angle formed by surface P30and surface P33is θ3(=180°−θ2).

As shown inFIG. 1, surface P30of prism20cand surface P21of prism20bare bonded together, and dichroic surface (film)21bis formed on this bonded surface. Surface P32of prism20cand surface P12(inclined surface) of prism20dare bonded together, and dichroic surface (film)21cis formed on the bonded surface.

When color-combining prism20is formed by prisms20a-20d, for example, orthogonal reference surfaces S1and S2are set and prisms20a-20dare bonded with these reference surfaces S1and S2as a reference to form color-combining prism20as shown inFIG. 12. Surface P22of prism20band surface P33of prism20care matched to reference surface S1and surface P11of prism20dis matched to reference surface S2. Prisms20b-20dare bonded in this state. When bonding prism20dto prism20cas well, the angled portion of prism20d(the angle formed by surface P11and surface P12) is matched to reference surface S1. Prism20ais further bonded to prism20b. When bonding prism20ato prism20bas well, the angled portion of prism20a(the angle formed by surface P11and surface P12) is matched to reference surface S1.

By means of the above-described bonding method, prism20bbetween prisms20aand20cis made a trapezoid shape, whereby interference between the angled portion of prism20a(the angle formed by surface P10and surface P12) and the angled portion of prism20c(the angle formed by surface P30and surface P31) can be prevented even when prisms20aand20care larger than the designed values.

Alternatively, prism20bmay be constituted by a triangular prism. More specifically, prism20bis formed by a prism (triangular prism) that lacks the truncated portion that forms surface P25inFIG. 3. In this case, however, upon applying the bonding method that is based on reference surfaces S1and S2shown inFIG. 12, prisms20aand20cwill in some cases interfere when prisms20aand20care larger than the designed values. Prisms20a-20cmust be shaped and bonded at high accuracy to prevent the occurrence of this interference.

In contrast, if trapezoid-shaped prism20bshown inFIG. 3is used, spacing corresponding to the width of surface P25occurs between prisms20aand20c, and because the interference between prisms20aand20ccan be limited to this extent, a certain amount of margin can be afforded in the accuracy demanded when shaping and bonding prisms20a-20c.

All of dichroic surfaces21a-21care made up of dielectric multilayer films. Dichroic surfaces21a-21care arranged in that order along the luminous flux of green fluorescent light that is emitted from phosphor wheel14and converted to parallel luminous flux by collimator lens15.

Dichroic surfaces21aand21bhave the same film characteristics.FIG. 5shows the spectral transmission characteristics with respect to P-polarized light and S-polarized light of these dichroic surfaces21aand21b. InFIG. 5, the alternate long and short dash line shows the spectral transmission characteristic with respect to S-polarized light, and the broken line shows the spectral transmission characteristic with respect to P-polarized light. B-LD is the spectrum of blue laser light that is supplied from blue laser11, and the spectrum that is on the lower wavelength side of this spectrum (Excitation) is the spectrum of excitation light that is supplied from excitation light sources12and13. The spectrum of blue laser light may be the same wavelength band as the spectrum of excitation light.

The cutoff wavelength is defined as the wavelength at which transmittance becomes 50%. The cutoff wavelength of dichroic surfaces21and21bwith respect to light that is incident as S-polarized light is set such that light of wavelengths equal to or shorter than the blue wavelength band is reflected and light of other wavelength bands (including the green and red wavelength bands) is transmitted. The cutoff wavelength of dichroic surfaces21aand21bwith respect to light incident as P-polarized light is set to the shorter wavelength side than the cutoff wavelength with respect to S-polarized light. The setting of the cutoff wavelength can be adjusted by the material, the number of layers, the film thickness, and the refractive index of the dielectric multilayer films.

In dichroic surfaces21aand21bthat have the spectral transmission characteristics shown inFIG. 5, S-polarized light having a wavelength equal to or shorter than the blue wavelength band is reflected and light of the green and red wavelength bands is transmitted.

FIG. 6shows the spectral transmission characteristics with respect to P-polarized light and S-polarized light of dichroic surface21c. InFIG. 6, the solid lines show the spectral transmission characteristic with respect to S-polarized light and the dotted lines show the spectral transmission characteristic with respect to P-polarized light. R-LD is the spectrum of red laser light supplied from red laser10.

The cutoff wavelength of dichroic surface21cwith respect to light that is incident as S-polarized light is set to reflect light of wavelengths equal to or greater than the red wavelength band and to transmit light of other wavelength bands (including the green and blue wavelength bands). The cutoff wavelength of dichroic surface21cwith respect to light incident as P-polarized light is set to the side of longer wavelengths than the cutoff wavelength with respect to S-polarized light. In this case as well, the setting of the cutoff wavelength can be adjusted by the material, the number of layers, the film thickness, and the refractive index of the dielectric multilayer films.

In dichroic surface21cthat has the spectral transmission characteristic shown inFIG. 6, S-polarized light having wavelengths equal to or longer than the red wavelength band is reflected and S-polarized light of the green and blue wavelength bands is transmitted.

In the lighting device of the present exemplary embodiment, excitation light that is supplied from excitation light source12and converted to parallel luminous flux by collimator lens18is incident to surface P10of prism20aof color-combining prism20. Excitation light that is supplied from excitation light source13and converted to parallel luminous flux by collimator lens19is incident to surface P10of prism20aof color-combining prism20by way of light path changing prism22. Light path changing prism22is a parallelogram-shaped prism and is used for changing the light path of excitation light from excitation light source13.

Blue laser light that is supplied from blue laser11and converted to parallel luminous flux by collimator lens17is incident to surface P31of prism20cof color-combining prism20. Red laser light that is supplied from red laser10and converted to parallel luminous flux by collimator lens16is incident to surface P10of prism20dof color-combining prism20.

In color-combining prism20, each excitation light that is incident to surface P10of prism20ais incident at an angle of incidence of approximately 45° to dichroic surface21a. Dichroic surface21areflects the excitation light that is incident in the direction of surface P11of prism20a.

Excitation light that is reflected by dichroic surface21aexits from surface P11of prism20a. The excitation light that exits from surface P11of prism20ais condensed in the phosphor region of phosphor wheel14by way of collimator lens15.

As shown inFIG. 1, when viewed from a direction perpendicular to the plane that contains the optical axis of collimator lens15(or the center ray of green fluorescent light from phosphor wheel14), and moreover, that is orthogonal to dichroic surface21a, the center ray of excitation light from excitation light source12that was reflected by dichroic surface21aand the center ray of excitation light from excitation light source13that was reflected by dichroic surface21aare in a substantially linear symmetrical positional relationship around the optical axis of collimator lens15. As a result, the center ray of excitation light from excitation light source12and the center ray of excitation light from excitation light source13are condensed and the excitation light is irradiated at substantially the same position on the phosphor region by collimator lens15.

In the phosphor region of phosphor wheel14, the phosphor is excited by the irradiation of the excitation light. Green fluorescent light is emitted from the excited phosphor.

The green fluorescent light (diverging light) that is emitted from the phosphor region of phosphor wheel14is converted to parallel luminous flux by collimator lens15and is then incident to surface P11of prism20aof color-combining prism20.

FIG. 7shows the superposition of the spectral transmission characteristics of each of dichroic surfaces21a-21c. InFIG. 7, the dotted lines show the spectral transmission characteristic with respect to S-polarized light, and the alternating long and short dash line shows the spectral transmission characteristic with respect to P-polarized light. The curved line shown by a solid line in the center ofFIG. 7is the spectrum of green fluorescent light from phosphor wheel14.

The green fluorescent light from phosphor wheel14is random polarized light (containing S-polarized light and P-polarized light) and virtually all of this light is transmitted by dichroic surfaces21a-21c.

In color-combining prism20, green fluorescent light that is incident from surface P11of prism20ais incident to dichroic surface21aat an angle of incidence of approximately 45°. Dichroic surface21atransmits the incident green fluorescent light.

The transmitted luminous flux of the green fluorescent light from dichroic surface21ais incident to dichroic surface21bfrom the side of prism20bat an angle of incidence of approximately 45°. Blue laser light from blue laser11is incident to dichroic surface21bfrom the side of prism20cat an angle of incidence of approximately 45°.

Dichroic surface21bis disposed at the intersection of the optical axis of blue laser11and the center ray of the luminous flux of the green fluorescent light from phosphor wheel14(more specifically, the optical axis of the system that includes phosphor wheel14and collimator lens15).

Dichroic surface21breflects blue laser light from blue laser11toward dichroic surface21cand transmits the transmitted luminous flux of green fluorescent light from dichroic surface21a. In this way, the blue laser light from blue laser11and the green fluorescent light from dichroic surface21aare color-combined.

Luminous flux from dichroic surface21b(blue laser light+green fluorescent light) is incident to dichroic surface21cfrom the side of prism20c. The red laser light from red laser10is incident to dichroic surface21cat an angle of incidence of approximately 45° from the side of prism20d.

Dichroic surface21cis disposed at the intersection of the optical axis of red laser10and the center ray of the luminous flux of green fluorescent light from phosphor wheel14(more specifically, the optical axis of the system that includes phosphor wheel14and collimator lens15).

Dichroic surface21creflects red laser light from red laser10toward surface P11of prism20dand transmits luminous flux from dichroic surface21b(blue laser light+green fluorescent light). In this way, the red laser light from red laser10and luminous flux from dichroic surface21b(blue laser light+green fluorescent light) are color-combined.

The luminous flux from dichroic surface21c(blue laser light+green fluorescent light+red laser light) exits from surface P11of prism20d. This light that exits from surface P11of prism20d(red, green, and blue) is the output light of the lighting device of the present exemplary embodiment.

The lighting device of the present exemplary embodiment as described hereinabove exhibits the following action and effect.

The light-emitting device described in Patent Document 1 suffers from the problem of the large size of the light-emitting devices due to the use of light sources (light-emitting devices) that uses phosphor material as the red, green and blue light sources. In contrast, in the lighting device of the present exemplary embodiment, red and blue light sources are made of solid-state light sources, and the green light source is made of a light source that uses phosphor material. By adopting hybrid light sources in which solid-state light sources and a light source that uses a phosphor material are mixed, a lighting device can be realized that features both compact size and high luminance.

In the lighting device of the present exemplary embodiment, dichroic surfaces21a-21care disposed to intersect with the center ray of the luminous flux of green fluorescent light from phosphor wheel14(more specifically, the optical axis of the system that includes phosphor wheel14and collimator lens15), and moreover, are disposed to be orthogonal to the plane that includes the center ray. Dichroic surfaces21a-21care then arranged in this order from the side of phosphor wheel14and in that order and the film characteristics of each of dichroic surfaces21a-21care assumed to have the characteristics shown inFIG. 5toFIG. 7. In this way, each source of heat, i.e., red laser10, blue laser11, and excitation light sources12and13can be disposed in a row on the same side of color-combining prism20.

By means of the above-described configuration, each source of heat can be simultaneously cooled by one cooling fan. In addition, a duct for guiding the cooling air current from the cooling fan to the sources of heat is not required. As a result, the cooling system can be realized by a simple configuration compared to the configuration described in Patent Document 2.

In addition, the lighting device of the present exemplary embodiment can obtain the following effects.

Typically, the luminance of fluorescent light emitted from a phosphor increases with increase in the intensity of the excitation light irradiated on the phosphor material.

In addition, the fluorescent size within a phosphor region is determined depending on the condensed size of the excitation light that is irradiated on the phosphor material. As a result, condensing and irradiating the excitation light by means of collimator lens15enables a reduction of the fluorescent size, whereby the problem of the reduction of the amount of light due to the limits of etendue can be eliminated.

In addition, the lighting device of the present exemplary embodiment enables the formation of red laser10, blue laser11, and excitation light sources12and13on the same substrate surface, thereby facilitating the alignment of the optical axes of each light source and enabling assembly of the lighting device with high precision.

In the above-described case, the light sources of red laser10, blue laser11, and excitation light sources12and13each may be disposed in one row, whereby each light source can be efficiently cooled by a single cooling fan.

Still further, in the above-described case, a heat sink, which is a heat-discharging means that discharges the heat energy from each of the light sources of red laser10, blue laser11, and excitation light sources12and13into space, may be provided on a portion of the substrate that is provided with red laser10, blue laser11, and excitation light sources12and13. In this way, the effect of cooling each of the light sources of red laser10, blue laser11, and excitation light sources12and13can be augmented.

FIG. 8shows an example of a configuration in which each of the light sources of red laser10, blue laser11, and excitation light sources12and13is provided on the same substrate surface.

Referring toFIG. 8, red laser10, blue laser11, and excitation light sources12and13are disposed in a row on the same substrate surface of substrate23that has an L-shaped profile. Heat sink24is provided on a portion of substrate23.

According to the configuration shown inFIG. 8, each light source can be effectively cooled by causing an air current (cooling wind) to flow along the row of each of the light sources of red laser10, blue laser11, and excitation light sources12and13. In addition, the cooling effect can be further increased by the action of the heat discharge realized by a heat sink.

FIG. 9shows a configuration in which a cooling fan has been installed on the substrate shown inFIG. 8.

Referring toFIG. 9, cooling fan25is provided on one end of substrate23(the side on which red laser10is located). Cooling fan25is, for example, a sirocco fan and is equipped with inflow port25athat takes in air and outflow port25bthat discharges air.

The air current that is discharged from outflow port25bflows over the substrate surface on which each of light sources of red laser10, blue laser11, and excitation light sources12and13are provided and along the direction of the row of light sources. Each light source is thus cooled.

In addition, the air current discharged from outflow port25bis also supplied to heat sink24. Heat sink24has a plurality of fins, and a portion of the air current from outflow port25bis supplied among these fins. Effective heat discharge can be provided by both the heat exchange between the fins and the air and the flow of air among the fins.

In addition, according to the lighting device of the present exemplary embodiment, the use of color-combining prism20in which dichroic surfaces21a,21c, and21bare formed on the bonded surfaces of prisms enables the adjustment of the inclination of dichroic surfaces21a,21c, and21bor the light path adjustment with respect to these dichroic surfaces (including adjustment of optical axes) to be carried out at one time. In this way, the assembly of the lighting device can be carried out simply and with high precision.

The lighting device of the above-described exemplary embodiment is one example of the present invention, and the configuration of the lighting device is open to various modifications that do not depart from the gist of the invention and that will be clear to one of ordinary skill in the art.

For example, the number of excitation light sources is not limited to two, and one excitation light source or three or more excitation light sources may be used.

In addition, light guide means or optics for guiding the light supplied from color-combining prism20may also be provided in the lighting device of the present exemplary embodiment.

Still further, in place of phosphor wheel14, a phosphor section may also be used that includes a region in which a phosphor material is formed on the substrate surface.

In addition, the positions of dichroic surfaces21band21ccan be reversed. In other words, dichroic surfaces21a,21c, and21bmay be arranged in that order from the side of phosphor wheel14. In this case, the positions of red laser10and blue laser11are also reversed.

Still further, a plurality of mirrors may be used in place of light path changing prism22.

Second Exemplary Embodiment

FIG. 10is a schematic view showing the configuration of a lighting device that is the second exemplary embodiment of the present invention.

The lighting device of the present exemplary embodiment differs from the first exemplary embodiment in that it is equipped with dichroic mirrors51a-51cin place of color-combining prism20, and further, includes mirrors52and53in place of light path changing prism22. The configuration is otherwise the same as the first exemplary embodiment (including modifications). InFIG. 10, the same reference numbers are given to constituent elements that are identical to those of the first exemplary embodiment.

Each of dichroic mirrors51a-51ccorresponds to dichroic surfaces21a-21c, respectively, and all are composed of dielectric multilayer films.

Dichroic mirrors51a-51ceach cross the center ray of the luminous flux of green fluorescent light that is emitted from phosphor wheel14, and moreover, are disposed orthogonal to the plane that contains the center ray. Dichroic mirrors51a-51care disposed successively and in that order from the side of phosphor wheel14.

When viewed from a direction perpendicular to the above-described plane, red laser10, blue laser11, and excitation light sources12and13are arranged on one side of the center ray of the luminous flux of green fluorescent light.

The film characteristics of dichroic mirrors51aand51bare the same as those of dichroic surfaces21aand21b. In other words, dichroic mirrors51aand51bboth have the characteristics shown inFIG. 5.

The film characteristics of dichroic mirror51care the same as those of dichroic surface21c. In other words, dichroic mirror51chas the characteristics shown inFIG. 6.

In the lighting device of the present exemplary embodiment, the excitation light that is supplied from excitation light source12and converted to parallel luminous flux by collimator lens18is incident to dichroic mirror51aat an angle of incidence of approximately 45°. The excitation light that is supplied from excitation light source13and converted to parallel luminous flux by collimator lens19is incident to dichroic mirror51aat an angle of incidence of approximately 45° by way of mirrors52and53.

Dichroic mirror51areflects the incident excitation light in the direction of phosphor wheel14. The excitation light that is reflected by dichroic mirror51ais condensed on the phosphor region of phosphor wheel by way of collimator lens15.

The center ray of the excitation light from excitation light source12and the center ray of the excitation light from excitation light source13are condensed on the phosphor region by collimator lens15. As a result, the excitation light from excitation light source12and the excitation light from excitation light source13are condensed and irradiated upon substantially the same position on the phosphor region.

Phosphor is excited by the irradiation of the excitation light in the phosphor region of phosphor wheel14. Green fluorescent light is emitted from the excited phosphor.

The green fluorescent light (diverging light) that is emitted from the phosphor region of phosphor wheel14is converted to parallel luminous flux by collimator lens15and then incident to dichroic mirror51a. Dichroic mirror51atransmits the incident green fluorescent light.

The transmitted luminous flux of the green fluorescent light from dichroic mirror51ais incident to dichroic mirror51bat an angle of incidence of approximately 45°. Dichroic mirror51bis disposed at the intersection of the optical axis of blue laser11and the luminous flux of green fluorescent light from phosphor wheel14(more specifically, the optical axis of the system that includes phosphor wheel14and collimator lens15). The blue laser light from blue laser11is incident to dichroic mirror51bat an angle of incidence of approximately 45°.

Dichroic mirror51breflects the blue laser light from blue laser11toward dichroic mirror51c, and transmits the transmitted luminous flux of green fluorescent light from dichroic mirror51a, whereby the blue laser light from blue laser11and the green fluorescent light from dichroic mirror51aare color-combined.

The luminous flux (blue laser light+green fluorescent light) from dichroic mirror51bis incident to dichroic mirror51cat an angle of incidence of approximately 45°. Dichroic mirror51cis disposed at the intersection of the optical axis of red laser10and the luminous flux of the green fluorescent light from phosphor wheel14(more specifically, the optical axis of the system that includes phosphor wheel14and collimator lens15). The red laser light from red laser10is incident to dichroic mirror51cat an angle of incidence of approximately 45°.

Dichroic mirror51creflects the red laser light from red laser10and transmits the luminous flux from dichroic mirror51b(blue laser light+green fluorescent light), whereby the red laser light from red laser10and the luminous flux (blue laser light+green fluorescent light) from dichroic mirror51bare color-combined.

The luminous flux (blue laser light+green fluorescent light+red laser light) from dichroic mirror51cis the output light of the lighting device of the present exemplary embodiment.

The lighting device of the present exemplary embodiment described hereinabove exhibits the same action and effect as the first exemplary embodiment. However, the lighting device of the present exemplary embodiment requires a holding construction that separately limits the inclination of the mirrors for dichroic mirrors51a-51c. In some cases, the inclination of these mirrors and light paths must be adjusted. As a result, the lighting device of the first exemplary embodiment enables simpler and more precise adjustment of the inclination of mirrors or adjustment of light paths than the lighting device of the present exemplary embodiment.

The lighting device of the present exemplary embodiment also allows the application of the various modifications described in the first exemplary embodiment (including the configuration shown inFIGS. 8 and 9).

In addition, light path changing prism22shown inFIG. 1may be used in place of mirrors52and53.

Another Exemplary Embodiment

The lighting device of this other exemplary embodiment includes: an excitation light source unit that supplies excitation light; a phosphor unit that emits fluorescent light by the excitation resulting from excitation light that is supplied from the excitation light source unit; first and second solid-state light sources in which the color of emitted light differs; and first to third reflection units that are each equipped with dichroic film, whose surfaces intersect with the center ray of the luminous flux of fluorescent light emitted from the phosphor unit, and moreover, that are disposed so as to be orthogonal to the plane that contains the center ray.

The excitation light source unit and the first and second solid-state light sources, when viewed from a direction that is perpendicular to the above-described plane, are disposed on one side of the center ray of the fluorescent luminous flux.

The dichroic film of the first reflection unit is provided at the position at which the luminous flux of excitation light that is supplied from the excitation light source unit crosses the luminous flux of fluorescent light that is emitted from the phosphor unit, and both reflects excitation light from the excitation light source unit toward the phosphor unit and transmits fluorescent light from the phosphor unit.

The dichroic film of the second reflection unit is provided at the position at which luminous flux of the first light that is supplied from the first light source unit intersects with luminous flux of fluorescent light from the first reflection unit, and both reflects the first light from the first light source unit toward the third reflection unit and transmits the fluorescent light from the first reflection unit.

The dichroic film of the third reflection unit is provided at the position at which the luminous flux of the second light that is supplied from the second light source unit crosses the luminous flux of the fluorescent light and the luminous flux of the first light from the second reflection unit, and both transmits the fluorescent light and the first light from the second reflection unit and reflects the second light from the second light source unit in the traveling direction of the transmitted light.

The phosphor unit may be phosphor wheel14that is shown inFIG. 1. The first solid-state light source may be made up of red laser10and collimator lens16shown inFIG. 1orFIG. 10. The second solid-state light source may be made up of blue laser11and collimator lens17shown inFIG. 1orFIG. 10. Alternatively, the second solid-state light source may be made up of red laser10and collimator lens16and the first solid-state light source may be made up of blue laser11and collimator lens17.

The excitation light source unit may be made up of excitation light sources12and13shown inFIG. 1orFIG. 10. The first to third reflection units may be made up of color-combining prism20shown inFIG. 1, or may be made up of dichroic mirrors51a-51cshown inFIG. 10.

When the first solid-state light source is blue laser11and the second solid-state light source is red laser10, the cutoff wavelength with respect to the first polarized light (more specifically, S-polarized light) of the dichroic film of the first and second reflection units is set so as to reflect light of the blue wavelength band and transmit light of at least the green wavelength band, and the cutoff wavelength with respect to the first polarized light of the third dichroic surface is set so as to transmit light of each of the blue and green wavelength bands and reflect light of the red wavelength band.

In contrast, when the first solid-state light source is red laser10and the second solid-state light source is blue laser11, the cutoff wavelength with respect to the first polarized light of the dichroic films of the first and third reflection units is set to reflect light of the blue wavelength band and transmit light of each of the red and green wavelength bands. The cutoff wavelength with respect to first polarized light of the second dichroic surface is set to transmit light of at least the green wavelength band and reflect light of the red wavelength band.

The various modifications described in the first exemplary embodiment can be applied to the lighting device of this other exemplary embodiment. The lighting device exhibits the same action and effect as the previously described lighting devices of the first and second exemplary embodiments.

The lighting device of the above-described present invention can be applied to all types of projection-type display devices of which projectors are representative.

A projection-type display device includes: the lighting device of the present invention, a display element that spatially modulates light that is supplied from this lighting device, and projection optics that project the image light that is formed by the display element. The display element is, for example, a DMD or a liquid crystal panel.

FIG. 11shows an example of a projection-type display device that is equipped with the lighting device of the present invention.

Referring toFIG. 11, the projection-type display device includes: DMD46that is a display element, a lighting device that is the first exemplary embodiment, optics for guiding the light from the lighting device to DMD46, a cooling fan that cools the lighting device, and projection optics47that project the image light that is formed in DMD46onto a screen (not shown).

Fly-eye lenses40and41, field lens42, and mirror43are disposed in this order in the traveling direction of light (red, green, and blue) that exits from surface P11of prism20dof color-combining prism20.

Condenser lens44and TIR prism45are disposed in this order in the traveling direction of light that is reflected by mirror43.

Fly-eye lenses40and41are elements for obtaining illumination light that is rectangular illumination and uniform on the irradiated surface of DMD46, are each composed of a plurality of micro lenses, and are disposed so as to have a mutual one-to-one correspondence.

Light that has passed through fly-eye lenses40and41is incident to TIR prism45by way of field lens42, mirror43, and condenser lens44.

TIR prism45is made up of two triangular prisms, and light that is condensed by condenser lens44is incident into TIR prism45from the side surface of one triangular prism. In TIR prism45, the incident light is totally reflected by the inclined surface of the triangular prism, and this reflected light exits toward DMD46from the other surface of the triangular prism. The surface at which the two triangular prisms are joined is also a total reflection surface, and an air layer is therefore necessary between the two surfaces. Accordingly, when joining the two triangular prisms, an air layer is maintained between the two triangular prisms by adhering interposed spacers to both triangular prisms.

DMD46spatially modulates light that is incident from TIR prism45. The modulated light (image light) from DMD46is again irradiated into TIR prism45from the other surface of the triangular prism, and this irradiated image light is transmitted unaltered through the junction surface of the triangular prisms and exits from the side surface of the other triangular prism.

The image light that exits from the side surface of the other triangular prism of TIR prism45is enlarged and projected upon an outside screen by projection optics47.

By controlling the lighting timing of excitation light sources12and13, red laser10, and blue laser11, luminous flux of each of the colors red, green, and blue exits from color-combining prism20in time divisions. The luminous flux of each color that exits in these time divisions is subjected to spatial modulation using DMD whereby image light of each color can be obtained.

A cooling fan discharges an air current. Each of the light sources of excitation light sources12and13, red laser10, and blue laser11are provided in the traveling direction of the air current that is discharged from the cooling fan. The air current of the cooling fan is supplied to each light source to cool each light source. A construction such as shown inFIG. 9can be applied as the cooling fan.

The lighting device of the previously described second exemplary embodiment or the other exemplary embodiment may be used in the above-described projection-type display device.