LIGHT SOURCE DEVICE AND PROJECTION DISPLAY APPARATUS

A light source device includes: a light source element emitting first light; a first selective reflection element disposed at a position where the first light is incident, the first selective reflection element transmitting a component of first linear polarized light and reflecting a component of second linear polarized light; a second selective reflection element disposed at a position for receiving incident light that has passed through or been reflected by the first selective reflection element, the second selective reflection element transmitting or reflecting the incident light in accordance with a wavelength region; and a first polarization direction conversion element disposed between the first and second selective reflection element, the first polarization direction conversion element converting the first linear polarized light into elliptical polarized light. The first polarization direction conversion element converts the elliptical polarized light reflected by the second selective reflection element into the second linear polarized light.

BACKGROUND

1. Technical Field

The present invention relates to a light source device and a projection display apparatus including the light source device.

2. Description of the Related Art

There are conventionally a light source device and a projection display apparatus including the light source device that irradiates a phosphor wheel with light from a light source to generate light having a wavelength converted, and emits the light from the light source and the light generated by the phosphor wheel.

For example, the light source device irradiates the phosphor wheel with blue light emitted from a light source unit to generate yellow light, and synthesizes the generated yellow light and blue light emitted from the light source unit to generate white light. The projection display apparatus further separates the white light into color light of three primary colors, and modulates the white light for each color light, and then synthesizes the modulated color light again to generate image light.

For example, Patent Literature (PTL) 1 discloses a configuration in which blue light emitted from a light source passes through a wavelength-selective polarized beam splitter element, and the blue light of P-polarized light, which has passed through the wavelength-selective polarized beam splitter element, passes through a quarter wave plate to be converted into circular polarized light. The blue light of the circular polarized light is reflected by a color wheel, and passes through the quarter wave plate again to be converted into S-polarized light. The blue light of the S-polarized light is reflected by the wavelength-selective polarized beam splitter element to travel to a phosphor wheel.

SUMMARY

Unfortunately, the technique disclosed in PTL 1 causes a demand for further improving utilization efficiency of light emitted from the light source.

It is an object of the present disclosure to provide a light source device that improves light utilization efficiency and a projection display apparatus.

A light source device according to the present disclosure includes: a light source element configured to emit first light in a first wavelength region; a first selective reflection element disposed at a position where the first light is incident, the first selective reflection element being configured to transmit a component of first linear polarized light, the component being defined by an incident direction and a reflection direction of incident light, and reflect a component of second linear polarized light having a vibration surface orthogonal to a vibration surface of the component of the first linear polarized light; a second selective reflection element disposed at a position for receiving incident light that has passed through or been reflected by the first selective reflection element, the second selective reflection element being configured to transmit or reflect the incident light in accordance with a wavelength region of the incident light; and a first polarization direction conversion element disposed between the first selective reflection element and the second selective reflection element, the first polarization direction conversion element being configured to convert the first linear polarized light having passed through or been reflected by the first selective reflection element into elliptical polarized light. The first polarization direction conversion element converts the elliptical polarized light reflected by the second selective reflection element into the second linear polarized light to be incident on the first polarization direction conversion element again.

Alternatively, a light source device according to the present disclosure includes: a light source element configured to emit first light in a first wavelength region; a first selective reflection element disposed at a position where the first light is incident, the first selective reflection element being configured to transmit or reflect first linear polarized light and reflect or transmit second linear polarized light, the first linear polarized light and the second linear polarized light being defined by an incident direction and a reflection direction of light incident on the first selective element; a second selective reflection element disposed at a position for receiving incident light that has passed through or been reflected by the first selective reflection element, the second selective reflection element being configured to transmit or reflect the incident light in accordance with a wavelength region of the incident light; a wavelength conversion element disposed at a position where the light reflected by or having passed through the first selective reflection element is incident, the wavelength conversion element being configured to convert the light reflected by or having passed through the first selective reflection element into second light in a second wavelength region; a reflection element configured to reflect light reflected by the wavelength conversion element and reflected by or having passed through the first selective reflection element; and a second polarization direction conversion element disposed between the first selective reflection element and the reflection element.

Then, a projection display apparatus according to the present disclosure includes: a light modulator unit that generates image light by using light emitted from a light source device; and a projection optical system that projects the image light.

The present disclosure can provide a light source device that improves utilization efficiency of light, and a projection display apparatus.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments will be described in detail with reference to the drawings as appropriate. However, details more than necessary may not be described. For example, details of a well-known matter and duplication of a substantially identical configuration will not be described in some cases. This is to avoid unnecessary redundancy of the following description and to facilitate understanding of those skilled in the art.

The accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

First Exemplary Embodiment

1-1. Configuration of Light Source Device

With reference toFIGS.1to3, a light source device according to a first exemplary embodiment will be described below. The light source device according to the first exemplary embodiment will be described when used in a projection display apparatus, for example.FIG.1is a schematic configuration diagram illustrating a configuration example of a light source device.FIG.2is a plan view of a wavelength conversion element.FIG.3is a plan view of a color wheel. Each drawing indicates a Z direction in which light is emitted from light source device1, an XY plane on which first polarization direction conversion element15receives light and that is formed in an X direction and a Y direction orthogonal to the X direction, and the XY plane is orthogonal to the Z direction.

Light source device1includes light source unit3, first selective reflection element13, first polarization direction conversion element15, color wheel20, and wavelength conversion element25. Color wheel20is an example of a second selective reflection element. Light source device1further includes convex lens5, diffuser plate7, and concave lens11on an optical path between light source unit3and first selective reflection element13, and condenser lenses21and23on an optical path between first selective reflection element13and wavelength conversion element25. Light source device1further includes light condensing element19between first polarization direction conversion element15and color wheel20, and includes rod integrator33in a subsequent stage of color wheel20.

Light source unit3includes light source element3athat emits first light Lc1in a first wavelength region, and collimator lens3bthat collimates first light Lc1emitted from light source element3a. Collimator lens3bis disposed corresponding to light source element3a, and light source unit3includes a plurality of sets of light source element3aand collimator lens3b. Light source element3aemits light in a blue wavelength region as light in a first wavelength region, for example. Light source element3ais also a laser light source element in the first exemplary embodiment, for example, and a configuration of light source element3ain which blue light occupied by linear polarized light having a vibration direction mainly in a Y-axis direction is emitted will be described.

Collimated first light Lc1is incident on convex lens5in a subsequent stage to be reduced in width of flux of the light, and is incident on and diffused by diffuser plate7to be improved in uniformity of light. First light Lc1improved in uniformity of light is incident on concave lens11in a subsequent stage to be collimated again.

First light Lc1collimated by concave lens11is incident on first selective reflection element13disposed at an angle of approximately 45 degrees about an X-axis with respect to an optical axis. First selective reflection element13is a dichroic-polarization separation mirror, for example. First selective reflection element13transmits first light Lc1in the first wavelength region emitted from light source element3a, and reflects second light Lc2that is yellow, for example, and is converted in wavelength by wavelength conversion element25using light in a wavelength region identical to the wavelength region of first light Lc1from light source element3aas excitation light. Thus, first light Lc1incident on first selective reflection element13passes through first selective reflection element13, and travels straight without changing a traveling direction to be incident on first polarization direction conversion element15. As described above, first selective reflection element13has spectral characteristics of transmitting first light Lc1that is blue light of P-polarized light with respect to a plane determined by incident light and reflected light, and reflecting blue light of S-polarized light and second light Lc2to be described later with respect to the plane determined by incident light and reflected light. Second light Lc2in the second wavelength region is acquired by converting light Lc1rin wavelength using wavelength conversion element25, light Lc1rbeing in the same wavelength region as the wavelength region of first light Lc1.

First polarization direction conversion element15converts incident linear polarized light into elliptical polarized light, and converts the incident elliptical polarized light into linear polarized light. First polarization direction conversion element15includes two retardation plates such as quarter wave plates, for example, and includes first quarter wave plate15aand second quarter wave plate15bin the present exemplary embodiment. First quarter wave plate15aand second quarter wave plate15bare different in slow axis from each other. For example, first quarter wave plate15ahas a slow axis at an angle of 45 degrees with respect to a reference axis, and second quarter wave plate15bhas a slow axis at an angle of 90 degrees with respect to the reference axis. Here, the reference axis is the Y-axis on the XY plane illustrated inFIG.1, for example. The slow axis of first quarter wave plate15ais adjustable for direction with respect to a direction of the slow axis of second quarter wave plate15b.

First light Lc1incident on first polarization direction conversion element15is converted from incident blue light of linear polarized light to blue light of elliptical polarized light. First light Lc1converted in polarization direction travels straight, and passes through light condensing element19to be incident on color wheel20.

Color wheel20includes a plurality of dichroic layers20aformed on a transparent board and motor20cfor rotating the transparent board. Dichroic layer20ahas four angular regions θR, θG, θB, θYe in a circumferential direction. Dichroic layer20aincludes dichroic layer20R that is formed in angular region θR and transmits red light, dichroic layer20G that is formed in angular region θG and transmits green light, dichroic layer20B that is formed in angular region θB and transmits blue light, and dichroic layer20Ye that is formed in angular region θYe and transmits yellow light.

When yellow light is incident on angular region θR of color wheel20, only a red component of the yellow light passes through dichroic layer20R, and light of other color components is reflected and output from color wheel20as red light R. When yellow light is incident on angular region θG of color wheel20, only a green component of the yellow light passes through dichroic layer20G, and light of other color components is reflected and output from color wheel20as green light G. That is, color wheel20can transmit or reflect incident light on color wheel20in accordance with a wavelength region of the incident light.

When yellow light is incident on angular region θYe of color wheel20, the yellow light passes through dichroic layer20Ye to be output from color wheel20as yellow light. When blue light is incident on angular region θB of color wheel20, the blue light passes through dichroic layer20B to be output from color wheel20. When yellow light is incident on angular region θB of color wheel20, the yellow light is reflected. The above configuration allows light source device1to emit red light R, green light G, yellow light Ye, and blue light B in a time division manner. Although the configurations of four types of dichroic layer20adifferent in characteristics have been exemplified here, the present invention is not limited to these configurations, and three types of dichroic layer20adifferent in characteristics may be provided. Alternatively, dichroic layer20Ye may have characteristics of reflecting an unnecessary wavelength region in the yellow spectrum.

Light Lc1rreflected by color wheel20is reflected by first selective reflection element13toward wavelength conversion element25, and passes through condenser lens21and condenser lens23in a subsequent stage to be condensed on wavelength conversion layer29in a ring shape provided in wavelength conversion element25. Wavelength conversion element25is a phosphor wheel, for example.

Wavelength conversion element25includes base plate27, wavelength conversion layer29formed on base plate27, and motor31attached to base plate27. Wavelength conversion element25is disposed such that light condensed by condenser lenses21,23is incident on wavelength conversion layer29in an annular shape. Wavelength conversion element25is rotationally driven by motor31. Wavelength conversion layer29has an incident surface disposed parallel to the XZ plane.

Wavelength conversion layer29generates second light Lc2in the second wavelength region from incident blue light, second light Lc2being different in wavelength from the incident blue light. For example, wavelength conversion layer29is a phosphor layer that is formed using a resin body such as silicone or alumina or an inorganic substance as a binder and contains internally a plurality of phosphor particles.

The phosphor particles of wavelength conversion layer29emit second light Lc2in a wavelength region longer than a wavelength region of the blue light received. For example, the phosphor of wavelength conversion layer29is a Ce-activated YAG-based yellow phosphor that is excited by blue color light received to emit yellow light containing wavelength components of green light and red light. The phosphor particles each include a crystalline matrix with a chemical composition that is typically Y3Al5O12.

Between base plate27and wavelength conversion layer29, a reflection layer that reflects incident light Lc1rand second light Lc2generated in wavelength conversion layer29may be disposed. This structure enables second light Lc2traveling toward base plate27in wavelength conversion layer29to travel toward first selective reflection element13, so that conversion efficiency of fluorescent light can be improved.

As described above, light Lc1r, which is the blue light condensed on wavelength conversion layer29of wavelength conversion element25by condenser lenses21and23, is not only converted in wavelength into fluorescent light, but also incident on condenser lenses21,23again in this order with a traveling direction of light changed by 180 degrees to be collimated. Second light Lc2being fluorescent light is in a yellow wavelength region, for example, and constitutes white light in combination with blue light emitted from light source element3a.

Second light Lc2output from condenser lens21and collimated is incident on first selective reflection element13. As described above, first selective reflection element13has characteristics of reflecting light in the wavelength region of second light Lc2, and thus changes the traveling direction of the light by 90 degrees. Second light Lc2with the traveling direction changed by 90 degrees by first selective reflection element13passes through first polarization direction conversion element15in a subsequent stage to be incident on light condensing element19.

For example, light condensing element19is a condenser lens, and is disposed at a position for receiving light guided in the third direction. Light condensing element19has a subsequent stage in which rod integrator33is disposed, and light condensing element19condenses incident light on rod integrator33.

The light passing through first polarization direction conversion element15and second light Lc2from wavelength conversion element25are incident on and condensed by light condensing element19. Then, each light passing through color wheel20is incident on rod integrator33with an incident end disposed at a substantially light condensing position of light condensing element19. The light having flux uniformed by rod integrator33is output from an emission end of rod integrator33.

1-2. Configuration of First Selective Reflection Element and First Polarization Direction Conversion Element

With reference toFIGS.4A to6, configurations of the first selective reflection element and the first polarization direction conversion element will be described.FIG.4Cis an explanatory view for illustrating an optical path of light obliquely incident and re-incident on first selective reflection element13.FIG.5Ais an explanatory diagram for illustrating an optical path from incidence to re-incidence on first selective reflection element13in a comparative example.FIG.5Bis an explanatory diagram for illustrating an optical path from incidence to re-incidence on first selective reflection element13in the first exemplary embodiment.FIG.6is an explanatory diagram illustrating an example of a state of linear polarized light.

Here, the P-polarized light and the S-polarized light for first selective reflection element13will be described. As illustrated inFIG.4A, P-polarized light Lp is a component of first light Lc1incident on first selective reflection element13, the component having a vibration plane parallel to plane P1determined by incident light Lc1aon first selective reflection element13and reflected light Lc1bfrom first selective reflection element13. First selective reflection element13is disposed with its polarization axis parallel to the vibration plane of P-polarized light Lp component of first light Lc1traveling on the optical axis, so that most of P-polarized light Lp component of first light Lc1incident on first selective reflection element13passes through first selective reflection element13. First light Lc1having passed through first selective reflection element13, or the vibration plane of P-polarized light Lp, is parallel to plane P1.

As illustrated inFIG.4B, S-polarized light is a component of first light Lc1, the component having a vibration plane of an electric field perpendicular to plane P1determined by incident light Lc1con first selective reflection element13and reflected light Lc1dfrom first selective reflection element13. Most of S-polarized light component Ls of first light Lc1is reflected by first selective reflection element13.

Although light source element3ais disposed such that a vibration plane of light passing through the optical axis of first light Lc1emitted from light source unit3passes through the polarization axis (transmission axis) of first selective reflection element13, first light Lc1emitted from light source unit3has a certain range of an angle of the vibration plane. Thus, P-polarized light Lp component having passed through first selective reflection element13includes the vibration plane that is not necessarily aligned with the polarization axis of first selective reflection element13depending on an incident direction of first light Lc1. As described above, the vibration plane of P-polarized component Lp1of first light Lc1having passed through first selective reflection element13varies depending on a direction of incident light.

As illustrated inFIG.4C, when first light Lc1, which is linear polarized blue light in the Y-axis direction, is incident on first selective reflection element13at the first incidence from light source unit3, for example, flux of first light Lc1incident on first selective reflection element13at an angle with respect to the optical axis includes a component of S-polarized light Ls perpendicular to incident and output surfaces determined by incident light and reflected light, respectively, so that a part of the amount of light is reflected by first selective reflection element13.

AlthoughFIG.4Cdoes not illustrate first polarization direction conversion element15, light condensing element19, and color wheel20, when light having passed through first selective reflection element13is reflected by color wheel20, and is incident on first selective reflection element13again at the second incidence, a direction of the reflected light is different from that at the first incident. Thus, the incident and output surfaces determined by the incident light and the reflected light, respectively, are different, so that light having passed through first selective reflection element13is not completely converted into the S-polarized light at the second incidence only with one quarter wave plate, thereby allowing a P-polarized component to pass through first selective reflection element13. As described above, light incident on first polarization direction conversion element15while deviating from the optical axis has the amount of light passing through first selective reflection element13at the second incidence, the amount of light causing decrease in light utilization efficiency.

As illustrated inFIG.1, first light Lc1includes a light beam that is not parallel to the Z-axis (optical axis) and has incident and output surfaces that do not coincide between the first incidence and the second incidence of blue light on first selective reflection element13(seeFIG.4C), and thus, P-polarized light and S-polarized light are different in direction from each other depending on an angle of incident light. P-polarized light (S-polarized light) at the first incidence on first selective reflection element13and P-polarized light (S-polarized light) at the second incidence thereon have respective polarization directions that are substantially symmetric with respect to the Y-axis.

First light Lc1includes light Lca traveling along the optical axis and light Lcb traveling obliquely with respect to the optical axis that have a difference in transmission and reflection conditions of first selective reflection element13, and the difference will be described next.FIG.5Aillustrates a comparative example in which first polarization direction conversion element15includes only one first quarter wave plate15a. First polarization direction conversion element15is disposed with a slow axis forming an angle of 45 degrees with respect to the Y-axis. Thus, first light Lcb inclined with respect to the optical axis causes second incident light on first selective reflection element13, or light converted from P-polarized light at the first incidence to S-polarized light with a polarization direction turned by 90 degrees, to include the P-polarized component. For this reason, the incident light at the second incidence on first selective reflection element13may include a component that passes through first selective reflection element13and returns to light source unit3.

Thus, as illustrated inFIGS.1and5B, first polarization direction conversion element15of the present exemplary embodiment including first quarter wave plate15aand second quarter wave plate15bwhose slow axes do not coincide with each other enables a polarization direction at the second incidence on first selective reflection element13to further coincide with a S polarization direction at the second incidence. In this manner, first polarization direction conversion element15converts linear polarized light and elliptical polarized light to each other.

First light Lc1includes light Lcb that is obliquely incident on first selective reflection element13with respect to the optical axis. As illustrated inFIG.6, light Lcb1that is linear polarized light of light Lcb having passed through first selective reflection element13is inclined with respect to the Y-axis. When light Lcb1is incident on first selective reflection element13again, the light is to be reflected toward wavelength conversion element25. At this time, S-polarized light reflected by first selective reflection element13is to be required to have a vibration plane of light Lcb2. The vibration plane of light Lcb2is obtained by further rotating a vibration plane of light Lcb1aby 90 degrees, the vibration plane being obtained by converting a vibration plane of light Lcb1in Y-axis symmetry.

Light Lca travels along the optical axis and passes through first selective reflection element13to be linearly polarized to serve as light Lca1having a vibration plane along the Y-axis. Thus, when light Lca1is incident on first selective reflection element13again, S-polarized light reflected toward wavelength conversion element25serves as light Lca2having a vibration plane on the X-axis.

First quarter wave plate15aand second quarter wave plate15bare disposed between first selective reflection element13and color wheel20. First quarter wave plate15ais disposed with a slow axis forming an angle of 45 degrees with respect to the Y-axis. When first quarter wave plate15ais used alone, as in the comparative example ofFIG.5A, the linear polarized light incident on the optical axis to be incident on first quarter wave plate15a(P-polarized light at the first incidence on first selective reflection element13) is converted into circular polarized light, and the circular polarized light reflected by color wheel20and being incident on first quarter wave plate15aagain is converted into linear polarized light (S-polarized light at the first incident on first selective reflection element13) acquired by rotating the circular polarized light by 90 degrees.

Second quarter wave plate15bis disposed with a slow axis parallel or orthogonal to the Y-axis. When second quarter wave plate15bis used alone, linear polarized light (P-polarized light at the first incidence on first selective reflection element13) with a polarization direction inclined with respect to the Y-axis (slow axis) is converted into elliptical polarized light with a major axis coinciding with the slow axis regardless of the inclination. The elliptical polarized light. reflected by color wheel20and incident on second quarter wave plate15bagain is converted into linear polarized light with a polarization direction inclined at an angle (symmetry) opposite to that at the first incidence with respect to the Y-axis (slow axis), the polarization direction substantially coinciding with a polarization direction of the P-polarized light at the second incidence on first selective reflection element13. When the linear polarized light is further rotated by 90 degrees, the linear polarized light becomes S-polarized light at the second incidence.

As a result, when first quarter wave plate15aand second quarter wave plate15bare used in combination, effects of both are combined. Thus, the polarization direction at the second incidence on first selective reflection element13substantially coincides with the S polarization direction at the second incidence. Thus, a P-polarized light component that passes through first selective reflection element13and returns to light source unit3can be reduced. Then, blue light reflected by first selective reflection element13can be prevented from being reduced, and the amount of fluorescent light converted by wavelength conversion element25can be prevented from being reduced.

First light Lc1emitted from light source element3apasses first quarter wave plate15aand second quarter wave plate15bto be converted from blue light of P-polarized light (P-polarized light on a first incident surface of first selective reflection element13) to blue light of elliptical polarized light. First light Lc1converted into blue light of the elliptical polarized light is reflected by color wheel20. Light Lc1rreflected by color wheel20passes through first quarter wave plate15aand second quarter wave plate15bagain to be converted from the blue light of the elliptical polarized light to blue light of S-polarized light. The converted blue light of the S-polarized light (S-polarized light on a second incident surface of first selective reflection element13) is reflected by first selective reflection element13and travels to wavelength conversion element25. Although the example has been described here in which the P-polarized light is converted into the S-polarized light, a similar configuration can be applied even when the S-polarized light is converted into the P-polarized light.

1-3. Effects and the Like

As described above, light source device1according to the first exemplary embodiment includes: light source element3aconfigured to emit first light Lc1that is blue light; first selective reflection element13disposed at a position where first light Lc1is incident, first selective reflection element13being configured to transmit incident first linear polarized light, and reflect second linear polarized light perpendicular to the first linear polarized light; color wheel20disposed at a position for receiving light having passed through first selective reflection element13, color wheel20being configured to transmit or reflect incident light in accordance with its wavelength region; and first polarization direction conversion element15disposed between first selective reflection element13and color wheel20, first polarization direction conversion element15being configured to convert the first linear polarized light having passed through first selective reflection element13into elliptical polarized light. First polarization direction conversion element15converts the elliptical polarized light, which is reflected by color wheel20and incident on first polarization direction conversion element15again, into second linear polarized light.

Converting the first linear polarized light into the elliptical polarized light enables the elliptical polarized light reflected by color wheel20to be converted into the second linear polarized light that can be reflected by first selective reflection element13. As a result, light that is not reflected by first selective reflection element13can be reduced, and thus utilization efficiency of light of light source device1can be improved.

The first linear polarized light is any one of P-polarized light and S-polarized light, and the second linear polarized light is the other of the P-polarized light and the S-polarized light. First polarization direction conversion element15converts first linear polarized light incident parallel to the optical axis into circular polarized light, and converts a component of the first linear polarized light incident at an angle with respect to the optical axis into elliptical polarized light other than the circular polarized light, and then converts the circular polarized light and the elliptical polarized light reflected by color wheel20and incident on first polarization direction conversion element15again into second linear polarized light.

As a result, both of the first linear polarized light incident parallel to the optical axis and the first linear polarized light incident at an angle with respect to the optical axis can be converted into the second linear polarized light, so that utilization efficiency of light can be improved.

In other words, the light utilization efficiency can be improved by converting the first linear polarized light obliquely having passed through first selective reflection element13with a first transmission axis into the elliptical polarized light that is to be converted into the second linear polarized light reflected by the first selective reflection element13with a second transmission axis on the optical path, the second transmission axis being disposed in mirror symmetry of the first transmission axis.

Although first selective reflection element13in the first exemplary embodiment illustrated inFIG.1is disposed at an angle of approximately 45 degrees about an x-axis with respect to the optical axis, the angle of first selective reflection element13with respect to the optical axis may be different from approximately 45 degrees to maximize the spectral characteristics of first selective reflection element13. In this case, other components may be disposed in accordance with the angle. Although the first exemplary embodiment has been described in which light emitted from light source element3ais P-polarized light, a similar configuration can be applied even for emitted light of S-polarized light.

First polarization direction conversion element15includes two quarter wave plates different in slow axis, but may include only one wave plate. First polarization direction conversion element15including two quarter wave plates different in slow axis enables conversion of light to linear polarized light to be more appropriately performed even when first selective reflection element13deviates from the optical axis. Alternatively, first polarization direction conversion element15may include three or more wave plates different in slow axis.

Next, light source device1A as a modification of light source device1of the first exemplary embodiment will be described with reference toFIG.7. Light source device1A has a configuration in which first polarization direction conversion element15of light source device1is rotatable. Light source device1of the first exemplary embodiment and light source device1A of the modification are common in configuration other than the point above and the point described below.

Light source device1A includes rotation mechanism18(an example of a rotation drive unit) that rotates first polarization direction conversion element15. Rotation mechanism18includes a motor and a gear mechanism, for example. Rotation mechanism18may individually rotate first quarter wave plate15aand second quarter wave plate15b, or may rotate only one of them. Rotation mechanism18can adjust the slow axis of first polarization direction conversion element15, so that an optimum linear polarization direction for first selective reflection element13can be set. Rotation mechanism18can be operated by a user.

Thus, light source device1A enables conversion from P-polarized light to S-polarized light by rotationally adjusting first quarter wave plate15aand second quarter wave plate15beven when first selective reflection element13deviates from linear polarized light incident from light source element3a, so that utilization efficiency of light can be improved.

Although light having passed through first selective reflection element13is used by causing color wheel20to transmit and reflect the light in the first exemplary embodiment, the present invention is not limited thereto. As a modification, light reflected by first selective reflection element13may be used by causing color wheel20to transmit and reflect the light. In this case, color wheel20is disposed at a position for receiving the light reflected by first selective reflection element13. First polarization direction conversion element15is disposed between first selective reflection element13and color wheel20to convert first linear polarized light reflected by first selective reflection element13into elliptical polarized light.

Second Exemplary Embodiment

Next, light source device1B according to a second exemplary embodiment will be described with reference toFIG.8.FIG.8is a schematic configuration diagram illustrating a configuration example of a light source device according to the second exemplary embodiment. Light source device1B of the second exemplary embodiment includes reflection element41and second polarization direction conversion element43in light source device1of the first exemplary embodiment. Light source device1B of the second exemplary embodiment and light source device1of the first exemplary embodiment are common in configuration other than the point above and the point described below.

Reflection element41reflects light, which is reflected by first selective reflection element13and travels in a direction opposite to wavelength conversion element25, toward first selective reflection element13. Reflection element41is a reflection mirror, for example.

Second polarization direction conversion element43is disposed between first selective reflection element13and reflection element41. Second polarization direction conversion element43is, a quarter wave plate with a slow axis of 45 degrees, for example. As illustrated inFIG.4C, first light Lc1reflected by first selective reflection element13toward reflection element41includes S-polarized light Ls that is converted from S-polarized light to elliptical polarized light by second polarization direction conversion element43. The light converted into the elliptical polarized light is reflected by reflection element41and passes through second polarization direction conversion element43again. At this time, the elliptical polarized light reflected by reflection element41is converted into P-polarized light.

The light converted into the P-polarized light passes through first selective reflection element13and is incident on wavelength conversion element25. As a result, a part of blue light of first light Lc1reflected by first selective reflection element13in the direction opposite to wavelength conversion element25can also be converted into yellow light, so that utilization efficiency of light can be improved. For example, second polarization direction conversion element43may include at least two quarter wave plates. The at least two quarter wave plates are different in slow axis. At least one of the at least two quarter wave plates is adjustable for direction of the slow axis. As described above, when at least one of the at least two quarter wave plates is adjusted for direction of the slow axis with respect to another quarter wave plate, light passing through second polarization direction conversion element43can be polarized in an identical direction. That is, the light can be polarized in an identical direction more reliably when two or more quarter wave plates are used as compared with when only one quarter wave plate is used. As a result, light source device1B can be further improved in utilization efficiency of light. For example, one of the quarter wave plates of second polarization direction conversion element43has a slow axis at an angle of 45 degrees with respect to a reference axis, and the other of the quarter wave plates has a slow axis at an angle of 90 degrees with respect to the reference axis. Here, the reference axis is the X-axis on the XZ plane illustrated inFIG.8, for example.

Dichroic layer20B of color wheel20may include a region through which a part of second light Lc2passes, second light Lc2being fluorescent light converted by wavelength conversion layer29.

Light source device1B further includes half wave plate65and rotation mechanism68(an example of the rotation drive unit). half wave plate65is disposed between concave lens11and first selective reflection element13, and is configured to be rotatable. Alternatively, half wave plate65can also be disposed between convex lens5and concave lens11. That is, half wave plate65is disposed between light source element3aand first selective reflection element13. Rotation mechanism68is connected to half wave plate65and is configured to rotate half wave plate65. Rotation mechanism68has a configuration similar to that of rotation mechanism18(seeFIG.7).

Rotating half wave plate65enables adjustment of a ratio between P-polarized light and S-polarized light in light having passed through half wave plate65and incident on first selective reflection element13. Adjusting the ratio between P-polarized light and S-polarized light enables adjustment of a ratio between light passing through first selective reflection element13and light reflected by first selective reflection element13. As a result, a ratio between blue and yellow of light incident on rod integrator33through color wheel20. That is, only rotating half wave plate65enables adjustment of the ratio between blue and yellow without changing a configuration behind first selective reflection element13.

The above configuration enables a manufacturer of light source device1B to adjust color of light to be emitted from light source device1B by rotating half wave plate65using rotation mechanism68. Then, even when light emitted by light source device1B has changed in color with time due to long-term use of light source device1B, the user of light source device1B can re-adjust the color to original color of light by rotating half wave plate65. The user of light source device1B further can intentionally change color of light to be emitted from light source device1B to a desired color by rotating half wave plate65.

Light source device1B does not necessarily require half wave plate65and rotation mechanism68. That is, light source device1B may not include half wave plate65and rotation mechanism68. When light source device1B does not include half wave plate65and rotation mechanism68, a decrease in light efficiency due to absorption of light with half wave plate65can be prevented, and cost also can be reduced.

Third Exemplary Embodiment

Next, light source device1C according to a third exemplary embodiment will be described with reference toFIG.9.FIG.9is a schematic configuration diagram illustrating a configuration example of the light source device according to the third exemplary embodiment. Light source device1C of the third exemplary embodiment further includes third polarization direction conversion element45disposed between wavelength conversion element25and first selective reflection element13in light source device1B of the second exemplary embodiment. An example of third polarization direction conversion element45is a quarter wave plate. Light source device1C of the third exemplary embodiment and light source device1B of the second exemplary embodiment are common in configuration other than the point above and the point described below.

First polarization direction conversion element15converts light Lc1rinto S-polarized light, and first selective reflection element13reflects this light toward wavelength conversion element25. Third polarization direction conversion element45converts blue light reflected by first selective reflection element13from S-polarized light on first selective reflection element13into elliptical polarized light. The blue light converted into the elliptical polarized light is converted from the blue light to yellow light by wavelength conversion element25. Here, the blue light of the elliptical polarized light that has not been converted into the yellow light is reflected by wavelength conversion element25, and passes through third polarization direction conversion element45again to be converted from the elliptical polarized light into P-polarized light that can pass through first selective reflection element13. The light converted into the P-polarized light and output from third polarization direction conversion element45passes through first selective reflection element13to pass through second polarization direction conversion element43. Second polarization direction conversion element43is, a quarter wave plate with a slow axis at an angle of 45 degrees, for example, so that the blue light having passed through second polarization direction conversion element43is converted from P-polarized light that can pass through first selective reflection element13into elliptical polarized light. The blue light converted into the elliptical polarized light is reflected by reflection element41and is incident on second polarization direction conversion element43again.

The blue light incident on second polarization direction conversion element43again is converted from the elliptical polarized light into blue light of P-polarized that can pass through first selective reflection element13. The blue light converted into the P-polarized light on first selective reflection element13passes through first selective reflection element13and third polarization direction conversion element45to be incident on wavelength conversion element25.

As a result, light reflected by wavelength conversion element25without being converted from blue to yellow can be reflected by reflection element41to be incident on wavelength conversion element25again. Thus, the light can be converted from blue into yellow again, so that utilization efficiency of light can be improved. For example, third polarization direction conversion element45may include at least two quarter wave plates. The at least two quarter wave plates are different in slow axis. At least one of the at least two quarter wave plates is adjustable for direction of the slow axis. As described above, when at least one of the at least two quarter wave plates is adjusted for direction of the slow axis with respect to another quarter wave plate, light passing through third polarization direction conversion element45can be polarized in an identical direction. That is, the light can be polarized in an identical direction more reliably when two or more quarter wave plates are used as compared with when only one quarter wave plate is used. As a result, light source device1C can be further improved in utilization efficiency of light. For example, one of the quarter wave plates of third polarization direction conversion element45has a slow axis at an angle of 45 degrees with respect to a reference axis, and the other of the quarter wave plates has a slow axis at an angle of 90 degrees with respect to the reference axis. Here, the reference axis is the X-axis on the XZ plane illustrated inFIG.9, for example.

Fourth Exemplary Embodiment

Next, light source device1D according to a fourth exemplary embodiment will be described with reference toFIG.10.FIG.10is a schematic configuration diagram illustrating a configuration example of the light source device according to the fourth exemplary embodiment. Light source device1D of the fourth exemplary embodiment includes selective reflection element17instead of color wheel20in light source device1C of the third exemplary embodiment. Light source device1D of the fourth exemplary embodiment and light source device1C of the third exemplary embodiment are common in configuration other than the point above and the point described below.

Light source device1D of the fourth exemplary embodiment is a light source device for a projection display apparatus of a three-chip liquid crystal system, for example. Selective reflection element17is disposed between first polarization direction conversion element15and light condensing element19.

Selective reflection element17reflects a part of first light Lc1and transmits the rest of first light Lc1, so that first light Lc1is separated into light Lc1rto be converted into fluorescent light later and Lc1tto be output as blue light, and transmits second light Lc2of yellow. Selective reflection element17is a single dichroic mirror, for example.

For example, selective reflection element17has a reflectance of 70% or more of first light Lc1, and a transmittance of 95% or more of second light Lc2. Selective reflection element17has a surface on which a dielectric layer is uniformly formed to achieve a uniform transmittance of first light Lc1. First light Lc1having passed through selective reflection element17is incident on light condensing element19(seeFIG.12).

Light Lc1r, which is a part of first light Lc1reflected by selective reflection element17, passes through the first polarization direction conversion element15and converted from elliptical polarized light to blue light of S-polarized light to be reflected by first selective reflection element13. Light Lc1r, which is the blue light of the S-polarized light, is changed in its traveling direction by 90 degrees by first selective reflection element13to be reflected toward wavelength conversion element25, and is converted into second light Lc2, which is yellow light, by wavelength conversion element25.

Light source device1D of the fourth exemplary embodiment enables emitting blue light and yellow light simultaneously, and thus enables improving utilization efficiency of light as with light source device1C of the third exemplary embodiment.

Fifth Exemplary Embodiment

Next, projection display apparatus101of a fifth exemplary embodiment will be described with reference toFIG.11.FIG.11is a diagram illustrating a configuration of projection display apparatus101according to the fifth exemplary embodiment. As illustrated inFIG.11, projection display apparatus101of the fifth exemplary embodiment is a projection display apparatus of a one-chip DLP system, for example. Projection display apparatus101includes light source device1C.

Light output from rod integrator33is imaged to DMD141described later through a relay lens system including convex lenses131,132,133.

The light having passed through convex lenses131,132,133to be incident on total reflection prism134is incident on small air gap135of total reflection prism134at an angle equal to or larger than an angle of total reflection, and is reflected to be changed in direction of traveling of light and is incident on DMD141.

DMD141changes a direction of a micromirror to change a traveling direction of light in response to a signal from an image circuit (not illustrated), the signal being synchronized with color light received from color wheel20, and outputs the light.

The light changed in direction of traveling by DMD141in response to an image signal is incident on total reflection prism134and incident on small air gap135of total reflection prism134at an angle less than or equal to the angle of total reflection. Then, the light directly passes through small air gap135to be incident on projection lens unit151serving as a projection optical system, and is projected on a screen (not illustrated).

Projection display apparatus101of the fifth exemplary embodiment enables improving utilization efficiency of light of light source device1C, and thus enables improving luminance of an image to be projected.

Sixth Exemplary Embodiment

Next, projection display apparatus101A of a sixth exemplary embodiment will be described with reference toFIG.12.FIG.12is a diagram illustrating a configuration of projection display apparatus101A according to the sixth exemplary embodiment. As illustrated inFIG.12, projection display apparatus101A according to the sixth exemplary embodiment uses light source device1D of the fourth exemplary embodiment.

Projection display apparatus101A according to the sixth exemplary embodiment is a so-called three-chip projection display apparatus. A three-chip DLP system is an example of a projection display device using the present device, and the number of display elements may be other than three.

Light emitted from light source device1D through light condensing element19and rod integrator33is imaged onto digital micromirror devices (DMDs)311,312,313as light modulators through a relay lens system including convex lenses301,302,303.

Light guided through the relay lens system including convex lenses301,302,303is incident on total reflection prism304provided with small air gap305. The light guided through the relay lens system and incident on total reflection prism304at an angle equal to or larger than an angle of total reflection is reflected by small air gap305to be changed in direction of traveling of the light, and is incident on color prism309including three glass blocks306,307,308provided with small air gap305.

Blue light and fluorescent light are incident on first glass block308of color prism309from total reflection prism304, and the blue light is first reflected on a spectral characteristic reflection layer that is provided in pre-stage a small air gap and that has characteristics of reflecting blue light, and then is changed in direction of traveling to travel to the total reflection prism304. Subsequently, the blue light is incident on the small air gap between total reflection prism304and color prism309at an angle equal to or larger than the angle of total reflection to be incident on DMD313to display a blue image.

Subsequently, red light of the fluorescent light having passed through the small air gaps is reflected on a spectral characteristic reflection layer that is provided between second glass block307and third glass block306of color prism309and that has spectral characteristics of reflecting light in a wavelength region of red color and transmitting green light. The red light is then changed in direction of traveling toward first glass block308.

The red light changed in direction of traveling is reflected again by the small air gap provided between first glass block308and second glass block307of color prism309, and then the red light is changed in direction of traveling to be incident on DMD312for red color.

The fluorescent light having passed through the small air gap also include green light that passes through the spectral characteristic reflection layer that is provided between second glass block307and third glass block306of the color prism and that has spectral characteristics of reflecting light in the wavelength region of red color and transmitting green light, and the green light directly travels to third glass block306to be directly incident on DMD311for green color.

DMD311,312,313changes a traveling direction of light from a video circuit (not illustrated) by changing a direction of a mirror for each pixel in response to an image signal of each color.

The green light changed in direction of traveling in response to an image signal by DMD311for green color is incident on third glass block306of color prism309, and passes through the spectral characteristic reflection layer provided between third glass block306and second glass block307of color prism309.

The red light changed in direction of traveling in response to an image signal by DMD312for red color is incident on second glass block307of color prism309, and is incident on a small air gap provided between second glass block307and first glass block308of color prism309at an angle equal to or larger than the angle of total reflection to be then reflected. After that, the red light changes in direction of traveling toward third glass block306of color prism309, and is reflected on the spectral characteristic reflection layer provided between second glass block307and third glass block306of color prism309. The red light then changes in direction of traveling to be combined with the green light.

The light combined by the spectral characteristic reflection layer travels toward first glass block308of color prism309, and is incident on the small air gap provided between second glass block307and first glass block308of color prism309at an angle less than or equal to the angle of total reflection to pass through the small air gap.

Then, the blue light changed in direction of traveling in response to an image signal by DMD313for blue color is incident on first glass block308of color prism309and travels toward total reflection prism304. The blue light is then incident on a gap provided between total reflection prism304and color prism309at an angle equal to or larger than the angle of total reflection to travel toward second glass block307of color prism309. After that, the blue light is reflected by a spectral characteristic reflection layer provided facing first glass block308and in front of the small air gap provided between the first glass block308and second glass block307of color prism309. The blue light is then changed in direction of traveling toward total reflection prism304, and is combined with light from DMD311for green color and DMD312for red color to be incident on total reflection prism304.

The light from DMDs311,312,313incident on total reflection prism304passes through total reflection prism304, and is incident on projection lens unit321as a projection optical system to project the screen (not illustrated).

Light source device1D and projection display apparatus101A of the sixth exemplary embodiment enables improving utilization efficiency of light of light source device1D, and thus enables improving luminance of an image to be projected.

Seventh Exemplary Embodiment

Next, projection display apparatus101B of a seventh exemplary embodiment will be described with reference toFIG.13.FIG.13is the diagram illustrating the configuration of projection display apparatus101B according to the seventh exemplary embodiment. As illustrated inFIG.13, projection display apparatus101B according to the seventh exemplary embodiment uses light source device1D of the fourth exemplary embodiment.

Projection display apparatus101B uses, as an image forming unit, an active matrix transmission liquid crystal panel in which a thin film transistor is formed in a pixel region in a TN (TwiSted Nematic) mode or a VA (Vertical Alignment) mode.

Light emitted from light source device1D is incident on projection lens224through an optical system including first lens array plate199, mirror200, second lens array plate201, polarization conversion element202, superposition lens203, green-reflecting dichroic mirror204, blue-reflecting dichroic mirror205, reflection mirrors206,207,208, relay lenses209,210, field lenses211,212,213, incident side polarizing plates214,215,216, liquid crystal panels217,218,219, emission side polarizing plates220,221,222, and color-combining prism223including a red-reflecting dichroic mirror and a blue-reflecting dichroic mirror.

White light from light source device1D is incident on first lens array plate199including a plurality of lens elements. Flux of the light incident on first lens array plate199is divided into many fluxes of light. The many divided fluxes of light are reflected by mirror200to be converged on second lens array plate201including a plurality of lenses. The lens elements of first lens array plate199each have an opening shape similar to that of liquid crystal panel217,218,219. The lens elements of second lens array plate201each have a focal distance determined to allow first lens array plate199and liquid crystal panels217,218,219to have a substantially conjugate relationship. Light output from second lens array plate201is incident on polarization conversion element202.

Polarization conversion element202includes a polarized separation prism and a half wave plate, and converts natural light from a light source into light in one polarization direction. Fluorescent light is natural light, and thus is polarized and converted in one polarization direction. However, blue light is incident as S-polarized light, so that the blue light is converted into P-polarized light. Light from polarization conversion element202is incident on superposition lens203. Superposition lens203is for superposing light received from each lens element of second lens array plate201on liquid crystal panels217,218,219to illuminate the panels. First lens array plate199, second lens array plate201, polarization conversion element202, and superposition lens203constitute an illumination optical system.

Light from superposition lens203is separated into light of colors such as blue, green, and red by blue-reflecting dichroic mirror204and green-reflecting dichroic mirror205, each of which serves as color separation means. The green light passes through field lens211and incident side polarizing plate214to be incident on liquid crystal panel217. The blue light is reflected by reflection mirror206, and then passes through field lens212and incident side polarizing plate215to be incident on liquid crystal panel218. The red light passes through relay lenses209,210to be refracted, and is reflected by reflection mirrors207,208, and then passes through field lens213and incident side polarizing plate216to be incident on liquid crystal panel219.

Three liquid crystal panels217,218,219change polarization states of incident light by controlling voltage applied to pixels in response to image signals, and modulate light with incident side polarizing plates214,215,216in combination with emission side polarizing plates220,221,222, respectively, the polarizing plates being disposed on both sides across corresponding liquid crystal panels217,218,219while being orthogonal to respective transmission axes, thereby forming images in green, blue, and red. Each color light having passed through corresponding one of emission side polarizing plates220,221,222is incident on color-combining prism223where color light in red and blue is reflected by the red-reflecting dichroic mirror and the blue-reflecting dichroic mirror, respectively, and combined with color light in green to be incident on projection lens224. The light incident on projection lens224is enlarged and projected on a screen (not illustrated).

Projection display apparatus101B of the seventh exemplary embodiment enables improving utilization efficiency of light of light source device1D, and thus enables improving luminance of an image to be projected.

Other Exemplary Embodiments

As described above, the above exemplary embodiments have been described as examples of the techniques disclosed in the present application. The attached drawings and the detailed descriptions have been accordingly presented. However, the technique in the present disclosure is not limited thereto, and can also be applied to exemplary embodiments in which changes, replacements, additions, omissions, and the like have been made. Alternatively, the components described in the above exemplary embodiments may be combined to make an additional exemplary embodiment.

Additionally, the components described in the accompanying drawings and the detailed description may include not only components essential for solving the problem but also components that are not essential for solving the problem to illustrate the above technique. For this reason, it should not be immediately construed that those non-essential components are essential only based on the fact that those non-essential components are illustrated in the accompanying drawings or described in the detailed description.

The above exemplary embodiments are for illustrating the techniques in the present disclosure, so that various modifications, substitutions, additions, omissions, and the like can be made within the scope of claims or an equivalent scope thereof.

Overview of Exemplary Embodiments

(1) A light source device according to the present disclosure includes: a light source element configured to emit first light in a first wavelength region; a first selective reflection element disposed at a position where the first light is incident, the first selective reflection element being configured to transmit a component of first linear polarized light, the component being defined by an incident direction and a reflection direction of incident light, and reflect a component of second linear polarized light having a vibration surface orthogonal to a vibration surface of the component of the first linear polarized light; a second selective reflection element disposed at a position for receiving incident light that has passed through or been reflected by the first selective reflection element, the second selective reflection element being configured to transmit or reflect the incident light in accordance with a wavelength region of the incident light; and a first polarization direction conversion element disposed between the first selective reflection element and the second selective reflection element, the first polarization direction conversion element being configured to convert the first linear polarized light having passed through or been reflected by the first selective reflection element into elliptical polarized light. The first polarization direction conversion element converts the elliptical polarized light. which is reflected by the second selective reflection element into the second linear polarized light to be incident on the first polarization direction conversion element again.

As a result, decrease in conversion efficiency can be suppressed to reduce change in a ratio of light to be received to each of two types of wavelength conversion layers to be converted into light different in wavelength region, the change being caused by a shift of a spot of light received.

(2) The light source device of item (1) is configured such that the first linear polarized light is any one of P-polarized light and S-polarized light, the second linear polarized light is the other of P-polarized light and S-polarized light, and the first polarization direction conversion element converts the first linear polarized light incident parallel to the optical axis into circular polarized light, converts the component of the first linear polarized light incident at an angle with respect to the optical axis into elliptical polarized light, and converts the circular polarized light and the elliptical polarized light reflected by the second selective reflection element and incident on the first polarization direction conversion element again into the second linear polarized light.

(3) The light source device of item (1) or (2) is configured such that the first polarization direction conversion element includes at least two wave plates.

(4) The light source device of item (3) is configured such that the at least two wave plates are different in slow axis from each other.

(5) The light source device of item (4) is configured such that the at least two wave plates include a wave plate having a slow axis at an angle of 45 degrees and a wave plate having a slow axis at an angle of 90 degrees.

(6) The light source device of any one of items (3) to (5) is configured such that at least one of the at least two wave plates is adjustable for direction of the slow axis.

(7) The light source device of item (6) further includes a rotation drive unit that rotates at least one wave plate of the at least two wave plates.

(8) A light source device of the present disclosure includes: a light source element configured to emit first light in a first wavelength region; a first selective reflection element disposed at a position where the first light is incident, the first selective reflection element being configured to transmit or reflect first linear polarized light and reflect or transmit second linear polarized light, the first linear polarized light and the second linear polarized light being defined by an incident direction and a reflection direction of light incident on the first selective element; a second selective reflection element disposed at a position for receiving incident light that has passed through or been reflected by the first selective reflection element, the second selective reflection element being configured to transmit or reflect the incident light in accordance with a wavelength region of the incident light; a wavelength conversion element disposed at a position where the light reflected by or having passed through the first selective reflection element is incident, the wavelength conversion element being configured to converts the light reflected by or having passed through the first selective reflection element into second light in a second wavelength region; a reflection element provided to allow the first selective reflection element to be disposed between the wavelength conversion element and the reflection element that is configured to reflect light reflected by the wavelength conversion element and having passed through or reflected by the first selective reflection element; and a second polarization direction conversion element disposed between the first selective reflection element and the reflection element.

(9) The light source device of the present disclosure is configured such that the second polarization direction conversion element includes at least two wave plates.

(10) The light source device of item (9) is configured such that the at least two wave plates are different in slow axis from each other.

(11) The light source device of item (9) or (10) is configured such that at least one of the at least two wave plates is adjustable for direction of the slow axis.

(12) The light source device of any one of items (1) to (7) includes: a wavelength conversion element that is disposed at a position on which light reflected by the first selective reflection element is incident, and is configured to convert light reflected by the first selective reflection element into second light in a second wavelength region; a reflection element configured to reflect the second light emitted from the wavelength conversion element and having passed through the first selective reflection element toward the first selective reflection element; a second polarization direction conversion element disposed between the wavelength conversion element and the reflection element; and a third polarization direction conversion element disposed between the wavelength conversion element and the first selective reflection element.

(13) The light source device of item (12) is configured such that the third polarization direction conversion element includes at least two wave plates.

(14) The light source device of item (13) is configured such that the at least two wave plates of the third polarization direction conversion element are different in slow axis from each other.

(15) The light source device of item (13) or (14) is configured such that at least one of the at least two wave plates of the third polarization direction conversion element is adjustable for direction of the slow axis.

(16) A projection display apparatus according to the present disclosure includes: the light source device of any one of items (1) to (15); a light modulator that generates image light by using light emitted from the light source device; and a projection optical system that projects the image light.

The present disclosure is applicable to a wavelength conversion device that receives illumination light to perform wavelength conversion of light, a phosphor wheel, a light source device that uses light subjected to wavelength conversion performed by the phosphor wheel, and a projection display apparatus.