Light source apparatus and image projection apparatus

A light source apparatus includes a light emitting element configured to emit light having a first wavelength band, a polarization separation element configured to separate the light having the first wavelength band into a first linear polarization light and a second linear polarization light having polarization directions different from each other, a wavelength conversion element configured to convert the first linear polarization light into a third linear polarization light having a wavelength band different from the first wavelength band, and a combination element configured to combine the second linear polarization light and the third linear polarization light with each other. Light from the light source apparatus maintains a polarization state and illuminates a light modulation element via an illumination optical system.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to a light source apparatus suitable for an image projection apparatus (projector) etc., and more particularly to a light source apparatus using a wavelength conversion element.

Description of the Related Art

As disclosed in Japanese Patent Application Laid-Open No. 2015-106130, some projectors generate fluorescent light by irradiating excitation light from a light source onto a fluorescent body as a wavelength conversion element, project and display an image using combined light of the fluorescent light and the unconverted excitation light that has not undergone the wavelength conversion. Japanese Patent No. 6084572 discloses an illumination device that improves a light utilization efficiency using a quantum rod configured to convert a wavelength of incident light and emits the converted light as linear polarization light.

In the projector disclosed in Japanese Patent Laid-Open No. 2015-106130, the light from the light source is the linear polarization light, but the fluorescent light is the nonpolarized light. Thus, in order to introduce illumination light as the linear polarization light into a light modulation element such as a liquid crystal panel, an illumination optical system that guides the illumination light to the light modulation element needs to include a polarization conversion element that converts the fluorescent light into the linear polarization light.

However, the illumination optical system using the polarization conversion element has small Etendue, and as a spot diameter of the fluorescent body is reduced in accordance with the small Etendue, the illumination efficiency lowers due to the fluorescence saturation (luminance saturation) of the fluorescent body.

SUMMARY OF THE INVENTION

The present invention provides a light source apparatus and an image projection apparatus using the same, each of which can emit linear polarization light and obtain a high illumination efficiency.

A light source apparatus according to one aspect of the present invention includes a light emitting element configured to emit light having a first wavelength band, a polarization separation element configured to separate the light having the first wavelength band into a first linear polarization light and a second linear polarization light having polarization directions different from each other, a wavelength conversion element configured to convert the first linear polarization light into a third linear polarization light having a wavelength band different from the first wavelength band, and a combination element configured to combine the second linear polarization light and the third linear polarization light with each other. Light from the light source apparatus maintains a polarization state and illuminates a light modulation element via an illumination optical system.

A light source apparatus according to another aspect of the present invention includes a first light emitting element configured to emit a first linear polarization light having a first wavelength band, a second light emitting element configured to emit a second linear polarization light having a wavelength band different from that of the first linear polarization light, a first wavelength conversion element configured to convert the first linear polarization light into a third linear polarization light having a wavelength band different from each the first wavelength band and the second wavelength band, a second wavelength conversion element configured to convert the second linear polarization light into a fourth linear polarization light having the same wavelength band as that of the first linear polarization light, and a combination element configured to combine the third linear polarization light and the fourth linear polarization light with each other.

An image projection apparatus according to another aspect of the present invention includes the above light source apparatus, and a light modulation element configured to modulate light from the light source apparatus. The image projection apparatus projects modulated light from the light modulation element onto a projection surface and displays an image.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the accompanying drawings, a description will be given of embodiments according to the present invention.

First Embodiment

FIG. 1illustrates a configuration of a projector as an image projection apparatus according to a first embodiment of the present invention. The projector includes a light source apparatus100, an illumination optical system300, a color separation optical system200, light modulation elements40R,40G, and40B, a cross dichroic prism50, and a projection optical system60.

The light source apparatus100includes a light source unit1, a polarization separation and combination element4, a first collimator lens5, a wavelength conversion element6, a first phase plate7, a second collimator lens8, and a reflection type diffusion plate9. The light source apparatus100further includes a first lens10, a second lens11, a lens array12, and a second phase plate13.

The illumination optical system300includes a first lens array (fly-eye lens)14, a second lens array (fly-eye lens)15, and a condenser lens16. The first lens array14is disposed in a matrix on a plane orthogonal to an optical axis in the illumination optical system300and includes a plurality of lens cells that divide the light from the light source apparatus100into a plurality of light fluxes.

The second lens array15includes a plurality of lens cells arranged in a matrix on a plane orthogonal to the optical axis in the illumination optical system300and each corresponding to each of the plurality of lens cells in the first lens array14. In addition to the condenser lens16, the second lens array15forms images (light source images) of the plurality of lens cells of the first lens array14near the light modulation elements40R,40G, and40B.

The condenser lens16condenses a plurality of divided light fluxes from the second lens array15and superimposes them on each light modulation element. The first lens array14, the second lens array15, and the condenser lens16constitute an integrator optical system that makes uniform the intensity distribution of light from the light source apparatus100.

The color separation optical system200has dichroic mirrors1021and1022, mirrors1023,1024, and1025, and relay lenses26and27. The color separation optical system200separates the white light from the illumination optical system300into red light, green light, and blue light, and guides these three color light fluxes to the corresponding light modulation elements40R,40G, and40B.

Condenser lenses30R,30G, and30B are arranged between the color separation optical system200and the light modulation elements40R,40G, and40B. The dichroic mirror1021has a characteristic of transmitting the red light and of reflecting the green light and the blue light. The dichroic mirror1022has a characteristic of reflecting the green light and of transmitting the blue light.

The red light that has passed through the dichroic mirror1021is reflected by the mirror1023, is condensed by the condenser lens30R, and enters the light modulation element40R for the red light. The green light reflected by the dichroic mirror1021is further reflected by the dichroic mirror1022, is condensed by the condenser lens30G, and enters the light modulation element40G for the green light. The blue light that has transmitted through the dichroic mirror1022enters light modulation element40B for the blue light via the relay lens26, the incident side mirror1024, the relay lens27, the exit side mirror1025, and the condenser lens30B.

Each of the light modulation elements40R,40G, and40B modulates the incident color light according to input image information to the projector.FIG. 1illustrates a transmission type liquid crystal panel as the light modulation elements40R,40G, and40B. However, a reflection type liquid crystal panel or a digital micro mirror device may be used for the light modulation elements. An incident side polarization plate41is disposed on the light incident side of the light modulation elements40R,40G, and40B, and an exit side polarization plate42is disposed on the light exit side.

The cross dichroic prism50combines the modulated light flux (image light flux) from the three light modulation elements40R,40G, and40B and guides them to the projection optical system60. The cross dichroic prism50has a cubic or rectangular parallelepiped shape formed by bonding four right angle prisms, and a dielectric multilayer film on the prism bonding surface. The image light combined by the cross dichroic prism50is enlarged and projected onto the projection surface of a screen or the like by the projection optical system60. Thereby, a full color image is displayed on the projection surface.

In the light source apparatus100, the light source unit1includes a blue laser diode (LD)2as a plurality of light emitting elements (light emitters) and a collimator lens3provided for each blue LD2. The blue light emitted from the blue LD2is linear polarization light whose polarization direction is aligned with the x direction perpendicular to the sheet ofFIG. 1as well as divergent light, and is collimated by the collimator lens3.

The blue light (first light) emitted from the light source unit1is condensed by the first lens10, is collimated by the second lens11, and enters the lens array12. The lens array12has a lens array surface on both sides. The light (parallel light flux) from the second lens11enters a first lens array surface12A of the lens array12, is split into a plurality of light fluxes, and then enters a second lens array surface12B. The plurality of divided light fluxes emitted from the second lens array surface12B pass through a second phase plate13and enters a polarization separation and combination element (a polarization separator and combiner)4that serves as a polarization separation element (polarization separator) and a combination element (combiner)4.

The p-polarized light and s-polarized light used in the following description are defined by the polarization direction of a light ray incident on the polarization separation surface in the polarization separation and combination element4. The s-polarized light in this embodiment and the following other embodiments is linear polarization light whose polarization direction is aligned with the x direction. The second phase plate13is an element that controls a ratio of the blue p-polarized light and s-polarized light.

The polarization separation and combination element4has a characteristic of reflecting the blue s-polarized light and of transmitting the blue p-polarized light and light in the green to red wavelength band. In other words, the polarization separation and combination element4separates the incident blue light into the blue s-polarized light (first linear polarization light) and the blue p-polarized light (second linear polarization light). The blue s-polarized light reflected by the polarization light separation and combination element4is condensed by the first collimator lens5and enters the wavelength conversion element6.

FIG. 2Aillustrates a configuration of a wavelength conversion element (wavelength converter)6. The wavelength conversion element6includes a first wavelength conversion layer22as a first wavelength converter disposed in order from a light incident side which the blue s-polarized light enters, a second wavelength conversion layer24as a second wavelength converter, and a reflection member25as a substrate. The first wavelength conversion layer22and the second wavelength conversion layer24are laminated on the reflection member25. The stacking order of the first wavelength conversion layer22and the second wavelength conversion layer24may be reversed.

In the first wavelength conversion layer22, as illustrated inFIG. 2B, a plurality of first quantum rods21are arranged such that their longitudinal directions extend in the x direction. The first quantum rod21converts the blue linear polarization light whose polarization direction is aligned with the x direction into the red linear polarization light whose polarization direction is aligned with the x direction. In other words, the first quantum rod21converts the blue s-polarized light (linear polarization light in the first wavelength band) into the red s-polarized light (linear polarization light in the second wavelength band) while maintaining its polarization direction.

In the second wavelength conversion layer24, the second quantum rods23are arranged such that their longitudinal directions extend in the x direction. The second quantum rod23converts the blue linear polarization light whose polarization direction is aligned with the x direction into the green linear polarization light whose polarization direction is aligned with the x direction. In other words, the second quantum rod21converts the blue s-polarized light into the green s-polarized light (linear polarization light in the third wavelength band) while maintaining its polarization direction.

The blue s-polarized light which has not undergone the wavelength conversion among the blue s-polarized light incident on the wavelength conversion element6as described above is reflected by the reflection member25and again its wavelength is converted to generate the red and green s-polarized light by the first and second wavelength conversion layers22and24(first and second quantum rods21and23). Thus, the green and red s-polarized light fluxes (third linear polarization light fluxes) are emitted from the wavelength conversion element6. The green and red s-polarized light fluxes emitted from the wavelength conversion element6are collimated by the first collimator lens5and enter the polarization separation and combination element4.

This embodiment arranges the quantum rods such that their longitudinal directions extend in the x direction in each wavelength conversion layer, gives each color light directivity in the x direction, and reduces the light flux diameter in the x direction. As a result, the size (height) of the projector is reduced in the x direction.

On the other hand, the blue p-polarized light that has transmitted through the polarization separating and combination element4is converted into circular polarization light by the first phase plate7, is condensed by the second collimator lens8, and enters a reflection type diffusion plate9as a diffusion element (diffusion). The blue circular polarized light diffused and reflected by the reflection type diffusion plate9is collimated by the second collimator lens8and converted into the s-polarized light by the first phase plate7. The first phase plate7is an element that causes the polarization direction of the blue linear polarization light (second linear polarization light) to coincide with that of each of the green and red linear polarization light fluxes (third linear polarization light flux).

The blue s-polarized light as diffusion light emitted from the first phase plate7is reflected by the polarization splitting and combination element4. This blue s-polarized light is combined with the green and red s-polarized light fluxes that have transmitted through the polarization splitting and combination element4to generate white illumination light, which is emitted from the light source apparatus100and input to the illumination optical system300.

This configuration enables the blue, green, and red s-polarized light fluxes to enter the illumination optical system300using no polarization conversion element that converts nonpolarized light into linear polarization light. The Etendue of the illumination optical system including the polarization conversion element is small, and if the spot diameter of the excitation light incident on the wavelength conversion element is made small in accordance with the small Etendue, the illumination efficiency decreases due to the fluorescence saturation of the wavelength conversion element. The fluorescence saturation is a phenomenon generated in the fluorescent body and quantum dot (including the quantum rod), in which the conversion efficiency lowers from the excitation light to the fluorescent light as the input energy of excitation light increases. Since the conversion efficiency depends on the light density, when the light density increases, the conversion efficiency decreases.

On the other hand, this embodiment that needs no polarization conversion element has large Etendue in the illumination optical system300, and suppresses the fluorescence saturation of the wavelength conversion element6to improve the illumination efficiency. No polarization conversion element can theoretically double the Etendue of the illumination optical system300and maintain the necessary illumination efficiency even if the spot diameter of the excitation light on the wavelength conversion element6is doubled and the optical density is halved. Therefore, the conversion efficiency can be prevented from deteriorating due to the fluorescence saturation.

When the output of the blue LD2changes, the conversion efficiency also decreases due to the fluorescence saturation. Thereby, the balance changes among the blue light and the red light and the green light as the light having a converted wavelength, and the tint of the illumination light changes. Then, the second phase plate13that properly adjusts a ratio between the blue p-polarized light and the s-polarized light can suppress the tint change of the illumination light when the output of the blue LD2changes.

This embodiment uses the wavelength conversion element6including the quantum rod, but may use any elements other than the quantum rod as long as they are wavelength conversion elements that convert the wavelength of the excitation light as linear polarization light while maintaining the linear polarization light. This is also applied to other embodiments to be described later.

This embodiment has discussed the polarization separation and combination element4having a characteristic of reflecting the blue s-polarized light and of transmitting the blue p-polarized light and the light in the green to red wavelength band, but the polarization separation and combination element4may have a characteristic of reflecting the blue p-polarized light and of transmitting the blue s-polarized light and the light in the green to red wavelength band. Then, a wavelength conversion element6′ illustrated inFIGS. 3A and 3Bmay be used so that the wavelength conversion element6′ can convert the wavelength of the transmitted s-polarized blue light to generate the green light and red light.

In the wavelength conversion element6′ illustrated inFIGS. 3A and 3B, the longitudinal directions of the first quantum rods21disposed in the first wavelength conversion layer72and the second quantum rods23disposed in the second wavelength conversion layer74extend in the z direction. This wavelength conversion element6′ emits the green and red p-polarized light whose polarization direction is aligned with the z direction. The green and red p-polarized light and the blue p-polarized light that has passed through an unillustrated reflection type diffusion plate and the like are led to the illumination optical system300.

A description will now be given of conditions suitable for this embodiment.

The wavelength conversion element6may include, between the first wavelength conversion layer22and the second wavelength conversion layer24, a dichroic film which transmits the light having the wavelength band from blue to green and reflects the red light. Unless the dichroic film is formed, part of the red light generated in the first wavelength conversion layer22passes through the second wavelength conversion layer24, is reflected by the reflection member25, again passes through the second wavelength conversion layer24, and is emitted from the wavelength conversion element6. Thus, an optical path length difference by the reciprocation through the second wavelength conversion layer24occurs between the red light and the green light. This optical path length difference reduces the parallelism of the light beam collimated by the first collimator lens5, and consequently decreases the illumination efficiency.

Assume that A is a total of light quantities of the blue, green, and red s-polarized light fluxes (second and third linear polarization light beams) out of the light emitted from the light source apparatus100and entering the illumination optical system300, and B is a light quantity of the P-polarized light as unnecessary light. Then, the following condition may be satisfied.
A/B≥4  (1)

If AB falls below a lower limit value, a loss of the illumination light due to the absorption or reflection on the incident side polarizing plate41increases and the illumination efficiency decreases. The following condition may be satisfied.
A/B≥6  (2)

The following condition may be satisfied.
A/B≥9  (3)

The following third to fifth embodiments described later may also satisfy the conditions of the expressions (1) to (3).

Second Embodiment

FIG. 4illustrates a configuration of a light source apparatus100A in a projector according to a second embodiment of the present invention. The projector according to this embodiment includes a light source apparatus100A, and other components configured similarly to the first embodiment, such as an illumination optical system, a color separation optical system, a light modulation element (light modulator), a cross dichroic prism, and a projection optical system.

The light source apparatus100A includes a first light source unit101, a second light source unit104, a dichroic mirror107, a first lens120, a second lens121, a lens array122, and a color separation and combination element (color separator and combiner)110. The light source apparatus100A further includes a first collimator lens111, a first wavelength conversion element112, a second collimator lens113, and a second wavelength conversion element114.

The first light source unit101has a blue LD102as a plurality of first light emitting elements, and a collimator lens103provided for each blue LD102. The blue light emitted from the blue LD102is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and is collimated by the collimator lens103.

The second light source unit104includes an ultraviolet LD105as a plurality of second light emitting elements, and a collimator lens106provided for each ultraviolet LD105. The ultraviolet light emitted from the ultraviolet LD105is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and is collimated by the collimator lens103.

The blue light (first linear polarization light) emitted from the first light source unit101and the ultraviolet light (second linear polarization light) emitted from the second light source unit104are combined with each other by the transmission and reflection by the dichroic mirror107. Then, it is condensed by the first lens120, is collimated by the second lens121, and enters the lens array122. The lens array122has a lens array surface on both sides. The light (parallel light flux) from the second lens121enters the first lens array surface122A of the lens array122, is divided into a plurality of light fluxes, and then these light fluxes enter the second lens array surface122B. The plurality of divided light fluxes emitted from the second lens array surface122B enter a color separation and combination element (color separator and combiner)110which also serves as a color separation element (color separator) and a combination element (combiner).

The color separation and combination element110has a characteristic of reflecting the blue light and of transmitting the ultraviolet light and light having the wavelength band from green to red. In other words, the color separation and combination element110separates the blue light and the ultraviolet light combined by the dichroic mirror107. The blue light reflected by the color separation and combination element110is condensed by the first collimator lens111and enters the first wavelength conversion element112.

FIG. 5Aillustrates the configuration of the first wavelength conversion element112. The first wavelength conversion element112includes, in order from a light incident side which blue light enters, a first wavelength conversion layer132as a first wavelength converter, a second wavelength conversion layer134as a second wavelength converter, and a reflection member135as a substrate. The first wavelength conversion layer132and the second wavelength conversion layer134are laminated on the reflection member135. The stacking order of the first wavelength conversion layer132and the second wavelength conversion layer134may be reversed.

As illustrated inFIG. 5B, the first wavelength conversion layer132has a plurality of first quantum rods131such that their longitudinal directions extend in the x direction. The first quantum rod131converts the blue linear polarization light whose polarization direction is aligned with the x direction, into the red linear polarization light whose polarization direction is aligned with the x direction. In other words, the first quantum rod131converts the blue s-polarized light (first linear polarization light) into the red s-polarized light while maintaining its polarization direction.

The second wavelength conversion layer134includes the second quantum rods133such that their longitudinal directions extend in the x direction. The second quantum rod133converts the blue linear polarization light whose polarization direction is aligned with the x direction, into the green linear polarization light whose polarization direction is aligned with the x direction. In other words, the second quantum rod131converts the blue s-polarized light into the green s-polarized light while maintaining its polarization direction.

Part of the blue light which has not undergone the wavelength conversion among the blue light incident on the first wavelength conversion element112is reflected by the reflection member135, and is converted into red and green s-polarized light by the first and second wavelength conversion layers132and134(first and second quantum rods131and133).

Thus, the wavelength-converted green and red s-polarized light fluxes (third linear polarization light fluxes) from the blue s-polarized light is emitted from the first wavelength conversion element112. The green and red s-polarized light fluxes emitted from the first wavelength conversion element112are collimated by the first collimator lens111and enter the color separation and combination element110.

On the other hand, the ultraviolet light that has transmitted through the color separation and combination element110is condensed by the second collimator lens113and enters the second wavelength conversion element114.FIG. 6Aillustrates the configuration of the second wavelength conversion element114. The second wavelength conversion element114includes, in this order from the light incident side which the ultraviolet light enters, a third wavelength conversion layer136as a third wavelength converter and a reflection member137as a substrate.

The third wavelength conversion layer136includes, as illustrated inFIG. 6B, a plurality of third quantum rods138such that their longitudinal directions extend in the x direction. The third quantum rod138converts the ultraviolet linear polarization light whose polarization direction is aligned with the x direction, into the blue linear polarization light whose polarization direction is aligned with the x direction. In other words, the third quantum rod138converts the ultraviolet s-polarized light (second linear polarization light), into the blue s-polarized light (fourth linear polarization light) while maintaining its polarization direction.

The ultraviolet s-polarized light which has not undergone the wavelength conversion as described above among the ultraviolet s-polarized light incident on the second wavelength conversion element114is reflected by the reflection member137and its wavelength is again converted by the third wavelength conversion layer136(third quantum rod138) into the blue s-polarized light. Thus, the blue s-polarized light is emitted from the second wavelength conversion element114. The blue s-polarized light emitted from the second wavelength conversion element114is collimated by the second collimator lens113and reflected by the color separation and combination element110. This blue s-polarized light is combined with the green and red s-polarized light fluxes that have transmitted through the color separation and combination element110, so that the white illumination light is generated. The illumination light is emitted from the light source apparatus100A and enters the illumination optical system.

This configuration enables the blue, green, and red s-polarized light to enter the illumination optical system using no polarization conversion element that converts the nonpolarized light into the linear polarization light. As a result, the Etendue of the illumination optical system becomes large, so that the fluorescence saturation of the first and second wavelength conversion elements112and114can be reduced and the illumination efficiency can be improved.

Assume that A is a total of light quantities of the blue, green and red s-polarized light fluxes (third and fourth linear polarization light fluxes) among the light emitted from the light source apparatus100A and entering the illumination optical system in this embodiment, and B is a light quantity of the p-polarized light as unnecessary light. Then, the expressions (1) to (3) described in the first embodiment may be satisfied. This is also applied to the fourth embodiment described later.

The first quantum rod disposed in the first wavelength conversion layer and the second quantum rod disposed in the second wavelength conversion layer have longitudinal directions extending in the z direction. The third quantum rod disposed in the second wavelength conversion layer has a longitudinal direction extending in the y direction. Then, the green, red, and blue p-polarized light are guided to the illumination optical system by causing the blue light and the ultraviolet light whose polarization directions are aligned with the z direction to enter the color separation and combination element110.

Third Embodiment

FIG. 7illustrates a configuration of a light source apparatus100B in a projector according to a third embodiment of the present invention. The projector according to this embodiment includes a light source apparatus100B, and other components configured similarly to the first embodiment, such as an illumination optical system, a color separation optical system, a light modulation element, a cross dichroic prism, and a projection optical system.

The light source apparatus100B includes a light source unit151, a first lens170, a second lens171, a lens array172, a second phase plate173, a polarization separation element160, a first collimator lens161, and a wavelength conversion element162. The light source apparatus100B includes a first mirror165, a second collimator lens167, and a combination element180. The light source apparatus100B includes a third collimator lens163, a transmission type diffusion plate164, a second mirror166, a fourth collimator lens168, and a first phase plate169.

The light source unit151includes a blue LD152as a plurality of light emitting elements, and a collimator lens153provided for each blue LD152. The blue light emitted from the blue LD152is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and it is collimated by the collimator lens153.

The blue light emitted from the light source unit101is condensed by the first lens170, is collimated by the second lens171, and enters the lens array172. The lens array172has a lens array surface on both sides. The light (parallel light flux) from the second lens171enters the first lens array surface172A of the lens array172, is divided into a plurality of light fluxes, and then the light fluxes enters the second lens array surface172B. The plurality of divided light fluxes emitted from the second lens array surface172B pass through the second phase plate173and enter the polarization separation element160. The second phase plate173is an element that controls a ratio between the blue p-polarized light and the s-polarized light.

The polarization separation element160has a characteristic of reflecting the blue s-polarized light and of transmitting the blue p-polarized light. In other words, the polarization separation element160separates the incident blue light into the blue s-polarized light (first linear polarization light) and the blue p-polarized light (second linear polarization light). The blue s-polarized light reflected by the polarization separating element160is condensed by the first collimator lens161and enters the wavelength conversion element162.

FIG. 8Aillustrates the configuration of the wavelength conversion element162. The wavelength conversion element162includes, in this order from the light incidence side which the blue s-polarized light enters, a light transmitting member185as a substrate, a first wavelength conversion layer182as a first wavelength converter, and a second wavelength conversion layer184as a second wavelength converter. The first wavelength conversion layer182and the second wavelength conversion layer184are stacked on the light transmitting member185. The stacking order of the first wavelength conversion layer182and the second wavelength conversion layer184may be reversed.

The first wavelength conversion layer182includes, as illustrated inFIG. 8B, a plurality of first quantum rods181such that their longitudinal directions extend in the x direction. The first quantum rod181converts the blue linear polarization light whose polarization direction is aligned with the x direction, into the red linear polarization light whose polarization direction is aligned with the x direction. In other words, the first quantum rod181converts the blue linear polarization light (linear polarization light in the first wavelength band) into the red linear polarization light (linear polarization light in the second wavelength band) while maintaining its polarization direction.

The second wavelength conversion layer184includes the second quantum rods183such that their longitudinal directions extend in the x direction. The second quantum rod183converts the blue linear polarization light whose polarization direction is aligned with the x direction into the green linear polarization light whose polarization direction is aligned with the x direction. In other words, the second quantum rod183converts the blue s-polarized light into the green s-polarized light (linear polarization light in the third wavelength band) while maintaining its polarization direction.

A dichroic film is formed at an interface185A of the light transmitting member185with the first wavelength conversion layer182. The dichroic film has a characteristic of transmitting the blue light and of reflecting the light in the wavelength band from green to red.

This configuration emits the green and red s-polarized light from the wavelength conversion element162. The green and red s-polarized light fluxes emitted from the wavelength conversion element162are reflected by the first mirror165, collimated by the second collimator lens167, and reflected by the combination element180. The combination element180has a characteristic of reflecting the blue light and of transmitting the light in the wavelength band from green to red.

On the other hand, the blue p-polarized light that has transmitted through the wavelength separation element160is condensed by the third collimator lens163and enters the transmission type diffusion plate164. The blue p-polarized light diffused by the transmission type diffusion plate164is reflected by the second mirror166, collimated by the fourth collimator lens168, and converted into the s-polarized light by the first phase plate169. The first phase plate169is an element that aligns the polarization direction of the blue linear polarization light (second linear polarization light) with that of the green and red linear polarization light (third linear polarization light).

The blue s-polarized light emitted from the first phase plate169passes through the combination element180and is reflected by the combination element180. This blue s-polarized light is combined with the green and red s-polarized light fluxes that have transmitted through the combination element180to generate white illumination light, and the illumination light is emitted from the light source apparatus100B and enters the illumination optical system.

This configuration enables the blue, green, and red s-polarized light to enter the illumination optical system using no polarization conversion element that converts the nonpolarized light into the linear polarization light. As a result, the Etendue of the illumination optical system becomes larger, so that the fluorescence saturation of the wavelength conversion element162can be reduced, and the illumination efficiency can be improved.

Fourth Embodiment

FIG. 9illustrates a configuration of a light source apparatus100C in a projector according to a fourth embodiment of the present invention. The projector according to this embodiment includes a light source apparatus100C, and other components configured similarly to the first embodiment, such as an illumination optical system, a color separation optical system, a light modulation element, a cross dichroic prism, and a projection optical system.

The light source apparatus100C includes a first light source unit201, a second light source unit204, a dichroic mirror207, a first lens220, a second lens221, a lens array222, and a color separation element210. The light source apparatus100C further includes a first mirror265, a second collimator lens217, and a combination element230. The light source apparatus100C further includes a third collimator lens213, a second wavelength conversion element214, a second mirror216, and a fourth collimator lens218.

The first light source unit201has a blue LD202as a plurality of first light emitting elements, and a collimator lens203provided for each blue LD202. The blue light emitted from the blue LD202is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and is collimated by the collimator lens203.

The second light source unit204includes an ultraviolet LD205as a plurality of second light emitting elements, and a collimator lens206provided for each ultraviolet LD205. The ultraviolet light emitted from the ultraviolet LD205is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and is collimated by the collimator lens203.

The blue light (first linear polarization light) emitted from the first light source unit201and the ultraviolet light (second linear polarization light) emitted from the second light source unit204are combined with each other by the transmission and reflection by the dichroic mirror207. The light is condensed by the first lens220, is collimated by the second lens221, and enters the lens array222. The lens array222has a lens array surface on both sides. The light (parallel light beam) from the second lens221enters the first lens array surface222A of the lens array222, is divided into a plurality of light fluxes, and then these light fluxes enters the second lens array surface222B. The plurality of divided light fluxes emitted from the second lens array surface222B enter the color separation element210.

The color separation element210has a characteristic of reflecting the blue light and of transmitting the ultraviolet light. In other words, the color separation element210separates the blue light and the ultraviolet light that have been combined with each other by the dichroic mirror207. The blue light reflected by the color separation element210is condensed by the first collimator lens211and enters the first wavelength conversion element212. The configuration of the first wavelength converting element212is the same as that of the first wavelength converting element162according to the third embodiment, and the first wavelength converting element212converts the incident blue s-polarized light into the green and red s-polarized light (third linear polarization light) while maintaining its polarization direction.

The green and red s-polarized light fluxes emitted from the first wavelength conversion element212are reflected by the first mirror215, are collimated by the second collimator lens217, are reflected by the combination element230, and enter the illumination optical system. The combination element230has a characteristic of reflecting the blue light and of transmitting the light in the wavelength band from green to red.

On the other hand, the blue p-polarized light that has transmitted through the color separation element210is condensed by the third collimator lens213and enters the second wavelength conversion element214.FIG. 10Aillustrates the configuration of the second wavelength conversion element214. The second wavelength conversion element214includes, in order from the light incident side which the ultraviolet light enters, a light transmitting member235as a substrate, and a third wavelength conversion layer236as a third wavelength converter.

The third wavelength conversion layer236includes, as illustrated inFIG. 10B, a plurality of third quantum rods238such that their longitudinal directions extend in the x direction. The third quantum rod238converts the ultraviolet linear polarization light whose polarization direction is aligned with the x direction, into the blue linear polarization light whose polarization direction is aligned with the x direction. In other words, the third quantum rod238converts the ultraviolet s-polarized light (second linear polarization light) into the blue s-polarized light (fourth linear polarization light) while maintaining its polarization direction.

The blue s-polarized light emitted from the second wavelength conversion element114is collimated by the second collimator lens113and transmits through the combination element230. Then, this blue S-polarized light is combined with the green and red s-polarized light fluxes reflected by the combination element110to generate white illumination light, and the illumination light is emitted from the light source apparatus100C to the illumination optical system.

This configuration enables the blue, green, and red s-polarized light to enter the illumination optical system using no polarization conversion element that converts the nonpolarized light into the linear polarization light. As a result, the Etendue of the illumination optical system becomes large, and the fluorescence saturation of the first and second wavelength conversion elements212and214can be reduced, so that the illumination efficiency can be improved.

Fifth Embodiment

FIG. 11illustrates a configuration of a light source apparatus100D in a projector according to a fifth embodiment of the present invention. The projector according to this embodiment includes a light source apparatus100D, and other components configured similarly to the first embodiment, such as an illumination optical system, a color separation optical system, a light modulation element, a cross dichroic prism, and a projection optical system.

The light source apparatus100D includes a first light source unit251, a second light source unit254, a dichroic mirror257, a first lens270, a second lens271, a lens array272, a wavelength selective phase plate273, and a polarization and color separation combination element110. The light source apparatus100D further includes a first collimator lens261, a wavelength conversion element262, a phase plate263, a second collimator lens264, and a reflection type diffusion plate265.

The first light source unit251includes a blue LD252as a plurality of first light emitting elements, and a collimator lens253provided for each blue LD252. The blue light emitted from the blue LD252is linear polarization light (s-polarized light) whose polarization direction is aligned with the x direction as well as divergent light, and is collimated by the collimator lens253.

The second light source unit254has a red LD255as a plurality of second light emitting elements, and a collimator lens256provided for each red LD255. The red light emitted from the red LD255is linear polarization light (P polarized light) whose polarization direction is aligned with the z direction as well as divergent light, and is collimated by the collimator lens256.

The blue light emitted from the first light source unit251and the red light emitted from the second light source unit254are combined with each other by the transmission and reflection by the dichroic mirror257and condensed by the first lens270. The combined light (light in the first wavelength band) of the blue light and the red light is collimated by the second lens271and enters the lens array272. The lens array272has a lens array surface on both sides. The light (parallel light beam) from the second lens271enters the first lens array surface272A of the lens array272, is divided into a plurality of light beams, and then these light beams enter the second lens array surface272B. The plurality of divided light fluxes emitted from the second lens array surface272B pass through the wavelength selective phase plate273and enter a polarization, color separation, and combination element260as a polarization separation element.

The wavelength selective phase plate273rotates part of the polarization direction of the incident blue light (s-polarized light) by 90° to align it with the z direction (or generates the blue p-polarized light) and transmits the red light (p-polarized light) as it is. The wavelength selective phase plate273is an element that controls the ratio between the p-polarized light and the s-polarized light contained in the blue light.

The polarization, color separation, combination element260has a characteristic of reflecting the blue and red s-polarized light fluxes, of transmitting blue and red p-polarized light fluxes, and of further transmitting the green light. In other words, the polarization, color separation, and combination element260separates the incident blue light and red light into the blue s-polarized light (first linear polarization light) and blue and red p-polarized light (second linear polarization light). The blue s-polarized light reflected by the polarization, color separation, and combination element260is condensed by the first collimator lens261and enters the wavelength conversion element262.

FIG. 12Aillustrates a configuration of the wavelength conversion element262. The wavelength conversion element262includes, in order from the light incident side which the s-polarized blue light enters, a wavelength conversion layer282and a reflection member283as a substrate. The wavelength conversion layer282includes, as illustrated inFIG. 12B, a plurality of quantum rods281such that their longitudinal directions extend in the x direction. The quantum rod281converts the blue linear polarization light whose polarization direction is aligned with the x direction, into the green linear polarization light whose polarization direction is aligned with the x direction. In other words, the quantum rod21converts the blue s-polarized light (first linear polarization light) into the green s-polarized light (third linear polarization light) while maintaining its polarization direction. The green s-polarized light emitted from the wavelength conversion element262is collimated by the first collimator lens261and enters the polarization, color separation, and combination element260.

On the other hand, the blue and red p-polarized light fluxes that have transmitted through the polarization, color separation, and combination element260are converted into circular polarization light by the phase plate263, are condensed by the second collimator lens264, and enter the reflection type diffusion plate265. The blue and red circular polarization light fluxes diffused and reflected by the reflection type diffusion plate265are collimated again by the second collimator lens264and converted into the s-polarized light by the phase plate263. The phase plate263is an element that causes the polarization directions of the blue and red linear polarization light fluxes (second linear polarization light fluxes) to coincide with the polarization direction of the green linear polarization light (third linear polarization light).

The blue and red s-polarized light fluxes as diffusion light fluxes emitted from the phase plate263are reflected by the polarization, color separation, and combination element260. The blue and red s-polarized light fluxes are combined with the green s-polarized light that has transmitted through the polarization, color separation, and combination element260to generate white illumination light, which is emitted from the light source apparatus100D to the illumination optical system300.

This configuration enables the blue, green, and red s-polarized light fluxes to enter the illumination optical system using no polarization conversion element that converts the nonpolarized light into the linear polarization light. As a result, the Etendue of the illumination optical system becomes large, and the fluorescence saturation of the wavelength conversion element262can be reduced to improve the illumination efficiency.

As described in the first embodiment, when the output of the blue LD252changes, the conversion efficiency decreases due to the fluorescence saturation, and the tint of the illumination light changes. On the other hand, this embodiment properly adjusts the ratio between the blue p-polarized light and the s-polarized light by the wavelength selective phase plate273, properly adjusts the output of the red LD255, and thereby suppress the tint change in the illumination light caused by the output change of the blue LD252.

This application claims the benefit of Japanese Patent Application No. 2018-75096, filed on Apr. 10, 2018, which is hereby incorporated by reference herein in its entirety.