WO2017018372A1

WO2017018372A1 - Light source device and projection device

Info

Publication number: WO2017018372A1
Application number: PCT/JP2016/071698
Authority: WO
Inventors: 小野雄樹; 三森満
Original assignee: コニカミノルタ株式会社
Priority date: 2015-07-28
Filing date: 2016-07-25
Publication date: 2017-02-02
Also published as: JPWO2017018372A1

Abstract

Provided are: a light source device capable of more efficiently separating original excitation light and the illumination light created therefrom while simplifying the structure of an optical system to thus improve light use efficiency; and a projection device incorporating the light source device. The light source device comprises: a laser array 51 that is an excitation light source for emitting excitation light EL; an irradiated body 41 for emitting illumination light L2 containing fluorescent light FL upon receiving the excitation light EL; an illumination optical system for introducing the illumination light L2 emitted from the irradiated body 41; and a polarization splitter 32 disposed on the optical path between the excitation light source and the irradiated body and having a polarization separation surface 32a for separating the illumination light L2 from the optical path of the excitation light EL by transmission or reflection. The polarization splitter 32 is arranged so that the angle between the normal line to the polarization separation surface 32a and an optical axis SX of the illumination optical system is 50° or more and 80° or less.

Description

Light source device and projection device

The present invention relates to a light source device suitable for illumination of an image display element incorporated in a projection device, and a projection device incorporating such a light source device.

In recent years, semiconductor lasers (LDs) and light emitting diodes (LEDs) are increasingly used as light sources for projectors.

High-pressure mercury lamps are generally used for large projectors used in offices and the like, but an increasing number of products use a semiconductor laser to excite a phosphor as a light source. For example, a technique for producing three primary colors for illumination using a semiconductor laser as an excitation light source is known (see Patent Documents 1 and 2).

However, in Patent Document 1, since the illumination optical system is a mixture of light having a wavelength that is transmitted through the phosphor wheel and light having a wavelength that is reflected by the phosphor wheel, it is necessary to ensure a wide space for the layout of the optical system. There is. Furthermore, since an optical system after passing through the phosphor wheel is required separately, the number of parts increases and the productivity is not good.

On the other hand, when an optical system that reflects light of all wavelengths including blue excitation light is adopted by the phosphor wheel as in Patent Document 2, it is advantageous in both downsizing the apparatus and improving productivity. There is. In an illumination optical system that uses a reflective phosphor wheel as a light source, a polarization beam splitter is used for the excitation light path from the light source to the phosphor and the illumination light path from the phosphor wheel to the display panel. In this case, the polarization beam splitter is disposed so as to be inclined at 45 ° with respect to the optical axis. However, when the polarization beam splitter is used at an angle of 45 ° with respect to the optical axis, the difference in cutoff wavelength between the S-polarized light and the P-polarized light cannot be increased. For this reason, there is a problem that separation of excitation light and illumination light tends to be insufficient when there is a shift in cutoff wavelength due to film thickness variations during the manufacture of a polarizing beam splitter, or when there are wavelength variations or wavelength changes in the light source. .

In addition, as in Patent Document 3, when using excitation light that is not blue but ultraviolet, a dichroic mirror is used instead of the polarization beam splitter, and the optical path of the excitation light from the light source to the phosphor and the phosphor wheel The light path from the illumination light to the display panel is separated from the light path. In this case, there is no problem of insufficient polarization separation, but it is not easy to efficiently generate ultraviolet excitation light with a small semiconductor laser. Further, since phosphors of three colors of blue, green and red are necessary, the cost is increased.

JP2011-13320A JP 2012-108486 A JP 2012-13897 A

The present invention has been made in view of the above-described background art, and can simplify the configuration of the optical system, can more efficiently separate the original excitation light and the illumination light obtained therefrom, and can improve the light utilization efficiency. It is an object of the present invention to provide an enhanced light source device and a projection device incorporating such a light source device.

In order to achieve the above object, a light source device according to the present invention includes an excitation light source that emits excitation light, an irradiated object that emits illumination light including fluorescent light upon irradiation with the excitation light, and an emitted light from the irradiated object. An illumination optical system that guides the emitted illumination light, and a polarization separation element that is disposed between the optical path of the excitation light source and the irradiated object, and has a polarization separation surface that separates the illumination light from the optical path of the excitation light by transmission and reflection The polarization separation element is arranged such that the angle formed between the normal line of the polarization separation surface and the optical axis of the illumination optical system is 50 ° or more and 80 ° or less.

In the above light source device, the polarization separation element is arranged at an angle of 50 ° or more and 80 ° or less between the normal line of the polarization separation surface and the optical axis of the illumination optical system. A large difference in the cutoff wavelength can be secured, and the separation of the excitation light and illumination light is sufficiently efficient even when there is a shift in the cutoff wavelength due to manufacturing variations of the polarization separation element, or when there is a wavelength variation or wavelength change in the light source. It can be done. As a result, the light can be used efficiently, and bright illumination light can be emitted.

A projection device according to the present invention includes the above-described light source device, an image display element illuminated by the light source device, and a projection optical system that projects an image formed by the image display element.

Since the light source device having high light utilization efficiency is incorporated in the above projection device, it is possible to provide a projection device that is small and capable of projecting with high brightness.

It is a figure explaining the projection apparatus containing the light source device which concerns on 1st Embodiment. 2A is an enlarged view for explaining a main part of the light source device, and FIG. 2B is a diagram for explaining a light irradiation plate incorporated in the light source device shown in FIG. 2A. 3A is a graph showing the transmission characteristics of the polarization separation element incorporated in the light source device of FIG. 2A, and FIG. 3B is a graph showing the transmission characteristics of the polarization separation element incorporated in the light source apparatus of the comparative example. 4A is an enlarged graph showing the transmission characteristics in the blue wavelength region of the polarization separation element, and FIG. 4B is a graph explaining the relationship between the angle at which the polarization separation element is tilted and the 80% transmission wavelength with respect to the P-polarized light. FIG. 4C is a graph illustrating the relationship between the angle at which the polarization separation element is tilted and the 80% transmission wavelength with respect to S-polarized light. It is a figure explaining the principal part of the light source device which concerns on 2nd Embodiment. FIG. 6A is a graph showing the transmission characteristics of the polarization separation element incorporated in the light source device of FIG. 5, and FIG. 6B is a graph showing the transmission characteristics of the polarization separation element incorporated in the light source apparatus of the comparative example.

[First Embodiment]
A projection apparatus incorporating the light source device according to the first embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the projection device 2 according to the first embodiment enables projection of images corresponding to various video signals, and includes a light source device 21, a polarization beam splitter 22, and a reflective liquid crystal element 23. A projection optical system 26 and a circuit unit 29.

The light source device 21 of the projection device 2 includes a beam forming unit 31 that emits laser light L1 functioning as excitation light EL in a substantially parallel state, and an optical path of illumination light L2 including fluorescent light FL from the optical path of the excitation light EL. , A phase difference plate 33 that changes the polarization state of the laser light L1, and the laser light L1 as the excitation light EL is condensed on the irradiated body 41 and the fluorescent light from the irradiated body 41 Passed through a condenser lens 34 for extracting FL or the like as a substantially parallel light beam, a light irradiation plate 35 having an irradiated body 41 that generates fluorescent light FL from the laser light L 1 and reflects the laser light L 1, and the polarization separation element 32. A uniformizing optical system 36 that equalizes the intensity of the illumination light L2 and a field lens 38 that adjusts the incident angle of the illumination light L2 to the reflective liquid crystal element 23 are provided. In the above, the homogenizing optical system 36, the field lens 38, etc. constitute an illumination optical system.

As will be described in detail later, the light irradiation plate 35 emits the illumination light L2 under the illumination of the laser light L1, and specifically, green light, red light, and blue light are cycled with the rotation. Inject while switching.

The polarization beam splitter (PBS) 22 is an optical element that branches an optical path according to the polarization direction. The polarization beam splitter 22 is formed by bonding a pair of right-angle prisms. On the bonding surface, the illumination light L2 that is linearly polarized light in a predetermined direction incident from the light source device 21 is selected on the inclined surface of one right-angle prism. A polarization separation surface 22a made of a polarization separation film that transmits light is formed. The polarization beam splitter 22 allows the illumination light L2 emitted from the light source device 21 to pass therethrough and enter a reflective liquid crystal element 23 described later. In addition, the image light L 3 reflected by the reflective liquid crystal element 23 can be reflected by the polarization beam splitter 22 and can be incident on the projection optical system 26. Here, the polarization splitting surface 22a transmits P-polarized light based on this and reflects S-polarized light.

The reflective liquid crystal element 23 is a display panel that forms the image light L3, that is, an image display element, and particularly a light valve or a spatial light in that the image light L3 is formed from the illumination light L2 by spatially changing the reflectance. It can be said that it is a modulation element. The reflective liquid crystal element (image display element) 23 includes an image display panel that is a plate-like electronic component. The reflection type liquid crystal element 23 is a micro display also called LCOS (liquid crystal on silicon), in which a circuit is directly formed on the surface of a silicon chip and a liquid crystal layer is sandwiched between a counter substrate. When a voltage corresponding to a drive signal is applied to the liquid crystal layer for each pixel, the reflective liquid crystal element 23 modulates the illumination light L2 by changing the arrangement of liquid crystal molecules, and displays a desired image by reflection. Is. As shown in the figure, when a configuration is adopted in which P-polarized light with reference to the polarization separation surface 22a is incident on the reflective liquid crystal element 23 as illumination light L2, S-polarized light with reference to the polarization separation surface 22a is reflected as image light L3. The

Although the detailed description is omitted, the projection optical system 26 enlarges and projects an image obtained from the reflective liquid crystal element 23 that is an image display element onto a screen or other projection target (not shown). The projection optical system 26 includes a plurality of lens groups and / or reflecting surfaces, and focusing and zooming can be performed by moving some lens groups in the direction of the optical axis SX.

In the circuit unit 29, the video drive circuit 25 causes the reflective liquid crystal element 23 to perform a display operation based on video signals input from various content sources (not shown) including terminal devices such as computers. The light source driving circuit 27 causes the laser array 51 provided in the beam forming unit 31 of the light source device 21 to perform a lighting operation, and irradiates the light irradiation plate 35 that is a phosphor wheel with the laser light L1.

The control circuit 28 comprehensively controls operations of the video drive circuit 25, the light source drive circuit 27, and the like. The control circuit 28 operates the light source device 21 via the light source driving circuit 27 and emits the illumination light L2 therefrom, and outputs a driving signal corresponding to the video signal to the reflective liquid crystal element 23 via the video driving circuit 25. The image is displayed. At this time, the video drive circuit 25 monitors the rotational position of the light irradiation plate 35 via the drive unit 39, and sequentially from the light irradiation plate 35 as the light irradiation plate 35 rotates around the rotation axis RX. The reflective liquid crystal element 23 is made to display each color in synchronization with the emitted blue light, green light, and red light.

Hereinafter, the components, functions, operations, and the like of the light source device 21 will be described in detail with reference to FIG. 2A.

First, the beam forming unit 31 includes a laser array 51, a fly-eye optical system 52 that is a collimator array, and a beam reduction lens 53. Here, the laser array 51 is an excitation light source for the phosphor incorporated in the irradiated object 41 and also an illumination light source for blue. The laser array (excitation light source) 51 is configured by two-dimensionally arranging laser diodes 51a (hereinafter also referred to as LDs) as light emitting sources that emit blue laser light L1, and have a polarization direction. A uniform light is emitted. Since the laser array 51 includes a plurality of laser diodes 51a arranged in an array, a large amount of excitation light EL can be obtained while reducing the size of the light source. The laser light L1 is S-polarized blue light with the polarization separation element 32 as a reference. The fly-eye optical system 52 includes a large number of lens elements corresponding to a large number of LDs (light emitting sources) 51 a constituting the laser array 51. The fly's eye optical system 52 converts the laser light L1 (blue light) emitted from each LD (light emitting source) 51a constituting the laser array 51 into a substantially parallel light beam. The beam contraction lens 53 is an afocal system in which a positive lens and a negative lens are combined, and the laser beam L1 is reduced to a substantially parallel beam while reducing the beam diameter to obtain a laser beam L1 having a desired cross-sectional area.

The polarization separation element 32 shown in FIG. 2A is a flat plate-like optical element between the beam forming unit 31 and the light irradiation plate 35, which is between the optical paths between the laser array (excitation light source) 51 and the irradiated object 41, or It arrange | positions between the light irradiation board 35 and the equalization optical system 36, and isolate | separates the illumination light L2 from the optical path of excitation light EL. More specifically, the polarization separation element 32 functions as a normal polarization separation mirror that transmits P-polarized light and selectively reflects S-polarized light with respect to blue light, and selectively transmits green light and red light. It has a function as a dichroic mirror. The polarization separation element 32 is formed by forming a polarization separation surface 32a made of a dielectric multilayer film on one side of a parallel plate, reflects blue excitation light EL that is S-polarized light, and emits blue light from the irradiated object 41 side. The blue light which has been reversed and changed the polarization direction to become P-polarized light is transmitted and guided to the uniformizing optical system 36. Further, the polarization separation element 32 transmits the green and red fluorescent lights FL generated in the irradiated body 41 by the irradiation of the excitation light EL and traveling backward with respect to the excitation light EL, regardless of the polarization direction, and uniformizing the optical system. Lead to 36. As described above, the polarization separation element 32 reflects the blue light incident from the laser array 51 side as the excitation light EL and transmits the fluorescent light FL and blue light incident from the irradiated body 41 side as the illumination light L2. Thereby, arrangement | positioning of the to-be-irradiated body 41 grade | etc., Can be simplified. Further, the polarized light FL emitted from the irradiated body 41 by the polarization separation element 32 by excitation with the excitation light EL and the light obtained by reflecting the excitation light EL by the irradiated body 41 are used as illumination light L2. By separating from the optical path of the excitation light EL from the laser array 51 toward the irradiation object 41, the fluorescent light FL can be efficiently extracted without waste. Further, with this configuration, the object to be irradiated 41 can be a reflective type that uses the excitation light EL and the fluorescent light FL as the illumination light L2, and a simple and compact illumination optical system can be obtained.

Here, the polarization separation surface 32a provided in the polarization separation element 32 is arranged at an angle θ of 50 ° or more and 80 ° or less with respect to the optical axis SX of the illumination light L2 with reference to the normal line. In other words, the inclination angle φ of the polarization separation surface 32a of the polarization separation element 32 with respect to the optical axis SX is 10 ° or more and 40 ° or less. Although the details will be described later by setting the angle θ of the polarization separation surface 32a to 50 ° or more and 80 ° or less, the difference between the reflection wavelength of S-polarized light and the transmission wavelength of P-polarized light in blue can be increased. Even when there is a shift in the cutoff wavelength due to manufacturing variations of the element 32, or variations or changes in the light source wavelength, the separation of the excitation light EL and the illumination light L2 can be improved, and the light utilization efficiency can be increased. . On the other hand, the angle θ of the polarization separation surface 32a is more preferably set to 50 ° or more and 70 ° or less, and the size of the polarization separation surface 32a can be prevented from becoming too large compared to the light beam cross section of the illumination light L2. The apparatus 21 can be easily downsized. The polarization separation element 32 may be configured by a prism.

The retardation film 33 is a quarter wave plate made of a birefringent material. The phase difference plate 33 transmits the S-polarized excitation light EL reflected by the polarization separation element 32 to change from S-polarized light to circularly-polarized light. In addition, the phase difference plate 33 transmits blue light (that is, laser light L1 that has not been used as excitation light EL) returned from the irradiated object 41 side without being used for excitation, and changes from circularly polarized light to P-polarized light. As a result, the blue light that has returned from the irradiated object 41 side through the phase difference plate 33, that is, the laser light L <b> 1 that has not been used for excitation, passes almost through the polarization separation element 32, and efficiently enters the uniformizing optical system 36. Led. That is, by combining the polarization separation element 32 and the phase difference plate 33, the blue light can be efficiently used as the illumination light L2 while being used as the excitation light EL.

The condenser lens 34 condenses the laser light L1 reflected by the polarization separation element 32 on the irradiated body 41 of the light irradiation plate 35 as excitation light EL. The condenser lens 34 collects the green and red fluorescent lights FL generated by the phosphor of the irradiated body 41 and guides them to the polarization separation element 32. The condenser lens 34 also has a role of collecting the laser light L1 reflected by the scattering reflecting surface provided separately from the phosphor in the irradiated body 41 of the light irradiation plate 35, that is, blue light and guiding it to the polarization separation element 32. .

As shown in FIG. 2B, the light irradiation plate 35 is a phosphor wheel, and has a ring-shaped irradiation object 41 and a substrate 42 that supports it. The irradiated object 41 is provided with three regions AR1 to AR3. In the irradiated object 41, the green region AR1 emits the fluorescent light FL in the green wavelength region formed by the irradiation of the excitation light EL so as to run backward with respect to the excitation light EL. The red region AR2 emits the fluorescent light FL in the red wavelength region formed by the irradiation of the excitation light EL so as to run backward with respect to the excitation light EL. The blue region AR3 reflects the laser light L1 while slightly diffusing it.

Referring back to FIG. 2A, the laser light L1 emitted from the beam forming unit 31 and reflected by the polarization separation element 32 is incident on the green region AR1 or the red region AR2 in the irradiated body 41 of the light irradiation plate 35 as the excitation light EL. In this case, green or red fluorescent light FL, that is, illumination light L2 is generated. Further, when the laser beam L1 emitted from the beam forming unit 31 and reflected by the polarization separation element 32 is incident on the blue region AR3 of the irradiated body 41 of the light irradiation plate 35, it is reflected as it is as the blue illumination light L2. The That is, the illumination light L2 includes blue light that is the laser light L1 itself, in addition to the green and red fluorescent light FL obtained from the laser light L1.

Although not described in detail, the homogenizing optical system 36 shown in FIG. 1 includes a condenser lens 36a that condenses the illumination light L2 that has passed through the polarization separation element 32, and an illumination light L2 from the condenser lens 36a. And a light guide rod 36b for emitting light from one end as a light bundle having a uniform intensity distribution. The field lens 38 includes a plurality of lenses in the illustrated example, and is adjusted so that the illumination light L2 emitted from the other end of the light guide rod 36b is incident on the reflective liquid crystal element 23 at an appropriate convergence angle or divergence angle. To do.

Hereinafter, the adjustment of the angle of the polarization separation element 32 incorporated in the light source device 21 with respect to the optical axis SX and its significance will be described.

In the polarization separation surface 32a of the polarization separation element 32, the angle θ between the normal line and the optical axis SX is set to 45 ° in a normal usage. However, the inventors of the present application have confirmed that when the angle θ is 45 °, the efficiency of transmitting blue P-polarized light while reflecting blue S-polarized light tends to decrease. Therefore, in this embodiment, the angle θ with respect to the optical axis SX of the polarization separation element 32 is set to 50 ° to 80 °.

It should be noted that the optical axis of the laser beam L1 incident on the polarization separation element 32 from the beam forming unit 31 is an angle substantially coincident with the inclination angle θ (= 50 ° to 80 °) with respect to the polarization separation element 32. Is set to That is, the beam forming unit 31 and the light irradiation plate 35 are disposed symmetrically with the polarization separation element 32 interposed therebetween.

FIG. 3A is a graph showing the light transmission characteristics of a specific example incorporated as the polarization separation element 32 shown in FIG. Here, the angle θ between the normal line of the polarization separation surface 32a of the polarization separation element 32 and the optical axis SX is set to 60 °. In the graph, the horizontal axis indicates the wavelength of incident light, and the vertical axis indicates the transmittance. The solid line indicates the transmittance of S-polarized light, and the dotted line indicates the transmittance of P-polarized light. FIG. 3B is a graph showing the light transmission characteristics of the same polarization separation element 32 when the angle θ is set to 45 °. A one-dot chain line indicates the transmittance of S-polarized light, and a two-dot chain line indicates the transmittance of P-polarized light.

In FIG. 3A of the specific example, the separation wavelength width Δλ, which is the difference between the cutoff wavelength of the S-polarized light indicated by the solid line and the cutoff wavelength of the P-polarized light indicated by the dotted line, is 37 nm, whereas in FIG. Δλ is as narrow as 23 nm. From this, it can be seen that, when arranged at θ = 60 °, separation of S-polarized light and P-polarized light can be made more reliable than when arranged at a general θ = 45 °.

When the separation wavelength width Δλ is narrow as in the comparative example, for example, if the emission wavelength of the laser array 51 is wide and varies, either the reflectance of S-polarized light or the transmittance of P-polarized light deteriorates. Furthermore, even if the cutoff wavelength is shifted due to a manufacturing error of the polarization separation surface 32a, either the reflectance of S-polarized light or the transmittance of P-polarized light deteriorates. Here, it is not easy to narrow the emission wavelength width of the laser array 51 or reduce the variation. In addition, it is not easy to accurately control the cutoff wavelength of the polarization separation surface 32a, and if an attempt is made to accurately control it, an excessive increase in cost is caused.

In other words, by setting the angle θ to 50 ° to 80 °, even if there is a deviation or variation in the light emission wavelength of the light source and a manufacturing error of the polarization separation surface, it is possible to reliably maintain S-polarization and P-polarization while maintaining high efficiency. It is possible to separate them.

FIG. 4A is an enlarged view of the cutoff wavelength and its surroundings of FIGS. 3A and 3B. When the angle θ between the normal line of the polarization separation surface 32a of the polarization separation element 32 and the optical axis SX is increased from 45 ° to 60 °, the band DB satisfying 80% of the polarization separation efficiency is expanded. For example, it can be seen that in applications where polarized light is separated within a range of ± 10 nm with a center wavelength of 450 nm, when the angle θ is 45 °, the band DB is narrow and sufficient polarization separation may not be ensured. On the other hand, when the angle θ is 60 °, the band DB becomes wide, sufficient polarization separation can be secured, and light can be used efficiently.

FIG. 4B is a graph showing the relationship between the wavelength of P-polarized light having a polarization separation efficiency of 80%, the normal line of the polarization separation surface 32a of the polarization separation element 32, and the angle θ between the optical axes SX. FIG. 4C is a graph showing the relationship between the wavelength of the S-polarized light with the polarization separation efficiency of 80% and the angle θ. According to FIG. 4B, the wavelength corresponding to the P-polarized light separation efficiency of 80% gradually shifts to the short wavelength side as the angle θ increases, and according to FIG. 4C, the S-polarized light separation efficiency increases as the angle θ increases. The wavelength corresponding to 80% is gradually shifted to the long wavelength side. From the above, if the angle θ is larger than 45 ° and about 60 °, the wavelength difference between the P-polarized light separation efficiency of 80% and the S-polarized light separation efficiency of 80% can be increased to about 1.5 times or more, Loss of blue light, that is, light source light in the polarization separation element 32 can be reduced.

As described above, in the light source device 21 according to the first embodiment, the normal line of the polarization separation surface 32a of the polarization separation element 32 is arranged at an angle of 50 ° or more with respect to the optical axis SX of the illumination optical system. Therefore, a large separation wavelength width Δλ, which is the difference between the cutoff wavelengths of the S-polarized light and the P-polarized light, can be secured, and the separation between the excitation light EL and the illumination light L2 can be made sufficiently efficient. As a result, the light can be used efficiently, so that a bright light source having a simple and space-saving optical system can be provided.

[Second Embodiment]
The light source device according to the second embodiment will be described below. The light source device according to the second embodiment is a modification of the light source device according to the first embodiment, and matters not specifically described are the same as those in the first embodiment.

As shown in FIG. 5, the light source device 21 of the second embodiment has the reflection and transmission characteristics of the polarization separation element 32 reversed and the arrangement of the light irradiation plate 35 is changed. Specifically, the polarization separation element 32 functions as a polarization separation mirror that selectively transmits P-polarized light and reflects S-polarized light with respect to the laser light L1 that is blue light, and fluorescent light FL having a wavelength longer than that of blue. And a function as a dichroic mirror that selectively reflects green light and red light. That is, the polarization separation element 32 transmits the excitation light EL that is P-polarized light, and reverses the blue light from the irradiated object 41 side, changes the polarization direction, and changes to the S-polarized light, or the excitation light. The green and red fluorescent lights FL generated by the irradiated object 41 after being irradiated with EL are reflected and guided to the uniformizing optical system 36.

FIG. 6A is a graph showing the light transmission characteristics of a specific example incorporated as the polarization separation element 32 shown in FIG. Here, the angle θ between the normal line of the polarization separation surface 32a of the polarization separation element 32 and the optical axis SX is set to 60 °. In the graph, the solid line indicates the transmittance of S-polarized light, and the dotted line indicates the transmittance of P-polarized light. FIG. 6B is a graph showing the light transmission characteristics of the same polarization separation element 32 when the angle θ is set to 45 °. A one-dot chain line indicates the transmittance of S-polarized light, and a two-dot chain line indicates the transmittance of P-polarized light.

The separation wavelength width Δλ in the specific example shown in FIG. 6A is sufficiently wider than the separation wavelength width Δλ in the comparative example shown in FIG. 6B. Thus, for example, the blue P-polarized laser beam L1 having a wavelength of 450 nm is transmitted through the polarization separation element 32 with high efficiency and guided to the light irradiation plate 35, while being reflected by the light irradiation plate 35 and returned. The laser beam L1 that is S-polarized light can be almost reflected at the polarization separation element 32 with high efficiency and guided to the uniformizing optical system 36.

The light source device according to the embodiment has been described above, but the light source device according to the present invention is not limited to the above. For example, the specific configurations of the light source device 21, the projection optical system 26, and the like are not limited to those shown in the drawings, and can be changed as appropriate according to the application.

Further, as the image display element, a digital micromirror device (DMD) can be used instead of the reflective liquid crystal element 23. In this case, instead of the polarization beam splitter 22, a prism that guides illumination light to the DMD and guides the reflected light from the DMD to the projection optical system 26 may be disposed. Further, as the image display element, a transmissive liquid crystal element or a liquid crystal panel may be used instead of the reflective liquid crystal element 23.

In the beam forming unit 31, an LED array may be used instead of the laser array 51. At this time, it is desirable to align the polarization direction of the light from the LED array before entering the polarization separation element 32.

In the above embodiment, the green and red fluorescent lights FL are generated by the irradiated body 41 of the light irradiation plate 35, but only the green fluorescent light FL can be generated by the irradiated body 41. In this case, in order to enable display of the three primary colors, in the optical system of FIG. 1, for example, a dichroic mirror or the like can be incorporated at an appropriate position to guide the red light to the optical path of the illumination light L2, or the polarization separation element 32 A red light source is disposed on the opposite side of the beam forming unit 31 with the optical characteristics of the polarization separation element 32 being changed, and the red light is reflected by the polarization separation element 32 and guided to the optical path of the illumination light L2. .

For example, in the optical system of FIG. 1, a general polarization beam splitter can be used instead of the polarization separation element 32 having a function as a dichroic mirror. In this case, the specific polarization component (specifically, the S component) of the green and red fluorescent light FL is cut in advance by the polarization separation element 32.

The homogenizing optical system 36 is not limited to the one using the light guide rod 36b or the like, but may be one using a fly-eye lens or the like. In addition, a polarization conversion element that aligns the polarization directions of green and red fluorescence may be disposed before the light guide rod 36b provided in the homogenizing optical system 36, for example, between the condenser lens 36a and the light guide rod 36b. it can.

The reflective liquid crystal element 23 can be disposed on the opposite side of the projection optical system 26 with the polarization beam splitter 22 interposed therebetween by switching the reflection characteristics of the polarization beam splitter 22 or changing the arrangement relationship with the light source device 21. In this case, the polarization beam splitter 22 can reflect the illumination light L2 emitted from the light source device 21 so as to be incident on the reflective liquid crystal element 23 and transmit the image light L3 reflected by the reflective liquid crystal element 23. And can be incident on the projection optical system 26.

Claims

An excitation light source that emits excitation light;
An irradiated body that emits illumination light including fluorescent light upon irradiation with excitation light;
An illumination optical system for guiding illumination light emitted from the irradiated body;
A polarization separation element that is disposed between the excitation light source and the irradiation target and has a polarization separation surface that separates illumination light from the excitation light path by transmission and reflection; and
With
The polarization separation element is a light source device arranged such that an angle formed between a normal line of the polarization separation surface and an optical axis of the illumination optical system is 50 ° or more and 80 ° or less.
The light source device according to claim 1, wherein the polarization separation element is arranged such that an angle formed between a normal line of the polarization separation surface and an optical axis of the illumination optical system is 70 ° or less.
The polarization separation element is configured to emit fluorescence light emitted from the irradiated object by excitation with excitation light and light obtained by reflecting excitation light on the irradiated object from the excitation light source as illumination light. The light source device according to any one of claims 1 and 2, wherein the light source device is separated from an optical path of excitation light toward the irradiated body.
The excitation light source emits blue light as excitation light,
The irradiated object has a region that reflects blue light, and a region that emits fluorescent light in a visible range different from the blue light by excitation with blue light,
The polarization separation element is used in combination with a retardation plate, guides blue light, which is polarized light in a specific direction, from the excitation light source to the irradiated body, and is reflected by the irradiated body and polarized by the retardation plate. The light source device according to any one of claims 1 to 3, wherein the blue light and the fluorescent light whose directions are changed are guided to an optical path of illumination light, respectively.
The polarization separation element is a flat member that reflects blue light incident from the excitation light source side as excitation light and transmits fluorescent light and blue light incident from the irradiated body side as illumination light. 5. The light source device according to 4.
The light source device according to any one of claims 1 to 5, wherein the excitation light source has a plurality of light emission sources arranged in an array.
A light source device according to any one of claims 1 to 6;
An image display element illuminated by the light source device;
A projection optical system for projecting an image formed by the image display element;
A projection apparatus comprising: