The present invention relates to a light source device.
In this technical field, a light source device which converts excitation light emitted from a fixed light source into visible light with a phosphor to efficiently emit light is provided. PTL 1 discloses a configuration which irradiates excitation light (blue laser light) emitted from a light source on a disk-like (phosphor wheel) on which a phosphor is formed to cause the disk-like wheel to emit a plurality of fluorescent lights (red light and green lights) and uses the fluorescent lights as illumination light.
PTL 1: Japanese Patent Application Laid-Open No. 2011-13313
According to PTL 1, excitation light transmitted through a transparent portion of the phosphor wheel and fluorescent light generated by the phosphor wheel are used as illumination light. However, both the lights are emitted in opposite directions with respect to the phosphor wheel. Thus, the number of optical components for combining the lights to each other increases to disadvantageously increase the light source device in size. An optical loss is caused by the plurality of optical components arranged in an optical system to disadvantageously decrease efficiency of utilizing light (illumination light intensity).
It is an object of the present invention to provide a light source device which causes a phosphor wheel to emit diffused excitation light and fluorescent light to the same side of the phosphor wheel, collects both the lights with a simple configuration, and uses the collected light as illumination light.
In order to solve the above problem, one of desirable aspects of the present invention is as follows.
The light source device includes an excitation light source which generates excitation light, a phosphor wheel having a phosphor which is excited by the excitation light from the excitation light source to generate fluorescent light, and a mirror which guides the excitation light from the excitation light source to the phosphor wheel and emits the fluorescent light from the phosphor wheel as illumination light, the phosphor wheel further including a diffusion/reflection portion which diffuses and reflects incident excitation light, and the mirror having a first region which reflects the excitation light and transmits the fluorescent light and a second region which transmits the fluorescent light and the diffused excitation light diffused and reflected by the diffusion/reflection portion.
According to the present invention, since the phosphor wheel is caused to emit the diffused excitation light and the fluorescent light to the same side, a small-sized light source device can be achieved without decreasing an illumination light intensity.
Embodiment of the present invention will be described below with reference to the accompanying drawings.
The mirror 4 is configured by two regions. The first region is a dichroic coat region 21 characterized by reflection of a wavelength band of excitation light (blue) and transmission of wavelength bands (red, yellow, and green) fluorescent light. The second region is a wide-wavelength transmission region 22 which transmits both the wavelength bands of excitation light and fluorescent light. The first region has an area smaller than that of the second region. A concrete example of the mirror 4 will be described with reference to
On the rotatable phosphor wheel 1, a phosphor 2 which is excited with the excitation light 10 to generate fluorescent light of a predetermined color is formed. For example, in order to generate fluorescent lights of three colors, e.g., red, yellow, and green, a disk surface is circumferentially divided into a plurality of regions, and red, yellow, and green phosphors are formed on the regions, respectively. Furthermore, on the disk surface, a diffusion/reflection portion which diffuses and reflects the excitation light 10 is formed. A concrete example of the phosphor wheel 1 will be described with reference to
The fluorescent light being incident on the mirror 4 is transmitted through both the dichroic coat region 21 and the wide-wavelength transmission region 22 in the mirror 4. On the other hand, the diffused excitation lights being incident on the mirror 4 are reflected by the dichroic coat region 21 but transmitted through the wide-wavelength transmission region 22. As a result, all the fluorescent lights and most of the diffused excitation lights are emitted as illumination light 11 downward in the drawing.
With this configuration, both the fluorescent lights and the diffused excitation lights generated by the phosphor wheel 1 are emitted from the phosphor wheel 1 to the same side (lower side in the drawing), and most of the fluorescent lights and the diffused excitation lights are transmitted through the mirror 4 and serve as illumination light. Thus, an additional optical system to combine both the fluorescent light and the excitation light need not be disposed, and a reduction in size of the device can be achieved.
In
On the other hand, the fluorescent lights and the diffused excitation lights generated by the phosphor wheel 1 are enlarged into spots 26 (broken lines) and incident on the incident surface of the mirror 4a. Of the fluorescent lights and the diffused excitation lights, all the fluorescent lights in the spots 26 are transmitted through the mirror 4 to serve as illumination light. Some of the diffused excitation lights being incident on the dichroic coat regions 21 cannot be transmitted through the dichroic coat region 21 to cause an optical loss of illumination light. However, most of the diffused excitation lights being incident on the large-area wide-wavelength transmission region 22 are transmitted through the wide-wavelength transmission region 22 to serve as illumination light.
In
The optical loss of illumination light in the dichroic coat region 21 depends on the area of the dichroic coat region 21. According to a simulation, the area of the dichroic coat 21 is reduced to, for example, 3% or less of the area of the incident spots 26 to make it possible to suppress the optical loss to an optical loss almost equal to that in PTL1 1.
In this manner, in each of the mirrors 4a and 4b according to the embodiment, the dichroic coat regions 21 are selectively formed in the wide-wavelength transmission region 22 to make it possible to reflect the excitation lights 10 from the excitation light source 5 to guide the excitation lights 10 to the phosphor wheel 1 and to make it possible to transmit the diffused excitation lights from the phosphor wheel 1 to use the diffused excitation lights as illumination light.
On the other hand, the diffused excitation lights from the diffusion/reflection portion 34 of the phosphor wheel 1 are emitted in a semi-spherical shape on the condenser lens 3 side. However, the degree of diffusion (diffusion angel θ) can be adjusted by materials of the diffusion plate, processing the diffusion plate, or the like. At this time, when the diffusion angles θ of the diffused excitation lights to be emitted are made excessively large, the diffused excitation lights leak out of the effective area of the condenser lens 3 to deteriorate the efficiency of utilizing light. In contrast to this, the diffusion angles θ are made excessively small, the diffused excitation lights pass through only the central portion of the effective area of the condenser lens 3. As a result, a ratio of diffused excitation lights being incident on the dichroic coat region 21 of the mirror 4 are relatively large, and an optical loss of the diffused excitation lights serving as the illumination light increases. Thus, the diffused excitation lights from the diffusion/reflection portion 34 preferably have the diffusion angles θ which are adjusted such that the diffused excitation lights are diffused in a size almost equal to that of the effective area of the condenser lens 3 and incident on the condenser lens 3.
A combination between the colors of the excitation lights and the colors of the phosphors, the number of segments, and the shapes (angles) of the segments are not limited to those in the above example, and may be arbitrarily changed depending on the specifications of required illumination light. For example, a yellow phosphor can be removed from the phosphor wheel while blue laser light is generated from the excitation light source to generate red and green fluorescent lights, or phosphors of other colors such as cyan and magenta can also be added to the above phosphors.
A second embodiment describes that a positional relationship between the phosphor wheel 1 and the excitation light source 5 is changed.
The excitation lights 10 being incident from the excitation light source 5 are transmitted through the dichroic coat region 21 of the mirror 4′, collected by the condenser lens 3, and incident on the phosphor wheel 1. When the phosphor wheel 1 receives the excitation lights 10, the phosphors 2 of the phosphor wheel 1 generate fluorescent lights of three colors, i.e., red, yellow, and green, and diffused excitation lights are generated from the diffusion/reflection portion. The fluorescent lights and the diffused excitation lights are converted into nearly parallel light rays with the condenser lens 3, and the nearly parallel light rays are incident on the mirror 4′.
The fluorescent lights being incident on the mirror 4′ are reflected both the regions, i.e., the dichroic coat region 21 and the wide-wavelength transmission region 22 in the mirror 4′. On the other hand, the diffused excitation lights being incident on the mirror 4′ are transmitted through the dichroic coat region 21, but reflected by a wide-wavelength reflection region 42. As a result, all the fluorescent lights and most of the diffused excitation lights are emitted to the left in the drawing as the illumination light 11.
With this configuration, both the fluorescent lights and the diffused excitation lights generated by the phosphor wheel 1 are emitted from the phosphor wheel 1 to the same side (lower side in the drawing), and most of the fluorescent lights and the diffused excitation lights are transmitted through the mirror 4′ and serve as illumination light. Thus, an additional optical system to combine both the fluorescent light and the excitation light need not be disposed, and a reduction in size of the device can be achieved.
Optical axis adjustment in the first and second embodiments is described here. In the light source device according to each of the embodiments, excitation light emitted from the excitation light source 5 must be reflected by a predetermined region (dichroic coat region 21) of the mirror 4 and collected on a specific position (phosphor 2) of the phosphor wheel 1. Thus, a mechanism for adjusting an error caused by misalignment of an emission position and an emission direction, resulting from the excitation light source 5, is disposed.
When the excitation light source 5 and the collimate lens 6 make an integrated structure, with respect to misalignment of the emission position and the emission direction, adjustment is performed such that the excitation light source 5 and the collimate lens 6 are integrally moved in a direction perpendicular to the optical axis. When the excitation light source 5 and the collimate lens 6 are formed as independent structures, respectively, with respect to misalignment of the emission position and the emission direction, adjustment is performed such that only the collimate lens 6 is moved in a direction perpendicular to the optical axis. With the adjusting mechanism, excitation light emitted from the excitation light source 5 can be reliably collected on a specific position of the phosphor wheel 1 through the mirror 4, and an illumination light intensity can be prevented from being decreased.
In a third embodiment, an example in which the light source device according to each of the embodiments is applied to a projection type video display device will be described.
The illumination lights (fluorescent light and diffused excitation light) 11 transmitted through the mirror 4 in the light source device 100 are collected by a condenser lens 57 and then incident on a dichroic mirror 58. The dichroic mirror 58 is characterized by transmission of green light (to be referred to as G light hereinafter) and blue light (to be referred to as B light hereinafter) and reflection of red light (to be referred to as R light hereinafter). Thus, the G light and the B light are transmitted through the dichroic mirror 58 and incident on a multiple reflection element 59. In this embodiment, in order to compensate for a luminous flux of the R light, a red light source 51 is disposed. The R light emitted from the red light source 51 becomes nearly parallel light in a collimate lens 53, collected by a condenser lens 56, reflected by the dichroic mirror 58, and incident on the multiple reflection element 59.
The R light, the G light, and B light being incident on the multiple reflection element 59 are reflected in the multiple reflection element 59 twice or more to obtain light having a uniform illuminance distribution. The R light, the G light, and the B light emitted from an emission aperture of the multiple reflection element 59 are transmitted through a condenser lens 60, reflected by a reflection mirror 61, and irradiated on a video display element 62 at a uniform illuminance distribution.
The video display element 62 employs a system which uses, for example, a digital mirror device (DMD named by Texas Installments) and time-divisionally irradiates the R light, the G light, and the B light thereon. The excitation light source 5 and the red light source 51 are solid-state light-emitting elements having high response speeds, and can be time-divisionally controlled. Thus, each of the color lights are time-divisionally modulated in units of colors by the video display element 62. The color lights reflected by the video display element 62 serve as video lights, and the video lights are incident on a projection lens 63, and projected on a screen (not shown).
The brightness of a specific color is secured by using the red light source 51 besides light source device 100 here. However, a configuration which uses only the light source device 100 without using the red light source 51 can also be effected. In this case, the dichroic mirror 58 may be removed, color lights emitted from the phosphor wheel 1 may be used, and the video display element 62 may be operated in synchronism with the color lights. Furthermore, the light source device 100′ according to the second embodiment (
The projection type video display device according to the embodiment uses a compact light source device which has a small size and a small optical loss of illumination light to contribute to a reduction in size and improvement in performance of the projection type video display device.
A fourth embodiment is another example of the projection type video display device and has a configuration using liquid crystal panels corresponding to three colors (R, G, and B) as a video display element.
The color separation optical system separates illumination light emitted from the light source device 100 into R light, G light, and B light, and guides the R light, the G light, and the B light to the liquid crystal panels corresponding to the color lights, respectively. The B light is reflected by the dichroic mirror 72 and incident on a B-light liquid crystal panel 82 through a reflection mirror 73 and a field lens 79. The G light and the R light are transmitted through the dichroic mirror 72 and then separated by a dichroic mirror 74. The G light is reflected by the dichroic mirror 74, transmitted through a field lens 80, and incident on a G-light liquid crystal panel 83. The R light is transmitted through the dichroic mirror 74 and incident on an R-light liquid crystal panel 84 through relay lenses 77 and 78, reflection mirrors 75 and 76, and a field lens 81.
The liquid crystal panels 82, 83, and 84 modulate the incident color lights depending on video signals, respectively, to form optical images of the color lights. The optical images of the color lights are incident on a color combining prism 85. In the color combining prism 85, a dichroic film which reflects the B light and a dichroic film which reflects the R light are formed in an nearly X shape. The B light and the R light being incident from the liquid crystal panels 82 and 84 are reflected by the B-light dichroic film and the R-light dichroic film, respectively. The G light being incident from the liquid crystal panel 83 is transmitted through the dichroic films. As a result, the optical images of the color lights are combined to each other and emitted as color video light. The combined light emitted from the color combining prism 85 is incident on the projection lens 86 and projected on a screen (not shown).
Also in the projection type video display device according to the embodiment, a compact light source device having a small size and a small optical loss of illumination light is used to contribute to a reduction in size and improvement in performance of the projection type video display device.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2013/055253 | 2/27/2013 | WO | 00 |