Patent Grant
11442347
One disclosed aspect of the embodiments relates to a light source device and an image projection apparatus including the same.
As a light source device for a projector (an image projection apparatus), a light source device discussed in the publication of Japanese Patent Application Laid-Open No. 2018-124445 is known. The light source device discussed in the publication of Japanese Patent Application Laid-Open No. 2018-124445 includes a first rotating wheel having a wavelength conversion element, and a second rotating wheel having a diffusion element (diffuser). The light source device also includes a first blue laser diode (hereinafter, “blue LD”) from which blue light is emitted toward the first rotating wheel, and a second blue LD from which blue light is emitted toward the second rotating wheel.
In the light source device discussed in the publication of Japanese Patent Application Laid-Open No. 2018-124445, blue light emitted from the first blue LD is diffusely reflected by the first rotating wheel and converted into yellow light by wavelength conversion. Then, the yellow light is projected onto a screen through a liquid crystal panel at the subsequent stage. Blue light emitted from the second blue LD diffusely passes through the second rotating wheel and is projected as the blue light onto the screen through the liquid crystal panel at the subsequent stage.
In the light source device discussed in the publication of Japanese Patent Application Laid-Open No. 2018-124445, since two rotating members, namely the first and second rotating wheels, are disposed, two motors for rotating the two rotating wheels are also disposed. Accordingly, the light source device discussed in the publication of Japanese Patent Application Laid-Open No. 2018-124445 is large in size due to the two rotating wheels and the two motors. In a case where the light source device is large in size, the projector is also large in size, which is not desirable.
According to an aspect of the embodiments, a light source device includes a light source unit and a rotating wheel. The light source unit is configured to emit first blue light and second blue light. The rotating wheel includes a diffusion element configured to diffuse and transmit the first blue light, and a wavelength conversion element configured to convert at least a part of the second blue light into yellow light.
Further features of the disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
(Configuration of Projector)
With reference to
In a first exemplary embodiment, a projector illustrated in
White light emitted from the light source device 100 is projected onto a screen S after passing through the illumination optical system 110, the color separating/combining unit 120, and the projection lens 42.
The light source device according to each exemplary embodiment can be mounted on any projectors that can project an image onto the screen (projection target surface) S, including a front projector that projects an image from the front side of a screen and also a rear projector that projects an image from the back side of a screen.
The projection lens 42 may be an interchangeable lens that can be detached from the lens holding unit 420, or may be a fixed lens that cannot be detached from the lens holding unit 420.
(Configuration of Illumination Optical System 110)
The illumination optical system 110 includes a first lens array 14, a second lens array 15, a polarization conversion element 17, and a condenser lens 16 that are disposed in this order from the light source device 100.
The first lens array 14 includes a plurality of lens cells that is arranged in a matrix in a plane orthogonal to the optical axis of the illumination optical system 110 and divides light emitted from the light source device 100 into a plurality of beams.
The second lens array 15 includes a plurality of lens cells arranged in a matrix in a plane orthogonal to the optical axis of the illumination optical system 110. Each of the plurality of lens cells of the second lens array 15 corresponds to a different one of the plurality of lens cells of the first lens array 14. The second lens array 15 and the condenser lens 16 form images of the plurality of lens cells of the first lens array 14 near light modulation elements 40R, 40G, and 40B.
Between the second lens array 15 and the condenser lens 16, the polarization conversion element 17 is disposed. The polarization conversion element 17 is configured to align the polarization direction of the light emitted from the light source device 100 in a predetermined direction.
The condenser lens 16 condenses the plurality of divided beams passed through the second lens array 15 to superimpose the condensed light on the light modulation elements 40R, 40G, and 40B. That is, the first lens array 14, the second lens array 15, and the condenser lens 16 form an integrator optical system that uniformizes intensity distribution of light emitted from the light source device 100. The integrator optical system may be an optical system using a rod integrator.
(Configuration of Color Separating/Combining Unit 120)
The color separating/combining unit 120 includes a color separating/combining system and the light modulation elements 40R, 40G, and 40B. The color separating/combining system includes optical elements described below. In
White light passed through the illumination optical system 110 is separated by color separation using a dichroic mirror 21. The dichroic mirror 21 has the property of reflecting red light and transmitting blue light and green light.
(Optical Path of Red Light)
Red light reflected from the dichroic mirror 21 is reflected by a mirror 23 and is incident on the red-light light modulation element 40R after passing through a condenser lens 30R and an incident-side polarizing plate 31R. Based on information transmitted from an input device of a computer connected to the projector, the red-light light modulation element 40R modulates the incident red light. The red light modulated by the red-light light modulation element 40R is projected onto the screen S after passing through an emission-side polarizing plate 32R, a cross dichroic prism 41, and the projection lens 42. The cross dichroic prism 41 has a cube or cuboid shape including four right angle prisms bonded together. On the surfaces on which the prisms are bonded together, dichroic films as dielectric multilayer films are formed.
(Optical Path of Green Light)
Green light reflected from the dichroic mirror 21 is incident on a dichroic mirror 22. The dichroic mirror 22 has the property of reflecting green light and transmitting blue light. The green light reflected from the dichroic mirror 22 is incident on the green-light light modulation element 40G after passing through a condenser lens 30G and an incident-side polarizing plate 31G. Similarly to the red-light light modulation element 40R, based on information transmitted from the input device, the green-light light modulation element 40G also modulates the incident green light. The green light modulated by the green-light light modulation element 40G is projected onto the screen S after passing through an emission-side polarizing plate 32G, the cross dichroic prism 41, and the projection lens 42.
(Optical Path of Blue Light)
Blue light reflected from the dichroic mirror 21 is incident on the dichroic mirror 22. As described above, the dichroic mirror 22 has the property of reflecting green light and transmitting blue light. Thus, the blue light reflected from the dichroic mirror 21 passes through the dichroic mirror 22 and is incident on the blue-light light modulation element 40B after passing through a relay optical system, a condenser lens 30B, and an incident-side polarizing plate 31B. The “relay optical system” refers to a relay lens 26, a mirror 24, a relay lens 27, and a mirror 25.
Similarly to the red-light light modulation element 40R, based on information transmitted from the input device, the blue-light light modulation element 40B also modulates the incident blue light. The blue light modulated by the blue-light light modulation element 40B is projected onto the screen S after passing through an emission-side polarizing plate 32B, the cross dichroic prism 41, and the projection lens 42.
The red light, the green light, and the blue light are projected onto the screen S through the above optical paths, whereby a color image is displayed.
With reference to
Each of the first light source unit 1 and the second light source unit 2 is a set of blue laser diodes (LDs) (a blue LD bank) held by the same member, but may be a single blue LD (light-emitting device). More specifically, in the first, second, and third exemplary embodiments, the first light source unit 1 is a single blue LD bank, and the second light source unit 2 is two blue LD banks disposed close to (in contact with) each other. A single blue LD bank includes a total of eight blue LDs, eight collimator lenses for converting light diverging from the blue LDs into parallel light, and a holding member that holds the plurality of blue LDs and the plurality of collimator lenses. Then, on a base member B, the blue LD bank as the first light source unit 1 is disposed at a position away from the set of the two blue LD banks, the second light source unit 2. The base member B is a cooling member (a heat dissipation member) such as a heat sink or a heat pipe and has the function of cooling the light source units.
The number and the wavelength of blue LDs of the first light source unit 1 may be the same as or different from the number and the wavelength of blue LDs of the second light source unit 2. The wavelength of blue light emitted from a blue LD of each of the first light source unit 1 and the second light source unit 2 is 465 nm. Alternatively, a blue LD that emits blue light of 445 nm or 455 nm may be used. In the present exemplary embodiment, the number of blue LDs included in the first light source unit 1 is smaller than the number of blue LDs included in the second light source unit 2. Alternatively, the relationship between the numbers of blue LDs may be reversed, or the numbers of blue LDs may be the same.
The first light source unit 1 and the second light source unit 2 are both disposed on the base member B. The base member B includes a heat dissipation unit such as a plurality of fins for dissipating heat generated by the first light source unit 1 and the second light source unit 2. In the present exemplary embodiment, a plurality of light source units shares a single cooling member.
The first light source unit 1 and the second light source unit 2 may be distinguished from each other as follows. In a case where a plurality of blue LD banks is disposed on the base member B, a blue LD bank from which light is emitted toward a condenser lens (first condenser lens unit) 81 among the plurality of blue LD banks is the first light source unit 1. In a case where there is a plurality of blue LD banks from which light is emitted toward the condenser lens 81, the plurality of blue LD banks is the first light source unit 1. Similarly, a blue LD bank from which light is emitted toward a condenser lens unit (second condenser lens unit) 6 among the plurality of blue LD banks disposed on the base member B is the second light source unit 2. In a case where there is a plurality of blue LD banks from which light is emitted toward the condenser lens unit 6, the plurality of blue LD banks is the second light source unit 2.
(Optical Path of Blue Light Emitted from First Light Source Unit 1)
Blue light (blue parallel light) L3 emitted from the first light source unit 1 is reflected by a mirror 7 and condensed on the diffuser layer (diffusion element) 90C of a rotating wheel 9 by the condenser lens 81. In the present exemplary embodiment, the condenser lens 81 is a single positive lens. Alternatively, the condenser lens 81 may include a set of a plurality of lenses collectively having positive power.
As illustrated in
The phosphor layer 9B is formed by applying a product, which is obtained by uniformly mixing fine phosphor particles with a transparent resin binder, on the rotating plate 90A. The phosphor layer 9B, however, is not limited to the above configuration so long as incident light can be diffused to the extent that the diffused light can be properly used, and blue light can also be sufficiently converted into yellow light. For example, instead of the phosphor layer 9B, a quantum dot or a quantum rod may be used. In the present exemplary embodiment, the main material of the phosphor particles is based on yttrium aluminum garnet (YAG) and converts at least a part of blue light emitted from the second light source unit 2 into yellow light. As the main material of the quantum rod, cadmium selenide (CdSe) may be used.
In the present exemplary embodiment, since the diffuser layer and the phosphor layer are formed on the same rotating wheel, a single rotating wheel is disposed, and therefore a single rotation support mechanism and a single motor M for the rotating wheel are disposed. Thus, significant downsizing can be achieved in comparison with a configuration in which a wavelength conversion element and a diffusion element (diffuser) are formed on separate rotating wheels as in a conventional technique.
While the rotating plate 90A is made of a metal such as aluminum, the configuration is not limited to the above-described one so long as light incident on the phosphor layer 9B can be sufficiently reflected for use. While, according to the present exemplary embodiment, the phosphor layer 9B is disposed outside the diffuser layer 90C, the phosphor layer 9B may be disposed at the inner side with respect to the diffuser layer 90C.
While, in the present exemplary embodiment, the diffuser layer 90C is diffusion glass, the configuration is not limited to the above-described one so long as incident light can be diffused to the extent that the diffused light can be properly used. For example, the diffuser layer 90C may be formed by pouring a product, which is obtained by uniformly mixing fine diffusing particles with a transparent resin binder, into the penetration portion of the rotating plate 90A, and then curing the poured product.
The rotating plate 90A may not be made of a metal, and may be made of a resin or glass. In a case where the rotating plate 90A is made of a resin or glass and is transparent, the diffuser layer 90C may be formed by applying a product, which is obtained by uniformly mixing fine diffusing particles with a transparent resin binder, on the rotating plate 90A. Annular metal coating (a reflecting portion) may be applied on the surface of the rotating plate 90A, and the phosphor layer 9B may be disposed on the metal coating. On the phosphor layer 9B, light is reflected by the metal coating and the reflected light is guided to the illumination optical system 110.
The blue light, passed through the condenser lens 81, incident on the diffuser layer 90C passes through the diffuser layer 90C while being diffused by the diffuser layer 90C. The blue light passes through the diffuser layer 90C is converted into parallel light by a collimator lens unit 8, and travels to a mirror 10. While, in the present exemplary embodiment, the collimator lens unit 8 is composed of two positive lenses, the collimator lens unit 8 may be composed of a single positive lens or a set of three or more lenses collectively having positive power.
Diffused light L4 passed through the collimator lens unit 8 is reflected on the mirror 10 and incident on a dichroic mirror (first dichroic mirror or first combining element) 5.
(Optical Path of Blue Light Emitted from Second Light Source Unit 2)
Blue light (blue parallel light) L1 from the second light source unit 2 is compressed by a positive lens 50 and a negative lens 51 and converted into parallel light having a smaller diameter. That is, the positive lens 50 and the negative lens 51 are included in an afocal optical system (a first afocal lens unit). By compressing the blue light L1 into parallel light having a smaller diameter, the diameters of the negative lens 51 and optical elements can be downsized. The configuration of the afocal optical system is not limited to the combination of the positive lens 50 and the negative lens 51. The configuration of the afocal optical system may be, for example, a set of three or more lenses so long as the afocal optical system can compress the blue light L1 into parallel light having a small diameter. Between the positive lens 50 and the negative lens 51, a mirror 3 is disposed to bend the optical path by 90 degrees.
The blue light L1 passed through the negative lens 51 is incident on a microlens array 52. The microlens array 52 is an optical element in which a plurality of lens cells is arranged in a matrix on its incident side and emission side. The blue light L1 from the negative lens 51 is divided into a plurality of partial beams by the microlens array 52, and the plurality of partial beams is superimposed on the phosphor layer 9B by the condenser lens unit (second condenser lens unit) 6. As a result, spots having shapes similar to those of the lens cells on the incident side of the microlens array 52 are formed on the phosphor layer 9B.
Since the dichroic mirror 5 has the property of transmitting blue light as described above, the blue light passed through the microlens array 52 passes through the dichroic mirror 5 and is incident on the phosphor layer 9B through the condenser lens unit 6. Instead of the microlens array 52, a rod integrator or, for example, a light diffusion element having a concavo-convex structure may be used.
While, in the present exemplary embodiment, the condenser lens unit 6 is composed of two positive lenses, a single positive lens or a set of a plurality of lenses may be used instead of the condenser lens unit 6 so long as the set of a plurality of lenses collectively has positive power.
The blue light passed through the condenser lens unit 6 and incident on the phosphor layer 9B is converted into yellow light L2 by the above-described phosphor particles, and the yellow light L2 is reflected by the rotating plate 90A and incident on the condenser lens unit 6. While the yellow light L2 from the phosphor layer 9B is emitted in a random direction without determining the direction of the yellow light L2, the yellow light L2 is converted into parallel light by the condenser lens unit 6, reflected by the dichroic mirror 5, and guided to the illumination optical system 110. Consequently, the light source device 100 can emit blue light and yellow light, i.e., white light. Since both the diffuser layer 90C and the phosphor layer 9B are formed on the rotating plate 90A, a light source device can be downsized more significantly than in a conventional technique.
(Settings of Optical Systems)
Specific examples of optical systems are described.
The focal length of the collimator lens unit 8 is f1, and the focal length of the condenser lens unit 6 is f2. In this case, the light source device 100 satisfies the following inequalities:
1.2≤f1/f2≤10 (1)
and
2.0≤f1/f2≤6.0 (1a)
In the present exemplary embodiment, f1/f2=4.0. It is, however, not essential to satisfy both conditional inequalities (1) and (1a). For example, in a case where the projector has room inside, a light source device satisfying f1/f2=1.5 may be mounted on the projector.
Conditional inequalities (1) and (1a) mean that the focal length f1 is greater than the focal length f2, i.e., the power of the collimator lens unit 8 is weaker than the power of the condenser lens unit 6. The effects obtained by the light source device 100 satisfying the conditional inequality (1) or (1a) are described with reference to
As can be seen from the comparison between
In the present exemplary embodiment, the focal length f1 is made great to make the diameter D1 large. This reduces the difference between the diameters D1 and D2, whereby occurrence of the above-described color unevenness is reduced. In a case where the focal length f2 is too great, the condenser lens unit 6 becomes large as illustrated in
The diffusion angle of the diffuser layer 90C is Φ. In this case, the light source device 100 satisfies the following inequalities:
1°≤Φ≤30° (2)
and
1°≤Φ≤15° (2a)
In the present exemplary embodiment, Φ=10°. It is, however, not essential to satisfy both conditional inequalities (2) and (2a). For example, in a case where the projector has room inside, a light source device satisfying Φ=20° may be mounted on the projector. The diffusion angle Φ may be measured as follows. A measurement position may be set at a position corresponding to half the distance in the direction of the optical axis of the collimator lens unit 8 between the surface of the diffuser layer 90C (or the surface of the rotating plate 90A) and the vertex on the surface of the collimator lens unit 8 closest to the rotating wheel 9. The illuminance distribution of light emitted from the diffuser layer 90C at the measurement position may be measured, and the full width at half maximum of the illuminance distribution may be calculated. Then, the angle between a total of three points including two points corresponding to end portions of the full width at half maximum and the center point of the diffuser layer 90C in the radial direction may be set as the diffusion angle Φ.
Conditional inequalities (2) and (2a) mean that the diffusion angle Φ of the diffuser layer 90C is not too small and not too great. The effects obtained by the light source device 100 satisfying conditional inequality (2) or (2a) are as follows.
In a case where the diffusion angle Φ is so small as to deviate from the lower limit of conditional inequality (2), this means that light emitted from a blue LD included in the first light source unit 1 is not sufficiently diffused by the diffuser layer 90C. In a case where the light emitted from the blue LD that is laser light having coherence is not sufficiently diffused, speckle noise (an unnecessary pattern such as a light and dark speckled pattern) is likely to be visually recognized on the screen S. Conversely, in a case where the diffusion angle Φ is so great as to deviate from the upper limit of conditional inequality (2), this means that the light emitted from the blue LD included in the first light source unit 1 is excessively diffused by the diffuser layer 90C. In a case where the light emitted from the blue LD is excessively diffused by the diffuser layer 90C, the above speckle noise is reduced, but the light emitted from the diffuser layer 90C spreads more than the case described in the present exemplary embodiment. As a result, loss occurs due to a part of the blue light emitted from the diffuser layer 90C not incident on the collimator lens unit 8, or there is no choice but to make the diameter of the collimator lens unit 8 large.
As described above, the diffusion angle Φ is set so that the light source device 100 satisfies conditional inequalities (2) and (2a). Accordingly, speckle noise is reduced, upsizing of the collimator lens unit 8 and the light source device 100 is prevented, and the loss of light is reduced.
As illustrated in
As illustrated in
(Variations)
As illustrated in
Instead of the rotating wheel 9, a rotating wheel 90 illustrated in
Instead of the condenser lens 81, a condenser lens 82 illustrated in
With reference to
(Optical Path of Blue Light Emitted from First Light Source Unit 1)
The optical path of blue light emitted from the first light source unit 1 according to the present exemplary embodiment is described. Blue light (parallel light) L3 emitted from the first light source unit 1 is incident on the diffuser layer 90C after passing through the condenser lens 81. Diffused light L4 from the diffuser layer 90C is converted into parallel light by a collimator lens 83 and incident on a dichroic mirror (second dichroic mirror or second combining element) 54. The dichroic mirror 54 has the property of reflecting blue light and transmitting infrared (IR) light. Thus, the blue light L4 from the collimator lens 83 is reflected by the dichroic mirror 54 and incident on an afocal optical system (second afocal lens unit) 84. The afocal optical system 84 is configured to enlarge the diameter of parallel light incident on the afocal optical system 84 and includes at least one negative lens and at least one positive lens. Thus, the blue light L4 from the dichroic mirror 54 is enlarged by the afocal optical system 84 and incident on a dichroic mirror (first dichroic mirror or first combining element) 53.
(Optical Path of Blue Light Emitted from Second Light Source Unit 2)
The optical path of blue light emitted from the second light source unit 2 is similar to that in the first exemplary embodiment except that the blue light passes through the dichroic mirror 53 instead of the dichroic mirror 5, and therefore the redundant description is omitted here.
(Optical Path of IR Light Emitted from Third Light Source Unit 55)
The third light source unit 55 includes a light-emitting device, such as an LD, that emits IR light (near-infrared light) having a wavelength of 750 nm or more, and a collimator lens that converts light diverging from the light-emitting device into parallel light. IR light L5 from the third light source unit 55 passes through the dichroic mirror 54 and is enlarged by the afocal optical system 84. Then, the IR light L5 from the afocal optical system 84 passes through the dichroic mirror 53 and is guided to the illumination optical system 110.
As described above, the light source device 200 can also emit IR light in addition to white light.
In a case where the light source device 101 is mounted on the projector illustrated in
With reference to
(Optical Path of Blue Light Emitted from First Light Source Unit 1)
The optical path of blue light emitted from the first light source unit 1 is similar to that in the first exemplary embodiment, and therefore the redundant description is omitted here.
(Optical Paths of Blue Light Emitted from Second Light Source Unit 2 and Fourth Light Source Unit 60)
In the first and second exemplary embodiments, the blue light L1 from the second light source unit 2 is s-polarized light. In the present exemplary embodiment, the blue light L1 is p-polarized light. Thus, the blue light L1 from the second light source unit 2 passes through a polarization beam splitter (PBS) (polarized light separating element or third combining element) 61. As illustrated in
Similarly to the second light source unit 2, the fourth light source unit 60 includes a plurality of blue LD banks, but blue light (third blue light) L6 from the fourth light source unit 60 is s-polarized light. Thus, the blue light L6 reflected on the mirror 10 is reflected by the PBS 61 and meets the blue light L1, and the resulting light proceeds along an optical path similar to that of the blue light L1 in the first exemplary embodiment.
As described above, in the present exemplary embodiment, blue light more than in the first exemplary embodiment can be incident on the phosphor layer 9B. Consequently, a brighter image can be projected.
Alternatively, the polarization direction of the blue light emitted from the fourth light source unit 60 may be made the same as the polarization direction of the blue light emitted from the second light source unit 2, and a half-wave plate may be disposed on the optical path from the fourth light source unit 60 to the PBS 61.
(Variations)
The first light source unit 1 and the second light source unit 2 according to each of the above exemplary embodiments may be integrally configured. For example, blue light emitted from a single light source unit may be separated into blue light (first blue light) L3 and blue light (second blue light) L1 by a half mirror (a separating element).
On the optical path from each of the above light source units to the rotating wheel 9, an optical element different from the optical elements illustrated in the figures may be disposed. For example, prism mirrors PM illustrated in
While the disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2019-131061, filed Jul. 16, 2019, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-131061 | Jul 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20140211170 | Kitano | Jul 2014 | A1 |
| 20180188640 | Huang | Jul 2018 | A1 |
| Number | Date | Country |
|---|---|---|
| 2012-137608 | Jul 2012 | JP |
| 2018-054780 | Apr 2018 | JP |
| 2018-087839 | Jun 2018 | JP |
| 2018-124445 | Aug 2018 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20210018822 A1 | Jan 2021 | US |
