JP4382434B2 - Polarized light source device for projection display device - Google Patents

Description

  The present invention relates to a light source device for a projection display device, and more particularly to a polarized light source device.

  Currently, a projection display device is known as an electronic device that allows users to easily enjoy images on a large screen. A projection display device is a device that uses a white light source to enlarge and project an image generated on a two-dimensional light modulator such as a liquid crystal panel or DMD (digital mirror device) onto a screen using a projection lens. As a light source, a high-intensity discharge lamp such as a high-pressure mercury lamp or a metal halide lamp is generally used. However, these discharge lamps have emission spectral characteristics ranging from wavelengths of 400 nm to over 700 nm. For this reason, in the projection display apparatus, wavelength regions corresponding to R (red), G (green), and B (blue) are selected and used by optical parts such as a dichroic filter, and are necessary for this image formation. The light having a non-wavelength component causes heat generation in the light in the infrared region, and causes problems such as damage to the two-dimensional optical modulator in the light in the ultraviolet region. Furthermore, even in the case of light in the visible light utilization region, the wavelength region of the yellow component is not selected by a dichroic filter or the like, and is a loss in terms of light utilization efficiency. Furthermore, the life of discharge lamps that have been put into practical use is about 1500 to 4000 hours, and improvement of life characteristics is desired for widespread use for consumer use.

  On the other hand, in order to respond to the demand for improving the life characteristics, a proposal has been made to configure a projection display device using a laser that is a solid light source as a light source (see Patent Document 1).

As a projection display device using a light emitting diode as a light source, a device disclosed in Patent Document 2 is known.
JP-A-5-210082 JP 2002-244212 A

  However, solid-state light sources such as semiconductor lasers and light-emitting diodes have a major problem that their light output is lower than that of discharge lamps, and this is the main cause of their practical application as light sources for projection display devices. It was inhibited. Recently, however, there has been remarkable progress in the development of light-emitting diodes (LEDs), and high-brightness and high-efficiency blue and green LEDs have begun to appear. The possibility of realizing a light source for a projection display device has come out. In particular, since light emitting diodes are less expensive than semiconductor lasers, the overall cost of the projection display device can be expected to be reduced. Thus, it is a very promising light emitting diode as a light source for a projection display device. However, when the two-dimensional light modulator is a liquid crystal panel, about half of the light is emitted because the emitted light is non-polarized light. Since it cannot be used for image display and is lost, it is necessary to unify the types of polarized light and use it as illumination light. In Patent Document 2, the types of polarized light are unified using a polarization conversion element array using a polarization beam splitter and a half-wave plate. The polarizing beam splitter is a substrate-like substrate in which a large number of two prisms each having a dielectric multilayer film formed on the bonding surface are bonded in a lattice shape, and is made of optical glass and is an expensive optical device that requires advanced bonding technology. Since it is an element, it is not preferable for realizing a low-cost projection display device.

  An object of the present invention is to provide a polarized light source device for a projection display device in which the types of polarization of non-polarized light are efficiently unified without using a prismatic glass polarizing beam splitter.

  The polarized light source device of the projection display device of the present invention includes a light source unit that generates non-polarized light, and a polarization forming unit that generates linearly polarized light from the non-polarized light emitted from the light source unit.

The polarization forming means includes an ellipsoidal reflecting mirror, a quarter-wave plate, a reflective polarizing element, and a planar reflecting mirror. The ellipsoidal reflecting mirror includes a first focal point inside the ellipsoidal reflecting mirror. And a second focal point where reflected light from the ellipsoidal reflecting mirror of the projection light from the first focal point is defined outside the ellipsoidal reflecting mirror, and the light source section is defined by the holding means. The plane reflecting mirror is arranged along the axis of the ellipsoidal reflecting mirror so that the surface opposite to the reflecting surface is close to the light source unit, and the quarter wave plate and the reflective type The polarizing element is arranged in the vicinity of the second focal point so that one surface of the quarter-wave plate is close to each other and faces the opening of the ellipsoidal reflecting mirror, and the non-polarized light emitted from the light source unit is elliptical. Reflected by the surface reflecting mirror, converged toward the second focal point of the ellipsoidal reflecting mirror, and after reaching the ¼ wavelength plate, ¼ wave Passes through the plate and incident on the reflective polarizing element, the incident light other than the predetermined linearly polarized light with the said reflective polarizing element passing only predetermined linearly polarized light as illumination light is reflected as reflected light, the reflected The light passes through an ellipsoidal reflecting mirror, a plane reflecting mirror, and a quarter-wave plate, becomes a predetermined linearly polarized light, and enters the reflective polarizing element again, and the reflective polarizing element passes as illumination light. It is characterized by.

The polarization forming means includes an ellipsoidal reflecting mirror, a quarter-wave plate, a reflective polarizing element, and a planar reflecting mirror, and the ellipsoidal reflecting mirror includes a first inner part of the ellipsoidal reflecting mirror. And a second focus on which the reflected light from the ellipsoidal reflecting mirror of the projection light from the first focus is focused outside the ellipsoidal reflecting mirror, The planar reflecting mirror is held along the axis of the ellipsoidal reflecting mirror so that the surface opposite to the reflecting surface is close to the light source unit so as to be positioned near the first focal point, The reflective polarizing element is arranged in the vicinity of the second focal point so that one surface of the reflective polarizing element faces the opening of the ellipsoidal reflecting mirror, and the quarter wavelength plate is close to the reflecting surface of the flat reflecting mirror. are arranged Te, unpolarized light emitted from the light source unit is incident on the reflective polarizing element becomes convergent light by the ellipsoidal reflector The reflective polarizing element transmits only predetermined linearly polarized light as illumination light and reflects incident light other than the predetermined linearly polarized light as reflected light. The reflected light is an ellipsoidal reflecting mirror, a plane reflecting mirror, And, it is characterized in that it becomes predetermined linearly polarized light through a quarter-wave plate and is incident again on the reflective polarizing element, and the reflective polarizing element is allowed to pass as illumination light.

The holding means of the light source unit is a plane reflecting mirror, and the plane reflecting mirror is a flat substrate on which the light source unit is supported, and the side that is the back side of the substrate supporting the light source unit is reflected. Mirror surface processing may be performed so as to be a surface.

  The light source unit is preferably a light emitting diode, and the light emission color of the light emitting diode is one of red, blue, green, and white.

  The polarized light source device according to the present invention can efficiently unpolarize light into linearly polarized light, and can use a reflective flat plate-shaped polarizing element instead of an expensive polarizing beam splitter. And a compact polarized light source device for a projection display device can be provided. By using non-polarized light generated by a light emitting diode which is a very inexpensive light source, there is an effect that the cost can be further reduced.

(First embodiment)
A first embodiment of a polarized light source device of a projection display device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional side view showing the configuration of the polarized light source device according to the first embodiment of the present invention. In FIG. 1, the ellipsoidal reflecting mirror 12 is shown as a cross section. The polarized light source device 10 according to the first embodiment of the present invention includes a light emitting diode 11, an ellipsoidal reflecting mirror 12, a quarter-wave plate 13, a reflective polarizing element 14, and a planar reflecting mirror 15.

  In the ellipsoidal reflecting mirror 12, a first focal point 12a inside the ellipsoidal reflecting mirror 12 and a second focal point 12b in which the radiated light from the first focal point 12a is reflected by the ellipsoid and converged are defined. . The plane reflecting mirror 15 is disposed inside the ellipsoidal reflecting mirror 12 so that the back surface thereof is close to the axis of the ellipsoidal reflecting mirror 12, and the light emitting diode 11 is disposed in the vicinity of the first focal point 12a inside the ellipsoidal reflecting mirror 12. The The quarter-wave plate 13 and the reflective polarizing element 14 are provided adjacent to each other, and the vicinity of the second focal point 12 b of the ellipsoidal reflector 12 so that one surface of the quarter-wave plate 13 faces the ellipsoidal reflector 12. Placed in.

  The light emitting diode 11 is a light source of the polarized light source device 10 and emits non-polarized light. As the emission color, R (red), G (green), B (blue), or W (white) is selected according to the purpose. As the light emitting diode 11, a light emitting element using a GaP-based, GaAsP-based, or GaAlAs-based material can be used. Normally, it is sealed with a thermosetting resin that transmits light, called a shell type, and has a lens surface that emits light, but it has a flat surface that does not have a lens surface. A resin-sealed structure may be used. Since the light emitting diode 11 has its light emitting portion disposed in the vicinity of the first focal point 12a of the ellipsoidal reflecting mirror 12, the luminous flux emitted from the light emitting diode 11 is caused by the ellipsoidal reflecting mirror 12 having an elliptical cross section. Most of them are once converged in the vicinity of the second focal point 12b.

  As the ellipsoidal reflecting mirror 12, those having various structures such as a glass whose base material is made of aluminum and coated with aluminum, or a resin lump that is hollowed into an elliptical shape and coated with aluminum can be used.

  As the quarter wavelength plate 13, a crystal material such as calcite or quartz, or a film type in which a stretched transparent PVA film is sandwiched between TAC films or the like is known. The quarter-wave plate 13 is a retardation plate, and has a characteristic of converting incident linearly polarized light into circularly polarized light when its optical axis is arranged at an angle of 45 degrees with the vibration direction of the incident linearly polarized light. . In addition, the circularly polarized light is converted into linearly polarized light when incident.

  The reflective polarizing element 14 is an element having a characteristic of transmitting one of linearly polarized light beams orthogonal to each other and reflecting the other, and as such a polarizing element, for example, ProFlux (registered by US MOTTEK) is registered. Trademark) and Sumitomo 3M's product name HMF (Heart Management Filter) are known. ProFlux is a glass substrate on which a fine grid of Al with a width of about 65 nm, a height of 100 to 200 nm, and a pitch of about 140 nm is formed. Is a polarizing element that transmits the light and reflects the s-polarized component. HMF is a polyester-based multi-layer resin film, and is used by being bonded to a glass substrate or the like via an acrylic adhesive. The p-polarized component is transmitted with respect to the incident randomly polarized light, and the s-polarized component is reflected. In any case, an antireflection film may be provided on the back surface of the polarization separation surface of the base material to reduce the light amount loss.

  In addition to the light emitting diode 11, a planar reflecting mirror 15 is disposed in the vicinity of the first focal point 12 a of the ellipsoidal reflecting mirror 12. The planar reflecting mirror 15 can be manufactured by using a flat plate as a substrate on which the light emitting diode 11 is supported and a mirror surface on the back surface. Further, the light emitting diode 11 and the planar reflecting mirror 15 may be arranged separately.

  Next, the polarization conversion of the polarized light source device 10 of the present invention will be described in detail with reference to FIGS. FIG. 2 is a schematic enlarged side view of the vicinity of the quarter-wave plate and the reflective polarizing element of FIG. A non-polarized light beam is emitted from the light emitting diode 11. The light emission center of the light emitting diode 11 is preferably disposed in the vicinity of the first focal point 12a of the ellipsoidal reflecting mirror 12, and most of these light beams are reflected by the ellipsoidal reflecting mirror 12 having an elliptical cross section. The light is converged as unpolarized light 201 toward the second focal point 12 b of the ellipsoidal reflecting mirror 12. A quarter-wave plate 13 and a reflective polarizing element 14 are provided in the vicinity of the second focal point 12b of the ellipsoidal reflecting mirror 12, and the unpolarized light 201 from the light emitting diode 11 is first a quarter wavelength. It reaches the plate 13, passes through the quarter-wave plate 13, and enters the reflective polarizing element 14. Of the incident non-polarized light in the reflective polarizing element 14, the p-polarized light is transmitted through the reflective polarizing element 14 and becomes an emitted light beam of the p-polarized light 202 from the polarized light source device 10, but the s-polarized light 203 is Reflected. The traveling direction of the s-polarized light 203 is reversed by reflection and proceeds toward the quarter wavelength plate 13. After passing through the quarter-wave plate 13, it becomes circularly polarized light 204, reaches the mirror surface of the ellipsoidal reflecting mirror 12 on the side opposite to the light projection side of the light emitting diode 11, is reflected there, and is reflected by the ellipsoidal reflecting mirror 12. The light beam converges in the vicinity of one focal point 12a. A plane reflecting mirror 15 is disposed at the convergence point, and is reflected again by the plane reflecting mirror 15 and then enters the quarter wavelength plate 13 again as the circularly polarized light 205 through the ellipsoidal reflecting mirror 12. Since the circularly polarized light 205 is converted into the p-polarized light 206 when passing through the quarter-wave plate, it can pass through the next reflective polarizing element 14, and the p-polarized light 206 is used as illumination light. The In this way, since most of the non-polarized light 201 from the light emitting diode 11 can be converted into p-polarized light 202 and 206, the highly efficient polarized light source device 10 is provided.

  In the present embodiment, the quarter-wave plate 13 and the reflective polarizing element 14 are prepared independently, but they may be integrated. For example, if a quarter wavelength plate is attached to one glass substrate and a reflective polarizing element is formed on the other glass substrate, the configuration becomes simpler. In this embodiment, the quarter wavelength plate 13 and the reflective polarizing element 14 are disposed adjacent to each other, but may not be disposed adjacent to each other.

(Second Embodiment)
FIG. 3 is a schematic partial cross-sectional side view showing the configuration of the polarized light source device according to the second embodiment of the present invention. The same components as those in the first embodiment will be described using the same reference numerals. In the first embodiment, the quarter wavelength plate 13 and the reflective polarizing element 14 are disposed adjacent to each other. However, in the polarization light source device 30 of the second embodiment, as shown in FIG. The / 4 wavelength plate 33 is bonded to the planar reflecting mirror 15 apart from the reflective polarizing element 14. Since other configurations are the same as those of the first embodiment, the description is omitted. The non-polarized light 301 emitted from the light emitting diode 11 reaches the reflective polarizing element 14 as convergent light by the elliptical reflecting mirror 12 having an elliptical cross section. The p-polarized light 302 of the p-polarized light component passes through the reflective polarizing element 14 and becomes the illumination light as it is, but the s-polarized light 303 of the s-polarized light component reflected by the reflective polarizing element 14 is the ellipsoidal reflecting mirror 12. , And is reflected by the ellipsoidal reflecting mirror 12 and converges toward the vicinity of the first focal point 12a. In the vicinity of this focusing point, there is a plane reflecting mirror 15 to which a quarter wavelength plate 33 is bonded, and the s-polarized light 303 is transmitted through the quarter wavelength plate 33, reflected by the plane reflecting mirror 15, and again 1/4. In the process of passing through the wave plate 33, polarization conversion is performed on the p-polarized light. The p-polarized light 306 is reflected by the ellipsoidal reflecting mirror 12 and is incident on the second focal point 12 b, that is, the reflective polarizing element 14. It becomes. In this way, most of the non-polarized light 301 emitted from the light emitting diode 11 is converted into p-polarized light 302 and 306 having a uniform polarization direction, and can be used as illumination light.

  Although the light source has been described as a light emitting diode so far, the present invention is not limited to this, and can be applied to a small light emitting element including a semiconductor light emitting element that projects non-polarized light.

  Next, a projection display device provided with the polarized light source device of the present invention will be described. FIG. 4 is a schematic partial cross-sectional side view showing the main configuration of an example of a projection display device provided with the polarized light source device of the present invention. Although the polarized light source device uses the polarized light source device 10 of the first aspect, the polarized light source device 30 of the second aspect may be used. Here, the light source diode 41 that emits white light, the ellipsoidal reflecting mirror 42, the quarter-wave plate 43, the polarizing element 44, and the planar reflecting mirror 45 constitute the polarized light source device 40. The display optical system 60 includes a color wheel 61, a rod integrator 62, a field lens 63, a condenser lens 64, a liquid crystal panel 65, and a projection lens 66.

  A rotary color wheel 61 that separates the white light emitted from the light emitting diode 41 into R, G, and B colors in a time-sharing manner is disposed immediately before the quarter-wave plate 43. Further, the light beam of polarized light emitted from the polarized light source device 40 is incident on the rod integrator 62. By using the rod integrator 62, the influence of uneven light emission of the light emitting diode 41 on the image display can be reduced. For example, p-polarized light whose polarization type is unified by the polarized light source device 40 is made uniform in light intensity by the rod integrator 62, and illumination information at the exit end of the rod integrator 62 is supplied to the liquid crystal panel by the field lens 63, the condenser lens 64, and the like. An image is formed on 65. A polarizer and an analyzer are provided before and after the liquid crystal panel 65, but are omitted in this drawing. The image on the liquid crystal panel 65 is enlarged and projected on a screen (not shown) by the projection lens 66. After most of the non-polarized white light emitted from the light emitting diode 41 as the light source is converted into polarized light, it is divided into R, G, and B by time division by the color wheel 61, and the liquid crystal panel 65 for each color light. Since the image is displayed in synchronization with each other, a single-plate projection display device 4 with high light use efficiency of the light source can be obtained.

  FIG. 5 is a schematic partial cross-sectional side view showing the main configuration of another example of a projection display device provided with the polarized light source device of the present invention. Although the polarized light source device uses the polarized light source device 10 of the first aspect, the polarized light source device 30 of the second aspect may be used. 4 is different from the projection display device of FIG. 4 in that three transmissive liquid crystal panels 751, 752, and 753 are used in the display optical system 70, and three types of polarized light source devices of R, G, and B are used without using the color wheel 61. 501, 502, 503 and a cross dichroic prism 71 are used. For example, in the R polarized light source device 501, the light emitting diode 51 that emits R color light is disposed in the vicinity of the first focal point of the ellipsoidal reflecting mirror 52, and the emitted non-polarized light beam is an ellipsoidal surface. Most of the light is reflected by the reflecting mirror 52 and converges in the vicinity of the second focal point of the ellipsoidal reflecting mirror 52. Since the quarter-wave plate 53 and the reflective polarizing element 54 are disposed adjacent to each other in the vicinity of the second focal point, the p-polarized light among the non-polarized light beams passes through the reflective polarizing element 54. Then, the light enters the rod integrator 72, and then the R liquid crystal panel 751 is illuminated via the field lens 73. The s-polarized light beam reflected by the reflective polarizing element 54 passes through the quarter-wave plate 53 to become circularly polarized light, is reflected by the ellipsoidal reflecting mirror 52, and is disposed at a position opposite to the radiation side of the light emitting diode 51. The reflected light reaches the plane reflecting mirror 55, is reflected there, and travels toward the second focal point of the ellipsoidal reflecting mirror 52 again as convergent light. When the light passes through the quarter-wave plate 53 near the second focal point of the ellipsoidal reflecting mirror 52, the polarized light is converted into p-polarized light and can pass through the reflective polarizing element 54, and enters the rod integrator 72. It becomes the illumination light of the liquid crystal panel 751 for use. Note that an analyzer and a polarizer are arranged before and after the liquid crystal panel 751, but they are omitted in this figure. Since the operations of the G polarized light source device 502 and the B polarized light source device 503 are the same as those of the R polarized light source device 501, the description thereof is omitted. By each polarized light source device 501 (R), 502 (G), 503 (B), the non-polarized light generated by the light source is efficiently polarized and converted, and the corresponding liquid crystal panels 751 (R), 752 (G), 753 are converted. Illuminating (B), these images are synthesized by the cross dichroic prism 71 and then enlarged and displayed on a screen (not shown) by the projection lens 76.

  As a polarized light source device using a light emitting diode as a light source, a display optical system can be used for an optical system of a projection display device of a liquid crystal panel.

It is a typical fragmentary sectional side view which shows the structure of the polarized light source device of the 1st Embodiment of this invention. FIG. 2 is a schematic enlarged side view of the vicinity of a quarter-wave plate and a reflective polarizing element in FIG. 1. It is a typical fragmentary sectional side view which shows the structure of the polarized light source device of the 2nd Embodiment of this invention. It is the typical partial cross section side view which showed the main structures of one example of the projection type display apparatus provided with the polarized light source device of this invention. It is the typical partial cross section side view which showed the main structures of the other example of the projection type display apparatus provided with the polarized light source device of this invention.

Explanation of symbols

10, 30, 40 Polarized light source device 11, 41, 51 Light emitting diode 12, 42, 52 Ellipsoidal reflector 12a First focal point 12b Second focal point 13, 33, 43, 53 1/4 wavelength plate 14, 44, 54 Reflective Polarizing Element 15, 45, 55 Planar Reflector 60, 70 Display Optical System 61 Color Wheel 62, 72 Rod Integrator 63, 73 Field Lens 64 Condenser Lens 65 Liquid Crystal Panel 66, 76 Projection Lens 71 Cross Dichroic Prism 201, 301 Non-polarized light 202, 206, 302, 306 p-polarized light 203, 303 s-polarized light 204, 205 Circularly polarized light 501 R polarized light source device 502 G polarized light source device 503 B polarized light source device 751 R liquid crystal panel 752 G Liquid crystal panel 751 B liquid crystal panel

Claims (5)

The projection type display device used for radiating a light beam of linearly polarized light to a light valve to form a projected image on the light valve, and enlarging and projecting the projected image on a projection surface to form an image on the projection surface. A polarized light source device for generating a luminous flux of linearly polarized light,
The polarized light source device includes a light source unit that emits non-polarized light, and a polarization forming unit that generates linearly polarized light from the non-polarized light emitted from the light source unit,
The polarization forming means includes an ellipsoidal reflecting mirror, a quarter-wave plate, a reflective polarizing element, and a planar reflecting mirror.
The ellipsoidal reflector has a first focal point inside the ellipsoidal reflector and the reflected light from the ellipsoidal reflector of the projection light from the first focal point is focused outside the ellipsoidal reflector. A second focus is defined,
The light source unit is held in the vicinity of the first focal point by holding means,
The plane reflecting mirror is disposed along the axis of the ellipsoidal reflecting mirror so that the surface opposite to the reflecting surface is close to the light source unit,
The quarter-wave plate and the reflective polarizing element are arranged in the vicinity of the second focus so that one surface of the quarter-wave plate faces the opening of the ellipsoidal reflecting mirror in close proximity to each other. And
The non-polarized light emitted from the light source unit is reflected by the ellipsoidal reflecting mirror, converged toward the second focal point of the ellipsoidal reflecting mirror, and reaches the ¼ wavelength plate. / 4 wave plate and incident on the reflective polarizing element, the reflective polarizing element allows only predetermined linearly polarized light to pass as illumination light and reflects incident light other than the predetermined linearly polarized light as reflected light Then, the reflected light becomes the predetermined linearly polarized light through the ellipsoidal reflecting mirror, the planar reflecting mirror, and the quarter wavelength plate, and is incident on the reflective polarizing element again. A polarizing light source device for a projection display device, wherein the polarizing element is passed as illumination light. The projection type display device used for radiating a light beam of linearly polarized light to a light valve to form a projected image on the light valve, and enlarging and projecting the projected image on a projection surface to form an image on the projection surface. A polarized light source device for generating a luminous flux of linearly polarized light,
The polarized light source device includes a light source unit that emits non-polarized light, and a polarization forming unit that generates linearly polarized light from the non-polarized light emitted from the light source unit,
The polarization forming means includes an ellipsoidal reflecting mirror, a quarter-wave plate, a reflective polarizing element, and a planar reflecting mirror.
The ellipsoidal reflector has a first focal point inside the ellipsoidal reflector and the reflected light from the ellipsoidal reflector of the projection light from the first focal point is focused outside the ellipsoidal reflector. A second focus is defined,
The light source unit is held by a holding unit so that the light emitting unit is positioned in the vicinity of the first focus,
The plane reflecting mirror is disposed along the axis of the ellipsoidal reflecting mirror so that the surface opposite to the reflecting surface is close to the light source unit,
The reflective polarizing element is disposed in the vicinity of the second focal point such that one surface of the reflective polarizing element faces the opening of the ellipsoidal reflecting mirror,
The quarter-wave plate is disposed close to the reflecting surface of the planar reflecting mirror;
The non-polarized light emitted from the light source unit becomes convergent light by the ellipsoidal reflecting mirror and enters the reflective polarizing element, and the reflective polarizing element allows only predetermined linearly polarized light to pass as illumination light and is predetermined. The incident light other than the linearly polarized light is reflected as reflected light, and the reflected light becomes the predetermined linearly polarized light via the elliptical reflecting mirror, the planar reflecting mirror, and the quarter wavelength plate. A polarized light source device for a projection display device, which is incident on the reflective polarizing element again and allows the reflective polarizing element to pass as illumination light. The holding means of the light source unit is the planar reflecting mirror, and the planar reflecting mirror is a flat substrate on which the light source unit is supported, and the surface of the substrate that supports the light source unit mirror finish so side becomes the reflective surface comprising a back Te have been made, the polarization light source of a projection display device according to claim 1 or 2. The light source unit is a light emitting diode, the polarization light source of a projection display device according to claim 1 or 2. The polarized light source device of the projection display device according to claim 4 , wherein a light emission color of the light emitting diode is any one of red, blue, green, and white.

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