Aspects of the invention can relate to a light source and a projector. More particularly, the invention can have an object to provide a light source and a projector capable of reducing an optical system in size while enlarging a color reproducible range and achieving higher luminance.
There has been a need to increase luminance for a light source used in a projector. In order to satisfy this need, a method of increasing luminance by combining two lights each having a different wavelength using a dichroic mirror has been proposed in the related art. See, for example, JP-A-2001-42431. FIG. 13 is a plan view showing the configuration of a light source 100 in the related art. The light source 100 adopts the method of increasing luminance as described above, and is used, for example, in a projector.
Referring to FIG. 13, an LED 101R, an LED 101G1, an LED 101G2, and an LED 101B are provided in the vicinity of three sides of a cross dichroic prism 104 described below, and they are solid-state light-emitting devices to generate, respectively, a red light (hereinafter, referred to as an R light), a first green light (hereinafter, referred to as a G1 light), a second green light (hereinafter, referred to as a G2 light), and a blue light (hereinafter, referred to as a B light). As is shown in FIG. 14, the R light, the G1 light, the G2 light, and the B light have spectrums having different peak wavelengths λR, λG1, λG2, and λB, respectively. By using lights of four colors, including the R light, G1 light, G2 light, and B light, in this manner, a color reproducible range can be enlarged in comparison with a case using lights of three colors (RGB).
Referring to FIG. 13 again, a liquid crystal light valve 102R is provided in close proximity to the LED 101R, and it is a transmission liquid crystal display device to modulate the R light emitted from the LED 101R according to an image signal. In other words, a video responding to a color corresponding to the R light is formed in the liquid crystal light valve 102R and the R light is modulated when it passes through the liquid crystal light valve 102R.
A dichroic mirror 103 is provided at an angle such that it can allow the G1 light emitted from the LED 101G1 and the G2 light emitted from the LED 101G2 to come incident thereon at 45 degrees, and it is an optical device having an optical characteristic to transmit the G1 light (peak wavelength: λG1) while reflecting the G2 light (peak wavelength: λG2). In short, the dichroic mirror 103 is an optical device to combine the G1 light and the G2 light. The light source 100 in the related art combines the G1 light and the G2 light in the dichroic mirror 103 as has been described, and thereby achieves high luminance with a green light. A white light is formed by combining a red light, a green light, and a blue light in the ratio of 2:7:1. It is therefore necessary for the light source 100 to increase luminance of a green light than lights of the other colors, and in order to satisfy this need, high luminance is achieved with a green light by combining the G1 light and the G2 light in the dichroic mirror 103.
A liquid crystal light valve 102G can be provided in close proximity to the dichroic mirror 103, and it is a transmission liquid crystal display device to modulate a green light (hereinafter, referred to as a G1G2 light) combined in the dichroic mirror 103 according to an image signal. In other words, a video responding to a color of the G1G2 light is formed in the liquid crystal light valve 102G, and the G1G2 light is modulated when it passes through the liquid crystal light valve 102G. A liquid crystal light valve 102B is provided in close proximity to the LED 101B, and it is a transmission liquid crystal display device to modulate the B light emitted from the LED 101B according to an image signal. That is to say, a video responding to a color corresponding to the B light is formed in the liquid crystal light valve 102B, and the B light is modulated when it passes through the liquid crystal light valve 102B.
The cross dichroic prism 104 has two filters, including a dichroic filter 105 and a dichroic filter 106. These dichroic filter 105 and dichroic filter 106 are disposed to intersect with each other at right angles in the shape of a capital X. The dichroic filter 105 has a transmission characteristic indicated by a broken line in FIG. 14, and thereby transmits the G2 light, the G1 light, and the B light while reflecting the R light. The dichroic filter 106 has a transmission characteristic indicated by an alternate long and short dash line in FIG. 14, and thereby transmits the R light, the G1 light, and the G2 light while reflecting the B light. The cross dichroic mirror 104 shown in FIG. 13 is furnished with a function of combining the R light, the G1G2 light (G1 light and G2 light), and the B light as has been described. A projection lens 107 is a lens to project lights combined in the cross dichroic mirror 104 onto a screen (not shown).
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USPTO Backgrounds