Light source device and image projection apparatus including a rod integrator and light guide

1. A light-source device, comprising:

a source including an excitation light source and a coupling lens, the excitation light source configured to emit first colored light;

an optical element having a surface to reflect the first colored light emitted from the excitation light source, the surface of the optical element including a first region and a second region;

a wavelength converter configured to emit the first colored light reflected by the surface, the wavelength converter including a wavelength conversion layer that converts at least a portion of the first colored light reflected by the surface and incident on the wavelength converter, into second colored light having a wavelength different from a wavelength of the first colored light and emit the second colored light;

a rod integrator configured to mix at least one of the first colored light and the second colored light emitted from the wavelength converter and transmitted by the second region of the optical element; and

a refractive light guide configured to guide at least one of the first colored light and the second colored light emitted from the wavelength converter to an incident aperture of the rod integrator, wherein

an angle β, smaller than 40°, is between the incident aperture of the rod integrator and the first colored light with respect to the incident aperture,

the first region has optical properties to reflect the first colored light and to transmit the second colored light,

the second region has optical properties to transmit the first colored light and the second colored light,

a light flux Q is a light flux of the first colored light emitted from the wavelength converter,

a point P is a center of the first colored light on the surface,

the point P does not intersect with the flux Q,

a plane is substantially parallel to a short side of the incident aperture of the rod integrator, the plane including:

a first straight line that connects the point P to a point S on the wavelength converter, and

a second straight line that connects a center of a first projection image of the first colored light on the incident aperture of the rod integrator and a point R that is a center of a second projection image of the first colored light on the wavelength converter, the point R being different from the point S,

the excitation light source includes a plurality of laser diodes arranged in rows along a row axis and columns along a column axis in a first plane normal to an optical axis, and each of the coupling lenses is disposed on an exit-plane side of a corresponding one of the plurality of laser diodes,

an interval between the laser diodes satisfies that:

1≤ P/L tan θ≤4, where

θ is a divergence angle of the first colored light emitted from each of the plurality of laser diodes, the divergence angle being a larger angle between a row angle from the optical axis in a second plane normal to a column axis and a column angle from the optical axis in a third plane normal to the row axis,

P is a pitch between adjacent laser diodes, and

L is a distance from a light-emitting point of each of the plurality of laser diodes to a corresponding one of the coupling lenses.

2. The light-source device according to claim 1 , wherein

the wavelength converter includes:

a first area to reflect or diffuse the first colored light reflected by the surface to emit the first colored light; and

a second area including the wavelength conversion layer, to convert the first colored light reflected by the surface and incident on the second area into the second colored light and emit the second colored light, and

upon the first colored light being incident on the wavelength converter, the wavelength converter is configured to alternately emit the first colored light and the second colored light to an incident-plane side of the wavelength converter that the first colored light has been incident on.

3. The light-source device according to claim 1 , wherein

the wavelength converter includes an area to receive the first colored light reflected by the surface and the area includes the wavelength conversion layer,

the wavelength conversion layer is configured to convert a portion of the first colored light incident on the area into the second colored light and reflect the other portion of the first colored light, and

upon the first colored light being incident on the wavelength converter, the wavelength converter is configured to emit the first colored light and the second colored light together to an incident-plane side of the wavelength converter that the first colored light has been incident on.

4. The light-source device according to claim 1 , wherein in a case that the point R is a center of a projection image of the first colored light projected on the wavelength converter, the light mixing device is disposed on the normal to the point R on an exit plane of the wavelength converter.

5. The light-source device according to claim 1 , wherein a center of a projection image of the first colored light projected on the incident aperture of the rod integrator, a center of a projection image of the second colored light projected on the incident aperture, and an optical axis of the refractive light guide intersect at one point.

6. The light-source device according to claim 1 , wherein the rod integrator has an exit aperture larger than the incident aperture.

7. The light-source device according to claim 1 , wherein

the refractive light guide includes a condenser lens disposed in an optical path between the optical element and the wavelength converter, the condenser lens configured to converge the first colored light reflected by the surface and substantially collimate the second colored light emitted from the wavelength converter, and

a position of the point S is a point of intersection of an incident plane of the wavelength converter, that the first colored light converged by the condenser lens has been incident on and a straight line connecting the point P and a center of a projection image on an incident plane of the condenser lens that the first colored light reflected by the surface has been incident on, the projection image being formed by the first colored light.

8. An image projection apparatus, comprising:

the light-source device according to claim 1 ;

an image display configured to generate an image of light emitted from the light-source device;

an illumination optical system configured to guide the light emitted from the light-source device to the image display; and

a projection optical system configured to project the image generated by the image display.

9. The light-source device according to claim 1 , wherein

the second region includes a first end and a second end,

the first end is further from the first region than the second end is from the first region, and

the first end is outside an optical path of the second colored light.

10. The light-source device according to claim 9 , wherein

the second end is outside of the optical path of the second colored light.

11. The light-source device according to claim 1 , wherein

θ 1 is <than θ 2 , where

θ 1 is a maximum incident angle of light rays of the first colored light with respect to the incident aperture of the rod integrator, and

θ 2 is a maximum incident angle of light rays of the second colored light with respect to the incident aperture of the rod integrator.

12. The light-source device according to claim 11 , wherein

the rod integrator is composed of glass,

θ glass is a total reflection condition of the rod integrator, and

θ glass is greater than each of θ 1 and θ 2 .

13. The light-source device according to claim 1 , wherein

the excitation light source includes a plurality of laser diodes arranged in an array, and

a projection range of the first colored light emitted from the laser diodes, on the incident aperture of the rod integrator, has an elliptical shape having a major axis substantially parallel to either a long side or a short side of the incident aperture of the rod integrator.