LIGHTING DEVICE AND PROJECTION DISPLAY APPARATUS

1 . A lighting device comprising:

a first light source unit including a plurality of laser elements having optical axes arranged in parallel and in a matrix, the first light source unit emitting a first light flux in a first direction;

a second light source unit including a plurality of laser elements having optical axes arranged in parallel and in a matrix, the second light source unit being arranged to emit a second light flux in the first direction and to be spaced apart from the first light source unit by a first distance in a second direction orthogonal to the first direction; and

an optical path shift optical system including

a first reflecting surface that reflects the second light flux emitted from the second light source unit toward the first light flux, and

a second reflecting surface that is parallel to the first reflecting surface and reflects the second light flux reflected by the first reflecting surface to be parallel to the first light flux at a second distance shorter than the first distance.

2 . The lighting device according to claim 1 , wherein

the optical path shift optical system is a prism having a parallelogram shape, and

the prism includes the first reflecting surface, the second reflecting surface, a first transmission surface through which the second light flux emitted from the second light source unit passes, and a second transmission surface parallel to the first transmission surface and through which the second light flux reflected by the second reflecting surface passes.

3 . The lighting device according to claim 1 , wherein the optical path shift optical system includes a first mirror including the first reflecting surface and a second mirror including the second reflecting surface.

4 . The lighting device according to claim 1 , wherein

each of the plurality of laser elements of each of the first and second light source units is a semiconductor laser element, and

each of the first and second light source units includes a collimating lens provided for the semiconductor laser element.

5 . The lighting device according to claim 4 , wherein each of the first and second light source units includes a collimating lens array in which a plurality of collimating lenses each being the collimating lens are arranged and integrated at a same arrangement pitch as an arrangement pitch of the plurality of semiconductor laser elements.

6 . The lighting device according to claim 5 , further comprising:

a heat transfer plate including a first heat transfer surface to which the first and second light source units are attached and a second heat transfer surface opposite to the first heat transfer surface; and

a cooling device attached to the second heat transfer surface of the heat transfer plate.

7 . The lighting device according to claim 6 , wherein the cooling device includes a first cooling device arranged to face the first light source unit with the heat transfer plate interposed between the cooling device and the first cooling device, and a second cooling device arranged to face the second light source unit with the heat transfer plate interposed between the cooling device and the second cooling device.

8 . The lighting device according to claim 7 , further comprising:

a first thermoelectric element including a heat absorption surface in contact with the second heat transfer surface of the heat transfer plate and a heat dissipating surface to which the first cooling device is attached; and

a second thermoelectric element including a heat absorption surface in contact with the second heat transfer surface of the heat transfer plate and a heat dissipating surface to which the second cooling device is attached.

9 . The lighting device according to claim 8 , wherein, as viewed in a first direction, the first light source unit is arranged at a central portion of the heat absorption surface of the first thermoelectric element, and the second light source unit is arranged at a central portion of the heat absorption surface of the second thermoelectric element.

10 . The lighting device according to claim 8 , wherein the heat transfer plate includes a first heat transfer plate to which the first light source unit is attached and which abuts on the first thermoelectric element, and a second heat transfer plate to which the second light source unit is attached and which abuts on the second thermoelectric element.

11 . The lighting device according to claim 8 , wherein the semiconductor laser element emits red laser light.

12 . A projection display apparatus comprising:

a lighting unit including at least one lighting device;

an image display unit configured to modulate illumination light from the lighting unit and output the modulated illumination light as image light; and

a projection optical system configured to enlarge and project the image light, wherein the at least one lighting device includes

a first light source unit including a plurality of laser elements having optical axes arranged in parallel and in a matrix, the first light source unit emitting a first light flux in a first direction,

a second light source unit including a plurality of laser elements having optical axes arranged in parallel and in a matrix, the second light source unit being arranged to emit a second light flux in the first direction and to be spaced apart from the first light source unit by a first distance in a second direction orthogonal to the first direction, and

an optical path shift optical system including

a first reflecting surface that reflects the second light flux emitted from the second light source unit toward the first light flux, and

a second reflecting surface that is parallel to the first reflecting surface and reflects the second light flux reflected by the first reflecting surface to be parallel to the first light flux at a second distance shorter than the first distance.