Patent ID: 8755716

Claim:
A light source device comprising: a light source; a package member that holds the light source; a splitting element that is arranged on an optical path of a light beam output from the light source and splits the light beam into a first light beam and a second light beam; and a cap member that holds the splitting element so that the surface of the splitting element is inclined with respect to a plane orthogonal to a traveling direction of the light beam output from the light source and that is attached to the package member to seal the light source, the cap member including a first window provided in the traveling direction of the light beam output from the light source through which the first light beam passes and a second window provided in a vertical direction orthogonal to the traveling direction of the light beam output from the light source through which the second light beam passes, one of the first window or the second window being covered by the splitting element; a first opening plate that is arranged on an optical path of the first light beam passing through the first window, has a first opening portion, and forms the first light beam; and a second opening plate that is arranged on an optical path of the second light beam passing through the second window, has a second opening portion, and forms the second light beam, wherein relationships P 1 ≈P 3 and P 2 ≈P 4 are satisfied where: in spacial light intensity distribution of a light beam passing through the first opening portion, P 1 indicates a light intensity at an edge of the first opening portion in a first direction relative to a maximum light intensity in a plane orthogonal to a traveling direction of the light beam passing through the first opening portion, the first direction being orthogonal to both the traveling direction of the light beam output from the light source through which the first light beam passes and the vertical direction, and P 2 indicates a light intensity at an edge of the first opening portion in a second direction orthogonal to the first direction relative to the maximum light intensity in the plane orthogonal to the traveling direction of the light beam passing through the first opening portion, the second direction being parallel to the vertical direction, and in spacial light intensity distribution of a light beam passing through the second opening portion, P 3 indicates a light intensity at an edge of the second opening portion in a direction corresponding to the first direction relative to a maximum light intensity in a plane orthogonal to a traveling direction of the light beam passing through the second opening portion, and P 4 indicates a light intensity at an edge of the second opening portion in a direction corresponding to the second direction relative to the maximum light intensity in the plane orthogonal to the traveling direction of the light beam passing through the second opening portion.