Patent ID: 8797641

Claim:
A pulse width conversion device which produces an output light pulse with a pulse width different from a pulse width of an input light pulse, the pulse width conversion device comprising: a spectroscopic element dispersing the input light pulse, input along a first optical path, to output the light rays at output angles according to their wavelengths along a second optical path, outputting a beam of light rays, input at incident angles according to their wavelengths along a third optical path, at a constant output angle along a fourth optical path, outputting the beam of light rays, input at a constant incident angle along a fifth optical path, at output angles according to their wavelengths along a sixth optical path, and coupling the beam of light rays, input at incident angles according to their wavelengths along a seventh optical path, to output it as the output light pulse along an eighth optical path; a first optical system configured such that the light rays, output at the output angles according to their wavelengths along the second optical path from the spectroscopic element, pass through the first optical system to be input at the incident angles according to their wavelengths along the third optical path to the spectroscopic element, and the light rays are then output at the constant output angle along the fourth optical path from the spectroscopic element; a second optical system configured such that the light rays, output at the constant output angle along the fourth optical path from the spectroscopic element, pass through the second optical system to be input at the constant incident angle along the fifth optical path to the spectroscopic element, and the light rays are then output at the output angles according to their wavelengths along the sixth optical path from the spectroscopic element; and a third optical system configured such that the light rays, output at the output angles according to their wavelengths along the sixth optical path from the spectroscopic element, pass through the third optical system to be input at the incident angles according to their wavelengths along the seventh optical path to the spectroscopic element, and the light rays are then coupled by the spectroscopic element to be output as the output light pulse along the eighth optical path from the spectroscopic element, wherein, regarding input-output directions of the beams of light rays at the spectroscopic element, the input-output direction in the combination of the third optical path and the fourth optical path is different from the input-output direction in the combination of the first optical path and the second optical path.