A system for providing illumination to a measurement head for optical metrology is configured to combine illumination beams from a plurality of illumination sources to deliver illumination at one or more selected wavelengths to the measurement head. The intensity and/or spatial coherence of illumination delivered to the measurement head is controlled. Illumination at one or more selected wavelengths is delivered from a broadband illumination source configured for providing illumination at a continuous range of wavelengths.

An illumination device includes at least four narrow band light sources, primary light combiners that combine narrow band light from at least two of the narrow band light sources, and a secondary light combiner that combines primary combined light combined by the primary light combiners. The device is configured to radiate, as illumination light, secondary combined light combined by the secondary light combiner. The light sources are grouped into groups based on illumination characteristics of the narrow band light so that light sources satisfying a condition for the illumination characteristics are grouped into the same group. The light sources in the same group are connected to the primary light combiners so that the light sources in the same group are distributed to the primary light combiners.

Systems and methods to generate spatially coherent electromagnetic radiation are disclosed. An example method includes receiving two or more incident wavelengths of electromagnetic radiation; applying the two or more incident wavelengths of electromagnetic radiation to an array of features; generating two or more spatially coherent optical resonating modes through the interaction of the one or more incident wavelengths of electromagnetic radiation and the array of features; and coupling the two or more spatially coherent optical resonating modes to two or more spatially coherent propagating wavelengths of electromagnetic radiation, wherein the spatially coherent propagating wavelengths of electromagnetic radiation are identical to the two or more incident wavelengths of electromagnetic radiation. An example system includes an array of features configured to receive wavelengths of electromagnetic radiation; medium(s) configured to generate spatially coherent optical resonating mode(s); and medium(s) configured to generate spatially coherent propagating wavelength(s) of electromagnetic radiation.

To provide a multiplexer that makes it possible to achieve a reduction in size and that minimizes the influence of the expansion of laser light on a multiplexing unit. A multiplexer is provided with a plurality of waveguides, multiplexing units that are provided at an intermediate location within the waveguides, and laser light sources, wherein: the first multiplexing unit is arranged at a position that is closest to the laser light sources; and the laser light sources that have an optical axis at a position that is separated from the transmission axis of the visible light that is introduced into the first multiplexing unit are arranged so that the optical axis is inclined with respect to the transmission axis and the outer periphery of laser light that expands at a predetermined expansion angle passes in front of the first multiplexing unit.

An optical multiplexer (10) that multiplexes a plurality of light beams having different wavelengths includes a first waveguide (101) that receives first-wavelength light, a second waveguide (102) that receives second-wavelength light having a shorter wavelength than the first-wavelength light, a third waveguide (103) that receives third-wavelength light having a shorter wavelength than the second-wavelength light, a first multiplexer (110) in which the light propagates between the first waveguide (101) and the second waveguide (102), and a second multiplexer (120) in which the light propagates between the first waveguide (101) and the third waveguide (103). The second-wavelength light is propagated to the first waveguide (101) at the first multiplexer (110). The third-wavelength light is propagated to the first waveguide (101) at the second multiplexer (120).

To provide a multiplexer that makes it possible to achieve a reduction in size and that minimizes the influence of the expansion of laser light on a multiplexing unit. A multiplexer is provided with a plurality of waveguides, multiplexing units that are provided at an intermediate location within the waveguides, and laser light sources, wherein: the first multiplexing unit is arranged at a position that is closest to the laser light sources; and the laser light sources that have an optical axis at a position that is separated from the transmission axis of the visible light that is introduced into the first multiplexing unit are arranged so that the optical axis is inclined with respect to the transmission axis and the outer periphery of laser light that expands at a predetermined expansion angle passes in front of the first multiplexing unit.

To provide a multiplexer that makes it possible to achieve a reduction in size and that minimizes the influence of the expansion of laser light on a multiplexing unit. A multiplexer is provided with a plurality of waveguides, multiplexing units that are provided at an intermediate location within the waveguides, and laser light sources, wherein: the first multiplexing unit is arranged at a position that is closest to the laser light sources; and the laser light sources that have an optical axis at a position that is separated from the transmission axis of the visible light that is introduced into the first multiplexing unit are arranged so that the optical axis is inclined with respect to the transmission axis and the outer periphery of laser light that expands at a predetermined expansion angle passes in front of the first multiplexing unit.

An endoscope system has observation modes making observations with lights having optical characteristics different from each other. The system includes an endoscope including an insertion section provided with an illumination window, a light guide arranged in the insertion section, and including an entrance end on which the lights enter and a plurality of light guide areas that guide the lights entered on the entrance end, and an entrance area switching unit that switches between the light guide areas through which the entered lights are guided by switching between areas on which the lights enter at the entrance end in accordance with an observation mode.

A light-source device includes: two long-wavelength light sources that emit red long-wavelength light beams (LWLs); a broadband light source that emits a green broadband light beam (BL); and a multiplexing portion that multiplexes a wavelength region greater than a first predetermined wavelength 1 of one of the LWLs having a longer peak wavelength and a wavelength region equal to or less than 1 of the other LWL having a shorter peak wavelength, and that multiplexes a wavelength region greater than a second predetermined wavelength 2 of the other LWL and a wavelength region equal to or less than 2 of the BL, wherein intensities of the LWLs at 1 are equal to or greater than 10% of the peak intensities thereof and intensities of the other LWL and the BL at 2 are equal to or greater than 10% of the peak intensities thereof.

A system for providing illumination to a measurement head for optical metrology is configured to combine illumination beams from a plurality of illumination sources to deliver illumination at one or more selected wavelengths to the measurement head. The intensity and/or spatial coherence of illumination delivered to the measurement head is controlled. Illumination at one or more selected wavelengths is delivered from a broadband illumination source configured for providing illumination at a continuous range of wavelengths.