A method includes irradiating a target droplet in an extreme ultraviolet light source of an extreme ultraviolet lithography tool with light from a droplet illumination module. Light reflected and/or scattered by the target droplet is detected. Particle image velocimetry is performed to monitor one or more flow parameters inside the extreme ultraviolet light source.

A method includes irradiating a target droplet in an extreme ultraviolet light source of an extreme ultraviolet lithography tool with light from a droplet illumination module. Light reflected and/or scattered by the target droplet is detected. Particle image velocimetry is performed to monitor one or more flow parameters inside the extreme ultraviolet light source.

Various sensors, including particulate matter sensors, are described. One particulate matter sensor includes a self-mixing interferometry sensor and a set of one or more optical elements. The set of one or more optical elements is positioned to receive an optical emission of the self-mixing interferometry sensor, split the optical emission into multiple beams, and direct each beam of the multiple beams in a different direction. The self-mixing interferometry sensor is configured to generate particle speed information for particles passing through respective measurement regions of the multiple beams.

Various sensors, including particulate matter sensors, are described. One particulate matter sensor includes a self-mixing interferometry sensor and a set of one or more optical elements. The set of one or more optical elements is positioned to receive an optical emission of the self-mixing interferometry sensor, split the optical emission into multiple beams, and direct each beam of the multiple beams in a different direction. The self-mixing interferometry sensor is configured to generate particle speed information for particles passing through respective measurement regions of the multiple beams.

The invention relates to a method for determining an actual value and/or an actual value range of at least one state variable of a fluid in a fluid flow by means of at least one indicator particle (9) introduced into the fluid. In addition it is proposed that the at least one indicator particle (9) is designed and provided for an irreversible property change of an indicator property of the indicator particle (9) in the case of a certain indicator value of the at least one state variable in the fluid flow and/or as a clear function of the actual value when a certain period of time has elapsed after the indicator particle (9) has been introduced into the fluid, wherein the indicator particle (9) is detected at a detection point, the indicator property of the indicator particle (9) is evaluated and the actual value and/or the actual value range of the state variable is inferred from the indicator property upstream of the detection point. The invention also relates to a method for operating a fluid-guiding device (7), an indicator particle (9) and a device (7) for determining the actual value and/or actual value range of the at least one state variable.

A measuring method enabling simple and accurate measurement of a flow velocity distribution in a flow field inside a flow passage of an optical cell and a particle size-measuring method using the measuring method are provided. Providing a tracer particle of a smaller size than wavelength λ of laser light into the flow passage and capturing a bright spot attributed to light scattering from tracer particles by camera, and obtaining the flow velocity distribution by the analysis unit by obtaining an amount of movement of each tracer particle from movement of the bright spot and correcting a Brownian motion component from a correlation between an average value of variations of the amount of movement and Brownian motion are performed.

[Problem] To provide: fluorescent particles that are used to create a fluorescent material for coating an object in the vicinity of a fluid, that move regularly in the fluid while suppressing halation generated by the objects, and that enable the motion/movement of the fluid to be sharply visualized; an inspection device; and an inspection method.

[Solution] Substantially spherical fluorescent particles comprising a mixture containing at least one fluorescent material and a synthetic resin, wherein: the fluorescent material is excited by any purple visible light and UV rays having a wave-length of 290-405 nm, and emits visible light having a peak wavelength within the range of 410-620 nm; and the fluorescent particles have diameters of 100 nm to 1 mm and are distinguishable from bubbles and/or foreign bodies in the fluid when irradiated with the light.

A wind turbine for generating electric energy including a tower equipped with rotatable nacelle with rotor which is rotatable about a horizontal rotational axis and which comprises an electric generator. The wind turbine additionally comprises a device for determining flow direction and speed of the wind and a device for or regulating the alignment of the rotor against the wind. The device for determining speed and flow direction comprises pair of receiving antennas, for obtaining electric signals using electrically influenced particles, molecules carried by the wind and are supplied to a correlation measurement device. Here, the time needed by the electrically influenced particles/molecules to traverse the distance between the receiving antennas of a pair of receiving antennas is determined. Subsequently, speed and flow direction of the wind are calculated in a computing device and are supplied to the device for controlling or regulating the alignment of the rotor.

A wind turbine for generating electric energy including a tower equipped with rotatable nacelle with rotor which is rotatable about a horizontal rotational axis and which comprises an electric generator. The wind turbine additionally comprises a device for determining flow direction and speed of the wind and a device for or regulating the alignment of the rotor against the wind. The device for determining speed and flow direction comprises pair of receiving antennas, for obtaining electric signals using electrically influenced particles, molecules carried by the wind and are supplied to a correlation measurement device. Here, the time needed by the electrically influenced particles/molecules to traverse the distance between the receiving antennas of a pair of receiving antennas is determined. Subsequently, speed and flow direction of the wind are calculated in a computing device and are supplied to the device for controlling or regulating the alignment of the rotor.

A flow velocity determining apparatus (10) includes an irradiating unit (20) that emits irradiation light (L1) toward a liquid mixture (BL) which contains a non-spherical solid (BC) and a liquid (BP) and flows through a flow path (TB), a detecting unit (30) that detects reflected light (L2) emitted by the irradiating unit (20) and reflected by the liquid mixture (BL) flowing through the flow path (TB), the detecting unit (32) being disposed on at least one side of an optical axis (L2A) of the reflected light (L2) when seen in a plan view of an imaginary plane including an optical axis (L1A) of the irradiation light (L1) and the optical axis (L2A) of the reflected light (L2), and a determining unit (40) that determines a flow velocity of the liquid mixture (BL) by using a light amount of the reflected light (L2) detected by the detecting unit (32).