An apparatus and method for inspecting an object by optical triangulation, where the signal of interest in a captured image corresponds to an interaction between a light beam and an environment surrounding the object rather than between a light beam and the object itself. The surrounding environment may be configured to interact in a manner that is detectable by filling it with a flowable scattering medium, e.g. a gas, mist or vapour comprising a suspension of fine particles in air. Light that is scattered by the flowable scattering medium is visible in a captured image. Where the flowable scattering medium is not present, e.g. because the object blocks it, the scattered signal is less. A boundary of a scattered signal region may thus provide information about the location of an object.

The subject fluid gauges measure actual position of a workpiece relative to a target position. A gauge body that is positionable relative to the workpiece and that includes multiple differential-pressure (DP) sensors has a measurement channel and respective reference channels. Each DP sensor measures, over a respective individual dynamic pressure range, a differential pressure established by a respective fluid flow in the measurement channel relative to a fluid flow in a respective reference channel. The dynamic pressure ranges of the DP sensors substantially overlap each other. A controller is connected to and monitors the DP sensors. The controller is configured to select, for obtaining a differential pressure indicative of the position of the workpiece, a DP sensor sensing the smallest magnitude of DP.

The subject fluid gauges measure actual position of a workpiece relative to a target position. A gauge body that is positionable relative to the workpiece and that includes multiple differential-pressure (DP) sensors has a measurement channel and respective reference channels. Each DP sensor measures, over a respective individual dynamic pressure range, a differential pressure established by a respective fluid flow in the measurement channel relative to a fluid flow in a respective reference channel. The dynamic pressure ranges of the DP sensors substantially overlap each other. A controller is connected to and monitors the DP sensors. The controller is configured to select, for obtaining a differential pressure indicative of the position of the workpiece, a DP sensor sensing the smallest magnitude of DP.

An apparatus, such as a lithographic apparatus, has a metrology frame that has a reference frame mounted thereon that includes a reference surface. A gas gauge is movable relative to the reference frame, metrology frame, and a measured surface. A reference nozzle in the gas gauge provides gas to the reference surface and a measurement nozzle provides gas to the measured surface. A microelectromechanical (MEM) sensor may be used with the gas gauge to sense a difference in backpressure from each of the reference nozzle and the measurement nozzle. Optionally, multiple gas gauges are positioned in an array, which may extend in a direction that is substantially parallel to a plane of the measured surface. The gauges may be fluidly connected to a reference nozzle of the gas gauge. A channel may distribute gas across the array.

An apparatus, such as a lithographic apparatus, has a metrology frame that has a reference frame mounted thereon that includes a reference surface. A gas gauge is movable relative to the reference frame, metrology frame, and a measured surface. A reference nozzle in the gas gauge provides gas to the reference surface and a measurement nozzle provides gas to the measured surface. A microelectromechanical (MEM) sensor may be used with the gas gauge to sense a difference in backpressure from each of the reference nozzle and the measurement nozzle. Optionally, multiple gas gauges are positioned in an array, which may extend in a direction that is substantially parallel to a plane of the measured surface. The gauges may be fluidly connected to a reference nozzle of the gas gauge. A channel may distribute gas across the array.

A measurement system includes a measurement device to detect measurement information relating to a position-modifiable component of a printing station during movement thereof. A calculation unit receives the measurement information from the measurement device. The calculation unit determines actual-position data of the position-modifiable component from the measurement data received and compares it with predetermined reference-position data to determine calibration information based on the actual-position data and the reference-position data. An interface permits then permits transfer of this calibration information.

A measurement system includes a measurement device to detect measurement information relating to a position-modifiable component of a printing station during movement thereof. A calculation unit receives the measurement information from the measurement device. The calculation unit determines actual-position data of the position-modifiable component from the measurement data received and compares it with predetermined reference-position data to determine calibration information based on the actual-position data and the reference-position data. An interface permits then permits transfer of this calibration information.

Methods and apparatus for measuring the position of an object relative to a reference are disclosed. In an arrangement, a pressurized fluid is used to drive rotation of a cylinder around a piston and to bias the cylinder longitudinally. Ducts are provided in the cylinder and arranged so at to provide pulses of the fluid out of the cylinder through a reading port, the pulses being such as to uniquely identify the position of the cylinder relative to the piston and thereby of the object relative to the reference.

Methods and apparatus for measuring the position of an object relative to a reference are disclosed. In an arrangement, a pressurized fluid is used to drive rotation of a cylinder around a piston and to bias the cylinder longitudinally. Ducts are provided in the cylinder and arranged so at to provide pulses of the fluid out of the cylinder through a reading port, the pulses being such as to uniquely identify the position of the cylinder relative to the piston and thereby of the object relative to the reference.

The present disclosure is directed toward a method for measuring a seal gap between a closing member and a fixed member. The method includes applying a liquid agent having transferable properties along one or more regions of a stamping member to form one or more base marks. The stamping member is one of the closing member or the fixed member. The method further includes engaging the closing member with the fixed member, disengaging the closing member from the fixed member, and assessing a seal gap between the closing member and the fixed member based on one or more remnant patterns formed on an imprinted member. The imprinted member is the other one of the closing member and the fixed member, and the remnant patterns are formed by the transfer of the liquid agent from the base marks.