Measurement cavities described herein include a cylindrical chamber having a first open end and a second open end; a first cap covering the first open end of the cylindrical chamber and a second cap covering the second open end of the cylindrical chamber, wherein the first and second caps hermetically seal the cylindrical chamber and wherein the first cap is rigidly coupled to the second cap; and a wafer holder positioned within and coupled to the cylindrical chamber. The measurement cavity has a mass m, a stiffness k, and a damping constant c configured such that the transmissibility $.Math.\frac{x}{F}.Math.$
of an input force at 60 Hz in the measurement cavity is reduced by a factor of at least 10 and the measurement cavity has a natural frequency of greater than 300 Hz.

Multichannel optical coherence systems and methods involving optical coherence tomography (OCT) subsystems are operably and respectively connected to optical fibers of a multichannel optical probe, such that each optical fiber forms at least a distal portion of a sample beam path of a respective OCT subsystem. The optical fibers are in optical communication with distal optical elements such that external beam paths associated therewith are directed towards a common spatial region external to the housing. Image processing computer hardware is employed to process OCT signals obtained from the plurality of OCT subsystems to generate an OCT image dataset comprising a plurality of OCT A-scans and process the OCT image dataset to generate volumetric image data based on known positions and orientations of the external beam paths associated with the OCT subsystems.

Multichannel optical coherence systems and methods involving optical coherence tomography (OCT) subsystems are operably and respectively connected to optical fibers of a multichannel optical probe, such that each optical fiber forms at least a distal portion of a sample beam path of a respective OCT subsystem. The optical fibers are in optical communication with distal optical elements such that external beam paths associated therewith are directed towards a common spatial region external to the housing. Image processing computer hardware is employed to process OCT signals obtained from the plurality of OCT subsystems to generate an OCT image dataset comprising a plurality of OCT A-scans and process the OCT image dataset to generate volumetric image data based on known positions and orientations of the external beam paths associated with the OCT subsystems.

A composite measurement system for measuring nanometer displacement is provided. The system includes: a light source, a polarization beam splitting prism, a first phase change module, a second phase change module, a first right-angle prism, a second right-angle prism, a non-polarization beam splitting prism, a scalar interference light collection module, a vector interference light collection module and a displacement calculation module. In the present disclosure, a photodetector is configured to collect an intensity of scalar interference light of the object to be measured being moving, to obtain a periodic light intensity change curve; a CCD camera is configured to collect images of interference vortex light of the object being moving; and the displacement calculation unit is configured to calculate a displacement of the object according to integer periods of the light intensity change curve and angles of image changes of the interference vortex light.

A composite measurement system for measuring nanometer displacement is provided. The system includes: a light source, a polarization beam splitting prism, a first phase change module, a second phase change module, a first right-angle prism, a second right-angle prism, a non-polarization beam splitting prism, a scalar interference light collection module, a vector interference light collection module and a displacement calculation module. In the present disclosure, a photodetector is configured to collect an intensity of scalar interference light of the object to be measured being moving, to obtain a periodic light intensity change curve; a CCD camera is configured to collect images of interference vortex light of the object being moving; and the displacement calculation unit is configured to calculate a displacement of the object according to integer periods of the light intensity change curve and angles of image changes of the interference vortex light.

A wavelength-swept light source projects a light beam. An interferometer includes a splitting unit that splits the light beam projected from the wavelength-swept light source into light beams radiated toward a plurality of spots on a measurement target. Each of the interference beam is generated by interference between a measurement beam radiated toward the measurement target and reflected at the measurement beam, and a reference beam passing through an optical path that is at least partially different from an optical path of the measurement beam. A light-receiving unit receives the interference beams from the interferometer. A processor calculates distance to the measurement target by associating a detected peak of the interference beams with one of the spots. The optical path length difference between the measurement target and the reference beam is made different among the light beams split in correspondence with the plurality of spots.

A wavelength-swept light source projects a light beam. An interferometer includes a splitting unit that splits the light beam projected from the wavelength-swept light source into light beams radiated toward a plurality of spots on a measurement target. Each of the interference beam is generated by interference between a measurement beam radiated toward the measurement target and reflected at the measurement beam, and a reference beam passing through an optical path that is at least partially different from an optical path of the measurement beam. A light-receiving unit receives the interference beams from the interferometer. A processor calculates distance to the measurement target by associating a detected peak of the interference beams with one of the spots. The optical path length difference between the measurement target and the reference beam is made different among the light beams split in correspondence with the plurality of spots.

A light source of a self-mixed interferometer (SMI) emits infrared light. The infrared light is directed to an eyebox location with the scanning module by scanning the infrared light into a waveguide. Feedback infrared light is measured by a light sensor of the SMI.

A distance sensing apparatus including a substrate, a light source, a sensing device and an encapsulation structure is provided. The sensing device includes a sensing element and a light-shielding structure. The light source disposed in a light source region emits a beam for irradiating an object to be sensed. The light-shielding structure is disposed on the sensing element. The light source and the sensing device are disposed in the encapsulation structure. The encapsulation structure has a first opening corresponding to a sensing region. The light-shielding structure is disposed between the sensing element and the first opening, and the sensing element receives a beam to be sensed reflected by the object to be sensed and penetrating the first opening and at least a light-transmitting hole of the light-shielding structure. The light source region and the sensing regions are interconnected in the encapsulation structure.

A distance sensing apparatus including a substrate, a light source, a sensing device and an encapsulation structure is provided. The sensing device includes a sensing element and a light-shielding structure. The light source disposed in a light source region emits a beam for irradiating an object to be sensed. The light-shielding structure is disposed on the sensing element. The light source and the sensing device are disposed in the encapsulation structure. The encapsulation structure has a first opening corresponding to a sensing region. The light-shielding structure is disposed between the sensing element and the first opening, and the sensing element receives a beam to be sensed reflected by the object to be sensed and penetrating the first opening and at least a light-transmitting hole of the light-shielding structure. The light source region and the sensing regions are interconnected in the encapsulation structure.