According to one embodiment, a registration mark includes a first step portion and a second step portion. The first step portion includes a plurality of first steps which descend step by step in a first direction from a surface of a substrate or a layer formed on the substrate. The second step portion includes a plurality of second steps which descend step by step from the surface in a second direction different from the first direction and have the same number as the number of the plurality of first steps, is spaced apart from the first step portion, and is disposed rotationally symmetrically to the first step portion.

Non-contacting caliper measurements of free-standing sheets detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface and scanning the laser beam through a selected wavelength range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Alternatively, the intensity of an interference pattern formed from the superposition of radiation that is directly transmitted through the web and radiation that is transmitted through the web after internal reflections from the internal surfaces of the web. Thickness can be extracted from the fringe separation in the interference pattern.

Non-contacting caliper measurements of free-standing sheets detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface and scanning the laser beam through a selected wavelength range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Alternatively, the intensity of an interference pattern formed from the superposition of radiation that is directly transmitted through the web and radiation that is transmitted through the web after internal reflections from the internal surfaces of the web. Thickness can be extracted from the fringe separation in the interference pattern.

According to the present invention, a measured distance is corrected in accordance with change in the surrounding environment. A distance measurement system includes: a first light-receiving unit configured to irradiate an object with one part of a split light beam as assessment light, and receive light reflected by the object to detect a target assessment beat signal; a second light-receiving unit configured to guide the other part of the split light beam as reference light to a reference optical path serving as a distance reference, and receive the reference light that has passed through the reference optical path to detect a reference optical path assessment beat signal; a distance measurement unit configured to measure a distance to the object on the basis of the target assessment beat signal and the reference optical path assessment beat signal; a temperature sensor configured to assess a temperature in the periphery of the reference optical path; and a correction unit configured to correct the measured distance on the basis of the assessed temperature.

According to the present invention, a measured distance is corrected in accordance with change in the surrounding environment. A distance measurement system includes: a first light-receiving unit configured to irradiate an object with one part of a split light beam as assessment light, and receive light reflected by the object to detect a target assessment beat signal; a second light-receiving unit configured to guide the other part of the split light beam as reference light to a reference optical path serving as a distance reference, and receive the reference light that has passed through the reference optical path to detect a reference optical path assessment beat signal; a distance measurement unit configured to measure a distance to the object on the basis of the target assessment beat signal and the reference optical path assessment beat signal; a temperature sensor configured to assess a temperature in the periphery of the reference optical path; and a correction unit configured to correct the measured distance on the basis of the assessed temperature.

An optical distance measurement device includes: a photodetector including PDs for receiving interference light output from an optical interference unit and outputting detection signals of the interference light; and a switch for selecting one of the detection signals output from the PDs, in which a distance calculation unit calculates a distance to a measurement object on the basis of the detection signal selected by the switch.

Multichannel optical coherence systems are disclosed in which 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 portable communication device includes one or more optical detectors to generate an analog signal in response to a change in an intra-cavity or an emitted optical power of a light source due to light backscattered from a particle and an application-specific integrated circuit (ASIC). The particle is illuminated via a light source. The ASIC includes an analog-to-digital converter (ADC) circuit, a digital delay circuit, a particle detector module and a processor. The ADC converts the analog signal to a digital signal. The digital delay circuit can store the digital signal for a predetermined or dynamically variable time interval. The particle detector module can analyze the digital signal and can generate an enable signal upon detecting a particle signature in the digital signal. The processor is coupled to the digital delay circuit and can start processing the digital signal in response to the enable signal.

In one general aspect, an apparatus can include a first laser subsystem configured to transmit a first laser beam at a first location on an object at a time and a second laser subsystem configured to transmit a second laser beam at a second location on the object at the time. The apparatus can include an analyzer configured to calculate a first velocity based on a first reflected laser beam reflected from the object in response to the first laser beam. The analyzer can be configured to calculate a second velocity based on a second reflected laser beam reflected from the object in response to the second laser beam. The first location can be targeted by the first laser subsystem and the second location can be targeted by the second laser subsystem such that the first velocity is substantially the same as the second velocity.

Quantum network devices, systems, and methods are provided to enable long-distance transmission of quantum bits (qubits) for applications such as Quantum Key Distribution (QKD), entanglement distribution, and other quantum communication applications. Such systems and methods provide for separately storing first, second, third, and fourth photons, wherein the first and second photons and the third and fourth photons are respective first and second entangled photon pairs, triggering a synchronized retrieval of the stored first, second, third, and fourth photons such that the first photon is propagated to a first node, the second and third photons are propagated to a second node, and the fourth photon is propagated to a third node, and creating a new entangled pair comprising the first and fourth photons at the first and third nodes to transmit quantum information.