Abstract: The present invention discloses a crack-resistant ultra-high performance concrete (UHPC) for underground engineering in water-rich strata, preparation method, and application thereof, belonging to the technical field of building materials. The concrete is prepared from the following raw materials in parts by weight: 550-650 parts of cement, 140-180 parts of fly ash, 120-150 parts of silica fume, 200-300 parts of calcined shield tunnel slag, 30-50 parts of micron-scale magnesium oxide, 30-50 parts of nano-scale magnesium oxide, 30-50 parts of rheology-modifying material, 800-1000 parts of lightweight aggregate, 4-8 parts of water reducer, and 50-200 parts of water. The rheology-modifying material has a fluidity ratio of 106%. The present invention incorporates calcined shield tunnel slag, micron/nano-scale magnesium oxide, and lightweight aggregate into the UHPC, which effectively suppresses shrinkage and reduces crack formation.

Abstract: A method of three-dimensional imaging includes scanning a LiDAR system in a first direction with a first frequency and in a second direction with a second frequency that is different from the first frequency, so that a laser beam emitted by each laser source of the LiDAR system follows a Lissajous pattern. The method further includes emitting, using each laser source, a plurality of laser pulses as the LiDAR system is scanned in the first direction and the second direction; detecting, using each detector of the LiDAR system, a portion of each laser pulse of the plurality of laser pulses reflected off of one or more objects; determining, using a processor, a time of flight for each respective laser pulse from emission to detection; and acquiring a point cloud of the one or more objects based on the times of flight of the plurality of laser pulses.

Abstract: A method of three-dimensional imaging includes scanning a LiDAR system in a first direction with a first frequency and in a second direction with a second frequency that is different from the first frequency, so that a laser beam emitted by each laser source of the LiDAR system follows a Lissajous pattern. The method further includes emitting, using each laser source, a plurality of laser pulses as the LiDAR system is scanned in the first direction and the second direction; detecting, using each detector of the LiDAR system, a portion of each laser pulse of the plurality of laser pulses reflected off of one or more objects; determining, using a processor, a time of flight for each respective laser pulse from emission to detection; and acquiring a point cloud of the one or more objects based on the times of flight of the plurality of laser pulses.

Abstract: A scanning lidar system includes an external frame, an internal frame attached to the external frame by vibration-isolation mounts, and an electro-optic assembly movably attached to the internal frame and configured to be translated with respect to the internal frame during scanning operation of the scanning lidar system.

Abstract: A scanning lidar system includes a fixed frame, a first platform, and a first electro-optic assembly. The first electro-optic assembly includes a first laser source and a first photodetector mounted on the first platform. The scanning lidar system further includes a first flexure assembly flexibly coupling the first platform to the fixed frame, and a drive mechanism configured to scan the first platform with respect to the fixed frame in two dimensions in a plane substantially perpendicular to an optical axis of the lidar system. The scanning lidar system further includes a controller coupled to the drive mechanism. The controller is configured to cause the drive mechanism to scan the first platform in a first direction with a first frequency and in a second direction with a second frequency. The second frequency is similar but not identical to the first frequency.

Abstract: A three-dimensional imaging system includes a first illumination source configured to project a first fan of light toward an object in a field of view, and a second illumination source configured to project a second fan of light substantially parallel to and spaced apart from the first fan of light. The first illumination source and the second illumination source are further configured to scan the first fan of light and the second fan of light synchronously laterally across the field of view. The three-dimensional imaging system further includes a camera configured to capture a plurality of image frames of the field of view as the first fan of light and the second fan of light are scanned over a plurality of regions the object, and a processor coupled to the camera and configured to construct a three-dimensional image of the object based on the plurality of image frames.

Abstract: A scanning lidar system includes a fixed frame, a first platform flexibly attached to the fixed frame, a lens assembly including a first lens and a second lens mounted on the first platform, a second platform flexible attached to the fixed frame, an electro-optic assembly including a first laser source and a first photodetector mounted on the second platform, a drive mechanism mechanically coupled to the first platform and the second platform and configured to translate the first platform and the second platform with respect to the fixed frame, and a controller coupled to the drive mechanism and configured to translate the first platform to a plurality of first positions through the drive mechanism and translate the second platform to a plurality of second positions through the drive mechanism such that a motion of the second platform is substantially opposite to a motion of the first platform.

Abstract: A scanning lidar system includes a fixed frame, a first platform, and a first electro-optic assembly. The first electro-optic assembly includes a first laser source and a first photodetector mounted on the first platform. The scanning lidar system further includes a first flexure assembly flexibly coupling the first platform to the fixed frame, and a drive mechanism configured to scan the first platform with respect to the fixed frame in two dimensions in a plane substantially perpendicular to an optical axis of the lidar system. The scanning lidar system further includes a controller coupled to the drive mechanism. The controller is configured to cause the drive mechanism to scan the first platform in a first direction with a first frequency and in a second direction with a second frequency. The second frequency is similar but not identical to the first frequency.

Abstract: Methods and systems for performing three dimensional LIDAR measurements with different illumination intensity patterns are described herein. Repetitive sequences of measurement pulses each having different illumination intensity patterns are emitted from a LIDAR system. One or more pulses of each repetitive sequence have a different illumination intensity than another pulse within the sequence. The illumination intensity patterns are varied to reduce total energy consumption and heat generated by the LIDAR system. In some examples, the illumination intensity pattern is varied based on the orientation of the LIDAR device. In some examples, the illumination intensity pattern is varied based on the distance between a detected object and the LIDAR device. In some examples, the illumination intensity pattern is varied based on the presence of an object detected by the LIDAR device or another imaging system.

Abstract: Methods and systems for performing three dimensional LIDAR measurements with different pulse repetition patterns are described herein. Each repetitive pattern is a sequence of measurement pulses that repeat over time. In one aspect, the repetition pattern of a pulsed beam of illumination light emitted from a LIDAR system is varied to reduce total energy consumption and heat generated by the LIDAR system. In some examples, the repetitive pattern is varied by skipping a number of pulses. In some examples, the repetitive pattern of pulses of illumination light emitted from the LIDAR system is varied by changing a repetition rate of the sequence of emitted pulses. In some examples, the pulse repetition pattern is varied based on the orientation of the LIDAR device. In some examples, the repetition pattern is varied based on an object detected by the LIDAR device or another imaging system.

Abstract: A scanning lidar system includes an external frame, an internal frame attached to the external frame by vibration-isolation mounts, and an electro-optic assembly movably attached to the internal frame and configured to be translated with respect to the internal frame during scanning operation of the scanning lidar system.

Abstract: A scanning lidar system includes a fixed frame, a first platform flexibly attached to the fixed frame, a lens assembly including a first lens and a second lens mounted on the first platform, a second platform flexible attached to the fixed frame, an electro-optic assembly including a first laser source and a first photodetector mounted on the second platform, a drive mechanism mechanically coupled to the first platform and the second platform and configured to translate the first platform and the second platform with respect to the fixed frame, and a controller coupled to the drive mechanism and configured to translate the first platform to a plurality of first positions through the drive mechanism and translate the second platform to a plurality of second positions through the drive mechanism such that a motion of the second platform is substantially opposite to a motion of the first platform.

Abstract: A three-dimensional imaging system includes a first illumination source configured to project a first fan of light toward an object in a field of view, and a second illumination source configured to project a second fan of light substantially parallel to and spaced apart from the first fan of light. The first illumination source and the second illumination source are further configured to scan the first fan of light and the second fan of light synchronously laterally across the field of view. The three-dimensional imaging system further includes a camera configured to capture a plurality of image frames of the field of view as the first fan of light and the second fan of light are scanned over a plurality of regions the object, and a processor coupled to the camera and configured to construct a three-dimensional image of the object based on the plurality of image frames.

Abstract: Methods and systems for performing three dimensional LIDAR measurements with different illumination intensity patterns are described herein. Repetitive sequences of measurement pulses each having different illumination intensity patterns are emitted from a LIDAR system. One or more pulses of each repetitive sequence have a different illumination intensity than another pulse within the sequence. The illumination intensity patterns are varied to reduce total energy consumption and heat generated by the LIDAR system. In some examples, the illumination intensity pattern is varied based on the orientation of the LIDAR device. In some examples, the illumination intensity pattern is varied based on the distance between a detected object and the LIDAR device. In some examples, the illumination intensity pattern is varied based on the presence of an object detected by the LIDAR device or another imaging system.

Abstract: Methods and systems for performing three dimensional LIDAR measurements with different pulse repetition patterns are described herein. Each repetitive pattern is a sequence of measurement pulses that repeat over time. In one aspect, the repetition pattern of a pulsed beam of illumination light emitted from a LIDAR system is varied to reduce total energy consumption and heat generated by the LIDAR system. In some examples, the repetitive pattern is varied by skipping a number of pulses. In some examples, the repetitive pattern of pulses of illumination light emitted from the LIDAR system is varied by changing a repetition rate of the sequence of emitted pulses. In some examples, the pulse repetition pattern is varied based on the orientation of the LIDAR device. In some examples, the repetition pattern is varied based on an object detected by the LIDAR device or another imaging system.