An apparatus for intraoral scanning includes an elongate handheld wand that has a probe. One or more light projectors and two or more cameras are disposed within the probe. The light projectors each has a pattern generating optical element, which may use diffraction or refraction to form a light pattern. Each camera may be configured to focus between 1 mm and 30 mm from a lens that is farthest from the camera sensor. Other applications are also described.

An alignment system aligns a laser beam to a desired position in a reference plane and to a desired direction in the reference plane. The system diffracts the laser light into different diffraction orders that are projected onto a detection plane using different lenses. As the locations of the projections of the different diffraction orders in the detection plane respond differently to changes in position and in direction of the beam in the reference plane, the locations of the projections enable to determine how to adjust the beam so as to get the beam properly aligned. The diffraction and the projection can be implemented by a hologram.

A diffractive optical element is configured to provide desired diffracted light and is excellent in durability. The diffractive optical element shapes light from a light source, wherein the diffractive optical element is provided with a diffractive layer having a periodic structure having low refractive index portions and high refractive index portions, and the high refractive index portions of the periodic structure include one having an aspect ratio of 2 or more.

A dental scanning system comprises an intraoral scanner and one or more processors. The intraoral scanner comprises one or more light projectors configured to project a pattern (comprising a plurality of pattern features) on a surface of a dental object, and two or more cameras configured to acquire one or more sets of images, wherein each set of images comprises at least one image from each camera, and wherein each image includes at least a portion of the projected pattern. The processors are configured to determine one or more image features within each set of images, solve a correspondence problem within each set of images such that points in 3D space are determined based on the image features, wherein said points form a solution to the correspondence problem, and wherein the correspondence problem is solved for groups of pattern features, and generate a digital 3D representation of the dental object using the solution to the correspondence problem.

A dental scanning system comprises an intraoral scanner and one or more processors. The intraoral scanner comprises one or more light projectors configured to project a pattern (comprising a plurality of pattern features) on a dental object, and two or more cameras configured to acquire sets of images, each comprising at least one image from each camera. The processor(s) are configured to determine a correspondence between pattern features in the pattern of light and image features in each set of images by determining intersections of projector rays corresponding to one or more of the plurality of pattern features and camera rays corresponding to the one or more image features in three-dimensional (3D) space based on calibration data that associates the camera rays corresponding to pixels on the camera sensor of each of the two or more cameras to the projector rays.

A diffractive optical element is configured to provide desired diffracted light and is excellent in durability. The diffractive optical element shapes light from a light source, wherein the diffractive optical element is provided with a diffractive layer having a periodic structure having low refractive index portions and high refractive index portions, and the high refractive index portions of the periodic structure include one having an aspect ratio of 2 or more.

An optical lens includes five aspheric lenses and an aperture stop. The five aspheric lenses are, arranged in order from a first side to a second side, a first lens, a second lens, a third lens, a fourth lens and a fifth lens, and the aperture stop is disposed between the first lens and the second lens. An image height at the image plane is denoted as H, the image height is equally divided into ten sections to from ten height positions 0.1H, 0.2H, 0.3H, 0.4H, 0.5H, 0.6H, 0.7H, 0.8H, 0.9H and 1H. Chief rays traveling through the optical lens and to the ten height positions respectively form ten angles with respect to a normal of an image plane, and each of the ten angles is smaller than 10 degrees.

A system for an extreme ultraviolet (EUV) light source includes a light-generation system configured to emit one or more light beams onto a beam path; one or more optical amplifiers, each of the one or more amplifiers including a gain medium on the beam path, each gain medium being configured to amplify the one or more light beams to produce one or more amplified light beams; and one or more diffractive optical elements on the beam path, where each of the one or more diffractive optical elements has a plurality of focal lengths, and each focal length of the diffractive optical element is associated with a particular polarization state.

A real-time variable parameter micro-nano optical field modulation system includes a light source, a 4F optical system and a set of light wave modulation optical components. The 4F optical system includes a first optical assembly and a second optical assembly arranged along an optical path in sequence. The light wave modulation optical components are arranged between the first optical assembly and the second optical assembly, and generate optical field distribution with adjustable patterns and structural parameters thereof on a back focal plane of the system by segmented modulation of sub-wavefronts.

A diffractive optical element includes: a substrate; a protrusion and recess portion that is formed on one surface of the substrate and imposes predetermined diffraction on incident light; and an antireflection layer provided between the substrate and the protrusion and recess portion. An effective refractive index difference n in a wavelength range of the incident light between a first medium constituting a protrusion of the protrusion and recess portion and a second medium constituting a recess of the protrusion and recess portion is 0.70 or more. An exit angle range .sub.out of diffraction light exiting from the protrusion and recess portion when the incident light enters the substrate from a normal direction of the substrate is 60 or more. Total efficiency of diffraction light exiting from the protrusion and recess portion in the exit angle range is 65% or more.