According to various embodiments, a direct magnetic gradiometer having intrinsic subtraction of rotation signals from two oppositely polarized atomic ensembles within a single multi-pass cell is disclosed. The gradiometer includes three convex spherical mirrors aligned in a V-shape geometry. The three convex spherical mirrors include a front mirror and two back mirrors. The gradiometer further includes a probe laser beam. The laser beam is configured to be initially focused at a near-zero angle into a hole at a center of the front mirror such that the laser beam expands at the back mirrors and nearly overlaps with itself while undergoing multiple reflections between the front and back mirrors. The laser beam is further configured to be refocused to the front mirror at different spots in a number equal to half of total beam passes before exiting.

A three-mirror anastigmat telescope comprises at least a concave first mirror, a convex second mirror and a concave third mirror, the three mirrors arranged so that the first mirror and the second mirror form, from an object at infinity, an intermediate image situated between the second mirror and the third mirror, the third mirror forming, from this intermediate image, a final image in the focal plane of the telescope. In the architecture of the telescope, at least the surface of the concave third mirror is a -polynomial surface.

An off-axis aspheric three-mirror optical system comprises a primary mirror, a secondary mirror, and a tertiary mirror. Relative to a first three-dimensional rectangular coordinates system in space, a second three-dimensional rectangular coordinates system is defined by a primary mirror location, a third three-dimensional rectangular coordinates system is defined by a secondary mirror location, and a fourth three-dimensional rectangular coordinates system is defined by a tertiary mirror location. The primary mirror in the second three-dimensional rectangular coordinates system, the secondary mirror in the third three-dimensional rectangular coordinates system, and the tertiary mirror in the fourth three-dimensional rectangular coordinates system are all sixth-order polynomial aspheric.

A freeform surface off-axial three-mirror imaging system comprising a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor. Each reflective surface of the primary mirror, the secondary mirror, and the tertiary mirror is an xy polynomial freeform surface. A field angle of the freeform surface off-axial three-mirror imaging system is larger than or equal to 601. An F-number of the freeform surface off-axial three-mirror imaging system is less than or equal to 2.5.

A head-up display device includes optical path deflecting means, a first mirror having power, a second mirror having power, and a light-blocking member that is provided with an aperture. Display light emitted from an image display surface is reflected by the optical path deflecting means, the first mirror, and the second mirror in this order, passes through the aperture, and reaches an image reflective surface. The image display surface and the optical path deflecting means are disposed on the same side as an observer and on a side opposite to the first mirror with respect to luminous flux that travels toward the aperture from the second mirror, and the image display surface is disposed on a side opposite to the second mirror with respect to luminous flux that travels toward the first mirror from the optical path deflecting means.

Techniques are disclosed for mounting optical elements in optical systems. A system may include a mirror assembly. The mirror assembly may include a mounting stem and a mirror. The system may further include a mounting ring. The system may further include a metering structure. The metering structure may include a receiving interface having an inner surface defining an aperture. The metering structure may be configured to receive the mounting stem within the aperture and receive the mounting ring within a gap between the mounting stem and the inner surface. The system may further include a bonding layer disposed between the mounting stem and the mounting ring. Additional apparatus and related methods are provided.

An off-axis aspheric three-mirror optical system comprises a primary mirror, a secondary mirror, and a tertiary mirror. Relative to a first three-dimensional rectangular coordinates system in space, a second three-dimensional rectangular coordinates system is defined by a primary mirror location, a third three-dimensional rectangular coordinates system is defined by a secondary mirror location, and a fourth three-dimensional rectangular coordinates system is defined by a tertiary mirror location. The primary mirror in the second three-dimensional rectangular coordinates system, the secondary mirror in the third three-dimensional rectangular coordinates system, and the tertiary mirror in the fourth three-dimensional rectangular coordinates system are all sixth-order polynomial aspheric.

A method for designing an off-axis aspheric optical system comprises establishing an initial system and selecting a plurality of feature rays R.sub.i (i=1, 2 . . . K); solving a plurality of feature data points (P.sub.1, P.sub.2, . . . P.sub.m) to obtain an initial off-axis aspheric surface A.sub.m by surface fitting the plurality of feature data points (P.sub.1, P.sub.2, . . . P.sub.m), wherein m is less than K; introducing an intermediate point G.sub.m to solve a (m+1)th feature data point P.sub.m+1, and fitting a plurality of feature data points (P.sub.1, P.sub.2, . . . P.sub.m, P.sub.m+1) to obtain an off-axis aspheric surface A.sub.m+1; repeating such steps until a Kth feature data point P.sub.K is solved, and fitting a plurality of feature data points (P.sub.1, P.sub.2, . . . P.sub.K) to obtain an off-axis aspheric surface A.sub.K; and repeating above steps until all the aspheric surfaces of the off-axis aspheric optical system are obtained.

A head up display arrangement for a motor vehicle includes an image source emitting a light field. A first freeform mirror is positioned to provide a first reflection of the light field. A generally concave second freeform mirror is positioned to receive the first reflection and provide a second reflection of the light field. The second reflection is reflected off of a windshield of the vehicle so as to be visible to a driver of the vehicle. An arcuate section of a surface of the generally concave second freeform mirror receives the first reflection and provides the second reflection. An angle between the first freeform mirror and an imaginary line that is tangent to a midpoint of the arcuate section of the surface of the generally concave second freeform mirror is approximately between thirty degrees and sixty degrees.

An off-axis three-mirror optical system with freeform surfaces comprised an aperture, a primary mirror, a secondary mirror, a tertiary mirror, and a detector. The aperture is located on an incident light path. The primary mirror is located on an aperture side. The secondary mirror is located on a primary mirror reflected light path. The tertiary mirror is located on a secondary mirror reflected light path. The detector located on a tertiary mirror reflected light path. The primary mirror and the tertiary mirror have a same fifth-order polynomial freeform surface expression. The primary mirror reflected light path, the secondary mirror reflected light path and the tertiary mirror reflected light path overlap with each other.