Patent Description:
As background, <CIT> describes a mirror, optical imaging system and use thereof; <CIT> describes Conic of Rotation (CoR) Optical Surfaces and Systems of Matched CoRs; <CIT> describes an optical beam expander; Risse et al [XP060020140, DOI: <NUM>/<NUM>] describe development and fabrication of a hyperspectral, mirror based IR-telescope with ultra-precise manufacturing and mounting techniques for a snap-together system assembly; Lovell Comstock [XP055470762, DOI: <NUM>/<NUM>] describes recent technology advances in diamond machining for spaceborne optical systems. Sub-micron alignment of optical surfaces such as mirrors is generally important to achieve high performance requirements in an optical instrument. Under some circumstances, such as during launch of a satellite with an optical instrument, the alignment needs to withstand significant vibration. At the same time, cost of production, complexity, and weight should be considered. It is with these and other considerations that the current methods and systems have been developed.

One aspect of the present disclosure relates to a method of manufacturing an optical assembly. Optical components are formed by rotating respective workpieces around a rotational axis while shaping their material to form respective optical surfaces having respective curvatures which are rotation symmetric around respective optical axes of the optical surfaces coinciding with the rotational axis. In the same rotation based manufacturing process, respective alignment structures are formed having predefined relative positions with respect to curvatures of the optical surfaces. The optical components thus formed are combined by connecting respective alignment structures.

Advantageously, various coordinates of the optical surfaces of different components can be aligned by the connection between the alignment structures and their predefined relative positions with respect to the optical surfaces. For example, by matching radial offsets in different components between respective optical axes and (concentric) edges of
respective alignment structures, the optical axes of different components can be aligned to coincide. By providing the optical surfaces with rotation symmetric curvatures, the alignment can be insensitive to limited rotation along a tangential coordinate. Also axial alignment can be achieved by setting a predefined height of connecting surfaces of the optical components or their alignment structures with respect to the alignment point of the curvatures defining the optical surfaces. For example, by aligning both the radial and axial coordinates, focal points of different optical surfaces, e.g. parabolic mirrors, can be overlapped e.g. to form a beam expander or other instrument. It will be appreciated, that an accuracy of the alignment may be determined by the rotation based manufacturing process. For example, both the optical surfaces and alignment structures can be shaped by high precision diamond turning, also referred to as single-point diamond turning (SPDT), which can achieve sub-micron precision. And because the alignment structure is integral with the optical surface (made from one piece), the alignment is much more robust than e.g. using intermediate alignment structures. It can be especially robust when the optical assembly is designed to directly reflect the light beam between the optical surfaces of interconnected components, without other reflecting surfaces in between.

<FIG> schematically illustrate an embodiment for manufacturing optical components to be combined in an optical assembly.

As illustrated by <FIG>, one embodiment comprises forming a first optical component by rotating a first workpiece <NUM> around a rotational axis R while shaping its material. The shaping may include forming a first optical surface <NUM> having a first curvature C1 which is rotation symmetric around a first optical axis A1 of the first optical surface <NUM> coinciding with the rotational axis R. The shaping may further include forming a first alignment structure <NUM> having a predefined first relative position Dr1,Dz1 with respect to the first curvature C1 of the first optical surface <NUM>.

As illustrated by <FIG>, a second optical component can be formed in some embodiments by rotating a second workpiece <NUM> around the rotational axis R while shaping its material. The shaping may include forming a second optical surface <NUM> having a second curvature C2 which is rotation symmetric around a second optical axis A2 of the second optical surface <NUM> coinciding with the rotational axis R. The shaping may further include forming a second alignment structure <NUM> having a predefined second relative position Dr2,Dz2 with respect to the second curvature C2 of the second optical surface <NUM>.

Preferably, the shaping of the respective optical surface <NUM> or <NUM> and the respective alignment structure <NUM> or <NUM> takes place in a single manufacturing process, e.g. without removing the respective optical component from the machine (indicated here by numeral <NUM>,<NUM>,<NUM>) between manufacturing of the respective optical surface and alignment structure. In this way the machine may better maintain relative alignment for each optical component.

In some embodiment, the workpieces <NUM>,<NUM> are rotated by a lathe <NUM> or derivative machine tools, e.g. turn-mills, rotary transfers. For example, the lathe <NUM> comprises a turn table or other rotating structure configured to hold or clamp the workpieces <NUM>,<NUM> while rotating. In some cases, e.g. wherein a center of mass of the optical component to be manufactured is offset (far) from the rotational center, such as the component <NUM> here, the lathe (or workpiece) may be provided with a counterweight during manufacturing, to at least partly compensate for this offset and allow a smoother rotation (without wobbling).

In a preferred embodiment, the workpieces <NUM>,<NUM> are shaped by a cutting tool <NUM>, e.g. tool bit. Alternatively, or in addition to a physical tool bit, also other cutting tools may be envisaged, e.g. a (focused) laser beam configured to cut away material e.g. by ablation. Alternatively, or in addition to a cutting tool, also other devices and methods may be envisaged to shape the material of workpieces, e.g. additive manufacturing or 3D printing. It can even be envisaged that optical components <NUM>,<NUM> are manufactured by molding from respective work pieces that are shaped by any of the processes described herein. For example, the optical surfaces and alignment structures are shaped as negatives in a respective mold. After manufacturing of respective shaped, also further processes may be applied e.g. to the optical surfaces for achieving desired optical function. For example, the optical surfaces may be coated with a metal, e.g. gold or aluminum, layer for achieving desired reflectivity in a specific wavelength domain. Processing may include electroless nickel plating (NiP). Also other, e.g. multiple, layers may be deposited, e.g. to form dielectric coated mirrors also referred to as Bragg mirrors. Coating may also be applied to other surfaces, e.g. adhesive.

In some embodiments, a relative position of the cutting tool <NUM> with respect to the workpieces <NUM>,<NUM> is controlled by an actuator <NUM>. Preferably, the cutting tool <NUM> is moved with sub-micron or even nanometer precision e.g. by a combination of electric motors and piezoelectric actuators. For example, the motion of the cutting tool <NUM> is controlled by a list of coordinates generated by a computer, also referred to as computer numerical control (CNC).

It will be appreciated that an accuracy of the relative positions Dr1,Dz1;Dr2,Dz2 of the respective alignment structures <NUM>,<NUM> with respect to the (curvatures of the) optical surfaces <NUM>,<NUM> can be determined by an accuracy of the manufacturing method. Preferably, the relative positions Dr1,Dz1;Dr2,Dz2 between the alignment structures <NUM>,<NUM> and respective optical surfaces <NUM>,<NUM> are manufactured with sub-micron accuracy. Accordingly, in the combined optical assembly <NUM> the optical axes A1,A2 and/or focal points F1,F2 may overlap within sub-micron accuracy. For example, the distance between the aligned optical axes A1,A2 or between the aligned focal points F1,F2 in the optical assembly <NUM> is less than hundred micrometer, less than ten micrometer, preferably less than one micrometer, less than a tenth of a micrometer, less than a hundredth of a micrometer, or even sub-nanometer, e.g. between <NUM> to a few micron.

In a preferred embodiment, the optical surfaces <NUM>,<NUM> and alignment structures <NUM>,<NUM> are shaped by a high-accuracy manufacturing process such as diamond turning, also referred to as single-point diamond turning SPDT. For example, SPDT uses a diamond-tipped tool bit to cut away material from the workpieces <NUM>,<NUM>. In principle, also other sufficiently hard materials can be used as tool bit, depending on the material of the workpieces. Typically diamond turning is a multi-stage process. Initial stages of machining are carried out using a series of CNC lathes of increasing accuracy. A diamond-tipped lathe tool is used in the final stages of the manufacturing process to achieve sub-nanometer level surface finishes and sub-micrometer form accuracies. The surface finish quality is typically measured as the peak-to-valley distance of the grooves left by the lathe and cutting tool. The form accuracy is typically measured as a mean deviation from the ideal target form. Similar processes may be used for other processes of shaping the work pieces.

<FIG> illustrates an embodiment of an optical assembly <NUM> which may be formed by combining the components manufactured in <FIG>. For example, one embodiment comprises combining the first optical component <NUM> with the second optical component <NUM> by (directly) connecting the first alignment structure <NUM> with the second alignment structure <NUM>. Advantageously, the first optical surface <NUM> is aligned with respect to the second optical surface <NUM> by the connection between the alignment structures <NUM>,<NUM> and their predefined relative positions Dr, Dz with respect to the optical surfaces <NUM>,<NUM>.

The alignment structures may be directly or indirectly aligned with predefined distances or angles with respect to the optical surfaces and/or alignment points/ lines defined by their curvatures such as a focal or apex point, or a (central) axis of symmetry. In the embodiment shown, the alignment structures alignment structures <NUM>,<NUM> are directly connected to each other, which may provide greater alignment precision than an indirect connection, e.g. via an intermediate structure.

In one embodiment, such as shown in <FIG>, the first relative position between the optical surface and alignment structure includes a first radial offset Dr1 of the first alignment structure <NUM> with respect to the first optical axis A1 of the first curvature C1. In another or further embodiment, such as shown in <FIG>, the second relative position between the optical surface and alignment structure includes a second radial offset Dr2 of the second alignment structure <NUM> with respect to the second optical axis A2 of the second curvature C2. In a preferred embodiment, the first radial offset Dr1 matches the second radial offset Dr2 to align the first optical axis A1 to coincide with the second optical axis A2 in the optical assembly <NUM> when the first alignment structure <NUM> is connected to the second alignment structure <NUM> e.g. as shown in <FIG>.

In some embodiments, such as shown in <FIG>, the first relative position includes a first axial offset Dz1 of the first alignment structure <NUM> with respect to a first alignment point (e.g. F1 or V1) defined by the first curvature C1. In other or further embodiments, such as shown in <FIG>, the second relative position Dr2,Dz2 includes a second axial offset Dz2 of the second alignment structure <NUM> with respect to a second alignment point (e.g. F2 or V2) defined by the second curvature C2. In a preferred embodiment, the first axial offset Dz1 matches, or has a predetermined difference, with the second axial offset Dz2 to align the first optical surface <NUM> with respect to the second optical surface <NUM> along a coordinate Z on the coinciding optical axes A1,A2.

In some embodiments, the first curvature C1 defines a first focal point F1 of the first optical surface <NUM> and/or the second curvature C2 defines a second focal point F2 of the second optical surface <NUM>. For example, an optical surface can be defined by a parabola equation Z = a · (X - Xv)<NUM> + Zv, where "a" gives the height to width ratio of the parabola having its vertex "V" (highest or lowest point) at coordinates [ Xv , Zv ], the focus F is at coordinates [ Xv, Zv + <NUM>/(4a) ]. For example, an optical surface can be defined by an ellipse equation (X - Xc)<NUM> / a<NUM> + (Z - Zc)<NUM> / b<NUM> = <NUM>, where "a" is the higher radius and "b" the lower radius of the ellipse having its center at [ Xc, Zc ], each focus "F" (there are two) is distanced from the center (along the higher radius) by "c" which can be calculated using c<NUM> = a<NUM> - b<NUM>. Instead of the coordinate X, a radial coordinate may be substituted to obtain a radially symmetric curvature. For example a curvature Z = a· R<NUM> may define a rotation symmetric parabola with its vertex at [<NUM>,<NUM>] and focus at [<NUM>,<NUM>/(<NUM>·a)]. Also other curvatures may define respective vertices and/or focal points.

In a preferred embodiment, such as illustrated in each of <FIG>,<FIG>, the first focal point F1 is aligned to coincide with the second focal point F2. For example, the first radial offset Dr1 matches the second radial offset Dr2 and the first axial offset Dz1 between the first focal point F1 and the first alignment structure <NUM> matches the second axial offset Dz2 between the second focal point F2 and the second alignment structure <NUM>.

With reference again to the embodiment of <FIG>, the optical surfaces <NUM>,<NUM> may be configured to reflect a light beam L, e.g. forming parabolic mirrors. Alternatively, or in addition, also other optical surfaces such as refractive surfaces may be envisaged. For example, one or more of the optical surfaces may form a lens (not shown), grating (not shown), et cetera. In a preferred embodiment, the optical assembly <NUM> is configured to reflect a light beam L from the first optical surface <NUM> directly to the second optical surface <NUM> without intermediate reflecting surface. In this way the beam alignment of the optical surfaces <NUM>,<NUM> is completely fixed.

Typically, the first curvature C1 has a first vertex V1 on the first optical axis A1 and/or the second curvature C2 has a second vertex V2 on the second optical axis A2. In the embodiment of <FIG>, a coinciding focal point F of the first curvature C1 and the second curvature C2 is between the first vertex V1 and the second vertex V2 in the combined optical assembly <NUM>. This is the typically case for two oppositely oriented curvatures C1,C2 as shown, e.g. a first parabola forming the first curvature C1 with a first vertex V1 at its minimum and a second parabola forming the second curvature C2 with a second vertex V2 at its maximum (here along the Z axis). In the embodiment shown, the optical assembly <NUM> is configured to maintain a general direction of the light beam L, i.e. the outgoing light beam travels in the same direction as the incoming light beam (here both traveling in the negative Z axis direction).

In some embodiments such as <FIG>, the optical assembly <NUM> comprises a cavity formed between the first optical component <NUM> and the second optical component <NUM>. Typically, the cavity is formed within an intersection of the first curvature C <NUM> and the second curvature C2. In other or further embodiments, the first optical component <NUM> and/or second optical component <NUM> comprise respective beam passages <NUM>,<NUM> to pass a light beam L between the first optical surface <NUM> and second optical surface <NUM> and/or between the cavity and external surroundings. For example, the cavity is formed between the second optical surface <NUM> and a plate which together with the first optical surface <NUM> forms a monolithic piece of the first optical component <NUM>.

In some embodiments, the first workpiece <NUM> and the second workpiece <NUM> are shaped from a respective manufacturing direction M1,M2, e.g. shown in <FIG> as the direction from which a shaping tool <NUM> operates on the workpieces <NUM>,<NUM>. In embodiment such <FIG>, in the combining of the first optical component <NUM> and second optical component <NUM> to form the optical assembly <NUM>, one of the optical components <NUM>,<NUM> is flipped upside down such that the manufacturing directions M1,M2 of the first optical component <NUM> and second optical component <NUM> face each other. Alternative to a shaping tool, e.g. cutting bit, working from one direction, the tool may work from a range of different directions either on one side of the work piece or two different sides, or even from more than two sides, e.g. front, back and side. Alternatively, to using one tool, multiple tools can be used sequentially or at the same time, working from the same direction, or different directions.

In some embodiments, such illustrated by <FIG>, the first curvature C1 is defined by a parabolic shape rotated around its central axis of symmetry coinciding with the first optical axis A1 and defining a first focal point F1 and a first vertex V1. In some embodiments such as <FIG>, the second curvature C2 is defined by a (different) parabolic shape rotated around its central axis of symmetry coinciding with the second optical axis A2 and defining a second focal point F2 and a second vertex V2. Because the parabolic shapes are preferably different, a distance between the first focal point F1 and the first vertex V1 is larger than a distance between the second focal point F2 and the second vertex V2. Combining parabolic having different focal distances typically means that a light beam L may change size while traversing the assembly. Accordingly, the optical assembly <NUM> form or be part of an optical instrument such as a telescope and/or beam expander. For example, as shown, the optical assembly <NUM> is configured to receive a collimated light beam L with a first diameter, expand or contract a diameter of the light beam and send out a collimated light beam with a second diameter, different from the first diameter.

In some embodiments, such illustrated by <FIG>, the first and/or second curvature C1,C2 is defined by an ellipsoid shape rotated around its (major) axis of symmetry coinciding with the first optical axis A1 and defining a respective primary focal point F and (closest) vertex V2. For example, an optical surface <NUM> defined by the ellipsoid is configured to refocus a light beam originating from its primary focal point F to its secondary focal point F', as shown. In some embodiments, the primary focal point of a second optical surface <NUM> coincides with a focal point F of a parabolic curve C1 defining the first optical surface <NUM>.

Also other types of curves can be used to define the optical surfaces <NUM>,<NUM>, including spherical and aspherical surfaces, preferably shapes defining respective focal points such as parabolic, ellipsoid, or even hyperbolic shapes. Also other rotation symmetric shapes can in principle be used such as cylindrical, toroidal, and/or cone shaped surfaces depending on the optical applications. Also combinations of these shapes can be used. And while the present embodiments show optical assemblies with two optical surfaces <NUM>,<NUM>, also more than two surfaces can be provided. For example, an optical component may comprise one, two, or more distinct optical surfaces, i.e. surfaces defined by distinct curvatures, typically wherein each curvature is continuous and continuously differentiable. Also more than two optical components may be combined, e.g. three components may be combined wherein a first set of alignment structures aligns the first and second component and a second set of alignment structures aligns the first and third component, or the second and third component. In this way, an optical assembly may be built from two, three, four or more components, each of the optical surfaces being aligned by respective alignments structures and/or by physical connection of multiple optical surfaces being shaped from one work piece.

<FIG> illustrates another embodiment of an optical assembly, wherein the curvatures of the optical surfaces both face upward.

In some embodiments, as shown, the optical assembly <NUM> is configured to reflect back a light beam L to the direction it was coming from, i.e. the outgoing light beam travels in the back in the direction (here along the Z axis direction) opposite the direction of the incoming light beam (here in the negative Z axis direction). Typically, the first curvature C1 has a first vertex V1 on the first optical axis A1 and the second curvature C2 has a second vertex V2 on the second optical axis A2. In the embodiment of the combined optical assembly <NUM>, as shown" the second vertex V2 is between the first vertex V1 and a coinciding focal point F of the first curvature C1 and the second curvature C2. In some embodiments, as shown here, a distance between the first vertex V1 and coinciding focal point F is larger that a distance between the second vertex V2 and the coinciding focal point F (or vice versa). In other words, the first optical surface <NUM> may typically have a different curvature and/or focal distance than the second optical surface <NUM>.

<FIG> illustrates an example not according to the claimed invention wherein one optical component <NUM>' comprises multiple optical surfaces <NUM>, <NUM>. For example, as shown, at least one optical component <NUM>', manufactured from a single work piece, comprises two, or more, distinct optical surfaces <NUM>,<NUM>. In some embodiments, the optical component <NUM>' comprises an alignment structure to couple with a second optical component (not shown).

<FIG> illustrate a cross-section and top view of another embodiment of an optical assembly <NUM>. Some embodiment, e.g. as illustrated here, may comprise combining the first optical component <NUM> with the second optical component <NUM> by (indirectly) connecting the first alignment structure <NUM> with the second alignment structure <NUM> via an intermediate structure <NUM>. The first optical surface <NUM> is thus aligned with respect to the second optical surface <NUM> by the indirect connection between the alignment structures <NUM>,<NUM> and their predefined relative positions Dr,Dz with respect to the optical surfaces <NUM>,<NUM>.

In a preferred embodiment, the intermediate structure <NUM> is formed by the same manufacturing process as the optical components <NUM>,<NUM>, e.g. all components <NUM>,<NUM>,<NUM> are manufactured by single point diamond turning or similar rotation based process. In the embodiment shown, the intermediate structure <NUM> comprises a circular edge <NUM> which can act as an intermediate alignment structure. For example, the edge is disposed at a radial distance Dr and the circular (outer) edges of the optical components <NUM>,<NUM> form the alignment structures <NUM>,<NUM> which can be pushed against the circular edge <NUM>. This can have similar advantages as described for the other embodiment, e.g. wherein the radial alignment is highly accurate while the tangential may allow some variation due to the circular symmetry of the optical surfaces <NUM>,<NUM> and alignment structures alignment structures <NUM>,<NUM>, and <NUM>. It will be appreciated that the circular alignment structures on the optical components <NUM>,<NUM> and/or intermediate structure <NUM> can also be arranged at other radial distances than shown. For example, the intermediate structure <NUM> may comprise two circular edges with different radii (not shown) e.g. both concentric with the center of the intermediate structure <NUM> to coincide with the optical axes A1=A2 of the optical components <NUM>,<NUM> to be aligned. Alignment can occur with an inner radial edge, outer radial edge, or both.

<FIG> illustrate CAD drawings of embodiment for a telescope/beam expander similar to <FIG>. <FIG> illustrate a perspective bottom and top view of a first optical component <NUM>. <FIG> illustrate a perspective bottom and top view of a corresponding second optical component <NUM>. <FIG> illustrate a cross-section views of the optical components <NUM>,<NUM> and how they may function together in an optical assembly <NUM>;.

With reference to <FIG> and <FIG>, the optical surfaces <NUM>,<NUM> may comprise concentric micro-grooves (concentric around the optical axis coinciding with the rotational axis R). The micro-grooves are highly exaggerated in the current figures for illustrative purposes and may normally be invisible to the naked eye. Typically the micro-grooves have sub-micron, e.g. down to nanometer scale, peak-to-valley height differences or roughness. This may e.g. be detectable with a precision microscope or optical means such as diffraction measurements. As also illustrated by these figures, the alignment structures <NUM>,<NUM> may comprise edges that are concentric with the optical axes of the respective optical surfaces <NUM>,<NUM>. It will be appreciated that alignment can be mostly invariant to rotation around the rotational axis R coinciding with the optical axis of the optical surfaces, because the optical surfaces are rotationally symmetric around that axis. Accordingly, the alignment structures <NUM>,<NUM> are preferably radially fixed, while some tangential, in the order of a few micron freedom may be allowed.

In some embodiments, as illustrated e.g. by <FIG> and <FIG>, one or both of the alignment structures <NUM>,<NUM> comprises one or more circular rims and/or grooves. Preferably, at least one of the circular rims and/or grooves has a certain tangential extent, that is extends over part of the circle, e.g. extending more than one degree (plane angle), preferably more than three degrees, more than five degrees, more than ten degrees, or even extending around the whole circle. In a preferred embodiment, at least one of the alignment structures <NUM> comprises at least two connectors at one radial coordinate to fixate the radial alignment optionally allowing some rotation along a tangential (round going) direction. In a more preferred embodiment, at least one of the alignment structures <NUM> comprises at least three connectors preferably equidistantly distributed around a circle concentric with the rotational axis R. In other or further embodiments, as shown, at least one of the alignment structures <NUM> comprises a tapered structure, preferably tapered inward, for helping to center the first optical component <NUM> with respect to the second optical component <NUM>.

In some embodiments, as illustrated e.g. by <FIG> and <FIG>, the optical components <NUM>,<NUM> comprise respective interconnecting fixation structures <NUM>,<NUM> such as screw holes to screw the components together. It will be appreciated that the interconnecting fixation structures <NUM>,<NUM> are separate here from the alignment structures <NUM>,<NUM>. For example, the alignment structures <NUM>,<NUM> are used for precise radial and axial alignment of the components <NUM>,<NUM> while the interconnecting fixation structures <NUM>,<NUM> are used for possibly less stringent tangential alignment, e.g. to align the apertures <NUM> in the first optical component <NUM> with respect to the second optical surface <NUM> of the second optical component <NUM>.

In one embodiment, e.g. as illustrated in <FIG>, the optical assembly <NUM> comprises an intermediate field stop <NUM>. For example, the intermediate field stop <NUM> comprises a pinhole centered on a focal point F <NUM>=F2 of the first optical surface <NUM> and/or second optical surface <NUM>. In a preferred embodiment, one or both of the first optical component <NUM> and/or second optical component <NUM> comprises a third alignment structure <NUM> for aligning the (pinhole of the) intermediate field stop <NUM> with respect to the (common or individual) focal point. For example, the intermediate field stop <NUM> may help to filter stray light entering an optical system and/or used for shaping a phase front of the light beam L.

In some aspects, e.g. as illustrated with reference to <FIG>, the present disclosure provides an optical assembly <NUM>. The optical assembly <NUM> comprises a first optical component <NUM> combined with a second optical component <NUM>. The first optical component <NUM> comprises a first optical surface <NUM> having a first curvature C1 which is rotation symmetric around a first optical axis A1 of the first optical surface <NUM>, and a first alignment structure <NUM> having a predefined first relative position Dr1,Dz1 with respect to the first curvature C1 of the first optical surface <NUM>. The second optical component <NUM> comprises a second optical surface <NUM> having a second curvature C2 which is rotation symmetric around a second optical axis A2 of the second optical surface <NUM>, and a second alignment structure <NUM> having a predefined second relative position Dr2,Dz2 with respect to the second curvature C2 of the second optical surface <NUM>. Due to the manufacturing process, as described herein, the optical components <NUM>,<NUM> each comprise a monolithic structure, i.e. are built from one piece (the respective work piece).

In the optical assembly <NUM> as illustrated by <FIG>, the first alignment structure <NUM> is connected with the second alignment structure <NUM>. In this way the first optical surface <NUM> is aligned with respect to the second optical surface <NUM> by the connection between the alignment structures <NUM>,<NUM> and their predefined relative positions with respect to the optical surfaces <NUM>,<NUM>. Due to some manufacturing processes as described herein, the optical surfaces <NUM>,<NUM> may comprise micro-groove structures concentric around the respective one or more optical axes A1,A2 (may be invisible to the naked eye but detectable by microscopic instruments). Furthermore, the alignment structures <NUM>,<NUM> may comprise corresponding concentric edges. In some aspects, the present disclosure may also provide an optical instrument comprising the optical assembly as described herein, e.g. wherein the optical assembly is configured as a telescope and/or beam expander in a satellite.

For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. For example, while embodiments were shown for optical assemblies comprising two monolithic optical components, each with a single optical surface, there can be more interconnected optical components.

Each one or more component may comprise one, two, or more optical surfaces. The various elements of the embodiments as discussed and shown offer certain advantages, such as high accuracy stable alignment.

It is appreciated that this disclosure offers particular advantages to optical instruments that may undergo heavy vibrations such as instruments for satellites, and in general can be applied for any application wherein high accuracy, simple construction, and/or cost saving is desired.

Claim 1:
A method of manufacturing an optical assembly (<NUM>), the method comprising
- forming a first optical component (<NUM>) by rotating a first workpiece (<NUM>) around a rotational axis (R) while shaping its material to form
a first optical surface (<NUM>) having a first curvature (C1) which is rotation symmetric around a first optical axis (A1) of the first optical surface (<NUM>) coinciding with the rotational axis (R), and
a first alignment structure (<NUM>) having a predefined first relative position (Dr1,Dz1) with respect to the first curvature (C1) of the first optical surface (<NUM>);
- forming a second optical component (<NUM>) by rotating a second workpiece (<NUM>) around the rotational axis (R) while shaping its material to form
a second optical surface (<NUM>) having a second curvature (C2) which is rotation symmetric around a second optical axis (A2) of the second optical surface (<NUM>) coinciding with the rotational axis (R), and
a second alignment structure (<NUM>) having a predefined second relative position (Dr2,Dz2) with respect to the second curvature (C2) of the second optical surface (<NUM>); and
- combining the first optical component (<NUM>) with the second optical component (<NUM>) by connecting the first alignment structure (<NUM>) with the second alignment structure (<NUM>), wherein the first optical surface (<NUM>) is aligned with respect to the second optical surface (<NUM>) by the connection between the alignment structures (<NUM>,<NUM>) and their predefined relative positions (Dr1,Dz1;Dr2,Dz2) with respect to the optical surfaces (<NUM>,<NUM>), wherein the first curvature (C <NUM>) defines a first focal point (F1) of the first optical surface (<NUM>), wherein the second curvature (C2) defines a second focal point (F2) of the second optical surface (<NUM>), characterized in that the first focal point (F1) is aligned to coincide with the second focal point (F2).