Provided is a reflective optical element that is lightweight and excellent in damping capacity. In the reflective optical element, a resin layer having an optical surface is formed on a metal substrate, and a reflective film is formed on the optical surface, and also, the metal substrate includes an alloy containing Mg as a main component.

In a beam splitter assembly 7, a beam splitter 22 is supported at three points by three bent portions 41 of a first spacer 24. Therefore, the beam splitter 22 can be prevented from being affected by the surface accuracy of a holder 21. Further, in the beam splitter assembly 7, the first spacer 24 faces the peripheral edge portion of the beam splitter 22. Each bent portion 41 is configured by bending each outer projection piece. Therefore, the external shape of the first spacer 24 can be prevented from becoming larger than the external shape of the beam splitter 22. And it is possible to suppress that the size of the holder 21 for providing the first spacer 24 becomes large. As a result, the miniaturization of the beam splitter assembly 7 can be realized.

A space optical instrument is disclosed including a primary mirror having an optical axis and including a first face, referred to as the front face, oriented towards an observed area, and a second face opposite to the first, referred to as the rear face, the optical instrument further including a thermal stabilization device for the primary mirror, comprising a thermally conductive wall extending around the optical axis (O) on the front face side of the primary mirror towards which this face is oriented. The thermal stabilization device further includes a temperature regulating device for the circumferential wall that is capable of using the measurement of an incident heat flux on the mirror, and adapting the temperature of the circumferential wall according to the measured incident heat flux, in order to keep the front face of the mirror at a constant temperature.

An optical module is provided. The optical module includes a substrate, an optical element, a cover plate, and a heat-dissipating device. The optical element is disposed on the substrate, wherein the optical element has a first side and a second side opposite the first side. The cover plate is disposed on the second side of the optical element, and extends over the substrate. In addition, the substrate is disposed between the heat-dissipating device and the optical element.

A mirror system including a primary mirror, and a secondary mirror with different coefficients of thermal expansion. A negative CTE strut can include a main body portion, a first coupling portion and a second coupling portion disposed opposite one another about the main body portion and defining a strut length. The first and second coupling portions can each interface with an external structure. The negative CTE strut can include an offsetting extension member having a first end coupled to the main body portion and a second end coupled to the first coupling portion by an intermediate extension member. The first and second ends can define an offset length parallel to the strut length. When the negative CTE strut increases in temperature, the offset length can be configured to increase due to thermal expansion of the offsetting extension member sufficient to cause the strut length to decrease.

An improved mount for, and method of mounting an, optical structure is provided. The mount has an optical structure comprising at least one mirror panel, the mirror panel comprising a reflective surface and a back surface substantially opposite the reflective surface, a protruding member extending from the back surface of the optical structure, the protruding member having a shape and the shape having an outside surface there-around, a base comprising a mounting element and an upper element extending from the mounting element, the upper element having a cavity for secured receipt therein of at least a portion of the protruding member, wherein the receiving cavity of the upper element has a shape identical to that of the shape of the protruding member, but where the shape of the protruding member is ten thousandths ( 1/10,000) of an inch smaller than the shape of the receiving cavity so that the outside surface of the protruding member is ten thousandths ( 1/10,000) of an inch away from the corresponding parts of the receiving cavity when the protruding member is secured within the cavity.

An optical assembly includes: an optical element, which is transmissive or reflective to radiation at a used wavelength and has an optically used region; and a thermally conductive component, which is arranged outside the optically used region of the optical element. The thermally conductive component can include a material having a thermal conductivity of more than 500 W m.sup.1 K.sup.1. Additionally or alternatively, the product of the thickness of the thermally conductive component in millimeters and the thermal conductivity of the material of the thermally conductive component is at least 1 W mm m.sup.1 K.sup.1.

A mirror element, in particular for a microlithographic projection exposure apparatus. According to one aspect, the mirror element includes a substrate (111, 112, 113, 114, 115, 211, 212, 213, 311a-311m, 411, 412, 413) and a layer stack (121, 122, 123, 124, 125, 221, 222, 223, 321a-321m, 421, 422, 423) on the substrate. The layer stack has at least one reflection layer system, wherein a curvature of the mirror element is generated on the basis of a setpoint curvature for a predetermined operating temperature by a non-vanishing bending force exerted by the layer stack, wherein the generated curvature varies by no more than 10% over a temperature interval (T) of at least 10 K.

Rotatable mirror assemblies and light detection and ranging systems containing rotatable mirror assemblies are described herein. An example rotatable mirror assembly may include (1) a housing having a top end, a bottom end, and a longitudinal axis intersecting the top and bottom ends, and (2) a set of reflective surfaces, where each reflective surface in the set is coupled to the top end of the housing and the bottom end of the housing such that each reflective surface possesses limited freedom of movement with respect to the housing.

A Micro-Electromechanical System (MEMS) device having improved thermal management, and methods of fabricating the same are described. Generally, the device includes a piston layer suspended over a surface of a substrate by posts at four corners thereof, the piston layer including an electrostatically deflectable piston and a number of flexures through which the piston is coupled to the posts. A faceplate including an aperture through which the piston is exposed is suspended over the piston layer. Thermal sinking structures project from the surface of the substrate and extend through void spaces between the posts, the flexures and the piston of the piston layer to provide thermal management of the piston layer. The thermal posts substantially fill the void spaces without contacting either the flexures or the piston, and without altering a deflection gap between the piston and the surface of the substrate. Other embodiments are also described.