An apparatus for generating extreme ultraviolet (EUV) radiation includes a droplet generator configured to generate target droplets. An excitation laser is configured to heat the target droplets using excitation pulses to convert the target droplets to plasma. A deformable mirror is disposed in a path of the excitation laser. A controller is configured to adjust parameters of the excitation laser by controlling the deformable mirror based on a feedback parameter.

An apparatus for generating extreme ultraviolet (EUV) radiation includes a droplet generator configured to generate target droplets. An excitation laser is configured to heat the target droplets using excitation pulses to convert the target droplets to plasma. A deformable mirror is disposed in a path of the excitation laser. A controller is configured to adjust parameters of the excitation laser by controlling the deformable mirror based on a feedback parameter.

The invention relates to arrangements for actuating an element in a microlithographic projection exposure apparatus. In accordance with one aspect, an arrangement for actuating an element in a microlithographic projection exposure apparatus comprises a first number (n.sub.R) of degrees of freedom, wherein an adjustable force can be transmitted to the optical element in each of the degrees of freedom, and a second number (n.sub.A) of actuators, which are coupled to the optical element in each case via a mechanical coupling for the purpose of transmitting force to the optical element, wherein the second number (n.sub.A) is greater than the first number (n.sub.R). In accordance with one aspect, at least one of the actuators is arranged in a node of at least one natural vibration mode of the optical element.

The invention relates to arrangements for actuating an element in a microlithographic projection exposure apparatus. In accordance with one aspect, an arrangement for actuating an element in a microlithographic projection exposure apparatus comprises a first number (n.sub.R) of degrees of freedom, wherein an adjustable force can be transmitted to the optical element in each of the degrees of freedom, and a second number (n.sub.A) of actuators, which are coupled to the optical element in each case via a mechanical coupling for the purpose of transmitting force to the optical element, wherein the second number (n.sub.A) is greater than the first number (n.sub.R). In accordance with one aspect, at least one of the actuators is arranged in a node of at least one natural vibration mode of the optical element.

A method for correcting the thermoelastic effects on performance parameters of a telescope on board a space satellite, comprises a first step prior to the flight of the satellite consisting in determining, a priori, a correction of the thermoelastic effects by using a prior model of variations of the thermoelastic effects on the orbital scale and an algorithm for determining correction fed by programming data of the space satellite, and a second step carried out in flight, based on the correction determined a priori, consisting in establishing control messages of correction means for correcting the performance parameters of said telescope.

A method for correcting the thermoelastic effects on performance parameters of a telescope on board a space satellite, comprises a first step prior to the flight of the satellite consisting in determining, a priori, a correction of the thermoelastic effects by using a prior model of variations of the thermoelastic effects on the orbital scale and an algorithm for determining correction fed by programming data of the space satellite, and a second step carried out in flight, based on the correction determined a priori, consisting in establishing control messages of correction means for correcting the performance parameters of said telescope.

An apparatus for transmitting and/or reflecting a laser beam for at least partially correcting astigmatism of the laser beam includes an optical element for transmitting and/or reflecting the laser beam. The optical element is deformable by an external force. The apparatus further includes at least four supports for the optical element arranged along an imaginary circle. The at least four supports are aligned diametrically opposite one another in pairs. The apparatus further includes at least two deformation elements for exerting the external force on the optical element. The at least two deformation elements are arranged diametrically to one another with respect to a center of the imaginary circle through the at least four supports. Each of the at least two deformation elements is arranged on an angle bisector of an angle defined by two adjacent supports and the center of the imaginary circle through the at least four supports.

An apparatus for transmitting and/or reflecting a laser beam for at least partially correcting astigmatism of the laser beam includes an optical element for transmitting and/or reflecting the laser beam. The optical element is deformable by an external force. The apparatus further includes at least four supports for the optical element arranged along an imaginary circle. The at least four supports are aligned diametrically opposite one another in pairs. The apparatus further includes at least two deformation elements for exerting the external force on the optical element. The at least two deformation elements are arranged diametrically to one another with respect to a center of the imaginary circle through the at least four supports. Each of the at least two deformation elements is arranged on an angle bisector of an angle defined by two adjacent supports and the center of the imaginary circle through the at least four supports.

The invention relates to arrangements for actuating an element in a microlithographic projection exposure apparatus. In accordance with one aspect, an arrangement for actuating an element in a microlithographic projection exposure apparatus comprises a first number (n.sub.R) of degrees of freedom, wherein an adjustable force can be transmitted to the optical element in each of the degrees of freedom, and a second number (n.sub.A) of actuators, which are coupled to the optical element in each case via a mechanical coupling for the purpose of transmitting force to the optical element, wherein the second number (n.sub.A) is greater than the first number (n.sub.R). In accordance with one aspect, at least one of the actuators is arranged in a node of at least one natural vibration mode of the optical element.

A projection exposure apparatus comprises an optical element. The optical element comprises a main body and an actuator for deforming an optically effective surface formed on the main body. The actuator is in a recess in the rear side of the main body.