Abstract: A method for heating an optical element in an optical system, such as a microlithographic projection exposure system, comprises introducing a heating power into the optical element using a thermal manipulator. The heating power is adjusted to a set of desired values. The set of desired values is adjusted to produce a thermally induced deformation depending on a first optical aberration to be compensated. Adjusting the set of desired values also includes taking into account the effect of introducing the heating power on a second optical aberration which is caused by useful light impinging on the optical element during operation of the optical system. The thermally induced deformation profile can be co-optimized.

Abstract: A method for heating an optical element in an optical system, such as in a microlithographic projection exposure system comprises using a thermal manipulator to introduce a heating power into the optical element to produce a thermally induced deformation. Before starting operation of the optical system in which useful light impinges on the optical element, the heating power is adjusted with respect to a desired state of the optical element in which a first optical aberration is at least partially compensated. After starting operation of the optical system, the heating power is regulated to the desired state depending on the heat load of the useful light impinging on the optical element. The heating power is regulated in such a way that the average temperature of the optical element remains constant up to a maximum deviation of 0.5 K.

Abstract: A method of operating a projection exposure apparatus for microlithography, comprises: heating an optical element of the projection exposure apparatus by irradiating a surface of the optical element with heating radiation during a break in operation in which the surface of the optical element is not irradiated by exposure radiation. An inhomogeneous temperature distribution which reduces aberrations of the projection exposure apparatus is created on a portion of the surface of the optical element during the heating in the break in operation, with the inhomogeneous temperature distribution being created by irradiating the portion with heating radiation with at least one continuous heating radiation profile formed by a beam shaping element. A related projection exposure apparatus for microlithography is disclosed.