Patent ID: 8767174

Claim:
An apparatus for holding a substantially planar article having a utility obverse surface and a reverse surface, the apparatus comprising: a movable body comprising a wall including a contact surface that receives the reverse surface of the article and that is substantially co-extensive with at least a heat-receiving area of the utility surface whenever the article is being held by the movable body, the wall also including a second surface separated from but proximal to the contact surface, the wall being thermally conductive from the contact surface to the second surface; a holding device that holds the article to the contact surface with the reverse surface contacting the contact surface; and a coolant circulation device that delivers flow of a coolant fluid to the second surface to urge conduction of heat from the contact surface to the second surface; wherein the wall comprises respective superposed constituent layers of at least two respective materials, the materials having different respective coefficients of thermal expansion selected such that, at a given temperature and with respect to at least a portion of the layer of material, distortion of one constituent layer is at least partially offset by thermal distortion of the other constituent layer to produce a net reduced distortion of the layer of material compared to when the layer of material comprises only one of the constituent layers; and the holding device and coolant-circulation device operate in concert to actively control shape of the article being held by the apparatus.