Field of the Invention
The present disclosure relates to a holding apparatus, a measurement apparatus, and an article manufacturing method.
Description of the Related Art
As an apparatus for measuring a shape of an object, a measurement apparatus using a pattern projection method is known. The pattern projection method finds the shape of an object by projecting a pattern onto the object, imaging the object, detecting a pattern in the captured image, and obtaining distance information in each pixel position according to the principle of triangulation.
The pattern to be projected is generated by, for example, illuminating an element having a function of spatially controlling transmittance or reflectance of light using an illumination optical system. The generated pattern is projected to the object through a projection optical system. The projected pattern can be changed if positional relationships between the illumination optical system, the element and the projection optical system change due to the influence of an environmental temperature. Therefore, in the holding apparatus in Japanese Patent Laid-Open No. 2002-365612, a movement direction of an element in a storage unit is defined as one direction, and the stability of a position of the element against change in temperature increases.
However, in the holding apparatus in Japanese Patent Laid-Open No. 2002-365612, since an influence of friction between the element and the storage unit is not considered, the reproducibility of the position of the element can be decreased by a frictional force applied therebetween if the change in the temperature causes the element and the storage unit to be expanded or contracted.