| 摘要 |
A measuring apparatus for work held on a chuck table is provided to measure upper surface height and/or thickness of a work, such as a semiconductor wafer, held by a chuck table provided in a machining apparatus such as a laser beam machining apparatus. A measuring apparatus for work held on a chuck table(36) comprises a white light source(61), a chromatic aberration lens(62), a beam splitter(63), a first condenser lens(64), a mask(65), a second condenser lens(66), a diffraction grating(67), a third condenser lens(68), a wavelength detecting unit(69) and a control unit. The white light source emits a white beam. The chromatic aberration lens condenses the white beam emitted from the white light source so as to irradiate the work held by the chuck table with the condensed white beam. The beam splitter is disposed between the white light source and the chromatic aberration lens and by which the reflected beam of the white beam irradiating the work therewith is split. The first condenser lens condenses the reflected beam which is again reflected by the beam splitter. The mask is provided with a pinhole which is disposed at a converging point position of the first condenser lens and through which the reflected beam condensed by the first condenser lens passes. The second condenser lens condenses the reflected beam having passed through the pinhole in the mask. The diffraction grating converts the reflected beam condensed by the second condenser lens into a diffracted beam. The third condenser lens condenses the diffracted beam diffracted by the diffraction grating. The wavelength detecting unit detects the wavelength of the diffracted beam condensed by the third condenser lens. The control unit determines the height position of the work held by the chuck table, based on a wavelength signal from the wavelength detecting unit.
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