| CPC G01B 11/06 (2013.01) | 11 Claims |
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1. A thickness measuring apparatus for measuring a thickness of a plate-shaped workpiece, the thickness measuring apparatus comprising:
a chuck table having, as a holding surface, an X-axis and Y-axis surface configured to hold the plate-shaped workpiece; and
a measuring instrument configured to measure the thickness of the plate-shaped workpiece held on the chuck table;
the measuring instrument including;
a light source configured to emit light in a predetermined wavelength range,
a scanning mirror including at least one mirror configured to rotate in an X-axis direction and a Y-axis direction, such that a speed of the measurement of the thickness of the plate-shaped workpiece is controlled by a speed of rotation of the at least one mirror, and the at least one mirror is configured to position the light emitted by the light source at coordinates specified by an X coordinate and a Y-coordinate on the plate-shaped workpiece held on the chuck table,
a diffusing film onto which reflected light is projected, the reflected light forming a spectral interference waveform by being reflected from a top surface and an undersurface of the plate-shaped workpiece held on the chuck table,
a light detector configured to detect light intensities corresponding to wavelengths of the spectral interference waveform projected onto the diffusing film,
a memory configured to store, for each coordinate, the light intensities corresponding to the wavelengths and being detected by the light detector, and
a calculating section configured to calculate a thickness at each coordinate by performing a Fourier transform of the light intensities corresponding to the wavelengths and being stored in the memory.
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