Ultrafast imaging apparatus

An ultrafast imaging apparatus comprising:

• a chuck table configured to support a workpiece thereon;
• and
• an imaging unit configured to capture images of the workpiece supported on the chuck table, wherein
• the imaging unit includes:
• an objective lens opposing the workpiece supported on the chuck table,
• a beam splitter disposed in a first optical path extending from the objective lens,
• an image processing unit disposed in a second optical path extending from the beam splitter, and
• an illumination unit disposed in a third optical path extending from the beam splitter,
• the illumination unit including
• a broadband pulsed light source, and
• a spectrometer configured to divide a single pulse of light, which has been emitted from the broadband pulsed light source, into a plurality of wavelengths and to produce a time lag between each two adjacent ones of the plurality of wavelengths, and
• the image processing unit including
• a diffraction grating configured to divide and diffract return light, which has been reflected by the workpiece supported on the chuck table after application of illumination light onto the workpiece with the time lag from the illumination unit, at different angles according to the wavelengths, and
• an image sensor configured to capture images, like a time-resolved photo, of the return light, which has been divided and diffracted by the diffraction grating, at areas for the respective angles corresponding to the wavelengths.