Inspection apparatus and inspection method

An inspection method for inspecting a subject, comprising:

• irradiating the subject with a terahertz wave;
• detecting a terahertz wave obtained from the subject;
• performing a wavelet transform on a time waveform of the terahertz wave obtained using the terahertz wave detected in the detecting step;
• selecting a second expansion coefficient stored in advance from a first expansion coefficient in the wavelet transform and included in the first expansion coefficient;
• and
• comparing a first value of the second expansion coefficient and a second value of the second expansion coefficient selected in the selecting step.

An extraction method for extracting, from a reference object having a characteristic part of spectrum, an expansion coefficient related to the characteristic part of spectrum, the extraction method comprising:

• acquiring the waveform of a terahertz wave reflected or scattered off of or transmitted through the reference object;
• performing a wavelet transform on a terahertz time waveform acquired in the acquiring step;
• performing an inverse wavelet transform on a portion of expansion coefficients in the wavelet transform;
• performing a Fourier transform on the terahertz time waveform acquired in the inverse-transforming step, wherein
• the inverse-transforming step and the second transforming step are repeatedly performed while changing the portion of the expansion coefficients.