Patent ID: 6842501

Claim:
An apparatus for measuring hardness of a material, comprising: inputting means for inputting a measured X-ray absorption value for a material to be measured; correspondence storing means for storing a correspondence relationship between X-ray absorption value data and hardness data of a plurality of reference materials; operating means for performing operations for converting the input X-ray absorption value of the material to be measured to the hardness of the material to be measured using the correspondence relationship; and outputting means for outputting the converted hardness of the material to be measured, wherein the hardness data is hardness data obtained from a frequency variation between a non-contact-frequency when a hardness measuring probe is not in contact with the material to be measured, and a contact-frequency when the probe is pressed against the material to be measured, a probe and a self-excited oscillation circuit connected to the probe forming a feedback loop for causing self-excited oscillation, and the contact-frequency is a frequency when a phase difference is reduced to zero by a correction circuit provided in the feedback loop, the phase difference being generated as a result of the material responding to the input vibration provided to the material to be measured from a vibrator in the probe.