Thickness measuring device

A thickness measuring device for measuring a thickness of a specimen positioned in a chamber the device comprising:

• a light which emits an electromagnetic wave in a direction toward the specimen;
• a detector which receives an electromagnetic wave output in a direction in which the chamber is positioned;
• and
• a controller which receives a signal from the detector and calculates the thickness of the specimen, wherein the detector receives a first electromagnetic wave having a first peak and a second electromagnetic wave having a second peak, wherein the first peak occurs at a first time point, and the second peak occurs at a second time point, wherein the first time point and the second time point have a difference at least a first time period, wherein at least a part of the chamber transmits a part of the electromagnetic wave and reflects the remaining part of the electromagnetic wave,
• wherein the first period is a period corresponding to a time duration of the first electromagnetic wave,
• wherein the time duration of the first electromagnetic wave is a period corresponding to a difference between a first periodic point and a second periodic point,
• wherein the first periodic point is a value which is earlier than the first time point, and a time point which is closest to the first time point among the time points which second differential values thereof are zero, and
• wherein the second periodic point is a value which is later than the first time point, and a time point which is closest to the first time point among the time points which second differential values thereof are zero.

A thickness measuring device for measuring a thickness of a specimen positioned in a chamber, the device comprising:

• a light which emits an electromagnetic wave in a direction toward the specimen;
• a detector which receives an electromagnetic wave output in a direction in which the chamber is positioned;
• and
• a controller which receives a signal from the detector and calculates the thickness of the specimen, wherein the detector receives a first electromagnetic wave having a first peak and a second electromagnetic wave having a second peak, wherein the first peak occurs at a first time point, and the second peak occurs at a second time point, wherein the first time point and the second time point have a difference at least a first time period, wherein at least a part of the chamber transmits a part of the electromagnetic wave and reflects the remaining part of the electromagnetic wave,
• wherein the first period is a period corresponding to a time duration of the first electromagnetic wave, wherein the time duration of the first electromagnetic wave is a period corresponding to a difference between a first periodic point and a second periodic point, wherein the first periodic point is earlier than the first time point, and the second periodic point is later than the first time point, wherein the first periodic point is a time point which is closest to the first time point among time points at which a positive second differential value of the first electromagnetic wave is changed to a negative second differential value thereof, and
• wherein the second periodic point is a time point which is closest to the first time point among time points at which a negative second differential value of the first electromagnetic wave is changed to a positive second differential value thereof.