Measurement principle and thickness measurement mode of spectral confocal

The spectral confocal displacement sensor passes through a beam of white light （ Or multi wavelength mixed light ） Through a small hole , Different wavelengths are focused on the optical axis through the lens , Dispersively form a rainbow like distribution band , Irradiate the sample , Part of the reflected light is reflected back . Not shining on the optical axis with the object table The light of the intersection of the faces passes through the beam splitter , Irradiating around another small hole is stop , Unable to irradiate the spectrum analyzer , Will not interfere with the measurement . Irradiate at the intersection of the optical axis and the object surface The light of the point passes through the beam splitter , through Irradiate the spectrum analyzer through a small hole . The distance between the lens and the object to be measured can be calculated according to the wavelength . today , The detection principle and thickness detection model of spectral confocal displacement sensor are introduced .

Measurement principle of spectral confocal and thickness measurement mode

Spectral confocal detection technology is used to analyze the position of the concentration point with different waviness on a specific surface , To achieve accurate size detection and micro morphological analysis . According to the detection principle , The specific wave degree can be concentrated in front of the sample , For transparent material samples , Two types of wavelets with different waviness can converge in front and behind the sample . This is a Spectral confocal Point provides two detection modes ( Displacement detection mode 、 Thickness detection mode ).

Thickness detection mode ：

Test glass 、 Lens and other transparent samples , Two lines with different waviness can converge on the front and back surfaces of the sample , Calculate the thickness of the sample after obtaining the refractive index parameters of the sample . Confocal detection is large , Compared with traditional contact detection tools such as calipers , It has all the advantages of non-contact detection , It also has the characteristic of obtaining the thickness value of the sample through one-sided detection .

The refractive index directly affects the data accuracy of thickness measurement , Therefore, the retro reflectance of the sample should be checked at the beginning of the test . The reflectance can be referred to the value of similar materials , But in order to obtain more accurate thickness measurement results , The retro reflectance of the sample must be measured with a retro reflectance meter .