White light interferometerDue to its high precision and wide spectral range, it has been widely used in many high-precision measurement fields. By analyzing its principle and working mechanism, we can gain a deeper understanding of the working principle of this instrument and its important role in various fields. It can not only measure the surface morphology of objects with high accuracy in a non-contact manner, but also perform rapid surface defect detection.
1、 Basic principles
A white light interferometer is a measurement tool that operates based on the principle of interference. Interference phenomenon refers to the phase change of two or more light waves when they meet, resulting in the formation of alternating bright and dark stripes at different positions in space. The variation of these stripes is closely related to the phase difference and optical path difference of light.
In a white light interferometer, the term "white light" refers to a broad-spectrum light source containing multiple wavelengths. Compared with traditional monochromatic light interferometers, it has a wider spectral range, thus providing higher measurement resolution. The wide spectral characteristics of this light source enable it to avoid errors that may occur when using a single wavelength light source for highly accurate measurements.
The basic working process of an interferometer is that the white light emitted by the light source is split into two beams by a beam splitter. One beam of light is directed onto the surface of the object being measured, while the other beam is reflected back to the interference area of the interferometer through a reference mirror. When these two beams of light converge again, interference fringes will form due to a change in their phase. By analyzing these interference fringes, precise information about small deformations or defects on the surface of the object can be obtained.
2、 Working mechanism
The working mechanism of a white light interferometer involves multiple key components, including the light source, beam splitter, reference mirror, object under test, and detector. The functions of each part work closely together to achieve precise measurement of the surface of the object.
1. Light source and beam splitter
Its light source is usually a high brightness white LED or white laser, which can emit a wide spectrum of light. The light emitted by the light source is split into two beams by a beam splitter, with one beam shining on the surface of the object and the other beam directly entering the reference mirror.
2. Reference mirror and object surface
A beam of light is guided to the surface of the object under test, and after reflection, it meets another beam of light reflected by a reference mirror. The small bumps or deformations on the surface of the object to be tested will change the phase of the reflected light, thereby affecting the interference effect of the two beams of light.
3. Formation of interference fringes
These two beams of light converge again in the interference area of the interferometer, producing interference fringes. Due to its use of a broadband light source, the morphology of interference fringes is closely related to factors such as phase difference and optical path difference of light. The changes in these stripes reflect small variations on the surface of the object.
4. Detector and Data Analysis
The interference fringes captured by the detector are analyzed by a computer to accurately measure surface height changes and surface defects. By analyzing the changes in stripes, a three-dimensional image of the surface morphology can be obtained, allowing for detailed morphological analysis of the object's surface.
3、 Advantages and Applications
As a high-precision measuring instrument, it has numerous significant advantages. Firstly, it can provide high spatial resolution and typically measure surface changes at the nanometer level, which gives it an irreplaceable advantage in precise measurements at the micrometer and nanometer scales. Secondly, due to the use of broad-spectrum white light, it avoids the dispersion error that may occur in monochromatic interferometers and is suitable for more complex measurement environments.
In terms of application, it is widely used in fields such as surface measurement, detection of optical components, measurement of film thickness, and microstructure analysis of materials. For example, in the semiconductor industry, it can be used for surface inspection and measurement of chips to ensure the flatness and accuracy of the chip surface. In the biomedical field, it can also be used for observing and analyzing cell surface morphology.