What is the measuring principle of interferoMETER?

The controller uses a spectrometer to convert any light signals that it receives from the sensor. It then calculates distance values using the integrated signal processor (CPU) and transfers the data via its interfaces or the analog output.


Polychromatic white light is generated by an SLED. The light is coupled into an optical fiber.



With a sensor for distance measurement, the light of the fiber is separated by a beam splitter. Part of it radiates a firmly installed reference object. The other part radiates the measurement object. The light reflected by both the reference and measurement object is received by the sensor and conducted into the controller.


This is followed by the spectral decomposition and radiation of the detector. The light reflected by both the reference object and the measurement object overlaps. The interferometric measuring principle (superposition of waves) is used. Detection of distances and thicknesses is possible with amplification and elimination.


With a sensor for thickness measurement, the reference is omitted. This is why no distance measurement is possible.


Sensor and controller are one unit, as the sensor’s linearization table is stored in the controller.


This unique measuring system allows for highly precise measurement of targets. It is possible to measure both diffuse and reflecting surfaces. For transparent layer materials, thickness measurements can be conducted in addition to distance measurements. Shadowing is avoided because sender and receiver are aligned along one axis.


The excellent resolution and the small beam spot diameter make it possible to measure surface structures. However, measurement deviations may occur if the structure is of a similar size to the beam spot diameter or if the maximum tilt angle is exceeded (e.g., with groove edges).


Term Definitions

SMR - Start of measuring range. Minimum distance between sensor surface and target

MMR - Mid of measuring range (=start of measuring range + 0.5*measuring range)

EMR - End of measuring range (=start of measuring range + measuring range)

         - Maximum distance between sensor face and target       

MR - Measuring range


Distance sensor IMP-DS, measuring range and output signal at the controller


Thickness sensor IMP-TH with working distance and operating range



Product and Technology News

Semiconductor Industry–interferoMETER 5400-DS

Product Selector

Micro Epsilon

Application Selector

Micro Epsilon

Download Catalogue