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The principle of deflectometry is very simple: an observer who looks at a reflective surface sees the distorted reflection of the environment around it.

The deformations are proportional to the shape of the reflective object. If we master the parameters of the reflected reference image, we can accurately deduce the shape of the reflective object.

The measurement system will therefore be composed of three main elements:

  • A target that represents the reference image,
  • The object whose surface is to be measured,
  • A camera that captures the distorted image reflected by the object to be measured.

In reality, it will be more complicated because a single image is not enough on the one hand, and also because it is necessary to accurately characterize the dimensions of the image and the distances between the objects and the observer. Indeed, the mathematical formulas that define the relationship between the image emitted by the target and the reflection captured by the camera are known, but they contain too many variables for the equation to have only one solution in practice. That’s where innovation lies. Yves SURREL has developed a calibration method that is simple to implement and very efficient and that makes it possible to sufficiently characterize the measurement system, so as to make usable the images reflected by the object to be measured.

The measuring system sold by Wyse Light:

It consists of a computer screen (sight) on which the reference images are displayed according to a well-known process. The reflection of the reference images is captured by a camera. The display and camera are connected to a computer that performs the complex calculations necessary to reconstruct the surface. The computer, the camera, and the positioning system of the camera are integrated into a box. The results are displayed on a second screen that presents the user interface.

The innovation developed by Yves Surrel has made it possible to reduce certain variables sufficiently to arrive at a unique and reliable solution whatever the object to be measured. The process was patented by Wyse Light.

The measurement results obtained are excellent since they reach in routine of the order of 15nm or lambda on 40.

But the development of such an instrument raises the problem of qualifying the measurement results. Indeed, how do you know if the measurement results are good? Do we arrive at the same degree of precision/uncertainty regardless of the forms to be measured? Whatever the materials and their reflective power? whatever the environmental conditions? (ambient light, temperature, hygrometry, air velocity, pollution level…) … We work on reference parts for which we have measurement sets obtained with reference interferometers such as luphoscan and others. The tests improved the understanding of the system’s behavior, and consequently the performance of the instrument. The results are excellent. Do you want to try on your parts? We are ready!

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