Patent Number: 
Section: claims

1. A method for measuring the surface state of a surface of a tube, the surface comprising at least one portion having a surface curvature, the method comprising the following successive steps in the following order:measuring the surface curvature of the portion,providing a support for the tube,providing a measurement head comprising a probe for being in contact with the surface portion, the head being configured to stress the probe on the surface and measure the displacement of the probe along a displacement axis,mounting the measurement head displaceable relatively to the support, at least a part of the head being mounting only displaceable relatively to the support along a trajectory corresponding to the measured surface curvature, the displacement axis being substantially perpendicular to the trajectory, thereby obtaining a device comprises the measurement head for measuring the surface state of the surface of the tube,mounting the tube on the support of the device for measuring the surface state of the surface of the tube, andmeasuring the surface state of a surface of the tube by displacing the head relatively to the support and the tube along the trajectory corresponding to the measured surface curvature and thereby obtaining the surface state of the surface of the tube. 2. A device for measuring the surface state of a surface of an tube, the device being fabricating during the implementation of the method of claim 1, the surface comprising at least one portion having a surface curvature, the device including:a support for the tube,a measurement head comprising a probe for being in contact with said surface portion, the measurement head being mounted to be relatively displaceable to the support, at least a part of the measurement head being mounted only displaceable relatively to the support along the trajectory, the measurement head being configured for stressing the probe on the surface with a substantially constant stress and for measuring the displacement of the probe along the displacement axis. 3. The device according to claim 2, wherein the a tube have a substantially torus portion shape, the portion having the surface curvature being the inner surface of the tube, the surface curvature of the inner surface being an inner generatrix of the tube, the trajectory corresponding to a path following the inner generatrix of the tube, when the tube is mounted on the support. 4. The device according to claim 3, wherein the support is a turntable for supporting the tube, the turntable being pivotably mounted in relation to the measurement head so as to allow the relative displacement of the measurement head along the generatrix when the turntable is turned. 5. The device according to claim 4, wherein the pivoting mounting of the turntable is motorized with an indexed displacement. 6. The device according to claim 4, wherein the device further includes an arm including a free end supporting the measurement head, the arm having a curvature identical to that of the torus portion so as to allow the relative displacement of the measurement head along the generatrix when the turntable is turned. 7. The device according to claim 6, wherein the measuring head includes a pivot at the free end of the arm, the pivot being arranged to allow a remaining of the measuring head to pivot about an axis tangential to the trajectory, the pivot being the part of the measuring head mounted relatively to the support displaceable relatively to the support only along the trajectory. 8. The device according to claim 3, the measurement head comprising a pivot rotatably displacing the head along the inner surface of the tube so as to change the generatrix along which the probe is relatively displaced. 9. The device according to claim 2, wherein the measurement head includes an optical type displacement sensor for measuring the displacement of the probe along an axis substantially perpendicular to predetermined trajectory. 10. The device according to claim 9, wherein the sensor is a confocal measurement displacement sensor. 11. The device according to claim 2, wherein the measurement head includes a pivotably mounted lever and at the end of which is provided the probe, the lever including a counterweight so as to stress the probe on the surface by the action of gravity. 12. The device according to claim 11, wherein the measuring head is configured for monitoring the stress of the probe on the surface. 13. The device according to claim 12, wherein measuring head present a configuration in which the probe moves away from the surface. 14. The device according to claim 13, wherein the measuring head includes a pivotably mounted lever at the end of which is mounted the probe, and a system for swinging the lever to move away the probe from the surface. 15. The device according to claim 14, wherein the system for swinging the lever includes a micromanipulator. 16. The device according to claim 15, wherein the micromanipulator is of the piezoelectric type. 17. The device according to claim 11, wherein the counterweight is displaceable along the lever. 18. The device according to claim 2, wherein the measurement head includes elastic return means arranged to apply a return force to the probe so as to stress the probe on the surface.