Instrument and method for measuring the curvature and reflectivity of a surface of a sample

A method for simultaneously measuring at least one radius of surface curvature and reflectivity of a sample, the method comprising:

• using a single light source for the simultaneous measurements of the at least one radius of the surface curvature and the reflectivity of the sample, a mask being disposed between the single light source and the surface of the sample, the mask having a transparent background and opaque patterns arranged at predetermined positions on the mask surface, the opaque patterns of the mask having a total surface area smaller than a surface area of the transparent background, the light source being used to illuminate the mask to generate by transmission through the mask a collimated light beam incident on the surface of the sample, and to form a light beam reflected by the sample;
• placing an optical beam splitter in order to receive the reflected light beam and to transmit one part of the reflected beam towards an imaging system and a camera that thereby form an image of the mask by reflection on the sample and another part of the reflected light beam toward a spectrometer that thereby measures a power of the other part of the reflected light beam;
• processing, with an image processing system, the image of the mask by reflection on the sample surface;
• calculating, with the image processing system, respective positions of the patterns in said image;
• comparing, using the image processing system, the predetermined positions of the mask patterns with the calculated positions of the patterns in the image, and
• performing, with the image processing system, the simultaneous measurements in real time at a frequency up to 100 Hz of (i) the at least one radius of the surface curvature of the sample based on the compared predetermined position with the calculated positions and (ii) the reflectivity of the sample based on the measured power of the other part of the reflected light beam.