Optical Glass Metrology â Techniques / Limitations - Owens Design

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Chromatic Confocal Measurement Principle: : A chromatic lens L generates the image of a point white-light source W as a continuum of monochromatic images located on the optical axis (“Chromatic coding”). A sample is located inside the color-coded segment and its surface scatters the incident light beam. : The backscattered light passes through the chromatic lens L in the opposite direction, and arrives at a pinhole P which filters out all wavelengths except a single wavelength, M . The collected light is analyzed by a spectrometer S. The sample position (point M) is directly related to the detected wavelength. Advantages: - High resolution - High signal-to-noise ratio - No motion in “Z” required - Works on all types of samples - Wide choice of measuring ranges - Steep slope compatibility - Coaxial (no shadowing) - “Speckle” free from low to high reflectivity - Measurement of transparent objects : SICK AG: : BU02 side session: high end displacement Patrick Nutz 19.03.2009 16
Principle of operation of an AutoFocus sensor The light source is projected by the object lens on the sample's surface. - The reflected light is collected by the very same lens, focused by the collimator lens and deflected towards the detector by a beam splitter. - In the absence of the cylindrical lens, the light would converge to a tiny spot on the detector. - The cylindrical lens deviates only one axis of the light, so a horizontal and a vertical focal line originate from the single spot. The detector is placed mid-way between the two focal lines. - A circular spot appears on the sensor if the surface is exactly in-focus. - Deviation from the focal position results in an elliptic spot on the detector. - The orientation and eccentricity of the spot depends on the magnitude and direction of the defocus. The spot's shape is detectable by the current distribution in a photodiode array. - The sensor's electronics generate an error signal resulting in a movement of the object lens to track the surface at exactly the focal distance. The motion of the lens is monitored by an incremental encoder (glass scale), comprising the profile signal. : SICK AG: : BU02 side session: high end displacement Patrick Nutz 19.03.2009 17
Page 1 and 2: Optical Glass Metrology - Technique
Page 3 and 4: Limitations of Optical Measurement
Page 5 and 6: Laser Triangulation Advantages : Si
Page 7 and 8: Detection of the Glass Plates Inter
Page 9 and 10: Glass Thickness Measurement with on
Page 11 and 12: LaserScanner with rotating Mirror D
Page 13 and 14: Confocal Laser Point Sensor : SICK
Page 15: Chromatic Confocal Measurement : SI
Page 19: : Thank you for your attention.

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Optical Glass Metrology â Techniques / Limitations - Owens Design