Apparatus for surface inspections

An apparatus in accordance with claim 31, wherein

• the means for determining the scanning position has a rotation-pulse emitter connected to a shaft of the drive means and a translation-pulse emitter connected to the computer unit, and
• the rotation-pulse emitter produces angular data and the translation-pulse emitter produces radial data which permit the determination of the scanning positions by polar coordinates,
• a look-up table is provided which has a number of storage positions for Cartesian coordinate addresses that correspond to the number of all pulses of the rotation-pulse emitter during a measurement, whereby addresses are stored in the storage positions to permit the determination of the XY coordinates in a Cartesian coordinate system,
• a pointer is provided in the form of an address register that is automatically incremented whenever a pulse from the rotation-pulse emitter is received, so that the pointer at all times points to the currently used address in the table,
• whereby the current address at any time is the address of a pixel of a Cartesian coordinate system, all of which make up a pixel area that produces the result of all measurements, and the position of each pixel in the pixel area corresponds to the position of the light spot on the surface.

An apparatus for making high-sensitivity measurements of dot-shaped, linear, and planiform surface defects comprising:

• a light source producing a light beam;
• a supporting disk on which an object having a surface to be inspected or examined is placed with the surface exposed;
• an objective passing the light beam from the source perpendicularly onto the surface of the object on the supporting disk:
• drive means connected to the supporting disk for moving the disk and the object thereon rotationally and translationally relative to the light beam so as to permit the light beam to scan the surface of the object along a spiral path;
• a photodetector positioned to receive light reflected by the surface of the object and collected by the objective and having an output providing a signal representative of the reflected light received;
• adjustable lens system means positioned on the optical path of the light beam between the light source and the objective for producing a first intermediate image of selected size and shape for a first scan of the surface of the object and a second intermediate image of selected size and shave for a second scan of the surface of the object;
• said drive means also being adjustable for changing the translational movement creating the spiral path and correspondingly changing the offset of each spiral forming the path in accordance with the selected one of the intermediate images used for a scan;
• a dark-field stop assembly positioned in the optical path of the light beam between the lens system means and the objective and having an adjustable dark-field field deflection system whereby the light beam after deflection is directed exactly centered through the objective and at right angles onto the surface of the object,
• electronic analysis means and a computer unit connected to receive output signals from the photo detector and for breaking down the output signals from the photo detector into measured values produced by dot-shaped, linear, and planiform defects in the surface of the object under inspection, and
• means for determining the effective scanning position of the light beam on the object surface at any time connected to the computer unit to associate the scanning positions with the measured values, wherein
• the electronic analysis means has a signal input connected with an output of the photo detector and to a haze channel having a haze filter and a peak suppressor,
• the signal input is connected to a particle channel which has a subtraction circuit and a peak detector with a digital output, a haze-filter output is connected to the input of an analog-digital converter which has an output;
• and
• the haze filter is connected to a nominal-bandwidth input and the peak detector is connected to a second input of the electronic analysis means,
• whereby the measurements due to planiform defects (haze) are available at the output of the analog-digital converter, the measurements due to dot-shaped defects (LPDs) and linear defects are available at the digital output of the peak detector, and all these measurements are then loaded and stored in the computer unit.