Chromatic range sensor including high sensitivity measurement mode

摘要

A method is provided for operating a chromatic range sensor (CRS) system, which may comprise a chromatic point sensor (CPS) system including an optical pen, to measure a low reflectivity surface. The CRS system may include a high sensitivity measurement mode in which it uses an unconventional low sampling rate or “long” self-saturating exposure time, to measure the low reflectivity surface. The “long” self-saturating exposure time may cause one or more detector pixels to self-saturate to at least a saturation threshold level, which prevents them from indicating a valid wavelength peak. Such pixels may define an invalid peak portion of a nominal total measurement range. The CRS may still detect a valid wavelength peak or height measurement, when the surface is located in a valid subset of the nominal total measurement range of the CRS system determined such that it excludes the invalid peak portion.

主权项

1. A method for operating a chromatic range sensor (CRS) system to perform a workpiece height measurement of a low reflectivity workpiece surface, the method comprising:
providing a CRS that provides a valid wavelength peak throughout a nominal total measurement range that is uninterrupted between nominal upper and lower measurement range limits when operated using an exposure time that is within a first nominal range of exposure times; operating the CRS using a self-saturating exposure time that is longer than exposure times in the first nominal range of exposure times, wherein:
regardless of whether a workpiece surface is located in the nominal total measurement range or not, the self-saturating exposure time saturates at least one detector pixel of the CRS, to at least a saturation threshold level which prevents a valid wavelength peak in an invalid peak portion of the nominal total measurement range corresponding to the at least one detector pixel saturated to at least the saturation threshold level by the self-saturating exposure time, leaving valid wavelength peak measurement positions only in a valid subset of the nominal total measurement range that excludes the invalid peak portion; and providing on a user interface portion of the CRS an indication of at least one of (a) a height measurement for a workpiece surface based on using the self-saturating exposure time, and (b) valid peak measurement positions included in the valid subset of the nominal total measurement range that corresponds to using the self-saturating exposure time.