Multi-parameter scanning system with moveable field mask

An apparatus for measuring the visual characteristics of a surface including:

• A. An illumination system comprising:
• a light source for providing an incident beam of light;
• and
• a scanner including a mirror disposed to intercept said incident beam of light and direct it onto a surface to be characterized so as to produce a reflected beam of light, said scanner further including a scan mechanism for moving said mirror so as to scan said incident beam of light across said surface;
• said apparatus further including,
• B. A measuring system comprising:
• a beam splitter disposed and operative to intercept said reflected beam and to split it into a first portion and a second portion;
• a control sensor which is disposed on a support member and positioned so as to intercept said first portion of said reflected beam and is operative to generate a control signal which corresponds to a spatial profile of said first portion;
• a measuring sensor which is disposed so as to intercept said second portion of said reflected beam and is operative to generate an output signal corresponding to said second portion;
• a field mask which is supported on said support member in a fixed positional relationship with said control sensor, and is interposed in said second portion of said reflected beam, said field mask defining an aperture which permits only a segment of the cross-sectional area of said second portion of said reflected beam to pass therethrough and be incident upon said measuring sensor;
• a tracking driver which is operative to receive said control signal and spatially displace said support member, control sensor and field mask in response thereto so as to establish a feedback loop between said control sensor and tracking driver wherein the tracking driver displaces the control sensor relative to the first portion of the reflected beam so as to maintain a preselected spatial relationship between the first portion of the beam and the control sensor, and wherein said field mask is also spatially displaced relative to the second portion of the reflected beam.

A method for characterizing the haze of a finished surface, said method comprising the steps of:

• providing a light source;
• projecting an incident beam of light from said source onto an object to be characterized, for reflection thereby, so as to provide a reflected beam of light, said reflected beam of light having a cross-sectional area;
• disposing a photo sensor in said reflected beam of light, said photo sensor being operative to provide an output signal proportional to the intensity of the reflected beam of light incident thereupon;
• interposing a field mask in said reflected beam of light between the surface and the photo sensor, said field mask having an aperture defined therethrough, said aperture having an area which is less than the cross-sectional area of the beam of reflected light;
• moving the field mask transversely through the reflected beam so as to sequentially pass portions of the cross-sectional area of the reflected beam therethrough and onto the photo sensor;
• and
• determining the rate of change of the output signal of said photo sensor, as said field mask is moved, whereby the rate of change of said output signal is proportional to the haze of said surface.