US 5,636,030 A · Optical method and apparatus for measuring surface topography of an object

Abstract

An optical method and apparatus are disclosed for determining characteristics of an object such as its size, shape, position, orientation, cross-sectional area, volume, surface topography and specific volume. The inventive method and apparatus utilize a laser beam which is reflected through a right angle by a multi-faceted mirror. The mirror rotates about its own axis as it orbits around the object to be measured, causing a plurality of rotary scanning beams to sweep inwardly across the object as the mirror orbits. Portions of the scanning beam that are not blocked by the object strike a retroreflective ring positioned around the object and are returned along the beam's incident path to a detector. By associating the corresponding orbital position and rotational orientation of the mirror with the detector signal each time a shadow is created by the object, tangents to the surface of the object can be calculated. The tangents gathered during each orbit can then be assimilated to determine the cross-section of the object in the plane of the mirror's orbit. Changing the relative longitudinal position between the orbiting mirror and the object allows successive cross-sections to be determined and combined to calculate the total surface topography or volume of the object.

Claims20

Dependent claims

An optical scanning apparatus comprising:

a beam source for generating a narrow beam of light;
an orbiting mirror which rotates about its own axis while orbiting around an object to be measured, wherein the orbiting mirror repetitively reflects the beam inwardly across the object in a rotary scanning fashion to produce a plurality of sweeps of a scanning portion of the beam across the object during each orbit;
and
a beam detector for producing an electrical signal in response to interruptions of the scanning portion by the object,
wherein the beam source does not orbit around the object to be measured.

2 more elements

An optical scanning apparatus comprising:

a beam source for generating a narrow beam of light, the beam having a axial portion generally aimed at an object to be measured;
tracking means for producing a tracking portion of the beam parallel to the axial portion and radially offset therefrom, wherein the tracking portion revolves around the object and about an axis through the axial portion;
an orbiting mirror which rotates about its own axis while orbiting around the object in synchronization with the tracking portion, wherein the orbiting mirror repetitively reflects the tracking portion inwardly across the object in a rotary scanning fashion to produce a plurality of sweeps of a scanning portion of the beam across the object during each orbit;
a beam detector for producing an electrical signal in response to interruptions of the scanning portion by the object;
means for associating a corresponding orbital position and a corresponding rotational orientation of the orbiting mirror with changes in the electrical signal, thereby allowing to be defined a plurality of tangents to the surface of the object;
and
means for assimilating the tangents to calculate the location of at least a portion of the object's surface.

4 more elements

Dependencies are inferred from the claim text.

Optical method and apparatus for measuring surface topography of an object

Life of this patent

Optical method and apparatus for measuring surface topography of an object

Life of this patent

Abstract

Claims20