Optical noncontacting surface sensor for measuring distance and angle of a test surface

Claim 2

An optical noncontacting surface sensor for measuring the distance and angle of a reflecting test surface and a predetermined reference plane comprising (A) a source of radiant energy; (B) means for focusing at least a portion of said radiant energy on the reflecting surface; (C) means for modulating said focusing of said portion of said radiant energy at one desired frequency along its optical path; and (D) means for modulating said focusing of said portion of said radiant energy at a second desired frequency perpendicular to the optical path; (E) means for collecting radiant energy reflected from the test surface onto a single photodetector; (F) means for monitoring the first harmonic of said collected radiant energy at the frequency of modulation of means (C), to obtain information with regard to the direction and amplitude of the distance between the test surface and the reference plane; (G) and means for monitoring one or both of the side-band frequencies of said reflected energy to obtain primary information with respect to the normality, both in magnitude and direction, of the test surface relative to the reference plane.

Claim 3

The apparatus of claim 1, in which the modulating means (C) is a mirror which oscillates along the optical axis about the focus of the energy delivered to it.

Claim 4

The apparatus of claim 1, in which the energy source is a laser.

Claim 5

The apparatus of claim 1, in which the energy source is a gas laser which emits polarized light which is directed into a beam expander which expands the light into a collimated beam, the collimated beam passes into a first polarization beam splitter which delivers a portion of the light through a quarter-wave retardation plate into a first lens which focuses the now circularly polarized light onto an oscillating mirror which serves both to modulate the light along its optical axis at a desired frequency and to change the handedness of the light so that the polarization of the reflected light is rotated by a total of 90*, so that all of the light incident on the beam splitter is delivered, through a half-wave phase retardation plate, to a second polarization beam splitter which directs a portion of the light through a second lens onto a photodetector, and a portion of the light through a second quarter-wave phase retardation plate through a third lens onto the test surface, and the light reflected from the test surface to the photodetector, so that substantially all of the light from the laser, minus accidental losses, is delivered to the photodetector.

Claim 6

The apparatus of claim 1, in which said source of radiant energy (A) is a beam of collimated light; said means (B) for focusing said portion of radiant energy on the test surface comprises at least one beam splitter and a first lens; said means (C) for modulating the energy comprises a second lens which focuses a portion of the light from the beam splitter onto a first mirror which oscillates along the optical path of the light about the focal point of the enErgy delivered to it and reflects the light as a modulated beam back through the beam splitter to deliver a portion of the now modulated light from the first lens onto the test surface, and delivers a portion of the light reflected from the test surface through said means (B) for collecting the reflected light which is a third lens which focuses the light onto the single photodetector.

Claim 7

The apparatus of claim 5, in which the first lens is is controlled so that the test object is maintained at its focal point, and the desired measurements are obtained from the position of the first lens.