Moiré interferometer with overlapping illumination and imaging systems
First Claim
Patent Images
1. An apparatus for measuring flatness of a test surface using moiré
- topography comprising;
an illuminating system including a light source and an optical pathway for conveying light from the light source to the test surface;
an imaging system including a fringe pattern detector and an optical pathway for conveying an image of the test surface to the fringe pattern detector;
a grating pattern that is illuminated on the test surface by the illuminating system and that is imaged onto the detector by the imaging system for producing together with a reference grating pattern a moiré
fringe pattern indicate of the flatness of the test surface;
a focusing optic positioned at an intersection of the optical pathways that convey light both to and from the test surface en route from the light source to the detector;
the focusing optic being arranged as a part of the illuminating system and as a part of the illuminating system to collimate light en route to the test surface at a first angle thereby contributing to forming on the test surface a telecentric reproduction of the grating pattern; and
the focusing optic being arranged as a part of the imaging system and as a part of the imaging system to relay collimated light at a different angle from the test surface thereby contributing to forming on the detector a telecentric image of the grating pattern reproduction appearing on the test surface.
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Abstract
A moiré interferometer has an illumination system and an imaging system that share a common focusing optic, which preferably takes the form of a concave mirror. Within the illumination system, the common focusing optic collimates light en route to a test surface. Within the imaging system, the common focusing optic telecentrically images a grating pattern appearing on the test surface onto a fringe pattern detector.
13 Citations
42 Claims
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1. An apparatus for measuring flatness of a test surface using moiré
- topography comprising;
an illuminating system including a light source and an optical pathway for conveying light from the light source to the test surface;
an imaging system including a fringe pattern detector and an optical pathway for conveying an image of the test surface to the fringe pattern detector;
a grating pattern that is illuminated on the test surface by the illuminating system and that is imaged onto the detector by the imaging system for producing together with a reference grating pattern a moiré
fringe pattern indicate of the flatness of the test surface;
a focusing optic positioned at an intersection of the optical pathways that convey light both to and from the test surface en route from the light source to the detector;
the focusing optic being arranged as a part of the illuminating system and as a part of the illuminating system to collimate light en route to the test surface at a first angle thereby contributing to forming on the test surface a telecentric reproduction of the grating pattern; and
the focusing optic being arranged as a part of the imaging system and as a part of the imaging system to relay collimated light at a different angle from the test surface thereby contributing to forming on the detector a telecentric image of the grating pattern reproduction appearing on the test surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- topography comprising;
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16. A moiré
- interferometer for detecting variations in a test surface comprising;
a light source that produces a beam of light for illuminating a grating pattern on the test surface;
a focusing optic positioned to convey the beam of light oblique to the test surface;
a directional optic that redirects the oblique beam of light towards the test surface;
a fringe pattern detector that receives an image of the grating pattern appearing on the test surface;
processor that evaluates a combination of a reference grating pattern and the image of the grating pattern appearing on the test surface to detect variations in the test surface;
said focusing optic also being positioned to collect light from the test surface independent of the directional optic for relaying the image of the grating pattern appearing on the test surface to the fringe pattern detector;
a grating located between the directional optic and the test surface for casting a shadow in the form of the grating pattern on the test surface; and
the focusing optic being arranged to collect light from both the grating and its shadow on the test surface for combining the reference grating pattern with the grating pattern appearing on the test surface. - View Dependent Claims (17, 18)
- interferometer for detecting variations in a test surface comprising;
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19. A moiré
- interferometer for detecting variations in a test surface comprising;
a light source that produces a beam of light for illuminating a grating pattern-on the test surface;
a focusing optic positioned to convey the beam of light oblique to the test surface;
a directional optic that redirects the oblique beam of light towards the test surface;
a fringe pattern detector that receives an image of the grating pattern appearing on the test surface;
a processor that evaluates a combination of a reference grating pattern and the image of the grating pattern appearing on the test surface to detect variations in the test surface;
said focusing optic also being positioned to collect light from the test surface independent of the directional optic for relaying the image of the grating pattern appearing on the test surface to the fringe pattern detector;
a first grating located between the light source and the focusing optic;
a projection optic for projecting an image of the first grating onto the test surface to form the grating pattern on the test surface; and
a second grating located between the focusing optic and the detector to combine the reference grating pattern with the image of the grating pattern on the test surface.
- interferometer for detecting variations in a test surface comprising;
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20. A moiré
- interferometer for detecting variations in a test surface comprising;
a light source that produces a beam of light for illuminating a grating pattern on the test surface;
a focusing optic positioned to convey the beam of light oblique to the test surface;
a directional optic that redirects the oblique beam of light towards the test surface;
a fringe pattern detector that receives an image of the grating pattern appearing on the test surface;
a processor that evaluates a combination of a reference grating pattern and the image of the grating pattern appearing on the test surface to detect variations in the test surface;
said focusing optic also being positioned to collect light from the test surface independent of the directional optic for relaying the image of the grating pattern appearing on the test surface to the fringe pattern detector; and
the light source being arranged to produce a coherent light beam, and the grating pattern on the test surface being formed by two interfering portions of the coherent light beam. - View Dependent Claims (21)
- interferometer for detecting variations in a test surface comprising;
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22. Apparatus for discerning surface topography with moiré
- fringes comprising;
a light source that produces a light beam;
an illumination pathway that conveys the light beam to a test surface;
a grating pattern forming structure located along the illumination pathway for illuminating a grating pattern on the test surface from a first angular perspective;
an imaging pathway that relays an image of the grating pattern appearing on the test surface from a second angular perspective;
said grating pattern on the test surface being combinable with a reference grating pattern for producing the moiré
fringes;
a focusing optic located along both the illumination pathway and the imaging pathway for conveying the light beam to the test surface and for relaying the image of the grating pattern on the test surface; and
the focusing optic-being a reflective optic that reflects the light beam traveling along the illumination pathway and the image relayed along the imaging pathway at a different angle. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
- fringes comprising;
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33. A method of determining the flatness of a test surface by moiré
- topography comprising the steps of;
directing a light beam along an illumination pathway to the test surface;
forming a grating pattern on the test surface from a first angular perspective;
relaying an image of the grating pattern from a second angular perspective along an imaging pathway to a fringe pattern detector;
combining the grating pattern on the test surface with a reference grating pattern for producing moiré
fringes;
intersecting both the illumination pathway and the imaging pathway with a common focusing optic that conveys the light beam to the test surface and relays the image of the grating pattern to the fringe pattern detector;
using the common focusing optic to collimate the light beam en route to the test surface forming the grating pattern on the test surface from the first angular perspective as a telecentric reproduction of the grating pattern; and
using the common focusing optic to relay a telecentric image of the grating pattern appearing on the test surface from the second angular perspective to the fringe pattern detector. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42)
- topography comprising the steps of;
Specification