System and method for compensating instability in an autofocus system
First Claim
1. A method for compensating instability in an optical autofocus system, which optical autofocus system uses light directed at and reflected from a substrate to determine changes in a height position of the substrate, the method comprising:
- a. deflecting a reference beam component of said light by a beam-deflecting optic located a predetermined distance from the substrate to form a deflected reference beam, said predetermined distance defining a first space;
b. providing a reflector, spaced from the beam-deflecting optic by said predetermined distance, to define a second space between the reflector and the beam-deflecting optic;
c. directing a measurement beam component of said light at the substrate to form a reflected measurement beam that is directed from the substrate through the first space between the substrate and the beam-deflecting optic, while directing the deflected reference beam at the reflector to form a reflected reference beam that is directed from the reflector through the second space;
d. returning the reflected reference beam and the reflected measurement beam such that the reference beam and the reflected measurement beam emerge substantially collinearly from the beam-deflecting optic;
e. detecting the reflected reference beam and the reflected measurement beam and producing from said beams information enabling compensation for changes in the height position of the substrate, said changes defined by instabilities in at least one of the optical autofocus system and environmental factors; and
f. propagating the deflected reference beam formed by the beam-deflecting optic and the reflected reference beam formed by the reflector along a first plane, which first plane crosses a second plane, said second plane defined by the measurement beam component incident onto the substrate and the reflected measurement beam formed at the substrate.
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Accused Products
Abstract
An autofocus system and method designed to account for instabilities in the system, e.g. due to instabilities of system components (e.g. vibrating mirrors, optics, etc) and/or environmental effects such as refractive index changes of air due to temperature, atmospheric pressure, or humidity gradients, is provided. An autofocus beam is split into a reference beam component (the split off reference channel) and a measurement beam component, by a beam splitting optic located a predetermined distance from (and in predetermined orientation relative to) the substrate, to create a first space between the beam splitting optic and the substrate. A reflector is provided that is spaced from the beam splitting optic by the predetermined distance, to create a second space between the reflector and the beam splitting optic. The measurement beam component is directed at the substrate and a reflected measurement beam component through the first space between the substrate and the beam splitting optic, while the reference beam component is directed at the reflector and a reflected reference beam component is directed from the reflector through the second space between the beam splitting optic and the reflector. The reflected reference and measurement beam components are returned to the beam splitting optic, and emerge substantially collinear from the beam splitting optic. The reference and measurement beam components are then detected, and provide information that enables compensation for changes in the z position of the substrate that are due to instabilities in the autofocus system components and/or environmental factors.
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Citations
24 Claims
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1. A method for compensating instability in an optical autofocus system, which optical autofocus system uses light directed at and reflected from a substrate to determine changes in a height position of the substrate, the method comprising:
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a. deflecting a reference beam component of said light by a beam-deflecting optic located a predetermined distance from the substrate to form a deflected reference beam, said predetermined distance defining a first space; b. providing a reflector, spaced from the beam-deflecting optic by said predetermined distance, to define a second space between the reflector and the beam-deflecting optic; c. directing a measurement beam component of said light at the substrate to form a reflected measurement beam that is directed from the substrate through the first space between the substrate and the beam-deflecting optic, while directing the deflected reference beam at the reflector to form a reflected reference beam that is directed from the reflector through the second space; d. returning the reflected reference beam and the reflected measurement beam such that the reference beam and the reflected measurement beam emerge substantially collinearly from the beam-deflecting optic; e. detecting the reflected reference beam and the reflected measurement beam and producing from said beams information enabling compensation for changes in the height position of the substrate, said changes defined by instabilities in at least one of the optical autofocus system and environmental factors; and f. propagating the deflected reference beam formed by the beam-deflecting optic and the reflected reference beam formed by the reflector along a first plane, which first plane crosses a second plane, said second plane defined by the measurement beam component incident onto the substrate and the reflected measurement beam formed at the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An optical autofocus system that uses light directed at and reflected from a substrate to determine changes in a height position of the substrate, said system comprising:
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a beam-deflecting optic located at a predetermined distance from the substrate, said predetermined distance creating a first space between the beam-deflecting optic and the substrate; a reflector spaced from the beam-deflecting optic by the predetermined distance and creating a second space between the beam-deflecting optic and the reflector, wherein the beam-deflecting optic is configured to deflect a reference beam component of said light to the reflector to form a deflected reference beam, propagating towards the reflector such that a) the deflected reference beam and a reflected reference beam, formed in reflection of said deflected reference beam from the reflector, propagate along a first plane, and wherein b) a measurement beam component of said light incident at the substrate and a reflected measurement beam, formed in reflection of said measurement beam component from the substrate propagate along a second plane, said second plane intersecting the first plane; detectors that respectively detect light from the reflected reference beam and the reflected measurement beam; and a processing device configured to generate, from so detected light, data based on which said system is configured to compensate for changes in the height position of the substrate, said changes defined by instabilities in at least one of system components and environmental factors. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification