System and method for compensating instability in an autofocus system
First Claim
1. A method of compensating instability in an optical autofocus system that uses light directed at and reflected from a substrate to determine changes in the z position of the substrate, comprisinga. splitting the light directed at the substrate into a reference beam component and a measurement beam component, by a beam splitting optic located a predetermined distance from the substrate, to create a first space between the beam splitting optic and the substrate,b. providing a reflector spaced from the beam splitting optic by the predetermined distance, to create a second space between the reflector and the beam splitting optic,c. directing the measurement beam component at the substrate and directing a reflected measurement beam component through the first space between the substrate and the beam splitting optic, while directing the reference beam component at the reflector and directing a reflected reference beam component from the reflector through the second space between the beam splitting optic and the reflector,d. returning the reflected reference and measurement beam components to the beam splitting optic, so that the reference and measurement beam components emerge substantially collinear from the beam splitting optic, ande. detecting the reference and measurement beam components and producing from the detected reference and measurement beam components information to enable compensation for changes in the z position of the substrate that are due to instabilities in system components and/or environmental factors.
1 Assignment
0 Petitions
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.
42 Citations
24 Claims
-
1. A method of compensating instability in an optical autofocus system that uses light directed at and reflected from a substrate to determine changes in the z position of the substrate, comprising
a. splitting the light directed at the substrate into a reference beam component and a measurement beam component, by a beam splitting optic located a predetermined distance from the substrate, to create a first space between the beam splitting optic and the substrate, b. providing a reflector spaced from the beam splitting optic by the predetermined distance, to create a second space between the reflector and the beam splitting optic, c. directing the measurement beam component at the substrate and directing a reflected measurement beam component through the first space between the substrate and the beam splitting optic, while directing the reference beam component at the reflector and directing a reflected reference beam component from the reflector through the second space between the beam splitting optic and the reflector, d. returning the reflected reference and measurement beam components to the beam splitting optic, so that the reference and measurement beam components emerge substantially collinear from the beam splitting optic, and e. detecting the reference and measurement beam components and producing from the detected reference and measurement beam components information to enable compensation for changes in the z position of the substrate that are due to instabilities in system components and/or environmental factors.
-
15. An optical autofocus system that uses light directed at and reflected from a substrate to determine changes in the z position of the substrate, and which is configured to compensate for instability due to environmental factors and/or mechanical factors involving system components, comprising
a. a beam splitting optic located a predetermined distance from the substrate, creating a first space between the beam splitting optic and the substrate, b. a reflector spaced from the beam splitting optic by the predetermined distance, and creating a second space between the beam splitting optic and the reflector, c. wherein the beam splitting optic is configured to split light directed at the substrate into a reference beam component and a measurement beam component, direct the reference beam component at the reflector and direct a reflected reference beam component from the reflector through the second space between the reflector and the beam splitting optic, direct the measurement beam component at the substrate and direct a reflected measurement beam component from the substrate through the first space between the beam splitting optic and the substrate, and to transmit the reflected reference and measurement beam components in a manner that causes the reference and measurement beam components to emerge substantially collinear from the beam splitting optic, and d. detectors for the reference and measurement beam components and a processing device configured to produce from the detected reference and measurement beam components information to enable compensation for changes in the z position of the substrate that are due to instabilities in system components and/or environmental factors.
Specification