Auto focus system

Abstract

An autofocus system includes (a) an illumination path configured to illuminate a sample using an emitted beam to form a plurality of point array groups on the sample, the point array groups including an upstream point array group formed on a first side of an imaging region and a downstream point array group formed on the other side of the imaging region; and (b) a collection path including (b.1) a first segment including a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimating relay consisting essentially of a first relay input spherical lens and a first relay output spherical lens; (b.2) a second segment including a second spherical telescope, a second field curvature compensator, a pair of second prisms, and a second collimating relay consisting essentially of a second relay input spherical lens and a second relay output spherical lens; and (b.3) a common module.

Claims

1. An autofocus system, comprising: An illumination path configured to illuminate a sample with an emitted beam, forming a plurality of point arrays on the sample, the plurality of point arrays including an upstream point array group formed on a first side of an imaging region and a downstream point array group formed on the other side of the imaging region; a controller configured to determine a focus state of an evaluation beam hitting the imaging region. A collection path for collecting the emitted beams reflected from the sampled beams includes: a first branch for collecting a first collected beam segmented from the reflected emitted beams, wherein the first branch includes a first spherical telescope, a first field curvature compensator, a pair of first prisms sequentially configured for the passage of the first collected beams, and a first collimating relay substantially composed of a first relay input spherical lens and a first relay output spherical lens; and a second branch for collecting a second collected beam segmented from the reflected emitted beams, wherein the second branch includes a second spherical telescope, a second field curvature compensator, a pair of second prisms sequentially configured for the passage of the second collected beams, and a second collimating relay substantially composed of a second relay input spherical lens and a second relay output spherical lens. A common module is configured to (i) receive the first collected beams and the second collected beams, (ii) perform optical processing on the first collected beams to provide them to the first branch, each first collected beam having a pair of first rays, and (iii) perform optical processing on the second collected beams to provide them to the second branch, each second collected beam having a pair of second rays; and a sensor along the first branch and the second branch and configured to generate a detection signal indicating the light output from the first branch and the light output from the second branch.

2. The autofocus system according to claim 1, wherein the common module includes a mask located at an inlet pupil, the mask including a pair of off-axis slits for cutting off each collected beam to provide a pair of light rays for each collected beam.

3. The autofocus system according to either claim 1 or 2, wherein the common module further includes a beam splitter configured to (i) direct a first ray associated with the first collected beams to the first branch, and (ii) direct a ray associated with the second collected beams to the second branch.

4. The autofocus system according to either claim 1 or 2, wherein the first collimator displays a primary optical power along a main axis and a residual optical power along a primary axis.

5. The autofocus system according to either claim 1 or 2, further comprising a selectable depth-of-field unit configured to select a reference focal plane of the autofocus system.

6. The autofocus system according to claim 5, wherein the selectable depth-of-field unit includes a first window selectively placed within the first spherical telescope and a second window selectively placed within the second spherical telescope.

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