System and Method for Enhanced Predictive Autofocusing

• US 20090195688A1
• Filed: 04/13/2009
• Published: 08/06/2009
• Est. Priority Date: 08/23/2007
• Status: Active Grant

• Current Assignee: Leica Microsystems CMS GmbH (Danaher Corporation)
• Original Assignee: General Electric Company
• Inventors: Yazdanfar, Siavash, Kenny, Kevin Bernard, Henderson, David LaVan
• Granted Patent: US 8,878,923 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G02B 21/002 Scanning microscopes scanning near field optical microscopes G01Q60/18
• CPC Class Codes: G02B 21/242 with coarse and fine adjustment mechanism
• CPC Class Codes: G02B 21/244 using image analysis techniques
• CPC Class Codes: G02B 21/245 using auxiliary sources, detectors
• CPC Class Codes: G02B 21/365 Control or image processing arrangements for digital or video microscopes G02B21/361, G02B21/362 take precedence

Abstract

In an imaging device having an objective and a stage for holding a sample to be imaged, a method for autofocusing is presented. The method includes determining a measured focus value corresponding to at least a first of a plurality of logical image segments. Further, the method includes imaging the first logical image segment using the measured focus value. The method also includes determining a predicted focus value for a second of the plurality of logical image segments using the measured focus value and a stored focus variation parameter. In addition, the method includes imaging the second logical image segment using the predicted focus value.

Claims

1. In an imaging device having an objective and a stage for holding a sample to be imaged, a method for autofocusing, comprising:

determining a measured focus value corresponding to at least a first of a plurality of logical image segments;

imaging the first logical image segment using the measured focus value;

determining a predicted focus value for a second of the plurality of logical image segments using the measured focus value and a stored focus variation parameter; and

imaging the second logical image segment using the predicted focus value.

2. The method of claim 1, further comprising:

determining a coarse focus location for imaging the sample supported by a scanning stage;

positioning the objective at the determined coarse focus location; and

determining a coarse focus value for imaging the sample supported by a scanning stage.

3. The method of claim 1, further comprising logically segmenting the sample into the plurality of logical image segments.

4. The method of claim 1, wherein the measured focus value is determined while the sample is repositioned relative to the imaging device.

5. The method of claim 1, wherein the predicted focus value is determined while the sample is repositioned from a first position corresponding to the first logical image segment to a second position corresponding to the second logical image segment.

6. The method of claim 1, wherein imaging the second logical image segment using the predicted focus value comprises increasing or decreasing a distance separating the sample and the objective.

7. The method of claim 1, wherein the stored focus variation parameter represents a reproducible variation in the imaging device, the sample, or both the imaging device and the sample.

8. The method of claim 7, wherein the stored focus variation parameter represents a tilt or wobble associated with the stage.

9. The method of claim 7, wherein the stored focus variation parameter represents a reproducible variation with a slide containing the sample.

10. The method of claim 1, wherein determining the predicted focus value comprises retrieving one or more stored focus variation parameter from a data repository.

11. The method of claim 1, wherein determining the measured focus value corresponding to at least the first of the plurality of logical image segments comprises:

acquiring at least three auxiliary images at different focus values;

determining a quantitative characteristic for each of the auxiliary images; and

interpolating the measured focus value from the quantitative characteristics.

12. The method of claim 11, wherein determining the measured focus value further comprises offsetting a region of interest in the at least three auxiliary images by a determined amount to facilitate selection of a substantially similar set of image pixels in each of the at least three auxiliary images.

13. The method of claim 12, wherein determining a quantitative characteristic comprises determining, for each pixel in subset of pixels, a difference in intensities between the pixel and a neighboring pixel laterally separated from the pixel by at least one other pixel, and summing the squared difference in intensities for each pixel across the height and width of the image.

14. The method of claim 12, wherein interpolating the measured focus value from the quantitative characteristics comprises:

interpolating the measured focus value by fitting the quantitative characteristics of the at least three auxiliary images to a unimodal function; and

identifying a mode on the curve.

15. The method of claim 14, wherein determining the measured focus value further comprises determining the measured focus value based upon the identified mode, the stored focus variation parameter, or a combination thereof.

16. An imaging device, comprising:

an objective lens;

a primary image sensor configured to generate a primary image of a sample at a primary frame rate;

an auxiliary image sensor configured to generate one or more auxiliary images of the sample at an auxiliary frame rate that is faster than the primary frame rate;

a controller configured to adjust a focus value between the objective lens and the sample along an optical axis to autofocus the image of the sample;

a scanning stage to support the sample and move the sample in at least a lateral direction that is substantially orthogonal to the optical axis,

wherein the controller is configured to;

determine a measured focus value corresponding to at least a first of a plurality of logical image segments;

image the first logical image segment using the measured focus value;

determine a predicted focus value for a second of the plurality of logical image segments using the measured focus value and a stored focus variation parameter; and

image the second logical image segment using the predicted focus value.

17. The imaging device of claim 16, further comprising a beam splitter configured to split light that is collected from the sample and passes through the objective lens into a primary light path and an auxiliary light path.

18. The imaging device of claim 16, wherein the imaging device comprises a digital optical microscope.

19. An imaging device, comprising:

an objective lens;

a primary image sensor configured to generate a primary image of a sample at a primary frame rate;

an auxiliary image sensor configured to generate one or more auxiliary images of the sample at an auxiliary frame rate that is faster than the primary frame rate;

a controller configured to adjust a focus value between the objective lens and the sample along an optical axis to autofocus the image of the sample;

a scanning stage to support the sample and move the sample in at least a lateral direction that is substantially orthogonal to the optical axis,

wherein the controller comprises;

a macro image and scan planning component to determine a scan plan of the sample;

an autofocusing component to acquire and process auxiliary images;

a motion control component to control motion of the sample relative to the objective; and

a timing component to synchronize timing for acquisition of the auxiliary images, the primary images, or both.

20. The imaging device of claim 19, further comprising an image acquisition module for acquisition of one or more primary images.

21. The imaging device of claim 19, wherein the imaging device comprises a digital optical microscope.