Auto-Focus Methods and Systems for Multi-Spectral Imaging

Abstract

Techniques for acquiring focused images of a microscope slide are disclosed. During a calibration phase, a “base” focal plane is determined using non-synthetic and/or synthetic auto-focus techniques. Furthermore, offset planes are determined for color channels (or filter bands) and used to generate an auto-focus model. During subsequent scans, the auto-focus model can be used to quickly estimate the focal plane of interest for each color channel (or filter band) rather than re-employing the non-synthetic and/or synthetic auto-focus techniques.

1 . A method for acquiring focused images of a microscope slide, the method comprising:
 in a calibration step, determining a Z-offset from a best focus plane for each of multiple color channels of a color digital imager that provides a best focus plane in each of the color channels;   in a scanning step, determining a best focus plane for a field of view of the color digital imager; and   obtaining image data in the field of view with the color digital imager in each of the color channels in accordance with the Z-offsets determined in the calibration step.   
     
     
         2 . The method of  claim 1 , wherein the Z-offsets vary depending on the a location of a slide region being imaged by the color digital imager. 
     
     
         3 . The method of  claim 1 , wherein the Z-offsets are obtained in the calibration step from one or more training slides. 
     
     
         4 . The method of any of  claims 1 , wherein the scanning step further comprises:
 obtaining images in the color channels at the best focus plane;   computing a sharpness metric for the images acquired at the best focus plane and at the Z-offset from the best focus plane; and   selecting the image with an optimum sharpness metric to output from the color digital imager.   
     
     
         5 . The method of  claim 1 , wherein the calibration step further comprises:
 performing a Z-slice scan of a calibration slide.   
     
     
         6 . The method of  claim 5 , the scanning step further comprising:
 performing a Z-slice scan of a slide.   
     
     
         7 . A method for acquiring focused images of a microscope slide using a microscope having an optical system and a digital color camera, the method comprising:
 characterizing chromatic aberration present in the optical system as a Z-offset from a best focus plane in each of multiple color channels of the digital color camera; and   scanning a microscope slide in a manner to reduce the effect of the characterized chromatic aberration by obtaining image data from the multiple color channels in accordance with the Z-offsets.   
     
     
         8 . The method of  claim 7 , wherein the characterizing is obtained from one or more calibration slides. 
     
     
         9 . The method of  claim 8 , wherein the characterizing is obtained from a Z-slice through a calibration slide. 
     
     
         10 . The method of  claim 9 , further comprising:
 adjusting the characterizing of the chromatic aberration during the scanning step.   
     
     
         11 . The method of  claim 10 , further comprising:
 acquiring images in the multiple color channels from the microscope slide at a best focus plane; and   comparing a focus metric of the multiple color channel images at the best focus plane with the multiple color channel images obtained by the scanning.   
     
     
         12 . The method of  claim 11 , further comprising:
 updating the Z-offsets depending on results of the comparing.   
     
     
         13 . A system, having a memory and a processor, the system comprising:
 a calibration component configured to determine an offset from a first focus plane for at least one of a color channel or a filter band;   a base component configured to determine, for a first slide, a base focus plane for a field of view of the first slide; and   a capture component configured to retrieve the offset and obtain an image of the first slide based at least in part on the base focus plane and the retrieved offset;   wherein at least one of the components comprises computer-executable instructions stored in the memory for execution by the processor.   
     
     
         14 . The system of  claim 13 , wherein the calibration component is configured to determine, for each of a plurality of filter bands, an offset from the first focus plane that provides a best focus plane for the filter band. 
     
     
         15 . The system of  claim 14 , wherein the capture component is configured to retrieve, for each of the plurality of filter bands, the offset determined for the filter band. 
     
     
         16 . The system of  claim 15 , wherein the capture component is configured to obtain, for each of the plurality of filter bands, an image based at least in part on the base focus plane and the offset determined for the filter band. 
     
     
         17 . The system of  claim 16 , wherein each obtained image is previously-captured z-slice. 
     
     
         18 . The system of  claim 13 , wherein the calibration component is configured to determine, for each of a plurality of color channels, an offset from the first focus plane that provides a best focus plane for the color channel.