Multifunction autofocus system and method for automated microscopy
Multifunction autofocus for automated microscopy includes automatic coarse focusing of an automated microscope by reflective positioning, followed by automatic image-based autofocusing of the automated microscope performed in reference to a coarse focus position. In some aspects, the image-based autofocusing utilizes astigmatism in microscope optics for multi-planar image acquisition along a Z axis direction of a microscope. In some other aspects, the image-based autofocusing utilizes astigmatism in microscope optics in combination with chromatic aberration for multi-planar image acquisition along the Z axis direction.
1. A method of focusing an automated microscopy system including an objective, a stage, and an optical axis passing through the objective and the stage, by:
obtaining a coarse focus value with a reflective positioning system using an image reflected from an object surface including a bottom surface or a top surface of a specimen holder;
obtaining a coarse focus corresponding to the coarse focus value;
obtaining a fine focus value with an image-based autofocus system using one or more of quality, sharpness or resolution of an image of a specimen mounted on the specimen holder;
updating the coarse focus value with the fine focus value; and,
causing relative movement between the objective and the stage to obtain a fine focus corresponding to the updated coarse focus value;
in which obtaining the fine focus value with an image-based autofocus system includes directing light from a specimen to the image-based autofocus system, introducing astigmatism into the light when the light is transferred to the image-based autofocus system, simultaneously generating a stack of focal plane images of the specimen from the light and obtaining a best focus value from the stack, wherein the best focus value is the fine focus value.
2. The method of claim 1 , in which simultaneously generating the stack of focal plane images of the specimen from the light includes introducing chromatic aberration into the light along with the astigmatism.
3. The method of claim 1 , in which directing light from the specimen to the Image-based autofocus system, includes directing oblique or dark field reflected illumination through the objective to the specimen, directing the oblique or dark field illumination scattered by the specimen through the objective to the image-based autofocus system.
4. The method of claim 3 , in which simultaneously generating the stack of focal plane images of the specimen from the light includes introducing chromatic aberration into the dark field illumination scattered by the specimen.
5. The method of claim 4 , in which obtaining the coarse focus value with a reflective positioning system includes sensing a reflected image through one of the objective and a sensor beside the objective.