Claims
- 1. Apparatus for increasing depth of field in a conventional Amplitude Contrast Imaging system having an illumination source, illumination optics, and an illumination mask placed before a Phase Object to be imaged, and an objective mask and objective optics after the Phase Object to form an image at a detector, the improvement comprising:
an optical Wavefront Coding mask placed between the Phase Object and the detector, said mask being constructed and arranged to alter the optical transfer function of the Amplitude Contrast Imaging system in such a way that the altered optical transfer function is substantially insensitive to the distance between the Phase Object and the objective optics over a greater range of object distances than was provided by the unaltered optical transfer function, wherein the mask affects the alteration to the optical transfer function substantially by affecting the phase of light transmitted by the mask; and a post processing element for processing the image captured by the detector by reversing the alteration of the optical transfer function accomplished by the mask.
- 2. The apparatus of claim 1 wherein the illumination mask and the objective mask are constructed and arranged for Hoffman modulation Contrast Imaging.
- 3. The apparatus of claim 1 wherein the illumination mask and the objective mask are constructed and arranged for Carl Zeiss VAREL Contrast Imaging.
- 4. The apparatus of claim 1 wherein the detector is a charge coupled device (CCD).
- 5. The method for increasing depth of field in a conventional Amplitude Contrast Imaging system having an illumination source, illumination optics, and an illumination mask placed before a Phase Object to be imaged, and an objective mask and objective optics after the Phase Object to form an image at a detector, the method comprising the steps of:
between the Phase Object and the detector, modifying the wavefront of transmitted light; the wavefront modification selected to alter the optical transfer function of the Amplitude Contrast Imaging system in such a way that the altered optical transfer function is substantially insensitive to the distance between the Phase Object and the objective optics over a greater range of object distances than was provided by the unaltered optical transfer function; and post processing the image captured by the detector by reversing the alteration of the optical transfer function accomplished by the mask.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] U.S. Pat. No. 5,748,371, issued May 5, 1998 and entitled “Extended Depth of Field Optical Systems,” is incorporated herein by reference.