Basic Method Patent (PDF)

Variable Pitch Patent (PDF)

Chromatic Method Patent (PDF)

Slit Aperture Patent (PDF)

Diffraction Range Finding System

Thomas D. Ditto
a.k.a Thomas D. DeWitt

1. Basic Method Patent US 4,678,324 (1987)

Diffraction range finders are devices which determine distance by measuring the displacement of the higher-order diffraction images of a source of illumination relative to the zero- order diffraction image of the same source.

2. Variable Pitch Patent US 6,490,028 (2002)

An improvement in the diffraction range finder is made by using a diffraction grating with a variable pitch or "chirp". Improvements include a magnification feature, controllable linearity, adjustable target to instrument stand-off, a lowered occlusion liability and a more compact instrument size. Variable pitch enables a novel method for 3D microscopy.

3. Chromatic Method Patent US 6,603,561 (2003)

An improvement in the diffraction range finder is made by correlating wavelength to distance. A polychromatic source is ranged. A color sensor or a spectrometer is used to make the range reading. Embodiments can exploit readily available and inexpensive diffraction materials. The method overcomes perspective foreshortening, because the size of a spectrum increases as a target recedes, providing a plurality of samples that can be averaged.

3. Slit Aperture Patent US 8,520,191 (2013)

In a variable pitch diffraction range finder depth-of-field can be preserved with an increase in lens aperture when the iris is a slit.


Tom DeWitt, "Novel methods for the acquisition and display of three-dimensional surfaces," Optical and Digital Pattern Recognition, 1987, SPIE, Vol. 754, pp. 55-63

Tom DeWitt, "Range Finding with Diffraction Gratings," Advanced Imaging, July/August 1988, No. 12, p. A50 ff.

Tom DeWitt, "Diffraction Range Finding for Machine Vision," Proceedings of Robotics 12/Vision 88, 1988, SME, Vol. 1, Section 5, pp. 139-150

Tom DeWitt, "3D Image Acquisition by Diffraction Profilometry," Paper Summaries of SPSE's 42nd Annual Conference, May 1989, pp. 51-54

Tom DeWitt, "A Guide to 3-D Surface Acquisition," Proceedings of the Tenth Symposium on Small Computers in the Arts, SCAN 90, Nov. 1990, pp. 40-46

Thomas D. DeWitt and Douglas A. Lyon, "A range finding method using diffraction gratings," Applied Optics, May 10, 1995, Vol. 34 No. 14, pp. 2510-2521

Thomas D. DeWitt and Douglas A. Lyon, "Three-dimensional microscope using diffraction gratings," Three-Dimensional and Unconventional Imaging for Industrial Inspection and Metrology, SPIE, Vol. 2599, pp. 228-239

Tom D. Ditto and Douglas A. Lyon, "Moly a prototype handheld three-dimensional digitizer with diffraction optics," Three-Dimensional Image Capture and Applications II, January 1999, SPIE Vol 3640 paper 08, PDF file 335KB

Tom Ditto and Douglas A. Lyon, "Moly a prototype handheld three-dimensional digitizer with diffraction optics," Optical Engineering, January 2000, Vol 39 No. 1, pp. 68-78

Tom Ditto and Douglas A. Lyon, "Anamorphic magnification using a chirped grating in grazing incidence mode" Conference on Machine Vision and Three-Dimensional Imaging Systems for Inspection and Metrology, October 2000, SPIE Vol 4189 paper 19. PDF file 770KB

Tom Ditto, "Compact 3D Profilometer with Grazing Incidence Diffraction Optics," Proceedings of the Third International Conference on 3-D Digital Imaging and Modeling, IEEE Computer Society, PR00984, June 2001 pp. 73-80, PDF file 445KB

Tom Ditto, "Three-dimensional microscopy using diffraction grating primary objective", Photonics North 2004, Proc. SPIE. Vol 5578, pp. 167-178

Tom Ditto and Jacques Farges, "Localizer with high occlusion immunity using diffraction optics,"", Photonics North 2004, Proc. SPIE Vol. 5578, pp. 428-436

Thomas D. Ditto, Jim Knapp, Shoshana Biro, "3D inspection microscope using holographic primary objective," Optical Inspection and Metrology for Non-Optics Industries, Proc. SPIE Vol 7432