Frequency domain range determination for a periodic or quasi-periodic target

Patent metadata

Field	Value
Publication number	US-10171723-B2
Application number	US-201415327290-A
Country	US
Kind code	B2
Filing date	Jul 18, 2014
Priority date	Jul 18, 2014
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

Examples disclosed herein relate to determining peak distances between an origin, point in the frequency domain and peak points of a discrete Fourier transform magnitude of an image of a periodic or quasi-periodic target. In some implementations, a range distance between the target and the imaging lens is determined based on the peak distances.

First claim

What is claimed is:

1. A method comprising:
determining one or more peak points in a half-plane of a discrete Fourier transform magnitude of an image of a target, wherein the one or more peak points each have a peak value relative to surrounding values, and further wherein the target is periodic or quasi-periodic, and further wherein a lens images the target on a sensor that captures the image;
based on a peak distance between an origin point in a frequency domain and each of the one or more peak points that are determined, determining a range distance between the target and the lens;
providing the range distance as a first output;
obtaining data from the image, wherein the obtained data includes a print resolution of the target and a fundamental spatial resolution of the target; and
receiving an empirically measured ratio of a lens-to-target distance and a target extent, wherein the empirically measured ratio is for a sample lens-to-target distance within an operating range of a system comprising the lens and the sensor, wherein the range distance is further based on the print resolution, the fundamental spatial resolution, and the empirically measured ratio.

2. The method of claim 1 , wherein the data that is obtained is recovered from the image and further comprising:
receiving a sensor size and a focal length of the lens, wherein the range distance is further based on the print resolution, the fundamental spatial resolution, the sensor size, and the focal length.

3. The method of claim 1 , further comprising:
receiving values for a sensor size and a focal length of the lens, wherein the range distance is further based on the print resolution, the fundamental spatial resolution, the sensor size, and the focal length.

4. The method of claim 1 , further comprising:
based on the peak distance of each of the one or more peak points that are determined, determining an autofocus distance between the lens and the sensor; and
providing the autofocus distance as a second output, or adjusting a distance between the lens and the sensor to the autofocus distance.

5. The method of claim 4 , further comprising:
receiving a sensor size and a focal length of the lens, wherein the autofocus distance is further based on the print resolution, the fundamental spatial resolution, the sensor size, and the focal length.

6. A method comprising:
determining one or more peak points in a half-plane of a discrete Fourier transform magnitude of an image of a target, wherein the one or more peak points each have a peak value relative to surrounding values, and further wherein the target is periodic or quasi-periodic, and further wherein a lens images the target on a sensor that captures the image;
based on a peak distance between an origin point in a frequency domain and each of the one or more peak points that are determined, determining a range distance between the target and the lens;
providing the range distance as a first output;
receiving values for a print resolution of the target and a fundamental spatial resolution of the target; and
receiving an empirically measured ratio of a lens-to-target distance and a target extent, wherein the empirically measured ratio is for a sample lens-to-target distance within an operating range of a system comprising the lens and the sensor, wherein the range distance is further based on the print resolution, the fundamental spatial resolution, and the empirically measured ratio, and further wherein the range distance is an approximation.

7. A system comprising:
a lens to image a target on a sensor, wherein the target is periodic or quasi-periodic;
the sensor to capture an image of the target; and
a processor to:
identify one or more peak points in a half-plane of a discrete Fourier transform magnitude of the image, wherein each of the one or more peak points have a greater value relative to neighboring values;
based on a peak distance between an origin point in a frequency domain and each of the one or more peak points that are determined, determine an autofocus distance between the lens and the sensor;
based on the autofocus distance, adjust a distance between the lens and the sensor to autofocus the system;
based on the peak distance for each of the one or more peak points that are determined, determine a range distance between the target and the lens;
provide the range distance as an output;
obtain data from the image, wherein the obtained data includes a print resolution of the target and a fundamental spatial resolution of the target; and
receive an empirically measured ratio of a lens-to-target distance and a target extent, wherein the empirically measured ratio is for a sample lens-to-target distance within an operating range of a system comprising the lens and the sensor, wherein the range distance is further based on the print resolution, the fundamental spatial resolution, and the empirically measured ratio.

8. The system of claim 7 , wherein the processor is further to:
receive a sensor size and a focal length of the lens, wherein the autofocus distance is further based on the print resolution, the fundamental spatial resolution, the sensor size, and the focal length.

Assignees

• Hewlett Packard Development Co

Inventors

• Ulichney Robert
• Gaubatz Matthew D
• Pollard Stephen

Classifications

• G02B7/365

  by analysis of the spatial frequency components of the image · CPC title

• G01S13/08

  Systems for measuring distance only (indirect measurement G01S13/46) · CPC title

• G01S11/12 Primary

  using electromagnetic waves other than radio waves · CPC title

• H04N5/23212 Primary

  Electricity · mapped topic

• G03B13/20

  Rangefinders coupled with focusing arrangements, e.g. adjustment of rangefinder automatically focusing camera · CPC title