System and method for auto-focusing a vision system camera on barcodes

Patent metadata

Field	Value
Publication number	US-12367361-B2
Application number	US-202418412900-A
Country	US
Kind code	B2
Filing date	Jan 15, 2024
Priority date	Jul 24, 2018
Publication date	Jul 22, 2025
Grant date	Jul 22, 2025

Abstract

This invention provides a system and method for detecting and acquiring one or more in-focus images of one or more barcodes within the field of view of an imaging device. A measurement process measures depth-of-field of barcode detection. A plurality of nominal coarse focus settings of a variable lens allow sampling, in steps, of a lens adjustment range corresponding to allowable distances between the one or more barcodes and the image sensor, so that a step size of the sampling is less than a fraction of the depth-of-field of barcode detection. An acquisition process acquires a nominal coarse focus image for each nominal coarse focus setting. A barcode detection process detects one or more barcode-like regions and respective likelihoods. A fine focus process fine-adjusts, for each high-likelihood barcode, the variable lens near a location of the barcode-like regions. The process acquires an image for decoding using the fine adjusted setting.

First claim

What is claimed is:

1. A method for focusing on a symbol with an imaging sensor, comprising:
acquiring coarse focus images for each of a plurality of coarse focus settings, the coarse focus settings corresponding to a range of distances between the symbol and the imaging sensor;
determining symbol-like regions within the coarse focus images and estimating a respective likelihood that each of the symbol-like regions contain an actual symbol; and
for each of the symbol-like regions having the respective likelihood, using a fine focus procedure to increase a sharpness measurement around the respective symbol-like regions by acquiring images at adjusted focus settings that define values in a range respectively around each of the coarse focus settings associated with each of the respective symbol-like regions,
wherein increasing the sharpness measurement adjusts the focus to acquire an image to enable successful decoding of the symbol at the respective symbol-like regions.

2. The method as set forth in claim 1 , wherein the step of using the fine focus procedure occurs for each of the symbol-like regions in order of highest to lowest likelihood.

3. The method as set forth in claim 1 , further comprising communicating with an electronically controlled variable focus lens assembly configured to produce selected focal lengths for the coarse focus images.

4. The method as set forth in claim 3 , further comprising, controlling a high speed liquid lens in which the focal length thereof is set based upon a diopter value.

5. The method as set forth in claim 3 , further comprising, adjusting the variable focus lens assembly based upon an iterative, numerical-step-based search technique over the coarse focus settings.

6. The method as set forth in claim 1 , wherein the steps of acquiring, determining, and using are performed according to a plurality of priority levels.

7. The method as set forth in claim 1 , wherein the symbol is characterized by a maximum focus error in which the symbol can be reliably detected, and further comprising, measuring an effective depth-of-field based upon the maximum focus error.

8. The method as set forth in claim 1 , wherein the symbol comprises at least one of a 1D barcode or a 2D barcode.

9. The method as set forth in claim 1 , wherein the coarse focus settings are based upon a distance measurement provided by a distance sensor relative to the imaging sensor.

10. The method as set forth in claim 9 , wherein the distance measurement is provided by at least one of a time-of-flight-sensor, a LIDAR, a radar, an ultrasonic sensor, a stereoscopic sensor, or a sonar sensor.

11. A vision system for focusing on a symbol on a surface containing symbol-like regions within a field of view of an imaging device having an image sensor and a processor comprising:
a variable lens configured to receive focus adjustment information and direct light to the image sensor;
coarse focus settings of the variable lens corresponding to samples of a lens adjustment range, in sampling steps, over a range of distances between the symbol and the image sensor,
wherein the image sensor is arranged to acquire a coarse focus image for a coarse focus setting of the variable lens; and
a fine focus process that, for at least one of the symbol-like regions within the coarse focus image, fine-adjusts the variable lens from the coarse focus setting to adjust a focus of the variable lens near a location of the symbol-like regions, and acquires an image via the image sensor using a fine-adjusted focus setting of the variable lens.

12. The vison system as set forth in claim 11 , further comprising a measurement process that measures an effective depth-of-field of symbol detection as the maximum focus error for which the symbols can be reliably detected, and wherein a step size of the sampling steps is less than a fraction of the effective depth-of-field of barcode detection.

13. The vision system as set forth in claim 11 , further comprising a symbol detector arranged to measure a respective likelihood of the symbol-like regions, and wherein the at least one of the symbol-like regions defines a likelihood above a predetermined level.

14. The vision system as set forth in claim 11 , wherein the symbol detector operates at a substantially maximum frame rate of reliably locating the symbol-like regions within an image acquired by the image sensor.

15. The vision system as set forth in claim 11 , wherein at least one of, (a) the variable lens comprises a high-speed liquid lens, or (b) the depth-of-field is measured in diopters and the focus adjustment information defines diopters.

16. The vision system as set forth in claim 11 , wherein the fine focus process is arranged to select an adjusted focus setting that maximizes an image sharpness score in a local region around the symbol-like regions.

17. A vision system for focusing on a symbol, the vision system comprising:
an imaging device having a field of view and comprising an image sensor and a variable lens;
at least one processor in communication with the imaging device and configured to:
acquire coarse focus images for each of a plurality of coarse focus settings, the coarse focus settings corresponding to a range of distances between the symbol and the image sensor;
determine symbol-like regions within the coarse focus images and estimate a respective likelihood that each of the symbol-like regions contain an actual symbol;
for each of the symbol-like regions having the respective likelihood, use a fine focus procedure to increase a sharpness measurement around the respective symbol-like regions by acquiring images at adjusted focus settings that define values in a range respectively around each of the coarse focus settings associated with each of the respective symbol-like regions,

wherein increasing the sharpness measurement adjusts the focus to enable successful decoding of the symbol at the respective symbol-like regions.

18. The vision system as set forth in claim 17 , wherein the at least one processor is further configured to receive a distance measurement provided by a distance sensor relative to the imaging sensor,
wherein the coarse focus settings are based upon the distance measurement.

19. The vision system as set forth in claim 17 , wherein the fine focus procedure is arranged to select an adjusted focus setting that maximizes an image sharpness score in a local region around the symbol-like regions.

20. The vision system as set forth in claim 17 , the at least one processor is configured to receive the acquired coarse focus images and operate a symbol decoder.

21. The vision system as set forth in claim 20 , wherein the at least one processor is at least one of a GPU or an FPGA.

Assignees

• Cognex Corp

Inventors

• Bachelder Ivan A
• Gao Chen
• Guerrero Francisco Azcona
• Dorado Jose Fernandez
• Lozano Esther Oteo
• Weber Andreas

Classifications

• H04N23/671

  in combination with active ranging signals, e.g. using light or sound signals emitted toward objects · CPC title

• H04N23/959

  by adjusting depth of field during image capture, e.g. maximising or setting range based on scene characteristics · CPC title

• G06K7/1413

  1D bar codes · CPC title

• G06K7/10722

  Photodetector array or CCD scanning · CPC title

• G06K7/1443 Primary

  locating of the code in an image · CPC title