Barcode-reading system that obtains ranging data via targeting illumination

1. A barcode-reading system for a mobile device, the mobile device comprising a camera assembly and a white light source for providing illumination, the barcode-reading system comprising:

a barcode-reading enhancement accessory securable to the mobile device, the barcode-reading enhancement accessory comprising an optic system that is positionable within a field of illumination of the white light source when the barcode-reading enhancement accessory is secured to the mobile device, the optic system being configured to shape and filter the illumination from the white light source to project targeting illumination onto a target surface;

calibration data that indicates a relationship between surface distance and at least one feature offset of the targeting illumination; and

a barcode-reading application stored in memory of the mobile device, the barcode-reading application being executable by a processor of the mobile device to:

determine a feature offset of the targeting illumination in an image that is captured by the camera assembly of the mobile device;

determine an estimated surface distance based on the calibration data and the feature offset; and

use the estimated surface distance to adjust at least one operating parameter of the mobile device.

2. The barcode-reading system of claim 1 , wherein adjusting the at least one operating parameter of the mobile device comprises adjusting intensity of the illumination provided by the white light source of the mobile device.

3. The barcode-reading system of claim 1 , wherein:

the targeting illumination comprises a rectangular targeting bar; and

determining the feature offset comprises determining a width of the rectangular targeting bar.

4. The barcode-reading system of claim 1 , wherein:

the optic system comprises an optical filter that is configured to pass a limited spectrum of the illumination emitted by the white light source;

the image comprises a plurality of channel images;

a channel image of the plurality of channel images is used to determine the feature offset of the targeting illumination; and

the channel image is more sensitive to the limited spectrum that is passed by the optical filter than other channel images of the plurality of channel images.

5. The barcode-reading system of claim 1 , wherein:

the calibration data comprises a plurality of surface distance fields and a plurality of feature offset fields; and

each feature offset field is associated with a corresponding surface distance field.

6. The barcode-reading system of claim 1 , wherein determining the estimated surface distance comprises:

identifying a feature offset field whose value is closest to the feature offset in the image; and

returning a value of a corresponding surface distance field as the estimated surface distance.

7. The barcode-reading system of claim 1 , wherein determining the estimated surface distance comprises interpolating the estimated surface distance using the calibration data and the feature offset in the image.

8. The barcode-reading system of claim 1 , wherein the calibration data comprises a plurality of records, and wherein each record comprises:

a surface distance field that indicates a surface distance;

a first location field that indicates a location of a first feature of the targeting illumination in a calibration image taken at the surface distance;

a second location field that indicates a location of a second feature of the targeting illumination in the calibration image; and

a feature offset field indicating a difference between the location of the first feature of the targeting illumination in the calibration image and the location of the second feature of the targeting illumination in the calibration image.

9. The barcode-reading system of claim 1 , wherein the calibration data comprises a mathematical formula that:

receives, as an input, the feature offset of the targeting illumination; and

provides, as output, the estimated surface distance.

10. The barcode-reading system of claim 1 , wherein the barcode-reading application is configured to:

cause the camera assembly to capture a plurality of calibration images; and

record information about the plurality of calibration images in the calibration data.

11. A barcode-reading application for a mobile device that comprises a processor, memory, a camera assembly, and a white light source for emitting illumination, the barcode-reading application comprising executable code that, when stored in the memory and executed by the processor:

determines a feature offset of targeting illumination in an image that is captured by the camera assembly of the mobile device, wherein the targeting illumination is produced by an optic system of a barcode-reading enhancement accessory that is secured to the mobile device;

determines an estimated surface distance based on calibration data and the feature offset; and

uses the estimated surface distance to adjust at least one operating parameter of the mobile device.

12. The barcode-reading application of claim 11 , wherein adjusting the at least one operating parameter of the mobile device comprises adjusting intensity of the illumination provided by the white light source of the mobile device.

13. The barcode-reading application of claim 11 , wherein:

the targeting illumination comprises a rectangular targeting bar; and

determining the feature offset comprises determining a width of the rectangular targeting bar.

14. The barcode-reading application of claim 11 , wherein:

the optic system comprises an optical filter that is configured to pass a limited spectrum of the illumination emitted by the white light source;

the image comprises a plurality of channel images;

a channel image of the plurality of channel images is used to determine the feature offset of the targeting illumination; and

the channel image is more sensitive to the limited spectrum that is passed by the optical filter than other channel images of the plurality of channel images.

15. The barcode-reading application of claim 11 , wherein:

the calibration data comprises a plurality of surface distance fields and a plurality of feature offset fields; and

each feature offset field is associated with a corresponding surface distance field.

16. The barcode-reading application of claim 11 , wherein determining the estimated surface distance comprises:

identifying a feature offset field whose value is closest to the feature offset in the image; and

returning a value of a corresponding surface distance field as the estimated surface distance.

17. The barcode-reading application of claim 11 , wherein determining the estimated surface distance comprises interpolating the estimated surface distance using the calibration data and the feature offset in the image.

18. The barcode-reading application of claim 11 , wherein the calibration data comprises a plurality of records, and wherein each record comprises:

a surface distance field that indicates a surface distance;

a first location field that indicates a location of a first feature of the targeting illumination in a calibration image taken at the surface distance;

a second location field that indicates a location of a second feature of the targeting illumination in the calibration image; and

a feature offset field indicating a difference between the location of the first feature of the targeting illumination in the calibration image and the location of the second feature of the targeting illumination in the calibration image.

19. The barcode-reading application of claim 11 , wherein the calibration data comprises a mathematical formula that:

receives, as an input, the feature offset of the targeting illumination; and

provides, as output, the estimated surface distance.

20. The barcode-reading application of claim 11 , wherein the executable code, when stored in the memory and executed by the processor:

causes the camera assembly to capture a plurality of calibration images; and

records information about the plurality of calibration images in the calibration data.