Aimer localization and triangulation in multi-sensor scanner

1 . An apparatus of an optical scanner for scanning a subject, the apparatus comprising:

interface circuitry including an input to receive a plurality of images from at least one image-capture device; and

controller circuitry coupled to the interface circuitry and the input, the controller circuitry operative to perform a ranging determination, the ranging determination including a localization phase and a triangulation phase, wherein:

in the localization phase:

project an aimer spot onto a subject;

receive a series of image frames via the input, the series of image frames collectively containing an aimer spot captured as a reflection off of a surface of the subject;

temporally modulate the aimer spot and an exposure of the at least one image-capture device according to a modulation pattern such that appearance of the aimer spot and ambient lighting each differs among image frames of the series, and wherein a captured intensity of the aimer spot is varied among the image frames in inverse relation to a captured exposure level of those image frames; and

process the series of image frames to discriminate the aimer spot from other light sources based on the modulation pattern to determine a probable location of the aimer spot within at least one of the image frames of the series; and

in the triangulation phase:

process the probable location of the aimer spot to produce the ranging determination based on evaluation of the aimer spot differing among the series of image frames according to the modulation pattern, wherein the ranging determination represents a distance between the at least one image-capture device and the surface of the subject.

2 . The apparatus of claim 1 , wherein the interface circuitry further includes an input to receive an activation signal, and wherein the controller is operative to perform the ranging determination in response to the activation signal.

3 . The apparatus of claim 1 , wherein the interface circuit is operative to receive a plurality of images from each of a plurality of image-capture devices.

4 . The apparatus of claim 3 , wherein the plurality of image-capture devices includes a near-field camera and a far-field camera, wherein the far-field camera has a narrower field of view than the near-field camera.

5 . The apparatus of claim 3 , wherein in the plurality of images from each of the plurality of image-capture devices has a device-specific positional offset of the captured aimer spot that varies based on a distance between a respective image-capture device and the surface of the subject, and further based on a relative position of that respective image-capture device and a projector of the aimer spot; and

wherein in the triangulation phase the probable location of the aimer spot is processed to assess whether that probable location is within a plausible location based on different device-specific positional offsets in image frames captured by different ones of the plurality of image-capture devices.

6 . The apparatus of claim 1 , wherein:

the interface circuitry includes an aimer output to control an aimer spot projector that is operative to produce an aimer emission that causes the aimer spot; and

the controller circuitry is operative to produce a modulation control signal based on the modulation pattern, and the aimer output is operative to couple the modulation control signal to the aimer spot projector.

7 . The apparatus of claim 1 , wherein the aimer spot is temporally modulated by intensity variation of the aimer spot.

8 . The apparatus of claim 1 , wherein in the localization phase, the controller is operative to cause variation of image-capture parameters of the at least one image-capture device.

9 . The apparatus of claim 1 , wherein the aimer spot is temporally modulated by variation of duration of aimer spot projection relative to a duration of an exposure of the at least one image-capture device for image frame capture.

10 . The apparatus of claim 1 , wherein in the localization phase, the series of image frames is processed to discriminate the aimer spot based on the modulation pattern by computing a pixel-wise comparison operation between successive image frames of the series of image frames to reveal a variation caused by the temporal modulation of the aimer spot at a location within the image frames corresponding to the aimer spot.

11 . The apparatus of claim 10 , wherein:

the comparison operation is determined over the series of image frames, and wherein the comparison operation varies in accordance with the modulation pattern; and

a filtering operation is applied to the comparison operation to filter out portions of the series of image frames that fail to meet a defined threshold.

12 . An apparatus of an optical scanner for scanning a subject, the apparatus comprising:

an aimer projector operative to project an aimer spot onto a subject such that the aimer spot is temporally modulated as it is projected according to a modulation pattern;

interface circuitry including an input to receive a plurality of images of varying exposure level from a plurality of image-capture devices collectively containing the aimer spot captured as a reflection off of a surface of the subject and such that an appearance of the aimer spot differs among image frames of the series, wherein the modulation pattern of the aimer spot produces a captured intensity of the aimer spot that is varied among the images in inverse relation to the exposure levels of those images; and

controller circuitry coupled to the aimer projector, the interface circuitry and the input, the controller circuitry operative to perform a ranging determination, the ranging determination including a localization phase and a triangulation phase, wherein:

each image of the plurality of images from each of the plurality of image-capture devices has a device-specific positional offset of the captured aimer spot that varies based on a distance between a respective image-capture device and the surface of the subject, and further based on a relative position of that respective image-capture device and a projector of the aimer spot;

the localization phase identifies a probable location of the aimer spot in a series of image frames that is received via the input based on an evaluation of the aimer spot differing among the series of image frames according to the modulation pattern and the varied exposure levels to determine the probable location of the aimer spot within at least one of the image frames of the series; and

in the triangulation phase the probable location of the aimer spot is processed to assess whether that probable location of the aimer spot is within a plausible location based on different device-specific positional offsets in image frames captured by different ones of the plurality of image-capture devices;

wherein the ranging determination represents a distance between the optical scanner and the surface of the subject.

13 . The apparatus of claim 12 , wherein a first image-capture device of the plurality of image-capture devices is associated with a first set of positional offsets of the captured aimer spot that is a function of distance of the first image-capture device and the surface of the subject, and wherein a second image-capture device of the plurality of image-capture devices is associated with a second set of positional offsets of the captured aimer spot that is a function of distance of the optical scanner and the surface of the subject.

14 . The apparatus of claim 13 , wherein the first set of positional offsets is stored in the controller circuitry, and wherein the second set of positional offsets is stored in the controller circuitry; and

wherein the controller circuitry is operative to compute the assessment of whether the probable location of the aimer spot is within a plausible location based on:

a determination of a first distance according to the first set of positional offsets based on a first positional offset of the probable location of the aimer spot in a first image captured by the first image-capture device; and

a comparison of (a) an expected second positional offset value corresponding to the first distance according to the second set of positional offsets and (b) a second positional offset of the probable location of the aimer spot in a second image captured by the second image-capture device.

15 . The apparatus of claim 13 , wherein the first set of positional offsets is stored in the controller circuitry, and wherein the second set of positional offsets is stored in the controller circuitry; and

wherein the controller circuitry is operative to compute the assessment of whether the probable location of the aimer spot is within a plausible location based on:

a determination of a first distance according to the first set of positional offsets based on a first positional offset of the probable location of the aimer spot in a first image captured by the first image-capture device; and

a determination of a second distance according to the second set of positional offsets based on a second positional offset of the probable location of the aimer spot in a second image captured by the second image-capture device; and

a comparison of the first distance and the second distance.

16 . The apparatus of claim 13 , wherein the first set of positional offsets is stored in the controller circuitry a first set of offset regions corresponding to different ranges of distances between the first image-capture device and the surface of the subject, and wherein the second set of positional offsets is stored in the controller circuitry a second set of offset regions corresponding to different ranges of distances between the second image-capture device and the surface of the subject, wherein certain offset regions of the first set correspond with certain offset regions of the second set according to correspondence criteria.

17 . The apparatus of claim 16 , wherein the controller circuitry is operative to compute the assessment of whether the probable location of the aimer spot is within a plausible location based on:

a determination of a first offset region of the first set that corresponds to a first positional offset of the probable location of the aimer spot in a first image captured by the first image-capture device;

a determination of a second offset region of the second set that corresponds to a second positional offset of the probable location of the aimer spot in a second image captured by the second image-capture device; and

an assessment of whether the first offset region and the second offset region are corresponding offset regions based on the correspondence criteria.

18 . A method for operating an optical scanner for scanning a subject, the method comprising:

projecting an aimer spot onto a target;

autonomously receiving a plurality of images from at least one image-capture device, the plurality of images having been captured at varying exposure levels; and

autonomously performing a ranging determination, the ranging determination including a localization phase and a triangulation phase, wherein:

in the localization phase, the aimer spot is temporally modulated as it is projected according to a modulation pattern, a series of image frames is received, the series of image frames collectively containing the aimer spot captured as a reflection off of a surface of the subject such that an intensity of the captured aimer spot differs among image frames of the series according to the modulation pattern, the modulation pattern being in inverse relation to the exposure levels of the captured image frames, and the series of image frames is processed to discriminate the aimer spot from other light sources based on the modulation pattern and the exposure levels to determine a probable location of the aimer spot within at least one of the image frames of the series; and

in the triangulation phase, the probable location of the aimer spot is processed to produce the ranging determination based on evaluation of the aimer spot differing among the series of image frames according to the modulation pattern, wherein the ranging determination represents a distance between the at least one image-capture device and the surface of the subject.

19 . The method of claim 18 , further comprising:

receiving a plurality of images from each of a plurality of image-capture devices,

wherein in the plurality of images from each of the plurality of image-capture devices has device-specific a positional offset of the captured aimer spot that varies based on a distance between a respective image-capture device and the surface of the subject, and further based on a relative position of that respective image-capture device and a projector of the aimer spot; and

wherein in the triangulation phase the probable location of the aimer spot is processed to assess whether that probable location is within a plausible location based on different device-specific positional offsets in image frames captured by different ones of the plurality of image-capture devices.

20 . The method of claim 18 , wherein in the localization phase, the series of image frames is processed to discriminate the aimer spot based on the modulation pattern by computing a pixel-wise difference between successive image frames of the series of image frames to reveal a difference caused by the temporal modulation of the aimer spot at a location within the image frames corresponding to the aimer spot.