Optimizing optical scanners for digital watermark detection
The present disclosure relates generally to digital watermarking for retail product packaging. A digital watermark can be carried in different color channels, and at with different signal polarities. Detection can utilize different illumination sources to highlight signal in one or more channels.
1. An apparatus comprising:
a first LED providing illumination in a red spectrum, in which the first LED provides illumination having a peak in a range between 630 nm-710 nm;
a second LED providing illumination in a blue spectrum, in which the second LED provides illumination having a peak in a range between 410 nm-490 nm;
a third LED providing illumination in a green spectrum, in which the third LED provides illumination having a peak in a range between 500 nm-565 nm;
a first 2D monochrome image sensor;
a controller configured to control illumination from the first LED, the second LED and the third LED;
a watermark detector for analyzing imagery captured by the first 2D monochrome image sensor, in which the imagery comprises a first image capture corresponding to illumination by the first LED and the second LED, minus a second image capture corresponding to illumination by the third LED, in which the first image capture comprises data representing a cyan channel and a yellow channel, with each of the cyan channel and the yellow channel comprising a digital watermark embedded therein at a first signal polarity, in which the second image capture comprises data representing a magenta channel, the magenta channel comprising a digital watermark embedded therein at a second signal polarity that is inversely related to the first signal polarity.
2. An apparatus comprising:
a first LED providing illumination in a red spectrum, in which the first LED provides illumination having a peak in a range between 630 nm-710 nm;
a second LED providing illumination in a blue spectrum, in which the second LED provides illumination having a peak in a range between 410 nm-490 nm;
a third LED providing illumination in a green spectrum, in which the third LED provides illumination having a peak in a range between 500 nm-565 nm;
a first 2D monochrome image sensor;
a second 2D monochrome image sensor;
a controller configured to control illumination from the first LED, the second LED and the third LED, in which the controller controls illumination from the first LED and the second LED at a time t, and then controls illumination from the third LED at a time t+x, where x is a time measured in milliseconds;
a watermark detector for analyzing imagery captured by the first 2D monochrome image sensor, in which the imagery comprises a first image capture corresponding to illumination by the first LED and the second LED, minus a second image capture captured by the second 2D monochrome image sensor, in which the second image captured corresponds to illumination by the third LED, in which the first image capture comprises data representing a cyan channel and a yellow channel, with each of the cyan channel and the yellow channel comprising a digital watermark embedded therein at a first signal polarity, in which the second image capture comprises data representing a magenta channel, the magenta channel comprising a digital watermark embedded therein at a second signal polarity that is inversely related to the first signal polarity.
3. An apparatus comprising:
an image sensor comprising:
rows and columns of photo-sensors;
a first set of green filters overlaying a first set of photo-sensors; and
a first set of magenta filters overlaying a second set of photo-sensors; and
a digital watermark detector configured to detect a digital watermark from grayscale imagery comprising image data filtered by the first set of magenta filters minus image data filtered by the first set of green filters, in which the first set of magenta filters optically combine first digital watermark data represented in a cyan channel component and second digital watermark data represented in a yellow channel component, and the green filters transmit light corresponding to a different channel component, and in which the grayscale imagery comprises digital watermark data emphasized relative to the first digital watermark data or the second digital watermark data.
4. An apparatus comprising:
an image sensor comprising:
rows and columns of photo-sensors;
a first set of green filters overlaying a first set of photo-sensors; and
a first set of magenta filters overlaying a second set of photo-sensors, in which for at least four co-located blocks of photo-detectors, there are two magenta filters diagonally arranged, and two green filters diagonally arranged within each 2×2 block of photo-detectors; and
a digital watermark detector configured to detect a digital watermark from grayscale imagery comprising image data captured by the second set of photo-detectors overlaid by the first set of magenta filters minus image data captured by the first set of photo-detectors overlaid by the first set of green filters.
5. An apparatus comprising:
an image sensor comprising:
rows and columns of photo-sensors;
a first set of green filters overlaying a first set of photo-sensors; and
a first set of magenta filters overlaying a second set of photo-sensors, in which for at least four co-located blocks of 2×2 photo-detectors, there are two magenta filters diagonally arranged, and two green filters diagonally arranged within each 2×2 block of photo-detectors; and
a digital watermark detector configured to detect a digital watermark from grayscale imagery comprising image data captured by the second set of photo-sensors minus image data captured by the first set of photo-sensors.
6. An apparatus comprising:
an image sensor comprising:
rows and columns of photo-sensors;
a first set of green filters overlaying a first set of photo-sensors; and
a first set of magenta filters overlaying a second set of photo-sensors, in which for at least a 4×4 block of photo-detectors, the first set of green filters comprises a 1:3 ratio relative to the first set of magenta filters; and
a digital watermark detector configured to detect a digital watermark from grayscale imagery comprising image data captured by the second set of photo-sensors minus image data captured by the first set of photo-sensors.
7. An apparatus comprising:
an image sensor comprising:
rows and columns of photo-sensors;
a first set of green filters overlaying a first set of photo-sensors; and
a first set of magenta filters overlaying a second set of photo-sensors, in which for at least four co-located blocks of 2×2 photo-detectors, there are three magenta filters arranged, per 1 green filter within each 2×2 block of photo-detectors; and
a digital watermark detector configured to detect a digital watermark from grayscale imagery comprising image data captured by the second set of photo-detectors overlaid by the first set of magenta filters minus image data captured by the first set of photo-detectors overlaid by the first set of green filters.