DOVID Verification Using Flash-Lit Image Similarity on Curved Surfaces
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Solution Overview
Problem
Existing methods for verifying the presence of diffractive optically variable elements (DOVIDs) in security elements are not robust, particularly on surfaces with strong specular reflections or curves, and require complex image processing and specific lighting conditions, leading to inefficiencies and potential misclassification.
Innovation Solution
Capture two images of the ROI under different lighting conditions, using a built-in flash, and analyze the structural similarity index (SSIM) and color transitions index (CTI) to classify the nature of the ROI using machine learning techniques, allowing for robust verification across various lighting conditions and surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the smartphone moves relative to the DOVID to capture images, then verification can be performed, but the process becomes more complex and consumes more energy
Solution Approach 1:
The patent uses periodic lighting (alternating between ambient light and flash) to capture multiple images without requiring smartphone movement. The flash is activated and deactivated in sequence to create different lighting conditions, achieving verification through temporal periodic action rather than spatial movement.
Solution Approach 2:
The patent introduces an intermediary light source (the smartphone's built-in flash) to create controlled lighting variations. This intermediary element enables the capture of images under different lighting conditions without requiring the smartphone to move relative to the DOVID, thus reducing energy consumption while maintaining verification reliability.
2Reliability
If the smartphone moves relative to the DOVID, then verification can be performed, but the device complexity and operational complexity increase
Solution Approach 1:
The patent employs periodic switching between ambient light and flash illumination to capture images. This temporal periodic action eliminates the need for users to manually move the smartphone, greatly simplifying operation while maintaining verification reliability through automated sequential image capture.
Solution Approach 2:
The smartphone's built-in flash serves the dual purpose of both illuminating the scene and providing the lighting variation needed for verification. This self-service approach eliminates the need for external equipment or complex user maneuvers, making the verification process simple and accessible.
3Illumination intensity
If images are captured with strong specular reflections (e.g., using flash on curved surfaces), then lighting conditions improve, but classification robustness decreases
Solution Approach 1:
The patent uses the flash as an intermediary light source that can be selectively activated. By capturing one image with ambient light and another with flash, the system obtains images under different lighting conditions. The algorithm then processes these images to compensate for specular reflections, maintaining classification robustness even when strong reflections are present in individual images.
Solution Approach 2:
The patent changes the lighting parameter by capturing images under two different lighting conditions (ambient light and flash). This parameter variation allows the verification algorithm to distinguish between genuine DOVID optical effects and artifacts caused by specular reflections, thereby maintaining classification robustness across different surface types.
4Reliability
If the light source is connected during capture of multiple images, then verification can be performed, but power consumption increases
Solution Approach 1:
The patent implements periodic activation of the flash light source, turning it on only during the capture of specific images and turning it off during ambient light capture. This periodic action significantly reduces power consumption compared to keeping the light source continuously connected, while still enabling verification through the alternating lighting conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides reliable and repeatable verification of DOVIDs with high robustness, simplicity, and low power consumption, suitable for consumer devices like smartphones, without requiring specialized equipment or complex movements.
Implementation Method 1
capturing a second image of the security element under a second lighting condition with the flash connected
Implementation Method 2
verifying the existence of a diffractive optically variable element
Data Source
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AI summary
The invention relates to computer implemented methods for verifying the existence of a diffractive optically variable image device (DOVID) on a surface of a security element by means of the processing of images captured of said security element. The security element can include a bidimensional graphical code, for example, a QR code (QR) or a logotype (LOG). The methods of the invention preferably comprise conversion steps from the RGB model (from the English Red, Green and Blue) of the images processed to the HSV color mode (from the English Hue, Saturation and Value), there being calculated structural similitude indexes and color transitions indexes for the classification of a DOVID or a non-DOVID. The methods of the present invention simultaneously present great robustness relative to the geometry and nature of the surfaces under analysis, provide reliable results in a wide range of uncontrolled lighting conditions, are simple to use and generate results with repeatability.