Handheld DPM Code Reader Using Time-of-Flight Distance Imaging
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Solution Overview
Problem
Existing methods for electro-optically reading direct part marking (DPM) codes on reflective, non-planar workpieces face challenges due to poor contrast and saturation issues, especially with handheld imaging readers, which are costly and slow, and require additional hardware or software to enhance readability.
Innovation Solution
A handheld imaging reader with a solid-state distance imaging sensor using a time-of-flight method to capture images based on distance differences between DPM code elements and the workpiece surface, relying on infrared light pulses to determine distances and identify elements through local maxima or minima in pixel values, rather than intensity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional moving laser beam readers are used to read DPM codes on reflective workpieces, then the reading process can be performed, but the highly reflective non-planar surfaces cause bright return light that saturates photodetectors and prevents reliable reading
Solution Approach 1:
The patent replaces the moving laser beam reader system with a solid-state imaging reader that captures images of the DPM code on the workpiece. This substitution eliminates the photodetector saturation problem by using an imaging sensor that can process the reflected light differently, allowing reliable reading of codes on highly reflective surfaces.
Solution Approach 2:
The patent changes the reading approach from direct photodetector measurement of reflected light intensity to image capture and processing. By capturing the image and analyzing pixel intensity variations across the code elements, the system can distinguish code features even when overall reflection is high, effectively changing the measurement parameter from absolute intensity to relative intensity differences.
2Ease of operation
If handheld imaging readers are used to read DPM codes, then image capture is possible, but the reading process becomes slow and requires additional hardware or software to enhance readability
Solution Approach 1:
The patent implements self-service by using the existing imaging sensor's distance measurement capability (time-of-flight data) to automatically distinguish code elements from the background. The system processes the depth information directly from the imaging sensor to identify raised or sunken elements, eliminating the need for additional hardware attachments or complex software processing, thereby maintaining fast reading speeds.
Solution Approach 2:
The patent adds the depth dimension to the imaging process by utilizing time-of-flight distance measurements from the imaging sensor. This third dimension (distance from sensor) allows automatic differentiation between code elements (which are raised or sunken) and the background surface, significantly improving reading speed and accuracy without requiring additional handheld accessories.
3Adaptability or versatility
If imaging readers capture DPM codes on non-planar surfaces, then code reading is possible, but poor contrast between code elements and background degrades reading performance
Solution Approach 1:
The patent resolves the contrast problem by introducing the depth dimension through time-of-flight measurements. Instead of relying solely on intensity contrast which fails on non-planar surfaces, the system measures the distance from the imaging sensor to each point on the surface. Code elements that are raised or sunken create distinct distance patterns that are easily distinguishable from the background, providing high contrast regardless of surface geometry or 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
This approach enables robust and rapid reading of DPM codes without extra hardware or software, minimizing specular reflections and improving readability by distinguishing distance patterns, thus enhancing the cost-efficiency and performance of code recognition.
Implementation Method 1
A handheld imaging reader with a solid-state distance imaging sensor using a time-of-flight method to capture images based on distance differences between DPM code elements and the workpiece surface, relying on infrared light pulses to determine distances
Data Source
AI summary
An apparatus and method electro-optically read indicia, such as a direct part marking (DPM) code, that is raised or sunken relative to a target surface on a target. A solid-state, distance imaging sensor captures a target image comprised of a first set of pixels having first distance values that correspond to a first distance of the code from the sensor, and a second set of pixels having second distance values that correspond to a second distance of the target surface from the sensor. A controller reads the indicia by distinguishing between the first set of pixels and the second set of pixels within the image, by determining abrupt changes in the distance values among neighboring pixels.