LED Illumination Device with Segmented Current Control for Uniform Imaging
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Solution Overview
Problem
Existing illumination devices for image capturing, particularly those using LEDs arranged around a camera's light axis, face challenges in versatility due to uneven illumination across the circumference of imaging targets like BGA components, limiting their applicability to specific types of components and reducing image recognition accuracy.
Innovation Solution
An illumination device with four LED-mounted boards arranged in a four-sided shape, where each board is inclined to face the imaging target, and a current adjusting device divides the LED-mounted areas into multiple illumination zones, allowing individual current adjustments to achieve even brightness levels across different areas, enabling adaptation to various component types and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are arranged on a dome-shaped surface centered around the imaging target, then the distance from the center to each LED is substantially equal providing uniform illumination, but it is difficult to form and mount LEDs at high accuracy leading to increased manufacturing complexity
Solution Approach 1:
The dome-shaped LED array is segmented into multiple flat LED-mounted boards (first through fourth boards) arranged in a stepped configuration. Each board contains multiple LEDs mounted on a flat surface, and the boards are positioned at different heights and angles to collectively form the dome shape. This segmentation transforms the difficult single-surface mounting problem into multiple manageable flat surfaces.
Solution Approach 2:
The invention transitions from a two-dimensional dome surface to a three-dimensional stepped structure composed of multiple flat boards at different heights and orientations. The LED-mounted boards are arranged in a stepped fashion around the light axis, with each board inclined at a specific angle, creating a multi-level configuration that achieves uniform illumination without requiring a single curved mounting surface.
2Illumination intensity
If twenty-four LED-mounted boards are arranged in an octagonal bowl shape, then illumination coverage is improved, but the configuration becomes complex increasing manufacturing costs and space requirements
Solution Approach 1:
The large number of LED-mounted boards (24 in octagonal configuration) is reduced to just four boards arranged in a stepped configuration. Each board contains multiple LEDs, and the four boards are positioned at different heights and angles to provide comprehensive illumination coverage, significantly simplifying the overall structure while maintaining effectiveness.
Solution Approach 2:
Multiple LED-mounted boards are merged into a compact stepped structure where the first, second, third, and fourth boards are vertically stacked and angularly arranged around the light axis. This merging consolidates the illumination function into a space-efficient configuration that reduces both the number of components and the overall space required.
3Measurement precision
If LEDs are arranged to illuminate outer circumferential section of bumps more than center section, then image recognition accuracy for BGA components is improved, but other types of components cannot be illuminated and versatility is poor
Solution Approach 1:
The illumination device incorporates independent current control for each LED-mounted board, allowing dynamic adjustment of illumination patterns. The current controlling device can individually adjust the current supplied to each board, enabling the system to adapt its illumination characteristics to match different component types and inspection requirements, thereby achieving both high image recognition accuracy and versatility.
Solution Approach 2:
The invention changes the illumination parameters by independently controlling the current to each LED-mounted board. By adjusting current magnitude and distribution across the four boards, the system can modify its illumination pattern to suit different component geometries, transitioning from fixed BGA-optimized illumination to adaptable multi-component illumination.
4Device complexity
If four LED-mounted boards are arranged in a four-sided shape, then manufacturing cost and space are reduced, but uneven illumination across different areas lowers image recognition accuracy
Solution Approach 1:
Each LED-mounted board is assigned a specific spatial region or illumination zone, and the current to each board is independently adjusted to compensate for positional differences. This local quality control ensures that each area of the imaging target receives appropriate illumination intensity, achieving overall uniformity despite the simplified four-board configuration.
Solution Approach 2:
The current magnitude supplied to each of the four LED-mounted boards is independently adjusted as a control parameter. By varying the current to each board based on its position and orientation, the system compensates for the simplified geometry and achieves even illumination across the entire imaging target area.
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 configuration simplifies and cost-reduces the illumination device, enhances its versatility by ensuring even illumination across the imaging target, and allows for precise brightness adjustments, improving image recognition accuracy regardless of component variations.
Implementation Method 1
an illumination device for image capturing which uses many LEDs arranged around a light axis of a camera
Data Source
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AI summary
An illumination device (13) configured to illuminate an imaging target, an image of which is to be captured by a camera, provided with a current adjusting device (26) configured to adjust a current flowing through the LEDs (21) of four LED-mounted boards (22) on which many of the LEDs are mounted, wherein the four LED-mounted boards are arranged in a four-sided shape centered around the light axis of the camera as viewed from the imaging target, and each of the LED-mounted boards is inclined at a specified angle so that the LEDs of the LED-mounted boards face the imaging target. The current adjusting device is configured to divide an LED-mounted area of each of the LED-mounted boards into multiple illumination areas (25) and to individually adjust the current flowing to the LEDs of each of the LED-mounted boards for each of the multiple illumination areas.