In high-precision manufacturing, automatic vision measuring machines (VMMs) have become essential tools for dimensional inspection. As the core of the imaging system, the design of the illumination unit directly affects the clarity of edge detection and the stability of measurement. This article focuses on three key design aspects of the illumination system in automatic vision measuring machines: multi-source integration, automatic lighting adjustment, and the principles and applications of variable lighting units.
1. Integration of Multiple Lighting Units: One System for Diverse Inspection Scenarios
Traditional vision measurement systems often require changing light sources based on the surface characteristics of the measured object—an inefficient and labor-intensive process. Modern automatic VMMs integrate multiple lighting types, including ring light, coaxial light, oblique light, and slit light, into a single device. The system automatically identifies the characteristics of the product and switches to the optimal lighting combination, allowing it to adapt to different materials and structures without manual intervention.
📌 Example:
When inspecting a black plastic button, the system automatically activates low-angle ring lighting to enhance edge contrast. For metallic frames, it switches to a combination of coaxial and oblique lighting to suppress reflections and highlight edges.
2. Automatic Adjustment to Optimal Lighting Conditions: Intelligent Coordination of Brightness and Angle
Equipped with light sensors and control systems, automatic VMMs can analyze ambient light intensity and image clarity in real time. The system dynamically adjusts the lighting height, brightness, and angle to ensure clear edge detection.
📌 Example:
When measuring transparent light guide strips, the system detects severe light scattering and automatically selects blue light while adjusting the lighting angle to reduce interference and enhance edge contrast. This fully automated process improves both measurement stability and operational efficiency.
3. Principles of Variable Lighting Units: Precision Lighting for Different Workpieces
a. Multi-Angle Lighting Design
The height and angle of the light source directly affect the illuminated cross-section. When placed at a higher position, the light provides broad and uniform coverage—ideal for large-area inspection. Lower positions increase local contrast, making them more suitable for edge or step detection.
📌 Example:
When inspecting chamfers on precision metal parts, low-angle oblique lighting creates shadow transitions at the edges, aiding in algorithmic edge recognition.
b. Slit Ring Lighting Principle
Slit lighting emits a narrow light beam horizontally. When positioned at a specific height relative to the target edge, it forms high-contrast images, making it ideal for reflective or transparent materials, especially for precise edge recognition.
📌 Example:
In the inspection of edge chipping on glass panels, slit lighting produces a clear light-dark contrast at the edge, enabling accurate identification of cracks or defects.
Conclusion
The illumination system in modern automatic vision measuring machines is no longer a passive imaging aid. It has evolved into an intelligent module that actively participates in optimizing the measurement process. By integrating multiple light sources, enabling real-time adjustments, and incorporating variable lighting structures, the system can handle complex inspection tasks with greater accuracy and efficiency.