Exploring the Principles of Non-Contact Optical Measurement: A Pillar of Precision and Flexible Manufacturing

In modern manufacturing, as miniaturization, high precision, and flexible materials become increasingly prevalent, traditional contact-based measurement methods can no longer fully meet the demands of every application. When dealing with deformable, micro-scale, or geometrically complex components, achieving high-precision measurement without physically touching the object has become a pressing need. Non-contact optical measurement technology has emerged as a powerful solution, forming an essential part of many industrial inspection systems.

1. What Is Non-Contact Optical Measurement?

As the name suggests, non-contact optical measurement refers to the acquisition and processing of dimensional, surface, and positional data through optical systems—without physically touching the object being measured. This approach integrates technologies such as image processing, light source control, precision optics, and geometric algorithms.

In a typical workflow, a light source projects specific illumination—such as contour lighting, coaxial illumination, or structured light—onto the surface of the workpiece. The reflected or transmitted light is then captured by high-resolution optical lenses (e.g., telecentric lenses) and focused onto a CCD or CMOS image sensor. The image processing system then performs edge detection, grayscale analysis, and geometric calculations to extract features and output dimensional data, including length, diameter, angle, and positional deviation.

One of the most important features of this method is its non-contact nature. It eliminates the risk of compressing or deforming the material, making it particularly suitable for delicate components such as flexible PCBs, thin films, and molded plastic parts.

2. Core Components and Operating Principles

Light Source System

The illumination setup is crucial in optical measurement. Different lighting techniques directly impact image clarity and contour extraction.

Contour lighting (backlight) produces high-contrast black-and-white silhouettes for accurate 2D edge profiling.

Coaxial illumination is ideal for reflective or complex surfaces, such as metallic or textured components.

Structured light (e.g., laser stripe) is used for precise 3D surface topography measurements.

Imaging System (Lens)

High-quality lenses determine both image resolution and geometric fidelity. Telecentric lenses maintain constant magnification across the entire field of view, eliminating errors caused by variations in object distance. This is essential for high-precision dimensional measurements.

Image Capture and Processing Unit

Once captured by the CCD or CMOS sensor, the image undergoes processing algorithms that detect edges, extract coordinates, and analyze geometry. Modern systems often support sub-pixel resolution, significantly enhancing measurement accuracy.

Motion Platform and Control System

In automated systems, X/Y/Z-axis platforms control the movement of either the sensor or the object, enabling multi-position and multi-angle measurements. Combined with auto-focus and region scanning functions, these systems can greatly improve throughput and consistency.

3. Advantages and Value in Industry

Compared to contact-based methods, non-contact optical measurement offers several key advantages:

Improved Efficiency

No need for mechanical probing, clamping, or cleaning probes between cycles. It enables rapid, high-volume inspection and suits fast-paced quality control environments.

Adaptability to Complex and Flexible Materials

Ideal for measuring components that are easily deformed, fragile, or too small for contact measurement—such as rubber parts, thin films, or microstructures.

Micron to Sub-Micron Accuracy

High-resolution optics and advanced image processing algorithms meet the stringent requirements of modern precision manufacturing.

Strong Automation and Digital Integration

Easy to integrate with production lines for in-line inspection, automated judgment, and data traceability. It supports the broader goals of smart and digital manufacturing.

4. Wide-Ranging Applications

Non-contact optical measurement is now widely used in sectors such as electronics, semiconductors, automotive components, medical devices, and precision tooling.

In FPC (flexible printed circuit) manufacturing, it helps inspect trace widths and spacing.

In mold production, it verifies dimensional conformity with CAD models.

In precision plastic injection, it detects defects such as flash, sink marks, and warpage—all without touching the part.

By understanding the principles and components of non-contact optical measurement, manufacturers can gain greater control over quality assurance. In real-world applications, this technology not only improves precision and efficiency but also supports the needs of flexible and customized production. As vision algorithms and optical hardware continue to evolve, the role of optical measurement in industrial inspection will only grow more prominent.