In the field of precision manufacturing, dimensional inspection plays a vital role in quality control. As parts become more complex, the demand for higher accuracy and efficiency increases. In certain cases, traditional contact-based measurement tools are no longer sufficient. As a result, non-contact devices such as video measuring machines offer an alternative by leveraging optical imaging and digital image processing.
Among them, the manual video measuring machine features a relatively simple structure and flexible operation, making it suitable for small-batch and multi-variety inspection tasks. It is commonly used in small and medium-sized manufacturing enterprises, laboratories, and R&D environments. This article provides an overview of its working principles, core structure, and operational characteristics.
1. Imaging Principle: Combining Optics with a Manual Stage
At the core of the manual video measuring machine is its optical imaging system. Using an industrial lens, the system magnifies the object, and the resulting image is captured by an industrial camera and displayed on a monitor.
Many such systems use telecentric lenses, which help reduce image distortion and ensure consistent edge definition even at different heights. This contributes to more repeatable measurements.
The workpiece is placed on a glass or metal stage. The operator adjusts the X and Y axes via manual knobs to bring the target area into the field of view. Focusing is done by manually adjusting the Z-axis. The entire process is manually controlled, relying on the operator’s judgment, with no automatic edge detection.
2. Image Capture and Display: Assisted by CCD Cameras
The magnified image is captured by a CCD camera and transmitted in real time to the measurement software. A high-resolution camera can provide clear images with sufficient contrast, making edge observation easier.
Image quality directly impacts measurement results. Operators must carefully adjust focus and lighting until the edges appear sharp and well-defined on the screen.
3. Image Processing: Edge Detection and Geometric Measurement
Once the image is captured, the software processes it using algorithms to detect edges and extract geometric features. Typical measurements supported include:
Hole diameters and center distances
Line lengths and angles
Arc radii and tangents
Point-to-point distances
Operators select target regions by clicking or drawing a box, and the system fits the corresponding geometry for measurement. Multiple features can also be measured in sequence to analyze form and spacing.
The accuracy of edge detection often depends on the user’s habits and proficiency. Improper focus or poor edge recognition may lead to inconsistent results.
4. Lighting System: Enhancing Contrast and Edge Clarity
Lighting is critical for image quality. Most systems include various lighting options such as:
Ring light: Highlights surface textures
Bottom (transmitted) light: For silhouette measurements
Coaxial light: For reflective surfaces like metal parts
Appropriate lighting improves contrast and helps define edges. Because workpieces vary in material, color, and geometry, the lighting system usually allows independent brightness control.
5. Operation Style: Manual Control for Flexible Tasks
All measurement steps are manually controlled, including platform movement, focus, feature selection, and result export. While it lacks automation, the manual system has some advantages:
No need for programming, suitable for non-repetitive tasks
Allows free movement to inspect complex shapes
Relatively lower cost for smaller businesses
However, effective operation requires some training, especially in focusing, image evaluation, and lighting adjustment.
6. Result Output: Basic Reporting Capability
After measurement, the system can export results as spreadsheets, annotated images, or CAD drawings. Common formats include Excel, PDF, and DXF. This makes it easier to track inspection records and generate quality reports.
Some software also supports basic tolerance checking, allowing users to flag out-of-spec dimensions.
7. Suitable Use Cases: Small Batch, R&D, or Complex Geometry
Manual video measuring machines are most appropriate for:
Small quantities and multiple part types
First-article inspection during product development
Parts with scattered or non-uniform measurement points
Educational or lab environments
While it is not designed for high-speed automation, it serves well as a supplementary inspection tool in many production settings.
Conclusion
As a basic form of video measurement, manual systems are valued for their practicality and accessibility. Their structure is relatively simple, and their functionality is sufficient for many everyday 2D inspection tasks.
They are especially useful in operations that need flexible manual control and where automated systems may be excessive. While they are not intended to replace high-end coordinate measuring machines or automated systems, manual video measuring machines remain a valid choice for many quality control scenarios—particularly where cost, variety, and flexibility matter.