In machine vision systems, selecting suitable cameras and lenses is critical to guarantee system performance. Improper selection of cameras or lenses may not only lead to blurry images and inaccurate detection results, but also reduce the efficiency of the entire production line. Therefore, knowing how to properly select cameras and lenses is essential. This article introduces how to select cameras and lenses according to diverse requirements, and provides practical calculation methods to facilitate your component selection.

1. Camera Sensor Selection

The camera sensor lays the foundation for imaging quality. When selecting a camera, the two most vital specifications are resolution and sensitivity.

Resolution: Higher resolution delivers richer image details. High-resolution cameras are indispensable for applications requiring precise inspection, such as defect detection and micro dimensional measurement. However, higher resolution generates larger data volume, which may slow down processing speed. Hence, you need to strike a balance based on practical application requirements.

Sensitivity: Sensitivity defines camera performance under low-light conditions. If your production environment is dim or requires round-the-clock operation at night, choosing a camera with a high-sensitivity sensor ensures sharp captured images and prevents image noise or blurriness.

2. Determine Field of View (FOV)

The Field of View (FOV) refers to the area that the camera can capture. Defining a proper FOV is extremely important, as it determines whether the camera can fully cover all objects to be inspected.

The required FOV generally depends on target dimensions and inspection task requirements. An overly small FOV may fail to capture complete objects; an excessively large FOV creates redundant image data and adds unnecessary processing load. Appropriately defined FOV can effectively improve system efficiency.

3. Calculation of Optical Magnification

For many machine vision applications, magnification plays a key role in image clarity. Especially for tasks that require examining fine object features, appropriate optical magnification enables clear observation of subtle characteristics on targets.

Optical Magnification Formula:

A proper magnification level not only enhances fine details in images, but also enables inspection systems to execute tasks with higher precision.

4. Application of Telecentric Lenses

Telecentric lenses are vital for high-precision inspection tasks including dimensional measurement and defect detection. Telecentric lenses eliminate perspective distortion caused by different shooting angles, maintain consistent apparent object size in captured images, and improve measurement and inspection accuracy. They are particularly suitable for precision inspection scenarios and preserve accurate geometric shapes within the frame.

5. Selection of Zoom Lenses

A key advantage of zoom lenses is adjustable focal length, making them ideal for inspections that require variable magnification. When inspection requirements change, zoom lenses allow flexible focal length adjustment to adapt to different application demands. When selecting a zoom lens, the primary consideration is whether its focal length range matches on-site requirements.

6. Focal Length Calculation

Focal length directly affects image clarity and FOV coverage. Correct focal length selection is essential to ensure the camera and lens properly capture target objects.

Focal Length Formula:

\(f=\frac{W\times d}{H}\) Where: f = Focal length W = CCD sensor dimension H = Target dimension (FOV size) d = Working distance between camera and target

Guidelines for Focal Length Calculation

When calculating focal length, choosing between the long edge or short edge of the FOV depends on the FOV aspect ratio:

• If the ratio of the FOV short side to long side ≥ 3/4: Use the short side of FOV and the short side of the camera sensor for calculation
• If the ratio of the FOV short side to long side < 3/4: Use the long side of FOV and the long side of the camera sensor for calculation

Example: Focal Length Calculation

Conditions: 2/3-inch CCD camera, sensor dimension: 8.8 mm × 6.6 mm Required FOV: 100 mm × 80 mm Working distance: 200 mm

Step 1: Calculate the ratio of FOV short side to long side 80 / 100 = 0.8

Since 0.8 > 3/4, adopt the FOV short side (80 mm) and camera sensor short side (6.6 mm) for calculation.

\(f=\frac{6.6\times200}{80}=16.5\ \text{mm}\)

According to the calculation result, a 16 mm focal length lens can satisfy the application requirements.

Summary

Selecting appropriate cameras and lenses is the key to a successful machine vision system. By properly choosing sensor resolution and sensitivity, defining suitable FOV, calculating accurate focal length, and selecting matching lenses (such as telecentric lenses or zoom lenses), inspection accuracy and efficiency can be greatly improved. Mastering these fundamental principles and calculation methods supports rational component selection in practical projects and ensures efficient and stable operation of machine vision systems.