Factors to Consider When Choosing Industrial Lenses

Factors to Consider When Choosing Industrial Lenses

Depth of Field

The performance of an optical system depends on the allowable degree of image blur, which can result from shifts in the position of the object plane or the image plane. Depth of Field (DOF) refers to the range of acceptable blur due to detector movement. It is influenced by the working F-number (F/#), which measures the lens's light-gathering capability. When the lens aperture is reduced, F/# increases. While increasing F/# enhances DOF by reducing the aperture size, it also diminishes the light reaching the sensor, requiring higher illumination to compensate.

DOF can also be understood as the depth range within which an object remains in focus as it moves along the optical axis. If an object's position shifts from the ideal focal point, resolution and contrast will degrade, leading to blurring. To maintain focus over a specific range, DOF can be increased by reducing the aperture size, thereby raising the F/# value, but this requires additional light.

Industrial Lenses

The DOF range depends on the effective focal length and the acceptable blur diameter. Some lenses are designed with hyperfocal or quasi-hyperfocal capabilities, allowing the far end of the in-focus range to extend to infinity. This technique is commonly used in fixed-focus lenses with deep DOF effects, which can be adjusted with the iris.

It's crucial not to confuse telecentric lenses with deep DOF lenses. Telecentric lenses control magnification and eliminate potential errors, ensuring consistent object height in images regardless of their distance from the industrial camera. This lens type is used in applications like analyzing computer circuit boards. Telecentric lenses generally have a range of working distances, with finite DOF at each point. When selecting a telecentric lens for a project, both the working distance range and DOF should be considered.

Conclusion

Industrial lenses significantly impact machine vision systems. Choosing a lens that meets system requirements based on actual applications ensures stability and maximizes the system's advantages.