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An industrial lens is a crucial component of a machine vision imaging system. The bi-telecentric lens is a relatively new addition to the lens family and has quickly become a leading solution due to its exceptional performance. However, because bi-telecentric lens has only recently been introduced, many of its features are not yet widely known.
Magnification Variation
One of the primary issues with conventional lenses is the change in image size when the working distance varies. This means that the same lens with a specific focal length will produce different magnifications depending on the distance of the object. This effect is similar to how human vision perceives objects as smaller when they are farther away. While this phenomenon may be negligible or even beneficial in certain scenarios, it becomes a significant limitation when precision measurement is required.
Depth of Field Limitations
Conventional lenses have a limited depth of field. When an object is positioned outside the lens's depth of field, the image becomes blurry and lacks sharp focus. Although standard lenses often include a focus adjustment ring to manage this issue, it remains challenging to capture objects with significant depth. If the object's depth exceeds the lens's capability, both the near and far ends cannot be clearly imaged simultaneously.
Measurement Accuracy
With the increasing resolution of imaging sensors, users are demanding higher measurement accuracy. Conventional lenses, due to their optical limitations, typically offer accuracy within 10 microns. However, applications requiring more precise measurements necessitate a higher-performing imaging solution.
Bi-telecentric lens is specifically designed to address these challenges. By incorporating an aperture stop at the midpoint of the optical system, they ensure that principal rays pass through the center of the aperture. This configuration ensures that both the object-side and image-side principal rays remain parallel to the optical axis.
Based on Canrill Optics' extensive experience in machine vision product selection, here are some scenarios where a bi-telecentric lens is recommended:
Large Object Thickness: When inspecting objects with significant thickness or multiple planes, such as food containers or beverage bottles.
Directional Defect Detection: If defects are only visible under parallel illumination from a specific direction.
High-Precision Measurement: For applications requiring extremely high measurement accuracy, with tolerances as low as 1 micron.
Complex or Three-Dimensional Objects: When inspecting objects with apertures, holes, or intricate three-dimensional structures.
Low Distortion and Uniform Brightness: If the application requires minimal distortion and uniform image brightness across the field of view.
Uncertain Object Positioning: When objects may not be perfectly aligned with the lens, potentially forming an angle with the lens axis.
Vibrating or Moving Objects: On production lines where objects may vibrate or shift vertically, causing variations in the working distance.
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