In the world of machine vision systems, achieving accurate and reproduceable image quality is crucial for tasks such as inspection, measurement, and quality control. Telecentric lenses and telecentric lighting play vital roles in enhancing imaging precision. In this article, we will give a brief introduction to telecentric lenses, then delve into the advantages and disadvantages of telecentric lighting. Additionally, we will explore the parallel backlight as an alternative lighting solution in certain scenarios.
Telecentric lenses are optical devices designed to minimize perspective errors and provide consistent magnification and perspective across the entire imaging area. Unlike conventional lenses, telecentric lenses have a unique property where the optical parts are positioned in a special configuration. We offer a variety of telecentric lenses. Our telecentric lens portfolio and pricing can be found on our website.
Telecentric lenses are designed to have parallel rays entering the lens, resulting in rays that are nearly perpendicular to the image sensor.
This property allows for accurate and consistent measurements as it minimizes perspective errors and distortions. This makes telecentric lenses ideal for precise dimensional measurements and accurate feature extraction. Other features of telecentric lenses are a constant magnification and minimal distortion. Big projects require relatively bigger telecentric lenses:
Telecentric lighting is an integral part of the telecentric imaging system, working in harmony with telecentric lenses. Unlike conventional back illumination methods where light rays are emitted diffuse or undirected, telecentric lights ensure that the light rays are parallel and have consistent intensity across the entire field of view. This parallel light beam configuration creates silhouettes, minimizes perspective errors and distortion, resulting in accurate measurements and consistent image quality.
To achieve telecentric lighting, the light rays are guided through a sequence of optical elements creating parallel light rays and consistent brightness across the beam. Sometimes this light beam is described as a collimated light beam.
The telecentric light can be considered as a telecentric lens used backwards.
In situations where space limitations or cost considerations are critical factors, a parallel backlight can serve as a viable alternative to telecentric lighting. Parallel backlights are equipped with a specialized filter which reduces the diffuse emission of light and creates a more uniform, directed light.
While it may not provide the same level of depth perception or perspective control, a parallel backlight offers advantages in specific scenarios:
1. Space-Saving Solution
Parallel backlighting systems are typically more compact than telecentric lighting setups, making them suitable for applications with limited space constraints or when space optimization is a priority.
2. Uniform Illumination
A parallel backlight, can provide even and uniform illumination across the object's surface. This ensures consistent image quality.
3. Edge Detection and Contrast Enhancement
Parallel backlighting improves edge detection capabilities by enhancing the visibility of object contours and boundaries. It also increases contrast, enabling better differentiation of object features, defects or irregularities.
Systems with telecentric lenses and telecentric lights offer notable advantages in terms of enhanced contrast and measurement precision. While they may involve higher costs and space requirements, the benefits they bring are invaluable. In situations where space limitations or cost considerations are a concern, a parallel backlight can provide a viable/feasible alternative. Parallel backlight offer a uniform illumination and improved edge detection capabilities. When carefully considering the specific requirements and limitations of each lighting technique, machine vision system designers can select the optimal solution for their applications, ensuring reliable and accurate imaging results.