Fujinon CF-ZA: one-for-all lens series
The technical advancement of image sensors for Machine Vision brings higher spatial resolution resulting in larger sensors and smaller pixels. This development created big challenges for vision system designers as it was difficult to find the right lenses for such sensors: High resolution power, strong light transmission, short minimum object distance (MOD), a small Chief Ray Angle (CRA), and all this from the center to the edges of the large image circle – these were just the optical requirements. Equally important remain the compact build of the lenses and their robustness against shocks and vibrations.
FUJIFILM thoroughly listened to the needs and pain-points of its Machine Vision customers and created the CF-ZA-1S series to meet all the above-mentioned requirements and goes even beyond. The CF-ZA-1S lens series is designed for use with all standard machine vision cameras that use C-mount, an image sensor of up to 1.1” optical format, and pixel pitches from 2.5 µm, which equals up to 23 megapixels.
The series provides a lineup of six different lens models with different focal lengths from 8 to 50 mm, allowing customers to choose the lens most appropriate for their desired application.
FUJINON’s patented Anti-Shock and Vibration design limits shifts of the optical axis to 10 µm and ensures constant resolution power in the typical, rough manufacturing environments.
The MOD is just 100 to 200 mm (even at 50mm focal length) and the maximum CRA is at 4.9° as required by the latest high-resolution sensors. This guarantees a high relative illumination across the entire image without vignetting.
These lenses also come with knurled screws which cannot accidentally fall out anymore and get lost or damage sensitive manufacturing machines during installation or maintenance.
All these features are designed in a compact build with the world-smallest external diameter of just 39 mm for the 1.1” optical format.
Innovation: High Relative Illumination Design
The new CF-ZA-1S lens series fulfills an essential requirement placed on machine vision lenses: an image illumination right down to the corners that is as uniform as possible, i.e. with minimum vignetting.
Some of the sensors currently used in cameras (e.g. Sony IMX253/255) are prone to such vignetting due to their design. This effect can be minimized with a suitable optical design. It is important to keep the angle of incidence of the light as small as possible in relation to the optical axis. The angle of the chief ray (CRA) should be less than 5º.
Thanks to their innovative High Relative Illumination design, all lenses of the CF-ZA series meet this high-level requirement. They deliver uniform illumination across the entire image – right down to the corners – even to the “critical” IMX253/255 sensors and up to a focal length as short as 8 mm. The relative illumination is clearly above 90% in the corners.
The focus for the lens design of the Fujinon CF-ZA series was set on the high resolution and the high relative illumination. Both requirements were clearly accomplished within the Fujinon CF-ZA series.
Since physical limitations prevent building a “perfect lens” that delivers a “perfect picture”, a compromise had to be made during the lens design process. To incorporate both features of high resolution and high relative illumination into a lens body as small as possible, this compromise was set on the distortion.
The distortion values of the Fujinon CF-ZA series are comparatively high, especially for the models with a short focal length of 8mm and 12mm. But what sounds like a huge disadvantage turns out to be an advantage in the end because the distortion of the lenses is a simple curve and can be corrected easily by commonly used software tools with just one or two correction parameters.
Compared to that neither the loss of resolution nor the lack of relative illumination can be corrected afterwards – if the loss is caused by a bad lens design.
So, in the end the distortion is high indeed for the short focal lengths. But it can be corrected easily and it´s the best compromise possible in order to keep resolution and relative illumination high.
Therefore, the Fujinon CF-ZA series is the universal one-for-all solution of modern machine vision systems.