LXG-500M / LXC-500M – Lenses for ams CMV50000 Sensor Cameras [AN201804]
Baumer Cameras: LXG-500, LXC-500
This application note describes the physical conditions for using ams CMV50000 sensor-based cameras with different lenses.
Technical Background
Baumer LXG-500 and LXC-500 cameras use the 47.5 megapixel ams CMV50000 sensor with a 46 mm sensor diagonal.
Due to the sensor size, it is not easy to find a suitable lens. Only a few lenses ensure that all incoming light fully illuminates the sensor. Therefore, in addition to constantly recurring parameters such as working distance and field of view, the choice of the optimal lens mount is also important.
Lens Mount and Image Circle
CMV50000-based cameras principally offer only two options: M42 or F-Mount. Both have advantages and disadvantages:
- M42It is currently the largest industrial lens mount and is suitable for applications where the imaging system is subject to shocks and vibrations, as the lens screws onto the camera. However, usually the optical image circle is smaller than 46 mm.
- F-Mount: Comes from consumer products and is not considered suitable for industrial use due to the lens being bayonet-mounted to the camera. However, such lenses may have a 46 mm optical image circle.
Baumer tested both M42 and F-Mount lenses.
Vignette Effect
Vignetting means that image brightness or saturation decreases towards the edges compared to the center of the image. Fading of the center of a clear image towards the periphery is achieved by partial shadowing of the sensor by lens geometry (natural vignetting) or apertures (true vignetting).
Tested Lenses
At Baumer, both F-Mount and M42 lenses from different brands were tested on the LXG-500M camera:
| Brand | Type | Link | Image Circle | Conclusion |
|---|---|---|---|---|
| myutron | LSF3528-F | F-Mount | 44mm | good lighting |
| Qioptiq | Rodagon F 40mm | F-Mount | 44mm | perfect illumination |
| Ricoh | FL-YFL3528 | F-Mount | 45mm | Deficiencies in lighting |
| zeiss | Biogon 2/35 | M42 | 43mm | Deficiencies in lighting |
In general, all lenses available for illuminating large sensors (35 mm and above) have vignetting. The degree of brightness decreasing towards the edges of the image depends on the manufacturer, focal length and aperture of the lens.
Update:
Myutron produces LSF2528, LSF3528, LSF5028, LSF10528 and LSF20035 models specifically for Baumer with M58 mounting and Baumer flange focal length. This combines an industrial lens mount with a large image circle with a diagonal size of 44mm.
Thanks to the Baumer rear focal length, there is no need to use an adapter when these lenses are used on an LXG-500M camera.
| Brand | Type | Link | Image Circle | Conclusion |
|---|---|---|---|---|
| myutron | LSF2528-U58 | M58 | 44mm | good lighting |
| myutron | LSF3528-U58 | M58 | 44mm | very good lighting |
| myutron | LSF5028-U58 | M58 | 44mm | very good lighting |
| myutron | LSF10528-U58 | M58 | 44mm | very good lighting |
| myutron | LSF20035-U58 | M58 | 44mm | good lighting |
Suggestions
Baumer recommends F-Mount lenses used with large f-numbers because the difference in brightness from the image center to the edges is smaller:
- 1 = small f-number
- 2 = large f-number
- x-axis: Distance towards image center [%]
- y-axis: Relative brightness [%]
Additionally, reducing the resolution with Partial Scan functionality helps limit the image size to the center; In this way, acceptable vignetting for the user and manageable algorithms in the application are achieved.
Additionally, software-based Shading Correction can help correct image edge darkening. This approach is supported in Baumer GAPI SDK version 2.9.1 and later.
