LXG-500M / LXC-500M – Lenses for cameras operating on ams CMV50000 sensors [AN201804]

The Baumer LXG-500 and LXC-500 cameras operate on the 47.5 megpapixel ams sensor CMV50000 with a 46 mm sensor diagonal.

Due to the sensor size, an appropriate lens is not easy to find. Only few lenses ensure that all incoming light will fully illuminate the sensor. So, besides the ever-recurring parameters of operating distance and view size there is also the question for optimal lens mount.

By principle, CMV50000 – based cameras leave only two options: M42 or F-Mount, both having their benefits and drawbacks:

• M42 is presently the largest industrial lens mount which thanks to the lens being screwed to the camera is suitable for applications where the vision system is exposed to shocks and vibration. However, most often the optical image circle is smaller than 46 mm.

• F-Mount originates from consumer products and due to lens docked onto the camera by bajonet, it is considered little suitable for industrial use. However, such lenses may be capable of 46 mm optical image circles.

Baumer tested both M42 and F-Mount lenses.

Vignetting means the reduction of image brightness or saturation towards the edges compared to the image center. The effect of a clear image center fading off toward the periphery is achieved by partial sensor shading, either by the lens geometry (natural vignetting) or apertures (real vignetting).

At Baumer, both F-Mount and M42 lenses of different brands were tested on a LXG-500M camera:

 In general, all presently available lenses to illuminate large sensors (35 mm and more) have vignetting. The degree of reduced brightness towards the edge of the image depends on the manufacturer, the focal length and the aperture of the lens.

Update

The lens manufacturer Myutron manufactures exclusively for Baumer the F-mount optics LSF2528, LSF3528, LSF5028, LSF10528 and LSF20035 with M58 mount and Baumer flange focal distance. This creates the connection of the large image circle with a diagonal of 44 mm and an industrial lens mount.

Due to the Baumer back focal distance, no adapter has to be used when using the lenses on an LXG-500M camera.

Baumer recommends F-Mount lenses used with large f-numbers as the difference in brightness between the image center and the edges is less severe:

• 1 = small f-number
• 2 = large f-number
• x-axis = distance towards image center [%]
• y-axis = relative brightness [%]

Furthermore, reducing resolution with the Partial Scan functionality helps to limit the image size to the center with still tolerable vignetting effect for the user respectively manageable algorithms in the application.

Also software-based Shading Correction may help to correct the image edge darkening. Baumer GAPI SDK version 2.9.1 and later will support this approach.

• Shading Correction (Flat-Field Correction) with the Baumer GAPI SDK [AN201803]

Please contact our Technical & Application Support Center with any questions.

Phone: +49 3528 4386 845
E-mail: [email protected]