Flat field correction improves machine vision camera uniformity

Posted by Gretchen Alper on Mon, Mar 14, 2011

Embedded flat-field correction in the camera improves uniformity, aids in-field set-up.

Flat Field Correction (FFC) processing can be used to minimize or even remove artifacts to improve the image uniformity.  The purpose of flat field correction is to ensure image uniformity regardless of exposure.  Several calibrations and corrections are required to make this work properly.

Figure 1.  Image from a CMOS camera without Flat field correction	Figure 2.  Image from a CMOS camera with Flat field correction

All sensors and lenses have imperfections.  The pixel response on exposure varies from pixel to pixel.  This is present with CCD sensors, but even more excessive with CMOS sensors.  Also, lenses have distortions in the glass.  These imperfections give rise to image artifacts which evidence themselves as non-uniformity in the 2D image.  

Some camera manufacturers perform flat field calibrations in the factory. More advanced cameras also support in-field calibration. This allows for compensation to address issues in the image acquisition set-up process, such as non-uniformity of lighting source(s) and optics used in setup.  Embedded in the camera, FFC gives you great performance enhancement while off-loading processing needs from the frame grabber and simplifying development efforts at system integration.

The Adimec QUARTZ camera series supports factory and in-field FFC through storage of multiple calibration setups so the camera can switch instantly during operation between different lighting-optics setups.  

Flat Field Corrections can also be applied to our color cameras with Bayer pattern sensors. We have developed proprietary algorithms to offer the same image quality as for the Monochrome sensor cameras.