An increase in resolution to a 25 Megapixel CMOS camera, can allow for a wider field of view (FOV), and better optical and/or measurement resolution. These cameras are a cost-effective way to make a performance leap in inspection and metrology systems.
Figure 1: Example of how a Large Sensor Array reduces number of acquisitions
The noise performance and sensitivity of the high-end 25 Megapixel CMOS sensors are impressive, allowing the use of existing lighting conditions at fast frame speed (up to 30 fps over Camera Link and 45 fps over Dual-CoaXPress). But, with more pixels, there are of course a greater number of deviating or defect pixels (although the overall percentage is low because the total number of pixels is high). There is also a greater chance for non-linear behavior across the sensor array. This is a problem as the most important performance parameters for most measurement algorithms are linearity, uniformity, and full well capacity combined with a high frame rate.
There are many 25 Megapixel cameras based on ON Semiconductor’s Vita 25k sensor available, which will have similar specifications on paper. The better measurement resolution can only be achieved with uniform and reliable starting images. The image sensor provides excellent source material, and some corrections and adjustments can be done during the initial calibration of the camera at the factory.
But, the image quality is also affected by various system conditions, such as optics imperfections, lighting artifacts, region of interest (ROI), and frame speed settings.
ROI is used for faster readout, which demands a lot of from the CMOS image sensor and can result in issues with the shutter. Additional adjustments for system conditions and poor shutter efficiency can be done automatically through active sensor control (ASC).
Cameras with active sensor control allow for calibrations in the system set-up and recalibrations in the field to optimize the image quality in all circumstances. This can be done with the touch of a button or in real-time and the adjustments are made as close to the sensor as possible for greater accuracy.
In our next post we will explain how to evaluate active sensor control in your system to see for yourself which image sensor artifacts and effects are solved and this can enable the performance enhancements from a 25 Megapixel camera in your system.
Figure 2a*. 25 megapixel image with no image sensor calibrations using active sensor control
Figure 2b*. 25 megapixel image of active sensor control
For tips on a successful camera evaluation, see: