For many global security systems, the optical format was decided by the initial choice of the image sensor, for instance a 1/3” VGA sensor or 2/3” HD CCD image sensors with pixel sizes of 6 or 7 µm. These legacy systems are now due for upgrades to take advantage of the sensitivity, lower read noise and higher pixel throughput of the latest CMOS image sensors. CMOS process technology improvements have allowed for shrinking of pixels while preserving important imaging parameters: (QE, charge handling capacity per square µm, and more). BUT much smaller pixel sizes can result in a much bigger overhaul of the system than is desired such as a change in optics and displays.
There is now a way for any new camera to fit on existing optics and on the existing interface/displays; for example, using a state-of-the-art Quad HD CMOS image sensor to replace an older VGA CCD with larger pixels on VGA displays.
Adimec’s proprietary Adaptive Resolution™ provides the option to emulate the original optical format using programmable digital image down-scaling.
Adaptive Resolution (Adimec proprietary) allows the system architect or designer to select a new CMOS image sensor without changing optics and losing dynamic range.
Adaptive Resolution can be used with a CMOS image sensor with more pixels and with the same (or larger) optical format than the existing cameras. Advanced interpolation algorithms for cropping and scaling in the camera create virtual pixels of the required size (same image format at output).
This results in the same FOV, combined with a better system performance (new CMOS pixels outperform CCD pixels of the same size):
- Higher sensitivity
- Higher dynamic range
- Higher MTF (especially for Bayer RGB color)
To verify the results, we compare Adimec’s TMX7-DHD camera using the ICX674 CCD sensor with 4.54 µm square pixel size, with the TMX50 camera using Sony’s IMX250 CMOS image sensor with 3.45 µm square pixel size using Adaptive Resolution technology to run at a virtual pixel size of 4.54 µm.
Figure 1a. TMX7-DHD CCD Camera (4.54 um pixels)
Figure 1b. TMX50 CMOS (4.54um Adaptive Resolution)
No difference is readily visible in the images. With zooming in, small sharpness improvements can be detected such as looking at the “Nieuw recept” lettering.
Figure 2. TMX7-DHD TMX50 with Adaptive Resolution