Metrology equipment upgrade considerations with increasing to high-resolution cameras

High resolution, high-speed metrology cameras can be a great way to increase accuracy and throughput of equipment even with smaller features to inspect or measure.  In order to realize these benefits, the optics, the frame grabber and other components in the imaging chain must be properly matched and optimized.  With increases from 4 Megapixels to 8 or even 12 Megapixels at fast frame speeds, there are several considerations at the system level to utilize the higher data rate.  Here we will mention a few…

1. One of the first changes required is optics which may become much more expensive when going to higher optical resolutions (smaller pixels AND greater number of pixels).

2. The power dissipation from the camera will be greater and if it is not managed in the camera electronics then an internal fan is required.

3. Another consideration is the video interface.  There have been several developments of new high-speed interfaces in order to take full advantage of the latest generation CMOS image sensors.  For a comparison of the different options, please see our free ePaper.  Or click here for a free comparison of Global machine vision Interface Standards from the AIA, JIIA, and EMVA.  For the purposes of this discussion, we will use CoaXPress as an example.

4. Then, there is data processing on system level:

Data is generated by the camera with a certain bandwidth and transmitted via a high speed video interface (CoaXPress).  Each pixel is transmitted via this interface with the selected pixel bit resolution (i.e. selectable 8 or 10 bit in Adimec cameras).  This data is received by the frame grabber of the system).  For more information on CoaXPress frame grabbers, click here.  For more information about the different versions of CoaXPress, click here.

The data from the frame grabber is transferred to the system’s memory where calculations will be performed to execute the metrology algorithms.  The systems bandwidth is limited and all processing on image data is restricted by the system performance specifications.  

With 8 bit per pixel resolution, the impact on the system is relatively straight forward.  With 10 bits (or more), it is a different story. To process data in a system with more then 8 bit/pixel, 2 bytes per pixel needs to be reserved (computer systems work with a multiple of bytes) which require higher system bandwidths.  For example 10 bits/pixel from the camera will require 16 bits/pixel in the system.  Overall this means a higher performance computer system to handle more data.

For a few of Adimec’s high resolution cameras, the related (maximum) bandwidths are shown below.  

(fps = frames per second)

(Gpixelps = gigapixels per second)

(Gbps = gigabit per second)

This means a 12 Megapixel camera at 180 fps needs three times the bandwidth as a 4 megapixel camera at the same frame rate.

We have supported the upgrades and integration of many high-resolution, high-speed metrology cameras into a variety of systems at our customers – please contact us with any questions. 

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