The CSG14K image sensor is built around a 3840- by 3584-pixel array, for a 14-megapixel resolution. The 12-bit output will afford the large dynamic range needed to handle the large variations of light intensity that is often encountered in modern manufacturing and inspection environments.
The CV50000, a member of the ams family that preceded the CSG14K.
The CSG14K is a CMOS image sensor that utilizes global shuttering as opposed to rolling shutter.
What Is Global Shuttering?
Global shuttering is a method of using an image sensor's shutter that allows clear capturing of even high-speed subjects. As explained by ams, “All pixels are sampled at the same moment in time, producing an image free of distortion." According to ams, they chose global shuttering over rolling shuttering because the latter produces artifacts "caused by the difference in the time of sampling for pixels at different locations in the sensor.”
Rolling shutter vs. global shutter. Image from Oxford Instruments
A camera based on the old rolling shutter mechanism could easily lead to wrong conclusions and unsatisfactory results in an Automated Optical Inspection (AOI) environment.
Correlated Double Sampling
The CSG14k also utilizes Correlated Double Sampling (CDS), which mandates that a sensor makes not one, but two measurements. The pixel’s output after reset is subtracted from the output measured when actually viewing the sample. This removes visual “noise” and renders a truer representation of the object under inspection.
The sensor’s high resolution is made possible in part by its exceptionally small 3.2µm x 3.2µm pixel size. These are 66% smaller than ams’s previous 10-bit devices.
The CSG14k allows designers to program its functionality to operate optimally in a wide range of application environments. A low-power mode is available for situations involving slower frame rates and fewer measurements.
The CSG14k is housed in a 218-pin, 22mm x 20mm x 3mm LGA package which is compatible with the 1” lenses widely used in small form factor camera designs.
ams’s CMV Family of Image Sensors
The CSG14k is preceded by ams’s CMV family of image sensors.
CMV8000 is an 8-megapixel global shutter image sensor that can run at 103 frame rate (fps) with 10-bit output, or at a lower fps with 12-bit output that supports a superior image quality. Its pixel size is 5.5 µm, and its resolution is 8.4 megapixels
CMV8000 evaluation kit. Image from ams
CMV20000 is a 19.7-megapixel global shutter. Resolution is 5120x3840 (19.7 megapixels) at 30 fps, and pixel size is 6.4 µm.
CMV50000. Unlike other members of the CMV family, this 48 megapixel CMOS image sensor for machine vision applications employs global shuttering and correlated double sampling. Resolution is 7920x6004 (47.6 megapixels) at 30 frames per second.
The CSV50000. Image from ams
Members of the CMV family of image sensors employ sub-LVDS output interface. To ensure compatibility, and perhaps to encourage updates, the CSG14k maintains compatibility with this.
Higher Speed Machine Vision
Machine vision is a wide-open field with many variations of need. Where ams has focused on high resolution, the Phantom S200 and S210 from Vision Research can operate at a far higher frame rate, though with correspondingly lower resolution
Phantom S200 and S210 from Vision Research. Image from Phantom High Speed
For comparison, here are their major relevant specs:
- Resolution of 640 x 480 pixels
- Maximum speed at full resolution is 7,000 fps
- Pixel size 11 µm
- Resolution of 1280 x 480 pixels
- Maximum speed at full resolution is 1,730 fps
- Pixel size 5.6 µm
Another AOI-oriented image sensor just released is the KAI-50140 from ON Semiconductor. Our recent article on that sensor discusses the difference between CCD and CMOS sensors rather than the differences between global and rolling shuttering.
How often do you work with image sensors in your job? What specifications are the most important for your applications? Let us know in the comments below.