With the technology advances in CCD and CMOS image sensor market and the lower production costs driven by the consumer market, there is a steady increase in high-resolution (4 Megapixels and higher) and ultra high-resolution (12 Megapixels and higher) OEM camera options from machine vision suppliers. The higher resolution cameras enable advances in demanding inspection applications such as flat panel inspection, PCB inspection, but also in wafer and component inspections. System designers are able to increase FOV (field of view) (inspect more parts at a time), measure smaller details, and/or throughput by increasing resolution.
So which resolution and camera is the best? This is of course a silly question, as best has to be put in terms of the application requirements. There are so many options– our own portfolio has more than 30 models with 4 Megapixels and greater and fast growing – so how do you decide?
There are the simple considerations such as resolution and frame speed, but then you need more information to make the right choice.
If you are replacing multiple cameras with fewer or 1 high-resolution camera this likely makes it easy for you to translate the resolution you require. If you are trying to increase your FOV, you also want to consider the pixel pitch, optical format match, etc. You don’t want to go to the highest resolution possible just because you can – the volume of data to process and optics costs would not be justified.
There are also many choices for different resolution/frame rate combinations. If multiple images are required per measurement, a faster frame rate may be required. If the frame rate of the camera is not a limiting factor to the throughput of the system, the speed of the camera might be critical. There are still many other camera parameters to consider that will influence your accuracy and other performance features.
Different image sensors are optimized in different ways such as read noise, full well capacity, frame rate, etc. The camera manufactures then have design choices (beyond mechanical outline) as well such as image enhancement, image processing, interface, temperature control, etc.
Camera manufacturers try to provide quantitative data (much of which is based on the image sensor performance) to help with camera selection. For example, here are some camera specifications from 3 different Adimec cameras:
*More interface options coming soon
All of these cameras offer excellent performance and are designed around exceptional image sensors (our humble opinion). But, more information is likely required to know which is best for a given application.
Since our QUARTZ 12 Megapixel (Q-12A65) based on the CMOSIS CMV12000 image sensor is entering volume production, let’s consider when this one is best. The Adimec QUARTZ Q-12A65 offers 12 Megapixels at 75 full frames per second over Camera Link (burst mode). It is optimized for systems for which sensitivity is important and sufficient dynamic range (e.g. contrast) is required. The QUARTZ camera is the best choice for systems with limited light, such as semiconductor defect inspection. The superb shutter performance of the Q-12A65 enables excellent performance in high-speed applications, such as electronics inspection and semiconductor metrology. Similar to the 2 Megapixel and 4 Megapixel QUARTZ options, the new camera offers a range of quality-enhancing features. It includes Adimec’s Active Sensor Control with local and global advanced Flat Field Correction (FFC) capabilities, even in color and semi-automatic in-field calibration. This allows the performance to be optimized for the temperature conditions in which the system is operating without requiring additional tooling. The camera has special additional functions such as signal-to-noise improvement through in-camera averaging and pixel binning compared to off-the-shelf CMV12000 sensor performance.
In comparison, the Sapphire S-25A30 based on the Vita 25k image sensor offers different advantages. The ROI implementation on the image sensor allows for frame rate increases with both reduced vertical and horizontal resolution should only certain parts of the image be needed or significantly higher frame rates are required. The Vita sensors have good shot noise performance and may be the better choice for systems with plenty of light.
Basically, the answer is that the general information on the camera specification sheets is probably not going to provide you with a clear answer on the right camera. A lot of choices are great but also confusing. A short consultation with a camera supplier could be helpful as they need to understand the design choices and pros and cons of the image sensors as well as the subsequent camera functionality. Our role is to support the translation of the information required for your measurement into the appropriate camera requirements.
Then, a live testing of a few cameras is probably necessary to finalize your selection. (Be sure to test the cameras under the same conditions that the system runs in or the information is not really useful.)
For more details on these cameras or the image sensors, please contact Adimec.