Isn’t the full well capacity more important for a high SNR than the pixel size?
Contine: The maximum SNR value depends on the pixel size. But if you are looking for the maximum SNR and you have a lot of light you can also use small pixel, because noise is negligible in low light condition. In general, the read noise is more relevant. In some way the absolute threshold sensitivity tells you how much photons you need to overcome the noise. The pixel size is not that relevant if you run with good lighting condition. But as mentioned before, the read noise can easily be different between one or two electrons, meaning that you have a factor of two. But increasing the pixel size by factor two, then it’s a very different sensor because at the same resolution you have a much bigger image sensor. Therefore, the read noise is more relevant than the pixel size. The pixel size matters when you really need high dynamic range, if you have both a dark and a bright situation in the same image.
Von Fintel: It’s sometimes a philosophic question of big or small pixels. We had seen a trend toward smaller pixel, especially for backside illumination sensors. It stopped around 2.5 micron. But the trend towards higher resolutions were only enabled by smaller pixel.
In the end, does it always come down to the price when choosing a camera or can other criteria outweigh the lowest price?
Von Fintel: There are always criteria which can outweigh the price. Of course, you have to meet a certain price range because each manufacturer has their own bill of material, and there’s a certain cost that they will spend for a camera. Nevertheless, at the end, in the overall system it matters whether you can reach a certain performance. You’re willing to spend more if you have specific needs on temperature ranges or the software side. There must be a certain prince range but it’s certainly not 100% of the decision.
Cocquelin: Price is always a question, but the real question is price for value. When you have an embedded system, you have less constraints than at a full camera system. In the end, it is the same question for the end customers using machine vision: what value does it bring to me and is it worth it? Sometimes you can use a camera and sometimes it’s not possible because the value is not really there. It’s not a pure price issue, but a value proposition depending on the application.
What about the usability of cameras and what role does software / SDK play for choosing a camera?
Cocquelin: SDKs plays an important role when you want to discover a new technology but also facilitate the integration afterwards in your application. It has always been the role of machine builders to start developing your own interface and software to be able to adapt to different kinds of cameras. But today we see more and more interest of having already built in SDKs to increase the time to market or increase the integration of new cameras. It’s important to have a good software/SDK especially for new technologies with a lot of new functionalities like polarized cameras. Before that you used to use maybe one image and now you have a lot of more information that you need to process and there are pre-functionalities already made in some SDKs e.g. for multi spectral cameras.