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Pixel pitch vs spectral response... Myth busted?

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Thanks Bill,

I knew you would explain this well :)

It is not necessarily better to reduce all pixels to a size less than 12um.

I remember Fuji once made a CCD for an SLR that contained a mix of large and small pixels. They wanted to increase pixel count yet also maintain sensitivity. Image processing dealt with the rest. You could almost have two 'layers' of pixels dealt with by separate read out IC's and then the two processed.

This is a cheat of course as the more sensitive pixels are far fewer in number than the claimed real resolution.

There are all manner of tricks that may be possible with the sensor is suitable image processing power is available.


For anyone interested in the 'Large + Small pixel' arrays that Fuji used in visible light cameras, take a look here.....


The Fuji system was more to increase dynamic range over the traditional CCDs of the time as opposed to increasing resolution.

Yes, my mistake. But the principle may be applied to a thermal camera array in order to increase pixel count. The more sensitive larger pixels provide the 'framework' and the less sensitive small pixels can provide more detail in images that provide enough energy to them. It would be a compromise system but then nothing is for free, even in physics. Image processing would hide the challenges from the user. In everyday use the user would see a nice high resolution image. In more challenging situations the image processing would 'see' the very poor output from the smaller pixels and either boost the gain on them or just app,y an offset to bring the levels into line with adjacent large pixels. A sort of 'active' interpolation.

All blue sky thinking but I thought if it when studying the human eye. The ey contains two types of sensors in the retina. Rods and Cones. The human brain uses the appropriate sensors 'data' to meet its needs. Why not build thermal sensors in a similar way I thought.

Anyway enough from me on this.


I find a definite answer here:

"Once two airy disks become any closer than half their width, they are also no longer resolvable (Rayleigh criterion). Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged."


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