Another imaging defect results from insufficient sampling of a target with discrete lines which are thicker than the pixel width is ghosting as illustrated in your shot and below where the vertical black line has double grey ghosts due to insufficient sampling.
I believe that the bandwidth of the pulse that you are trying to record in your scetch is too wide? A pulse containing infinitely sharp transitions translates into a spatial-frequency domain sinc of infinite extent, meaning that it occupies (towards) infinite bandwidth.
A "proper"*) sampling system cannot generally recreate that pulse at that sampling rate. The options are either to:
1. Prefilter before sampling (so as to remove frequencies that cannot be reliably recreated)
2. Increase the sampling rate (for this example: towards infinity)
3. Sample with insufficient prefiltering, violating Nyquist, living with aliasing
Your (computer-generated) example seems to use a simple pre filter (relying on the area integration of each sensel). Something sinc-like would probably give more accurate results, but is not usually possible in optical systems.
If the pulse had been shifted by 1/2 sensel left or right, the apparent sampling system would seem to work: the (boxcar filtered) output would be identical to the (boxcar filtered) input. This might be the case for font designers and graphics arts that have a high degree of control over the sampling grid. It cannot be relied upon for general cameras where scene elements move unpredictably around. I think there is a unnecessary big divide between how "dsp-people" think about this and how "graphics/image" people think about this.
*)Taken here to mean a close approximation to a Shannon-Nyquist sampler operating in the baseband