I designed the first pass of a toy pushbroom image sensor.  This should get me started, anyway.  The sensor is a TSL3301CL, with 100x1 pixels, 77x85 microns each (centered on 85 micron centers).  These are big pixels, so noise will be low, even if the resolution is poor.  The circuit is really just a breakout for the sensor:

The diode/resistor networks on the sensor input lines are there for ESD protection.  The inverter is used as a cable driver, and with the 91-ohm series termination, should give a good match to 100-ohm twisted pair.  I'm using ethernet jacks and cabling because they're cheap and plentiful.  Twisted pair and controlled impedance is a huge plus, too.

The front of the PCB has most of the components, including the sensor and a metal mount for a CS lens.

The back of the PCB has the 8P8C jack:

It's all very straightforward.  Now, I have to design the other side. A microcontroller, stepper driver, and a big flash memory to store images is probably all that's required.

Depending on how thick the solder ends up when I reflow the senor on the PCB, the flange distance may be a little short (I think about 0.35mm).  This is much easier to fix (by inserting a shim) than one that is too long.  I'll have to test it out once I have all the parts.

At first I thought that focusing would be difficult, but I think I can just image any sharp black/white edge and probably focus by eye.