Is there a tactile tabletop flat square ridge-forming display that would, upon receiving input from a computer, display the shape of a character or ideogram from an alphabet thus allowing a blind person to quickly understand the shape of such a character or ideogram? (Think about the 8,000 or so Chinese ideograms whose shape one could want to quickly learn.)
a) If you feel like spending then something like MIT's inFORM would be suitable for you (basically what you've asked for).
b) Look at braille "monitors", but that's far from what you've asked.
c) You could build one yourself if you have time but no money.
About choice c:
You can use standard (not LED) light bulbs (there are really small ones available too, like 3mm diameter ones), set them up in a 10x10 array. Light up the ones that need to form the display using a display controller, meaning a blind person can sense the heat generated by the bulbs. To control the bulbs you can use a microcontroller like Arduino Mega and send the characters to it with a PC program via USB. It would in overall cost you about ~50$ (plus 20$ for a uber cheap soldering iron) but hours of time, soldering together the array, programming the arduino and creating the desktop program will take respectively about 10h, 20h and 30h (about 60 work hours in total) if you have never done something like that ever and need to learn it all.