I'm building my own vactrols. The real ones are too expensive. So i took yellow LDRs and LDRs, made them look in the eyes, scotch-taped this nice pair and voilà, a vactrol was born.
Actually, its pretty linear when you get beyond a certain amount of current. My LDRs have a close-to-linear response from 4.7kOhm to close to 0 Ohms, which is good if I use another 4.7kOhm resistor to build a voltage divider. As the TLC has a grayscale of 4096 levels, I can spend some to get in the linear zone.
I will be happy if my last issue is the non-linearity of my LDRs : that's a problem I can cope with (firmware-based regression). ;D
Sure, I'll release my work (hope it will work :
). You can find some of it in the hardware section, I adapted some code to syncronize a vga screen.