I not sure if anyone has posted this before. Here is a simply technique to restore the focus of your poorly scanned images.
First, apply auto-contrast to each of the color channels (RGB). Next, duplicate the background layer and with the top layer selected choose filter>other>high pass. Usually a value between 9 and 14 is appropreate. Try somewhere around 10.5. Now, apply auto contrast to layer 2 (grey one) then change the blend mode to soft light. If it turns out to be a little too sharp then you just lower the opacity of the top layer. Last, press ctrl + E to merge the two layers..... and there you have it.
Enjoy!
First, apply auto-contrast to each of the color channels (RGB). Next, duplicate the background layer and with the top layer selected choose filter>other>high pass. Usually a value between 9 and 14 is appropreate. Try somewhere around 10.5. Now, apply auto contrast to layer 2 (grey one) then change the blend mode to soft light. If it turns out to be a little too sharp then you just lower the opacity of the top layer. Last, press ctrl + E to merge the two layers..... and there you have it.
Enjoy!