Create a new canvass with a size of 1x2 pixels..and with a transparent background
Zoom in the canvass..To ZOOM IN..U can use slide the NAVIGATOR or either use the ZOOM IN tool
Click the PENCIL tool set it into one(1) and make a pattern like this:
Next,Click EDIT then DEFINE PATTERN
Open the image that you want to add scan lines to
Go to LAYER->NEW->NEW LAYER and click OK
Go to Layer > Layer Style > Blending Options, and change the opacity to get the effect you want. Then press Ok.
BEEP..I'M ON HIATUS