This Photoshop tutorial will describe in detail how to add a scanned line effect on your images using two different methods.  Hopefully, one of them will make you happy.

Step 1

Open a new image 1x2 pixel with transparent background.

Zoom in as close as possible. 1600%.

Select the pencil tool and draw a black 1x1 pixel dot, leaving a 1x1 transparent pixel.

Select File > Save As > pixel.png

Select the Paint Bucket Tool

Select Edit > Define Pattern, give the new pattern a meaningful name e.g. scan line.

Step 2

Open any image that you want to apply scan lines to.

Create a new layer by clicking Layer > New > Layer or Shift+Ctrl+N

Give the layer a name, preferably something meaningful E.g. scan lines.

Step 3

On the newly created layer.

Select the Paint Bucket Tool.

Select the scan line pattern that you previously setup.

Fill the layer with scan line pattern.

This is one way.  For the another method, please continue on reading on page 2.