If your image has color or any grayscale, it needs to be turned into a halftone screen.
Start by opening your image
Image - Adjustments - Grayscale
Merge Layers
Discard Color Information
Image - Adjustments - Bitmap
Flatten Layers
Change the Method to Halftone Screen - Make sure your OUTPUT resolution matches your INPUT
Change the Shape to ROUND
Frequency can be anywhere between 10 and 40
the smaller the number, the bigger the dots
the larger the number, the smaller the dots and more resolution is visible
Here it is at 20 and 40