Printer with unfused toner process control

A method for operating a toner printer, the method comprising:

• providing first printing instructions to cause a print engine to form a toner image on a surface having first toner in a target area;
• printing a toner image according to the first printing instructions;
• illuminating the target area with a first light from a first illumination position that is on a first side of a plane that is normal to the target area so that any toner particles in the target area direct a reflected portion of the first light into the first side;
• sensing light at a sensing position on the first side of the plane to which toner particles at the target area direct the reflected portion of the first light;
• determining from the sensed light an amount of a first toner in the target area;
• and,
• generating second printing instructions causing the toner printer to print at least one subsequent toner image based upon the determined amount of first toner.