System and method for determining an amount of toner mass on a photoreceptor

A method of determining an amount of marking material present on a application surface, the method comprising:

• separately receiving electromagnetic radiation that has been specularly reflected by the application surface;
• generating a specular reflection output representative of one or more of the properties of the received electromagnetic radiation that has been specularly reflected by the application surface;
• separately receiving electromagnetic radiation that has been diffusely reflected by the application surface;
• generating a diffuse reflection output representative of one or more of the properties of the received electromagnetic radiation that has been diffusely reflected by the application surface;
• differencing the specular reflection output and the diffuse reflection output to create a combined output;
• and
• determining an amount of marking material present on the application surface based on the combined output.

A method of calibrating a system configured to determine an amount of marking material present on a application surface, the method comprising:

• a) directing electromagnetic radiation to the application surface while the application surface carries a known amount of marking material such that a portion of the electromagnetic radiation is specularly reflected by the application surface and a portion of the electromagnetic radiation is diffusely reflected by the application surface;
• wherein one or more properties of the portion of electromagnetic radiation that is specularly reflected by the application surface and the portion of electromagnetic radiation that is diffusely reflected by the application surface vary as a function of (i) the amount of toner present on the application surface and (ii) noise caused by light loss in the system being calibrated;
• b) receiving, with a specular reflection sensor, primarily electromagnetic radiation that has been specularly reflected from the application surface;
• c) generating, with the specular reflection sensor, a specular reflection output that represents one or more of the properties of the electromagnetic radiation that has been specularly reflected from the application surface;
• d) receiving, with a diffuse reflection sensor, primarily electromagnetic radiation that has been diffusely reflected from the application surface;
• e) generating, with the diffuse reflection sensor, a diffuse reflection output that represents one or more of the properties of the electromagnetic radiation that has been diffusely reflected from the application surface;
• and
• f) determining, based on the specular reflection output and the diffuse reflection output, at least one scaling factor that can be used to scale outputs generated by one or both of the specular reflection sensor and the diffuse reflection sensor such that when outputs generated by the specular reflection sensor and the diffuse reflection sensor are scaled and then differenced to create a combined output, the combined output is substantially free from the noise caused by light loss in the system being calibrated.