Characterization of toner patch sensor in an image forming device

A method of operating an electrophotographic image forming device having a power supply, comprising:

• emitting light from an emitter onto a first reference sample having a predetermined first reflectivity and measuring the light reflected therefrom with a detector, said emitter and said detector operatively coupled to the power supply;
• adjusting a duty cycle of a pulse width modulation control signal so as to cause a first signal corresponding to said reflected light from said first reference sample and measured by said detector to substantially match a predetermined target;
• storing said adjusted duty cycle in a memory as a first characterization value, said first characterization value comprising a first duty cycle value corresponding to said adjusted duty cycle used to amplify said first signal to substantially match said first predetermined target;
• thereafter, generating a first toner patch with the electrophotographic image forming device and measuring a reflectance of said first toner patch with said emitter and detector based on said first characterization value while said emitter and detector are operatively connected to said power supply;
• adjusting at least one electrophotographic image forming parameter based on said measured reflectance:
• and
• prior to said generating a first toner patch, removing said first reference sample, emitting light from said emitter with no reference sample for said light to reflect on, measuring a signal output of said detector while driving said detector according to said first characterization value, and determining an offset value corresponding to a difference between said signal output and the first signal as amplified by said adjusted duty cycle;
• wherein said adjusting at least one electrophotographic image forming parameter comprises adjusting at least one electrophotographic image forming parameter based on said measured reflectance and said offset value.

An electrophotographic image forming device, comprising:

• a toner patch sensor including an emitter and a detector, the emitter for emitting light onto a first reference sample having a predetermined first reflectivity, and the detector for measuring light reflected from the first reference sample and producing a first signal corresponding to the light reflected;
• an amplifier operatively coupled to an output of the detector for amplifying the first signal;
• and
• control circuitry including memory, the control circuitry providing a pulse width modulation control signal to the amplifier for controlling amplification of the first signal;
• wherein the control circuitry adjusts a duty cycle of the pulse width modulation control signal so as to cause the first signal to substantially match a first predetermined target, stores the adjusted duty cycle in the memory as a first characterization value, and subsequently adjusts a setting of the toner patch sensor based on the first characterization value depending on a type of toner patch being sensed by the toner patch sensor;
• and
• wherein the emitter emits light with no reference sample for the light to reflect on, and the detector produces a signal output corresponding to tight received by the detector with no reference sample while the control circuitry causes the detector to be driven according to the first characterization value, the control circuitry determining an offset value corresponding to a difference between the signal output and the first signal as amplified by the adjusted duty cycle, and adjusting at least one electrophotographic image forming parameter based on the offset value.

A method of operating an electrophotographic image forming device, comprising:

• providing a housing;
• associating a power supply with said housing;
• associating a control circuit including memory with said housing;
• associating an emitter and an associated detector with said housing;
• operatively coupling said emitter and said detector to said power supply and said control circuit;
• thereafter, while said emitter and detector are operatively connected to said power supply, emitting light from said emitter onto a first reference sample having a predetermined first reflectivity, measuring the light reflected therefrom with said detector, and producing a first signal corresponding to said light reflected from said first reference sample;
• adjusting a duty cycle of a pulse width modulation control signal so as to cause said first signal to substantially match a first predetermined target;
• storing said adjusted duty cycle in said memory as a first characterization value, said first characterization value comprising a first duty cycle value corresponding to said adjusted duty cycle used to amplify said first signal to substantially match said first predetermined target;
• and
• thereafter, generating a first toner patch inside said housing and measuring a reflectance of said first toner patch with said emitter and detector based on said first characterization value while said emitter and detector are operatively connected to said power supply, and adjusting at least one electrophotographic image forming parameter based thereon;
• wherein a gain of said detector is adjusted based on said first characterization value and depending on a type of toner patch being sensed by said detector.