Image forming apparatus with improved correction based on toner density
A sensor includes a light emitter and a photodetector. The light emitter outputs light with which a toner pattern or a surface material of an image carrier is irradiated. The photodetector receives reflection light from the toner pattern or the surface material. The sensor light intensity control unit provides a control voltage to the light emitter and thereby controls light intensity of the light emitter. The density determining unit determines a toner density on the basis of output of the photodetector. Further, the density determining unit (a) determines as a correction parameter a first-order coefficient of the control voltage of the light emitter for an output voltage of the photodetector corresponding to reflection light from the surface material, (b) determines a correction amount corresponding to the correction parameter and the toner density, and (c) corrects the toner density on the basis of the correction amount.
1. An image forming apparatus, comprising:
an image carrier configured to carry a toner pattern;
a sensor that comprises a light emitter and a photodetector, the light emitter configured to output light with which the toner pattern or a surface material of the image carrier is irradiated, the photodetector configured to receive reflection light from the toner pattern or the surface material of the image carrier;
a sensor light intensity control unit configured to provide a control voltage to the light emitter and thereby control light intensity of the light emitter; and
a density determining unit configured to determine a toner density on the basis of output of the photodetector;
wherein the density determining unit (a) determines as a correction parameter a first-order coefficient of a control voltage of the light emitter for an output voltage of the photodetector corresponding to reflection light from the surface material of the image carrier, (b) determines a correction amount corresponding to the correction parameter and the toner density, (c) corrects the toner density on the basis of the correction amount, and
(d) determines the output voltage of the photodetector corresponding to reflection light from the surface material of the image carrier at the control voltage of the light emitter; and
determines as the correction parameter the first-order coefficient on the basis of the control voltage, the output voltage, a light-emission-start voltage of the light emitter, and a dark potential of the photodetector.
2. The image forming apparatus according to claim 1 , wherein:
the sensor is a surface mount type sensor;
the light emitter is a chip-shaped light emitter arranged on a circuit board; and
the photodetector is a chip-shaped photodetector arranged on the circuit board.
3. The image forming apparatus according to claim 1 , wherein:
the sensor includes a first photodetector configured to receive specular reflection light in the reflection light, and a second photodetector configured to receive diffuse reflection light in the reflection light; and
the density determining unit (e) determines as the correction parameter the first-order coefficient of the control voltage of the light emitter for (e1) an output voltage of the first photodetector corresponding to reflection light from the surface material of the image carrier or (e2) a difference between the first photodetector and the second photodetector corresponding to reflection light from the surface material of the image carrier, (f) determines a correction amount corresponding to the correction parameter and the toner density, and (g) corrects the toner density on the basis of the correction amount.