Method and apparatus for electrically biasing developing electrode of electrophotographic device
AssigneeRicoh Company, Ltd.
InventorsSeiichi Miyakawa, Tadahiro Eda
Life of this patent
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Abstract
A photoconductive member is charged and radiated with a light image to produce an electrostatic image. Sensing electrodes automatically sense the remaining potential in a portion of the electrostatic image corresponding to a background area of the original document scanned to produce the light image. In one embodiment the area is a white reference document disposed adjacent to the original document. In another embodiment a reference document is not provided and a plurality of portions of the electrostatic image are sensed. The lowest value of the sensed potential is utilized. Computing means compute and apply the biasing voltage to the developing electrode as a predetermined function of the sensed potential.
Claims22
A method of electrically biasing a developing electrode disposed closely adjacent to a photoconductive member of an electrophotographic device after the photoconductive member has been charged and exposed to a light image, comprising the steps of:
- a. automatically sensing the potential remaining at a plurality of respective portions of the photoconductive member and automatically selecting the lowest value of the sensed potential;
- and
- b. automatically applying biasing voltage to the developing electrode in accordance with the lowest value of the sensed potential.
In an electrophotographic device having a photoconductive member, charging means for charging the photoconductive member, imaging means for radiating a light image of an original document onto the photoconductive member and a developing electrode disposed closely adjacent to the photoconductive member after the photoconductive member has been charged by the charging means and radiated with the light image by the imaging means, apparatus for electrically biasing the developing electrode comprising:
- sensing means comprising a plurality of sensors for automatically sensing the potential remaining at a plurality of respective portions of the photoconductive member;
- and
- computing means comprising a comparator for automatically selecting the output of the sensor having the lowest value of the sensed potential, automatically computing the viasing voltage to be applied to the developing electrode in accordance with the lowest value of the sensed potential and applying said biasing voltage to the developing electrode.
In an electrophotographic device having a photoconductive member, charging means for charging the photoconductive member, imaging means for radiating a light image of an original document onto the photoconductive member and a developing electrode disposed closely adjacent to the photoconductive member after the photoconductive member has been charged by the charging means and radiated with the light image by the imaging means, apparatus for electrically biasing the developing electrode comprising:
- sensing means for automatically sensing the potential remaining on the photoconductive member at a portion thereof where the potential has a predetermined value relative to the minimum potential remaining on the photoconductive member;
- and
- computing means to automatically compute the biasing voltage to be applied to the developing electrode as a predetermined function of the sensed potential and apply said biasing voltage to the developing electrode, said computing means comprising an operational amplifier and a switch, said switch being connected between the sensing means and the operational amplifier, said switch comprising a first fixed contact connected to the sensing means and a second fixed contact grounded and a movable contact connected to the operational amplifier.
Dependencies are inferred from the claim text.