US 4,277,162 AGranted

Electrophotographic apparatus comprising density sensor means

AssigneeRicoh Company, Ltd.

InventorsNobuo Kasahara, Kouji Yamanobe

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Abstract

One or more marks (34), (36) are provided on a non-image area of a platen (23) which supports an original document (16). Electrostatic images of the document (16) and mark (34) are formed on a photoconductive drum (12) and developed to form toner images. The toner image of the original document (16) is transferred to a copy sheet (21) which is fed into contact with the drum (12) by a roller (119) or belt (19). The toner image of the mark (34) is transferred to the roller (119) or belt (19) and the optical density thereof sensed by a photosensor (39). The toner density, transfer charge and other parameters are controlled in accordance with the sensed optical density. An auxiliary sensor (91) may be provided to sense the optical density of the toner image of the mark (34) on the drum (12) prior to transfer for improved parameter control.

Claims15

Dependent claims

An electrophotographic apparatus having a platen for supporting an original document on an image area of the platen, a photoconductive member, imaging means for forming an electrostatic image of the original document on an image area of the photoconductive member, developing means for developing the electrostatic image to form a toner image, transfer means including a transfer member for supporting a copy sheet on an image area of the transfer member and moving the copy sheet into engagement with the photoconductive member for transferring the toner image to the copy sheet, characterized by comprising:

mark means of predetermined optical density provided on a non-image area of the platen, the imaging means forming an electrostatic image of the mark means on a non-image area of the photoconductive member, the developing means developing the electrostatic image of the mark means to form a toner image thereof, the transfer means transferring the toner image of the mark means onto a non-image area of the transfer member;
sensor means for sensing an optical density of the toner image of the mark means on the transfer member;
and
auxiliary sensor means for sensing an optical density of the toner image of the mark means on the photoconductive member before transfer to the transfer member and computing means for producing an output corresponding to a predetermined function of a difference between outputs of the sensor means and the auxiliary sensor means.

1 more element

mark means of predetermined optical density provided on a non-image area of the platen, the imaging means forming an electrostatic image of the mark means on a non-image area of the photoconductive member, the developing means developing the electrostatic image of the mark means to form a toner image thereof, the transfer means transferring the toner image of the mark means onto a non-image area of the transfer member;
and
sensor means for sensing an optical density of the toner image of the mark means on the transfer member;
the mark means comprising first and second marks of first and second different optical densities, the sensor means comprising first and second sensors for sensing optical densities of first and second toner images on the transfer member corresponding to the first and second marks respectively, the apparatus further comprising control means for controlling at least one of the imaging means, the developing means and the transfer means in accordance with a predetermined function of the sensed optical densities of the first and second toner images on the transfer member in combination.

1 more element

Dependencies are inferred from the claim text.