Photocopying – Projection printing and copying cameras – Combined with or convertible to a contact printer
Patent
1987-05-08
1988-12-06
Braun, Fred L.
Photocopying
Projection printing and copying cameras
Combined with or convertible to a contact printer
355 3DD, G03G 1508
Patent
active
047898780
ABSTRACT:
A electrophotographic apparatus capable of operating both in a mode for obtaining a positive image from a negative original and in a mode for obtaining a positive image from a positive original and capable of constantly controlling the image density in either mode. The apparatus can be used selectively in either mode, and in both modes the image density can be controlled by a common operating member. The apparatus includes a device for forming an electrostat latent image on an image bearing member, first and second developers for developing the latent image with toners charged, respectively, in the same and in the opposite polarity as the image bearing member, a device for applying a bias voltage of determined polarity to the developers, a device for setting the density of the image on the image bearing member, first and second controls for controlling the bias voltage applying device to increase and or decrease the bias voltage, respectively, in response to increasing or decreasing the density of the image, and a device for selecting one of the first and second controls in response to the switching of the mode of the apparatus to change the bias voltage applied to the developers by the selected control.
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Endo Makoto
Saito Yoshihiro
Braun Fred L.
Canon Kabushiki Kaisha
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