Device for Adjusting Image Density in Composite Information Recording Apparatus

1. Field of the Invention:

The present invention relates to a device for adjusting or regulating an image density reproduced in a composite information copying apparatus imparted with a function for recording in a composite manner electric information signals available from external sources together with an image of an original to be copied.

2. Description of the Prior Art

The composite information recording apparatus of the above type comprises generally an optical system 3 for projecting an image of an original resting on a copy board 1 to a drum 2 having a photoconductive or light sensitive surface layer such as of Se, CdS thereon, a reproducing device 4 for reproducing electric information signals on the light sensitive drum 2 as an electrostatic latent image, and a developing device 5 such as a magnetic brush developing device for visualizing and recording the electrostatic latent image on the light sensitive drum 2 by using toner as per se well known in the field. With copying apparatus of such arrangement, it is possible to record the image of an original or electric information signals from the reproducing device, respectively, or alternatively a combination of the image of the original and the electric information signal in a composite matter in which a part of the recorded information is derived through the optical system, while the other part is derived from the reproducing device.

For preparing a sheet or a page of data containing image information from the original and the electric information signal from the external source in a composite manner in the composite information recording apparatus, there may arise the possibility that non-uniformity in the image density distribution will occur, if the light intensity of the image optically projected onto the drum surface and the intensity of the light beam flux output from the reproducing device (such as an optical fiber tube) are not balanced with each other.

The invention contemplates to solve the problem described above and has as an object to provide an image density adjusting device which assures a uniform image density in the composite record.

FIG. 1 shows schematically a general arrangement of a composite information recording apparatus, and

FIG. 2 is a circuit diagram illustrating a method of adjusting image density according to the invention.

FIG. 2 is a circuit diagram illustrating an apparatus for controlling image density in accordance with the invention. A broken line block 10 denotes an image density control unit for controlling the image density of an original to be copied and serves to control the bias voltage applied between the photoconductive medium and the developing device (e.g. a sleeve made of non-magnetic and electrically conductive material which is one element constituting a magnetic brush) in dependence on a preset density of the original to be copied, thereby to vary the quantity of toner deposited on the surface of the photoconductive medium for a constant intensity of irradiation by an illuminating lamp. More specifically, in dependence upon the inputs to the selecting switches S.sub.1, S.sub.2 and S.sub.3 for selecting a high density, a normal density and a low density of the image to be copied, respectively, a selected one of transistor switches Q.sub.1, Q.sub.2 and Q.sub.3 is turned on by a control unit CON, as a result of which the voltage dividing ratio of the voltage dividing resistor circuit including resistors R.sub.1 to R.sub.4 is correspondingly varied thereby to change the bias voltage applied to a developing electrode P from a bias voltage source PS.sub.B.

A broken line block 11 denotes a recording density control unit for controlling the output light intensity from an optical fiber tube constituting the output unit for recording electric information signals from a reproducing device. The recording control unit 11 includes a resistor type voltage dividing circuit composed of switching means or transistor switches Q.sub.4, Q.sub.5 and Q.sub.6 and resistors R.sub.5 to R.sub.9 for controlling the voltage applied to the cathode terminal of an optical fiber tube OFT for a video signal supplied from a video or pulse amplifier Vamp to the optical fiber tube OFT. By varying the voltage applied to the cathode of the tube OFT from a (cathode) voltage source PS.sub.K through the voltage dividing circuit, it is possible to control the output intensity of the optical fiber tube OFT. The on-off control of the transistor switches Q.sub.4, Q.sub.5 and Q.sub.6 is effected in association or correspondence with the transistor switches Q.sub.1, Q.sub.2 and Q.sub.3 through the control unit CON. Thus, the density control of the original image will result in corresponding density control for the recording of electric information signals.

In this manner, the density at which the electric information is recorded is automatically varied in dependence on the density set for copying the original image, whereby a uniform density distribution can be attained in the composite recording.

The number of steps at which the density is controlled can be arbitrarily changed by correspondingly modifying the configurations of the transistor switch circuits and the voltage dividing resistor circuits. Of course, the control may be effected in a continuous or linear manner. Furthermore, the density control may be accomplished by controlling the iris aperture of the optical system in place of controlling the bias voltage applied to the developing electrode. In the reproducing system, a gain control may be adopted in place of controlling the cathode voltage applied to the OFT.

As will be appreciated from the foregoing description, the output light intensity of the reproducing system for electrical information is controlled in correspondence with the density control for copying the original image according to the invention. Thus, a uniform density distribution can be accomplished in the composite recording.