JPS61208060A - Copying density controller for copying machine - Google Patents

Abstract

PURPOSE:To make a picture shaper and to attain a high speed copying by providing a control system which employs a normal exposure lighting device and a scan optical system, compares the reflected light quantity of an original with a reference value and adjusts the light quantity of an exposure lamp by utilizing a holding time. CONSTITUTION:With the use of the normal exposure lighting device, the reflected light quantity of the original 1 is compared with the reference value by utilizing the holding time caused by the rise of the lamp 8. Namely, a microcomputer 6 compares the reflected light quantity of the original 1 stored in its memory part with that of a reference reflecting plate 3. When the reflected light quantity of the original 1 is smaller than that of the reference reflecting plate 3 through the comparison, the microcomputer 6 controls a lamp lighting up device 7 so that the light quantity of the exposure lamp 8 can be increased. When the said quantity of the original 1 is larger, the microcomputer 6 controls the device 7 so that the light quantity of the lamp 8 can be reduced. Since these controls are executed in the holding time, the high speed copying can be possible without adversely affecting a copying mode, and moreover the picture can be clearer.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a copy density control device for a copying machine.

More specifically, the present invention relates to a density control device that detects the original density of a slit exposure type copying machine and controls the copy density by comparing the original density with a set reference density.

(Prior Art) Conventionally, when copying an original with a high background density or a colored original, the background of the copied image often becomes blurred, resulting in an unclear image.

This is thought to be due to the fact that copy images are always being obtained under the same copying conditions even for originals with high background density such as photographs, or originals with low background density such as characters.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks of the prior art, and makes it possible to always obtain clear copy images even with color-extended originals and originals with high background density, and to improve the copying speed. It is an object of the present invention to provide a copy density control device that can perform high-speed copying without causing any adverse effects.

(Means for Solving the Problems) According to the present invention, the above problems can be solved by copying density control of a copying machine in which a traveling body consisting of an exposure lamp and a mirror scans the surface of a document to expose it to slits. The apparatus includes a detection means for detecting the amount of light reflected from the document surface during the density control mode, and a detection means that compares the detected amount of reflected light with a reference value, and when the amount of light reflected from the document surface is higher than the reference value, the exposure lamp is activated. Comparisons that reduce the amount of light and/or reduce the development noise potential.
The present invention is solved by a copying density control device for a copying machine, which has a control means and is characterized in that in the density control mode, the traveling body scans at a higher speed than in the same-size copying mode P.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram of a slit exposure type copying machine equipped with a density control device of the present invention.

In FIG. 1, the density control device of the present invention includes a reference density reflecting plate 3 disposed at the end of a platen 2 on which a document 1 is placed.
, an optical sensor 4 as a detection means for detecting reflected light from the original 1 and the reference density reflector 3, an A/D converter 5 for converting the output from the optical sensor 4 into digital values, and the A A microcomputer 6 compares the outputs from the /D controllers 5 and outputs an optimal control value, and a lamp lighting device 7 adjusts the light amount of an exposure lamp 8, which will be described later, based on instructions from the microcomputer 6. Comparison and control means configured as shown in FIG.

A slit exposure type copying machine equipped with such a density control device has the same configuration as a conventional copying machine, and is provided with a back side of the platen 2 movable along the platen 2. The running body 10 and a group of mirrors (13, 14) to be described later
, 15, 16), a fixedly arranged lens 11, a drive device (not shown) that drives the traveling body 10 and can vary its driving speed, and a rotating photosensitive drum 12. There is.

The traveling body 10 is integrally provided with an exposure lamp 8 having a reflector 9 and a second mirror 13 for reflecting and projecting an original image exposed by the υ slit by the exposure lamp 8.

Further, the document image slit-exposed by the traveling body 10 is transferred to the second and sixth mirrors 14 and 15 of the pair structure, which move along the platen 2 at the speed of the traveling body 10, and the fixed mirrors 14 and 15. It is projected onto the photosensitive drum 12 via the lens 11 and the fourth mirror 16.

Further, a position detection switch 17 is disposed near the home decision point of the traveling body 10.

Next, the operating process of the present invention will be explained with reference to the timing diagram of FIG.

When the copying machine receives a copy start signal after setting the original 1, the copying machine turns on the exposure lamp 8, and at the same time lights up the traveling body 10 and the second . The document surface is scanned by the sixth mirror 14.15.

At this time, the traveling body 10 is scanned at a higher speed than the same-magnification copying speed of the copying machine, and this scanning speed is determined by the lamp start-up time of the exposure lamp 8. In other words, when using a normal tungsten lamp, it takes about 700 milliseconds for the light emission to stabilize, so the length of the document to be scanned is set to 300 milliseconds.
In millimeters, if the traveling body 10 scans the document at a speed of about 430 milJ meters/sec, the lamp output becomes stable at the end of one forward scan.

Therefore, in the conventional apparatus, the first forward scanning of the traveling body 10 immediately after setting the document is performed using the waiting time during which the lamp output is stabilized.

Next, the traveling body 10 shifts to backward scanning, and this backward scanning is performed at a higher speed than the forward scanning. Further, the transition to the backward scanning is performed by the movement of the traveling body 10.
This is done by the microcomputer 6 counting the elapsed time of operation from the position detection switch 17, which turns 10FF.

When the backward scanning of the traveling body 10 is started, the optical sensor 4 disposed near the optical path is activated by the microcomputer 6.
The amount of light reflected from the document 1 is detected multiple times based on the light amount detection timing according to the command. The detected amount of reflected light is amplified, converted into a digital value by the A/D converter 5, and inputted to the microcomputer B. micro·
The computer 6 determines the maximum value of the amount of reflected light as the density of the background portion of the original 1 and stores it.

Next, when the traveling body 10 finishes the backward scanning and returns close to the home position, the optical sensor 4 reads the amount of light reflected by the reference reflector 6.

The microcomputer 6 compares the amount of light reflected by the reference reflecting plate 6 with the amount of light reflected from the background portion of the document stored in the storage section. As a result of the comparison, if the amount of light reflected from the original 1 is smaller than the amount of light reflected from the reference reflector 6, the microcomputer 6 controls the lamp lighting device 7 to increase the amount of light from the exposure lamp 8. Furthermore, when the amount of light reflected from the original 1 is large, the amount of light from the lamp is controlled to be reduced.

These controls end before the traveling body 10 starts the next scan, that is, the copy mode.

Next, the traveling body 10 performs normal document exposure scanning in the copy mode P following the previous density control mode. On this occasion,
The scanning speed of the traveling body 10 is returned to a speed suitable for the copying magnification, and in the case of the same-size copying mode, the scanning speed of the photoreceptor P ram 12 is returned to a speed suitable for the copying magnification.
The speed is the same as the surface speed of

In this normal document exposure process, the document 1 is exposed to light by the exposure lamp 8 that has been corrected to an appropriate amount of light, so that, for example, when copying an original with a high background density and a small amount of reflected light using a conventional device, The fog that occurs in the image is suppressed, resulting in a clear image.

In the above embodiment, the reference reflection density was set to be obtained by exposing the reference reflection plate 6 each time, but a preset reference value may be stored in the microcomputer 6.

However, other embodiments of the present invention may be configured to vary the bias potential of the developing roll instead of varying the amount of light from the exposure lamp 8 in the previous embodiment. That is, as a result of detection by the optical sensor 4 and comparison by the microcomputer 6, when the amount of reflected light from the original is larger than the amount of reflected light for the reference density, the bias potential is lowered, and conversely, when the amount of reflected light from the original is smaller, the bias potential is increased. do it like this. By controlling the noise potential in this manner, when the amount of reflected light from the document is large, the amount of developer adhesion is suppressed to prevent fogging, and in the opposite case, the amount of developer adhesion is increased to eliminate skipped development.

Furthermore, another embodiment of the present invention provides the above-mentioned exposure lamp 8.
The light amount of the lamp and the noise potential of the developing roll may both be controlled.

(Effects of the Invention) As described above, according to the copy density control device of the present invention, using a normal exposure illumination device and a scanning optical system, the light amount of the exposure lamp is determined by comparing the amount of light reflected from the original with the reference value. By adding a control system for adjusting and/or development and 6-year ascent, suitable copying density control can be performed at low cost. In addition, since the scanning of the traveling body for performing this density control is performed using the standby time caused by the rise of the lamp output in the conventional device, high-speed copying can be performed without affecting the copying mode P. can be made possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a slit exposure type copying machine illustrating an embodiment of the present invention, and FIG. 2 is a timing chart illustrating the operation of the embodiment of FIG. Symbol in the diagram

Claims (1)

[Claims] In a copying density control device of a copying machine in which a traveling body consisting of an exposure lamp and a mirror scans the surface of a document and exposes it to slits, there is provided a detection means for detecting the amount of reflected light on the surface of the document in the density control mode, and a detected amount of reflected light. and a reference value, and when the amount of light reflected from the document surface is higher than the reference value, the light amount of the exposure lamp is lowered and/or the developing bias potential is lowered. A copy density control device for a copying machine, characterized in that a traveling body scans at a higher speed than in a full-size copying mode.