JPS5915947A - Picture control device of copying machine - Google Patents

Abstract

PURPOSE:To control a copying process condition, by providing an original sheet density detecting means in case when an optical system moves forward by a copying start command, and a reference density plate by which density is detected after detection, and correcting a variation of detected density in accordance with a performance variation of its deteced density value. CONSTITUTION:An original sheet density detector 16 is provided so as to be movable vertically on the paper face against a mirror unit 42, and in accordance with an end place of movement of the unit 42 in the direction A, a reference density plate 18 is placed on the almost same face as the face of glass 1. An optical beam emitted from the density detector 16 scans a part of an original 19 in the diagonal direction, the density of the original of its scanned part is detected succesively, and a detected data corresponding to a density value of the original is accumulated successively in the memory part. The density of the reference density plate 18 is detected by the detector 16, therefore, if the quantity of light of the detector 16 is dropped like an elapsed time, the detected reference density value also draws the same ratio as the original density value and is detected darkly with time. Accordingly, the relative relation of these two curves is not varied, irrespective of a drop of performance of the detector 16, and the copying process can be controlled exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image control device for a copying machine that detects the density of a document and controls the density of a copy.

First, a copying machine using electrophotography will be explained. This type of copying machine is schematically constructed as shown in FIG.

The original placed on the platen glass 1 is held down by the platen cover 2, and when the copy amount button is operated in this state, the exposure light source 3 starts exposure scanning in the six directions of the arrow, and the image of the original is exposed. A first mirror unit 4I with a light source 3 attached, a second mirror unit 42, and a lens system 43
, a mirror 44, etc., the light is guided to a photosensitive drum 5 as a photoconductive photosensitive drum.

The photosensitive drum 5 is formed by providing a photoconductive layer made of selenium or the like on the outer peripheral surface of a grounded metal cylinder, and rotates in the direction of arrow B in conjunction with the exposure scanning of the exposure light source 3. Before the image from the optical system 4 arrives, the photoconductor is charged uniformly by the charged electrode 6 to which a DC high voltage of, for example, 5 KV is applied, and the optical system 4 exposes and scans the original. When an image is received on the photosensitive drum 5, the conductivity of the part that receives the light increases, and the electrical charge in that part escapes to the metal tube, leaving a positive charge in the dark part. An electrostatic latent image corresponding to the image of the original is formed on the surface of the conductive layer.

When the photosensitive drum 5 rotates further, negatively charged toner from the developing device 7 is attracted to the remaining positively charged portion by electrostatic force. As a result, the toner is attracted to the portion where the positive charge remains, and a toner image is formed on the surface of the photosensitive drum 5.

In order to match the toner image on the photosensitive drum 5 from a selected paper feeding power center in the paper feeding unit 8, the copy paper is moved to the paper feed roller 10 at a timing such that the leading edge of the toner image and the copy paper match. The toner on the surface of the photosensitive tram 5 is transferred onto the fed copy paper by the transfer pole 9 to which a DC high voltage is applied.

Thereafter, the copy paper is separated from the photosensitive drum 5 by the separation electrode 11 to which AC high voltage is applied, for example, and the separated copy paper is conveyed by the conveyance heald 12 with a toner image transferred to its upper surface and heated. The toner image is fixed in a fixing device 13 having a fixed roller, and then discharged.
It is sent out to the receiving tray by the roller 14. Even if the toner image on the surface of the photosensitive drum 5 is transferred to the copy paper by the transfer pole 9, a small amount of the toner may remain.
The surface is cleaned by the cleaner 15 and is used for the next copying process. Through the above cycle,
The original is copied.

Image control in a copying machine as described above is performed by installing a document density detector in the optical system 4, and detecting the document density when the optical system 4 moves forward in the direction of arrow A (preliminary scanning) by operating the copy start button. The device detects the density of the original on the platen glass l, and controls the process conditions such as charging, exposure, and development after the return movement of the optical system 4 according to the detected density, so that the original can be printed at an appropriate density. It is possible to obtain a copy paper with a copy of it.

By the way, when using a reflection type sensor that is self-equipped with a light emitting part and a light receiving part as the document density detector, it is necessary to use a tungsten lamp because it is necessary to obtain a predetermined absolute amount of light. There is a problem in that the amount of light decreases due to aging and deterioration. Further, the amount of light of the original density detector changes depending on its contamination, temperature change, and the like.

Therefore, if the amount of light changes or deteriorates as described above, the density of the original will be inaccurately detected, and proper copy density control, that is, proper image control will not be performed.

The present invention has been made in view of the above, and an object of the present invention is to provide an image control device that allows image control to be performed without being affected by changes in the amount of light used to detect the density of an original. To this end, the present invention uses a reference density plate to correct changes in the detected density of the original due to changes in the amount of light.

Examples of the present invention will be described below. FIG. 2 shows an example of this, in which the document/density detector 16 is
Since it is necessary to take special heat-resistant measures near the first mirror unit 41, the second mirror unit 42, which does not require such measures, is provided so as to be movable in the direction perpendicular to the plane of the paper in FIG. Corresponding to the end point of movement of the second mirror unit 42 in the direction of arrow A, on the inner surface of the outer case 17, approximately the same surface as the surface of the platen glass 1,
A reference density plate 18 is arranged.

As shown in FIG. 3, the original density detector 16 is constituted by a reflective sensor that uses a tungsten lamp 16a as a light emitting element and a fumet transistor 16b as a light receiving element.

16C and 16d are condenser lenses.

In the above, when the second mirror unit 42 moves in the six directions of the arrows, the document density detector 16 simultaneously moves in a direction perpendicular to the six directions of the arrows, and the document density detector 16 emits light. Spot a (diameter approximately 11) of the light beam is placed on the platen glass 1 as shown in FIG.
A part of the original f1%19 set above is scanned diagonally. Then, the density of the document in the scanned portion of sub-section (a) is sequentially detected.

In this case, the characters on the original 19 are usually written along the edges of the original in a parallel or perpendicular direction, so if the original 19 is scanned diagonally as described above, one of the characters will always be written. As a result, the state of the image on the document 19 can be accurately detected. Also, at this time, the document density detector 16 is located away from the exposure light source 3, so if the document 19 is large, a portion of it will be scanned, but sufficient image information of the document 19 can be obtained. be able to.

After the document density detector (1) 6 has finished scanning the document, the document density detector (1) 6 applies the subograph 1-a to the reference density plate 18 and continuously detects the density of the reference density number 18.

The above operations can be performed by operating the copy start button.
This is performed as a preliminary scan prior to the exposure scan for copying the original, at which time the density information of the original 19 and the reference density plate 18 is detected, and then the exposure light 3 scans in the opposite direction to the direction of the arrow. An exposure scanning operation for copying is performed.

When the density of the original 19 is detected as described above, the original density signal is amplified by the amplifier 20 and then converted to a digital signal by the A/D converter 21, as shown in FIG. Detection data sent to the processing section 22 and corresponding to the density values of the original are sequentially stored in the memory section 23 for each density value, thereby obtaining density frequency distribution characteristics as shown in FIG. Note that here, the characteristic indicated by the broken line is the actual frequency distribution characteristic, but the data processing unit 22
The above is saturated. Then, the data processing section 22 detects the lowest density DI and the highest density D2 of this frequency m.

On the other hand, after detecting the density of the original 19, the original density detector 16 detects the density of the reference density plate 18, and sets it as the background reference density Do (FIG. 7).

By the way, conventionally, the reference density Do' of the background is set to a constant value, and therefore, as shown in FIG. If it is lighter, the light intensity of the original density detector 16 subsequently decreases, and the detected density value of the original at time T2 becomes darker than the standard density Do of the background (the density of a wide area, not a specific point of the original). In the case of,
The characteristic curve shown in FIG. 7 moves in the direction of higher density, that is, to the right), and even though the original density is the same, at time T2, the reference density Do of the background at time T'+ is no longer the same. "The relative relationship between the frequency and frequency distribution characteristic curves is different. Therefore, the same process condition control is not performed.

However, in this embodiment, as described above, the density of the reference density plate 18 as well as the density of the original are detected by the same original density detector 16.
Since detection is carried out under conditions such as Detection becomes more intense.

Therefore, by using the detection reference density value Do as the reference density of the background, the original density value becomes higher than the reference density DO of the background by the same ratio at both times Tl and T2.

That is, the reference density Do of the background of the characteristic curve shown in FIG.
corresponds to the decline in the performance of the document density detector 16, and moves to the right in the figure, where the density is higher. Therefore, the original density detector 1
6, the relative relationship between the background reference density Do and the characteristic curve remains unchanged.

When the frequency distribution shown in FIG. 7 is obtained, the lowest density D+ is the background density, and the highest density D2 is the image (character) iJ
At one time, the process control unit 24 copies the exposure amount control by controlling the voltage of the exposure light source 3, the developing bias control by controlling the pressure applied to the sleeve of the developing device 7, the exposure amount control by controlling the aperture of the lens of the optical system, etc. Process condition control begins to take place.

Here, an example of a specific method for controlling image density by detecting the density of a document will be described. If H is a certain value, tal, Do < DI... Original with dark background (b
l, Do > Dl, ID2 DI l >
H...The background is pale and the contrast is high (cl, Do > DI , ID2 DI l <
H...The background is pale and the contrast is low, so in the case of +a), the exposure amount is increased and/or the developing bias voltage is controlled to be high to lower the copy density, and in the case of (b), the copy density is lowered. The normal exposure amount and developing bias voltage are used (in the case of C1, the exposure amount is decreased and/or the developing bias voltage is controlled to be low to increase the copy density. The change in the detected density of the original due to the decrease was corrected by changing the reference density Do of the background. Therefore, depending on the detected density of the reference density plate 18, the dynamic range of the above-mentioned distribution characteristics is changed to change the frequency distribution. By changing the frequency distribution (toward the left in the figure), it is possible to similarly correct changes in the detected density of the original due to a decline in the performance of the original density detector 16.

As described above, the image control device for a copying machine according to the present invention is a copying machine that detects the density of an original to control the copy density. and a reference density plate whose density is detected by the original density detection means after the original density detection means detects the density of the original; The change in the detected density of the original document based on the change in the performance of the optical system is corrected, and the copying process conditions after the return movement of the optical system are controlled.

For this reason, the performance of the document density detection means may change over time, or
Another feature is that even if it deteriorates due to pollution or temperature, it can compensate for it and achieve an appropriate copy density.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a copying machine, FIG. 2 is a sectional view of a main part of an image control device according to an embodiment of the present invention, FIG. Figure 4 is a partial plan view of the copying machine for explaining spot movement for document density detection;
The figure is a concentration detection characteristic diagram, and Figure 6 is a block diagram of the control circuit.
FIG. 7 is a characteristic diagram of the frequency distribution of concentration. ■...Platen glass, 3...Light source for exposure, 4...
...Optical system, 16...Document density detector, 17...Outer box, 18...Reference density plate, 19...Document. Patent applicant Konishiroku Photo Industry Co., Ltd. Figure 4 Figure 5 Figure 6 Figure 7 ID, Do Da procedural amendment (
Own ship 1. Display of the case 1982 Patent Application No. 124462 2, Name of the invention Image control device for copying machine 3, Person making the amendment Relationship to the case 44th edition Applicant address 26-2, Nishi-Shinjuku 11, Shinjuku-ku, Tokyo Name
(127) Roku Konishi Photo Industry Co., Ltd. 4, Agent 6, Number of inventions increased by amendment None 1, From page 8, line 12 to page 9, line 1 of the specification [By the way, in the past...・・・・・・Move) and ” are corrected as follows. [By the way, if the reference 1 degree D' of the background is set to a constant value, at the time T1 in FIG. Even at this time, there is a problem that, due to subsequent changes over time such as a decrease in the light intensity of the document density detector 16, the detected document density value at time T2 is detected to be darker than the reference density Do' of the background. That is, the fifth
As shown by the solid line in the figure, the detected density value of the original changes over time due to changes in the original density detector 16 over time, and the relationship with this value becomes erroneous when the standard density value is fixed. Therefore,”

Claims (1)

[Claims] (1) In a copying machine that detects the density of the original and controls the copy density, the original density detection means detects the original density when the optical system moves forward in response to a copy start command, and the original is detected by the original density detection means. and a reference density plate whose density is detected by the original density detection means after density detection, and detects a change in the detected density of the original based on a change in the performance of the original density detector based on the detected density of the reference density plate. An image control device for a copying machine, characterized in that the image control device for a copying machine is configured to correct and control copying process conditions after the backward movement of the optical system.