JPS6046572A - Original density detector of copying machine - Google Patents

Abstract

PURPOSE:To make a necessary scan on an original sufficiently with simple structure by providing an original detecting member slidably onto the slide shaft of a movable mirror system, and moving the detecting member slantingly to an original surface associatively with the movement of the opticals system. CONSTITUTION:The original detecting member 20 which detects original density while a sensor 21 consisting of a light emission lamp and a photodetecting element is fixed thereto is provided slidably onto the slide shaft 22 where the movable mirror is fixed, and a lever 26 is fitted pivotally between a fitting seat 25 and the fitting seat 24 of a machine frame. When the moving body 12 moves as shown by an arrow A, the detecting member 20 draws a circle having a radius corresponding to the lever 26 as shown by an arrow B around the fitting seat 24, and scans on the original to detect the density by sensor 21. Thus, a necessary scan on the original is made sufficiently with the simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a document density detection device for a copying machine, which detects the density of a document placed on a document table in a copying machine such as an electrophotographic copying machine. .

In prior art electrophotographic copying machines, copies are made from originals of various densities. Therefore, conventional electrophotographic copying machines are equipped with a density adjustment device so that the optimum copy image can be obtained for documents of any density, and users can adjust the density based on their experience based on the density of the original. The density is adjusted manually. However, such manual density adjustment is cumbersome to operate.

A copying machine has been proposed that automatically detects the density of a document prior to copying and automatically adjusts the image density to 'fJ4'.

Conventionally, as a method of detecting the density of a document and automatically adjusting the image density, for example, as proposed in Japanese Patent Application Laid-Open No. 53-93834, density conditions are controlled from the maximum and minimum values of @ degree. However, for originals that have an image darker than the most necessary image density, such as a pencil original with printed ruled lines, there is an inconvenience that the density condition is adjusted for the printed ruled lines. . Therefore, as in Japanese Patent Application Laid-Open No. 120623/1982, a histogram is created by scanning a document placed on a document table according to the density distribution of each point on the document, and an image predetermined by the pattern of this histogram is created. A method of adjusting the density has been proposed, but the circuit configuration for creating the histogram is complicated. .

In order to detect the density of an M document using such a document density detection device, the document detection member is scanned over a certain range on the document without being limited locally, and the background portion of the document and the image are detected. It is necessary to detect the density of the original.

Scanning of the document by the detection member is performed prior to copy exposure, and control is performed by adjusting the amount of light or adjusting the developing bias voltage. However, the mechanism of such a detection member for scanning a document is generally complicated and occupies more space in the optical system than necessary, and such a complicated mechanism often causes failure.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a document density detection device for a copying machine which has a simple structure and is capable of scanning a document to the necessary and sufficient extent.

Structure of the Invention The present invention aims to achieve the above-mentioned object, and the present invention includes a transparent document placing table on which a document to be copied is placed, and a transparent document placing table arranged below the document placing table and on the yiC document placing table. In a copying machine having an IIX document detection member that moves along a predetermined path with respect to the document surface, the document detection member is swingably supported with respect to the machine frame, and is engaged with a part of the moving optical system, so that the document detection member is The present invention provides a document density detection device for a copying machine, characterized in that the document detection member can be moved diagonally with respect to the document surface by movement of the system.

Embodiment FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a perspective view of the main part thereof. First, the structure of the document table portion of the copying machine will be explained. In the figure, above a photoreceptor drum 1 which is driven to rotate in one direction, there is a transparent document placement table 2 on which a document to be copied is placed. In this embodiment, the document placement table 2
The scanner is of a fixed type, and a slit exposure optical system 3 for optically scanning the original placed on the original placing table 2 is located below the original placing table 2. The exposure optical system 3 includes an exposure lamp 4 and mirrors 5 and 6.
, 7, 8 and a lens 9, and the lens 9 forms an image of the original on the original table 2 onto the circumferential surface of the photosensitive drum l. Here, the imaging lens 9 and mirror 8 are fixed,
The exposure lamp 4 and mirrors 5, 6.7 are movable.

The exposure lamp 4 has a rod shape, and the light emitted from the exposure lamp 4 is reflected by a reflecting mirror 10 having an elliptical cross section.
The light is condensed and irradiated in a band form from the bottom surface of the document table 2.

The mirror 5 is a first mirror that reflects the belt-shaped document information, and has a rectangular shape. This exposure rung 4
And the mirror 5 is fixed on the first movable body 11.

The mirrors 6 and 7 are both strip-shaped second mirrors. In the third mirror,
They are fixed on the second movable body 12 while maintaining the carp angle with each other.

The first movable body 11 and the second movable body 12 move parallel to the document table 2, and the first movable body 11 moves in the same direction at a speed 202 times faster than that of the second movable body. As a result, the original image on the original table 2 is scanned, and an image is formed on the rotating photosensitive drum l.

Next, a description will be given of the original density detection device of the present invention, which is installed in a copying machine having the pick-pocket exposure optical system 3 described above.

FIG. 3 is an enlarged cross-sectional view of a sensor 21 installed on the top surface of an additional document detection unit that detects the density of a document using a reflective optical sensor. 21b, and a luminescent lamp 21m.
The light emitted from the source is reflected by the original M (indicated by the two-dot chain line), is received by the light emitting element 21b, and is emitted as an electrical output.

The document detection section addition is provided so as to slide on a sliding axis n provided perpendicularly to the scanning direction on the second movable body 12, which is the moving source material. It is constructed so that it is located at a constant distance from the document M at any position on the axis n.

On the other hand, the machine frame n of the copying machine is provided with a mounting outlet.
A lever of a certain length is mounted between the mounting lead and the mounting seat provided on the original detection section so as to be rotatable by respective pivots.

With this structure, when the second movable body 12 moves in the direction of arrow A in FIG. Then, detect the density of the original Mf).

Figure 4 shows the relationship between the operation of adding the original detection unit and the size of the original M. The addition of the original detection unit moves diagonally to the original surface, and the background part of the original and the image Detects the density of the original.

FIG. 5 shows a detection circuit of a document detection device according to the present invention.

The output from the center 21 is compared with the original density data stored in the storage circuit 32 by the original density determination circuit 31 to determine the original density.
The concentration is appropriately controlled by the output of 1. Various concentration control methods are known and are not the subject matter of the present invention, so they will not be described in further detail.

In step 5 of the detailed description of the invention, in the present invention, a document detecting section I' that runs along a predetermined path is provided at the bottom of a transparent document placing table, and this document detecting member is detected before a series of copying operations. Although the fiC document density is detected by running the scanner, the number of moving component parts such as the document detection member is extremely small according to the present invention, and the effects of cost reduction, man-hour reduction, and reliability improvement can be obtained. Ta. Furthermore, by directing the sensor bundle line from the moving original detection member to the -C copying machine frame along the lever, there was no accident of shearing, and the durability was improved by one twist.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG. 2 is a perspective view of the main part thereof. Fig. 3 is a sectional view of the main part of the detection member, Fig. M4 is a relationship diagram showing the relationship between the operation of the riC document detection member and the document size, and Fig. 5 is an electric circuit diagram of the document detection device according to the present invention. . 2... Document placement table 3... Optical unit 4... Exposure lamp 5.6.7.8... Mirror 9゛... Lens 11 °°° First movable body 12... Second movable body Body addition/
...Document detection member 21...Sensor n...Sliding axis...Machine frame Sae, 25...Mounting seat station...Lever agent Yoshi Kuwahara Mika 2nd ward, 65th ward, and 4th ward muscle diagram 5

Claims (1)

[Claims] A copying machine comprising a transparent document placing table on which a copy original is placed, and a document detecting member disposed below the document placing table and moving in a predetermined path with respect to the document surface on the document placing table. The document detecting member is swingably supported relative to the machine frame, and is engaged with a part of the moving optical system, so that movement of the moving optical system moves the document detecting member in an oblique direction with respect to the document surface. A document density detection device for a copying machine, characterized in that a document density detection device is used for a copying machine.