JPH0610722B2 - Reader printer - Google Patents

Description

The present invention relates to an improvement in an image forming apparatus such as an electrophotographic copying machine.

Generally, when copying in a copying machine, there are documents with high contrast such as printed matter and documents with low contrast such as newspaper or diazo copy. It is also necessary to change the bias voltage of the developing device. in this case,
The density of the original is detected, and the exposure amount and the like are controlled according to the detected density. The image density of the original is determined by detecting the reflected light or transmitted light of the whole or a part of the original with a light receiving element. In this photometric method, for example, when copying a document, the characters on the document have the same density. However, since the photometric value (amount of received light) varies depending on the proportion of characters in the photometric area (corresponding to the light receiving area of the light receiving element), the quality of the detected copy image may change depending on the size of the photometric area. become. In order to accurately detect the image density, photometry may be performed with a light receiving element having a small light receiving area. In this case, a large number of light receiving elements are provided to reliably detect the background density of the document and the image density of characters and the like. Although it is necessary, if the number of light receiving elements increases, the number of circuits associated therewith (for example, output amplifier circuit, photometric value detection circuit, etc.) increases, and the device becomes complicated and expensive. Particularly in a copying machine that performs copying by the slit exposure method, since the original image is moved with respect to the light receiving element placed at a fixed position, the light receiving element moves the original surface in a direction parallel to the moving direction of the original or the optical system. Therefore, when the original is a document, each light receiving element may scan only a blank portion (background) between the rows, which makes it impossible to accurately detect the image density. There is. Alternatively, if the user scans and measures the white part or the black solid part with the light receiving element when the part or the character whose density is remarkably different in the target range of the document surface intended for copying is set as the target range, the copy target range is appropriate. There was a drawback that it was difficult to obtain an image.

The present invention ignores the character information of the original, only the background portion is taken out, and only the density of the background portion can be measured,
The purpose of the present invention is to improve the measurement accuracy of the document density, and in order to achieve this purpose, the position of the detection means on the document can be confirmed on the screen.

In the present invention, the term "scanning system" means that when an optical system (mirror or the like) is fixed and an original is moved to make a copy, the original or a moving table that supports the original is moved while the original is stationary and the optical system is moved to make a copy. An optical system that moves. The present invention can be applied to either case. Furthermore, the present invention can be applied not only to the slit exposure method but also to the entire surface exposure method apparatus.
In the present invention, the "means for arbitrarily selecting the original density detection area" is not limited to moving the light-receiving device only in the width direction of the original, but also in the longitudinal direction of the original, the vertical direction or the oblique direction with respect to the original surface. Including those that move to. The light receiving device may be a movable type or a fixed type, and the document density is detected only by the signal from the portion corresponding to the density detection area of the selected document among the signals input to the light receiving device by using a micro switch or the like. May be.

Further, as another selecting means, there is a means for providing a light receiving device capable of detecting the entire width of the original and shielding the optical signal input to the light receiving device according to the density detection area of the selected original. At least one of the voltage applied to the original illumination lamp, the exposure amount on the photosensitive member surface, the developing bias, or the charging amount by the charger is determined by the means for determining the forming condition of the formed image based on the signal of the area selected by these selecting means. Variable control.

In the first embodiment of the present invention, the case where the optical system is moved to scan the original will be described.

FIG. 1 shows an electrophotographic copying machine, in which a microfilm original 1 is illuminated by an illuminating device comprising an illuminating lamp 2, a spherical reflecting mirror 3 and a condenser lens 4, and the image light of the original 1 passes through a projection lens 5, It is reflected by the plane mirrors 6 and 7, and is projected onto the photosensitive drum 10 through the slit 9 of the slit plate 8. The mirrors 6 and 7 are fixedly supported by the support 11 in a relationship intersecting at a right angle, and the support 11 reciprocates integrally with the mirrors 6 and 7 in the direction A indicated by the arrow. The mirrors 6 and 7 are normally at the home position, and move forward when copying, and the image of the document is exposed on the photosensitive drum 10 when moving forward,
When the exposure of the image is completed, it moves and returns to the home position. The photosensitive drum 10 rotates in the direction C indicated by the arrow at a constant speed, and the mirrors 6 and 7 move at a speed half the peripheral speed of the photosensitive drum 10 in synchronization with the rotation of the photosensitive drum 10.
A known charging device, a developing device, a transfer device, a cleaner (not shown), etc. are arranged around the photosensitive drum 10, and an electrostatic latent image formed on the photosensitive drum 10 is copied by electrophotography. The image is developed with developing toner, and the developed image is transferred to transfer paper.

In FIG. 2, the slit plate 8 is supported by the guide shaft 15 so as to be able to reciprocate in the B direction shown by the arrow, and one end thereof is fixed to the endless wire 18 hung on the pulleys 16 and 17. A roller 19 is attached to the other end of the slit plate 8, and when the slit plate 8 moves, the roller 19 moves while rotating on a rail (not shown) of the main body. The pulley 16 is engaged with a drive source (motor) (not shown) that moves the support body 11, and the slit plate 8 moves in synchronization with the movement of the mirrors 6 and 7. The pulley 16 is accurately and reversely rotated by the drive source, and the slit plate 8 reciprocates in the arrow B direction. A sliding plate 21 that is slidable in the direction of arrow E is arranged on the slit plate 8. The light receiving element 20 for detecting the image density of the document is arranged at the edge of the sliding plate 21 and is arranged so as to slide in the vicinity of the slit 9. Rollers 24 are arranged at the edges of the sliding plate 21. The roller 24 is loosely fitted in a groove rail 25 penetrating the slit plate 8, and when the sliding plate 21 slides, the roller 24 slides while rotating in the groove rail 25.
On the other hand, one end of the sliding plate 21 is fixed to the endless wire 22. The endless wire 22 has an endless circular shape, and one end thereof is engaged with a shaft 22a that is connected to the slit plate 8 and has a columnar engagement portion 22b.
The other is engaged with the rotating shaft of the gear 23 via. Gear 2
With the rotation of 3, the sliding plate 21 slides in the direction of arrow E.

When the slit plate 8 is located at the initial home position, the gear 23 is the gear 3 having the rotation shaft arranged in the main body.
Mesh with 2. At this time, the knob 3 connected to the gear 32
The rotation of the gear 3 causes the gear 32 and the gear 2 to rotate.
3, transmitted from the endless wire 22 to the slide plate 21, and slides in the direction of arrow E together with the light receiving element 20 arranged on the slide plate 21. When the slit plate 8 is located at the home position, the pawl releasing portion 28 arranged so as to be connected to the end of the slit plate 8 pushes up the pawl 29 provided on the main body by the shaft 34. Therefore, the knob 33 and the gear 32 connected to the knob 33 are in a rotatable state. However, after the copying process is started, the slit plate 8 starts sliding in the arrow F direction. For this reason, the pawl releasing portion 28 is disengaged from the pawl 29, and one end of the pawl releasing portion 28 is engaged with the gear 32a connected to the gear 32 by the urging force of the spring 30 fixed to the main body (not shown) and the other end of the pawl 29. Gear 32 and knob 3
3 is in a non-rotatable state. As a result, the knob 33 can be rotated only when the mirrors 6 and 7 and the slit plate 8 are located at the so-called home position, and the light receiving element 20 slides corresponding to the rotation of the knob 33. Therefore, in the case of a document table or a reader printer (not shown) having a screen, the user can previously receive light by providing a scale or an index corresponding to the rotation of the knob 33 on the screen 34 as shown in FIG. The position of the element 20 can be identified by the turning position of the knob 33. The light receiving element 20 is composed of a known photoelectric conversion element and has a small light receiving area, and detects the amount of light from the document. The light amount detection signal of the light receiving element is first transmitted through the flexible electric cord 26.
It is sent to the lamp brightness control circuit 27 shown in the figure, and the lamp brightness control circuit 27 controls the brightness of the lamp 2 based on the photometric value of the light receiving element 20 so that the optimum exposure amount according to the density of the original is obtained. I have to.

The detection of the image density by the light receiving element 20 is performed before the regular exposure process. In the present embodiment, the document is pre-scanned for this purpose, and the current supplied to the hump 2 is adjusted in accordance with the maximum luminous intensity and the minimum luminous intensity received by the light-receiving element 20 during this preliminary scanning, and the lamp is adjusted to an appropriate amount of light. After adjustment, a regular exposure scan is performed. In this embodiment, when a copy switch (not shown) is turned on, the lamp 2 is turned on and the mirrors 6 and 7 and the slit plate 8 are moved forward or backward in the A and B directions in synchronization with each other for preliminary scanning. During the preliminary scanning, the light receiving element 20 moves in the direction of arrow B, which is the scanning direction of the document, in synchronization with the movement of the slit plate 8 to scan and measure the document. After scanning and photometry on a predetermined range of the original, the brightness of the lamp 2 is adjusted based on the maximum and minimum values of the photometric value, the brightness of the lamp 2 is set to an appropriate state according to the density of the original, and then the mirror. 6 and 7 and the slit plate 8 return to the initial home position.
The moving speed of the mirrors 6 and 7 in this preliminary scan is made faster than the moving speed of the mirrors 6 and 7 in the regular exposure scan,
Time may be reduced.

The image quality of the copy image may be adjusted by adjusting the exposure time, the diaphragm, the bias voltage of the developing device, etc. based on the photometric value of the light receiving element 20.

When the preliminary scanning is completed and the mirrors 6 and 7 are returned to the home positions, the mirrors 6 and 7 are moved forward in synchronization with the rotation of the photosensitive drum 10, and the normal exposure scanning is performed. In the display scale shown in FIG. 3, the knob 33 and the screen SC are provided with corresponding scales or indexes to identify the position of the light receiving element 20, but in the display scale shown in FIG. , Wire 38 on pulleys 36 and 37
Are engaged. The index plate 35 is fixed to the wire 38. The pulley 37 is further pinched by the wire 39 with the knob 33.
Is engaged with. By rotating the knob 33, the amount of movement of the light receiving element 20 corresponds to the amount of movement of the index plate 35 on the screen 34. With such a configuration, the visibility is improved and the reading accuracy is improved. Only the display portion of the index plate 35 appears on the surface from the long hole portion 40 and slides in the long hole portion 40. A light emitting element such as a light emitting diode may be arranged in the display portion of the index plate 35. Long hole 4
It is also possible to dispose the index plate 35 so as to slide outside the screen 34 without penetrating 0.

As described above, according to the present invention, since the position of the detection unit with respect to the original can be confirmed on the screen, it is possible to prevent the white portion or the solid black portion of the original from being mainly detected, and the original density of the original can be prevented. It is possible to improve the measurement accuracy and always obtain an image with an appropriate density.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention of a movable optical system,
2 is a perspective view of the embodiment shown in FIG. 1, FIG. 3 is an explanatory view of a display scale which constitutes an embodiment of the present invention, and FIG.
It is explanatory drawing of another display scale. 1 ... manuscript, M1, M2 ... microswitch. 20 ... Light receiving element, 21 ... Sliding plate,

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuo Kashiwagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masaaki Yanagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Yoshihiro Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. A reader / printer which detects the density of an original document exposed to an electrophotographic photosensitive member and changes the image forming condition based on the detection result, is arranged between the original document and the photosensitive member in the vicinity of the photosensitive member. A light receiving unit which is provided and movable arbitrarily, and which optically reads the density of the irradiated original, and a detection region setting unit which manually sets the detection region of the light receiving unit which is movably supported by the supporting unit. And display means for displaying the detection area of the light receiving means set by the detection area setting means on the screen in synchronization with the setting operation by the detection area setting means, and the above-mentioned detection area when the original is exposed on the photoconductor. A reader printer, comprising: a light receiving unit driving unit that drives the light receiving unit in conjunction with the setting unit.