JPH0642095B2 - Liquid crystal display / printer control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention uses a display device for displaying images and character information, that is, a liquid crystal display device as a document of a copying machine or the like, and obtains a clear hard copy thereof, that is, a printout. The present invention relates to a liquid crystal display / printer control method that can be performed.

[Prior art]

A conventional image processing apparatus, for example, a general copying machine, illuminates a document placed on a document table made of a transparent material from under the document table, and reflects light according to the light and shade of the document through a lens or the like. The optical system used collects the light and forms an image of the original on the photosensitive drum.

On the other hand, a liquid crystal display device is known as an image output device such as a computer. Therefore, now, the display screen of the liquid crystal display device is aligned with the upper surface of the original table of the copying machine, placed on the original table, and an image is output on the display screen to perform the copying operation of the copying machine. If executed, a hard copy of the display image of the liquid crystal display device can be obtained.

FIG. 1 shows a copying machine capable of making such a hard copy. That is, it is a perspective view of an image processing apparatus in which a liquid crystal display device in which a liquid crystal display screen is attached to a cover of a copying machine and a copying machine are combined.

In the drawing, reference numeral 1 is an electrostatographic plain paper copying machine, 2 is a display device formed in a cover shape, and its display screen 3 is configured to be covered with a document table 4. Display device 2
Is connected to a personal computer 5 with a keyboard via a cable 6.

With this configuration, the display screen is used as the console output of the computer 5, the processing information is displayed on the display screen 3, the display contents are confirmed, and the cover-shaped display device 2 is tilted to start copying. If so, a hard copy of the displayed contents can be easily obtained. Especially, computer 5
When is used as a word processor, the document output on the display screen 3 is proofread and checked, and a hard copy can be obtained as it is, so operability is good and copying efficiency is good. In addition, in a system that introduces a local area network, connects multiple computers, and can transfer information, for example, transfer image information between offices,
Image information can be output on the display screen 3, the contents can be checked, and only the necessary information can be easily left as a hard copy.
It is extremely convenient. In addition, if the display screen 3 is left blank, the copying machine 1 can be used for copying general documents, which is very useful as a multipurpose office machine.

However, there are two types of liquid crystal display elements used as display screens, a reflective type and a transmissive type. The reflective type has a reflector on the back side of the liquid crystal display element, and the transmissive type has a light source on the back side. However, both have the characteristic that they are difficult to see unless a high contrast is obtained.

Then, even if the display is visually high in contrast, when the image on the liquid crystal display is copied, there is a problem that the contrast is insufficient and the image is very difficult to discriminate. This is due to the low sensitivity of the photoconductor of the copying machine.

[Object of the Invention]

An object of the present invention is to prevent a copy that is difficult to discriminate when making a display copy using the display unit.

Specifically, a reflective liquid crystal display element is used so that a hard copy having an optimum contrast can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a sectional view of the image processing apparatus. The same or equivalent parts as in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The primary charger 7 applies a fixed charge onto the photosensitive drum 8,
Image exposure is performed by the exposure lamp 9 and the self-locking lens array 10 to form a latent image on the photosensitive drum 8. The latent image is visualized by the developing device 11, and the image is copied by the transfer charger 12. 13 is a cleaner and 14 is exposure.

Copy paper is fed from the manual feed tray 15 to the paper feed rollers 16 and 1.
It is guided into the copying machine 1 by means of 7. Register roller 1
At 8 and 19, the toner image is transferred from the back surface by the transfer charger 12 at a timing synchronized with the image, and the toner image is transferred onto the copy paper. After that, the conveyor belt 20, the fixing roller 21,
The sheet is fixed through 22 and is discharged onto a discharge tray 24 by a discharge roller 23.

Reference numeral 25 is an electrometer for measuring the potential on the photosensitive drum 8 and is connected to a circuit (not shown) for controlling the potential on the photosensitive drum 8 to a prescribed level. A reflective plate 26 is provided on the display screen 3, that is, on the back side of the transmissive liquid crystal display element 3 to enhance the contrast of the liquid crystal.

With such a configuration, when the screen display is finished and the copying operation is started, the characters and images displayed on the liquid crystal are once erased, and the photosensitive drum 8 corresponding to the back ground (bright part) is displayed. Is measured by the electrometer 25.
Then, the light quantity of the exposure lamp 9 is increased until the back ground potential reaches a predetermined potential (a potential at which the back ground does not shake on the copy).

Next, the potential of the primary charger 7 on the photosensitive drum 8 is changed so that the entire liquid crystal display is black and the dark potential becomes a specified value, and this is repeated several times to set the potential between the light potential and the dark potential. The contrast is controlled until it converges to the specified value. During this period, the document table 4 may be stopped or moved.

When this control is completed, the stored image is called on the liquid crystal display screen 3 and a copying operation is performed, so that a copy with contrast and without fog on the ground can be obtained.

When the copy-finished paper is used again as a normal copying machine, the light amount and the voltage applied to the primary charger 7 are returned to the original values before use. Further, in the case of an input having no memory of the image, it is possible to control the potential of dark or light by using the front end or the rear end of the image while the pressure plate, that is, the display device 2 is stopped (outside the image area). May be.

FIG. 3 is a basic conceptual diagram of the display copy system according to the present invention. This is configured such that an image is formed on the photosensitive drum 30 by a combination of the reflective liquid crystal panel 27, the self-turning lens 28, and the light source 29. A feature of the present invention is that the reflection type liquid crystal panel 27 as described above is used to erase the displayed image once so that an optimum image quality can be obtained before copying in the display section, and a background (light section) is displayed. ), The potential ( _VL ) on the photoconductor drum 30 is measured, and the light quantity of the light source 29 (halogen lamp or fluorescent lamp) is changed until the potential reaches a specified potential, so that an optimum _VL value can be obtained. Also, the bias potential and the frequency are simultaneously changed.

Next, the liquid crystal display is entirely black, and the potential of the dark part (V _H )
The electric potential of the charging charger 31 (C.C) is changed until becomes the optimum value. This is sequentially performed to determine the appropriate charge amount, exposure amount, and bias value. Reference numeral 32 is a potential sensor. Note that both the black and white patterns may be formed on the same surface to perform the control. FIG. 4 illustrates the reflection type liquid crystal panel 27. In this example,
The feature is that it is also used as a document holding plate during normal copying.

FIG. 5 is a conceptual diagram of the control system in the present invention.

A light source 33 (fluorescent lamp or halogen lamp), a high-voltage power supply, a bias potential, and a frequency one-chip microcomputer 34 (hereinafter referred to as MCU) are used in order to change the process conditions when switching between display copy and normal copy. hand,
Concentrate on these controls. This is basically a PWM (Pulse Width Modulation) method, and the number of pulses and the pulse width are controlled by a combination of an internal pulse and a program in the MCU. As shown in FIG. 8, the basic generation method of these is to control the number of pulses in a fixed cycle (called a check cycle (tc)).
As shown in FIG. 9, there is one that changes the ratio of ON (tn) and OFF (tf) (duty ratio). The former is mainly used for controlling a light source such as a fluorescent lamp, and the latter is mainly used for controlling a high voltage power supply and a bias power supply. In FIG. 5, a fluorescent lamp was used here as an example of the light source. The fluorescent lamp uses a high-frequency oscillation method in order to stabilize the light intensity and linearity, and 20 KHz
The fundamental oscillation of is used as a 1 KHz cycle period. M
A high frequency output stabilized by the PWM control oscillated by the CU is generated on the secondary side of the transformer H · T, and the fluorescent lamp emits light. It is possible to change the amount of emitted light linearly by controlling the number of pulses during the cycle of the check.

High voltage power supply C. C is PWM control, similar to the principle of the former fluorescent lamp, and further rectifies the high frequency transformer to generate high voltage D
It is a C-DC converter. Also in this case, the generated voltage can be increased or decreased by the PWM control.

The potential sensor 35 is obtained by amplifying the electrostatic potential obtained by mechanically chopping the electric field with a ceramic oscillator. In recent years, a small-sized electrostatic field checker type potential sensor with good linearity has appeared and has been put into practical use. This output is A / D converted and serial output MC
Input to U.

The bias potential is controlled to an appropriate value by monitoring the surface potentials _VH and _VL . FIG. 6 is a graph showing the gradation of development and is a UD characteristic curve showing the relationship between the surface potential of the photosensitive drum 36 and the image density. It is easy to obtain a hard image on curve a and a soft image on curve b. This is obtained by increasing or decreasing the resistance of the photosensitive drum 36 during image formation. The other gradation switching method can be achieved by changing the thickness of the toner 37 coated on the surface of the developing roller. For example, at the time of a display copy, the bias voltage is set to 600V and the coating is made thicker for the hard contrast development, and at the time of the normal copying, the bias voltage is lowered to 450V and the toner coating is thinned to the soft contrast development. Further, in the case of the jumping developing method, by switching the frequency of the AC bias voltage, it is possible to select the hard tone developing (800 to 1600 Hz) and the soft tone developing (200 to 600 Hz).

In this example, as described above, the internal counter of the MCU 34 and the program are combined to perform PWM modulation,
The feature is that the bias voltage and the frequency are switched. DEV is a developing device.

FIG. 7 conceptually shows the structure of the present invention.

A LAN (Local Area Network) is used to connect to other computers and image processing equipment. In FIG. 7, the LAN interface is shown. The image memory is a memory for temporarily storing the transmitted image. The printer controller and image scanner are the controllers of the electrostatic imaging system as shown in the figure. Of course, copying as an ordinary copying machine is also possible. Day Play
As described above, in the present invention, in the case of a normal copy using a reflective liquid crystal, the back ground is used as a document holding plate with a color tone corresponding to white so as to reflect light,
In the case of display copy, the bias, the light amount, and the charge amount are controlled so that the optimum process conditions are obtained. This method will be described later.

FIG. 7 shows a schematic view of a belt (web) photoconductor 38, where DEU is a developing device, C.I. C is a charged corona, T.I. C is the transfer corona, D. C is the separation corona, 39
Is a potential sensor, 40 is a self-assembling lens, and 41 is a cassette.

As described above, according to the present invention, gradation control is performed by changing the amount of light between the display copy and the normal copy, adjusting the charging potential, and switching the developing characteristic according to the bias potential and the frequency. This makes it possible to prevent fogging and obtain an appropriate image.

〔The invention's effect〕

As described above, according to the present invention, the image information on the liquid crystal panel is once erased with the start of the operation of the image forming means, and the white and black patterns are formed on the liquid crystal panel. Detect image processing conditions based on
Since the process conditions of the image forming means are set based on this detection output, the stored image information is formed again on the liquid crystal panel, and the image is formed by the image forming means, the liquid crystal display panel is normally used. Can be used as a display body of the above, and a hard copy having an optimum contrast can be obtained by using the display of the liquid crystal display panel as an original during copying. Further, the liquid crystal panel can also be used as a document pressing plate during normal copying using a document such as paper.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional image processing apparatus, FIG. 2 is a sectional view of an image processing apparatus according to the present invention, FIG. 3 is a conceptual view of a display copy system according to the present invention, and FIG. 4 is a reflection type liquid crystal panel. FIG. 5 is a perspective view, FIG. 5 is a conceptual diagram of a control system in the present invention, FIG. 6 is a diagram showing the relationship between the surface potential of the photosensitive drum and image density, and FIG. 7 is a diagram conceptually showing the constitution of the present invention. , FIG. 8 and FIG. 9 are diagrams for explaining the pulse modulation method. 1 …… Copier 2 …… Display screen 5 …… Computer 7 …… Primary charger 8 …… Photosensitive drum 25 …… Electrometer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Tanioka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Tadashi Yamakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Yutaka Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masao Hosaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Toshiaki Yagasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-48-3543 (JP, A) JP-A-54-10743 (JP, A) Special Kai 57-35882 (JP, A) JP 57-124363 (JP, A) JP 57-125954 (JP, A) JP 57-125946 (JP, A) JP 57-104952 ( JP, A)

Claims (1)

[Claims] 1. A document table on which a document is placed, a reflection type liquid crystal panel having a white background for pressing the document on the document table and displaying computer output image information, and exposing the document or the reflection type liquid crystal panel. However, in the control method of the liquid crystal display / printer having the image forming means having means for projecting the image information on the original or the panel onto the photoconductor and means for visualizing the image on the photoconductor, When the image information output from the computer is printed, the image information output from the computer on the liquid crystal panel is once erased when the operation of the image forming unit is started,
Forming white and black patterns on the liquid crystal panel, detecting image forming conditions based on each pattern,
A process condition of the image forming unit is set based on the detected output, the stored image information of the computer output is formed again on the liquid crystal panel, and the image is formed by the image forming unit. LCD display
Printer control method.