JPH0441352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image display device, and more particularly to a device that forms and displays images on a belt-like image carrier that can be used repeatedly.

Conventionally, CRT (cathode ray tube) was used as an image display device.
is widely used, and this CRT is used to display characters,
When displaying a still image such as a figure, generally a RAM (Random Access Memory) is used as an IC memory corresponding to the picture element on the screen, and image information is stored in the RAM and read out and displayed. .

However, in general, image display devices are often required to display the previously displayed image again, so in order to meet such requests, image display devices using the CRT have multiple A RAM corresponding to the screen size is provided, and when displaying a new screen, the information on the currently displayed screen is stored in the RAM without erasing it, and when it is necessary to display this screen again. The stored information is called up and displayed at any time, but the RAM required to store all the display information for multiple screens is large and quite expensive, and it is not possible to use a CRT. Another problem is that the resolution of conventional image displays is often unsatisfactory.

By the way, as an image display device that displays a large amount of image information, for example, one using a _heat -sensitive recording method is known _. An image is recorded and displayed on a reversible thermosensitive recording medium using a thermosensitive recording head. Since Ag ₂ HgI ₄ changes color depending on temperature and has hysteresis with temperature, an image is recorded on a belt-shaped film containing Ag ₂ HgI ₄ using a thermal recording head, and this is transferred to a sheet heater. After the display is completed, the film can be cooled at room temperature or in a cooler to erase the image and be used repeatedly.

Still another example is an image display device using an electrophotographic method. This is a method in which a toner image is formed and displayed on an electrophotographic photoreceptor by scanning it with a light beam modulated by an image signal, and after displaying, the previous toner image is transferred to the next photoreceptor. The photoreceptor can be used repeatedly by removing it by beam scanning.

These thermal recording type or electrophotographic type image display devices are characterized in that extremely large-capacity displays can be performed with high resolution.
For example, if an image of 200 mm x 300 mm is displayed with 8 dots per mm, 3.84 million pixels can be displayed, and with 16 dots per mm, the number of pixels will be 15.36 million. Now, in order to display the previously displayed image again on such an image display device, all the display information (pixels) of one screen must be memorized, similar to what is done with the CRT-based image device mentioned above. However, using such a large capacity memory is not only extremely expensive, but also makes the device extremely large.
For example, to store information of 15.36 million pixels,
Assuming that 64k bit LSI memory is used,
235 units are required, and if you include the memory drive circuit, power supply unit, etc. that drive them, it will be quite large and expensive.

In addition, image display devices using such a thermal recording method have a problem in that the display speed is not very fast, which is also a drawback of the above-mentioned format using memory. For example, in the thermal recording method, each pixel is written with high accuracy in sequence while mechanically moving a belt-shaped image carrier, so it takes several seconds to several tens of seconds to display one screen.
Needless to say, this time cannot be shortened even if the previously displayed image is once stored in memory and then displayed again.

The present invention aims to eliminate the above-mentioned drawbacks of this type of image display device, and it is possible to display an image once displayed again without providing a large amount of memory, and also to The purpose of the above is to provide an image display device that can shorten the time required for displaying images again.

The image display device of the present invention that achieves the above object includes:
a display section for visually viewing images formed on a belt-shaped image carrier that moves inside the housing; and the belt-shaped image carrier having a length that allows formation of two or more images to be viewed on the display section. and a plurality of support members that support the image carrier in an endlessly movable manner,
a driving means for moving the image carrier along the support member; an image forming means for forming a visible image on the image carrier; and an image forming means for forming a visible image on the image carrier; When the image forming means is guided to the display section again, means is provided for releasing the operation of the image forming means with respect to the carrier.

In addition, when the endless belt-shaped image carrier is rotated forward or reverse in the operation of guiding the image that has been guided (exported) out of the display area from the display area to the display area again, the formation Image erasing devices or other elements that disturb the formed image are moved back from the rotational path of the belt as necessary to ensure proper image maintenance.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to an electrophotographic image display device, and the image display device includes a housing 1, in which
The output light beam of a semiconductor laser (not shown) modulated by an image electric signal is scanned in one direction by a scanner 8 of an optical system 7, and is sent to an endless belt-shaped photoreceptor via an f/θ lens 9 and a mirror 10. The back surface of the image carrier 11 (hereinafter referred to as a photoreceptor) containing the photoreceptor is exposed to light. This photoreceptor moves in the direction of the arrow, and is made of, for example, a polyethylene terephthalate film whose surface is made conductive by providing a thin indium tin oxide film on the surface of which is coated with CdS as a photoconductive layer using a resin as a binder. CdS is doped with copper and indium and is sensitive to near-infrared light emitted by a semiconductor laser. A developing device 12 is provided opposite the exposure position of the photoreceptor. The developing device 12 is provided with a sleeve 4 having a magnet 3 therein, and the magnet 3 rotates in the direction of the arrow.

The conductive and magnetic toner 5 supplied to the surface of the sleeve 4 is uniformly regulated by the blade 6 and comes into contact with the surface of the photoreceptor 11 . A DC voltage is applied between the sleeve 4 of the developer and the base of the photoreceptor by a DC voltage source (not shown). Rollers 13 and 14 are provided near the positions where exposure and development are performed, which keep the moving photoreceptor 11 flat and maintain a constant distance between the surface of the photoreceptor and the sleeve 4 of the developing device with high precision. ing. The toner image formed on the surface of the photoreceptor at a position facing the developing device is sent to the display section 15, and the movement of the photoreceptor 11 is temporarily stopped at this position. Transparent glass 16 in the display area
Through this, the toner image on the surface of the photoreceptor can be visually observed from the outside.

With this configuration, toner with opposite polarity induced charges is attached by Coulomb force according to the photo carrier generated in the bright area of the photoreceptor surface that is irradiated with the image light, and as the belt-shaped photoreceptor moves, the toner is A toner image is formed (that is, writing is performed by irradiation with image light), and the adhered toner developed in this way is transferred to the belt-shaped photoreceptor as it rotates to form an image again. The image display device of this example does not require any particular cleaning means for cleaning the residual toner on the photoreceptor because it does not affect the toner when it is used.

FIGS. 2 and 3 are explanatory diagrams illustrating the principle of image formation on the belt-shaped photoreceptor 11 used in the exemplary apparatus shown in FIG. 1.

FIG. 2 shows the state of charge in the brightness of information light. When the toner 5 to which a voltage is applied via the sleeve 4 comes into contact with the photoreceptor, an electric field is applied to the photoconductive layer 11c. At this time, when the information light is irradiated, photocarriers e are generated in the photoconductive layer 11c, and the photocarriers are guided near the surface of the photoconductive layer 11c by the action of an electric field. As a result, a strong electrostatic attraction acts between the toner 5 and the photoconductive layer 11c, and the toner 5 is transferred to the photoconductive layer 11c, that is, the photoreceptor 11.
attached to the surface.

In the illustrated example, the photoconductive layer 11c is an N-type semiconductor,
Since a positive voltage is applied to the toner 5, carriers e generated near the substrate in the photoconductive layer 11c by the irradiation with the information light L are well guided toward the surface of the photoconductive layer 2. As a result, toner 5 and photoreceptor 1
1, a strong electrostatic attraction acts between them, and the toner 5 adheres to the photoreceptor.

FIG. 3 shows the state of charge in the dark area. When an electric field is applied between the toner 5 and the transparent conductive layer 11b of the base, electrostatic attraction acts between the two, but there is a photoconductive layer 11c between them, so that they are separated from each other. Therefore, its power is small.
Therefore, due to the magnetic force of the rotating magnet 3 provided inside the fixed sleeve 4, the adhesion force between the toner 5 particles, etc., the toner 5 is transferred to the photoconductive layer 11c,
That is, it is pulled away from the surface of the photoreceptor 11.

Note that when changing the toner image on the photoreceptor 11, a new image can be formed simply by passing through the exposure position again. That is, when the toner holding portion changes to a bright area, the toner 5 whose electrostatic adsorption force has decreased is removed by the magnetic field of the magnet 3 and becomes the bright area. On the other hand, if the dark area remains, use the carrier e again.
is injected, the toner 5 is taken out by overcoming the magnetic field, and the dark area continues. Therefore, since the toner image on the surface of the photoreceptor does not have any adverse effect on the next image formation, there is no need to provide a separate cleaning means.

In FIGS. 2 and 3, 11a is a polyethylene terephthalate film supporting the conductive layer 11b, and E is a power source for applying voltage to the sleeve.

Among the toner images formed on the photoreceptor 11 based on the above-mentioned image forming principle, the first toner image that has finished being displayed on the display unit 15 moves the photoreceptor 11 again in the direction of the arrow after the display ends. Then, the toner image that has finished displaying leaves the display section 15, and
The next second toner image is sent to the display section 15, and at this position the movement of the photoreceptor 11 is stopped so that the second toner image can be viewed through the glass 16.

The feature of this embodiment of the image display device having such a configuration is that the circumference of the endless belt-like photoreceptor is determined by at least one other toner image in addition to the first toner image displayed on the image display section 15. The reason is that the length is set so that the image can be maintained.

That is, in the illustrated example of FIG. 1, the first toner image that has finished displaying is guided out of the display area by rotating the photoreceptor 11 counterclockwise in the figure by a driving means (not shown), and at the same time, the first toner image that has finished displaying is guided out of the display area. When the image is guided to the display section 15, the first toner image displayed last time is transferred to the area guided by the drive roller 17 and guide rollers 18, 19, and continues to carry the image. Therefore, by rotating the belt-shaped photoreceptor 11 in the opposite direction (clockwise in the figure), the first toner image that was previously displayed can be displayed again on the display section 15. There is no need to particularly form a new image. Further, the moving speed of the photoreceptor 11 can be set arbitrarily since image formation is not performed, and it is also possible to set the moving speed to several times the normal speed using a transmission.

When the photoconductor is moved in the opposite direction, the toner image currently displayed on the display section passes through the opposing section of the developing device 5, so there is a risk that the image will be erased. In order to make it possible to display the image inside again, when the belt moves in the opposite direction, the developing device 5 is lowered by a predetermined amount by a combination of a drive means such as a plunger and a link mechanism, so that the developing device 5 is lowered by a predetermined amount when the developing device is already formed. Does it have any influence on the image?
Alternatively, it is desirable to start recording again from the position where the belt was returned.

Another method for guiding the previously displayed image to the display section is to lower the developing device 5 and move it to a position where it does not affect all toner images on the photoreceptor, and then The belt may be rotated by a predetermined amount in the forward rotation direction (counterclockwise in the figure). This has the advantage that the driving direction of the belt only needs to be set in one direction.

Next, a driving example of the apparatus shown in FIG. 1 will be described with reference to the drawings.

FIG. 4 shows a drive mechanism for the photoreceptor 11, in which the photoreceptor 11 is driven by the rotation of the DC motor 20 being transmitted to the drive roller 17 through gears. Furthermore, since this DC motor rotates reversibly,
The drive roller 17 is rotated either clockwise or counterclockwise depending on the direction of the applied voltage. On the other hand, this
The DC motor 20 also drives an encoder 21, and since this encoder 21 is decelerated by a gear in the middle, one revolution corresponds to one image on the display unit of the photoreceptor 1.
corresponds to the amount of movement. Therefore, by detecting the notch 21a of the encoder 21 with the photo interrupter 22, it is possible to detect the amount of movement of the photoreceptor relative to the image display section.

FIG. 5 shows a circuit diagram showing an example of driving and overall control of the DC motor.

In the figure, the host computer is included in the control circuit.
When a positive (+) pulse is sent from the HC, the DC motor 20 starts rotating and rotates the photoreceptor 1 in the counterclockwise direction in FIG. And photo interrupter 2
2 detects the notch 21a of the encoder 21, this photoreceptor temporarily stops. When a positive pulse is sent from the host computer HC, the solenoid for separating the developing device 12 from the photoreceptor, which will be described later, remains OFF and starts driving the motor 20a for rotating the magnetic roller of the developing device. . At the same time, a command signal from the host computer sends a signal to a laser modulator (not shown) to start image formation based on the above principle. A bias is applied to the sleeve 4 of the developing device at the same time as the developing motor rotates. The above solenoid is ON except when writing images.
The sleeve 4 is maintained in a spaced position relative to the photoreceptor 11. Note that once an image for one screen has been formed on the photoreceptor 11, the photoreceptor is stopped by a detection signal from a photo interrupter.

In the above circuit, the
When SW1 is turned ON, the DC motor 20 rotates in reverse, rotates by one image, and then stops. Also, keep pressing
If you keep it ON, it will reverse for the length of time you keep pressing it and then turn OFF.
At this point, the photoreceptor 11 stops. When SW2 is pressed to turn on, the DC motor 20 rotates forward, moves the photoreceptor counterclockwise in FIG. 1, and stops the photoreceptor 11 after one image. The transistor TR of the DC motor 20 is TR1 when rotating the DC motor in the forward direction.
When TR4 turns on and reverses, TR2 and TR3 turn on.
Turn on.

In the above device, when an image is not formed on the photoreceptor, that is, when the solenoid SN is turned ON, it is effective to move the photoreceptor quickly. This is done by selecting the voltage of the drive power supply section using the relay contact RS. That is, the rotation speed of the motor is controlled by the voltage applied to the DC motor.

FIG. 6 is an explanatory view showing the elevating mechanism of the developing device 12. In the figure, 23 is a container of the developing device, 24 is a support shaft that swingably supports the container 23, and 25 is a spring that supports the container 2.
3 to rotate counterclockwise about the shaft 24. A plunger 26 urges the container to rotate clockwise, thereby separating the sleeve 4 from the photoreceptor surface 11. This solenoid 26 corresponds to solenoid SN in FIG.

FIG. 7 is a diagram showing an embodiment of an image display device using a heat-sensitive recording method. Recording body 28
The camera is configured to record images.

This belt-shaped heat-sensitive recording body 28 is attached to the recording head 2.
In order to maintain the state of image recording according to 7 within the image display range, a planar heater 29 is installed inside the image display section 15.
are placed facing each other to keep the temperature at about 40℃. 30 is a cooling unit for erasing recorded images.

The feature of this embodiment is that the circumference of the endless belt-shaped heat-sensitive recording medium 28 is set to form at least one other recorded image in addition to the first recorded image displayed on the image display section 15. In order to maintain the recorded image of the guided image recording region outside the display area, a predetermined planar heater 31 is arranged as in the illustrated embodiment. As a result, the image is maintained even after the display ends, and by driving the belt in the opposite direction, the previously displayed image can be displayed.

Note that operations for redisplaying the previously displayed recorded image may be performed in the same manner as in the previous embodiment. That is, when maintaining the first image or another image by rotating the belt forward or backward, if necessary, the thermal recording head 27 and/or the cooling unit 30 can be moved from the surface of the thermal recording medium by a plunger, a solenoid, etc. They are separated by a link mechanism such as a drive means or a lever. In the figure, 32 is a drive roller of the recording body 28, 33, 34
indicates a guide roller. The configuration of the first embodiment may be applied to drive the recording body 28 in the forward and reverse directions.

Next, a method of forming an image on the photoreceptor or the like after the first image that has passed through the display section is returned to the display section and viewed visually will be described. In this case, if the second image formed upstream of the first image is in the middle, the second image will be re-formed from the beginning, and if the second image is completed, the second image will be re-formed. It is better not to form.
This is because the object of image formation is the belt.
This is because a high-quality image cannot be expected if the image is re-formed halfway due to the slippage and elasticity of the belt. Whether the formation of the second image is in progress or completed can be detected by comparing the position of the encoder and the image formation signal.

In the example shown in FIG. 5, when the host computer sends pulses to form an image, an operation confirmation signal is sent to the host computer. At this time, a signal is sent from the host computer to the laser modulator, but if the confirmation signal disappears before the signal corresponding to one screen has been sent, it can be seen that the image formation is in progress.

According to the present invention as described above, it is possible to display a high-density, large-capacity image with good resolution without using a large amount of memory, and it is possible to display an image once it has been displayed, as well as to display it again. In this case, by increasing the driving speed of the image-bearing pair, high-speed display can be performed, and its usefulness is great.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of an image display device employing an electrophotographic method to which the present invention is applied; FIGS. 2 and 3 are explanatory diagrams illustrating the image forming principle of the device shown in FIG. 1;
Figure 4 is a perspective view of the photoreceptor drive unit, and Figure 5 is the first
FIG. 6 is a circuit diagram showing a control mode of the apparatus, FIG. 6 is a cross-sectional view showing a mechanism for separating the developing unit from the photoreceptor, and FIG. 7 is a cross-sectional view of a main part of another image display device to which the present invention is applied. In the figure, 11 is a photoreceptor which is an image carrier;
2 is a developing device which is part of the forming means; 15 is a display section; 20 is a carrier driving means and is a motor for driving the photoreceptor; and 26 is a means for releasing the image forming means from contact with the image carrier. Showing plunger.

Claims (1)

[Claims] 1. In an image display device for visually viewing a visible image formed on an image carrier, a display section for visually viewing an image formed on a belt-shaped image carrier that moves inside a housing, and a display section for viewing a visible image formed on a belt-shaped image carrier that moves inside a housing; The belt-shaped image carrier has a length that is set to form two or more images to be viewed, a plurality of support members support the image carrier in an endlessly movable manner, and the image carrier is supported along the support members. a driving means for moving;
an image forming means for forming a visible image on the image carrier, and an operation of the image forming means on the carrier when the image of the image carrier that has already passed through the image display section is guided to the display section again; and when the image carrier has a first image that has passed through the display section and a second image related to the display section, after the first image is returned to the display section. The image display device is characterized in that if the second image has been formed, the second image is guided to the display section again, and when the second image is in the middle of being formed, the second image is guided to the display section after being re-formed by the image forming means. .