JP5151547B2 - Image rewriting control device and information display device - Google Patents

Description

  The present invention relates to a technique for rewriting an image in an information display device.

  An information display device using a memory display element such as an electrophoretic display element is known. Since the memory-type display element does not require refresh driving for holding the display, it has a display quality close to that of paper and is easy on the eyes. Taking advantage of these features, devices called electronic books or electronic papers have been developed that can be used to read relatively long documents.

  The image displayed on the electronic paper is rewritten according to a user instruction. For example, Patent Document 1 discloses a method of rewriting display contents in an electrophoretic display device. However, according to the method described in Patent Document 1, an afterimage may be generated on the display unit. As a technique for reducing afterimages, a technique described in Patent Document 2 is known. Patent Document 2 discloses applying a high-frequency voltage to a common electrode.

JP 2002-149115 A JP 2004-325489 A

  If a high frequency voltage is continuously applied to the common electrode as in Patent Document 2, the power consumption increases. On the other hand, the present invention provides a technique for suppressing the number of rewrite processes as needed while suppressing afterimages.

The present invention provides a rewriting process including a first erasing step for erasing first image data supplied to a display device having a plurality of pixels and a writing step for supplying second image data to the display device. Means for each of the plurality of pixels, measuring means for measuring a parameter relating to a time when a predetermined voltage is applied to the pixel, storage means for storing the parameter measured by the measuring means for each pixel, An image having control means for controlling the rewriting means so that the pixel corresponding to the parameter exceeding the threshold value is not subjected to the rewriting process when the parameter stored in the storage means exceeds the threshold value A rewrite control device is provided.
According to this image rewriting control device, the rewriting process is not performed on the pixel whose parameter related to the time during which the predetermined voltage is applied exceeds the threshold value.

In a preferred aspect, when the ratio of the pixels that are not subjected to the rewrite processing out of all the pixels included in the display device exceeds a threshold value, the control unit uses the period longer than the first erasing step. The rewriting unit may be controlled to perform a refresh process including a second erasing step of erasing the first image data from the display device.
According to this image rewrite control device, the refresh process is performed when the ratio of pixels for which the rewrite process is not performed exceeds a threshold value.

In another preferable aspect, when the number of times that the rewrite processing is not continuously performed for one pixel among all the pixels included in the display device exceeds a threshold value, the control unit performs the first erasing step. The rewriting unit may be controlled to perform a refresh process including a second erasing step of erasing the first image data from the display device using a longer period.
According to this image rewrite control device, when the number of times that the rewrite process is not continuously performed for a certain pixel exceeds a threshold value, the refresh process is performed.

In still another preferred aspect, the parameter may indicate the number of times the same gradation display is continuously performed in each pixel.
According to this image rewriting control device, the rewriting process is not performed on the pixels in which the number of continuous display of the same gradation exceeds the threshold value.

In still another preferred aspect, the parameter may indicate a time during which application of a voltage having the same polarity is continued in each pixel.
According to this image rewriting control device, the rewriting process is not performed for the pixels whose time during which application of the voltage of the same polarity has exceeded the threshold value.

In still another preferred aspect, the parameter may indicate a ratio at which a predetermined gradation is displayed with respect to a predetermined number of past displays in each pixel.
According to this image rewriting control device, the rewriting process is not performed for pixels whose ratio of displaying a predetermined gradation with respect to the past predetermined number of displays exceeds a threshold value.

In still another preferred aspect, the parameter may indicate a ratio of a time during which the predetermined voltage is applied to a voltage of the past predetermined time in each pixel.
According to this image rewriting control device, the rewriting process is not performed for pixels in which the ratio of the time during which the predetermined voltage is applied exceeds the threshold value in the past voltage application for a predetermined time.

The present invention also provides an information display device comprising any one of the above image rewrite control devices and the display device driven by the image rewrite control device.
According to this information display device, the rewriting process is not performed on the pixel whose parameter related to the time when the predetermined voltage is applied exceeds the threshold value.

1. Configuration FIG. 1 is a diagram showing a functional configuration of an information display apparatus 1 according to an embodiment of the present invention. The operation means 20 outputs a signal corresponding to a user operation. The interrupt processing unit 30 outputs an interrupt signal for instructing generation of an image to be displayed to the image generation unit 40 in accordance with the signal output from the operation unit 20. The image generation unit 40 generates image data indicating an image (page image) to be displayed in response to the interrupt signal, and stores the generated image data in the storage unit 50. Further, the image generation means 40 outputs a command for causing the display device 60 to display an image to the image rewrite control device 10. Upon receiving this command, the image rewrite control device 10 reads the image data from the storage unit 50 and causes the display device 60 to display an image according to the image data. The display device 60 has a plurality of pixels.

  The image rewriting control device 10 is a device that controls image rewriting on the display device 60, that is, a device that supplies image data to the display device 60 and drives the display device 60. The image rewrite control device 10 has the following configuration in detail. The rewriting means 11 performs a rewriting process for rewriting the image displayed on the display device 60 from the first image to the second image. The rewriting process includes a first erasing step of erasing data indicating the first image supplied to the display device 60 (hereinafter referred to as “first image data”) in a predetermined period, and a second image of the display device 60. And a writing step for supplying data (hereinafter referred to as “second image data”). The measuring means 13 measures a parameter related to the time at which a predetermined voltage is applied to each of the plurality of pixels. The storage unit 14 stores the parameter measured by the measurement unit 13 for each pixel. When the parameter stored in the storage unit 14 exceeds the threshold value, the control unit 12 controls the rewriting unit 11 so that the pixel corresponding to the parameter exceeding the threshold value is not rewritten.

  FIG. 2 is a diagram illustrating a hardware configuration of the information display device 1. In this example, the information display device 1 is electronic paper. A CPU (Central Processing Unit) 101 is a control device that controls components of the information display device 1. A ROM (Read Only Memory) 102 is a non-volatile storage device that stores programs and data necessary for starting the information display device 1. A RAM (Random Access Memory) 103 is a storage device that functions as a work area when the CPU 101 executes a program. A video random access memory (VRAM) 104 is a storage device that stores data indicating an image to be displayed on the display body 107 (hereinafter referred to as “main image”). The VRAM 104 has a main image storage area, and the main image is stored in the storage area. An I / O (Input / Output) 105 is an interface for managing input / output of data and signals. A UI (User Interface) button group 106 is a device that outputs a signal according to a user's operation, for example, a button (rewrite button, page feed button, determination button, etc.), keypad, wheel, lever, touch panel, pen. This is an input device including an operator such as a device. The auxiliary storage device 115 is a storage device that stores data that can be displayed on the display unit 107. The UI button group 106 is connected to the I / O 105, and a signal output from the UI button group 106 is input to the CPU 101 via the I / O 105. The timer T is a time measuring device that outputs a signal indicating time.

  The display body 107 is an electrophoretic display (hereinafter referred to as “EPD”) having an electrophoretic display element which is a memory display element. The display control unit 108 is a device that outputs a signal for performing drawing control of the display body 107. Hereinafter, the display body 107 and the display control unit 108 are collectively referred to as “main display” as necessary. The power on / off circuit 111 is a circuit for supplying and stopping power supply to elements such as the display control unit 108 and the CPU 101. Hereinafter, supplying power to a certain component is referred to as “turning on the power”, and stopping supplying power is referred to as “turning off the power”. The power control unit 112 is a device that performs power management of the information display device 1. Specifically, the power control unit 112 controls the power on / off circuit 111 to turn on or off the power of the display control unit 108 and the CPU 101. Further, the power control unit 112 monitors the remaining amount of the battery 113. The battery 113 supplies power to the components of the information display device 1 such as the display control unit 108, the CPU 101, and the RAM 103. The bus 114 is a transmission path used for signal transmission between components.

  The fingerprint sensor 117 is a device that electrostatically reads a user's fingerprint and outputs a signal indicating an image of the read fingerprint. The fingerprint sensor 117 is connected to the I / O 105, and a signal output from the fingerprint sensor 117 is input to the CPU 101 via the I / O 105.

  The ROM 102 stores a control program for performing processing described below. The function shown in FIG. 1 is implemented in the information display device 1 by the CPU 101 executing this control program. Here, the display control unit 108 is an example of the image rewrite control device 10, the UI button group 106 and the fingerprint sensor 117 are examples of the operation unit 20, and the CPU 101 is an example of the interrupt processing unit 30 and the image generation unit 40. The VRAM 104 is an example of the storage unit 50, and the display body 107 is an example of the display device 60.

  FIG. 3 is a diagram illustrating an appearance of the information display device 1. The information display device 1 includes a display surface of the display body 107 and a UI button group 106 on the front surface of the housing. The UI button group 106 includes a page feed button 106b.

2. Operation FIG. 4 is a flowchart showing the operation of the information display apparatus 1. The flow in FIG. 4 is started when, for example, the user instructs display of a document. This document is composed of a plurality of pages of images.

In step S100, the CPU 101 initializes a variable (display image number n) indicating a page to be displayed on the display body 107 in the document as n = 1.
In step S110, the CPU 101 controls the display control unit 108 to update the pixel state. The pixel state refers to a parameter related to the time for which a predetermined voltage is applied to each of a plurality of pixels included in the display body 107. Here, a case will be described as an example where the parameter indicates the number of times that display of the same gradation is continued in each pixel.

  FIG. 5 is a diagram illustrating a pixel state. Here, a case where the display body 107 has a plurality of pixels arranged in a matrix of horizontal 1000 pixels × vertical 2000 pixels will be described as an example. An xy coordinate system is used to specify the position of each pixel. For example, the third pixel from the left and the fourth pixel from the top are specified as (x, y) = (2, 3). Now, the parameter value of each pixel is represented by P. When the parameter value is positive, the gradation value “black” is continuous (repeated), and when the parameter value is negative, “white” is continuous. Show. When the parameter value is zero, it indicates that the same gradation value is not continuous. In the example of FIG. 5, P (2,3) =-4. This indicates that the gradation “white” is continued four times in this pixel.

  The display control unit 108 has a memory (storage means 14) therein, and stores a pixel state as shown in FIG. In the initial state, the parameter values of all pixels are zero. The display control unit 108 reads from the VRAM 104 image data (hereinafter referred to as “nth image data”) of a page (nth page) to be displayed next. The display control unit 108 updates the pixel state according to the read image data. This process corresponds to a process (measuring means 13) for measuring a parameter relating to a time when a predetermined voltage is applied to the pixels included in the small section.

  A description will be given with reference to FIG. 4 again. In step S120, the display control unit 108 determines whether there is a pixel whose pixel state satisfies the non-driving condition. The “driven condition” is a condition that is used to determine a pixel that is not driven, and that indicates that the time during which a predetermined voltage is applied to the pixel has exceeded a threshold value. In this example, the upper limit (threshold value) of the number of repetitions is determined in advance (for example, 4 times), and it is used as a condition that the number of repetitions exceeds this upper limit. That is, when | P (x, y) |> 4 is satisfied, the pixel (x, y) satisfies the non-driving condition. If it is determined that the non-driving condition is satisfied (S120: YES), the display control unit 108 proceeds to step S130. When it is determined that the non-driving condition is not satisfied (S120: NO), the display control unit 108 moves the process to step S150.

In step S130, the display control unit 108 determines a pixel to be driven. That is, the display control unit 108 determines not to drive the pixels that satisfy the non-driving condition and to drive other pixels.
In step S140, the display control unit 108 sets pixels to be driven. The display control unit 108 includes a register that stores a flag used to distinguish between a pixel to be driven and a pixel that is not to be driven, and the flag is rewritten according to the determination in step S130.
In step S150, the display control unit 108 determines to drive all the pixels.

  In step S160, the display control unit 108 controls the display body 107 so as to display the n-th page image. That is, the display control unit 108 supplies the nth image data to the display body 107 and writes the data to each pixel. At this time, the display control unit 108 controls the display body 107 so as not to write data to the pixel indicated not to be driven by the flag. Although data corresponding to the difference between the common electrode and the pixel electrode is written in each pixel in the display body 107, the display control unit 108 applies a voltage to the pixel electrode so that a potential difference from the common electrode does not occur for a pixel that is not driven. Apply.

  In step S170, the CPU 101 determines whether an interrupt has occurred. Here, “interrupt” refers to an instruction to update an image to be displayed (page turning), that is, an instruction to generate an image to be newly displayed, or an instruction to turn off the power. In this example, the page turning interruption is an event that the page feed button 106b of the UI button group 106 is pressed. The power-off interrupt is an event that a power button (not shown) of the UI button group 106 is pressed or an event that a predetermined time has elapsed since the previous rewriting. If any other control is operated, it is processed here as if there was no interruption. If there is no interrupt (S170: none), the CPU 101 waits until an interrupt occurs. If a page turning interrupt has occurred (S170: page turning), the CPU 101 proceeds to step S180. When a power-off interrupt occurs (S170: power off), the CPU 101 ends the flow of FIG.

  In step S180, the CPU 101 updates the display image number n as n = n + 1. When the display image number n is updated, the CPU 101 shifts the process to step S110 again.

  6 and 7 are diagrams illustrating the first image and the second image, respectively. 8 and 9 are diagrams illustrating pixel states corresponding to the first image and the second image, respectively. Hereinafter, the change of the pixel state and determination of the pixel that is not driven will be described using these examples. In these drawings, only a region of 6 pixels × 6 pixels is shown for simplicity of explanation.

  FIG. 8 is a diagram illustrating a pixel state at the time when the writing of the first image is completed. At this time, no pixel parameter exceeds the threshold value (Th = 4). When the rewriting to the second image is instructed here, the parameter value is set to 1 for a pixel whose gradation value is black in both the first image and the second image, for example, the pixel (2, 1). Is added. For both the first image and the second image, 1 is subtracted from the parameter value for a pixel whose gradation value is white, for example, pixel (0, 0). For a pixel having a different gradation value between the first image and the second image, for example, the pixel (1, 0), the parameter value is set to zero. FIG. 9 shows the pixel state updated in this way. In the example of FIG. 9, since the parameters of the pixel (2, 1) and the pixel (2, 5) exceed the threshold value, these pixels are not driven. That is, data is not written to these pixels.

  As described above, according to the present embodiment, when the time during which a predetermined voltage is applied to a pixel exceeds the threshold value, more specifically, the number of times that the same gradation display is continued is the threshold value. If it exceeds, the pixel is not driven. In a memory-type display device such as an EPD, an afterimage may occur when data with the same gradation is continuously written. Therefore, data with the same gradation is continuously written as in the present embodiment. By preventing, afterimages are reduced.

3. Other Embodiments The present invention is not limited to the above-described embodiments, and various modifications can be made. Hereinafter, some modifications will be described. In the description of the modification, common reference symbols are used for elements that are common to the embodiment. Two or more of the modifications described below may be used in combination.

3-1. Modification 1
The rewriting means 11 may perform a refresh process. The “refresh process” is a rewrite process including a second erase step for erasing the first image from the display device 60 using a period longer than the first erase step (that is, taking a long time). Say. In this case, when the ratio of the pixels that are not rewritten (that is, the pixels that are not driven) out of all the pixels included in the display device 60 exceeds the threshold value, the control unit 12 When rewriting is instructed, the rewriting means 11 is controlled so that refresh processing is performed before writing image data to be rewritten. By using the refresh process, the afterimage is more effectively reduced. In addition, an increase in processing load or power consumption is suppressed by limiting the timing of performing the refresh process to a case where the ratio of pixels that are not driven exceeds a threshold value.

3-2. Modification 2
The refresh process may be performed when the number of times that the rewrite process is not continuously performed for one pixel among all the pixels included in the display device 60 exceeds a threshold value. In the above-described embodiment, a pixel whose parameter once exceeds a threshold value is not driven until data having a different gradation value is written, that is, rewriting processing is not performed. However, if the image is not rewritten for a long period of time, there is a case where the image quality is lowered such as a reduction in contrast, which is intended to prevent this.

3-3. Modification 3
Parameters used as pixel information are not limited to those described in the above embodiment. For example, the parameter may indicate a time during which application of a predetermined voltage (a voltage corresponding to the gradation value “black” or a voltage corresponding to the gradation value “white”) continues in each pixel. In this case, the threshold value used in the non-driving condition indicates the upper limit of time.

3-4. Modification 4
In another example, the parameter may indicate a ratio at which a predetermined gradation is displayed with respect to a predetermined number of past displays in each pixel. For example, the parameter indicates the ratio of black displayed in the past 10 displays. When P = 0.8, it indicates that 8 out of the past 10 displays have the gradation value “black”. In the case of P = 0.2, it indicates that 2 times of the display of the past 10 times were the gradation value “black”, that is, 8 times was “white”. In this case, the threshold value used in non-driving indicates the limit of gradation deviation allowed in the past 10 displays. For example, when the upper limit value of gradation bias is set to 8 times, the threshold value used in the non-driving condition is 0.8 as the upper limit value and 0.2 as the lower limit value.

3-5. Modification 5
In yet another example, the parameter is a predetermined voltage (a voltage corresponding to the gradation value “black” or a voltage corresponding to the gradation value “white”) applied to each pixel in the past predetermined time. It may indicate the percentage of time. In this case, the threshold value used in the non-driving condition indicates the upper limit of the time ratio.

3-6. Modification 6
In the second modification, the refresh process is performed for all the pixels of the display device 60. However, the refresh process may be performed only for a part of a region including pixels whose parameters exceed the threshold among the pixels of the display device 60.

3-7. Modification 7
The details of the refresh process may be anything. For example, the refresh process may be such that the step of writing data for making all pixels black is repeated a predetermined number of times, and then the step of writing data for making all pixels white is repeated a predetermined number of times. Alternatively, the refresh process may alternately repeat a step of writing data for making all pixels black and a step of writing data for making all pixels white by a predetermined number of times. Further alternatively, the refresh process may include only one of a step of writing data for making all pixels black and a step of writing data for making all pixels white. Instead of writing data for making all pixels black or writing data for making all pixels white, a step of writing a reverse image of the currently displayed image may be used. Further, a step of making a part of the screen black or white instead of making all pixels black or white may be used.

3-8. Modification 8
The functional configurations of the information display device 1 and the image rewrite control device 10 are not limited to those shown in FIG. The image rewrite control device 10 may have the functions described as those that the image rewrite control device 10 does not have, such as the interrupt processing unit 30 and the image generation unit 40. Further, the image rewrite control device 10 may not have a part of the functions described as the functions of the image rewrite control device 10.

  Further, the correspondence between the functional configuration and the hardware configuration is not limited to that described in the above embodiment. For example, in the above-described embodiment, the CPU 101 has functions as the interrupt processing unit 30 and the image generation unit 40. However, some or all of these functions may be realized by hardware elements other than the CPU 101. For example, an interrupt monitoring circuit having a function as the interrupt processing unit 30 may be separately provided. Alternatively, in another example, a device other than the display control unit 108, for example, the CPU 101 may have a function as the measurement unit 13. In this case, an aggregate of the CPU 101 and the display control unit 108 functions as the image rewrite control device 10. Furthermore, a device other than the display control unit 108 may have a function as the storage unit 14.

3-9. Modification 9
In the above-described embodiment, when the pixel state is updated, the parameter value is updated to zero for the pixels having different gradation values in the first image and the second image. However, the parameter update method is not limited to this. For example, if the tone value of the second image is white for a pixel with P = 4, the parameter value is set according to the tone value of the second image, such as P = 4-1 = 3. May be increased or decreased. According to this example, if the gradation value of the second image is black for a pixel with P = −3, P = −3 + 1 = −2.

3-10. Other Modifications The hardware configuration of the information display device 1 is not limited to that shown in FIG. An apparatus having any hardware configuration may be used as long as the necessary functional configuration can be realized. In the above-described embodiment, the example in which the information display device 1 is electronic paper has been described. However, the information display device 1 may be a device other than electronic paper.

  In the above-described embodiment, the program executed by the CPU 101 includes a magnetic recording medium (magnetic tape, magnetic disk (HDD (Hard Disk Drive), FD (Flexible Disk), etc.)), and optical recording medium (optical disk (CD (Compact Disk)). , DVD (Digital Versatile Disk), etc.), magneto-optical recording medium, semiconductor memory (flash ROM, etc.) and the like. The program may be downloaded via a network such as the Internet.

It is a figure which shows the function structure of the information display apparatus 1 which concerns on one Embodiment. It is a figure which shows the hardware constitutions of the information display apparatus. 1 is a diagram illustrating an appearance of an information display device 1. FIG. 3 is a flowchart showing an operation of the information display device 1. It is a figure which illustrates a pixel state. It is a figure which illustrates the 1st picture. It is a figure which illustrates the 2nd picture. It is a figure which illustrates the pixel state corresponding to a 1st image. It is a figure which illustrates the pixel state corresponding to a 2nd image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Information display apparatus, 10 ... Image rewriting control apparatus, 11 ... Rewriting means, 12 ... Control means, 13 ... Measuring means, 14 ... Memory | storage means, 15 ... Calculation means, 20 ... Operation means, 30 ... Interrupt processing means, 40 ... Image generation means, 50 ... Storage means, 60 ... Display device, 101 ... CPU, 102 ... ROM, 103 ... RAM, 104 ... VRAM, 105 ... I / O, 106 ... UI button group, 107 ... Display body, 108 ... Display control unit 111 ... Power on / off circuit, 112 ... Power control unit, 113 ... Battery, 114 ... Bus, 115 ... Auxiliary storage device, 117 ... Fingerprint sensor

Claims (7)

A first erasing step for refreshing a display of a display device on which an image according to first image data supplied to a display device having a plurality of pixels configured by a memory display element is displayed, and the display device Rewriting means for performing a rewriting process including a writing step of supplying second image data to
Measuring means for measuring, for each of the plurality of pixels, a parameter relating to a time during which a predetermined voltage is applied to the pixel;
Storage means for storing the parameters measured by the measurement means for each pixel;
And a control unit that controls the rewriting unit so that the pixel corresponding to the parameter exceeding the threshold value is not subjected to the rewriting process when the parameter stored in the storage unit exceeds the threshold value. And
When the ratio of the pixels that are not subjected to the rewrite processing among all the pixels included in the display device exceeds a threshold value, the control unit takes a longer period than the first erasing step, and The rewriting means is controlled to perform a refresh process including a second erasing step for refreshing the display of the display device on which the image is displayed according to the image data.
An image rewriting control device characterized by that . When the number of times that the rewrite processing is not continuously performed for one pixel among all the pixels included in the display device exceeds a threshold value, the control unit takes a longer period than the first erasing step. The image rewriting control device according to claim 1, wherein the rewriting unit is controlled to perform a refresh process including a second erasing step of erasing the first image data from the display device. The parameter image rewriting control apparatus according to claim 1 or 2, characterized in that indicating the number of times display of the same gradation is continuous at each pixel. The parameter image rewriting control apparatus according to claim 1 or 2, characterized in that indicating the time the application of the same polarity voltage is continuous at each pixel. The parameter image rewriting control apparatus according to claim 1 or 2, characterized in that it presents a ratio of the predetermined gradation on the display of the past predetermined number of times in each pixel is displayed. The parameter image rewriting control apparatus according to claim 1 or 2, characterized in that indicating the percentage of the time predetermined voltage to the voltage application in the past for a predetermined time in each pixel is applied. An image rewriting control device according to any one of claims 1 to 6 ,
An information display device comprising: the display device driven by the image rewrite control device.

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