JP2004233477A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which is free of a decrease in luminance during single-gradation display while displaying a natural image with proper gradation characteristics during multi-gradation display in a device which displays an image on the same LED display panel with multiple gradations or a single gradation. <P>SOLUTION: Multi-gradation or single-gradation display data to be displayed at a display part by light emission and a plurality of display conditions thereof are stored and when display data read out according to display conditions are multi-gradation display data, a frame in which light is emitted for a light emission period corresponding to 100% luminance and a frame with a light emission period corresponding to luminance less than 100% luminance are combined to constitute one picture; and nonlinearity is given between an input signal concerned with luminance of light emission display and light emission luminance of the LED display to make gamma correction. When the read-out display data are single-gradation display data consisting of only a turn-on signal and a turn-off signal, one picture is constituted with only a frame of a light emission period corresponding to 100% luminance to perform display wherein light emission luminance is given priority. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a device for displaying arbitrary characters, figures, symbols, patterns, and the like by selectively emitting light from light-emitting elements arranged in a dot matrix, and in particular, to a multi-gradation or single-level display on the same LED display panel. The present invention relates to a display device that displays images in tones.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known an apparatus that emits and displays arbitrary display content by arranging light emitting elements such as LEDs in a dot matrix on a printed circuit board and selectively driving the light emitting elements to emit light. Display contents include contents consisting of character data such as characters and symbols to which standard codes are assigned, and image contents consisting of image data represented by a collection of dot information. Or text news.
[0003]
When displaying an image including a shadow such as a video signal or a photograph on such a display device, a multi-level display is performed by a dynamic display method in which the light emission amount of the LEDs arranged in a dot matrix is controlled in a plurality of steps in dot units. . For example, in the case of displaying 16 gradations in a single color, one screen displayed on a dot matrix is composed of 16 frames as shown in FIG. 6, and in which of the 16 frames the lighting signal is included for each LED. Thus, gradation is expressed by 16 levels of brightness. According to this multi-gradation display, a display including gradation can be performed even in a single-color display, so that a higher expressive power can be obtained as compared with a single-gradation display using only lighting / extinguishing.
[0004]
[Problems to be solved by the invention]
Since the multi-gradation display displays one screen by superimposing a number of frames corresponding to the number of gradations, an address period for reading data for blinking in each frame is required. That is, in displaying one screen, an address period not related to the light emission of the light emitting element is required for the number of frames, and the light emission period is shortened accordingly, and the maximum light emission luminance is reduced as compared with the single gradation display. There's a problem.
[0005]
In addition, since the characteristics of the luminance and the signal input to the LED display show linearity, a sufficient contrast cannot be obtained if an image including a shadow is directly displayed as a gray scale. Therefore, gamma correction according to the characteristics of the LED is performed. There is a need. By performing the gamma correction processing, the characteristic of the input signal-LED emission luminance related to luminance shows a non-linearity, and is recognized as a natural-looking image by human eyes. However, by performing the gamma correction, several frames among the frames to be superimposed in a number corresponding to the number of gradations are driven to emit light with a luminance that does not reach 100%, and the gamma correction is not performed when the frame is recognized as one screen. There is also a problem that the maximum brightness is lower than in the case.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a multi-gradation display or a multi-gradation display on a single LED display panel. In this case, it is an object of the present invention to provide a display device that does not cause a decrease in luminance when displaying a single tone while displaying an image with a natural appearance with appropriate tone characteristics.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention provides a display capable of emitting and displaying characters, pictograms, and the like in multiple tones and single tones by selectively driving a plurality of light emitting elements arranged on a printed board to blink. A display unit in which a plurality of light emitting elements are arranged in a dot matrix; a storage unit for storing a plurality of multi-gradation or single-gradation display data to be displayed on the display unit and display conditions thereof; A storage area corresponding to the dot matrix formed in the display area, a display memory for expanding the display data read based on the content of the storage section in the storage area, and a display data expanded to the display memory, By displaying one screen in gray scale on the display unit in the frame of, and by driving a predetermined frame of a plurality of frames constituting one screen in a light emission period different from that of the other frames, the gamma is increased. A display drive unit for applying a positive value, the display drive unit having a function of changing a light emission period of a frame, and displaying one screen when display data read from the storage unit is multi-gradation display data. In this case, display driving is performed including frames having different light emission periods, and when data read from the storage unit is display data of a single gradation, display driving is performed in the same frame with the same light emission period in displaying one screen. A display device characterized by the following is proposed.
[0008]
Further, in a display device in which a plurality of light emitting elements arranged on a printed circuit board are selectively blinked and driven to display characters, pictograms, and the like in multiple gradations and single gradations, a plurality of light emitting elements are arranged in a dot matrix. Display unit, a storage unit for storing a plurality of grayscale or single-tone display data to be displayed on the display unit and a plurality of display conditions, and a storage area corresponding to a dot matrix formed in the display unit A display memory that expands display data read out based on the contents of the storage unit in the storage area, and a display memory that expands display data in the display memory. When displaying a screen and displaying one screen with a plurality of frames, gamma correction is performed by driving a predetermined frame of the plurality of frames with a different light emission period from the other frames. A display drive unit having a function of changing the number of frames constituting one screen. When the display data read from the storage unit is multi-gradation display data, one screen is displayed. When displaying, the display is driven by a plurality of frames including frames having different light emission periods, and when the display data read from the storage unit is display data of a single gradation, the display is performed with a minimum number of frames for displaying one screen. A display device characterized by being driven is proposed.
[0009]
[Action]
According to the above proposal, a plurality of multi-gradation or single-gradation display data to be displayed on a display unit and a plurality of display conditions are stored, and when the display data read according to the display conditions is multi-gradation display data, One screen is configured by combining a frame that emits light during a light emission period corresponding to 100% luminance and a frame that emits light during a light emission period that does not reach 100%, and an input signal related to luminance during light emission display and an LED. Gamma correction is performed by giving a non-linear characteristic to the light emission luminance of the display. When the read-out display data is display data of a single gradation consisting only of a lighting signal (brightness 100%) and a light-off signal (brightness 0%), one screen is formed only by a frame of a light emission period corresponding to 100% brightness. The display is configured to give priority to the light emission luminance.
[0010]
When the display data read according to the display condition is multi-gradation display data, one frame is a combination of a frame that emits light at a luminance of 100% and a frame that emits light at a luminance that does not reach 100%. A screen is formed, and when the read display data is display data of a single gradation, one screen is formed by continuously displaying a minimum number of frames, for example, one frame.
[0011]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the entire configuration of the display device according to the embodiment of the present invention. Reference numeral 1 denotes a display unit, which forms a dot matrix composed of a total of 256 LEDs by arranging 16 × 16 orange LEDs on a printed circuit board to constitute an LED display capable of emitting a single orange color. Reference numeral 2 denotes a common driver, which scans a row direction line of LEDs arranged in a dot matrix on the display unit 1 in a column direction. Reference numeral 3 denotes a segment driver, which applies LED blinking data to a row-direction line scanned and driven by the common driver 2. Reference numeral 4 denotes a storage unit, which is a ROM 4a in which an operation program relating to the movement of the entire display device is stored; a font ROM 4b, in which characters replaced by codes are stored in a dot pattern; A display content data storage unit 4c for storing a plurality of image contents composed of image data represented by a collection of information, and a data storage unit for storing display schedule data for giving a display timing of display content and various setting data relating to the display device 4d.
[0012]
The display content stored in the display content data storage unit 4c is roughly classified into two types, namely, text / text content and image content composed of image data. None) and content displayed with multiple gradations (with gradations). In the present embodiment, display with 4-bit gray scale is enabled, and both single-gray scale content and multi-gray scale content have 4-bit luminance information. The single-tone content is content having dot information consisting of only two types of brightness, the highest brightness and the lowest brightness (lights out), out of 16 levels of brightness represented by 4 bits. A flag representing "toneless" is provided. On the other hand, multi-tone content is content having 16 types of luminance information as dot information.
[0013]
Reference numeral 5 denotes a CPU that performs a display processing procedure in accordance with programs and data stored in the storage unit 4. Reference numeral 6 denotes a VRAM serving as a display memory, which corresponds to the dot matrix configuration of the display unit 1. The VRAM 6 uses a 16 × 16 dot matrix corresponding to one character data as a reference to convert dot data for a plurality of characters into luminance. It has a storage area that can be expanded as data. The display content data is data comprising an array of codes representing characters and file names given to the image data, and converted into dot information corresponding to the LED array of the display unit 1 for display on the display unit 1. The dot pattern read from the font ROM 4b or the like is developed in the storage area of the VRAM 6. At this time, 4 bits are allocated to one dot of the display unit 1 in the storage area of the VRAM 6, and 4-bit luminance information relating to gradation display is stored, and then output as display data. If a flag indicating “no gradation” is given to display content developed as a dot pattern in the VRAM, information on the presence or absence of the flag is stored in a predetermined area of the VRAM.
[0014]
Reference numeral 7 denotes a programmable logic device (hereinafter referred to as a PLD) as a display drive unit, which receives display data output from the VRAM 6 as luminance information, and performs gamma correction if the received data is multi-gradation display data. It outputs LED blinking data to the driver 3 and outputs a scan drive signal to the common driver 2 to drive the display unit 1 for dynamic display. If the display data output from the VRAM 6 is provided with the flag information of “no gradation”, the signal is output to the segment driver 3 and the common driver 2 without performing the gamma correction processing. Reference numeral 8 denotes a real-time clock IC which receives a request from the CPU at an arbitrary timing and outputs the time, year, date, and day of the week when the request is received.
[0015]
Next, gamma correction when displaying multi-tone content according to the present embodiment will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the relationship between the screen brightness and the lighting ratio. Luminance levels 0 to 15 represent 16 levels of luminance, and each luminance level basically depends on how many frames for turning on the LED out of 16 frames forming one screen. The luminance level 0 indicates a light-off state in which no light is emitted 0 times out of 16 frames, that is, the screen is not emitted at all. The luminance level 15 indicates a state where the screen in which the LED is turned on in all 16 frames is the brightest. The simplest way to obtain 16 levels of brightness can be realized by changing the frame in which the LED is turned on from 0 to 15 times in displaying one screen. In order to give a gamma characteristic to this, the following is done. First, 16 frames for displaying one screen are a frame that emits light only at a brightness of 25% once, a frame that emits light only at a brightness of 50% once, and a frame that emits light at a brightness of 100%. Is composed of a total of 16 frames, ie, 14 times, and 16 levels of brightness are realized by appropriately combining these three types of brightness frames. Thereby, the lighting ratio of one screen is changed from 0% [0 / ((0.25 × 1) + (0.5 × 1) + (1 × 14) = 14.75)] to 100% (14.75 / 14). .75) can be assigned a non-linearity when assigned to 16 levels.
[0016]
Specifically, as shown in FIG. 2, at a luminance level 1, a frame that emits light at a brightness of 25% out of 16 frames is regarded as one time, and a lighting ratio of 0.25 / 14.75 = 1.7% and a luminance level of 2 The lighting ratio is 0.5 / 14.75 = 3.4%, with one frame emitting light at 50% brightness out of 16 frames, and 25% and 50% of 16 frames are each one time at brightness level 3. 0.75 / 14.75 = 5.1% when lighted. Combining three types of brightness frames as shown in the figure, showing a gradual change in luminance in a low luminance level area and a steep change in a high luminance level area. Is given.
[0017]
By the way, as described above, the present embodiment has a function of performing single-tone display without performing gamma correction when displaying single-tone content having flag information of “no tone”. The relationship between the brightness of the screen and the lighting ratio when performing the single gradation display will be described with reference to FIG. Of the two types of luminance information included in the single-tone content, “light-off” is driven to emit light with the luminance level 0 and “light-on” is driven with the luminance level 1 to emit light. The luminance level 1 corresponds to the luminance level 15 at the time of multi-gradation display, and emits light at the highest luminance. However, at the time of single-gradation display, all of the 16 frames constituting one screen have 100% brightness. To emit light. As a result, the ratio of the light emission period to 16 frames is 14.75 in the case of multi-gradation display, but is improved to 16.00 (1 × 16), and higher luminance and excellent contrast can be obtained. it can.
[0018]
Next, the operation of the main part of the embodiment of the present invention will be described based on the flowchart of FIG. According to the display schedule data stored in the data storage unit 4d, the display content corresponding to the display timing is read from the display content data storage unit 4c (S1). Next, the read flag information of the display content is confirmed (S2), and it is determined whether the content is a single tone content having a flag of "no tone" or a multi-tone content. If the content is a multi-tone content, dot information corresponding to the LED array of the display unit 1 is developed in the VRAM 6 (S3). The dot information developed here is 16-step luminance information as described above, and 4-bit luminance data corresponding to each LED of the display unit is written in the VRAM. Next, the data expanded in the VRAM is output to the PLD 7 (S4). The PLD 7 confirms that the flag information of “no gradation” is not written in a predetermined area of the predetermined VRAM, performs gamma correction on the output data, and outputs LED blinking data to the segment driver 3. At the same time, a scan drive signal is output to the common driver 2 and a 16-stage multi-gradation display is performed on the display unit 1 (S5).
[0019]
If the content read out from the display content data storage unit 4c is given flag information of "no gradation" in S2, the flag information is written to a predetermined storage area in the VRAM 6 (S6) and read out. The dot information is developed in the VRAM 6 with the content as a single tone content (S7). The data to be developed here is luminance information of two stages, and 4-bit data representing ON or OFF for each LED of the display unit is written into the VRAM, and the data developed as a dot pattern for one screen is output to the PLD 7 ( S8). The PLD 7 confirms that flag information of “no gradation” exists in a predetermined area of the predetermined VRAM, and does not perform gamma correction on the output data (all 16 frames constituting one screen have a brightness of 100%). %) (Single light emission), a single gradation display is performed on the display unit 1 via the common driver 2 and the segment driver 3 (S9).
[0020]
Next, another embodiment of the present invention will be described with reference to FIG. The difference from the above-described embodiment lies in the LED driving method for displaying a single tone content in a single tone without gamma correction. FIG. 4 is an explanatory diagram showing the relationship between the luminance level and the LED drive pulse when performing the single gradation display. When the lighting is performed at the luminance level 1, one frame is continuously divided without being divided into 16 frames. To display one screen. With this driving method, only one address period for reading LED blinking data is required for displaying one screen, and the light emission period is greatly increased, so that high light emission luminance can be obtained. When displaying multi-gradation contents, one screen is displayed in 16 frames as in the above embodiment, and this driving method is used only when displaying single-gradation contents having flag information of "no gradation". It is good to switch with.
[0021]
Although the present embodiment is configured as described above, various embodiments are possible within the scope of the claims without being limited to the above embodiment. For example, in the embodiment, the flag information of “no gradation” given to the display content is stored in a predetermined area of the VRAM, and the PLD checks the flag information in the VRAM and switches to the single gradation display. However, when the read display content includes the flag information of "no gradation", the CPU may transmit the flag information directly to the PLD side via the port without passing through the VRAM. Further, in another embodiment, an example has been described in which one screen is displayed in one frame when displaying single tone content having flag information of “no tone”, but according to the rewrite cycle of one screen. Alternatively, one screen may be displayed in about two to three frames to prevent the screen from flickering.
[0022]
【The invention's effect】
As described above, according to the present invention, the presence or absence of gamma correction can be switched and displayed according to the type of content read from the storage unit according to the display schedule. Gamma processing is performed on multi-level content having multiple levels of luminance information, and multi-level display is performed with high expressive power while ensuring contrast between the multiple levels of luminance. For the gradation content, the emission luminance is prioritized without performing gamma correction, and high visibility can be secured.
[0023]
Further, when the content read from the storage unit is a single tone content, the driving method is switched from a light emission driving method in which one frame is displayed by switching a plurality of frames to a driving method in which a minimum number of frames, for example, one frame are continuously displayed. The address period of the LED blinking data required for the number of frames becomes one (minimum). Therefore, the light emission period of the LED is lengthened by the reduced address period, and the light emission luminance can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a display device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing the relationship between the brightness of the display screen and the lighting ratio during multi-gradation display.
FIG. 3 is an explanatory diagram showing a relationship between brightness of a display screen and a lighting ratio in a single gradation display.
FIG. 4 is an explanatory diagram showing a relationship between a luminance level and an LED drive pulse when performing a single gradation display according to another embodiment.
FIG. 5 is a flowchart showing a display operation according to the embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a method of multi-tone display.
DESCRIPTION OF SYMBOLS 1 Display part 2 Common driver 3 Segment driver 4 Storage part 4a ROM
4b font ROM
4c display content data storage unit 4d data storage unit 5 CPU
6. VRAM as display memory
7 PLD (Programmable Logic Device) as Display Driver

Claims (2)

In a display device capable of emitting and displaying characters and pictograms in multiple gradations and single gradations by selectively driving a plurality of light emitting elements arranged on a printed board to blink,
A display unit in which a plurality of light emitting elements are arranged in a dot matrix,
A storage unit for storing a plurality of grayscale or single-tone display data and a plurality of display conditions for light-emitting display on the display unit;
A display memory that has a storage area corresponding to a dot matrix formed in the display unit, and expands display data read based on the content of the storage unit in the storage area;
The display data expanded in the display memory is read, and one screen is displayed in gray scale on the display unit with a plurality of frames, and a predetermined frame among a plurality of frames constituting one screen is displayed with a light emission period different from other frames. A display drive unit that performs gamma correction by driving,
The display drive unit has a function of changing the light emission period of a frame. When the display data read from the storage unit is multi-gradation display data, the display drive unit includes frames having different light emission periods when displaying one screen. A display device, wherein when display driving is performed and data read out from a storage unit is display data of a single gradation, display driving is performed in the same frame in a light emission period in displaying one screen. In a display device capable of emitting and displaying characters and pictograms in multiple gradations and single gradations by selectively driving a plurality of light emitting elements arranged on a printed board to blink,
A display unit in which a plurality of light emitting elements are arranged in a dot matrix,
A storage unit for storing a plurality of grayscale or single-tone display data and a plurality of display conditions for light-emitting display on the display unit;
A display memory that has a storage area corresponding to a dot matrix formed in the display unit, and expands display data read based on the content of the storage unit in the storage area;
The display data expanded in the display memory is read, and one screen is displayed on the display unit in a single frame or a plurality of frames, and when one screen is displayed in a plurality of frames, a predetermined frame in the plurality of frames is used as another frame. A display drive unit that performs gamma correction by driving display in different light emission periods,
The display drive unit has a function of changing the number of frames constituting one screen, and when display data read from the storage unit is multi-gradation display data, a frame having a different light emission period for displaying one screen is used. When the display data read from the storage unit is single-gradation display data, display driving is performed in a minimum number of frames to display one screen. apparatus.

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