JP2004151187A - Led display device with automatic gamma correction curve changing function and automatic gamma correction curve changing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a picture displayed on an LED display unit to the best contrast according to light-dark components of data or variation of external light. <P>SOLUTION: An LED display device with an automatic gamma correction curve changing function is provided with a memory 1 which temporarily stores video input data to the LED display unit, a gamma table 4 which previously contains gamma correction values corresponding to a plurality of kinds of gamma correction curves, and a gamma correcting means 6 which selecting a gamma correction curve corresponding to the lightness of the video input data from the gamma table 4, multiplies the video input data stored in the memory 1 by the gamma correction value corresponding to the selected gamma correction value and then outputs the result to the LED display unit. When the video input data contain many light components, the gamma correction is increased to make the contrast high and when the video input data contain many dark components, on the other hand, the gamma correction is decreased to make the contrast high, thereby providing a high-contrast video display all the times. Consequently, a user is able to perform data generating operation without paying attention to the contrast of a display to be made. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an LED display device that drives an LED display using a light emitting diode.
[0002]
[Prior art]
A numerical value "gamma" is used to represent the response characteristics of the gradation of an image. For example, in the case of a display, the brightness of the surface varies exponentially without being directly proportional to the input voltage. When the input voltage is small, the change in brightness is gradual, and when the input voltage is large, the change in brightness becomes steep. When the relationship between the input voltage and the brightness forms a 2.2 power curve, the gamma is said to be 2.2. Scanners and color printers each have their own gamma value. In order to faithfully reproduce an image, it is necessary to make the overall gamma from the image input to the final output equal to 1. Correcting to an optimal curve according to the gamma value of the input / output device is called “gamma correction”.
[0003]
The same can be said for a full-color LED display. When digital data from a digital camera captured by a personal computer or the like is displayed on a full-color LED display as it is, a floating white image with no depth is obtained. The reason is that the product of the gamma value of the digital camera and the gamma value of the full color LED display is not 1.
[0004]
In a conventional full-color LED display, data output from a personal computer or the like is displayed by applying a fixed gamma correction value (a gradation is set to a fine step in a low gradation range and a coarse step is set in a high gradation range). (For example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-11-85104 (page 3-4, FIG. 3)
[0006]
[Problems to be solved by the invention]
However, depending on the video input data, there are mostly data with bright components and most data with dark components. At that time, if the same gamma correction value is used, the display becomes pure white or pure black, resulting in poor contrast.
[0007]
Further, in an LED signboard or the like installed outdoors, the external light hitting the LED display changes throughout the day. Especially during the daytime, the LED display may look whitish even when the LED display is exposed to strong external light and nothing is displayed.
[0008]
Conventionally, there is an LED display in which the gamma correction value is changed in a time zone. However, the brightness of the external light assumed in the time zone does not always correspond to the actual brightness.
[0009]
An object of the present invention is to provide an LED display device and an automatic gamma correction curve changing program which can correct an image displayed on an LED display to an optimum contrast in accordance with a change in light and dark components of data or external light. With the goal.
[0010]
[Means for Solving the Problems]
In an LED display device having an automatic gamma correction curve changing function according to the present invention, a memory means for temporarily storing video input data to an LED display, and a gamma table storing gamma correction values corresponding to a plurality of types of gamma correction curves in advance. A gamma correction curve corresponding to the brightness of video input data or the brightness of external light is selected from the gamma table, and a gamma correction value corresponding to the selected gamma correction curve is stored in the memory means. And a gamma correction means for outputting the result to the LED display.
[0011]
According to the present invention, it is possible to obtain an LED display device capable of correcting an image displayed on an LED display to an optimum contrast in accordance with a change in a light-dark component of data or a change in external light.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, there is provided a memory means for temporarily storing video input data to an LED display, a gamma table in which gamma correction values corresponding to a plurality of types of gamma correction curves are stored in advance, A gamma correction curve corresponding to the brightness of the input data is selected from the gamma table, and a gamma correction value corresponding to the selected gamma correction curve is multiplied by the video input data stored in the memory means to the LED display. Gamma correction means for outputting the gamma correction curve, the gamma correction curve is automatically changed, and the degree of gamma correction is automatically adjusted according to the image to be displayed. Is improved.
[0013]
According to a second aspect of the present invention, the gamma correction unit includes a threshold table in which a threshold for switching the gamma correction curve is set for video input data, and a video displayed in a predetermined area of the LED display. 2. The automatic gamma correction curve according to claim 1, further comprising: a counter for counting the number of data exceeding the threshold set in the threshold table in the input data; and means for determining a gamma correction value according to the count. This is an LED display device with a change function, and has an effect that an optimal gamma correction according to the brightness of video input data is calculated in real time.
[0014]
According to a third aspect of the present invention, there is provided a memory means for temporarily storing video input data to an LED display, a gamma table in which gamma correction values corresponding to a plurality of types of gamma correction curves are stored in advance, An illuminance sensor for detecting the illuminance of nearby external light, and a gamma correction curve corresponding to the brightness of the external light detected by the illuminance sensor selected from the gamma table, and a gamma correction corresponding to the selected gamma correction curve A gamma correction means for multiplying a value by video input data stored in the memory means and outputting the multiplied value to the LED display, wherein the gamma correction curve automatic change function-equipped LED display device, The degree of gamma correction is automatically adjusted in accordance with the brightness of external light, and the effect is that display contrast is improved.
[0015]
The invention according to claim 4, wherein a step of storing the input video input data in a memory means in a computer, a step of comparing the video input data with a threshold set in a threshold value table in advance, If the data is equal to or greater than the threshold value, the value of the counter is incremented by one, and if the data is not greater than the threshold value, the value of the counter is left as it is. When the video input data is equal to or greater than the first threshold value, Comparing the value of the counter with a first threshold value; selecting the first gamma table from a gamma table in which a plurality of gamma correction curves are set in advance if the counter value is equal to or greater than the first threshold value; If the value is less than a first threshold, comparing the counter value with a second threshold; and if the counter value is greater than or equal to the second threshold, If so, selecting a second gamma table from the gamma table; selecting the third gamma table from the gamma table if the counter value is less than the second threshold; Outputting a gamma correction value from a table and multiplying the video input data stored in the memory means by the output gamma correction value and outputting the multiplied gamma correction value to the LED display as video output data. The program is an automatic gamma correction curve changing program, and has an effect that the LED display device according to claim 1 is realized by a computer.
[0016]
According to a fifth aspect of the present invention, the step of storing the video input data input to the computer in the memory means, the step of detecting external light around the LED display with the illuminance sensor, and the step of detecting the external light with the illuminance sensor Comparing the illuminance value with a first threshold value, and selecting the first gamma table from a gamma table in which a plurality of gamma correction curves are set in advance if the illuminance value is equal to or greater than the first threshold value; Comparing the illuminance value with a second threshold value if the value is less than the first threshold value, and selecting a second gamma table from the gamma table if the illuminance value is equal to or greater than the second threshold value And if the illuminance value is less than a second threshold, selecting a third gamma table from the gamma table; and selecting a third gamma table from the selected gamma table. Outputting a gamma correction value, multiplying the video input data stored in the memory means by the output gamma correction value, and outputting the multiplied gamma correction value to the LED display as video output data. The program is an automatic gamma correction curve changing program, and has an effect that the LED display device with the automatic gamma correction curve changing function according to claim 3 is realized by a computer.
[0017]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 9.
[0018]
(Embodiment 1)
1 is an explanatory diagram showing a method according to Embodiment 1 of the present invention, FIG. 2 is a graph of a gamma correction curve, FIG. 3 is a block diagram showing a configuration of an LED display device according to Embodiment 1, and FIG. FIG. 5 and FIG. 6 are flowcharts showing the processing procedure, and FIG. 5 and FIG. 6 are explanatory diagrams showing examples of division of the LED display.
[0019]
An outline of the method according to the first embodiment will be described. First, video input data is temporarily stored in a memory. At this time, it detects how many pieces of data equal to or more than a specified value are included in the video input data, and divides the video input data into groups. That is, for example, a group in which “high gradation data occupies 80% of the whole”, a group in which “high gradation data occupies 50% or more”, a group in which “high gradation data occupies less than 50%”, etc. Into groups. An identification number is given to the grouped data, and which gamma correction value to use when displaying the data on the LED display is determined by the identification number. This identification number corresponds to a plurality of gamma correction curves A, B, and C shown in FIG. 2, and multiplies the uncorrected straight line (coefficient 1) by any coefficient to which video input data gradation. Output data. Although the correction curves A, B, and C gradually become steeper, the more the data that is equal to or more than the threshold value is included in the display data, the more whitish the image is when displayed, so that the correction curve is steep to improve the contrast. I do.
[0020]
FIG. 3 shows a configuration of the LED display device according to the first embodiment, in which a memory 1 for storing video input data, a threshold table 2 in which thresholds are set in advance, and a video input data exceeding a threshold are counted. Counter 3, a gamma table 4 storing gamma values corresponding to a plurality of gamma correction curves, a grouping means 5 for grouping video input data, and video input data output from the memory 1 with a predetermined gamma value. Gamma correction means 6 for correction.
[0021]
FIG. 4 shows a processing procedure of gamma correction according to the first embodiment.
S100: The input video input data is stored in the memory 1.
S110: Compare the threshold value set in the threshold value table 2 with the video input data.
S120: If the data is not larger than the threshold value, the counter value is left as it is.
S130: If the data is equal to or larger than the threshold, the counter value is increased by one.
S140: Compare the counter value with the threshold value β.
S150: If the counter value is equal to or larger than the threshold value β, the gamma table C is selected.
S160: If the counter value is less than the threshold value β, the counter value is compared with the threshold value α.
S170: If the counter value is equal to or larger than the threshold value α, the gamma table B is selected.
S180: If the counter value is less than the threshold value α, the gamma table A is selected.
S190: Output a gamma correction value from the selected gamma table.
S200: The video input data stored in the memory 1 is multiplied by the gamma correction value output in S190, and output as video output data to the LED display.
[0022]
The following criterion can be considered as a method for determining the correction curve.
[0023]
(Criterion 1) A correction curve is determined by the number exceeding the threshold.
[0024]
For example, when the size of the screen to be displayed is 48 dots horizontally and 32 dots vertically as shown in FIG. 5, signal data of 48 × 32 = 1536 bytes is checked. The number in which each value exceeds the reference value (threshold) TH is counted, and if the value is between 0 and α1, the gamma correction curve A shown in FIG. 2 is used. If it is between α1 and β1, the gamma correction curve B is used. If it is between β1 and 1536, the gamma correction curve C is used.
[0025]
(Criterion 2) A correction curve is determined based on the number of distributions exceeding the threshold.
[0026]
For example, when the size of the screen to be displayed is 48 dots horizontally and 32 dots vertically, as shown in FIG. 6, 48 × 32 = 1536 bytes of signal data are checked in six blocks of 16 × 16 dots. The number of the number exceeding the reference value (threshold) TH in each of the blocks a, b, c, d, and c is counted. If the value is in the range from 0 to α2 in all the regions from A to A, the gamma correction curve A is used. If it is between α2 and β2, the gamma correction curve B is used. If it is between β2 and 256, the gamma correction curve C is used. In other cases, an intermediate gamma correction curve B is used.
[0027]
Although an example of checking the values of all dots has been described above, one dot may be sampled for some dots and checked. In addition, although the block is divided into blocks of 16 × 16 dots in the criterion 2, any division method may be checked. Further, although three curves for gamma correction have been described, more curves may be prepared.
[0028]
(Embodiment 2)
FIG. 7 is a front view showing an attached state of the illuminance sensor according to the second embodiment of the present invention, FIG. 8 is an explanatory diagram showing a method according to the second embodiment, and FIG. 9 is a flowchart showing a processing procedure thereof.
[0029]
In the second embodiment of the present invention, the gamma correction value is changed in real time according to the external light received by the LED display, and the correction is applied. As shown in FIG. 7, the LED display 10 is provided with an illuminance sensor 11 for detecting the level of external light.
[0030]
As shown in FIG. 8, the video input data is grouped by the illuminance value according to the external light level detected by the illuminance sensor 11. An identification number is given to the grouped data, and the identification number is used to determine which gamma correction value to use when displaying the data on the LED display 10. This identification number corresponds to a plurality of gamma correction curves A, B, and C shown in FIG. 2, and multiplies the uncorrected straight line (coefficient 1) by any coefficient to which video input data gradation. Output data.
[0031]
If the peripheral illuminance value detected by the illuminance sensor 11 is between 0 and α, the gamma correction curve A is used. If it is between α and β, the gamma correction curve B is used. If β or more, the gamma correction curve C is used.
[0032]
FIG. 9 shows a processing procedure of gamma correction according to the second embodiment.
S300: Store the input video input data in the memory.
S310: The ambient light around the LED display is detected by the illuminance sensor 11.
S320: Compare the illuminance value with the threshold value β.
S330: If the illuminance value is equal to or larger than the threshold value β, the gamma table C is selected.
S340: If the illuminance value is less than the threshold value β, the illuminance sensor value is compared with the threshold value α.
S350: If the illuminance value is equal to or larger than the threshold α, the gamma table B is selected.
S360: If the illuminance value is less than the threshold value α, the gamma table A is selected.
S370: Output a gamma correction value from the selected gamma table.
S380: The video input data stored in the memory is multiplied by the gamma correction value output in S370, and output to the LED display as video output data.
[0033]
In the second embodiment, since the gamma correction value changes in real time in conjunction with the illuminance value detected by the illuminance sensor 11, the gamma correction value is changed in accordance with the surrounding brightness at that time, and the contrast is constantly changed. Good indication can be provided.
[0034]
Here, in the case of a moving image, normally, a fixed gamma correction value is used. This is because the video has already been edited by professional video technicians to make it look great on a television or personal computer.
[0035]
However, when the display data is created by an individual, such as a small LED signboard, it is generally an amateur to edit the data to be displayed, and it is impossible for the amateur to perform gamma correction.
[0036]
In the present embodiment, even if data of a still image or a moving image photographed by an amateur with a digital camera or the like is automatically corrected so that the display has the highest contrast in the LED display, there is a great advantage.
[0037]
Note that it is of course possible to implement the LED display device by combining Embodiment 1 and Embodiment 2.
[0038]
【The invention's effect】
As described above, in the invention in which the gamma correction value is changed according to the video input data, when the video input data has many bright components, the gamma correction is strengthened to increase the contrast, and when the video input data has many dark components. Reduces the gamma correction to increase the contrast, and can always provide a high-contrast image display. Therefore, the user can perform the data creation work without being conscious of the contrast when displaying.
[0039]
Also, in the invention in which the gamma correction value is changed according to the external light level, when the external light level is high, the gamma correction is strengthened to increase the contrast, and when the external light level is low, the gamma correction is reduced to display. It produces the original gradation of the data, and can always provide a high-contrast image display. Therefore, it is possible to suppress a decrease in contrast due to external light.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a method according to a first embodiment of the present invention; FIG. 2 is a graph of a gamma correction curve; FIG. 3 is a block diagram showing a configuration of an LED display device according to the first embodiment; FIG. 5 is a flowchart showing a processing procedure of the first embodiment. FIG. 5 is an explanatory diagram showing an example of division of an LED display. FIG. 6 is an explanatory diagram showing an example of division of an LED display. FIG. 7 is an embodiment of the present invention. FIG. 8 is a front view showing an attached state of the illuminance sensor in FIG. 2; FIG. 8 is an explanatory view showing a method according to the second embodiment; FIG. 9 is a flowchart showing a processing procedure in the second embodiment;
REFERENCE SIGNS LIST 1 memory 2 threshold table 3 counter 4 gamma table 5 grouping means 6 gamma correction means 10 LED display 11 illuminance sensor

Claims (5)

A memory means for temporarily storing video input data to the LED display, a gamma table storing gamma correction values corresponding to a plurality of types of gamma correction curves in advance, and a gamma correction curve corresponding to the brightness of the video input data. Gamma correction means for selecting from the gamma table, multiplying a gamma correction value corresponding to the selected gamma correction curve by video input data stored in the memory means, and outputting to the LED display. LED display device with gamma correction curve automatic change function. The gamma correction unit includes a threshold table that sets a threshold for switching the gamma correction curve with respect to the video input data, and a threshold table that is set in the video input data displayed in a predetermined area of the LED display. 2. The LED display device with a function of automatically changing a gamma correction curve according to claim 1, further comprising: a counter for counting the number of data exceeding the threshold value, and means for determining a gamma correction value according to the counted number. A memory for temporarily storing video input data to the LED display, a gamma table storing gamma correction values corresponding to a plurality of types of gamma correction curves in advance, and detecting the illuminance of external light near the LED display An illuminance sensor and a gamma correction curve corresponding to the brightness of external light detected by the illuminance sensor are selected from the gamma table, and a gamma correction value corresponding to the selected gamma correction curve is stored in the memory unit. Gamma correction means for multiplying video input data and outputting the data to the LED display device. On the computer,
Storing the input video input data in a memory means;
Comparing the threshold value previously set in the threshold value table with the video input data;
If the video input data is greater than or equal to the threshold, increase the value of the counter by one, and if not greater than the threshold, leave the value of the counter unchanged,
When the video input data is equal to or greater than the first threshold, comparing the value of the counter with a first threshold;
If the counter value is equal to or greater than a first threshold, selecting a first gamma table from a gamma table in which a plurality of gamma correction curves are set in advance;
If the counter value is less than a first threshold, comparing the counter value with a second threshold;
If the counter value is greater than or equal to the second threshold, selecting a second gamma table from the gamma table;
If the counter value is less than the second threshold, selecting a third gamma table from the gamma table;
Outputting a gamma correction value from the selected gamma table;
Multiplying the video input data stored in the memory means by the output gamma correction value and outputting the video input data to the LED display as video output data. On the computer,
Storing the input video input data in a memory means;
Detecting ambient light around the LED display with an illuminance sensor;
Comparing the illuminance value detected by the illuminance sensor with a first threshold value;
If the illuminance value is equal to or greater than the first threshold, selecting a first gamma table from a gamma table in which a plurality of gamma correction curves are set in advance;
If the illuminance value is less than the first threshold, comparing the illuminance value with a second threshold;
Selecting the second gamma table from the gamma table if the illuminance value is greater than or equal to a second threshold;
If the illuminance value is less than a second threshold, selecting a third gamma table from the gamma table;
Outputting a gamma correction value from the selected gamma table;
Multiplying the video input data stored in the memory means by the output gamma correction value and outputting the video input data to the LED display as video output data.

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