CN103077682B - LED (Light-Emitting Diode) display screen pulse control method capable of eliminating dynamic false contour - Google Patents

Abstract

The invention proposes a LED display screen pulse control method capable of eliminating dynamic false contours, which can improve the dynamic false contour phenomenon existing in the LED display screen when playing moving pictures. This method is to implement all the decimal weight bits bit by bit in a fixed position in the entire gray scale field in order, and the multiple subfields occupied by the fixed position are recorded as a decimal field as a whole; it will realize all the integer weight bits. Each pulse of each pulse is integrated into a wide pulse, and the wide pulse is realized at a position adjacent to the fractional field to complete the brightness control of the LED lamp point. With the LED display pulse control method of the present invention, when the human eyes watch the two successively realized gray levels, the integration will not visually perceive wrong brightness; the difference between the integration result and the original gray level will not be too large , so as to effectively avoid the appearance of dynamic false contour phenomenon.

Description

A pulse control method for LED display that can eliminate dynamic false contours

technical field

The invention is applied to an LED display screen that uses a pulse width modulation method to control the brightness of a lamp point, and relates to a pulse control method for improving the display effect of a moving picture on the LED display screen.

Background technique

With the wide application of LED display screens, the requirements for picture quality are becoming more and more stringent. However, when displaying video pictures, bright or dark lines other than the outline information of the image itself will be observed on the image, which is called dynamic false outline. (dynamic false contour DFC).

Gated pulse width modulation is one of the main methods to control the gray level at present. According to the received binary code to be displayed, the sub-fields arranged in a certain order are sequentially lit with a set duty cycle to achieve different gray levels. level (each bit of gated PWM corresponds to at least one subfield, and the purpose of controlling the duty cycle is achieved by turning on/off the gated switch). The sub-field is the time required to realize the lowest bit in the entire gray field in the digital display screen. The specific length of time is determined by the refresh frequency of the display screen, shift clock, and the number of series lights. Taking the control of 8bit gray level as an example, the steps of controlling the gray level by the gated pulse width modulation method are as follows: Assume that the number of subfields corresponding to each bit of the 8bit gray level field is 4, 2, 1, 1, 1, 1, 1 , 1, the turn-on rate (duty cycle) corresponding to each bit is 1, 1, 1, 1/2, 1/4, 1/8, 1/16, 1/32 (the modulation method is shown in Figure 1) .

In the existing pulse width modulation method, the sub-fields corresponding to each data bit of the display code are fixedly set bit by bit in order in the entire gray field corresponding to the display code, and the pulses of each data bit are realized in turn; in this way, the successively realized display The pulses are connected end to end, causing the human eyes to perceive wrong display content during the process of display data transformation. Take the 8-bit 128 gray level and 127 gray level as an example (the binary code of 128 is: 1000 0000, and the binary code of 127 is: 0111 1111): Assuming that the gray level is implemented sequentially from high to low, each data The position of the bit in the code is fixed, let D0 be the first subfield, the duty ratio is 1/32; D1 is the second subfield, the duty ratio is 1/16; D2 is the third subfield, the duty ratio is 1/8; D3 is the fourth subfield with a duty ratio of 1/4; D4 is the fifth subfield with a duty ratio of 1/2; D5 is the sixth subfield with a duty ratio of 1; D6 is the There are two sub-fields 7 and 8, with a duty ratio of 1; D7 is a total of four sub-fields 9, 10, 11, and 12, with a duty ratio of 1. The pulse width modulation waveforms of these two gray levels are realized successively through gated pulse width modulation (GPWM), as shown in Figure 3. The starting point to the end point of each arrow represents an integral interval of human eye perception, and the brightness level perceived by human eyes The information is not simply 127 and 128, but the following sequence is integrated [2 ⁷ ×1,2 ⁶ ×0,2 ⁵ ×0,2 ⁴ ×0,2 ³ ×0,2 ² ×0,2 ¹ ×0 ,2 ⁰ ×0],[2 ⁷ ×0,2 ⁶ ×1,2 ⁵ ×1,2 ⁴ ×1,2 ³ ×1,2 ² ×1,2 ¹ ×1,2 ⁰ ×1], integral The result is shown in Figure 4.

The integral values are 128, 129, 131, 135, 143, 159, 191, 255, and 127 in sequence. It can be seen that the pulses of the two fields before and after are connected, so that the gray levels other than the two gray levels of 127 and 128 will be felt, and the DFC phenomenon will appear.

Contents of the invention

The object of the present invention is to propose a pulse control method for LED display screens that can eliminate dynamic false contours, which can improve the phenomenon of dynamic false contours existing in LED display screens when playing moving pictures.

The purpose of the present invention is achieved through the following technical solutions:

A pulse control method for LED display screens that can eliminate dynamic false contours, the special features of which are:

For each weight bit in the display code, according to its corresponding pulse width, the data less than one subfield is recorded as a decimal weight bit, and the data bit greater than or equal to one subfield is recorded as an integer weight bit;

Realize all the decimal weight bits bit by bit in a fixed position in the entire grayscale field in order, and the multiple subfields occupied by the fixed position are recorded as a decimal field as a whole;

The various pulses required to realize all the integer weight bits are integrated into a wide pulse, and the wide pulse is realized at a position adjacent to the fractional field to complete the brightness control of the LED lamp point.

Based on the above-mentioned basic scheme, the present invention also makes the following optimization restrictions:

The above-mentioned fractional field can be set in the middle of the entire gray-scale field, then the wide pulse is divided into two parts, which are respectively adjacent to the two sides of the fractional field; or, the above-mentioned fractional field can also be set at the middle of the entire gray-scale field. Front position or rear position.

In the above scheme, for each display code, according to its corresponding pulse width, calculate the number of complete subfields N belonging to the integer weight bits that need to be lit for the gray level to be realized, then:

When N=0, realize the lighting of the decimal weight position in the decimal field;

For the case where the fractional field is set in the middle of the entire grayscale field, when N≥1 and N can be divisible by 2, the N subfields are evenly distributed on both sides of the fractional field, that is, before the fractional field, N For the lighting of /2 subfields, the lighting of N/2 subfields will be realized after the decimal field; if N cannot be divisible by 2, the N subfields will be lit by using the distribution method of less before and more after the decimal field, that is, before the decimal field The number of subfields realized is one less than the number of subfields realized after the fractional field.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention designs a way of separating integer field pulses from fractional field pulses, which is realized after integration of integer field pulses, and the luminescence time of the displayed data is more concentrated. There may be a phenomenon in which wrong brightness is perceived. The difference between the integration result and the original gray level will not be too large, thus effectively avoiding the phenomenon of dynamic false contours.

Description of drawings

FIG. 1 is a schematic diagram of realizing 127 gray levels by a pulse width modulation method in the prior art.

Fig. 2 is a schematic diagram of realizing 127 gray levels by a modulation method provided by an embodiment of the present invention.

Fig. 3 is a waveform diagram of realizing two gray levels of 127 and 128 by adopting the existing pulse width modulation technology.

Fig. 4 is a diagram of the integration results of two gray levels of 127 and 128 achieved by using the existing pulse control technology.

Fig. 5 is a waveform diagram of realizing two gray levels of 127 and 128 by adopting the method of the present invention.

Fig. 6 is a diagram of the integration results of two gray levels of 127 and 128 achieved by the method of the present invention.

detailed description

A specific embodiment of the present invention is shown in Fig. 2 and Fig. 5. In this embodiment, the fractional field is set at the middle position of the entire gray field. The specific method is as follows:

On the basis of the existing gated pulse width modulation technology, according to the binary code of the input gray level, the input gray level bits are divided into two parts according to the pulse width, and the integer weight bits (bits whose pulse width is greater than one subfield) and fractional weight bits (bits with a pulse width less than one subfield);

The decimal weight bit is still realized according to the existing pulse width modulation method, but the realized position is changed, as shown in Figure 2, the decimal place is no longer realized at the beginning or end of a field, but in the middle of a field accomplish;

The integer weight bit does not divide the weight, and calculates the number N of complete subfields that need to be lit in the gray level to be realized (except for the decimal weight bit);

Evenly distribute the N complete subfields that need to be lit on both sides of the decimal weight bit, realize N/2 subfields before the decimal field, and realize N/2 subfields after the decimal field is realized. If N cannot be divisible by 2, use the decimal number The principle that what is realized after the fractional field is 1 more than what was realized before the fractional field.

According to the pulse modulation method proposed by the present invention, the LED lamps are lit.

Taking 128 gray levels and 127 gray levels of 8 bits in the background technology as an example, according to the method of the present invention, the upper three bits are integer weight bits, and the lower five bits are decimal weight bits. Finally, as shown in Figure 5, the starting point to the end point of each arrow represents an integration interval, and the result of the integration is shown in Figure 6.

The integral values are: 127, 127, 127, 127, 143, 135, 131, 129, 128, 128, 128. It can be seen that, visually, the integral will not appear the phenomenon of connected time slices that are lit, thus effectively avoiding the phenomenon of dynamic false contours.

In the same way, it is also possible to concentrate the integer digits in front of or behind the decimal digits to realize lighting. This is the same idea as dividing the integer digits into two parts and allocating them on both sides of the decimal digits to realize lighting. Refer to the above-mentioned embodiment According to the solution, those skilled in the art can also implement the present invention, which can also effectively avoid the occurrence of dynamic false contour phenomenon.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (3)

1. can eliminate a LED display pulse control method for dynamic false outline, it is characterized in that:

By each the weight position in code displaying, according to the pulse width of its correspondence, the data being less than a subfield are designated as decimal weight position, the data bit being more than or equal to a subfield is designated as integer weight position;

Realized according to a certain fixed position of order by turn in whole gray scale field all decimal weight positions, the multiple subfields shared by this fixed position are integrally designated as decimal field;

Each pulse realized required for all integer weight positions is integrated into broad pulse, realizes this broad pulse in the position of adjacent described decimal field, complete the brilliance control of LED point.

2. method according to claim 1, is characterized in that:

Described decimal field is set in the centre position of whole gray scale field, then described broad pulse is divided into two parts, and the both sides abutting against decimal field respectively realize;

Or described decimal field is set in front position or the back-end location of whole gray scale field.

3. method according to claim 2, is characterized in that:

To each code displaying, according to the pulse width of its correspondence, calculate the complete subfield number N belonging to integer weight position lighted needed for the gray level that will realize, then:

As N=0, realize lighting of decimal weight position in decimal field;

Decimal field is set in the situation in the centre position of whole gray scale field, when N >=1 and N can be divided exactly by 2, then by this N number of subfield mean allocation in the both sides of decimal field, namely before decimal field, realize lighting of N/2 subfield, after decimal field, realize lighting of N/2 subfield; N can not be divided exactly by 2, then after few before taking, many methods of salary distribution realize lighting of this N number of subfield, the number of sub-frames namely realized before decimal field fewer than the number of sub-frames realized after decimal field 1.