CN104900188A - LED display screen uniformity correction method - Google Patents

The invention relates to an LED display screen uniformity correction method. The method includes the steps of: (i) adjusting a gray scale range of a target LED display screen from an initial value to a target value so as to increase the refreshing rate of the target LED display screen, wherein the target value is smaller than the initial value; (ii) controlling the target LED display screen to display a picture for correction after the step (i); (iii) collecting the picture for correction to obtain an image for correction; (iv) generating a correction coefficient of the target LED display screen according to the image for correction and transmitting the correction coefficient to hardware of the target LED display screen for storage; and (v) recovering the gray scale range of the target LED display screen from the target value to the initial value after storing the correction coefficient. Therefore, the LED display screen uniformity correction method provided by the invention can shorten exposure time required by correction, thereby shortening correction time, and improving correction efficiency.

LED display uniformity correcting method

Technical field

The present invention relates to LED and show alignment technique field, particularly a kind of LED display uniformity correcting method.

Background technology

Since 21 century, colored display industry is developed on an unprecedented scale, and LED display has also spread all over central plaza, the commercial mansion in each city.LED display enjoys people's favorable comment with its distinctive advantage such as high, low in energy consumption bright in luster, visual, but due to LED manufacturing technology level comparatively low, the LED self produced is made to there is larger bright chroma difference (such as same production batch LED, its brightness may differ nearly 50%, colourity may differ 15 ~ 20nm), and the display screen of multiple different production batch LED splicing, its bright chroma difference is just more serious.These bright chroma differences are intolerable for human eye vision, thus new production or the LED display that uses year in year out need to carry out effective bright chroma adjustment.

Current LED display industry is interior is adopt the correction based on machine vision for one of LED display processing mode that there is bright chroma difference, also the measuring equipments such as image capture device (as camera), chromascope are namely utilized to correct display screen in conjunction with point-to-point correction system, eliminate the bright chroma difference between LED point, reach the high uniformity consistance of display screen bright chroma.

In trimming process, correct primary colours (as the red, green, blue) image of librarian use image capture device collection shown by LED display, only have when the time shutter of image capture device much larger than the refresh time of LED time, the image photographed is only normally, and the such as time shutter is 200 times of refresh time; And if the time shutter of image capture device is not much larger than the refresh time of LED, the image collected will be caused to have refresh line, thus cause the effect after using this collection correct image undesirable.It is make the time shutter of image capture device extend to refresh time much larger than LED screen body, to make the image collected not have refresh line, to ensure not affect calibration result that tradition removes the method for refresh line.

But the time shutter of image capture device is long, correction time can be caused long, reduce correction efficiency, ectocine (noise effect) also can be made simultaneously to become large.

Summary of the invention

Therefore, for overcoming deficiency of the prior art, the present invention proposes a kind of LED display uniformity correcting method.

Particularly, a kind of LED display uniformity correcting method that the embodiment of the present invention provides, comprise step: the grey-scale range of target LED display is adjusted to desired value from initial value by (i), to increase the refresh rate of described target LED display, wherein said desired value is less than described initial value; (ii) after step (i), described target LED display display correction picture is controlled; (iii) described correction picture is gathered to obtain correction image; (iv) according to described correction Computer image genration, the correction coefficient of target LED display the hardware described correction coefficient being sent to described target LED display store; And (v) is after the described correction coefficient of storage, and the grey-scale range of described target LED display is returned to described initial value from described desired value.

In one embodiment of the invention, control described target LED display display correction picture in above-mentioned steps (ii) comprises: control described target LED display shows multiple different colours picture according to preset order, and the picture of described multiple different colours is respectively sprite or pure color picture.

In one embodiment of the invention, utilize image capture device to gather described correction picture in above-mentioned steps (iii), and the time shutter of described image capture device is set to the minimum exposure time that refresh line does not appear in satisfied gathered image.

In one embodiment of the invention, the correction coefficient in above-mentioned steps (iv) is brightness correction coefficients or bright chroma correction coefficient.

In one embodiment of the invention, above-mentioned LED display uniformity correcting method adopts brightness point by point to correct or the correction of pointwise bright chroma.

In addition, the LED display uniformity correcting method that the embodiment of the present invention provides on the other hand comprises step: the grey-scale range reducing target LED display; The time shutter of image capture device is regulated not occur refresh line to meeting the image gathered; Utilize described image capture device to have reduce the described target LED display of grey-scale range carry out image acquisition and according to gathered Computer image genration the brightness correction coefficients of target LED display or bright chroma correction coefficient; And after the described brightness correction coefficients of generation or bright chroma correction coefficient, increase the grey-scale range of described target LED display.

In one embodiment of the invention, there is not minimum exposure time of refresh line for satisfied gathered image in the above-mentioned time shutter.

In one embodiment of the invention, the grey-scale range of above-mentioned increase described target LED display is that the grey-scale range of described target LED display is returned to the value before reduction.

From above-described embodiment, the present invention reduces the grey-scale range of target LED display and the grey-scale range of target LED display is increased after generation correction coefficient again before image acquisition, such as return to initial value, like this then time shutter that can shorten needed for correction, thus can correction time be shortened, improve and correct efficiency.In addition, the invention enables the requirement of calibration equipment lower, the equipment that the time shutter is shorter can be adopted.

By the detailed description below with reference to accompanying drawing, other side of the present invention and feature become obvious.But it should be known that this accompanying drawing is only the object design of explanation, instead of as the restriction of scope of the present invention, this is because it should with reference to additional claim.Should also be appreciated that, unless otherwise noted, unnecessaryly draw accompanying drawing to scale, they only try hard to structure described herein and flow process are described conceptually.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail.

A kind of schematic diagram corrected with hardware structure that the LED display uniformity correcting method that Fig. 1 is the embodiment of the present invention adopts.

Fig. 2 is the process flow diagram of the LED display uniformity correcting method of the embodiment of the present invention.

Embodiment

For ease of understanding the present invention, first introduce several key concept below:

(a) LED display principle of luminosity and pulse-length modulation

LED (Light Emitting Diode sends out light emitting diode) is a kind of solid-state semiconductor devices, and it directly can be converted into light electricity; LED switch number of times in the unit interval is depended in the brightness of LED.The response time of LED generally only has a few nanosecond to hundreds of nanosecond, be suitable for the occasion of frequent switch and high frequency running, simultaneously due to LED specific electric current/luminous intensity characteristic, therefore can by periodic pulse-length modulation, also namely the mode of control output current dutycycle realizes the adjustment to LED luminance, such as brightness to be reduced by half, only need in the duty cycle of 50%, provide electric current just can achieve.For guaranteeing that the naked eyes impression of people is less than pwm pulse, the frequency of pwm signal must higher than 100Hz, and maximum PWM frequency depends on and power initiation and response time.For providing maximum dirigibility and integrated simplification, LED drive chip should be able to accept the PWM frequency up to 50KHz.The switching frequency of 200 ~ 300Hz generally can be selected to carry out PWM brightness regulation, this is because human eye is difficult to the change of the frequency differentiated more than 40Hz, and too high frequency can cause white light color that displacement occurs and brightness regulation is non-linear.

(b) GTG

Gray scale i.e. so-called GTG, refer to the bright-dark degree of brightness, shows in industry, refer in particular to the luminosity of often kind of primary colours at LED.Being divided by intensity size by the luminosity of primary colours, is exactly gray level.The gray level that display screen can produce is higher, and color and the image level of display are more.For digitized display technique, gray level is the determinative of display color number.Generally speaking gray level is higher, and the color of display is abundanter, and picture is also finer and smoother, more easily shows abundant details.

In digitization system, gray level control ability represented by number of grey levels, so-called number of grey levels just refer to the gray level grade can carrying out controlling number; Such as can control the gray scale of 16 ranks, its number of grey levels is exactly 16.In digital circuit, represent 16 different numbers with 4bit binary number.Can see, the bit quantity controlled for gray level is more, and the gray level that can produce is larger, and the image shown is finer and smoother.

Number of grey levels depends primarily on the digital-to-analog conversion figure place of system, and the video frequency processing chip of certain system, storer and transmission system all will provide the support of corresponding figure place.Current LED display mainly adopts:

One, 8 disposal systems are also 256 (8 powers of 2) level gray scale, and simple understanding is exactly from black to having 256 kinds of brightness changes in vain.

Two, 10 disposal systems are also 1024 (10 powers of 2) level gray scale, and simple understanding is exactly become from black to having 1024 kinds of brightness in vain

Three, 12 disposal systems are also 4096 (12 powers of 2) level gray scale, and simple understanding is exactly from black to having 4096 kinds of brightness changes in vain

Four, 14 disposal systems are also 16384 (14 powers of 2) level gray scale, and simple understanding is exactly from black to having 16384 kinds of brightness changes in vain

(c) LED display refresh rate

The number of times of image multiple scanning p.s. on the screen that refresh rate refers to LED display, that is to say the speed referring to that image upgrades on screen; Refresh rate is higher, and shown image (picture) stability is better.

Relation between (d) LED display refresh rate and grey-scale range

Grey-scale range refers to the brightness resolution of each LEDs in LED display, and for example, 4bit grey-scale range represents that LED has the brightness on 16 rank to change.The GTG of LED luminance is by the OE width on driving chip and SDI (Serial Data In, serial date transfer) control, GTG 5 to be shown for LED, SDI must OE width be 1 (0 powers of 2) and 4 (2 powers of 2) time open output switch, show GTG for 5 to obtain overall LED.GTG 9,4 and 11 then by that analogy, can realize different LED GTGs with the permutation and combination of different SDI and OE width, also will demonstrate different LED luminance.In addition, the cycle of OE is shorter, and the time completed needed for a GTG is also shorter, and in the namely unit interval, the getable refresh rate of institute is also higher.Usually, the cycle size of OE is relevant to grey-scale range, grey-scale range larger (the bit quantity also namely for gray level control is more), then the cycle of OE is longer, and correspondingly refresh rate is also lower; Otherwise grey-scale range is less, then the cycle of OE is shorter, and correspondingly refresh rate is also higher.

Namely the following embodiment of the present invention is utilize the grey-scale range of LED display (grey exponent number) and the characteristic becoming inverse relationship between refresh rate, also namely grey-scale range is larger, the displayable grey exponent number of LED display is more, so refresh rate is lower, if LED display is 14 disposal systems, also be 16384 (14 powers of 2) level gray scale, its refresh rate is maximum can reach 5KHZ, if but the grey exponent number making LED display show reduces, and (limit only has one-level gray scale, i.e. screen Chang Liang), so its refresh rate will improve, greatly as 50KHZ; Therefore, when LED display homogeneity correction, the grey-scale range of LED display can just be adjusted, the grey exponent number making it show reduces, so just can substantially increase the refresh rate of LED display, and then the time shutter of image acquisition can be reduced, accelerate trimming process.Certainly, this disposal route just adjusts in trimming process, after obtaining correction coefficient, again the grey-scale range of LED display and refresh rate are returned to original state.For enabling above-mentioned purpose of the present invention, feature and advantage become apparent more, are described in detail the specific embodiment of the present invention below in conjunction with accompanying drawing.

Refer to Fig. 1, a kind of schematic diagram corrected with hardware structure that its LED display uniformity correcting method provided for the embodiment of the present invention adopts.In FIG, corrective system 10 comprises image capture device 11 and correcting computer 13, and LED display screen system 20 comprises LED display 21 and control system 23.Wherein, image capture device 11 is such as mm professional camera special, takes to gather image for the picture shown LED display 21; Correcting computer 11 connects image capture device 13 and is provided with correction software, this correction software is for the image analyzing image capture device 13 and collect and generate correction coefficient after carrying out analyzing and processing, and the correction coefficient of generation will be sent to LED display 21 and store and use by the control system 23 in LED display screen system 20.LED display 21 generally includes multiple LED box be stitched together, and each LED box generally includes the receiving card (or claiming LED display control panel) of one or more LED lamp panel and electrical connection LED lamp panel.In addition, LED display screen system 20 can be synchronous LED display screen system or asynchronous LED display screen system, for synchronous LED display screen system, control system 23 comprises sending card (or claiming Video Controller) and host computer, host computer is connected to the receiving card of LED display 21 by sending card, host computer is double do video source when, LED display 21 show image content consistent with the content that host computer is play, host computer is once shut down, and LED display 21 cannot play media.For asynchronous LED display screen system, control system 23 comprises Asynchronism Card and (is generally a kind of embedded Control card with arm processor, also can be described as Video Controller), Asynchronism Card is connected to the receiving card of LED display 21, Asynchronism Card incorporates the basic function of the host computer in synchronous LED display screen system and the function of sending card, therefore asynchronous LED display screen system play media time without the need to connecting host computer.

Refer to Fig. 2, it is the process flow diagram of the LED display uniformity correcting method of the embodiment of the present invention.As shown in Figure 2, the LED display uniformity correcting method of the embodiment of the present invention comprises the following steps S210, S230 and S250.

Step S210: the grey-scale range of adjustment aim LED display is to desired value.Particularly, grey-scale range and the refresh rate of its display image due to target LED display have into the characteristic of inverse relationship, therefore the grey-scale range of target LED display is adjusted to desired value from initial value, to reduce the grey-scale range of target LED display, and then the refresh rate increasing target LED display is that follow-up trimming process is prepared.Be understandable that, because be the grey-scale range reducing target LED display, therefore described desired value is less than described initial value herein.In the present embodiment, target LED display is RGB three primary colours full-color LED display screens, but the present invention is not as limit, and it also can be monochromatic or dual-colored LED display screen.

Step S230: acquisition correction picture obtains correction image, carries out image procossing, generates correction coefficient and be uploaded to target LED display.Particularly, LED display 21 can be controlled by correcting computer 13 sending controling instruction to the control system 23 in Fig. 1 and show correction picture, with RGB three primary colours full-color LED display screen as an example, described correction picture can be the redness, green and the blue picture that show according to preset order, is also namely sprite; And the quantity that same colored picture shows continuously can be one also can be multiple; In addition, in certain embodiments, except display sprite, pure color picture such as white picture can also be shown further.

Hold above-mentioned, after each width correction picture of display, picture photographing is carried out to obtain correction image in the target viewing area of the LED display that can be aimed at the mark by the image capture device 11 (such as camera) in Fig. 1.In the present embodiment, before shooting first width correction picture, should first regulate the time shutter of image capture device 11 to dbjective state, dbjective state is herein preferably the minimum exposure time meeting the image gathered and do not occur refresh line.After obtaining required correction image, the correction software can installed by the correcting computer 11 in Fig. 1 carries out image procossing to correction image, such as, carry out location, viewing area, monochrome information or bright chroma information that LED point location scheduling algorithm obtains each LED point in target LED display.Afterwards, being generated the correction coefficient of each LED point according to the monochrome information of each LED point obtained or bright chroma information by the correction software on correcting computer 11, such as, is brightness correction coefficients, or is bright chroma correction coefficient.Next, after the correction coefficient obtaining each LED point, the receiving card that the correction coefficient of each LED point can be sent in LED display 21 by the control system 23 in Fig. 1 stores, thus can realize correcting or the correction of pointwise bright chroma the brightness point by point of target LED display.Be understandable that, for the show uniformity of target LED display is corrected to satisfactory state, then usually can perform once and once above step S230.

Step S250: the grey-scale range of target LED display is returned to initial value.As previously mentioned, because abundanter, the picture of color of gray level higher (corresponding grey-scale range is larger), display also finer and smoother, more easily show abundant details, therefore, after generation correction coefficient or even after the hardware correction coefficient of generation being uploaded to target LED display stores, the grey-scale range of target LED display is returned to initial value from aforementioned desired value.Certainly, also can not return to initial value, but according to the demand of practical application, the grey-scale range of target LED display be increased to other values from aforementioned desired value.

In sum, the above embodiment of the present invention reduces the grey-scale range of target LED display and again the increase of the grey-scale range of target LED display is such as returned to initial value after generation correction coefficient before image acquisition, like this then time shutter that can shorten needed for correction, thus can correction time be shortened, improve and correct efficiency.In addition, the invention enables the requirement of calibration equipment lower, the equipment that the time shutter is shorter can be adopted.

So far, apply specific case herein and set forth the principle of LED display uniformity correcting method of the present invention and embodiment, the explanation of above embodiment just understands method of the present invention and core concept thereof for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present invention; all will change in specific embodiments and applications; in sum, this description should not be construed as limitation of the present invention, and protection scope of the present invention should be as the criterion with appended claim.