A gray scale modulation method of single end injection type light emitting device

Abstract

The application provides a gray scale modulation method of a single-end injection type light emitting device. The single-end injection type light emitting device only emits light in a positive half cycle. In order to improve display brightness, according to the relationship between amplitude and brightness, a single driving cycle is evenly divided into N subframes. According to the relationship between amplitude and brightness, M reference voltages are selected, and each reference voltage corresponds to a reference gray scale. According to the relationship between relative duty cycle and brightness, the gray scale of the relative duty cycle is controlled. Through the mixed modulation method of amplitude, frequency and relative duty cycle, the precise modulation of the gray scale level of the single-end injection type light emitting device can be realized. In the application, the single-end injection type light emitting device is electrically coupled in a single-end mode, and the light emitting is driven by an induced electric field. Therefore, the line connection of the display device can be simplified, and the mass transfer process and the complex bonding process can be avoided.

Description

Technical Field

[0001] The present invention belongs to the technical fields of flat panel display, grayscale modulation and the like, and particularly relates to a grayscale modulation method for a single-end injection type light emitting device. Background Art

[0002] Micro-LED (Micro Light Emitting Diode) displays utilize micron-sized (typically less than 50μm) inorganic LEDs as light-emitting pixels to achieve an active light-emitting matrix display. Based on the principles of display technology, Micro-LEDs, along with Organic Light Emitting Diodes (OLEDs) and Quantum Dot Light Emitting Diodes (QLEDs), all belong to the category of active light-emitting display technologies. However, unlike OLED and QLED display technologies, Micro-LED displays utilize inorganic Ga-N LED chips, which offer excellent luminous performance and a long lifespan. However, the main challenges facing their industrialization lie in the integration process and associated materials.

[0003] The simple device structure of the single-ended injection light-emitting diode is expected to be applied to new micro-display technologies such as Micro-LED and nano-pixel light-emitting display. It is a technology based on the induced electric field through the internal carrier radiation recombination to emit light, which reduces the coupling between electrodes and solves the problem of precise docking of electrode chips in tiny sizes.

[0004] In the field of flat panel display technology, micro-light-emitting devices have many advantages, the most notable of which are low power consumption, high brightness, ultra-high definition, high color saturation, faster response speed, longer service life and higher work efficiency. It is a revolutionary new display technology that is expected to replace TFT liquid crystal displays in almost all applications in the field of flat panel displays.

[0005] Existing LED display control mostly uses PWM modulation scheme, but pulse width modulation is suitable for DC light-emitting devices. The use of pulse width modulation technology has no obvious effect on the grayscale modulation of single-ended injection light-emitting devices. Therefore, a new and suitable modulation scheme is urgently needed. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of existing technologies and fill the gap in grayscale modulation schemes for single-ended injection-type light-emitting devices, the present invention proposes a grayscale modulation method that uses a hybrid modulation of amplitude, frequency, and relative duty cycle. Based on the frequency-brightness curve, a single drive cycle is evenly divided into N subframes. Based on the relationship between amplitude and brightness, M reference voltages are selected, each corresponding to a reference grayscale. Based on the relationship between relative duty cycle and brightness, while the applied drive voltage and drive frequency remain constant, grayscale regulation is performed by varying the number of square waves (P) within a single cycle. This grayscale modulation scheme controls the number of times the device emits light within a single cycle and the driving time it takes.

[0007] The single-ended injection-type light-emitting device proposed in the present invention is single-ended electrically coupled and uses an induced electric field to drive light emission, which can simplify the circuit connection of the display device and avoid a large amount of transfer processes and complex bonding processes.

[0008] The technical solution specifically adopted by the present invention to solve the technical problem is:

[0009] A grayscale modulation method for a single-ended injection-type light-emitting device is disclosed. Considering that the single-ended injection-type light-emitting device emits light only in the positive half cycle, in order to improve display brightness, a single driving cycle is evenly divided into N subframes based on the relationship between amplitude and brightness. Then, based on the relationship between amplitude and brightness, M reference voltages are selected, each reference voltage corresponding to a reference grayscale. Grayscale control of the relative duty cycle is performed based on the relationship between the relative duty cycle and brightness.

[0010] Furthermore, according to the relationship between amplitude and brightness, the single driving period is divided into N subframes on average. Specifically, according to the frequency-brightness curve, the single driving period is divided into N subframes on average.

[0011] Furthermore, according to the relationship between amplitude and brightness, M reference voltages are selected specifically as follows: M reference voltages are selected according to an amplitude-brightness curve and the number of grayscales to be displayed.

[0012] Furthermore, according to the relationship between the relative duty cycle and the brightness, grayscale control of the relative duty cycle specifically includes:

[0013] According to the persistence of vision characteristics of the human eye, the grayscale level can be adjusted by changing the number P of square waves in a single cycle when the external driving voltage and driving frequency are constant.

[0014] Furthermore, the implementation process of the program includes the following steps:

[0015] Step S1: Divide a single driving cycle into N subframes on average according to the frequency-brightness curve;

[0016] Step S2: selecting M reference voltages according to the amplitude-brightness curve and the number of grayscales to be displayed, each reference voltage corresponding to a reference grayscale;

[0017] Step S3: determining the relative duty ratios corresponding to the intermediate grayscales between adjacent reference grayscales according to the relative duty ratio-brightness curve, and adjusting the grayscale according to the relative duty ratios.

[0018] Furthermore, the single-ended injection-type light-emitting device is driven by an alternating voltage, and the voltage waveform of the alternating electric field includes one of a sine wave, a triangle wave, a square wave, and a pulse, or a combination thereof.

[0019] Furthermore, the relative duty cycle refers to the number P of subframes having an AC driving waveform in a single driving cycle, ie, P / N.

[0020] Furthermore, at least one of the upper electrode and the lower electrode of the single-end injection type light-emitting device is a transparent electrode.

[0021] Compared to existing technologies, the present invention and its preferred embodiment design a grayscale modulation scheme suitable for single-end injection light-emitting devices based on the characteristics of single-end injection light-emitting devices in different emission modes and frequencies, combined with the visual characteristics of the human eye. Through a hybrid modulation of amplitude, frequency, and relative duty cycle, precise grayscale modulation of single-end injection light-emitting devices is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Figure 1 is a schematic diagram of an exemplary driving waveform according to an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of an exemplary driving voltage and light emitting waveform according to an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the luminous brightness of a device under different duty cycles according to an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of the luminous brightness of a device at different driving frequencies according to an embodiment of the present invention;

[0027] Figure 5 Schematic diagram of device luminance under different relative duty cycle driving waveforms according to an embodiment of the present invention;

[0028] Figure 6 Schematic diagram of device luminance under different relative duty cycle driving waveforms according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the features and advantages of this patent more clearly understood, the following embodiments are specifically described in detail as follows:

[0030] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art to which this application belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] The purpose of the present invention is to provide a grayscale modulation method for a single-end injection type light emitting device. In the design process of the scheme:

[0033] First, the brightness change curve of the single-ended injection light-emitting device as the amplitude, relative duty cycle, and frequency change are collected to obtain the amplitude-brightness curve, the relative duty cycle-brightness curve, and the frequency-brightness curve.

[0034] According to the amplitude-brightness curve, relative duty cycle-brightness curve, and frequency-brightness curve of the light-emitting device, it can be seen that the brightness is most affected by the amplitude, followed by the relative duty cycle, and the frequency has the least impact.

[0035] Considering that pulse width modulation is suitable for DC light-emitting devices, the use of pulse width modulation technology has no obvious effect and regularity on the grayscale modulation of single-ended injection light-emitting devices.

[0036] Consider again that a single-ended injection-type light-emitting device emits light in the positive half cycle of the AC driving voltage and does not emit light in the negative half cycle of the AC voltage.

[0037] Based on this, a grayscale modulation method for a single-ended injection-type light-emitting device is designed. According to the human eye integration and the human eye visual persistence effect, the brightness of different driving waveforms in a single light-emitting cycle is superimposed in the human eye vision to improve the brightness perceived by the human eye.

[0038] Specifically, a time-sharing drive method is employed based on the human eye's persistence of vision. When the human eye sees, an image is formed on it, and the image is perceived through input. However, when the object is removed, the visual nerve's impression of the object does not disappear immediately, but lingers for 0.1 seconds. Persistence of vision is a phenomenon in which the visual perception produced by light on the retina persists for a period of time after the light ceases to act.

[0039] The above design process can be summarized into the following steps:

[0040] Step 1: Collect the curve of the brightness of the single-ended injection light-emitting device as the amplitude, relative duty cycle, and frequency change, and obtain the amplitude-brightness curve, relative duty cycle-brightness curve, and frequency-brightness curve;

[0041] Step 2: Based on the amplitude-brightness curve, relative duty cycle-brightness curve, and frequency-brightness curve of the light-emitting device, it is found that the brightness is most affected by the amplitude, followed by the relative duty cycle, and the frequency has the least impact;

[0042] Step 3: Divide a single driving cycle into N subframes on average according to the frequency-brightness curve;

[0043] Step 4: Select M reference voltages based on the amplitude-brightness curve and the number of grayscales to be displayed, where each reference voltage corresponds to a reference grayscale;

[0044] Step 5: Based on the relative duty cycle-brightness curve, determine the relative duty cycle corresponding to each grayscale between adjacent reference grayscales. This relative duty cycle allows for precise grayscale adjustment.

[0045] The single-end injection light-emitting device shown in the embodiment of the present invention includes but is not limited to a single-end carrier injection inductive light-emitting device and a non-carrier injection inductive light-emitting device.

[0046] The light-emitting device uses a single-ended injection electroluminescence mode, meaning there is no ohmic contact between one of the external electrodes and the light-emitting device, and the other electrode is directly connected to the light-emitting device. The light-emitting device is driven to emit light through periodic, indirect, single-ended carrier injection.

[0047] Since the response speed of the single-ended injection light-emitting device is very fast, the period of the required AC driving waveform is very small, less than 0.01 second.

[0048] The luminous colors include but are not limited to any one of red, green, blue and white.

[0049] The voltage waveform of the driving waveform alternating electric field includes but is not limited to a sine wave, a triangle wave, a square wave, a pulse or a combination thereof.

[0050] At least one of the upper electrode and the lower electrode of the device is a transparent electrode, and the material of the transparent electrode includes but is not limited to graphene, indium tin oxide, carbon nanotubes, silver nanowires, copper nanowires or their combinations; the material of the non-transparent electrode includes but is not limited to gold, silver, aluminum, copper or their combinations.

[0051] The following is a specific example to further illustrate the design of the present invention:

[0052] The six driving waveforms designed in the example of the present invention have relative duty ratios of 1 / 10, 2 / 10, 4 / 10, 6 / 10, 8 / 10, and 10 / 10, respectively.

[0053] like Figure 1 As shown, in this embodiment, a single drive cycle is divided into ten equal parts, where a single cycle is T. The first drive waveform has a relative duty cycle of 1 / 10, the second drive waveform has a relative duty cycle of 2 / 10, the third drive waveform has a relative duty cycle of 4 / 10, the fourth drive waveform has a relative duty cycle of 6 / 10, the fifth drive waveform has a relative duty cycle of 8 / 10, and the sixth drive waveform has a relative duty cycle of 10 / 10. As the relative duty cycle increases within a single cycle, the number of square waves within the single cycle also increases.

[0054] A single driving cycle is evenly divided into N subframes, M reference voltages are selected, each reference voltage corresponds to a reference grayscale, six driving waveforms with relative duty cycles are selected, and each relative duty cycle waveform corresponds to a grayscale.

[0055] like Figure 2 As shown, this is the luminous image of the light-emitting device under the square wave driving signal. Figure 2 The two vertical axes represent voltage (V) and relative brightness (EL). The AC characteristics of the entire light-emitting device are the process of continuous light emission with a 2μs period. It can be seen that under the square wave drive signal, the light-emitting device only emits significant light in the first half of the square wave cycle, and emits light on the rising edge of the drive waveform.

[0056] Figure 2 It can be seen that the single-injection light-emitting device responds very quickly. The positive half cycle of the square wave emits light, and the second half cycle of the square wave prepares for the next light emission.

[0057] like Figure 3 As shown in the figure, the relative brightness of the light-emitting device changes with the duty cycle under the square wave driving signal. Figure 3 The vertical axis represents the relative brightness, and the horizontal axis represents the square wave duty cycle.

[0058] Visibly, in Figure 3 In the experiment, the relative brightness of the single-ended injection type light-emitting device does not increase regularly with the increase of the driving square wave duty cycle.

[0059] exist Figure 3 In the figure, the relative luminous intensity of the light-emitting device increases with the increase of the duty cycle within a certain range. After the duty cycle exceeds 10%, the duty cycle increases and the relative luminous intensity of the device decreases.

[0060] It can be seen that the method of modulating the grayscale of the device by changing the duty cycle is not applicable to the single-end injection type light-emitting device.

[0061] like Figure 4 As shown, in Figure 4 The vertical axis represents the relative brightness, and the horizontal axis represents the driving frequency. As the driving frequency increases, the relative brightness of the light-emitting device gradually increases.

[0062] It can be seen that the frequency can affect the brightness of the light-emitting device. It is feasible to control the brightness of the single-end injection light-emitting device by changing the driving frequency.

[0063] like Figure 5 As shown, six driving waveforms designed using this embodiment, the vertical axis is the relative brightness of the light-emitting device, the horizontal axis is the driving frequency, and the six curves represent driving waveforms with different relative duty cycles.

[0064] Visibly, in Figure 5 In the embodiment, the driving frequency is constant, and as the relative duty cycle increases, the relative brightness of the light-emitting device gradually increases.

[0065] It can be seen that when the external driving voltage remains unchanged, the luminous brightness corresponding to the six driving waveforms increases with the increase of frequency, achieving the effect of increasing the grayscale level of the light-emitting device as the relative duty cycle increases.

[0066] like Figure 6 , using the six driving waveforms designed in this embodiment, Figure 6 The vertical axis represents the relative brightness, and the horizontal axis represents the driving voltage. As the driving voltage increases, the relative brightness of the light-emitting device gradually increases.

[0067] Visibly, in Figure 6 In the embodiment, the driving voltage is constant. As the relative duty cycle increases, the relative brightness of the light-emitting device gradually increases. The brightness of the light-emitting device is controlled by mixing the voltage and the relative duty cycle.

[0068] Visibly, as Figure 6 When the external driving frequency remains unchanged, the luminous brightness corresponding to the six driving waveforms increases with the increase of the driving voltage, achieving the effect of increasing the grayscale level of the light-emitting device with the increase of the driving voltage.

[0069] When the frequency remains unchanged and the external driving voltage increases, the carrier transport speed inside the device increases, more carriers flow into the single-ended injection-type light-emitting device for radiative recombination, and the device's luminous brightness also increases accordingly.

[0070] In summary, the present invention designs a driving waveform with a relative duty cycle by utilizing the time domain characteristics that the device only emits light in the positive half cycle. By controlling the driving voltage and frequency, the brightness of the light-emitting device is mixedly controlled. When the brightness of the device remains unchanged, the driving voltage and driving frequency can be reduced, energy consumption is reduced, and the display grayscale level is improved, making the grayscale modulation of the single-injection light-emitting device more accurate.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

[0072] This patent is not limited to the above-mentioned optimal implementation method. Anyone can derive various other forms of grayscale modulation methods for single-end injection light-emitting devices based on the inspiration of this patent. All equivalent changes and modifications made within the scope of the patent application of this invention should be covered by this patent.

Claims

1. A grayscale modulation method for a single-end injection light-emitting device, characterized in that: The single-ended injection type light emitting device is driven by an AC voltage, and the single-ended injection type light emitting device emits light in the positive half cycle of the AC voltage and does not emit light in the negative half cycle of the AC voltage. The grayscale modulation method comprises the following steps: step 1: collecting a curve of the brightness change of the single-ended injection type light emitting device as the amplitude, relative duty cycle, and frequency change, and obtaining an amplitude-brightness curve, a relative duty cycle-brightness curve, and a frequency-brightness curve; step 2: comparing the amplitude-brightness curve, the relative duty cycle-brightness curve, and the frequency-brightness curve of the light emitting device, and obtaining that the brightness is most affected by the amplitude, followed by the relative duty cycle, and the frequency has the least influence; step 3 : According to the frequency-brightness curve, a single driving cycle is evenly divided into N subframes; Step 4: According to the amplitude-brightness curve and the number of grayscales to be displayed, M reference voltages are selected, and each reference voltage corresponds to a reference grayscale; Step 5: According to the relative duty cycle-brightness curve, the relative duty cycle corresponding to each grayscale in the middle of adjacent reference grayscales is determined, and the grayscale is controlled by the relative duty cycle. Specifically, according to the visual persistence characteristics of the human eye, when the external driving voltage and driving frequency are constant, the grayscale level is controlled by changing the number of square waves in a single cycle, that is, the grayscale control of the number of times the device emits light in a single cycle and the driving time occupied is controlled.

2. The grayscale modulation method of a single-end injection type light emitting device according to claim 1, characterized in that: At least one of the upper electrode and the lower electrode of the single-end injection type light emitting device is a transparent electrode.

3. The grayscale modulation method of a single-end injection light-emitting device according to claim 2, characterized in that: The material of the transparent electrode includes any one of graphene, indium tin oxide, carbon nanotubes, silver nanowires, and copper nanowires, or a combination thereof.

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