Display device using light emitting element and driving method thereof

Abstract

The present invention is applicable to the technical field related to display devices and relates to a display device using, for example, a light emitting diode (LED) and a method for driving the same. The present invention comprises: a wiring board on which a plurality of unit pixel regions are defined; a pixel unit including at least two groups of light emitting elements mounted in each unit pixel area to form unit sub-pixels; and a driver driving the pixel unit, in which one group of light emitting elements includes red, green, and blue light emitting elements, and the driver simultaneously operates at least two groups of light emitting elements under a first condition and independently drives the at least two groups of light emitting elements under a second condition.

Description

Technical Field

[0001] The present disclosure relates to a display device and a driving method thereof, which is applicable to a technical field related to display devices and uses, for example, a light emitting diode (LED). Background Art

[0002] Recently, display devices having advantageous characteristics such as thin profile or flexibility have been developed in the field of display technology. Currently, the main types of displays available on the market are represented by liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays.

[0003] Meanwhile, light-emitting diodes (LEDs) are well-known semiconductor light-emitting elements that convert electric current into light. The commercialization of red LEDs using GaAsP compound semiconductors began in 1962, and since then, GaP:N-based green LEDs have also been adopted as light sources for displaying images in electronic devices including information and communication equipment.

[0004] Such light emitting diodes (LEDs) have been used in various applications, such as pixels of display devices or flat lighting.

[0005] The target brightness of outdoor high-brightness display devices installed outdoors varies depending on the time of day (daytime / nighttime). The difference in target brightness is about tenfold. For example, during the day, a minimum brightness of 3,000 nits is required. In some cases, a brightness of up to 8,000 nits is required. However, at night, a brightness range of 300 to 500 nits is required.

[0006] Outdoor display devices are mainly used for advertising purposes, and a key aspect of such display devices is to attract the attention of nearby individuals. During the day, it may be advantageous for the display device to be visibly presented to pedestrians, drivers or passers-by at high brightness (at least 3000 nits).

[0007] Therefore, the gray level performance of the display device has been evaluated based on the maximum luminance, and the gray level performance at low luminance levels has not been considered important and therefore has not been the subject of evaluation.

[0008] However, since 2010, rapid technological advancements have led to an increase in the installation of displays for outdoor signage, which has led to light pollution at night. As a result, nighttime brightness levels have been regulated by law in individual countries or municipalities.

[0009] With the implementation of such nighttime brightness regulations, grayscale level representation at nighttime brightness levels (300 to 500 nits) has become necessary.

[0010] In particular, a display device using a light emitting diode (LED) requires the use of a separate light emitting element to achieve grayscale expression, and therefore, improvements in this situation are needed. Summary of the Invention

[0011] Technical issues

[0012] One aspect of the present disclosure is to provide a display device using a light-emitting element and a driving method thereof, which allows grayscale level representation to be accurately designed even at a minimum brightness level (corresponding to approximately one-tenth of the maximum brightness), thereby accurately and smoothly representing images within a low grayscale level range.

[0013] In addition, the present disclosure provides a display device using a light emitting element and a driving method thereof, which can achieve accurate grayscale level expression not only when external conditions of the display device require high brightness but also when low brightness is required.

[0014] In addition, the present disclosure provides a display device using light emitting elements and a driving method thereof, which can extend the life of the light emitting elements by individually and selectively driving at least two groups of light emitting elements forming each pixel.

[0015] In addition, the present disclosure provides a display device using a light-emitting element and a driving method thereof, which can improve the efficiency of the light-emitting element by reducing the deterioration of the efficiency of the light-emitting element due to heat and the reduction in the luminance of the light-emitting element due to direct external light (sunlight) and the heat generated thereby, thereby reducing the heat generation in the display device and improving its efficiency.

[0016] Technical Solution

[0017] According to a first aspect of the present disclosure for achieving the above-mentioned purpose, a display device using light-emitting elements includes: a wiring substrate having a plurality of unit pixel areas defined in the wiring substrate; a pixel portion including at least two groups of light-emitting elements installed in each of the unit pixel areas to form a unit sub-pixel; and a driver configured to drive the pixel portion, wherein a group of light-emitting elements includes a red light-emitting element, a green light-emitting element, and a blue light-emitting element, and wherein the driver can be configured to: simultaneously drive the at least two groups of light-emitting elements under a first condition, and independently drive the at least two groups of light-emitting elements under a second condition.

[0018] In an exemplary embodiment, independently driving the at least two groups of light emitting elements may include driving the at least two groups of light emitting elements at the same time or at different times.

[0019] In an exemplary embodiment, the first condition and the second condition may include a condition based on an external brightness level.

[0020] In an exemplary embodiment, the first condition may include a condition based on an external brightness level corresponding to daytime, and the second condition may include a condition based on an external brightness level corresponding to a time other than daytime.

[0021] In an exemplary embodiment, the first condition may correspond to an external brightness level within a range of 100 lux to 10,000 lux, and the second condition may correspond to an external brightness level equal to or less than 100 lux.

[0022] In an exemplary embodiment, the display device may further include an illuminance sensor configured to measure luminance of an external environment, and the first condition and the second condition may be distinguished based on an output value of the illuminance sensor.

[0023] In an exemplary embodiment, under the second condition, the at least two groups of light emitting elements may be driven differently from each other according to a grayscale level of the pixel part.

[0024] In an exemplary embodiment, under the second condition, parts of the at least two groups of light emitting elements may be driven according to a grayscale level of the pixel part.

[0025] In an exemplary embodiment, the driver may be configured to input the same drive signal (PWM) to the at least two groups of light-emitting elements under the first condition, and the driver may be configured to input the same or different drive signals (PWM) to the at least two groups of light-emitting elements under the second condition.

[0026] In an exemplary embodiment, the driver may be configured to input the same driving signal (PWM) to the at least two groups of light-emitting elements under the first condition, and the driver may be configured to input different driving signals (PWM) to the at least two groups of light-emitting elements according to the grayscale level of the pixel portion under the second condition.

[0027] In an exemplary embodiment, for minimum gray level representation, the driver may be configured to drive one group of light emitting elements among the at least two groups of light emitting elements, or may be configured to drive the at least two groups of light emitting elements in a separate manner.

[0028] In an exemplary embodiment, the driver may include: an illuminance sensor configured to measure the luminance of an external environment; a gate driver configured to apply a light-up signal to the pixel portion; a data driver configured to apply a luminance signal to the pixel portion; a current source configured to supply current to the data driver; and a controller configured to control at least one of the illuminance sensor, the gate driver, or the data driver.

[0029] According to a second aspect of the present disclosure for achieving the above-mentioned purpose, a method for driving a display device is provided, wherein the display device includes a pixel portion, the pixel portion including at least two groups of light-emitting elements installed in each unit pixel area in a unit pixel area to form a unit sub-pixel, and the method for driving the display device includes the following steps: detecting ambient luminance; determining a brightness range based on the ambient luminance; simultaneously driving the at least two groups of light-emitting elements within a first brightness range; and independently driving the at least two groups of light-emitting elements within a second brightness range.

[0030] In an exemplary embodiment, independently driving the at least two groups of light emitting elements may include driving the at least two groups of light emitting elements at the same time or at different times.

[0031] In an exemplary embodiment, the first brightness range may include a condition based on an external brightness level corresponding to daytime, and the second brightness range may include a condition based on an external brightness level corresponding to a time other than daytime.

[0032] In an exemplary embodiment, the first brightness range may be within a range of 100 lux to 10,000 lux, and the second brightness range may be equal to or less than 100 lux.

[0033] In an exemplary embodiment, the method may further include driving the at least two groups of light emitting elements differently from each other according to a grayscale level of the pixel part within the second luminance range.

[0034] In an exemplary embodiment, the method may further include driving parts of the at least two groups of light emitting elements according to a grayscale level of the pixel part within the second brightness range.

[0035] In an exemplary embodiment, the method may further include the following steps: within the first brightness range, inputting the same driving signal (PWM) to the at least two groups of light-emitting elements, and within the second brightness range, inputting the same or different driving signals (PWM) to the at least two groups of light-emitting elements.

[0036] In an exemplary embodiment, the method may further include the following steps: within the first brightness range, inputting the same driving signal (PWM) to the at least two groups of light-emitting elements, and within the second brightness range, inputting different driving signals (PWM) to the at least two groups of light-emitting elements according to the grayscale level of the pixel portion.

[0037] Beneficial effects

[0038] According to the embodiments of the present disclosure, the following effects can be achieved.

[0039] First, according to the embodiments of the present disclosure, grayscale representation can be accurately designed even at the minimum brightness level (corresponding to approximately one-tenth of the maximum brightness), thereby accurately and smoothly representing images in a low grayscale range.

[0040] Furthermore, the structure and driving method of the pixel portion according to the embodiment of the present disclosure can achieve accurate grayscale level expression not only when the external conditions of the display device require high brightness but also when low brightness is required.

[0041] In addition, according to embodiments of the present disclosure, the lifespan of the light-emitting elements can be extended by individually and selectively driving at least two groups of light-emitting elements that form each pixel. For example, depending on the driving conditions, only one light-emitting element in each pixel can be turned on, while the remaining light-emitting elements can be turned off, thereby improving the lifespan of the light-emitting elements.

[0042] In addition, according to the embodiments of the present disclosure, the efficiency of the light-emitting element can be improved by reducing the degradation of the efficiency of the light-emitting element due to heat generation and the reduction in the luminance of the light-emitting element due to direct external light (sunlight) and the heat generated thereby. Therefore, the heat generation in the display device can be reduced and its efficiency can be improved.

[0043] In addition, according to another embodiment of the present disclosure, additional technical effects not mentioned herein may also be exhibited, and those skilled in the art will understand this from the entire specification and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a block diagram illustrating a configuration of a display device using a light emitting element according to an embodiment of the present disclosure.

[0045] Figure 2 is a schematic cross-sectional view illustrating a display device using a light emitting element according to an embodiment of the present disclosure.

[0046] Figure 3 is a conceptual diagram illustrating a unit pixel of a display device using a light emitting element according to an embodiment of the present disclosure.

[0047] Figure 4 yes Figure 3 Circuit diagram.

[0048] Figure 5 is a conceptual diagram illustrating a unit pixel of a display device using a light emitting element according to another embodiment of the present disclosure.

[0049] Figure 6 yes Figure 5 Circuit diagram.

[0050] Figure 7 is a circuit diagram illustrating two pixels of a display device using a light emitting element according to another embodiment of the present disclosure.

[0051] Figure 8 is a plan view illustrating a pixel structure of a display device using a light emitting element according to an embodiment of the present disclosure.

[0052] Figure 9 and Figure 10 is a graph showing grayscale level expression during driving of a general display device using a light emitting element according to a comparative example.

[0053] Figure 11 : is a graph showing grayscale level expression based on driving of a display device using a light emitting element according to an embodiment of the present disclosure.

[0054] Figures 12 to 14 is a conceptual diagram illustrating a PWM driving state of a display device using a light emitting element according to an embodiment of the present disclosure.

[0055] Figure 15 and Figure 16 is a conceptual diagram illustrating a PWM driving state of a display device using a light emitting element according to another embodiment of the present disclosure.

[0056] Figure 17 is a flowchart illustrating a method of driving a display device using a light emitting element according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0057] Reference will now be made in detail to embodiments of the present disclosure, examples of which are shown in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the accompanying drawings to refer to the same or similar parts, and redundant descriptions thereof will be omitted. As used herein, the suffixes "module" and "unit" are added or used interchangeably to facilitate the preparation of this specification and are not intended to imply different meanings or functions. When describing the embodiments disclosed in this specification, the relevant known technologies may not be described in detail so as not to obscure the subject matter of the embodiments disclosed in this specification. In addition, it should be noted that the drawings are only used to easily understand the embodiments disclosed in this specification and should not be interpreted as limiting the technical spirit disclosed in this specification.

[0058] Furthermore, although the drawings are described separately for simplicity, an embodiment implemented by combining at least two or more drawings is also within the scope of the present disclosure.

[0059] In addition, when an element such as a layer, region or module is referred to as being “on” another element, it should be understood that the element can be directly on the other element or intervening elements may be present therebetween.

[0060] In addition, the semiconductor light-emitting device mentioned in this specification is a concept including LEDs, micro LEDs, etc., which can be used in a mixed manner.

[0061] Figure 1 is a block diagram showing a configuration of a display device using a light emitting element according to an embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view illustrating a display device using a light emitting element according to an embodiment of the present disclosure.

[0062] refer to Figure 1 , shows an overall configuration of a display device 100 including a pixel portion 110 and a driver 200 configured to drive the pixel portion 110.

[0063] For example, the pixel portion 110 may include at least two groups of light emitting elements forming a unit sub-pixel. In addition, a group of light emitting elements may include a red light emitting element R1(1), a green light emitting element G1(1), and a blue light emitting element B1(1).

[0064] Figure 1 An example is shown in which each pixel in the pixel portion 110 includes three groups of light-emitting elements. That is, one pixel may include three red light-emitting elements R1(1), R1(2), R1(3), three green light-emitting elements G1(1), G1(2), G1(3), and three blue light-emitting elements B1(1), B1(2), B1(3). Meanwhile, in other examples, one pixel may include two groups of light-emitting elements or may include more than three groups of light-emitting elements.

[0065] Pixels each including three groups of light emitting elements may be connected to each other via scan lines such as scan line 1, scan line 2, ..., and scan line n. In this way, a predetermined number of pixels may be provided on each of the scan lines such as scan line 1, scan line 2, ..., and scan line n. Figure 1 The figure shows a state where m pixels are arranged on one scan line. The m pixels may include 3m sub-pixels, and a total of 3*3m data lines such as data line 1, data line 2, ..., and data line 3*3m may be provided by three groups of light emitting elements.

[0066] Data lines such as data line 1, data line 2, ..., and data line 3*3m can be driven by a data driver 210. The data lines can be respectively connected to the light-emitting elements forming the sub-pixels. In addition, a current source 240 for providing current to the data driver 210 can be provided at the other end of each of the data lines. Therefore, a total of 3*3m current sources 240 can be provided.

[0067] In addition, each of the scan lines, such as scan line 1 , scan line 2 , . . . , scan line n, may be connected to the gate driver 220 .

[0068] At least one of the data driver 210 or the gate driver 220 may be controlled by the controller 230 .

[0069] Depending on the conditions, the at least two groups of light-emitting elements can be driven simultaneously or independently. Even when the at least two groups of light-emitting elements are driven independently, the two groups of light-emitting elements can also be driven together. In other words, the situations in which the at least two groups of light-emitting elements are driven independently include driving the two groups of light-emitting elements together, driving the two groups of light-emitting elements alternately, and driving only a portion of the two groups of light-emitting elements. For example, the two groups of light-emitting elements can be driven at the same time or at different times.

[0070] For example, at least two groups of light-emitting elements may be driven simultaneously under a first condition, and at least two groups of light-emitting elements may be driven independently under a second condition. As an example, the first condition and the second condition may be external light conditions at the location where the display device 100 is located. In other words, the first condition and the second condition may be brightness conditions at the location where the display device 100 is located. In other words, the first condition and the second condition may be conditions based on external brightness levels.

[0071] According to an exemplary embodiment, the first condition may be a condition in which the external brightness level corresponds to daytime, and the second condition may be a condition in which the external brightness level corresponds to a time other than daytime (eg, sunrise, sunset, or nighttime).

[0072] For example, under high brightness conditions (3000 to 8000 nits) during the day (first condition), at least two groups of light-emitting elements constituting each pixel can be driven simultaneously. Meanwhile, under low brightness conditions (300 to 500 nits) during the night (second condition), at least two groups of light-emitting elements constituting each pixel can be driven individually.

[0073] According to an exemplary embodiment, the first condition may correspond to a case where the external brightness level is within a range of 100 lux to 10,000 lux, and the second condition may correspond to a case where the external brightness level is 100 lux or less.

[0074] According to an exemplary embodiment, the driver 200 may include an illuminance sensor 250 configured to detect an external light condition or a brightness condition.

[0075] Therefore, the first condition and the second condition may be distinguished based on the output value of the illuminance sensor 250 .

[0076] According to an exemplary embodiment, under the second condition, at least two groups of light emitting elements may be driven differently according to the grayscale level of the pixel portion 110. For example, under the second condition, parts of at least two groups of light emitting elements may be driven according to the grayscale level of the pixel portion 110.

[0077] According to an exemplary embodiment, under a first condition, the driver 200 may input the same driving signal (pulse width modulation (PWM) signal) to at least two groups of light-emitting elements, and under a second condition, the driver 200 may input the same or different driving signals (PWM signals) to at least two groups of light-emitting elements.

[0078] According to an exemplary embodiment, under a first condition, the driver 200 may input the same driving signal (PWM) to at least two groups of light emitting elements, and under a second condition, the driver 200 may input different driving signals (PWM) to at least two groups of light emitting elements according to the grayscale level of the pixel portion 110.

[0079] According to exemplary embodiments, for minimum gray level representation, the driver 200 may drive only one group of light emitting elements among the at least two groups of light emitting elements, or may drive the at least two groups of light emitting elements in a divided manner.

[0080] Driving of the display device 100 according to such external light conditions will be described in detail later with reference to the accompanying drawings.

[0081] Thus, the driver 200 may include an illumination sensor 250 configured to measure the luminance of an external environment in which the display device 100 is located, a gate driver 220 configured to apply a lighting signal to the pixel portion 110, a data driver 210 configured to apply a luminance signal to the pixel portion 110, and a current source 240 configured to supply current to the data driver 210. Furthermore, the driver 200 may include a controller 230 configured to control at least one of the illumination sensor 250, the gate driver 220, or the data driver 210.

[0082] Reference Figure 2 The display device 100 may include a wiring substrate 120 in which a plurality of unit pixel regions P11 and P13 are defined.

[0083] The above-mentioned pixel portion 110 may include at least two groups of light emitting elements installed in each of the unit pixel regions P11 and P13 to form a unit sub-pixel.

[0084] A group of light emitting elements may include a red light emitting element R1(1), a green light emitting element G1(1), and a blue light emitting element B1(1). In this case, the driver 200 may simultaneously drive the at least two groups of light emitting elements under a first condition, and may independently drive the at least two groups of light emitting elements under a second condition.

[0085] For example, each of the light-emitting elements R1(1), G1(1), B1(1), R3(1), G3(1), and B3(1) installed in the unit pixel regions P11 and P13 may substantially correspond to a sub-pixel. For example, at least two groups of sub-pixels may constitute one pixel.

[0086] Each of the light emitting elements R1(1), G1(1), B1(1), R3(1), G3(1), and B3(1) may be electrically connected to a pair of electrode pads 141 and 142. In this case, for example, Figure 2 The electrode pad 141 in one direction (hereinafter referred to as the first electrode pad) can be connected to the above-mentioned scan line (or common electrode). In this case, the electrode pad 142 arranged in the opposite direction (hereinafter referred to as the second electrode pad) can be connected to the above-mentioned data line (or signal electrode). However, the opposite configuration is also possible. Figure 2 In order to make the layout of the electrode pads clear, the illustration of the scan lines and data lines is omitted.

[0087] Hereinafter, the same reference numerals will be used interchangeably for electrode pads and wiring electrodes. That is, the electrode pads and wiring electrodes may be denoted using the same reference numerals.

[0088] In this way, a unit sub-pixel can be defined at the intersection of the scan line and the data line.

[0089] Meanwhile, for example, the data line may be connected to a thin film transistor (TFT) layer 121. Therefore, each of the light emitting elements R1(1), G1(1), B1(1), R3(1), G3(1), and B3(1) may be driven by a switching operation through the TFT layer 121.

[0090] exist Figure 2 , the TFT layer 121 is schematically shown as a single layer. However, the TFT layer 121 may include a plurality of TFT regions capable of performing switching operations. For example, each TFT region may include a gate electrode, a source electrode, a drain electrode, an insulating layer disposed between the electrodes, and a through-hole electrode that may be connected to a data line or a second electrode pad 142. A detailed description thereof will be omitted. Each of the TFT regions may be connected to a corresponding one of the light emitting elements R1(1), G1(1), B1(1), R3(1), G3(1), and B3(1).

[0091] As described above, at least two groups of light emitting elements can form separate sub-pixels and can be repeatedly arranged on the wiring substrate 120. The light emitting element can include at least one of an organic light emitting element and an inorganic light emitting element. For example, the light emitting element can be an inorganic semiconductor light emitting diode (LED).

[0092] Such a semiconductor light emitting diode (LED) may have a size in the micrometer (μm) range. The size in the micrometer (μm) range may mean that at least one surface of the light emitting diode has a width ranging from a few micrometers (μm) to several hundred micrometers (μm).

[0093] TFT layer 121 may be provided on wiring substrate 120, and insulating layer 130 may be coated on TFT layer 121. Insulating layer 130 may cover connection portions between electrode pads 141 and 142 and the light emitting element.

[0094] Figure 3 is a conceptual diagram illustrating a unit pixel of a display device using a light emitting element according to an embodiment of the present disclosure. Figure 4 yes Figure 3 Circuit diagram.

[0095] Reference Figure 3 and Figure 4 , shows an example in which a unit pixel includes two groups of light-emitting elements. For example, a first pixel P11 on a wiring substrate 120 of a pixel portion 110 may include two groups of light-emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), and B1(2).

[0096] For example, R1(1), G1(1) and B1(1) may refer to a first group of light-emitting elements of the first pixel P11, and R1(2), G1(2) and B1(2) may refer to a second group of light-emitting elements of the first pixel P11. In this way, the first pixel P11 may include a total of six light-emitting elements. However, this is merely an example, and a group of light-emitting elements may also include more light-emitting elements in addition to R1(1), G1(1) and B1(1). For example, a group of light-emitting elements may also include a red light-emitting element or a green light-emitting element in addition to R1(1), G1(1) and B1(1). As another example, a group of light-emitting elements may also include a white light-emitting element in addition to R1(1), G1(1) and B1(1). In the following, an example in which a group of light-emitting elements includes R1(1), G1(1) and B1(1), i.e., red, green and blue light-emitting elements, is mainly described.

[0097] Figure 4 1 is a circuit diagram showing an example in which the first pixel P11 includes two groups of light emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), and B1(2).

[0098] A single pixel (eg, P11) may include two red light emitting elements R1(1) and R1(2), two green light emitting elements G1(1) and G1(2), and two blue light emitting elements B1(1) and B1(2).

[0099] One side of each of the two groups of light emitting elements R1(1), G1(1), B1(1), R1(2), G1(2) and B1(2) may be commonly connected, and the other side thereof may be connected to the current source 240.

[0100] Figure 5 is a conceptual diagram illustrating a unit pixel of a display device using a light emitting element according to another embodiment of the present disclosure. Figure 6 yes Figure 5 Circuit diagram.

[0101] Reference Figure 5 and Figure 6 , shows an example in which a unit pixel includes three groups of light-emitting elements. For example, a first pixel P11 on a wiring substrate 120 of a pixel portion 110 may include three groups of light-emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), B1(2), R1(3), G1(3), and B1(3).

[0102] Figure 6 is a circuit diagram showing an example in which the first pixel P11 includes three groups of light emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), B1(2), R1(3), G1(3) and B1(3).

[0103] A single pixel (e.g., P11) may include three red light-emitting elements R1(1), R1(2), and R1(3), three green light-emitting elements G1(1), G1(2), and G1(3), and three blue light-emitting elements B1(1), B1(2), and B1(3).

[0104] One side of each of the three groups of light emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), B1(2), R1(3), G1(3) and B1(3) can be connected in common, and the other side thereof can be connected to the current source 240.

[0105] Figure 7 is a circuit diagram illustrating two pixels of a display device using a light emitting element according to another embodiment of the present disclosure.

[0106] Reference Figure 7 , in the pixel portion 110, the first pixel P11 includes three groups of light emitting elements R1(1), G1(1), B1(1), R1(2), G1(2), B1(2), R1(3), G1(3) and B1(3), and the second pixel P12 includes three groups of light emitting elements R2(1), G2(1), B2(1), R2(2), G2(2), B2(2), R2(3), G2(3) and B2(3).

[0107] In this way, the plurality of pixels P11 and P12 may be configured to include the same number of light emitting elements.

[0108] Figure 8 is a plan view illustrating a pixel structure of a display device using a light emitting element according to an embodiment of the present disclosure.

[0109] Reference Figure 8 , a display device 100 using a light emitting element includes a pixel portion 110 provided on a wiring substrate 120, and the pixel portion 110 includes six pixels in a horizontal direction and four pixels in a vertical direction. Figure 8 The display device 100 shown in FIG. 1 may correspond to a portion of the entire display device 100 , and for example, may correspond to one module of the entire display device 100 .

[0110] The pixel portion 110 of the display device 100 may include six pixels P11 to P16 arranged in a horizontal direction. Each pixel may include three groups of light emitting elements, as described above with reference to FIG. Figures 5 to 7 As stated.

[0111] In addition, the pixel portion 110 may include four pixels P11 to P41 arranged in a vertical direction. Therefore, the pixel indicated by P46 may be located at the lower right corner.

[0112] Typically, the target brightness of outdoor high-brightness display devices installed outdoors varies depending on the time of day (daytime / nighttime). The difference in target brightness is about tenfold. For example, during the day, a minimum brightness of 3,000 nits is required. In some cases, a brightness of up to 8,000 nits is required. However, at night, a brightness range of 300 to 500 nits is required.

[0113] The reasons are as follows. Outdoor display devices are primarily used for advertising purposes, and a key aspect of such display devices is to attract the attention of nearby individuals. During daytime, it can be advantageous for the display device to be visibly presented to pedestrians, drivers, or passersby at high brightness (at least 3000 nits).

[0114] Therefore, the gray level performance of the display device has been evaluated based on the maximum luminance, and the gray level performance at low luminance levels has not been considered important and therefore has not been the subject of evaluation.

[0115] However, since 2010, rapid technological advancements have led to an increase in the installation of displays for outdoor signage, which has led to light pollution at night. As a result, nighttime brightness levels have been regulated by law in individual countries or municipalities.

[0116] With the implementation of such nighttime brightness regulations, grayscale level representation at nighttime brightness levels (300 to 500 nits) has become necessary.

[0117] In particular, a display device using a light emitting diode (LED) requires the use of a separate light emitting element to achieve grayscale expression, and therefore, improvements in this situation are needed.

[0118] Therefore, according to the display device 100 of the embodiment of the present disclosure having the above-described structure and driving conditions, grayscale representation can be accurately designed even at the lowest brightness level (corresponding to approximately one-tenth of the maximum brightness). Therefore, images can be accurately and smoothly represented at low grayscale levels.

[0119] In particular, in the case of a display device installed outdoors, under high brightness conditions due to, for example, sunlight, an image is displayed with high brightness. However, under low brightness conditions, for example, during nighttime, it may be difficult to achieve accurate grayscale representation using the same pixel structure.

[0120] In contrast, the structure and driving method of the pixel portion according to the embodiment of the present disclosure can achieve accurate grayscale representation not only when the external conditions of the display device require high brightness, but also when low brightness is required. This will be described in detail later.

[0121] Furthermore, the lifespan of the light-emitting elements can be extended by individually and selectively driving at least two groups of light-emitting elements that form each pixel. For example, depending on the driving conditions, only one light-emitting element in each pixel can be turned on, while the remaining light-emitting elements can be turned off, thereby increasing the lifespan of the light-emitting elements.

[0122] However, when a group of light emitting elements is driven at a high current, the efficiency of the light emitting elements may deteriorate due to heat generation, and the luminance of the light emitting elements may decrease due to direct external light (sunlight) and heat generated thereby.

[0123] In contrast, according to the embodiments of the present disclosure, the above-mentioned problems can be solved and the efficiency of the light-emitting element can be improved. Therefore, the heat generation in the display device can be reduced and the efficiency of the display device can be improved.

[0124] Figure 9 and Figure 10 is a graph showing grayscale level expression during driving of a general display device using a light emitting element according to a comparative example.

[0125] Figure 9 An example of low-luminance driving in a general display device including one red LED, one green LED, and one blue LED in each unit pixel is shown.

[0126] For example, reference Figure 9 (a), when the external light condition is 500 nits (nighttime condition) and the target brightness is 1000 nits, each LED may be driven with a current of, for example, 10 mA.

[0127] In this case, refer to Figure 9 In (b), it can be seen that when a total of 256 gray levels are represented, the gray levels are clearly represented in discrete steps even in a low gray level range.

[0128] Figure 10 Shown with Figure 9 The display device shown is an example of low-brightness driving and high-brightness driving in the same display device.

[0129] For example, reference Figure 10 In (a), when the external light condition is 3000 nits (daytime condition) and the target brightness is 3000 nits, each LED can be driven with a current of, for example, 30 mA. In this case, it can be seen that when a total of 256 gray levels are represented, the gray levels are clearly represented in discrete steps even in the low gray level range.

[0130] In another example, when the external light condition is 500 nits (nighttime condition) and the target brightness is 1000 nits, each LED may be driven with a current of, for example, 10 mA.

[0131] However, in this case, referring to Figure 10 As can be seen from (b), accurate grayscale representation is not achieved in the low grayscale range (e.g., the 60th grayscale level or lower). That is, in the low grayscale range, the change in brightness may not be represented in discrete steps. In addition, saturation may occur in the high grayscale range (e.g., the 200th grayscale level or higher), resulting in the inability to represent the brightness change corresponding to the grayscale levels between 200 and 256.

[0132] Therefore, reference Figure 10 In (b), when the target brightness is 1000 nits, the gamma 2.2 may not be satisfied. As a result, the grayscale level may not be smooth, resulting in the occurrence of banding.

[0133] Figure 11 : is a graph showing grayscale level expression based on driving of a display device using a light emitting element according to an embodiment of the present disclosure.

[0134] Figure 11 Examples of low-brightness driving and high-brightness driving in a display device including three groups of red, green, and blue LEDs in a unit pixel according to an embodiment of the present disclosure are shown.

[0135] For example, reference Figure 11 (a) shows that when the external light condition is 3000 nits (daytime condition) and the target brightness is 3000 nits, gray levels can be expressed by driving all three groups of light-emitting elements. In this case, it can be seen that when a total of 256 gray levels are expressed, the gray levels are clearly expressed in discrete steps even in the low gray level range.

[0136] In another example, when the external light condition is 500 nits (nighttime condition) and the target brightness is 1000 nits, the gray level may be expressed by driving one group of light emitting elements among three groups of light emitting elements.

[0137] In this case, it can be seen that when a total of 256 gray levels are expressed, the gray levels are clearly expressed in discrete steps also in the low gray level range.

[0138] Figures 12 to 14 is a conceptual diagram illustrating a PWM driving state of a display device using a light emitting element according to an embodiment of the present disclosure.

[0139] The driving of the display device 100 using a light-emitting element (i.e., the on / off operation of the light-emitting element) can adopt a pulse width modulation (PWM) scheme. However, the present disclosure is not limited thereto, and a pulse amplitude modulation (PAM) scheme or other driving schemes may also be adopted. Hereinafter, an example of driving a display device using a light-emitting element according to an embodiment of the present disclosure using a PWM scheme will be described.

[0140] Figures 12 to 14 The pixel portion 110 has the above reference Figure 3 and Figure 4 The driving process is expressed according to the grayscale level in the case of the described structure. That is, the driving process in the case where each pixel includes two groups of light emitting elements #1LED and #2LED will be described.

[0141] First reference Figure 12 , for example, when the target brightness is 3000 nits, that is, under daytime conditions, the gray level can be represented by driving two groups of light emitting elements #1LED and #2LED.

[0142] That is, when representing a total of 256 gray levels, the 256th gray level can be represented using a PWM waveform that turns on the two sets of light-emitting elements #1LED and #2LED throughout the entire cycle. Furthermore, the 128th gray level can be represented using a PWM waveform that turns on the two sets of light-emitting elements #1LED and #2LED for half of the entire cycle. Furthermore, the minimum gray level (gray level 1) can be represented using a PWM waveform that turns on the two sets of light-emitting elements #1LED and #2LED for the minimum duration within the entire cycle.

[0143] Through this process, it is possible to Figure 11 Grayscale levels are shown.

[0144] At the same time, reference Figure 13 , for example, when the target brightness is 1000 nits, the gray level can be expressed by driving two groups of light emitting elements #1LED and #2LED using two methods, Case 1 and Case 2.

[0145] First, according to the first method case 1, only one of the two groups of light emitting elements #1LED and #2LED (for example, #1LED) can be used, and Figure 12 The gray level can be expressed by the same process as shown in FIG. That is, the gray level can be expressed normally without turning on the #2 LED.

[0146] Meanwhile, according to the second method, case 2, within the high grayscale range, grayscale levels are expressed by simultaneously driving two groups of light-emitting elements #1LED and #2LED. However, in this case, since the two groups of light-emitting elements #1LED and #2LED are driven simultaneously, each pulse width can correspond to half the pulse width in case 1 of the first method.

[0147] In addition, according to the second method case 2, in the low gray level range, the gray level is expressed by selectively or alternately driving two groups of light emitting elements #1LED and #2LED. Figure 13 , shows an example of inputting a PWM signal to alternately drive two groups of light emitting elements #1LED and #2LED at a minimum grayscale level (1 / 256 grayscale level).

[0148] refer to Figure 14 , for example, when the target brightness is 500 nits (external light conditions other than daytime conditions), the gray level can be represented by driving two groups of light emitting elements #1LED and #2LED using two methods, Case 1 and Case 2.

[0149] First, according to the first method case 1, only one of the two groups of light emitting elements #1LED and #2LED (for example, #1LED) can be used to represent the gray level. That is, the gray level can be normally represented without turning on #2LED.

[0150] In this case, since the target brightness is 500 nits, it is Figure 13 Therefore, for high grayscale level expression (for example, 256 / 256 grayscale level) and middle grayscale level expression (for example, 128 / 256 grayscale level), the same Figure 13 The pixel portion 110 is driven by a waveform corresponding to half of the waveform in .

[0151] However, in a low grayscale level range (eg, 1 / 256), the minimum size waveform may be used to drive the pixel portion 110. Furthermore, the pixel portion 110 may be driven using a portion of the minimum size waveform.

[0152] Meanwhile, according to the second method, case 2, for high grayscale level representation (e.g., 256 / 256 grayscale level) and intermediate grayscale level representation (e.g., 128 / 256 grayscale level), grayscale levels are represented by simultaneously driving two groups of light-emitting elements #1LED and #2LED. However, in this case, since the two groups of light-emitting elements #1LED and #2LED are driven simultaneously, each pulse width can correspond to half the pulse width in case 1 of the first method.

[0153] In addition, according to the second method case 2, within the low gray level range (1 / 256 gray level), the gray level is expressed by selectively or alternately driving two groups of light emitting elements #1LED and #2LED. Figure 14 , shows an example of inputting a PWM signal to alternately drive two groups of light emitting elements #1LED and #2LED at a minimum grayscale level (1 / 256 grayscale level).

[0154] In this way, in order to express gray levels under dark external light conditions, for example, during nighttime, at least two groups of light emitting elements #1LED and #2LED may be driven differently from each other.

[0155] That is, according to an exemplary embodiment, under the second condition corresponding to non-daytime, parts of at least two groups of light emitting elements #1LED and #2LED may be driven according to the grayscale level of the pixel part 110 .

[0156] In an embodiment of driving the pixel portion 110 of the display device 100 by PWM driving, under a first condition corresponding to daytime, the driver 200 may input the same driving signal PWM to at least two groups of light-emitting elements #1LED and #2LED, and under a second condition corresponding to non-daytime (for example, at sunrise, sunset, or nighttime), the driver 200 may input the same or different driving signal PWM to at least two groups of light-emitting elements #1LED and #2LED.

[0157] According to an exemplary embodiment, under a first condition, the driver 200 may input the same driving signal PWM to at least two groups of light emitting elements #1LED and #2LED, and under a second condition, the driver 200 may input different driving signals PWM to at least two groups of light emitting elements #1LED and #2LED according to the grayscale level of the pixel portion 110.

[0158] In addition, for minimum grayscale level representation (e.g., 1 / 256 grayscale level), the driver 200 can drive only one group of light emitting elements among at least two groups of light emitting elements #1LED and #2LED, or can drive at least two groups of light emitting elements #1LED and #2LED in a separate manner.

[0159] Figure 15 and Figure 16 is a conceptual diagram illustrating a PWM driving state of a display device using a light emitting element according to another embodiment of the present disclosure.

[0160] As described above, the display device 100 using the light emitting element may be driven (ie, turned on / off) using a pulse width modulation (PWM) scheme. However, the present disclosure is not limited thereto, and a pulse amplitude modulation (PAM) scheme or other driving schemes may also be used.

[0161] Figure 15 and Figure 16 The pixel portion 110 has the above reference Figure 5 and Figure 6 The driving process is described in terms of grayscale level in the case of the described structure. That is, the driving process will be described in the case where each pixel includes three groups of light emitting elements #1LED, #2LED and #3LED.

[0162] First reference Figure 15 , for example, when the target brightness is 3000 nits, that is, under daytime conditions, the gray level can be represented by driving all three groups of light emitting elements #1LED, #2LED and #3LED.

[0163] That is, when representing a total of 256 gray levels, a PWM waveform that turns on all three groups of light-emitting elements #1, #2, and #3 can be used to represent the 256th gray level. In this case, one group of light-emitting elements (e.g., #3 LED) can be driven to achieve a brightness of 1000 nits, which corresponds to one-third of the target brightness of 3000 nits.

[0164] Furthermore, the 128th gray level can be represented using a PWM waveform that turns on all three groups of light-emitting elements #1LED, #2LED, and #3LED within half of the cycle used to represent the 256th gray level. Furthermore, the minimum gray level (1 / 256 gray level) can be represented using a PWM waveform that turns on all three groups of light-emitting elements #1LED, #2LED, and #3LED within the minimum duration within the entire cycle.

[0165] At the same time, reference Figure 16 For example, when the target brightness is 500 nits (external light conditions other than daytime conditions), the gray level can be represented by driving three groups of light emitting elements #1LED, #2LED and #3LED using two methods, Case 1 and Case 2.

[0166] First, according to the first method case 1, only one light emitting element (e.g., #1LED) among the three light emitting elements #1LED, #2LED, and #3LED can be used to represent the grayscale level. That is, the grayscale level can be normally represented without turning on #2LED and #3LED.

[0167] In this case, since the target brightness is 500 nits, it is Figure 15 Therefore, for high grayscale level expression (for example, 256 / 256 grayscale level) and middle grayscale level expression (for example, 128 / 256 grayscale level), the same Figure 16 A separate waveform corresponding to half of the waveform in the case is used to drive a group of light-emitting elements (for example, #1 LED).

[0168] However, in a low grayscale level range (eg, 1 / 256), a minimum size waveform may be used to drive the pixel portion 110. Additionally, a portion of the minimum size waveform may be used to drive a group of light emitting elements (eg, #1 LED).

[0169] Meanwhile, according to the second method case 2, for high gray level representation (e.g., 256 / 256 gray level) and intermediate gray level representation (e.g., 128 / 256 gray level), gray levels are represented by simultaneously driving three groups of light emitting elements #1LED, #2LED, and #3LED. However, in this case, since the three groups of light emitting elements #1LED, #2LED, and #3LED are driven simultaneously, each pulse width may correspond to one-third of the pulse width in the first method case 1 (the pulse width is Figure 16 Schematically shown in FIG).

[0170] In addition, according to the second method case 2, within the low gray level range (1 / 256 gray level), the gray level is represented by selectively or alternately driving three groups of light emitting elements #1LED, #2LED and #3LED. Figure 16 , shows an example of inputting a PWM signal to alternately drive two groups of light emitting elements #1LED and #2LED among three groups of light emitting elements #1LED, #2LED and #3LED at a minimum grayscale level (1 / 256 grayscale level).

[0171] In this way, in order to express gray levels under dark external light conditions (for example, at night), the three groups of light emitting elements #1LED, #2LED, and #3LED may be driven differently from each other.

[0172] That is, according to an exemplary embodiment, under the second condition corresponding to non-daytime, parts of the three groups of light emitting elements #1LED, #2LED, and #3LED may be driven according to the grayscale level of the pixel part 110 .

[0173] In an embodiment in which the pixel portion 110 of the display device 100 is driven by PWM driving, under a first condition corresponding to daytime, the driver 200 may input the same driving signal PWM to the three groups of light-emitting elements #1LED, #2LED, and #3LED, and under a second condition corresponding to non-daytime (for example, at sunrise, sunset, or nighttime), the driver 200 may input the same or different driving signals PWM to the three groups of light-emitting elements #1LED, #2LED, and #3LED.

[0174] According to an exemplary embodiment, under a first condition, the driver 200 may input the same driving signal PWM to the three groups of light emitting elements #1LED, #2LED, and #3LED, and under a second condition, the driver 200 may input different driving signals PWM to the three groups of light emitting elements #1LED, #2LED, and #3LED according to the grayscale level of the pixel portion 110.

[0175] In addition, for minimum grayscale level representation (e.g., 1 / 256 grayscale level), the driver 200 can drive only one group of light emitting elements among the three groups of light emitting elements #1LED, #2LED and #3LED, or can drive two groups of light emitting elements #1LED and #2LED in a separate manner.

[0176] Figure 17 is a flowchart illustrating a method of driving a display device using a light emitting element according to another embodiment of the present disclosure.

[0177] Reference Figure 17 , the above method of driving the display device 100 is shown using a flowchart. Figure 15 and Figure 16 The example of display device 100 described above includes three groups of light emitting elements #1LED, #2LED and #3LED per pixel. The driving signals for driving the three groups of light emitting elements #1LED, #2LED and #3LED can be referred to as pixel data, including data 1, data 2 and data 3.

[0178] First, the ambient brightness may be detected (S10). The process of detecting the ambient brightness may be a step of distinguishing between daytime conditions and nighttime conditions.

[0179] Therefore, the ambient luminance of the environment in which the display device 100 is located may be determined ( S20 ), and the brightness range of the display device 100 (LED display) may be determined ( S30 and S40 ).

[0180] For example, if the ambient luminance of the environment in which the display device 100 is located is higher than the ambient luminance under night conditions (yes in S20), that is, if it corresponds to daytime conditions, the driving brightness range of the display device 100 (LED display) can be determined as the first brightness range (S30).

[0181] Thus, if the driving brightness range of the display device 100 (LED display) is determined to be the first brightness range, the driver 200 can input the same PWM signal as pixel data to the pixel portion 110 (S31). That is, the driver 200 can input the same PWM signal to the three groups of light emitting elements #1LED, #2LED, and #3LED (S31).

[0182] At the same time, for example, if the ambient luminance of the environment in which the display device 100 is located is not higher than the ambient luminance under night conditions (No in S20), that is, if it corresponds to sunset, sunrise or night time, the driving brightness range of the display device 100 (LED display) can be determined as the second brightness range (S40).

[0183] In this way, if the driving brightness range of the display device 100 (LED display) is determined to be the second brightness range, the three groups of light emitting elements #1LED, #2LED, and #3LED can be driven independently.

[0184] For example, the driver 200 may input at least partially different PWM signals to the pixel portion 110 as pixel data (S41). That is, the driver 200 may input at least partially different PWM signals to the three groups of light emitting elements #1LED, #2LED, and #3LED (S41).

[0185] As described above, independently driving at least two groups of light emitting elements (in this example, three groups of light emitting elements #1LED, #2LED, and #3LED) may correspond to driving the at least two groups of light emitting elements at the same time or at different times.

[0186] Furthermore, the first brightness range may be a condition in which the external brightness level corresponds to daytime, and the second brightness range may be a condition in which the external brightness level corresponds to non-daytime.

[0187] As described above, according to an exemplary embodiment, the first brightness range may be from 100 lux to 10,000 lux, and the second brightness range may be equal to or less than 100 lux.

[0188] For details not described above, reference is equally applicable. Figures 12 to 14 The driving process of the first embodiment described and reference Figure 15 and Figure 16The driving process of the second embodiment is described.

[0189] The above description is provided by way of example only to illustrate the present invention, and those skilled in the art will appreciate that various modifications and changes may be made without departing from the essential characteristics of the present invention.

[0190] Therefore, the embodiments disclosed herein are intended to illustrate rather than limit the scope of the present invention, and the scope of the present invention should not be interpreted as being limited by these embodiments.

[0191] The protection scope of the present invention should be defined by the appended claims, and all modifications or equivalents falling within the scope of the claims should be construed as being included in the scope of the present invention.

[0192] Industrial Applicability

[0193] According to the present disclosure, there are provided a display device using a semiconductor light emitting element such as an LED and a driving method thereof.

Claims

1. A display device using a light-emitting element, the display device comprising: a wiring substrate having a plurality of unit pixel regions defined therein; a pixel portion including at least two groups of light emitting elements installed in each of the unit pixel regions to form a unit sub-pixel; as well as a driver configured to drive the pixel portion, wherein a group of light emitting elements includes a red light emitting element, a green light emitting element and a blue light emitting element, and Wherein, the driver is configured as follows: The at least two groups of light emitting elements are driven simultaneously under a first condition, and The at least two groups of light emitting elements are independently driven under a second condition.

2. The display device according to claim 1, wherein Driving the at least two groups of light emitting elements independently includes driving the at least two groups of light emitting elements at the same time or at different times.

3. The display device according to claim 1, wherein The first condition and the second condition include conditions based on an external brightness level.

4. The display device according to claim 3, wherein The first condition includes a condition based on an external brightness level corresponding to daytime, and Here, the second condition includes a condition based on an external brightness level corresponding to a time other than daytime.

5. The display device according to claim 3, wherein The first condition corresponds to the external brightness level within a range of 100 lux to 10,000 lux, and The second condition corresponds to the external brightness level being equal to or less than 100 lux.

6. The display device according to claim 1, further comprising an illuminance sensor configured to measure luminance of an external environment. in, The first condition and the second condition are distinguished based on an output value of the illuminance sensor.

7. The display device according to claim 1, wherein Under the second condition, the at least two groups of light emitting elements are driven differently from each other according to the grayscale level of the pixel portion.

8. The display device according to claim 7, wherein: Under the second condition, parts of the at least two groups of light emitting elements are driven according to the grayscale level of the pixel part.

9. The display device according to claim 1, wherein The driver is configured to input the same driving signal PWM to the at least two groups of light emitting elements under the first condition, and The driver is configured to input the same or different driving signals PWM to the at least two groups of light-emitting elements under the second condition.

10. The display device according to claim 1, wherein The driver is configured to input the same driving signal PWM to the at least two groups of light emitting elements under the first condition, and The driver is configured to input different driving signals PWM to the at least two groups of light emitting elements according to the grayscale level of the pixel portion under the second condition. The display device according to claim 10 , wherein: For minimum gray level representation, the driver is configured to drive one of the at least two groups of light emitting elements, or to drive the at least two groups of light emitting elements in a separate manner.

12. The display device according to claim 1, wherein The driver includes: an illuminance sensor configured to measure the luminance of an external environment; a gate driver configured to apply a lighting signal to the pixel portion; a data driver configured to apply a luminance signal to the pixel portion; a current source configured to supply current to the data driver; and A controller configured to control at least one of the illumination sensor, the gate driver, or the data driver.

13. A method for driving a display device, the display device comprising a pixel portion including at least two groups of light-emitting elements installed in each of unit pixel regions to form a unit sub-pixel, the method comprising the following steps: Detect environmental brightness; determining a brightness range based on the ambient luminance; Simultaneously driving the at least two groups of light-emitting elements within a first brightness range; as well as The at least two groups of light emitting elements are independently driven within a second brightness range.

14. The method for driving a display device according to claim 13, wherein: The step of independently driving the at least two groups of light emitting elements includes driving the at least two groups of light emitting elements at the same time or at different times.

15. The method for driving a display device according to claim 13, wherein: The first brightness range includes conditions based on an external brightness level corresponding to daytime, and Here, the second brightness range includes conditions based on an external brightness level corresponding to a time other than daytime.

16. The method for driving a display device according to claim 13, wherein: The first brightness range is in the range of 100 lux to 10,000 lux, and Wherein, the second brightness range is equal to or less than 100 lux.

17. The method for driving a display device according to claim 13, further comprising the following steps: The at least two groups of light emitting elements are driven differently from each other according to the grayscale level of the pixel part within the second luminance range.

18. The method for driving a display device according to claim 17, further comprising the following steps: Parts of the at least two groups of light emitting elements are driven according to the grayscale level of the pixel part within the second luminance range.

19. The method for driving a display device according to claim 13, further comprising the following steps: In the first brightness range, the same driving signal PWM is input to the at least two groups of light emitting elements, and In the second brightness range, the same or different driving signals PWM are input to the at least two groups of light emitting elements.

20. The method for driving a display device according to claim 13, further comprising the following steps: In the first brightness range, the same driving signal PWM is input to the at least two groups of light emitting elements, and Different driving signals PWM are input to the at least two groups of light emitting elements according to the grayscale levels of the pixel portions within the second brightness range.

Images