CN111868813B

CN111868813B - LED pixel package

Info

Publication number: CN111868813B
Application number: CN201980003583.4A
Authority: CN
Inventors: 金镇赫; 金钟善
Original assignee: Beijing Xinneng Electronic Technology Co ltd
Current assignee: Beijing Xinneng Electronic Technology Co ltd
Priority date: 2019-02-11
Filing date: 2019-12-26
Publication date: 2023-03-10
Anticipated expiration: 2039-12-26
Also published as: CN111868813A; KR20200097940A; WO2020166813A1; KR102222092B1

Abstract

The multi-pixel package according to the present embodiment includes: multi-pixel groups each including a plurality of unit pixels of R (red), G (green), and B (blue) LEDs having cathodes commonly connected; a data signal for controlling a luminance of light output by a unit pixel belonging to a pixel group; and a control section for receiving a control signal in which a pulse train including an activation signal and a plurality of pulses is embedded and controlling the multi-pixel group. Wherein, the control portion includes: a signal separation unit (110) for separating and outputting an activation signal and a pulse train, respectively; a charging signal activated by the activation signal and each pixel group controlled to charge energy to emit light from the pulse sequence; an emission control section for outputting an emission signal to control each pixel group to emit light from the pulse sequence; and a pixel group control section to which a charging signal is supplied to charge energy supplied as a data signal and which controls an emission signal to cause the pixel group to emit light.

Description

LED pixel package

Technical Field

The present technology relates to an LED pixel package.

Background

Recently, in the implementation of commercial outdoor and indoor billboards, it is a trend to increase the display area and increase the resolution of the display. In addition, LEDs are employed as light emitting devices in order to achieve high luminance, high contrast, and good color reproducibility.

The necessity of using an Active Matrix (Active Matrix) array for a display using LEDs is also emerging. In this case, the control pins have an advantage that they can be greatly reduced compared to the passive matrix method by controlling the horizontal and vertical axes using active elements, instead of directly controlling the LEDs constituting the pixels. Accordingly, after the driver circuit for driving is extremely simplified, it is very advantageous to reduce the pixel size and the pixel interval, and also to reduce power consumption.

For an LED display, the narrower the gap between the LEDs, the denser the number of pixels, and the higher the brightness of the individual LEDs, the better the resolution of the display, and hence the better the image quality. Preferably, in case of implementing the LED display as an active matrix, the LED display can be more efficiently implemented in terms of physical size and cost.

For this reason, pins for power supply, data input, ground, etc. must be formed in the LED pixel package, and in addition, switch control pins for respectively activating and emitting the red LED, the green LED, and the blue LED must be formed in the LED pixel package.

Disclosure of Invention

Technical problem

As described above, when the LED pixel package is implemented, since the size thereof can be configured to be large, there is a problem that it is not effective in implementing the active matrix in terms of physical size and cost. The technical problem to be solved by the present embodiment is to provide a novel LED pixel package capable of solving these problems.

Technical scheme

The multi-pixel package according to the present embodiment includes: multi-pixel groups each including a plurality of unit pixels of R (red), G (green), and B (blue) LEDs having cathodes (cathodes) connected in common; a data signal for controlling the luminance of light output by a unit pixel belonging to a pixel group; and a control section for receiving a control signal (S _ SIG) in which a pulse train including an activation signal and a plurality of pulses is embedded (embed) and controlling the multi-pixel group. Wherein, the control portion includes: a signal separating section for separating and outputting an activation signal (ON) and a pulse train (S _ OUT), respectively; charge signals (EN _1, EN _2, EN _3) activated by the activation signals, and each pixel group is controlled to charge energy to emit light from the pulse sequence; an emission control section for outputting an emission signal (emission signal) to control each pixel group to emit light (emission signal) from the pulse sequence; and a pixel group control section to which a charging signal is supplied to charge energy supplied as a data signal and which controls an emission signal to cause the pixel group to emit light.

According to an aspect of the present invention, anodes of the R LEDs included in the first pixel group and the second pixel group are electrically connected to each other to provide the R control signal, and anodes of the G LEDs are electrically connected to each other to provide the G control signal, and anodes of the B LEDs are electrically connected to each other to provide the B control signal.

According to one aspect of the invention, a control signal is embedded in a pulse train, the pulse train comprising: an activation signal that swings (swing) between a first level and a second level that is greater than the first level; and a plurality of pulse trains swinging between a second level and a third level greater than the second level, the signal separating section including: an activation signal separation circuit including a transistor having a threshold voltage between first and second levels and outputting after separating an activation signal to swing the activation signal between the first and third levels; a pulse train separation circuit comprising a transistor having a threshold voltage between the second level and the third level and separating the pulse train before output to swing the pulse train between the first and third levels.

According to one aspect of the present invention, a light emission control unit includes: a counter (counter) which counts and outputs pulses contained in the pulse signal after being activated by the activation signal (ON); and an encoder (encoder) for forming and outputting charge signals and emission signals of the multi-pixel groups corresponding to the outputs of the counters.

According to one aspect of the present technology, the pixel control section includes a capacitor that stores energy supplied as a data signal, and if an emission signal is supplied, a voltage charged by the capacitor is supplied to the resistor, so that the pixel emits light, thereby forming a luminance control signal for controlling and supplying the luminance of the pixel to the pixel.

According to one aspect of the present technology, a pixel control unit includes: a capacitor that stores energy supplied as a data signal; a charge transistor controlled by a charge signal and electrically connecting a data signal to the capacitor; an operational amplifier which supplies the voltage charged to the capacitor to one input, and the other input is connected to the resistor and supplies the voltage charged to the capacitor to the charging transistor through the resistor; a transmission transistor controlled by a transmission signal to isolate an output of the operational amplifier from ground; a transistor connected to be controlled by the output of the operational amplifier and to supply a brightness control signal to the pixel.

According to an aspect of the present technology, the R control signal, the G control signal, and the B control signal that do not overlap in one frame are supplied to the multi-pixel package at uniform times.

The multi-pixel package array according to the present technology configures a multi-pixel package in an array, and provides the same R, G, and B control signals to the multi-pixel packages connected to the same row (row) of the multi-pixel package array, and provides the same data signal to the multi-pixel packages connected to the same column (row) of the multi-pixel package array.

According to one aspect of the present technology, the multi-pixel packed array, after programming an image to be displayed at the nth row (row), performs the nth row emission, but starts the nth row emission and the programming of the (n + 1) th row at the same time.

According to an aspect of the present technology, the R control signal, the G control signal, and the B control signal that do not overlap in one frame are supplied to the multi-pixel package at a uniform time.

According to one aspect of the present technology, the R control signal, the G control signal, and the B control signal are alternately supplied at a frequency having a characteristic that the multi-pixel package array is observed with the naked eye, thereby enabling recognition of the frequency at which the R, G, and B LEDs display a full color image.

Effects of the invention

According to the present technology, a plurality of unit pixels and control circuits can be formed in a single package, thereby reducing the size thereof. Thus, there is provided an advantage of an active matrix capable of overcoming problems in physical size and cost and realizing a fine pixel pitch.

Drawings

Fig. 1 is a diagram showing an outline of an LED pixel package according to the present embodiment;

fig. 2 is a diagram showing an overview of the control section;

fig. 3A is a schematic circuit diagram of the signal separating section, and fig. 3B is a diagram showing an overview of an activation signal and a pulse sequence output by the control signal and signal separating section;

fig. 4A is a block diagram showing an outline of the light emission control section, and fig. 4B is a schematic timing chart of signals input to and output from the light emission control section.

Fig. 5 is a circuit diagram showing an overview of the one-pixel group control section.

Fig. 6 is a timing chart according to the operation of the pixel group control section according to the present embodiment shown in fig. 2;

fig. 7 is a diagram showing a state where a multi-pixel package according to the present embodiment is configured in an array and implemented as an active matrix;

fig. 8 is a timing diagram of signals provided in a multi-pixel package implemented in an active matrix;

fig. 9 is an exemplary timing chart when color is realized by configuring a multi-pixel package in an array according to the present embodiment.

Detailed Description

The invention relates to a multi-pixel package, comprising: multi-pixel groups each including a plurality of unit pixels of R (red), G (green), and B (blue) LEDs having cathodes (cathodes) connected in common; a data signal for controlling a luminance of light output by a unit pixel belonging to a pixel group; and a control section for receiving a control signal (S _ SIG) in which a pulse train including an activation signal and a plurality of pulses is embedded (embed) and controlling the multi-pixel group. Wherein, the control part includes: a signal separating section (110) for separating and outputting an activation signal (ON) and a pulse train, respectively; a charging signal activated by the activation signal and each pixel group is controlled to charge energy to emit light from the pulse sequence; an emission control section for outputting an emission signal (emission signal) to control each pixel group to emit light (emission signal) from the pulse sequence; and a pixel group control section to which a charging signal is supplied to charge energy supplied as a data signal and which controls an emission signal to cause the pixel group to emit light.

The description of the present invention is merely for purposes of describing example embodiments structurally or functionally, and therefore the scope of the claims herein should not be interpreted as limited by the example embodiments described herein. That is, since various modifications may be made to the embodiments and various forms may be made, it should be understood that the scope of the present invention includes equivalents which may achieve technical spirit.

Fig. 1 is a diagram showing an overview of an LED pixel package according to the present embodiment. Referring to fig. 1, a multi-pixel package 1 according to the present embodiment includes: multi-pixel groups each including a plurality of unit pixels (P1 a, P1B, P1c, P2a, P2B, P2 c) of R (red), G (green), and B (blue) LEDs having cathodes (cathodes) connected in common; a data signal for controlling the luminance of light output by the unit pixels (P1 a, P1b, P1c, P2a, P2b, P2 c) belonging to the pixel group (200a, 200b); and a control section 100 for receiving a control signal (S _ SIG) in which a pulse train including an activation signal and a plurality of pulses is embedded (embedded) and controlling the multi-pixel group. Wherein, the control part includes: a signal separation section (110) for separating and outputting an activation signal (ON) and a pulse train (S _ OUT), respectively; charge signals (EN _1, EN _2, EN _3) activated by the activation signals, and each pixel group is controlled to charge energy to emit light from the pulse sequence; an emission control section (120) for outputting an emission signal (emission signal) to control each pixel group to emit light (emission signal) from the pulse sequence; and a pixel group control section (130) to which a charging signal (EN _1, EN _2, EN _3) is supplied to charge energy supplied as the DATA signal (DATA 1, DATA 2), and to which a control emission signal (EMI) is supplied to cause the pixel group to emit light.

Each of the unit pixels (P1 a, P1B, P1c, P2a, P2B, P2 c) includes an LED emitting R, G, and B colors, and a cathode (cathode) of the LED included in the unit pixel is electrically connected to the control part 100. As described later, a luminance control signal (icon) is supplied to the unit pixels, and the luminance of light output by the unit pixels (P1 a, P1b, P1c, P2a, P2b, P2 c) is controlled by the luminance control signal.

Among the LEDs included in the unit pixels (P1 a, P1B, P1c, P2a, P2B, P2 c), the anodes of the LEDs (R1 a, R1B, R1c, R2a, R2B, R2 c) emitting the R color are all electrically connected to provide an R control signal (VLED _ R), and the anodes of the LEDs (R1 a, R1B, R1c, R2a, R2B, R2 c) emitting the G color are all electrically connected to provide a G control signal (VLED _ G), and the anodes of the LEDs (B1 a, B1B, B1c, B2a, B2B, B2 c) emitting the B color are all electrically connected to provide a B control signal (VLED _ B).

Fig. 2 is a diagram showing an overview of the control unit (100). Referring to fig. 2, the control unit 100 includes a signal separation unit 110, a light emission control unit 120, and multi-pixel group control units (130a 1,130a2,130a3,130b1,130b2,130b 3). Fig. 3A is a schematic circuit diagram of the signal separating section 110, and fig. 3B is a diagram showing an overview of the activation signal (ON) and the pulse train (S _ OUT) output by the control signal and signal separating section.

Referring to fig. 3 (a) and 3 (B), the control signal (S _ SIG) may swing (swing) between a first level, a second level, and a third level. As an example, the first level may be a ground voltage level, the third level may be a driving Voltage (VCC) level, the second level may be greater than a threshold voltage of an NMOS transistor included in the signal separator 110 but less than the third level, and may be a level less than twice the threshold voltage of the NMOS transistor.

A control signal (S SIG) is embedded in a pulse sequence comprising: an activation signal that swings between a ground voltage and a second level; and a pulse that swings between the second level and a third level as the driving Voltage (VCC).

The signal separator 110 includes: an activation signal separation circuit 112 for separating the activation signal (ON) from the control signal (S _ SIG); and a pulse train separation circuit 114 for separating the pulse train (S _ OUT) from the control signal (S _ SIG).

In the activation signal circuit 112, an inverter I1 including a resistor Ra and a transistor N1 having a threshold voltage between a first level and a second level, a schmitt trigger ST, and an inverter I2 are cascaded. The threshold voltage of the transistor N1 is greater than the first level but less than the second level. Accordingly, when the first level control signal S _ SIG is input to the inverter I1, the transistor N1 is turned off to output a logic high signal of the third level. However, if the second or third level control signal (S _ SIG) is input to the transistor N1, it is turned on. Accordingly, the inverter I1 outputs a logic low signal of the first level.

Schmitt trigger (schmitt trigger) is a circuit that does not respond to transient noise because the output response according to the magnitude and direction of the input has a hysteresis curve, and has a relatively high threshold voltage when the input rises and a relatively low threshold voltage when the input falls.

The output of the Schmitt Trigger (ST) is supplied to an inverter I2, the inverter I2 is a signal that inverts the supplied input and swings between the first level and the third level, and the output of the inverter I2 is an activation signal (ON) that controls the activation of the subsequent light emission control section 120.

The first-stage inverter I3 is connected with the ground voltage with the diode-connected NMOS transistor N3 interposed therebetween. The NMOS transistor N4 included in the inverter I3 is turned on with a voltage obtained by adding the threshold voltage of the diode-connected NMOS transistor N3 to the threshold voltage of the transistor N4.

As described above, the voltage obtained by adding the threshold voltage of N3 and the 4 threshold voltage of N is greater than the second level. Accordingly, if the control signal (S _ SIG) having the first and second levels is supplied to the inverter I3, the NMOS transistor N4 is not turned on, so that the inverter I3 outputs a logic high signal of the third level. However, if the control signal (S _ SIG) having the third level is supplied to the inverter I3, the NMOS transistor N4 is turned on, so that the inverter I3 outputs a logic low level signal of the first level. Accordingly, the pulse sequence embedded in the control signal (S _ SIG) can be separated. The inverter I4 inverts the output signal of the inverter I3 and then outputs the inverted output signal to a pulse train (S _ OUT) oscillating between the first level and the third level.

Fig. 4A is a block diagram showing an overview of the light emission control section, and fig. 4B is a schematic timing chart of signals input to and output from the light emission control section. Referring to fig. 4A and 4B, the light emission control section 120 includes: a counter (counter) 122 that counts and outputs pulses contained in the pulse signal (S _ OUT) after being activated by the activation signal (ON); and an encoder (encoder) 124 for forming and outputting charge signals (EN _1, EN _2, EN _3) and emission signals (EMI) corresponding to the

multi-pixel groups

200a,200b of the counter output.

As an embodiment, when the activation signal (ON) is in a logic high state, the counter 122 counts the number of pulses included in the pulse train (S _ OUT) provided after the activation (active high) and outputs in a binary form, and when the activation signal (ON) is in a logic low state, the output is reset. As shown in the illustrated embodiment, the counter may be a three-bit counter, and the counter 122, activated by an (ON) signal in a logic high state, may be reset by the activation signal after counting 001, 010, 011, 100, and 101 by incrementing 1 each time one pulse is counted from 000.

As an example, the pulse sequence (S _ OUT) may include pulses of the number of pixels included in the pixel group or more, and the number of pulses included in the pulse sequence may vary with the number of pixels included in the pixel group.

The encoder 124 may receive the output of the counter 122, and sequentially form and provide the charge signals (EN _1, EN _2, EN _3) and the emission signals (. EMI) of the unit pixels. As an example, since the output of the counter is three bits, the encoder can output eight different signals. Accordingly, seven pixel groups can be controlled by outputting one emission signal (-EMI) and seven charging signals.

In the illustrated embodiment, the transmit signal (EMI) is an output signal that is inverted from the encoder. The circuit is designed to include an inverter in the encoder 124, or the transmission signal (-EMI) may be output by connecting the output of the encoder 124 and the inverter.

Fig. 5 is a circuit diagram showing an overview of the one-pixel group control section 130. Referring to fig. 5, the charge transistor (SWD) is turned on by the charge signal (EN), and the capacitor (C) stores energy provided to the data signal (D) in the form of a voltage.

The non-inverting input of the operational amplifier is connected to the capacitor and the voltage (Vc) charged in the capacitor (C) is supplied to the non-inverting input and the inverting input is connected to the resistor. The voltage charged in the capacitor (C) is copied to the inverting input and supplied to one electrode of the resistor R.

The transmit transistor (SWE) is turned on with the transmit signal (-EMI) remaining in a logic high state. Accordingly, the output of the operational amplifier is equal to the ground potential, and the connection Transistor (TR) is turned off. Further, since a voltage charged by the capacitor (C) is supplied to one electrode of the resistor R, a luminance control signal (icon) for controlling the luminance of the pixel is supplied to the pixel through the turned-on connection Transistor (TR).

The magnitude of the luminance control signal (icon) corresponds to the voltage charged in the capacitor C, and may be represented by the following equation 1.

[ EQUATION 1 ]

The brightness of the LED is determined according to the magnitude of current supplied to the LED, and the magnitude of the brightness control signal (icon) is proportional to the voltage (Vd) charged in the capacitor according to equation 1. Accordingly, the luminance of the pixel can be controlled by controlling the magnitude of the voltage of the data signal D1 supplied to the capacitor.

Fig. 6 is a timing chart of the operation of the pixel group control section (130) according to the present embodiment shown in fig. 2. An embodiment of a multi-pixel package according to the present embodiment will be described with reference to fig. 2 and 6. The data signals D1 and D2 are supplied to each pixel belonging to the pixel group in synchronization with a pulse sequence included in the control signal (S _ SIG).

The light emission control portion 120 outputs charge signals (EN _1, EN _2, EN _3) to turn on the charge transistor, and charges the capacitor (C) with a voltage corresponding to the data signal. As shown, each pixel belonging to each pixel group may be charged with a different voltage.

When the charging of each pixel belonging to each pixel group is completed, an emission signal (-EMI) is outputted, and each pixel outputs a luminance control signal (icon), respectively, and the pixel emits light with a luminance corresponding to the luminance control signal (icon).

Fig. 7 is a diagram showing a state in which a multi-pixel package according to the present embodiment is configured in an array and implemented as an active matrix, and fig. 8 is a timing diagram of signals provided in the multi-pixel package implemented in the active matrix. Referring to fig. 7 and 8, the multi-pixel package array according to the present embodiment is supplied with the same R control signal (VLED _ R), the same G control signal (VLED _ R), and the same B control signal (VLED _ B).

In addition, in the multi-pixel package array according to the present embodiment, the same control signal (S _ SIG) and DATA1 signal (DATA 1) and the same DATA2 signal (DATA 2) are provided to the multi-pixel packages arranged in the same column.

According to the multi-pixel package in an array configuration of the present embodiment, a control signal S _ SIG [ n ] is provided for each row, and data signals of D11, D21. -, D1n, and D2n are provided for each column connected to each row and energy is charged in a capacitor. Subsequently, while the transmission of the first row is performed by the transmission signal supplied from the encoder, the programming of the second row is performed. That is, the programming of the n +1 th row is performed at the same time as the light emission of the programmed n th row.

Accordingly, the multi-pixel package array according to the present embodiment implemented by an active matrix may be controlled to supply a control signal (S _ SIG), a DATA1 signal (DATA 1), and a DATA2 signal (DATA 2) and to be charged, respectively, so as to emit light at the same time.

Fig. 9 is an exemplary timing chart when color is realized by configuring a multi-pixel package in an array according to the present embodiment. Referring to fig. 1 to 8, the LED included in each of the multi-pixel packages according to the present exemplary embodiment is electrically connected to an anode of each color to be displayed to provide a control signal of each color.

Accordingly, in a state where the luminance control signal (icon) is supplied, if the R control signal (VLED _ R) is supplied, all of the R LEDs included in the multi-pixel package emit light, if the G control signal (VLED _ G) is supplied, all of the G LEDs included in the multi-pixel package emit light, and if the B control signal (VLED _ B) is supplied, all of the B LEDs included in the multi-pixel package emit light.

Accordingly, if the R control signal (VLED _ R), the G control signal (VLED _ G), and the B control signal (VLED _ B) are alternated to such an extent that the alternating light emitting speeds of the R LED, the G LED, and the B LED cannot be recognized with the naked eye, the human recognizes them as a full color image. Although the example of fig. 9 shows that one frame is driven by dividing it into three equal parts, one frame may be divided into six or nine equal parts differently from this.

While the invention has been described with reference to the embodiments shown in the drawings, this is for the purpose of illustration only and is not intended to be limiting, as those skilled in the art will appreciate that various modifications and equivalent other embodiments may be made. Accordingly, the true technical scope of the present invention should be defined by the appended claims.

Claims

1. A multi-pixel package, comprising:

multi-pixel groups each including a plurality of unit pixels of R (red), G (green), and B (blue) LEDs having cathodes commonly connected;

a data signal for controlling a luminance of light output by a unit pixel belonging to a pixel group; and

a control section for receiving a control signal in which a pulse train including an activation signal and a plurality of pulses is embedded and controlling the multi-pixel group;

wherein, the control portion includes:

a signal separating part for separating and outputting an activation signal (ON) and a pulse train, respectively;

a charging signal activated by the activation signal and each pixel group controlled to charge energy to emit light from the pulse sequence;

a light emission control section for outputting an emission signal to control each pixel group to emit light from the pulse sequence; and

a pixel group control section supplied with a charging signal to charge energy supplied as a data signal and to cause the pixel group to emit light with the emission signal.

2. The multi-pixel package of claim 1,

anodes of the R LEDs in the multi-pixel group are electrically connected to each other to provide an R control signal, and anodes of the G LEDs are electrically connected to each other to provide a G control signal, and anodes of the B LEDs are electrically connected to each other to provide a B control signal.

3. The multi-pixel package of claim 1,

the control signal is embedded with a sequence of pulses,

the pulse sequence includes:

an activation signal that swings between a first level and a second level that is greater than the first level; and

a plurality of pulses that swing between a second level and a third level that is greater than the second level,

the signal separating part includes:

an activation signal separation circuit including a transistor between the first and the second levels and having a threshold voltage, and outputting after separating an activation signal to swing between the first and the third levels; and

a pulse train separation circuit comprising a transistor including a threshold voltage between the second level and the third level and separating a pulse train before output to swing between the first and the third levels.

4. The multi-pixel package of claim 1,

the light emission control section includes:

a counter that is activated by the activation signal and counts and outputs pulses included in the pulse train; and

an encoder for forming and outputting the charge signal and the emission signal corresponding to the multi-pixel group output by the counter.

5. The multi-pixel package of claim 1,

the pixel group control section includes a capacitor that stores energy supplied as the data signal,

and if the emission signal is supplied, the voltage charged by the capacitor is supplied to the resistor, so that the pixel emits light, thereby forming a luminance control signal for controlling and supplying the luminance of the pixel to the pixel.

6. The multi-pixel package of claim 5,

the pixel group control section includes:

a capacitor that stores energy provided as the data signal;

a charge transistor controlled by the charge signal and electrically connecting the data signal to the capacitor;

an operational amplifier which supplies the voltage charged to the capacitor to one input, and the other input is connected to a resistor and supplies the charged capacitor to the charging transistor through the resistor;

a transmit transistor controlled by the transmit signal to isolate an output of the operational amplifier from ground; and

a transistor connected to be controlled by the output of the operational amplifier and to provide a brightness control signal to the pixel.

7. The multi-pixel package of claim 2,

the R control signal, the G control signal, and the B control signal, which do not overlap in one frame, are provided at uniform times.

8. An array of multi-pixel packages, wherein the multi-pixel package of claim 1 is configured in an array,

and the same R control signal, G control signal and B control signal are supplied to the multi-pixel packages connected to the same row (row) of the multi-pixel package array,

the same data signal is provided to the multi-pixel packages connected to the same column (row) of the multi-pixel package array.

9. The multi-pixel package array of claim 8,

after programming the image to be displayed on the nth row, the nth row emission is performed, but the nth row emission and the programming of the (n + 1) th row are started simultaneously.

10. The multi-pixel package array of claim 8,

the R, G, and B control signals that do not overlap in one frame are provided at uniform times.

11. The multi-pixel package array of claim 10,

the R control signal, the G control signal, and the B control signal are alternately supplied at a frequency having a characteristic that the multi-pixel package array is observed with the naked eye, so that it is possible to recognize a frequency at which the R, G, and B LEDs display a full color image.