Light emitting device and a drive control method for driving a light emitting device

A drive control method for driving a light emitting device based on supplied image data, the light emitting device comprising a pixel array having a plurality of pixels, connected to each of a plurality of signal lines, and each comprising a light emitting element, and a pixel drive circuit having a drive transistor whose one end of a current path is connected to one terminal of the light emitting element for controlling the current supplied to the light emitting element, the pixel drive circuit having a holding capacity for storing charge by a voltage impressed on the control terminal of the drive transistor, including;

• a reference voltage impressing step for impressing a reference voltage on one end of the each signal line so that the electric potential difference of one end to the other end of the current path of the drive transistor is a value that exceeds the threshold voltage of the drive transistor;
• a measurement voltage acquisition step that interrupts the connection between one end of the each signal line and the voltage impressing circuit, then acquires a voltage of the one end of the each signal line as the measured voltage after elapsing of each of predetermined settling times after interrupting the connection;
• a property parameter acquisition step that acquires the property parameters that relate to the electrical properties of the drive transistor and the pixel drive circuit of the each pixel from the measured voltages;
• a corrected gradation signal generation step for outputting a corrected gradation signal by correcting the supplied image data based on the acquired property parameters;
• and
• a drive signal generation and impressing step for generating a drive signal based on the corrected gradation signal and impressing the drive signal on the one end of each signal line;
• wherein,
• the settling time in the measured voltage acquisition step is set to respective values of a first settling time group and a second settling time;
• the first settling time group is constituted of a plurality of different time values, each of which is larger than the ratio (C/β0),where C is total capacity, which is the sum of the parasitic capacity that is parasitic on a single signal line, the holding capacity, and the light emitting element capacity that is parasitic on the light emitting element, and β0 is the reference value of the current amplification factor, and the second settling time is constituted of the time value which is shorter than the ratio (C/β0);
• and
• the property parameter acquisition step, including:
• a first property parameter acquisition step that acquires the threshold voltage of the drive transistor of each pixel and the current amplification factor of the pixel drive circuit as the first property parameters in the property parameters, based on the values of measured voltages for the first settling time group;
• and
• a second property parameter acquisition step that acquires the irregularity parameter which indicates the irregularity of the current amplification factor as a second property parameter in the property parameters based on the value of the threshold voltage acquired for each pixel and the value of the measured voltage for the second settling time.

A light emitting device, comprising:

• a plurality of pixels, connected to each of a plurality of signal lines, each comprising a light emitting element, a drive transistor having a current path and a control terminal, which connects one end of the current path to one end of the light emitting element and which controls the electric current supplied to the light emitting element through the current path according to the control voltage impressed on the control terminal, and a holding capacity for storing charge determined by a voltage impressed to the drive transistor;
• a plurality of voltage measurement circuits each arranged and connected to each of the plurality of signal lines;
• a property parameter acquisition circuit for acquiring the property parameters that relate to the electrical properties of the each pixel;
• a signal correction circuit for outputting a corrected gradation signal by correcting the supplied image data based on the acquired property parameters;
• a drive signal impressing circuit for generating a drive signal based on the corrected gradation signal and impressing the drive signal on the one end of each signal line;
• wherein,
• the voltage measurement circuit acquires the voltage value of the one end of each signal line indicated in equation (9), as the measured voltage, after reference voltage is impressed between both ends of the current path of the drive transistor so as to exceed a threshold voltage of the drive transistor for each pixel, creating a high impedance state in the signal lines connected to the current path, thereby making the settling time t to be the elapsed time from when the impressing of the reference voltage stopped, and when C is total capacity, which is the sum of the holding capacity of the pixel connected to the signal line, the parasitic capacity that is parasitic on the signal line, and the light emitting element capacity that is parasitic on the light emitting element;
• and
• the property parameter acquisition circuit acquires the initial threshold voltage of the drive transistor of each pixel and the (C/β) value as a first property parameter in the property parameters based on the values of the plurality of measured voltages acquired by the voltage measurement circuit when the settling time is the first settling time group consisting of a plurality of differing values that satisfy the condition (C/β)/t<1;
• and the property parameter acquisition circuit acquires an irregularity parameter (Δβ/β) which indicates the irregularity of the current properties of the drive transistor of the plurality of pixels as a second property parameter in the property parameters based on the mean value <C/β> for the plurality of pixels of the values of (C/β) for the drive transistor of each pixel, and the value of the measured voltage acquired by the voltage measurement circuit when the settling time is the second settling time that satisfies the condition of (C/β)/t>1;
• and
• the signal correction circuit generates the corrected gradation signal by setting the off-set voltage, based on a third settling time that satisfies the condition (C/β)/t<1 and on the mean value of <C/β>, and adding threshold voltage of the drive transistor of each pixel in operation based on the off-set voltage and the value of the measured voltage acquired by the voltage measurement circuit when the settling time is the third settling time, to a corrected signal which is acquired by correcting the image data based on the irregularity parameter (Δβ/β) of each pixel acquired by the property parameter acquisition circuit;
• and
• the drive signal impressing circuit generates the voltage signal as the drive signal based on the corrected gradation signal.
• Vmeas
• 
• (
• t
• )
• =
• Vth
• +
• 1
• t
• (
• C
• /
• β
• )
• +
• 1
• Vref
• -
• Vth
• (
• 9
• )
• where, t:
• settling time
• Vmeas(t):
• the measured voltage acquired by the voltage measurement circuit that corresponds to the settling time t
• Vth:
• the threshold voltage of the drive transistor
• Vref:
• Reference voltage
• C:
• Total capacity(C=Cs+Cp+Ce1)
• Cs:
• Holding capacity
• Cp:
• Wiring parasitic capacity
• Ce1:
• Light emitting element capacity
• β:
• Constant