JP4507633B2 - Image processing apparatus, image processing method, display apparatus, and electronic apparatus - Google Patents

Description

  The present invention relates to an image processing device, an image processing method, a display device, and an electronic apparatus, and more specifically, image processing capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration. The present invention relates to a device, an image processing method, a display device, and an electronic device.

  Since image display devices that display television images have progressed with CRT as the mainstream, various standards are often compliant with CRT. Among them, there is a process called γ conversion. The three color phosphors of CRT do not emit light in proportion to the input video signal voltage, and the relationship between the input signal and the light output is non-linear. This characteristic is called a γ characteristic, and if the non-linearity of the CRT is corrected by the receiver, the receiver becomes complicated and expensive. Therefore, in the current television system, a video signal corrected by γ is transmitted on the transmission side.

  Since CRT has been the mainstream in the field of computer displays, display data output from the computer main body is output after being γ-corrected in advance inside the computer main body. In recent years, thin display devices called flat panel displays use light emitting elements such as LEDs, plasma, and EL as light emitters. In these light emitting elements, unlike a CRT, the relationship between an input signal and an optical output is almost linear and does not have non-linearity like a CRT. Therefore, when displaying a γ-corrected video signal on a display device whose input / output characteristics are linear, it is necessary to perform inverse γ correction to match the characteristics of the display element.

  Conventionally, as a method of inverse γ correction, for example, (1) a method using nonlinear pulse width modulation (for example, refer to Patent Document 1), (2) a method using LUT (for example, refer to Patent Document 2), ( 3) A method using a multiplier (for example, see Patent Document 3), (4) a method for approximating a polygonal line (for example, see Patent Document 4), and the like are known.

JP-A-6-161384 JP-A-6-233131 JP-A-8-18826 JP-A-6-189160

  However, in the above-described inverse γ correction method, (1) a ROM must be prepared according to the type of panel, which makes the circuit complicated and expensive. (2) Since there is an arithmetic circuit, correction in real time is possible. There are problems that cannot be realized, (3) there are many parameters, and the setting is complicated.

  The present invention has been made in view of the above, and an image processing apparatus, an image processing method, a display apparatus, and the like that are capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration, And an electronic device.

In order to solve the above-described problems and achieve the object, the present invention provides a luminance adjustment unit that generates a maximum input voltage according to luminance adjustment data, and a maximum generated by the luminance adjustment unit based on contrast adjustment data. A contrast adjustment unit that variably sets and outputs the voltage width of the input voltage, a D / A conversion unit that converts digital image data into an analog voltage signal using the voltage output from the contrast adjustment unit, A conversion unit that performs γ conversion or inverse γ conversion on the voltage signal generated by the A conversion unit, and the contrast adjustment units are arranged in series with each other and the maximum input voltage generated by the luminance adjustment unit is applied between both ends. And a first circuit and a second circuit for determining the voltage width of the maximum input voltage, and an inverter for inverting the contrast adjustment data input to the first circuit and supplying the inverted data to the second circuit And the first circuit is one of a plurality of first resistors connected in series and a plurality of potentials generated by dividing the plurality of first resistors based on the contrast adjustment data. A second selection circuit for selecting and outputting the plurality of second resistors based on the plurality of second resistors connected in series and the contrast adjustment data inverted by the inverter. A second selection unit that selects and outputs any one of a plurality of potentials generated by the divided voltage, and the D / A conversion unit has a first output potential output from the first selection unit. Based on digital image data and a plurality of third resistors connected in series between the supplied first wiring and the second wiring supplied with the second output potential output from the second selection unit. And a plurality of potentials generated by the divided voltages of the plurality of third resistors. A third selection unit that selects and outputs either of the first wiring and the conversion unit between the third wiring from which the third potential from the third selection unit is output and the first wiring or the second wiring. And selecting and outputting any one of a plurality of fourth resistors connected in series with each other and a plurality of potentials generated by voltage division of the plurality of fourth resistors based on the γ adjustment data. And a selection unit .

  As a result, non-linear conversion can be performed on the digital image data with an analog non-linear circuit including a linear element such as a resistor on the basis of adjustment data that is a simple parameter, and the digital image can be obtained with a simple and inexpensive analog circuit. A desired non-linear transformation can be performed on the data. As a result, it is possible to provide an image processing apparatus capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration.

  According to a preferred aspect of the present invention, it is desirable that the non-linear conversion means performs γ conversion / inverse γ conversion on the digital image data based on γ adjustment data. Thereby, γ conversion / inverse γ conversion can be performed by an analog nonlinear circuit including a linear element such as a resistor.

  According to a preferred aspect of the present invention, the luminance adjustment means comprising an analog circuit including a linear element that sets the maximum luminance value of the digital image data based on the luminance adjustment data, and the contrast of the digital image data is contrasted. It is desirable to include a contrast adjusting unit that is set based on the adjustment data and includes an analog circuit including a linear element. This enables analog circuits including linear elements to adjust the brightness and contrast of digital image data and control brightness and contrast independently, and achieve comprehensive image quality adjustment with minimum parameters. Can do.

  Further, according to a preferred aspect of the present invention, the brightness adjustment means sets a maximum voltage value corresponding to the maximum brightness value of the digital image data based on the brightness adjustment data, and the contrast adjustment means A voltage width corresponding to the contrast of the digital image data is set based on the contrast adjustment data, and the nonlinear conversion means performs γ conversion based on the γ adjustment data for a voltage value corresponding to the digital image data. / It is desirable to perform inverse γ conversion. Accordingly, when an image is displayed on a voltage-driven display panel such as a liquid crystal panel, a plasma panel, or a field emission panel, a high-quality image can be displayed.

  Further, according to a preferred aspect of the present invention, the brightness adjustment means sets a maximum current value corresponding to the maximum brightness value of the digital image data based on the brightness adjustment data, and the contrast adjustment means A current width corresponding to the contrast of the digital image data is set based on the contrast adjustment data, and the non-linear conversion means performs γ conversion based on the γ adjustment data for a current value corresponding to the digital image data. / It is desirable to perform inverse γ conversion. Thereby, when displaying an image on a current-driven display panel such as an organic EL panel or an LED panel, a high-quality image can be displayed.

Further, according to a preferred aspect of the present invention, the brightness adjusting unit is connected in series between the first power supply line to which the higher potential is supplied and the second power supply line to which the lower potential is supplied. And a fifth selection unit that selects and outputs any one of the plurality of potentials generated by the divided voltages of the plurality of fifth resistors based on the brightness adjustment data. It is desirable. More specifically, the fifth selection unit is connected to a plurality of fifth resistors, and includes a plurality of analog switches for selecting a divided voltage output of the plurality of fifth resistors based on luminance adjustment data. It is desirable. As a result, the brightness can be adjusted with a simple and inexpensive analog circuit comprising a resistor and an analog switch.

According to a preferred aspect of the present invention, the first selection unit in the contrast adjustment unit is connected to a plurality of first resistors, respectively, and the divided voltages of the plurality of first resistors are based on the contrast adjustment data. While the second selection unit includes a plurality of analog switches for selecting an output, the second selection unit is connected to each of the plurality of second resistors. Based on the contrast adjustment data inverted by the inverter, the second selection unit distributes the second resistors. It is desirable to include a plurality of analog switches that select the pressure output. Thereby, contrast adjustment can be performed by a simple and inexpensive analog circuit including a resistor and an analog switch.

According to a preferred aspect of the present invention, the fourth selection unit in the conversion unit is connected to each of a plurality of fourth resistors, and outputs a divided voltage output of the plurality of fourth resistors based on the γ adjustment data. It is desirable to include a plurality of analog switches to select. Thereby, γ adjustment can be performed by a simple and inexpensive analog circuit including a resistor and an analog switch.

According to a preferred aspect of the present invention, it is desirable to mount the image processing device according to any one of claims 1 to 5 on a display device. Accordingly, it is possible to provide a display device equipped with an image processing device capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration.

According to a preferred aspect of the present invention, it is desirable to mount the display device according to claim 7 on an electronic device. Accordingly, it is possible to provide an electronic apparatus equipped with an image processing apparatus capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration.

  In order to solve the above-described problems and achieve the object, the present invention performs non-linear conversion on an input digital image data by an analog non-linear circuit including a linear element based on adjustment data as an analog signal. A non-linear conversion step for outputting is included.

  As a result, non-linear conversion can be performed on the digital image data with an analog non-linear circuit including a linear element such as a resistor on the basis of adjustment data that is a simple parameter, and the digital image can be obtained with a simple and inexpensive analog circuit. A desired non-linear transformation can be performed on the data. As a result, it is possible to provide an image processing method capable of performing desired nonlinear conversion on digital image data with a simple and inexpensive circuit configuration.

  According to a preferred aspect of the present invention, in the nonlinear conversion step, it is desirable to perform γ conversion / inverse γ conversion on the digital image data based on γ adjustment data. Thereby, γ conversion / inverse γ conversion can be performed by an analog nonlinear circuit including a linear element such as a resistor.

  Further, according to a preferred aspect of the present invention, a brightness adjustment step of setting a maximum brightness value of the digital image data by an analog circuit including a linear element based on the brightness adjustment data, and a contrast of the digital image data It is desirable to include a contrast adjustment step that is set by an analog circuit including a linear element based on the adjustment data. This enables analog circuits including linear elements to adjust the brightness and contrast of digital image data and control brightness and contrast independently, and achieve comprehensive image quality adjustment with minimum parameters. Can do.

  According to a preferred aspect of the present invention, in the luminance adjustment step, a maximum voltage value corresponding to a maximum luminance value of the digital image data is set based on the luminance adjustment data, and in the contrast adjustment step, A voltage width corresponding to the contrast of the digital image data is set based on the contrast adjustment data. In the nonlinear conversion step, γ conversion is performed on the voltage value corresponding to the digital image data based on the γ adjustment data. / It is desirable to perform inverse γ conversion. Accordingly, when an image is displayed on a voltage-driven display panel such as a liquid crystal panel, a plasma panel, or a field emission panel, a high-quality image can be displayed.

  According to a preferred aspect of the present invention, in the luminance adjustment step, a maximum current value corresponding to a maximum luminance value of the digital image data is set based on the luminance adjustment data, and in the contrast adjustment step, A current width corresponding to the contrast of the digital image data is set based on the contrast adjustment data, and in the non-linear conversion step, γ conversion is performed on the current value corresponding to the digital image data based on the γ adjustment data. / It is desirable to perform inverse γ conversion. Thereby, when displaying an image on a current-driven display panel such as an organic EL panel or an LED panel, a high-quality image can be displayed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  FIG. 1 is a block diagram illustrating a configuration of a display device 100 to which an image processing device according to a first embodiment of the present invention is applied. The display device 100 shown in the figure includes an analog image signal input terminal 101, a digital image signal input terminal 102, an A / D conversion unit 103, a pixel conversion unit 104, an inverse γ correction unit 105, and a display panel drive unit. 106, a voltage-driven display panel 107, an operation unit 108, and a controller 109.

  The controller 109 controls each unit of the display device 100 based on an operation instruction input from the operation unit 108. The operation unit 108 is a user interface including various keys. An analog image signal is input to the analog image signal input terminal 101. A digital image signal (for example, 4-bit data) is input to the digital image signal input terminal 102 and is output to the pixel conversion unit 104.

  The A / D conversion unit 103 converts the input analog image signal into a digital image signal (for example, 4-bit data) and outputs the digital image signal to the pixel conversion unit 104. The pixel conversion unit 104 converts an input digital image signal (hereinafter, “digital image signal” is simply referred to as “image data”) into a progressive signal in the case of an interlaced signal, and further, in the horizontal and vertical directions. Are converted into the number of display pixels of the voltage-driven display panel 107 and output to the inverse γ correction unit 105.

  The inverse γ correction unit 105 performs inverse γ correction on the input image data based on the γ adjustment data input from the controller 109 and outputs the corrected image data to the display panel drive unit 106. The inverse γ correction unit 105 includes a luminance adjustment unit 201 that performs luminance adjustment in accordance with luminance adjustment data (3 bits) input from the controller 109 and a contrast adjustment in accordance with contrast adjustment data (3 bits) input from the controller 109. And a γ approximation unit 203 that performs inverse γ correction in accordance with γ adjustment data input from the controller 109.

  The display panel driving unit 106 drives the voltage driven display panel 107 based on the image data input from the inverse γ correction unit 105 to display an image. The voltage-driven display panel 107 is a voltage-driven display panel, and includes, for example, a liquid crystal panel, a plasma panel, an FED (light emission) panel, and the like.

  FIG. 2 shows an equivalent circuit of the inverse γ correction unit 105 of FIG. FIG. 3 is an explanatory diagram for explaining brightness adjustment, contrast adjustment, and γ adjustment. In FIG. 2, the luminance adjustment unit 201 determines the maximum luminance (maximum input voltage) according to the luminance adjustment data (3 bits). The contrast adjustment unit 202 determines the contrast (voltage width) according to the contrast adjustment data (3 bits). The γ approximation unit 203 performs inverse γ correction on the image data in accordance with the γ adjustment data input from the controller 109.

  FIG. 4 is a diagram illustrating an equivalent circuit of the gamma approximation unit 203. Assuming that the input voltage E and the output voltage Vout are the gamma approximation unit 203, the gamma approximation unit 203 can be represented by an equivalent circuit as shown in FIG. In FIG. 4, the output voltage Vout can be expressed as in the following formula (1).

  FIG. 5 is a diagram illustrating an example of a γ characteristic curve. In the figure, four types of γ characteristic curves are shown, where a0 is a = 0.1, a1 is a = 0.25, a2 is a = 0.45, and CRT (γ = 2.2) γ characteristics. A curve is shown. Here, a = 0.5 or less (γ = 1 or less) is inverse γ conversion, and a = 0.5 or more (γ = 1 or more) is γ conversion. By setting the parameter “a” in the above equation (1), desired γ / inverse γ correction can be performed.

  FIG. 6 is a diagram illustrating a specific circuit configuration of the inverse γ correction unit 105. In FIG. 6, the brightness adjusting unit 201 includes brightness adjusting means VR4, a transistor Q9, and a pull-down resistor R1. The luminance adjusting unit VR4 converts the input voltage Vcc into a maximum voltage corresponding to the maximum luminance and outputs the converted voltage to the contrast adjusting unit 202 via the transistor Q9.

  FIG. 7 is a diagram showing a specific circuit configuration example of the brightness adjusting means VR4. As shown in FIG. 7, the brightness adjusting means VR4 includes resistors R0 to R6 connected in series, analog switches SW1 to SW4 whose input terminals are connected to both ends of the resistors R0 to R6, and analog switches SW1 to SW4. Analog switches SW11 and SW12 whose input terminals are connected to the output terminals of the analog switches SW11 and 12, and analog switches SW21 whose input terminals are connected to the output terminals of the analog switches SW11 and SW12.

  The analog switches SW1 to SW4, SW11, SW12 and SW21 are supplied with D0 (LSB), D1 and D2 (MSB) of 3-bit brightness adjustment data from the controller 109 as SW signals, respectively, and the output of one input terminal Is selected and output. FIG. 8 is a diagram illustrating a specific circuit configuration example of the analog switch SW. As the brightness adjustment data D, the analog switch SW outputs “A input” when “0” is input, and “B input” when “1” is input.

  In the brightness adjusting unit VR4 of FIG. 7, when the total resistance value of R0 to R6 is 100Ω and each of R0 to R6 is 14.3KΩ, the input is performed by inputting 3 bits of brightness adjustment data D0 to D2. A voltage value obtained by dividing the voltage Vcc (for example, 15V) into seven equal parts is applied to the gate of the transistor Q9 according to the luminance adjustment data. The total resistance value can be determined as an appropriate value from the voltage value applied to the resistance.

  Since the output of the gate of the transistor Q9 is a source follower, the output voltage at the end of the resistor R1 is approximately equal to the voltage value obtained by subtracting the threshold voltage Vth from the gate voltage. In this case, the output voltage of the source follower varies between approximately 0V and 12V. The maximum value of the γ conversion output, that is, the maximum luminance is determined by the output voltage value of the source follower. The output voltage of the source follower is applied to both ends of the contrast adjustment unit 202.

  The contrast adjustment unit 202 includes contrast adjustment units VR5 and VR6 that determine the voltage width of the output voltage of the luminance adjustment unit 201. FIG. 9 is a diagram showing the configuration of the contrast adjusting means VR5 and VR6. As shown in FIG. 9, the contrast adjusting units VR5 and VR6 include resistors Rx0 to Rx6 connected in series, analog switches SW1 to SW4 whose input terminals are connected to both ends of the resistors Rx0 to Rx6, and an analog switch SW1. To SW4, analog switches SW11 and SW12 whose input terminals are connected to each other, and analog switches SW21 whose input terminals are connected to the output terminals of the analog switches SW11 and SW12. Further, the contrast adjusting means VR5 and VR6 include resistors Ry0 to Ry6 connected in series, analog switches SW5 to SW8 whose input terminals are connected to both ends of the resistors Ry0 to Ry6, and output terminals of the analog switches SW5 to SW8. Analog switches SW13, 14 having their input terminals connected to each other, analog switches SW22 having their input terminals connected to the output terminals of the analog switches SW13, 14, and D0 (LSB), D1, 3-bit luminance adjustment data. Inverters INV1, 2, and 3 for inverting D2 (MSB) are provided. The configuration of the analog switch SW is the same as that shown in FIG.

  The analog switches SW1 to SW4, SW11, SW12, and SW21 are supplied with 3 bits of contrast adjustment data D0 (LSB), D1, and D2 (MSB) from the controller 109 as SW signals, respectively, Output is selected and output. In addition, 3-bit contrast adjustment data D0 (LSB), D1, and D2 (MSB) supplied from the controller 109 are inverted by the inverters INV1, 2, and 3 to the analog switches SW5 to 8, SW13, 14, and SW22, respectively. The SW signal is supplied, and the output of one of the input terminals is selected and output.

  In FIG. 9, when the resistors Rx0 to Rx6 and the resistors Ry0 to Ry6 are all set to the same resistance value, the output voltages of the brightness adjusting means VR5 and 6 are 0-12 (V), 0.86-11.14 (V), It changes with a voltage width of 3.44-8.56 (V), 4.37-7 (V), 5.16-6.84 (V). This voltage width corresponds to the change in contrast because the change width of the luminance is determined.

  The γ approximation unit 203 includes a D / A conversion unit (Rx_R1-x) that converts image data into an analog voltage signal, a γ conversion unit Ra that γ-converts an analog voltage signal corresponding to the image data, and a transistor Q10. And a pull-down resistor R2. FIG. 10 is a diagram illustrating a specific circuit configuration example of the D / A conversion means (Rx_R1-x). As shown in FIG. 10, the D / A conversion means (Rx_R1-x) includes resistors R0 to R14 connected in series and analog switches SW1 to SW8 whose input terminals are connected to both ends of each of the resistors R0 to R14. The analog switches SW11 to SW14 whose input terminals are connected to the output terminals of the analog switches SW1 to SW8, the analog switches SW21 and 22 whose input terminals are connected to the output terminals of the analog switches SW11 to 14, and the analog switch SW21 , 22 and an analog switch SW31 having its input terminal connected to the output terminal. The configuration of the analog switch SW is the same as that shown in FIG.

  4-bit image data D0 (LSB), D1, D2, and D3 (MSB) are supplied as SW signals from the pixel conversion circuit 103 to the analog switches SW0 to SW14, SW11 to 14, SW21, 22 and SW31, respectively. The output (voltage value) of one input terminal is selected, and an analog voltage signal is output. That is, in this D / A conversion means (Rx_R1-x), a voltage value obtained by dividing the input voltage input from the contrast adjustment means VR5, 6 into 14 equal parts is output to the γ conversion means Ra according to the image data.

  FIG. 11 is a diagram showing a specific circuit configuration example of the γ conversion means Ra. As shown in FIG. 11, the γ conversion means Ra includes resistors R0 to R6 connected in series, analog switches SW1 to SW4 having input terminals connected to both ends of the resistors R0 to R6, and analog switches SW1 to SW4. The analog switch SW11, 12 whose input terminal is connected to the output terminal of the analog switch SW11, and the analog switch SW21 whose input terminal is connected to the output terminal of the analog switch SW11, 12 are provided, and the ground side of the resistor R0 is the analog switch It is connected to the output terminal of SW21.

  The analog switches SW1 to SW4, SW11, SW12 and SW21 of the γ conversion means Ra are respectively supplied with 3 bits of γ adjustment data D0 (LSB), D1 and D2 (MSB) as SW signals from the controller 109. The output of one input terminal is selected and output. The γ characteristic curve can be changed by changing the γ adjustment data input to the γ converting means Ra. In the γ conversion means Ra, a voltage value obtained by dividing the input voltage into seven equal parts is applied to the gate of the transistor Q10 according to the γ adjustment data. Since the output of the gate of the transistor Q10 is a source follower, the voltage at the resistor R2 terminal is approximately equal to the voltage obtained by subtracting the threshold voltage Vth from the gate voltage. The output voltage of the γ conversion means Ra is output as Vout to the subsequent display panel driving unit 106 via the transistor Q10.

  FIG. 12 is a diagram for explaining the relationship between the resistance of the γ approximation unit 203 and the parameter a. As shown in FIG. 11, when all the resistors R0 to R6 of the γ converting means Ra shown in FIG. 11 are set to 14 kΩ, the γ adjustment data is “001”, “010”, “011”, “100”, “101”. , “110”, “111”, a = “0.143”, “0.286”, “0.428”, “0.571”, “0.714”, “0.857”, respectively. , “1.000” can be set.

  As described above, according to the first embodiment, the input digital image data is subjected to inverse γ conversion (nonlinear conversion) by an analog non-linear circuit including a linear element based on the adjustment data as an analog signal. Since the inverse γ correction unit 105 for output is provided, inverse γ conversion (nonlinear conversion) is performed on the digital image data by an analog nonlinear circuit including a linear element such as a resistor based on adjustment data that is a simple parameter. The desired inverse γ conversion (nonlinear conversion) can be performed on the digital image data with a simple and inexpensive analog circuit.

  Further, according to the first embodiment, the luminance adjustment unit 201 including an analog circuit including a linear element that sets a maximum voltage value corresponding to the maximum luminance value of the digital image data based on the luminance adjustment data, and the digital image data And a contrast adjustment unit 202 made of an analog circuit including a linear element that sets a voltage width corresponding to the contrast of the digital image data by using an analog circuit including a linear element such as a resistor. Brightness adjustment and contrast adjustment can be performed to control brightness and contrast independently, and comprehensive image quality adjustment can be realized with minimum parameters. In addition, when an image is displayed on a voltage-driven display panel such as a liquid crystal panel, a plasma panel, or a field emission panel, a high-quality image can be displayed.

  Further, according to the first embodiment, the brightness adjusting unit 201 is connected to a plurality of resistors connected in series and a plurality of resistors to which driving voltage is input between both ends, and is input from the controller 109. Since the plurality of analog switches for selecting the divided voltage output of the plurality of resistors are provided based on the luminance adjustment data, the luminance adjustment can be performed by a simple and inexpensive analog circuit including the resistors and the analog switches.

  Further, according to the first embodiment, the contrast adjustment unit 202 is connected to the plurality of resistors connected in series to which the output of the luminance adjustment unit 201 is input and the plurality of resistors, and is input from the controller 109. Since it has a plurality of analog switches that select the divided voltage output of a plurality of resistors based on contrast adjustment data, contrast adjustment can be performed by a simple and inexpensive analog circuit composed of resistors and analog switches. .

  Further, according to the first embodiment, the γ approximation unit 204 converts the digital image data into an analog signal having the maximum luminance value set by the luminance adjustment unit 201 and the contrast set by the contrast adjustment unit 202. D / A conversion means including an analog circuit including elements, a plurality of resistors connected in series to which the analog signal is input between both ends, and a plurality of resistors, respectively. Since it has a plurality of analog switches for selecting the divided voltage output of a plurality of resistors based on the γ adjustment data, the γ adjustment can be performed by a simple and inexpensive analog circuit comprising a resistor and an analog switch. .

  In the first embodiment, the voltage-driven display panel has been described. In the second embodiment, a current-driven display panel will be described. FIG. 13 is a block diagram illustrating a configuration of a display device 500 to which the image processing apparatus according to the second embodiment is applied. The display device 500 shown in the figure includes an analog image signal input terminal 501, a digital image signal input terminal 502, an A / D conversion unit 503, a pixel conversion unit 504, an inverse γ correction unit 505, and a display panel drive unit. 506, a current drive type display panel 507, an operation unit 508, and a controller 509. Description of the parts common to the first embodiment (FIG. 1) is omitted, and only different points will be described here.

  The inverse γ correction unit 505 performs inverse γ correction on the input image data based on the adjustment data input from the controller 509 and outputs the image data to the display panel drive unit 508. The inverse γ correction unit 505 includes a luminance adjustment unit 601 that performs luminance adjustment in accordance with luminance adjustment data (3 bits) input from the controller 509 and a contrast adjustment in accordance with contrast adjustment data (3 bits) input from the controller 509. And a γ approximation unit 603 that performs γ adjustment according to γ adjustment data input from the controller 509.

  The display panel driving unit 506 displays an image by driving the current driven display panel 507 based on the image data input from the inverse γ correction unit 505. The current drive type display panel 507 is formed of a current driven display panel, and includes, for example, an organic EL panel, an LED panel, or the like.

  FIG. 14 shows an equivalent circuit of the inverse γ correction unit 505 of FIG. In FIG. 14, the luminance adjusting unit 601 determines the maximum luminance (maximum input current) according to the luminance adjustment data (3 bits). The contrast adjustment unit 602 determines the contrast (current width) according to the contrast adjustment data (3 bits). The γ approximation unit 603 performs γ conversion on the image data in accordance with the γ adjustment data input from the controller 509 and outputs a corresponding current value.

  FIG. 15 is a diagram showing an equivalent circuit of the gamma approximation unit 603 in FIG. Assuming that the input current I and the output current Iout are the γ approximation unit 603, it can be represented by an equivalent circuit as shown in FIG. This output current Iout can be expressed as the following equation (2).

  FIG. 16 is a diagram illustrating a specific circuit configuration example of the inverse γ correction unit 505. In FIG. 16, the brightness adjusting unit 601 includes brightness adjusting means VR1 and a current mirror circuit CM1 including transistors Q1 and Q2. The output current of the current mirror circuit CM1 is determined by the brightness adjusting means VR1. In the current mirror circuit CM1, the current flowing through the transistor Q2 has the same magnitude as the transistor Q1. The brightness adjustment unit VR1 outputs a maximum current corresponding to the maximum brightness to the contrast adjustment unit 602 via the transistor Q2 of the current mirror circuit CM1. The brightness adjusting means VR1 can have a circuit configuration similar to that shown in FIG.

  In FIG. 10, when the total resistance value of the resistors R0 to R6 of the luminance adjusting means VR1 is 100 KΩ and each of the resistors R0 to R6 is 1.43 KΩ, the maximum current is (001) when the luminance adjustment data is “001”. 15-3) If V / 1.43 KΩ≈8.4 mA, “010”, then (15-3) /2.86 KΩ≈4.2 mA can be set. The total resistance value can be determined by setting several current values at the minimum luminance.

  The contrast adjustment unit 602 adds and subtracts the output current of the luminance adjustment unit 601 to determine the current width, and the first contrast adjustment unit VR2 and the transistor Q3 connected to the first contrast adjustment unit VR2 , Q4, a current mirror circuit CM3 composed of transistors Q5, Q6 connected to the analog switch SW100, the second contrast adjusting means VR3, and the second contrast adjusting means VR3, And an analog switch SW200. The circuit configurations of the first contrast adjusting means VR2 and the second contrast adjusting means VR3 can be the same as those shown in FIG.

  The analog switches SW100 and SW200 are supplied with the MSB (D3) of 4-bit image data as the SW signal and controlled to be turned ON / OFF. When the MSB is “0”, the analog switch SW100 is turned ON and the MSB Is “1”, the analog switch SW200 is turned ON. The current mirror circuit CM2 functions to subtract the current value set by the first contrast adjustment unit VR2 from the input current input from the luminance adjustment unit 601 when the MSB of the image data is “0”. To do. Further, when the MSB of the image data is “1”, the current mirror circuit CM3 adds the current value set by the second contrast adjusting unit VR3 to the input current input from the luminance adjusting unit 601. To work.

  The current value to be subtracted and added is set by giving contrast adjustment data to the contrast adjustment means VR2 and VR3. In FIG. 11, for example, when the total resistance value of the resistors R0 to R6 of the contrast adjusting means VR2 and 3 is 100 KΩ and each of the resistors R0 to R6 is 1.43 KΩ, the current value to be subtracted and added is the contrast adjustment data. “001” can be set to 840 μA, and “010” can be set to 420 μA.

  Thus, in the contrast adjustment unit 602, when the image data is “0000” to “0111”, the luminance is increased, and when the image data is “1000” to “1111”, the luminance is decreased. The current is controlled and supplied to the γ approximation unit 603. Since the current change width corresponds to the brightness change width, the contrast of the image data is controlled.

  The γ approximation unit 603 includes a first D / A conversion unit R (1 / 1-x), a second D / A conversion unit R (1 / x), a γ conversion unit R (1 / a), a capacitor Q7, A current mirror circuit CM4 composed of Q8 is provided. FIG. 17 is a diagram showing a specific circuit configuration of the first D / A conversion means R (1 / 1-x). As shown in FIG. 17, the first D / A converting means R (1 / 1-x) includes resistors R0 to R14 connected in series and an analog switch having input terminals connected to both ends of the resistors R0 to R14. SW1 to SW8, analog switches SW11 to 14 whose input terminals are connected to the output terminals of analog switches SW1 to SW8, and analog switches SW21 and 22 whose input terminals are connected to the output terminals of analog switches SW11 to 14 The analog switch SW31 has an input terminal connected to the output terminals of the analog switches SW21 and 22 and inverters INV1 to INV4. The ground side of the resistor R0 is connected to the output terminal of the analog switch SW31. The configuration of the analog switch SW is the same as that shown in FIG.

  The analog switches SW1 to SW8, SW11 to 14, SW21, 22 and SW31 respectively receive D0 (LSB), D1, D2, and D3 (MSB) of 4-bit image data from the pixel conversion circuit 504 by inverters INV1 to INV4. The inverted signal is supplied as the SW signal, and the output of one input terminal is selected and output.

  FIG. 18 is a diagram showing a specific circuit configuration of the second D / A conversion means R (1 / x). As shown in FIG. 18, the second D / A conversion means R (1 / x) includes resistors R0 to R14 connected in series and analog switches SW1 to SW1 whose input terminals are connected to both ends of the resistors R0 to R14. SW8, analog switches SW11-14 having their input terminals connected to the output terminals of analog switches SW1-SW8, analog switches SW21, 22 having their input terminals connected to the output terminals of analog switches SW11-14, and analog The switch SW21, 22 includes an analog switch SW31 whose input terminal is connected to the output terminal, and the ground side of the resistor R0 is connected to the output terminal of the analog switch SW31. The configuration of the analog switch SW is the same as that shown in FIG.

  4-bit image data D0 (LSB), D1, D2, D3 (MSB) are supplied as SW signals to the analog switches SW1 to SW8, SW11 to 14, SW21, 22 and SW31 from the pixel conversion circuit 504, respectively. The output of one of the input terminals is selected and output.

  The specific circuit configuration of the γ conversion means R (1 / a) can be the same as that shown in FIG. In FIG. 11, analog switches SW1 to SW4, SW11, 12, and SW21 of the γ converting means R (1 / a) are supplied to the D0 (LSB), D1, and D2 (MSB) of 3-bit γ adjustment data from the controller 509, respectively. ) Is supplied as the SW signal, and the output of one of the input terminals is selected and output. By changing the γ adjustment data input to the γ conversion means R (1 / a), the γ characteristic curve can be changed. The output current of the γ conversion means R (1 / a) is output to the subsequent display panel drive unit 506 as Iout through the current mirror circuit CM4.

  FIG. 19 is a diagram for explaining the relationship between the resistance of the γ approximation unit 603 and the parameter a. As shown in the figure, when the values of the resistors R0 to R6 of the γ converting means R (1 / a) shown in FIG. 11 are selected, the γ adjustment data is “001”, “010”, “011”, “100”. , “101”, “110”, “111”, a = “0.143”, “0.286”, “0.428”, “0.571”, “0.714”, “0.857” and “1.000” can be set.

  As described above, according to the second embodiment, the brightness adjustment unit 601 sets the maximum current value corresponding to the maximum brightness value of the digital image data based on the brightness adjustment data input from the controller 509, and the contrast. The adjustment unit 602 sets the current width corresponding to the contrast of the digital image data based on the contrast adjustment data input from the controller 509, and the γ approximation unit 603 performs the current value corresponding to the digital image data with respect to the current value. Since the inverse γ conversion is performed based on the γ adjustment data, a high-quality image can be displayed when an image is displayed on a current-driven display panel such as an organic EL panel or an LED panel.

  In addition, this invention is not limited to the said Examples 1-2, It is also possible to implement combining each Example. In the first and second embodiments, the case where the inverse γ correction is performed has been described. However, the present invention can be applied to the case where the γ correction is performed by changing the value of the parameter a.

(Application example to electronic equipment)
Next, specific examples of electronic devices to which the display device according to the present invention can be applied will be described with reference to FIGS. FIG. 20 is a perspective view showing an example in which the display device according to the present invention is applied to a display unit of a portable personal computer (so-called notebook personal computer) 700. As shown in the figure, the personal computer 700 includes a main body 702 having a keyboard 701 and a display 703 to which the display device according to the present invention is applied.

  FIG. 21 is a perspective view showing an example in which the display device according to the present invention is applied to a display unit of a mobile phone 800. As shown in the figure, the mobile phone 800 includes a plurality of operation buttons 801, a reception port 802, a transmission port 803, and a display unit 804 to which the display device according to the present invention is applied.

  The display device according to the present invention includes a portable information device called a PDA (Personal Digital Assistants), a personal computer, a workstation, a vehicle monitor, a digital video camera in addition to the above-described mobile phone, notebook computer, and digital still camera. Can be widely applied to electronic devices such as liquid crystal televisions, viewfinder type, monitor direct view type video tape recorders, car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, video phones, and POS terminals. .

  The image processing apparatus and the image processing method of the present invention can be widely used in various fields. The display device of the present invention can be widely used for organic EL display devices, LED display devices, FED display devices, electrochromic glass, electronic paper, and the like. The electronic device according to the present invention includes a mobile phone, a portable information device called PDA (Personal Digital Assistants), a portable personal computer, a personal computer, a workstation, a digital still camera, an in-vehicle monitor, a digital video camera, and a liquid crystal display. It can be widely used in electronic devices such as televisions, viewfinder type, monitor direct view type video tape recorders, car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, video phones, and POS terminals.

1 is a block diagram illustrating a configuration of a display device to which an image processing apparatus according to a first embodiment is applied. The figure which shows the equivalent circuit of a reverse (gamma) correction | amendment part. Explanatory drawing for demonstrating luminance adjustment, contrast adjustment, and (gamma) adjustment. The figure which shows the equivalent circuit of (gamma) approximation part. The figure which shows an example of (gamma) curve. The figure which shows the specific circuit structure of an inverse (gamma) correction | amendment part. The figure which shows the specific circuit structural example of a brightness | luminance adjustment means. The figure which shows the specific circuit structural example of analog switch SW. The figure which shows the structure of a contrast adjustment means. The figure which shows the specific circuit structural example of a 1st (gamma) conversion means (Rx_R1-x). The figure which shows the specific circuit structural example of 2nd gamma conversion means Ra. The figure for demonstrating the resistance value of (gamma) approximation part. FIG. 6 is a block diagram illustrating a configuration of a display device to which an image processing apparatus according to a second embodiment is applied. The figure which shows the equivalent circuit of a reverse (gamma) correction | amendment part. The figure which shows the equivalent circuit of a gamma approximation part. The figure which shows the specific circuit structure of an inverse (gamma) correction | amendment part. The figure which shows the specific circuit structure of the 1st D / A conversion means R (1 / 1-x). The figure which shows the specific circuit structure of the 2nd D / A conversion means R (1 / x). The figure for demonstrating the resistance value of (gamma) approximation part. The perspective view which shows the example which applied the display apparatus which concerns on this invention to the display part of a portable personal computer. The perspective view which shows the example which applied the display apparatus which concerns on this invention to the display part of a mobile telephone.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Display apparatus, 101 Analog image signal input terminal, 102 Digital image signal input terminal, 103 A / D conversion part, 104 Pixel conversion part, 105 Reverse gamma correction part, 106 Display panel drive part, 107 Voltage drive type display panel, 108 Operation unit, 109 controller, 201 brightness adjustment unit, 202 contrast adjustment unit, 203 gamma approximation unit, 500 display device, 501 analog image signal input terminal, 502 digital image signal input terminal, 503 A / D conversion unit, 504 pixel conversion unit , 505 Reverse γ correction unit, 506 Display panel drive unit, 507 Current drive type display panel, 508 Operation unit, 509 Controller, 601 Brightness adjustment unit, 602 Contrast adjustment unit, 603 γ approximation unit, 700 Personal computer, 701 Keyboard, 702 Body part, 70 Display unit, 800 mobile phones, 801 operation buttons 802 earpiece, 803 mouthpiece, 804 display unit

Claims (7)

A brightness adjustment unit that generates a maximum input voltage according to the brightness adjustment data;
A contrast adjustment unit configured to variably set the voltage width of the maximum input voltage generated by the luminance adjustment unit based on the contrast adjustment data; and
A D / A converter that converts digital image data into an analog voltage signal using the voltage output from the contrast adjustment unit;
A conversion unit that performs γ conversion or inverse γ conversion on the voltage signal generated by the D / A conversion unit,
The contrast adjustment unit
A first circuit and a second circuit, which are arranged in series with each other and have a maximum input voltage generated by the luminance adjustment unit applied between both ends, and determine a voltage width of the maximum input voltage;
An inverter that inverts the contrast adjustment data input to the first circuit and supplies the inverted data to the second circuit,
The first circuit includes:
A plurality of first resistors connected in series;
A first selection unit that selects and outputs any one of a plurality of potentials generated by dividing the plurality of first resistors based on the contrast adjustment data;
The second circuit includes:
A plurality of second resistors connected in series;
A second selection unit that selects and outputs any one of a plurality of potentials generated by the divided voltages of the plurality of second resistors based on the contrast adjustment data inverted by the inverter. ,
The D / A converter is
The first wiring supplied with the first output potential output from the first selection unit and the second wiring supplied with the second output potential output from the second selection unit are in series with each other. A plurality of connected third resistors;
A third selection unit that selects and outputs any one of a plurality of potentials generated by dividing the plurality of third resistors based on the digital image data;
The converter is
A plurality of fourth resistors connected in series between the third wiring from which the third output potential from the third selection unit is output and the first wiring or the second wiring;
A fourth selection unit that selects and outputs one of a plurality of potentials generated by dividing the plurality of fourth resistors based on the γ adjustment data,
An image processing apparatus. The brightness adjusting unit is
A plurality of fifth resistors connected in series between the first power supply line to which the higher potential is supplied and the second power supply line to which the lower potential is supplied;
A fifth selection unit that selects and outputs any one of a plurality of potentials generated by the divided voltages of the plurality of fifth resistors based on the brightness adjustment data;
The image processing apparatus according to claim 1. The first selection unit is connected to the plurality of first resistors, and includes a plurality of analog switches for selecting a divided voltage output of the plurality of first resistors based on the contrast adjustment data.
The second selection unit is connected to each of the plurality of second resistors, and selects a plurality of divided voltage outputs of the plurality of second resistors based on the contrast adjustment data inverted by the inverter. Including analog switches,
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. The fourth selection unit includes a plurality of analog switches that are respectively connected to the plurality of fourth resistors and that select a divided output of the plurality of fourth resistors based on the γ adjustment data.
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. The fifth selection unit includes a plurality of analog switches that are connected to the plurality of fifth resistors, respectively, and that select a divided voltage output of the plurality of fifth resistors based on the luminance adjustment data.
The image processing apparatus according to claim 2, characterized in that.   A display device comprising the image processing device according to any one of claims 1 to 5.   An electronic apparatus comprising the display device according to claim 6.

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