JP2013092548A - Drive unit for liquid crystal display element, liquid crystal display device, and drive method for liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive unit for a liquid crystal display element, a liquid crystal display device, and a drive method for a liquid crystal display element that achieve high picture quality even for a dynamic picture image by improving color breakup and generating few animation pseudo contours.SOLUTION: A first sub-frame turns to a drive state for a maximum value n of drive gradation in a prescribed field when the drive gradation is 1. The first and (n/2 + 1)th sub-frames turn to a drive state when the drive gradation is 2. As drive gradation increases, the number of sub-frames turning to a drive state increases as time passes. In a field next to the prescribed field, when the drive gradation is 1, the (n/2 + 1)th sub-frame turns to a drive state. When the drive gradation is 2, the first and (n/2 + 1)th sub-frames turn to a drive state. As drive gradation increases, the number of sub-frames turning to a drive state increase one by one as time passes. A sub-frame data creation part creates sub-frame data using a drive gradation table in which the sequence described above is performed.

Description

  The present invention relates to a liquid crystal display element driving apparatus, a liquid crystal display apparatus, and a liquid crystal display element driving method for displaying an image by dividing one frame into a plurality of subframes using a digitized video signal as an input signal.

  The driving method of the liquid crystal display element used in the liquid crystal display device is an analog method in which the voltage value applied to the pixel is a continuous analog value, and the voltage applied to the pixel is binary, and the luminance of the image There is a digital method for controlling an effective voltage value applied to a pixel of a liquid crystal by changing a time width of an applied voltage corresponding to (gradation). In the case of the digital method, since only information of 0 or 1 is applied to the pixel, it is difficult to be influenced by external factors such as noise.

  In the digital method, it is common to use a subfield method in order to obtain a halftone. In the subfield method, a predetermined number of subfields with different relative ratios of drive (light emission) periods are prepared in one field period of the video signal, and the subfield is appropriately selected according to the gradation of the video signal to be displayed. Display, and halftone display is performed using the visual integration effect of the viewer.

The subfield method is known to generate a pseudo contour when displaying a moving image, although a good display image can be obtained in the case of still image display. As a method of solving the pseudo contour, a method of arranging subfields that causes as little change in the center of gravity of light emission as possible even when image data changes is being studied.
In Patent Document 1, a portion corresponding to the upper bits is a plurality of subfields with equal weighting, and a portion corresponding to the lower bits is a plurality of subfields of binary weighting. A subfield method is described in which a field is arranged, a plurality of subfields corresponding to upper bits are divided into two, and arranged on both sides of a plurality of binary weighted subfields. Moreover, there is a problem of color breakup as a point to be considered when using the subfield method. Color breakup has been studied as a major problem in the plane sequential drive system, and Patent Document 2 describes increasing the field frequency in order to prevent color breakup in a DLP projector.

JP 2006-171651 A JP 2006-171174 A

With recent increases in resolution and contrast in image display devices, it is required to further reduce pseudo contours when displaying moving images. Further, the color breaking phenomenon is a problem to be improved even in a three-plate type in which display elements are used for every three primary colors.
It is an object of the present invention to provide a liquid crystal display element driving device, a liquid crystal display device, and a liquid crystal display element driving method for displaying a high-quality image by improving a moving image pseudo contour and color breakage that cause image quality degradation. And

In order to solve the above-described problems of the conventional technique, the present invention performs reverse gamma correction and linear interpolation on input video signal data of N bits when N, M, F, and D are natural numbers. A lookup table unit for converting large (M + F + D) bit data; an error diffusion unit for converting (M + F + D) bit data processed by the lookup table unit into (M + F) bit data by error diffusion processing; A frame rate control unit that converts (M + F) -bit data processed by the error diffusion unit into M-bit data by frame rate control;
The M-bit data processed by the frame rate control unit is used, and all subframes are formed by step bit pulses. When the number of subframes in one frame is a natural number s, n = s when s is an even number. In the predetermined field, when the driving gradation is 1, the first subframe is in the driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th subframes are in the driving state. When the gradation is 3, the first, second, and (n / 2 + 1) subframes are in a driving state, and when the driving gradation is 4, the first, second, (n / 2 + 1) th, and (n / 2 + 2) ) The subframe in which the first subframe is in the driving state and the subframe in which the driving state is already driven one by one as the driving gradation further increases is temporally In the field next to the predetermined field, when the driving gradation is 1, the (n / 2 + 1) th subframe is in the driving state, and when the driving gradation is 2, the first subframe is When the (n / 2 + 1) th subframe is in a driving state and the driving gradation is 3, the first, (n / 2 + 1) th and (n / 2 + 2) th subframes are in a driving state, and the driving gradation is 4 In this case, the 1st, 2nd, (n / 2 + 1) th, and (n / 2 + 2) th subframes are in the drive state, and one subframe that is in the drive state is already driven each time the drive gradation is further increased. The drive order is switched for each frame so that the subframes in the state increase in time later. When s is an odd number, n = s + 1 is set. In a predetermined field, the drive gradation is 1 When When the driving gradation is 2, the first and (n / 2 + 1) th subframes are in the driving state, and when the driving gradation is 3, the first, second, (n / 2 + 1) ) The sub-frame is in the driving state, and when the driving gradation is 4, the first, second, (n / 2 + 1) -th and (n / 2 + 2) -th sub-frames are in the driving state, and the driving gradation further increases. Each time a subframe is driven, the number of subframes that are in the driving state increases one after another with respect to the subframes that are already in the driving state. When (1/2) is 1, the (n / 2) th subframe is in a driving state, when the driving gradation is 2, the first and (n / 2) th subframes are in a driving state, and when the driving gradation is 3, Th, (n / 2) th, ( When the / 2 + 1) th subframe is in a driving state and the driving gradation is 4, the first, second, (n / 2) th, and (n / 2 + 1) th subframes are in a driving state, and the driving gradation is Each time the number of subframes further increases, the number of subframes that are in the driving state is increased by one by the drive gradation table that changes the driving order for each frame so that the subframes that are already in the driving state increase in time. There is provided a drive device for a liquid crystal display element, comprising a subframe data creation unit for creating frame data, and driving the liquid crystal display element based on the subframe data.

  In order to solve the above-described problems of the prior art, the present invention performs inverse gamma correction and linear interpolation on the input video signal data of bit number N when N, M, F, and D are natural numbers. A lookup table unit for converting to larger (M + F + D) bit data; and an error diffusion unit for converting (M + F + D) bit data processed by the lookup table unit into (M + F) bit data by error diffusion processing; A frame rate control unit that converts (M + F) -bit data processed by the error diffusion unit into M-bit data by frame rate control; and M-bit data processed by the frame rate control unit, All subframes are composed of step bit pulses, and the number of subframes in one frame When s is an even number, n = s when s is an even number. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th subframe is set. When the (n / 2) th subframe is in a driving state and the driving gradation is 3, the sth, (s-1) th, and (n / 2) th subframes are in a driving state, and the driving gradation is 4 In this case, the sth, (s-1) th, (n / 2) th, and (n / 2-1) th subframes are in the driving state, and the subframe is in the driving state each time the driving gradation further increases. Increases one by one with respect to the subframes that are already driven one by one, and in the next field of the predetermined field, when the driving gradation is 1 (n / 2 ) The second subframe is in the driving state, and the driving gradation is 2. The (n / 2) th and sth subframes are in the driving state, and when the driving gradation is 3, the (n / 2) th, (n / 2-1) th, and sth subframes are in the driving state. When the drive gradation is 4, the (n / 2) th, (n / 2-1) th, sth, and (s-1) th subframes are in the drive state, and the drive gradation further increases. The driving order is changed for each frame so that the number of subframes in the driving state increases one by one in time in the subframes that are already in the driving state, and when s is an odd number, n = s− In a predetermined field, when the driving gradation is 1, the s-th subframe is in the driving state, and when the driving gradation is 2, the s-th and (n / 2) -th subframe are in the driving state. When drive gradation is 3, sth, (s-1) th, (n / 2) The sth, (s-1) th, (n / 2) th, and (n / 2-1) th subframes are in the driving state when the driving gradation is 4, and the driving gradation is 4, and the driving is performed. Each time the gray level further increases, the number of subframes that are in the driving state increases one by one with respect to the subframe that is already in the driving state, and the next field after the predetermined field. , The (n / 2 + 1) th subframe is in the driving state when the driving gradation is 1, and the (n / 2 + 1) th and sth subframes are in the driving state when the driving gradation is 2. When the key is 3, the (n / 2 + 1) th, (n / 2) th, and sth subframes are in the driving state, and when the driving gradation is 4, the (n / 2 + 1) th, (n / 2) th, sth, (s-1) th subframe is driven Each time the driving gradation further increases, the driving order for each frame is increased so that the number of subframes that are in the driving state increases one by one in time in the subframe that is already in the driving state. And a sub-frame data generating unit that generates sub-frame data using a driving gradation table for switching between, and a liquid crystal display element driving device based on the sub-frame data.

  In order to solve the above-described problems of the conventional technology, the present invention provides a driving device for a liquid crystal display element having any one of the above configurations, a liquid crystal display element driven by the driving device, and illumination for the liquid crystal display element. Provided is a liquid crystal display device comprising: an illumination optical system that makes light incident; and a projection lens that projects modulated light emitted from the liquid crystal display element.

  In order to solve the above-described problems of the prior art, the present invention performs inverse gamma correction and linear interpolation on N-bit input video signal data when N, M, F, and D are integers. A first step of converting to larger (M + F + D) bit data, and a second step of converting the (M + F + D) bit data processed in the first step into (M + F) bit data by error diffusion processing A third step of converting the (M + F) -bit data processed in the second step into M-bit data by frame rate control, and the M-bit data processed in the third step. In addition, all subframes are formed by step bit pulses, and when the number of subframes in one frame is a natural number s, s is an even number. In this case, n = s, and in a predetermined field, when the driving gradation is 1, the first subframe is in the driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th subframes are in the driving state. When the driving gradation is 3, the first, second, (n / 2 + 1) th subframe is in the driving state, and when the driving gradation is 4, the first, second, (n / 2 + 1) th , The (n / 2 + 2) th subframe is in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is later in time with respect to the subframe that is already in the driving state. In the field next to the predetermined field, when the driving gradation is 1, the (n / 2 + 1) th subframe is in the driving state, and when the driving gradation is 2, the first subframe is ( n / 2 + 1) th When the driving gradation is 3, the first, (n / 2 + 1) th, (n / 2 + 2) th subframe is in the driving state, and when the driving gradation is 4, the first and second , The (n / 2 + 1) th and (n / 2 + 2) th subframes are in a driving state, and one subframe that is in a driving state each time the driving gradation is further increased is already in a driving state. In the predetermined field, when the driving gradation is 1, in the predetermined field, the first sub-frame is changed to n = s + 1. When the driving gradation is 2, the first and (n / 2 + 1) th subframes are in the driving state, and when the driving gradation is 3, the first, second, and (n / 2 + 1) th subframes. Is driven When the drive gradation is 4, the first, second, (n / 2 + 1) th, and (n / 2 + 2) th subframes are in the drive state, and the drive state is increased each time the drive gradation is further increased. The number of frames increases one by one with respect to the subframes that have already been driven one by one, and in the next field after the predetermined field, when the driving gradation is 1 (n / 2 ) Th subframe is in the driving state, the first when the driving gradation is 2, and the (n / 2) th subframe is in the driving state, the first when the driving gradation is 3, and the (n / 2) th , The (n / 2 + 1) th subframe is in a driving state, and when the driving gradation is 4, the first, second, (n / 2) th, and (n / 2 + 1) th subframes are in a driving state, and driving Each time the gradation further increases, the drive state is entered. A fourth step of creating subframe data by a driving gradation table that changes the driving order for each frame so that the subframes are increased one by one in time in the subframes that have already been driven. A method for driving a liquid crystal display element is provided.

In order to solve the above-described problems of the prior art, the present invention performs inverse gamma correction and linear interpolation on N-bit input video signal data when N, M, F, and D are integers. A first step of converting to larger (M + F + D) bit data, and a second step of converting the (M + F + D) bit data processed in the first step into (M + F) bit data by error diffusion processing A third step of converting the (M + F) -bit data processed in the second step into M-bit data by frame rate control, and the M-bit data processed in the third step. In addition, all subframes are formed by step bit pulses, and when the number of subframes in one frame is a natural number s, s is an even number. In the case where n = s, in a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th and (n / 2) -th subframes are driven. When the driving gradation is 3, the sth, (s-1) th, and (n / 2) th subframes are in the driving state, and when the driving gradation is 4, the sth and (s-1) th The (n / 2) th and (n / 2-1) th subframes are in a driving state, and one subframe that is in a driving state every time driving gradation is further increased is already in a driving state. With respect to the subframe, it increases in time, and in the field next to the predetermined field, when the driving gradation is 1 (n / 2), the subframe is in the driving state, and driving When gradation is 2 (n / 2) and sth When the frame is in the drive state and the drive gradation is 3, the (n / 2) th, (n / 2-1) th, and sth subframes are in the drive state and the drive gradation is 4 (n / 2) The (n / 2-1) th, sth, and (s-1) th subframes are in the driving state, and one subframe is already in the driving state each time the driving gradation further increases. The drive order is changed for each frame so that the subframes in the drive state increase in time.
When s is an odd number, n = s−1. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th subframe is (n / 2). When the driving gradation is 3, the sth, (s-1) th, and (n / 2) th subframes are in the driving state, and when the driving gradation is 4, the sth, The (s−1) th, (n / 2) th, and (n / 2−1) th subframes are in the driving state, and one subframe that is in the driving state each time the driving gradation further increases is already one by one. With respect to the subframe in the driving state, it increases toward the front in time, and in the field next to the predetermined field, the driving gradation is 1 (n / 2 + 1) th subframe. Is in a driving state and the driving gradation is 2 (n / 2 1) When the driving gradation is 3, the (n / 2 + 1) th, (n / 2) th, and sth subframes are driving when the driving gradation is 3, and the driving gradation is 4 In this case, the (n / 2 + 1) th, (n / 2) th, sth, and (s-1) th subframes are in the driving state, and the subframe that is in the driving state every time the driving gradation is further increased is 1. A fourth step of creating subframe data by a driving gradation table that changes the driving order for each frame so that the subframes that are already in the driving state increase in time in the order of time. A method for driving a liquid crystal display element is provided.

  According to the present invention, there are provided a liquid crystal display element driving device, a liquid crystal display device, and a liquid crystal display element driving method for improving a moving image pseudo contour and color breakage that cause image quality degradation and displaying a high quality image. Can do.

It is a schematic block diagram which shows the liquid crystal display device using a reflection type liquid crystal display element. It is a figure which shows the drive circuit structure of each pixel in the reflection type liquid crystal display element of a digital drive. It is a figure which shows the relationship between the input voltage of a reflection type liquid crystal display element, and the intensity | strength of output light. It is a block diagram which shows a drive circuit (drive device). It is a figure for demonstrating gradation expression. It is a figure which shows an error diffusion diagram. It is a figure which shows an error diffusion flow. It is a figure which shows a frame rate control flow. It is a figure which shows a frame rate control table. It is a figure which shows a drive pattern. It is a figure which shows the drive gradation table in 1st Embodiment. It is a figure for demonstrating generation | occurrence | production of the moving image pseudo | simulation outline by the conventional digital drive. FIG. 10 is a diagram illustrating a driving gradation table comparative example 1; FIG. 10 is a diagram illustrating a driving gradation table comparative example 2; It is a figure for demonstrating the moving image pseudo contour generation state at the time of using the drive gradation table comparative example 1. FIG. It is a figure for demonstrating the moving image pseudo contour generation state at the time of using the drive gradation table comparative example 2. FIG. It is a figure for demonstrating the animation false contour generation state at the time of using the drive gradation table in 1st Embodiment. It is a figure for demonstrating the color breakage generation | occurrence | production state when the R, G, B level is equal using the drive gradation table comparative example 1. FIG. It is a figure for demonstrating the color breakage generation | occurrence | production state when the R, G, and B levels differ using the drive gradation table comparative example 1. FIG. It is a figure for demonstrating the color breakage generation | occurrence | production state in the drive gradation table in 1st Embodiment. It is a figure which shows the drive gradation table in 2nd Embodiment. It is a figure for demonstrating the animation false contour generation state at the time of using the drive gradation table in 2nd Embodiment. It is a figure for demonstrating the color breakage generation | occurrence | production state at the time of using the drive gradation table in 2nd Embodiment.

  Hereinafter, an image display device and a driving method thereof according to the present invention will be described with reference to the accompanying drawings. In the following, a projection type display device provided with an active matrix type reflective liquid crystal display element as a display panel will be described as an example. First, schematic configurations of the projection display device and the reflective liquid crystal display element will be described.

  FIG. 1 is a schematic configuration diagram showing a liquid crystal display device using a reflective liquid crystal display element. The liquid crystal display device 100 generally includes a reflective liquid crystal display element 6, a polarization beam splitter 5 (hereinafter referred to as PBS), and a projection lens 11. The reflective liquid crystal display element 6 has a structure in which a liquid crystal 9 is sealed between a counter electrode (also referred to as a transparent electrode) 10 and a pixel electrode 8.

  Light 2 including S-polarized light 3 and P-polarized light 4 emitted from the illumination optical system 1 enters the PBS 5 and is polarized and separated by the PBS 5. The S-polarized light 3 is reflected by the polarization separation surface of the PBS 5 and proceeds to the reflective liquid crystal display element 6 side. P-polarized light is transmitted through the polarization separation surface of PBS 5. The liquid crystal 9 of the reflective liquid crystal display element 6 modulates incident S-polarized light according to the voltage applied between the pixel electrode 8 and the counter electrode 10 by the pixel circuit 7. The S-polarized light incident on the counter electrode 10 is modulated in the process from being reflected by the pixel electrode 8 and being emitted from the counter electrode 10, and is emitted from the counter electrode 10 as light composed of P-polarized light and S-polarized light. In the light emitted from the counter electrode 10, only the P-polarized component, which is modulated light, passes through the PBS 5, and the S-polarized component is reflected by the PBS 5. The P-polarized light that has passed through the PBS 5 is emitted by the projection lens 11, and the emitted light 12 is projected on the screen 13 to display an image. The intensity of the output light described later refers to the illuminance of the output light measured on the screen 13.

  FIG. 2 is a diagram showing the drive circuit configuration of each pixel in the digitally driven reflective liquid crystal display element 6. Each pixel of the reflective liquid crystal display element 6 has a structure in which a liquid crystal 9 is sandwiched between a pixel electrode 8 and a counter electrode 10. A pixel circuit 7 indicated by a broken line includes a sample hold unit 16 and a voltage selection circuit 17. The sample hold unit 16 is composed of an SRAM structure flip-flop. The sample hold unit 16 is connected to the column data line D and the row selection line W. The output of the sample hold unit 16 is connected to the voltage selection circuit 17. The voltage selection circuit 17 is connected to the blanking voltage line V0 and the drive voltage line V1. The voltage selection circuit 17 is connected to the pixel electrode 8 and applies a predetermined voltage to the pixel electrode 8. The value of the voltage of the counter electrode 10 is called a common voltage Vcom.

  FIG. 3 is a diagram showing the relationship between the input voltage of the reflective liquid crystal display element 6 and the intensity of output light. In FIG. 3, the horizontal axis represents the input voltage, and shows the potential difference between the pixel electrode 8 and the counter electrode 10, that is, the driving voltage of the liquid crystal 9. The vertical axis indicates the intensity of output light emitted from the liquid crystal 9. The voltage at which the intensity of the output light emitted from the liquid crystal 9 starts to increase is the dark value voltage Vth. When the voltage is 0 (for example, both the pixel electrode 8 and the counter electrode are GND), the intensity of the output light is small and the state is black (blanking voltage), and the voltage at which the output light begins to saturate is the saturation voltage Vw (white). Level.)

  FIG. 4 is a block diagram showing a drive circuit (drive device). FIG. 5 is a diagram for explaining gradation expression, and shows an example of gradation expression in each process unit when the number of bits of input video signal data is 8 bits. FIG. 6 is a diagram showing an error diffusion flow. FIG. 7 is a diagram showing an error diffusion diagram. FIG. 8 is a diagram showing a frame rate control flow. FIG. 9 shows a frame rate control table.

  In FIG. 4, video signal data with N bits input is converted into (M + F + D) bit data larger than N by the look-up table unit 21. Here, M is the number of bits when the number of subframes is expressed in binary, D is the number of bits to be interpolated by the error diffusion processing unit 23, and F is the number of bits to be interpolated by the frame rate control unit 24. . N, M, F, and D are integers.

In the example of FIG. 5, the number of bits of the input video signal data is 8 bits (N = 8), the number of bits to be interpolated by the error diffusion processing unit 23 is 4 bits (D = 4), and the frame rate control unit 24 The number of bits to be interpolated is set to 2 bits (F = 2). When the number of subframes is expressed in binary, the number of bits is 4 bits (M = 4), and the drive gradation is 12 (not including black).

Here, the operation of the lookup table unit 21 will be described. Generally, video signals are subjected to gamma correction. On the image display device side, it is necessary to perform inverse gamma correction processing on the video signal that has been subjected to gamma correction to restore the linear gradation. Inverse gamma correction is correction in which the output is X raised to the power of 2.2 with respect to the input X. In this case, the output characteristic is expressed as “gamma 2.2” below. The look-up table unit 21 has a function of realizing a liquid crystal display device having an output characteristic of gamma 2.2 by converting input / output characteristics of the reflective liquid crystal display element 6. The look-up table is adjusted in advance so that the 10-bit output has an arbitrary output characteristic (for example, gamma 2.2). For example, an image obtained by driving each of twelve driving gradations (not including black) in a driving gradation table to be described later is projected by the liquid crystal display device shown in FIG. Keep measuring. By linearly interpolating the illuminance between the respective drive gradations with 6 bits (M + D = 6) (64 gradations), illuminance data for each gradation of 0 to 768 is predicted. It is assumed that 256 pieces of data having arbitrary output characteristics (for example, gamma 2.2) are selected from those illuminance data and are stored as a lookup table in advance.

The lookup table unit 21 has a lookup table of 256 × 10 bits (that is, “2 to the 8th power” gradation x (4 + 2 + 4) bits). Here, the “2 to the 8th power” gradation x (4 + 2 + 4) bit means that N = 8, M = 4, F = 2, and D = 4 with respect to the “2 to the Nth power” gradation x (M + F + D) bit. Is equivalent to the value of. The look-up table unit 21 converts the input 8-bit image data into 10-bit data and outputs it.

Returning to FIG. 4, the video signal data converted into (M + F + D) bits by the look-up table unit 21 is (M + F) bit data by diffusing the lower D bits of information to surrounding pixels by the error diffusion unit 23. Is converted to In the example of FIG. 5, the converted 10-bit data is output by the error diffusion unit 23 by diffusing the lower 4 bits of information to surrounding pixels, quantizing the data into upper 6 bits.

  The error diffusion method is a method of compensating for the lack of gradation by diffusing an error (display error) between a video signal to be displayed and an actual display value to surrounding pixels. In the first embodiment, the lower 4 bits of the video signal to be displayed are set as display errors, and as shown in FIG. 6, 7/16 of the display error is displayed in the right adjacent pixel and 3/16 of the display error is displayed in the lower left pixel. , 5/16 of the display error is added to the pixel immediately below, and 1/16 of the display error is added to the pixel on the lower right.

  The operation of the error diffusion unit 23 will be described in more detail with reference to FIG. A video signal at a certain coordinate diffuses an error as described above, and an error obtained by diffusing the previous video is added. In the input 10-bit data, first, an error in which the previous image is diffused is added by the error buffer. The input video signal data is divided into upper 6 bits and lower 4 bits after the error buffer value is added.

The divided lower 4 bits are shown below. The value on the right is a display error.
Lower 4 bits Display error 0000 0
0001 +1
0010 +2
0011 +3
0100 +4
0101 +5
0110 +6
0111 +7
1000-7
1001-6
1010-5
1011 -4
1100-3
1101 -2
1110 -1
1111 0

  The display error corresponding to the divided lower 4-bit value is added to the error buffer and held as shown in FIG. Also, a threshold comparison is performed on the divided lower 4-bit value, and if the value is larger than 1000 (the row after the row where the value on the left is 1000), 1 is added to the upper 6-bit value. Is added. Then, the upper 6-bit data is output from the error diffusion unit.

  Returning to FIG. 4, the video signal data converted into (M + F) bits by the error diffusion unit 23 is input to the frame rate control unit 24. The frame rate control unit 24 includes a frame rate control table. The frame rate control unit 24 specifies the position in the frame rate control table from the lower F bit value, the pixel position information, and the frame count information, and the value (1 or 0, hereinafter 0/1) Are added to the upper M bits and converted to M bit data. Here, the frame rate control method refers to an m (m: m ≧ 2, natural number) frame as one period for display of one pixel of the display element, and n (n: n> 0, m> n) of the period. In this method, pseudo gradation is displayed by performing on display in the (natural number) frame and performing off display in the remaining (mn) frames.

  In the example of FIG. 5, the 6-bit data output from the error diffusion unit 23 is input to the frame rate control unit 24. The frame rate control unit 24 derives a value of 0/1 from the frame rate control table from the lower 2 bits information, the position information in the display area, and the frame counter information, and the upper 4 bits separated from the input 6 bits. Add to the value of the bit.

  The operation of the frame rate control unit 24 will be specifically described with reference to FIG. The input 6-bit data is divided into upper 4 bits and lower 2 bits. The lower 2 bits of the input 6-bit data, the position information in the pixel display area (that is, the lower bits of the X coordinate and the lower 2 bits of the Y coordinate, which are coordinate data), and the lower 2 bits of the frame counter A value of “0” or “1” shown in the frame rate control table of FIG. 9 is specified using a total of 8 bits. The specified value “0” or “1” is added to the upper 4 bits of data and output as 4 bits of data.

  Returning to FIG. 5, the 4-bit data output from the frame rate control unit 24 is limited to 12 which is the maximum value of the drive gradation by the limiter unit 25 shown in FIG. At 26, the data is converted into 12-bit data to be transferred to the reflective liquid crystal display element 6. The drive gradation table 27 is used for conversion to 12-bit data.

  Returning to FIG. 4, the 12-bit data output from the subframe data creation unit 26 is stored in the frame buffer 29 divided for each subframe by the memory control unit 28. The frame buffer 29 has a double buffer structure. While data is being stored in the frame buffer 0, the data in the frame buffer 1 is transferred to the reflective liquid crystal display element 6 via the data transfer unit. In the next frame, the data in the frame buffer 0 stored during the previous frame period is transferred to the liquid crystal display element 6 via the data transfer unit 30, and the subframe data of the video signal data input to the frame buffer 1. Output data from the creation unit 26 is stored.

  The drive control unit 31 controls processing timing for each subframe, and performs a transfer instruction to the data transfer unit 30 and control of the gate driver 34. The data transfer unit 30 instructs the memory control unit 28 in accordance with an instruction from the drive control unit 31, receives the designated subframe data from the memory control unit 28, and transfers the data to the source driver 33. Each time the source driver 33 receives data for one line from the data transfer unit 30, it simultaneously transfers the data to the corresponding pixel circuit 7 of the reflective liquid crystal display element 6 using the column data lines D0-Dn. At this time, the gate driver 34 activates the row selection line Wy of the row designated by the vertical start signal (VST) / vertical shift clock signal (VCK) from the drive control unit 31, and all the designated rows y are activated. Data is transferred to the pixels in the column.

  FIG. 10 shows a driving pattern. FIG. 10 shows a case where the video signal is 60 frames per second and the number of subframes is 12. WC represents a data transfer period (WC period) in which data for each subframe is transferred to all pixels in the liquid crystal display element. DC represents a driving period (DC period) when driving the liquid crystal. The WC period is 694 [μs], and the DC period is 694 [μs]. In one frame, the WC period and the DC period are alternately repeated 12 times. Data of 0 or 1 assigned to each subframe in the order of SF1, SF2,..., SF11, SF12 from the beginning is transferred in the WC period, and the liquid crystal of all the pixels in the DC period is driven. When the data sampled and held in the pixel is 0, the pixel is in a blanking state, and when it is 1, it is in a driving state.

<First Embodiment>
FIG. 11 is a diagram showing a drive gradation table in the first embodiment.
In FIG. 11, as in FIG. 10, the video signal is 60 frames per second, the number of subframes is 12, the data transfer period (WC period) is 694 [μs], and the drive period (DC period) is 694 [μs]. Yes. FIG. 11 shows the state of the DC period for each subframe with respect to the drive gradation in two consecutive frames (frame A and frame B). The gradation in the vertical column in FIG. 11 is 4-bit data obtained by the frame rate control unit 24 and is limited by the limiter unit 25 by 12 which is the maximum value of the drive gradation. SF1-SF12 represents the order of subframes within one frame. When the DC period column is 1, it indicates a driving state. A zero in the DC period column indicates a blank state.

In FIG. 11, in the frame A, when the gradation shown in the vertical column is 1, only the first subfield SF1 is driven. When the gradation is 2, only SF1 and SF7 are driven. When the gradation is 3, SF1, SF2, and SF7 are in a driving state, and when the gradation is 4, SF1, SF2, SF7, and SF8 are in a driving state. Hereinafter, as the number of gradations increases, the number of subframes in the driving state increases, and in the case of 12 which is the highest gradation, all subframes are in the driving state. In other words, as the number of gradations increases, the number of subframes that are in the driving state increases backward in time starting from SF1 and SF7.

In the frame B, when the gradation is 1, only the seventh subfield SF7 is driven. When the gradation is 2, only SF1 and SF7 are driven. When the gradation is 3, SF1, SF7, and SF8 are in a driving state, and when the gradation is 4, SF1, SF2, SF7, and SF8 are in a driving state. Hereinafter, as the number of gradations increases, the number of subframes in the driving state increases, and in the case of 12 which is the highest gradation, all subframes are in the driving state. In other words, as the number of gradations increases, the subframes that are in the driving state increase backward in time starting from SF7 and SF1. In this way, the gradation driving table is set such that the frame A in which SF1 is first driven and the frame B in which SF7 is first driven appear alternately. In other words, the gradation driving table is set such that the frame in which SF1 is first driven and the frame in which SF7 is first driven are switched for each frame.

10 and FIG. 11 is that step bit pulses having the same width are used without using binary bit pulses that cause moving image pseudo contours. The binary bit pulse performs so-called “binary weighting” in which a weight is expressed by 2n (n = 0, 1, 2, 3,...) For each subfield. When there are pulses with a pulse width ratio of 1, 2, 4, 8, 16, there are pulses with a pulse width ratio of [2, 16] in the drive state and pulses with a pulse width ratio of [1, 4, 8]. By setting the ranking state, luminance “18” can be expressed. In this example, 31 levels of luminance can be expressed with five pulses, and many gradations can be expressed with a small number of pulses. On the other hand, when there are 1, 2, 4, 8, 16 binary bit pulses, step bit pulses are pulses having the same weight, such as 32, 32, 32, 32, 32, 32, 32. Compared to the case where all binary bit pulses are used, the combined use of step bit pulses has the effect of reducing the moving image pseudo contour.

  FIG. 12 is a diagram for explaining the generation of the moving image pseudo contour in the conventional digital drive. In the case of the conventional digital drive, it is necessary to use a binary bit pulse in order to express many gradations. Video pseudo-contour means that in a similar gradation of adjacent pixels, most of the binary bit pulses in one pixel are in the driving state, and many of the binary bit pulses in the other pixel are in the blanking state In this case, when the line of sight is moved or when an image such as a face is moved, unintended luminance is perceived by the eyes.

  12 (a) to 12 (c) show the display state of the pixels. In each of the upper figures, the middle figure shows the next display state in time, and the lowermost figure shows these display conditions. It represents the luminance level perceived by the viewer when the pixels are viewed continuously. In the pixels of FIGS. 12A to 12C, the left half has a luminance level 127 and the right half has a luminance level 128. 12A shows the case where the display pixel does not move, FIG. 12B shows the case where the display image moves to the left by two pixels in one frame, and FIG. 12C shows the display image in one frame. The case where it moves to the right by 2 pixels is shown.

In FIG. 12A, since the display pixel does not move, the viewer can perceive the original luminance level. In FIG. 12B, since the display pixel has moved to the left, the viewer perceives an extremely low luminance level near the boundary between the luminance levels 127 and 128. In FIG. 12C, the display pixel has moved to the right, so that the viewer perceives an extremely high luminance level near the boundary between the luminance levels 127 and 128. A phenomenon in which a luminance change extremely different from the original luminance is perceived and the image appears as if it has a contour is called a pseudo contour.
This phenomenon is a cause of image quality deterioration, especially when a person's face moves, such as contour lines appearing along the contour of the face.

Hereinafter, the moving image pseudo contour and the color break-up occurrence state in the present embodiment will be described in comparison with the case of using another drive gradation table. FIG. 13 shows a driving gradation table comparative example 1 and FIG. 14 shows a driving gradation table comparative example 2.
In the drive gradation table of frame A in FIG. 13, when the gradation shown in the vertical column is 1, only the first subfield SF1 is in the drive state. When the gradation is 2, only SF1 and SF2 are driven. When the gradation is 3, SF1, SF2, and SF3 are in a driving state, and when the gradation is 4, SF1, SF2, SF7, and SF8 are in a driving state. Hereinafter, as the number of gradations increases, the number of subframes in the driving state increases, and in the case of 12 which is the highest gradation, all subframes are in the driving state. In other words, as the number of gradations increases, the subframes in the drive state increase backward in time starting from SF1. The continuous frame B also has the same table as the frame A.
FIG. 15 shows a pseudo contour generation situation when the driving gradation table comparative example 1 of FIG. 13 is used. FIG. 15 shows an image in which the luminance level changes stepwise in the horizontal direction. In the same manner as in FIG. 12, the middle figure shows the next display state in time, and the display image is displayed in one frame. This represents a state where the pixel has moved to the left by two pixels. The bottom diagram shows the luminance level perceived by the viewer when these pixels are viewed continuously. Since the luminance level perceived by the viewer does not change significantly, the moving image pseudo contour is hardly perceived.

The drive gradation table in FIG. 14 is a table in which the drive gradation table in the present embodiment described in FIG.
FIG. 16 shows a pseudo contour generation situation when the driving gradation table comparative example 2 of FIG. 14 is used. FIG. 16 shows an image in which the luminance level changes stepwise in the horizontal direction. In the same way as in FIG. 12, the figure in the upper figure represents the next display state in time, and the display image is displayed in one frame. This represents a state where the pixel has moved to the left by two pixels. The bottom diagram shows the luminance level perceived by the viewer when these pixels are viewed continuously. As in the case of FIG. 14, since the luminance level perceived by the viewer does not change significantly, the moving image pseudo contour is hardly perceived. However, the brightness change is uneven.

FIG. 17 shows a pseudo contour generation situation when the drive gradation table in the present embodiment described in FIG. 11 is used. In FIG. 17, as in the case of FIG. 15, since the luminance level perceived by the viewer does not change significantly, the moving image pseudo contour is hardly perceived and the change in brightness is uniform.

Next, the occurrence of color breakup will be described with reference to the drawings.
FIG. 18 shows the occurrence of color breakup when an image having the same level of R, G, B is displayed using the driving gradation table comparative example 1 shown in FIG. In FIG. 18, the middle figure represents the next display state in time with respect to the upper figure, and the lowermost figure represents an image perceived by the viewer when these pixels are viewed continuously. Yes. Among the images perceived by the viewer, the range a is originally displayed. In the range of b and c, an area where no image is displayed is also perceived, and an image having a lower luminance than that of a is perceived. However, in the image perceived by the viewer, R, G, and B are always at the same level, so that the regions b and c are not perceived to be colored as in the region a.

FIG. 19 shows a state of occurrence of color breakup when images having different levels of R, G, and B are displayed using the driving gradation table comparative example 1 shown in FIG.
In FIG. 19, the range a is originally displayed. The range of b is an image of only R component and G component, and the range of c is an image of only R component. In this way, when an image moves between frames or a viewer's line of sight moves, an unnatural color is perceived at the edge portion is called color breakup. Here, the case where the pixels have moved by two pixels between frames is illustrated, but the greater the amount of movement of the pixels, the wider the range of colors, and the greater the effect of color breakup.

FIG. 20 shows the state of occurrence of color breakup when an image having different levels of R, G, and B is displayed using the drive gradation table according to the present embodiment shown in FIG. 11 as in the case of FIG.
In FIG. 20, as compared with FIG. 19, the image region b having only the R component and the G component and the image region c having only the R component are significantly reduced, and it can be seen that color breakup is improved.

<Second Embodiment>
The second embodiment is the same as the first embodiment except that the drive gradation table is different from the first embodiment. Hereinafter, the same or similar contents as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
FIG. 21 shows a drive gradation table in the second embodiment.

In FIG. 21, in the frame A, when the gradation shown in the vertical column is 1, only the twelfth sub-field SF12 is in the drive state. When the gradation is 2, only SF6 and SF12 are driven. When the gradation is 3, SF6, SF11, and SF12 are in a driving state, and when the gradation is 4, SF5, SF6, SF11, and SF12 are in a driving state. Hereinafter, as the number of gradations increases, the number of subframes in the driving state increases, and in the case of 12 which is the highest gradation, all subframes are in the driving state. In other words, as the number of gradations increases, the number of subframes that are in the driving state increases forward in time starting from SF12 and SF6.

In the frame B, when the gradation is 1, only the sixth subfield SF6 is in the drive state. When the gradation is 2, only SF6 and SF12 are driven. When the gradation is 3, SF5, SF6, and SF12 are in a driving state, and when the gradation is 4, SF5, SF6, SF11, and SF12 are in a driving state. Hereinafter, as the number of gradations increases, the number of subframes in the driving state increases, and in the case of 12 which is the highest gradation, all subframes are in the driving state. In other words, as the number of gradations increases, the number of subframes that are in the driving state increases forward in time starting from SF6 and SF12. In this way, the gradation driving table is set such that the frame A in which SF12 is first driven and the frame B in which SF6 is first driven appear alternately. In other words, the gradation driving table is set so that the frame in which SF6 is first driven and the frame in which SF12 is first driven are switched for each frame.

FIG. 22 shows a pseudo contour generation situation when the drive gradation table in the present embodiment described in FIG. 21 is used. In FIG. 22, as in the case of the first embodiment, since the luminance level perceived by the viewer does not change significantly, the moving image pseudo contour is hardly perceived and the change in brightness is uniform.
FIG. 23 shows the occurrence of color breakup when an image with different levels of R, G, and B is displayed using the drive gradation table according to the present embodiment, as in FIG.
In FIG. 23, as in the first embodiment, the image area b with only the R component and the G component and the image area c with only the R component are significantly smaller than those in FIG. I understand that.

  In the first and second embodiments, the number of bits of the input video signal data is N, the number of bits when the number of gradations that can be driven by the display element is expressed in binary, and the number of bits as an error by error diffusion processing. The case where N = 8, M = 4, D = 4, and F = 2 has been described, where D is the number of bits to be diffused and F is the number of bits expressed as a pseudo gradation by frame rate control. . However, the values of N, M, D, and F are not limited to the above values, and various values can be used. Among them, it is more preferable that N = 8 to 12, M = 4 to 6, D = 4 to 8, and F = 2 to 3.

1 illumination optical system, 2 light, 3 S polarized light, 4 P polarized light,
5 Polarizing beam splitter (PBS), 6 Reflective liquid crystal display element
7 pixel circuit, 8 pixel electrode, 9 liquid crystal, 10 counter electrode (transparent electrode),
11 projection lens, 12 emission light, 13 screen,
16 sample hold unit, 17 voltage selection circuit,
21 Look-up table section,
23 error diffusion unit, 24 frame rate control unit,
25 limiter section, 26 subframe data creation section,
27 drive gradation table, 28 memory control unit, 29 frame buffer,
30 data transfer unit, 31 drive control unit, 32 voltage control unit,
33 source driver, 34 gate driver 100 liquid crystal display device, 102 drive circuit

Claims (5)

A lookup table unit for converting input video signal data of bit number N into (M + F + D) bit data larger than N by performing inverse gamma correction and linear interpolation when N, M, F, and D are natural numbers;
An error diffusion unit that converts (M + F + D) bit data processed by the lookup table unit into (M + F) bit data by error diffusion processing;
A frame rate control unit that converts (M + F) -bit data processed by the error diffusion unit into M-bit data by frame rate control;
Using M-bit data processed by the frame rate control unit, and configuring all subframes by step bit pulses,
When the number of subframes in one frame is a natural number s,
When s is an even number, n = s. In a predetermined field, when the driving gradation is 1, the first subframe is in a driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th When the sub-frame is in a driving state, the first, second, and (n / 2 + 1) th sub-frames are in a driving state when the driving gradation is 3, and when the driving gradation is 4, the first, second, (n / The 2 + 1) th and (n / 2 + 2) th subframes are in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is timed with respect to the subframe that is already in the driving state. In the next field after the predetermined field, when the drive gradation is 1, the (n / 2 + 1) th subframe is in the drive state, and when the drive gradation is 2, the first subframe is 1 And (n / 2 + The first sub-frame is in the driving state, and the first (n / 2 + 1) -th and (n / 2 + 2) -th sub-frame is in the driving state when the driving gradation is 3, and the first when the driving gradation is 4. The second, (n / 2 + 1) th, and (n / 2 + 2) th subframes are in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is already in the driving state. The driving order is changed for each frame so that it increases later in time with respect to the subframes.
When s is an odd number, n = s + 1. In a predetermined field, when the driving gradation is 1, the first subframe is in a driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th When the sub-frame is in a driving state, the first, second, and (n / 2 + 1) th sub-frames are in a driving state when the driving gradation is 3, and when the driving gradation is 4, the first, second, (n / The 2 + 1) th and (n / 2 + 2) th subframes are in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is timed with respect to the subframe that is already in the driving state. In the next field after the predetermined field, when the driving gradation is 1, the (n / 2) th subframe is in the driving state, and when the driving gradation is 2, the first subframe is 1 Th and (n / 2) The first subframe is in the driving state, the first (n / 2) th, (n / 2 + 1) th subframe is in the driving state when the driving gradation is 3, and the first in the driving gradation is 4, The second, (n / 2) th, and (n / 2 + 1) th subframes are in a driving state, and one subframe that is in a driving state each time the driving gradation further increases is already in a driving state. A sub-frame data creation unit that creates sub-frame data by a drive gradation table that changes the drive order for each frame so as to increase later in time of the sub-frame,
A driving device for a liquid crystal display element, wherein the liquid crystal display element is driven based on the subframe data. A lookup table unit for converting input video signal data of bit number N into (M + F + D) bit data larger than N by performing inverse gamma correction and linear interpolation when N, M, F, and D are natural numbers;
An error diffusion unit that converts (M + F + D) bit data processed by the lookup table unit into (M + F) bit data by error diffusion processing;
A frame rate control unit that converts (M + F) -bit data processed by the error diffusion unit into M-bit data by frame rate control;
Using M-bit data processed by the frame rate control unit, and configuring all subframes by step bit pulses,
When the number of subframes in one frame is a natural number s,
When s is an even number, n = s. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th and (n / 2) -th When the sub-frame is in the driving state, the driving gradation is 3, the s-th, (s−1) -th, (n / 2) -th sub-frame is in the driving state, and when the driving gradation is 4, the s-th, (s -1) The (n / 2) th and (n / 2-1) th subframes are in a driving state, and each time the driving gradation further increases, one subframe that is in a driving state is already in a driving state. In the next field after the predetermined field, the (n / 2) th subframe is driven when the driving gradation is 1 in the next field. When the driving gradation is 2 (n / 2) and The (n / 2) th, (n / 2−1) th, and sth subframes are in the driving state when the driving gradation is 3, and the driving gradation is 4, The (n / 2) th, (n / 2-1) th, sth, and (s-1) th subframes are in the driving state, and one subframe is in the driving state each time the driving gradation further increases. The driving order is changed for each frame so that the subframes that are already in the driving state increase in time toward the front.
When s is an odd number, n = s−1. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th subframe is (n / 2). When the driving gradation is 3, the sth, (s-1) th, and (n / 2) th subframes are in the driving state, and when the driving gradation is 4, the sth, The (s−1) th, (n / 2) th, and (n / 2−1) th subframes are in the driving state, and one subframe that is in the driving state each time the driving gradation further increases is already one by one. With respect to the subframe in the driving state, it increases toward the front in time, and in the field next to the predetermined field, the driving gradation is 1 (n / 2 + 1) th subframe. Is in a driving state and the driving gradation is 2 (n / 2 1) When the driving gradation is 3, the (n / 2 + 1) th, (n / 2) th, and sth subframes are driving when the driving gradation is 3, and the driving gradation is 4 In this case, the (n / 2 + 1) th, (n / 2) th, sth, and (s-1) th subframes are in the driving state, and the subframe that is in the driving state every time the driving gradation is further increased is 1. A sub-frame data creation unit that creates sub-frame data by a driving gradation table that changes the driving order for each frame so that the sub-frames that are already in the driving state increase in time in the order of time. Prepared,
A driving device for a liquid crystal display element, wherein the liquid crystal display element is driven based on the subframe data. A drive device for a liquid crystal display element according to claim 1 or 2,
A liquid crystal display element driven by the driving device;
An illumination optical system for making illumination light incident on the liquid crystal display element;
A liquid crystal display device, comprising: a projection lens that projects the modulated light emitted from the liquid crystal display element. A first step of converting input video signal data of bit number N into (M + F + D) bit data larger than N by performing inverse gamma correction and linear interpolation when N, M, F, and D are integers;
A second step of converting the (M + F + D) bit data processed in the first step into (M + F) bit data by error diffusion processing;
A third step of converting the (M + F) bit data processed in the second step into M bit data by frame rate control;
While using the M-bit data processed in the third step, configuring all subframes with step bit pulses,
When the number of subframes in one frame is a natural number s,
When s is an even number, n = s. In a predetermined field, when the driving gradation is 1, the first subframe is in a driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th When the sub-frame is in the driving state, the first, second, and (n / 2 + 1) th sub-frames are in the driving state when the driving gradation is 3, and when the driving gradation is 4, the first, second, (n / The 2 + 1) th and (n / 2 + 2) th subframes are in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is timed with respect to the subframe that is already in the driving state. In the next field after the predetermined field, when the drive gradation is 1, the (n / 2 + 1) th subframe is in the drive state, and when the drive gradation is 2, the first subframe is 1 And (n / 2 + 1 The first subframe is in the driving state, the first (n / 2 + 1) th and (n / 2 + 2) th subframes are in the driving state when the driving gradation is 3, and the first when the driving gradation is 4, The second, (n / 2 + 1) th, and (n / 2 + 2) th subframes are in the driving state, and one subframe that is in the driving state every time the driving gradation further increases is already in the driving state. The drive order is changed for each frame so that it increases toward the later of the subframe,
When s is an odd number, n = s + 1. In a predetermined field, when the driving gradation is 1, the first subframe is in a driving state, and when the driving gradation is 2, the first and (n / 2 + 1) th When the sub-frame is in the driving state, the first, second, and (n / 2 + 1) th sub-frames are in the driving state when the driving gradation is 3, and when the driving gradation is 4, the first, second, (n / The 2 + 1) th and (n / 2 + 2) th subframes are in the driving state, and each time the driving gradation further increases, one subframe that is in the driving state is timed with respect to the subframe that is already in the driving state. In the next field after the predetermined field, when the driving gradation is 1, the (n / 2) th subframe is in the driving state, and when the driving gradation is 2, the first subframe is 1 Th and (n / 2) th When the driving gradation is 3, the first, (n / 2) th, (n / 2 + 1) th subframe is in the driving state, and when the driving gradation is 4, the first, 2 The (n / 2) th and (n / 2 + 1) th subframes are in the driving state, and one subframe that is in the driving state each time the driving gradation is further increased is already in the driving state. And a fourth step of generating subframe data by a drive gradation table for changing the drive order for each frame so that the frame increases in time later. The method for driving a liquid crystal display element, comprising: . A first step of converting input video signal data of bit number N into (M + F + D) bit data larger than N by performing inverse gamma correction and linear interpolation when N, M, F, and D are integers;
A second step of converting the (M + F + D) bit data processed in the first step into (M + F) bit data by error diffusion processing;
A third step of converting the (M + F) bit data processed in the second step into M bit data by frame rate control;
While using the M-bit data processed in the third step, configuring all subframes with step bit pulses,
When the number of subframes in one frame is a natural number s,
When s is an even number, n = s. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th and (n / 2) -th When the sub-frame is in the driving state, the driving gradation is 3, the s-th, (s−1) -th, (n / 2) -th sub-frame is in the driving state, and when the driving gradation is 4, the s-th, (s -1) The (n / 2) th and (n / 2-1) th subframes are in a driving state, and each time the driving gradation further increases, one subframe that is in a driving state is already in a driving state. In the next field after the predetermined field, the (n / 2) th subframe is driven when the driving gradation is 1 in the next field. When the driving gradation is 2 (n / 2) and The (n / 2) th, (n / 2−1) th, and sth subframes are in the driving state when the driving gradation is 3, and the driving gradation is 4, The (n / 2) th, (n / 2-1) th, sth, and (s-1) th subframes are in the driving state, and one subframe is in the driving state each time the driving gradation further increases. The driving order is changed for each frame so that the subframes that are already in the driving state increase in time toward the front.
When s is an odd number, n = s−1. In a predetermined field, when the driving gradation is 1, the s-th subframe is in a driving state, and when the driving gradation is 2, the s-th subframe is (n / 2). When the driving gradation is 3, the sth, (s-1) th, and (n / 2) th subframes are in the driving state, and when the driving gradation is 4, the sth, The (s−1) th, (n / 2) th, and (n / 2−1) th subframes are in the driving state, and one subframe that is in the driving state each time the driving gradation further increases is already one by one. With respect to the subframe in the driving state, it increases toward the front in time, and in the field next to the predetermined field, the driving gradation is 1 (n / 2 + 1) th subframe. Is in a driving state and the driving gradation is 2 (n / 2 1) When the driving gradation is 3, the (n / 2 + 1) th, (n / 2) th, and sth subframes are driving when the driving gradation is 3, and the driving gradation is 4 In this case, the (n / 2 + 1) th, (n / 2) th, sth, and (s-1) th subframes are in the driving state, and the subframe that is in the driving state every time the driving gradation is further increased is 1. A fourth step of creating subframe data by a driving gradation table that changes the driving order for each frame so that the subframes that are already in a driving state increase in time in the forward direction;
A method for driving a liquid crystal display element comprising: