JP6917224B2 - Liquid crystal element drive control device and its program - Google Patents

Description

The present invention relates to a liquid crystal element drive control device and a program thereof.

Conventionally, liquid crystal elements used as display devices such as direct-view display devices and projectors have a short life when they are driven by direct current, so they are generally driven by alternating current voltage. (Patent Document 1).

At this time, if the DC component remains, the orientation of the liquid crystal element is disturbed and deteriorates. Therefore, the liquid crystal element is driven with the same frame image according to the positive and negative polarities of the AC voltage so that the DC component does not remain. As shown in FIG. 5A, consider the case where the frame rate of the frame image S is 60 Hz. In this case, as shown in FIG. 5B, the liquid crystal element displays the same frame images S (t) and S (t + 2) with a polarity of ± of 1/120 seconds, and therefore every 1/60 seconds. The frame image S is switched.
In FIG. 5B, if the polarity of the AC voltage for driving the liquid crystal element is positive, ‘+’ is shown, and if the polarity of the AC voltage is negative, ‘−’ is shown. Further, t represents a frame image number.

Here, in the highest-level format of 8K Super Hi-Vision, not only the number of pixels is 8K (7680 × 4320 pixels), but also a high frame rate (120 Hz or more) is realized, so that it is compared with a moving image having a low frame rate. , Enables clearer motion expression. As shown in FIG. 6A, consider the case where the frame rate of the frame image S is 120 Hz. In this case, as shown in FIG. 6B, the liquid crystal element displays the same frame images S (t) to S (t + 3) with a polarity of ± of 1/240 seconds, and therefore every 1/120 seconds. The frame image S is switched.
As described above, it is necessary to drive the liquid crystal element at a frequency twice the actual frame rate, and it is extremely difficult to display an image having a huge data rate such as 8K pixels and 120Hz frame rate.

For the above reasons, when displaying a high frame rate using a liquid crystal element, forced double speed drive may be performed such that different frame images are displayed by the liquid crystal element depending on the positive and negative polarities of the AC voltage. In the case of this forced double speed drive, as shown in FIG. 7B, the liquid crystal element displays the frame images S (t) and S (t + 2) with a + polarity of 1/120 second, and the minus of 1/120 second. The frame images S (t + 1) and S (t + 3) are displayed according to the polarity. That is, in the forced double speed drive, the frame image S is switched every 1/120 second even though the liquid crystal element is driven in 1/60 second (= 60 Hz).

Japanese Unexamined Patent Publication No. 2002-277682

The forced double speed drive described above is not recommended because a DC component may remain in the liquid crystal element, but it does not pose a big problem when displaying a general moving image because the frame difference is small. However, there may be a moving image in which the frame difference becomes large, such as a test moving image in which changes are drastic, or a moving image in which a scene in which a flash is emitted is captured. When the liquid crystal element is forcibly driven at double speed for a long time with such a moving image, the liquid crystal element deteriorates, and in the worst case, the liquid crystal element may be damaged.

An object of the present invention is to provide a liquid crystal element drive control device and a program thereof that can prevent damage to the liquid crystal element while allowing forced double speed drive.

In view of the above-mentioned problems, the liquid crystal element drive control device according to the present invention has a normal drive that outputs the same frame image twice according to the positive and negative polarities of the AC voltage that drives the liquid crystal element, and the normal drive. A liquid crystal element drive control device that switches forced double-speed drive that outputs two consecutive frame images according to the positive and negative polarities so as to double the frame rate. It was configured to include.

According to the liquid crystal element drive control device, the determination means calculates the amount of change in the frame image included in the input video, and determines the normal drive or the forced double speed drive by determining the threshold value of the calculated change amount. Then, the switching means switches between normal drive and forced double speed drive based on the determination result of the determination means.

That is, when the change amount of the frame image is less than the threshold value, the determination means determines that the forced double speed drive is performed because the change amount of the frame image is small and the risk of damaging the liquid crystal element is low even if the forced double speed drive is performed. .. On the other hand, when the amount of change in the frame image is not less than the threshold value, the determination means determines that the normal drive is performed because the amount of change in the frame image is large and there is a high risk of damage to the liquid crystal element.

According to the present invention, the following excellent effects are obtained.
The liquid crystal element drive control device according to the present invention allows forced double speed drive because the liquid crystal element is forcibly driven at double speed when the risk of damage to the liquid crystal element is low and the liquid crystal element is normally driven when the risk is high. However, damage to the liquid crystal element can be prevented.

It is a block diagram which shows the structure of the liquid crystal element drive control apparatus which concerns on embodiment of this invention. It is explanatory drawing explaining the calculation of the difference integration amount by the signal analysis means of FIG. (A) is an explanatory diagram for explaining forced double speed drive, and (b) is an explanatory diagram for explaining normal drive. It is a flowchart which shows the operation of the liquid crystal element drive control device of FIG. (A) represents a moving image having a low frame rate, and (b) is an explanatory diagram when a conventional liquid crystal element is normally driven at 60 Hz. (B) represents a moving image having a high frame rate, and (b) is an explanatory diagram when a conventional liquid crystal element is normally driven at 120 Hz. (B) represents a moving image having a high frame rate, and (b) is an explanatory diagram when a conventional liquid crystal element is forcibly driven at double speed at 120 Hz.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the embodiment, the same means are designated by the same reference numerals, and the description thereof is omitted.

(Embodiment)
[Outline of liquid crystal element drive control device]
The outline of the liquid crystal element drive control device 1 according to the embodiment of the present invention will be described with reference to FIG.
The liquid crystal element drive control device 1 drives the liquid crystal element 9 by switching between normal drive and forced double speed drive.
The normal drive is to display the same frame image every other frame with the positive and negative polarities of the AC voltage that drives the liquid crystal element 9.
Further, the forced double speed drive is to display two consecutive frame images with positive and negative polarities of the AC voltage for driving the liquid crystal element 9.
Details of these normal drive and forced double speed drive will be described later (Fig. 3).

The liquid crystal element 9 displays an input signal (input image) from the liquid crystal element drive control device 1. In the present embodiment, the liquid crystal element 9 is driven at 60 Hz. Here, the driving method of the liquid crystal element 9 is not particularly limited, for example, a simple matrix method, an active matrix method, or the like. The operation mode of the liquid crystal element 9 is not particularly limited, for example, a TN (Twisted Nematic) method, a VA (Vertical Alignment) method, an IPS (In Plane Switching) method, or the like.

In the present embodiment, the input signal displayed by the liquid crystal element 9 is input to the signal analysis means (determination means) 11 and the switching means 15 described later from the outside such as a transmission device (not shown). It is assumed that the frame rate of this input signal is 120 Hz and the resolution is 8K (7680 × 4320 pixels).

[Configuration of liquid crystal element drive control device]
Hereinafter, the configuration of the liquid crystal element drive control device 1 will be described.
As shown in FIG. 1, the liquid crystal element drive control device 1 includes a signal analysis means 11, a storage means 13, and a switching means 15.

The signal analysis means 11 calculates the amount of change in the frame image included in the input signal from the outside, and determines the normal drive or the forced double speed drive by determining the threshold value of the calculated change amount. In the present embodiment, the signal analysis means 11 calculates the difference integration amount as the change amount of the frame image.
The storage means 13 is a storage device such as a memory, an HDD (Hard Disk Drive), or an SSD (Solid State Drive) that stores the calculation result of the signal analysis means 11.

<Calculation of difference integration amount and threshold judgment>
With reference to FIG. 2, the calculation of the difference integration amount and the threshold value determination by the signal analysis means 11 will be described in detail (see FIG. 1 as appropriate).
Specifically, the signal analysis means 11 obtains the absolute difference value of the pixel values for each corresponding pixel of the preceding and following frame images. Then, the signal analysis means 11 obtains the difference amount for each frame image by averaging the difference absolute values for each corresponding pixel, and calculates the difference integration amount by integrating the difference amount for each frame image by the number of determination frames.
The corresponding pixel is a pixel having the same coordinates in each frame image constituting the input signal.

Here, the time series of the input signal is S (x, y, t). That is, in the input signal, the difference integration amount D is calculated from the current frame image S (t + N) to be processed to the previous frame image S (t) that goes back by the number of determination frames N. x represents the horizontal coordinates of the input signal and satisfies 1 ≦ x ≦ X (X is the number of horizontal pixels of the input signal). y represents the vertical coordinates of the input signal and satisfies 1 ≦ y ≦ Y (Y is the number of vertical pixels of the input signal). The input signal S (x, y, t) is normalized so as to satisfy 0 ≦ S (x, y, t) ≦ 1.
The number of determination frames N will be described in detail in a modified example described later.

As shown in FIG. 2, the signal analysis means 11 obtains the absolute difference value of the pixel values for each corresponding pixel (x, y) between the frame image S (t) and the frame image S (t + 1). Then, the signal analysis means 11 obtains the average of the absolute difference values for each corresponding pixel (x, y). The average of the difference absolute value and the difference amount d _1.

Next, the signal analysis means 11 obtains the average of the absolute difference values for each corresponding pixel (x, y) between the frame image S (t + 1) and the frame image S (t + 2), and calculates the _{difference amount d 2.} .. _{After that, the signal analysis means 11 sequentially repeats the calculation of the difference amounts d 3 to d n} from the frame image S (t + 2) to the frame image S (t + N) (where n is a natural number satisfying 1 ≦ n ≦ N). ..

Then, the signal analysis means 11 calculates the difference integration amount D by integrating _{the calculated difference amounts d 1 to d n.} That is, the signal analysis means 11 calculates the difference integration amount D using the following equations (1) and (2).

Here, the signal analysis means 11 may calculate the difference integration amount D from all the corresponding pixels of the frame image S.
When the image size of the frame image S is large, obtaining the absolute difference value of all the corresponding pixels is itself a large calculation cost. Therefore, the signal analysis means 11 may set the interval between the corresponding pixels to two or more pixels. That is, the signal analysis means 11 may calculate the difference integration amount D from the corresponding pixels obtained by discretely sampling the entire frame image S with the corresponding pixels i pixels in the horizontal direction and j pixels in the vertical direction. As a result, the signal analysis means 11 has X / i × Y / j pixels for calculating the difference integration amount D, and the calculation cost can be reduced to 1 / (i × j) (however, i, i, j is a natural number of 2 or more).

Next, the signal analysis means 11 determines whether to perform the normal drive or the forced double speed drive based on the threshold value determination of the difference integration amount D. Here, when the difference integration amount D is less than the preset threshold value T, the signal analysis means 11 determines that the forced double speed drive is performed because the risk of damage to the liquid crystal element 9 is low. On the other hand, if the difference integration amount D is not less than the threshold value T, the signal analysis means 11 has a high risk of damaging the liquid crystal element 9, and therefore determines that the normal drive is performed. The threshold value T will be described in detail in a modified example described later.
After that, the signal analysis means 11 outputs a determination result representing the normal drive or the forced double speed drive to the switching means 15.

<Memory of calculation results>
The storage of the calculation result by the storage means 13 will be described with reference to FIG. 2 (see FIG. 1 as appropriate).
Here, when the current frame image S (t + N) is input, the signal analysis means 11 calculates the difference integration amount D in the above procedure and stores the calculation result for the current frame image S (t + N) in the storage means 13. You may write. _{Here, the signal analysis means 11 has a difference amount d 2} from the current frame image S (t + N) to the previous frame image S (t + 1) that goes back by the number of frames (N-1) obtained by subtracting 1 from the number of determination frames N. writing to d _n in the storage unit 13.

Then, when the next frame image S (t + N + 1) is input, the signal analysis means 11 obtains the difference amount d _{n + 1} between the current frame image S (t + N) and the next frame image S (t + N + 1), and the difference amount d ₂ ~ D _n is read from the storage means 13. Furthermore, the signal analyzing means 11, a differential amount _{d n + 1} which is newly calculated, by multiplying the difference amount _d 2 to d _n read from the storage unit 13, the difference integrated value for the next frame image S (t + N + 1) D can be calculated.

As described above, when the signal analysis means 11 stores the calculation result (difference amount d _{2 to d n} ) in the storage means 13 and calculates the difference integration amount D for the next frame image S (t + N + 1), this calculation is performed. It is preferable to refer to the result because the calculation cost can be further reduced.
Needless to say, the difference integration amount D can be calculated in the same manner for the next frame image S (t + N + 2) and thereafter.

Returning to FIG. 1, the configuration of the liquid crystal element drive control device 1 will be described.
The switching means 15 switches between normal drive and forced double speed drive based on the determination result input from the signal analysis means 11.

Here, when the determination result of the signal analysis means 11 is forced double speed drive, the switching means 15 outputs the frame image included in the input signal to the liquid crystal element 9 as it is. That is, as shown in FIG. 3A, the switching means 15 outputs the frame images S (t) to S (t + 3) in order. As a result, the frame rate of the input signal output by the switching means 15 is equivalent to 120 Hz.

On the other hand, when the determination result of the signal analysis means 11 is normally driven, the switching means 15 repeats the frame image included in the input signal twice every other frame and outputs it to the liquid crystal element 9. That is, as shown in FIG. 3B, the switching means 15 outputs the frame image S (t + 2) twice without outputting the frame image S (t + 1) after outputting the frame image S (t) twice. Output times. As a result, the input signal output by the switching means 15 has a frame rate equivalent to 60 Hz.

As described above, the liquid crystal element drive control device 1 may damage the liquid crystal element 9 while forcibly driving the liquid crystal element 9 at 120 Hz by performing the above procedure each time a new frame image is input. If it is high, it can be switched to the normal drive of 60 Hz. As a result, the liquid crystal element drive control device 1 can prevent damage to the liquid crystal element 9 while allowing forced double speed drive.

[Operation of liquid crystal element drive control device]
The operation of the liquid crystal element drive control device 1 of FIG. 1 will be described with reference to FIG. 4 (see FIG. 1 as appropriate).
As shown in FIG. 4, the signal analysis means 11 calculates the difference integration amount D (step S1).
The signal analysis means 11 obtains the absolute difference value of the pixel values for each corresponding pixel of the preceding and following frame images. Then, the signal analysis means 11 obtains the difference amount for each frame image by averaging the difference absolute values for each corresponding pixel, and calculates the difference integration amount D by integrating the difference amount for each frame image by the number of determination frames. That is, the signal analysis means 11 calculates the difference integration amount D by using the above equations (1) and (2).

The signal analysis means 11 determines whether to perform normal drive or forced double speed drive depending on whether or not the difference integration amount D is less than the threshold value T (step S2).
When the difference integration amount D is less than the threshold value T (Yes in step S2), the signal analysis means 11 determines that the forced double speed drive is performed, and proceeds to the process of step S3.
When the difference integration amount D is not less than the threshold value T (No in step S2), the signal analysis means 11 determines that the normal drive is performed, and proceeds to the process of step S4.

The switching means 15 drives the liquid crystal element 9 by forced double speed drive (step S3). That is, the switching means 15 outputs the frame image included in the input signal to the liquid crystal element 9 as it is. As a result, the frame rate of the input signal output by the switching means 15 is equivalent to 120 Hz.

The switching means 15 normally drives the liquid crystal element 9 (step S4). That is, the switching means 15 repeats the frame image included in the input signal twice every other frame and outputs it to the liquid crystal element 9. As a result, the input signal output by the switching means 15 has a frame rate equivalent to 60 Hz.

[Action / Effect]
As described above, the liquid crystal element drive control device 1 according to the embodiment of the present invention forcibly drives the liquid crystal element 9 at double speed when the risk of damage to the liquid crystal element 9 is low, and the liquid crystal element when the risk is high. Since the 9 is normally driven, it is possible to prevent the liquid crystal element 9 from being damaged while allowing the forced double speed drive.
In particular, since the liquid crystal element drive control device 1 can suppress the drive frequency of the liquid crystal element 9, it is useful for a display device such as a projector, which tends to have a high drive frequency because the element area of the liquid crystal element 9 is small.

(Example)
The setting of the number of determination frames N will be described as the following embodiment of the present invention.
The determination frame number N is set in advance at an arbitrary value from the viewpoint of how long a frame image having a large difference may be input to damage the liquid crystal element 9. If the value of the number of determination frames N is reduced, quick determination is possible, but it is not recommended because switching operation between forced double speed drive and normal drive may occur frequently.

Here, when it is necessary to eliminate the possibility that a DC component remains in the liquid crystal element 9 with a high probability, the threshold value may be determined in a short time of about 1 second, the number of determination frames N = 120, and the threshold value T = 0. It is recommended to set it to 1 × N. Further, normally, the threshold value may be determined in a long time of about 5 seconds, and the number of determination frames N = 600 and the threshold value T = 0.2 × N may be set.

(Modification example)
Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and includes design changes and the like within a range that does not deviate from the gist of the present invention.
In the above-described embodiment, the liquid crystal element is driven at 60 Hz, but the present invention is not limited thereto.
In the above-described embodiment, the frame rate of the input video is 120 Hz and the resolution is 8 K, but the present invention is not limited thereto.

In the above-described embodiment, the difference integration amount is calculated from the entire frame image, but the present invention is not limited to this. That is, in the present invention, the difference integration amount may be obtained from a part of the image area in the frame image. At this time, if an image region with little change is set, the threshold value cannot be determined correctly, and the liquid crystal element may be damaged. Therefore, it is preferable to set the image area in a place where the frame image changes a lot.

In the above-described embodiment, the difference integration amount is calculated as the change amount of the frame image, but the present invention is not limited to this. That is, in the present invention, it suffices to calculate the amount of change in the frame image that is continuous by the number of determination frames, and it is preferable to use the amount of change with a low calculation cost.

In the above-described embodiment, the liquid crystal element drive control device and the liquid crystal element have been described as separate configurations, but the present invention is not limited thereto. For example, the present invention may be a liquid crystal display device in which a liquid crystal element drive control device and a liquid crystal element are integrated.

In the above-described embodiment, the liquid crystal element drive control device has been described as independent hardware, but the present invention is not limited thereto. For example, the present invention can also be realized by a program in which hardware resources such as a CPU, a memory, and a hard disk included in a computer are cooperatively operated as the above-mentioned liquid crystal element drive control device. These programs may be distributed via a communication line, or may be written and distributed on a recording medium such as a CD-ROM or a flash memory.

1 Liquid crystal element drive control device 11 Signal analysis means (determination means)
13 Storage means 15 Switching means 9 Liquid crystal element

Claims (5)

Normal drive that outputs the same frame image twice according to the positive and negative polarities of the AC voltage that drives the liquid crystal element, and the positive and negative polarities so that the frame rate is twice that of the normal drive. A liquid crystal element drive control device that switches forced double-speed drive to output two consecutive frame images.
The amount of change in the frame image included in the input video is calculated, and if the calculated amount of change in the frame image is less than a preset threshold value, it is determined that the forced double speed drive is performed, and the amount of change in the frame image is the said. If it is not less than the threshold value, the determination means for determining that the normal drive is performed, and
A switching means for switching between the normal drive and the forced double speed drive based on the determination result of the determination means.
A liquid crystal element drive control device comprising. The determination means obtains the difference absolute value of the pixel value for each corresponding pixel of the frame image before and after, obtains the difference amount for each frame image by averaging the difference absolute value for each corresponding pixel, and uses the change amount as the change amount. The liquid crystal element drive control device according to claim 1, wherein the difference integrated amount is calculated by integrating the difference amount for each frame image by the number of determination frames set in advance. The liquid crystal element drive control device according to claim 2, wherein the determination means has a distance between the corresponding pixels of 2 pixels or more. The determination means
The difference amount from the current frame image to the previous frame image that goes back by the number of frames obtained by subtracting 1 from the determination frame number is stored in the storage means.
When the next frame image is input, the difference amount between the current frame image and the next frame image is obtained, and the calculated difference amount between the current frame image and the next frame image and the difference stored in the storage means are obtained. The liquid crystal element drive control device according to claim 2 or 3, wherein the difference integrated amount for the next frame image is calculated by integrating the amount. A program for causing a computer to function as the liquid crystal element drive control device according to any one of claims 1 to 4.

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