JP2007108286A - Method of adjusting liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of adjusting a liquid crystal display, that can make its uneven display evaluation and adjustment within a short period considering the effects of the viewing angle characteristics specific to liquid crystal displays. <P>SOLUTION: This method uses a measuring means to measure the two-dimensional luminance distributions on a liquid crystal display, a means to output the viewing angle data showing the luminance variations due to the viewing angle characteristics of the liquid crystal display, a calculation means to calculate to cancel the luminance variations due to the viewing angle from the two-dimensional luminance distribution information by using the viewing angle data and the viewing angle of the measuring means to the liquid crystal display and to output a second two-dimensional luminance distribution information, and an uneven display discriminating means to discriminate the uneven luminance distributions in the second two-dimensional luminance distribution information. Then, it corrects the two-dimensional luminance distributions based on the viewing angle characteristics of the liquid crystal display. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device adjustment method and evaluation method.

  In recent years, the liquid crystal display device has been expanding its market while increasing the screen size while changing the use from a personal computer monitor to a television. There are several problems with image quality and quality of liquid crystal display devices, but the following two points will be taken up.

  First, viewing angle characteristics will be described as a first problem. The viewing angle characteristic is a characteristic peculiar to a liquid crystal display device that changes its appearance depending on the angle at which an observer looks at the screen of the liquid crystal display device.

  As a method for measuring the viewing angle characteristic, as shown in FIG. 7A, a single point measurement type luminance meter is arranged at an arbitrary angle with respect to the screen, and a distribution is obtained by a plurality of measurements. As shown in (b), there is known a method of obtaining viewing angle characteristics in all directions in one measurement by performing two-dimensional measurement using a collimator lens system and a camera (Patent Document 1).

  Display unevenness will be described as a second problem. Although display unevenness can occur in all display devices, the cause of the display depends on the display device. In the case of a liquid crystal display device, a liquid crystal material is sealed in a glass substrate, and therefore, due to the gap between the glass substrates, the in-plane unevenness of the gap length, etc. It has become difficult and difficult to maintain.

  As a method for measuring display unevenness, as shown in FIG. 8 (a), a single-point measurement type luminance meter is slid in parallel with the screen to obtain a distribution by measuring a plurality of times, or FIG. 8 (b). As shown, there is known a method of obtaining a two-dimensional luminance distribution characteristic by one measurement by performing a two-dimensional measurement using a CCD camera 203 (Patent Document 2). The features are shown in Table 1 with the former being the unevenness measuring method A and the latter being the unevenness measuring method B.

  While the unevenness measurement method B can acquire data in a short time, as shown in FIG. 8B, the measurement is performed at the angle ζ at the corner of the screen, and is affected by the viewing angle characteristics.

  Here, after obtaining the two-dimensional luminance distribution by the above-described unevenness measurement method A and unevenness measurement method B, the degree of display unevenness is evaluated, or the voltage applied to the liquid crystal cell is adjusted for each pixel to reduce display unevenness. Think about making adjustments.

  In a liquid crystal display device, it is ideal that there is no display unevenness. For example, it is desirable that a uniform display is obtained when a uniform image such as a solid screen is displayed. When a uniform image is displayed, it is preferable that the two-dimensional luminance distribution obtained by the unevenness measuring method A is numerically uniform, or the two-dimensional luminance distribution obtained by the unevenness measuring method B is numerically The following example considers whether it is preferable to be uniform.

  It is said to be 3H in high-definition television (screen aspect ratio is 16: 9), but viewing from a distance three times the height of the screen (Height) is from the viewpoint of a sense of reality and difficulty in seeing scanning lines. It is said that it is most suitable. Assume that an observer D exists at a distance of 3H in the normal direction from the point C in the center of the screen as shown in FIG. Furthermore, it is assumed that the distance between the observer's eyes is sufficiently small relative to the screen size and can be regarded as a point. Then, as shown in FIG. 9, the left and right ends of the screen are viewed at an angle θ (≈16.5 °) where tan θ = 8 ÷ 27 on one side in the left-right direction. Similarly, the edge of the screen is viewed at an angle of φ≈9.5 ° in the vertical direction and ψ≈18.8 ° in the diagonal (diagonal) direction. Such an observation state is close to the measurement state of the unevenness measurement method B.

  Then, what kind of display is performed will consider whether the two-dimensional luminance distribution measured by the unevenness measurement method B is numerically uniform. Assume that the camera 203 in the unevenness measurement method B is at the position of the observer D, and only the θ direction in FIG. As shown in FIG. 10, the viewing angle characteristic of the liquid crystal panel used in the liquid crystal display device is such that the luminance in front view is 1 (reference) and the luminance is reduced by 10% at the viewing angle θ. Since the relationship between the screen position and the viewing angle is shown in FIG. 11B, when a uniform image as shown in FIG. 11A is displayed on the liquid crystal display device, the relationship between FIG. 10 and FIG. The two-dimensional luminance distribution is as shown in FIG. 11C and is not numerically uniform.

  Next, consider a case where a non-uniform image as shown in FIG. The relationship between the screen position and the viewing angle is shown in FIG. 12B, which is the same as FIG. 11B. From the relationship between FIG. 10 and FIG. 12B, the two-dimensional luminance distribution is as shown in FIG. In this case, a uniform display can be obtained for the camera 203 and thus the observer D.

  However, in this case, consider the case where the observer F is on the normal line of the point E at the right end of the screen in FIG. That is, the observer F corresponds to the case where the observer D moves in parallel to the screen.

  For the observer F, the relationship between the screen position and the viewing angle is as shown in FIG. When the display is as shown in FIG. 13A (as in FIG. 12A), the two-dimensional luminance distribution is as shown in FIG. 13C from the relationship between FIG. 10 and FIG. 13B. On the other hand, when a uniform image is displayed as shown in FIG. 14A, the two-dimensional luminance distribution viewed from the observer F is as shown in FIG.

  Comparing FIG. 13 (c) and FIG. 14 (c), FIG. 13 (c) has a larger difference between light and dark, and it is difficult to say that the characteristics are gentle.

  That is, this indicates that in the adjustment method as shown in FIG. 12A, when the observer deviates from the optimized point, the unevenness increases and becomes a harmful effect. For example, if the positional relationship between the observer and the display device is fixed to some extent, such as an instrument that the driver of the car sees, this may be sufficient, but multiple people such as a liquid crystal display device used for television in the living room This is inconvenient when the posture changes. From this, in the case of uniform display, the characteristics as shown in FIG. 11C for the observer D and the characteristics as shown in FIG. It will be.

Strictly speaking, in the liquid crystal display device, it is assumed that the viewing angle characteristics are slightly different depending on the gradation to be displayed, but are the same in this example.
Japanese Patent Laid-Open No. 5-288638 JP-A-6-300998

  As described above, the liquid crystal display device originally has problems of viewing angle characteristics and display unevenness. The unevenness measurement method A, which is a method for measuring display unevenness, takes time, and the unevenness measurement method B includes the influence of viewing angle characteristics on the obtained luminance distribution. In any case, display unevenness is evaluated or display unevenness is reduced. It was an obstacle to make adjustments.

  In order to solve this problem, the liquid crystal display device adjustment method of the present invention evaluates display unevenness or reduces display unevenness based on a two-dimensional luminance distribution obtained from a CCD camera or the like and including the influence of viewing angle characteristics. In such adjustment, the influence of the two-dimensional luminance distribution information on the viewing angle characteristics of the liquid crystal panel is corrected.

  The evaluation method and adjustment method of the liquid crystal display device of the present invention can evaluate and adjust display unevenness in a short time in consideration of the effect of viewing angle characteristics unique to the liquid crystal display device.

  The present invention will be described below with reference to the drawings.

  FIG. 1 shows a block diagram of an evaluation method for a first liquid crystal display device of the present invention. A two-dimensional luminance distribution when a uniform image is displayed on the liquid crystal display device 101 is captured by the CCD camera 102 and input to the calculation unit 104. This two-dimensional luminance distribution is calibrated for factors other than the viewing angle characteristics of the liquid crystal display device, for example, in-plane unevenness of the sensitivity of the CCD sensor itself. Separately, the viewing angle characteristic data 103 of the liquid crystal display device obtained by a known technique is also input to the calculation unit 104.

  The calculation unit 104 corrects the two-dimensional luminance distribution based on the information on the viewing angle characteristic data 103 and the information on which direction and how many viewing angles each element of the two-dimensional luminance distribution is obtained. In order to perform this calculation, the size of the liquid crystal display device 101 and the positional relationship between the liquid crystal display device 101 and the CCD camera 102 are required.

  As shown in FIG. 2, the screen size of the liquid crystal display device is 16d wide and 9d long, and the CCD camera 102 is located at a distance of 27d from the screen on the normal line of the point G at the center of the screen of the liquid crystal display device 101. . Then, the obtained two-dimensional luminance distribution is assumed to be 4 × 3 = 12 elements, as shown in FIG. 3, with a small surface of 4d horizontal and 3d vertical of the screen of the liquid crystal display device 101 as one element. Here, attention is paid to the element (d-1) in FIG. A point corresponding to the center of the region of the element (d-1) on the screen of the liquid crystal display device as shown in FIG. From FIG. 2, it can be seen that the point H is an element obtained by measurement with an angle of tan θ = 6d / 27d in the horizontal direction and an angle of tan φ = 3d / 27d in the vertical direction when viewed from the camera 102. . The viewing angle characteristic data is used to correct the elements of the two-dimensional luminance distribution to see what the viewing angle characteristic is at such a viewing angle (θ, φ). For example, when viewing angle (θ, φ) with k as a positive number, it can be seen from viewing angle characteristic data that the luminance changes to 1 / k compared to the front view, and the element of the two-dimensional luminance distribution is multiplied by k. Can cancel the influence of viewing angle characteristics. By performing such calculation on all elements, a two-dimensional luminance distribution that is not affected by the viewing angle characteristic can be obtained and output to the determination unit 105.

  The determination unit 105 determines the degree of display unevenness based on the two-dimensional luminance distribution input from the calculation unit 104. For example, the absolute value of the difference between the average of all the elements of the two-dimensional luminance distribution and the value of each element is integrated as a non-uniform component with all the elements, and compared with a predetermined criterion. If it is larger than that, it is determined as rejected, and the determination result is displayed on the monitor 106. In the present invention, the details of the method for extracting unevenness components and the criteria for determination are not limited. On the contrary, since there is no unified index applicable to all of the evaluation and determination of display unevenness, it should be appropriately changed according to the type of display unevenness and the point of view.

  FIG. 4 shows a block diagram of the adjustment method of the second liquid crystal display device of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and only differences from the first embodiment will be described below.

  The determination and adjustment unit 107 determines whether or not the display unevenness is acceptable based on the two-dimensional luminance distribution input from the calculation unit 104 without the influence of the viewing angle characteristic. As a result of the determination, if the result is acceptable, the process is terminated by satisfying the set standard. If the result is unacceptable, adjustment is performed. For example, when the two-dimensional luminance distribution data has an average of 10 as shown in FIG. 5A, the adjustment data is dark when each element is brighter than the average in two dimensions as shown in FIG. In contrast, it is assumed that all elements are close to the average so that they are bright when dark. The adjustment data is output to the liquid crystal display device 101 and stored in a ROM or the like inside the liquid crystal display device. The liquid crystal display device refers to the adjustment data and changes the relationship of gradation display with respect to the input video signal in the display area corresponding to the element of the adjustment data. For example, since the adjustment data for the element (c-2) is -3 from FIG. 5B, the gradation display characteristics as shown in FIG. 6B are obtained. In FIG. 6, FIG. 6A shows the gradation display characteristics when nothing is adjusted, and FIG. 6C shows the gradation obtained from the two-dimensional luminance distribution.

  Then, after performing such adjustment, the two-dimensional luminance distribution is obtained and determined again, and is repeated until the reference is satisfied, whereby display unevenness can be reduced to a predetermined range.

  The present invention can perform adjustment for evaluating or reducing display unevenness, which is a problem of a liquid crystal display device, and can provide a liquid crystal display device with little display unevenness.

Block diagram of the evaluation method of the present invention Explanatory drawing of the calculation part of this invention 2D luminance distribution data of the present invention Block diagram of the adjustment method of the present invention Explanatory drawing of adjustment data of the present invention Explanatory drawing of the display method by the adjustment data of this invention Diagram of conventional method for measuring viewing angle characteristics Figure of conventional method of measuring display unevenness Illustration of viewing angle of liquid crystal display View angle characteristics of liquid crystal display devices LCD display and luminance distribution diagram LCD display and luminance distribution diagram LCD display and luminance distribution diagram LCD display and luminance distribution diagram

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Liquid crystal display device 102 CCD camera 103 Viewing angle characteristic data 104 Operation part 105 Judgment part 106 Monitor 107 Judgment and adjustment part 201 Luminance meter 202 Collimator lens system 203 Camera 204 Image processing part

Claims (1)

A liquid crystal display device; measuring means for measuring two-dimensional luminance distribution information of the liquid crystal display device; means for outputting viewing angle data representing a luminance change due to a viewing angle characteristic of the liquid crystal display device; the viewing angle data; and Calculating means for calculating second luminance distribution information by outputting the two-dimensional luminance distribution information from the two-dimensional luminance distribution information by using a viewing angle of the measuring means with respect to the liquid crystal display device, and outputting the second two-dimensional luminance distribution information; Display unevenness determining means for determining unevenness of the luminance distribution of the two-dimensional luminance distribution information of 2 and correcting the influence of the two-dimensional luminance distribution information due to the viewing angle characteristics when adjusting to reduce the display unevenness And adjusting the liquid crystal display device.

Images