Brightness evaluation device and brightness evaluation method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON SEIKI CO LTD
- Filing Date
- 2025-01-22
- Publication Date
- 2026-08-03
Smart Images
Figure 2026125224000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a luminance evaluation apparatus and a luminance evaluation method for evaluating the luminance of a backlight module.
Background Art
[0002] For example, Patent Document 1 describes a backlight module including a plurality of light sources configured to illuminate a display panel and a grid-shaped reflector surrounding each of the plurality of light sources.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When evaluating the uniformity of the luminance of a backlight module, there is a risk that the decrease in uniformity caused by the shape of the reflector cannot be properly evaluated by simply evaluating the surface luminance distribution result measured by a surface luminance meter using existing evaluation parameters.
[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a luminance evaluation apparatus and a luminance evaluation method capable of favorably evaluating the uniformity of a backlight module.
Means for Solving the Problems
[0006] To achieve the above object, a luminance evaluation apparatus according to a first aspect of the present disclosure is a luminance evaluation apparatus for evaluating the luminance of a backlight module including a plurality of light sources arranged in horizontal and vertical directions and a grid-shaped reflector surrounding each of the plurality of light sources, A luminance ratio calculation unit calculates a horizontal luminance ratio, which is the ratio of the maximum luminance at any horizontal cross-sectional luminance over the horizontal width of the active area, based on the measurement results of the surface luminance of the active area of the backlight module, and a vertical luminance ratio, which is the ratio of the maximum luminance at any vertical cross-sectional luminance over the vertical width of the active area, A division width calculation unit calculates a horizontal division width by dividing a first number obtained by dividing the horizontal arrangement pitch of the plurality of light sources by an arbitrary natural number, and a second number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number, and a vertical division width by dividing a number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number. An average brightness calculation unit calculates the average horizontal brightness, which is the average of the horizontal brightness ratios, for each of the multiple horizontal areas obtained by dividing the horizontal width of the active area by the horizontal division width, and calculates the average vertical brightness, which is the average of the vertical brightness ratios, for each of the multiple vertical areas obtained by dividing the vertical width of the active area. The system includes an evaluation unit that calculates a horizontal brightness change, which is the change in the horizontal average brightness of adjacent horizontal areas among the plurality of horizontal areas, calculates a vertical brightness change, which is the change in the vertical average brightness of adjacent vertical areas among the plurality of vertical areas, and evaluates the degree of uniformity based on the maximum values of the calculated horizontal brightness change and vertical brightness change.
[0007] To achieve the above objective, the luminance evaluation method relating to the second aspect of this disclosure is: A luminance evaluation method for evaluating the luminance of a backlight module comprising a plurality of light sources arranged horizontally and vertically, and a grid-shaped reflector surrounding each of the plurality of light sources, A luminance ratio calculation step is performed to calculate a horizontal luminance ratio, which is the ratio of the maximum luminance at any horizontal cross-sectional luminance over the horizontal width of the active area to the maximum luminance, based on the measurement results of the surface luminance of the active area of the backlight module, and to calculate a vertical luminance ratio, which is the ratio of the maximum luminance at any vertical cross-sectional luminance over the vertical width of the active area to the maximum luminance, A division width calculation step in which a first number obtained by dividing the horizontal arrangement pitch of the plurality of light sources by an arbitrary natural number is divided by the measurement pitch of the horizontal cross-sectional brightness to calculate the horizontal division width, and a second number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number is divided by the measurement pitch of the vertical cross-sectional brightness to calculate the vertical division width, The average brightness calculation step involves calculating the average horizontal brightness, which is the average of the horizontal brightness ratios, for each of the multiple horizontal areas obtained by dividing the horizontal width of the active area by the horizontal division width, and calculating the average vertical brightness, which is the average of the vertical brightness ratios, for each of the multiple vertical areas obtained by dividing the vertical width of the active area by the vertical division width. The system includes an evaluation step of calculating a horizontal brightness change, which is the amount of change in the horizontal average brightness of adjacent horizontal areas among the plurality of horizontal areas, calculating a vertical brightness change, which is the amount of change in the vertical average brightness of adjacent vertical areas among the plurality of vertical areas, and evaluating the degree of uniformity based on the maximum values of the calculated horizontal brightness change and vertical brightness change. [Effects of the Invention]
[0008] According to this disclosure, the uniformity of the backlight module can be evaluated effectively. [Brief explanation of the drawing]
[0009] [Figure 1] A figure showing a luminance evaluation device, a backlight module, and a surface luminance meter according to one embodiment of the present disclosure. [Figure 2] A plan view of the light source and reflector according to the same embodiment. [Figure 3] This figure shows the parameters obtained from the measurement results using a surface luminance meter according to the same embodiment. [Figure 4] A diagram illustrating the division width calculation step, average brightness calculation step, and evaluation step according to the above embodiment. [Modes for carrying out the invention]
[0010] One embodiment of this disclosure will be described with reference to the drawings.
[0011] The luminance evaluation device 10 shown in Figure 1 is configured to evaluate the luminance of the backlight module 1. The backlight module 1 is a direct-lit module that illuminates a liquid crystal panel (not shown) from behind. The backlight module 1 comprises a plurality of light sources 2, a PCB (Printed Circuit Board) 3 on which the plurality of light sources 2 are mounted, a grid-shaped reflector 4 surrounding each of the plurality of light sources 2, an optical sheet 5 positioned between the plurality of light sources 2 and the liquid crystal panel, and a housing 6 that houses these. The light sources 2 are LEDs (Light-Emitting Diodes) and are arranged in a matrix in the horizontal and vertical directions as shown in Figure 2. The reflector 4 is, for example, made of resin and is white in color, and reflects the light emitted by the light sources 2 toward the liquid crystal panel to be illuminated. The optical sheet 5 is a diffuser plate or the like, and its configuration is arbitrary. The backlight module 1 emits light in the active area A by lighting up all of the plurality of light sources 2. As shown in Figure 3, the active area A is rectangular in plan view and corresponds to the area where the liquid crystal panel can display an image.
[0012] The luminance evaluation device 10 is a computer equipped with a CPU (Central Processing Unit) and well-known memory, and acquires measurement results from a surface luminance meter 7 that measures the surface luminance of the active area A of the backlight module 1. The surface luminance meter 7 is a two-dimensional color luminance meter, etc. When measuring surface luminance with the surface luminance meter 7, the measurement is performed with all of the multiple light sources 2 lit. The following parameters are input to the luminance evaluation device 10 based on the measurement results from the surface luminance meter 7 and the specifications of the backlight module 1. At least some of each parameter may be manually input to the luminance evaluation device 10.
[0013] (Parameters obtained from measurement results using the surface luminance meter 7) As shown in Figure 3, the parameters obtained from the measurement results by the surface luminance meter 7 are as follows. Note that the horizontal direction is sometimes referred to as the horizontal direction, and the vertical direction as the vertical direction. HL: Luminance of any horizontal cross-section [nit] H Camera Pitch: Measurement pitch of the horizontal cross-section luminance (HL) [mm] VL: Luminance of any vertical cross-section [nit] V Camera Pitch: Measurement pitch of the vertical cross-section luminance (VL) [mm] Here, let the width of the active area A in the horizontal direction from one end to the other end be 0 to a [mm], and the width of the active area A in the vertical direction from one end to the other end be 0 to b [mm]. Specifically, the luminance of any horizontal cross-section (HL) is the luminance across the entire horizontal width (0 to a) of the active area A at any vertical position (any position within 0 to b). The measurement pitch (H Camera Pitch) of the horizontal cross-section luminance (HL) is the measurement pitch when the surface luminance meter 7 scans the horizontal direction of the active area A. The luminance of any vertical cross-section (VL) is the luminance across the entire vertical width (0 to b) of the active area A at any horizontal position (any position within 0 to a). The measurement pitch (V Camera Pitch) of the vertical cross-section luminance (VL) is the measurement pitch when the surface luminance meter 7 scans the vertical direction of the active area A.
[0014] (Parameters obtained from the specifications of the backlight module 1) As shown in FIG. 2, the parameters obtained from the specifications of the backlight module 1 are as follows. H LED Pitch: Horizontal array pitch of the plurality of light sources 2 [mm] V LED Pitch: Vertical array pitch of the plurality of light sources 2 [mm]
[0015] The luminance evaluation device 10 includes, as functional units, a luminance ratio calculation unit 11, a division width calculation unit 12, an average luminance calculation unit 13, and an evaluation unit 14. Hereinafter, these functional units will be described together with each step of the luminance evaluation method using the luminance evaluation device 10.
[0016] (Luminance ratio calculation step) In the luminance ratio calculation step, the luminance ratio calculation unit 11 calculates the horizontal luminance ratio (HR), which is the ratio of the maximum luminance (HLmax) at an arbitrary horizontal cross-sectional luminance (HL) over the horizontal width of the active area A, based on the measurement results of the surface luminance of the active area A of the backlight module 1, and also calculates the vertical luminance ratio (VR), which is the ratio of the maximum luminance (VLmax) at an arbitrary vertical cross-sectional luminance (VL) over the vertical width of the active area. Although not shown in the diagram, HR and VR can be expressed by the following formulas. HLn represents the luminance value at any position in the transverse cross-sectional luminance (HL), and VLm represents the luminance value at any position in the longitudinal cross-sectional luminance (VL). The ratios below may also be calculated as percentages (%). HR = HLn[nit] / HLmax[nit] VR = VLm[nit] / VLmax[nit]
[0017] (Step to calculate the division width) In the division width calculation step, the division width calculation unit 12 calculates the horizontal division width (X) by dividing a first number (N1), obtained by dividing the horizontal array pitch (H LED Pitch) of the multiple light sources 2 by an arbitrary natural number (K1), and then dividing the measurement pitch (H Camera Pitch) of the horizontal cross-sectional brightness (HL). It also calculates the vertical division width (Y) by dividing a second number (N2), obtained by dividing the vertical array pitch (V LED Pitch) of the multiple light sources 2 by an arbitrary natural number (K2), and then dividing the measurement pitch (H Camera Pitch) of the vertical cross-sectional brightness (VL). The first number (N1), horizontal division width (X), second number (N2), and vertical division width (Y) can be expressed by the following formulas. N1 = (H LED Pitch [mm] / K1) X = (H LED Pitch [mm] / K1) / H Camera Pitch[mm] = N1 / H Camera Pitch[mm] N2 = (V LED Pitch [mm] / K2) Y = (V LED Pitch [mm] / K2) / V Camera Pitch[mm] = N2 / V Camera Pitch[mm]
[0018] In other words, the horizontal division width (X) is obtained by dividing the array pitch (H LED Pitch) into arbitrary natural numbers (K1) and determining how many measurement pitches (H Camera Pitch) each resulting first number (N1) corresponds to. The same applies to the vertical division width (Y). Note that the natural numbers (K1) and (K2) only need to be 1 or greater, and they can be the same or different from each other.
[0019] The luminance evaluation device 10 performs the average luminance calculation step using the functions of the average luminance calculation unit 13, following the luminance ratio calculation step and the division width calculation step. Note that the luminance ratio calculation step and the division width calculation step may be performed in any order.
[0020] (Average luminance calculation step) In the average luminance calculation step, the average luminance calculation unit 13 calculates the average horizontal luminance, which is the average of the horizontal luminance ratio (HR), for each of the multiple horizontal areas obtained by dividing the horizontal width of the active area A by the horizontal division width (X), and calculates the average vertical luminance, which is the average of the vertical luminance ratio, for each of the multiple vertical areas obtained by dividing the vertical width of the active area A by the vertical division width (Y).
[0021] Here, the multiple horizontal areas obtained by dividing the horizontal width of the active area A by the horizontal division width (X) are the areas represented by the symbols (X1, X2, ..., Xn) in Figure 4. The average luminance calculation unit 13 calculates the horizontal average luminance (HRx1, HRx2, ..., HRxn), which is the average of the horizontal luminance ratio (HR), for each of the multiple horizontal areas (X1, X2, ..., Xn). Although not shown in the figure, the average luminance calculation unit 13 similarly calculates the vertical average luminance for each of the multiple vertical areas.
[0022] (Evaluation Steps) In the evaluation step following the average luminance calculation step, the evaluation unit 14 (i) calculates the horizontal luminance change amount, which is the change in the horizontal average luminance of adjacent horizontal areas among a plurality of horizontal areas, (ii) calculates the vertical luminance change amount, which is the change in the vertical average luminance of adjacent vertical areas among a plurality of vertical areas, and (iii) evaluates the degree of uniformity based on the maximum values of the calculated horizontal luminance change amount and vertical luminance change amount.
[0023] To explain (i) in detail, the evaluation unit 14 calculates the horizontal brightness change amount (ΔHRx1,2) as the change in the horizontal average brightness (HRx1,HRx2) of adjacent horizontal areas (X1,X2) using the formula ΔHRx1,2 = |HLx1-HLx2|. The evaluation unit 14 performs this calculation over the entire horizontal width of the active area A to obtain multiple horizontal brightness change amounts (ΔHRx1,2…ΔHRx(n-1),n). For (ii) above, similar to (i), the evaluation unit 14 performs this calculation over the entire vertical width of the active area A to obtain multiple vertical brightness change amounts. Then, (iii) the evaluation unit 14 evaluates the degree of uniformity based on the maximum value (ΔHRmax) among the multiple horizontal brightness change amounts and the maximum value (ΔVRmax) among the multiple vertical brightness change amounts. Specifically, ΔHRmax and ΔVRmax are values that indicate the brightness unevenness of the backlight module 1, and the lower the value, the lower the brightness unevenness and the higher the brightness uniformity. According to the brightness evaluation device 10 and brightness evaluation method described above, the uniformity of the backlight module 1 can be evaluated well.
[0024] The present invention is not limited by the embodiments and drawings described above. Modifications (including the deletion of components) can be made as appropriate, without altering the essence of the invention.
[0025] In the above explanation, explanations of publicly known technical matters have been omitted where appropriate to facilitate understanding of this disclosure.
[0026] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of this invention is indicated not by the embodiments, but by the claims. Various modifications made within the scope of the claims and the equivalent scope of the meaning of the invention are considered to be within the scope of this invention. [Explanation of Symbols]
[0027] 10…Brightness evaluation device 11...Brightness ratio calculation unit 12...Division width calculation section 13...Average luminance calculation unit 14…Evaluation Department 1...Backlight module, A...Active area 2...Light source, 3...PCB, 4...Reflector, 5...Optical sheet, 6...Enclosure 7… Surface luminance meter
Claims
1. A luminance evaluation device for evaluating the luminance of a backlight module comprising a plurality of light sources arranged horizontally and vertically, and a grid-shaped reflector surrounding each of the plurality of light sources, A luminance ratio calculation unit calculates a horizontal luminance ratio, which is the ratio of the maximum luminance at any horizontal cross-sectional luminance over the horizontal width of the active area, based on the measurement results of the surface luminance of the active area of the backlight module, and a vertical luminance ratio, which is the ratio of the maximum luminance at any vertical cross-sectional luminance over the vertical width of the active area, A division width calculation unit calculates a horizontal division width by dividing a first number obtained by dividing the horizontal arrangement pitch of the plurality of light sources by an arbitrary natural number, and a second number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number, and a vertical division width by dividing a number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number. An average brightness calculation unit calculates the average horizontal brightness, which is the average of the horizontal brightness ratios, for each of the multiple horizontal areas obtained by dividing the horizontal width of the active area by the horizontal division width, and calculates the average vertical brightness, which is the average of the vertical brightness ratios, for each of the multiple vertical areas obtained by dividing the vertical width of the active area. The system includes an evaluation unit that calculates a horizontal brightness change, which is the change in the horizontal average brightness of adjacent horizontal areas among the plurality of horizontal areas, calculates a vertical brightness change, which is the change in the vertical average brightness of adjacent vertical areas among the plurality of vertical areas, and evaluates the degree of uniformity based on the maximum values of the calculated horizontal brightness change and vertical brightness change. Brightness evaluation device.
2. A luminance evaluation method for evaluating the luminance of a backlight module comprising a plurality of light sources arranged horizontally and vertically, and a grid-shaped reflector surrounding each of the plurality of light sources, A luminance ratio calculation step is performed to calculate a horizontal luminance ratio, which is the ratio of the maximum luminance at any horizontal cross-sectional luminance over the horizontal width of the active area to the maximum luminance, based on the measurement results of the surface luminance of the active area of the backlight module, and to calculate a vertical luminance ratio, which is the ratio of the maximum luminance at any vertical cross-sectional luminance over the vertical width of the active area to the maximum luminance, A division width calculation step in which a first number obtained by dividing the horizontal arrangement pitch of the plurality of light sources by an arbitrary natural number is divided by the measurement pitch of the horizontal cross-sectional brightness to calculate the horizontal division width, and a second number obtained by dividing the vertical arrangement pitch of the plurality of light sources by an arbitrary natural number is divided by the measurement pitch of the vertical cross-sectional brightness to calculate the vertical division width, The average brightness calculation step involves calculating the average horizontal brightness, which is the average of the horizontal brightness ratios, for each of the multiple horizontal areas obtained by dividing the horizontal width of the active area by the horizontal division width, and calculating the average vertical brightness, which is the average of the vertical brightness ratios, for each of the multiple vertical areas obtained by dividing the vertical width of the active area by the vertical division width. The evaluation step includes calculating the change in horizontal brightness, which is the change in the horizontal average brightness of adjacent horizontal areas among the plurality of horizontal areas, calculating the change in vertical brightness, which is the change in the vertical average brightness of adjacent vertical areas among the plurality of vertical areas, and performing an evaluation of the degree of uniformity based on the maximum values of the calculated horizontal brightness change and vertical brightness change. Brightness evaluation method.