Video display device

Abstract

To provide a video display device capable of suppressing the glare on a screen and shortening a recovery time, when the display screen is restored to a bright state in accordance with surroundings.SOLUTION: A video display device 100 includes: a video signal receiving unit 110, a display driver 112, a display panel 114, and a backlight 116 for displaying an image on a screen; an illuminance sensor 130 and an illuminance detection unit 152 for detecting brightness around the screen; a brightness setting unit 156 for setting the brightness of the screen based on the detected brightness of surroundings; a transmission amount calculation unit 154 for calculating an amount of light transmitted through the image; and a change coefficient setting unit 158 for varying an amount of change in brightness of the screen set by the brightness setting unit 156 based on the amount of light transmitted through the image, when the detected brightness of surroundings changes from a dark state to a bright state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a video display device for displaying still images and moving images.

Background Art

[0002] Conventionally, there has been known a display control device that suppresses a decrease in visibility of a display video on a display panel by controlling the luminance of a backlight according to the ambient illuminance detected using an illuminance sensor (see, for example, Patent Document 1). In this display control device, the luminance of the backlight is controlled according to the ambient illuminance and the luminance of the input video. Thereby, for example, the luminance of the display screen of an in-vehicle device can be set to be bright during the day and dark at night.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the display control device disclosed in Patent Document 1 described above, when the surrounding environment changes from a dark environment to a bright environment, the luminance of the display screen becomes bright. However, when the illuminance changes suddenly and the luminance of the display screen is suddenly increased, the user looking at the screen feels dazzled. Therefore, it is desirable to increase the luminance over a predetermined time. However, depending on the content of the display screen (a dark screen with a small amount of light transmitted through the backlight and a bright screen with a large amount of transmitted light), even if the time required to brighten the display screen is the same, there is a difference in the dazzle felt by the user. For this reason, when setting the time to brighten the display screen in consideration of suppressing the dazzle of a bright screen with a large amount of transmitted light, there is a problem that it takes time for the luminance of a dark screen with a small amount of transmitted light to return.

[0005] The present invention was created in consideration of the above points, and its purpose is to provide a video display device that can reduce glare on the screen and shorten the recovery time when restoring the display screen to a bright state in accordance with the surroundings. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the video display device of the present invention comprises an image display means for displaying an image on a screen, a brightness detection means for detecting the brightness around the screen, a screen brightness setting means for setting the brightness of the screen based on the ambient brightness detected by the brightness detection means, a transmission amount calculation means for calculating the amount of light transmitted through the image, and a brightness change amount setting means for varying the amount of change in screen brightness set by the screen brightness setting means based on the transmission amount calculated by the transmission amount calculation means when the ambient brightness detected by the brightness detection means changes from a dark state to a bright state.

[0007] When the display screen is restored to a bright state in accordance with the ambient brightness, the restoration time (amount of change in brightness) is varied taking into account the amount of light transmitted through the image, thereby reducing glare on the screen and shortening the restoration time.

[0008] Furthermore, it is desirable that the above-mentioned screen brightness setting means darkens the screen brightness when the surrounding brightness is low, and brightens the screen brightness when the surrounding brightness is high, thereby making it possible to improve the visibility of the screen by making the screen brighter when the surrounding brightness is high and darker when the surrounding brightness is low.

[0009] Furthermore, it is desirable that the image display means has a backlight that irradiates light onto the image from behind, and that the screen brightness setting means sets the brightness of the screen by controlling the brightness of the backlight. By controlling the brightness of the backlight, the brightness of the display screen can be reliably varied.

[0010] In addition, it is desirable that the above-described transmittance calculation means calculate the light transmittance of the image based on each pixel value constituting the image. Since the light transmittance changes depending on the shade (color) of each pixel, it becomes possible to accurately calculate the light transmittance of the entire image based on each pixel value.

[0011] In addition, it is desirable that the above-described luminance change amount setting means set a small change amount per unit time of the screen luminance when the transmittance calculated by the transmittance calculation means is large, and set a large change amount per unit time of the screen luminance when the transmittance is small. Thereby, for a bright image with a large light transmittance, the luminance can be slowly increased to suppress the glare of the screen, and for a dark screen with a small light transmittance, the time for quickly increasing the luminance to make it a bright screen can be shortened.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0013] Hereinafter, a video display device according to an embodiment to which the present invention is applied will be described with reference to the drawings.

[0014] Fig. 1 is a diagram showing the configuration of an image display device according to one embodiment. The image display device 100 shown in Fig. 1 is incorporated into, for example, a head unit mounted on a vehicle, and displays an image based on a video signal output from a head unit main body (not shown). Note that this usage is just one example, and the image display device 100 may also be used in a form separated from the head unit main body, or as an electronic mirror that displays a rearward image captured by a camera.

[0015] The video display device 100 includes a video signal receiving unit 110, a display driver 112, a display panel 114, a backlight 116, a PWM signal generating unit 120, a backlight driver 122, an illuminance sensor (L) 130, a power supply circuit 140, and a control unit 150.

[0016] The video signal receiving unit 110 receives a video signal in LVDS (Low Voltage Differential Signaling) format input from the head unit body via a video input terminal, performs serial / parallel conversion on the received signal, and outputs a video signal in RGB format.

[0017] The display driver 112 drives the display panel 114 based on the RGB video signal output from the video signal receiving unit 110, and displays the image represented by this video signal. The image to be displayed may be either a moving image or a still image. The display panel 114 is, for example, a color liquid crystal panel, and is mounted facing a backlight 116 that illuminates from behind. The backlight 116 is, for example, formed by an LED, but other light sources may also be used.

[0018] The PWM signal generating unit 120 generates a PWM signal for adjusting the luminance (brightness) of the backlight 116 by controlling the drive voltage of the backlight 116 using PWM (Pulse Width Modulation).

[0019] The illuminance sensor 130 is attached to a part of the video display device 100 and detects the illuminance around it. Note that the illuminance sensor may be set at a position away from the video display device 100.

[0020] The power supply circuit 140 is connected to a battery (not shown) via the battery terminal BATT and supplies operating power to each part of the video display device 100.

[0021] The control unit 150 controls the entire video display device 100. This control unit 150 is connected to the head unit main body via the communication terminal C, and transmits and receives various data to and from the head unit main body by communication according to, for example, the CAN (Controller Area Network) protocol. Further, the control unit 150 includes an illuminance detection unit 152, a transmittance calculation unit 154, a luminance setting unit 156, and a change coefficient setting unit 158 in order to set the luminance of the screen (display panel 114) according to the ambient brightness.

[0022] The illuminance detection unit 152 totals the ambient illuminance detected using the illuminance sensor 130 over a predetermined detection period T. For example, by averaging the illuminances for a plurality of times captured from the illuminance sensor 130 at a predetermined time interval within the predetermined detection period T, an illuminance L as a detection result corresponding to the detection period T is obtained.

[0023] The transmittance calculation unit 154 calculates the light transmittance for the image to be displayed based on the RGB - format video signal output from the video signal receiving unit 110. For example, the case of averaging the pixel values (each gradation information of RGB) of each pixel constituting the image for all pixels is conceivable.

[0024] The luminance setting unit 156 sets the luminance of the screen displayed on the display panel 114 based on the illuminance (ambient brightness) detected by the illuminance detection unit 152. In this embodiment, the luminance of the backlight 116 is changed by varying the on-duty when the drive voltage of the backlight 116 is PWM controlled, thereby changing the luminance of this screen without changing the pixel values of the pixels that make up the screen displayed on the display panel 114.

[0025] The variation coefficient setting unit 158 sets a coefficient K for varying the amount of change per unit time in the brightness of the backlight 116 set by the brightness setting unit 156 when the surroundings switch from a dark state to a bright state, based on the illuminance obtained by the illuminance detection unit 152.

[0026] FIG. 2 is a diagram showing the relationship between the amount of light transmitted through an image and the amount of change in screen brightness. In FIG. 2, the horizontal axis represents the amount of light transmitted through the screen to be displayed. The vertical axis represents the value of coefficient K, which indicates the amount of change in screen brightness. This coefficient K is a value that variably adjusts the amount of change in brightness when increasing the screen brightness relative to a reference value A (fixed value), and is set in the range of 1 to 1.5. In other words, the amount of change in brightness taking into account the amount of light transmitted through the image is K×A.

[0027] In this embodiment, as shown in FIG. 2, the coefficient K is set to a large value of 1.5 for images with low light transmission (dark images), a small value of 1.0 for images with high light transmission (bright images), and a value between 1.0 and 1.5 for images with intermediate transmission.

[0028] The above-mentioned video signal receiving unit 110, display driver 112, display panel 114, and backlight 116 correspond to image display means, the illuminance sensor 130 and illuminance detection unit 152 correspond to brightness detection means, the luminance setting unit 156 corresponds to screen luminance setting means, the transmittance calculation unit 154 corresponds to transmittance calculation means, and the variation coefficient setting unit 158 corresponds to luminance variation setting means.

[0029] The video display device 100 of this embodiment has such a configuration. Next, the operation of changing the brightness of the screen when the brightness of the surroundings changes will be described.

[0030] FIG. 3 is a diagram showing the brightness change of the backlight 116 corresponding to the change in the ambient brightness. In FIG. 3, the horizontal axis represents the passage of time, and the vertical axis represents the brightness of the screen.

[0031] In this embodiment, when the surroundings are bright (when the ambient illuminance detected using the illuminance sensor 130 is equal to or higher than a predetermined value), the backlight 116 is set to high brightness (brightness value I1), and when the surroundings are dark (when the ambient illuminance detected using the illuminance sensor 130 is lower than the predetermined value), the backlight 116 is set to low brightness (brightness value I0).

[0032] Until time t1, the surroundings are bright, and the brightness setting unit 156 sets the backlight 116 to high brightness (brightness value I1).

[0033] Next, when the surroundings become dark after time t1, the brightness setting unit 156 switches the backlight 116 to low brightness (brightness value I0). This switching from high brightness to low brightness is performed rapidly.

[0034] Next, when the surroundings become bright again after time t2, the brightness setting unit 156 switches the backlight 116 from low brightness to high brightness. This switching to high brightness is gradually performed so that the amount of change in brightness corresponds to the amount of light transmitted through the image. Specifically, the brightness setting unit 156 uses a value K×A obtained by multiplying a reference value A (a fixed value) by a coefficient K set by the change coefficient setting unit 158 to switch the backlight 116 to high brightness.

[0035] In the example shown in FIG. 3, when the image when switching the backlight 116 from low brightness to high brightness is bright and the amount of light transmitted through the image is large, a small brightness change amount (solid line) corresponding to the coefficient K = 1 is set, and the brightness gradually increases. This increase in brightness continues until the backlight 116 reaches high brightness I1 at time t3.

[0036] On the other hand, if the image is dark and the amount of light transmitted through the image is small when the backlight 116 is switched from low brightness to high brightness, a large brightness change amount (dotted line) corresponding to K=1.5 is set, and the brightness increases quickly. This increase in brightness continues until the backlight 116 reaches high brightness I1 at time t4, which is earlier than time t3.

[0037] Fig. 4 is a diagram showing a modified example of the change in luminance of the backlight 116 in response to a change in the ambient brightness. In the example shown in Fig. 3, a case has been described in which the value of the coefficient K remains constant until the operation of switching the backlight 116 to high brightness ends at time t2 when the ambient brightness becomes bright. There are cases in which the value of K, which is set according to the amount of light transmitted through the image at time t2, is maintained from the start to the end of the change in luminance of the backlight 116, or cases in which the amount of light transmitted through the image at time t2 remains unchanged from the start to the end of the change in luminance of the backlight 116.

[0038] 4 shows an example in which the amount of light transmitted through the image at time t2 changes over time from the start to the end of the luminance change of the backlight 116. When the surroundings become brighter after time t2, the luminance setting unit 156 switches the backlight 116 from low luminance to high luminance. This switch to high luminance is initially performed by an amount of change in luminance corresponding to a coefficient K=1.5 (when the image is dark) set in accordance with the amount of light transmitted through the image at time t2. However, at time t5, the image becomes brighter, and the amount of change in luminance corresponds to a coefficient K=1.0 set in accordance with the amount of light transmitted through this image. This increase in luminance continues until the backlight 116 reaches high luminance I1 at time t6.

[0039] In the example shown in FIG. 4, the brightness of the image is switched once while the brightness of the backlight 116 is changing. However, when displaying a moving image, the brightness of the image changes from moment to moment. Therefore, the value of the coefficient K corresponding to the brightness of the image may be set each time, and the amount of change in the brightness of the backlight 116 may be varied.

[0040] In this way, in the image display device 100 of this embodiment, when the display screen is returned to a bright state in accordance with the ambient brightness, the return time (amount of change in brightness) is varied taking into account the amount of light transmitted through the image, thereby making it possible to reduce glare on the screen and shorten the return time.

[0041] Specifically, the visibility of the screen can be improved by making the screen brighter when the surroundings are bright, and by making the screen darker when the surroundings are dark. Also, by controlling the brightness of the backlight 116, the brightness of the display screen can be reliably varied.

[0042] In addition, because the amount of light transmitted varies depending on the shade (color) of each pixel that makes up the image, it is possible to accurately calculate the amount of light transmitted throughout the image based on the value of each pixel. Also, for bright images with a high amount of light transmitted, the brightness can be increased slowly to reduce glare on the screen, and for dark images with a low amount of light transmitted, the brightness can be increased quickly to brighten the screen, shortening the recovery time.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. For example, in the above-described embodiment, the case where the device is installed in a vehicle is described, but the present invention can also be applied to cases where the device is used inside or outside a building other than a vehicle.

[0044] In the above-described embodiment, the brightness of the entire screen is changed by varying the brightness of the backlight 116, but the brightness of the entire screen may be changed by other methods. For example, when an image is displayed using an organic EL display, the brightness of the entire image may be changed by changing the RGB gradation values of each pixel. [Industrial Applicability]

[0045] As described above, according to the present invention, when the display screen is restored to a bright state in accordance with the ambient brightness, the restoration time (amount of change in brightness) is varied taking into account the amount of light transmitted through the image, thereby making it possible to reduce glare on the screen and shorten the restoration time. [Explanation of symbols]

[0046] 100 Video display device 110 Video signal receiving unit 112 Display Driver 114 Display Panel 116 Backlight 120 PWM signal generation section 122 Backlight Driver 130 Illuminance sensor 140 Power supply circuit 150 control section 152 Illuminance detection unit 154 Transmission amount calculation section 156 Brightness setting section 158 Change coefficient setting section

Claims

1. Image display means for displaying an image on a screen; Brightness detection means for detecting the brightness around the screen; Screen brightness setting means for setting the brightness of the screen based on the ambient brightness detected by the brightness detection means; Transmission amount calculation means for calculating the amount of light transmitted through the image; Brightness change amount setting means for varying the amount of change in the brightness of the screen set by the screen brightness setting means based on the amount of light transmission calculated by the transmission amount calculation means when the ambient brightness detected by the brightness detection means changes from a dark state to a bright state; A video display device comprising the same.

2. The video display device according to claim 1, wherein the screen brightness setting means sets the brightness of the screen to be dark when the ambient brightness is dark and sets the brightness of the screen to be bright when the ambient brightness is bright.

3. The image display means has a backlight for irradiating light from the back side of the image, The video display device according to claim 1, wherein the screen brightness setting means sets the brightness of the screen by controlling the brightness of the backlight.

4. The video display device according to claim 3, wherein the transmission amount calculation means calculates the amount of light transmitted through the image based on each pixel value constituting the image.

5. The video display device according to claim 1, wherein the brightness change amount setting means sets the amount of change in the brightness of the screen per unit time to be small when the amount of light transmission calculated by the transmission amount calculation means is large, and sets the amount of change in the brightness of the screen per unit time to be large when the amount of light transmission is small.

Images