JP2021162686A - Video display device - Google Patents

Abstract

To provide a video display device which can suppress reduction in visibility due to temporary change of surrounding illuminance.SOLUTION: A video display device 100 includes: a display panel 114, or the like, for displaying a video on a screen; an illuminance sensor 130 and an illuminance detection unit 152 which detect surrounding illuminance with a predetermined detection time; and a luminance setting unit 154 which changes luminance of the screen displayed on the display panel 114 with a predetermined adjustment time, on the basis of the detected surrounding illuminance, and increases a degree of the change with time in the adjustment time.SELECTED DRAWING: Figure 1

Description

The present invention relates to a video display device that displays a video corresponding to an input video signal.

Conventionally, there is known a display device in which the light intensity of a display panel is controlled according to the ambient brightness detected by using an illuminance sensor (see, for example, Patent Document 1). In this display device, the backlight of the display panel is dimmed when the surroundings become dark. This prevents the brightness from being too high and the contrast from being lowered in a dark environment.

Japanese Unexamined Patent Publication No. 2006-72255

By the way, the display device disclosed in Patent Document 1 described above is supposed to be mainly used as a computer display or a television receiver, and is not supposed to repeat a sudden change in illuminance. On the other hand, when it is used in a vehicle, it may pass under the lighting installed at regular intervals at night, and the surrounding light and dark may be repeatedly reversed.

Generally, in an in-vehicle device that changes the brightness of the display panel according to the ambient brightness, the dimming time is set in consideration of the followability in a scene where the illuminance changes suddenly such as when entering or exiting a tunnel. However, in scenes where light and dark are repeated (such as in an underground parking lot or driving on a night bypass), the dimming cannot keep up with the changes in light and dark, and the display panel is bright in a dark environment, while the display panel is bright in a bright environment. There is a problem that it may become dark and the visibility is lowered due to a temporary change in illuminance. One of the causes of these phenomena is considered to be that a certain detection period is provided to prevent erroneous detection of ambient brightness, and a delay occurs before the start of dimming. As a countermeasure for this, it is conceivable to set a long dimming time, but it is not practical to make the dimming time too long because the dimming followability at the time of entering and exiting the tunnel becomes poor.

The present invention has been created in view of these points, and an object of the present invention is to provide an image display device capable of suppressing a decrease in visibility due to a temporary change in ambient illuminance.

In order to solve the above-mentioned problems, the image display device of the present invention includes an image display means for displaying an image corresponding to an input image signal on the screen and an illuminance for detecting the ambient illuminance over a predetermined detection time. Based on the detection means and the ambient illuminance detected by the illuminance detecting means, the brightness of the screen displayed on the image display means is changed over a predetermined adjustment time, and the degree of this change is timed within the adjustment time. It is equipped with a brightness setting means that increases with the passage of time.

When changing the screen brightness according to the detected ambient illuminance, the screen brightness changes sensitively to the temporary change in the ambient brightness by reducing the amount of brightness change immediately after the start of the change. It suppresses the change. As a result, it is possible to suppress the situation where the screen is bright in a dark environment and the screen is dark in a bright environment, and it is possible to improve the deterioration of visibility due to a temporary change in illuminance.

Further, it is desirable that the brightness setting means described above gradually increases the degree of change in brightness with the passage of time. This makes it possible to reduce the sense of discomfort when changing the brightness of the screen.

Further, it is desirable to set the adjustment time longer than the above-mentioned detection period. In particular, it is desirable that the above-mentioned brightness setting means changes the brightness of the screen over an adjustment time based on the changed illuminance when the ambient illuminance detected by the illuminance detecting means changes. As a result, when the ambient brightness changes temporarily and then returns to the original value, a large change in screen brightness corresponding to the temporary change is suppressed, and the surroundings after the temporary change is completed. It is possible to set the screen brightness so as to correspond to the brightness.

Further, it is desirable that the above-mentioned video display device is mounted on the vehicle. As a result, it is possible to suppress a decrease in visibility due to a temporary change in ambient illuminance, particularly in an in-vehicle device having a large change in ambient brightness.

It is a figure which shows the structure of the image display device of one Embodiment. It is a figure which shows the relationship between the detection period T and dimming control which changes brightness. It is a flow chart which shows the operation procedure which sets the brightness of a screen (backlight) according to the brightness of the surroundings. It is a figure which shows an example of the luminance control corresponding to the detected illuminance. It is a figure which shows an example of the luminance control corresponding to the detected illuminance. It is a figure which shows the specific example of the illuminance change and the luminance control.

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

FIG. 1 is a diagram showing a configuration of a video display device according to an embodiment. The video display device 100 shown in FIG. 1 is incorporated in, for example, a head unit mounted on a vehicle, and displays an image based on a video signal output from the head unit main body (not shown). Note that such a usage pattern is an example, and the image display device 100 may be used in a form separated from the head unit main body, or may be used as an electronic mirror for displaying a rear image captured by a camera.

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 generation unit 120, a backlight driver 122, an illuminance sensor (L) 130, a power supply circuit 140, and a control unit 150. It is configured to include.

The video signal receiving unit 110 receives the LVDS (Low Voltage Differential Signaling) format video signal input from the head unit main body via the video input terminal, performs serial / parallel conversion, and outputs the RGB format video signal. .. Further, the video signal receiving unit 110 monitors the presence or absence of input interruption of the video signal, and outputs a high-level lock signal when the input interruption of the video signal is detected.

The display driver 112 drives the display panel 114 based on the RGB format video signal output from the video signal receiving unit 110, and displays the image indicated by the video signal. The display panel 114 is, for example, a color liquid crystal panel, and is assembled so as to face the backlight 116 illuminated from the back surface. The backlight 116 is formed of, for example, an LED, but other light sources may be used.

The PWM signal generation unit 120 generates a PWM signal for adjusting the brightness (brightness) of the backlight 116 by controlling the driving voltage of the backlight 116 by PWM (Pulse Width Modulation).

The illuminance sensor 130 is attached to a part of the image display device 100 and detects the illuminance around the image display device 100.

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 image display device 100.

The control unit 150 controls the entire video display device 100. The 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, a CAN (Controller Area Network) protocol. Further, the control unit 150 includes an illuminance detection unit 152 and a brightness setting unit 154 in order to set the brightness of the screen (display panel 114) according to the ambient brightness.

The illuminance detection unit 152 aggregates the ambient illuminance detected by the illuminance sensor 130 over a predetermined detection period T. For example, by averaging the illuminances of a plurality of times taken from the illuminance sensor 130 at predetermined time intervals within the predetermined period T, the illuminance L as the detection result corresponding to the detection period T can be obtained.

The brightness setting unit 154 has a predetermined adjustment time (preferably longer than the detection period T, for example, 2T, which is twice the detection period T, is used as the adjustment time) based on the illuminance detected by the illuminance detection unit 152. To change the brightness of the screen displayed on the display panel 114. Further, the degree to which the brightness is changed (change rate) is set so as to increase (faster) with the passage of time within the adjustment time. In the present embodiment, the pixel value of each pixel constituting the screen to be displayed on the display panel 114 is set by changing the on-duty when PWM-controlling the drive voltage of the backlight 116 to change the brightness of the backlight 116. The brightness of this screen is changed without changing.

FIG. 2 is a diagram showing the relationship between the detection period T and the dimming control for changing the brightness. In the example shown in FIG. 2, the brightness for performing the adjustment control in the next time 2T is set based on the illuminance L detected in the detection period T from t0 to t1. Specifically, the brightness B3 at the end time point (t3) of this time 2T is set based on the detected illuminance L. Further, assuming that the brightness at the start time (t1) of the time 2T is B1, the brightness changes from B1 to B3 over this time 2T, and the degree of change in the brightness gradually increases with the passage of time. As you can see, the brightness is changed.

Similarly, the brightness for performing the adjustment control in the next time 2T is set based on the illuminance L detected in the detection period T from t3 to t4. Specifically, the brightness B6 at the end time point (t6) of this time 2T is set based on the detected illuminance L. Further, assuming that the brightness at the start time (t4) of the time 2T is B4, the brightness changes from B4 to B6 over this time 2T, and the degree of change in the brightness gradually increases with the passage of time. As you can see, the brightness is changed.

In the example shown in FIG. 2, the brightness value is changed according to the γ characteristic with the passage of time, but it is changed along another characteristic curve (arc, quadratic curve, etc.), or changed in a bent or stepped shape. You may let it.

The video signal receiving unit 110, the display driver 112, the display panel 114, the backlight 116, the PWM signal generating unit 120, and the backlight driver 122 are used as the image display means, and the illuminance sensor 130 and the illuminance detecting unit 152 are used as the illuminance detecting means. The brightness setting unit 154 corresponds to each of the brightness setting means.

The video display device 100 of the present embodiment has such a configuration, and the operation thereof will be described next.

FIG. 3 is a flow chart showing an operation procedure for setting the brightness of the screen (backlight) according to the brightness of the surroundings.

The illuminance detection unit 152 detects the illuminance L in the detection period T (step 100). As described above, the illuminance detection unit 152 detects the ambient illuminance that changes with the passage of time in the detection period T, and when this period T elapses, the average value of these detected illuminances is the detection result (illuminance L). Output as.

Next, the illuminance detection unit 152 determines whether or not the illuminance L detected by the illuminance detection unit 152 is the same as the previous detection result (step 102). It should be noted that this determination may be performed by the brightness setting unit 154. If they are different, a negative judgment is made.

Next, the luminance setting unit 154 sets the luminance B2 which is the luminance corresponding to the detected illuminance L and after a predetermined time (for example, twice the illuminance detection period T) elapses from that time (for example). Step 104). After that, the luminance setting unit 154 sets the luminance corresponding to the elapsed time so that the luminance B1 becomes the luminance B2 over time 2T from the luminance B1 at that time, and the degree of change in the luminance increases with the passage of time. Specifically, the brightness setting unit 154 starts dimming control to realize this brightness by sending an instruction to generate a PWM signal so as to have the brightness corresponding to each elapsed time to the PWM signal generation unit 120. (Step 106). After that, the process returns to step 00 and the detection operation of the illuminance L over the detection period T is repeated. If the illuminance L detected in step 100 is the same as the illuminance L detected in the previous detection cycle and an affirmative judgment is made in the determination in step 102, the new luminance after step 104 is added. The control is not started, and the process returns to step 100 and the detection operation of the illuminance L over the next detection period T is repeated.

4 and 5 are diagrams showing an example of luminance control corresponding to the detected illuminance. In the examples shown in these figures, the illuminance detected in the detection period T from t0 to t1 is L1, the illuminance detected in the next detection period T from t1 to t2 is L2, and the illuminance detected in the next t2 to t3. Let L3 be the illuminance detected in the detection period T.

When the illuminance L1 is detected corresponding to the first detection period T, the luminance B2 (L1) after 2T corresponding to the illuminance L1 is set, and in parallel with the illuminance detection operation in the next detection period T, Luminance control is performed so that the change in brightness increases with the passage of time toward the brightness B2 (L1) (b1 in FIGS. 4 and 5).

Further, when the illuminance L2 (≠ L1) is detected corresponding to the next detection period T, the luminance B2 (L2) after 2T corresponding to the illuminance L2 is set, and the illuminance is detected in the next detection period T. In parallel with the operation, the brightness is controlled so that the change in brightness increases with the passage of time toward the brightness B2 (L2) (b2 in FIGS. 4 and 5).

Further, when the illuminance L3 (≠ L2) is detected corresponding to the next detection period T, the luminance B2 (L3) after 2T corresponding to the illuminance L3 is set, and the illuminance is detected in the next detection period T. In parallel with the operation, the brightness is controlled so that the change in brightness increases with the passage of time toward the brightness B2 (L3) (b3 in FIG. 4).

However, when the illuminance L3 detected in this way is the same as the previous illuminance L2 (affirmative judgment in step 102 of FIG. 3), the luminance B2 (L3) after 2T corresponding to this illuminance L3 is obtained. Since the new luminance control based on this is not started, the previous luminance control is continued as it is (b2'in FIG. 5). When the same illuminance is detected for three or more cycles, the brightness set corresponding to the illuminance detected in the first cycle is reached and the brightness value is maintained as it is.

FIG. 6 is a diagram showing specific examples of illuminance change and luminance control. In the example shown in FIG. 6, the illuminance detected for each detection period changes periodically, but the corresponding brightness change is gentle, and the brightness may change significantly in response to the temporary illuminance change. No.

As described above, in the image display device 100 of the present embodiment, when the brightness of the screen is changed according to the detected ambient illuminance, the amount of change in brightness immediately after the start of the change is reduced to reduce the brightness of the surroundings. It suppresses the change in screen brightness due to hypersensitivity to temporary changes. As a result, it is possible to suppress the situation where the screen is bright in a dark environment and the screen is dark in a bright environment, and it is possible to improve the deterioration of visibility due to a temporary change in illuminance.

In particular, by gradually increasing the degree of change in brightness with the passage of time, it is possible to reduce a sense of discomfort when changing the brightness of the screen.

In addition, the adjustment time for changing the brightness corresponding to the detected illuminance is set longer than the detection period of the illuminance. In particular, when the detected illuminance changes with respect to the previous detection result, the brightness control based on the changed illuminance is started. As a result, when the ambient brightness changes temporarily and then returns to the original value, a large change in screen brightness corresponding to the temporary change is suppressed, and the surroundings after the temporary change is completed. It is possible to set the screen brightness so as to correspond to the brightness.

Further, the image display device 100 of the present embodiment is mounted on a vehicle, and it is possible to suppress a decrease in visibility due to a temporary change in illuminance of the surroundings, especially when the change in ambient brightness is large. ..

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the above-described embodiment, the case where the vehicle is mounted on a vehicle has been described, but the present invention can also be applied to the case where the vehicle is used inside or outside a building other than the vehicle.

As described above, according to the present invention, when the brightness of the screen is changed according to the detected ambient illuminance, the amount of change in brightness immediately after the start of the change is reduced to temporarily change the ambient brightness. It suppresses the change in screen brightness by following changes sensitively. As a result, it is possible to suppress the situation where the screen is bright in a dark environment and the screen is dark in a bright environment, and it is possible to improve the deterioration of visibility due to a temporary change in illuminance.

100 Video display device 110 Video signal receiver 112 Display driver 114 Display panel 116 Backlight 120 PWM signal generator 122 Backlight driver 130 Illuminance sensor 140 Power supply circuit 150 Control unit 152 Illuminance detection unit 154 Brightness setting unit 154

Claims (5)

A video display means that displays the video corresponding to the input video signal on the screen,
An illuminance detecting means that detects the ambient illuminance over a predetermined detection time, and
Based on the ambient illuminance detected by the illuminance detecting means, the brightness of the screen displayed on the image display means is changed over a predetermined adjustment time, and the degree of this change is changed over time within the adjustment time. Brightness setting means to increase with
An image display device characterized by being provided with. The image display device according to claim 1, wherein the brightness setting means gradually increases the degree of changing the brightness with the passage of time. The video display device according to claim 1 or 2, wherein the adjustment time is set longer than the detection period. The brightness setting means is characterized in that when the ambient illuminance detected by the illuminance detecting means changes, the brightness of the screen is changed over the adjustment time based on the changed illuminance. The video table device according to any one of 1 to 3. The video display device according to any one of claims 1 to 4, wherein the image display device is mounted on a vehicle.

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