Electronic device and ambient light sensing method thereof

An electronic device includes: a OLED display including a first display area, wherein a saturation of the first display area remains constant in a first period; a display driver for driving the OLED display and changing a brightness coefficient of the first display area from a first brightness coefficient to a second brightness coefficient during the first period; an ambient light sensor under the first display area for sensing light, wherein during the first period, the ambient light sensor generates a first sensing value when the brightness coefficient of the first display area is the first brightness coefficient and generates a second sensing value when the brightness coefficient of the first display area is the second brightness coefficient; and a controller for calculating an ambient light intensity according to the first brightness coefficient, the second brightness coefficient, the first sensing value and the second sensing value.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an electronic device, particularly to an electronic device with an OLED (Organic Light-Emitting Diode) display and an ambient light sensing method thereof.

Description of the Related Art

A mobile electronic device or a wearable electronic device, which is equipped with a display, is likely to use an ambient light sensor to sense an ambient light, whereby to adjust screen brightness. The present ambient light sensor is disposed in the perimeter of the screen. However, the screen-to-body ratio is growing higher and higher. Hence, the space around the screen, which is available for an ambient light sensor, becomes smaller and smaller. Arranging the ambient light sensor below the screen may be a solution to meet the requirement of high screen-to-body ratio.FIG. 1shows a mobile phone10, andFIG. 2shows the sectional view taken along line AA′ inFIG. 1. As shown inFIG. 1andFIG. 2, an ambient light sensor14is disposed under a display12of the mobile phone10. The architecture shown inFIG. 1andFIG. 2still has some problems to overcome. The first problem is that the ambient light AL must pass through the display12such that the ambient light AL can be detected by the ambient light sensor14. The second problem is that the light DL emitted by the display12affects the detection of the ambient light sensor14.

SUMMARY OF THE INVENTION

One objective of the preset invention is to provide an electronic device with an OLED display and an ambient light sensing method thereof.

In one embodiment, the present invention provides an electronic device, which comprises an OLED display including a first display area, wherein a saturation of the first display area remains constant in a first period; a display driver coupled to the OLED display, wherein the display driver changes a brightness coefficient of the first display area from a first brightness coefficient to a second brightness coefficient during the first period; an ambient light sensor under the first display area for sensing light, wherein during the first period, the ambient light sensor senses light to generate a first sensing value when the brightness coefficient of the first display area is the first brightness coefficient and the ambient light sensor senses light to generate a second sensing value when the brightness coefficient of the first display area is the second brightness coefficient; and a controller for calculating an ambient light intensity according to the first brightness coefficient, the second brightness coefficient, the first sensing value and the second sensing value.

In one embodiment, the present invention provides an ambient light sensing method of an electronic device with an OLED display, wherein the electronic device includes an ambient light sensor under a first display area of the OLED display. The ambient light sensing method comprises step A: sensing light to generate a first sensing value by the ambient light sensor when the brightness coefficient of the first display area is a first brightness coefficient in a first period; step B: sensing light to generate a second sensing value by the ambient light sensor when the brightness coefficient of the first display area is a second brightness coefficient in the first period; and step C: calculating an ambient light intensity according to the first brightness coefficient, the second brightness coefficient, the first sensing value and the second sensing value, wherein the a saturation of the first display area remains constant in the first period.

The electronic device and the ambient light sensing method of the present invention can correctly sense ambient light without being affected by the light emitted from the OLED display.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3shows a block diagram of an electronic device according to one embodiment of the present invention. The electronic device20inFIG. 3comprises a controller22, an ambient light sensor24, a display driver26and an OLED display28.FIG. 4shows a sectional view of the ambient light sensor24and the OLED display28of the electronic device according to one embodiment of the present invention. As shown inFIG. 3andFIG. 4, the OLED display28includes a first display area DA. The display driver26is coupled to the OLED display28and used to drive the OLED display28. The ambient light sensor24is disposed under the first display area DA and used to sense light to obtain a sensing value. The controller22is coupled to the ambient light sensor24and the display driver26. The controller22receives a first brightness coefficient L1and a second brightness coefficient L2from the display driver26and receives a first sensing value C1and a second sensing value C2from the ambient light sensor24. The electronic device20of the present invention does not need a backlight module because the OLED display28is a self-luminescent display. Therefore, ambient light AL can easily pass through the OLED display28and can be sensed by the ambient light sensor24under the OLED display28. The lights detected by the ambient light sensor24include the ambient light AL and the light DL emitted by the OLED display28. Thus, the sensing value generated by the ambient light sensor24may be expressed by the following formula:
C=ALS+L×Color  (Formula 1)
wherein C is the sensing value generated by the ambient light sensor24; ALS is the intensity of the ambient light AL; L is the brightness coefficient of the first display area DA; Color is the saturation of the first display area DA. According to Formula 1, in a period that the ambient light AL and the saturation Color of the first display area DA remain constant, while the brightness coefficient L of the first display area DA is a first brightness coefficient L1, the ambient light sensor24obtains a first sensing value:
C1=ALS+L1×Color  (Formula 2)
while the brightness coefficient L of the first display area DA is a second brightness coefficient L2, the ambient light sensor24obtains a second sensing value:
C2=ALS+L2×Color  (Formula 3)
According to the Formula 2 and Formula 3, the ambient light intensity ALS can be expressed as follows.

ALS=L⁢2×C⁢1-L⁢1×C⁢2L⁢2-L⁢1(Formula⁢⁢4)
It is learned from Formula 4: in the case that the saturation Color of the first display area DA remains constant, after the ambient light sensor24generates the first sensing value C1and the second sensing value C2, the first brightness coefficient L1, the second brightness coefficient L2, the first sensing value C1and the second sensing value C2may be used to correctly calculate the ambient light intensity ALS.

In the electronic device20of the present invention, the saturation Color of the first display area DA of the OLED display28remains constant during a first period T1. In general, the saturation of the pixels of the OLED display28remains constant in a frame of the OLED display28. Therefore, the first period T1may be within the frame time of a frame. However, the first period T1of the present invention is not limited within a frame. If the saturation of the first display area DA of the OLED display28remains constant during several frames, the first period T1may be several frame time. The display driver26of the electronic device20changes the brightness coefficient of the first display area DA from the first brightness coefficient L1to the second brightness coefficient L2during the first period T1. While the brightness coefficient of the first display area DA is the first brightness coefficient L1during the first period T1, the ambient light sensor24senses light to generate the first sensing value C1, as shown in step S10ofFIG. 5. While the brightness coefficient of the first display area DA is the second brightness coefficient L2during the first period T1, the ambient light sensor24senses light to generate the second sensing value C2, as shown in step S12ofFIG. 5. The time interval between step S10and step S12is very short. Therefore, the ambient light intensity ALS in step S10and step S12may be regarded as the same. The time interval between step S10and step S12may be but is not limited to be 16 ms. The ambient light sensor24transmits the first sensing value C1and the second sensing value C2to the controller22, and the display driver26provides the first brightness coefficient L1and the second brightness coefficient L2for controller22. According to the first brightness coefficient L1, the second brightness coefficient L2, the first sensing value C1and the second sensing value C2, the controller22executes the operation of Formula 4 to calculate the intensity ALS of the ambient light AL, as shown in step S14ofFIG. 5. The controller22may use a software or a hardware to execute the calculation of Formula 4. According to the calculated ambient light intensity ALS, the controller22generates a light regulation signal Sc to the display driver26. According to the light regulation signal Sc, the display driver26regulates the brightness of the OLED display28. In the present invention, the electronic device20may regulate the brightness of the OLED display28by a DC dimmingor a PWM dimming.

In one embodiment, the controller22and the ambient light sensor24are integrated in an integrated circuit.

In one embodiment, the software, which the controller22uses to execute the calculation of Formula 4, is incorporated into the operating system of the electronic device20.

In one embodiment, the controller22provides the first brightness coefficient L1and the second brightness coefficient L2to the display driver26.