Electronic device having display and method for controlling display brightness

An electronic device having a display unit, an indicator, an illuminance sensor and a controller is provided. The indicator is configured to be turned on for emitting light and to be turned off. The illuminance sensor is configured to sense ambient illuminance. The controller is connected to the display unit, the indicator and the illuminance sensor. The controller is configured to turn on and off the indicator. The controller is configured to set brightness of the display unit depending on a value of the ambient illuminance sensed by the illuminance sensor while the indicator continues to be off.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-006108 filed on Jan. 14, 2009; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to an electronic device having a display and an illuminance sensor for controlling display brightness on the basis of ambient illuminance, and to a method for controlling the display brightness. The electronic device is configured to control measurement of illuminance by means of the illuminance sensor on the basis of an on-or-off state of an LED provided to the electronic device.

(ii) Description of the Related Art

A recent trend of some electronic device such as a mobile phone or a mobile data terminal is that it consumes more power as it is equipped with a display of a greater size or a processor of a higher operating frequency. Thus, a lot of electronic devices are configured to measure ambient brightness by using their illuminance sensors, and to control use of their displays with minimally required backlight brightness these days.

A mobile communication device configured to consume less power is disclosed, e.g., in Japanese Patent Publication of Unexamined Application (Kokai) No. 2005-236524. The mobile communication device of JP 2005-236524 is configured to minimize an effect of turning on and off of a light for illuminating the surroundings, and to optimize brightness levels of an operation unit and a display unit so as to consume less power. The mobile communication device of JP 2005-236524 is configured to control, as usual, a brightness level of a backlight for the operation unit in accordance with an ambient illuminance level sensed by a photosensor. If the light is turned on, though, the mobile communication device turns on the backlight for the operation unit regardless of a sensing level of the photosensor while taking an effect of the light to the sensing level of the photosensor into account.

It is generally known that an electronic device such as a mobile phone has an LED for indicating that its battery is being recharged, or that a missed call or an unread email exists. If, however, the LED and the illuminance sensor are arranged close to each other, such an arrangement may cause a problem that the illuminance sensor senses light of the LED resulting in that the backlight brightness cannot be properly controlled.

The present invention has been made in view of the above circumstances and provides electronic equipment in which the brightness of a back light is properly controlled on the basis of illuminance even when LED and an illuminance sensor are provided in proximity to each other.

SUMMARY OF THE INVENTION

Accordingly, an advantage of the present invention is that display brightness of an electronic device can be properly controlled even if the electronic device is provided with an indicator such as an LED and an illuminance sensor arranged close to each other.

To achieve the above advantage, one aspect of the present invention is to provide an electronic device having a display unit, an indicator, an illuminance sensor and a controller. The indicator is configured to be turned on for emitting light and to be turned off. The illuminance sensor is configured to sense ambient illuminance. The controller is connected to the display unit, the indicator and the illuminance sensor. The controller is configured to turn on and off the indicator. The controller is configured to set brightness of the display unit depending on a value of the ambient illuminance sensed by the illuminance sensor while the indicator continues to be off.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A first embodiment of the present invention will be described with reference toFIGS. 1A-7. A mobile phone1, which includes two housing sections connected to each other in such a way as to slide against each other and configured to be open and closed to each other, will exemplify an electronic device of the first embodiment.

FIGS. 1A and 1Bare perspective views showing the mobile phone1being closed and being open, respectively. As shown inFIGS. 1A and 1B, the mobile phone1is constituted by a rectangular planar-shaped upper housing10and a lower housing11of substantially the same shape as the upper housing10. While being closed to each other, the upper and lower housings10and11are stacked so that the upper housing10covers a face of the lower housing11and vice versa. The upper housing10and the lower housing11are connected to each other in such a way as to slide against each other in a particular direction (e.g., in a longer side direction of the housings10and11) by a certain length. The upper housing10is configured to slide against the lower housing11so that the mobile phone1can change its state from closed to open, and vice versa.

An outer face of the upper housing10(on the side not facing the lower housing11) is provided with a touch screen12and a speaker13. The touch screen12is configured to display a screen formed by text, images and so on, and to accept an entered direction by sensing contact with a finger, a stylus and so on. The speaker13is configured to produce voice and sound. The touch screen12is a display unit having both a display function and an input operation function. The display function is for displaying a screen formed by text, images and so on. The input operation function is for accepting data represented by a position where a finger or a dedicated stylus is in contact with the touch screen12.

The touch screen12is formed, e.g., by a plurality of elements arranged on an upper surface of the display for sensing contact on the surface, and a transparent screen layered on top of the elements. The touch screen12may sense contact by using a pressure sensing method for sensing a pressure change, an electrostatic method for sensing an electrical signal caused by static electricity, or other methods.

The outer face of the upper housing10is provided with an LED (light emitting diode)14and an illuminance sensor15. The LED14is turned on so as to indicate that a battery is being recharged, that a missed call or an unread email exists and so on. The illuminance sensor15is configured to sense ambient illuminance. The illuminance sensor15may include, e.g., a phototransistor, a photodiode, a photodiode plus an amplifier circuit, or the like.

The touch screen12, the speaker13, the LED14and the illuminance sensor15are provided in such a way as to be exposed to the outside regardless of whether the mobile phone1is closed or open. Accordingly, the mobile phone1can allow a user to view a screen and to enter a direction on the touch screen12, and the illuminance sensor15can sense ambient illuminance, regardless of whether the mobile phone1is closed or open.

An inner face of the lower housing11(on the side facing the upper housing10) is provided with a microphone16for collecting voice and sound, and a plurality of operation keys17which a user can press so as to provide the mobile phone1with a direction. If the mobile phone1is closed, the operation keys17are covered by the upper housing10and thus are not exposed to the outside. If the upper housing10slides against the lower housing11and thus the mobile phone1opens, the operation keys17are exposed to the outside. Accordingly, if the mobile phone1is open, a user can provide the mobile phone1with a direction through the operation keys17. If the mobile phone1is closed, the user cannot provide the mobile phone1with a direction through the operation keys17.

A side face of the lower housing11is provided with a plurality of operation keys17awhich a user can press so as to provide the mobile phone1with a direction. The operation keys17aare provided in such a way as to be exposed to the outside regardless of whether the mobile phone1is closed or open. Accordingly, the mobile phone1can allow a user to enter a direction through the operation keys17aregardless of whether the mobile phone1is closed or open.

Then, functions of the mobile phone1will be described with reference to a block diagram shown inFIG. 2. As shown inFIG. 2, the mobile phone1has a main controller20, a power supply circuit21, an operation input controller22, a display controller23, a memory24, a voice/sound controller25, a communication controller26and an illuminance detector27which are connected to one another through a bus so as to communicate with one another.

The main controller20includes a CPU (central processing unit) and comprehensively controls the mobile phone1, and also performs an illuminance sensor control process described later and other various arithmetic and control processes. The power supply circuit21has a power supply source such as a battery or the like. The power supply circuit21turns the power supply on and off depending on a user's input operation through the operation keys17. If the power supply is turned on, the power supply circuit21supplies each of portions of the mobile phone1with power from the power supply source so as to activate the mobile phone1.

The operation input controller22has an input interface for the touch screen12and the operation keys17and17a. Upon sensing an operation such as contact on the touch screen12or a press of one of the operation keys17and17a, the operation input controller22generates a signal indicating the operation and transmits the signal to the main controller20.

The display controller23has a display interface for the touch screen12and the LED14. The display controller23is controlled by the main controller20so as to display a screen formed by text, an image and so forth on the touch screen12, and to turn on or off the LED14. The display controller23is controlled by the main controller20so as to adjust brightness of the touch screen12(or brightness of a backlight provided to the touch screen12). Moreover, the display controller23is controlled by the main controller20so as to generate a signal indicating whether the LED14is lit (on) or not (off), and to transmit the signal to the main controller20.

The memory24includes a ROM (read only memory) or a hard disk for storing a program of a process to be performed by the main controller20, data required for the process and so on, a non-volatile memory, a database, a RAM (random access memory) for temporarily storing data which the main controller20uses while performing the process. Moreover, it is assumed that a program for the illuminance sensor control process described later is stored, e.g., in the ROM. Moreover, the memory24stores a reference value of the brightness of the touch screen12(or of the backlight).

The voice/sound controller25is controlled by the main controller20so as to generate an analog voice signal from voice collected by the microphone, and to convert the analog voice signal into a digital voice signal. Moreover, upon obtaining a digital voice signal, the voice/sound controller25is controlled by the main controller20so as to convert the digital voice signal into an analog voice signal, and produces voice from the speaker13.

The communication controller26is controlled by the main controller20so as to de-spread a spread spectrum signal received from a base station (not shown) through an antenna26a, and to restore data carried by the received signal. The communication controller26can be controlled by the main controller20so as to provide the data to the voice/sound controller25so that voice based on the data is produced through the speaker13, to the display controller23so that the data is displayed on the touch screen12, or to the memory24so that the data is stored in the memory24.

Moreover, upon obtaining voice data collected by the microphone16, data entered through the touch screen12or the operation keys17or17aor the like, or data stored in the memory24under the control of the main controller20, the communication controller26performs a spectrum spreading process and transmits the processed data to the base station through the antenna26a.

The illuminance detector27has an interface for the illuminance sensor15. Upon obtaining illuminance data sensed by the illuminance sensor15, the illuminance detector27generates a signal representing the illuminance data and transmits the signal to the main controller20.

The mobile phone1has a function for adjusting brightness of the touch screen12to a proper value in accordance with ambient illuminance sensed by the illuminance sensor15. In some cases, however, where the LED14and the illuminance sensor15are arranged close to each other, there is a possibility that the mobile phone1cannot properly control the brightness of the touch screen12, as the illuminance sensor15senses light of the LED14. Therefore, the mobile phone1has an illuminance sensor control function for controlling the illuminance sensor15in such a way that the illuminance sensor15measures illuminance only after the LED14is turned off. Accordingly, the mobile phone1can measure the ambient illuminance by using the illuminance sensor15so as to control the touch screen12in such a way as to keep the brightness to a requisite minimum.

FIG. 3shows a relationship between a change of an on-or-off state of the LED14while it is blinking and a change of an on-or-off state of the illuminance sensor15. As shown inFIG. 3, the mobile phone1is configured to periodically measure the ambient illuminance affected by the on-or-off state of the LED14, to calculate a proper brightness value of the touch screen12on the basis of the measured value of the illuminance at that time, and to update the brightness of the touch screen12.

It is assumed that the mobile phone1checks the on-or-off state of the LED14, and that it measures the illuminance by using the illuminance sensor15while the LED14is being off. That is, the mobile phone1does not measure the illuminance while the LED14is being on (the LED14is being lit), and measures the illuminance only while the LED14is being off (the LED14is not being lit). The mobile phone1can thereby prevent the illuminance sensor15from sensing light of the LED14.

As described above, the mobile phone1performs the illuminance sensor control process for controlling the illuminance measurement by means of the illuminance sensor15on the basis of the on-or-off state of the LED14. A procedure for the illuminance sensor control process performed by the mobile phone1will be described with reference to flowcharts shown inFIGS. 4 and 6. It is assumed that the LED14has been turned on and is lit at the beginning. Hereafter, a term such as “step S101” is shortened as “S101” by omitting the term “step”.

First, the main controller20judges whether the LED14continues to be on for a long time (S101). At this time, if the LED14continues to be on for a time length equal to or longer than a given time length (e.g., one second), the main controller20judges that the LED14continues to be on for a long time. In a case where the battery of the mobile phone1is being recharged, e.g., the main controller20judges that the LED14continues to be on for a long time. In a case where the LED14is blinking, e.g., to indicate existence of a missed call, the main controller20judges that the LED14does not continue to be on for a long time.

Upon judging that the LED14does not continue to be on for a long time, i.e., the LED14is blinking (“NO” of S101), the main controller20judges whether the LED14was turned off after being on (S103). At this time, the main controller20receives a signal indicating the on-or-off state of the LED14from the display controller23, and judges on the basis of the above signal whether the LED14was turned off after being on. If the LED14was not turned off (“NO” of S103), the process returns to S101, and the main controller20judges whether the LED14continues to be on for a long time.

If the LED14was turned off after being on (“YES” of S103), the main controller20measures the ambient illuminance by using the illuminance sensor15in order to adjust the brightness of the touch screen12on a real-time basis in accordance with the ambient illuminance (S105). Moreover, the main controller20adjusts the brightness of the touch screen12in accordance with the illuminance measured at S105(S107).

The main controller20judges whether the LED14was turned on again after judging that the LED14was turned off at S103(S109). At this time, the main controller20receives a signal indicating the on-or-off state of the LED14from the display controller23, and judges whether the LED14was turned on after being off depending on the above signal.

If the LED14was not turned on (“NO” of S109), the process returns to S105, and the main controller20performs the process from S105to S109. If the LED14was turned on (“YES” of S109), the process returns to S101, and the main controller20waits for the LED14to be turned off again.

FIG. 5shows a relationship between the on-or-off state of the LED14and the brightness of the touch screen12while the LED14is blinking. In such a case, as the LED14continues to be on for a short time, a period of time for which the illuminance is not measured is short as well, and thus it is unnecessary to control the brightness of the touch screen12in accordance with an illuminance change while the illuminance is not being measured. Moreover, if the main controller20controls the brightness of the touch screen12in accordance with the illuminance change for such a short period of time, a screen displayed on the touch screen12may possibly flicker and usability may be degraded.

Therefore, upon judging that the LED14does not continue to be on for a given time length, the main controller20controls the brightness of the touch screen12in accordance with the ambient illuminance, as shown inFIG. 5. If the LED14is turned on, the main controller20maintains the brightness value of the touch screen12that was set before the LED14is turned on in accordance with the measured illuminance value.

Meanwhile, upon judging that the LED14continues to be on for a long time (“YES” of S101), the main controller20obtains a reference value β of the brightness of the touch screen12from the memory24(S201shown inFIG. 6). The main controller20calculates an adjustment value θ of the brightness of the touch screen12depending on the reference value obtained at S201(S203).

FIG. 7shows a relationship between the on-or-off state of the LED14and the brightness of the touch screen12in a case where the LED14continues to be on for a long time. If the main controller20controls the brightness similarly as in the case where the LED14is blinking in such an occasion, and if the brightness of the touch screen12finally set while the LED14is being off is improper (e.g., too bright or too dark), there will be a problem that the improper brightness is fixed while the LED14continues to be on.

In order to address the above problem, as shown inFIG. 7, upon judging that the LED14continues to be on for a given time length, the main controller20controls the brightness of the touch screen12so that it comes close to the reference value β step by step by θ (the adjustment value calculated at S203). The above brightness control of the touch screen12performed step by step by θ is for preventing the touch screen12from changing the brightness a lot and causing a screen displayed on the touch screen12to flicker.

The adjustment value θ of the brightness of the touch screen12equals a difference between the brightness value finally set while the LED14was being off and the reference value β divided by n (a natural number). Let the brightness value finally set while the LED14was being off be x. Then, the adjustment value θ is represented by Equation (1).
θ=|x−β|/n(1)

After a given time length since the LED14was turned on (as indicated by “a” inFIG. 7), the brightness of the touch screen12is updated depending on following Equations (2) and (3). If a difference between a currently set brightness value x(now) of the touch screen12and the reference value β is greater than θ, an updated brightness value x(new) of the touch screen12is made closer to β by θ than x(now) is. The above process will be repeated until the brightness of the touch screen12reaches β. If the difference is equal to or less than θ, let x(new) be the reference value β, and the brightness of the touch screen12is fixed to β while the LED14is being on.

If the difference between the reference value β and the currently set brightness value x(now) of the touch screen12is greater than θ,
X(new)=x(now)±θ  (2)

If the difference between the reference value β and the currently set brightness value x(now) of the touch screen12is equal to or less than θ,
X(new)=β  (3)

The main controller20adjusts the brightness of the touch screen12depending on the adjustment value calculated at S203(S205). Then, the main controller20compares a lapse of time after adjusting the brightness of the touch screen12at S205with a given period of time (e.g., one second) (S207). If the above lapse of time is longer than the given period of time (“YES” at S207), the process returns to S205, and the main controller20adjusts the brightness of the touch screen12.

If the above lapse of time is not longer than the given period of time (“NO” of S207), the main controller20judges whether the brightness of the touch screen12comes close to the reference value obtained at S201(S209). At this time, if a difference between an actual brightness value of the touch screen12and the reference value is equal to or less than the adjustment value calculated at S203, e.g., the main controller20judges that the brightness of the touch screen12comes close to the reference value.

Unless the brightness of the touch screen12comes close to the reference value (“NO” of S209), the process returns to S207, and the main controller20compares a lapse of time after adjusting the brightness of the touch screen12at S205with a given period of time. If the brightness value of the touch screen12comes close to the reference value (“YES” of S209), the process returns to S101, and the main controller20waits for the LED14to be turned off. It is noted that the process always branches to “NO” at S101before the LED14is turned off (“YES” of S103).

As described above, the mobile phone1measures the illuminance only while the LED14is being off. Moreover, if the LED14blinks after being turned on, the mobile phone1adjusts the brightness of the touch screen12on the basis of the ambient illuminance. If the LED14continues to be on for a long time, the mobile phone1adjusts the brightness of the touch screen12step by step on the basis of the preset reference value. Accordingly, the mobile phone1can set optimum brightness on the touch screen12in any circumstances.

According to the first embodiment, the mobile phone1can adjust the brightness of the touch screen12on the basis of the on-or-off state of the LED14so as to prevent the illuminance sensor15from sensing light of the LED14, even if the LED14and the illuminance sensor15are arranged close to each other. The mobile phone1can thereby properly control the brightness of the touch screen12on the basis of the ambient illuminance.

Second Embodiment

A second embodiment of the present invention will be described with reference toFIGS. 8 and 9. In the following, each of portions of the second embodiment which is a same as the corresponding one of the first embodiment is given a same reference numeral, and its explanation is omitted. An electronic device of the second embodiment has a same configuration as the mobile phone1of the first embodiment shown inFIGS. 1 and 2. The electronic device of the second embodiment has, similarly as the first embodiment as shown inFIG. 3, the main controller20, the power supply circuit21, the operation input controller22, the display controller23, the memory24, the voice/sound controller25, the communication controller26and the illuminance detector27which are connected to one another through a bus so as to communicate with one another.

The mobile phone1of the first embodiment controls the brightness of the touch screen12without regard to the ambient illuminance while the LED14is being on. Therefore, if the LED14continues to be on for a long time, the ambient illuminance may possibly greatly change while the LED14is being on. In such a case, currently set brightness of the touch screen12may possibly be much different from optimal brightness of the touch screen12for actual ambient illuminance, and the brightness of the touch screen12may change a lot if the LED14is turned off after being on, causing a screen displayed on the touch screen12to look flickering as viewed by a user.

In order to address the above problem that may occur in a case where the brightness of the touch screen12that was set while the LED14was being on is much different from the brightness of the touch screen12calculated depending on illuminance measurement after the LED14is turned off, the electronic device of the second embodiment is configured to change the brightness of the touch screen12step by step so that it comes closer to the brightness of the touch screen12calculated depending on the illuminance measurement, and to thereby reduce flickering of a screen on the touch screen12.

A procedure for the illuminance sensor control process for controlling the on-or-off state of the illuminance sensor15performed by the mobile phone1of the second embodiment on the basis of the on-or-off state of the LED14will be described with reference to a flowchart shown inFIG. 8. The process from S101to S109is performed similarly as for the first embodiment, and the process after branching to “YES” at S101is different from that of the first embodiment.

Upon judging that the LED14continues to be on for a long time at S101(“YES” of S101), the main controller20performs a process from S301to S315described later, if the LED14is turned off after being on. First, the main controller20measures ambient illuminance by using the illuminance sensor15(S301). Then, the main controller20calculates an adjustment value Δ of the brightness of the touch screen12on the basis of the illuminance value measured at S301(S303).

The above adjustment value Δ corresponds to a value by which the brightness of the touch screen12changes at once while changing step by step. As indicated by Equation (4), Δ equals a difference between a brightness value y that was set while the LED14was being on and a brightness value z of the touch screen12calculated on the basis of the illuminance measurement just after the LED14was turned off at S301divided by p (a natural number).
Δ=|z−y|/p(4)

The main controller20adjusts the brightness of the touch screen12on the basis of the adjustment value Δ calculated at S303so that the brightness of the touch screen12comes close to an optimal value for the illuminance measured at S301(S305).

That is, as shown in following Equations (5) and (6), if a difference between a brightness x(now) of the touch screen12that is set just after the LED14is turned off and a brightness value x(led) of the touch screen12calculated on the basis of the illuminance measured at S301is equal to or more than Δ, an updated brightness value x(new) of the touch screen12is closer to x(led) by Δ than x(now) is.

If the difference between the brightness x(led) of the touch screen12calculated on the basis of the illuminance measurement and the currently set brightness x(now) of the touch screen12is greater than Δ,
x(new)=x(led)±Δ  (5)

If the difference between the brightness x(led) of the touch screen12calculated on the basis of the illuminance measurement and the currently set brightness x(now) of the touch screen12is equal to or less than Δ,
x(new)=x(led)  (6)

The adjustment of the brightness of the touch screen12based on the adjustment value calculated at S303is performed until the difference between the brightness set on the touch screen12and the reference value decreases to Δ or less. If this difference is equal to or less than Δ, x(new) is equal to x(led), and the main controller20controls adjustment of the brightness of the touch screen on the basis of the brightness x(led) of the touch screen12which is calculated on the basis of the illuminance measurement.

The main controller20compares a lapse of time after adjusting the brightness of the touch screen12at S305with a given period of time (e.g., one second) (S307). If the above lapse of time is longer than the given period of time (“YES” of S307), the process returns to S305, and the main controller20performs the process from S305to S307.

If the above lapse of time is not longer than the given period of time (“NO” of S307), the main controller20judges whether the brightness of the touch screen12adjusted at S305comes close to the reference value based on the illuminance value obtained at S301(S309). At this time, if a difference between an actual brightness value of the touch screen12and the reference value is equal to or less than the adjustment value Δ calculated at S303, the main controller20judges that the brightness of the touch screen12comes close to the reference value. Unless the brightness of the touch screen12comes close to the reference value (“NO” of S309), the process returns to S307, and the main controller20again compares a lapse of time after adjusting the brightness of the touch screen12at S305with a given period of time.

When the brightness of the touch screen12comes close to the reference value (“YES” of S309), the main controller20measures the ambient illuminance by using the illuminance sensor15in order to adjust the brightness of the touch screen12on a real-time basis in accordance with the ambient illuminance (S311). Moreover, the main controller20adjusts the brightness of the touch screen12on the basis of the illuminance measured at S311(S313).

The main controller20judges whether LED14was turned on again after the LED14was turned off before S301(S315). At this time, the main controller20receives a signal indicating the on-or-off state of the LED14from the display controller23and judges on the basis of the above signal whether the LED14was turned on after being off.

If the LED14was not turned on (“NO” of S315), the process returns to S311, and the main controller20performs the process from S311to S315. If the LED14was turned on (“YES” of S315), the process returns to S101and the main controller20waits for the LED14to be turned off again.

As described above, the mobile phone1measures the illuminance only while the LED14is being off. Moreover, if the LED14blinks before being turned off, the mobile phone1adjusts the brightness of the touch screen12on the basis of the ambient illuminance. If the LED14continues to be on for a long time, the mobile phone1adjusts the brightness of the touch screen12on the basis of the ambient illuminance just after the LED14is turned off. Accordingly, the mobile phone1can set optimal brightness on the touch screen12in any circumstances.

According to the second embodiment, the mobile phone1can adjust the brightness of the touch screen12on the basis of the on-or-off state of LED14and the ambient illuminance so as to prevent the illuminance sensor15from sensing light of the LED14, even if the LED14and the illuminance sensor15are arranged close to each other. The mobile phone1can thereby properly control the brightness of the touch screen12on the basis of the ambient illuminance.

Although the mobile phone1has been explained as an example, the electronic device of the present invention is not limited to the mobile phone1. The present invention can be applied to any kind of electronic device having a display, an LED and an illuminance sensor, such as a PHS (personal handy phone system), a PDA (personal digital assistant) and so on.