JP2008287175A - Reproduction display device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save electric power while keeping good appearance of an LCD even when a battery is used. <P>SOLUTION: When an AC adaptor 11 is not inserted into a DC jack 10, since a measured voltage A (v) inputted from a voltage detection circuit 31 is lower than the power voltage of the AC adaptor 11, the display device judges that the power source is a secondary battery 9 as well as judges whether or not a relation of measured voltage A (v)≥threshold voltage α (v) is satisfied. When A≥α is satisfied, this means the secondary battery 9 is just sufficiently charged and has a sufficient electric capacity, initial setting is carried out in a normal mode in the same way as when the AC adaptor 11 is connected. When A<α, initial setting in a power saving mode is carried out. In the power saving mode, the luminance of a backlight 12b is set to be lower than a normal level, as well as the gain of a liquid crystal panel 12a is set to be higher than a normal level, which contributes to power saving of a digital camera 1 while maintaining good appearance of a through image and a reproduced image displayed on a LCD 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reproduction display apparatus and method, and more particularly to a reproduction display apparatus and method capable of using a plurality of types of power supplies.

  Portable reproduction display devices that reproduce images (including characters) and display them on a liquid crystal display including a liquid crystal panel and a backlight, such as digital cameras, notebook computers, and game machines, are widely used. Such a playback display device generally uses either a primary battery such as an AA dry battery or a secondary battery such as a rechargeable lithium ion battery as a power source for driving, and is connected to an AC adapter. Many of them are capable of receiving power from commercial AC power. Hereinafter, when it is not necessary to distinguish between a primary battery and a secondary battery, they are simply referred to as “batteries”.

  When the playback display device is driven by a battery, since the electric capacity is finite, drive control such as switching to a power saving mode is performed (for example, Patent Documents 1 to 5). In the camera-integrated VTR described in Patent Document 1, when the power supply system determination unit detects a battery, the display system switching unit is set to the power saving mode. When the power supply system determination unit detects the AC adapter, the normal mode is set. In the power saving mode, only one of the finder unit and the liquid crystal panel unit is turned on. In the normal mode, the finder unit is turned on, and the ON / OFF state of the liquid crystal panel unit is switched according to the situation.

  The imaging system described in Patent Document 2 uses a secondary battery pack or a charging device. When a secondary battery pack is mounted as a power source, this is detected by the power source detection means and controlled to reduce the brightness of the backlight unit of the display unit, thereby reducing the power consumption in the display unit.

  In the electronic still camera described in Patent Document 3, in order to reduce power consumption, the drive frequency of the image sensor is lowered and the drive voltage required for reading is lowered.

  When the notebook computer described in Patent Document 4 is switched from AC drive to battery drive, the display brightness is reduced to save battery power. At this time, the decrease in the display brightness is moderately noticed by the user. To do.

The digital camera described in Patent Document 5 detects whether a battery or a power source from an AC power source is used as a power source by a power source detection circuit, and the battery used when the battery is used as a power source Detects whether the battery is a dedicated battery, performs power supply control to the display unit, and performs power supply control to the character liquid crystal display device.
Japanese Patent Application No. 11-0666828 JP-A-11-146254 JP 2003-153093 A JP 2001-184046 A JP 2001-230960 A

  As described above, in the case of using a battery, generally, the luminance of the backlight used in the liquid crystal display is lowered. However, when the brightness of the backlight is lowered, there is a problem that the screen becomes dark and looks bad.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a reproduction display device and method that can save power while maintaining a good appearance of a liquid crystal display even when a battery is used. .

  In order to solve the above-described problems, the display device of the present invention can use a battery and an AC adapter as a power source, and also includes a liquid crystal panel that reproduces and displays an image, and a backlight that illuminates the image from behind. In a playback display device having a display, a power source type discriminating unit that discriminates whether the power source is a battery or an AC adapter, and when the power source type discriminating unit discriminates that the power source is a battery, the power source is an AC adapter. Compared to the above case, a control unit is provided which lowers the luminance of the backlight and simultaneously increases the gain of the liquid crystal panel. The battery may be a primary battery or a secondary battery whose voltage is lower than a predetermined threshold value.

  The reproduction display method of the present invention is a reproduction display method in which a battery and an AC adapter can be used as a power source, and an image is reproduced and displayed on a liquid crystal display including a liquid crystal panel and a backlight that illuminates the liquid crystal panel from behind. A power source type determining step for determining whether the power source is a battery or an AC adapter; and when the power source is determined to be a battery, the brightness of the backlight is lowered at the same time as the case where the power source is an AC adapter. And a control step for increasing the gain. The battery may be a primary battery or a secondary battery whose voltage is lower than a predetermined threshold value.

  According to the reproduction display device and method of the present invention, when a battery is used as a power source, the backlight brightness is lowered below a predetermined luminance value at the same time as increasing the gain of the liquid crystal panel above a predetermined gain value. Even when using a battery, it is possible to save power while maintaining a good appearance of the liquid crystal display. In addition, since the battery is a primary battery or a secondary battery whose voltage is lower than a predetermined threshold value, the appearance of the liquid crystal display is kept good even when a battery having an insufficient electric capacity is used. Power saving can be achieved as it is.

  The digital camera which is an embodiment of the playback display device of the present invention can use a known secondary battery and an AC adapter as a power source, and when the secondary battery is used and its voltage is lower than a predetermined threshold, liquid crystal By increasing the gain of the liquid crystal panel that constitutes the display above the gain in the normal mode using an AC adapter, and simultaneously reducing the brightness of the backlight that constitutes the liquid crystal display from that in the normal mode, the appearance of the liquid crystal display is improved. It is intended to save power while maintaining almost the same quality as in the normal mode.

  As shown in FIG. 1, a retractable photographing lens 3 and a strobe light emitting unit 4 are provided on the front surface of the cassette body 2 of the digital camera 1. Further, on the upper surface of the cassette body 2, there are provided a shutter button 5, a mode switching dial 6 provided rotatably around the shutter button 5, and a power button 7 having a button shape.

  A battery cover 8 is provided on the lower surface of the cassette body 2, and when the battery cover 8 is opened, a battery chamber and a memory card slot (not shown) are exposed. In the battery chamber, a rechargeable secondary battery (for example, a nickel metal hydride battery) 9 (see FIG. 3), which serves as a power supply when the digital camera 1 is carried, is detachably loaded. A memory card 58 (see FIG. 3) for storing image data is detachably loaded in the memory card slot. Note that the secondary battery 9 may be incorporated in the cassette body 2 so as not to be detachable.

  A DC jack 10 is provided on the side surface of the cassette body 2. The plug 11 a of the AC adapter 11 is inserted into the DC jack 10. The AC adapter 11 includes a plug 11a, an AC adapter main body 11b, a cable 11c for connecting them, and a plug 11d provided directly on the AC adapter main body 11b and inserted into a power outlet.

  When the plug 11a is inserted into the DC jack 10 and the plug 11d is inserted into a power outlet, the AC adapter main body 11b converts the commercial AC power supplied from the power outlet into a direct current, and the cable 11c, the plug 11a, and the DC jack 10 are used. The digital camera 1 is supplied.

  As shown in FIG. 2, a liquid crystal display (LCD) 12, a zoom button 13, a multi-function cross button 14, a menu / execution button 15, a liquid crystal display / return button 16, and a playback mode button 17 are displayed on the back of the cassette body 2. Etc. are provided. Hereinafter, when these buttons 13 to 17 and the mode switching dial 6 are collectively called, they are referred to as an operation unit 18 (see FIG. 3).

  The LCD 12 displays a through image before shooting and is used as an electronic viewfinder, and displays various setting screens, messages (characters) and the like in addition to a preview image of the shot image and a reproduced image read from the memory card 58. indicate. The LCD 12 includes a light-transmissive liquid crystal panel 12a that displays an image and a backlight 12b that illuminates the liquid crystal panel 12a from behind (see FIG. 3).

  As shown in FIG. 3, the main electrical configuration of the digital camera 1 includes a power supply type determination unit 25, an imaging unit 26, and a control unit 27. The power supply type discriminating unit 25 includes a secondary battery 9, a DC jack 10, a resistor 28, a switch circuit 29, a charge control circuit 30, a voltage detection circuit 31, and a CPU 35.

  A power supply circuit 32 is connected to the switch circuit 29. When the switch circuit 29 is turned on, the power supply circuit 32 boosts and lowers the power supply voltage from the secondary battery 9 or the AC adapter 11 to a voltage corresponding to each part of the digital camera 1 and supplies it to each part.

  The DC jack 10 includes three terminals 10 a, 10 b, and 10 c, and the terminal 10 a is connected to the switch circuit 29 and the charge control circuit 30. The terminal 10 b is connected to one end of the resistor 28, the charging control circuit 30, and the negative terminal of the secondary battery 9. The terminal 10c is connected to the other end of the resistor 28 and grounded. The switch circuit 29 is turned on / off by the CPU 35 of the control unit 27 that has received the pressing operation of the power button 7.

  When the plug 11a is not inserted into the DC jack 10, since the terminals 10b and 10c are short-circuited, the negative terminal of the secondary battery 9 is grounded, and the positive terminal of the secondary battery 9 is connected to the charging control circuit 30. To the switch circuit 29. In this state, when the switch circuit 29 is turned on, the power from the secondary battery 9 is supplied to the power supply circuit 32, and the power adjusted in voltage by the power supply circuit 32 is supplied to each part of the digital camera 1.

  The voltage detection circuit 31 measures the power supply voltage from the secondary battery 9 applied to the charge control circuit 30 and sends it to the CPU 35. Since the power supply voltage from the secondary battery 9 is lower than the power supply voltage of the AC adapter 11, the CPU 35 determines that the power supply is the secondary battery 9.

  Further, the CPU 35 compares the measured voltage A (v) input from the voltage detection circuit 31 with a predetermined threshold voltage α (v), and determines whether A ≧ α. The threshold voltage α is a voltage at which the secondary battery 9 is almost fully charged. When A ≧ α, the CPU 35 performs initial setting in the normal mode without any restrictions same as when the AC adapter 11 is connected. When A <α, the CPU 35 performs initial setting in the power saving mode.

  In the power saving mode, the brightness of the backlight 12b of the LCD 12 is lowered from the normal level in the normal mode, and at the same time, the gain of the liquid crystal panel 12a of the LCD 12 is raised from the normal level in the normal mode. Even if the brightness of the backlight 12b is lowered, the screen of the LCD 12 becomes dark and the display image becomes less vivid and looks worse. However, by increasing the gain of the liquid crystal panel 12a, the contrast of the display image is increased and the vividness is increased. Therefore, the power consumption of the LCD 12 can be reduced without deteriorating the appearance of the LCD 12.

  When the plug 11 a is inserted into the DC jack 10, the short circuit between the terminals 10 b and 10 c is released by the plug 11 a, so that the negative terminal 34 of the AC adapter 11 is grounded and the secondary battery 9 is connected via the resistor 28. The negative terminal of the AC adapter 11 is grounded, and the positive terminal 33 of the AC adapter 11 is connected to the switch circuit 29 and the charge control circuit 30. In this state, when the switch circuit 29 is off, the charging control circuit 30 is driven by the AC adapter 11 and the secondary battery 9 is charged.

  When the switch circuit 29 is on, power is supplied from the AC adapter 11 to the power supply circuit 32, and power adjusted in voltage by the power supply circuit 32 is supplied to each part of the digital camera 1. Further, since the power supply voltage from the AC adapter 11 is applied to the charging control circuit 30, the voltage detection circuit 31 detects this voltage and sends it to the CPU 35. The CPU 35 determines that the power source is the AC adapter 11 based on the voltage input from the voltage detection circuit 31, and performs the initial setting in the normal mode in which the performance of the digital camera 1 is fully exhibited.

  In the normal mode, the luminance of the backlight 12b of the LCD 12 is set to a normal level that is high enough that the display image on the liquid crystal panel 12a is sufficiently bright and clear. The gain of the liquid crystal panel 12a is set to a normal level.

  The imaging unit 26 includes a photographing lens 3, a CCD 38, an AFE (analog front end) 40, a motor driving unit 41, a CCD driver 42, and a TG (timing generator) 43. A CMOS image sensor may be used instead of the CCD 38.

  The photographing lens 3 incorporates a zoom mechanism, a focus mechanism, and a diaphragm device. In response to the zoom operation of the operation unit 18, the zoom mechanism performs zooming by moving the zoom lens constituting the photographing lens 3. The focus mechanism moves the focus lens to perform focusing. The diaphragm device adjusts the light intensity of the subject light incident on the CCD 38 by adjusting the diaphragm. The zoom mechanism, the focus mechanism, and the diaphragm device are each driven by the motor drive unit 41 based on a command from the CPU 35.

  The CCD 38 is disposed behind the photographing lens 3, and subject light transmitted through the photographing lens 3 enters the light receiving surface of the CCD 38. The CCD 38 is provided with a large number of light receiving portions on its light receiving surface, and is driven by a drive signal from the CCD driver 42 to convert an object optical image exposed by each light receiving portion into an analog imaging signal and output it.

  The CCD driver 42 is driven by a synchronization pulse from the TG 43, and reads a through image signal from the CCD 38 when displaying a through image or calculating an appropriate exposure value, and reads out an image signal of a frame image from the CCD 38 at the time of shooting.

  The imaging signal output from the CCD 38 is sent to the AFE 40. The AFE 40 includes a CDS circuit 40a, an AMP circuit 40b, and an A / D converter 40c, and operates in synchronization with the charge reading operation of the CCD 38 by receiving a synchronization pulse from the TG 43.

  The CDS circuit 40a removes noise from the imaging signal by performing correlated double sampling. The AMP circuit 40b amplifies the imaging signal with a gain corresponding to the imaging sensitivity set by the CPU 35. The A / D converter 40c converts the imaging signal from the AMP circuit 40b into digital image data.

  The control unit 27 includes a CPU 35, an image input controller 45, a digital image processing unit 46, a compression / decompression processing unit 47, an AF detection unit 48, an AE / AWB detection unit 49, a media controller 50, an internal memory 51, a panel driver 52 and BL ( It comprises a backlight) driver 53. These are controlled by the CPU 35 via the data bus 54 and can exchange data with each other.

  The CPU 35 controls each unit based on various signals from the shutter button 5, the power button 7, and the operation unit 18. A ROM 55, a RAM 56, and a flash device 57 are connected to the CPU 35. The strobe device 57 causes the strobe light emitting unit 4 to emit light in accordance with a command signal from the CPU 35.

  In the ROM 55, a program for executing various sequences, a program corresponding to various program diagrams for determining a combination of shutter speed, aperture value, and photographing sensitivity, and the like are written. To control. The RAM 56 is used as a work memory that temporarily stores data necessary for executing a shooting sequence and the like.

  The image input controller 45 controls input / output of image data to / from each unit via the data bus 54 in accordance with a control command from the CPU 35. The digital image processing unit 46 performs various image processing such as gradation conversion, white balance correction, and γ correction processing and YC conversion processing on the input image data.

  The AF detection unit 48 detects the contrast of the image being photographed using the image data output from the image input controller 45 to focus the photographing lens 3, and sends the contrast information to the CPU 35. The CPU 35 refers to the contrast information and drives the focus mechanism of the photographing lens 3 via the motor driving unit 41 so that the contrast of the image being photographed is maximized.

  Based on the image data from the image input controller 45, the AE / AWB detection unit 49 detects the subject luminance and the type of the light source, and sends them to the CPU 35. The CPU 35 calculates the exposure value using the subject luminance from the AE / AWB detection unit 49. Further, the CPU 35 sets the white balance parameter of the digital image processing unit 46 based on the type of the light source.

  The CPU 35 converts the exposure value when displaying the through image into a combination of the aperture value, shutter speed, and shooting sensitivity according to the through image program, and the exposure value when shooting is determined according to the shooting program. Convert to a combination of

  The media controller 50 controls writing and reading of data in the memory card 58. The image data to be recorded is processed by the digital image processing unit 46 and the compression / decompression processing unit 47, sent to the media controller 50, and written to the memory card 58. Further, at the time of reproduction, the image data recorded on the memory card 58 is read out by the media controller 50, sent to the compression / decompression processing unit 47 and decompressed, and then sent to the internal memory 51.

  The internal memory 51 is, for example, an SDRAM capable of high-speed reading and writing. The internal memory 51 is used for temporarily writing through image data to be displayed on the LCD 12 and frame image data to be recorded on the memory card 58.

  The panel driver 52 reads the image data from the internal memory 51 in synchronization with the vertical synchronizing signal for reproduction when displaying the through image and the reproduced image, and drives the liquid crystal panel 12a of the LCD 12 based on the image data. As a result, a through image captured by the CCD 38 is displayed in real time on the liquid crystal panel 12a, and an image read from the memory card 58 is reproduced and displayed.

  In addition, the panel driver 52 increases the gain of the liquid crystal panel 12a above the normal level in the power saving mode. Accordingly, since the contrast of the liquid crystal panel 12a is increased, it is possible to prevent the appearance of the LCD 12 from being deteriorated even when the luminance of the backlight 12b is lowered from the normal level in the power saving mode.

  The BL driver 53 is controlled by the CPU 35 via the data bus 54 and drives the backlight 12 b of the LCD 12. The BL driver 53 lowers the luminance of the backlight 12b below the normal level in the power saving mode.

  The operation of the digital camera 1 configured as described above will be described with reference to the flowcharts of FIGS. 4, 5, and 6. The secondary battery 9 is preloaded in the battery chamber of the cassette body 2. When the power button 7 is pressed (st1), the CPU 35 sends a command signal to the switch circuit 29 of the power supply type determination unit 25 to turn on the switch circuit 29.

  When the plug 11a of the AC adapter 11 is inserted into the DC jack 10 (st2), the power from the AC adapter 11 is supplied to the power circuit 32, and the power adjusted by the power circuit 32 is supplied to each part of the digital camera 1. Supplied.

  The voltage detection circuit 31 detects the power supply voltage from the AC adapter 11 applied to the charge control circuit 30 and sends it to the CPU 35. The CPU 35 determines that the type of power supply is the AC adapter 11 and performs initial setting in the normal mode (st3).

  In the initial setting in the normal mode, as shown in FIG. 5, the backlight 12b of the LCD 12 is driven at a sufficiently high normal level brightness (st11) and the gain of the liquid crystal panel 12a is normally set during shooting and playback. The level is set (st12). Thereby, since the liquid crystal panel 12a is illuminated by the sufficiently bright backlight 12b, it is possible to observe a through image and a reproduced image with good appearance.

  Returning to FIG. 4, when the plug 11 a of the AC adapter 11 is not inserted into the DC jack 10 (st <b> 2), the power from the secondary battery 9 is supplied to the power circuit 32 and the power adjusted by the power circuit 32. Is supplied to each part of the digital camera 1.

  Since the measurement voltage A (v) input from the voltage detection circuit 31 is lower than the power supply voltage of the AC adapter 11, the CPU 35 determines that the power supply is the secondary battery 9, and the measurement voltage A (v) ≧ threshold. It is determined whether or not the voltage is α (v) (st4).

  When A ≧ α, the secondary battery 9 has a sufficient electric capacity immediately after being fully charged. Therefore, the initial setting in the same normal mode as when the AC adapter 11 is connected is performed (st3). When A <α Since the electric capacity is not sufficient, for example, the time has elapsed since the battery was charged, the initial setting in the power saving mode is performed (st5).

  In the initial setting in the power saving mode, as shown in FIG. 6, the luminance of the backlight 12b of the LCD 12 is set lower than the normal level (st21), and at the same time, the gain of the liquid crystal panel 12a is set higher than the normal level ( st22). Thereby, it is possible to achieve power saving of the digital camera 1 while maintaining a good appearance of the through image and the reproduced image displayed on the LCD 12.

  In the above embodiment, the secondary battery is used as the power battery, but an example of the power supply type determination unit using the primary battery will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same member as the said embodiment, and description is abbreviate | omitted. In the power supply type discriminating unit 60, the primary battery 61 is connected between the terminals 10 a and 10 b of the DC jack 10.

  One terminal of the primary battery 61 is connected to the power supply circuit 32 via the switch circuit 29. The other terminal of the primary battery 61 is connected to the input of the power supply circuit 32 through the resistor 28. An intermediate terminal 62 between the other terminal of the primary battery 61 and the resistor 28 is connected to the voltage detection circuit 31. The voltage detection circuit 31 measures the voltage at the intermediate terminal 62 and inputs the result to the CPU 35.

  When the AC adapter 11 is not connected to the DC jack 10, since the terminals 10b and 10c are short-circuited, the other terminal of the primary battery 61 is grounded, and when the switch circuit 29 is turned on, the power is supplied from the primary battery 61. Power is supplied to the circuit 32. At this time, since the intermediate terminal 62 is grounded, the measured voltage of the intermediate terminal 62 is substantially 0 (v) (Low), and this is input from the voltage detection circuit 31 to the CPU 35. Thereby, CPU35 discriminate | determines that a power supply is the primary battery 61, and performs the initial setting by a power saving mode.

  When the AC adapter 11 is connected to the DC jack 10, the short circuit between the terminals 10b and 10c is released. Therefore, when the switch circuit 29 is turned on, the power from the primary battery 61 is cut off, and instead from the AC adapter 11. Power is supplied to the power supply circuit 32. Since the power supply voltage from the AC adapter 11 is applied to the intermediate terminal 62 via the resistor 28, the measured voltage at the intermediate terminal 62 becomes higher than Low (Hi), and this is input from the voltage detection circuit 31 to the CPU 35. Is done. Thus, the CPU 35 determines that the power source is the AC adapter 11 and performs initial setting in the normal mode.

  As a power supply battery, both a primary battery and a secondary battery can be used. In the case of a digital camera that selects and uses one of these, for example, the charge control circuit 30 of the power supply type determination unit 25 shown in FIG. May be controlled by the CPU 35. This will be briefly described. When the primary battery 61 is loaded instead of the secondary battery 9 of the power supply type determination unit 25, if the switch circuit 29 is in an off state, the primary battery 61 is charged when the AC adapter 11 is connected to the DC jack 10, An accident such as a rupture can occur. However, if it is determined that the primary battery 61 is loaded by the measured voltage from the voltage detection circuit 31 before connecting the AC adapter 11 to the DC jack 10, the CPU 35 sends a control signal to the charge control circuit 30. Since the charging operation of the charging control circuit 30 is stopped, the primary battery 61 is prevented from being charged by mistake.

  In general, a primary battery such as an AA alkaline battery has a higher voltage than a secondary battery such as a nickel metal hydride battery. For example, the voltage of a new alkaline dry battery is generally about 1.6 (v), whereas the voltage immediately after a nickel-metal hydride battery is fully charged is about 1.2 (v).

  In the embodiment described above, a digital camera has been described as an example of a reproduction display device. However, the present invention is not limited to this, and any device that reproduces and displays an image on a backlit LCD may be used. For example, a notebook computer, a game machine, a PDA, or the like may be used.

It is a perspective view which shows the external appearance of the digital camera which implemented this invention from diagonally forward. It is a top view which shows the back side of a digital camera. It is a block diagram which shows the electrical structure of a digital camera. It is a flowchart which shows the procedure of initial setting. It is a flowchart which shows the setting in normal mode. It is a flowchart which shows the setting in a power saving mode. It is a block diagram which shows the example of another power supply type discrimination | determination part.

Explanation of symbols

1 Digital Camera 9 Secondary Battery 10 DC Jack 11 AC Adapter 12 LCD
12a Liquid crystal panel 12b Backlight 25, 60 Power supply type determination unit 26 Imaging unit 27 Control unit 29 Switch circuit 31 Voltage detection circuit 32 Power supply circuit 35 CPU
52 Panel driver 53 BL driver 61 Primary battery

Claims (4)

In a playback display device comprising a liquid crystal panel that can use a battery and an AC adapter as a power source, and that includes a liquid crystal panel that reproduces and displays an image and a backlight that illuminates the panel from behind,
A power source type discriminating unit for discriminating whether the power source is a battery or an AC adapter;
A controller that increases the gain of the liquid crystal panel at the same time as lowering the luminance of the backlight when the power supply type determination unit determines that the power supply is a battery, as compared with the case where the power supply is an AC adapter. A playback display device.   The reproduction display device according to claim 1, wherein the battery is a primary battery or a secondary battery having a voltage lower than a predetermined threshold value. In a playback display method in which a battery and an AC adapter can be used as a power source, and an image is played back and displayed on a liquid crystal display including a liquid crystal panel and a backlight that illuminates the panel from behind.
A power source type determining step for determining whether the power source is a battery or an AC adapter;
And a control step of increasing the gain of the liquid crystal panel at the same time as lowering the luminance of the backlight when the power source is determined to be a battery than when the power source is an AC adapter.   4. The reproduction display method according to claim 3, wherein the battery is a primary battery or a secondary battery having a voltage lower than a predetermined threshold.

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