JP5807546B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device driven by a battery in order to display an image with image light, and more particularly to a technique for reducing power consumption by the image display device.

  Patent Document 1 discloses a conventional example of an image display device driven by a battery in order to display an image with image light. In this conventional example, the target image is reproduced as a still image or a complete or partial moving image by sequentially reproducing the plurality of frames based on an image signal representing the target image configured as a sequence of a plurality of frames. Configured to display as

  Patent Document 1 discloses a technique for switching the luminance value and frame rate of an image to be displayed in accordance with the switch operation of a viewer of the display image, thereby reducing power consumption.

JP 2002-189464 A

  However, in the conventional technique disclosed in Patent Document 1, the luminance value and the frame rate of the display image are manually switched, and are not automatically switched. For this reason, in this conventional technique, in order to reduce the power consumption by switching the luminance value and the frame rate of the display image, an additional operation is required for the user, which is troublesome.

  Based on such knowledge, the present invention is an image display device that is driven by a battery to display an image with image light, and sequentially transfers a plurality of frames representing the target image to the display unit. It is an object of the present invention to provide a device that controls the image to match the type of target image, which is a still image or a moving image.

In order to solve the problem, according to one aspect of the present invention, the target is obtained by sequentially reproducing the plurality of frames based on an image signal representing a target image configured as a sequence of a plurality of frames. An image display device driven by a battery to display an image as a still image or a complete or partial moving image, wherein at least a part of the plurality of frames is transferred at a fixed or variable transfer rate A transfer unit; and a display unit that displays the target image by reproducing a plurality of frames transferred from the transfer unit at a fixed frame rate or a variable frame rate that changes according to the transfer rate; Power consumption that controls the power consumption of the image display device so that the power consumption of the image display device is reduced when the remaining battery level is below the reference level The power consumption control unit includes a plurality of image types including the target image as a moving image and a still image based on the image attribute signal or image attribute data representing the attribute of the target image. Classified as one of
The moving image refers to the type of a certain object that moves in a movement area, which is an area where a certain object moves on the screen, the size of the movement area, which means a ratio to the area of the entire screen, and its movement From the three viewpoints of the occurrence frequency of the area, using the first moving image or the table software that the cursor moves sporadically in a very small area in response to the user's operation on the screen with the background of the still image When creating a table on the screen, the frame of the table being created sporadically moves in a small area, and the object in the frame displayed on a part of the screen is medium A third moving image that continuously moves within a region of size or a fourth moving image whose display image moves continuously over the entire screen,
(A) When the target image is classified as the still image , the power consumption control unit is different from the previous frame among the plurality of frames while maintaining the transfer rate at a normal rate. The transfer unit is controlled so that only the frame is transferred to the display unit, thereby reducing the number of frames transferred, which is the number of frames transferred by the transfer unit among the plurality of frames. ) When the target image is classified into the first moving image or the second moving image, the transfer rate is reduced to a first rate lower than the normal rate, or the transfer rate is While maintaining the normal rate, the luminance value when the target image is displayed is reduced, and (c) when the target image is classified into the third moving image or the fourth moving image, Transfer An image display device is provided that includes a transfer control unit that reduces the second rate to a second rate lower than the first rate.
The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is numbered, and is described in the form of quoting the section numbers of other sections as necessary. In this way, each section is referred to the section number of the other section. By describing in the format, the technical features described in each section can be appropriately made independent according to the properties.

(1) Displaying the target image as a still image or a complete or partial video by sequentially reproducing the plurality of frames based on an image signal representing the target image configured as a sequence of a plurality of frames. An image display device driven by a battery to
A transfer unit that transfers at least a part of the plurality of frames at a fixed or variable transfer rate;
A display unit that displays the target image by reproducing a plurality of frames transferred from the transfer unit at a fixed frame rate or a variable frame rate that changes according to the transfer rate;
A power consumption control unit that controls the power consumption so that the power consumption by the image display device decreases when the remaining amount of the battery is less than or equal to a reference remaining amount,
The power consumption control unit, based on the image signal or an image attribute signal or image attribute data representing the attribute of the target image, the target image as one of a plurality of image types including a moving image and a still image. If the target image is classified as a still image, the number of frames transferred, which is the number of frames transferred by the transfer unit among the plurality of frames, is reduced, or when the target image is classified as a still image, or An image display device including a transfer control unit that controls the transfer unit so that the transfer rate is lowered.

  Here, in order to explain the relationship between the “number of frames transferred” and the “transfer rate”, the term “transfer rate” focuses on the clock transfer operation of the transfer unit, and the transfer unit represents the original image. When it is defined to mean a time interval between frames (that is, a frequency of a reference clock input to the transfer unit) when it is assumed that a plurality of frames are sequentially transferred without thinning out, “frame transfer number” is obtained. In the first place, the term means the number of frames actually transferred by the transfer unit among a plurality of frames representing the original image. According to those definitions, even if the “transfer rate” is not reduced, It is possible to reduce the “frame transfer number”. On the other hand, if the term “transfer rate” is defined to mean the number of frames actually transferred by the transfer unit per certain time in consideration of the presence or absence of frame thinning, the term “transfer rate” This is synonymous with the term “frame transfer number”. However, in this specification, “transfer rate” is used in the former sense for convenience of explanation.

(2) Displaying the target image as a still image or a complete or partial video by sequentially reproducing the plurality of frames based on an image signal representing the target image configured as a sequence of a plurality of frames. An image display device driven by a battery to
A transfer unit that transfers at least a part of the plurality of frames at a fixed or variable transfer rate;
A display unit that displays the target image by reproducing a plurality of frames transferred from the transfer unit at a fixed frame rate or a variable frame rate that changes according to the transfer rate;
A power consumption control unit that controls the power consumption so that the power consumption by the image display device decreases when the remaining amount of the battery is less than or equal to a reference remaining amount,
The power consumption control unit, based on the image signal or image attribute signal or image attribute data representing the attribute of the target image, the target image, a still image, a moving image with a low moving image, a moving image with a high moving image Into one of multiple image types, including
(A) When the target image is classified as a still image, only the frame different from the previous frame is transferred to the display unit while maintaining the transfer rate at a normal rate. And controlling the transfer unit, thereby reducing the number of frames transferred, which is the number of frames transferred by the transfer unit among the plurality of frames,
(B) When the target image is classified as a moving image having a low moving image degree, the transfer rate is reduced to a first rate lower than the normal rate, or the transfer rate is maintained at the normal rate. While reducing the luminance value when the target image is displayed,
(C) An image display device including a transfer control unit that reduces the transfer rate to a second rate lower than the first rate when the target image is classified as a moving image having a high moving image degree.

(3) Furthermore,
The image display device according to (1) or (2), further including a remaining amount determination unit that determines the remaining amount of the battery during an invalid display period in which no image is displayed in the image signal.

(4) The transfer control unit includes first classification means for classifying the target image into one of the plurality of image types based on a temporal correlation between frames of the target image. (3) The image display device according to any one of items.

(5) The transfer control unit
The image signal has a predetermined cutoff frequency so as to be lower than the frame frequency of the image signal. When the image signal is input, a component having a frequency equal to or higher than the frame frequency is included in the image signal. A low-pass filter having attenuation characteristics;
A second classification for classifying the target image into one of the plurality of image types based on the amplitude of the signal output from the low-pass filter with respect to the image signal input to the low-pass filter. The image display device according to any one of (1) to (3), including:

(6) The image display device stores the image data representing the image signal as a file and associated with the file name and the file type identifier,
The transfer control unit includes a third classification unit that classifies the target image into one of the plurality of image types based on the file type identifier that is related to the type of the target image. The image display device according to any one of items 1) to (3).

(7) The image display device displays the target image by activating an application program whose type is selected according to the type of the target image,
The transfer control unit includes fourth classification means for classifying the target image into one of the plurality of image types based on the type of the activated application program. (1) to (3) An image display device according to any one of the above.

(8) When the target image is further classified as a moving image, the power consumption control unit displays the target image without reducing the frame transfer number or the transfer rate. The image display device according to any one of items (1) to (7), further including a luminance value control unit that reduces a luminance value at the time.

(9) The transfer control unit controls the transfer unit so that the frame transfer number decreases or the transfer rate decreases as the remaining battery level decreases. An image display device according to any one of the above.

(10) The transfer control unit
(A) reduce the transfer rate,
(B) Decreasing the number of frames transferred by controlling the transfer unit so that transfer of at least a part of the plurality of frames is temporarily stopped without reducing the transfer rate. Or
(C) In the continuation of the plurality of frames, if the current frame does not match the previous frame, the current frame is transferred, but if the current frame matches the previous frame, the current frame is not transferred. The image display device according to any one of (1) to (9), wherein the number of frame transfers is reduced by controlling the transfer unit.

(11) The display unit is mounted on a head of a user who observes the target image, and projects light that forms the target image onto the eyes of the user, thereby displaying the target image (1). Or the image display device according to any one of (10).

(12) Furthermore,
A receiving unit connected to the transfer unit so as to be communicable by wire or wirelessly, the receiving unit receiving a frame transferred from the transfer unit, and outputting the received frame to the display unit (1) Or the image display device according to any one of (11).

  According to the present invention, when the battery that drives the image display device is low, the transfer mode of the transfer unit is controlled according to the type of the target image without requiring user intervention, and as a result, Power consumption by the image display device is reduced.

FIG. 1 is a functional block diagram showing an image display device according to the first embodiment of the present invention. FIG. 2 is a diagram for conceptually explaining how a plurality of frames representing a target image are transferred and the frame transfer is temporarily stopped in the image display apparatus shown in FIG. FIG. 3 is a flowchart conceptually showing a power consumption control program executed by the CPU of the display control unit shown in FIG. FIG. 4 is a flowchart conceptually showing a power consumption control program executed by the CPU of the image display device according to the second embodiment of the present invention. FIG. 5 is a flowchart conceptually showing a power consumption control program executed by the CPU of the image display device according to the third embodiment of the present invention. FIG. 6 is a functional block diagram showing an image display device according to the fourth embodiment of the present invention. FIG. 7 is a flowchart conceptually showing a power consumption control program executed by the CPU of the display control unit shown in FIG. FIG. 8 is a table for explaining an execution example of step S103 shown in FIG. FIG. 9 is a flowchart conceptually showing a power consumption control program executed by the CPU of the image display device according to the fifth embodiment of the present invention. FIG. 10 is a table for explaining steps S111 to S113 shown in FIG.

  Hereinafter, some of the exemplary embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a functional block diagram showing an image display device 10 according to the first exemplary embodiment of the present invention. The image display device 10 is configured to project image light representing an image onto the eyes of an observer. Specifically, the image display device 10 sequentially reproduces the plurality of frames based on an image signal representing a target image (hereinafter, also simply referred to as “image”) configured as a sequence of a plurality of frames. Thus, the display is configured to be driven by a battery in order to display the target image as a still image or a complete or partial moving image.

  In order to realize such a function, the image display apparatus 10 controls the display unit 12 (an example of the “display unit” in the above (1)) that is worn on the observer's head and the display unit 12. The display control unit 14 is configured to be included. In the present embodiment, the image display apparatus 10 is a separate type configured by combining a display unit 12 and a display control unit 14 which are both independent components. For example, the display control unit 14 is a display unit. It is also possible to change to an integrated type that is built in the unit 12.

  The display unit 12 is monocular, and projects image light representing an image onto one eye of the observer to display the image to the observer. Furthermore, the display unit 12 is a see-through type, and allows the observer to observe the display image superimposed on the actual outside world.

  Further, the display unit 12 is a spatial modulation type, and planar light (for example, a backlight) from a light source is spatially applied to each pixel using an LCD (liquid crystal display) 20 which is an example of a spatial modulation element. And modulating the modulated light onto the viewer's retina.

  In addition, in the present embodiment, the display unit 12 is a monocular type, a spatial modulation type, and a see-through type. However, the display unit 12 can be changed to a binocular type, or a retinal scanning type, that is, an image from a light source such as a laser. A type that allows the observer to observe an image as a virtual image by two-dimensionally scanning a light beam having an intensity corresponding to a signal and projecting the two-dimensionally scanned light beam onto the retina of the observer. It is possible to change to a closed type in which the actual outside world cannot be observed in parallel with the display image observation.

  In order to perform the spatial modulation type image display, the display unit 12 further includes the LCD controller 22 that controls the LCD 20 and the backlight control signal received from the display control unit 14. And a backlight control circuit 24 for controlling (reflected in the luminance value of the display image). The display unit 12 further includes a DVI receiver 30 conforming to DVI (abbreviation of Digital Visual Interface, which is an example of a video output interface standard), and a frame memory 32.

  The DVI receiver 30 receives image data (hereinafter also referred to as “video data”) from the display control unit 14 in units of frames, and sends the received frames to the frame memory 32. The frame memory 32 temporarily stores image data in units of frames, and at each frame start timing triggered by an interrupt signal (in this embodiment, the vertical synchronization signal VSYNC may be a horizontal synchronization signal HSYNC). The frame signal representing the stored frame is sent to the LCD controller 22. The LCD controller 22 reproduces a frame on the screen of the LCD 20 by controlling the LCD 20 based on the received frame signal at every frame start timing.

  When the DVI receiver 30 receives a frame from the display control unit 14, the DVI receiver 30 sends the frame to the frame memory 32, but does not send any data to the frame memory 32 during a period in which no frame is received from the display control unit 14. The frame memory 32 stores the frame received from the DVI receiver 30 until the next frame is received from the DVI receiver 30, and when the next frame is received, the previous frame is rewritten with the latest frame.

  A display control unit 14 is electrically connected to the display unit 12 via a cable 34. The cable 34 includes a data line for transmitting image data, a signal line for transmitting a control signal including the backlight control signal and VSYNC, and a power line for transmitting power. While the display unit 12 is mounted on the observer's head, the display control unit 14 is mounted on a portion of the observer other than the head (for example, the waist).

  The display control unit 14 connects a CPU (Central Processing Unit) 40 as a processor, a ROM (Read Only Memory) 42 as a nonvolatile memory, and a RAM (Ramdom Access Memory) 44 as a volatile memory. The bus 46 is provided.

  The display control unit 14 further includes an AD converter 50 wired to a PC (Personal Computer) 48 as an external image input device, a frame buffer 52, and a DVI transmitter 54 that conforms to DVI as the transmission unit (the above ( 1), an example of a “transfer unit”. The image display device 10 is designed to reproduce (streaming reproduction) image data received from a PC in real time or to reproduce after recording.

  The AD converter 50 converts the image signal (analog signal) received from the PC 48 into image data. The frame buffer 52 temporarily stores the same frame as that last transferred to the display unit 12 by the display control unit 14 among the plurality of frames constituting the image data output from the AD converter 50. The DVI transmitter 54 transmits the image data output from the AD converter 50 in a frame unit to the DVI receiver 30 at a fixed (time-invariant) transfer rate at each frame start timing, thereby displaying the display unit. 12 for transfer.

  Specifically, as illustrated in FIG. 2, in the DVI transmitter 54, a transfer permission / inhibition signal for controlling transfer permission / inhibition thereof is switched between ON and OFF. The ON / OFF control for the transfer permission / prohibition signal (in FIG. 1 and FIG. 2, simply represented by “ON / OFF control”) is performed, and the DVI transmitter 54 is in a period during which the transfer permission / prohibition signal is ON. During frame transfer, frame transfer is performed at each frame start timing. However, during the period when the transfer permission / prohibition signal is OFF, frame transfer is not performed even when the frame start timing arrives.

  In FIG. 2, a series of a plurality of frames input from the DVI transmitter 54 to the frame memory 32 via the DVI receiver 30 is shown as an input image. Among these frames, those shown as black square frames indicate that the DVI transmitter 54 does not transfer any data to the DVI receiver 30 at the frame start timing.

  By the ON / OFF control of the transfer permission / inhibition signal, the DVI transmitter 54 is switched between a state in which frame transfer is performed and a state in which frame transfer is not performed. As a result, when ON / OFF control is executed, some frames are thinned out and transferred from the DVI transmitter 54 to the DVI receiver 30, so that the transfer permission / prohibition signal is maintained ON (ie, , The number of frames transferred by the DVI transmitter 54 among the plurality of frames representing the original target image (hereinafter referred to as “frame transfer number”) is reduced. Power consumption by the DVI transmitter 54 and the DVI receiver 30 is reduced.

  In FIG. 2, in addition to the input image, a series of a plurality of frames output by the LCD 20 is shown as an output image. As described above, since the frame memory 32 continues to store the previous frame during a period in which no new frame is received from the DVI transmitter 54 via the DVI receiver 30, the LCD 20 stores the new frame from the DVI transmitter 54 to the DVI. During a period not received via the receiver 30, a frame having the same image as the latest frame stored in the frame memory 32 is continuously reproduced.

  In addition, as shown in FIG. 2, there is an invalid display period A between the end timing of a certain frame and the start timing of the next frame, followed by an effective display period B for one frame. Exists. In the example shown in FIG. 2, the invalid display period A starts from the frame start timing triggered by VSYNC, but can be changed to start from another timing.

  In short, in this embodiment, the transfer rate, that is, the total number of frames that the DVI transmitter 54 transfers to the DVI receiver 30 per fixed time is a fixed value, and the frame rate (reproduction rate), that is, per fixed time. The total number of frames reproduced by the LCD 20 is also a fixed value. However, in the present invention, the transfer rate is a variable value, and the frame rate is also a variable value that changes to match the transfer rate. It can be implemented in some manner.

  Further, in the present embodiment, at least a part of the frames is not reduced without lowering the transfer rate by the DVI transmitter 54 in order to realize the power saving mode at the time of reproducing a still image (an image with a low moving image defined later). By controlling the DVI transmitter 54 so that the transfer is temporarily stopped, the number of frames transferred is reduced. However, the present invention can be implemented in a manner in which the transfer rate of the DVI transmitter 54 is reduced. is there.

  As shown in FIG. 1, the display control unit 14 further includes a battery 60 and a power circuit 62 connected to the battery 60. The battery 60 supplies power to the components in the display control unit 14 and also supplies power to the components in the display unit 12 via the cable 34. That is, the battery 60 is a common power source for the display unit 12 and the display control unit 14. Reduction of power consumption by the DVI transmitter 54 and the DVI receiver suppresses the consumption of the battery 60, thereby promoting the extension of the life of the battery 60. As is well known, the power supply circuit 62 is provided to stabilize the output of the battery 60 or to charge the battery 60.

  The display control unit 14 further includes a remaining battery level detection circuit 64 and an AD converter 66. The battery remaining amount detection circuit 64 defines the remaining amount of the battery 60 (for example, the remaining drive time during which the image display apparatus 10 can be continuously driven until the battery 60 is completely consumed). (A quantity SOC (State of Charge) that can be defined in units of charge) is detected, and an analog signal representing the detected value is output. The remaining battery level detection circuit 64 may voluntarily perform the remaining battery level detection operation, but may perform the remaining battery level detection operation in accordance with a command from the CPU. The AD converter 66 converts the output signal of the remaining battery level detection circuit 64 into remaining battery level data that is digital data representing the remaining battery level. The battery remaining amount data output from the AD converter 66 is sent to the CPU 40.

  FIG. 3 conceptually shows a power consumption control program repeatedly executed by the CPU 40 during operation of the image display apparatus 10 in a flowchart.

  The display control unit 14 has a power consumption control unit (not shown) when attention is paid to functions to be realized instead of a physical configuration. The power consumption control unit includes a transfer control unit, a luminance value control unit, and the like. It has. The power consumption control unit reduces the power consumption by the image display device 10 when the remaining amount of the battery 60 is equal to or less than the reference remaining amount based on the image signal or the image attribute signal or image attribute data representing the attribute of the target image. As such, the power consumption is controlled. The transfer control unit controls the transfer unit so that when the target image is classified as a still image, the number of frame transfers is smaller than when the target image is classified as a complete or partial moving image.

  The transfer control unit includes a first classification unit that classifies the target image into one of a plurality of image types including a moving image and a still image based on a temporal correlation between frames of the target image. When the target image is classified as a moving image, the luminance value control unit does not reduce the number of frame transfers and does not reduce the transfer rate, and the luminance value when the target image is displayed (that is, the backlight (Hereinafter also referred to as “screen brightness”).

  And a power consumption control part is comprised when CPU40 and the power consumption control program shown in FIG. 3 mutually cooperate. The transfer control unit is configured by the CPU 40 and steps S1 to S7 shown in FIG. The first classification means is configured by the CPU 40 and step S5 shown in FIG. The luminance value control unit is configured by the CPU 40 and steps S8 and S9 shown in FIG.

  When the CPU 40 executes the power consumption control program shown in FIG. 3, first, in step S <b> 1, the frame start timing triggered by VSYNC is awaited. When the frame start timing arrives, steps S2 and S3 are executed during the invalid display period A. In step S2, the battery remaining amount detection circuit 64 is instructed to detect the remaining battery amount. In response to the command, the remaining battery level detection circuit 64 detects the remaining battery level and outputs remaining battery level data representing the result, which is captured by the CPU 40. Subsequently, in step S3, it is determined whether or not the remaining battery level represented by the taken-in remaining battery level data is equal to or less than a threshold value (an example of “reference remaining level” in the item (1)). The

  In this embodiment, since the battery remaining amount acquisition and suitability determination are performed during the invalid display period A, the calculation load of the CPU 40 during the valid display period B is different from the case where it is performed during the valid display period B. And the concentration of the maximum power consumption during the effective display period B is reduced, thereby reducing the load concentration of the battery 60.

  If the remaining battery level is not less than or equal to the threshold value, in step S4, the current frame is permitted to be in the normal display mode, that is, the frame transfer by the DVI transmitter 54 is permitted, and the backlight luminance value is the normal value ( Default value or value adjusted by the user). Thereafter, the process returns to step S1, and the processing described above is executed for the next frame. On the other hand, when the remaining battery level is equal to or less than the threshold value, the process proceeds to step S5.

  In this step S5, the latest frame received from the PC 48 and the current frame that the display control unit 14 is about to transfer to the display unit 12 is the previous frame transferred immediately before in relation to the image and the frame buffer 52. It is determined whether or not it is the same as that stored in. That is, based on the image signal of the target image, it is determined whether or not the target image has a still image property stronger than a moving image property.

  Specifically, for each pixel, based on the temporal correlation between frames, it is determined whether the current frame is the same as the previous frame with respect to the image. This time, assuming that the current frame is the same as the previous frame, in step S6, the transfer of the current frame by the DVI transmitter 54 is prohibited, and as a result, the transfer permission / inhibition signal is turned off. Then, it returns to step S1.

  On the other hand, assuming that the current frame is not the same as the previous frame this time, transfer of the current frame by the DVI transmitter 54 is permitted in step S7. As a result, the transfer permission / inhibition signal is turned ON. . Thereafter, in step S8, it is determined whether or not the current luminance value is the lowest value in the changeable range. This time, assuming that the luminance value is not the lowest value, the backlight control signal is generated and transmitted to the backlight control circuit 24 in step S9 in order to command the luminance value to be lowered by one step. Is done. Then, it returns to step S1. On the other hand, assuming that the luminance value is the lowest value this time, after step S9 is skipped, the process returns to step S1.

  Next, the image display apparatus 10 according to the second exemplary embodiment of the present invention will be described. However, in the present embodiment, the content of the power consumption control program is only the power consumption control program in the first embodiment, which is different from that shown in FIG. Only the contents of the control program will be described, and common elements will not be described repeatedly by using the same names and symbols.

  FIG. 4 conceptually shows a power consumption control program executed by the CPU 40 of the display control unit 14 of the image display apparatus 10 according to the present embodiment in a flowchart. When this power consumption control program is executed by the CPU 40, steps S51 and S52 are executed prior to starting the reproduction of a series of frames. However, these steps S51 and S52 may be executed each time reproduction of video content different from that during the series of operations of the image display device 10 is started.

  In any case, in step S51, the battery remaining amount detection circuit 64 is instructed to detect the remaining battery amount. In response to the command, the remaining battery level detection circuit 64 detects the remaining battery level and outputs remaining battery level data representing the result, which is captured by the CPU 40. Next, in step S52, it is determined whether or not the remaining battery level represented by the captured remaining battery level data is equal to or less than the threshold value.

  If the remaining battery level is not less than or equal to the threshold value, a series of frames are displayed in the normal display mode in step S53. On the other hand, when the remaining battery level is equal to or less than the threshold value, the process proceeds to step S54.

  In step S54, the arrival of the frame start timing triggered by VSYNC is awaited. When the frame start timing arrives, in step S55, the current frame that the display control unit 14 is about to transfer to the display unit 12 is captured from the PC 48 in the image signal. Subsequently, in step S56, an inter-frame difference for each pixel is calculated for the fetched current frame and the previous frame stored in the frame buffer 52. Thereafter, in step S57, it is determined whether or not the calculated inter-frame difference is substantially 0 for all pixels, thereby determining whether or not the current frame is the same as the previous frame.

  Assuming that the current frame is not the same as the previous frame this time, transfer of the current frame by the DVI transmitter 54 is permitted in step S58, and as a result, the transfer permission / inhibition signal is turned ON. Subsequently, in step S59, the current frame is stored in the frame buffer 52 as the previous frame in preparation for the next calculation of the interframe difference. Thereafter, the process returns to step S54, and the next frame start timing is awaited.

  On the other hand, this time, assuming that the current frame is the same as the previous frame, in step S60, the transfer of the current frame by the DVI transmitter 54 is prohibited, and as a result, the transfer permission / prohibition signal is turned off. . Thereafter, the process returns to step S54.

  On the other hand, after that, in step S8, it is determined whether or not the current luminance value is the lowest value within the range in which the luminance value can be changed. This time, assuming that the luminance value is not the lowest value, the backlight control signal is generated and transmitted to the backlight control circuit 24 in step S9 in order to command the luminance value to be lowered by one step. Is done. Then, it returns to step S1. On the other hand, assuming that the luminance value is the lowest value this time, after step S9 is skipped, the process returns to step S1.

  Next, an image display apparatus 10 according to an exemplary third embodiment of the present invention will be described. However, since the content of the power consumption control program of this embodiment is different from that shown in FIG. 4 in the power consumption control program in the second embodiment, and other elements are common, the power consumption Only the contents of the control program will be described, and common elements will not be described repeatedly by using the same names and symbols.

  In the second embodiment, an inter-frame difference for each pixel is calculated to determine whether the current frame is the same as the previous frame. However, in this embodiment, the accuracy of the determination is sacrificed. In order to reduce the calculation load of the CPU 40, the total value of the plurality of pixel values constituting the current frame and the total value of the plurality of pixel values constituting the previous frame are compared with each other, and the inter-frame difference between these total values Is substantially zero, it is determined that the current frame is the same as the previous frame. Therefore, in this embodiment, it is not necessary to use the frame buffer 52 to calculate the temporal correlation between frames.

  FIG. 5 conceptually shows a power consumption control program executed by the CPU 40 of the display control unit 14 of the image display apparatus 10 according to the present embodiment in a flowchart. Since this power consumption control program is a power consumption control program in the second embodiment and has steps common to those shown in FIG. 4, common steps are duplicated by using the same step number. Will be omitted and only the different steps will be described in detail.

  In the power consumption control program shown in FIG. 5, when the current frame is captured from the PC 48 in step S55, the total value of a plurality of pixel values constituting the captured current frame is calculated in step S61. Calculated as a value. Thereafter, in step S62, the total pixel value calculated for the current frame and the total pixel value of the previous frame and stored in the RAM 44 are compared with each other, and the inter-frame difference of these total pixel values is substantially reduced. Is 0, it is determined that the current frame is the same as the previous frame.

  If the current frame is not the same as the previous frame, the total pixel value of the current frame is stored as the total pixel value of the previous frame in step S62 in step S62 in preparation for the next calculation of the interframe difference. Is done. On the other hand, if the current frame is the same as the previous frame, the process proceeds to step S60.

  Next, an image display apparatus 100 according to the fourth exemplary embodiment of the present invention will be described. However, since there are elements in common with the second embodiment in the present embodiment, the duplicate description will be omitted by using the same names and symbols for the common elements, and only different elements will be described in detail. .

  FIG. 6 conceptually shows the image display device 100 according to the present embodiment in a functional block diagram. The image display apparatus 100 includes a display unit 12 having the same configuration and a display control unit 114 having a partially different configuration from the image display apparatus 10 according to the second embodiment shown in FIG.

  The display control unit 114 receives an image signal by wireless communication with an external image input device (not shown, for example, a PC, a mobile phone, a smart phone, etc.). Therefore, the display control unit 114 stores image data represented by an antenna 120, an interface 122 that enables a wireless local area network (LAN), and an image signal received from the external image input device via the wireless LAN. A memory card (an example of an image memory).

  The display control unit 114 uses image data representing an image signal received from the outside as a file, and a file name and file type identifier (for example, doc or jpg representing a still image, mpg representing a moving image) The file is saved in the memory card 124 in association with the file extension. The file type identifier is related to the type of the target image.

  Therefore, in the present embodiment, by referring to the file type identifier assigned to each target image (video content) to be reproduced, the target image is selected from among a plurality of image types including moving images and still images. Classify either. That is, the display control unit 114 has means for classifying the target image into one of a plurality of image types including moving images and still images based on a file type identifier that is an example of the image attribute data. This means is an example of the “third classification means” in the above section (6).

  By the way, in the second embodiment, during the reproduction of the same target image (video content), the temporal change of the frame image is observed, and a certain segment of the target image has a strong property as a still image. For each segment, each segment can be classified into a different image type from the other segments so that the segment has a strong nature as a moving image.

  On the other hand, in the present embodiment, prior to the reproduction of the target image, by referring to the file type identifier assigned thereto, the entire target image is uniformly a still image or a moving image. If the image is determined to be a still image, the transfer rate is set lower than the normal value throughout the playback period of the target image, whereas if it is determined to be a video, The transfer rate is set to the normal value throughout the reproduction period of the target image. Throughout this specification, the term “still image” means both an image in which the display image does not move at all and an image in which the display image moves discontinuously (frame-advanced image) throughout the reproduction period. As used.

  FIG. 7 conceptually shows a power consumption control program executed by the CPU 40 of the display control unit 114 of the image display apparatus 100 according to the present embodiment in a flowchart. Since this power consumption control program is a power consumption control program in the second embodiment and has steps common to those shown in FIG. 4, common steps are duplicated by using the same step number. Will be omitted and only the different steps will be described in detail.

  In the power consumption control program shown in FIG. 7, steps S51 through S53 and S101 through S103 are executed prior to the start of reproduction of each target image every time the target image (video content) changes. If the remaining battery level is not less than or equal to the threshold value, in step S53, the display mode is selected so that the target image is displayed in the normal mode. If the remaining battery level is less than or equal to the threshold value, in step S101, the file type identifier assigned to the target image received from the outside and stored in the memory card 124 is referred to, so that the target image is It is determined whether or not the image is classified as a still image. For example, when the file type identifier is jpg, the target image is classified as a still image. If the target image is classified as a moving image instead of a still image, the transfer rate is maintained at the normal rate in step S102. If the target image is classified as a still image, the transfer is performed in step S103. The rate is reduced below the normal rate.

  In step S103, the transfer rate is lowered to a predetermined value lower than the normal rate. The predetermined value may be a fixed value, but in one example, the transfer rate (the number of files transferred per second) according to the relationship between the transfer rate and the remaining battery level as illustrated in FIG. Is a variable value that increases as the remaining battery level increases.

  In this example, when the threshold value in step S52 is “50%”, if the remaining battery level is “50%”, the transfer rate is the normal rate (maximum rate) as shown in FIG. ) And when the remaining battery level is “30%”, the transfer rate is reduced to one-fourth of the normal rate. According to this example, the maximum drive time of the image display device 100 is maximized as compared to the case where the transfer rate is reduced to a fixed value determined regardless of the remaining battery level.

  Next, an image display apparatus 100 according to an exemplary fifth embodiment of the present invention will be described. However, since this embodiment has elements in common with the fourth embodiment, the description of the common elements will be omitted by using the same names and symbols, and only different elements will be described in detail. .

  FIG. 9 conceptually shows a power consumption control program executed by the CPU 40 of the display control unit 114 of the image display apparatus 100 according to the present embodiment. Since this power consumption control program is a power consumption control program in the fourth embodiment and has steps common to those shown in FIG. 7, the common steps are duplicated by using the same step number. Will be omitted and only the different steps will be described in detail.

  In the power consumption control program shown in FIG. 9, steps S51 to S53, S101 and S111 to S114 are executed prior to the start of reproduction of each target image every time the target image (video content) changes. In step S101, if the target image is classified as a still image, in step S114, only the frames that do not match the previous freight among the plurality of frames representing the original target image are processed by the DVI receiver 30 by the DVI transmitter 54. Forwarded to On the other hand, when the target image is classified as a moving image, the process proceeds to step S111.

  In the present embodiment, the moving image is classified into one of a plurality of image types including a partial moving image having local motion and a complete moving image. By the way, in the present embodiment, as illustrated in FIG. 10, the moving degree of the target image (for example, the degree to which the image data changes temporally between frames) moves the specific target on the screen of the LCD 20. It is defined from three viewpoints: the type of a specific object moving within a region (hereinafter referred to as “motion region”), the size of the motion region (ratio to the area of the entire screen), and the frequency of occurrence of the motion region.

  By using the concept of moving image degree defined in this way, in this embodiment, the moving image is (a) on a screen with a still image as a background, the cursor is in a very small area in accordance with the user's operation. Created when creating a table on the screen using the first movie (an example of a partial movie) that moves sporadically in (b) and table software such as Excel (registered trademark) of US Microsoft Corporation A second moving image (another example of a partial moving image) in which the frame of the inner table moves sporadically within a small area, and (c) a specific object is within the frame displayed in a part of the screen. A third movie that moves continuously in a medium-sized area (another example of a partial movie), and (d) a fourth movie that moves the display image continuously throughout the screen (completely) Video).

  As illustrated in FIG. 10, when the target image is classified into the first or second moving image, the property as a still image is stronger than the case where the target image is classified into the third or fourth moving image. Nevertheless, the amount by which the transfer rate is reduced from the normal rate (maximum rate) is reduced, or the backlight brightness of the LCD 20, that is, the screen brightness is lowered while maintaining the transfer rate at the normal rate. Therefore, it is considered desirable to realize the power save mode.

  The possible reason is that, when the target image is classified into the first or second moving image, unlike the case where the target image is classified into the third or fourth moving image, a specific motion on the screen of the LCD 20 is selected. This is because it is comfortable for the user who observes the screen and there is no stress to display the target object so as to move sensitively and smoothly according to the operation of the user. In addition, when the target image is classified as the third or fourth moving image, more than half of the screen is moving, so even if the transfer rate is lowered and the frame rate (reproduction rate) is lowered, It is considered that the user does not feel so uncomfortable or stressed.

  In order to realize this, in the power consumption control program shown in FIG. 9, in step S111, the file type identifier of the target image (for example, whether it is a still image, a moving image, or a table). And whether or not the target image is classified into an image of a type in which only a part of the image changes based on whether or not the cursor exists on the screen, ie, first or second It is determined whether or not the image is classified into the image. When the target image is classified into the first or second moving image, the screen brightness is lowered in step S113. On the other hand, when the target image is not classified into the first moving image or the second moving image, that is, when the target image is classified into the third or fourth moving image, the transfer rate is set to normal in step S112. The first rate is lower than the rate.

  In addition, in the present embodiment, when the target image is classified into the first or second moving image, the screen brightness is lowered from the normal brightness while the transfer rate is maintained at the normal rate. In another example, instead, it is adopted when the transfer rate is lower than the normal rate while maintaining the screen luminance at the normal luminance, but the target image is classified into the third or fourth moving image. It is possible to lower the second rate higher than the first rate.

  In addition, in this embodiment and the above-described another example, when the target image is classified into the first or second moving image, a decrease in transfer rate and a decrease in screen luminance are alternatively performed. Although executed, in yet another example, a decrease in transfer rate and a decrease in screen brightness are performed together. According to this example, when the target image is classified into the first or second moving image, it is possible to save power without causing the observer to feel stress, and that the remaining battery level is low. There is an advantage that the observer can be made aware through the phenomenon that the screen becomes dark. On the other hand, when the target image is classified into the third or fourth moving image, the observer can recognize that the remaining battery level is low through the phenomenon that the screen motion becomes dull. There are advantages.

  In addition, in some embodiments described above, the types of target images are classified by referring to temporal correlation between frames, file type identifiers, etc., but other examples are adopted. It is possible.

  In one example, the display control unit 14 or 114 has a low-pass filter that filters the image signal of the target image. The low-pass filter has a predetermined cutoff frequency so as to be lower than the frame frequency of the image signal. When the image signal is input, a component having a frequency equal to or higher than the frame frequency is included in the image signal. It is an electronic circuit designed to have a characteristic that attenuates more than a certain amount.

  In this example, the display control unit 14 or 114 further selects the target image as a still image and a moving image based on the amplitude of the signal output from the low-pass filter with respect to the image signal input to the low-pass filter. A second electronic circuit that classifies the image into any one of a plurality of image types. An example of the second electronic circuit is a comparator. For example, an output signal of a low-pass filter and a reference signal are input to the comparator, and are determined in advance according to the magnitude of the two input signals. It is designed to output any of binary signals.

  In this example, the cut-off frequency of the low-pass filter is the same as the reference signal of the comparator when the target image is classified as a still image in which the same frame signal repeats in the same cycle. Set to do. Since the level of the output signal of the comparator changes when the level of the output signal of the low-pass filter exceeds or falls below the level of the reference signal, the CPU 40 refers to the level change of the output signal, so that the target image is A program for determining whether the image is classified as a still image is executed.

  According to this example, the determination of the type of the target image is performed mainly using the low-pass filter and the comparator that both consume less power, and the low-pass filter and the comparator operate independently from the CPU 40. As compared with the case where all processes for determining the type of the target image are performed using the CPU 40, the calculation load on the CPU 40 is reduced and the design for reducing the power consumption is facilitated.

  In another example, the image display device 10 or 100 is configured to display a target image by starting an application program whose type is selected according to the type of the target image. In the image display device 10 or 100 configured as described above, the CPU 40 selects the target image as one of a plurality of image types including a still image and a moving image based on the type of the activated application program. Run the program to be classified.

  As is apparent from the above description, according to some embodiments described above, the target image is automatically classified with respect to the type without requiring user intervention, and the type of the target image is determined. The DVI transmitter 54 is controlled in a corresponding operation mode (transfer mode), whereby the frame transfer number or transfer rate is automatically switched. As a result, power consumption by the image display device 10 or 100, particularly power consumption by the DVI transmitter 54 and the DVI receiver 30, is reduced without requiring an additional operation for the user.

  In addition, since the image display apparatus 10 or 100 is a head-mounted type, there is a possibility that the limit value of the fineness of the image that can be visually recognized by the user is influenced by the speed of the movement of the user's head. . Specifically, the faster the movement of the user's head, the lower the limit value of the fineness of the image that the user can visually recognize. Therefore, regardless of the speed of the user's head movement, setting a high frame transfer rate from the DVI transmitter 54 to the DVI receiver 30 requires a transfer rate when the user's head movement is fast. It becomes higher than that, and power is consumed wastefully. Therefore, the remaining battery level is low, and the speed of movement of the user's head (for example, the acceleration mounted on the part of the image display device 10 or 100 that is mounted on the user's head and moves integrally therewith) If it is faster than the reference value (which can be detected by the sensor), it is desirable to lower the transfer rate than otherwise.

  As mentioned above, although several embodiment of this invention was described in detail based on drawing, these are illustrations and are based on the knowledge of those skilled in the art including the aspect as described in the above-mentioned [summary of invention] column. The present invention can be implemented in other forms with various modifications and improvements.

Claims (11)

In order to display the target image as a still image or a complete or partial video by sequentially reproducing the plurality of frames based on an image signal representing the target image configured as a sequence of a plurality of frames. An image display device driven by a battery,
A transfer unit that transfers at least a part of the plurality of frames at a fixed or variable transfer rate;
A display unit that displays the target image by reproducing a plurality of frames transferred from the transfer unit at a fixed frame rate or a variable frame rate that changes according to the transfer rate;
A power consumption control unit that controls the power consumption so that the power consumption by the image display device decreases when the remaining amount of the battery is less than or equal to a reference remaining amount,
Its power consumption control unit, based on the image signal or the target image attribute signal or image attribute data representing an attribute of the image, the target image, in any of a plurality of image types including a moving image and a still image Classify and
The moving image refers to the type of a certain object that moves in a movement area, which is an area where a certain object moves on the screen, the size of the movement area, which means a ratio to the area of the entire screen, and its movement From the three viewpoints of the occurrence frequency of the area, using the first moving image or the table software that the cursor moves sporadically in a very small area in response to the user's operation on the screen with the background of the still image When creating a table on the screen, the frame of the table being created sporadically moves in a small area, and the object in the frame displayed on a part of the screen is medium A third moving image that continuously moves within a region of size or a fourth moving image whose display image moves continuously over the entire screen,
The power consumption control unit
(A) When the target image is classified as the still image, only the frame that is different from the previous frame among the plurality of frames is maintained in the display unit while maintaining the transfer rate at a normal rate. Controlling the transfer unit to be transferred, thereby reducing the number of frames transferred, which is the number of frames transferred by the transfer unit among the plurality of frames,
(B) When the target image is classified into the first moving image or the second moving image, the transfer rate is reduced to a first rate lower than the normal rate, or the transfer rate Maintaining the normal rate while reducing the luminance value when the target image is displayed,
(C) An image including a transfer control unit that reduces the transfer rate to a second rate lower than the first rate when the target image is classified into the third moving image or the fourth moving image. Display device. further,
The image display device according to claim 1, further comprising a remaining amount determination unit that determines a remaining amount of the battery during an invalid display period in which no image is displayed in the image signal.   3. The transfer control unit according to claim 1, further comprising: a first classification unit that classifies the target image into one of the plurality of image types based on a temporal correlation between frames of the target image. Image display device. The transfer control unit
The image signal has a predetermined cutoff frequency so as to be lower than the frame frequency of the image signal. When the image signal is input, a component having a frequency equal to or higher than the frame frequency is included in the image signal. A low-pass filter having attenuation characteristics;
A second classification for classifying the target image into one of the plurality of image types based on the amplitude of the signal output from the low-pass filter with respect to the image signal input to the low-pass filter. The image display apparatus according to claim 1, further comprising: means. The image display device stores the image data representing the image signal as a file and associated with the file name and the file type identifier,
The transfer control unit includes a third classifying unit that classifies the target image into one of the plurality of image types based on the file type identifier that is related to the type of the target image. Item 3. The image display device according to Item 1 or 2. The image display device displays the target image by activating an application program whose type is selected according to the type of the target image,
3. The transfer control unit according to claim 1, wherein the transfer control unit includes a fourth classification unit that classifies the target image into one of the plurality of image types based on the type of the activated application program. Image display device.   The power consumption control unit further includes a luminance when the target image is displayed without reducing the number of frame transfers or the transfer rate when the target image is classified as a moving image. The image display device according to claim 1, further comprising a luminance value control unit that decreases the value.   The transfer control unit according to any one of claims 1 to 7, wherein the transfer control unit controls the transfer unit so that the number of frame transfers decreases or the transfer rate decreases as the remaining amount of the battery decreases. Image display device. The transfer control unit
(A) reduce the transfer rate,
(B) Decreasing the number of frames transferred by controlling the transfer unit so that transfer of at least a part of the plurality of frames is temporarily stopped without reducing the transfer rate. Or
(C) In the continuation of the plurality of frames, if the current frame does not match the previous frame, the current frame is transferred, but if the current frame matches the previous frame, the current frame is not transferred. The image display device according to claim 1, wherein the number of frames transferred is reduced by controlling the transfer unit.   The said display part is mounted | worn with the user's head which observes the said target image, and projects the light which forms the said target image on the said user's eyes, Thereby, the said target image is displayed. The image display device according to any one of the above. further,
2. A receiving unit connected to the transfer unit so as to be communicable by wire or wirelessly, the receiving unit receiving a frame transferred from the transfer unit, and outputting the received frame to the display unit. Or an image display device according to any one of items 10 to 10;

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