JP5459569B2 - Display control apparatus and display control method - Google Patents

Description

  The present invention relates to a display control device and a display control method, and more particularly to a display control device and a display control method used in combination with an external monitor such as a projector.

  An external monitor such as a projector is used, for example, to enlarge and display the screen of a personal computer and show it to many people. Such a monitor device is generally used on a one-to-one basis with one personal computer. For example, while switching the screens of a plurality of personal computers brought by conference attendees, An enlarged display is also performed on an external monitor.

  In such one-to-many usage situations, the brightness often changes suddenly when the screen is switched. For example, a personal computer outputs a white character screen with a black background, and another personal computer outputs a black character screen with a white background following the screen. In such a case, a sudden change in the brightness of the screen makes the person watching the external monitor feel dazzled for a moment and makes it difficult to read the image information (black characters in the white background) immediately after switching. There is an inconvenience of becoming.

  FIG. 8 is a diagram illustrating an example of a screen change that causes a momentary illusion. In this figure, the first screen 1 is a screen with white characters on a black background, and the second screen 2 displayed subsequent to the first screen 1 is a screen with black characters on a white background contrary to the above. It is. In addition, the character string (xxx (triangle | delta) * ...) in a screen is a convenience example.

  Since the display information of an external monitor such as a projector is light emission information unlike printed matter such as paper, the human eye receives a greater stimulus in white (that is, the maximum luminance) than in black (that is, the minimum luminance). The pupil of the human eye becomes smaller when it feels dazzling, and has the function of preventing dazzling by reducing the amount of light taken into the retina, but it still cannot escape from the glare of the moment.

  Therefore, as a first conventional technique for automatically controlling the brightness of a screen, for example, one described in Patent Document 1 is known. In this first conventional technique, depending on the brightness of a use environment. Controls the brightness of the LCD backlight.

  Further, as a second conventional technique for automatically controlling the brightness of the screen, for example, a technique described in Patent Document 2 is known. In this second conventional technique, an average luminance of a display image is calculated. When the luminance is low, the amplification degree related to contrast and brightness is increased, and when the luminance is high, the amplification degree is lowered.

JP 2002-156949 A JP 2003-283154 A

  However, since the first conventional technique controls the brightness of the screen in accordance with the brightness of the use environment (for example, the brightness of the room lighting), the first technique as described above (FIG. 8). The screen 1 and the second screen 2 cannot be switched. When the room lighting is bright, both the first screen 1 and the second screen 2 are darkened. On the other hand, when the room lighting is dark, both the first screen 1 and the second screen 2 are brightened. Because it can only be done.

  The second prior art described above is to increase the degree of amplification related to contrast and brightness when the luminance is low, and to reduce the degree of amplification when the luminance is high. When applied to switching between the first screen 1 and the second screen 2 as shown in FIG. 8), the luminance of the first screen 1 is increased while the luminance of the second screen 2 is decreased. Although it seems that the sudden brightness change of the screen can be eased and the momentary glare can be avoided, the idea of this second prior art is described in paragraphs “0003” and “0004” in the literature. Focus on the fact that it is “darker than the intended image” and “it is displayed too dark in a dark image and too bright in a bright image”, and the inconveniences, ie, image reproduction Avoiding sexual deterioration This technology is intended only to prevent glare in the moment when switching from a black background white character screen (first screen 1) to a white background black character screen (second screen 2). It does not include the thought to do.

  Therefore, the present invention proactively prevents a momentary illusion when switching from a black background white character screen (first screen 1) to a white background black character screen (second screen 2). It is an object of the present invention to provide a display control device and a display control method in which the image information is improved so as to be easily viewable.

The present invention is an image acquisition means for acquiring a plurality of image data from a plurality of terminals, and an image before change based on the image data acquired from one of the plurality of terminals, acquired by the image acquisition means, Detection means for detecting switching to a post-change image based on image data acquired from two of the plurality of terminals acquired by the image acquisition means, and image switching is detected by the detection means. Determining means for determining whether or not a luminance difference between the pre-change image and the post-change image exceeds a predetermined value and a luminance value of the post-change image is higher than the pre-change image; When the determination result of the means is affirmative, the brightness of the image after the change is corrected in a decreasing direction, and when the determination result of the determination means is changed from affirmation to negative, the brightness of the image after the change is corrected. initial And a correcting means for returning to said correction means, after the determination result of said determining means is corrected to decrease direction the brightness of the after-image in a positive, the brightness of the after-image after a predetermined time has elapsed The initial value is returned to.

In the present invention, when a change in the projected image projected on the screen or the like is detected, the luminance difference between the pre-change image and the post-change image exceeds a predetermined value, and the post-change image has a higher luminance value than the pre-change image. It is determined whether or not. When the determination result is affirmative, that is, when the luminance difference between the pre-change image and the post-change image exceeds a predetermined value, and the luminance value of the post-change image is higher than the pre-change image. The brightness of the post-change image is corrected in the decreasing direction.
Therefore, for example, when switching from a black background white character screen (first screen 1) to a white background black character screen (second screen 2), the brightness of the changed image (second screen 2) decreases. Since the direction is corrected, it is possible to provide a display control device and a display control method that can positively prevent glare for a moment and make the image information after switching easier to see.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking application to a projector as an example. It should be noted that the specific details or examples in the following description and the illustrations of numerical values, character strings, and other symbols are only for reference in order to clarify the idea of the present invention, and the present invention may be used in whole or in part. Obviously, the idea of the invention is not limited. In addition, a well-known technique, a well-known procedure, a well-known architecture, a well-known circuit configuration, and the like (hereinafter, “well-known matter”) are not described in detail, but this is also to simplify the description. Not all or part of the matter is intentionally excluded. Such well-known matters are known to those skilled in the art at the time of filing of the present invention, and are naturally included in the following description.

First, the configuration will be described.
FIG. 1 is a system configuration diagram of this embodiment. In this figure, on the table 4 near the screen 3, n personal computers PC1 to PCn as terminals (here, n = 4 for convenience), one projector 5 as an external monitor, For example, a wireless LAN access point 6 that relays data transmission / reception between the terminals and the external monitor is mounted. The illustrated user U1 is an operator of the personal computer PC1, the user U2 is an operator of the personal computer PC2, and the user Un is an operator of the personal computer PCn.

  Each personal computer PCi (where i is 1 to n: the same shall apply hereinafter) is a general-purpose OS (for example, Windows: registered trademark) compatible with a GUI (graphical user interface) capable of displaying window objects, and operates on the OS. The projector 5 transmits display image data (maximum n display image data) output from each personal computer PCi via the wireless LAN access point 6. The n pieces of display image data are projected and displayed on the screen 3 while being switched in the input order or in an arbitrary designated order.

  Each personal computer PCi and projector 5 are each equipped with a wireless LAN card. For example, an international standard (IEEE802.11a or g / b) is provided between the wireless LAN card and the wireless LAN access point 6. Standard wireless communication can be performed and digital packet data can be exchanged between each other. The “card” of the wireless LAN card has no particular meaning. Any device for wireless LAN that operates in pairs with the wireless LAN access point 6 may be used. For example, a device built in a personal computer PCi, a device mounted in a removable form or cabled, or the like This type of device may be used. Hereinafter, the same applies to a wireless LAN card.

  FIG. 2 is a simplified block diagram of the personal computer PCi. In this figure, a personal computer PCi includes a CPU 7, a RAM 8, a disk controller 9, a disk device 10, a display controller 11, a display device 12, a keyboard controller 13, a keyboard device 14, a pointing device device 15, and a communication control device including a wireless LAN card. 16, a main bus 17, a bus interface 18, an internal bus 19, and the like.

  The personal computer PCi can access the wireless LAN access point 6 via the communication control device 16 by loading a communication program stored in advance in the disk device 10 into the RAM 8 and executing it by the CPU 7. .

  Further, the personal computer PCi loads a presentation program, a word processor program, a spreadsheet program, or other application programs, which are also stored in advance in the disk device 10, into the RAM 8 and executes them by the CPU 7. The execution screen (window object) of these programs can be displayed on the screen of the computer 5. Further, the personal computer PCi transmits the display image data of the display device 12 via the wireless LAN access point 6 to the projector 5. Can be output to.

  FIG. 3 is an internal block diagram of the projector 5. The projector 5 includes a communication control device 20 including a wireless LAN card, a speaker 21, a sound processing unit 22, a display drive unit 23, a main body operation display unit 24 (a flat display device 24a, a touch panel 24b), an operation unit 25, a buffer memory 26, Central control unit 27 including CPU 27a, ROM 27b and RAM 27c, input / output connector 28, input / output I / F 29, image conversion unit 30, video RAM 31 (including at least R image plane 31a, G image plane 31b and B image plane 31c), Projection encoder 32, projection drive unit 33, reflector 34, light source 35, light source drive unit 35a, color wheel 36, color wheel drive motor 37, color wheel rotation angle sensor 38, DMD 39, projection lens 40, focus / zoom drive motor 41, cooling fan 42 Including blocks, such as the cooling fan drive motor 43.

  The central control unit 27 loads a control program written in the ROM 27b in advance into the RAM 27c, and executes the program by the CPU 27a. For example, the flat display device of the main body operation display unit 24 via the display drive unit 23 The required operation buttons are graphically displayed on 24a. When any operation button is touch-operated by any of the users U1 to Un of FIG. 1, the touch coordinates are detected by the touch panel 24b, and the central control unit 27 performs the touch-operated button based on the detected coordinates. And a control mode (for example, a projection condition setting mode such as focus and zoom) corresponding to the identification result is executed.

  The central control unit 27 graphically displays operation buttons necessary for setting the resolution of the input image, the presence / absence of sound, and the like on the flat display device 24a of the main body operation display unit 24 via the display driving unit 23. Further, it is necessary to select a route for image input, that is, selection of wired input for capturing an image via the input connector unit 20 or wireless input (wireless LAN input) for capturing an image via the communication control device 20. Graphical display of various operation buttons. When an arbitrary operation button is touched by the user, the touch coordinates are detected by the touch panel 24b, and the central control unit 27 specifies the type of the touch-operated button based on the detected coordinates, and the specification result The input mode setting operation corresponding to is executed.

  For example, in the case of wireless input by wireless LAN, the communication control device 20 is controlled, and each input image and sound from the personal computer PCi input via the wireless LAN access point 6 are sequentially captured and input. The image is stored in the buffer memory 26 and the input sound is transferred to the sound processing unit 22.

  The sound processing unit 22 amplifies the input sound and outputs the sound through the speaker 21. The image conversion unit 30 adjusts the size and display position of the input image signal from each personal computer PCi stored in the buffer memory 26, and transfers the adjusted image signal to the projection encoder 32.

  The projection encoder 32 develops and stores the transmitted image signal in the video RAM 31 (R image signal → R image plane 31a, G image signal → G image plane 31b, B image signal → B image plane 31c), The contents stored in each plane of the video RAM 31 are read in the order of R image signal, G image signal, and B image signal.

  The projection drive unit 33 drives the DMD 39 with a frame screen of, for example, 30 frames / second composed of the R image signal, the G image signal, and the B image signal.

  The DMD 39 (Digital Micro-mirror Device) is a semiconductor integrated optical switch in which a large number of minute movable mirrors are spread on a plane. The size of the movable mirror is, for example, a dozen μm square, and the movable mirror is attached to the column so that the inclination changes by about ± 10 degrees when the mirror is on and off. A memory element is formed immediately below the mirror, and the on / off state of the mirror is switched by the positive electric field effect of the memory element. The amount of light reflected by the DMD 39 is maximum (white gradation) when the mirror is turned on and is minimum (black gradation) when the mirror is turned off, but the switching speed (switching speed between on and off) of each mirror is set every second. Since the number of times can be increased to 500,000 times or more, the amount of reflected light of the DMD 39 can be set to an intermediate gradation (gray scale) by changing the switching ratio of each mirror.

  When such a DMD 39 is irradiated with a high-intensity white spot light Pa from a light source 35 such as an ultra-high pressure mercury lamp disposed in the reflector 34, the reflected light Pb is turned on and off for each mirror of the DMD 39 and its switching. The light is modulated for each pixel corresponding to the ratio (light modulation is performed for each pixel in accordance with the content of the image signal), and the reflected light Pb is projected onto the screen 3 via the projection lens 40, thereby being applied to the screen 3. An enlarged image of the image signal can be projected.

  However, in the illustrated example, the number of DMDs 39 is one, and the spot light Pa emitted from the light source 35 is “white light”. In this case, only a monochrome image can be projected on the screen. Therefore, in practice, a color wheel 36 is disposed in front of the light source 35, and the color wheel 36 is rotationally driven by a color wheel driving motor 37, and when an image signal is developed and stored in the video RAM 31. The video signal components (R image signal, G image signal, B image signal) for each of the three primary colors (RGB) of light are developed and stored.

Next, the operation will be described.
FIG. 4 is a diagram illustrating a flowchart of a main part of a control program executed by the central control unit 27 of the projector 5. In this figure, first, the central control unit 27 controls the light source driving unit 35a to set the brightness of the light source 35 to an initial value (step S1). The initial value of the brightness of the light source 35 is a predetermined brightness, a brightness arbitrarily designated by the user, or a brightness appropriately set corresponding to the amount of use environment light of the projector 5. Say.

  Once the brightness of the light source 35 is set to the initial value, the central control unit 27 next determines whether to change the projected image, that is, the developed image on the video RAM 31 (step S2). If there is no change in the projected image, the process directly returns to step S1. On the other hand, if there is a change in the projected image, a luminance difference ΔF between the pre-change image and the post-change image is calculated (step S3). It is determined whether or not the difference ΔF is greater than or equal to a predetermined value SL (step S4).

  Here, the predetermined value SL represents a change of “dark → light” when the luminance difference ΔF between the pre-change image and the post-change image indicates a positive direction, that is, the pre-change image is dark and the post-change image is bright. In this case, the threshold value is used to determine whether or not to make a momentary illusion accompanying the change from dark to light. Specifically, it is a threshold value for identifying a change from the first screen 1 (dark image) to the second screen 2 (bright image) as in the example of FIG. When the average luminance value of the screen 1 is Fa and the average luminance value of the second screen 2 is Fb, the predetermined value SL is set to a value slightly larger than the difference between Fa and Fb.

  If the luminance difference ΔF is not equal to or greater than the predetermined value SL, it is determined that the instant image is not dazzled as the image is changed, and the process directly returns to step S1, while if the luminance difference ΔF is equal to or greater than the predetermined value SL, With this change, it is determined that there is a possibility that a moment of illusion may be felt. In this case, next, a change direction of luminance is determined (step S5).

  The direction of change in luminance means a change of “dark → light” in which the image before change is dark and the image after change is bright, and a change in “light → dark” where the image before change is bright and the image after change is dark. . In the case of a change from “dark to light”, there is a possibility that a momentary illusion may be felt as the image is changed. On the contrary, in the case of a change from “light to dark”, a momentary change is caused as the image is changed. There is no possibility of making you feel illusion.

  The point of this embodiment is that the brightness of the light source 35 is lowered when a change of “dark → bright” is determined (step S6), and the brightness of the light source 35 is determined when a change of “bright → dark” is determined. Is returned to the initial value (step S7).

  In this way, for example, the projection image is switched in the order of the first screen 1 (dark image) → second screen 2 (bright image) → first screen 1 (dark image) in FIG. In this case, that is, when the projection image is switched in the order of dark image → bright image → dark image, first, the first dark image is projected on the screen 3 with the brightness of the initial value of the light source 35, The subsequent second bright image is projected onto the screen 3 with the brightness lowered from the initial value of the light source 35, and the last third dark image is the screen 3 with the original brightness (initial value brightness) of the light source 35. Will be projected.

  Accordingly, the brightness of the light source 35 is lowered from the initial value when switching from the first dark image, which may cause a momentary illusion, to the second bright image, thereby reducing the display brightness of the second bright image. In addition, the possibility of illusion can be avoided, and the readability of character information and the like included in the second bright image can be improved.

  FIG. 5 is a diagram for explaining the operation of the present embodiment, and shows a state of switching from the first dark image to the second bright image. In this figure, the brightness of the light source 35 when projecting the first screen 1 (dark image) is an initial value, but the light source 35 when projecting the subsequent second screen 2 (bright image). The brightness of is reduced from the initial value and becomes darker. For this reason, the brightness of the white background portion, which is the highlight portion of the second screen 2, decreases corresponding to the brightness of the light source 35, and as a result, a slightly grayish background color (indicated by hatching in the figure). ), And it is easy to read the character information and the like contained in the second screen 2 because it appears gentle to the human eye.

  In the above embodiment, when the luminance difference ΔF between the pre-change image and the post-change image is equal to or greater than the predetermined value SL, the brightness of the light source 35 is changed according to the change direction of the luminance. This idea is not limited to this. In short, if there is a possibility that a moment of illusion may be caused by the change of the image, it is sufficient if the mechanism can eliminate the possibility. For example, the following may be adopted.

  FIG. 6 is a diagram illustrating a first modification. In this modification, the brightness of the light source 35 is not changed as it is, but instead the gamma characteristic of the image is switched. The gamma characteristic is a characteristic representing the input / output relationship of the luminance level (black ← → white) of an image. When the gamma characteristic is “1”, the input / output has a one-to-one linear relationship, and when the gamma characteristic is negative less than “1” or positive above “1”, the input / output has a non-linear relationship. .

  In this first modification, two gamma correction characteristics (bright image gamma correction characteristics and dark image gamma correction characteristics) are prepared. When the luminance change direction is “dark → bright”, the gamma characteristic of the changed image is corrected using the gamma correction characteristic for bright image (step S6a), while the luminance change direction is “bright”. In the case of “→ dark”, the gamma characteristic of the changed image is corrected using the gamma correction characteristic for the dark image (step S7a).

  The gamma correction characteristic for a bright image is obtained by reducing the output sensitivity on the white level side of the image as indicated by the white arrow a in the figure, and the gamma correction characteristic for the dark image is indicated by a white arrow in the figure. As shown, the output sensitivity on the white level side of the image is restored.

  Here, the dark image gamma correction characteristic is a linear characteristic and the bright image gamma correction characteristic is curved downward, but this is an example. For example, the gamma correction characteristics for bright images may be S-characteristics or other nonlinear characteristics. The important point is to lower the output sensitivity on the “white level side” of the gamma correction characteristic for the dark image than the gamma correction characteristic for the bright image.

  Even in this case, when there is a possibility that the first screen 1 (dark image) is switched to the second screen 2 (bright image) and a momentary illusion is felt, the gamma correction characteristic for the bright image is used. By doing so, the output sensitivity on the white level side of the image after the change is lowered, so that the luminance of the white background portion that is the highlight portion of the second screen 2 is lowered as in the above embodiment, and as a result The background color is slightly grayish (see the hatching in FIG. 5), so that the background image appears gentle to the human eye, and the character information and the like included in the second screen 2 can be easily read.

  FIG. 7 is a diagram illustrating a second modification. In this modification, the brightness of the light source 35 is not changed as it is, but instead the image histogram is switched. A histogram is a graph showing the luminance value distribution of each pixel constituting an image. In general, the horizontal axis of the histogram represents the luminance value, and the vertical axis represents the appearance frequency of pixels having the same luminance value. The histogram of the dark image has a characteristic having a peak on the left side (dark side) of the horizontal axis, and the histogram of the bright image has a characteristic having a peak on the right side (bright side) of the horizontal axis.

  In the second modification, two histograms (bright image histogram and dark image histogram) are prepared. When the luminance change direction is “dark → light”, the changed image is corrected using the bright image histogram (step S6b). On the other hand, when the luminance change direction is “bright → dark”. In this case, the changed image is corrected using the dark image histogram (step S7b).

  As shown by the white arrow C in the figure, the bright image histogram has a shape in which the bright peak of the image is slightly shifted to the dark side. The dark image histogram is indicated by the white arrow D in the figure. As shown, the dark side peak of the image is slightly shifted to the bright side.

  Even in this case, if there is a possibility that the first screen 1 (dark image) is switched to the second screen 2 (bright image) and an instant illusion is felt, the histogram for the bright image should be used. Therefore, the bright side peak of the image after the change is slightly shifted to the dark side, so that the brightness of the white background portion which is the highlight portion of the second screen 2 is reduced as in the above-described embodiment, and as a result, a little. It becomes a grayish background color (see the hatching in FIG. 5), so that it appears to be gentle to the human eye, and the character information and the like included in the second screen 2 can be easily read.

  In each of the embodiments described above, the change direction of the luminance of the projected image is determined (see step S5 in FIGS. 4, 6, and 7), and the light source 35 is determined when the change direction is “dark → bright”. (See step S6 in FIG. 4), or using a gamma correction characteristic for bright images and a histogram for bright images (see steps S6a and S6b in FIGS. 6 and 7), while the direction of change Is “bright → dark”, the brightness of the light source 35 is returned to the original initial value (see step S7 in FIG. 4), or the gamma correction characteristic for dark image and the histogram for dark image are used (see FIG. 6 and FIG. 6). However, the present invention is not limited to this mode. For example, the luminance change direction of the projected image changes from “dark to light” and the above-described required correction (reducing the brightness of the light source 35, using the gamma correction characteristic for a bright image, or using the histogram for a bright image). ), The brightness of the light source 35 is returned to the original initial value (the state before brightness correction) when a predetermined time elapses without waiting for the projection image to change from “bright to dark”. Or you may. It is only a short time immediately after the change direction of the brightness of the projected image changes from “dark to light” that makes the human eye feel illusion. This is because they get used to bright images and do not interfere with the interpretation of characters.

It is a system configuration figure of this embodiment. It is a simplified block diagram of personal computer PCi. 3 is an internal block diagram of the projector 5. FIG. It is a figure which shows the flowchart of the principal part of the control program performed with the central control part 27 of the projector 5. FIG. It is operation | movement explanatory drawing of this embodiment. It is a figure which shows a 1st modification. It is a figure which shows a 2nd modification. It is a figure which shows an example of the screen change which makes a momentary illusion feel.

Explanation of symbols

S2 step (detection process)
S4 step (judgment process)
S5 step (judgment process)
S6 step (correction process)
1 First screen (projected image)
2 Second screen (projected image)
20 Projector (display control device)
27 Central control unit (detection means, determination means, correction means)
35 Light source 35a Light source drive unit (correction means)

Claims (6)

Image acquisition means for acquiring a plurality of image data from a plurality of terminals;
The pre-change image based on the image data acquired by the image acquisition unit and acquired from one of the plurality of terminals is acquired by the image acquisition unit and acquired from two of the plurality of terminals. Detecting means for detecting switching to a post-change image based on the image data;
Whether the brightness difference between the pre-change image and the post-change image exceeds a predetermined value when the switching of the image is detected by the detection means, and the brightness value of the post-change image is higher than the pre-change image Determining means for determining whether or not;
When the determination result of the determination unit is positive, the brightness of the post-change image is corrected in a decreasing direction, and when the determination result of the determination unit changes from positive to negative, the brightness of the post-change image is corrected. Correction means for returning to the previous initial value ;
With
The correction means returns the brightness of the changed image to the initial value after a predetermined time has elapsed after the determination result of the determination means is affirmative and the brightness of the changed image is corrected in a decreasing direction. Display control device.   The display control apparatus according to claim 1, wherein the correction unit corrects the brightness of the image after the change in the decreasing direction by operating the brightness of the light source of the image in the decreasing direction.   The display control apparatus according to claim 1, wherein the correction unit corrects the brightness of the changed image in a decreasing direction by operating a gamma characteristic or a histogram of the changed image. An image acquisition step of acquiring a plurality of image data from a plurality of terminals, and an image before change based on the image data acquired from one of the plurality of terminals acquired by the image acquisition step. A detection step of detecting switching to a post-change image based on image data acquired and acquired from two of the plurality of terminals;
Whether the luminance difference between the pre-change image and the post-change image exceeds a predetermined value when the switching of the image is detected in the detection step, and the luminance value of the post-change image is higher than the pre-change image A determination step of determining whether or not,
When the determination result of the determination step is affirmative, the brightness of the post-change image is corrected in a decreasing direction, and when the determination result of the determination unit changes from positive to negative, the brightness of the post-change image is corrected. A correction process for returning to the previous initial value ;
Including
The correction step is to return the brightness of the changed image to the initial value after a lapse of a predetermined time after the determination result of the determination step is affirmative and the brightness of the changed image is corrected in a decreasing direction. Display control method to be performed. The display control method according to claim 4 , wherein the correcting step corrects the brightness of the changed image in the decreasing direction by operating the brightness of the light source of the image in the decreasing direction. 5. The display control method according to claim 4 , wherein the correcting step corrects the brightness of the post-change image in a decreasing direction by operating a gamma characteristic or a histogram of the post-change image.

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