JP2006301049A - Display device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the light quantity of a light source by a peak detection method close to human senses. <P>SOLUTION: The display device includes: a pixel luminance calculation part for calculating the luminance value of each of pixels constituting input image data as a first luminance value; a high luminance pixel judgment part for selecting a pixel of which the first luminance value is a prescribed luminance threshold and more as a high luminance pixel; a number of high luminance pixels judgment part for judging whether a high luminance pixel group consisting of a plurality of high luminance pixels which are adjacently arrayed includes pixels of the prescribed number-of-pixels threshold and more or not; and a light source light quantity setting part for controlling the light quantity of the light source on the basis of the statistical result of the first luminance values of the pixels included in the high luminance pixel group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device and a display method for displaying an image defined by a video signal, and more particularly to a display device and a display method for dynamically adjusting the light amount of a light source according to the video signal.

  There is a liquid crystal image display device as an image display device that displays an image by modulating light emitted from a light source. In a direct-view type liquid crystal image display device, a light irradiation unit called a backlight is provided on the back of a liquid crystal panel, and a fluorescent tube called a cold cathode tube is generally used as a light source. In a projection type liquid crystal image display device commonly called a liquid crystal projector, a halogen lamp, a metal halide lamp, or the like is employed as a light source.

  Conventionally, as a method for adjusting the light amount of the light source, for example, in Patent Document 1, the light amount of the light source is controlled according to the average luminance of the input video, and when the average luminance is high, the light amount of the light source is increased, and when the average luminance is low, Judgment is made based on whether or not the number of pixels (peak pixels) having a luminance higher than the predetermined luminance is greater than a predetermined number. If the number is larger than the predetermined number, the light amount of the light source is increased, and if it is smaller than the predetermined number, the light amount of the light source is decreased. Has been done.

Japanese Patent No. 3583122

  However, in Patent Document 1 described above, the number of pixels having a luminance higher than a predetermined luminance is obtained from the entire screen. In other words, it is impossible to distinguish whether the peak pixels are spatially concentrated or dispersed, so even if the peak pixels are scattered on the screen like a starry sky, for example, There is a problem that the light amount adjustment of the same light source is performed as in the case where the peak pixels are concentrated at the location, and the dark portion is blackened and the image becomes unclear.

  In view of the above, an object of the present invention is to provide a display device and a display method capable of displaying a high-quality image by controlling the light amount of the light source by a peak pixel detection method that is closer to a human visual sense. And

  In order to solve the above problems, in the display device of the present invention, in a display device that displays an image by modulating light emitted from a light source, the luminance of each pixel constituting the image data input to the display device A pixel luminance calculation unit that calculates a value as a first luminance value, a high luminance pixel determination unit that selects a pixel having the first luminance value equal to or higher than a predetermined luminance threshold as a high luminance pixel, and a plurality of the high luminance pixels A high-brightness pixel group determination unit that generates a determination result as to whether or not high-brightness pixel groups formed adjacent to each other have pixels equal to or greater than a predetermined pixel number threshold; and the determination result and the high-brightness pixel group include And a light source light amount setting unit that adjusts the light amount of the light source based on a statistical result of the first luminance value of the pixel.

  According to this configuration, pixels that are equal to or greater than a predetermined luminance threshold are extracted from the input image data as high-luminance pixels, and consecutively adjacent high-luminance pixels are defined as a high-luminance pixel group. If the number of high-luminance pixels included in the pixel is greater than or equal to a predetermined pixel number threshold, it is determined that the high-luminance pixels are concentrated. If the number of high-luminance pixels is less than the predetermined pixel number threshold, the high-luminance pixels are dispersed. Judgment can be made. As a result, it is possible to determine whether high-luminance pixels are concentrated or dispersed in the input image data. Therefore, the light amount of the light source can be adjusted according to the concentration degree of the high-luminance pixels. High-quality video can be displayed.

  In the display device of the present invention, the image data is further subjected to a low-pass filter with a first cutoff frequency to generate second image data, and the luminance of each pixel of the second image data. A second luminance value calculation unit that calculates a value as a second luminance value, wherein the high luminance pixel determination unit has the first luminance value equal to or greater than the luminance threshold value, and the first luminance value and the A pixel having a second luminance value difference equal to or greater than a predetermined luminance difference threshold is selected as a high luminance pixel.

  According to this configuration, as a condition for extracting a high luminance pixel from the image data, after the first luminance value of the pixel is equal to or higher than a predetermined luminance threshold value and the image data is subjected to a low-pass filter with the first cutoff frequency The second luminance value of each pixel of the second image data is calculated, and the difference between the first luminance value and the second luminance value is equal to or greater than a predetermined luminance difference threshold. And pixels with too high luminance can be removed. As a result, when the light amount adjustment of the light source is performed in accordance with the brightness that is too high, it is possible to eliminate the light amount adjustment that makes the entire screen dazzled and difficult to see.

  In the display device of the present invention, a third filter unit that generates a third image data by applying a low-pass filter to the image data at a second cutoff frequency, and a luminance of each pixel of the third image data A third luminance value calculation unit that calculates a value as a third luminance value, wherein the high luminance pixel determination unit has the first luminance value equal to or greater than the luminance threshold, and the first luminance value and the A pixel whose third luminance value ratio is equal to or greater than a predetermined luminance ratio threshold is selected as a high luminance pixel.

  According to this configuration, as a condition for extracting a high luminance pixel from the image data, the first luminance value of the pixel is equal to or higher than a predetermined luminance threshold, and the input image data is subjected to a low-pass filter with the second cutoff frequency. Since the third luminance value of each pixel of the subsequent third image data is calculated and the ratio between the first luminance value and the third luminance value exceeds a predetermined luminance ratio threshold, image noise in a small area In addition, a high-luminance pixel group in a region that is too wide can be excluded. This makes it possible to eliminate the light amount adjustment that makes the entire screen dazzling and difficult to see when the light amount adjustment of the light source is performed in accordance with the high-luminance pixel group in an excessively wide region.

  In the display device according to the aspect of the invention, when the determination result is “the high-luminance pixel group has pixels equal to or greater than the pixel number threshold value”, the light source light amount setting unit is included in the high-luminance pixel group. The light quantity of the light source is increased according to the luminance value having the highest frequency distribution of the first luminance value of the high luminance pixel.

  According to this configuration, since the high luminance pixel number determination unit determines that “the high luminance pixel group has a pixel equal to or greater than the predetermined pixel number threshold”, the first luminance value of the high luminance pixel of the high luminance pixel group is determined. Among them, a glossy image can be obtained by increasing the light amount of the light source according to the luminance value having the highest frequency distribution of the same luminance value.

  In the display device according to the aspect of the invention, when the determination result is “the high-luminance pixel group does not have a pixel equal to or larger than the pixel number threshold value”, the light source light amount setting unit calculates an average of all the pixels of the image data. The light quantity of the light source is controlled according to the luminance value.

  According to this configuration, since the high luminance pixel number determination unit determines that “the high luminance pixel group has no pixels equal to or greater than the predetermined pixel number threshold value”, the average luminance value of all the pixels of the image data is calculated. Since the light quantity of the light source is adjusted according to the average luminance value, it is possible to obtain an image with a well-defined brightness with no black float.

  In the display device of the present invention, when the average luminance value is higher than a predetermined average luminance threshold, the light source light amount setting unit increases the light amount of the light source according to the average luminance value.

  According to this configuration, the average luminance value of all the pixels of the image data is calculated, and when the average luminance value is higher than the predetermined average luminance threshold, the light amount of the light source is increased according to the average luminance value. It is possible to obtain an image that is completely bright.

  In the display device of the present invention, when the average luminance value is lower than the average luminance threshold, the light source light amount setting unit dims the light amount of the light source according to the average luminance value.

  According to this configuration, the average luminance value of all the pixels of the image data is calculated, and when the average luminance value is lower than the predetermined average luminance threshold, the light amount of the light source is reduced according to the average luminance value. It is possible to obtain an image with a well-lit brightness.

  According to the display method of the present invention, in the display method of a display device that displays an image by modulating light emitted from the light source, the luminance value of each pixel constituting the image data input to the display device is changed. A pixel luminance calculating step for calculating as one luminance value, a high luminance pixel determining step for selecting a pixel having the first luminance value equal to or higher than a predetermined luminance threshold as a high luminance pixel, and a plurality of the high luminance pixels adjacent to each other A high-brightness pixel group determination step for generating a determination result as to whether or not the high-brightness pixel group formed has a pixel equal to or greater than a predetermined pixel number threshold; and A light source light quantity setting step for adjusting the light quantity of the light source based on the statistical result of the first luminance value.

  According to this configuration, pixels that are equal to or greater than a predetermined luminance threshold are extracted from the input image data as high-luminance pixels, and consecutively adjacent high-luminance pixels are defined as a high-luminance pixel group. If the number of high-luminance pixels included in the pixel is greater than or equal to a predetermined pixel number threshold value, it is determined that the high-luminance pixels are concentrated. Judgment can be made. As a result, it is possible to determine whether high-luminance pixels are concentrated or dispersed in the input image data. Therefore, the light amount of the light source can be adjusted according to the concentration degree of the high-luminance pixels. High-quality video can be displayed.

  Embodiments of a display device according to the present invention will be described below with reference to the drawings.

(First embodiment)
First, a schematic configuration of a display device according to a first embodiment embodying the present invention will be described with reference to FIG.

<Configuration of display device>
FIG. 1 is a configuration diagram when a display device according to the present invention is applied to a liquid crystal projector.
The display device 1 includes a CPU 11, a RAM 12, a ROM 13, an input interface (I / F) 14, an image calculation processing unit 15, an image signal generation unit 16, and a light source control unit 17 as a whole. Are connected to each other. Further, the image signal generation unit 16 sends an image signal to the light valve 31, and the light source control unit 17 sends a control signal to the light source 30.

  The image calculation processing unit 15 includes a pixel luminance calculation unit 100, a peak pixel determination unit 102 that is a high luminance pixel determination unit, a peak pixel group generation unit 104 and a peak pixel number determination unit 106 that form a high luminance pixel number determination unit, and a light source light amount. Each function of the setting unit 108 and the image correction unit 110 is executed.

  The RAM 12 serves as a working memory for each process, and stores various data after the process. The RAM 12 stores in the image data table 41 information on the results of calculations performed by the image calculation processing unit 15 on at least the input image data 40 received from the input I / F 14.

  The ROM 13 is configured by an EEPROM (Electrically Erasable Programmable Read-Only Memory), a flash memory, and the like, and includes a program, a luminance threshold Pth, a peak pixel number threshold Nth that is a pixel number threshold, a luminance difference threshold ΔPth, a luminance ratio threshold α, The average luminance threshold Ath is stored in a rewritable manner.

  The input I / F 14 serves as an interface for receiving input image data 40 from an external device (not shown). When the input I / F 14 receives the input image data 40, it stores it in the RAM 12 via the bus 20.

  The pixel luminance calculation unit 100 calculates the luminance from the RGB value of the input image data 40 stored in the RAM 12 and stores it in the luminance value Y0 of the image data table 41.

  The peak pixel determination unit 102 applies a low-pass filter having a high cutoff frequency to the luminance value Y0 of the image data table 41, stores the low-pass filter in the luminance value Y1 of the image data table 41, and the luminance value Y1 of each pixel of the image data table 41. Is compared with the luminance threshold value Pth, a pixel having the luminance value Y1 equal to or higher than the luminance threshold value Pth is determined as a peak pixel that is a high luminance pixel, and whether or not the peak pixel determination result P in the image data table 41 is a peak pixel. Store the result of.

  The peak pixel group generation unit 104 refers to the peak pixel determination result P of each pixel in the image data table 41 and sets the peak pixels adjacent to each other as a peak pixel group that is a high luminance pixel group. The peak pixel group number GNO is recorded in the peak pixel group G, and the number of peak pixels included in the peak pixel group is counted as the adjacent peak pixel number Cp.

  The peak pixel number determination unit 106 checks whether the adjacent peak pixel number Cp counted by the peak pixel group generation unit 104 exceeds the peak pixel number threshold Nth, and generates a peak determination result as a determination result.

  The light source light amount setting unit 108 sets a gradation correction curve based on the peak determination result generated by the peak pixel number determination unit 106 and sets the light amount of the light source.

  The image correction unit 110 corrects the luminance value Y1 of the image data table 41 based on the gradation correction curve set by the light source light quantity setting unit 108.

  The image signal generation unit 16 converts the corrected image data from the corrected luminance value Y1 stored in the image data table 41 into an image signal that can be displayed by the light valve 31, and controls the light valve 31.

  The light source control unit 17 controls the light amount of the light source 30 based on the light amount of the light source set by the light source light amount setting unit 108.

<Peak Pixel Group Determination Method 1>
Next, a peak pixel group determination method according to the first embodiment will be described with reference to FIG.
FIG. 2 is a schematic diagram illustrating a peak pixel group determination method according to the first embodiment.

  In FIG. 2, for simplification of description, as shown in (A1) and (B1) of FIG. 2, the image 200 is searched in the X-axis direction to continuously find adjacent peak pixels and peak pixel groups. It is illustrated about. In the images 200 of (A1) and (B1) in FIG. 2, a pixel region having a luminance lower than the luminance threshold Pth is a low luminance pixel group 210, and a pixel region having a luminance equal to or higher than the luminance threshold Pth is a peak pixel group 220. 2A is a graph showing the luminance Y of the pixel on the X axis in FIG. 2A1, and FIG. 2B2 is the pixel on the X axis in FIG. 2B1. It is a graph which shows the brightness | luminance Y of.

  In the case of (A2) in FIG. 2, since the adjacent peak pixel number Cp on the X axis of the peak pixel group 220 in which pixels equal to or higher than the luminance threshold Pth continue is smaller than the peak pixel number threshold Nth, the peak determination result is “peak “No pixel group exists (No)”. On the other hand, in the case of (B2) in FIG. 2, the adjacent peak pixel number Cp on the X-axis of the peak pixel group 220 in which pixels equal to or higher than the luminance threshold Pth continue is larger than the peak pixel number threshold Nth, and thus the peak determination result is “Peak pixel group exists (Yes)”.

  Although the peak pixel group continuous in the X-axis direction has been described with reference to FIG. 2, the determination is actually made based on the area of the peak pixel group.

<Process of Peak Pixel Determination Unit>
Next, the processing of the peak pixel determination unit 102 of the first embodiment will be described with reference to FIG.
FIG. 3 is a flowchart for explaining processing of the peak pixel determination unit 102 of the first embodiment.

  In the present embodiment, since the input image data 40 may include image noise in a small area, a low-pass filter having a high cutoff frequency is applied to the input image data 40 so as not to be affected by the image noise. The case will be described.

  First, in step S100, a low-pass filter having a high cutoff frequency is applied to the luminance value Y0 in the image data table 41 of the RAM 12.

  Next, in step S102, the luminance value after applying the low-pass filter is stored in Y1 of the image data table 41.

  In step S104, an unprocessed pixel in the image data table 41 is selected.

  Next, in step S106, it is determined whether or not the luminance value Y1 of the selected pixel in the image data table 41 is equal to or higher than the luminance threshold Pth. If the luminance value Y1 is equal to or higher than the luminance threshold Pth, the process proceeds to step S108. The process proceeds to S112.

  Next, in step S108, since it was determined that it is a peak pixel, 1 is stored in the peak pixel determination result P of the image data table 41, and the process proceeds to step S110.

  On the other hand, since it is determined in step S112 that the pixel is not a peak pixel, 0 is stored in the peak pixel determination result P of the image data table 41, and the process proceeds to step S110.

  Next, in step S110, it is determined whether or not there is an unselected pixel in the image data table 41. If there is, the process proceeds to step S104, and if not, the process ends.

<Processing of Peak Pixel Group Generation Unit and Peak Pixel Number Determination Unit>
Next, processing of the peak pixel group generation unit 104 and the peak pixel number determination unit 106 according to the first embodiment will be described with reference to FIG.
FIG. 4 is a flowchart for explaining processing of the peak pixel group generation unit 104 and the peak pixel number determination unit 106 according to the first embodiment.

  First, in step S122, the number of adjacent peak pixels Cp is reset to 0, and 1 is added to the peak pixel group number GNO (the initial value of GNO is 0).

  Next, in step S124, an unselected peak pixel (P = 1 pixel) is selected from the image data table 41 stored in the RAM 12, and is put into the peak pixel group.

  In step S126, an unselected peak pixel adjacent to the peak pixel group is searched from the image data table 41.

  Next, in step S128, it is determined whether or not an unselected peak pixel adjacent to the peak pixel group is found. If a peak pixel is found, the process proceeds to step S130, and if no peak pixel is found, The process proceeds to step S136.

  In step S130, the peak pixel group number GNO is input to the peak pixel group G of the found peak pixel image data table 41, and 1 is added to the number of adjacent peak pixels Cp (Cp = Cp + 1).

  On the other hand, in step S136, it is determined whether or not there is an unselected peak pixel in the image data table 41. If there is an unselected peak pixel, the process proceeds to step S122, and if there is no unselected peak pixel, The process ends.

  Next, in step S132, it is determined whether or not the adjacent peak pixel number Cp is equal to or greater than the peak pixel number threshold Nth. If it is equal to or greater than the peak pixel number threshold Nth, the process proceeds to step S134, and the peak pixel number threshold Nth is determined. If it is less, the process proceeds to step S138.

  In step S134, the peak determination result is “the number of pixels in the peak pixel group is equal to or greater than the peak pixel number threshold Nth”, and the process ends.

  On the other hand, in step S138, it is determined whether or not there is an unselected peak pixel in the image data table 41. If there is an unselected peak pixel, the process proceeds to step S126, and if there is no unselected peak pixel, The process ends.

<Relationship between gradation correction curve and light intensity setting>
Next, the relationship between the gradation correction curve and the light amount setting will be described with reference to FIG.
FIG. 5 is a graph for explaining the relationship between the gradation correction curve and the light amount setting.

  FIG. 5A shows the relationship between the input luminance and the output luminance corrected by the gradation correction curve 300 when the peak determination result is “the number of pixels in the peak pixel group is equal to or greater than the peak pixel number threshold Nth”. It is a graph. The gradation correction curve 300 is stored in advance in a look-up table (LUT) memory of the ROM 13 or is obtained by performing a product-sum operation for each pixel without using the LUT. As shown in FIG. 5A, the gradation correction curve 300 draws a curve that protrudes downward, and when the input luminance is high, the output luminance is further lowered when the input luminance is low. The output brightness is set to be higher. The light amount of the light source is the difference between the luminance value of the maximum frequency in the frequency distribution of the luminance value of the peak pixel included in the peak pixel group and the luminance value after the luminance value of the maximum frequency is corrected by the gradation correction curve 300, that is, The light is increased by the amount of the arrow 301 in FIG.

  FIG. 5B shows that the peak determination result is “the number of pixels in the peak pixel group is less than the peak pixel number threshold Nth” and “the average luminance of all the pixels of the input image data is higher than the average luminance threshold”. 6 is a graph showing the relationship between the input luminance and the output luminance corrected by the gradation correction curve 302. As shown in FIG. 5B, the gradation correction curve 302 is set so as to draw a downwardly convex curve, and the output brightness is lower than the input brightness as a whole. The light amount of the light source is increased by the difference between the average luminance value of all the pixels of the input image data and the luminance value after the average luminance value is corrected by the gradation correction curve 300, that is, the amount indicated by the arrow 303 in FIG. Is done.

  FIG. 5C shows that the peak determination result is “the number of pixels of the peak pixel group is less than the peak pixel number threshold Nth” and “the average luminance of all the pixels of the input image data is lower than the average luminance threshold”. 6 is a graph showing the relationship between the input luminance and the output luminance corrected by the gradation correction curve 304. As shown in FIG. 5C, the gradation correction curve 304 is set so as to draw a curve bulging upward and the output brightness is higher than the input brightness as a whole. The light amount of the light source is reduced by the difference between the average luminance value of all the pixels of the input image data and the luminance value after the average luminance value is corrected by the gradation correction curve 300, the amount indicated by the arrow 305 in FIG. Is done.

<Processing of light source quantity setting unit>
Next, processing of the light source light quantity setting unit 108 will be described with reference to FIG.
FIG. 6 is a flowchart for explaining processing of the light source light quantity setting unit 108.

  First, in step S152, the peak determination result is checked. If “the number of pixels in the peak pixel group is equal to or greater than the peak pixel number threshold Nth” (Yes), the process proceeds to step S154, and “the number of pixels in the peak pixel group is If it is less than the peak pixel number threshold Nth (No), the process proceeds to step S156.

  Next, in step S154, the image correction unit 110 is instructed to correct the input image data using the gradation correction curve 300 in FIG. 5A, and the light source control unit 17 determines the light amount of the light source as shown in FIG. Is instructed to increase the amount of light by the amount of the arrow 301 in FIG.

  On the other hand, in step S156, the average luminance is calculated from the luminance value Y1 of all the pixels in the image data table 41 stored in the RAM 12.

  Next, in step S158, it is determined whether or not the average luminance is equal to or higher than the average luminance threshold Ath. If “average luminance threshold Ath or higher” (Yes), the process proceeds to step S160, and “less than average luminance threshold Ath is reached. If “Yes” (No), the process proceeds to step S162.

  Next, in step S160, the image correction unit 110 is instructed to correct the input image data using the gradation correction curve 302 in FIG. 5B, and the light source control unit 17 determines the light amount of the light source as shown in FIG. (B) is instructed to brighten by the amount of arrow 303, and the process ends.

  On the other hand, in step S162, the image correction unit 110 is instructed to correct the input image data by using the gradation correction curve 304 in FIG. 5C, and the light source control unit 17 determines the light amount of the light source in FIG. An instruction is given to dimming by the amount of arrow 305 in (C), and the process ends.

  According to the embodiment described above, the following effects can be obtained.

  In this embodiment, since it is possible to determine whether or not the peak pixels whose pixel values of the image data are greater than or equal to the luminance threshold Pth are concentrated, the light amount of the light source is adjusted according to the degree of concentration of the peak pixels. Can display high-quality video.

(Second Embodiment)
Next, a second embodiment of the display device according to the present invention will be described. In the first embodiment, the case where the peak pixel determination unit 102 selects a peak pixel as a condition for selecting a peak pixel has been described as a pixel whose luminance value is greater than or equal to the luminance threshold Pth. In the embodiment, as a condition for the peak pixel determination unit 102 to select a peak pixel, the first luminance value of the pixel is equal to or higher than the luminance threshold Pth, and the image data is subjected to a low-pass filter having a low cutoff frequency. A case will be described in which the second luminance value of each pixel of the second image data is calculated, and the difference between the first luminance value and the second luminance value is greater than or equal to the luminance difference threshold value ΔPth.

<Peak Pixel Group Determination Method 2>
First, the peak pixel group determination method of the second embodiment will be described with reference to FIG.
FIG. 7 is a schematic diagram illustrating a peak pixel group determination method according to the second embodiment. In order to simplify the description, FIG. 7 illustrates a method of searching the image 200 in the X-axis direction and finding adjacent peak pixels and peak pixel groups in the same manner as in FIG.

  Graphs Y1 of (A1), (B1), and (C1) in FIG. 7 indicate the original input image data or the luminance Y1 (first) of the pixel on the X axis of the image data after applying a low-pass filter with a high cutoff frequency. The graph Y2 is a graph showing the image data (second image data) obtained by applying a low-pass filter (second filter unit) having a low cutoff frequency (first cutoff frequency) to the original input image data. ) Is a graph showing the luminance Y2 (second luminance value) of the pixel on the X-axis. Further, (A2), (B2), and (C2) in FIG. 7 are graphs showing the luminance difference ΔY (= Y1−Y2) between the luminance Y1 and the luminance Y2.

  (A1) and (A2) of FIG. 7 show that the number of adjacent peak pixels Cp on the X axis of the peak pixel group 220 in which pixels having a luminance difference ΔY of pixels continue with a luminance difference threshold ΔPth or more is greater than the peak pixel number threshold Nth. Since it is small, the peak determination result indicates “a peak pixel group does not exist (No)”.

  (B1) and (B2) of FIG. 7 show that the number of adjacent peak pixels Cp on the X axis of the peak pixel group 220 in which pixels having a luminance difference ΔY of pixels continue with a luminance difference threshold ΔPth or more is greater than the peak pixel number threshold Nth. Since it is large, the peak determination result indicates a case where “a peak pixel group exists (Yes)”.

  In (C1) and (C2) of FIG. 7, when only the luminance Y1 of the original input image data is viewed, the adjacent peak pixel number Cp on the X axis is sufficiently larger than the peak pixel number threshold Nth. The peak pixel group 220 in which the pixels having the luminance difference ΔY equal to or greater than the luminance difference threshold ΔPth are divided into two, and the adjacent peak pixel number Cp on each X axis is smaller than the peak pixel number threshold Nth. Indicates a case where “a peak pixel group does not exist (No)”.

<Process 2 of Peak Pixel Determination Unit>
Next, processing of the peak pixel determination unit 102 of the second embodiment will be described with reference to FIG.
FIG. 8 is a flowchart for describing processing of the peak pixel determination unit 102 of the second embodiment.

  In the present embodiment, a description will be given after steps S100 and S102 in FIG. 3 for applying a low-pass filter having a high cutoff frequency to the input image data 40 have already been performed and Y1 of the image data table 41 in the RAM 12 is set. .

  First, in step S172, a low-pass filter having a lower cutoff frequency LPF2 (LPF1 <LFP2) is applied to the luminance value of each pixel stored in Y1 of the image data table 41 stored in the RAM 12.

  Next, in step S174, the luminance value after the low-pass filter is applied is stored in Y2 of the image data table 41.

  In step S176, an unprocessed pixel in the image data table 41 is selected.

  Next, in step S178, it is determined whether or not the luminance value Y1 of the selected pixel in the image data table 41 is greater than or equal to the luminance threshold value Pth. If the luminance value is greater than or equal to the luminance threshold value Pth, the process proceeds to step S180. The process proceeds to S186.

  Next, in step S180, it is determined whether or not the luminance difference ΔY = Y1−Y2 between the luminance value Y1 and the luminance value Y2 of the selected pixel in the image data table 41 is greater than or equal to the luminance difference threshold ΔPth. If it is less than the brightness difference threshold value ΔPth, the process proceeds to step S186.

  Next, in step S182, since it is determined that the pixel is a peak pixel, 1 is stored in P of the image data table 41, and the process proceeds to step S184.

  On the other hand, in step S186, since it is determined that the pixel is not a peak pixel, 0 is stored in P of the image data table 41, and the process proceeds to step S184.

  Next, in step S184, it is determined whether or not there is an unselected pixel in the image data table 41. If there is, the process proceeds to step S176, and if not, the process ends.

  According to the second embodiment described above, the following effects can be obtained.

  In the second embodiment of the present invention, not only image noise in a small area, but also pixels having luminance that is too high can be removed. Thereby, when the light amount adjustment of the light source is performed in accordance with the luminance that is too high, it is possible to eliminate the light amount adjustment that makes the entire screen dazzling and difficult to see.

(Third embodiment)
Next, a third embodiment of the display device according to the present invention will be described. In the first embodiment, the case where the peak pixel determination unit 102 selects a peak pixel as a condition for selecting the peak pixel has been described as a pixel whose luminance value is equal to or higher than the luminance threshold Pth. In the embodiment, as a condition for selecting the peak pixel, the peak pixel determination unit 102 applies a low-pass filter having a first luminance value of the pixel equal to or higher than the luminance threshold Pth and a slightly lower cutoff frequency to the image data. A case will be described in which the third luminance value of each pixel of the subsequent third image data is calculated and the ratio between the first luminance value and the third luminance value is equal to or greater than the luminance ratio threshold value α.

<Peak Pixel Group Determination Method 3>
First, a peak pixel group determination method according to the third embodiment will be described with reference to FIG.
FIG. 9 is a schematic diagram illustrating a peak pixel group determination method according to the third embodiment. In order to simplify the description, FIG. 9 illustrates a method of searching the image 200 in the X-axis direction and finding adjacent peak pixels and peak pixel groups in the same manner as in FIG.

  The graph Y1 of (A1), (B1), and (C1) in FIG. 9 shows the luminance Y1 (first) of the pixel on the X axis of the original input image data or image data after applying a low-pass filter with a high cutoff frequency. The graph Y3 is a graph showing the image data after the low-pass filter (third filter unit) having a slightly lower cutoff frequency (second cutoff frequency) is applied to the original input image data (third luminance value). It is a graph which shows the brightness | luminance Y3 (3rd brightness | luminance value) of the pixel on the X-axis of (image data). Further, (A2), (B2), and (C2) in FIG. 9 are graphs showing the luminance ratio Ry (= Y1 / Y3) between the luminance Y1 and the luminance Y3.

  (A1) and (A2) in FIG. 9 show that the number of adjacent peak pixels Cp on the X axis of the peak pixel group 220 in which pixels having a luminance ratio Ry of pixels continue with the luminance ratio threshold α or more is greater than the peak pixel number threshold Nth. Since it is small, the peak determination result indicates “a peak pixel group does not exist (No)”.

  (B1) and (B2) in FIG. 9 show that the number of adjacent peak pixels Cp on the X axis of the peak pixel group 220 in which pixels having a luminance ratio Ry of pixels continue with the luminance ratio threshold value α or more is greater than the peak pixel number threshold value Nth. Since it is large, the peak determination result indicates a case where “a peak pixel group exists (Yes)”.

  In (C1) and (C2) of FIG. 9, when only the luminance Y1 of the original input image data is viewed, the adjacent peak pixel number Cp on the X axis is sufficiently larger than the peak pixel number threshold Nth. The peak pixel group 220 in which pixels having the luminance ratio Ry equal to or greater than the luminance ratio threshold α are divided into two, and the number of adjacent peak pixels Cp on each X-axis is smaller than the peak pixel number threshold Nth. Indicates a case where “a peak pixel group does not exist (No)”.

<Process 3 of Peak Pixel Determination Unit>
Next, with reference to FIG. 10, the processing of the peak pixel determination unit 102 of the third embodiment will be described.
FIG. 10 is a flowchart illustrating the processing of the peak pixel determination unit 102 of the third embodiment.

  In this embodiment, a description will be given after steps S100 and S102 in FIG. 3 for applying a low-pass filter having a high cutoff frequency to the input image data 40 have already been performed and Y1 of the image data table 41 of the RAM 12 is set.

  First, in step S202, a low-pass filter with a slightly lower cutoff frequency LPF3 (LPF1 <LPF3 <LFP2) is applied to the luminance value of each pixel stored in Y1 of the image data table 41 stored in the RAM 12.

  In step S204, the image data after the low-pass filter is stored in Y3 of the image data table 41.

  Next, in step S206, an unprocessed pixel in the image data table 41 is selected.

  Next, in step S208, it is determined whether or not the luminance value Y1 of the selected pixel in the image data table 41 is equal to or higher than the luminance threshold Pth. If the luminance value Y1 is equal to or higher than the luminance threshold Pth, the process proceeds to step S210. The process proceeds to S216.

  Next, in step S210, it is determined whether or not the luminance ratio Ry (= Y1 / Y3) between the luminance value Y1 and the luminance value Y3 of the selected pixel in the image data table 41 is equal to or greater than the luminance ratio threshold α. If so, the process proceeds to step S212, and if less than the luminance ratio threshold value α, the process proceeds to step S216.

  Next, in step S212, since it is determined that the pixel is a peak pixel, 1 is stored in P of the image data table 41, and the process proceeds to step S214.

  On the other hand, since it is determined in step S216 that the pixel is not a peak pixel, 0 is stored in P of the image data table 41, and the process proceeds to step S214.

  Next, in step S214, it is determined whether or not there is an unselected pixel in the image data table 41. If there is, the process proceeds to step S206, and if not, the process ends.

  According to the third embodiment described above, the following effects can be obtained.

  In the third embodiment of the present invention, not only image noise in a small area but also a peak pixel group having an excessively wide area can be excluded. Thereby, when the light amount adjustment of the light source is performed in accordance with the peak pixel group having an area that is too wide, it is possible to eliminate the light amount adjustment that makes the entire screen dazzling and difficult to see.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, In the range which does not deviate from the meaning of this invention, it can be implemented with various forms. Hereinafter, a modification will be described.

  (Modification 1) A first modification of the display device according to the present invention will be described. In the first embodiment, the case where one luminance threshold value Pth and one peak pixel number threshold value Nth are set has been described, but a plurality of luminance threshold values Pth and peak pixel number threshold value Nth may be set. For example, in the case of input image data whose luminance is high overall, the luminance threshold value Pth is set high, and in the case of input image data whose luminance is low overall, the luminance threshold value Pth is set low. Alternatively, a plurality of brightness threshold values Pth and peak pixel number threshold values Nth may be prepared in succession so that they can be selected flexibly.

  (Modification 2) A second modification of the display device according to the present invention will be described. In the first embodiment, the case where it is determined whether or not the adjacent peak pixel number Cp is equal to or greater than the peak pixel number threshold Nth has been described. However, the lower limit peak pixel is set so that the peak pixel group that is too wide can be excluded. A number threshold value Nth1 and an upper limit peak pixel number threshold value Nth2 may be provided to determine whether or not the adjacent peak pixel number Cp is in the range of Nth1 ≦ Cp ≦ Nth2.

  (Modification 3) A third modification of the display device according to the present invention will be described. In the first embodiment, the processing of the peak pixel group generation unit 104 and the peak pixel number determination unit 106 is shown in the flowchart of FIG. Although it has been described that “the number of pixels in the peak pixel group is equal to or greater than the peak pixel number threshold Nth” when Nth is determined, the process is terminated, but the present invention is not limited to this. Even after it is determined that Cp ≧ Nth, an unselected peak pixel adjacent to the peak pixel group is searched, and the process may be terminated when there is no adjacent pixel. In addition, after one peak pixel group is generated, another peak pixel group may be searched for and the peak pixel group in the maximum region may be generated.

  (Modification 4) A fourth modification of the display device according to the present invention will be described. In the first to third embodiments, as the processing of the peak pixel determination unit 102, the input image data 40 may include image noise in a small area, so that it is not affected by image noise. Although the case where a low-pass filter with a high cutoff frequency is applied to the input image data 40 has been described, it is not necessary to apply a low-pass filter with a high cutoff frequency to the input image data 40.

  (Modification 5) A fifth modification of the display device according to the present invention will be described. In the first to third embodiments, the peak pixel group generation unit 104 has been described as searching for adjacent peak pixels. However, it is accurate to sequentially search for adjacent peak pixels. Because it is heavy, it may be further simplified. For example, assuming that the peak is circular / elliptical in advance, the search may be made within the circular / elliptical range. Further, as described with reference to FIG. 2, a search is performed with peak pixels adjacent on the Y axis, and then scanning is performed in the vertical direction at the X coordinate of the continuous central position to search for the number of continuous pixels. May be judged.

1 is a configuration diagram of a display device according to a first embodiment of the present invention. Schematic explaining the determination method of the peak pixel group of 1st Embodiment. The flowchart explaining the process of the peak pixel determination part of 1st Embodiment. The flowchart explaining the process of a peak pixel group production | generation part and a peak pixel number determination part. The graph explaining the relationship between a gradation correction curve and light quantity setting. The flowchart explaining the process of a light source light quantity setting part. Schematic explaining the determination method of the peak pixel group of 2nd Embodiment. The flowchart explaining the process of the peak pixel determination part of 2nd Embodiment. Schematic explaining the determination method of the peak pixel group of 3rd Embodiment. The flowchart explaining the process of the peak pixel determination part of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... Input I / F, 15 ... Image operation process part, 16 ... Image signal generation part, 17 ... Light source control part, 20 ... Bus, 30 ... Light source, 31 ... light valve, 40 ... input image data, 41 ... image data table, 100 ... pixel luminance calculation unit, 102 ... peak pixel determination unit, 104 ... peak pixel group generation unit, 106 ... peak pixel number determination unit, 108 ... light source quantity setting unit, 110 ... image correction unit.

Claims (8)

In a display device that displays an image by modulating light emitted from a light source,
A pixel luminance calculation unit that calculates a luminance value of each pixel constituting the image data input to the display device as a first luminance value;
A high-brightness pixel determination unit that selects, as a high-brightness pixel, a pixel whose first luminance value is equal to or greater than a predetermined luminance threshold;
A high-brightness pixel number determination unit that generates a determination result as to whether or not a high-brightness pixel group formed by a plurality of the high-brightness pixels adjacent to each other has a pixel equal to or greater than a predetermined pixel number threshold;
A light source light quantity setting unit that adjusts the light quantity of the light source based on the determination result and the statistical result of the first luminance value of the pixels included in the high luminance pixel group;
A display device comprising: The display device according to claim 1,
A second filter unit that generates a second image data by applying a low-pass filter to the image data at a first cutoff frequency;
A second luminance value calculation unit that calculates a luminance value of each pixel of the second image data as a second luminance value;
The high-luminance pixel determination unit determines a pixel having the first luminance value that is equal to or higher than the luminance threshold and the difference between the first luminance value and the second luminance value is equal to or higher than a predetermined luminance difference threshold as high luminance. Elect as pixel,
A display device characterized by that. The display device according to claim 1,
A third filter unit that generates a third image data by applying a low-pass filter to the image data at a second cutoff frequency;
A third luminance value calculation unit that calculates a luminance value of each pixel of the third image data as a third luminance value;
The high-luminance pixel determination unit is configured to detect pixels whose first luminance value is equal to or higher than the luminance threshold and whose ratio between the first luminance value and the third luminance value is equal to or higher than a predetermined luminance ratio threshold. Elect as pixel,
A display device characterized by that.   The display device according to any one of claims 1 to 3, wherein when the determination result is "the high-luminance pixel group includes pixels equal to or greater than the pixel number threshold value", the light source light amount setting unit includes: A display device, wherein the light intensity of the light source is increased according to a luminance value having a maximum frequency distribution of the first luminance value of the high luminance pixels included in the high luminance pixel group.   In the display device according to any one of claims 1 to 3, when the determination result is "the high-luminance pixel group does not have a pixel equal to or greater than the pixel number threshold value", the light source light amount setting unit includes: A display device, wherein the light amount of the light source is controlled in accordance with an average luminance value of all pixels of the image data.   6. The display device according to claim 5, wherein when the average luminance value is higher than a predetermined average luminance threshold, the light source light amount setting unit increases the light amount of the light source according to the average luminance value. Display device.   6. The display device according to claim 5, wherein when the average luminance value is lower than the average luminance threshold, the light source light amount setting unit dimmes the light amount of the light source according to the average luminance value. Display device. In a display method of a display device that displays an image by modulating light emitted from a light source,
A pixel luminance calculation step of calculating a luminance value of each pixel constituting the image data input to the display device as a first luminance value;
A high-luminance pixel determination step of selecting, as the high-luminance pixel, a pixel having the first luminance value equal to or higher than a predetermined luminance threshold;
A high-brightness pixel number determination step for generating a determination result as to whether or not a high-brightness pixel group formed by a plurality of the high-brightness pixels adjacent to each other has a pixel equal to or greater than a predetermined pixel number threshold;
A light source light amount setting step of adjusting the light amount of the light source based on the determination result and the statistical result of the first luminance value of the pixels included in the high luminance pixel group;
A display method characterized by comprising:

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