JP5300601B2 - Display device and display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for displaying an input image without causing reduction in feeling of contrast, even when a highlight region that includes specular components and a bright region having a relatively a wide region coexists in the input image. <P>SOLUTION: A calculation section 603 is configured to obtain the maximum average luminance level (APL1) from among the average luminance level of each of horizontal lines constituting the input image. A correction gain calculating section 604 is configured to obtain a correction gain based on the APL1, when the target line is a line not including the object region. The correction gain calculating section 604 is configured to, when the target line includes the object region, obtain the correction gain, based on the average luminance level APL2 in the target line, when the average luminance level APL2 in the target line is lower than APL1, and on the other hand, when APL2 is equal to or higher than APL1, obtain the correction gain based on the APL1. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image display technique.

  In recent years, an electron source is provided at the intersection of mutually orthogonal electrode groups, and the amount of electrons emitted from the electron source is controlled by adjusting the voltage or time applied to each electron source. A self-luminous matrix display that irradiates phosphors has attracted attention. Examples of the electron source used in this type of display include those using a field emission cathode, those using a thin film electron source, those using a carbon nanotube, and those using a surface conduction electron-emitting device.

  In this type of display, element groups for one row are driven simultaneously by sequentially scanning the row wiring and modulating in the column direction. In the case of driving in this way, there is a problem of a decrease in luminance due to a voltage drop between power supply portions at both ends due to electric resistance due to the wiring in the row wiring.

  In line sequential scanning, the drive current of the electron-emitting devices connected to the wiring flows through the selected scanning line. The scanning line current is very large, from several tens to several hundreds mA, and a voltage drop is caused by the scanning line resistance value. For this reason, there is a problem of luminance gradient in which the luminance decreases as the far-end pixel is viewed from the drive circuit side. In addition, this luminance gradient varies depending on the luminance of each pixel, and is a major factor in causing uneven luminance in the horizontal band.

  FIG. 1 is a diagram illustrating an example of luminance reduction due to voltage drop. Consider the case where the input image is an image in which a white cross-shaped pattern is superimposed on a black background as shown by 101. Then, when driving the line L in the input image 101 (actually, the line L on the screen displaying the input image 101), since the number of lit pixels is small, the line L is almost on the scanning line of the line. There is no voltage drop. As a result, a desired amount of emission current is emitted from the surface conduction electron-emitting device of each pixel, and light can be emitted with a desired luminance. On the other hand, when driving the line L ′ in the input image 101 (actually, the line L ′ on the screen displaying the input image 101), all the pixels are lit at the same time, so that a voltage drop occurs on the scanning line. . As a result, as the distance from the drive circuit increases, the emission current from the surface conduction electron-emitting devices of each pixel decreases, and as indicated by 102, the brightness is greatly reduced at the center in line L ′.

  Therefore, in order to correct the luminance decrease due to such a voltage drop due to the wiring resistance, a method of calculating the correction data by statistical calculation has been proposed. Patent Document 1 describes a method of calculating a correction gain by calculating an average luminance level of each horizontal scanning line, estimating a voltage drop amount based on the maximum value of the average luminance level in a frame. Patent Document 2 describes a method of calculating a correction amount for each light emitter because the voltage drop amount is different for each light emitter.

  Patent Document 3 describes a method of adding a first scanning signal corresponding to an input video signal and a second scanning signal for compensating for a voltage drop amount depending on the wiring resistance of the first scanning signal. .

  Recently, a display including an ABL (Automatic Brightness Limiter) circuit for limiting emission luminance has been proposed for the purpose of suppressing heat generation of the display panel and power consumption of the display. The ABL circuit performs an operation of suppressing the amount of electrons emitted from the electron-emitting device when the line average luminance exceeds a preset upper limit luminance.

  FIG. 2 is a diagram illustrating an example of an operation result by the ABL circuit. Consider a case where the input image is an image in which a white rectangular pattern is superimposed on a black background as shown in FIG. The white rectangular pattern has a width of about 80% of the horizontal resolution, and the height can be changed variably. FIG. 2B is a diagram showing the relationship between the luminance of the rectangular pattern and the average value of the high-voltage load current when the height of the white rectangular pattern is changed. When gradually increasing the height of the input image, the ABL circuit operates so that the high-voltage load current is constant. As a result, even if the horizontal scanning line signals are the same, as the area of the white rectangular pattern increases, the amount of current flowing through the surface conduction electron-emitting device decreases and the luminance decreases.

  The voltage drop correction due to the wiring resistance is a correction for each pixel. When the current amount is changed by the ABL control, it is necessary to perform the voltage drop correction for the changed current amount. Patent Document 4 describes a voltage drop correction method when an ABL circuit is provided.

JP 2003-22044 A JP 2005-266155 A JP 2006-154665 A JP 2006-133548 A

  However, in the methods of Patent Documents 1 and 2, other display pixels are corrected so as to match the display pixels that become the darkest due to a voltage drop in order to make the luminance in the frame uniform. Will fall. FIG. 3 is a diagram illustrating an example of conventional voltage drop correction. As shown in FIG. 3, the luminance value of the white cross-shaped pattern is lowered. Therefore, it is necessary to correct the luminance gradient in the panel, but there is a problem that the contrast is lowered because the maximum luminance in the frame is lowered.

  Further, in the method of Patent Document 3, it is possible to reduce the amount of luminance decrease by the second scanning signal, but the circuit becomes complicated and large-scale hardware is required. Similarly, the method of Patent Document 4 also corrects the in-frame brightness based on the brightness suppression amount by the ABL circuit, so that the overall brightness is lowered and, as a result, the contrast is lowered.

  The above-described decrease in contrast becomes a problem particularly when a specular component is included in the input image. In an input image in which a highlight area containing specular components and a relatively bright area coexist, the maximum brightness in the frame is determined based on the line average brightness of the bright area, so the maximum brightness of the specular area decreases. Resulting in. Therefore, it is difficult to reproduce a specular area that is dazzling in real space on a display.

  FIG. 4 is a diagram illustrating an example of a decrease in contrast feeling due to a decrease in luminance. Let us consider a case in which a spectacle light (specular component) such as a building light and a firework coexist in a night view as shown in FIG. FIG. 4B is a diagram showing line luminance distributions in two lines A and B in the image shown in FIG. For example, assume that the average luminance level in line A is 100 and the average luminance level in line B is 200. In the conventional technique, since the maximum luminance is determined based on the line B that is the maximum average luminance level in the frame, the luminance of the line A including the specular component is also set low. As a result, an image as shown in FIG. 4C is displayed, and the line luminance distribution at that time is as shown in FIG.

  As described above, when a highlight region including a specular component and a bright region in a relatively wide range coexist in the input image, the luminance of the specular component is reduced, and the contrast is lowered.

  The present invention has been made in view of the above problems. Even when a highlight area including a specular component and a bright area coexist in a relatively wide area coexist in an input image, this contrast is not reduced. An object is to provide a technique for displaying an input image.

In order to achieve the object of the present invention, for example, a display device of the present invention comprises the following arrangement. That is, a plurality of image forming elements arranged in a matrix,
Driving means for driving the image forming element group of the row corresponding to the horizontal line based on the video signal of each horizontal line of the image input as the display target image;
A display device comprising:
Means for calculating an average luminance level in the horizontal line for each horizontal line constituting the input image input as a display target image, and specifying a maximum average luminance level among the calculated average luminance levels;
A region overlapping across a plurality of horizontal lines in the input image, and means for detecting the area as an object area and having a less area defining area having a specified level or more luminance levels,
Means for determining whether a horizontal line of interest in the input image is a horizontal line having a portion overlapping with the object area;
Means for obtaining a correction gain for correcting the luminance level of the horizontal line of interest based on the maximum average luminance level when the horizontal line of interest is not a horizontal line having a portion overlapping the object area;
When the horizontal line of interest is a horizontal line having a portion overlapping the object area,
If the inequality of the average luminance level in the horizontal line of interest <the maximum average luminance level is satisfied, the correction gain is obtained based on the average luminance level, and if the inequality is not satisfied, the correction gain is determined based on the maximum average luminance level. Means for obtaining a correction gain;
Means for correcting the luminance level of the horizontal line of interest using the correction gain, and causing the driving means to drive the image forming element group in the row corresponding to the horizontal line of interest based on the video signal of the corrected luminance level; It is characterized by including these.

  According to the configuration of the present invention, even when a highlight area including a specular component and a bright area in a relatively wide range coexist in the input image, the input image can be displayed without reducing contrast. .

The figure which shows the example of the brightness | luminance fall by voltage drop. The figure which shows the example of the operation result by an ABL circuit. The figure which shows the example of the conventional voltage drop correction | amendment. The figure which shows the example of the feeling of contrast fall by luminance fall. The figure which shows the hardware structural example of the display apparatus which concerns on embodiment of this invention. The figure which shows the structural example of the image | video process part. The flowchart of the process (display method) which the video process part 504 performs. The figure for demonstrating the process which concerns on embodiment of this invention. The figure for demonstrating correction | amendment gain.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The embodiment described below shows an example when the present invention is specifically implemented, and is one of the specific examples of the configurations described in the claims.

<Overall configuration>
FIG. 5 is a diagram illustrating a hardware configuration example of the display device according to the present embodiment. As shown in FIG. 5, the display device according to the present embodiment includes a video processing unit 504, a column wiring driving unit 502, a row wiring driving unit 503, and a display panel 501.

  The display panel 501 includes a multi-electron source in which surface conduction electron-emitting devices, which are electron-emitting devices (image forming devices), are arranged in a matrix (m rows × n columns), and electron beam irradiation from the electron sources. And a light receiving surface for receiving and emitting light. A high voltage bias for accelerating the emitted electron beam is applied to the light receiving surface.

  The column wiring driving unit 502, the row wiring driving unit 503, and the video processing unit 504 are arranged around the display panel 501 as a display driving circuit. A signal (input video signal) indicating an input image as a display target image is input to the video processing unit 504. The video processing unit 504 performs various processes on the input video signal, including a process for correcting a luminance decrease due to a voltage drop due to the wiring resistance, and drives the column wiring based on the processed video signal. The unit 502 and the row wiring driving unit 503 are driven and controlled.

  The row wiring driving unit 503 sequentially selects lines to be lit in the display panel 501 (hereinafter, “line” means “horizontal line”), and selects a voltage via a wiring (row wiring) corresponding to the selected line. A pulse is applied to the display panel 501.

  The column wiring driving unit 502 displays a video signal (luminance data) corresponding to the row selected by the row wiring driving unit 503, that is, a voltage pulse having a pulse width proportional to the required electron beam emission amount via the column wiring. Application (modulation) to the panel 501 (modulation operation).

  Accordingly, the plurality of image forming elements arranged in a matrix are driven by the column wiring driving unit 502 and the row wiring driving unit 503 via the plurality of column wirings and the plurality of row wirings. Next, the video processing unit 504 will be described in more detail.

<Video processing unit 504>
FIG. 6 is a diagram illustrating a configuration example of the video processing unit 504. As illustrated in FIG. 6, the video processing unit 504 includes an object region detection unit 601, a calculation unit 602, a calculation unit 603, a correction gain calculation unit 604, and a voltage drop correction unit 605.

  FIG. 7 is a flowchart of processing (display method) performed by the video processing unit 504. In the following, the operation of each unit shown in FIG. 6 will be described according to the flowchart shown in FIG. Note that the processing according to the flowchart shown in FIG. 7 is for one frame of image, and therefore when a video signal for a plurality of frames is input to the video processing unit 504, the processing according to the flowchart of FIG. Processing may be performed on the video signal of each frame.

  The object area detection unit 601 receives an input video signal of an image for one frame. Accordingly, in step S701, the object area detection unit 601 detects an area having a luminance level within a predetermined luminance range as an object area from the image (input image) indicated by the input video signal. In the present embodiment, a case where the object region is a highlight region having a small area and a high luminance level will be described. However, even if the object region is another type of region, the following description can be applied similarly.

  Here, the process of detecting the object region from the image may be performed for each image, or may be detected from the correlation of a plurality of frames. In this embodiment, an object region in this image is detected from one image. Such detection is performed as follows, for example.

  First, in the line of interest, a range having a luminance level equal to or higher than a specific luminance level (for example, 95% of the maximum luminance level in the input video signal) is obtained. Next, a luminance gradient is obtained for each of the both end positions of the obtained range, and a position that is equal to or greater than a specific threshold (for example, 10% of the maximum amplitude in the input video signal) is calculated. A distance within a range having the calculated position as both ends is obtained.

  By performing such processing for each line and obtaining the sum of the respective distances, this sum can be obtained as the area of the object region as the highlight region. If the obtained area is equal to or less than a specific threshold (for example, 5% of the area of the image), it is determined that this object area is a highlight area.

  Note that the method for detecting the highlight area in the image is not limited to this, and the highlight area may be detected using a histogram, and an HPF (High Pass Filter) or the like is used to prevent erroneous detection. Detection may be performed based on the edge information extracted by using.

  Here, let us consider a case in which a building light and a specular light such as fireworks coexist in a night view as shown in FIG. When such an input image is input to the object region detection unit 601, the object region detection unit 601 detects two object regions 801 and 802 shown in FIG.

  Returning to FIG. 7, in step S <b> 702, the calculation unit 603 obtains an average luminance level within one line for each line constituting the input image. The average luminance level in one line can be easily obtained by an adder and a register. Then, the calculation unit 603 specifies the average luminance level indicating the maximum level among the average luminance levels obtained for each line as the maximum average luminance level (APL1). Next, in step S703, the calculation unit 602 selects one of the lines constituting the input image as the target line.

  In step S704, the calculation unit 602 determines whether the target line selected in step S703 is a line including the object area detected in step S701. That is, it is determined whether or not a part of the object area is included in the line of interest. As a result of the determination, if it is included, the process proceeds to step S705. If it is not included, the process proceeds to step S708.

  In step S705, the calculation unit 602 obtains an average luminance level (APL2) in the line of interest. The process for obtaining the average luminance level in one line is the same as the process performed in step S702.

  Next, in step S706, the calculation unit 602 determines whether or not APL2 <APL1 (whether or not the average luminance level in the line of interest <the maximum average luminance level). If it is determined that APL2 <APL1, the process advances to step S707. On the other hand, if APL2 ≧ APL1 (average luminance level in the line of interest ≧ maximum average luminance level), the process proceeds to step S708.

  For example, as shown in FIGS. 8A and 8B, the average luminance level of line A that is a line including the object region 801 is 100, and the average luminance level of line B that is a line including the object region 802 is 200. And Further, it is assumed that the maximum average luminance level is 200. In this case, if the line of interest is line A, the process proceeds to step S707. If the line of interest is line B, the process proceeds to step S708.

  FIG. 8C is a diagram showing the distribution of luminance levels in each of the lines A and B. Returning to FIG. 7, in step S707, the correction gain calculation unit 604 obtains a correction gain for correcting the luminance level of the line of interest based on APL2. The correction gain calculation can be easily calculated from the luminance level.

  FIG. 9A shows the relationship between the average luminance level and the output luminance. As shown in FIG. 9, as the average luminance level increases, the output luminance decreases proportionally. Therefore, as shown in FIG. 9B, the output luminance can be kept constant by determining the gain.

  Returning to FIG. 7, on the other hand, in step S708, the correction gain calculation unit 604 obtains a correction gain for correcting the luminance level of the line of interest based on APL1. The method for obtaining the correction gain may be the same as in step S707.

  Next, in step S709, the voltage drop correction unit 605 corrects the luminance level of the line of interest using the correction gain obtained in step S707 or step S708, and the column wiring driving unit 502 according to the corrected luminance level. Is controlled (voltage drop correction). For example, a drive signal (electron beam emission amount request value signal) of the column wiring drive unit 502 is generated based on the result of multiplying the luminance level of the target line by the correction gain, and this generated drive signal is sent to the column wiring drive unit 502. Send it out.

  FIG. 8D is a diagram showing a display example of an image displayed on the display panel 501 by the above processing. Returning to FIG. 7, next, if the above processing is performed for all lines, this processing ends via step S <b> 710 (processing for this frame ends). On the other hand, if the process target line remains, the process returns to step S703 via step S710, the next unprocessed line is newly selected as the target line, and the subsequent processes are performed.

  As described above, according to the present embodiment, the contrast of the highlight area can be improved. As a result, it is possible to extract the maximum brightness inherent in the device in the region having the specular component, and to reproduce the glare of the specular region in real space.

Claims (3)

A plurality of image forming elements arranged in a matrix;
Driving means for driving the image forming element group of the row corresponding to the horizontal line based on the video signal of each horizontal line of the image input as the display target image;
A display device comprising:
Means for calculating an average luminance level in the horizontal line for each horizontal line constituting the input image input as a display target image, and specifying a maximum average luminance level among the calculated average luminance levels;
A region overlapping across a plurality of horizontal lines in the input image, and means for detecting the area as an object area and having a less area defining area having a specified level or more luminance levels,
Means for determining whether a horizontal line of interest in the input image is a horizontal line having a portion overlapping with the object area;
Means for obtaining a correction gain for correcting the luminance level of the horizontal line of interest based on the maximum average luminance level when the horizontal line of interest is not a horizontal line having a portion overlapping the object area;
When the horizontal line of interest is a horizontal line having a portion overlapping the object area,
If the inequality of the average luminance level in the horizontal line of interest <the maximum average luminance level is satisfied, the correction gain is obtained based on the average luminance level, and if the inequality is not satisfied, the correction gain is determined based on the maximum average luminance level. Means for obtaining a correction gain;
Means for correcting the luminance level of the horizontal line of interest using the correction gain, and causing the driving means to drive the image forming element group in the row corresponding to the horizontal line of interest based on the video signal of the corrected luminance level; A display device comprising:   The display device according to claim 1, wherein the object region is a highlight region including a specular component. A plurality of image forming elements arranged in a matrix;
Driving means for driving the image forming element group of the row corresponding to the horizontal line based on the video signal of each horizontal line of the image input as the display target image;
A display method performed by a display device comprising:
Calculating an average luminance level in the horizontal line for each horizontal line constituting the input image input as a display target image, and specifying a maximum average luminance level among the calculated average luminance levels;
A region overlapping across a plurality of horizontal lines in the input image, and detecting the region as an object region and having a less area defining area having a specified level or more luminance levels,
Determining whether the horizontal line of interest in the input image is a horizontal line having a portion overlapping the object region;
When the horizontal line of interest is not a horizontal line having a portion that overlaps the object region, obtaining a correction gain for correcting the luminance level of the horizontal line of interest based on the maximum average luminance level;
When the horizontal line of interest is a horizontal line having a portion overlapping the object area,
If the inequality of the average luminance level in the horizontal line of interest <the maximum average luminance level is satisfied, the correction gain is obtained based on the average luminance level, and if the inequality is not satisfied, the correction gain is determined based on the maximum average luminance level. Obtaining a correction gain; and
Correcting the luminance level of the horizontal line of interest using the correction gain, and causing the driving means to drive the image forming element group in the row corresponding to the horizontal line of interest based on the video signal of the corrected luminance level; A display method comprising: and.